depositional environments sediment: Topics by Science.gov

Sample records for depositional environments sediment

Depositional environments during the Late Palaeozoic ice age (LPIA) in northern Ethiopia, NE Africa

NASA Astrophysics Data System (ADS)

Bussert, Robert

2014-11-01

The Late Palaeozoic sediments in northern Ethiopia record a series of depositional environments during and after the Late Paleozoic ice age (LPIA). These sediments are up to 200 m thick and exceptionally heterogeneous in lithofacies composition. A differentiation of numerous types of lithofacies associations forms the basis for the interpretation of a large range of depositional processes. Major glacigenic lithofacies associations include: (1) sheets of diamictite, either overlying glacially eroded basement surfaces or intercalated into the sediment successions, and representing subglacial tillites, (2) thick massive to weakly stratified muddy clast-poor diamictites to lonestone-bearing laminated mudstones originating from a combination of suspension settling of fines and iceberg rainout, (3) lensoidal or thin-bedded diamictites deposited from debris flows, (4) wedges of traction and gravity transported coarse-grained sediments deposited in outwash fans, (5) irregular wedges or sheets of mudstones deformed primarily by extension and incorporating deformed beds or rafts of other lithofacies formed by slumping, and (6) irregular bodies of sandstone, conglomerate and diamictite deformed by glacial pushing. The dominance of laminated or massive clast-bearing mudstones in most successions indicates ice-contact water bodies as the major depositional environment. Into this environment, coarse-grained sediments were transported by various gravity driven transport processes, including dropstone activity of ice-bergs, slumping, cohesive debris flow, hyperconcentrated to concentrated flow, hyperpycnal flow, and by turbidity flow. Close to glacier termini, wedge-shaped bodies of conglomerate, sandstone, diamictite and mudstone were deposited primarily in subaqueous outwash-fans. Soft-sediment deformation of these sediments either records ice push during glacier advance or re-sedimentation by slumping. Apart from an initial glacier advance when thick ice of temperate or polythermal glaciers covered the whole basin, many sections document at least a second major phase of ice advance and retreat, and some sections additional minor advance-retreat cycles. Whether most of the LPIA sediments in northern Ethiopia were deposited in lakes or in fjords is not yet clear. Although univocal evidence of marine conditions is missing, the presence of carbonate-rich beds and the trace fossil assemblage are compatible with a restricted marine environment such as broad palaeofjords affected by strong freshwater discharge during deglaciation. A restricted marine environment for most of the sediments in northern Ethiopia could challenge models of the LPIA sediments in Arabia as primarily glaciolacustrine and glaciofluviatile deposits.
Seafloor environments within the Boston Harbor- Massachusetts Bay sedimentary system: A regional synthesis

USGS Publications Warehouse

Knebel, H.J.; Circe, R.C.

1995-01-01

Modern seafloor sedimentary environments within the glaciated, topographically complex Boston Harbor and Massachusetts Bay area have been interpreted and mapped from an extensive collection of sidescan sonar records and supplemental marine geologic data. Three categories of environments are present that reflect the dominant long-term processes of erosion or nondeposition, deposition, and sediment reworking. (1) Environments of erosion or nondeposition comprise exposures of bedrock, glacial drift, coarse lag deposits, and possibly coastal plain rocks that contain sediments (where present) ranging from boulder fields to gravelly sands and occur in areas of relatively strong currents. (2) Environments of deposition contain fine-grained sediments ranging from muddy sands to muds that have accumulated in areas of predominantly weak bottom currents. (3) Environments of sediment reworking contain patches with textures ranging from sandy gravels to muds that have been produced by a combination of erosion and deposition in areas with variable bottom currents. The distribution of sedimentary environments across the Boston Harbor-Massachusetts Bay area is extremely patchy. Locally, this patchiness is due either to modifications of bottom-current strength (caused by the irregular topography and differences in water depth) or to small-scale changes in the supply of fine-grained sediments. Regional patchiness, however, reflects differences in geologic and oceanographic conditions among the estuarine, inner shelf, and basinal parts of the sedimentary system. The estuarine part of the system (Boston Harbor) is a depositional trap for fine-grained sediments because it is protected from large waves, has generally weak and variable tidal currents, and receives a large supply of fine grained detritus from natural and anthropogenic sources. The inner shelf, on the other hand, is largely an area of erosion or nondeposition due to sediment removal and redistribution during past sea-level changes, to sediment resuspension and winnowing by modern waves and currents, and to an inadequate supply of fine-grained sediments. The basinal part of the system (Stellwagen Basin) is mainly a tranquil depositional environment in which fine-grained sediments from several potential sources settle through the water column and accumulate under weak bottom currents. This study indicates areas within the Boston Harbor-Massachusetts Bay sedimentary system where fine-grained sediments and associated contaminants are likely to be either moved or deposited. It also provides a guide to the locations and variability of benthic habitats.
Grain size analysis and depositional environment of shallow marine to basin floor, Kelantan River Delta

NASA Astrophysics Data System (ADS)

Afifah, M. R. Nurul; Aziz, A. Che; Roslan, M. Kamal

2015-09-01

Sediment samples were collected from the shallow marine from Kuala Besar, Kelantan outwards to the basin floor of South China Sea which consisted of quaternary bottom sediments. Sixty five samples were analysed for their grain size distribution and statistical relationships. Basic statistical analysis like mean, standard deviation, skewness and kurtosis were calculated and used to differentiate the depositional environment of the sediments and to derive the uniformity of depositional environment either from the beach or river environment. The sediments of all areas were varied in their sorting ranging from very well sorted to poorly sorted, strongly negative skewed to strongly positive skewed, and extremely leptokurtic to very platykurtic in nature. Bivariate plots between the grain-size parameters were then interpreted and the Coarsest-Median (CM) pattern showed the trend suggesting relationships between sediments influenced by three ongoing hydrodynamic factors namely turbidity current, littoral drift and waves dynamic, which functioned to control the sediments distribution pattern in various ways.
Seafloor environments in Cape Cod Bay, a large coastal embayment

USGS Publications Warehouse

Knebel, H.J.; Rendigs, R. R.; List, J.H.; Signell, R.P.

1996-01-01

Cape Cod Bay is a glacial, semi-enclosed embayment that has a patchy distribution of modern seafloor sedimentary environments of erosion or nondeposition, deposition, and sediment reworking. Sidescan-sonar records and supplemental bathymetric, sedimentary, subbottom, and physical- oceanographic data indicate that the characteristics and distribution of these three categories of bottom environments are controlled by a combination of geologic and oceanographic processes that range from episodic to long-term and from regional to local. (1) Environments of erosion or nondeposition comprise exposares of bedrock, glacial drift, and coarse lag deposits that contain sediments (where present) ranging from boulder fields to gravelly coarse-to-medium sands. These environments are dominant on the shallow margins of the bay (water depths <30 m) where they reflect sediment resuspension, winnowing, and transport during modern northerly storms. (2) Environments of deposition are blanketed by fine-grained sediments ranging from muds to muddy fine sands. These environments are dominant across the floor of the central basin (water depths= 30-60 m) where fine- grained sediments (derived from regional and local sources and emplaced primarily during episodic wind- and density-driven flow) settle through the water column and accumulate under weak bottom currents during nonstorm conditions. (3) Environments of sediment reworking contain patches with diverse textures ranging from gravelly sands to muds. These environments occupy much of the transitional slopes between the margins and the basin floor and reflect a combination of erosion and deposition. The patchy distribution of sedimentary environments within the bay reflects not only regional changes in processes between the margins and the basin but local changes within each part of the bay as well. Small-scale patchiness is caused by local changes in the strengths of wave- and wind-driven currents and (on the margins) by local variations in the supply of fine-grained sediments. This study indicates areas within Cape Cod Bay where fine-grained sediments and associated contaminants are likely to be either moved or deposited. It also provides a guide to the locations and variability of benthic habitats.
Seafloor environments in Cape Cod Bay, a large coastal embayment

USGS Publications Warehouse

Knebel, H.J.; Rendigs, R. R.; List, J.H.; Signell, Richard P.

1996-01-01

Cape Cod Bay is a glacial, semi-enclosed embayment that has a patchy distribution of modern seafloor sedimentary environments of erosion or nondeposition, deposition, and sediment reworking. Sidescan-sonar records and supplemental bathymetric, sedimentary, subbottom, and physical-oceanographic data indicate that the characteristics and distribution of these three categories of bottom environments are controlled by a combination of geologic and oceanographic processes that range from episodic to long-term and from regional to local. (1) Environments of erosion or nondeposition comprise exposures of bedrock, glacial drift, and coarse lag deposits that contain sediments (where present) ranging from boulder fields to gravelly coarse-to-medium sands. These environments are dominant on the shallow margins of the bay (water depths < 30 m) where they reflect sediment resuspension, winnowing, and transport during modern northerly storms. (2) Environments of deposition are blanketed by fine-grained sediments ranging from muds to muddy fine sands. These environments are dominant across the floor of the central basin (water depths = 30–60 m) where fine-grained sediments (derived from regional and local sources and emplaced primarily during episodic wind- and density-driven flow) settle through the water column and accumulate under weak bottom currents during nonstorm conditions. (3) Environments of sediment reworking contain patches with diverse textures ranging from gravelly sands to muds. These environments occupy much of the transitional slopes between the margins and the basin floor and reflect a combination of erosion and deposition.The patchy distribution of sedimentary environments within the bay reflects not only regional changes in processes between the margins and the basin but local changes within each part of the bay as well. Small-scale patchiness is caused by local changes in the strengths of wave- and wind-driven currents and (on the margins) by local variations in the supply of fine-grained sediments.This study indicates areas within Cape Cod Bay where fine-grained sediments and associated contaminants are likely to be either moved or deposited. It also provides a guide to the locations and variability of benthic habitats.
Oligocene Fluvio-Deltaic Depositional Environments Salin Sub-Basin, Central Myanmar

NASA Astrophysics Data System (ADS)

Gough, A.; Hall, R.

2017-12-01

A recent increase in accessibility for research in Myanmar has allowed rapid advancements in the understanding of the geology of the country. Evolving depositional environments can be reconstructed in largely unstudied Oligocene deposits of the Salin sub-basin, of the Central Myanmar Basin. Data has been collected through a fieldwork campaign to target well-exposed sediments along the western margin of the basin. The studied outcrops span approximately one hundred kilometres from north to south, and a series of sedimentary logs, palaeocurrent data, 2D panel diagrams, and samples for petrographical analysis have been collected and interpreted. The Oligocene formations studied include the Shwezetaw, Paduang, and Okhmintaung, each of which show a broadly southwards-trending fluvio-deltaic environment of deposition. Towards the north, the lower Rupelian Shwezetaw Formation comprises thick fluviatile sandstones which grade southwards through macrotidal-dominated fluvio-deltaic interbedded siltstones and rare sandstones, into marine sandstones. Overlying this, the upper Rupelian Paduang Formation grades rapidly from rare fluvial sandstones towards the north of the basin into deltaic and marine interbedded sandstones and siltstones to the south. This formation is more marine in nature, suggesting a minor transgression throughout the lower Oligocene. By the time of deposition of the Okhmintaung Formation in the Chattian the observed deposits solely represent a tidally-influenced deltaic depositional environment, with very little temporal variation, suggesting a stable sea level. Despite the relatively unchanging depositional environment, the formations are approximately 4000 m thick, suggesting that sedimentation kept pace with relatively rapid subsidence. This current study, which will combine depositional environment reconstruction, provenance, and sediment routing analysis, will provide important insights into both the tectonic setting and the huge sediment accumulation of the poorly understood Central Myanmar Basin.
Deposition and deformation of stratified rocks in the northern Nia Mensa region of Valles Marineris, Mars

NASA Astrophysics Data System (ADS)

Okubo, C. H.

2016-12-01

Large-scale structural and geologic mapping based on HiRISE (High Resolution Imaging Science Experiment) digital elevation models reveals new details of the depositional environment for the stratified rocks in the northern Nia Mensa region of eastern Candor Chasma, Valles Marineris, Mars. The map area encompasses the contact between massive sedimentary rocks that comprise most of Nia Mensa and the stratified sedimentary and mass-wasting deposits exposed between Nia Mensa and the north wall of eastern Candor Chasma. The area contains a stratified fan-like deposit on the lower slopes of Nia Mensa. The strata within this deposit dip outward at < 10°, away from its morphologic apex, consistent with an origin as a depositional fan (rather than being carved into a fan shape by erosion). Whether this fan has a subaerial or submarine origin has not yet been determined. Additionally, the fan and surrounding stratified rocks exhibit evidence of soft-sediment deformation in the form of clastic dikes and contorted bedding, indicating that these deposits were water-saturated at the time of deformation. Finally, the northern section of the map area encompasses part of a fractured rise, and deposits interpreted as mud flows mantle the top of this rise. Inferred flow directions suggest that the mud erupted out of these fractures. These findings place constraints on the depositional environment of the local stratified bedrock. The presence of the fan deposit indicates that lateral transport was a component in the depositional history of these sediments. Therefore the sediments did not form entirely as a mantling deposit, such as air fall ash or sediments settled out of a water column. The soft-sediment deformation and subsurface mobilized sediments indicate that groundwater was present in the area after emplacement of the stratified deposits, but before its lithification. These findings point to a wet-playa to lacustrine depositional environment.
Stratigraphy of a proposed wind farm site southeast of Block Island: Utilization of borehole samples, downhole logging, and seismic profiles

NASA Astrophysics Data System (ADS)

Sheldon, Dane P. H.

Seismic stratigraphy, sedimentology, lithostratigraphy, downhole geophysical logging, mineralogy, and palynology were used to study and interpret the upper 70 meters of the inner continental shelf sediments within a proposed wind farm site located approximately two to three nautical miles to the southeast of Block Island, Rhode Island. Core samples and downhole logging collected from borings drilled for geotechnical purposes at proposed wind turbine sites along with seismic surveys in the surrounding area provide the data for this study. Cretaceous coastal plain sediments that consist of non-marine to marine sand, silt, and clay are found overlying bedrock at a contact depth beyond the sampling depth of this study. The upper Cretaceous sediments sampled in borings are correlated with the Magothy/Matawan formations described regionally from New Jersey to Nantucket. An unconformity formed through sub-aerial, fluvial, marine, and glacial erosion marks the upper strata of the Cretaceous sediments separating them from the overlying deposits. The majority of Quaternary deposits overlying the unconformity represent the advance, pulsing, and retreat of the Laurentide ice sheet that reached its southern terminus in the area of Block Island approximately 25,000 to 21,000 years before present. The sequence consists of a basal glacial till overlain by sediments deposited by meltwater environments ranging from deltaic to proglacial lakefloor. A late Pleistocene to early Holocene unconformity marks the top of the glacial sequence and was formed after glacial retreat through fluvial and subaerial erosion/deposition. Overlying the glacial sequence are sediments deposited during the late Pleistocene and Holocene consisting of interbedded gravel, sand, silt, and clay. Sampling of these sediments was limited and surficial reflectors in seismic profiles were masked due to a hard bottom return. However, two depositional periods are interpreted as representing fluvial and estuarine/marine environments respectively. One sample recovered at five meters contained shell fragments within a gray fine to coarse sand possibly representing a shallow estuarine to marine environment. A coarse near surface deposit described but not recovered in all borings may represent a transgressive unconformity and resulting lag deposit however due to lack of sampling and seismic resolution in the upper 5 meters, the nature of this deposit is merely speculation. In areas where depth to the glacial surface increased, sediments ranging from sand to fine-grained silt and clay were encountered in borings. In summary, the upper 70 meters of the inner continental shelf section within the study site consists of unconsolidated sediments spanning three major depositional periods. Sediments derived from glacial activity represent the bulk of samples collected. The glacial sequences represent various depositional environments, although most samples are interpreted to be the product of glacial meltwater deposition with distribution determined by source as well as highs and lows present in the antecedent topography. Finely laminated (varved) sediment to the south of Block Island indicates the presence of proglacial lakes in the area during the time of glacial retreat. Overlying sediments represent environments ranging from fluvial to marine.
Origin and depositional environment of fine-grained sediments since the last glacial maximum in the southeastern Yellow Sea: evidence from rare earth elements

NASA Astrophysics Data System (ADS)

Um, In Kwon; Choi, Man Sik; Lee, Gwang Soo; Chang, Tae Soo

2015-12-01

Despite the well-reconstructed seismic stratigraphy of the Holocene mud deposit in the southeastern Yellow Sea, known as the Heuksan mud belt (HMB), the provenances of these sediments and their depositional environments are unclear, especially for the fine-grained sediments. According to seismic data (extracted from another article in this special issue), the HMB comprises several sedimentary units deposited since the last glacial maximum. Based on analytical results on rare earth elements, fine-grained sediments in all sedimentary units can be interpreted as mixtures of sediments discharged from Chinese and Korean rivers. The proportions of fine-grained sediments from Chinese rivers (74.5 to 80.0%) were constant and higher than those from Korean rivers in all units. This fact demonstrates that all units have the same fine-grained sediment provenance: units III-b and III-a, located in the middle and northern parts of the HMB and directly deposited from Chinese rivers during the sea-level lowstand, could be the sediment source for units II-b and II-a. Unit I, while ambiguous, is of mixed origin combining reworked sediments from nearby mud deposits and Changjiang River-borne material with those of the Keum River. The results of this study indicate that at least 18.6% of bulk sediments in the HMB clearly originate from Chinese rivers, despite its location close to the southwestern coast of Korea.
Grain size statistics and depositional pattern of the Ecca Group sandstones, Karoo Supergroup in the Eastern Cape Province, South Africa

NASA Astrophysics Data System (ADS)

Baiyegunhi, Christopher; Liu, Kuiwu; Gwavava, Oswald

2017-11-01

Grain size analysis is a vital sedimentological tool used to unravel the hydrodynamic conditions, mode of transportation and deposition of detrital sediments. In this study, detailed grain-size analysis was carried out on thirty-five sandstone samples from the Ecca Group in the Eastern Cape Province of South Africa. Grain-size statistical parameters, bivariate analysis, linear discriminate functions, Passega diagrams and log-probability curves were used to reveal the depositional processes, sedimentation mechanisms, hydrodynamic energy conditions and to discriminate different depositional environments. The grain-size parameters show that most of the sandstones are very fine to fine grained, moderately well sorted, mostly near-symmetrical and mesokurtic in nature. The abundance of very fine to fine grained sandstones indicate the dominance of low energy environment. The bivariate plots show that the samples are mostly grouped, except for the Prince Albert samples that show scattered trend, which is due to the either mixture of two modes in equal proportion in bimodal sediments or good sorting in unimodal sediments. The linear discriminant function analysis is dominantly indicative of turbidity current deposits under shallow marine environments for samples from the Prince Albert, Collingham and Ripon Formations, while those samples from the Fort Brown Formation are lacustrine or deltaic deposits. The C-M plots indicated that the sediments were deposited mainly by suspension and saltation, and graded suspension. Visher diagrams show that saltation is the major process of transportation, followed by suspension.
Stratigraphy and paleoenvironment of Miocene phosphatic rocks in the East San Francisco Bay region, California

USGS Publications Warehouse

Hill, James M.

1979-01-01

A stratigraphic study of the Monterey Group in the East San Francisco Bay Region, California, indicates that a depositional basin began to subside in early to middle Miocene time. The Miocene sea transgressed from the west or southwest, and the area subsided to a possible water depth of 500 to 2,500 m. The Monterey Group within the study area is a time-transgressive sequence of six sandstone and shale formations. Stratigraphic cycles of interbedded sandstone and shale formations are related to the amount of terrigenous sediment input into the basin as well as the depositional environment. During periods of low terrigenous sedimentation, biogenetic sedimentation in the form of diatomite layers were interbedded with hemipelagic muds and thin turbidite sands. These diatom-rich sediments were probably deposited within the upper bathyal zone (180 to 500 m) and, during lithification, diagenetically altered to form siliceous shales and cherts. As terrigenous sedimentation increased, probably due to periodic uplift east of the study area, biogenetic sedimentation was masked until finer grained sediment at a lower rate of deposition reoccurred. As the basin filled and a higher energy environment prevailed; coarse-grained sediment was again deposited until a lower energy environment resumed. Three types of inorganic phosphate are present within the study area: nodular, Pelletal, and pebbles of sandy phosphatic mudstone. The nodular phosphate is associated with the siliceous shale formations and formed within diatomite layers before compaction and lithification. The other two types of phosphate are found within the sandstone formations and probably originated in a shallower, higher energy environment than the siliceous shales. Faulting was active during middle to late Miocene time. The change in stratigraphic thickness across the Mission fault is 350 m which may approximate the vertical (?) displacement along this fault. This displacement took place in middle to upper Miocene time and apparently caused erosion of the upper formations of the Monterey Group on the west side of the Mission fault before the Briones Formation was deposited in late Miocene time. Depositional thinning of the Monterey Group in the southern portion of the study area may imply that the Hayward and Calaveras faults were also active at this time.
Depositional environment of near-surface sediments, King George Basin, Bransfield Strait, Antarctica

NASA Astrophysics Data System (ADS)

Yoon, H. I.; Park, B. K.; Chang, S. K.; Han, M. W.; Oh, J. K.

1994-03-01

Four sediment cores were collected to determine the depositional environments of the King George Basin northeast of Bransfield Strait, Antarctica. The cored section revealed three distinct lithofacies: laminated siliceous ooze derived from an increased paleoproductivity near the receding sea-ice edges, massive muds that resulted from hemipelagic sedimentation in open water, and graded sediments that originated from nearby local seamounts by turbidity currents. Clay mineral data of the cores indicate a decreasing importance of volcanic activity through time. Active volcanism and hydrothermal activity appear to be responsible for the enrichment of smectite near the Penguin and Bridgeman Islands.
Provenance and depositional environment of epi-shelf lake sediment from Schirmacher Oasis, East Antarctica, vis-à-vis scanning electron microscopy of quartz grain, size distribution and chemical parameters

NASA Astrophysics Data System (ADS)

Shrivastava, Prakash K.; Asthana, Rajesh; Roy, Sandip K.; Swain, Ashit K.; Dharwadkar, Amit

2012-07-01

The scientific study of quartz grains is a powerful tool in deciphering the depositional environment and mode of transportation of sediments, and ultimately the origin and classification of sediments. Surface microfeatures, angularity, chemical features, and grain-size analysis of quartz grains, collectively reveal the sedimentary and physicochemical processes that acted on the grains during different stages of their geological history. Here, we apply scanning electron microscopic (SEM) analysis to evaluating the sedimentary provenance, modes of transport, weathering characteristics, alteration, and sedimentary environment of selected detrital quartz grains from the peripheral part of two epi-shelf lakes (ESL-1 and ESL-2) of the Schirmacher Oasis of East Antarctica. Our study reveals that different styles of physical weathering, erosive signatures, and chemical precipitation variably affected these quartz grains before final deposition as lake sediments. Statistical analysis (central tendencies, sorting, skewness, and kurtosis) indicates that these quartz-bearing sediments are poorly sorted glaciofluvial sediments. Saltation and suspension seem to have been the two dominant modes of transportation, and chemical analysis of these sediments indicates a gneissic provenance.
Earth Surface Processes, Landforms and Sediment Deposits

NASA Astrophysics Data System (ADS)

Bridge, John; Demicco, Robert

Earth surface processes, landforms and sediment deposits are intimately related - involving erosion of rocks, generation of sediment, and transport and deposition of sediment through various Earth surface environments. These processes, and the landforms and deposits that they generate, have a fundamental bearing on engineering, environmental and public safety issues; on recovery of economic resources; and on our understanding of Earth history. This unique textbook brings together the traditional disciplines of sedimentology and geomorphology to explain Earth surface processes, landforms and sediment deposits in a comprehensive and integrated way. It is the ideal resource for a two-semester course in sedimentology, stratigraphy, geomorphology, and Earth surface processes from the intermediate undergraduate to beginning graduate level. The book is also accompanied by a website hosting illustrations and material on field and laboratory methods for measuring, describing and analyzing Earth surface processes, landforms and sediments.
Sedimentary architecture and depositional environment of Kudat Formation, Sabah, Malaysia

NASA Astrophysics Data System (ADS)

Ghaheri, Samira; Suhaili, Mohd; Sapari, Nasiman; Momeni, Mohammadsadegh

2017-12-01

Kudat Formation originated from deep marine environment. Three lithofacies association of deep marine turbidity channel was discovered in three Members of the Kudat Formation in Kudat Peninsula, Sabah, Malaysia. Turbidite and deep marine architecture elements was described based on detailed sedimentological studies. Four architecture elements were identified based on each facies association and their lithology properties and character: inner external levee that was formed by turbidity flows spill out from their confinement of channel belt; Lobes sheet that was formed during downslope debris flows associated with levee; Channel fill which sediments deposited from high to low density currents with different value of sediment concentration; and overbank terrace which was formed by rapid suspension sedimentation. The depositional environment of Kudat Formation is shelf to deep marine fan.
Depositional environments and processes in Upper Cretaceous nonmarine and marine sediments, Ocean Point dinosaur locality, North Slope, Alaska

USGS Publications Warehouse

Phillips, R.L.

2003-01-01

A 178-m-thick stratigraphic section exposed along the lower Colville River in northern Alaska, near Ocean Point, represents the uppermost part of a 1500 m Upper Cretaceous stratigraphic section. Strata exposed at Ocean Point are assigned to the Prince Creek and Schrader Bluff formations. Three major depositional environments are identified consisting, in ascending order, of floodplain, interdistributary-bay, and shallow-marine shelf. Nonmarine strata, comprising the lower 140 m of this section, consist of fluvial distributaries, overbank sediments, tephra beds, organic-rich beds, and vertebrate remains. Tephras yield isotopic ages between 68 and 72.9 Ma, generally consistent with paleontologic ages of late Campanian-Maastrichtian determined from dinosaur remains, pollen, foraminifers, and ostracodes. Meandering low-energy rivers on a low-gradient, low-relief floodplain carried a suspended-sediment load. The rivers formed multistoried channel deposits (channels to 10 m deep) as well as solitary channel deposits (channels 2-5 m deep). Extensive overbank deposits resulting from episodic flooding formed fining-upward strata on the floodplain. The fining-upward strata are interbedded with tephra and beds of organic-rich sediment. Vertical-accretion deposits containing abundant roots indicate a sheet flood origin for many beds. Vertebrate and nonmarine invertebrate fossils along with plant debris were locally concentrated in the floodplain sediment. Deciduous conifers as well as abundant wetland plants, such as ferns, horsetails, and mosses, covered the coastal plain. Dinosaur skeletal remains have been found concentrated in floodplain sediments in organic-rich bone beds and as isolated bones in fluvial channel deposits in at least nine separate horizons within a 100-m-thick interval. Arenaceous foraminifers in some organic-rich beds and shallow fluvial distributaries indicate a lower coastal plain environment with marginal marine (bay) influence. Marginal marine strata representing interdistributary bay deposits overlie the nonmarine beds and comprise about 15 m of section. Extensive vegetated sand flats, shoals, and shallow channels overlain by shallow bay deposits (less than 7 m deep), containing storm-generated strata characterize the marginal marine beds. Abundant bioturbation and roots characterize the stratigraphic lowest bay deposits; bioturbated sediment, pelecypods, barnacles, and benthic microfossils are found in the overlying bay storm deposits. The sediments abruptly change upward from hummocky cross-stratified bay deposits to a muddy marsh deposit containing shallow organic-rich channels to prograding nonmarine to marginal marine beds. Transgressive, abundantly fossiliferous shallow-marine strata more than 13 m thick comprise the uppermost exposures at Ocean Point. The marine beds overlie nonmarine and bay strata and represent an environment dominated episodically by storms. The age of the marginal marine and marine beds is late Maastrichtian based on pollen. ?? 2003 Elsevier Ltd. All rights reserved.
Stratigraphy, depositional environments, and carbonate petrology of the Toroweap and Kaibab Formations (lower Permian), Grand Canyon region, Arizona

NASA Astrophysics Data System (ADS)

Clark, R. A.

Sediments deposited in northwestern Arizona during Late Leonardian and Early Guadalupian (Permian) were controlled chiefly by an arid climate and the tectonic setting. Eastward thrusting of eugeosynclinal rocks onto miogeosynclinal deposits during Middle Devonian to Early Mississippian had a major influence on shelf sedimentation. The Toroweap and Kaibab formations represent two such platform sequences of northwestern Arizona and southern Utah deposited during this phase of sedimentation. The Toroweap Formation is subdivided into three members and represents sediments deposited during initial transgression, maximum extent of the sea, and regression (Seligman, Brady Canyon, and Woods Ranch members respectively). The Fossil Mountain Member of the Kaibab Formation documents the most extensive phase of sedimentation for all members of the Toroweap and Kaibab formations. The Harrisburg Member documents the final phase of sedimentation at the close of the Paleozoic Era.
Sedimentary record of erg migration

NASA Astrophysics Data System (ADS)

Porter, M. L.

1986-06-01

The sedimentary record of erg (eolian sand sea) migration consists of an idealized threefold division of sand-sea facies sequences. The basal division, here termed the fore-erg, is composed of a hierarchy of eolian sand bodies contained within sediments of the flanking depositional environment. These sand bodies consist of eolian strata deposited by small dune complexes, zibars, and sand sheets. The fore-erg represents the downwind, leading edge of the erg and records the onset of eolian sedimentation. Basin subsidence coupled with erg migration places the medial division, termed the central erg, over the fore-erg strata. The central erg, represented by a thick accumulation of large-scale, cross-stratified sandstone, is the product of large draa complexes. Eolian influence on regional sedimentation patterns is greatest in the central erg, and most of the sand transported and deposited in the erg is contained within this region. Reduction in sand supply and continued erg migration will cover the central-erg deposits with a veneer of back-erg deposits. This upper division of the erg facies sequence resembles closely the fore-erg region. Similar types of eolian strata are present and organized in sand bodies encased in sediments of the upwind flanking depositional environment(s). Back-erg deposits may be thin due to limited eolian influence on sedimentation or incomplete erg migration, or they may be completely absent because of great susceptibility to postdepositional erosion. Tectonic, climatic, and eustatic influences on sand-sea deposition will produce distinctive variations or modifications of the idealized erg facies sequence. The resulting variants in the sedimentary record of erg migration are illustrated with ancient examples from western North America, Europe, southern Africa, and South America.
An interpretation of carbon and sulfur relationships in Black Sea sediments as indicators of environments of deposition

USGS Publications Warehouse

Leventhal, J.S.

1983-01-01

Syngenetic iron sulfides in sediments are formed from dissolved sulfide resulting from sulfate reduction and catabolism of organic matter by anaerobic bacteria. It has been shown that in recent marine sediments deposited below oxygenated waters there is a constant relationship between reduced sulfur and organic carbon which is generally independent of the environment of deposition. Reexamination of data from recent sediments from euxinic marine environments (e.g., the Black Sea) also shows a linear relationship between carbon and sulfur, but the slope is variable and the line intercepts the S axis at a value between 1 and 2 percent S. It is proposed that the positive S intercept is due to watercolumn microbial reduction of sulfate using metabolizable small organic molecules and the sulfide formed is precipitated and accumulates at the sediment-water interface. The variation in slope and intercept of the C to S plots for several cores and for different stratigraphic zones for the Black Sea can be interpreted in relation to thickness of the aqueous sulfide layer or thinness of the oxygen containing layer and to deposition rate, but also may be influenced by availability of iron, and perhaps the type of organic matter (Leventhal, 1979). ?? 1983.
Reconstructing the Holocene depositional environments along the northern coast of Sfax (Tunisia): Mineralogical and sedimentological approaches

NASA Astrophysics Data System (ADS)

Lamourou, Ali; Touir, Jamel; Fagel, Nathalie

2017-05-01

A sedimentological and mineralogical study of sedimentary cores allowed reconstructing the evolution of depositional environments along the Northern coast of Sfax (Tunisia). The aim of this research work is to identify the factors controlling the sedimentation from the Holocene to the Present time. Three 30-m sediment cores collected by drilling at 30 m water depth were analyzed for their color, magnetic susceptibility signal, grain size by laser diffraction, organic matter content by loss of ignition, carbonate content by calcimetry and mineralogy by X-ray diffraction on bulk powder and clay <2 μm. They broadly present the same sedimentological and mineralogical features. Microscopical observations of petrographic slides allowed identifying six main sedimentary facies. Bulk mineralogical assemblages comprised clay minerals, quartz, calcite, gypsum and K-feldspars were examined. Considerable change was observed in the carbonate content that mimicked the bioclaste abundance and diluted the detrital minerals (clay minerals, quartz and feldspars). The gypsum mainly occurred in the lower sedimentary columns (SC12 and SC9) and in the upper/middle of core SC6. The clay fraction was made of a mixture of kaolinite, illite, smectite and palygorskite with no clear variation through core depth. Both grain-size parameters and magnetic susceptibility profile showed a sharp transition in the upper 2-5 m of the sedimentological columns. Coarse, sandy to gravely sediments characterized by a low magnetic susceptibility signal were replaced by fine bioclastic-rich clayey sediments. The analysis of vertical succession of depositional facies revealed a fluvial depositional environment (coastal plain) basically marked by fluvial channels and inundation plains at the bottom of all cores. However, core-top sediments recorded a littoral marine environment with sand depositions rich in gastropods, lamellibranches and algæ. Depositional facies, sedimentological and mineralogical parameters were consistent with a transition from a fluviatile depositional environment with some emersion phases marked by the gypsum precipitation, to a marine littoral environment. Such evolution was accompanied with a relative sea-level rise which flooded the fluvial system at the coastal plain during the Holocene, in agreement with sea-level fluctuations in southeast Tunisia during the Holocene.

Modern Estuarine Sedimentation in Suisun Bay, California

NASA Astrophysics Data System (ADS)

Chin, J. L.; Orzech, K.; Anima, R. J.; Jaffe, B.

2002-12-01

Suisun Bay is the northeasternmost part of San Francisco Bay (California), the largest estuary on the Pacific Coast of the United States. Suisun Bay's geographic and morphologic position are unique in that it occupies the head of the estuary and is subject to the maximum freshwater inflow and sediment input of the Sacramento-San Joaquin Rivers, whose drainage basin covers 40% of the land area of California. Suisun Bay consists of two smaller subembayments, Grizzly and Honker Bays. Gravity cores obtained in 1990-1991 and 1999 were analyzed to delineate depositional environments and sedimentation patterns in Suisun Bay. Major depositional environments include: tidal channel (subtidal), tidal channel banks (subtidal), tidal flat (intertidal to subtidal), and bay mouth (subtidal). The tidal channel environment includes both large and small channels in Suisun Bay as well as the tidal sloughs Suisun and Montezuma Sloughs. The coarsest sediment, usually sand or muddy sand, characterize this environment and water depths range from 2 to 11 m. Thin (1-2 mm) and discontinuous silt and clay laminae are common. Suisun and Montezuma Sloughs are the exception to this pattern in that they consist of massive, intensely bioturbated muds. Tidal channel banks (both "cut" and "accretionary" channel margins), particularly accretionary banks, are characterized by low-to-moderate bioturbation and sandy mud to muddy sand lithology. Typically alternating sand and mud beds (1-6 cm thick) are present; both types of beds consist of 1mm to 1cm thick subhorizontal to inclined laminae. Laminae composed of organic detritus are also present. Where this environment is transitional with the tidal flat environment water depths range from 2-8 m. Tidal flat environments include the "sand" shoals present on bathymetry charts, and are typically a bioturbated muddy sand to sandy mud. Sand and mud beds, 1-3 cm thick, are often characterized by very fine 1-2 mm thick silt and mud laminae. Water depths range from 2 to 4.5 m where these laminated tidal flat sediments occur. Bay mouth environments occur only in the distal portions of Grizzly and Honker Bays, subembayments of Suisun Bay proper. This environment is transitional with both tidal channel bank and tidal flat environments and shares characteristics with each. Massive to interbedded mud is the most common lithology, although sandy mud to muddy sand also occurs. Centimeters thick sand and mud beds typically alternate vertically. Bioturbation is low to moderate. Water depths over this environment range from 2 to 3 m. Depositional environments present in Suisun Bay are the result of a full range of tidal and fluvial processes as shown by the lithologies and alternating sediment stratigraphic patterns observed in cores. Very thin beds and intense bioturbation evidence intervals of very slow to negligible sedimentation. Rapid deposition and/or resuspension are evidenced by thick sediment intervals and by laminae that are continuous and apparently unbioturbated. Very fine scale sedimentation that may represent individual ebb and flood events as well as longer term seasonal sedimentation patterns are also present. An additional observation is that almost a quarter of the gravity cores reveal that modern estuarine deposits overlie an erosional surface that separate them from an organic-rich mud. This organic-rich mud, in one core to date, has been radiocarbon dated at roughly 4500 yrs. B.P. (J.Chin and K. Orzech, 2002, unpublished data). The organic-rich mud is interpreted as a tidal marsh deposit that pre-dates the present tidal marshes occurring in Suisun Bay.
Sediment-hosted gold deposits of the world: database and grade and tonnage models

USGS Publications Warehouse

Berger, Vladimir I.; Mosier, Dan L.; Bliss, James D.; Moring, Barry C.

2014-01-01

All sediment-hosted gold deposits (as a single population) share one characteristic—they all have disseminated micron-sized invisible gold in sedimentary rocks. Sediment-hosted gold deposits are recognized in the Great Basin province of the western United States and in China along with a few recognized deposits in Indonesia, Iran, and Malaysia. Three new grade and tonnage models for sediment-hosted gold deposits are presented in this paper: (1) a general sediment-hosted gold type model, (2) a Carlin subtype model, and (3) a Chinese subtype model. These models are based on grade and tonnage data from a database compilation of 118 sediment-hosted gold deposits including a total of 123 global deposits. The new general grade and tonnage model for sediment-hosted gold deposits (n=118) has a median tonnage of 5.7 million metric tonnes (Mt) and a gold grade of 2.9 grams per tonne (g/t). This new grade and tonnage model is remarkable in that the estimated parameters of the resulting grade and tonnage distributions are comparable to the previous model of Mosier and others (1992). A notable change is in the reporting of silver in more than 10 percent of deposits; moreover, the previous model had not considered deposits in China. From this general grade and tonnage model, two significantly different subtypes of sediment-hosted gold deposits are differentiated: Carlin and Chinese. The Carlin subtype includes 88 deposits in the western United States, Indonesia, Iran, and Malaysia, with median tonnage and grade of 7.1 Mt and 2.0 g/t Au, respectively. The silver grade is 0.78 g/t Ag for the 10th percentile of deposits. The Chinese subtype represents 30 deposits in China, with a median tonnage of 3.9 Mt and medium grade of 4.6 g/t Au. Important differences are recognized in the mineralogy and alteration of the two sediment-hosted gold subtypes such as: increased sulfide minerals in the Chinese subtype and decalcification alteration dominant in the Carlin type. We therefore recommend using the appropriate grade and tonnage model presented in this study for mineral resource assessments depending on the geologic and mineralogical data available for a region. Tonnage and contained gold within the general sediment-hosted gold model are analyzed based on major geologic features such as tectonic setting and magmatic (dikes, sills, and stocks) or amagmatic environment. The results show a significant difference in tonnage and contained gold, with higher median values in deposits spatially associated with igneous rocks, regardless of structural style of the deposit. These results suggest that magmatic environments control mineralization intensity—an important consideration in the regional assessment of prospective areas for sediment-hosted gold deposits.
Paleoclimatological analysis of Late Eocene core, Manning Formation, Brazos County, Texas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yancey, T.; Elsik, W.

1994-09-01

A core of the basal part of the Manning Formation was drilled to provide a baseline for paleoclimate analysis of the expanded section of siliciclastic sediments of late Eocene age in the outcrop belt. The interdeltaic Jackson Stage deposits of this area include 20+ cyclic units containing both lignite and shallow marine sediments. Depositional environments can be determined with precision and the repetitive nature of cycles allows comparisons of the same environment throughout, effectively removing depositional environment as a variable in interpretation of climate signal. Underlying Yegua strata contain similar cycles, providing 35+ equivalent environmental transacts within a 6 m.y.more » time interval of Jackson and Yegua section, when additional cores are taken. The core is from a cycle deposited during maximum flooding of the Jackson Stage, with deposits ranging from shoreface (carbonaceous) to midshelf, beyond the range of storm sand deposition. Sediments are leached of carbonate, but contain foram test linings, agglutinated forams, fish debris, and rich assemblages of terrestrial and marine palynomorphs. All samples examined contain marine dinoflagellates, which are most abundant in transgressive and maximum flood zones, along with agglutinated forams and fish debris. This same interval contains two separate pulses of reworked palynomorphs. The transgressive interval contains Glaphyrocysta intricata, normally present in Yegua sediments. Pollen indicates fluctuating subtropical to tropical paleoclimates, with three short cycles of cooler temperatures, indicated by abundance peaks of alder pollen (Alnus) in transgressive, maximum flood, and highstand deposits.« less
Depositional environment of the Onverwacht sedimentary rocks Barberton greenstone belt, South Africa

NASA Astrophysics Data System (ADS)

Paris, I. A.

The Onverwacht Group is the basal part of the ca 3.5 Ga succession forming the Barberton greenstone belt. It comprises a volcanic pile overlain by a thin layer of volcaniclastic sediments which, due to silicification, are extremely well preserved. There has been a controversy as to how and in what environment these sediments were formed, different sets of data being presented to reach opposite conclusions. The Onverwacht Group has been extensively repeated tectonically and here for the first time, sediments from different structural levels are studied together. Three separate facies have been recognised, a distal and proximal turbidite facies and a subaerial facies. Deposition of Onverwacht Group sedimentary rocks occurred in an oceanic basin characterised by the presence of emergent volcanic islands. After eruption, material was deposited both subaerially and in a shallow submarine environment on the volcanic slopes and, as a result of pyroclastic flow, in the deeper parts of the basin.
Sedimentological characteristics and depositional processes of sediment gravity flows in rift basins: The Palaeogene Dongying and Shahejie formations, Bohai Bay Basin, China

NASA Astrophysics Data System (ADS)

Liu, Lei; Chen, Hongde; Zhong, Yijiang; Wang, Jun; Xu, Changgui; Chen, Anqing; Du, Xiaofeng

2017-10-01

Sediment gravity flow deposits are common, particularly in sandy formations, but their origin has been a matter of debate and there is no consensus about the classification of such deposits. However, sediment gravity flow sandstones are economically important and have the potential to meet a growing demand in oil and gas exploration, so there is a drive to better understand them. This study focuses on sediment gravity flow deposits identified from well cores in Palaeogene deposits from the Liaodong Bay Depression in Bohai Bay Basin, China. We classify the sediment gravity flow deposits into eight lithofacies using lithological characteristics, grain size, and sedimentary structures, and interpret the associated depositional processes. Based on the scale, spatial distribution, and contact relationships of sediment gravity flow deposits, we defined six types of lithofacies associations (LAs) that reflect transformation processes and depositional morphology: LA1 (unconfined proximal breccia deposits), LA2 (confined channel deposits), LA3 (braided-channel lobe deposits), LA4 (unconfined lobe deposits), LA5 (distal sheet deposits), and LA6 (non-channelized sheet deposits). Finally, we established three depositional models that reflect the sedimentological characteristics and depositional processes of sediment gravity flow deposits: (1) slope-apron gravel-rich depositional model, which involves cohesive debris flows deposited as LA1 and dilute turbidity currents deposited as LA5; (2) non-channelized surge-like turbidity current depositional model, which mainly comprises sandy slumping, suspended load dominated turbidity currents, and dilute turbidity currents deposited as LA5 and LA6; and (3) channelized subaqueous-fan depositional model, which consists of non-cohesive bedload dominated turbidity currents, suspended load dominated turbidity currents, and dilute turbidity currents deposited as LA2-LA5, originating from sustained extrabasinal turbidity currents (hyperpycnal flow). The depositional models may be applicable to oil and gas exploration and production from sediment gravity flow systems in similar lacustrine depositional environments elsewhere.
Recent Developments in Facies Models for Siliciclastic Sediments.

ERIC Educational Resources Information Center

Miall, Andrew D.

1982-01-01

Discusses theory of facies models (attempts to synthesize/generalize information about depositional environments), strengths/weaknesses of facies modelling, recent advances in facies models for siliciclastic sediments (focusing on fluvial, lacustrine, eolian and glacial environments, clastic shorelines and continental shelves, and clastic…
Textural characteristics and sedimentary environment of sediment at eroded and deposited regions in the severely eroded coastline of Batu Pahat, Malaysia.

PubMed

Wan Mohtar, Wan Hanna Melini; Nawang, Siti Aminah Bassa; Abdul Maulud, Khairul Nizam; Benson, Yannie Anak; Azhary, Wan Ahmad Hafiz Wan Mohamed

2017-11-15

This study investigates the textural characteristics of sediments collected at eroded and deposited areas of highly severed eroded coastline of Batu Pahat, Malaysia. Samples were taken from systematically selected 23 locations along the 67km stretch of coastline and are extended to the fluvial sediments of the main river of Batu Pahat. Grain size distribution analysis was conducted to identify its textural characteristics and associated sedimentary transport behaviours. Sediments obtained along the coastline were fine-grained material with averaged mean size of 7.25 ϕ, poorly sorted, positively skewed and has wide distributions. Samples from eroded and deposition regions displayed no distinctive characteristics and exhibited similar profiles. The high energy condition transported the sediments as suspension, mostly as pelagic and the sediments were deposited as shallow marine and agitated deposits. The fluvial sediments of up to 3km into the river have particularly similar profile of textural characteristics with the neighbouring marine sediments from the river mouth. Profiles were similar with marine sediments about 3km opposite the main current and can go up to 10km along the current of Malacca Straits. Copyright © 2017 Elsevier B.V. All rights reserved.
Sedimentary environments within a glaciated estuarine-inner shelf system: Boston Harbor and Massachusetts Bay

USGS Publications Warehouse

Knebel, H.J.

1993-01-01

Three modern sedimentary environments have been identified and mapped across the glaciated Boston Harbor estuary and adjacent inner shelf of Massachusetts Bay by means of an extensive set of sidescan sonar records and supplemental bathymetric, sedimentary, subbottom and bottom-current data. 1. (1) Environments of erosion and nondeposition appear on the sonographs either as patterns with isolated reflections (caused by outcrops of bedrock, glacial drift, and coastal plain rocks) or as patterns of strong backscatter (caused by coarse-grained lag deposits). Sediments in these environments range from boulder fields to gravelly sands with megaripples. Inside the harbor, areas of erosion or nondeposition are found primarily near mainland and insular shores and within constricted tidal channels, whereas, on the shelf, they are present over extensive areas of hummocky topography near the coast and atop local bathymetric highs offshore. 2. (2) Environments of sediment reworking are characterized on the sonographs by patterns with patches of strong to weak backscatter caused by a combination of erosional and depositional processes. These environments have diverse grain sizes that range from sandy gravels to muds. Within the harbor, the locations of reworked sediments are uncorrelated with the bottom topography, but, on the shelf, they are found on the lower flanks of bathymetric highs, within broad lows and in relatively deep water (30-50 m). 3. (3) Environments of deposition are depicted on the sonographs as uniform patterns of weak backscatter. These areas contain relatively fine-grained muddy sands and muds. Inside the harbor, depositional environments are found over extensive subtidal flats and within sheltered depressions, whereas, on the shelf, they are restricted to broad lows mainly in deep water. The extreme patchiness of modern sedimentary environments within the Boston Harbor-Massachusetts Bay system reflects the interaction between the irregular bottom topography and both geologic and oceanographic processes. The estuarine part of the system is an effective trap for fine-grained detritus because of its protected nature, low wave climate, and large supply of sediments. The open shelf, however, is largely mantled by winnowed and sorted sediments as a result of erosion during past sea-level fluctuations, sediment resuspension and transport by modern waves and currents, and a spatially variable supply of fine-grained sediments.
Estuarine abandoned channel sedimentation rates record peak fluvial discharge magnitudes

NASA Astrophysics Data System (ADS)

Gray, A. B.; Pasternack, G. B.; Watson, E. B.

2018-04-01

Fluvial sediment deposits can provide useful records of integrated watershed expressions including flood event magnitudes. However, floodplain and estuarine sediment deposits evolve through the interaction of watershed/marine sediment supply and transport characteristics with the local depositional environment. Thus extraction of watershed scale signals depends upon accounting for local scale effects on sediment deposition rates and character. This study presents an examination of the balance of fluvial sediment dynamics and local scale hydro-geomorphic controls on alluviation of an abandoned channel in the Salinas River Lagoon, CA. A set of three sediment cores contained discrete flood deposits that corresponded to the largest flood events over the period of accretion from 1969 to 2007. Sedimentation rates scaled with peak flood discharge and event scale sediment flux, but were not influenced by longer scale hydro-meteorological activities such as annual precipitation and water yield. Furthermore, the particle size distributions of flood deposits showed no relationship to event magnitudes. Both the responsiveness of sedimentation and unresponsiveness of particle size distributions to hydro-sedimentological event magnitudes appear to be controlled by aspects of local geomorphology that influence the connectivity of the abandoned channel to the Salinas River mainstem. Well-developed upstream plug bar formation precluded the entrainment of coarser bedload into the abandoned channel, while Salinas River mouth conditions (open/closed) in conjunction with tidal and storm surge conditions may play a role in influencing the delivery of coarser suspended load fractions. Channel adjacent sediment deposition can be valuable records of hydro-meteorological and sedimentological regimes, but local depositional settings may dominate the character of short term (interdecadal) signatures.
Depositional environments and paleocurrent directions in the Precambrian Moeda Formation, Minas Gerais, Brazil

USGS Publications Warehouse

Lindsey, David A.

1975-01-01

The middle Precambrian Moeda Formation of Minas Gerais, Brazil, contains uranium and other minerals believed to be of detrital origin. Two areas of anomalously high concentrations of uranium have been discovered in conglomeratic zones that are interpreted as paleochannels. Because the distribution of uranium is believed to be controlled at least in part by sedimentation, a reconnaissance study was undertaken to assess the depositional environment and sediment dispersal pattern of the Moeda Formation.
Geochemical partitioning of lead in biogenic carbonate sediments in a coral reef depositional environment.

PubMed

Horta-Puga, Guillermo

2017-03-15

The fate of trace elements in reef depositional environments has not been extensively investigated. The aim of this study was to determine the partitioning of Pb in sediments of the Veracruz Reef System, and its relation to local environmental sources. Lead was determined in four geochemical fractions: exchangeable (3.8±0.4μgg -1 ), carbonate (57.0±13.6μgg -1 ), organic matter (2.0±0.9μgg -1 ), and mineral (17.5±5.4μgg -1 ). For the mineral fraction, lead concentrations were higher in those reefs influenced by river discharge or by long-distance transport of terrigenous sediments. The bioavailable concentration of lead (range: 21.9-85.6μgg -1 ) indicates that the Veracruz Reef System is a moderately polluted area. As expected, the carbonate fraction contained the highest proportion of Pb (70%), and because the reef framework is largely made up of by biogenic carbonate sediments, hence, it is therefore the most important repository of Pb in coral reef depositional environments. Copyright © 2016 Elsevier Ltd. All rights reserved.
Lithofacies and seismic-reflection interpretation of temperate glacimarine sedimentation in Tarr Inlet, Glacier Bay, Alaska

USGS Publications Warehouse

Cai, J.; Powell, R.D.; Cowan, E.A.; Carlson, P.R.

1997-01-01

High-resolution seismic-reflection profiles of sediment fill within Tart Inlet of Glacier Bay, Alaska, show seismic facies changes with increasing distance from the glacial termini. Five types of seismic facies are recognized from analysis of Huntec and minisparker records, and seven lithofacies are determined from detailed sedimentologic study of gravity-, vibro- and box-cores, and bottom grab samples. Lithofacies and seismic facies associations, and fjord-floor morphology allow us to divide the fjord into three sedimentary environments: ice-proximal, iceberg-zone and ice-distal. The ice-proximal environment, characterized by a morainal-bank depositional system, can be subdivided into bank-back, bank-core and bank-front subenvironments, each of which is characterized by a different depositional subsystem. A bank-back subsystem shows chaotic seismic facies with a mounded surface, which we infer consists mainly of unsorted diamicton and poorly sorted coarse-grained sediments. A bank-core depositional subsystem is a mixture of diamicton, rubble, gravel, sand and mud. Seismic-reflection records of this subsystem are characterized by chaotic seismic facies with abundant hyperbolic diffractions and a hummocky surface. A bank-front depositional subsystem consists of mainly stratified and massive sand, and is characterized by internal hummocky facies on seismic-reflection records with significant surface relief and sediment gravity flow channels. The depositional system formed in the iceberg-zone environment consists of rhythmically laminated mud interbedded with thin beds of weakly stratified diamicton and stratified or massive sand and silt. On seismic-reflection profiles, this depositional system is characterized by discontinuously stratified facies with multiple channels on the surface in the proximal zone and a single channel on the largely flat sediment surface in the distal zone. The depositional system formed in the ice-distal environment consists of interbedded homogeneous or laminated mud and massive or stratified sand and coarse silt. This depositional system shows continuously stratified seismic facies with smooth and flat surfaces on minisparker records, and continuously stratified seismic facies which are interlayered with thin weakly stratified facies on Huntec records.
Assessment of Lead and Beryllium deposition and adsorption to exposed stream channel sediments

NASA Astrophysics Data System (ADS)

Pawlowski, E.; Karwan, D. L.

2016-12-01

The fallout radionuclides Beryllium-7 and Lead-210 have been shown to be effective sediment tracers that readily bind to particles. The adsorption capacity has primarily been assessed in marine and coastal environments with an important assumption being the radionuclides' uniform spatial distribution as fallout from the atmosphere. This neglects localized storm events that may mine stratospheric reserves creating variable distributions. To test this assumption atmospheric deposition is collected at the University of Minnesota St. Paul Campus weather station during individual storm events and subsequently analyzed for Beryllium-7 and Lead-210. This provides further insight into continental effects on radionuclide deposition. The study of Beryllium-7 and Lead-210 adsorption in marine and coastal environments has provided valuable insights into the processes that influence the element's binding to particles but research has been limited in freshwater river environments. These environments have greater variation in pH, iron oxide content, and dissolved organic carbon (DOC) levels which have been shown to influence the adsorption of Beryllium and Lead in marine settings. This research assesses the adsorption of Beryllium and Lead to river sediments collected from in-channel deposits by utilizing batch experiments that mimic the stream conditions from which the deposits were collected. Soils were collected from Difficult Run, VA, and the West Swan River, MN. Agitating the soils in a controlled solution of known background electrolyte and pH while varying the level of iron oxides and DOC in step provides a better understanding of the sorption of Lead and Beryllium under the conditions found within freshwater streams. Pairing the partitioning of Lead and Beryllium with their inputs to streams via depositional processes, from this study and others, allows for their assessment as possible sediment tracers and age-dating tools within the respective watersheds.
Allogenic and autogenic controls on sedimentation in the central Sumatra basin as an analogue for Pennsylvanian coal-bearing strata in the Appalachian basin

USGS Publications Warehouse

Cecil, C. Blaine; Dulong, Frank T.; Cobb, James C.

1993-01-01

Recent sedimentation patterns in the central Sumatra basin, Republic of Indonesia, may help to explain the cyclic stratigraphy of the Pennsylvanian System of the eastern United States. Modern influx of fluvial siliciclastic sediment to the epeiric seas of the Sunda shelf, including the Strait of Malacca, appears to be highly restricted by rain forest cover within the ever-wet climate belt of equatorial Sumatra. As a result, much of the marine and estuarine environments appear to be erosional or nondepositional except for localized deposition of sediment in slack water areas, such as the down-stream end of islands. Contemporaneously, thick (>13 m), laterally extensive (>70,000 km2), peat deposits are forming on poorly drained coastal lowlands. Modern peat formation in this study, therefore, is not coeval with aggrading fluvial siliciclastic systems, a situation that commonly is assumed in many depositional models of coal formation. The stratigraphy of Pleistocene and Holocene sediments on the Sunda shelf, as well as those of the Pennsylvanian System, appears to be better explained by the allocyclic controls of climate and sea-level change on sediment flux rather than by depositional models that are based on autocyclic processes. The objective of this paper is to evaluate allocyclic and autocyclic controls on sedimentation in an epeiric setting in a humid (ever-wet) tropical region. Of particular interest are the factors that control peat formation and siliciclastic sediment flux in rivers, estuaries, and open marine environments.
Modern sedimentary environments in Boston Harbor, Massachusetts

USGS Publications Warehouse

Knebel, H.J.; Rendigs, R. R.; Bothner, Michael H.

1991-01-01

Analyses of sidescan-sonar records supplemented by available bathymetric, sedimentary, subbottom, and bottom-current data reveal the distributions of the following three categories of sedimentary environments within the glaciated, topographically complex Boston Harbor estuary in Massachusetts. 1) Environments of erosion appear on the sonographs either as patterns with isolated strong reflections or as uniform patterns of strong reflectivity. These patterns define outcrops of bedrock or till and coarse lag deposits that are being scoured and winnowed by tidal- and wave-induced currents. Erosional areas are located primarily along mainland and insular shores, within large channels that have strong tidal currents, atop submerged ridges and knolls, and across much of the harbor entrance. 2) Environments of deposition are depicted on the sidescan-sonar records as smooth, featureless surfaces that have low to moderate reflectivity. Depositional environments are found predominantly over shallow subtidal flats and in broad bathymetric lows where tidal currents are weak. Sediments within depositional areas are organic-rich sandy and clayey silts that are accumulating at rates ranging from 0.01 to 0.11 g/cm 2 /yr or 4000 to 46,100 metric tons/yr. The cumulative mass of modern mud in harbor depocenters is 24.3 million metric tons. 3) Environments of sediment reworking constitute areas affected by a combination of erosional and depositional processes. They are characterized on the sonographs by mosaics of light and dark patches produced by relatively subtle and gradational changes in reflectivity. Reworked sediments have diverse grain sizes that overlap and are transitional between those of the other two sedimentary environments, and they are indicative of highly variable bottom currents.
Glaciomarine sedimentation and bottom current activity on the north-western and northern continental margins of Svalbard during the late Quaternary

NASA Astrophysics Data System (ADS)

Chauhan, Teena; Noormets, Riko; Rasmussen, Tine L.

2016-04-01

Palaeo-bottom current strength of the West Spitsbergen Current (WSC) and the influence of the Svalbard-Barents Sea Ice Sheet (SBIS) on the depositional environment along the northern Svalbard margins are poorly known. Two gravity cores from the southern Yermak Plateau and the upper slope north of Nordaustlandet, covering marine isotope stage (MIS) 1 to MIS 5, are investigated. Five lithofacies, based on grain size distribution, silt/clay ratio, content and mean of sortable silt (SS), are distinguished to characterise the contourite-dominated sedimentary environments. In addition, depositional environments are described using total organic carbon (TOC), total sulphur (TS) and calcium carbonate (CaCO3) contents of sediments. Facies A, containing coarse SS, suggests strong bottom current activity and good bottom water ventilation conditions as inferred from low TOC content. This facies was deposited during the glacial periods MIS 4, MIS 2 and during the late Holocene. Facies B is dominated by fine SS indicating weak bottom current and poor ventilation (cf. high TOC content of 1.2-1.6%), and correlates with the MIS 4/3 and MIS 2/1 transition periods. With an equal amount of clay and sand, fine SS and high content of TOC, facies C indicates reduced bottom current strength for intervals with sediment supply from proximal sources such as icebergs, sea ice or meltwater discharge. This facies was deposited during the last glacial maximum. Facies D represents mass-flow deposits on the northern Svalbard margin attributed to the SBIS advance at or near the shelf edge. Facies E sediments indicating moderate bottom current strength were deposited during MIS 5 and MIS 3, and during parts of MIS 2. This first late Quaternary proxy record of the WSC flow and sedimentation history from the northern Svalbard margin suggests that the oceanographic conditions and ice sheet processes have exerted first-order control on sediment properties.
Sedimentation rates in eastern North America reveal strong links between regional climate, depositional environments, and sediment accumulation

NASA Astrophysics Data System (ADS)

Goring, S. J.; McLachlan, J. S.; Jackson, S. T.; Blaauw, M.; Christen, J.; Marlon, J.; Blois, J.; Williams, J. W.

2011-12-01

PalEON is a multidisciplinary project that combines paleo and modern ecological data with state-of-the-art statistical and modelling tools to examine the interactions between climate, fire and vegetation during the past two millennia in the northeastern United States. A fundamental challenge for PalEON (and paleo research more broadly) is to improve age modelling to yield more accurate sediment-core chronologies. To address this challenge, we assessed sedimentation rates and their controls for 218 lakes and mires in the northeastern U.S. Sedimentation rates (yr/cm) were calculated from age-depth models, which were obtained from the Neotoma database (www.neotomadb.org) and other contributed pollen records. The age models were recalibrated to IntCal09 and augmented in some cases using biostratigraphic markers (Picea decline, 16 kcal BP - 10.5 kcal BP; Quercus rise, 12 - 9.1 kcal BP; and Alnus decline, 11.5 - 10.6 kcal BP) as described in Blois et al. (2011). Relationships between sedimentation rates and sediment age, site longitude, and depositional environment (lacustrine or mire) are significant but weak. There are clear and significant links between variations in the NGRIP record of δ18O and sedimentation in mires across the PalEON region, but no links to lacustrine sedimentation rates. This result indicates that super-regional climatic control of primary productivity, and thus autochthonic sediment deposition, dominates in mires while deposition in lacustrine basins may be driven primarily by local and regional factors including watershed size, surficial materials,and regional vegetation. The shape of the gamma probability functions that best describe sedimentation rate distributions are calculated and presented here for use as priors in Bayesian age modelling applications such as BACON (Blaauw and Christen, in press). Future applications of this research are also discussed.
Fine-grained sediment gravity flow deposits induced by flood and lake slope failure events: examples of lacustrine varved sediments in Japan

NASA Astrophysics Data System (ADS)

Ishihara, Yoshiro; Sasaki, Yasunori; Sasaki, Hana; Onishi, Yuri

2016-04-01

Fine-grained sediment gravity flow deposits induced by flood and lake slope failure events are frequently intercalated in lacustrine successions. When sediment gravity flow deposits are present in varved sediments, it is suggested that they provide valuable information about sediment gravity flows, because they can easily trace laterally and can give the magnitude of erosion and recurrence interval of events. In addition, because large sedimentary bodies of stacked sediment gravity flow deposits in varved sediments of a calm lake are not suggested, a relatively simple depositional environment is expected. In the present study, we analysed sedimentary facies of sediment gravity flow deposits in varved lacustrine diatomites in the Middle Pleistocene Hiruzenbara and Miyajima formations in Japan, and concluded a depositional model of the lacustrine sediment gravity flow deposits. Varved diatomites: The Hiruzenbara Fm., a dammed lake fill as foots of Hiruzen Volcanos, is deposited during an interglacial period during MIS12 to 15. Varves of ca. 8000 yr were measured in a 20 m intercalating flood and lake slope failure-induced sediment gravity flow deposits. The Miyajima Fm., distributed in a paleo-caldera lake in NE Japan, includes many sediment gravity flow deposits possibly originated from fandeltas around the lake. These formations have differences in their depositional setting; the Hiruzebara Fm. was deposited in a large lake basin, whereas the Miyajima Fm. was deposited in a relatively small basin. Because of the depositional setting, intercalation of volcaniclastics is dominant in the Miyajima Fm. Lacustrine sediment gravity flow deposits: Sediment gravity flow deposits in both formations can be classified into flood- and lake slope failure-induced types based on the sedimentary facies. Composites of the both types are also found. Flood-induced types comprise fine-grained silts dominated by carbonaceous fragments, whereas lake slope failure-induced types are dominated by rip-up clasts of diatomite. The former is well continued in outcrops; however, the thickness of the latter is changeable and the lower contact is erosive. In the Hirzenbara Fm., flood-induced type includes epiphytic diatom valves as river inflows, whereas slope failure-induced type is composed of diatom valves of varved diatomite. Flood-induced types are suggested to be classified into hyperpycnal flow and hypopycnal flow types with regard to the presence of basal erosion. On the other hand, slope failure-induced types can be interpreted as debris flow deposits occurred in the lakes. Differences in the two types are also shown as bed-thickness frequency distributions indicating event magnitude.
Sediment Resuspension by Ship Traffic in Newark Bay, New Jersey

DTIC Science & Technology

2015-04-01

increased turbidity and sediment deposition on corals (Bermuda). Bulletin of Marine Science 87(3):659- 679. Kelderman, P., D. B . Kassie, M . Bijlsma, L. C...in the coastal marine environment. Marine Ecology Progress Series 315:13-18. Maa, J. P.-Y., and B . Chadwick . 2007. Estimation of annual average... B . Ward, B . Boyd, W. Murphy.R. Nolen-Hoeksema, M . Art, and D. A. Rosales. 2011a. Sediment, sedimentation, and environments of the lower Hackensack
Three depositional states and sedimentary processes of the western Taiwan foreland basin system

NASA Astrophysics Data System (ADS)

Lin, Yi-Jung; Wu, Pei-Jen; Yu, Ho-Shing

2010-05-01

The western Taiwan foreland basin formed during the Early Pliocene as the flexural response to the loading of Taiwan orogen on the Eurasian plate. What makes Taiwan interesting is the oblique collision, which allows the foreland basin to be seen at different stages in its evolution at the present day. Due to oblique arc-continent collision from north to south, the western Taiwan foreland basin has evolved into three distinct subbasins: an over-filled basin proximal to the Taiwan orogen, mainly distributed in the Western Foothills and Coastal Plain provinces, a filled basin occupying the shallow Taiwan Strait continental shelf west of the Taiwan orogen and an under-filled basin distal to the Taiwan orogen in the deep marine Kaoping Slope offshore southwest Taiwan, respectively. The over-filled depositional phase is dominated by fluvial environments across the structurally controlled piggy-back basins. The filled depositional state in the Taiwan Strait is characterized by shallow marine environments and is filled by Pliocene-Quaternary sediments up to 4,000 m thick derived from the Taiwan orogen with an asymmetrical and wedge-shaped cross section. The under-filled depositional state is characteristic of deep marine environments in the wedge-top basins accompanied by active structures of thrust faults and mud diapers. Sediments derived from the Taiwan orogen have progressively filled the western Taiwan foreland basin across and along the orogen. Sediment dispersal model suggests that orogenic sediments derived from oblique dischronous collisional highlands are transported in two different ways. Transport of fluvial and shallow marine sediments is perpendicular to hill-slope and across-strike in the fluvial and shallow marine environments proximal to the orogen. Fine-grained sediments mainly longitudinally transported into the deep marine environments distal to the orogen. The present sedimentary processes in the over-filled basin on land are dominated by fluvial processes of small mountainous rivers. Tidal currents are prevalent in the filled basin in Taiwan Strait, transporting shelf sands and forming sand ridges. The deep marine under-filled basin are dominated by down-slope mass wasting processes, eroding slope strata and transporting sediments to the basin floor. In addition, many submarine canyons on the continental slope offshore southwest Taiwan serve as major sediment pathways, delivering shallow marine sediments to the basin floor.

Palaeoenvironmental evolution at Plio-Pleistocene Hominin sites in Western Kenya: Preliminary results

NASA Astrophysics Data System (ADS)

Vincent, Thomas; Whitfield, Elizabeth; Bishop, Laura; Plummer, Thomas; Ditchfield, Peter; Blumenthal, Scott; Finestone, Emma; Kiriakoulakis, Kostas

2017-04-01

This research uses a multiproxy approach to create detailed reconstructions of Plio-Pleistocene hominin landscapes and environments on the Homa Peninsula, western Kenya. Sedimentary sequences associated with this time period, containing hominin archaeological traces and faunal remains, are studied using analyses of particle size, phytoliths and lipid biomarkers. Reconstructing the palaeoenvironmental substrate here is critical in developing an understanding of the activity and behaviour of previous hominin inhabitants. Three archaeological sites exist in the region that form the bases of this research; these include Kanjera South, Nyayanga and Sare River. Research at Kanjera began in the early 20th century, but systematic investigation of the artefact and faunal assemblages of the southern exposures (Kanjera South), dating to ca. 2 Ma, did not begin until 1995. Field investigations and isotopic analyses of palaeosol carbonate nodules and fauna suggested that Kanjera South sediments were deposited in alluvial and lake marginal environments, on a grassy plain between wooded slopes and a permanent water body. Nyayanga and Sare River are new sites which have been little studied until present. Sediments at Nyayanga are thought to be ca. 2.6 Ma, whilst those at Sare River are ca. 1.77 Ma in age. This research refines previous reconstructions of the depositional environment at Kanjera South using analyses of particle size and end member mixing. These suggest that deposition occurred mainly through low-energy, ephemeral flows in a marginal lacustrine environment, with high energy, hyper-concentrated and viscous flows occurring intermittently. In contrast, these same techniques and field investigations at Nyayanga suggest there was a more consistent energy regime here than at Kanjera South, with sediments being deposited under low-energy conditions. Sediment samples at Sare River are undergoing similar analyses. Through detailed analyses of sediments at three archaeological sites, insights into the depositional dynamics of the ca. 2 Ma palaeoenvironments inhabited by hominins have been made accessible.
Tsunami sediments and their grain size characteristics

NASA Astrophysics Data System (ADS)

Sulastya Putra, Purna

2018-02-01

Characteristics of tsunami deposits are very complex as the deposition by tsunami is very complex processes. The grain size characteristics of tsunami deposits are simply generalized no matter the local condition in which the deposition took place. The general characteristics are fining upward and landward, poor sorting, and the grain size distribution is not unimodal. Here I review the grain size characteristics of tsunami deposit in various environments: swale, coastal marsh and lagoon/lake. Review results show that although there are similar characters in some environments and cases, but in detail the characteristics in each environment can be distinguished; therefore, the tsunami deposit in each environment has its own characteristic. The local geological and geomorphological condition of the environment may greatly affect the grain size characteristics.
The transitional depositional environment and sequence stratigraphy of Chasma Boreale

NASA Astrophysics Data System (ADS)

Brothers, S. C.; Kocurek, G.

2018-07-01

The depositional system within Chasma Boreale is unique in that it contains active aeolian environments, expressed as dune fields, and active cryosphere environments, present as layered ice deposits, as well as environments that transition between these. This work presents a new analysis of the Chasma Boreale sediment system that creates an interpretative framework addressing: (a) controls on the balance between aeolian and cryospheric processes in the modern depositional system, (b) the stratigraphic architecture of related sedimentary deposits, and (c) processes of sediment accumulation and preservation. Images from Context Camera (CTX; 6 m/pixel) are used to classify and map sedimentary environments, surfaces, and deposits on the reentrant floor, to refine the established geologic map of the reentrant, and to infer the stratigraphic record of the accumulation from Chasma Boreale's depositional system. A spectrum of sedimentary environments occurring between those dominated by aeolian and by cryospheric processes are identified. Through time, the boundaries of these sedimentary environments have shifted, resulting in complex lateral changes in the configuration of sedimentary environments on the reentrant's floor. Vertically, the stratigraphic record is characterized by the punctuation of sandy aeolian deposits by icy surfaces that indicate episodes of ice growth that preserve underlying deposits, resulting in accumulation. Stabilized icy surfaces occur at multiple vertical (temporal) scales and lateral extents, suggesting the influence of both regional climate change due to allogenic forcing, as well as autogenic dynamics within the transitional system. These observations demonstrate that the Chasma Boreale accumulation can be interpreted in an aeolian sequence stratigraphic framework. This work contributes the first detailed description of the processes forming polar aeolian sequences, with an emphasis on the competing and complementary dynamics between aeolian and cryospheric systems.
Linking Monsoon Activity with River-Derived Sediment Deposition in the northern South China Sea

NASA Astrophysics Data System (ADS)

Ge, Q.; Xue, Z. G.; Liu, P.; Chu, F.

2016-02-01

Sediments retrieved from a gravity core were analyzed to examine the connection between East Asian Monsoon (EAM) and river-derived sediment deposition on the continental slope in the South China Sea since the Last Glacial Maximum. Combined clay mineralogy and grain size index analysis provided evidence of the sources of fine-grained sediment as well as for rebuilding the history of paleo-EAM. A shift of sediment source from the Pearl River to southwestern Taiwanese rivers was identified during the Holocene. The 4-8μm grain size fraction, as an environmental sensitive component and thus the EAM proxy, indicated the local deposition environment is mainly controlled by sea-level variations. And during the Holocene, the East Asian summer monsoon exhibited an in-phase relationship with East Asian winter monsoon, both following variations of the insolation intensity.
Characteristics of depositional environments in the Nakdong River Estuary, South Korea

NASA Astrophysics Data System (ADS)

Woo, Han Jun; Lee, Jun-Ho; Kang, Jeongwon; Choi, Jae Ung

2017-04-01

Most of the major Korean estuaries, under high pressure from development, have dams with environmental problems, including restricted water circulation, low water quality, decreased biodiversity and wetland destruction. The Nakdong estuary on the southeastern coast of Korean Peninsula is an enclosed type with two large estuarine dams that were constructed in 1934 and between 1983 and 1987. The construction of dams has led to geomorphologic evolution of the barrier islands within Nakdong estuary. The estuary has been characterized as barrier-lagoon system with various subenvironments and microtidal with a 1.5 m tidal range. The sedimentary analyses and monitoring short-term sedimentation rates were investigated to understand characteristics of depositional environments in barrier-lagoon system of the Nakdong River Estuary. The surface sediments in the system were classified into three sedimentary facies in summer 2015. Generally, sand sediment was dominated in the seaward side of barrier islands and muddy sand sediment was dominated on the lagoon. Sandy mud and mud sediments were distributed in the tidal flat near Noksan industrial district and channels near dams. Fourteen a priori subenvironments were distinguished based on differences in landscape characterization (sediment texture, salinity, total organic carbon, pH and C/N ratios). The dendrogram resulting from cluster analysis of environmental variables from 14 a priori subenvironments could be clustered into 4 groups that were characterized by different sediment texture and hydrodynamic energy. The short-term sedimentation rates were obtained seasonally from three lines by burying a plate at sub-bottom depth from May 2015 to May 2016. The deposition was dominated on the tidal flat between mainland and Jinudo (JW- Line) and Sinjado (SJ-Line) with the net deposition rate of 10.09 mm/year and 12.38 mm/year, respectively. The erosion was dominated on the tidal flats at Eulsukdo (ES-Line) on the east side of the system with an annual erosion rate of -13.15 mm/year. Two 12.5-hours anchoring surveys at inlets were revealed that net suspended sediments were transported to the open sea during a tidal cycle in summer 2015 and 2016. The sedimentary processes of the anthropogenically altered barrier-lagoon system in Nakdong estuary showed that sediments transported into the lagoon through inlets during flood condition and moved to westward and deposited sediments on the tidal flat and channels near dams in low energy environments. In the east side of the system, sediments flowed out the sea with discharge from Nakdong Dam during ebb condition. These data will provide an important baseline for future assessments of environmental quality on dam open.
The Effect of Source Suspended Sediment Concentration on the Sediment Dynamics of a Macrotidal Creek and Salt Marsh

NASA Astrophysics Data System (ADS)

Poirier, E.; van Proosdij, D.; Milligan, T. G.

2017-12-01

Seasonal variability in the sediment dynamics of a Bay of Fundy tidal creek and salt marsh system was analyzed to better understand the ecomorphodynamics of a high suspended sediment concentration intertidal habitat. Data were collected over 62 tides for velocity, suspended sediment concentration, deposition, and grain size at four stations from the creek thalweg to the marsh surface. Five topographic surveys were also conducted throughout the 14-month study. Deposition rates per tide varied spatially from 56.4 g·m-2 at the creek thalweg to 15.3 g·m-2 at the marsh surface. Seasonal variations in deposition in the creek and marsh surface were from 38.0 g·m-2 to 97.7 g·m-2 and from 12.2 g·m-2 to 19.6 g·m-2 respectively. Deposition and erosion were greatest in late fall and winter. This seasonal change, led by higher suspended sediment concentrations, was observed in the creek and at the marsh bank but notably absent from the marsh edge and marsh surface. Sediments were predominantly deposited in floc form (76-83%). Because of high floc content, higher suspended sediment concentrations led to more rapid loss of sediment from suspension. With increasing sediment concentration, deposition increased in the tidal creek and at the marsh bank but not at the marsh edge or marsh surface. This suggests that in highly flocculated environments the water column clears fast enough that very little sediment remains in suspension when the water reaches the marsh and that the sediment concentration during marsh inundation is independent of the initial concentration in the creek.
The effect of source suspended sediment concentration on the sediment dynamics of a macrotidal creek and salt marsh

NASA Astrophysics Data System (ADS)

Poirier, Emma; van Proosdij, Danika; Milligan, Timothy G.

2017-09-01

Seasonal variability in the sediment dynamics of a Bay of Fundy tidal creek and salt marsh system was analyzed to better understand the ecomorphodynamics of a high suspended sediment concentration intertidal habitat. Data were collected over 62 tides for velocity, suspended sediment concentration, deposition, and grain size at four stations from the creek thalweg to the marsh surface. Five topographic surveys were also conducted throughout the 14-month study. Deposition rates per tide varied spatially from 56.4 g m-2 at the creek thalweg to 15.3 g m-2 at the marsh surface. Seasonal variations in deposition in the creek and marsh surface were from 38.0 g m-2 to 97.7 g m-2 and from 12.2 g m-2 to 19.6 g m-2 respectively. Deposition and erosion were greatest in late fall and winter. This seasonal change, led by higher suspended sediment concentrations, was observed in the creek and at the marsh bank but notably absent from the marsh edge and marsh surface. Sediments were predominantly deposited in floc form (76-83%). Because of high floc content, higher suspended sediment concentrations led to more rapid loss of sediment from suspension. With increasing sediment concentration, deposition increased in the tidal creek and at the marsh bank but not at the marsh edge or marsh surface. This suggests that in highly flocculated environments the water column clears fast enough that very little sediment remains in suspension when the water reaches the marsh and that the sediment concentration during marsh inundation is independent of the initial concentration in the creek.
A Layered Past: the Transformation and Development of Legacy Sediments as Alluvial Soils

NASA Astrophysics Data System (ADS)

Wade, A.; Richter, D. D., Jr.

2017-12-01

Legacy sediments are a widespread consequence of post-colonial upland erosion in the United States. Although these deposits are ubiquitous in valley bottoms of the southeastern Piedmont, mature hardwood forests and collapsed stream banks mask their occurrence. While these deposits have been studied for their fluvial dynamics and water quality impacts, they have received less attention in regards to soil structure and formation. In this study, we characterized legacy sediment mineraology, composition and structure to understand how pedogenic processes are overprinting sediment layering in a 40-hectare Piedmont floodplain. To constrain the timing of deposition, we used Pb-210 and C-14 dating on buried charcoal and tree stumps. Our results show that in 100 years of forest regeneration, vegetation and oscillating floodplain conditions have driven these eroded sediment deposits to evolve as soil profiles both in structure and composition. These textural and nutrient gradients have ramifications for the subsurface flow of nutrients through the floodplain. Given the estimated millennia it will take to erode legacy sediment from Piedmont floodplains, it is important to think of these deposits as new stable environments on their own trajectory of soil evolution.
Stratigraphy, correlation, depositional setting, and geophysical characteristics of the Oligocene Snowshoe Mountain Tuff and Creede Formation in two cored boreholes

USGS Publications Warehouse

Larsen, Daniel; Nelson, Philip H.

2000-01-01

Core descriptions and geophysical logs from two boreholes (CCM-1 and CCM-2) in the Oligocene Snowshoe Mountain Tuff and Creede Formation, south-central Colorado, are used to interpret sedimentary and volcanic facies associations and their physical properties. The seven facies association include a mixed sequence of intracaldera ash-flow tuffs and breccias, alluvial and lake margin deposits, and tuffaceous lake beds. These deposits represent volcanic units related to caldera collapse and emplacement of the Snowshoe Mountain Tuff, and sediments and pyroclastic material deposited in the newly formed caldera basin, Early sedimentation is interpreted to have been rapid, and to have occurred in volcaniclastic fan environments at CCM-1 and in a variery of volcaniclastic fan, braided stream shallow lacustrine, and mudflat environments at CCM-2. After an initial period of lake-level rise, suspension settling, turbidite, and debris-flow sedimentation occurred in lacustrine slope and basin environments below wave base. Carbonate sedimentation was initially sporadic, but more continuous in the latter part of the recorded lake history (after the H fallout tuff). Sublacustrine-fan deposition occurred at CCM-1 after a pronounced lake-level fall and subsequent rise that preceded the H tuff. Variations in density, neutron, gamma-ray, sonic, and electrical properties of deposits penetrated oin the two holes reflect variations in lithology, porosity, and alteration. Trends in the geophysical properties of the lacustrine strata are linked to downhole changes in authigenic mineralology and a decrease in porosity interpreted to have resulted primarily from diagenesis. Lithological and geophysical characteristics provide a basis for correlation of the cores; however, mineralogical methods of correlation are hampered by the degree of diagenesis and alteration.
Continuous in situ monitoring of sediment deposition in shallow benthic environments

NASA Astrophysics Data System (ADS)

Whinney, James; Jones, Ross; Duckworth, Alan; Ridd, Peter

2017-06-01

Sedimentation is considered the most widespread contemporary, human-induced perturbation on reefs, and yet if the problems associated with its estimation using sediment traps are recognized, there have been few reliable measurements made over time frames relevant to the local organisms. This study describes the design, calibration and testing of an in situ optical backscatter sediment deposition sensor capable of measuring sedimentation over intervals of a few hours. The instrument has been reconfigured from an earlier version to include 15 measurement points instead of one, and to have a more rugose measuring surface with a microtopography similar to a coral. Laboratory tests of the instrument with different sediment types, colours, particle sizes and under different flow regimes gave similar accumulation estimates to SedPods, but lower estimates than sediment traps. At higher flow rates (9-17 cm s-1), the deposition sensor and SedPods gave estimates >10× lower than trap accumulation rates. The instrument was deployed for 39 d in a highly turbid inshore area in the Great Barrier Reef. Sediment deposition varied by several orders of magnitude, occurring in either a relatively uniform (constant) pattern or a pulsed pattern characterized by short-term (4-6 h) periods of `enhanced' deposition, occurring daily or twice daily and modulated by the tidal phase. For the whole deployment, which included several very high wind events and suspended sediment concentrations (SSCs) >100 mg L-1, deposition rates averaged 19 ± 16 mg cm-2 d-1. For the first half of the deployment, where SSCs varied from <1 to 28 mg L-1 which is more typical for the study area, the deposition rate averaged only 8 ± 5 mg cm-2 d-1. The capacity to measure sedimentation rates over a few hours is discussed in terms of examining the risk from sediment deposition associated with catchment run-off, natural wind/wave events and dredging activities.
Mineralogy and geochemistry of the sediments of the Etosha Pan Region in northern Namibia: a reconstruction of the depositional environment

NASA Astrophysics Data System (ADS)

Buch, M. W.; Rose, D.

1996-04-01

The paper presents the results of mineralogical and chemical analyses of the clay fraction (<2 μm) of samples from boreholes in the Etosha Pan and smaller pans of the Owambo-Pans-Plain in the Etosha National Park, northern Namibia. Four mineral associations can be differentiated within the vertical succession of the profiles in the Etosha Pan: I) analcime/K-feldspar and mica association; II) analcime/K-feldspar and sepiolite (loughlinite) association; III) expandable sheet silicate (saponite/stevensite) association; and IV) calcite and dolomite association. These mineral associations are the expression of the seasonal saline-alkaline to calciferous, saline-alkaline environment of the present Etosha Pan. The sedimentological and pedological descriptions, combined with the results of the mineralogical and chemical analyses, show a clear differentiation of the profiles of the Etosha Pan in: i) disintegrated sedimentary rocks of the Andoni Formation (mineral association I); ii) par-autochthonous sediments (mineral associations I and II); and iii) allochthonous sediments (mineral associations III and IV). Based on this vertical mineralogical differentiation, four sedimentological-mineralogical/ chemical zones are defined for the actual floor of the Etosha Pan. The zonation shows that a thin cover of allochthonous sediments is only present along the southern margin of the Etosha Pan, including Fisher's Pan. The results support the hypothesis that the Etosha Pan is an erosional form rather than a palaeolake. In principle, the zonal configuration of the recent allochthonous and parautochthonous sediments identified on the Etosha Pan provides a small-scale depositional environment model for the formation of the Etosha limestone and sediments of the Andoni Formation during the Oligocene and Miocene. Thus, the findings help to reconstruct the depositional environment of the evolution of the extensive depocentre of the Etosha basin during the Late Tertiary.
Sea-Floor Character and Sedimentary Processes in the Vicinity of Woods Hole, Massachusetts

USGS Publications Warehouse

Poppe, Lawrence J.; McMullen, Katherine Y.; Foster, David S.; Blackwood, Dann S.; Williams, S. Jeffress; Ackerman, Seth D.; Barnum, Steven R.; Brennan, Rick T.

2008-01-01

Continuous-coverage multibeam bathymetric models and sidescan-sonar imagery have been verified with high-resolution seismic-reflection profiles, sediment sampling, and bottom photography. Together these data layers provide detailed base maps that yield topographic, compositional, and environmental perspectives of the sea floor in the vicinity of Woods Hole, an important harbor and major passage between the Elizabeth Islands and Cape Cod, Massachusetts. Tidally dominated high-energy environments within Woods Hole have prevented deposition of Holocene marine sediments, exposed underlying glacial drift of the Buzzards Bay moraine, and winnowed finer grained sediments, leaving lag deposits of boulders and gravel. These conditions have also enlarged and preserved depressions in the moraine surface that were originally kettle holes and formed ebb-tidal deltas at the entrances to passages. Fields of transverse and barchanoid sand waves dominate across the southern part of the study area in Vineyard Sound, where benthic environments are characterized by processes associated with coarse-bedload transport. Transverse sand waves dominate near shoals where sediment supply is greater and have asymmetries that indicate that the shoals are shaped and maintained by clockwise gyres of net sediment transport. Barchanoid sand waves, which are most common where Holocene sediments are thinner, commonly align into elongate fields that have smaller isolated waves concentrated at the eastern ends and that progressively widen and have waveforms that increase in amplitude, wavelength, and complexity westward. The northern, protected parts of the Little and Inner Harbors are characterized by muddy sediment and processes associated with deposition. A pockmark field in Little Harbor and the muddy, organic-rich sediments that form a scarp along the edge of Parker Flat are evidence for the presence of submerged marsh deposits formed during the Holocene rise in sea level.
Nature and classification of waterlain glaciogenic sediments, exemplified by Pleistocene, Late Paleozoic and Late Precambrian deposits

NASA Astrophysics Data System (ADS)

Gravenor, C. P.; von Brunn, V.; Dreimanis, A.

1984-03-01

This study of waterlain glaciogenic sediments is designed to present both a review and new information on glaciogenic subaquatic deposits of differing age in a number of localities in North and South America and South Africa. The Late Paleozoic glaciogenic deposits of the ParanáBasin in Brazil and the Karoo Basin of South Africa are singled out for special attention as they show a reasonably complete lateral sequence of terrestrial to off-shore glaciogenic sedimentation. Although the environment of subaquatic glaciogenic sedimentation varies from one area to the next, certain common elements are found which can be used to develop a generalized model for both glaciomarine and glaciolacustrine sedimentation. For descriptive purposes, the model is divided into two broad categories: a shelf facies and a basinal facies. The shelf facies is marked by massive diamicton(ite) which may be 200 m or more in thickness and which is frequently overlain by a complex of clastic sediments consisting primarily of gravity and fluid flows. The basinal facies is marked by products of subaquatic slumps and more distal turbidites and glaciomarine sediments. New terminology is introduced. The massive diamicton(ite), which is diagnostic of the shelf facies, probably represents deposition from the base of active ice in a subaquatic environment and is termed undermelt diamicton(ite). The gravity and fluid flows which are usually found overlying undermelt diamicton(ite) and in the basinal facies are subdivided into six categories: glaciogenic subaquatic outwash, glaciogenic suspension flow, glaciogenic chaotic debris flow, glaciogenic subaquatic debris flow, glaciogenic slurry flow and glaciogenic turbidity flow. The relative abundance of undermelt diamicton(ite) and the various types of gravity and fluid flows can be used to define inner shelf, outer shelf, inner basin and outer basin facies of glaciomarine sedimentation.
Paleogeography and Depositional Systems of Cretaceous-Oligocene Strata: Eastern Precordillera, Argentina

NASA Astrophysics Data System (ADS)

Reat, Ellen J.; Fosdick, Julie C.

2016-04-01

New data from the Argentine Precordillera in the southern Central Andes document changes in depositional environment and sediment accumulation rates during Upper Cretaceous through Oligocene basin evolution, prior to the onset Miocene foredeep sedimentation. This work presents new sedimentology, detrital geochronology, and geologic mapping from a series of continental strata within this interval to resolve the timing of sedimentation, nature of depositional environments, and basin paleogeography at the nascent phase of Andean orogenic events, prior to the uplift and deformation of the Precordillera to the west. Five stratigraphic sections were measured across both limbs of the Huaco Anticline, detailing sedimentology of the terrestrial siliciclastic upper Patquía, Ciénaga del Río Huaco (CRH), Puesto la Flecha, Vallecito, and lower Cerro Morado formations. Paleocurrent data indicate a flow direction change from predominantly NE-SW in the upper Patquía and the lower CRH to SW-NE directed flow in the upper CRH, consistent with a large meandering river system and a potential rise in topography towards the west. This interpretation is further supported by pebble lag intervals and 1-3 meter scale trough cross-bedding in the CRH. The thinly laminated gypsum deposits and siltstones of the younger Puesto la Flecha Formation indicate an upsection transition into overbank and lacustrine sedimentation during semi-arid climatic conditions, before the onset of aeolian dune formation. New maximum depositional age results from detrital zircon U-Pb analysis indicate that the Puesto la Flecha Formation spans ~57 Myr (~92 to ~35 Ma) across a ~48 m thick interval without evidence for major erosion, indicating very low sedimentation rates. This time interval may represent distal foredeep or forebulge migration resultant from western lithospheric loading due to the onset of Andean deformation at this latitude. Detrital zircon U-Pb age spectra also indicate shifts in sediment routing pathways over time, consistent with a transition from local basement-sourced quartz-rich sediments during the Triassic-Cretaceous to increased volcanic and sedimentary lithics from the rising Andes in the west during Paleocene-Eocene time. We therefore interpret these changes in depositional character as representing a transition from a large fluvial system with craton-sourced sediments during the Triassic-Cretaceous CRH to low energy lacustrine and ephemeral playa environments with an increase in westerly derived sediments during the Paleocene-Eocene Puesto la Flecha, prior to the reported Oligocene onset of the Andean continental foredeep represented by the Vallecito Formation.
Sedimentation rates and patterns in beaver ponds in a mountain environment

NASA Astrophysics Data System (ADS)

Butler, David R.; Malanson, George P.

1995-09-01

Sediment depth was measured at several sites within each of eight beaver ponds in Glacier National Park, Montana, and sediment samples wen; collected from five of these ponds. Accumulation rates of sediments far exceeded published rates from boreal forest landscapes in eastem and central North America. Pond area strongly predicts volume of sedimentation. Textural differences illustrated spatial variations associated with position in a pond and along a pond sequence. Organic matter content was significantly higher in older ponds, and has ramifications for the development of the benthos and the long-term storage of matter in ponds. The role of beavers as biogeomorphic agents is profound, but requires further elucidation to distinguish between fluvial sediment deposition in ponds and sediment deposition associated with beaver excavational activity.
Biological influences on modern sulfates: Textures and composition of gypsum deposits from Guerrero Negro, Baja California Sur, Mexico

NASA Astrophysics Data System (ADS)

Vogel, Marilyn B.; Des Marais, David J.; Parenteau, Mary N.; Jahnke, Linda L.; Turk, Kendra A.; Kubo, Michael D. Y.

2010-01-01

Gypsum (CaSO 4·2H 2O) deposits from a range of sedimentary environments at Guerrero Negro, Baja California Sur, Mexico were investigated for microscale texture and composition in order to differentiate features formed under substantial microbial influence from those for which microbial effects were relatively minor or absent. Gypsum deposits were classified according to their sedimentary environment, textures, crystal habit, brine composition and other geochemical factors. The environments studied included subaqueous sediments in anchialine pools and in solar salterns, as well as subsurface sediments of mudflats and saltpans. Gypsum that developed in the apparent absence of biofilms included crystals precipitated in the water column and subsedimentary discs that precipitated from phreatic brines. Subsedimentary gypsum developed in sabkha environments exhibited a sinuous microtexture and poikilitically enclosed detrital particles. Water column precipitates had euhedral prismatic habits and extensive penetrative twinning. Gypsum deposits influenced by biofilms included bottom nucleated crusts and gypsolites developing in anchialine pools and saltern ponds. Gypsum precipitating within benthic biofilms, and in biofilms within subaerial sediment surfaces provided compelling evidence of biological influences on crystal textures and habits. This evidence included irregular, high relief surface textures, accessory minerals (S°, Ca-carbonate, Sr/Ca-sulfate and Mg-hydroxide) and distinctive crystal habits such as equant forms and crystals having distorted prism faces.
Holocene sediment distribution on the inner continental shelf of northeastern South Carolina: implications for the regional sediment budget and long-term shoreline response

USGS Publications Warehouse

Denny, Jane F.; Schwab, William C.; Baldwin, Wayne E.; Barnhardt, Walter A.; Gayes, Paul T.; Morton, R.A.; Warner, John C.; Driscoll, Neal W.; Voulgaris, George

2013-01-01

High-resolution geophysical and sediment sampling surveys were conducted offshore of the Grand Strand, South Carolina to define the shallow geologic framework of the inner shelf. Results are used to identify and map Holocene sediment deposits, infer sediment transport pathways, and discuss implications for the regional coastal sediment budget. The thickest deposits of Holocene sediment observed on the inner shelf form shoal complexes composed of moderately sorted fine sand, which are primarily located offshore of modern tidal inlets. These shoal deposits contain ~67 M m3 of sediment, approximately 96% of Holocene sediment stored on the inner shelf. Due to the lack of any significant modern fluvial input of sand to the region, the Holocene deposits are likely derived from reworking of relict Pleistocene and older inner-shelf deposits during the Holocene marine transgression. The Holocene sediments are concentrated in the southern part of the study area, due to a combination of ancestral drainage patterns, a regional shift in sediment supply from the northeast to the southwest in the late Pleistocene, and proximity to modern inlet systems. Where sediment is limited, only small, low relief ridges have formed and Pleistocene and older deposits are exposed on the seafloor. The low-relief ridges are likely the result of a thin, mobile veneer of sediment being transported across an irregular, erosional surface formed during the last transgression. Sediment textural trends and seafloor morphology indicate a long-term net transport of sediment to the southwest. This is supported by oceanographic studies that suggest the long-term sediment transport direction is controlled by the frequency and intensity of storms that pass through the region, where low pressure systems yield net along-shore flow to the southwest and a weak onshore component. Current sediment budget estimates for the Grand Strand yield a deficit for the region. Volume calculations of Holocene deposits on the inner shelf suggest that there is sufficient sediment to balance the sediment budget and provide a source of sediment to the shoreline. Although the processes controlling cross-shelf sediment transport are not fully understood, in sediment-limited environments such as the Grand Strand, erosion of the inner shelf likely contributes significant sediment to the beach system.
Modeling of the Contaminated Sediment in the Erft River

NASA Astrophysics Data System (ADS)

Hu, Wei; Westrich, Bernhard; Rode, Michael

2010-05-01

Sediment transport processes play an important role in the surface water systems coupled with rainfall-runoff and contaminant transport. Pollutants like heavy metals adsorbed mainly by fine sediment particles can be deposited, eroded or transported further downstream. When the toxic pollutants deposited before and covered by cleaner sediment are remobilized by large flow events such as floods, they pose a hidden threat to the human health and environment. In the Erft River, due to mining activities in the past, the heavy metals release from the tributary Veybach on the downstream water and sediment quality is significant. Recent measurements prove the decreasing concentration trend of heavy metals in the river bed sediment from the Veybach. One-dimensional hydrodynamic model COSMOS is used to model the complicated water flow, sediment erosion, deposition and contaminant mixing and transport in the mainstream of the Erft River. It is based on a finite-difference formulation and consists of one-dimensional, unsteady sub-model of flow and transport, coupled with a sub-model of the layered sediment bed. The model accounts for the following governing physical-chemical processes: convective and dispersive transport, turbulent mixing deposited sediment surface, deposition, consolidation, aging and erosion of sediment, adsorption-desorption of pollutants to suspended particles and losses of pollutants due to decay or volatilization. The results reproduce the decreasing profile of the pollutant concentration in the river bed sediment nicely. Further modeling is to analysis the influence of the mixing process at the water-riverbed interface on the contaminant transport, hydrological scenarios impact on the remobilization of the sink of pollutant and its negative consequences on the river basin.
Geochemistry of Permian rocks from the margins of the Phosphoria Basin

USGS Publications Warehouse

Perkins, Robert B.; McIntyre, Brandie; Hein, James R.; Piper, David Z.

2003-01-01

The Permian Phosphoria Formation and interbedded units of the Park City Formation and Shedhorn Sandstone in western Wyoming represent deposition along a carbonate ramp at the eastern margin of the Phosphoria Basin, with portions of the Phosphoria units reflecting periods of upwelling and widespread phosphogenesis. Thickness-weighted slab-samples of these units were collected at a maximum interval of 3 m along an 80+ m-length of unweathered core and analyzed for major-, minor-, and trace-element contents. Interpretations of geochemistry were made within the confines of a previously recognized sequence stratigraphy framework. Major shifts in element ratios characteristic of terrigenous debris that occur at sequence boundaries at the base of the Meade Peak and Retort Members of the Phosphoria Formation are attributed to changing sediment sources. Inter-element relationships in the marine fraction indicate that bottom waters of the Phosphoria Basin were predominantly denitrifying during deposition of the Ervay, Grandeur, and Phosphoria sediments, although sulfate-reducing conditions may have existed during deposition of the lower Meade Peak sediments. Oxic conditions were prevalent during deposition of a large part of the Franson Member, which represents sedimentation in a shallow, inner- to back-ramp setting. Variations in sediment facies and organic matter and trace element contents largely reflect changes in Permian sea level. Changes in sea level in basin-margin areas, such as represented by the study section, may have affected the oxidation of settling organic matter, the foci of intersection of upwelling bottom waters with the photic zone, the rate of terrigenous sedimentation, and, ultimately, the overall environment of deposition. Our study suggests that phosphogenesis can occur under lowstand, transgressive, and highstand conditions in marginal areas, assuming water depths sufficient for upwelling to occur. Formation of phosphorite layers under upwelling conditions appears to have been most dependent on a lack of dilution by terrigenous sedimentation and carbonate shoaling. Differences in the geochemistry between two similar environments represented by the upper and lower Phosphoria units are largely attributed to higher rates of diluting terrigenous sediment during deposition of the upper unit. This is consistent with prior interpretations of a more shoreward setting for the upper Phosphoria.
Sediment compaction in deepwater basin of the South China Sea: estimation from ODP 184 and IODP 349 drilling well data.

NASA Astrophysics Data System (ADS)

Tuoyu, W.; Xie, Y.

2017-12-01

Abnormal compaction in deepwater basins not only cause serious soft sediment deformation, but also significantly affect the safety of the drilling campaign. Therefore, study the compaction condition in the sediments would be an important task in the deepwater basin and associate with the environment variation. We analyze the drilling data from the ODP Leg 184 Site 1144, 1146, 1148 and the IODP Leg 349 Site U1431, U1432, U1433, U1435 to study the sediment compaction and controls in the northern South China Sea. We have found the sedimentation rate, sediment content, distribution area and buried depth control the sediment compaction in deepwater basin of the South China Sea. Among all the factors, the sediment content is the most important factor. The fitted normal compacted coefficients and the mudline porosity for interval 50 m shows disciplinary variation versus depth. The pore pressure predicted from different fitted results shows different overpressure situation. The normal compaction trend from Site 1144 reflects the porosity variation trend in stable deposition basins in the northern South China Sea. The predicted pore pressure shows overpressure at Site 1144, which is attributed to compaction disequilibrium. Nevertheless, the mixed lithology column may influence the predicted overpressure at Site 1148, which is responsible for the confusing result. Above all. we find that sediment compaction should be act as a proxy for pore pressure in the deepwater basin of the South China Sea. The study will help us to nature of sedimentation in the deepwater basin set up and can be used as analog for older sediments deposited in the similar kind of depositional environment in deepwater basin of the South China Sea.

Sediment-hosted contaminants and distribution patterns in the Mississippi and Atchafalaya River Deltas

USGS Publications Warehouse

Flocks, James G.; Kindinger, Jack G.; Ferina, Nicholas; Dreher, Chandra

2002-01-01

The Mississippi and Atchafalaya Rivers transport very large amounts of bedload and suspended sediments to the deltaic and coastal environments of the northern Gulf of Mexico. Absorbed onto these sediments are contaminants that may be detrimental to the environment. To adequately assess the impact of these contaminants it is first necessary to develop an understanding of sediment distribution patterns in these deltaic systems. The distribution patterns are defined by deltaic progradational cycles. Once these patterns are identified, the natural and industrial contaminant inventories and their depositional histories can be reconstructed. Delta progradation is a function of sediment discharge, as well as channel and receiving-basin dimensions. Fluvial energy controls the sediment distribution pattern, resulting in a coarse grained or sandy framework, infilled with finer grained material occupying the overbank, interdistributary bays, wetlands and abandoned channels. It has been shown that these fine-grained sediments can carry contaminants through absorption and intern them in the sediment column or redistribute them depending on progradation or degradation of the delta deposit. Sediment distribution patterns in delta complexes can be determined through high-resolution geophysical surveys and groundtruthed with direct sampling. In the Atchafalaya and Mississippi deltas, remote sensing using High-Resolution Single-Channel Seismic Profiling (HRSP) and Sidescan Sonar was correlated to 20-ft vibracores to develop a near-surface geologic framework that identifies variability in recent sediment distribution patterns. The surveys identified bedload sand waves, abandoned-channel back-fill, prodelta and distributary mouth bars within the most recently active portions of the deltas. These depositional features respond to changes in deltaic processes and through their response may intern or transport absorbed contaminants. Characterizing these features provides insight into the fate of sediment-hosted contaminants.
Flocculation and sediment deposition in a hypertidal creek

NASA Astrophysics Data System (ADS)

O'Laughlin, C.; van Proosdij, D.; Milligan, T. G.

2014-07-01

In the hypertidal Bay of Fundy, environmental impacts in response to commercial-scale tidal power development remain to be fully understood. The extraction of tidal energy may impact sediment dynamics in far-field environments, such as the intertidal zone, through potential alterations to tidal amplitude in the Minas Basin. Tidal conditions (e.g. current velocity, turbulence, suspended sediment concentration) were monitored in a sheltered salt marsh creek over 18 tidal cycles in various stages of the spring-neap cycle. Samples of deposited and suspended sediments were collected and analyzed for grain size using a Beckman Coulter Multisizer III. Results suggest that the flocculated component of both deposited and suspended sediment is consistently high over a wide range of tidal conditions. A routinely high incoming concentration of highly-flocculated material results in large amounts of sediment deposition in tidal creeks in response to individual tidal cycles. Resuspension and removal of newly deposited material is shown to vary with over-marsh, bankfull and channel-restricted tides. Disruption of the tidal regime due to a reduction in Minas Basin tidal amplitude may lessen the cumulative export capacity of tidal channels over time, potentially leading to gradual infilling of tidal creeks. The long-term effects of tidal power development on intertidal areas are generally unknown.
Morphology and processes associated with the accumulation of the fine-grained sediment deposit on the southern New England shelf

USGS Publications Warehouse

Twichell, David C.; McClennen, Charles E.; Butman, Bradford

1981-01-01

A 13,000 km2 area of the southern New England Continental Shelf which is covered by anomalously fine-grained sediment has been surveyed by means of high-resolution, seismic-reflection and side-scan sonar techniques to map its morphology and structure, and a near-bottom instrument system contributed to understanding present activity of the deposit. Seismic-reflection profiles show that the fine-grained deposit, which is as much as 13 m thick, has accumulated during the last transgression because it rests on a reflector that is geomorphically similar to and continuous with the Holocene transgressive sand sheet still exposed on the shelf to the west. The ridge and swale topography comprising the sand sheet on the shelf off New Jersey and Long Island are relict in origin as these same features are found buried under the fine sediment deposit. Southwestward migrating megaripples observed on the sonographs in the eastern part of the deposit are evidence that sediment is still actively accumulating in this area. In the western part of the deposit, where surface sediment is composed of silt plus clay, evidence of present sediment mobility consists of changes in the near-bottom, suspended-matter concentrations primarily associated with storms. Nantucket Shoals and Georges Bank are thought to be the sources for the fine-textured sediment. Storms and strong tidal currents in these shoal areas may still erode available fine-grained material, which then is transported westward by the mean drift to the southern New England Shelf, where a comparatively tranquil environment permits deposition of the fine material.
Surficial geology of the sea floor in west-central Long Island Sound as shown by sidescan-sonar imagery

USGS Publications Warehouse

McMullen, K.Y.; Poppe, L.J.; DiGiacomo-Cohen, M. L.; Moser, M.S.; Christman, E.B.

2005-01-01

We used sidescan-sonar imagery detailing almost 300 km2 of the sea floor in west-central Long Island Sound in conjunction with bathymetry, sediment samples, bottom video, and seismic data to interpret the area's surficial geology. The distribution of sediments and sedimentary environments interpreted from these data sets represents the Quaternary geology, regional bathymetry, and effects of modern tidal- and wave-driven currents. Four distinct sedimentary environments consisting of 1) fine-grained deposition, 2) sorting and reworking, 3) coarse-grained bedload transport, and 4) erosion or nondeposition, were identified and mapped. Relatively low-energy environments prevail where deposition of clayey silts occurs in deeper water throughout the central part of the study area, and in the protected areas of the far northeastern corner. As low-energy environments transition to relatively high-energy environments, sorting and reworking of sand, silty sand, and sand-silt-clay takes place on the flanks of the shoals and over smaller bathymetric highs. Environments of coarse-grained bedload transport, distinguished by sandy sediments with current-derived bedforms, are located on an unnamed shoal in the northwestern part of the study area and directly to the south of this on Stratford Shoal. High-energy conditions are reflected by environments of erosion or nondeposition, which occur on bathymetric highs where gravel and gravelly sediments are present.
Evaluating the Effect of Autogenic Sedimentation on the Preservation of Climate Proxy Records: Modeling and Examples from the Paleocene Eocene Thermal Maximum

NASA Astrophysics Data System (ADS)

Trampush, S. M.; Hajek, E. A.

2016-12-01

The stratigraphic record provides a vital opportunity to investigate how changes in climate can impact many different landscapes and seascapes. However, the inherent variability in sedimentation within many depositional environments may mask or remove the signature of climate change. A common solution is to use geochemical proxies - usually collected at regular stratigraphic intervals - to independently identify climate events. This approach doesn't account for the potentially significant variability in deposition and erosion time series resulting from autogenic landscape dynamics. In order to explore how geochemical proxy records could be overprinted by landscape dynamics, we use a 1D stochastic sedimentation model where we mimic fluvial, lacustrine, shallow marine, and deep marine environmental dynamics by varying the frequency-magnitude distributions of sedimentation rates. We find that even conservative estimates of the frequency and magnitude of stochastic sedimentation variability can heavily modify proxy records in characteristic ways by alternately removing, compressing, and expanding portions of the record, regardless of the magnitude or duration of the climatic event. Our model results are consistent with observations of the carbon isotope excursions of the Paleocene Eocene Thermal Maximum (PETM) preserved within both fluvial (e.g. the Bighorn Basin, Wyoming and the Piceance Basin, Colorado) and shallow marine (e.g. the New Jersey shelf) deposits. Our results suggest that we may be able to use existing geochemical proxy records within well studied, global climate events, such as the PETM, to constrain the variability in sedimentation present within different depositional environments.
Data on nearshore wave process and surficial beach deposits, central Tamil Nadu coast, India.

PubMed

Joevivek, V; Chandrasekar, N

2017-08-01

The chronicles of nearshore morphology and surficial beach deposits provide valuable information about the nature of the beach condition and the depositional environment. It imparts an understanding about the spatial and temporal relationship of nearshore waves and its influence over the distribution of beach sediments. This article contains data about wave and sediment dynamics of the ten sandy beaches along the central Tamil Nadu coast, India. This present dataset comprises nearshore wave parameters, breaker wave type, beach morphodynamic state, grain size distribution and weight percentage of heavy and light mineral distribution. The dataset will figure out the beach morphology and hydrodynamic condition with respect to the different monsoonal season. This will act as a field reference to realize the coastal dynamics in an open sea condition. The nearshore entities were obtained from the intensive field survey between January 2011 and December 2011, while characteristics of beach sediments are examined by the chemical process in the laboratory environment.
Geology of the Holocene surficial uranium deposit of the north fork of Flodelle Creek, northeastern Washington ( USA).

USGS Publications Warehouse

Johnson, S.Y.; Otton, J.K.; Macke, D.L.

1987-01-01

The N fork of Flodelle Creek drainage basin in NE Washington contains the first surficial U deposit to be mined in the US. The U was leached from granitic bedrock and fixed in organic-rich pond sediments. The distribution of these pond sediments and, therefore, the U has been strongly influenced by relict glacial topography, slope proceses, and beaver activity. Ponds in the drainage basin have been sinks for fine-grained, organic-rich sediments. These organic-rich sediments provide a suitable geochemical environment for precipitation and adsorption of uranium leached from granitic bedrock into ground, spring, and surface waters. Processes of pond formation have thus been important in the development of surficial U deposits in the N fork of Flodelle Creek drainage basin and may have similar significance in other areas.-from Authors
Iron Oxide Deposition from Aqueous Solution and Iron Formations on Mars

NASA Technical Reports Server (NTRS)

Catling, David; Moore, Jeff

2000-01-01

Iron formations are ancient, laminated chemical sediments containing at least 15 wt% Fe. We discuss possible mechanisms for their formation in aqueous environments on early Mars. Such iron oxide deposits may be detectable today.
Beryllium-7 as a tracer of short-term sediment deposition and resuspension in the Fox River Wisconsin

USGS Publications Warehouse

Fitzgerald, S.A.; Klump, J.V.; Swarzenski, P.W.; Mackenzie, R.A.; Richards, K.D.

2001-01-01

Short-term (???monthly) sediment deposition and resuspension rates of surficial bed sediments in two PCB-laden impoundments on the Fox River, WI, were determined in the summer and fall of 1998 using 7Be, a naturally occurring radioisotope produced in the atmosphere. Decay-corrected activities and inventories of 7Be were measured in bed sediment and in suspended particles. Beryilium-7 activities generally decreased with depth in the top 5-10 cm of sediments and ranged from undetectable to ???0.9 pCi cm-3. Inventories of 7Be, calculated from the sum of activities from all depths, ranged from 0.87 to 3.74 pCi cm-2, and the values covaried between sites likely reflecting a common atmospheric input signal. Activities of 7Be did not correlate directly with rainfall. Partitioning the 7Be flux into "new" and "residual" components indicated that net deposition was occurring most of the time during the summer. Net erosion, however, was observed at the upstream site from the final collection in the fall. This erosion event was estimated to have removed 0.10 g (cm of sediment)-2, corresponding to ???0.5 cm of sediment depth, and ???6-10 kg of polychlorinated biphenyls (PCBs) over the whole deposit. Short-term accumulation rates were up to ???130 times higher than the long-term rates calculated from 137Cs profiles, suggesting an extremely dynamic sediment transport environment, even within an impounded river system.Short-term (approximately monthly) sediment deposition and resuspension rates of surficial bed sediments in two PCB-laden impoundments on the Fox River, WI, were determined in the summer and fall of 1998 using 7Be, a naturally occurring radioisotope produced in the atmosphere. Decay-corrected activities and inventories of 7Be were measured in bed sediment and in suspended particles. Beryllium-7 activities generally decreased with depth in the top 5-10 cm of sediments and ranged from undetectable to approximately 0.9 pCi cm-3. Inventories of 7Be, calculated from the sum of activities from all depths, ranged from 0.87 to 3.74 pCi cm-2, and the values covaried between sites likely reflecting a common atmospheric input signal. Activities of 7Be did not correlate directly with rainfall. Partitioning the 7Be flux into `new' and `residual' components indicated that net deposition was occurring most of the time during the summer. Net erosion, however, was observed at the upstream site from the final collection in the fall. This erosion event was estimated to have removed 0.10 g (cm of sediment)-2, corresponding to approximately 0.5 cm of sediment depth, and approximately 6-10 kg of polychlorinated biphenyls (PCBs) over the whole deposit. Short-term accumulation rates were up to approximately 130 times higher than the long-term rates calculated from 137Cs profiles, suggesting an extremely dynamic sediment transport environment, even within an impounded river system.
Recognition of maximum flooding events in mixed siliciclastic-carbonate systems: Key to global chronostratigraphic correlation

USGS Publications Warehouse

Mancini, E.A.; Tew, B.H.

1997-01-01

The maximum flooding event within a depositional sequence is an important datum for correlation because it represents a virtually synchronous horizon. This event is typically recognized by a distinctive physical surface and/or a significant change in microfossil assemblages (relative fossil abundance peaks) in siliciclastic deposits from shoreline to continental slope environments in a passive margin setting. Recognition of maximum flooding events in mixed siliciclastic-carbonate sediments is more complicated because the entire section usually represents deposition in continental shelf environments with varying rates of biologic and carbonate productivity versus siliciclastic influx. Hence, this event cannot be consistently identified simply by relative fossil abundance peaks. Factors such as siliciclastic input, carbonate productivity, sediment accumulation rates, and paleoenvironmental conditions dramatically affect the relative abundances of microfossils. Failure to recognize these complications can lead to a sequence stratigraphic interpretation that substantially overestimates the number of depositional sequences of 1 to 10 m.y. duration.
Sinks and sources: Assessing microplastic abundance in river sediment and deposit feeders in an Austral temperate urban river system.

PubMed

Nel, Holly A; Dalu, Tatenda; Wasserman, Ryan J

2018-01-15

Microplastics are important novel pollutants in freshwaters but their behaviour in river sediments is poorly understood due to the large amounts of coloured dissolved organic matter that impede sample processing. The present study aimed to 1.) estimate the microplastic pollution dynamics in an urban river system experiencing temporal differences in river flow, and 2.) investigate the potential use of chironomids as indicators of microplastic pollution levels in degraded freshwater environments. Microplastic levels were estimated from sediment and Chironomus spp. larvae collected from various sites along the Bloukrans River system, in the Eastern Cape South Africa during the summer and winter season. River flow, water depth, channel width, substrate embeddedness and sediment organic matter were simultaneously collected from each site. The winter season was characterised by elevated microplastic abundances, likely as a result of lower energy and increased sediment deposition associated with reduced river flow. In addition, results showed that particle distribution may be governed by various other external factors, such as substrate type and sediment organic matter. The study further highlighted that deposit feeders associated with the benthic river habitats, namely Chironomus spp. ingest microplastics and that the seasonal differences in sediment microplastic dynamics were reflected in chironomid microplastic abundance. There was a positive, though weakly significant relationship between deposit feeders and sediment suggesting that deposit feeders such as Chironomus spp. larvae could serve as an important indicator of microplastic loads within freshwater ecosystems. Copyright © 2017 Elsevier B.V. All rights reserved.
Site formation processes at Pinnacle Point Cave 13B (Mossel Bay, Western Cape Province, South Africa): resolving stratigraphic and depositional complexities with micromorphology.

PubMed

Karkanas, Panagiotis; Goldberg, Paul

2010-01-01

Site PP13B is a cave located on the steep cliffs of Pinnacle Point near Mossel Bay in Western Cape Province, South Africa. The depositional sequence of the cave, predating Marine Isotopic Stage 11 (MIS 11) and continuing to present, is in the form of isolated sediment exposures with different depositional facies and vertical and lateral variations. Micromorphological analysis demonstrated that a suite of natural sedimentation processes operated during the development of the sequence ranging from water action to aeolian activity, and from speleothem formations to plant colonization and root encrustation. At the same time, anthropogenic sediments that are mainly in the form of burnt remains from combustion features (e.g., wood ash, charcoal, and burnt bone) were accumulating. Several erosional episodes have resulted in a complicated stratigraphy, as discerned from different depositional and post-depositional features. The cave is associated with a fluctuating coastal environment, frequent changes in sea level and climate controlled patterns of sedimentation, and the presence or absence of humans. Copyright © 2010 Elsevier Ltd. All rights reserved.
Impacts of sewer deposits on the urban river sediment after rainy season and bioremediation of polluted sediment.

PubMed

Chang, Suyun; Tang, Yinqi; Dong, Lixin; Zhan, Qiang; Xu, Wei

2018-05-01

Impacts of deposits discharged from a municipal pipe on urban river sediment were investigated in the Hucang River in Tianjin, China. At the outlet of the pump station, the average concentrations of total nitrogen (TN), total phosphorus (TP), and total organic carbon (TOC) in the sediment increased sharply from 2390, 799, and 14,600 mg/kg to 6500, 3700, and 153,000 mg/kg, respectively, and remained stable at high level after the rainy season. A portion of pollutants would migrate along the river, and the concentration was usually in a negative relationship with the distance. The average Shannon-Wiener value on the upstream section was higher than those on the downstream sections. This revealed that the deposits discharged decreased the bacterial diversity in the sediment, and high concentrations of pollutants may markedly change the bacterial community structure in the sediment. To reduce the pollution of the urban river after rainy season, four kinds of microbial consortiums A (Zhangda), B (Aiersi), C (Qinghe), and D (Inpipe) were applied to bioremediate the polluted sediment in lab scale. Bioaugmentation with microbial consortium A showed good performance on the bioremediation of the polluted sediment. The average removal efficiency of TN, TP, and organic matter reached 35.5, 43.7, and 39.1%, respectively, after 22 days of treatment. Moreover, the bacterial evenness and diversity in the sediment markedly increased, indicating that the microbial environment was more favourable after bioaugmentation and sustainable development would be guaranteed. This study improves our understanding of the impacts of deposits discharged from a stormwater drain system on urban river sediment, and explores the effectiveness of bioaugmentation for the bioremediation of polluted sediment, which will provide the basis of sewer deposit pollution control.
Sediment characteristics and configuration within the Otsego City Dam impoundment on the Kalamazoo River, Michigan, 2001-02

USGS Publications Warehouse

Rheaume, S.J.; Hubbell, D.L.; Rachol, C.M.; Simard, A.; Fuller, L.M.

2004-01-01

The removal of the Otsego City Dam on the Kalamazoo River at Otsego, Mich., is under consideration by the Michigan Department of Environmental Quality and the city of Otsego. The historical discharge of papermill waste containing polychlorinated biphenyls from sources upstream from the dam has led the U.S. Environmental Protection Agency to designate the Kalamazoo River from Morrow Dam near Comstock to its mouth near Saugatuck as a Federal Superfund site. The papermill waste is concentrated in organic sediment and kaolinite clay, with the sediment containing as much as 94 milligrams per kilogram polychlorinated biphenyls. This contaminated sediment could move if the dam is removed; therefore, it is necessary to estimate the characteristics and configuration of the sediment before removal plans begin. Data from augered sections and sediment cores show that the current Otsego City impoundment sediments were deposited in two distinctly different sedimentary environments: (1) lacustrine sediments consisting of organic-rich silt and clay, fine to medium sand, and some gravel deposited in a repetitive, cyclic fashion related to former stream velocities when the Otsego City impoundment water levels were 2-4 feet higher (1880s-1960s), and from downstream movement of lacustrine sediments during the removal of the upstream Plainwell Dam superstructure in the 1980s; and (2) more recent (1980s-2002) coarse-grained alluvium deposited on top of the lacustrine sediments. The volume of instream sediment contained within the Otsego City impoundment is estimated to be about 457,270 cubic yards. This estimate is based on the composite thicknesses of the lacustrine deposits and overlying alluvium, which were determined to contain PCBs, and does not include bank or flood-plain deposits.
Organic sedimentation in modern lacustrine systems: A case study from Lake Malawi, East Africa

USGS Publications Warehouse

Ellis, Geoffrey S.; Barry J. Katz,; Christopher A. Scholz,; Peter K. Swart,

2015-01-01

This study examines the relationship between depositional environment and sedimentary organic geochemistry in Lake Malawi, East Africa, and evaluates the relative significance of the various processes that control sedimentary organic matter (OM) in lacustrine systems. Total organic carbon (TOC) concentrations in recent sediments from Lake Malawi range from 0.01 to 8.80 wt% and average 2.83 wt% for surface sediments and 2.35 wt% for shallow core sediments. Hydrogen index (HI) values as determined by Rock-Eval pyrolysis range from 0 to 756 mg HC g−1 TOC and average 205 mg HC g−1 TOC for surface sediments and 228 mg HC g−1 TOC for shallow core samples. On average, variations in primary productivity throughout the lake may account for ~33% of the TOC content in Lake Malawi sediments (as much as 1 wt% TOC), and have little or no impact on sedimentary HI values. Similarly, ~33% to 66% of the variation in TOC content in Lake Malawi sediments appears to be controlled by anoxic preservation of OM (~1–2 wt% TOC), although some component of the water depth–TOC relationship may be due to physical sediment transport processes. Furthermore, anoxic preservation has a minimal effect on HI values in Lake Malawi sediments. Dilution of OM by inorganic sediment may account for ~16% of variability in TOC content in Lake Malawi sediments (~0.5 wt% TOC). The effect of inputs of terrestrial sediment on the organic character of surface sediments in these lakes is highly variable, and appears to be more closely related to the local depositional environment than the regional flux of terrestrial OM. Total nitrogen and TOC content in surface sediments collected throughout the lake are found to be highly correlated (r2 = 0.95), indicating a well-homogenized source of OM to the lake bottom. The recurring suspension and deposition of terrestrial sediment may account for significant amounts of OM deposited in offshore regions of the lake. This process effectively separates denser inorganic sediment from less dense OM and allows terrestrial OM to preferentially be transported farther offshore. The conclusion is that for the organic carbon content in these regions to be elevated a mixed terrestrial-lacustrine origin is required. The hydrodynamic separation of mineral and organic constituents is most pronounced in regions with shallow bathymetric gradients, consistent with previous findings from Lake Tanganyika.
Geologic framework of the long bay inner shelf: implications for coastal evolution in South Carolina

USGS Publications Warehouse

Barnhardt, W.; Denny, J.; Baldwin, W.; Schwab, W.; Morton, R.; Gayes, P.; Driscoll, N.

2007-01-01

The inner continental shelf off northern South Carolina is a sediment-limited environment characterized by extensive hardground areas, where coastal plain strata and ancient channel-fill deposits are exposed at the sea floor. Holocene sand is concentrated in large shoals associated with active tidal inlets, an isolated shore-detached sand body, and a widespread series of low-relief sand ridges. The regional geologic framework is a strong control on the production, movement and deposition of sediment. High-resolution geologic mapping of the sea floor supports conceptual models indicative of net southwestward sediment transport along the coast.
Seafloor environments in the Long Island Sound estuarine system

USGS Publications Warehouse

Knebel, H.J.; Signell, R.P.; Rendigs, R. R.; Poppe, L.J.; List, J.H.

1999-01-01

Four categories of modern seafloor sedimentary environments have been identified and mapped across the large, glaciated, topographically complex Long Island Sound estuary by means of an extensive regional set of sidescan sonographs, bottom samples, and video-camera observations and supplemental marine-geologic and modeled physical-oceanographic data. (1) Environments of erosion or nondeposition contain sediments which range from boulder fields to gravelly coarse-to-medium sands and appear on the sonographs either as patterns with isolated reflections (caused by outcrops of glacial drift and bedrock) or as patterns of strong backscatter (caused by coarse lag deposits). Areas of erosion or nondeposition were found across the rugged seafloor at the eastern entrance of the Sound and atop bathymetric highs and within constricted depressions in other parts of the basin. (2) Environments of bedload transport contain mostly coarse-to-fine sand with only small amounts of mud and are depicted by sonograph patterns of sand ribbons and sand waves. Areas of bedload transport were found primarily in the eastern Sound where bottom currents have sculptured the surface of a Holocene marine delta and are moving these sediments toward the WSW into the estuary. (3) Environments of sediment sorting and reworking comprise variable amounts of fine sand and mud and are characterized either by patterns of moderate backscatter or by patterns with patches of moderate-to-weak backscatter that reflect a combination of erosion and deposition. Areas of sediment sorting and reworking were found around the periphery of the zone of bedload transport in the eastern Sound and along the southern nearshore margin. They also are located atop low knolls, on the flanks of shoal complexes, and within segments of the axial depression in the western Sound. (4) Environments of deposition are blanketed by muds and muddy fine sands that produce patterns of uniformly weak backscatter. Depositional areas occupy broad areas of the basin floor in the western part of the Sound. The regional distribution of seafloor environments reflects fundamental differences in marine-geologic conditions between the eastern and western parts of the Sound. In the funnel-shaped eastern part, a gradient of strong tidal currents coupled with the net nontidal (estuarine) bottom drift produce a westward progression of environments ranging from erosion or nondeposition at the narrow entrance to the Sound, through an extensive area of bedload transport, to a peripheral zone of sediment sorting. In the generally broader western part of the Sound, a weak tidal-current regime combined with the production of particle aggregates by biologic or chemical processes, cause large areas of deposition that are locally interrupted by a patchy distribution of various other environments where the bottom currents are enhanced by and interact with the seafloor topography.
Middle Eocene Nummulites and their offshore re-deposition: A case study from the Middle Eocene of the Venetian area, northeastern Italy

NASA Astrophysics Data System (ADS)

Bassi, Davide; Nebelsick, James H.; Puga-Bernabéu, Ángel; Luciani, Valeria

2013-11-01

The Middle Eocene Calcari nummulitici formation from northeastern Italy, Venetian area, represents a shallow-marine carbonate ramp developed on the northern Tethyan margin. In the Monti Berici area, its main components are larger foraminifera and coralline red algal communities that constitute thick carbonate sedimentary successions. Middle ramp and proximal outer ramp environments are recognized using component relationships, biofacies and sedimentary features. The middle-ramp is characterized by larger flattened-lenticular Nummulites on palaeohighs between which rhodoliths formed. Larger Nummulites palaeohighs containing Nummulites millecaput, Nummulites crassus, Nummulites discorbinus and Nummulites cf. gizehensis developed more basin-wards. The following relatively quiet environments of basin-wards of the palaeohighs represent areas of maximum carbonate production. The transition between the distal middle- and the proximal outer-ramp settings is marked in the study area by a large erosional surface which is interpreted to have been formed as a result of an erosive channel body filled in by deposits re-sedimented from shallower depths. These off-shore re-sedimented channelized deposits, ascribed to the Shallow Benthic Zone SBZ 15, lying on hemipelagic marls (planktonic foraminiferal zone E9 (P11)) allow for a biostratigraphic correlation to the Late Lutetian. The studied deposits, represented by packstone to rudstones, were displaced whilst still unlithified. The Lutetian-Bartonian regression along with the local tectonic activity promoted the production of a high amount of biogenic shallow-water carbonates mainly produced in the Mossano middle-ramp settings. These prograded towards the basinal areas with high-sedimentation rate of carbonate deposits characterized by the larger Nummulites rudstones. Such high amounts of sediment led to sediment instability which potentially could be mobilized either by return currents due to occasional major storms or by earthquakes induced by tectonic activity. These will have led to the offshore re-deposition of the Nummulites sediments into deeper water setting via the observed channels. Since potential migration pathways are short, such distal re-sedimented channel-filled material surrounded by hemipelagic marls is optimally placed for the formation of potential subsurface oil reservoirs.
Radioecologycal study of {sup 239/240}Pu in Bangka Island and Muria Peninsula: Determination of {sup 239/240}Pu in marine sediment and seawater as part of baseline data collecting for sitting of candidates of first Indonesia NPP

DOE Office of Scientific and Technical Information (OSTI.GOV)

Suseno, Heny, E-mail: henis@batan.go.id; Wisnubroto, Djarot S.

Radioisotope Pu-239/240 are alpha emitting nuclides important indicators of radioactive contamination of the marine environment. Global fallout is the main source of plutonium in the marine environment. There are very limited study on {sup 239/240}Pu in Indonesia coastal environments. The data of this radioisotopes is needed for baseline data of nuclear power plant (NPP) site candidates both in Bangka Island and Muria Peninsula. Bottom sediments play an important role in radioecological studies of the marine environment because a large proportion of radioactive substances entering the sea is adsorbed over time onto suspended particulate matter and deposited in sediments. Plutonium ismore » particle reactive and deposited in marine sediment. Radioisotope {sup 239/240}Pu was determinated by alpha spectrometry after radiochemical procedure that was performed in both water and marine sediment from Bangka Island and Muria Peninsula. The sediment baseline of concentration {sup 239/240}Pu in Bangka Island and Muria Peninsula were range from 0.013 to 0.021 Bq.kg{sup −1} and 0.018 to 0.024 Bq.kg{sup −1} respectively. The water baseline concentration this isotope were range from 2.73 to 4.05 mBq.m{sup −3} and 2.98 to 4.50 mBq.m{sup −3}.« less
Sea-floor morphology and sedimentary environments of western Block Island Sound, northeast of Gardiners Island, New York

USGS Publications Warehouse

McMullen, Katherine Y.; Poppe, Lawrence J.; Danforth, William W.; Blackwood, Dann S.; Clos, Andrew R.; Parker, Castle E.

2014-01-01

Multibeam-echosounder data, collected during survey H12299 by the National Oceanic and Atmospheric Administration in a 162-square-kilometer area of Block Island Sound, northeast of Gardiners Island, New York, are used along with sediment samples and bottom photography, collected at 37 stations in this area by the U.S. Geological Survey during cruise 2013-005-FA, to interpret sea-floor features and sedimentary environments. These data and interpretations provide important base maps for future studies of the sea floor, focused, for example, on benthic ecology and resource management. The features and sedimentary environments on the sea floor are products of the glacial history and modern tidal regime. Features include bedforms such as sand waves and megaripples, boulders, a large current-scoured depression, exposed glaciolacustrine sediments, and areas of modern marine sediment. Sand covers much of the study area and is often in the form of sand waves and megaripples, which indicate environments characterized by coarse-grained bedload transport. Boulders and gravelly lag deposits, which indicate environments of erosion or nondeposition, are found off the coast of Gardiners Island and on bathymetric highs, probably marking areas where deposits associated with recessional ice-front positions, the northern flank of the terminal moraine, or coastal-plain sediments covered with basal till are exposed. Bottom photographs and video of boulders show that they are commonly covered with sessile fauna. Strong tidal currents have produced the deep scour depression along the northwestern edge of the study area. The eastern side of this depression is armored with a gravel lag. Sea-floor areas characterized by modern marine sediments appear featureless at the 2-meter resolution of the bathymetry and flat to current rippled in the photography. These modern environments are indicative of sediment sorting and reworking.

To what extent can intracrater layered deposits that lack clear sedimentary textures be used to infer depositional environments?

NASA Astrophysics Data System (ADS)

Cadieux, Sarah B.; Kah, Linda C.

2015-03-01

Craters within Arabia Terra, Mars, contain hundreds of meters of layered strata showing systematic alternation between slope- and cliff-forming units, suggesting either rhythmic deposition of distinct lithologies or similar lithologies that experienced differential cementation. On Earth, rhythmically deposited strata can be examined in terms of stratal packaging, wherein the interplay of tectonics, sediment deposition, and base level (i.e., the position above which sediment accumulation is expected to be temporary) result in changes in the amount of space available for sediment accumulation. These predictable patterns of sediment deposition can be used to infer changes in basin accommodation regardless of the mechanism of deposition (e.g. fluvial, lacustrine, or aeolian). Here, we analyze sedimentary deposits from three craters (Becquerel Crater, Danielson Crater, Crater A) in Arabia Terra. Each crater contains layered deposits that are clearly observed in orbital images. Although orbital images are insufficient to specifically determine the origin of sedimentary deposits, depositional couplets can be interpreted in terms of potential accommodation space available for deposition, and changes in the distribution of couplet thickness through stratigraphy can be interpreted in terms of changing base level and the production of new accommodation space. Differences in stratal packaging in these three craters suggest varying relationships between sedimentary influx, sedimentary base level, and concomitant changes in accommodation space. Previous groundwater upwelling models hypothesize that layered sedimentary deposits were deposited under warm climate conditions of early Mars. Here, we use observed stacking patterns to propose a model for deposition under cold climate conditions, wherein episodic melting of ground ice could raise local base level, stabilize sediment deposition, and result in differential cementation of accumulated strata. Such analysis demonstrates that a first-order understanding of sedimentary deposition and accumulation-despite a lack of textural information that inhibits interpretation of depositional mechanism-can provide insight into potentially changeable depositional conditions of early Mars.
Hadal disturbance in the Japan Trench induced by the 2011 Tohoku–Oki Earthquake

PubMed Central

Oguri, Kazumasa; Kawamura, Kiichiro; Sakaguchi, Arito; Toyofuku, Takashi; Kasaya, Takafumi; Murayama, Masafumi; Fujikura, Katsunori; Glud, Ronnie N.; Kitazato, Hiroshi

2013-01-01

In situ video observations and sediment core samplings were performed at two hadal sites in the Japan Trench on July, 2011, four months after the Tohoku–Oki earthquake. Video recordings documented dense nepheloid layers extending ~30–50 m above the sea bed. At the trench axis, benthic macrofauna was absent and dead organisms along with turbid downslope current were observed. The top 31 cm of sediment in the trench axis revealed three recent depositions events characterized by elevated 137Cs levels and alternating sediment densities. At 4.9 km seaward from the trench axis, little deposition was observed but the surface sediment contained 134Cs from the Fukushima Dai–ichi nuclear disaster. We argue that diatom blooms observed by remote sensing facilitated rapid deposition of 134Cs to hadal environment and the aftershocks induced successive sediment disturbances and maintained dense nepheloid layers in the trench even four months after the mainshock. PMID:23715086
Sedimentologic characteristics of recent washover deposits from Assateague Island, Maryland

USGS Publications Warehouse

Bernier, Julie C.; Zaremba, Nicholas J.; Wheaton, Cathryn J.; Ellis, Alisha M.; Marot, Marci E.; Smith, Christopher G.

2016-06-08

This report describes sediment data collected using sand augers in active overwash zones on Assateague Island in Maryland. Samples were collected by the U.S. Geological Survey (USGS) during two surveys in March/April and October 2014 (USGS Field Activity Numbers [FAN] 2014-301-FA and 2014-322-FA, respectively). The physical characteristics (for example, sediment texture or bedding structure) of and spatial differences among these deposits will provide information about overwash processes and sediment transport from the sandy barrier-island reaches to the back-barrier environments. Metrics derived from these data, such as mean grain size or deposit thicknesses, can be used to ground-truth remote sensing and geophysical data and can also be incorporated into sediment transport models. Data products, including sample location tables, descriptive core logs, core photographs and x-radiographs, the results of sediment grain-size analyses, and Geographic Information System (GIS) data files with accompanying formal Federal Geographic Data Committee (FGDC) metadata can be downloaded from the Data Downloads page.
Simulations of dredged sediment spreading on a Posidonia oceanica meadow off the Ligurian coast, Northwestern Mediterranean.

PubMed

Capello, M; Cutroneo, L; Ferranti, M P; Budillon, G; Bertolotto, R M; Ciappa, A; Cotroneo, Y; Castellano, M; Povero, P; Tucci, S

2014-02-15

The sandy deposits from dredging can have negative effects on the environment such as increase in suspended solids in the water column and their consequent transport. An experimental study was conducted to characterize water masses, dynamics, and sedimentation rates on the Ligurian continental shelf (Italy), where both a sand deposit, that could be used for beach nourishment, and a nearby Posidonia oceanica meadow coexist. The environmental plan provides a mathematical simulation of the sediment-dispersion to evaluate the possible impact on the meadow. It has been calculated that the dredging could double the concentration of suspended particles, but its scheduling will preclude a sediment accumulation. All the information obtained from this work will be used to study the environmental feasibility of the sand deposit exploitation and as starting point for drawing up the monitoring plan in case of dredging. Copyright © 2013 Elsevier Ltd. All rights reserved.
Surface texture analysis of southern Tuli Basin sediments: Implications for Limpopo Valley geoarchaeological contexts

NASA Astrophysics Data System (ADS)

Le Baron, Joel C.; Grab, Stefan W.; Kuman, Kathleen

2011-03-01

The Hackthorne 1 site (southern Tuli Basin, South Africa) is situated on a sand-covered plateau adjacent to the Limpopo River Valley. Although the site is well known for its Stone Age archaeology, the past environmental contexts (particularly sedimentological/geomorphological) are not well known. We examine the Hackthorne sand grain surface textures, so as to provide some insight on the site specific and regional depositional history. Quartz sands at Hackthorne were collected from surface sands and from underlying weathered calcrete. SEM analysis was performed on sand grains, through which several mechanical and chemical microtextures were identified. Microtextures typical of fluvial environments were found only on grains derived from the plateau calcrete host sediment, whilst the surface sands exhibited only textures associated with aeolian environments. The results indicate that the calcrete host sediment is composed of alluvium, and that the surface sands mantling the Hackthorne Plateau are not deflated from the alluvial deposits in the Limpopo Valley, but may rather be derived from distant aeolian sources. The deposition of aeolian sands is consistent with OSL dates which place sand deposition, or remobilization, at 23 and 15 kya, periods in southern Africa associated with increased aridity.
Radioactive contamination of the Balchug (Upper Yenisey) floodplain, Russia in relation to sedimentation processes and geomorphology.

PubMed

Linnik, V G; Brown, J E; Dowdall, M; Potapov, V N; Surkov, V V; Korobova, E M; Volosov, A G; Vakulovsky, S M; Tertyshnik, E G

2005-03-01

The radioactive contamination of a riverine floodplain, heavily influenced by discharges from Krasnoyarsk-26, has been studied with respect to sedimentation processes and the geomorphology of the Upper Yenisey floodplain. The study was effected by implementation of a regime of in situ observations and measurements, sampling, and the interpretation of satellite images. The results of the study indicate that on the Balchug Bypass Floodplain, radionuclide contamination is primarily influenced by the thickness of the deposited sediments, and the area can be considered as two depositional environments. The Balchug floodplain area was contaminated due to sedimentation of radionuclide-contaminated alluvium, whose depositional regime significantly changed after the construction of a hydroelectric power station in 1967. Contamination levels are lower on the upstream part of the floodplain where sediment depth is less than 0.2-0.3 m, and this contamination started to accumulate in 1967, while the downstream part of the floodplain, exhibiting deeper deposits, displays higher levels of radionuclide contamination because radionuclides began to deposit here in 1958 when the Krasnoyarsk-26 Mining and Chemical Combine (KMCC) commenced operation. Radionuclide contamination of the floodplain is also related to the elevation of the floodplain, higher regions of the floodplain typically having lower contamination than low-lying areas, which tend to be frequently inundated with sediments being deposited during such inundations. Local relief, its orientation, and vegetation cover have also combined to form sediment traps with significantly higher radionuclide contamination. Lithological analysis combined with radiometric assay indicates a total 137Cs floodplain inventory of 33.7 GBq.
Evolution of Fine-Grained Channel Margin Deposits behind Large Woody Debris in an Experimental Gravel-Bed Flume

NASA Astrophysics Data System (ADS)

ONeill, B.; Marks, S.; Skalak, K.; Puleo, J. A.; Wilcock, P. R.; Pizzuto, J. E.

2014-12-01

Fine grained channel margin (FGCM) deposits of the South River, Virginia sequester a substantial volume of fine-grained sediment behind large woody debris (LWD). FGCM deposits were created in a laboratory setting meant to simulate the South River environment using a recirculating flume (15m long by 0.6m wide) with a fixed gravel bed and adjustable slope (set to 0.0067) to determine how fine sediment is transported and deposited behind LWD. Two model LWD structures were placed 3.7 m apart on opposite sides of the flume. A wire mesh screen with attached wooden dowels simulated LWD with an upstream facing rootwad. Six experiments with three different discharge rates, each with low and high sediment concentrations, were run. Suspended sediment was very fine grained (median grain size of 3 phi) and well sorted (0.45 phi) sand. Upstream of the wood, water depths averaged about 0.08m, velocities averaged about 0.3 m/s, and Froude numbers averaged around 0.3. Downstream of the first LWD structure, velocities were reduced tenfold. Small amounts of sediment passed through the rootwad and fell out of suspension in the area of reduced flow behind LWD, but most of the sediment was carried around the LWD by the main flow and then behind the LWD by a recirculating eddy current. Upstream migrating dunes formed behind LWD due to recirculating flow, similar to reattachment bars documented in bedrock canyon rivers partially obstructed by debouching debris fans. These upstream migrating dunes began at the reattachment point and merged with deposits formed from sediment transported through the rootwad. Downstream migrating dunes formed along the channel margin behind the LWD, downstream of the reattachment point. FGCM deposits were about 3 m long, with average widths of about 0.8 m. Greater sediment concentration created thicker FGCM deposits, and higher flows eroded the sides of the deposits, reducing their widths.
Attribute of trace fossils of Laisong flysch sediments, Manipur, India

NASA Astrophysics Data System (ADS)

Khaidem, Kumar S.; Rajkumar, Hemanta S.; Soibam, Ibotombi

2015-07-01

The depositional basin in which the Late Eocene-Early Oligocene Laisong flysch sediments Barail Group, Manipur region (Indo-Myanmar ranges) have been deposited is generally considered to be of deep marine environment. However, field observation indicates the presence of many shallow environment signature characteristics of marginal to sublittoral marine settings, in addition to the general occurrence of deep marine turbidites. To address this aspect, ichnological analyses of the Laisong Formation has been attempted for elucidating palaeoenvironmental setting prevalent during the deposition of these sediments. Presence of 36 ichnospecies belonging to 33 ichnogenera has so far been identified. The ichnospecies may be grouped into different ichnofacies such as Skolithos-Cruziana mixed ichnofacies, Cruziana ichnofacies, Skolithos ichnofacies, Zoophycos ichnofacies, Nereites ichnofacies and Teredolites ichnofacies which decrease in abundance in this order of sequence with Skolithos-Cruziana mixed ichnofacies being the most dominant. The above-mentioned ichnofacies are found associated with sedimentary structures such as large sole marks, parallel laminations, massive and structureless beds, rip-up clasts, etc., which are characteristics of submarine fan deposits below the storm wave base and current ripples, herringbone structures, hummocky cross stratifications, pot casts, rain prints, etc., that marked shallow marginal marine setting such as tidal flats, deltas and shoreface. With such observations it is very likely that the Laisong sediments were formed in a tectonically active basin with varied bathymetric ranges indicating alternate transgressive and regressive nature.
Variation of heavy metals in recent sediments from Piratininga Lagoon (Brazil): interpretation of geochemical data with the aid of multivariate analysis

NASA Astrophysics Data System (ADS)

Huang, W.; Campredon, R.; Abrao, J. J.; Bernat, M.; Latouche, C.

1994-06-01

In the last decade, the Atlantic coast of south-eastern Brazil has been affected by increasing deforestation and anthropogenic effluents. Sediments in the coastal lagoons have recorded the process of such environmental change. Thirty-seven sediment samples from three cores in Piratininga Lagoon, Rio de Janeiro, were analyzed for their major components and minor element concentrations in order to examine geochemical characteristics and the depositional environment and to investigate the variation of heavy metals of environmental concern. Two multivariate analysis methods, principal component analysis and cluster analysis, were performed on the analytical data set to help visualize the sample clusters and the element associations. On the whole, the sediment samples from each core are similar and the sample clusters corresponding to the three cores are clearly separated, as a result of the different conditions of sedimentation. Some changes in the depositional environment are recognized using the results of multivariate analysis. The enrichment of Pb, Cu, and Zn in the upper parts of cores is in agreement with increasing anthropogenic influx (pollution).
How Connecting Sediment Transport Between Environments Solves First-Order Questions Regarding Construction of the Land- and Seascape Recorded by the Permian Brushy Canyon Fm., West Texas, USA

NASA Astrophysics Data System (ADS)

Mohrig, D. C.; Ustipak, K.

2016-12-01

Exposures in the Guadalupe and Delaware mountains together with well logs and core from the Delaware Basin capture a system-wide picture of the stratigraphy defining the terrestrial, shallow marine, basin slope and basin floor environments associated with the Permian Brushy Canyon Formation. Patterns of erosion and styles of deposition characterizing any one of these environments cannot be fully understood without explicit consideration of sediment transport in the adjacent environments. Properties of an inherited basin margin and slope are particularly important to unraveling the transport histories in the linked terrestrial - to - deep marine environments defining the Brushy Canyon Fm. A one-dimensional turbidity current model will be used to show that the inherited submarine slope of about six degrees is steep enough that all sand-transporting currents are erosional down its length. This slope segment detaches the terrestrial and shallow marine environments from the deeper marine environments and decreases the potential for sediment accumulation in the former. All sediment transported to the brink of the basin slope is efficiently moved to deeper water, promoting a tendency for very little sediment to be preserved in the terrestrial environment; a property of the Brushy Canyon system that has spurred on considerable debate and speculation amongst geoscientists studying the formation. The steep inherited slope and its ability to generate erosional sandy turbidity currents also provides an explanation for the high relative fraction of thin-bedded, mud-rich deposits that are present in the most proximal deep marine setting. Again, a one-dimensional turbidity current model is used to show that only very dilute, muddy currents are expected to accumulate in significant quantity at this position in the long profile of the system. Coarser sediment load is confined to and efficiently transported through erosionally based channels onto the basin floor. Finally, the observed spatial trends in sediment erosion over the proximal 20 - 30 km of the basin floor and net sedimentation out to distances approaching 160 km from the shelf edge will be explored and further quantified using the one-dimensional numerical model for turbidity currents.
A New Late Glacial Site in the Central Appalachians of Virginia. Preliminary Findings From Paleobotany, Palynology, and Geomorphology

NASA Astrophysics Data System (ADS)

Schwartz, B. F.; Upchurch, G. R.; Willard, D. A.; Bernhardt, C. E.; Valella, P. A.

2009-12-01

Thick clay deposits in a recently identified paleo-lake bed in a central Appalachian karst system in Highland County, Virginia have yielded well-preserved pollen and macroflora that provide the opportunity to refine the understanding of Pleistocene climate, vegetation dynamics, and erosion in the region. A radiocarbon date of 22,000 14C yr B.P. on wood fragments near the top of the sequence establishes the age of the sediments. Pollen and plant macrofloras characteristic of modern boreal forests are present in sediments at this site. Pollen assemblages show a dominance of conifers, mostly Pinus banksiana and Picea, with Lycopodium as important ground cover. Leaf fossils sieved from the clay show a dominance of Picea needles and common dicot leaf fragments, suggesting that Pinus is either over-represented in the pollen flora or more distal to the paleo-lake. Macrofossil assemblages sieved from the clay contain a variety of non-leaf remains, including fruits, seeds, mosses, insects, feathers, and fungi. Test augering and geophysical results indicate that these clay deposits are at least 9m and perhaps as much as 15m thick. The amount and temporal distribution of sediment loads to the paleo-lake (a depositional environment) from the surrounding landscape (an erosional environment) will be modeled using analysis of sediment facies in and above (>12m) these clays, combined with sediment volume calculations and drainage basin analysis, and constrained by dates from the sediments themselves. Due to the rare occurrence of still-water depositional environments in the Appalachians, this site provides paleo-climate and sedimentological data that will refine regional models of landscape evolution and incision. This work also has implications for the development and modification of a significant karst system that surrounds and underlies the paleo-lake bed. The same karst system is responsible both for the formation of the paleo-lake (after the drain in a blind valley became plugged), and its later draining and current removal of lake sediments through the underlying karst system.
Middle Pleistocene infill of Hinkley Valley by Mojave River sediment and associated lake sediment: Depositional architecture and deformation by strike-slip faults

USGS Publications Warehouse

Miller, David; Haddon, Elizabeth; Langenheim, Victoria; Cyr, Andrew J.; Wan, Elmira; Walkup, Laura; Starratt, Scott W.

2018-01-01

Hinkley Valley in the Mojave Desert, near Barstow about 140 km northeast of Los Angeles and midway between Victorville Valley and the Lake Manix basin, contains a thick sedimentary sequence delivered by the Mojave River. Our study of sediment cores drilled in the valley indicates that Hinkley Valley was probably a closed playa basin with stream inflow from four directions prior to Mojave River inflow. The Mojave River deposited thick and laterally extensive clastic wedges originating from the southern valley that rapidly filled much of Hinkley Valley. Sedimentary facies representing braided stream, wetland, delta, and lacustrine depositional environments all are found in the basin fill; in some places, the sequence is greater than 74 m (245 ft) thick. The sediment is dated in part by the presence of the ~631 ka Lava Creek B ash bed low in the section, and thus represents sediment deposition after Victorville basin was overtopped by sediment and before the Manix basin began to be filled. Evidently, upstream Victorville basin filled with sediment by about 650 ka, causing the ancestral Mojave River to spill to the Harper and Hinkley basins, and later to Manix basin.Initial river sediment overran wetland deposits in many places in southern Hinkley Valley, indicating a rapidly encroaching river system. These sediments were succeeded by a widespread lake (“blue” clay) that includes the Lava Creek B ash bed. Above the lake sediment lies a thick section of interlayered stream sediment, delta and nearshore lake sediment, mudflat and/or playa sediment, and minor lake sediment. This stratigraphic architecture is found throughout the valley, and positions of lake sediment layers indicate a successive northward progression in the closed basin. A thin overlapping sequence at the north end of the valley contains evidence for a younger late Pleistocene lake episode. This late lake episode, and bracketing braided stream deposits of the Mojave River, indicate that the river avulsed through the valley, rather than continuing toward Lake Manix, during the late Pleistocene. Two dextral strike-slip fault zones, the Lockhart and the Mt. General, fold and displace the distinctive stratigraphic units, as well as surficial late Pleistocene and Holocene deposits. The sedimentary architecture and the two fault zones provide a framework for evaluating groundwater flow in Hinkley Valley.
Characteristics and origin of Earth-mounds on the Eastern Snake River Plain, Idaho

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tullis, J.A.

1995-09-01

Earth-mounds are common features on the Eastern Snake River Plain, Idaho. The mounds are typically round or oval in plan view, <0.5 m in height, and from 8 to 14 m in diameter. They are found on flat and sloped surfaces, and appear less frequently in lowland areas. The mounds have formed on deposits of multiple sedimentary environments. Those studied included alluvial gravel terraces along the Big Lost River (late Pleistocene/early Holocene age), alluvial fan segments on the flanks of the Lost River Range (Bull Lake and Pinedale age equivalents), and loess/slopewash sediments overlying basalt flows. Backhoe trenches were dugmore » to allow characterization of stratigraphy and soil development. Each mound has features unique to the depositional and pedogenic history of the site; however, there are common elements to all mounds that are linked to the history of mound formation. Each mound has a {open_quotes}floor{close_quotes} of a sediment or basement rock of significantly different hydraulic conductivity than the overlying sediment. These paleosurfaces are overlain by finer-grained sediments, typically loess or flood-overbank deposits. Mounds formed in environments where a sufficient thickness of fine-grained sediment held pore water in a system open to the migration to a freezing front. Heaving of the sediment occurred by the growth of ice lenses. Mound formation occurred at the end of the Late Pleistocene or early in the Holocene, and was followed by pedogenesis. Soils in the mounds were subsequently altered by bioturbation, buried by eolian deposition, and eroded by slopewash runoff. These secondary processes played a significant role in maintaining or increasing the mound/intermound relief.« less
Diagenetic Crystal Growth in the Murray Formation, Gale Crater, Mars

NASA Technical Reports Server (NTRS)

Kah, L. C.; Kronyak, R. E.; Ming, D. W.; Grotzinger, J. P.; Schieber, J.; Sumner, D. Y.; Edgett, K. S.

2015-01-01

The Pahrump region (Gale Crater, Mars) marks a critical transition between sedimentary environments dominated by alluvial-to-fluvial materials associated with the Gale crater rim, and depositional environments fundamentally linked to the crater's central mound, Mount Sharp. At Pahrump, the Murray formation consists of an approximately 14-meter thick succession dominated by massive to finely laminated mudstone with occasional interbeds of cross-bedded sandstone, and is best interpreted as a dominantly lacustrine environment containing tongues of prograding fluvial material. Murray formation mudstones contain abundant evidence for early diagenetic mineral precipitation and its subsequent removal by later diagenetic processes. Lenticular mineral growth is particularly common within lacustrine mudstone deposits at the Pahrump locality. High-resolution MAHLI images taken by the Curiosity rover permit detailed morphological and spatial analysis of these features. Millimeter-scale lenticular features occur in massive to well-laminated mudstone lithologies and are interpreted as pseudomorphs after calcium sulfate. The distribution and orientation of lenticular features suggests deposition at or near the sediment-water (or sediment-air) interface. Retention of chemical signals similar to host rock suggests that original precipitation was likely poikilotopic, incorporating substantial amounts of the primary matrix. Although poikilotopic crystal growth is common in burial environments, it also occurs during early diagenetic crystal growth within unlithified sediment where high rates of crystal growth are common. Loss of original calcium sulfate mineralogy suggests dissolution by mildly acidic, later-diagenetic fluids. As with lenticular voids observed at Meridiani by the Opportunity Rover, these features indicate that calcium sulfate deposition may have been widespread on early Mars; dissolution of depositional and early diagenetic minerals is a likely source for both calcium and sulfate ion-enrichment in burial fluids that precipitated in ubiquitous late-stage hydrofracture veins
Depositional History of the Western Amundsen Basin, Arctic Ocean, and Implications for Neogene Climate and Oceanographic Conditions

NASA Astrophysics Data System (ADS)

Hopper, J. R.; Castro, C. F.; Knutz, P. C.; Funck, T.

2017-12-01

Seismic reflection data collected in the western Amundsen Basin as part of the Law of the Sea program for the Kingdom of Denmark show a uniform and continuous cover of sediments over oceanic basement. An interpretation of seismic facies units shows that the depositional history of the basin reflects changing tectonic, climatic, and oceanographic conditions throughout the Cenozoic. In this contribution, the Miocene to present history is summarized. Two distinct changes in the depositional environment are proposed, first in response to the development of a deep water connection between the Arctic and North Atlantic, and the second in response to the onset of perennial sea ice cover in the Arctic. In the early to mid-Miocene, a buildup of contourite deposits indicates a distinct change in sedimentation that is particularly well developed near the flank of the Lomonosov Ridge. It is suggested that this is a response to the opening of the Fram Strait and the establishment of geostrophic bottom currents that flowed from the Laptev Sea towards Greenland. These deposits are overlain by a seismic facies unit characterized by buried channels and erosional features. These include prominent basinward levee systems that suggest a channel morphology maintained by overbank deposition of muddy sediments carried by suspension currents periodically spilling over the channel pathway. These deposits indicate a change to a much higher energy environment that is proposed to be a response to brine formation associated with the onset of perennial sea ice cover in the Arctic Ocean. This interpretation implies that the development of extensive sea ice cover results in a significant change in the energy environment of the ocean that is reflected in the depositional and erosional patterns observed. The lack of similar high energy erosional features and the presence of contourite deposits throughout most of the Miocene may indicate the Arctic Ocean was relatively ice-free until the very latest Miocene.
Perennially ice-covered Lake Hoare, Antarctica: physical environment, biology and sedimentation

NASA Technical Reports Server (NTRS)

Wharton, R. A. Jr; Simmons, G. M. Jr; McKay, C. P.; Wharton RA, J. r. (Principal Investigator)

1989-01-01

Lake Hoare (77 degrees 38' S, 162 degrees 53' E) is a perennially ice-covered lake at the eastern end of Taylor Valley in southern Victoria Land, Antarctica. The environment of this lake is controlled by the relatively thick ice cover (3-5 m) which eliminates wind generated currents, restricts gas exchange and sediment deposition, and reduces light penetration. The ice cover is in turn largely controlled by the extreme seasonality of Antarctica and local climate. Lake Hoare and other dry valley lakes may be sensitive indicators of short term (< 100 yr) climatic and/or anthropogenic changes in the dry valleys since the onset of intensive exploration over 30 years ago. The time constants for turnover of the water column and lake ice are 50 and 10 years, respectively. The turnover time for atmospheric gases in the lake is 30-60 years. Therefore, the lake environment responds to changes on a 10-100 year timescale. Because the ice cover has a controlling influence on the lake (e.g. light penetration, gas content of water, and sediment deposition), it is probable that small changes in ice ablation, sediment loading on the ice cover, or glacial meltwater (or groundwater) inflow will affect ice cover dynamics and will have a major impact on the lake environment and biota.
Sediment storage time in a simulated meandering river's floodplain, comparisons of point bar and overbank deposits

NASA Astrophysics Data System (ADS)

Ackerman, T. R.; Pizzuto, J. E.

2016-12-01

Sediment may be stored briefly or for long periods in alluvial deposits adjacent to rivers. The duration of sediment storage may affect diagenesis, and controls the timing of sediment delivery, affecting the propagation of upland sediment signals caused by tectonics, climate change, and land use, and the efficacy of watershed management strategies designed to reduce sediment loading to estuaries and reservoirs. Understanding the functional form of storage time distributions can help to extrapolate from limited field observations and improve forecasts of sediment loading. We simulate stratigraphy adjacent to a modeled river where meander migration is driven by channel curvature. The basal unit is built immediately as the channel migrates away, analogous to a point bar; rules for overbank (flood) deposition create thicker deposits at low elevations and near the channel, forming topographic features analogous to natural levees, scroll bars, and terraces. Deposit age is tracked everywhere throughout the simulation, and the storage time is recorded when the channel returns and erodes the sediment at each pixel. 210 ky of simulated run time is sufficient for the channel to migrate 10,500 channel widths, but only the final 90 ky are analyzed. Storage time survivor functions are well fit by exponential functions until 500 years (point bar) or 600 years (overbank) representing the youngest 50% of eroded sediment. Then (until an age of 12 ky, representing the next 48% (point bar) or 45% (overbank) of eroding sediment), the distributions are well fit by heavy tailed power functions with slopes of -1 (point bar) and -0.75 (overbank). After 12 ky (6% of model run time) the remainder of the storage time distributions become exponential (light tailed). Point bar sediment has the greatest chance (6%) of eroding at 120 years, as the river reworks recently deposited point bars. Overbank sediment has an 8% chance of eroding after 1 time step, a chance that declines by half after 3 time steps. The high probability of eroding young overbank deposits occurs as the river reworks recently formed natural levees. These results show that depositional environment affects river floodplain storage times shorter than a few centuries, and suggest that a power law distribution with a truncated tail may be the most reasonable functional fit.
Geomorphology-based interpretation of sedimentation rates from radiodating, lower Passaic River, New Jersey, USA.

PubMed

Erickson, Michael J; Barnes, Charles R; Henderson, Matthew R; Romagnoli, Robert; Firstenberg, Clifford E

2007-04-01

Analysis of site geomorphology and sedimentation rates as an indicator of long-term bed stability is central to the evaluation of remedial alternatives for depositional aquatic environments. In conjunction with various investigations of contaminant distribution, sediment dynamics, and bed stability in the Passaic River Estuary, 121 sediment cores were collected in the early 1990s from the lower 9.7 km of the Passaic River and analyzed for lead-210 (210Pb), cesium-137 (137Cs), and other analytes. This paper opportunistically uses the extensive radiochemical dataset to examine the spatial patterns of long-term sedimentation rates in, and associated geomorphic aspects of, this area of the river. For the purposes of computing sedimentation rates, the utility of the 210Pb and 137Cs depositional profiles was assessed to inform appropriate interpretation. Sedimentation rates were computed for 90 datable cores by 3 different methods, depending on profile utility. A sedimentation rate of 0 was assigned to 17 additional cores that were not datable and for which evidence of no deposition exists. Sedimentation patterns were assessed by grouping results within similar geomorphic areas, delineated through inspection of bathymetric data. On the basis of channel morphology, results reflect expected patterns, with the highest sedimentation rates observed along point bars and channel margins. The lowest rates of sedimentation (and the largest percentage of undatable cores) were observed in the areas along the outer banks of channel bends. Increasing sedimentation rates from upstream to downstream were noted. Average and median sedimentation rates were estimated to be 3.8 and 3.7 cm/y, respectively, reflecting the highly depositional nature of the Passaic River estuary. This finding is consistent with published descriptions of long-term geomorphology for Atlantic Coastal Plain estuaries.
Sediment characteristics and configuration within three dam impoundments on the Kalamazoo River, Michigan, 2000

USGS Publications Warehouse

Rheaume, S.J.; Rachol, C.M.; Hubbell, D.L.; Simard, Andreanne

2002-01-01

The removal of the remnants of three hydroelectric dams on the Kalamazoo River near Plainwell, Otsego, and Allegan, Michigan, has been proposed. The benefits of this removal include returning the Kalamazoo River to its pre-dam flow, increasing recreational use and safety on the river, and improving aquatic habitat. The U.S. Environmental Protection Agency has designated this reach of the Kalamazoo River as a Federal Superfund site because of the historical discharge of papermill waste containing polychlorinated biphenyls. Much of this waste material remains concentrated in organic sediment and kaolinite clay deposited upstream from the three dam foundations. Sediment containing up to 150 milligrams per kilogram polychlorinated biphenyls could move if dam foundations are removed; therefore, it is necessary to estimate the characteristic and configuration of the sediment before work begins. Data collected from augered sections and sediment cores show that impoundment sediments were deposited in two distinctly different sedimentary environments. Interbedded lacustrine sediments that overlie the pre-dam channel surface consist of organic-rich silt and clay, fine to medium sand, and some gravel. These materials were deposited in a repetitive, cyclic fashion related to former stream velocities when the impoundment water levels were 5-10 feet higher. Lowering of these water levels and demolition of the superstructures of these dams resulted in erosion of much of these instream lacustrine sediments and subsequent deposition of coarse-grained alluvium in the impounded channel behind the remaining dam foundations. The composite thicknesses of the lacustrine deposits and overlying alluvium was determined from sediment cores collected from each impoundment. The volume of instream sediment contained in each impoundment is estimated to be about 77,600 cubic yards at the Plainwell impoundment; 268,900 cubic yards at the Otsego impoundment; and 1,192,600 cubic yards at the Trowbridge impoundment. Estimates do not include bank or flood-plain deposits.
Sedimentological Characteristics and Classification of Depositional Processes and Deposits in the Glacial Environment,

DTIC Science & Technology

1981-12-01

I characteristics and classification of depositional processes and d,4, r -%sits in the glacial environment C",. 44k (1-I J For conversion of SI metric...Discussion with Dr. John Shaw, Dr. Geoffrey Boulton, Dr. David Croot and Dr. Ross Powell helped considerably in formulating ideas presented in this report...glacial or non- glacial origins of diamictites of Precambrian and COMPARISON OF MELT-OUT other ages (e.g., Schermerhorn 1974, Edwards AND SEDIMENT FLOW

Late Pleistocene dune-sourced alluvial fans in coastal settings: Sedimentary facies and related processes (Mallorca, Western Mediterranean)

NASA Astrophysics Data System (ADS)

Pomar, F.; del Valle, L.; Fornós, J. J.; Gómez-Pujol, L.

2018-05-01

Aeolian-alluvial sedimentary interaction results in the formation of deposits characterized by typical alluvial sedimentary structures, but is composed of conspicuous amounts of aeolian sediments. The literature on this topic is limited and most works relate more with continental aeolian dunes or fluvial dune interference with fan bodies. Furthermore, there is a lack of examples of aeolian-alluvial sedimentary interference in coastal settings. In the western Mediterranean, there are many Pleistocene alluvial fan deposits built up partly by sediment originating from coastal dunes dismantled by alluvial streams. Very often, these deposits show a continuous sedimentary sequence through which we can derive the contribution and predominance of coastal, alluvial-colluvial and aeolian processes and their controls on landscape formation. This is an outstanding feature within coastal systems since it shows marine sediments reworked and integrated within coastal dune fields by aeolian transport, and the latter built up into alluvial fan bodies. In this sense, aeolian-alluvial interaction is the geomorphic-sedimentary expression of the coexistence and overlapping of alluvial and aeolian environments resulting in deposits sharing sedimentary features from both environments. The aim of this paper is to unravel the contribution of coastal dunes in the construction of alluvial fans bodies and identify the main sedimentary facies that constitute these deposits, as well as their climatic controls. For this reason, Es Caló fan (northern Mallorca) has been selected due to its well-exposed deposits exhibiting the alternation of aeolian, alluvial and colluvial deposits. Sedimentological and stratigraphic analyses based on 33 logs and complementary analyses demonstrate that most of the facies constituting the fan body are made up completely of marine bioclastic sands. These deposits record an alluvial fan sedimentary environment characterized by sediments inputs that do not proceed from non-alluvial/fluvial/colluvial systems. In fact they relate with a marine source. Chronologies on aeolianites of northern Mallorca indicate that up to four periods of aeolian deposition took place during cooling stages and marine regressions over the last 100 kyr. Moreover, the alternation of short warming-cooling fluctuations between the cooling stages may have provided the conditions necessary to generate stormy weather in the western Mediterranean, resulting in aeolian-alluvial interactions. Additionally, the dynamics of this sedimentary environment were only possible because during the Last Glacial Maximum, the sea level remained low enough to allow for the formation of coastal dune fields and fans.
Sedimentary architecture and depositional controls of a Pliocene river-dominated delta in the semi-isolated Dacian Basin, Black Sea

NASA Astrophysics Data System (ADS)

Jorissen, Elisabeth L.; de Leeuw, Arjan; van Baak, Christiaan G. C.; Mandic, Oleg; Stoica, Marius; Abels, Hemmo A.; Krijgsman, Wout

2018-06-01

Sedimentological facies models for (semi-)isolated basins are less well developed than those for marine environments, but are critical for our understanding of both present-day and ancient deltaic sediment records in restricted depositional environments. This study considers an 835 m thick sedimentary succession of mid-Pliocene age, which accumulated in the Dacian Basin, a former embayment of the Black Sea. Detailed sedimentological and palaeontological analyses reveal a regression from distal prodelta deposits with brackish water faunas to delta-top deposits with freshwater faunas. Sediments contain frequent hyperpycnal plumes and an enrichment in terrestrial organic material, ichnofossils and in situ brackish and freshwater faunas. Deltaic progradation created thin, sharply-based sand bodies formed by multiple terminal distributary channels, covering a wide depositional area. The system experienced frequent delta-lobe switching, resulting in numerous thin parasequences. Parasequences are overlain by erosive reddish oxidized sand beds, enriched in broken, abraded brackish and freshwater shells. These beds were formed after sediment starvation, on top of abandoned delta lobes during each flooding event. A robust magnetostratigraphic time frame allowed for comparison between the observed sedimentary cyclicity and the amplitude and frequency of astronomical forcing cycles. Our results indicate that parasequence frequencies are significantly higher than the number of time equivalent astronomical cycles. This suggests that delta-lobe switching was due to autogenic processes. We consider the observed facies architecture typical for a delta prograding on a low-gradient slope into a shallow, brackish, protected, semi-isolated basin. Furthermore, in the absence of significant wave and tidal influence, sediment progradation in such a protected depositional setting shaped a delta, strongly river-dominated.
The Jianchuan Basin, Yunnan: Implications on the Evolution of SE Tibet During the Eocene

NASA Astrophysics Data System (ADS)

Gourbet, L.; Mahéo, G.; Leloup, P. H.; Jean-Louis, P.; Sorrel, P.; Eymard, I.; Antoine, P. O.; Sterb, M.; Wang, G.; Cao, K.; Chevalier, M. L.; Lu, H.

2015-12-01

The Jianchuan basin, Yunnan Province, China, is the widest continental Cenozoic sedimentary basin in the southeastern Tibetan plateau. It is located ~10 km east of the Red River fault zone. Climatic simulations and palaeoenvironment studies suggest that SE Asia has experienced a variable intensity monsoon system for 40 Ma. Because sediments can record deformation, climate and environment changes, the Jianchuan basin provides the opportunity to assess the relative role of climate and tectonics on the Tibetan plateau formation. Sediments consist of floodplain siltites, massive fluvial sandstone, few carbonate levels, coal and volcanosedimentary deposits. U/Pb dating of zircons from dykes, volcanodetrital deposits and lava flows respectively cutting and interbedded within the sediments was performed by in-situ LA-ICPMS. All ages range from 38 to 35 Ma. Such absolute dating is confirmed by palaeontological evidence. Dental remains of Zaisanamynodonwere found in coal deposits. This giant Rhino lived in Asia during the Ergilian (late Eocene). Our data allow us to propose a revised stratigraphy for the Jianchuan basin: contrary to what was suggested by previous studies, i.e. a continuous sedimentation from the Paleocene to the Miocene, nearly no sedimentation occurred after 34 Ma. Combined with a sedimentological analysis, the data indicate that during the late Eocene, the Jianchuan area was covered by a large (>15 km) braided river system that coexisted with local transient lakes, in a moderate-slope and semi-arid environment. This major sedimentation event was followed by a period of more humid conditions that may be related to an intensification of the monsoon. The end of the sedimentation seems to be contemporaneous with the Ailao Shan-Red River fault activation. The new stratigraphy has also implications for regional studies that need robust age constraints, for example for reconstructing palaeoelevation or provenance of sediments.
Controls on subglacial patterns and depositional environments in western Ireland

NASA Astrophysics Data System (ADS)

Knight, J.

2009-12-01

In western Ireland, Late Devensian ice flow dynamics and resultant patterns of landforms and sediments reflect the interplay between internal (glaciological) forcing and external forcing by rapid climate changes centred on the adjacent Atlantic Ocean. This interplay can be best demonstrated where ice from climatically-sensitive mountain source regions flowed into surrounding lowlands, such as the Connemara region of west County Galway, western Ireland. Here, a semi-independent ice cap was present over the Twelve Bens mountains, and interacted with ice from the much larger regional ice sheet from central Ireland. Landform and sediment patterns in the flat lowland region (c. 100 km2 below 30 m asl) to the south of the Twelve Bens reflect elements of this ice interaction. In detail, landform and sediment distributions here are highly complex with marked spatial differences in patterns of sediment availability. Across much of the region, sculpted bedrock forms (whaleback and bedrock drumlin ridges, roches mountonnées, striae) reflect subglacial abrasion across the underlying igneous and metamorphic bedrock that forms a relatively flat and lake-dominated landscape. Glacigenic sediments are found only at or around ice-retreat margins, and within isolated bedrock valleys. Here, diamicton drumlins are relatively uncommon but yet must represent depositional conditions that are not reflected elsewhere in this ice sheet sector where subglacial sediments are generally absent. This paper explores the interrelationship between local and regional ice flows through their impact on spatial patterns of glacial landforms and sediments. The paper presents field data on the characteristics of bedrock forms (erosional) and diamicton drumlins (depositional). Subglacial sediments are described from drumlin outcrops at key sites around Connemara, which helps in the understanding of the evolution of the subglacial environment in response to ice interactions from different source regions.
Holocene evolution of the western Orinoco Delta, Venezuela

USGS Publications Warehouse

Aslan, A.; White, W.A.; Warne, A.G.; Guevara, E.H.

2003-01-01

The pristine nature of the Orinoco Delta of eastern Venezuela provides unique opportunities to study the geologic processes and environments of a major tropical delta. Remote-sensing images, shallow cores, and radiocarbon-dating of organic remains form the basis for describing deltaic environments and interpreting the Holocene history of the delta. The Orinoco Delta can be subdivided into two major sectors. The southeast sector is dominated by the Rio Grande-the principal distributary-and complex networks of anastomosing fluvial and tidal channels. The abundance of siliciclastic deposits suggests that fluvial processes such as over-bank flooding strongly influence this part of the delta. In contrast, the northwest sector is represented by few major distributaries, and overbank sedimentation is less widespread relative to the southeast sector. Peat is abundant and occurs in herbaceous and forested swamps that are individually up to 200 km2 in area. Northwest-directed littoral currents transport large volumes of suspended sediment and produce prominent mudcapes along the northwest coast. Mapping of surface sediments, vegetation, and major landforms identified four principal geomorphic systems within the western delta plain: (1) distributary channels, (2) interdistributary flood basins, (3) fluvial-marine transitional environments, and (4) marine-influenced coastal environments. Coring and radiocarbon dating of deltaic deposits show that the northern delta shoreline has prograded 20-30 km during the late Holocene sea-level highstand. Progradation has been accomplished by a combination of distributary avulsion and mudcape progradation. This style of deltaic progradation differs markedly from other deltas such as the Mississippi where distributary avulsion leads to coastal land loss, rather than shoreline progradation. The key difference is that the Orinoco Delta coastal zone receives prodigious amounts of sediment from northwest-moving littoral currents that transport sediment from as far away as the Amazon system (???1600 km). Late Holocene progradation of the delta has decreased delta-plain gradients, increased water levels, and minimized over-bank flooding and siliciclastic sedimentation in the northwest sector. These conditions, coupled with large amounts of direct precipitation, have led to widespread peat accumulation in interdistributary basins. Because peat-forming environments cover up to 5000 km2 of the delta plain, the Orinoco may be an excellent analogue for interpreting ancient deltaic peat deposits.
Geology of the Ivanhoe Hg-Au district, northern Nevada: Influence of Miocene volcanism, lakes, and active faulting on epithermal mineralization

USGS Publications Warehouse

Wallace, A.R.

2003-01-01

The mercury-gold deposits of the Ivanhoe mining district in northern Nevada formed when middle Miocene rhyolitic volcanism and high-angle faulting disrupted a shallow lacustrine environment. Sinter and replacement mercury deposits formed at and near the paleosurface, and disseminated gold deposits and high-grade gold-silver veins formed beneath the hot spring deposits. The lacustrine environment provided abundant meteoric water; the rhyolites heated the water; and the faults, flow units, and lakebeds provided fluid pathways for the hydrothermal fluids. A shallow lake began to develop in the Ivanhoe area about 16.5 Ma. The lake progressively expanded and covered the entire area with fine-grained lacustrine sediments. Lacustrine sedimentation continued to at least 14.4 Ma, and periodic fluctuations in the size and extent of the lake may have been responses to both climate and nearby volcanism. The eruption of rhyolite and andesite flows and domes periodically disrupted the lacustrine environment and produced interfingered flows and lake sediments. The major pulse of rhyolitic volcanism took place between 15.16 ± 0.05 and 14.92 ± 0.05 Ma. High-angle faulting began in the basement about 15.2 Ma, penetrated to and disrupted the paleosurface after 15.10 ± 0.06 Ma, and largely ceased by 14.92 ± 0.05 Ma. Ground motion related to both faulting and volcanism created debris flows and soft-sediment deformation in the lakebeds. Mercury-gold mineralization was coeval with rhyolite volcanism and high-angle faulting, and it took place about 15.2 to 14.9 Ma. At and near the paleosurface, hydrothermal fluids migrated through tuffaceous sediments above relatively impermeable volcanic and Paleozoic units, creating chalcedonic, cinnabar-bearing replacement bodies and sinters. Disseminated gold was deposited in sedimentary and volcanic rocks beneath the mercury deposits, although the hydrologic path between the two ore types is unclear. Higher-grade gold-silver deposits formed in massive rhyolites and Paleozoic quartzites at deeper levels, and these mineralized zones possibly represent the feeder zones for the higher-level deposits. Fluctuations in the ground-water table locally produced hydrothermal oxidation of the near-surface mercury and disseminated gold deposits. The locus of mineralization shifted with time, moving south and east from its inception point in the west-central part of the district. Thus, although mineralization in the district took place during a span of 300,000 years, the duration of mineralization at any one place probably was much shorter. The low-sulfidation deposits of the Ivanhoe district formed at the same time and under similar conditions as those in the nearby Midas district, 15 km to the northwest, which includes the large, high-grade Ken Snyder gold-silver epithermal vein deposit. The exposures in the Ivanhoe district are interpreted to represent the near-surface example of the paleosurface that originally was present above the Midas mineralizing system. The resulting combined Ivanhoe-Midas model provides an exploration guide for epithermal deposits in similar geologic environments in northern Nevada.
Changes in wetland sediment elevation following major storms: implications for estimating trends in relative sea-level rise

USGS Publications Warehouse

Cahoon, D.R.

2003-01-01

Hurricanes can be important agents of geomorphic change in coastal marshes and mangrove forests. Hurricanes can cause large-scale redistribution of sediments within the coastal environment resulting in sedimentation, erosion, disruption of vegetated substrates, or some combination of these processes in coastal wetlands. It has been proposed that such sediment pulsing events are important at maintaining wetland sediment elevations in sediment-poor settings with high rates of relative sea-level rise, such as the Mississippi River Delta. But do these pulsing events result in a net gain in sediment elevation even when substantial amounts of sediment are deposited? Clearly sediment erosion and scour would result in a loss of elevation. But will a substantial sediment deposit on poorly consolidated sediments always result in a net gain in elevation? If the wetland vegetation is killed by wind, tidal surge, or the introduction of saline water, will there be a collapse of sediment elevation in the absence of root production and ongoing decomposition of root matter? During the past decade several wetlands where my colleagues and I have monitored sedimentation and elevation change have been struck by one to several hurricanes. This paper describes the range of sediment elevation responses to hurricane strikes, the suggested mechanisms driving those responses, the implications for estimating long-term trends in relative sea-level rise, and future research needs for improving our understanding of the role that major storms play in wetland sediment elevation dynamics. For many wetlands the change in sediment elevation was directly proportional to the amount of sediment deposited by the storm. But surprisingly, there was a loss of elevation in some wetlands with substantial sediment deposits. In these wetlands, the impact of the storm was either direct (sedimentation and compaction) or indirect (vegetation death), and the effect on sediment elevation was either permanent or temporary. For example, 2 cm of sediment deposited by Hurricane Andrew on a healthy salt marsh in south Louisiana had a direct and positive effect on sediment elevation. But in a deteriorated salt marsh a 3 cm thick sediment deposit was associated with a permanent loss in elevation (we have monitored this site for 10 years). The apparent mechanism driving elevation loss was compaction of the weakened substrate by the weight of the sediment deposit, the storm surge waters, or both. Clearly, storm-related sediment pulses are not going to save this marsh from becoming submerged by rising sea level. A temporary loss in elevation, as much as 2 cm, was observed in a North Carolina salt marsh with a highly organic substrate after each of 3 successive hurricanes even when sediment was deposited. The loss in elevation was apparently related to degassing of the chronically flooded substrate while the rebound in elevation was apparently related to a temporary drawdown of marsh water levels. Interestingly, sediment elevation increased after Hurricane Dennis in 1999, although the increase was less than the thickness of the sediment deposit. Further research is required to determine the mechanisms driving storm-related elevation change (i.e., compaction and expansion) in this marsh. There were two marshes where the gain in sediment elevation was greater than the thickness of the sediment deposit, but the effect was short-lived. In a high salt marsh in southern California, we hypothesize that the temporary spike in elevation was related to the flushing of salts from the hypersaline soils, which enhanced root growth that led to an increase in elevation. In a marsh with a highly organic substrate in north Florida, temporary increases in elevation (as much as 2 cm) greater than the thickness of the sediment deposit were apparently related to groundwater fluxes, which may have been influenced by enhanced runoff from storm rainfall. Lastly, Hurricane Mitch
Mudstone sedimentation at high latitudes: Ice as a transport medium for mud and supplier of nutrients

USGS Publications Warehouse

Macquaker, J.H.S.; Keller, M.A.

2005-01-01

Controls on mudstone deposition at high latitudes are poorly known relative to low latitudes. In recent sediments deposited in these environments, ice significantly influences sediment transport and primary productivity. The products of ice transport are relatively well known in glacimarine settings, but are less well known from below melting sea ice. This latter setting is significant as today it is associated with high primary organic productivity. The aim of this study is to assess how sea ice might have controlled lithofacies variability and organic-matter distribution and preservation in an ancient marine, siliciclastic mudstone-dominated succession deposited at high latitudes. Combined sedimentary logging, optical and electron optical (back-scatte red electron imagery), geochemical, and isotopic methods were used to determine sample variability in forty-five samples collected from the Lower Cretaceous succession in the Mikkelsen Bay State #1 borehole (North Slope, Alaska). The succession overall fines upward and contains muddy sandstones and sand- and silt-bearing, clay-rich mudstones towards its base in contrast to clay-rich and clay-dominated mudstones towards its top. Some of the mudstone units exhibit thin (< 5 mm), relic-beds that fine upward weakly. In some units small (0.5 mm), bed-parallel silt-filled microburrows disrupt depositional laminae whereas in others pervasive burrowing completely obliterates original depositional textures. Many of the units are pelleted. These mudstones are unusual in that they contain minor but very striking outsize grains, composed of subrounded to rounded sand and granule-size material. In addition, they are good petroleum source rocks, with between 2.8 and 5.9 wt % total organic carbon, of predominantly Type II kerogen. The organic matter has an isotopic signature ranging from -25.4??? ??13C to -28.1??? ??13C. Thin tuffs (< 20 mm) and carbonate-cemented units are also present. Given the absence of significant polar ice in the Early Cretaceous the outsized grains are interpreted to have been deposited from a combination of melting, dirty anchor, and fast ice. The mud fraction, which forms the bulk of the sediment, is interpreted to have been deposited from melting, sediment-laden frazil ice, and fast ice. After deposition sediments were partially reworked by bottom currents generated by brine rejection during sea ice formation. Sympagic organisms, grazing on algae and bacteria both within and below the ice, pelleted the sediment. Bioturbation, which varies through the succession, indicates that sedimentation probably occurred beneath a predominantly oxic or dysoxic water column. In this setting productivity was fueled by nutrients released from melting sea ice in the marginal ice zone. The good petroleum source potential of these mudstones is attributed to high organic productivity coupled to episodic and rapid sedimentation rather than existence of bottom-water anoxia linked to upwelling. Because sea-ice rafting was probably the dominant sediment transport mechanism it is not appropriate to use sequence stratigraphic methodology to predict lithofacies variability in this environment. Copyright ?? 2005, SEPM (Society for Sedimentary Geology).
Predictions of Bedforms in Tidal Inlets and River Mouths

DTIC Science & Technology

2016-07-31

that community modeling environment. APPROACH Bedforms are ubiquitous in unconsolidated sediments . They act as roughness elements, altering the...flow and creating feedback between the bed and the flow and, in doing so, they are intimately tied to erosion, transport and deposition of sediments ...With this approach, grain-scale sediment transport is parameterized with simple rules to drive bedform-scale dynamics. Gallagher (2011) developed a
Origin of intraformational folds in the Jurassic Todilto Limestone, Ambrosia Lake uranium mining district, McKinley and Valencia counties, New Mexico

USGS Publications Warehouse

Green, M.W.

1982-01-01

The Todilto Limestone of Middle Jurassic age in the Ambrosia Lake uranium mining district of McKinley and Valencia Counties, New Mexico, is the host formation for numerous small- to medium-sized uranium deposits in joints, shear zones, and fractures within small- to large-scale intraformational folds. The folds probably were formed as a result of differential sediment loading when eolian sand dunes of the overlying Summerville Formation of Middle Jurassic age migrated over soft, chemically precipitated, lime muds of the Todilto shortly after their deposition in a regressive, mixed fresh and saline lacustrine or marine environment of deposition. Encroachment of Summerville eolian dunes over soft Todilto lime muds was apparently a local phenomenon and was restricted to postulated beltlike zones which trended radially across the Todilto coastline toward the receding body of water. Intraformational folding is believed to be confined to the pathways of individual eolian dunes or clusters of dunes within the dune belts. During the process of sediment loading by migrating sand dunes, layers of Todilto lime mud were differentially compacted, contorted, and dewatered, producing both small- and large-scale plastic deformation structures, including convolute laminations, mounds, rolls, folds, and small anticlines and synclines. With continued compaction and dewatering, the mud, in localized areas, reached a point of desaturation at which sediment plasticity was lost. Prolonged loading by overlying dune sands thus caused faulting, shearing, fracturing, and jointing of contorted limestone beds. These areas or zones of deformation within the limestone became the preferred sites of epigenetic uranium mineralization because of the induced transmissivity created by sediment rupture. Along most of the prograding Todilto coastline, adjacent to the eolian dune belts, both interdune and coastal sabkha environments dominated during Todilto-Summerville time. Sediments in coastal areas consisted mainly of clay, silt, sandy silt, and very fine-grained sand, which was apparently derived from the winnowing of the finer grained fraction of sediment from adjacent dune fields during periods of eolian activity. Most of the sabkha sediments were probably carried in airborne suspension to the low-lying, ground-water-saturated coastal areas, where they were deposited as relatively uniform blanket-like layers. Deposition of sabkha deposits was apparently slow and uniform over most of the Todilto coastal areas and crested only small-scale deformation features in underlying Todilto rocks. Large-scale deformation features and uranium deposits are both notably absent in the Todilto where it is overlain by finer textured sabkha deposits in the Summerville.
Archean sedimentary styles and early crustal evolution

NASA Technical Reports Server (NTRS)

Lowe, D. R.

1986-01-01

The distinctions between and implications of early and late Archean sedimentary styles are presented. Early Archean greenstone belts, such as the Barberton of South Africa and those in the eastern Pilbar Block of Australia are characterized by fresh or slightly reworked pyroclastic debris, orthochemical sediments such as carbonates, evaporites, and silica, and biogenic deposits including cherts and stromatolitic units. Terrigenous deposits are rare, and it is suggested that early Archean sediments were deposited on shallow simatic platforms, with little or no components derived from sialic sources. In contrast, late Archean greenstone belts in the Canadian Shield and the Yilgarn Block of Australia contain coarse terrigenous clastic rocks including conglomerate, sandstone, and shale derived largely from sialic basement. Deposition appears to have taken place in deepwater, tectonically unstable environments. These observations are interpreted to indicate that the early Archean greenstone belts formed as anorogenic, shallow water, simatic platforms, with little or no underlying or adjacent continental crust, an environment similar to modern oceanic islands formed over hot spots.
Structural deformation and sedimentation in an active Caldera, Rabaul, Papua New Guinea

USGS Publications Warehouse

Greene, H. Gary; Tiffin, D.L.; McKee, C.O.

1986-01-01

Recent seismic and tectonic activity in Rabaul Caldera, Papua New Guinea, suggests that magma is accumulating at a shallow depth beneath this partially submerged structure and that a new volcano may be developing. Changes in onshore elevation since 1971 (as much as 2 m on south Matupit Island) indicate that rapid and large-scale uplifts have occurred on the seafloor near the center of the caldera. The frequency of seismic events within the caldera has also increased during this period. Earthquake locations define an elliptical ring surrounding the center of this uplift within the caldera. A marine geophysical survey in 1982 by the U.S. Geological Survey's R/V "S.P. Lee" in Rabaul Caldera shows the development of a bulge in the seafloor near the center of the caldera. High-resolution seismic reflection profiles show that this bulge consists of two domal uplifts bounded and separated by two major north-south-trending fault zones. Deformed sediments overlie these zones; a prominent slump flanks the area of the bulge. Five major acoustic units were identified in the seismic reflection profiles: an acoustic basement and four sedimentary units consisting of irregularly layered, cross-layered, contorted, and well-layered sequences. The acoustic basement is probably composed of crystalline volcanic rocks, and the layered acoustic units are probably sediments, primarily ash deposited in different environments. The cross-layered, irregularly layered, and contorted units appear to have been deposited in a dynamic environment subjected to strong currents, seismicity, and/or mass wasting, while the well-layered units were deposited in a low-energy environment. Locally, well-layered sequences interfinger with the other sedimentary units, indicating a transitional environment that alternated between high-energy and low-energy depositional processes. A submarine channel cuts most of the acoustic units and appears to be the conduit for sediment transport out of the caldera; it occupies an older buried channel north of the caldera that is presently being exhumed. In the south, active erosion of well-layered sediments is taking place. What are believed to be several young volcanic cones also disrupt the depositional layers. We conclude that the bulge in the seafloor and the associated fault zones are a result of emplacement of magma at a shallow depth. Contorted sediment and slumps adjacent to the bulge are probably the result of uplift and seismic activity. The pattern of seismicity appears to reflect increased magma pressure at depth beneath the caldera floor. This activity may eventually lead to an eruption. ?? 1986.
Stratigraphy, sedimentology, and volume of sediments behind a dam relic on the Muskegon River, Big Rapids, Michigan

USGS Publications Warehouse

Westjohn, David B.

1997-01-01

The proposed removal of the remnants of a hydroelectric dam in the Muskegon River at Big Rapids, Michigan, will potentially affect flow of the river at the city's water intake system. Fifteen boreholes were augered in bottom sediments in the river just upstream from the dam relic, and streambottom profiles were made using ground-penetrating radar. Data from boreholes show that sediments captured by the dam foundation were deposited in two distinctly different sedimentary environments. Sediments that overlie the pre-dam channel surface consist of lacustrine clay, wood chips, silt, and sand. These lacustrine sediments are interbedded in a cyclical fashion, and they were deposited under low flow to stagnant water conditions during 1916-66, when a 17-foot-tall hydroelectric dam was in place. Demolition of the upper 13 feet of this dam in 1966 resulted in erosion of most of the lacustrine sediments, and subsequent deposition of coarser alluvium in the impoundment behind the remaining dam foundation. Lacustrine sediments are present in the active part of the stream channel and extend from the dam foundation to about 1,300 feet upstream. The composite thickness of lacustrine sediments and overlying coarser alluvium was determined from sediment cores collected from the boreholes. The volume of these sediments is estimated to be about 19,000 cubic yards.
Aquatic ecosystems in Central Colorado are influenced by mineral forming processes and historical mining

USGS Publications Warehouse

Schmidt, T.S.; Church, S.E.; Clements, W.H.; Mitchell, K.A.; Fey, D. L.; Wanty, R.B.; Verplanck, P.L.; San, Juan C.A.; Klein, T.L.; deWitt, E.H.; Rockwell, B.W.

2009-01-01

Stream water and sediment toxicity to aquatic insects were quantified from central Colorado catchments to distinguish the effect of geologic processes which result in high background metals concentrations from historical mining. Our sampling design targeted small catchments underlain by rocks of a single lithology, which allowed the development of biological and geochemical baselines without the complication of multiple rock types exposed in the catchment. By accounting for geologic sources of metals to the environment, we were able to distinguish between the environmental effects caused by mining and the weathering of different mineralized areas. Elevated metal concentrations in water and sediment were not restricted to mined catchments. Impairment of aquatic communities also occurred in unmined catchments influenced by hydrothermal alteration. Hydrothermal alteration style, deposit type, and mining were important determinants of water and sediment quality and aquatic community structure. Weathering of unmined porphyry Cu-Mo occurrences resulted in water (median toxic unit (TU) = 108) and sediment quality (TU = 1.9) that exceeded concentrations thought to be safe for aquatic ecosystems (TU = 1). Metalsensitive aquatic insects were virtually absent from streams draining catchments with porphyry Cu-Mo occurrences (1.1 individuals/0.1 m2 ). However, water and sediment quality (TU = 0.1, 0.5 water and sediment, respectively) and presence of metalsensitive aquatic insects (204 individuals/0.1 m2 ) for unmined polymetallic vein occurrences were indistinguishable from that for unmined and unaltered streams (TU = 0.1, 0.5 water and sediment, respectively; 201 individuals/0.1 m2 ). In catchments with mined quartz-sericite-pyrite altered polymetallic vein deposits, water (TU = 8.4) and sediment quality (TU = 3.1) were degraded and more toxic to aquatic insects (36 individuals/0.1 m2 ) than water (TU = 0.4) and sediment quality (TU = 1.7) from mined propylitically altered polymetallic vein deposits. The sampling approach taken in this study distinguishes the effects of different mineral deposits on ecosystems and can be used to more accurately quantify the effect of mining on the environment.
On the application of contemporary bulk sediment organic carbon isotope and geochemical datasets for Holocene sea-level reconstruction in NW Europe

NASA Astrophysics Data System (ADS)

Wilson, Graham P.

2017-10-01

Bulk organic stable carbon isotope (δ13C) and element geochemistry (total organic carbon (TOC) and organic carbon to total nitrogen (C/N)) analysis is a developing technique in Holocene relative sea-level (RSL) research. The uptake of this technique in Northern Europe is limited compared to North America, where the common existence of coastal marshes with isotopically distinctive C3 and C4 vegetation associated with well-defined inundation tolerance permits the reconstruction of RSL in the sediment record. In Northern Europe, the reduced range in δ13C values between organic matter sources in C3 estuaries can make the identification of elevation-dependent environments in the Holocene sediment record challenging and this is compounded by the potential for post-depositional alteration in bulk δ13C values. The use of contemporary regional δ13C, C/N and TOC datasets representing the range of physiographic conditions commonly encountered in coastal wetland sediment sequences opens up the potential of using absolute values of sediment geochemistry to infer depositional environments and associated reference water levels. In this paper, the application of contemporary bulk organic δ13C, C/N and TOC to reconstruct Holocene RSL is further explored. An extended contemporary regional geochemical dataset of published δ13C, C/N and TOC observations (n = 142) from tidal-dominated C3 wetland deposits (representing tidal flat, saltmarsh, reedswamp and fen carr environments) in temperate NW Europe is compiled, and procedures implemented to correct for the 13C Suess effect on contemporary δ13C are detailed. Partitioning around medoids analysis identifies two distinctive geochemical groups in the NW European dataset, with tidal flat/saltmarsh and reedswamp/fen carr environments exhibiting characteristically different sediment δ13C, C/N and TOC values. A logistic regression model is developed from the NW European dataset in order to objectively identify in the sediment record geochemical groups and, more importantly, group transitions, thus allowing the altitude of reference water levels to be determined. The application of this method in RSL research is demonstrated using the Holocene sediments of the Mersey Estuary (UK), in which δ13C, C/N and TOC variability is typical of that encountered in Holocene sediments from C3 coastal wetlands in NW Europe. Group membership was predicted with high probability in the depositional contexts studied and the accuracy of group prediction is verified by microfossil evidence. The method presented facilitates the application of δ13C, C/N and TOC analysis in RSL reconstruction studies in C3 vegetated wetlands throughout temperate NW Europe.
Evaluating post-glacial aggradational rates and transport processes, and assessing impacts of the Grand Ditch on the Lulu City wetland, Rocky Mountain National Park, Colorado

NASA Astrophysics Data System (ADS)

Rubin, Z.; Rathburn, S. L.; Wohl, E. E.

2009-12-01

The success of channel restoration rests in accurately assessing the context for, and goal of, restoration. This research aims to assess the historical range of variability of sedimentation rates and identify historic depositional environments, and to therefore contextualize the impacts of recent anthropogenic sediment inputs. In May 2003, a breach in Grand Ditch initiated a debris flow in Rocky Mountain National Park that transported approximately 36,000 m3 of sediment into the Upper Colorado River. Several other failures of Grand Ditch have occurred since 1937. This research was conducted in the Lulu City wetland, a wide, low gradient portion of the Upper Colorado River where fine sediment deposition occurred in 2003. Similarly, aerial photos show a change from a single thread, meandering channel in 1937 to the presently braided system- suggesting an altered sediment regime that has persisted for seventy years. A ground penetrating radar (GPR) survey was completed to investigate post-glacial sedimentation history of the valley. Trenching, coring, and radiocarbon dating methods were also used to further map sediment deposits, assess aggradational rates, and quantify dominant transport processes (channel, overbank, hillslope, beaver dams). Preliminary interpretation of the GPR reflections suggests approximately 10 meters of sediment exists above bedrock. It appears there is a marked difference between the modern (with anthropogenic influence) and historical sediment regimes. Specifically, the dominant transport process has shifted away from overbank and beaver dam deposits towards a regime dominated by hillslope inputs.
Modern sedimentary environments in a large tidal estuary, Delaware Bay

USGS Publications Warehouse

Knebel, H.J.

1989-01-01

Data from an extensive grid of sidescan-sonar records reveal the distribution of sedimentary environments in the large, tidally dominated Delaware Bay estuary. Bathymetric features of the estuary include large tidal channels under the relatively deep (> 10 m water depth) central part of the bay, linear sand shoals (2-8 m relief) that parallel the sides of the tidal channels, and broad, low-relief plains that form the shallow bay margins. The two sedimentary environments that were identified are characterized by either (1) bedload transport and/or erosion or (2) sediment reworking and/or deposition. Sand waves and sand ribbons, composed of medium to coarse sands, define sites of active bedload transport within the tidal channels and in gaps between the linear shoals. The sand waves have spacings that vary from 1 to 70 m, amplitudes of 2 m or less, and crestlines that are usually straight. The orientations of the sand waves and ribbons indicate that bottom sediment movement may be toward either the northwest or southeast along the trends of the tidal channels, although sand-wave asymmetry indicates that the net bottom transport is directed northwestward toward the head of the bay. Gravelly, coarse-grained sediments, which appear as strongly reflective patterns on the sonographs, are also present along the axes and flanks of the tidal channels. These coarse sediments are lag deposits that have developed primarily where older strata were eroded at the bay floor. Conversely, fine sands that compose the linear shoals and muddy sands that cover the shallow bay margins appear mainly on the sonographs either as smooth featureless beds that have uniform light to moderate shading or as mosaics of light and dark patches produced by variations in grain size. These acoustic and textural characteristics are the result of sediment deposition and reworking. Data from this study (1) support the hypothesis that bed configurations under deep tidal flows are functions of current velocity, sediment size, and depth; (2) suggest criteria that could be used to distinguish between open estuarine tidal deposits in the geologic record; and (3) provide a guide to future utilization of the bay floor. ?? 1989.
Residence times of reef-island sediments constrained by post-mortem precipitates

NASA Astrophysics Data System (ADS)

Mann, Thomas; Wizemann, André; Kench, Paul; Jompa, Jamaluddin; Westphal, Hildegard

2017-04-01

The precipitation of carbonate cements is a rapid process in tropical marine environments. Distinct from calcification, the onset of cementation coincides with the termination of 14C uptake within carbonate-sediment forming organisms. Here we show that this relationship presents new opportunities for examining the temporal lag between organism death and deposition in carbonate systems - the prerequisite for reliable depositional chronologies. We dated skeletal constituents collected from discretely stratified reef-island deposits in Indonesia. In each of the strata, internally least cemented segments of the calcifying green alga Halimeda yield the youngest ages. Complementary mesocosm experiments on cementation rates reveal that post-mortem cement growth initiates within months after transport commences. Continuous pore-filling cementation promptly stabilizes the initially fragile Halimeda skeleton. Furthermore, abrasion experiments show that such cementation significantly increases the durability of segments during transport. Implications of these findings are profound in two respects; first, evaluating residence times of skeletal carbonate constituents based on abrasion features is far from being adequate. Second, the absence of cements within sedimentary Halimeda segments signals that post-mortem transport through the intertidal zone occurred quasi-instantaneously. Radiometric ages from such specimens should minimize the temporal lag between organism death and deposition thus making them reliable indicators of sedimentation in supratidal environments.
The system controlling the composition of clastic sediments

USGS Publications Warehouse

Johnsson, Mark J.

1993-01-01

The composition of clastic sediments and rocks is controlled by a complex suite of parameters operating during pedogenesis, erosion, transport, deposition, and burial. The principal first-order parameters include source rock composition, modification by chemical weathering, mechanical disaggregation and abrasion, authigenic inputs, hydrodynamic sorting, and diagenesis. Each of these first-order parameters is influenced to varying degrees by such factors as the tectonic settings of the source region, transportational system and depositional environment, climate, vegetation, relief, slope, and the nature and energy of transportational and depositional systems. These factors are not independent; rather a complicated web of interrelationships and feedback mechanisms causes many factors to be modulated by others. Accordingly, processes controlling the composition of clastic sediments are best viewed as constituting a system, and in evaluating compositional information the dynamics of the system must be considered as whole.
Legacy Sediments in U.S. River Environments: Atrazine and Aggradation to Zinc and Zoobenthos

NASA Astrophysics Data System (ADS)

Wohl, E.

2014-12-01

Legacy sediments are those that are altered by human activities. Alterations include (i) human-caused aggradation (and subsequent erosion), such as sediment accumulating upstream from relict or contemporary dams, (ii) human-caused lack of continuing deposition that results in changing moisture and nutrient levels within existing sediments, such as on floodplains that no longer receive lateral or vertical accretion deposits because of levees, bank stabilization, and other channel engineering, and (iii) human-generated contaminants such as PCBs and pesticides that adsorb to fine sediment. Existing estimates of human alterations of river systems suggest that legacy sediments are ubiquitous. Only an estimated 2% of river miles in the United States are not affected by flow regulation that alters sediment transport, for example, and less than half of major river basins around the world are minimally altered by flow regulation. Combined with extensive but poorly documented reduction in floodplain sedimentation, as well as sediment contamination by diverse synthetic compounds, excess nutrients, and heavy metals, these national and global estimates suggest that legacy sediments now likely constitute a very abundant type of fluvial sediment. Because legacy sediments can alter river form and function for decades to centuries after the cessation of the human activity that created the legacy sediments, river management and restoration must be informed by accurate knowledge of the distribution and characteristics of legacy sediments. Geomorphologists can contribute understanding of sediment dynamics, including: the magnitude, frequency, and duration of flows that mobilize sediments with adsorbed contaminants; sites where erosion and deposition are most likely to occur under specified flow and sediment supply; residence time of sediments; and the influence of surface and subsurface water fluxes on sediment stability and geochemistry.

Accuracy of post-bomb 137Cs and 14C in dating fluvial deposits

USGS Publications Warehouse

Ely, L.L.; Webb, R.H.; Enzel, Y.

1992-01-01

The accuracy and precision of 137Cs and 14C for dating post-1950 alluvial deposits were evaluated for deposits from known floods on two rivers in Arizona. The presence of 137Cs reliably indicates that deposition occurred after intensive above-ground nuclear testing was initiated around 1950. There was a positive correlation between the measured level of 137Cs activity and the clay content of the sediments, although 137Cs was detected even in sandy flood sediments with low clay content. 137Cs is a valuable dating tool in arid environments where organic materials for 14C or tree-ring dating are scarce and observational records are limited. The 14C activity measured in different types of fine organic detritus yielded dates within 1 to 8 yr of a 1980 flood deposit, and the accuracy was species-dependent. However, undifferentiated mixtures of fine organic materials from several post-bomb deposits of various ages repeatedly yielded dates between 1958 and 1962, and detrital charcoal yielded a date range of 1676-1939. In semiarid environments, the residence time of most types of organic debris precludes accurate annual resolution of post-bomb 14C dates. ?? 1992.
The effect of surface charge, negative and bipolar ionization on the deposition of airborne bacteria.

PubMed

Meschke, S; Smith, B D; Yost, M; Miksch, R R; Gefter, P; Gehlke, S; Halpin, H A

2009-04-01

A series of experiments were conducted to evaluate the effect of surface charge and air ionization on the deposition of airborne bacteria. The interaction between surface electrostatic potential and the deposition of airborne bacteria in an indoor environment was investigated using settle plates charged with electric potentials of 0, +/-2.5kV and +/-5kV. Results showed that bacterial deposition on the plates increased proportionally with increased potential to over twice the gravitational sedimentation rate at +5kV. Experiments were repeated under similar conditions in the presence of either negative or bipolar air ionization. Bipolar air ionization resulted in reduction of bacterial deposition onto the charged surfaces to levels nearly equal to gravitational sedimentation. In contrast, diffusion charging appears to have occurred during negative air ionization, resulting in an even greater deposition onto the oppositely charged surface than observed without ionization. Static charges on fomitic surfaces may attract bacteria resulting in deposition in excess of that expected by gravitational sedimentation or simple diffusion. Implementation of bipolar ionization may result in reduction of bacterial deposition. Fomitic surfaces are important vehicles for the transmission of infectious organisms. This study has demonstrated a simple strategy for minimizing charge related deposition of bacteria on surfaces.
Lithostratigraphie, sédimentologie et évolution de deux bassins molassiques intramontagneux de la chaine Pan-Africaine: la Série pourprée de l'Ahnet, Nord-Ouest du Hoggar, Algérie

NASA Astrophysics Data System (ADS)

Ait-Kaci Ahmed, Ali; Moussine-Pouchkine, Alexis

The study of two of the intermontane molassic basins of the 'Série pourprée de l'Ahnet' shows that they developed independently both in time and space. The characteristics of their thick sedimentary infillings are quite different. The Ouallen basin is filled by essentially fine-grained sediments which were deposited in continental then marine or lacustrine environments; these sediments thicen from east to west. The In Semmen basin is characterised by coarser sediments which were deposited from south to north, in alluvial fan, fluvial, deltaic and slope environments. This basin is also characterised by an episode of carbonate sedimentation leading to the formation of a remarkable thin layer of carbonate, covering the entire sedimentary area, and perhaps related to a volcanic rhyolitic event. The history of the two basins is also marked by obvious tectonic events simultaneous with the sedimentation and related to the recurrent faulting of major Pan-African faults. These led to the formation of very coarse fanglomerates located near the fault scarps, and are probably responsible for the shape and the evolution of the basins.
Environment and Climate Changes during the Holocene: Inferred from Sedimentary Record/Proxies of a Paleodelta Region, Southwest Coast of India

NASA Astrophysics Data System (ADS)

Allu, N. C.; Prakash, V.; Gautam, P. K.; Bera, S. K.

2014-12-01

This work explains the sedimentation history and environment and climate changes during the Holocene along the southwest coast of India. The area is characterized by various landforms such as lagoons, barrier islands, beach ridges, paleostrandlines, alluvial plains, marshy lands and flood plains. Paleodelta, located at the mouth of the modern Periyar River is an important geomorphic marker. A borehole of 40 m depth was drilled in the paleodelta and sediment samples were recovered at different depth intervals. Paleoclimate and paleo-environment were inferred based on geochronology, textural and geotechnical parameters, clay minerals, and pollen analysis results. The bottom of the borehole represents an age of ~ 12 ka BP. Sediments exhibit coarsening texture upwards of the borehole, with fine mud and peat intercalations at the bottom. Six litho facies - muddy sand, sand, sandy mud, silty sand, sandy silt, and mud - were recorded. Geotechnical properties comprising moisture content, organic carbon, plasticity index record high values, whereas low bulk density associated with a low critical shear stress, are recorded. An increase in illite and to a lesser degree smectite with concomitant decrease in kaolinite is observed. Sediment texture represents a major change of depositional environment from marine to fluvial sedimentary facies during the major sea level fall i.e., after 7 ka B.P. The present sea level attained during 4-5 ka B.P; major rise of sea level has taken place from 7-11 ka BP and regression during 7 - 5 ka B.P. These transgression and regression phases introduced the changes in the environment of deposition. The monsoon was dynamic and more intense after the major fall of sea level causing the fluctuations in the fluvial facies. Upward coarsening of grain size in the borehole indicates change in sediment deposition due to increased hydrodynamic conditions and strong fluvial action, which can be linked to marine regression. Geotechnical properties suggest textural changes and sedimentary facies. An upward increase in smectite and kaolinite and decreasing illite supports major fall in sea level and also the aridity. Pollen record of sediment strata supports the paleo-environment dominated by the presence of semi-evergreen type of mangrove plants during mid- to early-Holocene times.
Subsidence driving forces in large Delta Plain

NASA Astrophysics Data System (ADS)

Grall, C.; Steckler, M. S.

2017-12-01

Recent studies show large variability in subsidence rates among large delta plains that directly impact coastal management of these highly vulnerable environments. Observations show both significant spatial variation in subsidence across each delta, as well as large differences in magnitude between different deltas. This variability raises the question of what are the driving forces that control subsidence in large delta plains that this study aims to address. Subsidence and sediment compaction is studied in 4 end-member large Delta Plains: the Ganges-Brahmaputra, the Mekong, the Mississippi and the Nile. Those large delta plains drastically contrast in subsidence rates (from values to several mm/yr to several cm/yr), in the nature of the sediment (notably in clay and organic matter content), and in the volume of sediment supplied by the large rivers that feed those coastal environments. The volume of sediment deposited in each delta plain during the Holocene is estimated and the compaction of the underlying sedimentary column is computed by using a backstripping approach. Sediment compaction behaviors are defined accordingly to the observed clay, silt and organic contents, and the rate of subsidence associated with compaction is determined. Results suggest that about 2/3 of observed Holocene subsidence may be associated with the mechanical and chemical compaction of the underlying sedimentary column due to the load of sediment deposited. The compaction appears to be significantly higher in delta plains characterized by a high sediment input and a high organic matter and clay content. Thus, the observed subsidence rates in the (muddy) Mekong delta appear to be one order of magnitude higher than other delta plains. In contrast, subsidence rates are modest in the Ganges-Brahmaputra, the Mississippi and the Nile delta plains, except away from the major rivers where deposits are muddier.
Sedimentary Processes on Earth, Mars, Titan, and Venus

NASA Astrophysics Data System (ADS)

Grotzinger, J. P.; Hayes, A. G.; Lamb, M. P.; McLennan, S. M.

The production, transport and deposition of sediment occur to varying degrees on Earth, Mars, Venus, and Titan. These sedimentary processes are significantly influenced by climate that affects production of sediment in source regions (weathering), and the mode by which that sediment is transported (wind vs. water). Other, more geological, factors determine where sediments are deposited (topography and tectonics). Fluvial and marine processes dominate Earth both today and in its geologic past, aeolian processes dominate modern Mars although in its past fluvial processes also were important, Venus knows only aeolian processes, and Titan shows evidence of both fluvial and aeolian processes. Earth and Mars also feature vast deposits of sedimentary rocks, spanning billions of years of planetary history. These ancient rocks preserve the long-term record of the evolution of surface environments, including variations in climate state. On Mars, sedimentary rocks record the transition from wetter, neutral-pH weathering, to brine-dominated low-pH weathering, to its dry current state.
Iron and manganese oxide mineralization in the Pacific

USGS Publications Warehouse

Hein, J. R.; Koschinsky, A.; Halbach, P.; Manheim, F. T.; Bau, M.; Jung-Keuk, Kang; Lubick, N.

1997-01-01

Iron, manganese, and iron-manganese deposits occur in nearly all geomorphologic and tectonic environments in the ocean basins and form by one or more of four processes: (1) hydrogenetic precipitation from cold ambient seawater, (2) precipitation from hydrothermal fluids, (3) precipitation from sediment pore waters that have been modified from bottom water compositions by diagenetic reactions in the sediment column and (4) replacement of rocks and sediment. These processes are discussed.
Volcaniclastic habitats for early life on Earth and Mars: A case study from ˜3.5 Ga-old rocks from the Pilbara, Australia

NASA Astrophysics Data System (ADS)

Westall, Frances; Foucher, Frédéric; Cavalazzi, Barbara; de Vries, Sjoukje T.; Nijman, Wouter; Pearson, Victoria; Watson, Jon; Verchovsky, Alexander; Wright, Ian; Rouzaud, Jean-Noel; Marchesini, Daniele; Anne, Severine

2011-08-01

Within the context of present and future in situ missions to Mars to investigate its habitability and to search for traces of life, we studied the habitability and traces of past life in ˜3.5 Ga-old volcanic sands deposited in littoral environments an analogue to Noachian environments on Mars. The environmental conditions on Noachian Mars (4.1-3.7 Ga) and the Early Archaean (4.0-3.3 Ga) Earth were, in many respects, similar: presence of liquid water, dense CO 2 atmosphere, availability of carbon and bio-essential elements, and availability of energy. For this reason, information contained in Early Archaean terrestrial rocks concerning habitable conditions (on a microbial scale) and traces of past life are of relevance in defining strategies to be used to identify past habitats and past life on Mars. One such example is the 3.446 Ga-old Kitty's Gap Chert in the Pilbara Craton, NW. Australia. This formation consists of volcanic sediments deposited in a coastal mudflat environment and is thus a relevant analogue for sediments deposited in shallow water environments on Noachian Mars. Two main types of habitat are represented, a volcanic (lithic) habitat and planar stabilized sediment surfaces in sunlit shallow waters. The sediments hosted small (<1 μm in size) microorganisms that formed colonies on volcanic particle surfaces and in pore waters within the volcanic sediments, as well as biofilms on stabilised sediment surfaces. The microorganisms included coccoids, filaments and rare rod-shaped organisms associated with microbial polymer (EPS). The preserved microbial community was apparently dominated by chemotrophic organisms but some locally transported filaments and filamentous mat fragments indicate that possibly photosynthetic mats formed nearby. Both microorganisms and sediments were silicified during very early diagenesis. There are no macroscopic traces of fossilised life in these volcanic sediments and sophisticated instrumentation and specialized sample preparation techniques are required to establish the biogenicity and syngenicity of the traces of past life. The fact that the traces of life are cryptic, and the necessity of using sophisticated instrumentation, reinforces the challenges and difficulties of in situ robotic missions to identify past life on Mars. We therefore recommend the return of samples from Mars to Earth for a definitive search for traces of life.
Pre-Holocene to Modern Evolution of the Lower Delaware Estuary: Constraints from High-Resolution Chirp Subbottom Profiles

NASA Astrophysics Data System (ADS)

Daw, Julianne

Throughout the Quaternary Period, the Delaware Estuary, which is located within the Mid-Atlantic region of the United States, has undergone substantial change as a result of sea-level fluctuations. To better understand the recent (late Pleistocene to Holocene) evolution of the region, chirp subbottom profiles were analyzed within Delaware Bay near the southern end of the Delaware River Navigation Channel including the adjacent shoals and sloughs, using RoxAnn bottom classification data and available vibracores to aid in interpreting sediment types and depositional environments within the study area. Using seismic processing software (SonarWiz6), chirp profiles were processed and reflection events were identified and their positions digitized. Major reflection events were analyzed using a seismic facies approach. The identified facies were each characterized as distinct units composed of reflections with unique elements, such as configuration, amplitude, and continuity. Five seismic facies were identified and their thicknesses determined. Depths to the major reflection events were correlated with sediment boundaries as observed in the available vibracores, allowing the seismic facies to be interpreted in terms of their associated sediment types and inferred environments of deposition. The distributions of surficial and subsurface seismic and sedimentological features were visualized using three-dimensional images. The interpretations of the identified facies are as follows: Facies I is a surficial unit of the modern Holocene estuarine deposits; Facies II is a beach-berm washover zone deposition; Facies III is a deposit of a lagoonal environment; Facies IV is a deposit of an open water environment; and Facies V is a marsh deposition. The chirp data, when integrated with available information from vibracores and RoxAnn bottom sediment classification, was also used to map the position of a former major river system (paleochannel). This paleochannel, trending generally northwest to southeast, can be correlated with the southern channel that was identified in previous work by Knebel and Circe (1988). In addition to the knowledge gained by studying the geological evolution of Delaware Bay, our data can be used by decision makers and stakeholders to inform future management of the Delaware Estuary in practical applications that range from planning for maintenance dredging of the navigation channel to determining locations and thicknesses of suitable sand resources for shoreline replenishment. The surficial layer that would be most affected by such applications is mostly composed of sand & muddy sand, but in the deeper portions and along the shoals, it is composed of mixed and coarse sediments and mud & sandy mud, respectively. Furthermore, the surficial unit is thickest (between 1.5 and 4 meters) in the central and eastern regions of the study area encompassing the deeper portions, and it is thinnest (up to 1 meter) along the western and northern regions that include the shoals.
Improving the monitoring of a dumping site in a dynamic environment. Example of the Octeville site (Bay of Seine, English Channel).

PubMed

Méar, Yann; Poizot, Emmanuel; Murat, Anne; Beryouni, Khadija; Baux, Noémie; Dauvin, Jean-Claude

2018-04-01

Dredged sediments have different physical and chemical characteristics compared with the sediments in place, which generates multiple effects on the environment. In this study, we show that the sampling strategy used to monitor the effects of dredge spoil deposition on the surrounding environment can lead to different interpretations. It appears that sediment sample replicates may or may not be necessary, depending on the studied area, the prevailing environmental forcings before sediment sampling and the combination of these two factors. The proposed modus operandi allows us to optimize both the confidence on the obtained results and the cost of the sediment studies (sampling and laboratory analyses). The results are based on the sediment fine fraction, which is considered as a key environmental component due, for example, to its strong association with the structure of benthic faunal communities as well as its role in the build-up of pollutants. Copyright © 2017 Elsevier Ltd. All rights reserved.
Sulfur- and oxygen-isotopes in sediment-hosted stratiform barite deposits

USGS Publications Warehouse

Johnson, C.A.; Emsbo, P.; Poole, F.G.; Rye, R.O.

2009-01-01

Sulfur- and oxygen-isotope analyses have been obtained for sediment-hosted stratiform barite deposits in Alaska, Nevada, Mexico, and China to examine the environment of formation of this deposit type. The barite is contained in sedimentary sequences as old as Late Neoproterozoic and as young as Mississippian. If previously published data for other localities are considered, sulfur- and oxygen-isotope data are now available for deposits spanning a host-rock age range of Late Neoproterozoic to Triassic. On a ??34S versus ??18O diagram, many deposits show linear or concave-upward trends that project down toward the isotopic composition of seawater sulfate. The trends suggest that barite formed from seawater sulfate that had been isotopically modified to varying degrees. The ??34S versus ??18O patterns resemble patterns that have been observed in the modern oceans in pore water sulfate and water column sulfate in some anoxic basins. However, the closest isotopic analog is barite mineralization that occurs at fluid seeps on modern continental margins. Thus the data favor genetic models for the deposits in which barium was delivered by seafloor seeps over models in which barium was delivered by sedimentation of pelagic organisms. The isotopic variations within the deposits appear to reflect bacterial sulfate reduction operating at different rates and possibly with different electron donors, oxygen isotope exchange between reduction intermediates and H2O, and sulfate availability. Because they are isotopically heterogeneous, sediment-hosted stratiform barite deposits are of limited value in reconstructing the isotopic composition of ancient seawater sulfate.
Physical abrasion of mafic minerals and basalt grains: application to Martian aeolian deposits

USGS Publications Warehouse

Cornwall, Carin; Bandfield, Joshua L.; Titus, Timothy N.; Schreiber, B. C.; Montgomery, D.R.

2015-01-01

Sediment maturity, or the mineralogical and physical characterization of sediment deposits, has been used to locate sediment source, transport medium and distance, weathering processes, and paleoenvironments on Earth. Mature terrestrial sands are dominated by quartz, which is abundant in source lithologies on Earth and is physically and chemically stable under a wide range of conditions. Immature sands, such as those rich in feldspars or mafic minerals, are composed of grains that are easily physically weathered and highly susceptible to chemical weathering. On Mars, which is predominately mafic in composition, terrestrial standards of sediment maturity are not applicable. In addition, the martian climate today is cold, dry and sediments are likely to be heavily influenced by physical weathering rather than chemical weathering. Due to these large differences in weathering processes and composition, martian sediments require an alternate maturity index. Abrason tests have been conducted on a variety of mafic materials and results suggest that mature martian sediments may be composed of well sorted, well rounded, spherical basalt grains. In addition, any volcanic glass present is likely to persist in a mechanical weathering environment while chemically altered products are likely to be winnowed away. A modified sediment maturity index is proposed that can be used in future studies to constrain sediment source, paleoclimate, mechanisms for sediment production, and surface evolution. This maturity index may also provide details about erosional and sediment transport systems and preservation processes of layered deposits.
Mineralogy, geochemistry, and radiocarbon ages of deep sea sediments from the Gulf of Mexico, Mexico

NASA Astrophysics Data System (ADS)

Armstrong-Altrin, John S.; Machain-Castillo, María Luisa

2016-11-01

The mineralogy, geochemistry, and radiocarbon ages of two sediment cores (GMX1 and GMX2) collected from the deep sea area of the Southwestern Gulf of Mexico (∼876-1752 m water depth) were studied to infer the sedimentation rate, provenance, heavy metal contamination, and depositional environment. The sediments are dominated by silt and clay fractions. The mineralogy determined by X-Ray diffractometry for the sediment cores reveals that montmorillonite and muscovite are the dominant clay minerals. The sections between 100 and 210 cm of the sediment cores GMX1 and GMX2, respectively, are characterized by the G. menardii group and G. Inflata planktonic foraminiferal species, which represent the Holocene and Pleistocene, respectively. The radiocarbon-age measurements of mixed planktonic foraminifera varied from ∼268 to 45,738 cal. years B.P and ∼104 to 25,705 cal. years B.P, for the sediment cores GMX1 and GMX2, respectively. The variation in age between the two sediment cores is due to a change in sediment accumulation rate, which was lowest at the location GMX1 (0.006 cm/yr) and highest at the location GMX2 (0.017 cm/yr). The chemical index of alteration (CIA), chemical index of weathering (CIW), and index of chemical maturity (ICV) values indicated a moderate intensity of weathering in the source area. The total rare earth element concentrations (∑REE) in the cores GMX1 and GMX2 vary from ∼94 to 171 and ∼78 to 151, respectively. The North American Shale Composite (NASC) normalized REE patterns showed flat low REE (LREE), heavy REE (HREE) depletion with low negative to positive Eu anomalies, which suggested that the sediments were likely derived from intermediate source rocks. The enrichment factor of heavy metals indicated that the Cd and Zn concentrations in the sediment cores were impacted by an anthropogenic source. The redox-proxy trace element ratios such as V/Cr, Ni/Co, Cu/Zn, (Cu + Mo)/Zn, and Ce/Ce* indicated that the sediments were deposited under an oxic depositional environment. The similarity in major element concentrations, REE content, and the NASC normalised REE patterns between the cores GMX1 and GMX2 revealed that the provenance of sediments remained relatively uniform or constant during deposition for ∼4.5 Ma. The major and trace element based multidimensional discrimination diagrams showed a rift setting for the core sediments, which is consistent with the geology of the Gulf of Mexico.
Sediment-hosted stratabound copper deposit model: Chapter M in Mineral deposit model for resource assessment

USGS Publications Warehouse

Hayes, Timothy S.; Cox, Dennis P.; Bliss, James D.; Piatak, Nadine M.; Seal, Robert R.

2015-01-01

This report contains a descriptive model of sediment-hosted stratabound copper (SSC) deposits that supersedes the model of Cox and others (2003). This model is for use in assessments of mineral resource potential. SSC deposits are the second most important sources of copper in the world behind porphyry copper deposits. Around 20 percent of the copper in the world is produced from this class of deposits. They are also the most important sources of cobalt in the world, and they are fourth among classes of ore deposits in production of silver. SSC deposits are the basis of the economies of three countries: Democratic Republic of Congo, Poland, and Zambia. This report provides a description of the key features of SSC deposits; it identifies their tectonic-sedimentary environments; it illustrates geochemical, geophysical, and geoenvironmental characteristics of SSC deposits; it reviews and evaluates hypotheses on how these deposits formed; it presents exploration and assessment guides; and it lists some gaps in our knowledge about the SSC deposits. A summary follows that provides overviews of many subjects concerning SSC deposits.
The Scientific and Societal Need for Accurate Global Remote Sensing of Marine Suspended Sediments

NASA Technical Reports Server (NTRS)

Acker, James G.

2006-01-01

Population pressure, commercial development, and climate change are expected to cause continuing alteration of the vital oceanic coastal zone environment. These pressures will influence both the geology and biology of the littoral, nearshore, and continental shelf regions. A pressing need for global observation of coastal change processes is an accurate remotely-sensed data product for marine suspended sediments. The concentration, delivery, transport, and deposition of sediments is strongly relevant to coastal primary production, inland and coastal hydrology, coastal erosion, and loss of fragile wetland and island habitats. Sediment transport and deposition is also related to anthropogenic activities including agriculture, fisheries, aquaculture, harbor and port commerce, and military operations. Because accurate estimation of marine suspended sediment concentrations requires advanced ocean optical analysis, a focused collaborative program of algorithm development and assessment is recommended, following the successful experience of data refinement for remotely-sensed global ocean chlorophyll concentrations.
Pelagic erosion and sedimentation north of Carnegie Ridge, eastern equatorial Pacific

NASA Astrophysics Data System (ADS)

Brooks, C. K.; Lyle, M. W.; Marcantonio, F.; Lewis, D. M.; Paul, C.

2011-12-01

The Carnegie Ridge is one of three bathymetric highs bounding the Panama Basin and is known to exhibit erosion and redeposition of pelagic sediments. The extent of erosion and redeposition was studied during the R/V Melville cruise MV1014 in November 2010 to compare with geochemical estimates of sediment focusing. The MV1014 cruise acquired geochemical, geological and geophysical data using multichannel 2-D seismic and 3.5 kHz sub-bottom profiler, swathmap bathymetry, coring, and water casts. The seismic reflection, digital sub-bottom profiler and swathmap bathymetry data were used to investigate biogenic sedimentary deposition in the Panama Basin and erosion from Carnegie Ridge. We compare the new geophysical results with drilling on ODP Leg 202, the NEMO-03 site survey cruise for Leg 202, an early survey from 1969 and other data compiled by Ecuadorian surveys. Areas of non-deposition and/or erosion include the bathymetric highs along the ridge, seamounts, and an area of interest, a valley located on the northwestern flank of the ridge. The valley encompasses 183 km2 and exhibits large scale erosion, cutting down through sediments deposited over the 10-million year life of this segment of the Carnegie Ridge. All other valleys located within the Carnegie Ridge study area demonstrate ample deposition with sedimentary packages ranging from 200-800m with an average value trending around 400m. Higher sediment deposition is found in basins to the north of the erosional valley but similar sedimentation is also found even further north, beyond intervening high topography. The thickest sediment deposit near the Carnegie Ridge is actually found on the southern flank of the ridge, more than 100 km to the south of the survey area. Digital chirp sub-bottom profiler data combined with high-resolution seismic illustrate changes in sedimentation and erosion on the Carnegie Ridge, highlighting the dynamic sedimentary environment.
The application of Caesium-137 and Plutonium-239+240 measurements to investigate floodplain deposition in a semi-arid, low-fallout environment

NASA Astrophysics Data System (ADS)

Amos, K. J.; Croke, J. C.; Timmers, H.; Owens, P. N.

2009-04-01

Floodplains comprise geomorphologically important sources and sinks for sediments and associated pollutants, yet the sedimentology of large dryland floodplains is not well understood. Processes occurring on such floodplains are often difficult to observe, and techniques used to investigate smaller perennial floodplains are often not practical in these environments. This study assesses the utility of Cs-137 inventory and depth-profile techniques for determining relative amounts of floodplain sedimentation in the Fitzroy River, north-eastern Australia; a 143 000 km2 semi-arid river system. Caesium-137 inventories were calculated for floodplain and reference location bulk soil cores collected from four sites. Depth profiles of Cs-137 concentration from each floodplain site and a reference location were recorded. The areal density of Cs-137 at reference locations ranged from 13-978 Bq m-2 (0-1367 Bq m-2 at the 95% confidence interval), and the mean value ± 2(standard error of the mean) was 436±264 Bq m-2, similar to published data from other southern hemisphere locations. Floodplain inventories ranged from 68-1142 Bq m-2 (0-1692 Bq m-2 at the 95% confidence interval), essentially falling within the range of reference inventory values, thus preventing calculation of erosion or deposition. Depth-profiles of Cs-137 concentration indicate erosion at one site and over 66 cm of deposition at another since 1954. Analysis of 239+240Pu concentrations in a depositional core substantiated the interpretation made from Cs-137 data, and depict a more tightly constrained peak in concentration. Average annual deposition rates range from 0-15 mm. The similarity between floodplain and reference bulk inventories does not necessarily indicate a lack of erosion or deposition, due to low Cs-137 fallout in the region and associated high measurement uncertainties, and a likely influence of gully and bank eroded sediments with no or limited adsorbed Cs-137. In this low-fallout environment, detailed depth-profile data are necessary for investigating sedimentation using Cs-137.
Investigating the effect of storm events on the particle size distribution in a combined sewer simulator.

PubMed

Biggs, C A; Prall, C; Tait, S; Ashley, R

2005-01-01

The changes in particle size of sewer sediment particles rapidly eroded from a previously deposited sediment bed are described, using a rotating annular flume as a laboratory scale sewer simulator. This is the first time that particle size distributions of eroded sewer sediments from a previously deposited sediment bed have been monitored in such a controlled experimental environment. Sediments from Loenen, The Netherlands and Dundee, UK were used to form deposits in the base of the annular flume (WL Delft Netherlands) with varying conditions for consolidation in order to investigate the effect of changing consolidation time, temperature and sediment type on the amount and size of particles eroded from a bed under conditions of increasing shear. The median size of the eroded particles did not change significantly with temperature, although the eroded suspended solids concentration was greater for the higher temperature under the same shear stresses, indicating a weaker bed deposit. An increase in consolidation time caused an increase in median size of eroded solids at higher bed shear stresses, and this was accompanied by higher suspended solids concentrations. As the shear stress increased, the solids eroded from the bed developed under a longer consolidation time (56 hours) tended towards a broad unimodal distribution, whilst the size distribution of solids eroded from beds developed under shorter consolidation times (18 or 42 hours) retained a bi- or tri-modal distribution. Using different types of sediment in the flume had a marked effect on the size of particles eroded.
DOE Office of Scientific and Technical Information (OSTI.GOV)

Burnett, W.C.

Hundreds of islands in the tropical Pacific Ocean contain phosphate deposits ranging from inconsequential to economically significant in size. Although many of these deposits clearly have formed by the interaction of avian guano with underlying limestone, some display evidence of having developed within an aqueous environment. Several of the emergent carbonate islands in the southern part of Palau contain phosphate deposits that the authors speculate formed in anoxic marine lakes, similar to those which still occur on a few of these islands. Lake water, sediments, and sediment pore waters from Jellyfish Lake, on the island of Eil Malk in Palau,more » were analyzed during an expedition in 1987. The results of this investigation supported, but did not provide, conclusive evidence of our hypothesis. Pore water profiles of phosphate and fluoride confirmed precipitation of carbonate fluorapatite. However, the extremely high bulk sediment accumulation rate, driven by the high biological productivity of the surface waters of the lake, dilutes authigenic phosphate to low levels. They have refined their original proposal to suggest that phosphate deposits may form either by: (1) subaerial weathering and concentration of phosphatic sediments after these lakes disappear; or (2) interaction of phosphate-enriched sediment pore solutions with limestone at the underlying contact. Another expedition to test these concepts is being planned.« less
Facies interfingering and synsedimentary tectonics on late Ladinian-early Carnian carbonate platforms (Dolomites, Italy)

NASA Astrophysics Data System (ADS)

Keim, Lorenz; Brandner, Rainer

2001-11-01

A stratigraphic model for carbonate platform evolution in the Dolomites during the late Ladinian-early Carnian is presented. New light on pre-Raibl growth of individual carbonate platforms of the western Dolomites was shed by biostratigraphic data combined with a revised lithostratigraphy. At the Schlern, Langkofel and Sella, the carbonate factory (Upper Schlern Dolomite) remained productive into the lowermost Carnian (Cordevolian = Aon Zone), and caused a levelling-out of the former steep platform-to-basin relief. In the eastern Dolomites, platforms were producing till basal Julian 2 (Austriacum Zone). At the Sella and Langkofel, the sedimentation pattern after deposition of the Upper Schlern Dolomite was strongly influenced by synsedimentary tectonics. A first phase of extensional tectonics led to local fissures, block-tilting, graben structures and breccia deposits. Composition and fabric of the reworked clasts argue for local-source sediments and short transport distances. The extensional structures are sealed by sediments of Lower Carnian age. Two facies belts (Schlernplateau beds and Dürrenstein Dolomite), which interfinger at the western side of the Sella, reflect the shallow marine environment with terrigenous-volcanoclastic input in the western Dolomites. A second generation of breccias at the Sella documents local fracturing of the Dürrenstein and Upper Schlern Dolomite. Depositional environments across the western and eastern Dolomites were largely dependent on differential subsidence. The sediments of early Carnian age on top of the Schlern platform are a few metres thick only, whereas, in the eastern Dolomite, up to 400-m-thick carbonate sediments ('Richthofen reef' and Settsass platform) were deposited. The most incomplete stratigraphic record is present at the Mendel platform in the west, where Ladinian volcanics are unconformably overlain by late Carnian 'Raibl beds'. The increase in sediment thickness towards the eastern Dolomites becomes partly visible at the eastern flank of the Sella platform. Differential subsidence across western and eastern Dolomites caused local fracturing of platform sediments. Synsedimentary extensional tectonics was a significant controlling factor to the lithofacies and thickness variations of early Carnian platform sediments in the Dolomites.

Sediment-Hosted Copper Deposits of the World: Deposit Models and Database

USGS Publications Warehouse

Cox, Dennis P.; Lindsey, David A.; Singer, Donald A.; Diggles, Michael F.

2003-01-01

Introduction This publication contains four descriptive models and four grade-tonnage models for sediment hosted copper deposits. Descriptive models are useful in exploration planning and resource assessment because they enable the user to identify deposits in the field and to identify areas on geologic and geophysical maps where deposits could occur. Grade and tonnage models are used in resource assessment to predict the likelihood of different combinations of grades and tonnages that could occur in undiscovered deposits in a specific area. They are also useful in exploration in deciding what deposit types meet the economic objectives of the exploration company. The models in this report supersede the sediment-hosted copper models in USGS Bulletin 1693 (Cox, 1986, and Mosier and others, 1986) and are subdivided into a general type and three subtypes. The general model is useful in classifying deposits whose features are obscured by metamorphism or are otherwise poorly described, and for assessing regions in which the geologic environments are poorly understood. The three subtypes are based on differences in deposit form and environments of deposition. These differences are described under subtypes in the general model. Deposit models are based on the descriptions of geologic environments and physical characteristics, and on metal grades and tonnages of many individual deposits. Data used in this study are presented in a database representing 785 deposits in nine continents. This database was derived partly from data published by Kirkham and others (1994) and from new information in recent publications. To facilitate the construction of grade and tonnage models, the information, presented by Kirkham in disaggregated form, was brought together to provide a single grade and a single tonnage for each deposit. Throughout the report individual deposits are defined as being more than 2,000 meters from the nearest adjacent deposit. The deposit models are presented here as a PDF file. The database can be most conveniently read in FileMaker Pro. For those who do not have the FileMaker application, Microsoft-Excel, tab-delimited-ASCII and comma-separated-value files are included. The reader may be interested in a similar publication on porphyry copper deposits (Singer and others, 2005) also available online. The Google Earth image is not intended to be viewed at the highest possible magnification because the resolution of the database is plus or minus two kilometers. At extreme zoom settings, the deposit locations may not coincide with the Google-Earth images of the mine workings.
Numerical experiment on tsunami deposit distribution process by using tsunami sediment transport model in historical tsunami event of megathrust Nankai trough earthquake

NASA Astrophysics Data System (ADS)

Imai, K.; Sugawara, D.; Takahashi, T.

2017-12-01

A large flow caused by tsunami transports sediments from beach and forms tsunami deposits in land and coastal lakes. A tsunami deposit has been found in their undisturbed on coastal lakes especially. Okamura & Matsuoka (2012) found some tsunami deposits in the field survey of coastal lakes facing to the Nankai trough, and tsunami deposits due to the past eight Nankai Trough megathrust earthquakes they identified. The environment in coastal lakes is stably calm and suitable for tsunami deposits preservation compared to other topographical conditions such as plains. Therefore, there is a possibility that the recurrence interval of megathrust earthquakes and tsunamis will be discussed with high resolution. In addition, it has been pointed out that small events that cannot be detected in plains could be separated finely (Sawai, 2012). Various aspects of past tsunami is expected to be elucidated, in consideration of topographical conditions of coastal lakes by using the relationship between the erosion-and-sedimentation process of the lake bottom and the external force of tsunami. In this research, numerical examination based on tsunami sediment transport model (Takahashi et al., 1999) was carried out on the site Ryujin-ike pond of Ohita, Japan where tsunami deposit was identified, and deposit migration analysis was conducted on the tsunami deposit distribution process of historical Nankai Trough earthquakes. Furthermore, examination of tsunami source conditions is possibly investigated by comparison studies of the observed data and the computation of tsunami deposit distribution. It is difficult to clarify details of tsunami source from indistinct information of paleogeographical conditions. However, this result shows that it can be used as a constraint condition of the tsunami source scale by combining tsunami deposit distribution in lakes with computation data.
Early diagenesis in the sediments of the Congo deep-sea fan dominated by massive terrigenous deposits: Part II - Iron-sulfur coupling

NASA Astrophysics Data System (ADS)

Taillefert, Martial; Beckler, Jordon S.; Cathalot, Cécile; Michalopoulos, Panagiotis; Corvaisier, Rudolph; Kiriazis, Nicole; Caprais, Jean-Claude; Pastor, Lucie; Rabouille, Christophe

2017-08-01

Deep-sea fans are well known depot centers for organic carbon that should promote sulfate reduction. At the same time, the high rates of deposition of unconsolidated metal oxides from terrigenous origin may also promote metal-reducing microbial activity. To investigate the eventual coupling between the iron and sulfur cycles in these environments, shallow sediment cores (< 50 cm) across various channels and levees in the Congo River deep-sea fan ( 5000 m) were profiled using a combination of geochemical methods. Interestingly, metal reduction dominated suboxic carbon remineralization processes in most of these sediments, while dissolved sulfide was absent. In some 'hotspot' patches, however, sulfate reduction produced large sulfide concentrations which supported chemosynthetic-based benthic megafauna. These environments were characterized by sharp geochemical boundaries compared to the iron-rich background environment, suggesting that FeS precipitation efficiently titrated iron and sulfide from the pore waters. A companion study demonstrated that methanogenesis was active in the deep sediment layers of these patchy ecosystems, suggesting that sulfate reduction was promoted by alternative anaerobic processes. These highly reduced habitats could be fueled by discrete, excess inputs of highly labile natural organic matter from Congo River turbidites or by exhumation of buried sulfide during channel flank erosion and slumping. Sulfidic conditions may be maintained by the mineralization of decomposition products from local benthic macrofauna or bacterial symbionts or by the production of more crystalline Fe(III) oxide phases that are less thermodynamically favorable than sulfate reduction in these bioturbated sediments. Overall, the iron and sulfur biogeochemical cycling in this environment is unique and much more similar to a coastal ecosystem than a deep-sea environment.
Changes in Depositional Setting Reflect Rising Sealevel in Latest Holocene Sediments of the Hudson River

NASA Astrophysics Data System (ADS)

Slagle, A.; Carbotte, S. M.; Ryan, W. B.; Bell, R.; Nitsche, F. O.; McHugh, C. M.

2002-12-01

An extensive database of geophysical and sampling data in the Hudson River has been obtained in ten study areas between the New York Harbor and the Troy Dam. These data include bathymetry, bank-to-bank coverage of side-looking sonar imagery, subbottom reflection profiles, sediment cores and grabs. Geophysical properties, including gamma density, magnetic susceptibility and P-wave velocity, have been measured in a 9.3 m Vibracore (SD-30) from the near-channel tidal flats of the Tappan Zee area. Three distinct sedimentary facies have been identified, based on changes in physical properties, lithology and seismic reflections. Facies 1 is an oyster-rich unit with unstratified sediments and high sound velocities, and is found in the upper 1.5 m of core SD-30. Chirp subbottom data, which provide reflectors down to approximately 4 m depth, show a distinct horizon at 1.5 m, supporting the change seen in physical property data and lithology at this depth. A unit characterized by laminated sediments, interbedded with homogeneous layers and coquina layers, is identified as Facies 2 and is found between 1.5 and 6.1 m. This facies has high magnetic susceptibility and the appearance of discrete density cycles. The oldest unit, Facies 3, extends from 6.1 m to the base of the core at 9.3 m. It is made up of oyster-rich, unbedded sediments and thick coquina layers, and is characterized by low magnetic susceptibility. Radiocarbon dating of oysters and bivalves indicates that the different facies in SD-30 correspond to different sedimentation rates, with highest values occurring during deposition of Facies 2. The facies changes and variations in sedimentation rates are attributed to an evolving depositional environment in the tidal flats of the Tappan Zee area due to rising sealevel. Extrapolating from nearby cores that penetrate deeper into the sedimentary record, Facies 3 sits above post-glacial fluvial sands and represents the transition from a fresh to more brackish environment, suitable for development of oyster beds. The laminated sediments of Facies 2 are attributed to infilling of the tidal flats during a rapid rise in sealevel. The lack of laminated sediments and low sedimentation rates of Facies 1 are attributed to the modern wave-base dominated depositional setting in the Tappan Zee area.
Using tsunami deposits to determine the maximum depth of benthic burrowing

PubMed Central

Shirai, Kotaro; Murakami-Sugihara, Naoko

2017-01-01

The maximum depth of sediment biomixing is directly related to the vertical extent of post-depositional environmental alteration in the sediment; consequently, it is important to determine the maximum burrowing depth. This study examined the maximum depth of bioturbation in a natural marine environment in Funakoshi Bay, northeastern Japan, using observations of bioturbation structures developed in an event layer (tsunami deposits of the 2011 Tohoku-Oki earthquake) and measurements of the radioactive cesium concentrations in this layer. The observations revealed that the depth of bioturbation (i.e., the thickness of the biomixing layer) ranged between 11 and 22 cm, and varied among the sampling sites. In contrast, the radioactive cesium concentrations showed that the processing of radioactive cesium in coastal environments may include other pathways in addition to bioturbation. The data also revealed the nature of the bioturbation by the heart urchin Echinocardium cordatum (Echinoidea: Loveniidae), which is one of the important ecosystem engineers in seafloor environments. The maximum burrowing depth of E. cordatum in Funakoshi Bay was 22 cm from the seafloor surface. PMID:28854254
Using tsunami deposits to determine the maximum depth of benthic burrowing.

PubMed

Seike, Koji; Shirai, Kotaro; Murakami-Sugihara, Naoko

2017-01-01

The maximum depth of sediment biomixing is directly related to the vertical extent of post-depositional environmental alteration in the sediment; consequently, it is important to determine the maximum burrowing depth. This study examined the maximum depth of bioturbation in a natural marine environment in Funakoshi Bay, northeastern Japan, using observations of bioturbation structures developed in an event layer (tsunami deposits of the 2011 Tohoku-Oki earthquake) and measurements of the radioactive cesium concentrations in this layer. The observations revealed that the depth of bioturbation (i.e., the thickness of the biomixing layer) ranged between 11 and 22 cm, and varied among the sampling sites. In contrast, the radioactive cesium concentrations showed that the processing of radioactive cesium in coastal environments may include other pathways in addition to bioturbation. The data also revealed the nature of the bioturbation by the heart urchin Echinocardium cordatum (Echinoidea: Loveniidae), which is one of the important ecosystem engineers in seafloor environments. The maximum burrowing depth of E. cordatum in Funakoshi Bay was 22 cm from the seafloor surface.
Active subsurface cellular function in the Baltic Sea Basin, IODP Exp 347

NASA Astrophysics Data System (ADS)

Reese, B. K.; Zinke, L. A.; Bird, J. T.; Lloyd, K. G.; Marshall, I.; Amend, J.; Jørgensen, B. B.

2016-12-01

The Baltic Sea Basin is a unique depositional setting that has experienced periods of glaciation and deglaciation as a result of global temperature fluctuations over the course of several hundred thousand years. This has resulted in laminated sediments formed during periods with strong permanent salinity stratification. The high sedimentation rates (100-500 cm/1000 y) make this an ideal setting to understand the microbial structure of a deep biosphere community in a high-organic matter environment. The responses of deep sediment microbial communities to variations in conditions during and after deposition are poorly understood. Samples were collected through scientific drilling during the International Ocean Discovery Program (IODP) Expedition 347 on board the Greatship Manisha, September-November 2013. We examined the active microbial community structure using the 16S rRNA gene transcript and active functional genes through metatranscriptome sequencing. Major biogeochemical shifts have been observed in response to the depositional history between the limnic, brackish, and marine phases. The microbial community structure in the BSB is diverse and reflective of the unique changes in the geochemical profile. These data further define the existence life in the deep subsurface and the survival mechanisms required for this extreme environment.
Quaternary sedimentation and subsidence history of Lake Baikal, Siberia, based on seismic stratigraphy and coring

USGS Publications Warehouse

Colman, Steven M.; Karabanov, E.B.; Nelson, C. H.

2003-01-01

The long, continuous, high-latitude, stratigraphic record of Lake Baikal was deposited in three broad sedimentary environments, defined by high-resolution seismic-reflection and coring methods: (1) turbidite depositional systems, by far the most widespread, characterizing most of the margins and floors of the main basins of the lake, (2) large deltas of major drainages, and (3) tectonically or topographically isolated ridges and banks. Holocene sedimentation rates based on radiocarbon ages vary by more than an order of magnitude among these environments, from less than about 0.03 mm/yr on ridges and banks to more than about 0.3 mm/yr on basin floors. Extrapolating these rates, with a correction for compaction, yields tentative estimates of about 25 and 11 Ma for the inception of rifting in the Central and North basins, respectively, and less than 6 Ma for the 200-m sediment depth on Academician Ridge. The Selenga Delta has the distinctive form of a classic prograding Gilbert-type delta, but its history appears to represent a complex combination of tectonism and sedimentation. The central part of the delta is underlain by prograding, shallow-water sequences, now several hundred meters below the lake surface. These deposits and much of the delta slope are mantled by fine-grained, deep-water, hemipelagic deposits whose base is estimated to be about 650,000 years old. Modern coarse-grained sediment bypasses the delta slope through fault-controlled canyons that feed large, subaqueous fans at the ends of the South and Central basins. These relations, along with abundant other evidence of recent faulting and the great depths of the Central and South basins, suggest that these two rift basins have experienced a period of unusually rapid subsidence over the last 650,000 years, during at least part of which sedimentation has failed to keep pace.
Isotopic studies of epigenetic features in metalliferous sediment, Atlantis II Deep, Red Sea

USGS Publications Warehouse

Zierenberg, Robert A.; Shanks, Wayne C.

1988-01-01

The unique depositional environment of the Atlantis II Deep brine pool in the Red Sea produces a stratiform metalliferous deposit of greater areal extent than deposits formed by buoyant-plume systems typical of the midocean ridges because of much more efficient metal entrapment. Isotopic analyses of strontium, sulfur, carbon, and oxygen from the metalliferous sediments indicate that three major sources contribute dissolved components to the hydrothermal system: seawater, Miocene evaporites, and rift-zone basalt. An areally restricted magnetite-hematite-pyroxene assemblage formed at high temperatures, possibly in response to hydrothermal convection initiated by intrusion of basalt into the metalliferous sediment. A correlation between smectite Fe/(Fe+Mg) ratios and oxygen isotope temperatures suggests that smectite is a potentially important chemical geothermometer, and confirms geochemical calculations indicating that Mg-rich smectite is more stable than Fe-rich smectite at elevated temperatures.
Acoustic measurement and morphological features of organic sediment deposits in combined sewer networks.

PubMed

Carnacina, Iacopo; Larrarte, Frédérique; Leonardi, Nicoletta

2017-04-01

The performance of sewer networks has important consequences from an environmental and social point of view. Poor functioning can result in flood risk and pollution at a large scale. Sediment deposits forming in sewer trunks might severely compromise the sewer line by affecting the flow field, reducing cross-sectional areas, and increasing roughness coefficients. In spite of numerous efforts, the morphological features of these depositional environments remain poorly understood. The interface between water and sediment remains inefficiently identified and the estimation of the stock of deposit is frequently inaccurate. In part, this is due to technical issues connected to difficulties in collecting accurate field measurements without disrupting existing morphologies. In this paper, results from an extensive field campaign are presented; during the campaign a new survey methodology based on acoustic techniques has been tested. Furthermore, a new algorithm for the detection of the soil-water interface, and therefore for the correct esteem of sediment stocks is proposed. Finally, results in regard to bed topography, and morphological features at two different field sites are presented and reveal that a large variability in bed forms is present along sewer networks. Copyright © 2017 Elsevier Ltd. All rights reserved.
Sedimentology of the lower part of the Upper Triassic Chinle Formation and its relationship to uranium deposits, White Canyon area, southeastern Utah

USGS Publications Warehouse

Dubiel, Russell F.

1983-01-01

Closely spaced measured stratigraphic sections of the lower part of the Late Triassic Chinle Formation in the White Canyon area of southeastern Utah depict a fluvial-deltaic-lacustrine depositional sequence that hosts uranium deposits in basal fluvial sandstones. The basal Shinarump Member consists of predominantly trough-crossbedded, coarse-grained sandstone and minor gray, carbonaceous mudstone and is interpreted as a valley-fill sequence overlain by deposits of a braided stream system. The overlying Monitor Butte Member is composed of cyclic- and foreset-bedded siltstone, sandstone, and mudstone and is interpreted as a succession of low-energy fluvial, deltaic and orqanicrich, lacustrine-marsh sediments. The overlying Moss Back Member is composed of a laterally extensive, coarse- to medium-grained, conglomeratic sandstone and is interpreted as a braided-stream system that flowed north to northwest. The entire sequence was deposited in response to changes in local base level associated with a large lake that lay to the west. Isopachs of lithofacies indicate distinct lacustrine basins and a correspondence between these facies and modern structural synclines. Facies changes and coincidence of isopach thicks suggest that structural synclines were active in the Late Triassic and influenced the pattern of sediment distribution within the basins. Uranium mineralization appears to be related to certain low-energy depositional environments in that uranium is localized in fluvial sandstones that lie beneath organic-rich lacustrine-marsh mudstones and carbonaceous delta-front sediments. The reducing environment preserved in these facies may have played an important role in the localization of uranium.
Contrasts in Sediment Delivery and Dispersal from River Mouth to Accumulation Zones in High Sediment Load Systems: Fly River, Papua New Guinea and Waipaoa River, New Zealand

NASA Astrophysics Data System (ADS)

Ogston, A. S.; Walsh, J. P.; Hale, R. P.

2011-12-01

The relationships between sediment-transport processes, short-term sedimentary deposition, subsequent burial, and long-term accumulation are critical to understanding the morphological development of the continental margin. This study focuses on processes involved in formation and evolution of the clinoform in the Gulf of Papua, Papua New Guinea in which much of the riverine sediment accumulates, and comparison to those processes active off the Waipaoa River, New Zealand that form mid-shelf deposits and export sediment to the slope. In tidally dominated deltas, sediment discharged from the river sources must transit through an estuarine region located within the distributary channels, where particle pathways can undergo significant transformations. Within the distributaries of the Fly River tidally dominated delta, near-bed fluid-mud concentrations were observed at the estuarine turbidity maximum and sediment delivery to the nearshore was controlled by the morphology and gradient of the distributary. El Niño results in anonymously low flow and sediment discharge conditions, which limits transport of sediment from the distributaries to the nearshore zone of temporary storage. Because the sediment stored nearshore feeds the prograding clinoform, this perturbation propagates throughout the dispersal system. In wave-dominated regions, transport mechanisms actively move sediment away from the river source, separating the site of deposition and accumulation from the river mouth. River-flood and storm-wave events each create discrete deposits on the Waipaoa River shelf and data has been collected to determine their form, distribution, and relationship to factors such as flood magnitude or wave energy. In this case, transport pathways appear to be influenced by structurally controlled shelf bathymetry. In both cases, the combined fluvial and marine processes can initiate and maintain gravity-driven density flows, and although their triggers and controls differ vastly, these flows play a significant role in the morpholigcal development of the continental margin. These sites, synthesized with examples from multiple other environments, provide a basis for understanding the interactions between physical processes responsible for the transport of sediment from river mouths to the sites of ultimate deposition.
Development of recent chronologies and evaluation of temporal variations in Pb fluxes and sources in lake sediment and peat cores in a remote, highly radiogenic environment, Cairngorm Mountains, Scottish Highlands

NASA Astrophysics Data System (ADS)

Farmer, John G.; MacKenzie, Angus B.; Graham, Margaret C.; Macgregor, Kenneth; Kirika, Alexander

2015-05-01

The use of stable Pb isotope analyses in conjunction with recent (210Pb and anthropogenic radionuclide) chronologies has become a well-established method for evaluating historical trends in depositional fluxes and sources of atmospherically deposited Pb using archival records in lake sediment or peat cores. Such studies rely upon (i) simple radioactive disequilibrium between unsupported 210Pb and longer-lived members of the 238U decay series and (ii) well-defined values for the isotopic composition of contaminant Pb and indigenous Pb in the study area. However, areas of high natural radioactivity can present challenging environments for such studies, with potential complications arising from more complex disequilibria in the 238U decay series and the occurrence, at local or regional level, of anomalous, ill-defined stable isotope ratios due to the presence of elevated levels of radiogenic Pb. Results are presented here for a study of a sediment core from a freshwater lake, Loch Einich, in the high natural radioactivity area of the Cairngorm Mountains of Scotland. 238U decay series disequilibria revealed recent diagenetic re-deposition of both U and 226Ra, the latter resulting in a requirement to use a modified calculation to derive a 210Pb chronology for the core. Confidence in the chronology was provided by good agreement with the independent 241Am chronology, but the 137Cs distribution was affected by significant post-depositional mobility in the organic-rich sediment. The systematics of variations in 230Th, 232Th and stable Pb isotope ratio distributions were used to establish the indigenous Pb characteristics of the sediment. The relatively high radiogenic content of the indigenous Pb resulted in complications in source apportionment, in particular during the 20th century, with multiple natural and anthropogenic sources precluding the use of a simple binary mixing model. Consequently, 206Pb/207Pb ratios in Scottish moss samples from an archive collection were used to provide the input term for atmospheric deposition in order to establish historical trends in indigenous and anthropogenic Pb fluxes. A test of the accuracy of the derived Pb fluxes was provided by analysis of a core from a nearby blanket peat deposit, Great Moss. Independent atmospheric and basal inputs gave a complex distribution of 210Pb in the peat, but this did not affect calculation of a 210Pb chronology. Once again, the 210Pb chronology was supported by the 241Am distribution. Temporal trends in anthropogenic Pb deposition derived for the Loch Einich sediment core were in generally good agreement with those for the Great Moss peat core, other peat cores and some other lake sediment cores from northern Scotland, providing confidence in the use of the archive moss data to characterise atmospheric deposition. However, sustained input of Pb to Loch Einich sediment at relatively high levels in the late 20th century, after the regional decline in atmospheric Pb deposition, suggested that catchment-derived Pb is now a significant component of the depositional flux for Loch Einich.
Sedimentation and bathymetry changes in Suisun Bay: 1867-1990

USGS Publications Warehouse

Cappiella, Karen; Malzone, Chris; Smith, Richard; Jaffe, Bruce

1999-01-01

Understanding patterns of historical erosion and deposition in San Francisco Bay is crucial in managing such issues as locating deposits of sediment-associated contaminants, and the restoration of wetland areas. These problems were addressed by quantitatively examining historical hydrographic surveys. The data from five hydrographic surveys, made from 1867 to 1990, were analyzed using surface modeling software to determine long-term changes in the sediment system of Suisun Bay and surrounding areas. A surface grid displaying the bathymetry was created for each survey period, and the bathymetric change between survey periods was computed by differencing these grids. Patterns and volumes of erosion and deposition, sedimentation rates, and shoreline changes were derived from the resulting change grids. Approximately 115 million cubic meters of sediment were deposited in the Suisun Bay area from 1867 to 1887, the majority of which was debris from hydraulic gold mining in the Sierra Nevada. Just under two-thirds of the area of the study site was depositional during this time period, while less than one-third of it was erosional. However, over the entire study period, the Suisun Bay area lost sediment, indicating that a large amount of erosion occurred from1887 to 1990. In fact, this area lost sediment during each of the change periods between 1887 and 1990. Because erosion and deposition are processes that may vary over space and time, further analyses of more specific areas were done to examine spatial and temporal patterns. The change in the Suisun Bay area from being a largely depositional environment to an erosional one is the result of a combination of several factors. These factors include the regulation and subsequent cessation of hydraulic mining practices, and the increase in flood control and water distribution projects that have decreased sediment supply to the bay by reducing the frequency and duration of peak flow conditions. Another pattern shown by the changing bathymetry is the substantial decrease in the area of tidal flat (defined in this study as the area between mean lower low water and the shoreline), particularly in Grizzly Bay and Honker Bay. These tidal flats are important to the bay ecosystem, providing stability and biologic diversity.
Hydrogeology and water quality in the Cedar Rapids area, Iowa, 1992-96

USGS Publications Warehouse

Schulmeyer, P.M.; Schnoebelen, D.J.

1998-01-01

Several areas in the Cedar River alluvial aquifer with large iron and manganese concentrations could be related to the original depositional environment of the sediment. In general, large iron and manganese concentrations in ground water are often associated with abundant organic and argillaceous material in sediment near old meander channels and sloughs.
Texture, mineralogy and geochemistry of the continental slope sediments in front of Los Tuxtlas, Gulf of Mexico, Mexico: implications on weathering, origin and depositional environments

NASA Astrophysics Data System (ADS)

Marca-Castillo, M. E.; Armstrong-Altrin, J.

2017-12-01

The textural analysis, mineralogy and geochemistry of two sediment cores recovered from the deep water zone of the southwestern part of the Gulf of Mexico ( 1666 and 1672 m water depth) were studied to infer the provenance and depositional behavior. The textural analysis revealed that both cores are dominated by silt, which occupy more than 50% in both samples and the clay occupy 40%. The petrographic analysis revealed remains of biogenic origin sediments and lithic fragments with an angular shape and low sphericity, indicating a low energy environment and therefore a low level of weathering in the sediment, which suggests that the sediments were not affected by transport and derived from a nearby source rock. In both cores quartz fragments were identified; also volcanic lithic and pyroxenes fragments, which are rocks of intermediate composition and are generally associated with the volcanic activity of the continental margins. SEM-EDS studies showed that the analysed samples have concentrations of minerals such as barite, gibbsite, kaolinite, grossular, magnetite, plagioclase and chlorite, which are probably derived from the mainland to the deep sea zone. In the trace element analysis it was observed a low Sc content, while Co, Ni, V and Cu are slightly enriched with respect to the upper continental crust; this enrichment is related to sediments from intermediate sources. The sediments are classified as shale in the log (SiO2 / Al2O3) - log (Fe2O / K2O) diagram. The fine particles of the shale indicate that a deposit occurred as a result of the gradual sedimentation due to relatively non-turbulent currents, which is consistent with the petrographic analysis. The geochemical features of major and trace elements suggest sediments were derived largely from the natural andesite erosion of coastal regions along the Gulf of Mexico. High values of Fe2O3 and MnO are observed in the upper intervals, reflecting the influence of volcanic sediments. The major element discriminant function diagrams indicate the provenance of sediments from a passive margin, which is consistent with the geology of the Gulf of Mexico.
Current-use pesticides and organochlorine compounds in precipitation and lake sediment from two high-elevation national parks in the Western United States

USGS Publications Warehouse

Mast, M.A.; Foreman, W.T.; Skaates, S.V.

2007-01-01

Current-use pesticides (CUPs) and banned organochlorine compounds (OCCs) were measured in precipitation (snowpack and rain) and lake sediments from two national parks in the Western United States to determine their occurrence and distribution in high-elevation environments. CUPs frequently detected in snow were endosulfan, dacthal, and chlorothalonil in concentrations ranging from 0.07 to 2.4 ng/L. Of the OCCs, chlordane, hexachlorobenzene, and two polychlorinated biphenyl congeners were detected in only one snow sample each. Pesticides most frequently detected in rain were atrazine, carbaryl, and dacthal in concentrations from 3.0 to 95 ng/L. Estimated annual deposition rates in one of the parks were 8.4 ??g/m2 for atrazine, 9.9 ??g/m2 for carbaryl, and 2.6 ??g/m2 for dacthal, of which >85% occurred during summer. p,p'-DDE and p,p'-DDD were the most frequently detected OCCs in surface sediments from lakes. However, concentrations were low (0.12 to 4.7 ??g/kg) and below levels at which harmful effects for benthic organisms are likely to be observed. DDD and DDE concentrations in an age-dated sediment core suggest that atmospheric deposition of DDT and its degradates, and possibly other banned OCCs, to high-elevation areas have been decreasing since the 1970s. Dacthal and endosulfan sulfate were present in low concentrations (0.11 to 1.2 ??g/kg) and were the only CUPs detected in surface sediments. Both pesticides were frequently detected in snow, confirming that some CUPs entering high-elevation aquatic environments through atmospheric deposition are accumulating in lake sediments and potentially in aquatic biota as well. ?? 2007 Springer Science+Business Media, Inc.
Distribution of surficial sediment in Long Island Sound and adjacent waters: Texture and total organic carbon

USGS Publications Warehouse

Poppe, L.J.; Knebel, H.J.; Mlodzinska, Z.J.; Hastings, M.E.; Seekins, B.A.

2000-01-01

The surficial sediment distribution within Long Island Sound has been mapped and described using bottom samples, photography, and sidescan sonar, combined with information from the geologic literature. The distributions of sediment type and total organic carbon (TOC) reveal several broad trends that are largely related to the sea-floor geology, the bathymetry, and the effects of modern tidal- and wind-driven currents. Sediment types are most heterogeneous in bathymetrically complex and shallow nearshore areas; the heterogeneity diminishes and the texture fines with decreasing bottom-current energy. Lag deposits of gravel and gravelly sand dominate the surficial sediment texture in areas where bottom currents are the strongest (such as where tidal flow is constricted) and where glacial till crops out at the sea floor. Sand is the dominant sediment type in areas characterized by active sediment transport and in shallow areas affected by fine-grained winnowing. Silty sand and sand-silt-clay mark transitions within the basin from higher- to lower-energy environments, suggesting a diminished hydraulic ability to sort and transport sediment. Clayey silt and silty clay are the dominant sediment types accumulating in the central and western basins and in other areas characterized by long-term depositional environments. The amount of TOC in the sediments of Long Island Sound varies inversely with sediment grain size. Concentrations average more than 1.9% (dry weight) in clayey silt, but are less than 0.4% in sand. Generally, values for TOC increase both toward the west in the Sound and from the shallow margins to the deeper parts of the basin floor. Our data also suggest that TOC concentrations can vary seasonally.
Evidence for a palaeo-subglacial lake on the Antarctic continental shelf

PubMed Central

Kuhn, Gerhard; Hillenbrand, Claus-Dieter; Kasten, Sabine; Smith, James A.; Nitsche, Frank O.; Frederichs, Thomas; Wiers, Steffen; Ehrmann, Werner; Klages, Johann P.; Mogollón, José M.

2017-01-01

Subglacial lakes are widespread beneath the Antarctic Ice Sheet but their control on ice-sheet dynamics and their ability to harbour life remain poorly characterized. Here we present evidence for a palaeo-subglacial lake on the Antarctic continental shelf. A distinct sediment facies recovered from a bedrock basin in Pine Island Bay indicates deposition within a low-energy lake environment. Diffusive-advection modelling demonstrates that low chloride concentrations in the pore water of the corresponding sediments can only be explained by initial deposition of this facies in a freshwater setting. These observations indicate that an active subglacial meltwater network, similar to that observed beneath the extant ice sheet, was also active during the last glacial period. It also provides a new framework for refining the exploration of these unique environments. PMID:28569750
An acoustic method for predicting relative strengths of cohesive sediment deposits

NASA Astrophysics Data System (ADS)

Reed, A. H.; Sanders, W. M.

2017-12-01

Cohesive sediment dynamics are fundamentally determined by sediment mineralogy, organic matter composition, ionic strength of water, and currents. These factors work to bind the cohesive sediments and to determine depositional rates. Once deposited the sediments exhibit a nonlinear response to stress and they develop increases in shear strength. Shear strength is critically important in resuspension, transport, creep, and failure predictions. Typically, shear strength is determined by point measurements, both indirectly from free-fall penetrometers or directly on cores with a shear vane. These values are then used to interpolate over larger areas. However, the remote determination of these properties would provide continuos coverage, yet it has proven difficult with sonar systems. Recently, findings from an acoustic study on cohesive sediments in a laboratory setting suggests that cohesive sediments may be differentiated using parametric acoustics; this method pulses two primary frequencies into the sediment and the resultant difference frequency is used to determine the degree of acoustic nonlinearity within the sediment. In this study, two marine clay species, kaolinite and montmorillonite, and two biopolymers, guar gum and xanthan gum were mixed to make nine different samples. The samples were evaluated in a parametric acoustic measurement tank. From the parametric acoustic measurements, the quadratic nonlinearity coefficient (beta) was determined. beta was correlated with the cation exchange capacity (CEC), an indicator of shear strength. The results indicate that increased acoustic nonlinearity correlates with increased CEC. From this work, laboratory measurements indicate that this correlation may be used evaluate geotechnical properties of cohesive sediments and may provide a means to predict sediment weakness in subaqueous environments.

Sulfur- and oxygen-isotopes in sediment-hosted stratiform barite deposits

NASA Astrophysics Data System (ADS)

Johnson, Craig A.; Emsbo, Poul; Poole, Forrest G.; Rye, Robert O.

2009-01-01

Sulfur- and oxygen-isotope analyses have been obtained for sediment-hosted stratiform barite deposits in Alaska, Nevada, Mexico, and China to examine the environment of formation of this deposit type. The barite is contained in sedimentary sequences as old as Late Neoproterozoic and as young as Mississippian. If previously published data for other localities are considered, sulfur- and oxygen-isotope data are now available for deposits spanning a host-rock age range of Late Neoproterozoic to Triassic. On a δ 34S versus δ 18O diagram, many deposits show linear or concave-upward trends that project down toward the isotopic composition of seawater sulfate. The trends suggest that barite formed from seawater sulfate that had been isotopically modified to varying degrees. The δ 34S versus δ 18O patterns resemble patterns that have been observed in the modern oceans in pore water sulfate and water column sulfate in some anoxic basins. However, the closest isotopic analog is barite mineralization that occurs at fluid seeps on modern continental margins. Thus the data favor genetic models for the deposits in which barium was delivered by seafloor seeps over models in which barium was delivered by sedimentation of pelagic organisms. The isotopic variations within the deposits appear to reflect bacterial sulfate reduction operating at different rates and possibly with different electron donors, oxygen isotope exchange between reduction intermediates and H 2O, and sulfate availability. Because they are isotopically heterogeneous, sediment-hosted stratiform barite deposits are of limited value in reconstructing the isotopic composition of ancient seawater sulfate.
Pulmonary Deposition of Aerosols in Microgravity

NASA Technical Reports Server (NTRS)

Prisk, G. Kim

1997-01-01

The intrapulmonary deposition of airborne particles (aerosol) in the size range of 0.5 to 5 microns is primarily due to gravitational sedimentation. In the microgravity (muG) environment, sedimentation is no longer active, and thus there should be marked changes in the amount and site of the deposition of these aerosol. We propose to study the total intrapulmonary deposition of aerosol spanning the range 0.5 to 5 microns in the KC-135 at both muG and at 1.8-G. This will be followed by using boli of 1.0 micron aerosol, inhaled at different points in a breath to study aerosol dispersion and deposition as a function of inspired depth. The results of these studies will have application in better understanding of pulmonary diseases related to inhaled particles (pneumoconioses), in studying drugs delivered by inhalation, and in understanding the consequence of long-term exposure to respirable aerosols in long-duration space flight.
Manganese oxide mineralogy in an exhalative environment from the Solomon Islands

NASA Astrophysics Data System (ADS)

Taylor, G. R.

1983-04-01

The mineralogy and chemistry of oxidate facies sediments associated with a Solomon Island cupriferous pyrite deposit are described. Systematic variations in sediment composition are consistent with the gradual imposition of an oxidising environment on a pool of exhaled solution lying in a topographic depression on the sea floor. Manganese is first precipitated in the Mn2+ oxidation state as pyrochroite, γMn(OH)2. With later seafloor weathering and diagenesis, this oxidises initially to the Mn3+ intermediate minerals manganite (γMnO.OH) or, in the presence of iron hydroxides, to groutite (αMnO.OH). Subsequently, these oxidise further to Mn4+ as the βMnO2 dimorphs pyrolusite or ramsdellite, respectively. Todorokite (δMnO2) is indicative of more oxidising conditions and is found in the upper horizons of the manganiferous sediment. It is invariably non-stoichiometric in composition and its Mn2+/Mn4+ ratio is a direct function of the Eh prevailing during its precipitation. Adsorption of Na+, K+, Ca2+ and Ba2+ions at the time of formation stabilises the todorokite structure and provides an explanation for its persistence (with its Mn2+ions) in association with the completely oxidised Mn4+ mineral, βMnO2, pyrolusite. The enrichment of Cu, Zn and Pb in manganiferous sediments from both pelagic and exhalative environments is associated with the occurrence of goethite. The enrichment of K, Ba and Ca in manganiferous sediments from a similar range in environments is associated with the occurrence of todorokite. Both the mineralogy and trace element characteristics of a manganiferous sediment are thus a function of the environment of deposition rather than the ultimate source of the metals concerned. The trace element contents of manganiferous “floaters” should therefore only be used as an indicator of related sulphide mineralisation in the presence of other favourable factors.
Immediate propagation of deglacial environmental change to deep-marine turbidite systems along the Chile convergent margin

NASA Astrophysics Data System (ADS)

Bernhardt, Anne; Schwanghart, Wolfgang; Hebbeln, Dierk; Stuut, Jan-Berend W.; Strecker, Manfred R.

2017-09-01

Understanding how Earth-surface processes respond to past climatic perturbations is crucial for making informed predictions about future impacts of climate change on sediment fluxes. Sedimentary records provide the archives for inferring these processes, but their interpretation is compromised by our incomplete understanding of how sediment-routing systems respond to millennial-scale climate cycles. We analyzed seven sediment cores recovered from marine turbidite depositional sites along the Chile continental margin. The sites span a pronounced arid-to-humid gradient with variable relief and related sediment connectivity of terrestrial and marine environments. These sites allowed us to study event-related depositional processes in different climatic and geomorphic settings from the Last Glacial Maximum to the present day. The three sites reveal a steep decline of turbidite deposition during deglaciation. High rates of sea-level rise postdate the decline in turbidite deposition. Comparison with paleoclimate proxies documents that the spatio-temporal sedimentary pattern rather mirrors the deglacial humidity decrease and concomitant warming with no resolvable lag times. Our results let us infer that declining deglacial humidity decreased fluvial sediment supply. This signal propagated rapidly through the highly connected systems into the marine sink in north-central Chile. In contrast, in south-central Chile, connectivity between the Andean erosional zone and the fluvial transfer zone probably decreased abruptly by sediment trapping in piedmont lakes related to deglaciation, resulting in a sudden decrease of sediment supply to the ocean. Additionally, reduced moisture supply may have contributed to the rapid decline of turbidite deposition. These different causes result in similar depositional patterns in the marine sinks. We conclude that turbiditic strata may constitute reliable recorders of climate change across a wide range of climatic zones and geomorphic conditions. However, the underlying causes for similar signal manifestations in the sinks may differ, ranging from maintained high system connectivity to abrupt connectivity loss.
Deposit model for heavy-mineral sands in coastal environments: Chapter L in Mineral deposit models for resource assessment

USGS Publications Warehouse

Van Gosen, Bradley S.; Fey, David L.; Shah, Anjana K.; Verplanck, Philip L.; Hoefen, Todd M.

2014-01-01

Regional exploration for deposits of heavy-mineral sands can utilize the analyses of stream sediment samples for Ti, Hf, the rare earth elements, Th, and U, and geophysical surveys, particularly radiometric (gamma-ray spectrometry for K, U, and Th) and magnetic methods. Geophysical anomalies may be small, and surveys are generally more successful when conducted close to sources of interest.
Records of continental slope sediment flow morphodynamic responses to gradient and active faulting from integrated AUV and ROV data, offshore Palos Verdes, southern California Borderland

USGS Publications Warehouse

Maier, Katherine L.; Brothers, Daniel; Paull, Charles K.; McGann, Mary; Caress, David W.; Conrad, James E.

2016-01-01

Variations in seabed gradient are widely acknowledged to influence deep-water deposition, but are often difficult to measure in sufficient detail from both modern and ancient examples. On the continental slope offshore Los Angeles, California, autonomous underwater vehicle, remotely operated vehicle, and shipboard methods were used to collect a dense grid of high-resolution multibeam bathymetry, chirp sub-bottom profiles, and targeted sediment core samples that demonstrate the influence of seafloor gradient on sediment accumulation, depositional environment, grain size of deposits, and seafloor morphology. In this setting, restraining and releasing bends along the active right-lateral Palos Verdes Fault create and maintain variations in seafloor gradient. Holocene down-slope flows appear to have been generated by slope failure, primarily on the uppermost slope (~ 100–200 m water depth). Turbidity currents created a low relief (< 10 m) channel, up-slope migrating sediment waves (λ = ~ 100 m, h ≤ 2 m), and a series of depocenters that have accumulated up to 4 m of Holocene sediment. Sediment waves increase in wavelength and decrease in wave height with decreasing gradient. Integrated analysis of high-resolution datasets provides quantification of morphodynamic sensitivity to seafloor gradients acting throughout deep-water depositional systems. These results help to bridge gaps in scale between existing deep-sea and experimental datasets and may provide constraints for future numerical modeling studies.
Rock magnetic characterization of faulted sediments with associated magnetic anomalies in the Albuquerque Basin, Rio Grande rift, New Mexico

USGS Publications Warehouse

Hudson, M.R.; Grauch, V.J.S.; Minor, S.A.

2008-01-01

Variations in rock magnetic properties are responsible for the many linear, short-wavelength, low-amplitude magnetic anomalies that are spatially associated with faults that cut Neogene basin sediments in the Rio Grande rift, including the San Ysidro normal fault, which is well exposed in the northern part of the Albuquerque Basin. Magnetic-susceptibility measurements from 310 sites distributed through a 1200-m-thick composite section of rift-filling sediments of the Santa Fe Group and prerift Eocene and Cretaceous sedimentary rocks document large variations of magnetic properties juxtaposed by the San Ysidro fault. Mean volume magnetic susceptibilities generally increase upsection through eight map units: from 1.7 to 2.2E-4 in the prerift Eocene and Cretaceous rocks to 9.9E-4-1.2E-3 in three members of the Miocene Zia Formation of the Santa Fe Group to 1.5E-3-3.5E-3 in three members of the Miocene-Pleistocene Arroyo Ojito Formation of the Santa Fe Group. Rock magnetic measurements and petrography indicate that the amount of detrital magnetite and its variable oxidation to maghemite and hematite within the Santa Fe Group sediments are the predominant controls of their magnetic property variations. Magnetic susceptibility increases progressively with sediment grain size within the members of the Arroyo Ojito Formation (deposited in fluvial environments) but within members of the Zia Formation (deposited in mostly eolian environments) reaches highest values in fine to medium sands. Partial oxidation of detrital magnetite is spatially associated with calcite cementation in the Santa Fe Group. Both oxidation and cementation probably reflect past flow of groundwater through permeable zones. Magnetic models for geologic cross sections that incorporate mean magnetic susceptibilities for the different stratigraphic units mimic the aeromagnetic profiles across the San Ysidro fault and demonstrate that the stratigraphic level of dominant magnetic contrast changes with different exposure levels into the fault. These data indicate that tectonic juxtaposition of primary variations of magnetic properties of strata across the fault is the source of the associated magnetic anomaly. This study indicates that magnetic anomalies over faults and folds can be generated by sediments (1) deposited within tectonic basins having volcanic or basement source areas rich in magnetite, (2) having depositional environments with sufficient but varying energy to transport dense magnetic minerals and cause stratigraphic changes of magnetic properties, and (3) having magnetic minerals preserved owing to their youth or nonreactive geochemical environments. ?? 2007 Geological Society of America.
Sediment grain-size characteristics and relevant correlations to the aeolian environment in China's eastern desert region.

PubMed

Zhang, Chunlai; Shen, Yaping; Li, Qing; Jia, Wenru; Li, Jiao; Wang, Xuesong

2018-06-15

To identify characteristics of aeolian activity and the aeolian environment in China's eastern desert region, this study collected surface sediment samples from the main desert and sandy lands in this region: the Hobq Desert and the Mu Us, Otindag, Horqin, and Hulunbuir sandy lands. We analyzed the grain-size characteristics and their relationships to three key environmental indicators: drift potential, the dune mobility index, and vegetation cover. The main sediment components are fine to medium sands, with poor (Hulunbuir) to moderate (all other areas) sorting, of unimodal to bimodal distribution. This suggests that improved sorting is accomplished by the loss of both relatively coarser and finer grains. Since 2000, China's eastern desert region has generally experienced low wind energy environmental conditions, resulting in decreased dune activity. In the Hobq Desert, however, the dry climate and sparse vegetation, in conjunction with the most widely distributed mobile dune area in the eastern desert region, have led to frequent and intense aeolian activity, including wind erosion, sand transport, and deposition, resulting in conditions for good sediment sorting. In the Mu Us, Otindag, and Horqin sandy lands, mosaic distribution has resulted from wind erosion-dominated and deposition-dominated aeolian environments. In the Hulunbuir Sandy Land, high precipitation, low temperatures, and steppe vegetation have resulted in well-developed soils; however, strong winds and flat terrain have created an aeolian environment dominated by wind erosion. Copyright © 2018. Published by Elsevier B.V.
Open-water and under-ice seasonal variations in trace element content and physicochemical associations in fluvial bed sediment.

PubMed

Doig, Lorne E; Carr, Meghan K; Meissner, Anna G N; Jardine, Tim D; Jones, Paul D; Bharadwaj, Lalita; Lindenschmidt, Karl-Erich

2017-11-01

Across the circumpolar world, intensive anthropogenic activities in the southern reaches of many large, northward-flowing rivers can cause sediment contamination in the downstream depositional environment. The influence of ice cover on concentrations of inorganic contaminants in bed sediment (i.e., sediment quality) is unknown in these rivers, where winter is the dominant season. A geomorphic response unit approach was used to select hydraulically diverse sampling sites across a northern test-case system, the Slave River and delta (Northwest Territories, Canada). Surface sediment samples (top 1 cm) were collected from 6 predefined geomorphic response units (12 sites) to assess the relationships between bed sediment physicochemistry (particle size distribution and total organic carbon content) and trace element content (mercury and 18 other trace elements) during open-water conditions. A subset of sites was resampled under-ice to assess the influence of season on these relationships and on total trace element content. Concentrations of the majority of trace elements were strongly correlated with percent fines and proxies for grain size (aluminum and iron), with similar trace element grain size/grain size proxy relationships between seasons. However, finer materials were deposited under ice with associated increases in sediment total organic carbon content and the concentrations of most trace elements investigated. The geomorphic response unit approach was effective at identifying diverse hydrological environments for sampling prior to field operations. Our data demonstrate the need for under-ice sampling to confirm year-round consistency in trace element-geochemical relationships in fluvial systems and to define the upper extremes of these relationships. Whether contaminated or not, under-ice bed sediment can represent a "worst-case" scenario in terms of trace element concentrations and exposure for sediment-associated organisms in northern fluvial systems. Environ Toxicol Chem 2017;36:2916-2924. © 2017 SETAC. © 2017 SETAC.
U-Th and 10Be constraints on sediment recycling in proglacial settings, Lago Buenos Aires, Patagonia

NASA Astrophysics Data System (ADS)

Cogez, Antoine; Herman, Frédéric; Pelt, Éric; Reuschlé, Thierry; Morvan, Gilles; Darvill, Christopher M.; Norton, Kevin P.; Christl, Marcus; Märki, Lena; Chabaux, François

2018-03-01

The estimation of sediment transfer times remains a challenge to our understanding of sediment budgets and the relationships between erosion and climate. Uranium (U) and thorium (Th) isotope disequilibria offer a means of more robustly constraining sediment transfer times. Here, we present new uranium and thorium disequilibrium data for a series of nested moraines around Lago Buenos Aires in Argentine Patagonia. The glacial chronology for the area is constrained using in situ cosmogenic 10Be analysis of glacial outwash. Sediment transfer times within the periglacial domain were estimated by comparing the deposition ages of moraines to the theoretical age of sediment production, i.e., the comminution age inferred from U disequilibrium data and recoil loss factor estimates. Our data show first that the classical comminution age approach must include weathering processes accounted for by measuring Th disequilibrium. Second, our combined data suggest that the pre-deposition history of the moraine sediments is not negligible, as evidenced by the large disequilibrium of the youngest moraines despite the equilibrium of the corresponding glacial flour. Monte Carlo simulations suggest that weathering was more intense before the deposition of the moraines and that the transfer time of the fine sediments to the moraines was on the order of 100-200 kyr. Long transfer times could result from a combination of long sediment residence times in the proglacial lake (recurrence time of a glacial cycle) and the remobilization of sediments from moraines deposited during previous glacial cycles. 10Be data suggest that some glacial cycles are absent from the preserved moraine record (seemingly every second cycle), supporting a model of reworking moraines and/or fluctuations in the extent of glacial advances. The chronological pattern is consistent with the U-Th disequilibrium data and the 100-200 kyr transfer time. This long transfer time raises the question of the proportion of freshly eroded sediments that escape (or not) the proglacial environments during glacial periods.
Sedimentological and geochemical record of submarine mine tailing footprint in Repparfjorden (Northern Norway)

NASA Astrophysics Data System (ADS)

Sternal, Beata; Junttila, Juho; Pedersen, Kristine Bondo; Skirbekk, Kari; Forwick, Matthias; Carroll, JoLynn

2016-04-01

The knowledge on understanding the physical, chemical and biological processes dominating in marine system affected by submarine tailings disposal (STD) remains limited and further knowledge to make reliable long-term predictions of future environmental impacts is needed. One way of contributing to this is by investigation of marine environments already affected by the tailings discharge in the past. We present preliminary results from a multidisciplinary study of marine sediments from Repparfjorden in northern Norway, a fjord that was influenced by the deposition of tailings from a copper mine during the 1970's. The study is a part of the competence cluster Environmental Waste Management (EWMA) that as one of its important aims has advancing the knowledge of spreading of mine-tailing related contaminants. Here we give particular attention to the reconstruction of sedimentation style, rate of sediment accumulation, as well as potential sediment transport paths (contaminants dispersion). Seventeen short cores (up to 21 cm long) were retrieved from sites covering the entire area of Repparfjorden. The cores were sliced into 1-cm intervals that are and will be analysed for grain-size, concentration of heavy metals and total organic carbon content of bulk sediment. Sediment chronologies are and will be derived using 210Pb and 137Cs dating techniques. An approximately 7-cm thick interval which is different from present fjord sedimentation was observed below c. 10 cm depth in three of the cores retrieved from the area of tailings deposition in the 1970's. Sediments of this discrete depth interval are mainly composed of mud or sandy mud with bimodal grain-size distribution (first mode: medium silt fraction; second mode: very coarse silt). They are characterised by very high Cu concentrations (>250 mg/kg). Preliminary measurements of the 210Pb activity indicate an increase in sediment accumulation rate during the deposition of this interval. Therefore, we interpret it to be mainly composed of mine tailing sediments. As this sediment interval was only observed in 3 of 17 cores, we suggest that the lateral extent of the tailings is restricted to a relatively small area of the fjord. However, elevated concentrations of Cu (40-80 mg/kg) were also detected in a discrete sediment interval (3-10 cm) in one core ˜3 km beyond the tailing deposition site. In addition, high Cu concentrations (60-190 mg/kg) in sediments between the seafloor and the tailing deposit, as well as some centimetres below the deposit (in all cores from the old tailing deposition site) suggest possible dispersion of Cu to the immediate surrounding sediments in the cores.
Impact of sedimentary provenance and weathering on arsenic distribution in aquifers of the Datong basin, China: Constraints from elemental geochemistry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xie, Xianjun; Wang, Yanxin; Ellis, Andre

Arsenic (As)-contaminated aquifer sediments from Datong basin, China have been analyzed to infer the provenance and depositional environment related to As distribution in the aquifer sediments. The As content in the sediments ranged from 2.45 to 27.38 mg/kg with an average value of 9.54 mg/kg, which is comparable to the average value in modern unconsolidated sediments. However, minor variation in As concentration with depth has been observed in the core. There was a significant correlation between Fe, and Al and As, which was attributed to the adsorption or co-precipitation of As onto/with Fe oxides/hydroxides and/or Fe-coated clay minerals. Post-Archean Australianmore » Shale (PAAS)-normalized REEs patterns of sediment samples along the borehole were constant, and the sediments had a notably restricted range of La-N/Yb-N ratios from 0.7 to 1.0. These results suggested that the provenance of the Datong basin remained similar throughout the whole depositional period. The analysis of major geochemical compositions confirmed that all core sediments were from the same sedimentary source and experienced significant sedimentary recycling. The co-variation of As, V/Al, Ni/Al and chemical index of alteration (CIA) values in the sediments along the borehole suggested that As distribution in the sediments was primarily controlled by weathering processes. The calculated CIA values of the sediments along the borehole indicate that a relative strong chemical weathering occurred during the deposition of sediments at depths of similar to 35 to 88 m, which was corresponding to the depth at which high As groundwater was observed at the site. Strong chemical weathering favored the deposition of Fe-bearing minerals including poorly crystalline and crystalline Fe oxide mineral phases and concomitant co-precipitation of As with these minerals in the sediments. Subsequent reductive dissolution of As-bearing poorly crystalline and crystalline Fe oxides would result in the enrichment of As in groundwater. In general, the chemical weathering during the deposition of the sediments governed the co-accumulation of Fe oxides and As in the aquifer sediments. And then, the reductive dissolution of Fe oxides/hydroxides is the mechanism of As enrichment in the groundwater in the Datong basin« less
Discriminating between natural and anthropogenic features of the sedimentary record in the coastal Beaufort Sea

NASA Astrophysics Data System (ADS)

Trefry, J. H.; Trocine, R. P.; Fox, A. L.; Fox, S. L.; Durell, G.; Kasper, J.

2016-02-01

The coastal Beaufort Sea is at a crossroads with respect to the impacts of human activities. Accurate discrimination of regional and global anthropogenic impacts, versus those due to natural physical and biogeochemical processes, is an important tool for managing environmental issues in the Arctic. We have investigated several natural and anthropogenic features in age-dated sediment cores from the coastal Beaufort Sea. For example, Hg enrichment (by 20 to >50% or +20 to 40 ng/g) was identified in some surface sediments using Hg/Al ratios in cores from nearshore, outer shelf and slope environments. Nearshore Hg anomalies, although quite limited in number, have been linked to drilling fluids deposited during oil and gas exploration in the 1980s. In contrast, similar offshore Hg anomalies are likely due to natural sediment diagenesis as previously noted by others in the deeper Arctic Ocean. We also found Ba enrichment in surface sediments that can be best explained by the deposition of natural, Ba-rich suspended particles from the Colville River; yet, Ba enrichment can sometimes be explained by the presence of drilling fluids in sediments near historic drilling sites. Human induced diagenetic changes are likely to follow current increases in river runoff and coastal erosion. Higher deposition rates for sediment and organic carbon in the coastal Beaufort Sea may create future anomalies for As, Cd and other metals. For example, metal anomalies can presently be found in older subsurface sediments where a layer of carbon-rich sediment was previously deposited. Correct identification of natural versus anthropogenic forcing factors that lead to distinct diagenetic features in the sedimentary record will help us to identify problem areas and make informed regulatory decisions.
A Comparison of Recent Organic and Inorganic Carbon Isotope Records: Why Do They Covary in Some Settings and Not In Others?

NASA Astrophysics Data System (ADS)

Oehlert, A. M.; Swart, P. K.

2013-12-01

Covariance between inorganic and organic δ13C records has been used to determine whether a deposit has been altered by diagenesis, how the dynamics of the global carbon cycle changed during the production of the sediments in the deposit, and also for chronostratigraphic correlations. Although covariant records are observed in the ancient geologic record in a variety of depositional environments, such comparisons are not widely applied to modern deposits where definitive data regarding sediment producers, sea level fluctuations, and changes in the global carbon cycle are available. This study uses paired δ13C records from cores collected by the Ocean Drilling Program from three modern periplatform settings (the Great Bahama Bank, the Great Australian Bight, and the Great Barrier Reef), and two pelagic settings (the Walvis Ridge, and the Madingley Rise). These sites were selected in order to assess the influence of several different environmental factors including; sediment and organic matter producers, sediment mineralogy, margin architecture, sea level oscillations, and sediment transport pathways. In the three periplatform settings, multiple cores arranged in a margin to basin transect were analyzed in order to provide insights into the effects of downslope sediment transport. The preliminary results of this study suggest that sea level oscillations and margin architecture may artificially generate a covarying relationship in periplatform sediments that is unrelated to changes in the global carbon cycle. Furthermore, preliminary results from the Walvis Ridge and the Madingley Rise sediments suggest that the relationship between inorganic and organic δ13C records may not always exhibit a positive covariance as is currently assumed for pelagic carbonates.
Sediment storage and severity of contamination in a shallow reservoir affected by historical lead and zinc mining

USGS Publications Warehouse

Juracek, K.E.

2008-01-01

A combination of sediment-thickness measurement and bottom-sediment coring was used to investigate sediment storage and severity of contamination in Empire Lake (Kansas), a shallow reservoir affected by historical Pb and Zn mining. Cd, Pb, and Zn concentrations in the contaminated bottom sediment typically exceeded baseline concentrations by at least an order of magnitude. Moreover, the concentrations of Cd, Pb, and Zn typically far exceeded probable-effects guidelines, which represent the concentrations above which toxic biological effects usually or frequently occur. Despite a pre-1954 decrease in sediment concentrations likely related to the end of major mining activity upstream by about 1920, concentrations have remained relatively stable and persistently greater than the probable-effects guidelines for at least the last 50 years. Cesium-137 evidence from sediment cores indicated that most of the bottom sediment in the reservoir was deposited prior to 1954. Thus, the ability of the reservoir to store the contaminated sediment has declined over time. Because of the limited storage capacity, Empire Lake likely is a net source of contaminated sediment during high-inflow periods. The contaminated sediment that passes through, or originates from, Empire Lake will be deposited in downstream environments likely as far as Grand Lake O' the Cherokees (Oklahoma). ?? 2007 Springer-Verlag.
Characterization and origin of spongillite-hosting sediment from João Pinheiro, Minas Gerais, Brazil

NASA Astrophysics Data System (ADS)

Almeida, A. C. S.; Varajão, A. F. D. C.; Gomes, N. S.; Varajão, C. A. C.; Volkmer-Ribeiro, C.

2010-03-01

Spongillite from João Pinheiro, Minas Gerais, Brazil is mainly known for its use in brick production and in the refractory industry. Very few studies have focused on its geological context. Spongillite-rich deposits occur in shallow ponds on a karstic planation surface developed on rocks of the Neoproterozoic São Francisco Supergroup. Cenozoic siliciclastic sediments are related to this surface. A field study of these deposits and analysis of multispectral images showed a SE-NW preferential drainage system at SE, suggesting that Mesozoic Areado Group sandstones were the source area of the spongillite-hosting sediments. Mineralogical and textural characterization by optical microscopic analysis, X-ray diffraction (XRD), differential and gravimetric thermal analysis (DTA-GTA), infrared spectroscopy (IR) and scanning electron microscopy (SEM) of seven open-pit spongillite-rich deposits (Avião, Carvoeiro, Vânio, Preguiça, Divisa, Severino, Feijão) showed a sedimentological similarity between the deposits. They are lens-shaped and are characterized at the bottom by sand facies, in the middle by spicules-rich muddy-sand facies and at the top by organic matter-rich muddy-sand facies. Petrographically, the spongillite-hosting sediments and the siliclastic sediments of the Areado Group show detrital phases with similar mineralogical and textural features, such as the presence of well-sorted quartz grains and surface features of abrasion typical of aeolian reworking that occurred in the depositional environment in which the sandstones of the Areado Group were formed. Detrital heavy minerals, such as staurolite, zircon, tourmaline, and clay minerals, such as kaolinite, low amounts of illite, scarce chlorite and mixed-layer chlorite/smectite and illite/smectite occur in the spongillite-hosting sediments and in sandstones from the Areado Group. In both formations, staurolite has similar chemical composition. These mineralogical and textural features show that the sediments of the Areado Group constitute the main source of the pond sediments that host spongillite.
Coal depositional models in some Tertiary and Cretaceous coal fields in the U.S. Western Interior

USGS Publications Warehouse

Flores, R.M.

1979-01-01

Detailed stratigraphic and sedimentological studies of the Tertiary Tongue River Member of the Fort Union Formation in the Powder River Basin, Wyoming, and the Cretaceous Blackhawk Formation and Star Point Sandstone in the Wasatch Plateau, Utah, indicate that the depositional environments of coal played a major role in controlling coal thickness, lateral continuity, potential minability, and type of floor and roof rocks. The potentially minable, thick coal beds of the Tongue River Member were primarily formed in long-lived floodbasin backswamps of upper alluvial plain environment. Avulsion of meandering fluvial channels contributed to the erratic lateral extent of coals in this environment. Laterally extensive coals formed in floodbasin backswamps of a lower alluvial plain environment; however, interruption by overbank and crevasse-splay sedimentation produced highly split and merging coal beds. Lacustrine sedimentation common to the lower alluvial plain, similar to the lake-covered lower alluvial valley of the Atchafalaya River Basin, is related to a high-constructive delta. In contrast to these alluvial coals are the deltaic coal deposits of the Blackhawk Formation. The formation consists of three coal populations: upper delta plain, lower delta plain, and 'back-barrier'. Coals of the lower delta plain are thick and laterally extensive, in contrast to those of the upper delta plain and 'back-barrier', which contain abundant, very thin and laterally discontinuous carbonaceous shale partings. The reworking of the delta-front sediments of the Star Point Sandstone suggests that the Blackhawk-Star Point delta was a high-destructive system. ?? 1979.
Deposition, exhumation, and paleoclimate of an ancient lake deposit, Gale crater, Mars

USGS Publications Warehouse

Grotzinger, J.P.; Gupta, S.; Malin, M.C.; Rubin, D.M.; Schieber, J.; Siebach, K.; Sumner, D.Y.; Stack, K.M.; Vasavada, A.R.; Arvidson, R.E.; Calef, F.; Edgar, Lauren; Fischer, W.F.; Grant, J.A.; Griffes, J.L.; Kah, L.C.; Lamb, M.P.; Lewis, K.W.; Mangold, N.; Minitti, M.E.; Palucis, M.C.; Rice, M.; Williams, R.M.E.; Yingst, R.A.; Blake, D.; Blaney, D.; Conrad, P.; Crisp, J.A.; Dietrich, W.E.; Dromart, G.; Edgett, K.S.; Ewing, R.C.; Gellert, R.; Hurowitz, J.A.; Kocurek, G.; Mahaffy, P.G.; McBride, M.J.; McLennan, S.M.; Mischna, M.A.; Ming, D.; Milliken, R.E.; Newsom, H.; Oehler, D.; Parker, T.J.; Vaniman, D.; Wiens, R.C.; Wilson, S.A.

2015-01-01

The landforms of northern Gale crater on Mars expose thick sequences of sedimentary rocks. Based on images obtained by the Curiosity rover, we interpret these outcrops as evidence for past fluvial, deltaic, and lacustrine environments. Degradation of the crater wall and rim probably supplied these sediments, which advanced inward from the wall, infilling both the crater and an internal lake basin to a thickness of at least 75 meters. This intracrater lake system probably existed intermittently for thousands to millions of years, implying a relatively wet climate that supplied moisture to the crater rim and transported sediment via streams into the lake basin. The deposits in Gale crater were then exhumed, probably by wind-driven erosion, creating Aeolis Mons (Mount Sharp).
DOE Office of Scientific and Technical Information (OSTI.GOV)

Simpson, H.J.; Williams, S.C.

We have obtained a large set of cores from the Hudson Estuary covering nearly all of the ambient salinity range. A number of core sections have been analyzed for /sup 137/Cs, /sup 134/Cs, /sup 60/Co and /sup 40/K by direct gamma counting and for /sup 239/,/sup 240/Pu and /sup 238/Pu by alpha-spectrometry. Rapid accumulation, up to 20 cm/year, of sediments containing /sup 239/,/sup 240/Pu, /sup 137/Cs, /sup 134/Cs and /sup 60/Co occurs in New York Harbor. Marginal coves upstream from the harbor also serve as depositional environments. The ratio of sediment /sup 239,240/Pu to /sup 137/Cs is higher than themore » fallout ratio in the seaward end of New York Harbor, despite the presence of a significant component of reactor /sup 137/Cs in the sediments, but lower than the range of ratios observed by others for nearshore environments with low sediment deposition rates. A substantial portion of gamma emitting fission product and activation nuclides released from the Indian Point nuclear facility have accumulated in New York Harbor, more than 60 km downstream from the release area. We have not yet established whether local transuranic releases to the Hudson have occurred.« less
Total Suspended Matter (TSM) and Maximum Signal Depth (Z90_max) for Monitoring the Evolution of Sediment Resuspension Process in Shallow Coastal Environments

NASA Astrophysics Data System (ADS)

Filipponi, Federico; Zucca, Francesco; Taramelli, Andrea; Valentini, Emiliana

2015-12-01

Monitoring sediment fluxes patterns in coastal area, like dispersion, sedimentation and resuspension processes, is a relevant topic for scientists, decision makers and natural resources management. Time series analysis of Earth Observation (EO) data may contribute to the understanding and the monitoring of processes in sedimentary depositional marine environment, especially for shallow coastal areas. This research study show the ability of optical medium resolution imagery to interpret the evolution of sediment resuspension from seafloor in coastal areas during intense wind forcings. Intense bora wind events in northern Adriatic Sea basin during winter season provoke considerable wave-generated resuspension of sediments, which cause variation in water column turbidity. Total Suspended Matter (TSM) product has been selected as proxy for qualitative and quantitative analysis of resuspended sediments. In addition, maximum signal depth (Z90_max), has been used to evaluate the evolution of sediment concentration in the water column.

Quantification of Fine-grained Sediment Concentration in the Aquatic Environment Using Optical and Acoustic Sensors: Insight from Lab Experiments

NASA Astrophysics Data System (ADS)

Xu, K.; Champagne, B. N.

2017-12-01

The transport of sediment in the coastal zone and continental shelf is highly impacted by fluvial and oceanographic dynamics. In Louisiana, the Mississippi River delivers a bulk of water, sediment, and nutrients to the coast. However, coastal land loss highlights the importance of the sediment deposited at the mouth of the river. Sediment is the foundation to build land and suspended sediment concentration (SSC) tracks the delivery, deposition, and erosion of sediment. On a more applicable scale, variables such as SSC can be used to calculate sediment transport flux, an important parameter for projects such as sediment diversions and barrier island restoration. In order to rely on suspended sediment concentration (SSC) as continuous data, lab experiments are needed to establish the relationship between turbidity and SSC. Factors such as sensor type (optical or acoustic) and grain size (coarse or fine) can greatly impact the estimated SSC. In this study, fine-grained sediment was collected from multiple sites in coastal Louisiana and used to calibrate both optical backscatter (OBS) and acoustic backscatter (ABS) sensors to establish the relationship between sensor type and accuracy of the SSC estimation. Multiple grain-size analyses using a Laser Diffraction Particle Size Analyzer helped determine the effects of sensor accuracy regarding grain size. The results of these experiments were combined in order to establish the calibration curves of SSC. Our results indicated that the OBS-3A sensor's turbidity data were more correlated with the SSC than the OBS-5+'s data. Possible explanations for this could be due to differences between the instruments' measuring ranges and their sensitivity to various grain sizes. This technology development has a broad impact to the studies of sediment delivery, transport, and deposition in multiple types of coastal protection and restoration projects.
Modeling chemical accumulation in sediment of small waterbodies accounting for sediment transport and water-sediment exchange processes over long periods.

PubMed

Patterson, David Albert; Strehmel, Alexander; Erzgräber, Beate; Hammel, Klaus

2017-12-01

In a recent scientific opinion of the European Food Safety Authority it is argued that the accumulation of plant protection products in sediments over long time periods may be an environmentally significant process. Therefore, the European Food Safety Authority proposed a calculation to account for plant protection product accumulation. This calculation, however, considers plant protection product degradation within sediment as the only dissipation route, and does not account for sediment dynamics or back-diffusion into the water column. The hydraulic model Hydrologic Engineering Center-River Analysis System (HEC-RAS; US Army Corps of Engineers) was parameterized to assess sediment transport and deposition dynamics within the FOrum for Co-ordination of pesticide fate models and their USe (FOCUS) scenarios in simulations spanning 20 yr. The results show that only 10 to 50% of incoming sediment would be deposited. The remaining portion of sediment particles is transported across the downstream boundary. For a generic plant protection product substance this resulted in deposition of only 20 to 50% of incoming plant protection product substance. In a separate analysis, the FOCUS TOXSWA model was utilized to examine the relative importance of degradation versus back-diffusion as loss processes from the sediment compartment for a diverse range of generic plant protection products. In simulations spanning 20 yr, it was shown that back-diffusion was generally the dominant dissipation process. The results of the present study show that sediment dynamics and back-diffusion should be considered when calculating long-term plant protection product accumulation in sediment. Neglecting these may lead to a systematic overestimation of accumulation. Environ Toxicol Chem 2017;36:3223-3231. © 2017 SETAC. © 2017 SETAC.
Areal distribution of sedimentary facies determined from seismic facies analysis and models of modern depositional systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seramur, K.C.; Powell, R.D.; Carpenter, P.J.

1988-02-01

Seismic facies analysis was applied to 3.5-kHz single-channel analog reflection profiles of the sediment fill within Muir Inlet, Glacier Bay, southeast Alaska. Nine sedimentary facies have been interpreted from seven seismic facies identified on the profiles. The interpretations are based on reflection characteristics and structural features of the seismic facies. The following reflection characteristics and structural features are used: reflector spacing, amplitude and continuity of reflections, internal reflection configurations, attitude of reflection terminations at a facies boundary, body geometry of a facies, and the architectural associations of seismic facies within each basin. The depositional systems are reconstructed by determining themore » paleotopography, bedding patterns, sedimentary facies, and modes of deposition within the basin. Muir Inlet is a recently deglaciated fjord for which successive glacier terminus positions and consequent rates of glacial retreat are known. In this environment the depositional processes and sediment characteristics vary with distance from a glacier terminus, such that during a retreat a record of these variations is preserved in the aggrading sediment fill. Sedimentary facies within the basins of lower Muir Inlet are correlated with observed depositional processes near the present glacier terminus in the upper inlet. The areal distribution of sedimentary facies within the basins is interpreted using the seismic facies architecture and inferences from known sediment characteristics proximal to present glacier termini.« less
Areal distribution of sedimentary facies determined from seismic facies analysis and models of modern depositional systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seramur, K.C.; Powell, R.D.; Carpenter, P.J.

1988-01-01

Seismic facies analysis was applied to 3.5-kHz single-channel analog reflection profiles of the sediment fill within Muir Inlet, Glacier Bay, southeast Alaska. Nine sedimentary facies have been interpreted from seven seismic facies identified on the profiles. The interpretations are based on reflection characteristics and structural features of the seismic facies. The following reflection characteristics and structural features are used: reflector spacing, amplitude and continuity of reflections, internal reflection configurations, attitude of reflection terminations at a facies boundary, body geometry of a facies, and the architectural associations of seismic facies within each basin. The depositional systems are reconstructed by determining themore » paleotopography, bedding patterns, sedimentary facies, and modes of deposition within the basin. Muir Inlet is a recently deglaciated fjord for which successive glacier terminus positions and consequent rates of glacial retreat are known. In this environment the depositional processes and sediment characteristics vary with distance from a glacier terminus, such that during a retreat a record of these variations is preserved in the aggrading sediment fill. Sedimentary facies within the basins of lower Muir Inlet are correlated with observed depositional processes near the present glacier terminus in the upper inlet.« less
Pleistocene environments and glacial history of the northern North Sea

NASA Astrophysics Data System (ADS)

Reinardy, Benedict; Hjelstuen, Berit; Petter Sejrup, Hans; Augedal, Hans; Jørstad, Arild

2017-04-01

Based on new geochronological and lithological data combined with analyses of 3D seismic data, the Pliocene-Pleistocene development of the central northern North Sea has been investigated. At the start of the Plio-Pleistocene Transition the study area was dominated by a deltaic, shallow marine or tidal depositional environment with sediments mainly sourced from the west with a local provenance. Directly above the base Quaternary a 60 m thick layer of mud-rich sediments of glacimarine origin were deposited at a rate of 12 cm/ka between 2-1.5 Ma and up to 80 cm/ka between 1.5 - 1.2 Ma possibly reflecting glacial ice advancing to the Norwegian coastline. The high rate of deposition in the Early Pleistocene occurred immediately before the initiation of the Norwegian Channel Ice Stream at 1.1 Ma. Following this, a large part of the sediment input from Fennoscandia seems to have been directed away from the study area to the shelf break. At the start of the Mid Pleistocene Transition (MPT), subaerial conditions allowed the formation of a >50 km long fluvial channel across the study area draining water from the east to the south west. The earliest evidence of grounded ice in the investigated area comes from mega scale glacial lineations formed during the MPT, at or just after 1.2 Ma. Following this, a regional unconformity was formed by one or more grounded ice advances across the study area possibly during or directly after the MPT and likely marks the boundary between the Early and Mid Pleistocene glacimarine sediments. The Mid to Late Pleistocene stratigraphy is dominated by glacimarine sediments and tills and is associated with multiple generations of tunnel valleys observed within the seismic data. A high shear strength till containing chalk clasts transported from the west and/or south of the study area was likely deposited during MIS6 and may have been more conducive to tunnel valley formation in comparison to lower shear strength tills deposited by later ice advances. A thick till unit overlain by a sand layer in the study area was deposited by grounded ice during the Last Glacial Maximum and subsequent drainage of an ice dammed lake in the southern North Sea during the last deglaciation (MIS2) of the study area. This study shows that much of the Quaternary age sediments within the northern North Sea were deposited relatively rapidly during short periods of time probably leaving significant hiatuses within the stratigraphic record. This finding has implications for previous studies that use a chronological framework assuming a relatively continuous sedimentation rate and record for the Early Pleistocene within the North Sea.
Permian of Southeast Asia: an overview

NASA Astrophysics Data System (ADS)

Fontaine, Henri

2002-08-01

Permian rocks are widely distributed throughout Southeast Asia. Because of the tropical-equatorial climate the rocks are commonly deeply weathered and covered by dense vegetation over much of the region. Elsewhere, Permian rocks are well exposed and easy to access, particularly where limestone outcrops have weathered to form spectacular, castellated, tower karst. Many limestone outcrops, containing abundant fusulinaceans, were early recognized to be of Permian age, but many outcrops without fusulinaceans, erroneously assigned to the Permian, were found subsequently to be of Triassic age, and more careful studies have established the Permian age of rocks of other lithologies. It is now recognized that different depositional environments are represented by the Permian deposits in various parts of the region. Massive limestones, widespread throughout the region, represent extensive carbonate platforms; local occurrences of thick bedded cherts indicate deposition in deep marine environments, coal, bauxite and clastic sediments with vertebrate remains in North Vietnam and Laos indicate deposition in a continental environment, and pebbly mudstones in Myanmar, Peninsular Thailand, northwest Malaysia and Sumatra, are considered to have been formed in a glacial environment. Volcanic rocks are absent in northwest Peninsular Malaysia and Peninsular Thailand, but are extensively developed in North Vietnam, Sumatra, the eastern Malay Peninsula and Timor. Fossils, representing many fossil groups, are often prolific in Permian sediments, with fusulinaceans, for example, occurring in astronomical numbers in many limestone outcrops. Age-diagnostic fossils demonstrate that the whole of the Permian is represented in different areas of Southeast Asia. Fossil faunal and floral assemblages have been used to establish climatic conditions and environments of deposition, to define distinct crustal blocks and to provide the basis for reconstructing the palaeogeography during Permian times.
An application of excess lead-210 analysis for the study of fine sediment connectivity in a Mediterranean mountain basin with badlands, the Vallcebre research catchments

NASA Astrophysics Data System (ADS)

Moreno de las Heras, Mariano; Gallart, Francesc; Latron, Jérôme; Martínez-Carreras, Núria; Ferrer, Laura; Estrany, Joan

2017-04-01

Analysis of sediment dynamics in Mediterranean environments is fundamental to basin management, particularly for mountain catchments with badlands, which affect water bodies and freshwater ecosystems. Connectivity has emerged in Environmental and Earth Sciences as an evolution of the sediment delivery concept, providing a useful framework for understanding how sediments are transferred between geomorphic zones of the catchment. This study explores the feasibility of excess lead-210 (210Pbex) to analyse sediment connectivity in a 4-km2 Mediterranean mountain basin with badlands (the Vallcebre research catchments, Eastern Pyrenees) by applying simple 210Pbex mass-balance models for hypothesis generation and experimental testing in the field. Badland surfaces in the basin are weathered by freezing during the winter and are further eroded in summer by the effect of high-intensity storms. The eroded sediments may remain deposited within the catchment streams from months to years. Application of 210Pbex balance models in our basin proposes: (i) a saw-tooth seasonal pattern of badland surface 210Pbex activities (increasing from October to May, and depleted in summer) and (ii) a downstream increase in sediment activity due to fallout lead-210 accumulation in streambed sediment deposits. Both deposited and suspended sediments collected at the Vallcebre catchments showed, in general, low sediment 210Pbex concentrations, illustrating their fresh-rock origin at the badland sites, but also hampering the understanding of sediment 210Pbex patterns due to high measurement uncertainty (particularly for sediments with d50>20µm) and to strong dependence on sediment sampling methodology. Suspended sediment 210Pbex activity reproduced the simulated seasonal activity patterns for the badland surfaces. Contrary to the in-stream transit increases of sediment 210Pbex activity that were predicted by our model simulations, fallout lead-210 concentrations in the suspended sediments decreased towards the basin outlet, suggesting that fine sediment flushing by flooding prevented 210Pbex accumulation in the coarser streambed sediment deposits. These results indicate a high fine-sediment connectivity between the badlands, streams and basin outlet of the Vallcebre catchments, as well as the sequestration and fast transmission of fallout lead-210 by the finest and most dynamic fraction of sediments.
Sediment deposition rate in the Falefa River basin, Upolu Island, Samoa.

PubMed

Terry, James P; Kostaschuk, Ray A; Garimella, Sitaram

2006-01-01

The (137)Cs method was employed to investigate the recent historical rate of sediment deposition on a lowland alluvial floodplain in the Falefa River basin, Upolu Island, Samoa. Caesium stratigraphy in the floodplain sediment profile was clearly defined, with a broad peak at 145-175 cm depth. The measured rate of vertical accretion over the last 40 years is 4.0+/-0.4 cm per year. This rate exceeds observations in humid environments elsewhere, but is similar to that recorded on other tropical Pacific Islands. Available flow data for the Vaisigano River in Samoa give a 'near-catastrophic' index value of 0.6 for flood variability. This is associated with the occurrence of tropical cyclones and storms in the Samoa area. Large floods therefore probably contribute to the high rate of floodplain sedimentation on Upolu Island. A small but growing body of evidence suggests that fluvial sedimentation rates on tropical Pacific islands are some of the highest in the world.
Sediment records of Yellow River channel migration and Holocene environmental evolution of the Hetao Plain, northern China

NASA Astrophysics Data System (ADS)

Wang, Jingzhong; Wu, Jinglu; Pan, Baotian; Jia, Hongjuan; Li, Xiao; Wei, Hao

2018-05-01

The origin and evolution of lakes in the Hetao Plain, northern China, were influenced by climate variation, channel migration, and human activity. We analyzed a suite of sediment cores from the region to investigate Yellow River channel migration and environmental change in this region over the Holocene. Short sediment cores show that environmental indicators changed markedly around CE 1850, a time that corresponds to flood events, when large amounts of river water accumulated in the western part of the Hetao Plain, giving rise to abundant small lakes. Multiple sediment variables (environmental proxies) from two long cores collected in the Tushenze Paleolake area show that sediments deposited between 12.0 and 9.0 cal ka BP were yellow clay, indicative of fluvial deposition and channel migration. From 9.0 to 7.5 cal ka BP, sand was deposited, reflecting a desert environment. From 7.5 to 2.2 cal ka BP, however, the sediments were blue-gray clay that represents lacustrine facies of Lake Tushenze, which owes its origin to an increase in strength of the East Asian monsoon. At about 2.2 cal ka BP, the north branch of the Yellow River was flooded, and the Tushenze Paleolake developed further. Around 2.0 cal ka BP, the paleolake shrank and eolian sedimentation was recorded. The analyzed sediment records are consistent with the written history from the region, which documents channel migration and environmental changes in the Hetao Plain over the Holocene.
Increased Oxygenation of the Oceans Since the Mid-Cenozoic as Constrained by Cr/Co and Os/Ir Ratios in Oxic Pelagic Sediments

NASA Astrophysics Data System (ADS)

Hu, M.; Lee, C.

2005-12-01

In terms of redox, the marine sediments can be roughly divided into anoxic to suboxic sediments on the margins and oxic sediments in pelagic (open ocean) environments. The relative amounts of anoxic/suboxic sediments being deposited at any given time could be related to biological productivity and/or the efficiency of the ocean circulation system. How the depositional area of anoxic/suboxic deposition has changed through time is thus of concern. One way to track redox conditions is to investigate variations in the concentrations of redox sensitive trace metals. Most studies along these lines have focused on anoxic sediments. However, one problem with using anoxic sediments to study the global oceans is that such sediments are typically deposited in somewhat isolated basins, whose redox conditions may vary from basin to basin. An alternative approach, taken here, is to examine redox-sensitive elemental ratios in oxic pelagic sediments. This is motivated by the fact that pelagic sediments are more likely to reflect average ocean chemistry. In addition, the redox-sensitive metal contents of oxic sediments represent the complement to anoxic sediments. Choosing an appropriate redox-sensitive elemental ratio which eliminates dilution/concentration effects, requires the identification of trace metals that are preferentially precipitated in oxic conditions and those precipitated in more reducing conditions. Overall elemental behaviors were estimated by comparing hydrogenous or authigenic burial fluxes of various trace metals at given pelagic ODP sites to global riverine input fluxes. If the pelagic burial fluxes of a given element are significantly smaller than the riverine input flux, other burial outputs are implied, and it is hypothesized here that this element may precipitate in reducing conditions, such as in oceanic margin. If, on the other hand, the pelagic burial flux is equal to or greater than the riverine input flux, the implication is that oxic pelagic sediments must account for a significant proportion of the burial output of that element. In this case, we assume that this element is oxic-loving. Results of this work reveal that V, Cr, and Co may be particularly redox-sensitive: V and Cr precipitate in reducing environments while Co precipitates in more oxidizing environments. Results of our study, combined with existing data from the literature, show that Cr/Co ratios decrease with depth in DSDP596, 39, 801A, 319, 321, 465A, 577 in the N and S Pacific. After correcting for sedimentation rate, it is shown that the variation of Cr/Co versus time in all of these cores converge, which suggests that the variations in Cr/Co reflect a true variation in seawater composition. This also supported by the lack of sedimentation constrained by Cr/Co and Ce flux. Cr/Co remains low during the Cretaceous but begins to rise at ~25Ma across the entire Pacific. If the Cr/Co and Os/Ir ratio of inputs to the ocean have not changed much, this trend also matches that Os/Ir in the DSDP 596 site in the south Pacific. One interpretation of these results is that there has been a decrease in the area of anoxic/suboxic sedimentation beginning at this time. If correct, the implication is that there was a fundamental change in the redox conditions of the ocean in the mid-Cenozoic. We speculate that this might have been related to mid-Cenozoic global cooling, which may have increased the efficiency of the oceanic circulation system.
Potential urban runoff impacts and contaminant distributions in shoreline and reservoir environments of Lake Havasu, southwestern United States.

PubMed

Wilson, Doyle C

2018-04-15

Heavy metal, nutrient, and hydrocarbon levels in and adjacent to Lake Havasu, a regionally significant water supply reservoir with a highly controlled, dynamic flow regime, are assessed in relation to possible stormwater runoff impacts from an arid urban center. Shallow groundwater and sediment analyses from ephemeral drainage (wash) mouths that convey stormwater runoff from Lake Havasu City, Arizona to the reservoir, provided contaminant control points and correlation ties with the reservoir environment. Fine-grain sediments tend to contain higher heavy metal concentrations whereas nutrients are more evenly distributed, except low total organic carbon levels from young wash mouth surfaces devoid of vegetation. Heavy metal and total phosphate sediment concentrations in transects from wash mouths into the reservoir have mixed and decreasing trends, respectively. Both series may indicate chemical depositional influences from urban runoff, yet no statistically significant concentration differences occur between specific wash mouths and corresponding offshore transects. Heavy metal pollution indices of all sediments indicate no discernible to minor contamination, indicating that runoff impacts are minimal. Nevertheless, several heavy metal concentrations from mid-reservoir sediment sites increase southward through the length of the reservoir. Continual significant water flow through the reservoir may help to disperse locally derived runoff particulates, which could mix and settle down gradient with chemical loads from upriver sources and local atmospheric deposition. Incorporating the shoreline environment with the reservoir investigation provides spatial continuity in assessing contaminant sources and distribution patterns. This is particularly acute in the investigation of energetic, flow-through reservoirs in which sources may be overlooked if solely analyzing the reservoir environment. Copyright © 2017 Elsevier B.V. All rights reserved.
Diatoms in sediments of perennially ice-covered Lake Hoare, and implications for interpreting lake history in the McMurdo Dry Valleys of Antarctica

USGS Publications Warehouse

Spaulding, S.A.; McKnight, Diane M.; Stoermer, E.F.; Doran, P.T.

1997-01-01

Diatom assemblages in surficial sediments, sediment cores, sediment traps, and inflowing streams of perennially ice-covered Lake Hore, South Victorialand, Antarctica were examined to determine the distribution of diatom taxa, and to ascertain if diatom species composition has changed over time. Lake Hoare is a closed-basin lake with an area of 1.8 km2, maximum depth of 34 m, and mean depth of 14 m, although lake level has been rising at a rate of 0.09 m yr-1 in recent decades. The lake has an unusual regime of sediment deposition: coarse grained sediments accumulate on the ice surface and are deposited episodically on the lake bottom. Benthic microbial mats are covered in situ by the coarse episodic deposits, and the new surfaces are recolonized. Ice cover prevents wind-induced mixing, creating the unique depositional environment in which sediment cores record the history of a particular site, rather than a lake=wide integration. Shallow-water (<1 m) diatom assemblages (Stauroneis anceps, Navicula molesta, Diadesmis contenta var. parallela, Navicula peraustralis) were distinct from mid-depth (4-16 m) assemblages (Diadesmis contenta, Luticola muticopsis fo. reducta, Stauroneis anceps, Diadesmis contenta var. parallela, Luticola murrayi) and deep-water (2-31 m) assemblages (Luticola murrayi, Luticola muticopsis fo. reducta, Navicula molesta. Analysis of a sediment core (30 cm long, from 11 m water depth) from Lake Hoare revealed two abrupt changes in diatom assemblages. The upper section of the sediment core contained the greatest biomass of benthic microbial mat, as well as the greatest total abundance and diversity of diatoms. Relative abundances of diatoms in this section are similar to the surficial samples from mid-depths. An intermediate zone contained less organic material and lower densities of diatoms. The bottom section of core contained the least amount of microbial mat and organic material, and the lowest density of diatoms. The dominant process influencing species composition and abundance of diatom assemblages in the benthic microbial mats is episodic deposition of coarse sediment from the ice surface.
Sediment facies, depositional environments, and distribution of phytoclasts in the recent Mahakam River delta, Kalimantan, Indonesia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gastaldo, R.A.; Huc, A.Y.

1992-12-01

The Mahakam River delta is a tide- and wave-dominated delta located on the edge of the Kutei basin, eastern Kalimantan, Borneo. It is a coastal deltaic sequence, Neogene to Holocene in age, from which all recoverable hydrocarbons (crude oil and natural gas) are considered to be derived from kerogen III predecessors. However, a complete understanding of the types of sediments sourcing the hydrocarbons has not yet been achieved. A vibracoring program sampled the principal fine-grained depositional environments in two transects; one within the fluvially-dominated regime, one within the tidally-dominated regime. Ten sedimentary facies are distinguished and phytoclasts have been recoveredmore » from all environments of deposition. Canopy parts from the mixed tropical forest community are preserved throughout the delta, whereas dicotyledonous angiosperm mangroves are restricted to the subtidal zone and delta front. Nypa parts are preserved in most depositional environments. In sites where there appears to be an absence of macrodetritus, dispersed cuticle is recoverable. Identifiable plant parts include wood and fibrous tissues, Nypa petioles and leaf laminae, dicotyledonous angiosperm leaves and isolated cuticles, fruits and seeds, roots and rootlets, and moss. Dammar is found either as dispersed resin ducts or amorphous clasts. Additional biotic components found in bedded plant litters include insects, gastropods, bivalves, sand dollars, ostracods, and crabs. Fluvial channels and depositional sites associated with these systems in the delta front can be differentiated from Nypa swamps and mixed tropical hardwood-palm swamps based on their phytological components and accessory biotic elements. 39 refs., 10 figs., 3 tabs.« less
Latest Pleistocene glaciomarine and marine deposition in the northern Puget lowland, Washington

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dethier, D.P.

Latest Pleistocene (Fraser) continental ice deposited thick, narrow zones of ice-marginal debris and widespread pebbly silt into marine water as it retreated from the northern Puget lowland of Washington at about 14,000 B.P. Exposed deposits include several collapsed terrestrial ice-contact complexes. Most sediment accumulated in marine water during or after ice retreat, but before glacioisostatic rebound lifted the area about sea level. Gravelly sand, pebbly silt, gravelly diamicton, cross bedded silty sand, and massive to laminated silt were deposited in glaciomarine, marine, estuarine, and shoreline environments now exposed at elevations as high as 150 m. Ice-proximal facies formed from sediment-richmore » fresh-water plumes and mass movements at the margins of grounded ice lobes; transitional and distal deposits incorporated sediment from dispersed meltwater, turbidity flows and icebergs hundreds of m to tens of km from the grounding line. Macrofossils assemblages in the glaciomarine deposits formed in water < 40 meters deep whereas the marine deposits represent intertidal depths to over 80 meters. [sup 14]C shell ages demonstrate that ice retreated 125 km from the E. Strait of Juan de Fuca between about 14.0 ka and 13.5 ka, and that a fluctuating ice margin persisted near the international Border until sometime after 11.5 ka. More than 10 km[sup 3] of ice-marginal sediment, now bands of submerged banks, outline grounding-line positions in the 50 km between the E. Strait of Juan de Fuca and the San Juan Islands.« less
Sediment-Hosted Zinc-Lead Deposits of the World - Database and Grade and Tonnage Models

USGS Publications Warehouse

Singer, Donald A.; Berger, Vladimir I.; Moring, Barry C.

2009-01-01

This report provides information on sediment-hosted zinc-lead mineral deposits based on the geologic settings that are observed on regional geologic maps. The foundation of mineral-deposit models is information about known deposits. The purpose of this publication is to make this kind of information available in digital form for sediment-hosted zinc-lead deposits. Mineral-deposit models are important in exploration planning and quantitative resource assessments: Grades and tonnages among deposit types are significantly different, and many types occur in different geologic settings that can be identified from geologic maps. Mineral-deposit models are the keystone in combining the diverse geoscience information on geology, mineral occurrences, geophysics, and geochemistry used in resource assessments and mineral exploration. Too few thoroughly explored mineral deposits are available in most local areas for reliable identification of the important geoscience variables, or for robust estimation of undiscovered deposits - thus, we need mineral-deposit models. Globally based deposit models allow recognition of important features because the global models demonstrate how common different features are. Well-designed and -constructed deposit models allow geologists to know from observed geologic environments the possible mineral-deposit types that might exist, and allow economists to determine the possible economic viability of these resources in the region. Thus, mineral-deposit models play the central role in transforming geoscience information to a form useful to policy makers. This publication contains a computer file of information on sediment-hosted zinc-lead deposits from around the world. It also presents new grade and tonnage models for nine types of these deposits and a file allowing locations of all deposits to be plotted in Google Earth. The data are presented in FileMaker Pro, Excel and text files to make the information available to as many as possible. The value of this information and any derived analyses depends critically on the consistent manner of data gathering. For this reason, we first discuss the rules applied in this compilation. Next, the fields of the data file are considered. Finally, we provide new grade and tonnage models that are, for the most part, based on a classification of deposits using observable geologic units from regional-scaled maps.
Do Leached Authigenic Fractions Reflect the Neodymium Seawater Composition?

NASA Astrophysics Data System (ADS)

Pimbert, A.; Gourlan, A. T.; Chauvel, C.

2016-12-01

Leaching of marine sediment is often used to recover past Nd seawater composition and reconstruct past ocean circulation. It is assumed to reliably extract REE from the authigenic fraction of sediment [1]. However, while most studies assume that the recovered signal is that of past seawater, very few report complete isotopic and trace element data that clearly demonstrate it is the case. We present new ɛNd values and REE contents measured on leachates of sediments from two Cretaceous marine sections deposited at shallow water depth (Taghazoute in Morocco) and at greater depth in the Atlantic (DSDP Site 367). REE patterns of leachates vary according to lithology: bell-shaped patterns or positive Ce anomalies for organic-poor samples and seawater-like patterns (negative Ce anomaly, low Nd/Yb ratio) for black shales. ɛNd values also vary: between -5.6 and -9.6 at Taghazoute and between -10 and -8.1 at Site 367. Interestingly, ɛNd values correlate with Ce anomalies for Taghazoute black shales. Samples with the largest Ce negative anomalies have the highest ɛNd while samples with no Ce anomalies have much lower ɛNd. This suggests the presence in the leached material of detritus mixed up with the authigenic fraction for sediments deposited in shallow environment. This confirms the findings made by Huck et al. [2] for fish teeth in a similar environment. In such environment, recovering the pristine seawater signal requires (a) the acquisition of both Nd isotopes and trace element contents, and (b) selection of the only Nd isotopic compositions associated to clear seawater trace element characteristics. For sediments deposited in open-ocean setting (Site 367), no detrital contamination affects leached fractions. The REE patterns vary depending on the nature of authigenic fraction but ɛNd remains constant. Here, ɛNd values can be used to discuss oceanic reconstructions. [1] Martin et al. (2010), Chem. Geol, 269, 414-431. [2] Huck et al. (2016), G3, 17, 679-698.
Sand ridges off Sarasota, Florida: A complex facies boundary on a low-energy inner shelf environment

USGS Publications Warehouse

Twichell, D.; Brooks, Gillian L.; Gelfenbaum, G.; Paskevich, V.; Donahue, Brian

2003-01-01

The innermost shelf off Sarasota, Florida was mapped using sidescan-sonar imagery, seismic-reflection profiles, surface sediment samples, and short cores to define the transition between an onshore siliciclastic sand province and an offshore carbonate province and to identify the processes controlling the distribution of these distinctive facies. The transition between these facies is abrupt and closely tied to the morphology of the inner shelf. A series of low-relief nearly shore-normal ridges characterize the inner shelf. Stratigraphically, the ridges are separated from the underlying Pleistocene and Tertiary carbonate strata by the Holocene ravinement surface. While surficial sediment is fine to very-fine siliciclastic sand on the southeastern sides of the ridges and shell hash covers their northwestern sides, the cores of these Holocene deposits are a mixture of both of these facies. Along the southeastern edges of the ridges the facies boundary coincides with the discontinuity that separates the ridge deposits from the underlying strata. The transition from siliciclastic to carbonate sediment on the northwestern sides of the ridges is equally abrupt, but it falls along the crests of the ridges rather than at their edges. Here the facies transition lies within the Holocene deposit, and appears to be the result of sediment reworking by modern processes. This facies distribution primarily appears to result from south-flowing currents generated during winter storms that winnow the fine siliciclastic sediment from the troughs and steeper northwestern sides of the ridges. A coarse shell lag is left armoring the steeper northwestern sides of the ridges, and the fine sediment is deposited on the gentler southeastern sides of the ridges. This pronounced partitioning of the surficial sediment appears to be the result of the siliciclastic sand being winnowed and transported by these currents while the carbonate shell hash falls below the threshold of sediment movement and is left as a lag. The resulting facies boundaries on this low-energy, sediment-starved inner continental shelf are of two origins which both are tied to the remarkably subtle ridge morphology. Along the southeastern sides of the ridges the facies boundary coincides with a stratigraphic discontinuity that separates Holocene from the older deposits while the transition along the northwestern sides of the ridges is within the Holocene deposit and is the result of sediment redistribution by modern processes. ?? 2003 Elsevier B.V. All rights reserved.
Effect of geometrical configuration of sediment replenishment on the development of bed form patterns in a gravel bed channel

NASA Astrophysics Data System (ADS)

Battisacco, Elena; Franca, Mário J.; Schleiss, Anton J.

2016-04-01

Dams interrupt the longitudinal continuity of river reaches since they store water and trap sediment in the upstream reservoir. By the interruption of the sediment continuum, the transport capacity of downstream stretch exceeds the sediment supply, thus the flow becomes "hungry". Sediment replenishment is an increasingly used method for restoring the continuity in rivers and for re-establishing the sediment regime of such disturbed river reaches. This research evaluates the effect of different geometrical configurations of sediment replenishment on the evolution of the bed morphology by systematic laboratory experiments. A typical straight armoured gravel reach is reproduced in a laboratory flume in terms of slope, grain size and cross section. The total amount of replenished sediment is placed in four identical volumes on both channel banks, forming six different geometrical configurations. Both alternated and parallel combinations are studied. Preliminary studies demonstrate that a complete submergence condition of the replenishment deposits is most adequate for obtaining a complete erosion and a high persistence of the replenished material in the channel. The response of the channel bed morphology to replenishment is documented by camera and laser scanners installed on a moveable carriage. The parallel configurations create an initially strong narrowing of the channel section. The transport capacity is thus higher and most of the replenished sediments exit the channel. The parallel configurations result in a more spread distribution of grains but with no clear morphological pattern. Clear bed form patterns can be observed when applying alternated configurations. Furthermore, the wavelength of depositions correspond to the replenishment deposit length. These morphological forms can be assumed as mounds. In order to enhance channel bed morphology on an armoured bed by sediment replenishment, alternated deposit configurations are more favourable and effective. The present study is supported by FOEN (Federal Office for the Environment, Switzerland).
Estimated post-Messinian sediment supply and sedimentation rates on the Ebro continental margin, Spain

USGS Publications Warehouse

Nelson, C.H.

1990-01-01

Because of the extensive data base of seismic profiles, radiometric ages, and stratigraphic time markers such as the subaerial Messinian surface, sedimentation rates and Ebro River sediment discharge can be estimated for different periods and environments of the Ebro continental margin. New values for sediment discharge (i.e., 6.2 versus previous estimates of 2-3.5 million t/yr) for the Holocene highstand are more reliable but remain minimum estimates because a small proportion of Ebro sediment advected to the Balearic Rise and Abyssal Plain cannot be accounted for, especially during lowstands. The general highstand conditions of the Pliocene, which were similar to those of the Holocene, resulted in a low discharge of Ebro River sediment (ca. 6.5 million t/yr) and an even thickness of sediment across the margin that deposited at rates of about 24-40 cm/ky. In contrast, sediment supply increased two-three times during the Pleistocene, the margin prograded rapidly and deposition occurred at rates of 101-165 cm/ky on the outer shelf and slope, but basin floor rates remained anomalously low (21-26 cm/ky) because sediment was drained and broadly dispersed eastward in Valencia Trough. During the late Pleistocene rise of sea level, the main depocenters progressively shifted shoreward and sedimentation rates greatly decreased from 175 cm/ky on the upper slope during the early transgression to 106 cm/ky on the outer shelf and then to 63 cm/ky on the mid-shelf during the late transgression as the river sediment discharge dropped to half by Holocene time. Maximal sedimentation rates occurred in active depocenters of sediment dispersal such as the Holocene delta (370 cm/ky) or the youngest Pleistocene Oropesa channel-levee complex (705 cm/ky) where deposition rates increased by an order of magnitude or more compared to average Ebro shelf (38 cm/ky) or base-of-slope rates in the Pleistocene (21 cm/ky). The sedimentation rates verify the importance of sea-level control on the progressive change in location of depocenters and amount of sediment supply, but Pleistocene climatic change and deforestation alone can be observed to double river sediment discharge. The latter observation helps explain the anomalously high deposition rates in Pleistocene turbidite systems compared with older systems that may be controlled more by tectonic and sea-level changes alone. During the past 2000 years, in contrast, man has controlled deposition in the Ebro margin system, first by deforestation that more than doubled river sediment discharge and shelf deposition rates to equal those of Pleistocene time; and second by dam contruction that reduced sediment discharge to less than 5% of the normal Holocene discharge. Similar recent discharge reductions from the Nile and Rhone Rivers suggest that loss of the majority of the river sediment supply in the Mediterranean Sea may result in significant erosion of biologically and agriculturally important lobate delta areas. ?? 1990.
Biomonitoring for deposited sediment using benthic invertebrates: A test on 4 Missouri streams

USGS Publications Warehouse

Zweig, L.D.; Rabeni, Charles F.

2001-01-01

The response of stream benthic invertebrates to surficially deposited fine sediment was investigated in 4 Missouri streams. Twenty to 24 sampling sites in each stream were selected based on similarities of substrate particle-size distributions, depths, and current velocities but for differences in amounts of deposited sediment, which ranged from 0 to 100% surface cover. Deposited sediment was quantified 2 ways: a visual estimate of % surface cover, and a measurement of substrate embeddedness, which were highly correlated with each other and with the amount of sand. Invertebrates were collected using a kicknet for a specified time in a 1-m2 area. Five commonly used biomonitoring metrics (taxa richness, density, Ephemeroptera, Plecoptera, and Trichoptera [EPT] richness, EPT density, and EPT/Chironomidae richness) were consistently significantly correlated across streams to deposited sediment. Shannon diversity index, Chironomidae richness, Chironomidae density, a biotic index, and % dominant taxon did not relate to increasing levels of deposited sediment. Tolerance values representing taxa responses to deposited sediment were developed for 30 taxa. Deposited-sediment tolerance values were not correlated with biotic index tolerance values, indicating a different response by taxa to deposited sediment than to organic enrichment. Deposited-sediment tolerance values were used to develop the Deposited Sediment Biotic Index (DSBI). The DSBI was calculated for all samples (n = 85) to characterize sediment impairment of the sampled streams. DSBI values for each site were highly correlated with measures of deposited sediment. Model validation by a resampling procedure confirmed that the DSBI is a potentially useful tool for assessing ecological effects of deposited sediment.

The depositional setting of the Late Quaternary sedimentary fill in southern Bannu basin, Northwest Himalayan fold and thrust belt, Pakistan.

PubMed

Farid, Asam; Khalid, Perveiz; Jadoon, Khan Zaib; Jouini, Mohammed Soufiane

2014-10-01

Geostatistical variogram and inversion techniques combined with modern visualization tools have made it possible to re-model one-dimensional electrical resistivity data into two-dimensional (2D) models of the near subsurface. The resultant models are capable of extending the original interpretation of the data to depict alluvium layers as individual lithological units within the 2D space. By tuning the variogram parameters used in this approach, it is then possible to visualize individual lithofacies and geomorphological features for these lithologic units. The study re-examines an electrical resistivity dataset collected as part of a groundwater study in an area of the Bannu basin in Pakistan. Additional lithological logs from boreholes throughout the area have been combined with the existing resistivity data for calibration. Tectonic activity during the Himalayan orogeny uplifted and generated significant faulting in the rocks resulting in the formation of a depression which subsequently has been filled with clay-silt and dirty sand facies typical of lacustrine and flood plain environments. Streams arising from adjacent mountains have reworked these facies which have been eroded and replaced by gravel-sand facies along channels. It is concluded that the sediments have been deposited as prograding fan shaped bodies, flood plain, and lacustrine deposits. Clay-silt facies mark the locations of paleo depressions or lake environments, which have changed position over time due to local tectonic activity and sedimentation. The Lakki plain alluvial system has thus formed as a result of local tectonic activity with fluvial erosion and deposition characterized by coarse sediments with high electrical resistivities near the mountain ranges and fine sediments with medium to low electrical resistivities towards the basin center.
An overview of the Tertiary geology and hydrogeology of the northern part of the Arabian Gulf region with special reference to Kuwait

NASA Astrophysics Data System (ADS)

Mukhopadhyay, A.; Al-Sulaimi, J.; Al-Awadi, E.; Al-Ruwaih, F.

1996-06-01

Tertiary sediments constitute the main source of usable groundwater in Kuwait. Tectonics, depositional environment, lithology and the hydrogeology of these sediments have been reviewed on a regional scale, with special reference to Kuwait. The review showed that Kuwait was situated at the boundary of the stable shelf towards southwest and the unstable shelf towards northeast throughout the Tertiary period. The Tertiary sedimentation started in this area with a marine transgression in the Palaeocene. Shallow marine to sabkha conditions prevailed in the area until the end of the Eocene; a carbonate-evaporite sequence (Umm Er-Radhuma, Rus and Dammam Formation) was deposited during this period. The sea regressed at the end of Eocene, and a widespread unconformity, causing the absence of Oligocene deposits over most of the area, marked the event. The karstification of the Dammam Limestone Formation, that provides localized easier pathways for ground water, took place during this period. The deposition of the clastic sediments of the Kuwait Group and its equivalents on the stable shelf, under mostly continental conditions, started in the early Miocene. The Tertiary aquifers of the area are recharged by occasional rainstorms in the outcrops of Saudi Arabia and Iraq. The water flows towards the north and east in the direction of the regional dip and discharges along the present-day coast of the Gulf. The water quality deteriorates in the same direction, being more mineralized as it flows through the aquifers. The aquifers are presently being exploited at a comparatively high rate. Since the aquifers extend beyond the political boundaries, cooperation among the countries of the region is recommended to ensure the optimum utilization of the scarce water resources of this desert environment.
Subglacial Depositional Processes in the Port Askaig Formation (Neoproterozoic) of Ireland

NASA Astrophysics Data System (ADS)

Knight, J.

2004-12-01

The Port Askaig Formation was deposited during the Vendian glaciation (c. 650 Ma) and is a range of tillites that outcrop discontinuously from Banffshire (Scotland) to Connemara (Ireland). Sedimentary structures commonly observed include dropstones and sediment drapes, interpreted as deposition from a floating glacial ice shelf in a shallow marginal sea. Other structures, such as intersecting clastic dikes, have been interpreted as evidence for subaerial exposure of the tillite surface. Exposures of the Port Askaig Formation were examined at its Irish type area at Kiltyfanned Lough, County Donegal. Here, homogeneous sandy beds with internal planar bedding structures are separated by laminated fine sand beds which have erosional upper surfaces. The laminated beds are clast-free and individual laminae are laterally continuous and undisturbed. Larger clasts lie bed-parallel and are draped by overlying beds. Occasionally drapes are asymmetric with a thickened sediment prow, suggestive of flow direction. The clastic dikes are polygonal in plan view, may be isolated or interconnected, and are often arranged in parallel sheets which pinch out laterally. Internally, the clastic dikes are infilled with coarse sand to gravel. Infills are often aligned parallel to dike margins. The presence of draped and deformed sediments suggest a subglacial environment with free water availability. The flat-lying morphology of clasts also favours a subglacial rather than a full marine environment. The morphology and disposition of clastic dikes is interpreted as due to subglacial hydrofracturing of a till sheet and upward passage of sediment-charged water through the fracture zone, which is known from late Pleistocene and Precambrian tillites elsewhere. Variations in water availability can be reconciled by a sub-ice shelf depositional model with spatial and temporal changes in tidally-induced ice-bed coupling.
Braided fluvial sedimentation in the lower paleozoic cape basin, South Africa

NASA Astrophysics Data System (ADS)

Vos, Richard G.; Tankard, Anthony J.

1981-07-01

Lower Paleozoic braided stream deposits from the Piekenier Formation in the Cape Province, South Africa, provide information on lateral and vertical facies variability in an alluvial plain complex influenced by a moderate to high runoff. Four braided stream facies are recognized on the basis of distinct lithologies and assemblages of sedimentary structures. A lower facies, dominated by upward-fining conglomerate to sandstone and mudstone channel fill sequences, is interpreted as a middle to lower alluvial plain deposit with significant suspended load sedimentation in areas of moderate to low gradients. These deposits are succeeded by longitudinal conglomerate bars which are attributed to middle to upper alluvial plain sedimentation with steeper gradients. This facies is in turn overlain by braid bar complexes of large-scale transverse to linguoid dunes consisting of coarse-grained pebbly sandstones with conglomerate lenses. These bar complexes are compared with environments of the Recent Platte River. They represent a middle to lower alluvial plain facies with moderate gradients and no significant suspended load sedimentation or vegetation to stabilize channels. These bar complexes interfinger basinward with plane bedded medium to coarse-grained sandstones interpreted as sheet flood deposits over the distal portions of an alluvial plain with low gradients and lacking fine-grained detritus or vegetation.
Assessment of sedimentary Cu availability: A comparison of biomimetic and AVS approaches

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Z.; Mayer, L.M.

1999-02-15

Sedimentary Cu bioavailability during deposit feeding is determined by both the digestive physiology of the organisms and the geochemistry of the sediments. The authors assessed the contribution of these two factors by using a biomimetic approach involving extraction of Cu with digestive fluids of two deposit feeders and one suspension feeder and a geochemical approach measuring Cu associated with acid-volatile sulfide (AVS) in sediments. Cu bioavailability determined by the biomimetic method varied among species with varying digestive physiology but all showed a marked increase when SEM{sub Cu}-AVS {ge} 0, corroborating the premise underlying the AVS method in determining sedimentary Cumore » bioavailability. The existence of a positive SEM{sub Cu}-AVS threshold suggests the existence of additional Cu-binding phases or mixed Cu(I)--Cu(II) sulfides in sediments. In addition, Cu bioavailable to digestive fluids was much less than that measured as SEM{sub Cu}-AVS, indicating that the AVS method overestimates Cu bioavailability to digestive fluid of deposit feeders. Incubation of digestive fluids with two Cu-bound model phases, goethite and sulfide, corroborated the relative unavailability of sulfide-bound Cu. Subsurface deposit feeders feeding on anoxic sediments may be exposed to less Cu than their surface-feeding counterparts in Cu-contaminated environments.« less
Paleoenvironmental analysis of a middle Wisconsinan biota site, southwestern Virginia, U.S.A.

NASA Astrophysics Data System (ADS)

Whittecar, G. Richard; Wynn, Thomas C.; Bartlett, Charles S.

2007-07-01

The Ratcliff Site in southwestern Virginia lies in a small second-order stream valley filled with approximately 3.5 m of organic-rich deposits that contain bones of mammoth, mastodon, deer (or antelope), logs, and plant macrofossils. Radiocarbon analyses indicate the age of the organic-rich sediment ranges from > 44,000 to 29,100 14C yr BP, a time period with no fossil remains reported in this region of the Appalachians. Analyses of field observations, textural data, organic carbon content, and plant macrofossils indicate that the organic-rich sediments contain interbedded standing-water and debris-flow deposits. Up to 6 m of oxidized debris-flow sediments bury the organic-rich sediments. The presence of Rubus parviflorus (Thimble Berry) throughout the deposit indicates the site had a boreal environment from > 44,000 to 29,100 14C yr BP. Plant macrofossil evidence indicates the uplands had stands of spruce/jack-pine forests while the valley contained ponds and associated wetlands. Three debris flows occurred at the site between approximately 38,000 and 29,000 14C yr BP, suggesting a recurrence interval for major storms of approximately 3000 yr, even though the apparent stability of the boreal environment implies a climate not conducive to catastrophic rainstorms. This conflicting combination of features suggests that during the middle Wisconsinan this area experienced generally cool climates, dominated by polar air masses, but was punctuated by relatively brief warm periods marked by incursions of tropical air masses.
Late Pliocene-Pleistocene environments and glacial history of the northern North Sea

NASA Astrophysics Data System (ADS)

Reinardy, Benedict T. I.; Hjelstuen, Berit O.; Sejrup, Hans Petter; Augedal, Hans; Jørstad, Arild

2017-02-01

Based on new geochronological (amino acids and Sr-isotopes) and lithological data combined with analyses of 3D seismic data, the Pliocene-Pleistocene development of the central northern North Sea has been investigated. At the start of the Plio-Pleistocene Transition the study area was dominated by a deltaic, shallow marine or tidal depositional environment with sediments mainly sourced from the west. These sand-rich sediments include green glauconitic grains that belong to the Utsira Sand with a local provenance. Directly above the base Quaternary (R2) a 60 m thick layer of mud-rich sediments of glacimarine origin were deposited at a rate of ∼12 cm/ka between ∼2-1.5 Ma and up to 80 cm/ka between 1.5 and 1.2 Ma possibly reflecting glacial ice advancing to the Norwegian coastline. The high rate of deposition in the Early Pleistocene occurred immediately before the initiation of the Norwegian Channel Ice Stream at ∼1.1 Ma. Following this, a large part of the sediment input from Fennoscandia seems to have been directed away from the study area to the shelf break. At the start of the Mid Pleistocene Transition (MPT), subaerial conditions allowed the formation of a >50 km long fluvial channel across the study area draining water from the east to the south west. The earliest evidence of grounded ice in the investigated area comes from mega scale glacial lineations formed during the MPT, at or just after ∼1.2 Ma. Following this, a regional unconformity (R4) was formed by one or more grounded ice advances across the study area possibly during or directly after the MPT and likely marks the boundary between the Early and Mid Pleistocene glacimarine sediments. The Mid to Late Pleistocene stratigraphy is dominated by glacimarine sediments and tills and is associated with multiple generations of tunnel valleys observed within the seismic data. A high shear strength till containing chalk clasts transported from the west and/or south of the study area was likely deposited during MIS6 and may have been more conducive to tunnel valley formation in comparison to lower shear strength tills deposited by later ice advances. A thick till unit overlain by a sand layer in the study area was deposited by grounded ice during the Last Glacial Maximum and subsequent drainage of an ice dammed lake in the southern North Sea during the last deglaciation (MIS2) of the study area. This study shows that much of the Quaternary age sediments within the northern North Sea were deposited relatively rapidly during short periods of time probably leaving significant hiatuses within the stratigraphic record. This finding has implications for previous studies that use a chronological framework assuming a relatively continuous sedimentation rate and record for the Early Pleistocene within the North Sea.
Sedimentary Carbon, Sulfur, and Iron Relationships in Modern and Ancient Diagenetic Environments of the Eel River Basin (U.S.A.)

USGS Publications Warehouse

Sommerfield, C.K.; Aller, R.C.; Nittrouer, C.A.

2001-01-01

Depositional and diagenetic controls on the distributions of carbon, sulfur, and iron (C-S-Fe) in modern sediments and upper Pleistocene mudrocks of the Eel River Basin (ERB), northern California continental margin, were investigated using a combination of geochemical, radioisotopic, and sedimentological methods. A mass balance based on down-core profiles of porewater and solid-phase constituents and diagenetic modeling suggests that only 12-30% of the pyrite-S produced via SO4-2 reduction during burial is retained in modern shelf and upper slope deposits of the ERB. Bioturbational reoxidation of initially reduced S is inferred to be the major control on S preservation, on the basis of an observed inverse relationship between pyrite-S retention and biological mixing intensity, estimated from profiles of excess 234Th. Importantly, these findings argue that massive depositional episodes on the shelf following floods of the Eel River have a negligible long-term impact on bioturbating macrofauna and the potential to affect geochemical properties of the sediments. Down-core profiles of reactive Fe3+and Py-Fe(II) for the modern deposits suggest that highly reactive Fe phases are sulfidized well within ∼ 500-2000 years of burial, thereby limiting later pyritization, which could occur through sulfidation of less reactive phases. This result explains the low (≤ 0.4) degree of pyritization (DOP) values exhibited by both modern and ancient deposits of the ERB and lends support to the notion that pyritization in aerobic continental-margin sediments is largely associated with highly reactive detrital Fe oxides. Comparable mean C/S weight ratios for modern sediments (5.4 ± 3.3, 1σ) and mudrocks (6.9 ± 4.5) of the ERB suggest that the upper Pleistocene strata reflect a geochemical environment analogous to that of the modern margin. Specifically, the C-S-Fe signatures shared by the modern and ancient deposits are a consequence of similar detrital Fe mineralogies, initial organic-matter content (Corg ≤ 1%) and composition (C/N = 13 to 17, δ13Corg = -22 to -25‰), burial rate, and importantly, bioturbation intensity. The findings of this study have important implications for the use of C-S-Fe signatures as indicators of diagenetic processes in dynamic, continental-margin environments.
Paleoecology of the Devonian-Mississippian black-shale sequence in eastern Kentucky with an atlas of some common fossils

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barron, L.S.; Ettensohn, F.R.

The Devonian-Mississippian black-shale sequence of eastern North America is a distinctive stratigraphic interval generally characterized by low clastic influx, high organic production in the water column, anaerobic bottom conditions, and the relative absence of fossil evidence for biologic activity. The laminated black shales which constitute most of the black-shale sequence are broken by two major sequences of interbedded greenish-gray, clayey shales which contain bioturbation and pyritized micromorph invertebrates. The black shales contain abundant evidence of life from upper parts of the water column such as fish fossils, conodonts, algae and other phytoplankton; however, there is a lack of evidence ofmore » benthic life. The rare brachiopods, crinoids, and molluscs that occur in the black shales were probably epiplanktic. A significant physical distinction between the environment in which the black sediments were deposited and that in which the greenish-gray sediments were deposited was the level of dissolved oxygen. The laminated black shales point to anaerobic conditions and the bioturbated greenish-gray shales suggest dysaerobic to marginally aerobic-dysaerobic conditions. A paleoenvironmental model in which quasi-estuarine circulation compliments and enhances the effect of a stratified water column can account for both depletion of dissolved oxygen in the bottom environments and the absence of oxygen replenishment during black-shale deposition. Periods of abundant clastic influx from fluvial environments to the east probably account for the abundance of clays in the greenish-gray shale as well as the small amounts of oxygen necessary to support the depauparate, opportunistic, benthic faunas found there. These pulses of greenish-gray clastics were short-lived and eventually were replaced by anaerobic conditions and low rates of clastic sedimentation which characterized most of black-shale deposition.« less
The use of hydroxyacids as geochemical indicators

NASA Technical Reports Server (NTRS)

Cardoso, J. N.; Eglinton, G.

1983-01-01

The distributions of hydroxyacids in a variety of recent and ancient sediments have been determined by gas chromatography-mass spectrometry. A lacustrine sediment (Rostherne Mere, U.K.) and two marine situations (Cariaco Trench, Black Sea) were analyzed as examples of recent depositional environments. Beta-hydroxyacids occurred in all of the recent sediments, consistent with their presumed microbial origin, whereas di- and trihydroxyacids were present in the sediments with a significant higher plant input (Black Sea and Rostherne Mere sediments). The two ancient (Eocene) sediments examined, viz, the Greene River (U.S.) and Messel (Germany) oil shales, contained only trace amounts of hydroxyacids. These results provide evidence that hydroxyacids are in general not well preserved over geological time.
Provenance and depositional history of continental slope sediments in the Southwestern Gulf of Mexico unraveled by geochemical analysis

NASA Astrophysics Data System (ADS)

Armstrong-Altrin, John S.; Machain-Castillo, María Luisa; Rosales-Hoz, Leticia; Carranza-Edwards, Arturo; Sanchez-Cabeza, Joan-Albert; Ruíz-Fernández, Ana Carolina

2015-03-01

The aim of this work is to constrain the provenance and depositional history of continental slope sediments in the Southwestern Gulf of Mexico (~1089-1785 m water depth). To achieve this, 10 piston sediment cores (~5-5.5 m long) were studied for mineralogy, major, trace and rare earth element geochemistry. Samples were analyzed at three core sections, i.e. upper (0-1 cm), middle (30-31 cm) and lower (~300-391 cm). The textural study reveals that the core sediments are characterized by silt and clay fractions. Radiocarbon dating of sediments for the cores at different levels indicated a maximum of ~28,000 year BP. Sediments were classified as shale. The chemical index of alteration (CIA) values for the upper, middle, and lower sections revealed moderate weathering in the source region. The index of chemical maturity (ICV) and SiO2/Al2O3 ratio indicated low compositional maturity for the core sediments. A statistically significant correlation observed between total rare earth elements (∑REE) versus Al2O3 and Zr indicated that REE are mainly housed in detrital minerals. The North American Shale Composite (NASC) normalized REE patterns, trace element concentrations such as Cr, Ni and V, and the comparison of REE concentrations in sediments and source rocks indicated that the study area received sediments from rocks intermediate between felsic and mafic composition. The enrichment factor (EF) results indicated that the Cd and Zn contents of the upper section sediments were influenced by an anthropogenic source. The trace element ratios and authigenic U content of the core sediments indicated the existence of an oxic depositional environment.
Energy Gradients Structure Microbial Communities Across Sediment Horizons in Deep Marine Sediments of the South China Sea

PubMed Central

Graw, Michael F.; D'Angelo, Grace; Borchers, Matthew; Thurber, Andrew R.; Johnson, Joel E.; Zhang, Chuanlun; Liu, Haodong; Colwell, Frederick S.

2018-01-01

The deep marine subsurface is a heterogeneous environment in which the assembly of microbial communities is thought to be controlled by a combination of organic matter deposition, electron acceptor availability, and sedimentology. However, the relative importance of these factors in structuring microbial communities in marine sediments remains unclear. The South China Sea (SCS) experiences significant variability in sedimentation across the basin and features discrete changes in sedimentology as a result of episodic deposition of turbidites and volcanic ashes within lithogenic clays and siliceous or calcareous ooze deposits throughout the basin's history. Deep subsurface microbial communities were recently sampled by the International Ocean Discovery Program (IODP) at three locations in the SCS with sedimentation rates of 5, 12, and 20 cm per thousand years. Here, we used Illumina sequencing of the 16S ribosomal RNA gene to characterize deep subsurface microbial communities from distinct sediment types at these sites. Communities across all sites were dominated by several poorly characterized taxa implicated in organic matter degradation, including Atribacteria, Dehalococcoidia, and Aerophobetes. Sulfate-reducing bacteria comprised only 4% of the community across sulfate-bearing sediments from multiple cores and did not change in abundance in sediments from the methanogenic zone at the site with the lowest sedimentation rate. Microbial communities were significantly structured by sediment age and the availability of sulfate as an electron acceptor in pore waters. However, microbial communities demonstrated no partitioning based on the sediment type they inhabited. These results indicate that microbial communities in the SCS are structured by the availability of electron donors and acceptors rather than sedimentological characteristics. PMID:29696012
Volcanic influences: International working group on volcanogenic sediments

NASA Astrophysics Data System (ADS)

A conclusion of the Geological Society of America Penrose Conference on Volcanic Influences on Terrestrial Sedimentation (August 28 to September 2, 1988) was that establishment of an informal working group would enhance our understanding of volcanogenic sedimentation. To establish the group, an ad hoc steering committee was formed at the conference and consists of W. J. Fritz (Georgia State University), R. S. Hildebrand (Geological Survey of Canada), R. Iverson (U.S. Geological Survey), P. Kokelaar (Chairman, University of Liverpool), T. C. Pierson (USGS), and G. A. Smith (University of New Mexico). The working group is open to researchers of any nation interested in the study of secondary transport and deposition of volcaniclastic materials in subaerial or subaqueous environments (e.g., transport, deposition, nomenclature, volcanic history, experiment, theory, hazard).
Insights from the metagenome of an acid salt lake: the role of biology in an extreme depositional environment.

PubMed

Johnson, Sarah Stewart; Chevrette, Marc Gerard; Ehlmann, Bethany L; Benison, Kathleen Counter

2015-01-01

The extremely acidic brine lakes of the Yilgarn Craton of Western Australia are home to some of the most biologically challenging waters on Earth. In this study, we employed metagenomic shotgun sequencing to generate a microbial profile of the depositional environment associated with the sulfur-rich sediments of one such lake. Of the 1.5 M high-quality reads generated, 0.25 M were mapped to protein features, which in turn provide new insights into the metabolic function of this community. In particular, 45 diverse genes associated with sulfur metabolism were identified, the majority of which were linked to either the conversion of sulfate to adenylylsulfate and the subsequent production of sulfide from sulfite or the oxidation of sulfide, elemental sulfur, and thiosulfate via the sulfur oxidation (Sox) system. This is the first metagenomic study of an acidic, hypersaline depositional environment, and we present evidence for a surprisingly high level of microbial diversity. Our findings also illuminate the possibility that we may be meaningfully underestimating the effects of biology on the chemistry of these sulfur-rich sediments, thereby influencing our understanding of past geobiological conditions that may have been present on Earth as well as early Mars.
Rock magnetic properties of sediments from Lake Sanabria and its catchment (NW Spain): paleoenvironmental implications

NASA Astrophysics Data System (ADS)

Larrasoaña, J. C.; Borruel, V.; Gómez-Paccard, M.; Rico, M.; Valero-Garces, B.; Moreno-Caballud, A.; Soto, R.

2013-12-01

Lake Sanabria is located in the NW Spanish mountains at 1000 m a.s.l., and constitutes the largest lake of glacial origin in the Iberian Peninsula. Here we present an environmental magnetic study of a Late Pleistocene-Holocene sediment core from Lake Sanabria and from different lithologies that crop out in its catchment, which includes Paleozoic plutonic, metamorphic and vulcanosedimentary rocks, and Quaternary deposits of glacial origin. This study was designed to complement sedimentologic and geochemical studies aimed at unraveling the climatic evolution of the NW Iberian Peninsula during the last deglaciation. Our results indicate that magnetite and pyrrhotite dominate the magnetic assemblage of both the sediments from the lower half of the studied sequence (25.6 - 13 cal kyr BP) deposited in a proglacial environment, and the Paleozoic rocks that make up most of the catchment of the lake. The occurrence of these minerals both in the catchment rocks and in the lake sediments indicates that sedimentation was then driven by the erosion of a glacial flour, which suffered minimal chemical transformation in response to a rapid and short routing to the lake. Sediments from the upper half of the studied sequence, accumulated after 12.4 cal kyr BP in a fluviolacustrine environment, contain magnetite and greigite. This points to a prominent role of post-depositional reductive dissolution, driven by a sharp increase in the accumulation of organic matter into the lake and the creation of anoxic conditions in the sediments, in shaping the magnetic assemblage of Holocene sediments. Pyrrhotite is stable under reducing conditions as opposed to magnetite, which is unstable. We therefore interpret that previous pedogenic processes occurred in the then deglaciated catchment of the lake were responsible for the oxidation of pyrrhotite and authigenic formation of magnetite, which survived subsequent reductive diagenesis given its initial larger concentrations. This interpretation is supported by the magnetic properties of Quaternary till sediments, which in some cases retain their original magnetic assemblage (magnetite and pyrrhotite) and in other cases include larger concentrations of magnetite. The Holocene sequence includes some discrete layers with a magnetic signature identical to that of the glacial flour. These layers are interpreted as being deposited during extreme runoff events that eroded Quaternary tills. The sharp change in magnetic properties observed in the lake sediments between 13 and 12.4 kyr BP supports the rapid deglaciation of the catchment of Lake Sanabria inferred in previous studies on the basis of sedimentological, geochemical and geomorphological data.
100 Myr record of sequences, sedimentary facies and sea level change from Ocean Drilling Program onshore coreholes, US Mid-Atlantic coastal plain

USGS Publications Warehouse

Browning, J.V.; Miller, K.G.; Sugarman, P.J.; Kominz, M.A.; McLaughlin, P.P.; Kulpecz, A.A.; Feigenson, M.D.

2008-01-01

We analyzed the latest Early Cretaceous to Miocene sections (???110-7Ma) in 11 New Jersey and Delaware onshore coreholes (Ocean Drilling Program Legs 150X and 174AX). Fifteen to seventeen Late Cretaceous and 39-40 Cenozoic sequence boundaries were identified on the basis of physical and temporal breaks. Within-sequence changes follow predictable patterns with thin transgressive and thick regressive highstand systems tracts. The few lowstands encountered provide critical constraints on the range of sea-level fall. We estimated paleowater depths by integrating lithofacies and biofacies analyses and determined ages using integrated biostratigraphy and strontium isotopic stratigraphy. These datasets were backstripped to provide a sea-level estimate for the past ???100 Myr. Large river systems affected New Jersey during the Cretaceous and latest Oligocene-Miocene. Facies evolved through eight depositional phases controlled by changes in accommodation, long-term sea level, and sediment supply: (1) the Barremian-earliest Cenomanian consisted of anastomosing riverine environments associated with warm climates, high sediment supply, and high accommodation; (2) the Cenomanian-early Turonian was dominated by marine sediments with minor deltaic influence associated with long-term (107 year) sea-level rise; (3) the late Turonian through Coniacian was dominated by alluvial and delta plain systems associated with long-term sea-level fall; (4) the Santonian-Campanian consisted of marine deposition under the influence of a wave-dominated delta associated with a long-term sea-level rise and increased sediment supply; (5) Maastrichtian-Eocene deposition consisted primarily of starved siliciclastic, carbonate ramp shelf environments associated with very high long-term sea level and low sediment supply; (6) the late Eocene-Oligocene was a starved siliciclastic shelf associated with moderately high sea-level and low sediment supply; (7) late early-middle Miocene consisted of a prograding shelf under a strong wave-dominated deltaic influence associated with major increase in sediment supply and accommodation due to local sediment loading; and (8) over the past 10 Myr, low accommodation and eroded coastal systems were associated with low long-term sea level and low rates of sediment supply due to bypassing. ?? 2008 The Authors. Journal compilation ?? 2008 Blackwell Publishing.
A Geochemical Analysis of Rare Earth Elements Associated with Significant Phosphate Deposits of West-Central Florida

NASA Astrophysics Data System (ADS)

Turner, K. M.; Owens, J. D.

2017-12-01

Rare earth elements (REEs) such as the lanthanide series as well as yttrium, uranium, and thorium are an important industrial resource for expanding technological sectors; therefore, demand and production will continue to increase. Increased market prices resulting in decreased demand has led to new exploration for REE mineral resources in North America. Phosphorite deposits are being investigated as a possible supply but the overall concentrations, depositional environments, and ages are relatively unexplored. Phosphorite is commonly associated with ocean floor sediment deposition and upwelling; however, it may also form in estuarine and supratidal zones with low wave activity, present along Florida's west coast. Interestingly, it seems that major ancient phosphorite deposits are often, if not always, associated with major icehouse conditions (widespread glaciations) and rarely observed during greenhouse conditions. By analyzing a set of sonic drill cores, spatiotemporal REE concentrations can be better constrained for a wide-age range of the Miocene-Pliocene aged Bone Valley Member of the Peace River Formation, the largest North American phosphate deposit. We present concentrations from a depth-transect of samples collected in West-Central Florida, showing the phosphatic sands and silts of the area are highly enriched sedimentary archives for REE, yielding concentrations up to 200 ppm for some REE. The weathering and transport of igneous and metamorphic minerals from the southern Appalachians to the Florida coast where a series of winnowing events occurred may explain the enrichment seen by our data. Sediment cores showing well-rounded quartz sands, dolomitic silts, teeth, bones, and marine fossils commonly found in a near shore depositional environment support this hypothesis. Previous analysis of phosphate grains, teeth, bones, and bulk sediment indicate REE are not associated with and/or sourcing from biogenic components, but rather entering the lattice structure of the phosphate grains through secondary diagenetic processes. Though concentrations do not reach values as high as other mining sources the relative ease of extraction from sedimentary deposits may make them a valuable source.
DOE Office of Scientific and Technical Information (OSTI.GOV)

Davis, R.J.; Johnson, C.A.; Gilreath, J.A.

Depositional systems in the Medina Group (Lower Silurian) of western New York have been studied using stratigraphic dipmeter data. Results of this study indicate a nearshore-deltaic-interdeltaic depositional environment. Only minor deltaic episodes are preserved in the study area. This fits the generally arid climate with seasonal wet periods suggested by C.D. Laughrey. Facies recognized include: longshore-current sand waves in a shoreface environment, distributary mouth bars, distributary channels, tidal inlets, flood deltas, beaches, sandy tidal flats on which beach ridges were formed, and possible upper delta-plain sediments. Once the depositional sequences are recognized, paleocurrents within key sand units can be interpretedmore » to determine favorable directions for successfully locating offset wells.« less
Morphology and palaeoenvironmental interpretation of deformed soft-sediment clasts: examples from within Late Pleistocene glacial outwash, Tempo Valley, Northern Ireland

NASA Astrophysics Data System (ADS)

Knight, Jasper

1999-10-01

Glacial outwash, deposited during deglaciation of the late Devensian ice sheet, is present as a flat-topped valley fill in the Tempo Valley on the southern flanks of the Fintona Hills, Northern Ireland. Sedimentologically, the outwash comprises well-sorted and interbedded rippled to massive sands which record distal deposition within a proglacial water body. Beds of ripple-drift cross-laminated sands contain deformed (folded and contorted) soft-sediment clasts which are composed mainly of silt and clay. The soft-sediment clasts were deformed prior to final deposition because clast a- b planes lie conformable to sand laminae which are undeformed. Morphological characteristics of the soft-sediment clasts, and their facies context, provide evidence for transport mechanisms, depositional environment, and processes of clast deformation. The soft-sediment clasts were transported into a proglacial water body by unidirectional water currents (˜1.5-2.5 m s -1). Sediment transport processes include sediment bypassing within the water column, a low bedload component, and grain flow activity during waning flow stages. The overall morphology of soft-sediment clasts records between 1 and 3 distinct phases of hydroplastic deformation prior to emplacement. The deformation phases are recognised on the basis of morphologically `unrolling' the superimposed folds of the soft-sediment clasts. Deformation structures (i.e. fold style) and direction of the principal stress axis relative to clast axes suggest that clasts were reoriented with respect to water flow direction following each deformation phase. Processes of deformation include folding-over of the clast along its b axis into two or more components, crumpling and abrasion of the outer margins of the b plane, and squashing of the clast c axis (some of which may be post-depositional deformation). The presence of silt- and clay-rich soft-sediment clasts within the outwash succession suggests that they were ripped-up from shallow and irregular pools on the glacier forefield, into which fine sediments accumulated after flood or meltwater events, and transported distally into a proglacial water body. These inferences based on facies evidence and styles of hydroplastic deformation impact on reconstructions of local palaeogeography, and the wider interpretation of similar soft-sediment clasts in the geological record.
Recent paleorecords document rising mercury contamination in Lake Tanganyika

USGS Publications Warehouse

Conaway, C.H.; Swarzenski, P.W.; Cohen, A.S.

2012-01-01

Recent Lake Tanganyika Hg deposition records were derived using 14C and excess 210Pb geochronometers in sediment cores collected from two contrasting depositional environments: the Kalya Platform, located mid-lake and more removed from watershed impacts, and the Nyasanga/Kahama River delta region, located close to the lake's shoreline north of Kigoma. At the Kalya Platform area, pre-industrial Hg concentrations are 23??0.2ng/g, increasing to 74ng/g in modern surface sediment, and the Hg accumulation rate has increased from 1.0 to 7.2??g/m 2/a from pre-industrial to present, which overall represents a 6-fold increase in Hg concentration and accumulation. At the Nyasanga/Kahama delta region, pre-industrial Hg concentrations are 20??3ng/g, increasing to 46ng/g in surface sediment. Mercury accumulation rate has increased from 30 to 70??g/m 2/a at this site, representing a 2-3-fold increase in Hg concentration and accumulation. There is a lack of correlation between charcoal abundance and Hg accumulation rate in the sediment cores, demonstrating that local biomass burning has little relationship with the observed Hg concentration or Hg accumulation rates. Examined using a sediment focusing-corrected mass accumulation rate approach, the cores have similar anthropogenic atmospheric Hg deposition profiles, suggesting that after accounting for background sediment concentrations the source of accumulating Hg is predominantly atmospheric in origin. In summary, the data document an increase of Hg flux to the Lake Tanganyika ecosystem that is consistent with increasing watershed sediment delivery with background-level Hg contamination, and regional as well as global increases in atmospheric Hg deposition. ?? 2011.

Overbank Sedimentation from the 2011 Flood along the Lower Mississippi River: Characterization and Comparison of Two Extreme Events

NASA Astrophysics Data System (ADS)

Hudson, P. H.; Heitmuller, F. T.; Kesel, R. H.

2012-04-01

The geomorphic effectiveness of extreme events has long been a fundamental topic within Earth sciences. The 2011 flood along the lower Mississippi River (3.2 x 10-6 km2) was an extreme event and presented an ideal opportunity to consider controls on the magnitude and pattern of floodplain sedimentation. The study reach was located between Natchez, Mississippi and St. Francisville, Louisiana, the lowermost reaches of the alluvial valley, and the same location utilized in a well documented sedimentation study from a comparable flood event in 1973. Thus, the 2011 field study provided a rare opportunity to directly compare floodplain sedimentation from two extreme events on Earth's third largest fluvial system. Although flood stage along the Lower Mississippi River is influenced by an extensive levee system the field setting is distinctive because it is not embanked by main-line levees. The field site was flooded for nearly two months, from early May to late June 2011. The flood crest exceeded long standing (> 100 yr) stage heights, including the infamous 1927, 1937, and 1973 events. The maximum discharge at Vicksburg, Mississippi, upstream of the study sites, was 65,695 m3/s, one of the larger discharge events along the Lower Mississippi River. Field work was conducted soon after flood waters receded and before bioturbation disrupted the integrity of the flood deposits. We sampled flood deposits at fifty-five locations within a range of floodplain depositional environments to quantify and qualify the sedimentary, hydrologic, and hydraulic characteristics of the flood, and to make explicit comparison with the 1973 study. The average thickness of flood deposits ranged from < 1 mm to 650 mm, but was highly variable. Although natural levees had the thickest flood deposits several reaches along natural levees had no measureable deposits, despite being inundated by ~4 m of flood water. In such cases the angle of the upstream channel relative to the downstream cutbank is suggested as a possible control on the pattern of sedimentation. Despite the magnitude and duration of the 2011 flood, the overall thickness of flood deposits was not very high and the geologic legacy of the event is likely to be unimpressive. Most sediment samples was < 10 mm in thickness, which could be due to the timing of the flood event superimposed upon an overall declining trend in suspended sediment load. The peak discharge was associated with a suspended sediment load of 727,400 tonnes/day. This is notably lower than the maximum suspended sediment load of 1,046,000 tonnes/day, which likely caused sediment exhaustion because of occurring about two months prior to inundation. The thickness of the 2011 flood deposits were about an order of magnitude less than the 1973 flood deposits (11 to 530 mm). Since the early 1900s the sediment budget of the Lower Mississippi has been fundamentally altered. Suspended sediment loads have declined by more than fifty percent, and could contribute to the overall low amount of sedimentation.
Exploring Mars for Evidence of Habitable Environments and Life

NASA Technical Reports Server (NTRS)

DesMarais, David J.

2014-01-01

The climate of Mars has been more similar to that of Earth than has the climate of any other planet in our Solar System. But Mars still provides a valuable alternative example of how planetary processes and environments can affect the potential presence of life elsewhere. For example, although Mars also differentiated very early into a core, mantle and crust, it then evolved mostly if not completely without plate tectonics and has lost most of its early atmosphere. The Martian crust has been more stable than that of Earth, thus it has probably preserved a more complete record of its earliest history. Orbital observations determined that near-surface water was once pervasive. Orbiters have identified the following diverse aqueous sedimentary deposits: layered phyllosilicates, phyllosilicates in intracrater fans, plains sediments potentially harboring evaporitic minerals, deep phyllosilicates, carbonate-bearing deposits, intracrater clay-sulfate deposits, Meridiani-type layered deposits, valles-type layered deposits, hydrated silica-bearing deposits, and gypsum plains. These features, together with evidence of more vigorous past geologic activity, indicate that early climates were wetter and perhaps also somewhat warmer. The denser atmosphere that was required for liquid water to be stable on the surface also provided more substantial protection from radiation. Whereas ancient climates might have favored habitable environments at least in some localities, clearly much of the Martian surface for most of its history has been markedly less favorable for life. The combination of dry conditions, oxidizing surface environments and typically low rates of sedimentation are not conducive to the preservation of evidence of ancient environments and any biota. Thus a strategy is required whereby candidate sites are first identified and then characterized for their potential to preserve evidence of past habitable environments. Rovers are then sent to explore the most promising candidates. The Mars Exploration Rover (MER) Opportunity revealed that water once flowed to the surface across the vast Meridiani plains, creating saline lakes whose waters were roiled by ancient winds that also sculptured their salt deposits into sand dunes. Opportunity then drove more than 30 km to explore even older deposits on a crater rim. MER Spirit found evidence that thermal waters (heated by volcanism or by impacts?) altered rocks to create sulfate salts, and siliceous sinters. These discoveries indicate that an early hydrological cycle apparently sustained precipitation, streams and lakes. Liquid water participated in rock weathering reactions, such as iron and sulfur oxidation, that created distinctive weathering regimes. Volcanism, impacts, groundwater and ice interacted at least locally. Redox chemical energy from volcanism, hydrothermal activity and weathering of crustal materials would have been available for any life. Thus conditions might have supported life in the past, at least locally. The main objective of the Mars Science Laboratory (MSL) Curiosity rover is to determine the extent to which Gale crater hosted environments capable of supporting microbial life. The rover has already found stream gravels as well as sediments that might have been deposited in an ancient lake. The rover is now traversing to Mt. Sharp, a 5 km-high mound that is located on the crater floor and that exhibits layered sedimentary rocks having diverse minerals (sulfates and clays) that apparently formed in the presence of liquid water. This rock sequence was deposited over an extended time period in diverse potentially habitable watery environments. Curiosity is poised to characterize a a well-preserved rock record of hundreds of millions of years of diverse environments and profound climate change.
"THE DYNAMICS OF ARSENIC IN SATURATED POROUS MEDIA: FATE AND TRANSPORT MODELING FOR DEEP-WATER SEDIMENTS, WETLAND SEDIMENTS, AND GROUNDWATER ENVIRONMENTS," WATER ROCK INTERACTIONS, ORE DEPOSITS, AND ENVIRONMENTAL GEOCHEMISTRY: A TRIBUTE TO DAVID CRERAR. (R827288)

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...
Distribution of long-lived radioactive iodine isotope (I-129) in pore waters from the gas hydrate fields on the continental margins: Indication for methane source of gas hydrate deposits

NASA Astrophysics Data System (ADS)

Tomaru, H.; Lu, Z.; Fehn, U.

2011-12-01

Because iodine has a strong association with organic matters in marine environments, pore waters in high methane potential region, in particular gas hydrate occurrences on the continental margins, are enriched significantly in iodine compared with seawater. Natural iodine system is composed of stable and radioactive species, I-129 (half-life of 15.7 Myr) has been used for estimating the age of source formations both for methane and iodine, because iodine can be liberated into pore water during the degradation of organic matter to methane in deep sediments. Here we present I-129 age data in pore waters collected from variety of gas hydrate occurrences on the continental margins. The I-129 ages in pore waters from these locations are significantly older than those of host sediments, indicating long-term transport and accumulation from deep/old sediments. The I-129 ages in the Japan Sea and Okhotsk Sea along the plate boundary between the North American and Amurian Plates correspond to the ages of initial spreading of these marginal seas, pointing to the massive deposition of organic matter for methane generation in deep sediments within limited periods. On the Pacific side of these areas, organic matter-rich back stop is responsible for methane in deep-seated gas hydrate deposits along the Nankai Trough. Deep coaly sequences responsible for deep conventional natural gas deposits are also responsible for overlying gas hydrate deposits off Shimokita Peninsula, NE Japan. Those in the Gulf of Mexico are correlative to the ages of sediments where the top of salt diapirs intrude. Marine sediments on the Pacific Plate subducting beneath the Australian Plate are likely responsible for the methane and iodine in the Hikurangi Trough, New Zealand. These ages reflect well the regional geological settings responsible for generation, transport, and accumulation of methane, I-129 is a key to understand the geological history of gas hydrate deposition.
Sediment reallocations due to erosive rainfall events in the Three Gorges Reservoir Area, Central China

NASA Astrophysics Data System (ADS)

Stumpf, Felix; Goebes, Philipp; Schmidt, Karsten; Schindewolf, Marcus; Schönbrodt-Stitt, Sarah; Wadoux, Alexandre; Xiang, Wei; Scholten, Thomas

2017-04-01

Soil erosion by water outlines a major threat to the Three Gorges Reservoir Area in China. A detailed assessment of soil conservation measures requires a tool that spatially identifies sediment reallocations due to rainfall-runoff events in catchments. We applied EROSION 3D as a physically based soil erosion and deposition model in a small mountainous catchment. Generally, we aim to provide a methodological frame that facilitates the model parametrization in a data scarce environment and to identify sediment sources and deposits. We used digital soil mapping techniques to generate spatially distributed soil property information for parametrization. For model calibration and validation, we continuously monitored the catchment on rainfall, runoff and sediment yield for a period of 12 months. The model performed well for large events (sediment yield>1 Mg) with an averaged individual model error of 7.5%, while small events showed an average error of 36.2%. We focused on the large events to evaluate reallocation patterns. Erosion occurred in 11.1% of the study area with an average erosion rate of 49.9Mgha 1. Erosion mainly occurred on crop rotation areas with a spatial proportion of 69.2% for 'corn-rapeseed' and 69.1% for 'potato-cabbage'. Deposition occurred on 11.0%. Forested areas (9.7%), infrastructure (41.0%), cropland (corn-rapeseed: 13.6%, potatocabbage: 11.3%) and grassland (18.4%) were affected by deposition. Because the vast majority of annual sediment yields (80.3%) were associated to a few large erosive events, the modelling approach provides a useful tool to spatially assess soil erosion control and conservation measures.
Elevated olivine weathering rates and sulfate formation at cryogenic temperatures on Mars.

PubMed

Niles, Paul B; Michalski, Joseph; Ming, Douglas W; Golden, D C

2017-10-17

Large Hesperian-aged (~3.7 Ga) layered deposits of sulfate-rich sediments in the equatorial regions of Mars have been suggested to be evidence for ephemeral playa environments. But early Mars may not have been warm enough to support conditions similar to what occurs in arid environments on Earth. Instead cold, icy environments may have been widespread. Under cryogenic conditions sulfate formation might be blocked, since kinetics of silicate weathering are typically strongly retarded at temperatures well below 0 °C. But cryo-concentration of acidic solutions may counteract the slow kinetics. Here we show that cryo-concentrated acidic brines rapidly chemically weather olivine minerals and form sulfate minerals at temperatures as low as -60 °C. These experimental results demonstrate the viability of sulfate formation under current Martian conditions, even in the polar regions. An ice-hosted sedimentation and weathering model may provide a compelling description of the origin of large Hesperian-aged layered sulfate deposits on Mars.
Can barrier islands survive sea level rise? Tidal inlets versus storm overwash

NASA Astrophysics Data System (ADS)

Nienhuis, J.; Lorenzo-Trueba, J.

2017-12-01

Barrier island response to sea level rise depends on their ability to transgress and move sediment to the back barrier, either through flood-tidal delta deposition or via storm overwash. Our understanding of these processes over decadal to centennial timescales, however, is limited and poorly constrained. We have developed a new barrier inlet environment (BRIE) model to better understand the interplay between tidal dynamics, overwash fluxes, and sea-level rise on barrier evolution. The BRIE model combines existing overwash and shoreface formulations [Lorenzo-Trueba and Ashton, 2014] with alongshore sediment transport, inlet stability [Escoffier, 1940], inlet migration and flood-tidal delta deposition [Nienhuis and Ashton, 2016]. Within BRIE, inlets can open, close, migrate, merge with other inlets, and build flood-tidal delta deposits. The model accounts for feedbacks between overwash and inlets through their mutual dependence on barrier geometry. Model results suggest that when flood-tidal delta deposition is sufficiently large, barriers require less storm overwash to transgress and aggrade during sea level rise. In particular in micro-tidal environments with asymmetric wave climates and high alongshore sediment transport, tidal inlets are effective in depositing flood-tidal deltas and constitute the majority of the transgressive sediment flux. Additionally, we show that artificial inlet stabilization (via jetty construction or maintenance dredging) can make barrier islands more vulnerable to sea level rise. Escoffier, F. F. (1940), The Stability of Tidal Inlets, Shore and Beach, 8(4), 114-115. Lorenzo-Trueba, J., and A. D. Ashton (2014), Rollover, drowning, and discontinuous retreat: Distinct modes of barrier response to sea-level rise arising from a simple morphodynamic model, J. Geophys. Res. Earth Surf., 119(4), 779-801, doi:10.1002/2013JF002941. Nienhuis, J. H., and A. D. Ashton (2016), Mechanics and rates of tidal inlet migration: Modeling and application to natural examples, J. Geophys. Res. Earth Surf., 121(11), 2118-2139, doi:10.1002/2016JF004035.
Winnowing and Flocculation in Bio-physical Cohesive Substrate: A Flume Experimental and Estuarine Study

NASA Astrophysics Data System (ADS)

Ye, L.; Parsons, D. R.; Manning, A. J.

2016-12-01

Cohesive sediment, or mud, is ubiquitously found in most aqueous environments, such as coasts and estuaries. The study of cohesive sediment behaviors requires the synchronous description of mutual interactions of grains (e.g., winnowing and flocculation), their physical properties (e.g., grain size) and also the ambient water. Herein, a series of flume experiments (14 runs) with different substrate mixtures of sand-clay-EPS (Extracellular Polymeric Substrates: secreted by aquatic microorganisms) are combined with an estuarine field survey (Dee estuary, NW England) to investigate the behavior of suspensions over bio-physical cohesive substrates. The experimental results indicate that winnowing and flocculation occur pervasively in bio-physical cohesive flow systems. Importantly however, the evolution of the bed and bedform dynamics and hence turbulence production can be lower when cohesivity is high. The estuarine survey also revealed that the bio-physical cohesion provided by both the clay and microorganism fractions in the bed, that pervasively exists in many natural estuarine systems, plays a significant role in controlling the interactions between bed substrate and sediment suspension and deposition, including controlling processes such as sediment winnowing, flocculation and re-deposition. Full understanding of these processes are essential in advancing sediment transport modelling and prediction studies across natural estuarine systems and the work will report on an improved conceptual model for sediment sorting deposition in bio-physical cohesive substrates.
Exobiology site selection for future Mars missions: Martian paleolake sediments and terrestrial analogs

NASA Technical Reports Server (NTRS)

Wharton, Robert A., Jr.

1989-01-01

This research was conducted to establish the scientific framework for the exobiological study of sediments on Mars and to encourage the selection of these sedimentary deposits as sampling sites for future Mars missions. A study was completed on the Antarctic Dry Valley Lakes (terrestrial analogs of the purported Martian paleolakes) and their sediments that allowed the development of quantitative models relating environmental factors to the nature of the biological community and sediment forming processes. The publications presented include: (1) Diversity of micro-fungi isolated in an Antarctic dry valley; (2) Lake Hoare, Antarctica--sedimentation through a thick perennial ice cover; (3) The possibility of life on Mars during a water-rich past; (4) An Antarctic research outpost as a model for planetary exploration; (5) Early Martian environments--the Antarctic and other terrestrial analogs; (6) Lipophilic pigments from the benthos of a perennially ice-covered Antarctic lake; and (7) Perennially ice-covered Lake Hoare, Antarctica--physical environment, biology, and sedimentation.
Lasting Impact of a Tsunami Event on Sediment-Organism Interactions in the Ocean

NASA Astrophysics Data System (ADS)

Seike, Koji; Sassa, Shinji; Shirai, Kotaro; Kubota, Kaoru

2018-02-01

Although tsunami sedimentation is a short-term phenomenon, it may control the long-term benthic environment by altering seafloor surface characteristics such as topography and grain-size composition. By analyzing sediment cores, we investigated the long-term effect of the 2011 tsunami generated by the Tohoku Earthquake off the Pacific coast of Japan on sediment mixing (bioturbation) by an important ecosystem engineer, the heart urchin Echinocardium cordatum. Recent tsunami deposits allow accurate estimation of the depth of current bioturbation by E. cordatum, because there are no preexisting burrows in the sediments. The in situ hardness of the substrate decreased significantly with increasing abundance of E. cordatum, suggesting that echinoid bioturbation softens the seafloor sediment. Sediment-core analysis revealed that this echinoid rarely burrows into the coarser-grained (medium-grained to coarse-grained) sandy layer deposited by the 2011 tsunami; thus, the vertical grain-size distribution resulting from tsunami sedimentation controls the depth of E. cordatum bioturbation. As sandy tsunami layers are preserved in the seafloor substrate, their restriction on bioturbation continues for an extended period. The results demonstrate that understanding the effects on seafloor processes of extreme natural events that occur on geological timescales, including tsunami events, is important in revealing continuing interactions between seafloor sediments and marine benthic invertebrates.
Ancestral Rocky Mountian Tectonics: A Sedimentary Record of Ancestral Front Range and Uncompahgre Exhumation

NASA Astrophysics Data System (ADS)

Smith, T. M.; Saylor, J. E.; Lapen, T. J.

2015-12-01

The Ancestral Rocky Mountains (ARM) encompass multiple crustal provinces with characteristic crystallization ages across the central and western US. Two driving mechanisms have been proposed to explain ARM deformation. (1) Ouachita-Marathon collision SE of the ARM uplifts has been linked to an E-to-W sequence of uplift and is consistent with proposed disruption of a larger Paradox-Central Colorado Trough Basin by exhumation of the Uncompahgre Uplift. Initial exhumation of the Amarillo-Wichita Uplift to the east would provide a unique ~530 Ma signal absent from source areas to the SW, and result in initial exhumation of the Ancestral Front Range. (2) Alternatively, deformation due to flat slab subduction along a hypothesized plate boundary to the SW suggests a SW-to-NE younging of exhumation. This hypothesis suggests a SW-derived Grenville signature, and would trigger uplift of the Uncompahgre first. We analyzed depositional environments, sediment dispersal patterns, and sediment and basement zircon U-Pb and (U-Th)/He ages in 3 locations in the Paradox Basin and Central Colorado Trough (CCT). The Paradox Basin exhibits an up-section transition in fluvial style that suggests a decrease in overbank stability and increased lateral migration. Similarly, the CCT records a long-term progradation of depositional environments from marginal marine to fluvial, indicating that sediment supply in both basins outpaced accommodation. Preliminary provenance results indicate little to no input from the Amarillo-Wichita uplift in either basin despite uniformly westward sediment dispersal systems in both basins. Results also show that the Uncompahgre Uplift was the source for sediment throughout Paradox Basin deposition. These observations are inconsistent with the predictions of scenario 1 above. Rather, they suggest either a synchronous response to tectonic stress across the ARM provinces or an SW-to-NE pattern of deformation.
DOE Office of Scientific and Technical Information (OSTI.GOV)

Cregg, A.K.

Kenya basins have evolved primarily through extension related to episodic continental rifting. In eastern Kenya, thick accumulations of sediments formed within grabens during the prerift phase (Precambrian to Carboniferous) of the Gondwana breakup. Synrift sedimentation (Late Carboniferous to Middle Jurassic) occurred within a north-south rift system, which included the Mandera basin, South Anza basin, and Lamu embayment. During the Early Jurassic, a marine transgression invaded the margins of the eastern Kenya rift basins, resulting in the deposition of platform carbonates and shales. A Callovian-aged salt basin formed in the offshore regions of the Lamu embayment. Intermittent tectonic activity and eustaticmore » sea-level changes controlled sedimentation, which produced marine shales, carbonates or evaporites, and fluvio-deltaic to lacustrine sandstones. From the Early Cretaceous to recent, continental sediments were deposited within the North Anza and Turkana basins. These fluvial-lacustrine sediments are similar to the Lower Cretaceous sequences that have produced oil in the Mesozoic Sudanese Abu Gabra rift. Although exploration activities began in the early 1950s, significant occurrences of potential reservoir, source, and seal lithologies as well as trapping configurations remain in many areas. Favorable structures and sequences of reservoir sandstones and carbonates overlain by potentially sealing lacustrine or marine shales, evaporites, or volcanics have been noted. Potential source beds are believed to be present within shales of the lacustrine or marine depositional environments.« less
Sedimentary processes on the Mekong subaqueous delta: Clay mineral and geochemical analysis

NASA Astrophysics Data System (ADS)

Xue, Zuo; Paul Liu, J.; DeMaster, Dave; Leithold, Elana L.; Wan, Shiming; Ge, Qian; Nguyen, Van Lap; Ta, Thi Kim Oanh

2014-01-01

Sedimentary processes on the inner Mekong Shelf were investigated by examining the characteristics of sediments sampled in gravity cores at 15 locations, including grain size, clay mineralogy, sediment accumulation rates, and the elemental and stable carbon isotopic composition of organic matter (atomic C/N ratios and δ13C). Deltaic deposits exhibit contrasting characteristics along different sides of the delta plain (South China Sea, SCS hereafter, to the east and Gulf of Thailand, GOT hereafter, to the west) as well as on and off the subaqueous deltaic system. On one hand, cores recovered from the subaqueous delta in the SCS/GOT are consisted of poorly/well sorted sediments with similar/different clay mineral assemblage with/from Mekong sediments. Excess 210Pb profiles, supported by 14C chronologies, indicate either "non-steady" (SCS side) or "rapid accumulation" (GOT side) processes on the subaqueous delta. The δ13C and C/N ratio indicate a mixture of terrestrial and marine-sourced organic matter in the deltaic sediment. On the other hand, cores recovered from areas with no deltaic deposits or seaward of the subaqueous delta show excess 210Pb profiles indicating "steady-state" accumulation with a greater proportion of marine-sourced organic matter. Core analysis's relevance with local depositional environment and previous acoustic profiling are discussed.
The record of iceberg roll generated waves from sediments and seismics

NASA Astrophysics Data System (ADS)

Rosser, N. J.; Szczucinski, W.; Strzelecki, M.; Long, A. J.; Norman, E. C.; Dunning, S.; Drewniak, M.

2013-12-01

Iceberg-roll tsunamis in coastal settings have been observed to generate significant local waves, that hold potential to be recorded in coastal depositional records. Capturing the past magnitude and frequency of such events remains challenging, hindered by a lack of a good understanding of the nature, recurrence and scale of iceberg rolls, and more specifically those rolls that generate waves. Here we consider the sedimentary evidence for iceberg rolls in West Central Greenland, based upon survey of depositional environments in a range of open and confined coastal environments. We examine both an open 80 km fjord setting, and a series of confined ice-marginal beaches. We combine a detailed interpretation of sediment deposits from shore-normal transects with wider-scale high-resolution terrestrial laser scanning of sediments. Our sites - Vaigat, which separates Disko Island from the Nussuaq Peninsular, and the northern shore of Icefjord - both have a recent history of tsunamis, triggered variously by large rock avalanches, landslides and iceberg rolls. Icebergs in Vaigat and Icefjord are observed to undergo frequent failure and roll, generating - where circumstances permit - nearshore waves of meter-scale. To obtain a more detailed understanding of the likely recurrence of such iceberg roll waves and to consider their influence upon the preserved sedimentary record, we undertook an intensive 2-month monitoring campaign during sea-ice free conditions in summer 2013 to determine the patterns in the location, magnitude, frequency and timing of iceberg roll waves. Innovatively, using microseismic monitoring combined with time-lapse photography and weather monitoring, we derive a first-order model of the occurrence of iceberg roll waves. We then use this to inform our interpretation of deposits in these two environments, and consider the presence and absence of records of iceberg roll deposits in such settings. The study was funded by Polish National Science Centre grant No. 2011/01/B/ST10/01553.
Deposition, exhumation, and paleoclimate of an ancient lake deposit, Gale crater, Mars.

PubMed

Grotzinger, J P; Gupta, S; Malin, M C; Rubin, D M; Schieber, J; Siebach, K; Sumner, D Y; Stack, K M; Vasavada, A R; Arvidson, R E; Calef, F; Edgar, L; Fischer, W F; Grant, J A; Griffes, J; Kah, L C; Lamb, M P; Lewis, K W; Mangold, N; Minitti, M E; Palucis, M; Rice, M; Williams, R M E; Yingst, R A; Blake, D; Blaney, D; Conrad, P; Crisp, J; Dietrich, W E; Dromart, G; Edgett, K S; Ewing, R C; Gellert, R; Hurowitz, J A; Kocurek, G; Mahaffy, P; McBride, M J; McLennan, S M; Mischna, M; Ming, D; Milliken, R; Newsom, H; Oehler, D; Parker, T J; Vaniman, D; Wiens, R C; Wilson, S A

2015-10-09

The landforms of northern Gale crater on Mars expose thick sequences of sedimentary rocks. Based on images obtained by the Curiosity rover, we interpret these outcrops as evidence for past fluvial, deltaic, and lacustrine environments. Degradation of the crater wall and rim probably supplied these sediments, which advanced inward from the wall, infilling both the crater and an internal lake basin to a thickness of at least 75 meters. This intracrater lake system probably existed intermittently for thousands to millions of years, implying a relatively wet climate that supplied moisture to the crater rim and transported sediment via streams into the lake basin. The deposits in Gale crater were then exhumed, probably by wind-driven erosion, creating Aeolis Mons (Mount Sharp). Copyright © 2015, American Association for the Advancement of Science.
Effect of receiving environment on the transport and fate of polybrominated diphenyl ethers near two submarine municipal outfalls.

PubMed

Dinn, Pamela M; Johannessen, Sophia C; Macdonald, Robie W; Lowe, Christopher J; Whiticar, Michael J

2012-03-01

The fate of contaminants entering the marine environment through wastewater outfalls depends on the contaminant's persistence and affinity for particles. However, the physical characteristics of the receiving environment, for example, current velocity and sedimentary processes, may be even more important. Because of the complexity of natural settings and the lack of appropriate comparative settings, this is not frequently evaluated quantitatively. The authors investigated the near-field accumulation of particle-reactive polybrominated diphenyl ethers (PBDEs) entering coastal waters by way of two municipal outfalls: one discharging into a high-energy, low-sedimentation environment near Victoria, BC, Canada; the other into a low-energy, high-sedimentation environment, near Vancouver, BC. The authors used ²¹⁰Pb profiles in box cores together with an advection-diffusion model to determine surface mixing and sedimentation rates, and to model the depositional history of PBDEs at these sites. Surprisingly, 88 to 99% of PBDEs were dispersed beyond the near-field at both sites, but a greater proportion of PBDEs was captured in the sediment near the Vancouver outfall where rapid burial was facilitated by inorganic sediment supplied from the nearby Fraser River. Although the discharge of PBDEs was much lower from the Victoria outfall than from Vancouver, some sediment PBDE concentrations were higher near Victoria. Copyright © 2011 SETAC.
Assessment of field-related influences on polychlorinated biphenyl exposures and sorbent amendment using polychaete bioassays and passive sampler measurements

USGS Publications Warehouse

Janssen, E.M.; Oen, A.M.; Luoma, S.N.; Luthy, R.G.

2011-01-01

Field-related influences on polychlorinated biphenyl (PCB) exposure were evaluated by employing caged deposit-feeders, Neanthes arenaceodentata, along with polyoxymethylene (POM) samplers using parallel in situ and ex situ bioassays with homogenized untreated or activated carbon (AC) amended sediment. The AC amendment achieved a remedial efficiency in reducing bioaccumulation by 90% in the laboratory and by 44% in the field transplants. In situ measurements showed that PCB uptake by POM samplers was greater for POM placed in the surface sediment compared with the underlying AC amendment, suggesting that tidal exchange of surrounding material with similar PCB availability as untreated sediment was redeposited in the cages. Polychlorinated biphenyls bioaccumulation with caged polychaetes from untreated sediment was half as large under field conditions compared with laboratory conditions. A biodynamic model was used to confirm and quantify the different processes that could have influenced these results. Three factors appeared most influential in the bioassays: AC amendment significantly reduces bioavailability under laboratory and field conditions; sediment deposition within test cages in the field partially masks the remedial benefit of underlying AC-amended sediment; and deposit-feeders exhibit less PCB uptake from untreated sediment when feeding is reduced. Ex situ and in situ experiments inevitably show some differences that are associated with measurement methods and effects of the environment. Parallel ex situ and in situ bioassays, passive sampler measurements, and quantifying important processes with a model can tease apart these field influences. ?? 2010 SETAC.
Flow and suspended-sand behavior in large rivers after dredging.

NASA Astrophysics Data System (ADS)

Yuill, B. T.; Wang, Y.; Allison, M. A.; Meselhe, E. A.

2017-12-01

Dredging is commonly used in large rivers to promote navigation and provide sediment for engineering projects. Channel bars typically have thicker, coarser sediment deposits than elsewhere on the channel bed and are often the focus of dredging projects. Bar dredging may create deep pits ("borrow pits") that significantly alter flow and sediment transport. Locally, the pit acts as a large bedform, contracting and expanding the flow field and enhancing turbulence. At the reach scale, the pit acts as a new sediment sink and disrupts the sediment budget which may have consequences for channel stability and aquatic ecosystem health. In this study, we focus on the local impact of the borrow pit and how it, similar to dunes, creates a turbulent wake within the downstream flow column. We hypothesize that this wake may have implications for the overlapping suspended-sediment transport fields. Efficient dredging operations requires the ability to predict channel infilling/recovery timescales and in large, sandy rivers, a substantial fraction of the sediment infilling results from the settling of suspended sediment. However, if the turbulent wake significantly alters pathways of sediment settling within the borrow pit, typical models of sediment deposition that do not account for the wake effects may not apply. To explore this problem, we use numerical modelling to predict sand behavior with and without resolving the effects of wake turbulence. Wake turbulence is resolved using detached-eddy simulation and sand settling is simulated using Lagrangian particle tracking. Our study area is a >1 km2 channel bar in the lower Mississippi River, which was dredged in October 2016. We used vessel-based measurements (MBES, ADCP) to characterize the post-dredge hydrodynamic environment. Study results indicate that the turbulent wake significantly impacted suspended-sand behavior as it entered the borrow pit and large eddies increased the vertical grain velocities, mean grain settling was reduced, and initial sediment deposition was reduced by up to 20%. Study results may be used to optimize dredging in a manner to reduce channel recovery time. In coastal environments, dredged sand is becoming an increasingly precious commodity, useful for construction as well as restoration purposes such as delta land building and beach nourishment.
The Hei River Basin in northwestern China - tectonics, sedimentary processes and pathways

NASA Astrophysics Data System (ADS)

Rudersdorf, Andreas; Nottebaum, Veit; Schimpf, Stefan; Yu, Kaifeng; Hartmann, Kai; Stauch, Georg; Wünnemann, Bernd; Reicherter, Klaus; Diekmann, Bernhard; Lehmkuhl, Frank

2014-05-01

The Hei River Basin (catchment area of c. 130,000 km²) is situated at the transition between the northern margin of the Tibetan Plateau and the southern slopes of Gobi-Tien-Shan. As part of the northwestern Chinese deserts, the Ejina Basin (Gaxun Nur Basin) constitutes the endorheic erosion base of the drainage system. The basin - hosting the second largest continental alluvial fans in the world, is tectonically strongly shaped by the Gobi belt of left-lateral transpression. The tectonic setting in combination with competing climatic driving forces (Westerlies and summer/winter monsoon currents) has supported the formation of a valuable long-time sediment archive comprises at least the last 250,000 yrs. of deposition. It is composed by the interplay of eolian, fluvial and lacustrine sedimentation cycles and today is dominated by widespread (gravel) gobi surfaces, insular dune fields and shallow evaporitic playa areas. Thus, it provides excellent conditions to investigate tectonic evolution and Quaternary environmental changes. Recently, geomorphological, geophysical, neotectonic and mineralogical studies have enhanced the understanding of the environmental history and the modern depositional environment. Moreover, the role of the Hei River Basin as an important source area of silt particles which were later deposited on the Chinese Loess Plateau is evaluated. Therefore, a 230 m long drill core, sediment sections and ca. 700 surface samples throughout the whole catchment and basin were analyzed. Instrumental and historical seismicity are very low, but the proximity to active fault zones and dating irregularities in earlier publications indicate evidence for deformation in the study area. Despite flat topography, indications of active tectonics such as fault-related large-scale lineations can be observed. Seismically deformed unconsolidated lacustrine deposits (seismites), presumably of Holocene age, are evident and must be related to the nearby faults. The upper catchment is represented by the Qilian Shan mountain range and its immediate foreland. Here, a tripartite altitudinal distribution of terrestrial sediment archives is evident, which is representative of catchment-wide sedimentological processes. Insights into their formation mechanisms, therefore, add valuable perspective regarding the reconstruction of sedimentological and paleoenvironmental conditions in the depositional area of the Hei River Basin. For the characterization of provenance and dispersal of Quaternary sediments in relation to the modern depositional environment, over 200 surface samples from the whole catchment were analyzed using XRD and XRF measurements on the clay fractions, heavy minerals and bulk sediments. The clay mineral results in-particular show that it is possible to discriminate between the chlorite rich metamorphic sediments originating from greenschist bearing rocks in the Qilian Shan Mountain Range in the south, and the more intrusive rocks from the Bei Shan Mountain Range west of the Hei River Basin. Additionally, these two main sources reflect different transportation processes; the Qilian Shan sediments are mainly transported by the rivers Heihe and Beida He, and the deposition of the Bei Shan sediments is mainly driven by wind or local runoff. Grain size results of primary loess deposits indicate different eolian transport pathways, i.e., far-travelled dust input (medium silty) vs. local deflation from active fluvial channels (fine sandy). Along the altitudinal transect, the varying geomorphological settings exert a significant influence on the grain size composition showing an increased contribution of far-travelled dust at higher altitudes.
Climate oscillations reflected in the microbiome of Arabian Sea sediments

NASA Astrophysics Data System (ADS)

Orsi, W. D.; Coolen, M.; He, L.; Wuchter, C.; Irigoien, X.; Hemingway, J. D.; Johnson, C.; Chust, G.; Moore, K.; Galy, V.; Giosan, L.

2016-12-01

More than 1029 microbial cells reside in marine sediment, but the forces underlying their vertical distribution are poorly understood. Sedimentary communities are shaped to a large extent through selection by the modern environment such as energy availability and porosity. However, some microbes within certain settings reflect depositional conditions suggesting they have experienced no or weak selection after burial. Here, we show that in sediments underlying the Arabian Sea oxygen minimum zone (OMZ), the stratigraphy of some subsisting bacteria records their selection to changing paleo-environmental conditions over relatively short (e.g., centennial to millennial) timescales. We performed the highest resolved sedimentary metagenomic profile to date and coupled it with multiple paleoceanographic proxies. Despite being vertically separated, bacterial communities deposited under recurring low-oxygen conditions are more similar to one another than those deposited under higher oxygen. Furthermore, genomic potential for denitrification recurringly correlates with OMZ strength and paleo-denitrification proxies. In contrast, the genomic potential for oxygen-dependent metabolism, specifically genes encoding mono-oxygenases, is correlated with bioturbated sediment intervals deposited under higher oxygen concentrations. These patterns correlate strongly with the strength of the OMZ whose strength is teleconnected to North Atlantic climate. While the primary electron acceptors nitrate and nitrite are depleted at the sediment surface, metagenomes revealed mixed acid and Entner-Dourdoroff fermentation pathways encoded by many of the denitrifier groups. Fermentation has thus enabled the long-term subsistence of these bacteria whose stratigraphy serves as a proxy for changing paleoceanographic conditions and potential climate feedback mechanisms.

Sedimentology of the Essaouira Basin (Meskala Field) in context of regional sediment distribution patterns during upper Triassic pluvial events

NASA Astrophysics Data System (ADS)

Mader, Nadine K.; Redfern, Jonathan; El Ouataoui, Majid

2017-06-01

Upper Triassic continental clastics (TAGI: Trias Argilo-Greseux Inferieur) in the Essaouira Basin are largely restricted to the subsurface, which has limited analysis of the depositional environments and led to speculation on potential provenance of the fluvial systems. Facies analysis of core from the Meskala Field onshore Essaouira Basin is compared with tentatively time-equivalent deposits exposed in extensive outcrops in the Argana Valley, to propose a process orientated model for local versus regional sediment distribution patterns in the continuously evolving Moroccan Atlantic rift during Carnian to Norian times. The study aims to unravel the climatic overprint and improve the understanding of paleo-climatic variations along the Moroccan Atlantic margin to previously recognised Upper Triassic pluvial events. In the Essaouira Basin, four facies associations representing a progressive evolution from proximal to distal facies belts in a continental rift were established. Early ephemeral braided river systems are succeeded by a wet aeolian sandflat environment with a strong arid climatic overprint (FA1). This is followed by the onset of perennial fluvial deposits with extensive floodplain fines (FA2), accompanied by a distinct shift in fluvial style, suggesting increase in discharge and related humidity, either locally or in the catchment area. The fluvial facies transitions to a shallow lacustrine or playa lake delta environment (FA3), which exhibits cyclical abandonment. The delta is progressively overlain by a terminal playa with extensive, mottled mudstones (FA4), interpreted to present a return from cyclical humid-arid conditions to prevailing aridity in the basin. In terms of regional distribution and sediment source provenance, paleocurrent data from Carnian to Norian deposits (T5 to T8 member) in the Argana Valley suggest paleoflow focused towards the S and SW, not directed towards the Meskala area in the NW as previously suggested. A major depo-centre for fluvial sediments is instead located in the southern Argana Valley, possibly the Souss Basin. To effectively source the reservoir sandstones found in the Meskala Field, a more local provenance area has hence to be envisaged. Despite this, the direct comparison of the genetic evolution of sedimentary sequences in the Argana Valley and Essaouira Basin shows a similar progression from dominantly arid ephemeral depositional environments to humid perennial sedimentation, returning to prominent arid conditions. This suggests climatic control in both regions, where an enhanced humid signal drives perennial fluvial flow in otherwise arid dominated sequences. On a regional scale, this is suggested to record the impact of strong Triassic pluvial events previously recognised in other basins along the Central Atlantic margin during the Carnian to Norian periods.
Spatial and temporal variability in sediment deposition and seabed character on the Waipaoa River margin, New Zealand

NASA Astrophysics Data System (ADS)

Walsh, J. P.; Corbett, D. R.; Kiker, J. M.; Orpin, A. R.; Hale, R. P.; Ogston, A. S.

2014-09-01

The stratigraphic record is the manifestation of a wide range of processes, interactions and responses to environmental drivers. Understanding the functioning of river sediment dispersal systems is necessary to determine the fate of sediment and associated material in the marine environment and differentiate key influences in the development of the stratigraphic record. To that end, this study uses sediment cores collected on four successive cruises (January, May and September 2010 and February 2011) on the Waipaoa River margin, New Zealand, to provide insight into spatial and temporal variability in sediment deposition and seabed character. The Waipaoa River discharges a large sediment load into an energetic coast that has a complex margin morphology. Several flood and wave events occurred during the study, and sedimentation varied spatially and temporally. X-radiographs and short-lived radioisotopes indicate emplacement of new event layers prior to all cruises. Notable variation in surficial seabed character (grain-size composition, loss-on-ignition percentage) was apparent on the inner shelf (water depths <40 m), but mid-shelf areas and seaward had more homogeneous sediment properties. 7Be inventories indicate variable patterns of deposition related to fluvial and oceanographic conditions prior to cruises. Ephemeral sediment storage occurs on the inner-shelf of Poverty Bay, into which the Waipaoa River discharges directly, and subsequent export and dispersal patterns are linked to the relative timing and size of flood and wave events. Surficial deposits with characteristics of fluid muds and wave-enhanced sediment gravity flows were noted at some (<25 sites total) mid-shelf and shallower sites from all cruises. During the last cruise considerable inter- and intra-site seabed variability occurred in the interbedded river-proximal inner-shelf deposits over spatial scales of less than a few kilometers. Evidence from earlier sidescan data infer that this could be related to variation in bedform development or influence. Contrasts in the observed event layering recorded over the experiment with the longer pattern of accumulation suggests stochastic dispersal behavior and reworking over time must shape the seabed to produce the time-averaged pattern of shelf sediment accumulation. This research highlights our improved ability to comprehend strata development and sheds light on the challenge of interpreting historical and ancient strata across spatial and temporal scales.
The erosion behaviour of biologically active sewer sediment deposits: observations from a laboratory study.

PubMed

Banasiak, Robert; Verhoeven, Ronny; De Sutter, Renaat; Tait, Simon

2005-12-01

The erosion behaviour of various fine-grained sediment deposits has been investigated in laboratory experiments. This work mainly focused on tests using sewer sediment in which strong biochemical reactions were observed during the deposit formation period. A small number of initial tests were conducted in which the deposits were made from mixtures of "clean" mineral and organic sediments. The erosion behaviour observed in these tests was compared with the erosion characteristics for sediments taken from deposits in a sewer. The impact of the biological processes on physical properties such as bulk density, water content, deposit structure and the erosive behaviour as a function of bed shear stress are quantified and discussed. Based on these observations it is believed that bio-processes weaken the strength of the in-pipe sediment deposits. A significantly weaker sediment surface layer was observed during deposition under quiescent oxygen-rich conditions. This resulted in a deposit with low shear strength which may be a cause of a first foul flush of suspended sediment when flow rates were increased. Comparison between tests with sewer sediments and the artificial representative surrogates suggested that the deposits of the later did not correctly simulate the depositional development and the resultant erosion patterns observed with the more bio-active sewer sediment.
Stratigraphy of the Mesaverde Group in the central and eastern greater Green River basin, Wyoming, Colorado, and Utah

USGS Publications Warehouse

Roehler, Henry W.

1990-01-01

This paper establishes a stratigraphic framework for the Mesaverde Group, nearly 5,000 ft thick, in the central and eastern greater Green River basin based on data from measured outcrop sections and drill holes. Stratigraphic correlations are supported by ammonite zonation. No new stratigraphic names are introduced, and no nomenclature problems are discussed. Five long measured sections through the Mesaverde Group are described. The lower part of the Mesaverde Group, comprising the Rock Springs, Blair, Haystack Mountains, Allen Ridge, and Iles Formations, was deposited during a major eastward regression of the interior Cretaceous seaway of North America during the late Santonian and early Campanian. This regression was followed by regional uplift of the central Rocky Mountain area during the middle Campanian. The regional uplift was accompanied by widespread nondeposition and erosion, which, in turn, were followed by deposition of the Ericson and Pine Ridge Sandstones. The upper part of the Mesaverde Group, comprising the Almond and Williams Fork Formations, was deposited during a major westward transgression of the interior seaway in the early Maestrichtian. The major marine transgressions and regressions of the interior seaway were caused by eustatic changes of sea level, whereas intervening periods of nondeposition and erosion resulted from tectonism in the Sevier orogenic belt west of the study area. Formations of the Mesaverde Group are composed of sediments deposited in a landward-seaward progression of alluvial-plain, floodplain, coastal-plain, barrier-plain, tidal-flat, delta-plain, marine-shoreline, and marine-shelf and slope depositional environments. Each of these depositional environments is represented by specific lithofacies, sedimentary structures, and fossils, which are characteristic of depositional settings determined by water salinity, water depth, sedimentary and diagenetic processes, and the nature of sediment source terranes. The Mesaverde Group was deposited mainly along the western margins of the interior Cretaceous seaway as marine shorelines that trended north to northeast across the study area. Arcuate deltas, which formed at the mouths of major rivers along these shorelines, spread eastward onto shallow marine shelves. Embayed shoreline areas between the deltas were the sites of barrier-island and tidal-flat deposition. Alluvial-plain, flood-plain, and coastal-plain environments were present inland. The marine shorelines were tidally influenced and wave dominated, and shoreline deposits were mostly thick, linear sheets of quartzose sandstone. Deposition was largely controlled by the emergence or submergence of shoreline areas. Stillstands occurred close to local transgressions and regressions, depending on rates of sedimentation and subsidence.
Toward an integrated genetic model for vent-distal SEDEX deposits

NASA Astrophysics Data System (ADS)

Sangster, D. F.

2018-04-01

Although genetic models have been proposed for vent-proximal SEDEX deposits, an equivalent model for vent-distal deposits has not yet appeared. In view of this, it is the object of this paper to present a preliminary integrated vent-distal genetic model through exploration of four major components: (i) nature of the ore-forming fluid, (ii) role of density of the unconsolidated host sediments, (iii) dynamics of sulfate reduction and (iv) depositional environment. Two sub-groups of SEDEX Pb-Zn deposits, vent-proximal and vent-distal, are widely recognized today. Of the two, the latter is by far the largest in terms of metal content with each of the 13 largest containing in excess of 7.5 M (Zn+Pb) metal. In contrast, only one vent-proximal deposit (Sullivan) falls within this size range. Vent-proximal deposits are characteristically underlain by local networks of sulfide-filled veins (commonly regarded as feeder veins) surrounded by a discordant complex of host rock alteration. These attributes are missing in vent-distal deposits, which has led to the widespread view that vent-distal ore-forming fluids have migrated unknown distances away from their vent sites. Because of the characteristic fine grain size of ore minerals, critical fluid inclusion data are lacking for vent-distal ore-stage sulfides. Consequently, hypothetical fluids such as those which formed MVT deposits (120 °C, 20% NaCl equiv.) are considered to represent vent-distal fluids as well. Such high-salinity fluids are capable of carrying significant concentrations of Pb and Zn as chloride complexes while the relatively low temperatures preclude high Cu contents. Densities of such metalliferous brines result in bottom-hugging fluids that collect in shallow saucer-shaped depressions (collector basins). Lateral metal zoning in several deposits reveals the direction from which the brines came. Relative densities of the ore-forming fluid and sediment determine whether the ore-forming fluid stabilizes on top of the sediment column or sinks into it. Metal sulfide precipitation occurs when bacterially produced H2S, diffusing upward from anoxic conditions within the sediment, reacts with metal-bearing chloride complexes in the ore-forming fluid. Since H2S is produced by bacterial sulfate reduction within the first 2 m of the sediment column even where overlain by oxic water, sulfide precipitation will always occur within the anoxic sediment regardless of where the ore-forming fluid comes to rest. Because of the high porosity of the sediment, replacement is precluded as a mechanism of sulfide emplacement in favour of void filling. Detailed textural analyses of the HYC and Howards Pass deposits have demonstrated the abundance of pre-exhalative framboidal pyrite and provide evidence for sulfate-reducing bacteria operating in these basins under normal steady-state conditions before arrival of the ore-forming fluids. The sudden presence of ore-forming fluid, however, dramatically changes the formerly steady-state situation of the local bacterial environment. A major result of this new condition is recorded in the sulfur isotope compositions of the sulfides. Whereas pre-exhalative framboidal pyrite is isotopically light, ore-stage sulfides are significantly heavier and display a reduced fractionation relative to contemporaneous seawater sulfate. Much of the reduced fractionation is linked to the increase in H2S production by sulfate-reducing bacteria. The major factor contributing to this increase is the life-saving action of sulfate-reducing bacteria during which the metal toxicity is mitigated by removal of the toxic ions by precipitating them out as sulfides. Several scenarios representing hypothetical thermochemical sulfate reduction (TSR) conditions convincingly demonstrate the extreme improbability that TSR played a role in formation of vent-distal deposits. A wide range of depositional environments is suggested by host rocks which range from impure carbonate to calcareous or dolomitic siliciclastics to normal siltstones and greywackes to calcareous and siliceous siliciclastics to highly siliceous (cherty) shales. Using the analyses of Mo concentrations as a proxy indicator of euxinia in ancient bottom waters in three vent-distal deposits ranging from Late Cambrian to Early Silurian, euxinia was excluded in all three cases. Regardless of the redox condition of the water column, however, the overriding necessary condition for vent-distal deposits to form is that the water column be quiescent to permit the establishment of a pre-exhalative sulfate-reducing bacterial community. The paper concludes with a six-stage genetic model beginning with exhalation of a dense brine and concluding with sulfide preservation in anoxic sediment.
Depositional analysis of Hill sand of Rodessa Formation (lower Cretaceous) in north Shongaloo-Red Rock field, Webster Parish, Louisiana

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adamick, J.A.; Sartin, A.A.

1988-09-01

Hill sand is an informal subdivision of the Lower Cretaceous Rodessa Formation and is a common hydrocarbon reservoir in northeastern Texas, northern Louisiana, and southern Arkansas. The Hill sand is lithologically variable within the study area and consists of conglomerate, fine-grained sandstone, siltstone, mottled red-green claystone, black shale, and limestone. Five depositional environments were interpreted for lithofacies present in Hill sand cores from the North Shongaloo-Red Rock field. These include facies A, fluvial point bar; facies B, crevasse system; facies C, interdistributary bay; facies D, swamp; and facies E, carbonate interdistributary bay. Fluvial point bar and crevasse deposits commonly formmore » hydrocarbon reservoirs in the field. On a regional scale, depositional environments observed in the Hill sand include several fluvial deposystems trending northeast-southwest through Webster Parish. These deposystems terminate into deltaic distributary mouth bars along a northwest-southeast-trending coastline. Areas west of the coastline were occupied by shallow marine environments. Interchannel areas east of the coastline were occupied by interdistributary bay, lake, and crevasse environments in lower deltaic areas, and by lake, swamp, and crevasse environments in upper deltaic areas. Lowermost deposits of the Hill sand throughout the region are interpreted to consist of shallow marine environments. These marine deposits were overlain by thick, predominantly nonmarine sediments. Near the end of Hill sand deposition, the entire region was covered by very shallow marine environments, prior to deposition of the overlying First Lower Anhydrite Stringer.« less
Depositional history and inventories of polychlorinated biphenyls (PCBs) in sediment cores from an Antarctic Specially Managed Area (Admiralty Bay, King George Island).

PubMed

Combi, Tatiane; Martins, César C; Taniguchi, Satie; Leonel, Juliana; Lourenço, Rafael André; Montone, Rosalinda Carmela

2017-05-15

Temporal patterns, fluxes and inventories of polychlorinated biphenyls (PCBs) were assessed in nine sediment cores collected from selected areas of Admiralty Bay off the Antarctic Peninsula. Concentrations of total PCBs were low, but slightly higher in comparison to low-impacted, remote environments in the world, ranging from below the detection limit to 11.9ngg -1 in dry weight. PCB concentrations and inventories suggest a possible minor influence related to the nearby logistic activities, especially in the sediment core collected close to the Ferraz Station. Despite being the most remote and protected area on the planet, the Antarctic continent is no longer a pristine environment. Copyright © 2017 Elsevier Ltd. All rights reserved.
Transport and deposition of carbon at catchment scale: stabilization mechanisms approach

NASA Astrophysics Data System (ADS)

Martínez-Mena, María; Almagro, María; Díaz-Pereira, Elvira; García-Franco, Noelia; Boix-Fayos, Carolina

2016-04-01

Terrestrial sedimentation buries large amounts of organic carbon (OC) annually, contributing to the terrestrial carbon sink. The temporal significance of this sink will strongly depend on the attributes of the depositional environment, but also on the characteristics of the OC reaching these sites and its stability upon deposition. The fate of the redistributed OC will ultimately depend on the mechanisms of its physical and chemical protection against decomposition, its turnover rates and the conditions under which the OC is stored in sedimentary settings. This framework is more complex in Mediterranean river basins where sediments are often redistributed under a range of environmental conditions in ephemeral, intermittent and perennial fluvial courses, sometimes within the same catchment. The OC stabilization mechanisms and their relations with aggregation at different transport and sedimentary deposits is under those conditions highly uncertain. The main objective of this work was to characterize the stabilization and mineralization of OC in sediments in transit (suspended load), at a range of depositional settings (alluvial bars, reservoir sediments) and soils from the source areas in a sub-catchment (111 km2) at the headwaters of the Segura catchment in South East Spain. In order to obtain a deeper knowledge on the predominant stabilization mechanism corresponding to each erosional phase, the following organic carbon fractionation method was carried out: Four aggregate size classes were distinguished by sieving (large and small macroaggregates, free microaggregates, and free silt plus clay fraction), and the microaggregates occluded within macroaggregates (SMm) were isolated. As a further step, an oxidation of the OC occluded in silt plus clay fraction and that of the free silt plus clay fraction was performed to estimate the oxidant resistant OC pool. Measured OC in these fractions can be related to three functional pools: active (free particulate organic matter), slow (carbon associated to clay and silt or stabilized in aggregates) and passive (oxidation-resistant OC). In addition, the potential mineralized C (incubation method) in each deposit and soil was determined. Preliminary results indicate a higher OC content in the suspended sediments in transit and in the reservoir deposited sediments than in the alluvial bars, being in all sediments the total OC content lower than in the source soils. Slow and passive pools prevailed in suspended sediments and in reservoir sediments compared to alluvial bars, indicating different OC stabilization mechanisms. In addition, in the alluvial bars, mineralization rates were higher in bars located in channels with ephemeral flow conditions and vegetated areas than in bars located in channels with perennial flow conditions.
Sediment Sources, Depositional Environment, and Diagenetic Alteration of the Marcellus Shale, Appalachian Basin, USA: Nd, Sr, Li and U Isotopic Constraints

NASA Astrophysics Data System (ADS)

Phan, T. T.; Capo, R. C.; Gardiner, J. B.; Stewart, B. W.

2017-12-01

The organic-rich Middle Devonian Marcellus Shale in the Appalachian Basin, eastern USA, is a major target of natural gas exploration. Constraints on local and regional sediment sources, depositional environments, and post-depositional processes are essential for understanding the evolution of the basin. In this study, multiple proxies, including trace metals, rare earth elements (REE), the Sm-Nd and Rb-Sr isotope systems, and U and Li isotopes were applied to bulk rocks and authigenic fractions of the Marcellus Shale and adjacent limestone/sandstone units from two locations separated by 400 km. The range of ɛNd values (-7.8 to -6.4 at 390 Ma) is consistent with a clastic sedimentary component derived from a well-mixed source of fluvial and eolian material of the Grenville orogenic belt. The Sm-Nd isotope system and bulk REE distributions appear to have been minimally affected by post-depositional processes, while the Rb-Sr isotope system shows evidence of limited post-depositional redistribution. While REE are primarily associated with silicate minerals (80-95%), REE patterns of sequentially extracted fractions reflect post-depositional alteration at the intergranular scale. Although the chemical index of alteration (CIA = 54 to 60) suggests the sediment source was not heavily weathered, Li isotope data are consistent with progressively increasing weathering of the source region during Marcellus Shale deposition. δ238U values in bulk shale and reduced phases (oxidizable fraction) are higher than those of modern seawater and upper crust. The isotopically heavy U accumulated in these authigenic phases can be explained by the precipitation of insoluble U in anoxic/euxinic bottom water. Unlike carbonate cement within the shale, the similarity between δ238U values and REE patterns of the limestone units and those of modern seawater indicates that the limestone formed under open ocean (oxic) conditions.
Dinocyst taphonomy, impact craters, cyst ghosts, and the Paleocene-Eocene thermal maximum (PETM)

USGS Publications Warehouse

Edwards, Lucy E.

2012-01-01

Dinocysts recovered from sediments related to the Chesapeake Bay impact structure in Virginia and the earliest Eocene suboxic environment in Maryland show strange and intriguing details of preservation. Features such as curled processes, opaque debris, breakage, microborings and cyst ghosts, among others, invite speculation about catastrophic depositional processes, rapid burial and biological and chemical decay. Selected specimens from seven cores taken in the coastal plain of Virginia and Maryland show abnormal preservation features in various combinations that merit illustration, description, discussion and further study. Although the depositional environments described are extreme, many of the features discussed are known from, or could be found in, other environments. These environments will show both similarities to and differences from the extreme environments here.
Recent marine deposits reconstruction of two depositional environments of the French Atlantic coast

NASA Astrophysics Data System (ADS)

Pouzet, Pierre; Maanan, Mohamed; Schmidt, Sabine; Athimon, Emmanuelle; Robin, Marc

2017-04-01

This work provides a 300-yr high-resolution record of past storm and/or tsunami events using a multi-proxy analysis (137Cs and 210Pb dating, chemical composition and grain size) of sedimentary deposits from two coastal depositional environments of the French Atlantic coast. We analyse two wetland areas situated just behind a narrow coastal sand strip: 1) the Mer Blanche and 2) the Turballe. Evidence for strong extratropical storms and /or tsunamis events can be identified in this central part of the Bay of Biscay from the XIXth to the XXth century. Nine short sediment cores were collected in August 2016 using gravity type corer of 10 inner diameter and 100 cm length. Each core was longitudinally sliced, each half section photographed and described. High-resolution elemental analyses of split sediment cores were done using an Avaatech XRF core scanner. Then sediment cores were sampled every 0.5 cm. Grain size analysis was done using a Malvern 2600 laser beam grain sizer; organic carbon was measured by Leco induction furnace. 137Cs, 210Pb and 226Ra activities were measured on about 2 g dried sediment using a low background, well-type γ spectrometer (Canberra). The 210Pb in excess, which is used for dating, was calculated as the difference of measured 210Pb and of its supported activities (226Ra). The history information is performed using historical documents including narrative sources, ancient maps, records of cities repairs, surveys conducted after a disaster, newspaper from different departmental and national archives, and meteorological data. Coastal depositional environments were affected hardest by extreme environmental and climatological events during the last century. In the Mer Blanche core, three extreme episodes can be observed: i) at 36 cm, sediment is characterized by coarser sand and higher Sr/Al ratio, this episode coincides with a high tidal wave in spring 1937; ii) at 55 cm, we observe the presence of many gravels, they dates back to the high tidal wave of 1924 and iii) at 65 cm, the presence of another coarse pebble layer is attributed to a series of severe storms associated with coastal flooding episodes between 1910 and 1913. Acknowledgements The authors gratefully acknowledge Isabelle Billy (EPOC, University of Bordeaux 1) for XRF spectrometric core scanner analysis. This work was supported by grants from the Fondation de France through the research program « Quels littoraux pour demain? » and OR2C PDL regional framework.
Comment on Mars as the Parent Body of the CI Carbonaceous Chondrites by J. E. Brandenburg

NASA Technical Reports Server (NTRS)

Treiman, Allan H.

1996-01-01

Geological and chemical data refute a martian origin for the CI carbonaceous chondrites. Here, I will first consider Brandenburg's [1996] proposal that the CI's formed as water-deposited sediments on Mars, and that these sediments had limited chemical interactions with their martian environment. Finally, I will address oxygen isotope ratios, the strongest link between the CIs and the martian meteorites.
Flashy Water and Sediment Delivery to Fluvial Megafan andFan Delta Systems on Opposing Shorelines of an Early Eocene Lake

NASA Astrophysics Data System (ADS)

Jones, E. R.; Plink-Bjorklund, P.

2015-12-01

Flashy delivery of water and sediment had distinct effects on the process of deposition in coeval fluvial megafan and fan delta deposits on opposing shorelines of a paleolake that occupied the Uinta Basin throughout the Eocene. The Tertiary Uinta Basin was an asymmetric continental interior basin with a steep northern margin, adjacent to the block uplift controlling basin subsidence, and a low gradient southern margin. A ~140 km wide fluvial megafan with catchments as far as ~750 km away occupied the southern margin of the lacustrine basin. Within this megafan system, fluvial deposits contain within-channel continental bioturbation and paleosol development on bar accretion surfaces that are evidence of prolonged periods of groundwater flow or channel abandonment. These are punctuated by channel fills exhibiting a suite of both high-deposition rate and upper flow regime sedimentary structures that were deposited by very rapid suspension-fallout during seasonal to episodic river flooding events. A series of small (~8 km wide) and proximally sourced fan deltas fed sediment into the steeper northern margin of the lacustrine basin. 35-50% of the deposits in the delta plain environment of these fan deltas are very sandy debris flows with as low as 5% clay and silt sized material. Detrital zircon geochronology shows that these fan deltas were tapping catchments where mostly unconsolidated Cretaceous sedimentary cover and thick Jurassic eolianites were being eroded. A combination of flashy precipitation, arid climate, catchments mantled by abundant loose sand-sized colluvium, and steep depositional gradients promoted generation of abundant very sandy (5-10% clay and silt sized material) debris flows. In this way, the Wasatch and Green River Formations in the Uinta Basin, Utah, U.S.A. gives us two very different examples of how routing flashy water and sediment delivery (associated with pulses of hyperthermal climate change during the Early Eocene) through different depositional systems produced unique processes of deposition, and also gives us an opportunity to isolate the effects of other variables (e.g. sediment caliber, system gradient, catchment size) that can modulate the flashy precipitation signal in stratigraphy.
Relationships between sedimentation, depositional environments, and coal quality: upper Potomac coalfield, West Virginia and Maryland

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jake, T.R.

1987-09-01

Evaluations were made of sedimentation patterns and depositional environments from approximately 450 core logs and 225 surface exposures in the Upper Potomac coalfield. The relationships between the clastic depositional facies and the distribution and quality of the Bakerstown and upper Freeport coals were also investigated. Data from 61 Bakerstown and 35 upper Freeport coal samples from selected cores indicate a change from uniform coal quality to highly variable coal quality when moving from related interchannel and bay-fill facies to channel, channel-fill, levee, and crevasse-splay facies. Areas of uniform coal quality range from 20-26% ash and 55-62% fixed carbon (weight percent,more » dry basis), whereas areas of highly variable coal quality range from 26-54% ash and 33-55% fixed carbon. The channel and related facies represent areas where increased fresh water was introduced into the topogenous swamp system, causing increased microbial degradation and the concentration of authigenic minerals within the peat material. These conditions, combined with the introduction of detrital minerals, resulted in areas of lower quality coal.« less
Comparison of hot hydroxylamine hydrochloride and oxalic acid leaching of stream sediment and coated rock samples as anomaly enhancement techniques

USGS Publications Warehouse

Filipek, L.H.; Chao, T.T.; Theobald, P.K.

1982-01-01

A hot hydroxylamine hydrochloride (H-Hxl) extraction in 25% acetic acid is compared with the commonly used oxalic acid extraction as a method of anomaly enhancement for Cu and Zn in samples from two very different metal deposits and climatic environments. Results obtained on minus-80-mesh stream sediments from an area near the Magruder massive sulfide deposit in Lincoln County, Georgia, where the climate is humid subtropical, indicate that H-Hxl enhances the anomaly for Cu by a factor of 2 and for Zn by a factor of 1.5, compared to the oxalic method. Analyses of Fe oxide-coated rock samples from outcrops overlying the North Silver Bell porphyry copper deposit near Tucson, Arizona, where the climate is semi-arid to arid, indicate that both techniques effectively outline the zones of hydrothermal alteration. The H-Hxl extraction can also perform well in high-carbonate or high-clay environments, where other workers have suggested that oxalic acid is not very effective. Therefore, the H-Hxl method is recommended for general exploration use. ?? 1982.
Bacterial Diversity Across a Turbidite-Stranded Sediment-Water Interface, La Jolla Canyon, CA

NASA Astrophysics Data System (ADS)

Harrison, B. K.; Flood, B.; Myrbo, A.; Bailey, J.

2016-12-01

The emplacement of gravity-driven sediment flows imposes a significant physical and geochemical impact on underlying sediment and microbial communities. Although previous studies have established lasting mineralogical (e.g., McKay and Pederson, 2014) and biological signatures (e.g., Anschutz et al., 2002) of turbidite deposition, the response of prokaryotes within and beneath debris flows remains poorly constrained. Both bacterial cells associated with the underlying sediment and allocthonous material must respond to substantially altered selective pressures. As a consequence, turbidites and underlying sediments provide an exceptional opportunity to examine 1) microbial community response to sedimentation 2) preservation and identification of microbial dispersal mechanisms. We collected Illumina MiSeq sequence libraries across an intact marine turbidite boundary at 25cm sediment depth in La Jolla canyon off the coast of California. 16S rRNA gene signatures of relict and active bacterial populations exhibit persistent differences attributable to turbidite deposition. In particular, the sedimentary boundary is sharply demarcated at the cm scale by the diversity and abundance of Chloroflexi, Planctomycetes, and Actinobacteria. Variations in the abundance of putative dissimilatory sulfate-reducing Deltaproteobacteria across the stranded sediment-water interface reflect persistent turbidite-induced changes to the geochemical environment. This work raises the possibility that abrupt sedimentological events may alter the microbial community in a manner that persists with burial.
Seismic stratigraphy of the Heuksan mud belt in the southeastern Yellow Sea, Korea

NASA Astrophysics Data System (ADS)

Lee, Gwang-Soo; Yoo, Dong Geun; Bae, Sung Ho; Min, Gun-Hong; Kim, Seong-Pil; Choi, Hunsoo

2015-12-01

To establish the seismic stratigraphy of the Heuksan mud belt (HMB) and reconstruct its depositional history, approximately 1,600 km of high-resolution seismic data were newly obtained using chirp acoustic sub-bottom profiler, sparker, and air-gun seismic systems. Based on seismic stratigraphic analysis, the HMB can be divided into three major seismic units (I, II, and III, from top to bottom) and four subunits (II-a, II-b, III-a, and III-b) overlying transgressive sands, pre-last glacial maximum (LGM) deposits, and the acoustic basement. Each unit and subunit show different seismic facies and geometry, being clearly separated from each other by bounding surfaces formed since the LGM. The spatial distribution, thicknesses and volumes of the seismic units were determined and plotted to document the sequential formation of the HMB. The correlation between deep drill core data (HMB-101, HMB-102, HMB-103, YSDP-101, and YSDP-102) and the seismic data suggests that subunits III-b and III-a were formed by the continuous accumulation of fine-grained sediment with partial sandy sediment in an estuarine/deltaic environment during the early to middle transgressive stage, accompanied by landward migration of the shoreline. Subunits II-b and II-a were probably formed by re-deposition of large volumes of sediment eroded from unit III during the middle transgressive to early highstand stage. Unit I is interpreted as the most recent mud deposit representing the highstand systems tract when sea-level rise terminated. The careful definition of seismic units and their interpretation proposed in this study, on the basis of the large and partly new seismic dataset covering the entire HMB together with deep drill core data, have been instrumental in reconstructing the depositional environment and formation mechanisms of the HMB.
Sulfate reduction and oxic respiration in marine sediments: implications for organic carbon preservation in euxinic environments

NASA Technical Reports Server (NTRS)

Canfield, D. E.; DeVincenzi, D. L. (Principal Investigator)

1989-01-01

Compilations have been made of sulfate reduction rates and oxic respiration rates over the entire range of marine sedimentation rates, and sedimentary environments, including several euxinic sites. These data show, consistent with the findings of Jorgensen (1982, Nature, 296, 643-645), that sulfate reduction and oxic respiration oxidize equal amounts of organic carbon in nearshore sediments. As sedimentation rates decrease, oxic respiration, becomes progressively more important, and in deep-sea sediments 100-1000 times more organic carbon is oxidized by oxic respiration than by sulfate reduction. By contrast, nearly as much organic carbon is oxidized by sulfate reduction in euxinic sediments as is oxidized by the sum of sulfate reduction and oxic respiration in normal marine sediments of similar deposition rate. This observation appears at odds with the enhanced preservation of organic carbon observed in euxinic sediments. However, only small reductions in (depth-integrated) organic carbon decomposition rates (compared to normal marine) are required to give both high organic carbon concentrations and enhanced carbon preservation in euxinic sediments. Lower rates of organic carbon decomposition (if only by subtle amounts) are explained by the diminished ability of anaerobic bacteria to oxidize the full suite of sedimentary organic compounds.
Development of integrated protocols to track the deposition and impacts of metal contaminants in tidal riverine environments

NASA Astrophysics Data System (ADS)

Roe, Helen M.; Patterson, R. Timothy; Nasser, Nawaf; Edwards, Robin J.; Graham, Conor

2016-04-01

Tidally-influenced rivers are particularly vulnerable to the effects of metal contamination, yet are amongst the most complex fluvial environments in terms of their sediment deposition and transport patterns. We present the results of an interdisciplinary study that aims to elucidate the fluxes and deposition of metal contaminants in a tidally-influenced river system in Northern Ireland, with a view to developing protocols that will have wide applicability for the monitoring and assessment of metal contaminants in similar environments in other regions. We employ a novel methodology that combines ICPMS analysis of sediments, ITRAX-based core analysis and the examination a important group of shelled protozoans (foraminifera), which occur widely in tidal riverine environments, and which are highly sensitive to metal contamination. The responses shown by the group vary between species and with different levels of contaminant exposure. Some species, for example, show increased relative abundances in proximity to discharge sources, whilst others develop chamber deformities. Application of our integrated multiproxy approach to the analysis of surface sediment samples and cores provides a framework for assessing both the spatial and temporal patterns of metal deposition and the impact of contaminants on the biota. Modern sediment samples (n=90) were collected at varying distances from a point contamination source (a former industrial site) in different morpho-sedimentary settings. The impact of 25 measured variables on the modern foraminiferal faunas was considered, including 20 metals, pH, conductivity, elevation and particle size. Channel sediments in close proximity to the contamination source and with the highest levels of Fe, Cu, Zn, Mg and As, yielded the sparsest foraminiferal faunas (Shannon Diversity Index values 0-1.5), whilst the highest prevalence of foraminiferids showing chamber deformities were observed in channel edge and levée bank sites. Kernal density plots showing metal loading and foraminiferal concentrations across the site aided in determining spatial trends. The sediment core data revealed that deformed foraminiferal specimens can extend >15 cm below the contemporary floodplain surface to horizons that pre-date the historical onset of the contamination, suggesting vertical mobilisation of sediment and/or infaunal migration. Etching of the foraminiferal tests in association with reduced pH conditions was also observed for some species. Biometric analysis of tests using SEM imagery further aided in the identification of deformities and the delimitation of graded responses to contaminants. The results of this study of core and surficial samples indicate that the adoption of integrated methodologies that combine established geochemical analysis techniques (e.g. ICPMS analysis) with the observed ecophenotypic response of key indicator microfossil groups (e.g. foraminifera) can provide invaluable data on habitat responses to environmental contamination. Such long-term habitat evaluation data is invaluable to policy makers and planners when prioritising management and remediation efforts.
The Late Miocene paleogeography of the Amazon Basin and the evolution of the Amazon River system

NASA Astrophysics Data System (ADS)

Latrubesse, Edgardo M.; Cozzuol, Mario; da Silva-Caminha, Silane A. F.; Rigsby, Catherine A.; Absy, Maria Lucia; Jaramillo, Carlos

2010-05-01

On the basis of paleontological content (vertebrates and palynology) and facies analysis from river banks, road cuts, and three wells, we have assigned the uppermost levels of the Solimões Formation in western Amazonia, Brazil, to the Late Miocene. The vertebrate fossil record from outcropping sediments is assigned to the Huayquerian-Mesopotamian mammalian biozones, spanning 9-6.5 Ma. Additionally, we present results that demonstrate that deposits in Peruvian Amazonia attributed to Miocene tidal environments are actually fluvial sediments that have been misinterpreted (both environmentally and chronologically) by several authors. The entire Late Miocene sequence was deposited in a continental environment within a subsiding basin. The facies analysis, fossil fauna content, and palynological record indicate that the environment of deposition was dominated by avulsive rivers associated with megafan systems, and avulsive rivers in flood basins (swamps, lakes, internal deltas, and splays). Soils developed on the flatter, drier areas, which were dominated by grasslands and gallery forest in a tropical to subtropical climate. These Late Miocene sediments were deposited from westward of the Purus arch up to the border of Brazil with Peru (Divisor Ranges) and Bolivia (Pando block). Eastward of the Iquitos structural high, however, more detailed studies, including vertebrate paleontology, need to be performed to calibrate with more precision the ages of the uppermost levels of the Solimões Formation. The evolution of the basin during the late Miocene is mainly related to the tectonic behavior of the Central Andes (˜ 3°-15°S). At approximately 5 Ma, a segment of low angle of subduction was well developed in the Nazca Plate, and the deformation in the Subandean foreland produced the inland reactivation of the Divisor/Contamana Ranges and tectonic arrangements in the Eastern Andes. During the Pliocene southwestern Brazilian Amazonia ceased to be an effective sedimentary basin, and became instead an erosional area that contributed sediments to the Amazon fluvial system. At that time, the lowland fluvial systems of southwestern Amazonia (the Purus, Jurua and Javarí basins) become isolated from the Andes by the newly formed north-flowing Ucayali system and south-east flowing Madre de Dios System. It was during the early Pliocene that the Amazon fluvial system integrated regionally and acquired its present appearance, and also when it started to drain water and sediments on a large scale to the Atlantic Ocean.

Application of individual foraminifera Mg/Ca and δ18O analyses for paleoceanographic reconstructions in the Bay of Bengal and other active depositional environments

NASA Astrophysics Data System (ADS)

Fritz-Endres, T.; Dekens, P.; Fehrenbacher, J. S.; Spero, H. J.; Stine, A.

2017-12-01

Paleoceanographic research traditionally focuses on regions where sediment deposition is minimally affected by transport. However, sediment fans near tectonically active regions provide an opportunity to link oceanographic climate to terrestrial processes. Sediment cores recovered during IODP Expedition 354 in the Bay of Bengal include hemipelagic sections that record the history of tectonic uplift and the development of the Indian Monsoon through the last 10 Ma. Although these cores provide a unique opportunity to link marine and terrestrial climate, the complex depositional environment requires that the source of foraminifera is carefully considered before using these proxies to reconstruct oceanographic conditions. Foraminifera in Bengal Fan sediments may have been transported via turbidity currents from the northern Bay of Bengal, where the seasonal variability of SST and SSS is larger compared to the southern Bay of Bengal. We measured single Globigerinoides sacculifer Mg/Ca and δ18O from mudline samples of IODP Site U1454 (8.4°N, 85.5°E, 3721 m water depth) near the modern active channel and Site U1449 (8.4°N, 88.7°E, 3653 m water depth) far from channel activity. We compare these sites to single G. sacculifer from the core-top sample of Site 342KL (20.6°N, 90.1°E, 1256 m water depth) located on the continental shelf. Each foraminifera lives 2-4 weeks and the distribution of 60 to 80 data points reflects the seasonal range of SST and SSS at the location where the foraminifera calcified. Measurements in foraminifera from Site U1449 (away from active channel) are statistically different from the site in the northern Bay of Bengal and more consistent with local conditions. Conversely, foraminifera from the site near the active channel reflect a combined signal of local conditions recorded from the site far from channel activity and those recorded from the continental shelf. This suggests a portion of foraminifera from the active channel site have been transported from the northern Bay of Bengal. Our data show that foraminifera can be used to reconstruct SST and δ18O in this complex depositional environment, but caution must be taken when the down-core lithology indicates turbidites and possible sediment transport
Solid waste deposits as a significant source of contaminants of emerging concern to the aquatic and terrestrial environments - a developing country case study from Owerri, Nigeria.

PubMed

Arukwe, Augustine; Eggen, Trine; Möder, Monika

2012-11-01

In developing countries, there are needs for scientific basis to sensitize communities on the problems arising from improper solid waste deposition and the acute and long-term consequences for areas receiving immobilized pollutants. In Nigeria, as in many other African countries, solid waste disposal by way of open dumping has been the only management option for such wastes. Herein, we have highlighted the challenges of solid waste deposit and management in developing countries, focusing on contaminants of emerging concern and leaching into the environment. We have analyzed sediments and run-off water samples from a solid waste dumping site in Owerri, Nigeria for organic load and compared these with data from representative world cities. Learning from previous incidents, we intend to introduce some perspective for awareness of contaminants of emerging concerns such as those with potential endocrine disrupting activities in wildlife and humans. Qualitative and quantitative data obtained by gas chromatography and mass spectrometric analysis (GC-MS) provide an overview on lipophilic and semi-polar substances released from solid waste, accumulated in sediments and transported via leachates. The chromatograms of the full scan analyses of the sediment extracts clearly point to contamination related to heavy oil. The homologous series of n-alkanes with chain lengths ranging between C16 and C30, as well as detected polyaromatic hydrocarbon (PAH) compounds such as anthracene, phenanthrene, fluoranthene and pyrene support the assumption that diesel fuel or high boiling fractions of oil are deposited on the site. Targeted quantitative analysis for selected compounds showed high concentration of substances typically released from man-made products such as plastics, textiles, household and consumer products. Phthalate, an integral component of plastic products, was the dominant compound group in all sediment samples and run-off water samples. Technical nonylphenols (mixture of isomers), metabolites of non-ionic surfactants (nonylphenol-polyethoxylates), UV-filter compound ethyl methoxy cinnamate (EHMC) and bisphenol A (BPA) were particularly determined in the sediment samples at high μg/kg dry weight concentration. Measuring contaminants in such areas will help in increasing governmental, societal and industrial awareness on the extent and seriousness of the contamination both at waste disposal sites and surrounding terrestrial and aquatic environments. Copyright © 2012 Elsevier B.V. All rights reserved.
Facies analysis and depositional environments of upper part of Richmond group (upper Ordovician), Richmond, Indiana, to Xenia, Ohio

DOE Office of Scientific and Technical Information (OSTI.GOV)

Betz, C.E.; Martin, W.D.

Rock sections of the Drakes, Elkhorn, and Whitewater Formations were studied along an east-west-trending line in order to distinguish facies changes in a slope direction across the paleodepositional basin. The Richmond limestones, shales, and dolostones formed from fine-grained, terrigenous and carbonate sediments deposited on a shallow marine ramp within the humid, tropical, low latitudes of the Southern Hemisphere. Depositional environments on the ramp are represented by five main facies type. The five Richmond facies form a subtidal to supratidal shallowing-upward sequence. This progressive shallowing during the Late Ordovician resulted from the westward regional progradation of Queenston deltaic facies.
Non-Fluvial Controls of Erosion, Sediment Transport and Fluvial Morphology in a mid-Atlantic Piedmont Watershed, White Clay Creek, Pennsylvania, U.S.A.

NASA Astrophysics Data System (ADS)

McCarthy, K.; Affinito, R. A.; Pizzuto, J. E.; Stotts, S.; Henry, T.; Krauthauser, M.; O'Neal, M. A.

2017-12-01

Quantifying contemporary sediment budgets is essential for restoration and ecosystem management of mid-Atlantic watersheds, but relevant processes and controls are poorly understood. In the 153 km2 White Clay Creek watershed in southeastern Pennsylvania, longitudinal profiles reflect migration of knickpoints though bedrock over Quaternary timescales. In bank exposures along stream valleys, saprolite, bedrock, and matrix-supported cobbly and bouldery diamicton (likely colluvial) commonly underlie finer-grained clay, silt, sand, and gravel deposits of valley floor depositional environments. Overbank sedimentation rates were quantified by measuring the thickness of sediment deposited over the roots of floodplain trees. The sampled trees range in age from 25-270 years with median sediment accumulation rates of approximately 2 mm/yr (range 0-10 mm/yr). Rates of bank retreat (measured from historical aerial imagery or root-exposure dendrochronology) vary from 6-36 cm/yr, with median rates of 10 cm/yr. While bank erosion rates are subject to a variety of controls, including channel curvature, the density of riparian trees, and freeze-thaw processes, the strongest influence appears to be the grain size and thickness of bouldery diamicton exposed along the toes of retreating banks. Cobbles and boulders supplied by eroding diamicton also mantle the bed of the channel, such that 33- 80% of the bed material remains immobile at bankfull stage. A conceptual model of fluvial processes and sediment budgets for these channels must account for the watershed's history of changing climate, tectonics, and land use, requiring mapping of bedrock, colluvium, former mill dam sediments, and other non-alluvial deposits and controls. Efforts to apply hydraulic geometry principles (requiring a precise adjustment to contemporary hydraulic and sediment regime) or to treat these channels as traditional "threshold" rivers are unlikely to be successful.
Syn-eruptive, soft-sediment deformation of deposits from dilute pyroclastic density current: triggers from granular shear, dynamic pore pressure, ballistic impacts and shock waves

NASA Astrophysics Data System (ADS)

Douillet, G. A.; Taisne, B.; Tsang-Hin-Sun, E.; Muller, S. K.; Kueppers, U.; Dingwell, D. B.

2015-05-01

Soft-sediment deformation structures can provide valuable information about the conditions of parent flows, the sediment state and the surrounding environment. Here, examples of soft-sediment deformation in deposits of dilute pyroclastic density currents are documented and possible syn-eruptive triggers suggested. Outcrops from six different volcanoes have been compiled in order to provide a broad perspective on the variety of structures: Soufriere Hills (Montserrat), Tungurahua (Ecuador), Ubehebe craters (USA), Laacher See (Germany), and Tower Hill and Purrumbete lakes (both Australia). The variety of features can be classified in four groups: (1) tubular features such as pipes; (2) isolated, laterally oriented deformation such as overturned or oversteepened laminations and vortex-shaped laminae; (3) folds-and-faults structures involving thick (>30 cm) units; (4) dominantly vertical inter-penetration of two layers such as potatoids, dishes, or diapiric flame-like structures. The occurrence of degassing pipes together with basal intrusions suggest fluidization during flow stages, and can facilitate the development of other soft-sediment deformation structures. Variations from injection dikes to suction-driven, local uplifts at the base of outcrops indicate the role of dynamic pore pressure. Isolated, centimeter-scale, overturned beds with vortex forms have been interpreted to be the signature of shear instabilities occurring at the boundary of two granular media. They may represent the frozen record of granular, pseudo Kelvin-Helmholtz instabilities. Their recognition can be a diagnostic for flows with a granular basal boundary layer. Vertical inter-penetration and those folds-and-faults features related to slumps are driven by their excess weight and occur after deposition but penecontemporaneous to the eruption. The passage of shock waves emanating from the vent may also produce trains of isolated, fine-grained overturned beds that disturb the surface bedding without occurrence of a sedimentation phase in the vicinity of explosion centers. Finally, ballistic impacts can trigger unconventional sags producing local displacement or liquefaction. Based on the deformation depth, these can yield precise insights into depositional unit boundaries. Such impact structures may also be at the origin of some of the steep truncation planes visible at the base of the so-called "chute and pool" structures. Dilute pyroclastic density currents occur contemporaneously with seismogenic volcanic explosions. They can experience extremely high sedimentation rates and may flow at the border between traction, granular and fluid-escape boundary zones. They are often deposited on steep slopes and can incorporate large amounts of water and gas in the sediment. These are just some of the many possible triggers acting in a single environment, and they reveal the potential for insights into the eruptive and flow mechanisms of dilute pyroclastic density currents.
Lithology, mineralogy and geochemical characterizations of sediment-hosted Sr-F deposits in the eastern Neo-Tethyan region - With special reference to evaporation and halokinesis in Tunisia

NASA Astrophysics Data System (ADS)

Dill, H. G.; Nolte, N.; Hansen, B. T.

2014-04-01

The Neo-Tethyan basin is known for its sediment-hosted Sr deposits in Spain, Turkey, Cyprus, and the Gulf Region. Sediment-hosted Sr-F deposits with base metals formed in the rim sinks and on top of salt domes resulting from halokinesis of Triassic evaporites near the southern edge of the Mediterranean Sea in Tunisia. These evaporites delivered part of the elements, created a basin-and-swell topography and provided the local and regional unconformities to which many of the mineral deposits are related. Five mineralizing processes, each with characteristic sedimentary ore textures, are related to this subsurface salt movement: (1 + 2) Early- and late-stage replacement ("zebra rocks"), (3) hydraulic fracturing ("fitting breccia" sensuDill and Weber, 2010b), (4) remobilization ("spinifex structures"), and (5) open-space filling ("caves and vein-like deposits"). Basinal brines from Mesozoic aquifers delivered Pb, Zn, Cd, REE, Y, Hg, and Se, while Sr, Cs, Be, Li, Cu and Co have been derived from Cenozoic salinas of the Neo-Tethyan basin. Mixing of Mesozoic and Cenozoic brines between 28 and 19 Ma provoked the emplacement of Sr-F mineralization at temperatures below 200 °C under strong alkaline conditions. Epigenetic polyphase Sr-F deposits bearing base-metals which are closely related to salt domes (Tunisian-Type) may be traced into epigenetic monophase Sr deposits within bioherms (Cyprus-Type) devoid of Pb, Zn and F. Moving eastward, syndiagenetic monophase Sr deposits in biostromes (Gulf-Type) herald the beginning of Sr concentration in Miocene sabkhas of the Neo-Tethys. The current results are based upon field-related sediment petrography and on mineralogical studies, which were supplemented by chemical studies. The present studies bridge the gap between epigenetic carbonate-hosted MVT and syndiagenetic evaporite deposits, both of which developed during the same time span (Neogene) and were hosted by the same environment (near-shore marine marginal facies of the Neo-Tethys basin).
Provenance, age, and environment of mid-Wisconsinan slackwater lake sediment in the St. Louis Metro East area, USA

USGS Publications Warehouse

Curry, B. Brandon; Grimley, D.A.

2006-01-01

Valleys tributary to the Mississippi River contain fossiliferous slackwater lake sediment (Equality Formation) deposited in response to aggradation of the Mississippi River valley during the last glaciation. In the St. Louis Metro East area, the lower part of the Equality Formation is primarily laminated, fossiliferous silt and clay deposited from about 44,150 to 24,310 14C yr B.P. The upper Equality Formation is primarily very fine sand to silt deposited from about 21,200 to 17,000 14C yr B.P. Among the four cores that sample this succession in the St. Louis Metro East area, core MNK-3 (38.64EN, 90.01EW) was selected for detailed study. Three sources are distinguished by the following characteristics: (1) gray smectite-quartz-Se-rich, feldspar-poor material of the Des Moines, Wadena, and James lobes; (2) reddish brown kaolinite-Cu-Fe-rich sediment of the Superior and Rainy lobes; and (3) brown illite-dolomite-Sr-rich sediment of the Lake Michigan and Green Bay lobes. The earliest sediments (44,150 to 41,700 14C yr B.P.) were derived from the central and western provenances and are chronocorrelative with the lower Roxana Silt. A hiatus occurred from about 41,700 to 29,030 14C yr B.P. when much of the middle Roxana Silt (Meadow Member) was deposited on adjacent uplands. The youngest sediment includes evidence of heightened activity of the Superior Lobe at about 29,000 14C yr B.P., the Lake Michigan and Green Bay lobes from about 25,000 to 24,000 14C yr B.P., and the Wadena-Des Moines-James lobes at about 21,000 14C yr B.P. ?? 2005 Society. Published by University of Washington. All rights reserved.
Response of PAH-degrading genes to PAH bioavailability in the overlying water, suspended sediment, and deposited sediment of the Yangtze River.

PubMed

Xia, Xinghui; Xia, Na; Lai, Yunjia; Dong, Jianwei; Zhao, Pujun; Zhu, Baotong; Li, Zhihuang; Ye, Wan; Yuan, Yue; Huang, Junxiong

2015-06-01

The degrading genes of hydrophobic organic compounds (HOCs) serve as indicators of in situ HOC degradation potential, and the existing forms and bioavailability of HOCs might influence the distribution of HOC-degrading genes in natural waters. However, little research has been conducted to study the relationship between them. In the present study, nahAc and nidA genes, which act as biomarkers for naphthalene- and pyrene-degrading bacteria, were selected as model genotypes to investigate the response of polycyclic aromatic hydrocarbon (PAH)-degrading genes to PAH bioavailability in the overlying water, suspended sediment (SPS), and deposited sediment of the Yangtze River. The freely dissolved concentration, typically used to reflect HOC bioavailability, and total dissolved, as well as sorbed concentrations of PAHs were determined. Phylogenetic analysis showed that all the PAH-ring hydroxylating dioxygenase gene sequences of Gram-negative bacteria (PAH-RHD[GN]) were closely related to nahAc, nagAc, nidA, and uncultured PAH-RHD genes. The PAH-RHD[GN] gene diversity as well as nahAc and nidA gene copy numbers decreased in the following order: deposited sediment>SPS>overlying water. The nahAc and nidA gene abundance was not significantly correlated with environmental parameters but was significantly correlated with the bioavailable existing forms of naphthalene and pyrene in the three phases. The nahAc gene copy numbers in the overlying water and deposited sediment were positively correlated with freely dissolved naphthalene concentrations in the overlying and pore water phases, respectively, and so were nidA gene copy numbers. This study suggests that the distribution and abundance of HOC-degrading bacterial population depend on the HOC bioavailability in aquatic environments. Copyright © 2015 Elsevier Ltd. All rights reserved.
Process recognition in multi-element soil and stream-sediment geochemical data

USGS Publications Warehouse

Grunsky, E.C.; Drew, L.J.; Sutphin, D.M.

2009-01-01

Stream-sediment and soil geochemical data from the Upper and Lower Coastal Plains of South Carolina (USA) were studied to determine relationships between soils and stream sediments. From multi-element associations, characteristic compositions were determined for both media. Primary associations of elements reflect mineralogy, including heavy minerals, carbonates and clays, and the effects of groundwater. The effects of groundwater on element concentrations are more evident in soils than stream sediments. A "winnowing index" was created using ratios of Th to Al that revealed differing erosional and depositional environments. Both soils and stream sediments from the Upper and Lower Coastal Plains show derivation from similar materials and subsequent similar multi-element relationships, but have some distinct differences. In the Lower Coastal Plain, soils have high values of elements concentrated in heavy minerals (Ce, Y, Th) that grade into high values of elements concentrated into finer-grain-size, lower-density materials, primarily comprised of carbonates and feldspar minerals (Mg, Ca, Na, K, Al). These gradational trends in mineralogy and geochemistry are inferred to reflect reworking of materials during marine transgressions and regressions. Upper Coastal Plain stream-sediment geochemistry shows a higher winnowing index relative to soil geochemistry. A comparison of the 4 media (Upper Coastal Plain soils and stream sediments and Lower Coastal Plain soils and stream sediments) shows that Upper Coastal Plain stream sediments have a higher winnowing index and a higher concentration of elements contained within heavy minerals, whereas Lower Coastal Plain stream sediments show a strong correlation between elements typically contained within clays. It is not possible to calculate a functional relationship between stream sediment-soil compositions for all elements due to the complex history of weathering, deposition, reworking and re-deposition. However, depending on the spatial separation of the stream-sediment and soil samples, some elements are more highly correlated than others. Crown Copyright ?? 2009.
Distribution and region-specific sources of Dechlorane Plus in marine sediments from the coastal East China Sea.

PubMed

Wang, Guoguang; Peng, Jialin; Hao, Ting; Liu, Yao; Zhang, Dahai; Li, Xianguo

2016-12-15

Dechlorane Plus (DP) is a highly chlorinated flame retardant and found to be ubiquitously present in the environment. We reported here the first record of DP in sediments from the coastal East China Sea (ECS). DP was detected in most of the surface sediments, and the concentrations ranged from 14.8 to 198pg/g dry weight (dw) with a mean value of 64.4pg/g dw. Overall, DP levels exhibited a seaward decreasing trend from the inshore toward outer sea. The fractional abundance of anti-DP (f anti ) showed regional discrepancies, attributing to different environmental behaviors of DP isomers. Depth profiles of DP in a sediment core from estuarine environment showed distinct fluctuation, and the core in open sea had stable deposition environment with two peak values of DP in ~1978 and 2000. The f anti exhibited downward decreasing trend prior to mid-1950s, indicating a preferential degradation of anti-DP and/or a greater adsorption capacity of syn-DP after its burial. Lignin and lipid biomarkers (∑C 27 +C 29 +C 31 n-alkanes) of terrestrial organic matters were introduced to identify region-specific sources of DP, and the results showed that DP in the northern inner shelf, southern inner shelf of 29 °N and mud area southwest of Cheju Island was mainly come from Yangtze River (YR) input, surface runoffs after discharge of local sources close to the Taizhou-Wenzhou Region and the atmospheric deposition from the North China and East Asia, respectively. The coastal ECS was an important reservoir of DP in the world, with mass inventory of approximately 310.7kg in the surface sediments (0-5cm). Copyright Â© 2016 Elsevier B.V. All rights reserved.
Stratigraphic Evidence for Environmental Change in a Bermudian Coastal Underwater Cave (Palm Cave System) in Response to Holocene Sea-level Rise

NASA Astrophysics Data System (ADS)

Cresswell, J. N.; van Hengstum, P. J.; Iliffe, T. M.

2016-12-01

Unique environments exist worldwide in coastal underwater caves, including those from Bermuda, which has been a global epicenter for interdisciplinary cave research. However, the development of environments, ecosystems, and sedimentary deposits in coastal underwater caves, particularly over millennial timescales is poorly understood, with previous research from Bermuda indicating a critical role for sea-level rise in driving environmental change. A multi-proxy stratigraphic analysis of 14 sediment cores that were collected from the Palm Cave System in Bermuda from 2 m to 20 m water depths was conducted to better understand Holocene-scale environmental change in coastal underwater caves (e.g., textural analysis, x-radiographs, microfossil analysis, radiocarbon dating). The rate of deposition was found to be variable throughout time and dependent upon the proximity of core locations to cave openings (`karst windows') and conduit geometry. The oldest recovered sediment was likely Pleistocene-aged, terra-rosa soil deposits that predate the Holocene inundation. By 9500 Cal yrs BP, deposition was dominated by organic-rich facies (gyttja), with agglutinated brackish foraminifera (Trochammina, Polysaccammina) and bivalves indicating brackish aquatic conditions in the system by 9200 Cal yrs BP. A system-wide shift to carbonate deposition occurred 8500 Cal yrs BP, which indicates the onset of oxygenated marine water entering the cave and development of a marine-dominated (i.e., submarine) cave environment. Comparison with local maximum sea-level indicators shows that inundation of the Bermuda platform by Holocene sea-level rise likely drove environmental change in the Palm Cave System.
Insights from the Metagenome of an Acid Salt Lake: The Role of Biology in an Extreme Depositional Environment

PubMed Central

Johnson, Sarah Stewart; Chevrette, Marc Gerard; Ehlmann, Bethany L.; Benison, Kathleen Counter

2015-01-01

The extremely acidic brine lakes of the Yilgarn Craton of Western Australia are home to some of the most biologically challenging waters on Earth. In this study, we employed metagenomic shotgun sequencing to generate a microbial profile of the depositional environment associated with the sulfur-rich sediments of one such lake. Of the 1.5 M high-quality reads generated, 0.25 M were mapped to protein features, which in turn provide new insights into the metabolic function of this community. In particular, 45 diverse genes associated with sulfur metabolism were identified, the majority of which were linked to either the conversion of sulfate to adenylylsulfate and the subsequent production of sulfide from sulfite or the oxidation of sulfide, elemental sulfur, and thiosulfate via the sulfur oxidation (Sox) system. This is the first metagenomic study of an acidic, hypersaline depositional environment, and we present evidence for a surprisingly high level of microbial diversity. Our findings also illuminate the possibility that we may be meaningfully underestimating the effects of biology on the chemistry of these sulfur-rich sediments, thereby influencing our understanding of past geobiological conditions that may have been present on Earth as well as early Mars. PMID:25923206
Mixed siliciclastic and carbonate sedimentation within Spar Mountain Member of Ste. Genevieve Limestone, Hamilton County, Illinois

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roberts, M.J.; Pryor, W.A.

1985-02-01

The Spar Mountain Member of the Ste. Genevieve Limestone (middle Mississippian) in Hamilton County, Illinois, consists of 40-60 ft (12-18 m) of interbedded limestones, shales, and sandstones. Five cores and 1400 electric logs were used to delineate two shallowing-upward carbonate cycles and 2 major clastic pulses within the Spar Mountain. Eight lithofacies representing 6 depositional environments were identified. They are: (A) echinoderm-brachiopod dolostone to packstone (outer ramp), (B) ooid-peloidal grainstone (intermediate ramp), (C) skeletal grainstone (intermediate ramp), (D) ooid-molluscan-intraclastic wackestone to grainstone (inner ramp), (E) pelletal-skeletal wackestone (inner ramp), (F) quartzarenite (channelized nearshore), (G) quartz-sublithic arenite to wacke (delta platform),more » and (H) quartz mudstone (prodelta, delta platform). Deposition occurred on a southwest-dipping carbonate ramp, with siliciclastic sediments originating from the northeast. The sequence of facies and their inferred depositional environments record 2 major progradational episodes. Oolitic facies are interpreted to be of tidal-bar belt origin and quartzarenite facies are interpreted to be of delta-distributary channel origin. Their distribution is partially controlled by antecedent and syndepositional topography. Many of these paleotopographic highes are positive features today and yield pinch-out stratigraphic relationships. Paleogeographic reconstructions demonstrate that the primary control on facies distribution was the position of the delta proper along strike. However, depositional topography also influenced sedimentation, particularly in the sand-sized fraction. Using this concept, better prediction of underlying porous buildups (ooid shoals) is possible if thickness of the overlying siliciclastic is known. Within buildups, a complex diagenetic history complicates the distribution of porosity.« less
Efficient Retention of Mud for Land Building on the Mississippi Delta Plain

NASA Astrophysics Data System (ADS)

Esposito, C. R.; Shen, Z.; Tornqvist, T. E.; Marshak, J.; White, C. D.

2016-02-01

Levee breaching and crevasse splay deposition are fundamental drivers of floodplain and delta plain aggradation in lowland river systems, but questions persist as to whether floodplains and delta plains are faithful recorders of riverine sediment load. In the Mississippi River Delta, where land preservation strategies depend on the sediment delivery capability of human-made, managed crevasse splays, this gap in understanding is also a major management concern. Here we present data characterizing the deposit of the Attakapas Crevasse Splay, which was active in the Lafourche Subdelta of the Mississippi River Delta approximately 1100 to 600 years ago. At the time of its inception the splay was 100 river kilometers from the shoreline, and discharged into a mature cypress swamp. We use LiDAR data and 132 cores (up to 13 m deep and described at 10 cm intervals for sediment texture and organic matter) to develop a three-dimensional model of the crevasse splay deposit. Our model is sufficient to measure the sedimentary composition and volume of the entire deposit, and to resolve the channel bodies preserved within it. We demonstrate that the Attakapas Crevasse Splay deposit is dominated by mud, with only 5-8% of its mass consisting of sand. The sand fraction preserved in the splay is very similar to the sand fraction in suspension in the upper 5 to 10 meters of the modern Mississippi River, suggesting that the splay was a highly efficient trap for material that escaped the confines of the trunk channel. Accretion rates in the splay of 1-4 cm/yr persisted over centennial timescales, and sediment retention rates were between 70 and 100%. We attribute the extremely high sediment retention rate to the splay's protected inland location and its densely vegetated environment, and we note the contrast with lower sediment retention rates (20 to 30% according to various studies, although these estimates may be too low) estimated in settings on the open coast such as the Wax Lake Delta.
Particulate organic matter in rivers of Fukushima: An unexpected carrier phase for radiocesiums.

PubMed

Naulier, Maud; Eyrolle-Boyer, Frédérique; Boyer, Patrick; Métivier, Jean-Michel; Onda, Yuichi

2017-02-01

The role of particulate organic matter in radiocesium transfers from soils to rivers was investigated in areas contaminated by the Fukushima Daiichi Nuclear Power Plant accident. Suspended and deposited sediments, filtered water, macro organic debris and dead leaves were sampled along the six most contaminated coastal river catchments of the Fukushima prefecture in the early autumns 2013 and 2014. Radiocesium concentrations of river samples and total organic carbon concentrations in suspended and deposited sediments were measured. Radiocesium concentrations of suspended and deposited sediments were significantly correlated to 137 Cs inventories in soils and total organic carbon. The distributions of radiocesium between the organic and mineral phases of both types of sediment were assessed by using a modelling approach. The results suggest that, during the early autumn season, the organic fraction was the main phase that carried the radiocesiums in deposited sediments and in suspended sediments for suspended loads <25mg·L -1 . For higher suspended loads like those occurring during typhoon periods, the mineral fraction was the main carrier phase. Thus, high apparent distribution coefficient values noted by various authors in Fukushima could be attributed to the high radiocesium contents of particulate organic matter. Since it is well known that organic compounds generally do not significantly adsorb radiocesium onto specific sites, several hypotheses are suggested: 1) Radiocesiums may have been absorbed into organic components at the early stage of atmospheric radioactive deposits and/or later due to biomass recycling and 2) Those elements would be partly carried by glassy hot particles together with organic matter transported by rivers in Fukushima. Both hypotheses would lead to conserve the amount of radiocesiums associated with particles during their transfers from the contaminated areas to the marine environment. Finally, such organically bound radiocesium would lead to significant deliveries of bioavailable radiocesium for living organisms at Fukushima. Copyright © 2016 Elsevier B.V. All rights reserved.
Cohesive and mixed sediment in the Regional Ocean Modeling System (ROMS v3.6) implemented in the Coupled Ocean-Atmosphere-Wave-Sediment Transport Modeling System (COAWST r1234)

NASA Astrophysics Data System (ADS)

Sherwood, Christopher R.; Aretxabaleta, Alfredo L.; Harris, Courtney K.; Rinehimer, J. Paul; Verney, Romaric; Ferré, Bénédicte

2018-05-01

We describe and demonstrate algorithms for treating cohesive and mixed sediment that have been added to the Regional Ocean Modeling System (ROMS version 3.6), as implemented in the Coupled Ocean-Atmosphere-Wave-Sediment Transport Modeling System (COAWST Subversion repository revision 1234). These include the following: floc dynamics (aggregation and disaggregation in the water column); changes in floc characteristics in the seabed; erosion and deposition of cohesive and mixed (combination of cohesive and non-cohesive) sediment; and biodiffusive mixing of bed sediment. These routines supplement existing non-cohesive sediment modules, thereby increasing our ability to model fine-grained and mixed-sediment environments. Additionally, we describe changes to the sediment bed layering scheme that improve the fidelity of the modeled stratigraphic record. Finally, we provide examples of these modules implemented in idealized test cases and a realistic application.
Extracting paleo-climate signals from sediment laminae: A new, automated image processing method

NASA Astrophysics Data System (ADS)

Gan, S. Q.; Scholz, C. A.

2010-12-01

Lake sediment laminations commonly represent depositional seasonality in lacustrine environments. Their occurrence and quantitative attributes contain various signals of their depositional environment, limnological conditions and climate. However, the identification and measurement of laminae remains a mainly manual process that is not only tedious and labor intensive, but also subjective and error prone. We present a batch method to identify laminae and extract lamina properties automatically and accurately from sediment core images. Our algorithm is focused on image enhancement that improves the signal-to-noise ratio and maximizes and normalizes image contrast. The unique feature of these algorithms is that they are all direction-sensitive, i.e., the algorithms treat images in the horizontal direction and vertical direction differently and independently. The core process of lamina identification is to use a one-dimensional (1-D) lamina identification algorithm to produce a lamina map, and to use image blob analyses and lamina connectivity analyses to aggregate and smash two-dimensional (2-D) lamina data for the best representation of fine-scale stratigraphy in the sediment profile. The primary output datasets of the system are definitions of laminae and primary color values for each pixel and each lamina in the depth direction; other derived datasets can be retrieved at users’ discretion. Sediment core images from Lake Hitchcock , USA and Lake Bosumtwi, Ghana, were used for algorithm development and testing. As a demonstration of the utility of the software, we processed sediment core images from the top of 50 meters of drill core (representing the past ~100 ky) from Lake Bosumtwi, Ghana.
Holocene Depositional History of the Southern New Jersey Barrier and Backbarrier Regions

DTIC Science & Technology

1990-02-01

1954) that the continental shelf is a source for beach sediment. 25. Biederman (1962) and Charlesworth (1968) compared sediments along- shore and...perpendicular to the coast in a number of barrier and backbarrier environments. Biederman (1962) found that mean grain size decreased from north to south...Geology and Stratigraphic Preser- vation Potential and Evolution of Delaware’s Barrier Systems," Marine Geology. Vol 63, pp 235-262. Biederman , E. W
Quaternary geology of the Duck Hawk Bluffs, southwest Banks Island, Arctic Canada: a re-investigation of a critical terrestrial type locality for glacial and interglacial events bordering the Arctic Ocean

NASA Astrophysics Data System (ADS)

Evans, David J. A.; England, John H.; La Farge, Catherine; Coulthard, Roy D.; Lakeman, Thomas R.; Vaughan, Jessica M.

2014-05-01

Duck Hawk Bluffs, southwest Banks Island, is a primary section (8 km long and 60 m high) in the western Canadian Arctic Archipelago exposing a long record of Quaternary sedimentation adjacent to the Arctic Ocean. A reinvestigation of Duck Hawk Bluffs demonstrates that it is a previously unrecognized thrust-block moraine emplaced from the northeast by Laurentide ice. Previous stratigraphic models of Duck Hawk Bluffs reported a basal unit of preglacial fluvial sand and gravel (Beaufort Fm, forested Arctic), overlain by a succession of three glaciations and at least two interglacials. Our observations dismiss the occurrence of preglacial sediments and amalgamate the entire record into three glacial intervals and one prominent interglacial. The first glacigenic sedimentation is recorded by an ice-contact sandur containing redeposited allochthonous organics previously assigned to the Beaufort Fm. This is overlain by fine-grained sediments with ice wedge pseudomorphs and well-preserved bryophyte assemblages corresponding to an interglacial environment similar to modern. The second glacial interval is recorded by ice-proximal mass flows and marine rhythmites that were glacitectonized when Laurentide ice overrode the site from Amundsen Gulf to the south. Sediments of this interval have been reported to be magnetically reversed (>780 ka). The third interval of glacigenic sedimentation includes glacifluvial sand and gravel recording the arrival of Laurentide ice that overrode the site from the northeast (island interior) depositing a glacitectonite and constructing the thrust block moraine that comprises Duck Hawk Bluffs. Sediments of this interval have been reported to be magnetically normal (<780 ka). The glacitectonite contains a highly deformed melange of pre-existing sediments that were previously assigned to several formally named, marine and interglacial deposits resting in an undeformed sequence. In contrast, the tectonism associated with the thrust block moraine imparted pervasive deformation throughout all underlying units, highlighted by a previously unrecognized raft of Cretaceous bedrock. During this advance, Laurentide ice from the interior of Banks Island coalesced with an ice stream in Amundsen Gulf, depositing the interlobate Sachs Moraine that contains shells as young as ˜24 cal ka BP (Late Wisconsinan). During deglaciation, meltwater emanating from these separating ice lobes deposited outwash that extended to deglacial marine limit (11 m asl) along the west coast of Banks Island. Our new stratigraphic synthesis fundamentally revises and simplifies the record of past Quaternary environments preserved on southwest Banks Island, which serves as a key terrestrial archive for palaeoenvironmental change.
Micropaleontologic record of Quaternary paleoenvironments in the Central Albemarle Embayment, North Carolina, U.S.A.

USGS Publications Warehouse

Culver, Stephen J.; Farrell, Kathleen M.; Mallinson, David J.; Willard, Debra A.; Horton, Benjamin P.; Riggs, Stanley R.; Thieler, E. Robert; Wehmiller, John F.; Parham, Peter; Snyder, Scott W.; Hillier, Caroline

2011-01-01

To understand the temporal and spatial variation of eustatic sea-level fluctuations, glacio-hydro-isostacy, tectonics, subsidence, geologic environments and sedimentation patterns for the Quaternary of a passive continental margin, a nearly complete stratigraphic record that is fully integrated with a three dimensional chronostratigraphic framework, and paleoenvironmental information are necessary. The Albemarle Embayment, a Cenozoic regional depositional basin in eastern North Carolina located on the southeast Atlantic coast of the USA, is an ideal setting to unravel these dynamic, interrelated processes.Micropaleontological data, coupled with sedimentologic, chronostratigraphic and seismic data provide the bases for detailed interpretations of paleoenvironmental evolution and paleoclimates in the 90. m thick Quaternary record of the Albemarle Embayment. The data presented here come from a transect of cores drilled through a barrier island complex in the central Albemarle Embayment. This area sits in a ramp-like setting between late Pleistocene incised valleys.The data document the episodic infilling of the Albemarle Embayment throughout the Quaternary as a series of transgressive-regressive (T-R) cycles, characterized by inner shelf, midshelf, and shoreface assemblages, that overlie remnants of fluvial to estuarine valley-fill. Barrier island and marginal marine deposits have a low preservation potential. Inner to mid-shelf deposits of the early Pleistocene are overlain by similar middle Pleistocene shelf sediments in the south of the study area but entirely by inner shelf deposits in the north. Late Pleistocene marine sediments are of inner shelf origin and Holocene deposits are marginal marine in nature. Pleistocene marine sediments are incised, particularly in the northern half of the embayment by lowstand paleovalleys, partly filled by fluvial/floodplain deposits and in some cases, overlain by remnants of transgressive estuarine sediments. The shallowing through time of Quaternary sediments reflects the eastward progradational geometry of the continental shelf.The preservation potential of marginal marine deposits (barrier island, shoreface, backbarrier deposits) is not high, except in topographic lows associated with late Pleistocene paleovalleys and inlets because the current interglacial highstand has not yet reached its highest level. Given the documented increase in rate of relative sea-level rise in this region, shallow marine conditions are likely to return to the central Albemarle Embayment in the near future. ?? 2011 Elsevier B.V.

High-resolution seismic-reflection interpretations of some sediment deposits, Antarctic continental margin: Focus on the western Ross Sea

USGS Publications Warehouse

Karl, Herman A.

1989-01-01

High-resolution seismic-reflection data have been used to a varying degree by geoscientists to interpret the history of marine sediment accumulations around Antarctica. Reconnaissance analysis of 1-, 3.5-, and 12-kHz data collected by the U.S. Geological Survey in the western Ross Sea has led to the identification of eight echo-character facies and six microtopographic facies in the sediment deposits that overlie the Ross Sea unconformity. Three depositional facies regions, each characterized by a particular assemblage of echo-character type and microtopographic facies, have been identified on the continental shelf. These suites of acoustic facies are the result of specific depositional processes that control type and accumulation of sediment in a region. Evidence of glacial processes and products is uncommon in regions 1 and 2, but is abundant in region 3. McMurdo Sound, region 1, is characterized by a monospecific set of acoustic facies. This unique assemblage probably represents turbidity current deposition in the western part of the basin. Most of the seafloor in region 2, from about latitude 77??S to 75??S, is deeper than 600 m below sealevel. The microtopographic facies and echo-character facies observed on the lower slopes and basin floor there reflect the thin deposits of pelagic sediments that have accumulated in the low-energy conditions that are typical of deep-water environments. In shallower water near the boundary with region 3, the signature of the acoustic facies is different from that in deeper water and probably indicates higher energy conditions or, perhaps, ice-related processes. Thick deposits of tills emplaced by lodgement during the most recent advance of the West Antarctic Ice Sheet are common from latitude 75??S to the northern boundary of the study area just south of Coulman Island (region 3). The signature of microtopographic facies in this region reflects the relief of the base of the grounded ice sheet prior to decoupling from the seafloor. Current winnowing and scour of shallow parts of the seafloor inhibits sediment deposition and maintains the irregular, hummocky relief that characterizes much of the region. Seafloor relief of this type in other polar areas could indicate the former presence of grounded ice. ?? 1989.
Contaminant distribution and accumulation in the surface sediments of Long Island Sound

USGS Publications Warehouse

Mecray, E.L.; Buchholtz ten Brink, Marilyn R.

2000-01-01

The distribution of contaminants in surface sediments has been measured and mapped as part of a U.S. Geological Survey study of the sediment quality and dynamics of Long Island Sound. Surface samples from 219 stations were analyzed for trace (Ag, Ba, Cd, Cr, Cu, Hg, Ni, Pb, V, Zn and Zr) and major (Al, Fe, Mn, Ca, and Ti) elements, grain size, and Clostridium perfringens spores. Principal Components Analysis was used to identify metals that may covary as a function of common sources or geochemistry. The metallic elements generally have higher concentrations in fine-grained deposits, and their transport and depositional patterns mimic those of small particles. Fine-grained particles are remobilized and transported from areas of high bottom energy and deposited in less dynamic regions of the Sound. Metal concentrations in bottom sediments are high in the western part of the Sound and low in the bottom-scoured regions of the eastern Sound. The sediment chemistry was compared to model results (Signell et al., 1998) and maps of sedimentary environments (Knebel et al., 1999) to better understand the processes responsible for contaminant distribution across the Sound. Metal concentrations were normalized to grain-size and the resulting ratios are uniform in the depositional basins of the Sound and show residual signals in the eastern end as well as in some local areas. The preferential transport of fine-grained material from regions of high bottom stress is probably the dominant factor controlling the metal concentrations in different regions of Long Island Sound. This physical redistribution has implications for environmental management in the region.
The geochemical characteristics and sedimentary environment of abyss and hadal sediments of Yap-trench

NASA Astrophysics Data System (ADS)

Huang, Y.; Wang, M.; Sun, C.; Yang, G.; Ding, H.

2017-12-01

Based on ICP-ES analysis, concentrations of 6 constant elements and 9 trace elements in five sediment columnar samples collected from Yap-trench by the Jiaolong Submersiblein June, 2016, were determined. According to the distribution of elements, the sources of sediment and the implications on sedimentary environment were investigated through the correlation of elements and the ratios between special elements. The results showed that the carbonate compensation depthwas between 4500m and 5000m, and the depth of 5000m should be an ideal condition for the formation of iron and manganese nodules. Based on the ratios of Fe/Al and Ti/Al, and the correlation of elements, we inferred that Yap-trench sediments were mainly derived from biogenic, terrestrial, volcanic and autogenic source. The values of Ni/Co and V/Cr indicated that the depositional environment belongs to the oxidative environment and might have inflow of the Antarctic bottom oxygen-rich water. The high content of Ca in the 371-Yap-S02 station below 4cm indicated that this area should be no large-scale volcanic eruption, and volcanic material in the sediment may come from the Mariana volcanic arc. The Caroline ridge located in the east of Yap-trench keep sinking due to plate subduction.
Carotenoids in the Gulf of Gdansk sediments- useful markers of environmental conditions in the past

NASA Astrophysics Data System (ADS)

Krajewska, Magdalena; Szymczak-Żyła, Małgorzata; Kowalewska, Grażyna

2017-04-01

Carotenoids are a large group of natural compounds widespread in the aquatic environment. Most of carotenoids in sediments originate from phytoplankton, macroalgae, vascular plants and bacteria. Carotenoids undergo different reactions in water column and after deposition in sediments. Concentration and relative composition of pigments in sediments depend on such factors like primary production, phytoplankton taxonomy, sedimentation and accumulation rate, hydrological and post-depositional conditions. Because some pigments are unstable and can be degraded both by abiotic and biotic factors - in the presence of light, oxygen, herbivores or microorganisms activity, they provide information about conditions in water column and in sediments. They differ in stability and, due to that, carotenoids in marine sediments are indicators, not only of organic matter sources but also of pre- and post-depositional conditions. This work presents a concentration and distribution of selected carotenoids in recent (6 cores 0-20 cm) and deep (1 core, up to 400 cm) sediments of the Gulf of Gdansk- a highly eutrophic area of high primary production and high sedimentation rate. The sediments were collected during two cruises and analysed in framework of CLISED ('Climate Change Impact on Ecosystem Health- Marine Sediment Indicators') Polish- Norwegian research Project, grant no. 196128. Just after collection, the samples were frozen and kept in such a state until analysis in land laboratory. There, after extraction, carotenoids were analysed using high performance liquid chromatography (HPLC-DAD). Sediment age has been defined using C-14 dating. Sediments contained parent carotenoids, markers of the main phytoplankton groups occurring in the Baltic, e.g. diatoms, green algae and cyanobacteria. B-carotene in sediments is a better, averaged, marker of primary production than chlorophyll- a and similarly stable one as sum of chloropigments-a. Presentation will focus on cyanobacteria and their pigments record in sediments, because cyanobacterial blooms are good indicators of eutrophication and anaerobic conditions in the past. Carotenoids record in deep sediments was varied and there are periods of better or worse carotenoids preservation which proves climate changes.
Reconstructing the deposition environment and long-term fate of Chernobyl 137Cs at the floodplain scale through mobile gamma spectrometry.

PubMed

Varley, Adam; Tyler, Andrew; Bondar, Yuri; Hosseini, Ali; Zabrotski, Viachaslau; Dowdall, Mark

2018-09-01

Cs-137 is considered to be the most significant anthropogenic contributor to human dose and presents a particularly difficult remediation challenge after a dispersal following nuclear incident. The Chernobyl Nuclear Power Plant meltdown in April 1986 represents the largest nuclear accident in history and released over 80 PBq of 137 Cs into the environment. As a result, much of the land in close proximity to Chernobyl, which includes the Polessie State Radioecology Reserve in Belarus, remains highly contaminated with 137 Cs to such an extent they remain uninhabitable. Whilst there is a broad scale understanding of the depositional patterns within and beyond the exclusion zone, detailed mapping of the distribution is often limited. New developments in mobile gamma spectrometry provide the opportunity to map the fallout of 137 Cs and begin to reconstruct the depositional environment and the long-term behaviour of 137 Cs in the environment. Here, full gamma spectrum analysis using algorithms based on the peak-valley ratio derived from Monte Carlo simulations are used to estimate the total 137 Cs deposition and its depth distribution in the soil. The results revealed a pattern of 137 Cs distribution consistent with the deposition occurring at a time of flooding, which is validated by review of satellite imagery acquired at similar times of the year. The results were also consistent with systematic burial of the fallout 137 Cs by annual flooding events. These results were validated by sediment cores collected along a transect across the flood plain. The true merit of the approach was confirmed by exposing new insights into the spatial distribution and long term fate of 137 Cs across the floodplain. Such systematic patterns of behaviour are likely to be fundamental to the understanding of the radioecological behaviour of 137 Cs whilst also providing a tracer for quantifying the ecological controls on sediment movement and deposition at a landscape scale. Copyright © 2018 Elsevier Ltd. All rights reserved.
Comparison of Physical Properties of Marine and Arctic Gas-Hydrate-Bearing Deposits

NASA Astrophysics Data System (ADS)

Winters, W. J.; Walker, M.; Collett, T. S.; Bryant, S. L.; Novosel, I.; Wilcox-Cline, R.; Bing, J.; Gomes, M. L.

2009-12-01

Gas hydrate (GH) occurs in both marine settings and in arctic environments within a wide variety of sediment types. Grain-size analyses from both environments indicate that intrinsic host-sediment properties have a strong influence on gas-hydrate distribution and morphologic characteristics. Depending on the amount formed or dissociated, gas hydrate can significantly change in situ sediment acoustic, mechanical, and hydraulic properties. The U.S. Geological Survey, in cooperation with the U.S. Dept. of Energy, BP Expl.-Alaska, Nat. GH Prog. of India, Canadian Geological Survey, Int. Ocean Drilling Program, Japan Oil Gas and Metals Nat. Corp., Japan Pet. Expl. Co., Int. Marine Past Global Changes Study (IMAGES) program, and Paleoceanography of the Atlantic and Geochemistry (PAGE) program, determined physical properties from marine and arctic sediments and their relation to the presence of GH. At two arctic sites, the Mount Elbert well on the Alaskan North Slope and the Mallik wells on the Mackenzie Delta, NWT, >10-m thick gas-hydrate-bearing (GHB) sandy deposits are capped by finer-grained sediments that may reduce gas migration. In the Mount Elbert well, average median grain sizes (MGS) for the two thickest GHB deposits are 65 and 60 µm. Finer-grained (average MGS of 9 and 28 µm) sediments have plug permeabilities that are 300 and 14 times smaller than underlying GHB sediment. Average MGS of GHB sediment from the Mallik 2L well is ~ 111 µm, compared to overlying sediment with an average MGS of ~ 32 µm. Gas hydrate morphology in the Gulf of Mexico (GOM) and offshore India is substantially more complex than in the arctic, and is related to pervasive, although not exclusive, finer-grained deposits. Massive, several-cm thick, GH layers were recovered in piston cores in the northern GOM, in sediment with little visible lithologic variability (average MGS ~ 0.8 µm). In wells off the east coast of India, GH was present in sand-rich, fractured clay, and reservoirs with both characteristics. Maximum MGS measured on more than 1200 samples was 46 µm, but the average MGS for 14 wells varied from 5 to 10 µm. At Site 10, in the Krishna-Godavari Basin, GH was observed in several morphologic configurations, including complex high-angle planar and rotational veins, solid nodules, and disseminated, in sediment with average MGS of 5 µm, liquid limits between 70 and 98, and plastic limits between 33 and 49. Sediment in a 692-m deep well drilled off the Andaman Islands sporadically hosted disseminated GH in thin coarser-grained ash beds and ash-rich zones. Average and maximum MGS in this well is 6 and 17 µm, respectively. To date, sandy GH reservoirs (with some exceptions, e.g., Nankai Trough) are typically associated with the arctic. However, the presence of thick offshore sand-rich GHB reservoirs is the subject of current investigations, such as by the Gulf of Mexico Joint Industry Project (JIP).
Descriptive models, grade-tonnage relations, and databases for the assessment of sediment-hosted copper deposits: with emphasis on deposits in the Central Africa Copperbelt, Democratic Republic of the Congo and Zambia: Chapter J in Global mineral resource assessment

USGS Publications Warehouse

Taylor, Cliff D.; Causey, J. Douglas; Denning, Paul; Hammarstrom, Jane M.; Hayes, Timothy S.; Horton, John D.; Kirschbaum, Michael J.; Parks, Heather L.; Wilson, Anna B.; Wintzer, Niki E.; Zientek, Michael L.

2013-01-01

Chapter 1 of this report summarizes a descriptive model of sediment-hosted stratabound copper deposits. General characteristics and subtypes of sediment-hosted stratabound copper deposits are described based upon worldwide examples. Chapter 2 provides a global database of 170 sediment-hosted copper deposits, along with a statistical evaluation of grade and tonnage data for stratabound deposits, a comparison of stratabound deposits in the CACB with those found elsewhere, a discussion of the distinctive characteristics of the subtypes of sediment-hosted copper deposits that occur within the CACB, and guidelines for using grade and tonnage distributions for assessment of undiscovered resources in sediment-hosted stratabound deposits in the CACB. Chapter 3 presents a new descriptive model of sediment-hosted structurally controlled replacement and vein (SCRV) copper deposits with descriptions of individual deposits of this type in the CACB and elsewhere. Appendix A describes a relational database of tonnage, grade, and other information for more than 100 sediment-hosted copper deposits in the CACB. These data are used to calculate the pre-mining mineral endowment for individual deposits in the CACB and serve as the basis for the grade and tonnage models presented in chapter 2. Appendix B describes three spatial databases (Esri shapefiles) for (1) point locations of more than 500 sediment-hosted copper deposits and prospects, (2) projected surface extent of 86 selected copper ore bodies, and (3) areal extent of 77 open pits, all within the CACB.
Stratigraphic evolution of the inner continental shelf in response to late Quaternary relative sea-level change, northwestern Gulf of Maine

USGS Publications Warehouse

Barnhardt, W.A.; Belknap, D.F.; Kelley, J.T.

1997-01-01

Accumulations of deltaic and littoral sediments on the inner continental shelf of Maine, Gulf of Maine, preserve a record of postglacial sea-level changes and shoreline migrations. The depositional response of coastal environments to a cycle of regression, lowstand, and transgression was examined with seismic-reflection profiles, vibracores, and radiocarbon dates collected from sediments at the mouths of the Kennebec and Penobscot Rivers. Sequence-stratigraphie analysis of these data reveals two distinctly different successions of late Quaternary deposits that represent end members in an evolutionary model for this glaciated coast. Seaward of the Kennebec River, coarsegrained shorelines with foreset beds occur at depths of 20-60 m and outline the lobate margin of the Kennebec River paleodelta, a complex, rock-framed accumulation of glaciomarine and deltaic sediments capped by estuarine and marine deposits. Sand derived from this system today supports large barrier spits and extensive salt marshes. In contrast, the mouth of the Penobscot River is characterized by thick deposits of glaciomarine mud overlain by marine mud of Holocene age, including gas-charged zones that have locally evolved into fields of pockmarks. The distinct lack of sand and gravel seaward of the Penobscot River and its abundance seaward of the Kennebec River probably reflect differences in sediment sources and the physiography of the two watersheds. The contrasting stratigraphie framework of these systems demonstrates the importance of understanding local and regional differences in sediment supply, sea-level change, bedrock structure, and exposure to waves and tides in order to model river-mouth deposition on glaciated coasts. Evolution of shelf deposits was largely controlled by relative sea level, which locally fell from a highstand (+60 to +70 m at 14 ka) contemporary with deglaciation to a lowstand (-55 m at 10.8 ka). The sea-level lowering was accompanied by fluvial incision of older deposits, producing a regressive, basal unconformity. Major rivers deposited abundant sediment over this surface. Sea level then rose at varying rates, extensively reworking formerly emergent parts of the shelf and producing a shoreface ravinement surface in areas exposed to waves. A tidal ravinement surface has developed in sheltered embayments where erosion is due mainly to tidal currents. Incised valleys in both settings preserve transgressive estuarine deposits that contain lagoonal bivalves and salt-marsh foraminifera at depths of 15-30 m. These deposits accumulated ca. 9.2-7.3 ka, locally a period of relatively slow sea-level rise.
Solid-state 13C NMR studies of dissolved organic matter in pore waters from different depositional environments

USGS Publications Warehouse

Orem, W.H.; Hatcher, P.G.

1987-01-01

Dissolved organic matter (DOM) in pore waters from sediments of a number of different depositional environments was isolated by ultrafiltration using membranes with a nominal molecular weight cutoff of 500. This > 500 molecular weight DOM represents 70-98% of the total DOM in these pore waters. We determined the gross chemical structure of this material using both solid-state 13C nuclear magnetic resonance spectroscopy and elemental analysis. Our results show that the DOM in these pore waters appears to exist as two major types: one type dominated by carbohydrates and paraffinic structures and the second dominated by paraffinic and aromatic structures. We suggest that the dominance of one or the other structural type of DOM in the pore water depends on the relative oxidizing/reducing nature of the sediments as well as the source of the detrital organic matter. Under dominantly anaerobic conditions carbohydrates in the sediments are degraded by bacteria and accumulate in the pore water as DOM. However, little or no degradation of lignin occurs under these conditions. In contrast, sediments thought to be predominantly aerobic in character have DOM with diminished carbohydrate and enhanced aromatic character. The aromatic structures in the DOM from these sediments are thought to arise from the degradation of lignin. The large amounts of paraffinic structures in both types of DOM may be due to the degradation of unidentified paraffinic materials in algal or bacterial remains. ?? 1987.
Geologic processes influence the effects of mining on aquatic ecosystems

USGS Publications Warehouse

Schmidt, Travis S.; Clements, William H.; Wanty, Richard B.; Verplanck, Philip L.; Church, Stan E.; San Juan, Carma A.; Fey, David L.; Rockwell, Barnaby W.; DeWitt, Ed H.; Klein, Terry L.

2012-01-01

Geologic processes strongly influence water and sediment quality in aquatic ecosystems but rarely are geologic principles incorporated into routine biomonitoring studies. We test if elevated concentrations of metals in water and sediment are restricted to streams downstream of mines or areas that may discharge mine wastes. We surveyed 198 catchments classified as “historically mined” or “unmined,” and based on mineral-deposit criteria, to determine whether water and sediment quality were influenced by naturally occurring mineralized rock, by historical mining, or by a combination of both. By accounting for different geologic sources of metals to the environment, we were able to distinguish aquatic ecosystems limited by metals derived from natural processes from those due to mining. Elevated concentrations of metals in water and sediment were not restricted to mined catchments; depauperate aquatic communities were found in unmined catchments. The type and intensity of hydrothermal alteration and the mineral deposit type were important determinants of water and sediment quality as well as the aquatic community in both mined and unmined catchments. This study distinguished the effects of different rock types and geologic sources of metals on ecosystems by incorporating basic geologic processes into reference and baseline site selection, resulting in a refined assessment. Our results indicate that biomonitoring studies should account for natural sources of metals in some geologic environments as contributors to the effect of mines on aquatic ecosystems, recognizing that in mining-impacted drainages there may have been high pre-mining background metal concentrations.
Sources and contamination rate of port sediments: evidences from dimensional, mineralogical, and chemical investigations

NASA Astrophysics Data System (ADS)

Lucchetti, Gabriella; Cutroneo, Laura; Carbone, Cristina; Consani, Sirio; Vagge, Greta; Canepa, Giuseppe; Capello, Marco

2017-04-01

Ports are complex environments due to their complicated geometry (quays, channels, and piers), the presence of human activities (vessel traffic, yards, industries, and discharges), and natural factors (stream and torrent inputs, sea action, and currents). Due to the many activities that take place in a port, sediments and waters are often contaminated by different kinds of chemicals, such as hydrocarbons, dioxins, pesticides, nutrients, and metals. The contamination rate of a port basin is site specific and depends on the sources of contamination in the nearby urban system as well as the port system itself, such as city discharges and sewers, river intake, vessel traffic, factories (Taylor and Owens, 2009). Moreover, two important sources and vehicles of contaminants are: a) anthropogenic road deposited sediments derived from the runoff of the port and city area, and natural road deposited sediments derived from rivers and torrents, and b) airborne particulate matter and sediments (Taylor and Owens, 2009). The Port of Genoa is situated at the apex of the Ligurian Sea in the north western Mediterranean Sea and is characterised by the presence of several commercial activities that have contributed, over the years, and still contribute today, to the contaminant accumulation in both the water column and the bottom sediments. This port basin includes the mouth of several streams and the mouth of the Bisagno and the Polcevera Torrents, along the banks of which can be found several small towns, quarries, factories, and the suburbs of the city of Genoa, a ferry terminal, different container terminals, marinas, dry docks, the coal power plant of Genoa, and different wastewater treatment plant discharges. Starting from these considerations, we have examined the marine environment of a port from the point of view of the water mass circulation, hydrological characteristics, distribution of the sediment grain size, mineralogical characteristics, and metal concentrations of the bottom sediments. Our results show that, in the case of the Port of Genoa (north western Italy), both the impact of the human activities (such as coal power plant, oil depots, yards, dredging of the bottom sediments, etc.) and the natural processes (such as currents, fresh water and sediment inputs from the torrents), together with the morphology of the basin, are important factors in sediment, water and metal distributions and give rise to a complex environment. Taylor, K.G., Owens, P.N., 2009. Sediments in urban river basins: a review of sediment contaminant dynamics in an environmental system conditioned by human activities. Journal of Soils and Sediments 9: 281-303.
Is cratonic sedimentation consistent with available models? An example from the Upper Proterozoic of the West African craton

NASA Astrophysics Data System (ADS)

Bertrand-Sarfati, Janine; Moussine-Pouchkine, Alexis

1988-08-01

The Atar Group, part of the Upper Proterozoic sequence covering the West African craton, stable since 2000 Ma, is characterized by an alternation of extensive carbonate beds and mixed siliciclastic and carbonate facies. The carbonate beds comprise essentially columnar stromatolite biostromes and bioherms which reflect sublittoral environments. The mixed facies contain a variety of laterally discontinuous facies which imply more variable environmental conditions. The settings of the mixed facies are not always clear but they do not contain thick sequences of high-energy facies. Few obvious facies sequences are discernable; those that are present are considered to be punctuated aggradational cycles (PACs) and they always start with biostromes of columnar stromatolites with very few sediments. Composite sequences are interpreted as due to shallowing upward or increasing energy environments that may be laterally contiguous, despite the fact that the contacts are not gradational. However, much of the stratigraphic sequence cannot be subdivided into cycles and seems to consist of unrelated individual facies, bound by sharp boundaries. The basin analysis reveals that biostromes of columnar stromatolites start after an instantaneous geological event corresponding to a sea-level rise. Consequently, their appearance can be considered as a time-line. We describe, in the Atar Group and its equivalents, three sedimentation trends, all of which are interpreted to be of shallowing upward character. The Atar Group appears to have been deposited in an epeiric sea (i.e. an extremely flat ramp). There are two contrasting styles of sedimentation: (1) after the submergence of the whole area, columnar stromatolites built extensive biostromes; (2) during the stable phase, sediments are deposited in a mosaic of laterally-discontinuous facies. Tidal influence cannot be recognized in the sequence, neither can a salinity increase toward the land; both common features in published epeiric sea models. A cratonic sedimentation area such as this is characterized by its size and flatness. Only during the stable phase of the cycle does small-scale topographic relief lead to deposition of a mosaic of facies. The sedimentation is storm- and wave-dominated.
Sequential extraction techniques applied to a porphyry copper deposit in the basin and range province

USGS Publications Warehouse

Filipek, L.H.; Theobald, P.K.

1981-01-01

Samples of minus-80-mesh (<180 ??m) stream sediment, rock containing exposed fracture coatings, and jarosite and chrysocolla were collected from an area surrounding the North Silver Bell porphyry Cu deposit near Tucson, Arizona. The samples were subjected to a series of extractions in a scheme originally designed for use on samples from humid or sub-humid environments, in which the following fractions can effectively be separated: (1) carbonates and exchangeable metals; (2) Mn oxides; (3) organic compounds and sulfides; (4) hydrous Fe oxides; and (5) residual crystalline minerals. Jarosite and chrysocolla, two major minerals of the North Silver Bell area, were found to dissolve over two or more steps of the extraction scheme. The results represent only a limited number of samples from one copper deposit. Nevertheless, they do suggest that in a semiarid to arid environment, where mechanical dispersion of such minerals predominates, uncritical assignment of unique phases, such as Mn oxides or organics to a given extraction would lead to false interpretations of weathering processes. However, the relative proportions of elements dissolved in each step of the jarosite and chrysocolla extractions could be used as a "fingerprint" for recognition of the presence of these two minerals in the stream-sediment and rock samples. The relative abundance of hydrous Fe oxide and jarosite and the alteration zoning could be mapped using data from jarosite and chrysocolla extractions. Manganese oxides were also found to have a greater influence on Zn than on Cu or Pb during supergene alteration. The rapid change in relative importance of the first (1M-acetic acid) extraction for Cu, Zn, and Pb near the mineralized zone suggested the occurrence of minor hydromorphic processes within the stream sediments. Thus, the acetic acid extraction proved the most effective for pinpointing mineralization in sediments. In contrast, the residual fraction had the longest dispersion train, suggesting that total metal concentrations are most effective in arid environments for reconnaissance surveys. ?? 1981.
Demise of reef-flat carbonate accumulation with late Holocene sea-level fall: Evidence from Molokai, Hawaii

USGS Publications Warehouse

Engels, M.S.; Fletcher, C.H.; Field, M.; Conger, C.L.; Bochicchio, C.

2008-01-01

Twelve cores from the protected reef-flat of Molokai revealed that carbonate sediment accumulation, ranging from 3 mm year-1 to less than 1 mm year-1, ended on average 2,500 years ago. Modern sediment is present as a mobile surface veneer but is not trapped within the reef framework. This finding is consistent with the arrest of deposition at the end of the mid-Holocene highstand, known locally as the "Kapapa Stand of the Sea," ???2 m above the present datum ca. 3,500 years ago in the main Hawaiian Islands. Subsequent erosion, non-deposition, and/or a lack of rigid binding were probable factors leading to the lack of reef-flat accumulation during the late Holocene sea-level fall. Given anticipated climate changes, increased sedimentation of reef-flat environments is to be expected as a consequence of higher sea level. ?? 2008 Springer-Verlag.
Living (Rose-Bengal-Stained) benthic foraminifera along the Kveithola Trough (NW Barents Sea), environmental implications

NASA Astrophysics Data System (ADS)

Sabbatini, Anna; Morigi, Caterina; Lucchi, Renata G.; de Vittor, Cinzia; Bazzano, Matteo

2017-04-01

The distribution and composition of benthic foraminiferal fauna in the Kveithola Trough (NW Barents Sea) were studied in three depositional settings identified on the basis of surface depositional structures, sediment types and present ecosystem characteristics. Sediment samples were collected during the CORIBAR cruise (Hanebuth et al., 2013) aimed at drilling glacigenic sediments in a palaeo-ice stream depositional system in the western Barents Sea. In particular, we report the quantitative data of the living benthic foraminiferal density, biodiversity and vertical distribution in three box-core sediment samples (0-10 cm) collected in two inner trough sites, the drift area and the channel/fault area and one outer shelf site. Rose-Bengal-stained foraminiferal assemblages were investigated from two different size fractions (63-150 and >150 micrometres). In the drift area, the living benthic foraminiferal assemblage is characterized by the presence of oxygen-depleted environmental taxa with low foraminiferal density and biodiversity. This area appears a stagnant environment, strongly affected by low-oxygen, stressed environmental conditions in which foraminifera developed a life strategy aimed to increase the efficiency of food utilization and maximum resistance to ecological stress. As a further support to this interpretation, all the sediments recovered in the drift area are rich in organic matter and in Siboglinid-like tubes together with pockmark evidences on the surface of the box-corer. The sedimentation in the channel/fault area is very similar to that described for the drift area, evidencing stressed environmental conditions. Opportunistic species dominate the benthic foraminiferal fauna. The species distribution of the internal trough sites is consistent with the lithology and with data of quantity and biochemical composition (in terms of phytopigment, protein, lipid, carbohydrate and biopolymeric carbon) of the organic matter. Values of biopolymeric carbon are typical of eutrophic setting and the presence of tolerant low oxygen condition species as Nonionellina labradorica, Nonionella iridea and Fursenkoina fusiformis suggests that the sediment is dysoxic. In the inner part of the trough, the presence of Leptohalysis scottii and the decreasing of N. labradorica could indicate the presence of organic carbon input with higher nutritional quality, probably due to the shallower depth of the station (151 m water depth). The site corresponding to the outer shelf is characterized by the presence of diverse and abundant benthic foraminiferal assemblage suggesting a high oxygenated and mesotrophic environment. The sedimentological evidences characterized by clean sand with large-scale ripple-like features suggest the presence of moderately strong, and persistent bottom currents. We notice in all sites the presence of delicate monothalamous taxa (organic-walled allogromiids, agglutinated saccamminids, psammosphaerids and tubular forms). Therefore, preliminary faunal and sedimentological data allow to describe sediments of the Kveithola Drift, deposited under persistent dense bottom currents, appears today as a stagnant environment strongly affected by low-oxygen concentration, possibly chemosynthetic conditions with likely ongoing gas seep activity from pockmarks.
Sedimentation, sediment quality, and upstream channel stability, John Redmond Reservoir, east-central Kansas, 1964-2009

USGS Publications Warehouse

Juracek, Kyle E.

2010-01-01

A combination of available bathymetric-survey information, bottom-sediment coring, and historical streamgage information was used to investigate sedimentation, sediment quality, and upstream channel stability for John Redmond Reservoir, east-central Kansas. Ongoing sedimentation is reducing the ability of the reservoir to serve several purposes including flood control, water supply, and recreation. The total estimated volume and mass of bottom sediment deposited between 1964 and 2009 in the conservation pool of the reservoir was 1.46 billion cubic feet and 55.8 billion pounds, respectively. The estimated sediment volume occupied about 41 percent of the conservation-pool, water-storage capacity of the reservoir. Water-storage capacity in the conservation pool has been lost to sedimentation at a rate of about 1 percent annually. Mean annual net sediment deposition since 1964 in the conservation pool of the reservoir was estimated to be 1.24 billion pounds per year. Mean annual net sediment yield from the reservoir basin was estimated to be 411,000 pounds per square mile per year Information from sediment cores shows that throughout the history of John Redmond Reservoir, total nitrogen concentrations in the deposited sediment generally were uniform indicating consistent nitrogen inputs to the reservoir. Total phosphorus concentrations in the deposited sediment were more variable than total nitrogen indicating the possibility of changing phosphorus inputs to the reservoir. As the principal limiting factor for primary production in most freshwater environments, phosphorus is of particular importance because increased inputs can contribute to accelerated reservoir eutrophication and the production of algal toxins and taste-and-odor compounds. The mean annual net loads of total nitrogen and total phosphorus deposited in the bottom sediment of the reservoir were estimated to be 2,350,000 pounds per year and 1,030,000 pounds per year, respectively. The estimated mean annual net yields of total nitrogen and total phosphorus from the reservoir basin were 779 pounds per square mile per year and 342 pounds per square mile per year, respectively. Trace element concentrations in the bottom sediment of John Redmond Reservoir generally were uniform over time. As is typical for eastern Kansas reservoirs, arsenic, chromium, and nickel concentrations typically exceeded the threshold-effects guidelines, which represent the concentrations above which toxic biological effects occasionally occur. Trace element concentrations did not exceed the probable-effects guidelines (available for eight trace elements), which represent the concentrations above which toxic biological effects usually or frequently occur. Organochlorine compounds either were not detected or were detected at concentrations that were less than the threshold-effects guidelines. Stream channel banks, compared to channel beds, likely are a more important source of sediment to John Redmond Reservoir from the upstream basin. Other sediment sources include surface-soil erosion in the basin and shoreline erosion in the reservoir.
Assessment of the Efficiency of Sediment Deposition Reduction in the Zengwen River Watershed in Taiwan

NASA Astrophysics Data System (ADS)

Wu, M.; Tan, H. N.; Lo, W. C.; Tsai, C. T.

2015-12-01

The river upstream of watersheds in Taiwan is very steep, where soil and rock are often unstable so that the river watershed typically has the attribute of high sand yield and turbid runoff due to the excessive erosion in the heavy rainfall seasons. If flood water overflows the river bank, it would lead to a disaster in low-altitude plains. When flood retards or recesses, fine sediment would deposit. Over recent decades, many landslides arise in the Zengwen river watershed due to climate changes, earthquakes, and typhoons. The rocks and sands triggered by these landslides would move to the river channel through surface runoff, which may induce sediment disasters and also render an impact on the stability and sediment transport of the river channel. The risk of the sediment disaster could be reduced by implementing dredging works. However, because of the nature of the channel, the dredged river sections may have sediment depositions back; thus, causing an impact on flood safety. Therefore, it is necessary to evaluate the effectiveness of dredged works from the perspectives of hydraulic, sediment transport, and flood protection to achieve the objective of both disaster prevention and river bed stability. We applied the physiographic soil erosion-deposition (PSED) model to simulate the sediment yield, the runoff, and sediment transport rate of the Zengwen river watershed corresponding to one-day rainstorms of the return periods of 25, 50, and 100 year. The potential of sediment deposition and erosion in the river sections of the Zengwen river could be simulated by utilizing the alluvial river-movable bed two dimensional (ARMB-2D) model. The results reveal that the tendency for the potential of river sediment deposition and erosion obtained from these two models is agreeable. Furthermore, in order to evaluate the efficiency of sediment deposition reduction, two quantized values, the rate of sediment deposition reduction and the ratio of sediment deposition reduction were utilized. According to the simulation results obtained from the PESD and ARMB-2D models, the river sections with severe sediment depositions and high efficiency of sediment deposition reduction will be referred to as the dredging-to-be areas.
Sedimentology and architecture of De Geer moraines in the western Scottish Highlands, and implications for grounding-line glacier dynamics

NASA Astrophysics Data System (ADS)

Golledge, Nicholas R.; Phillips, Emrys

2008-07-01

Sedimentary exposures in moraines in a Scottish Highland valley (Glen Chaorach), reveal stacked sequences of bedded and laminated silt, sand and gravel, interspersed or capped with diamicton units. In four examples, faults and folds indicate deformation by glaciotectonism and syndepositional loading. We propose that these sediments were laid down in an ice-dammed lake, close to the last ice margin to occupy this glen. Individual units within cross-valley De Geer moraine ridges are interpreted by comparison with examples from similar environments elsewhere: stratified diamictons containing laminated or bedded lenses are interpreted as subaqueous ice-marginal debris-flow deposits; massive fine-grained deposits as hyperconcentrated flow deposits, and massive gravel units as high-density debris-flow deposits. Using an allostratigraphic approach we argue that glaciotectonically deformed coarsening-upward sand and gravel sequences that culminate in deposition of subglacial diamicton represent glacier advances into the ice-marginal lake, whereas undisturbed cross-bedded sand and gravel reflects channel or fan deposits laid down during glacier retreat. A flat terrace of bedded sand and gravel at the northern end of Glen Chaorach is interpreted as subaerial glaciofluvial outwash. On the basis of these inferences we propose the following three stage deglacial event chronology for Glen Chaorach. During glacier recession, ice separation and intra-lobe ponding first led to subaquaeous deposition of sorted and unsorted facies. Subsequent glacier stabilisation and ice-marginal oscillation produced glaciotectonic structures in the ice-marginal sediment pile and formed De Geer moraines. Finally, drainage of the ice-dammed lake allowed a subaerial ice-marginal drainage system to become established. Throughout deglaciation, deposition within the lake was characterized by abrupt changes in grain size and in the architecture of individual sediment bodies, reflecting changing delivery paths and sediment supply, and by dynamic margin oscillations typical of water-terminating glaciers.
The impacts of tracer selection and corrections for organic matter and particle size on the results of quantitative sediment fingerprinting. A case study from the Nene basin, UK.

NASA Astrophysics Data System (ADS)

Pulley, Simon; Ian, Foster; Paula, Antunes

2014-05-01

In recent years, sediment fingerprinting methodologies have gained widespread adoption when tracing sediment provenance in geomorphological research. A wide variety of tracers have been employed in the published literature, with corrections for particle size and organic matter applied when the researcher judged them necessary. This paper aims to explore the errors associated with tracer use by a comparison of fingerprinting results obtained using fallout and lithogenic radionuclides, geochemical, and mineral magnetic tracers in a range of environments located in the Nene basin, UK. Specifically, fingerprinting was undertaken on lake, reservoir and floodplain sediment cores, on actively transported suspended sediment and on overbank and channel bed sediment deposits. Tracer groups were investigated both alone and in combination to determine the differences between their sediment provenance predictions and potential causes of these differences. Additionally, simple organic and particle size corrections were applied to determine if they improve the agreement between the tracer group predictions. Key results showed that when fingerprinting contributions from channel banks to actively transported or recently deposited sediments the tracer group predictions varied by 24% on average. These differences could not be clearly attributed to changes in the sediment during erosion or transport. Instead, the most likely cause of differences was the pre-existing spatial variability in tracer concentrations within sediment sources, combined with highly localised erosion. This resulted in the collected sediment source samples not being representative of the actual sediment sources. Average differences in provenance predictions between the different tracer groups in lake, reservoir and floodplain sediment cores were lowest in the reservoir core at 19% and highest in some floodplain cores, with differences in predictions in excess of 50%. In these latter samples organic enrichment of the sediment, selective transport of fine particles and post-depositional chemical changes to the sediment were determined to be the likely cause of the differences. It was determined that organic and particle size corrections made the differences between tracer groups larger in most cases, although differences between tracer group predictions were reduced in two of the four floodplain cores.
Outstanding Universal Values of the Korean Archipelago Getbol: Its potential for World Heritage Nomination

NASA Astrophysics Data System (ADS)

Woo, K. S.; Chun, S. S.; Moon, K. O.

2017-12-01

The `Korean Archipelago Getbol (KAG; Getbol means tidal flat deposits in Korean)' has developed due to the decreasing accommodation space during the Holocene sea-level rise on the broad epicontinental shelf of the southeastern part of the Yellow Sea. Sedimentation and evolution show a variety of quite distinctive tidal flat patterns with intertidal and subtidal drainage systems depending upon the location and orientation of rocky shores. The following KAG`s Outstanding Universal Values are suggested to support the WH: 1) It is the unique coastal sedimentary environment formed by special geological and oceanographic setting in the world. It is the only place in the world where tide-controlled sedimentation processes have produced special tidal flats surrounding numerous rocky islands on a broad epicontinental shelf near convergent tectonic boundary. Macrotidal currents combined with waves and typhoons in this semi-closed oceanographic setting have provided unique geological and oceanographic conditions for their formation. 2) It diplays the most dynamic and complicated, but stable coastal depositional system in the world. Even though the property has been constantly influenced by strong microtidal currents combined with East Asian Monsoon climate (winter erosion and summer deposition) with occasional typhoons during summer, Getbol has maintained its stable depositional system and tidal flat sediments have been accumulated for the past 9,000 years. Sufficient supply of suspended load through Geumgang River provides sustainable depositional system within the property. Complicated island-topography also produced the most complicated and divese depositional systems as well as the deepest tidal channels in the world. (3) The KAG shows the thickest tidal flat sediments protected by numerous islands. Aggradation of tidal sediments has caught up with the rapid Holocene sealevel rise and produced the thickest tidal flat sediments in the world. As a results, numerous former islands of relatively elevated areas have been vanished and hidden. In addition, the KAG shows a complete story of geological, ecological and conservational integrity (the wholeness and intactness). Thus, we strongly believe that the KAG has great potential to be inscribed on a World Heritage List for the criterion (viii).

Evaluation of conditions along the grounding line of temperate marine glaciers: An example from Muir Inlet, Glacier Bay, Alaska

USGS Publications Warehouse

Seramur, K.C.; Powell, R.D.; Carlson, P.R.

1997-01-01

In the marine environment, stability of the glacier terminus and the location of subglacial streams are the dominant controls on the distribution of grounding-line deposits within morainal banks. A morainal bank complex in Muir Inlet, Glacier Bay, SE Alaska, is used to develop a model of terminus stability and location of subglacial streams along the grounding line of temperate marine glaciers. This model can be used to interpret former grounding-line conditions in other glacimarine settings from the facies architecture within morainal bank deposits. The Muir Inlet morainal bank complex was deposited between 1860 A.D. and 1899 A.D., and historical observations provide a record of terminus positions, glacial retreat rates and sedimentary sources. These data are used to reconstruct the depositional environment and to develop a correlation between sedimentary facies and conditions along the grounding line. Four seismic facies identified on the high-resolution seismic-reflection profiles are used to interpret sedimentary facies within the morainal bank complex. Terminus stability is interpreted from the distribution of sedimentary facies within three distinct submarine geomorphic features, a grounding-line fan; stratified ridges, and a field of push ridges. The grounding-line fan was deposited along a stable terminus and is represented on seismic-reflection profiles by two distinct seismic facies, a proximal and a distal fan facies. The proximal fan facies was deposited at the efflux of subglacial streams and indicates the location of former glacifluvial discharges into the sea. Stratified ridges formed as a result of the influence of a quasi-stable terminus on the distribution of sedimentary facies along the grounding line. A field of push ridges formed along the grounding line of an unstable terminus that completely reworked the grounding-line deposits through glacitectonic deformation. Between 1860 A.D. and 1899 A.D. (39 years), 8.96 x 108 m3 of sediment were deposited within the Muir Inlet morainal bank complex at an average annual sediment accumulation rate of 2.3 x 107 m3/a. This rate represents the annual sediment production capacity of the glacier when the Muir Inlet drainage basin is filled with glacial ice.
Uranium-bearing copper deposits in the Coyote district, Mora County, New Mexico

USGS Publications Warehouse

Zeller, H.D.; Baltz, Elmer Harold

1954-01-01

Uranium-bearing copper deposits occur in steeply dipping beds of the Sangre de Cristo formation of Pennsylvanian and Permian(?) age south of Coyote, Mora County, N. Mex. Mapping and sampling of these deposits indicate that they are found in lenticular carbonaceous zones in shales and arkosic sandstones. Samples from these zones contain as much as 0.067 percent uranium and average 3 percent copper. Metatyuyamunite is dissemihatedin some of the arkosic sandstone beds, and uraninite is present in some of the copper sulfide nodules occurring in the shale. These sulfide nodules are composed principally of chalcocite but include some bornite, covellite, pyrite, and malachite. Most of the samples were collected near the surface from the weathered zone. The copper and uranium were probably deposited with the sediments and concentrated into zones during compaction and lithification. Carbonaceous material in the Sangre de Cristo formation provided the environment that precipitated uranium and copper from mineral-charged connate waters forced from the clayey sediments.
The Role of the Sedimentary Regime in Shaping the Distribution of Subtidal Sandbank Environments and the Associated Meiofaunal Nematode Communities: An Example from the Southern North Sea

PubMed Central

Schratzberger, Michaela; Larcombe, Piers

2014-01-01

We combined sediment and faunal data to explore the role of the sedimentary regime in shaping the distribution of subtidal sandbank environments and the associated meiofaunal nematode communities at Broken Bank and Swarte Bank, in the southern North Sea. A variety of sediment transport processes occur in the area, differing in the frequency and magnitude of sediment mobility, and the continuum between erosion, translation and sediment accumulation. The seabed contained a variety of bedforms, including longitudinal furrows, and small to very large sandwaves. The bed sediments were dominated by fine and medium sands, with admixtures of silt and gravel. Based on sedimentary bedforms and grain size analysis, a total of 11 sedimentary facies were delineated, of which 8 were analysed in detail for their relationships with the meiofauna. The sedimentary facies fell clearly into groups of facies, respectively representing high, high-moderate and moderate, and episodic sediment mobility. For those sedimentary facies where daily movement of sediments and bedforms occurred (‘high’ sediment mobility), the resulting spatially homogeneous environments were dominated by an impoverished nematode community comprising small deposit feeders and large predators. Resistance to sediment movement and the ability to exploit alternative food sources were prominent functional features of the successful colonisers. Those facies characterised by relatively infrequent sediment mobility (‘episodic’ and ‘high-moderate and moderate’ sediment mobility) comprised a heterogeneous suite of benthic habitats, containing taxonomically and functionally diverse assemblages of nematodes of various sizes, feeding types and reproductive potential. Faunal distribution patterns here indicated trade-offs between the resistance to sediment movement, environmental tolerance and competitive abilities. Our focus on diverse assemblages of organisms with high turnover times, inhabiting highly dynamic sedimentary environments, has revealed new animal-sediment relationships of relevance to pure and applied science. PMID:25296029
Applications of ichnology to hydrogeology, with examples from the Cape Fear Formation (Cretaceous), South Carolina

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martin, A.J.; Simones, G.C.

Ichnology, the study of modern and ancient traces left by organisms, has provided supplemental information to geologic subdisciplines such as sedimentology and stratigraphy. The major objective of the authors paper is to emphasize the valuable information that can be conveyed by trace fossils in the investigation of hydrogeologic units. Bioturbation has a net effect of mixing different types and layers of sediments, such as introducing clays into sands and vice versa. This mixing can decrease porosity and permeability of sandy units, thus changing potential aquifers into confining units. For example, a sandy fluvial deposit will contain distinctive nonmarine trace fossils,more » thus defining channel sands that may serve as permeable conduits for ground-water flow. In contrast, a sandy shelf deposit will contain marine trace fossils in a sand body geometry that will be markedly different from aquifers produced in nonmarine environments. Bioturbation also causes geochemical and diagenetic changes in sediments, causing irrigation of previously anoxic sediments and precipitation of ion oxides. The Cretaceous Cape Fear Formation of the Atlantic Coastal Plain, in the subsurface of South Carolina, is presented as an example of a hydrogeologic unit that has been reinterpreted using ichnologic data. Extensive bioturbation caused mixing of clays and sands in Cape Fear sediments, which resulted in the Cape Fear becoming a regional confining system. Trace fossil assemblages indicate a brackish water environment, perhaps estuarine, for the Cape Fear, as opposed to previous interpretations of fluvial and deltaic environments. Bioturbated zones also have significantly more oxidized iron than unbioturbated zones, highlighting potential effects on ground-water quality.« less
Brief communication: beyond the South African cave paradigm--Australopithecus africanus from Plio-Pleistocene paleosol deposits at Taung.

PubMed

Hopley, Philip J; Herries, Andy I R; Baker, Stephanie Edwards; Kuhn, Brian F; Menter, Colin G

2013-06-01

Following the discovery of the "Taung Child" (Australopithecus africanus) in 1924 in the Buxton-Norlim Limeworks near Taung, the fossil-bearing deposits associated with the Dart and Hrdlička pinnacles have been interpreted as the mined remnants of cave sediments that formed within the Plio-Pleistocene Thabaseek Tufa: either as a younger cave-fill or as contemporaneous carapace caves. When combined with the Plio-Pleistocene dolomitic cave deposits from the "Cradle of Humankind," a rather restricted view emerges that South African early hominins derived from cave deposits, whereas those of east and central Africa are derived from fluvio-lacustrine and paleosol deposits. We undertook a sedimentological and paleomagnetic analysis of the pink-colored deposit (PCS) from which the "Taung Child" is purported to have derived and demonstrate that it is a calcrete, a carbonate-rich pedogenic sediment, which formed on the paleo-land surface. The deposit extends 100 s of meters laterally beyond the Dart and Hrdlička Pinnacles where it is interbedded with the Thabaseek Tufa, indicating multiple episodes of calcrete development and tufa growth. The presence of in situ rhizoconcretions and insect trace fossils (Celliforma sp. and Coprinisphaera sp.) and the distinctive carbonate microfabric confirm that the pink deposit is a pedogenic calcrete, not a calcified cave sediment. Paleomagnetic and stratigraphic evidence indicates that a second, reversed polarity, fossil-bearing deposit (YRSS) is a younger fissure-fill formed within a solutional cavity of the normal polarity tufa and pink calcrete (PCS). These observations have implications for the dating, environment, and taphonomy of the site, and increase the likelihood of future fossil discoveries within the Buxton-Norlim Limeworks. Copyright © 2013 Wiley Periodicals, Inc.
The depositional environments of Schöningen 13 II-4 and their archaeological implications.

PubMed

Stahlschmidt, Mareike C; Miller, Christopher E; Ligouis, Bertrand; Goldberg, Paul; Berna, Francesco; Urban, Brigitte; Conard, Nicholas J

2015-12-01

Geoarchaeological research at the Middle Pleistocene site of Schöningen 13 II-4, often referred to as the Speerhorizont, has focused on describing and evaluating the depositional contexts of the well-known wooden spears, butchered horses, and stone tools. These finds were recovered from the transitional contact between a lacustrine marl and an overlying organic mud, originally thought to be a peat that accumulated in place under variable moisture conditions. The original excavators proposed that hominin activity, including hunting and butchery, occurred on a dry lake shore and was followed by a rapid sedimentation of organic deposits that embedded and preserved the artifacts. Our geoarchaeological analysis challenges this model. Here, we present evidence that the sediments of Schöningen 13 II-4 were deposited in a constantly submerged area of a paleolake. Although we cannot exclude the possibility that the artifacts were deposited during a short, extreme drying event, there are no sedimentary features indicative of surface exposure in the sediments. Accordingly, this paper explores three main alternative models of site formation: anthropogenic disposal of materials into the lake, a geological relocation of the artifacts, and hunting or caching on lake-ice. These models have different behavioral ramifications concerning hominin knowledge and exploitation of the landscape and their subsistence strategies. Copyright © 2015 Elsevier Ltd. All rights reserved.
Refining the model of barrier island formation along a paraglacial coast in the Gulf of Maine

USGS Publications Warehouse

Hein, Christopher J.; FitzGerald, Duncan M.; Carruthers, Emily A.; Stone, Byron D.; Barnhardt, Walter A.; Gontz, Allen M.

2012-01-01

Details of the internal architecture and local geochronology of Plum Island, the longest barrier in the Gulf of Maine, have refined our understanding of barrier island formation in paraglacial settings. Ground-penetrating radar and shallow-seismic profiles coupled with sediment cores and radiocarbon dates provide an 8000-year evolutionary history of this barrier system in response to changes in sediment sources and supply rates as well as variability in the rate of sea-level change. The barrier sequence overlies tills of Wisconsinan and Illinoian glaciations as well as late Pleistocene glaciomarine clay deposited during the post-glacial sea-level highstand at approximately 17 ka. Holocene sediment began accumulating at the site of Plum Island at 7–8 ka, in the form of coarse fluvial channel-lag deposits related to the 50-m wide erosional channel of the Parker River that carved into underlying glaciomarine deposits during a lower stand of sea level. Plum Island had first developed in its modern location by ca. 3.6 ka through onshore migration and vertical accretion of reworked regressive and lowstand deposits. The prevalence of southerly, seaward-dipping layers indicates that greater than 60% of the barrier lithosome developed in its modern location through southerly spit progradation, consistent with a dominantly longshore transport system driven by northeast storms. Thinner sequences of northerly, landward-dipping clinoforms represent the northern recurve of the prograding spit. A 5–6-m-thick inlet-fill sequence was identified overlying the lower stand fluvial deposit; its stratigraphy captures events of channel migration, ebb-delta breaching, onshore bar migration, channel shoaling and inlet infilling associated with the migration and eventual closure of the inlet. This inlet had a maximum cross-sectional area of 2800 m2 and was active around 3.5–3.6 ka. Discovery of this inlet suggests that the tidal prism was once larger than at present. Bay infilling, driven by the import of sediment into the backbarrier environment through tidal inlets, as well as minor sediment contribution from local rivers, led to a vast reduction in the bay tidal prism. This study demonstrates that, prior to about 3 ka, Plum Island and its associated marshes, tidal flats, and inlets were in a paraglacial environment; that is, their main source of sediment was derived from the erosion and reworking of glaciogenic deposits. Since that time, Plum Island has been in a state of dynamic equilibrium with its non-glacial sediment sources and therefore can be largely considered to be in a stable, “post-paraglacial” state. This study is furthermore the first in the Gulf of Maine to show that spit accretion and inlet processes were the dominant mechanisms in barrier-island formation and thus serves as a foundation for future investigations of barrier development in response to backbarrier infilling.
Direct sampling during multiple sediment density flows reveals dynamic sediment transport and depositional environment in Monterey submarine canyon

NASA Astrophysics Data System (ADS)

Maier, K. L.; Gales, J. A.; Paull, C. K.; Gwiazda, R.; Rosenberger, K. J.; McGann, M.; Lundsten, E. M.; Anderson, K.; Talling, P.; Xu, J.; Parsons, D. R.; Barry, J.; Simmons, S.; Clare, M. A.; Carvajal, C.; Wolfson-Schwehr, M.; Sumner, E.; Cartigny, M.

2017-12-01

Sediment density flows were directly sampled with a coupled sediment trap-ADCP-instrument mooring array to evaluate the character and frequency of turbidity current events through Monterey Canyon, offshore California. This novel experiment aimed to provide links between globally significant sediment density flow processes and their resulting deposits. Eight to ten Anderson sediment traps were repeatedly deployed at 10 to 300 meters above the seafloor on six moorings anchored at 290 to 1850 meters water depth in the Monterey Canyon axial channel during 6-month deployments (October 2015 - April 2017). Anderson sediment traps include a funnel and intervalometer (discs released at set time intervals) above a meter-long tube, which preserves fine-scale stratigraphy and chronology. Photographs, multi-sensor logs, CT scans, and grain size analyses reveal layers from multiple sediment density flow events that carried sediment ranging from fine sand to granules. More sediment accumulation from sediment density flows, and from between flows, occurred in the upper canyon ( 300 - 800 m water depth) compared to the lower canyon ( 1300 - 1850 m water depth). Sediment accumulated in the traps during sediment density flows is sandy and becomes finer down-canyon. In the lower canyon where sediment directly sampled from density flows are clearly distinguished within the trap tubes, sands have sharp basal contacts, normal grading, and muddy tops that exhibit late-stage pulses. In at least two of the sediment density flows, the simultaneous low velocity and high backscatter measured by the ADCPs suggest that the trap only captured the collapsing end of a sediment density flow event. In the upper canyon, accumulation between sediment density flow events is twice as fast compared to the lower canyon; it is characterized by sub-cm-scale layers in muddy sediment that appear to have accumulated with daily to sub-daily frequency, likely related to known internal tidal dynamics also measured in the experiment. The comprehensive scale of the Monterey Coordinated Canyon Experiment allows us to integrate sediment traps with ADCP instrument data and seafloor core samples, which provides important new data to constrain how, when, and what sediment is transported through submarine canyons and how this is archived in seafloor deposits.
Dynamic depositional and early diagenetic processes in a deep-water shelf setting, upper cretaceous Austin Chalk, North Texas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hovorka, S.D.; Nance, H.S.

1994-12-31

The Austin Chalk of north Texas was deposited on a deep-water shelf north of the Sea Marcos Platform during a worldwide Coniacian and Santonian sea-level highstand. Transgressive (lowermost lower Austin Chalk), highstand (uppermost lower Austin Chalk), and regressive (middle and upper Austin Chalk) phases of cyclic chalk and marl sedimentation are recognized in excavations and tunnels created in Ellis County for the Superconducting Super Collider provide new evidence of sediment transport during Austin Chalk deposition. During transgression, bottom currents syndepositionally reworked nannoplankton oozes, incising channels as much as 120 ft across and 8 ft deep. Weakly burrowed channel fills havingmore » preservation of fine lamination document rapid infilling. Channel fills are composed of pyritized and carbonized wood and Inoceramus lag deposits, pellets, echinoderm fragments, and globigerinid grainstones, and coccolith ooze. During maximum highstand, bottom reworking was suppressed. Detrital content of highstand marls is low (>20 percent); organic content is high (1.4 to 3.5 percent). Coccolith preservation is excellent because of minimal diagenetic alteration. Regression is marked by resumed channel cutting and storm-bed winnowing in the middle and upper Austin Chalk. Suppressed resistivity log response and recessive weathering characteristics of the middle Austin Chalk are not primarily related to depositional environment but rather to increased input of volcanic ash during the accumulation of this interval. Early stabilization of ash produced clay-coated microfabrics in sediments that are otherwise similar to the transgressive deposits.« less
Surface-water, ground-water, and sediment geochemistry of epizonal and shear-hosted mineral deposits in the Tintina Gold Province--arsenic and antimony distribution and mobility: Chapter G in Recent U.S. Geological Survey studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada--results of a 5-year project

USGS Publications Warehouse

Mueller, Seth H.; Goldfarb, Richard J.; Verplanck, Philip L.; Trainor, Thomas P.; Sanzolone, Richard F.; Adams, Monique; Gough, Larry P.; Day, Warren C.

2007-01-01

Epigenetic mineral deposits in the Tintina Gold Province are generally characterized by high concentrations of arsenic and antimony in their mineral assemblage. A total of 347 samples (ground water, surface water, and stream sediment) were collected to investigate the distribution and mobility of arsenic and antimony in the environment near known mineral deposits. Samples were collected from east to west at Keno Hill and Brewery Creek, Yukon, Canada; and Cleary Hill, True North, Scrafford Mine, Fairbanks, Ryan Lode, Stampede Creek, Slate Creek, and Donlin Creek, all in Alaska. Surface- and ground-water samples are all slightly acidic to near-neutral in pH (5-8), have a wide range in specific conductance (surface water 17-2,980 microsiemens per centimeter and ground water 170-2,940 microsiemens per centimeter), and show elevated dissolved arsenic and antimony concentrations (arsenic in surface water is less than 1 to 380 micrograms per liter and in ground water is less than 1 micrograms per liter to 1.5 milligrams per liter; antimony in surface water is less than 2 to 660 micrograms per liter and in ground water is less than 2 to 60 micrograms per liter). Stream sediments downstream from these deposits have high concentrations of arsenic and antimony (arsenic median is 1,670 parts per million, maximum is 10,000 parts per million; antimony median is 192 parts per million, maximum is 7,200 parts per million). The mobility of arsenic and antimony is controlled by the local redox environment, with arsenic being less mobile in oxidized surface waters relative to antimony, and arsenic more mobile in reduced ground water. These factors suggest that both antimony and arsenic may be useful pathfinder elements in water and sediment for targeting similar style deposits elsewhere in the Tintina Gold Province.
Transport and transportation pathways of hazardous chemicals from solid waste disposal.

PubMed Central

Van Hook, R I

1978-01-01

To evaluate the impact of hazardous chemicals in solid wastes on man and other organisms, it is necessary to have information about amounts of chemical present, extent of exposure, and chemical toxicity. This paper addresses the question of organism exposure by considering the major physical and biological transport pathways and the physicochemical and biochemical transformations that may occur in sediments, soils, and water. Disposal of solid wastes in both terrestrial and oceanic environments is considered. Atmospheric transport is considered for emissions from incineration of solid wastes and for wind resuspension of particulates from surface waste deposits. Solid wastes deposited in terrestrial environments are subject to leaching by surface and ground waters. Leachates may then be transported to other surface waters and drinking water aquifers through hydrologic transport. Leachates also interact with natural organic matter, clays, and microorganisms in soils and sediments. These interactions may render chemical constituents in leachates more or less mobile, possibly change chemical and physical forms, and alter their biological activity. Oceanic waste disposal practices result in migration through diffusion and ocean currents. Surface area-to-volume ratios play a major role in the initial distributions of chemicals in the aquatic environment. Sediments serve as major sources and sinks of chemical contaminants. Food chain transport in both aquatic and terrestrial environments results in the movement of hazardous chemicals from lower to higher positions in the food web. Bioconcentration is observed in both terrestrial and aquatic food chains with certain elements and synthetic organics. Bioconcentration factors tend to be higher for synthetic organics, and higher in aquatic than in terrestrial systems. Biodilution is not atypical in terrestrial environments. Synergistic and antagonistic actions are common occurrences among chemical contaminants and can be particularly important toxicity considerations in aquatic environments receiving runoff from several terrestrial sources. PMID:367772
Depositional and diagenetic processes of Qa Khanna playa, North Jordan basaltic plateau, Jordan

NASA Astrophysics Data System (ADS)

Howari, F. M.; Banat, K. M.; Abu-Salha, Y. A.

2010-09-01

The present study explored mineral occurrences and sediment characteristics of playas from northern Jordan and explained depositional and diagenetic processes as reflected from bulk chemistry and sedimentary structures. Mudcracks of different sizes and shape patterns, laminations, intersediment vesicles, and bioturbation pipes are the main sedimentary structures. Plagioclase, olivine, orthopyroxene, nepheline and other opaque minerals are all of detrital origin, and are derived from the basaltic bedrocks surrounding the studied playa. Evaporites are very rare; they are represented only by trace amounts of gypsum. The identified clay minerals in the clay fraction of the studied sediments, arranged according to their decreasing abundances are palygorskite, illite, kaolinite, smectite and chlorite. The elemental abundances were tied to clay, CaCO 3 and nearby igneous rocks. The type of clay minerals, the high pH values of the studied sediments, and the considerable incorporation of Mg and K in palygorskite and illite respectively, may strongly reflect a high evaporative and alkaline environment under arid to semi-arid conditions in an ephemeral lake of the Qa Khanna. Concentrations and distributions of both major and trace elements are essentially controlled by the clay mineralogy and the calcium carbonate content; Ca is mainly incorporated in the CaCO 3, which is either generated authigenically or by aeolian deposition. Fe and K are incorporated and fixed by illite under an evaporative and alkaline environment. Mg is incorporated in palygorskite while Mn is adsorbed on various clay minerals. Sr substitutes for Ca in the aeolian CaCO 3 and its presence in the studied sediments is independent of the prevailing conditions during the playa evolution. Rb substitutes for K in illite under the prevailing chemical conditions in the studied playa.
Anthropogenic Mercury Accumulation in Watersheds of the Northern Appalachian Mountains

NASA Astrophysics Data System (ADS)

Boyer, E. W.; Drohan, P. J.; Lawler, D.; Grimm, J.; Grant, C.; Eklof, K. J.; Bennett, J.; Naber, M. D.

2014-12-01

Atmospheric deposition of mercury (Hg) is a critical environmental stress that affects ecosystems and human health. Mercury emissions to the atmosphere from coal-fired power plants and other sources such as waste incineration can be deposited over large geographic areas to downwind landscapes in precipitation and in dry fallout. The northern Appalachian Mountains are downwind of major atmospheric mercury emissions sources. Some mercury reaches watersheds and streams, where it can accumulate in sediments and biota. Human exposure to mercury occurs primarily through fish consumption, and currently mercury fish eating advisories are in place for many of the streams and lakes in the region. Here, we explored mercury accumulation in forested landscapes - in air, soils, water, and biota. To quantify atmospheric mercury deposition, we measured both wet and dry mercury deposition at 10 forested locations, from which we present variation in mercury deposition and initial assessments of factors affecting the patterns. To quantify mercury accumulation in terrestrial environments, we measured soil mercury concentrations within and surrounding 12 vernal pools spanning various physiographic settings in the region. Given that vernal pools have large inputs of water via precipitation yet do not have any stream discharge outflow, they are likely spots within the forested landscape to accumulate pollutants that enter via wet atmospheric deposition. To quantify mercury accumulation in aquatic environments, we sampled mercury concentrations in streams draining 35 forested watersheds, spanning gradients of atmospheric deposition, climate and geology. Mercury concentrations were measured in stream water under base-flow conditions, in streambed sediments, aquatic mosses, and in fish tissues from brook trout. Results indicate that wet and dry atmospheric deposition is a primary source of mercury that is accumulating in watersheds of the Northern Appalachian Mountains.
Numerical simulation of streamflow distribution, sediment transport, and sediment deposition along Long Beach Creek in Northeast Missouri

USGS Publications Warehouse

Heimann, David C.

2001-01-01

This report presents the results of a study conducted by the U.S. Geological Survey in cooperation with the Missouri Department of Conservation to describe the hydrology, sediment transport, and sediment deposition along a selected reach of Long Branch Creek in Macon County, Missouri. The study was designed to investigate spatial and temporal characteristics of sediment deposition in a remnant forested riparian area and compare these factors by magnitude of discharge events both within and outside the measured range of flood magnitudes. The two-dimensional finite-element numerical models RMA2-WES and SED2D-WES were used in conjunction with measured data to simulate streamflow and sediment transport/deposition characteristics during 2-, 5-, 10-, and 25-year recurrence interval floods. Spatial analysis of simulated sediment deposition results indicated that mean deposition in oxbows and secondary channels exceeded that of the remaining floodplain areas during the 2-, 5-, 10-, and 25-year recurrence interval floods. The simulatedmass deposition per area for oxbows and secondary channels was 1.1 to 1.4 centimeters per square meter compared with 0.1 to 0.60 centimeters per square meter for the remaining floodplain. The temporal variability of total incremental floodplain deposition during a flood was found to be strongly tied to sediment inflowconcentrations. Most floodplain deposition, therefore, occurred at the beginning of the streamflow events and corresponded to peaks in sediment discharge. Simulated total sediment deposition in oxbows and secondary channels increased in the 2-year through 10-year floods and decreased in the 25- year flood while remaining floodplain deposition was highest for the 25-year flood. Despite increases in sediment inflows from the 2-year through 25-year floods, the retention ratio of sediments (the ratio of floodplain deposition to inflow load) was greatest for the 5-year flood and least for the 25-year flood. The decrease in retention ratio at greater flows is likely the result of higher velocities on the floodplain, resulting in higher bed shear stress, greater suspension time of deposited material, and greater sediment transport through the system. Simulated sediment deposition was most sensitive to sediment inflow concentrations and modification of floodplain roughness?factors that can be controlled through management practices. The increase in floodplain sediment deposition resulting from a simulated increase in vegetation density (increase in floodplain roughness from a Manning?s n of 0.11 to 0.12) was 142,000 kilograms, or 6.5 percent for a 10-year recurrence interval flood. This increase was comparable to total oxbow and secondary channel depositionmass in the simulations, but would result in amean increase in floodplain deposition thickness of only 0.025 centimeter. The hydrodynamic model results show the importance of the secondary channels and meander cutoff channels in this system because these areas quickly bring floodwaters and sediment to areas not close to the main channel. The meander cutoff channels in the simulation also effectively decrease flow and velocities in somemain channel sections thereby affecting sediment deposition in the vicinity of these features.
Genesis and continuity of quaternary sand and gravel in glacigenic sediment at a proposed low-level radioactive waste disposal site in east-central Illinois

USGS Publications Warehouse

Troost, K.G.; Curry, B. Brandon

1991-01-01

The Illinois Department of Nuclear Safety has characterized the Martinsville Alternative Site (MAS) for a proposed low-level radioactive waste disposal facility. The MAS is located in east-central Illinois approximately 1.6 km (1 mi) north of the city of Martinsville. Geologic investigation of the 5.5-km2 (1380-acre) site revealed a sequence of chiefly Illinoian glacigenic sediments from 6 to 60 m (20-200 ft) thick overlying two major bedrock valleys carved in Pennsylvanian strata. Relatively permeable buried units include basal, preglacial alluvium; a complex of intraglacial and subglacial sediment; englacial deposits; and supraglacial fluvial deposits. Postglacial alluvium underlies stream valleys on and adjacent to the site. In most areas, the buried sand units are confined by low-permeability till, lacustrine sediment, colluvium, and loess. The distribution and thickness of the most extensive and continuous buried sand units have been modified considerably by subglacial erosion, and their distributions have been influenced by the buried bedrock valleys. The most continuous of the various sand units were deposited as preglacial and postglacial alluvium and are the uppermost and lowermost stratigraphic units at the alternative site. Sand units that were deposited in englacial or ice-marginal environments are less continuous. Aquifer pumping tests, potentiometric head data, and groundwater geochemistry analyses indicate minimal interaction of groundwater across localized interconnections of the permeable units. ?? 1991 Springer-Verlag New York Inc.
Micromorphology in unconsolidated landslide sediments - investigating mass movement deposits at a different scale

NASA Astrophysics Data System (ADS)

Jaeger, Daniel; Menzies, John

2015-04-01

In order to reliably reconstruct a landslide event, its triggers, movements and the main factors of influence, a profound knowledge of the slide masses' inner architecture and their internal processes is of great importance. As van der Meer (1996) states, micromorphology permits a complete examination of particles, matrix and all components contained in unconsolidated sediments, as well as an insight into their internal arrangement. So far, thin sections and micromorphology are mainly used for studying marine, periglacial and glacial sediments (e.g. Maltman 1988; van der Meer 1993, Menzies 2000, van Fliet-Lanoe 2010, van der Meer & Menzies 2011). Comparatively little work has been carried out with a focus on landslides (e.g. Bertran & Texier 1999). Therefore, our work is a first attempt at investigating unconsolidated deposits of landslides in the low mountain areas of southern Germany using micromorphological tools. The objective was to observe sedimentary microstructures in order to gain an understanding of the sediments' internal movement, deformation etc. during a slide event. On the investigated landslides near Ebermannstadt (Franconian Alb), Gailnau (Frankenhöhe region) and Talheim (Swabian Alb) samples were taken from small pits or outcrops (depths between 50 cm - 300 cm below the surface) in the upper, central and lower part (foot) of the slide mass. The thin section analyses revealed several differences between the three environments and within the specific landslides themselves. Most prominently, several structures (e.g. water-escape-structures, flow-noses and rotational structures) indicate a crucial impact of water in all three slide masses. Furthermore, the thin sections showed heterogeneous compositions of different sediment materials and aggregates, presumably transported, mixed together and deformed during the slide movement. In Ebermannstadt and Talheim, several ductile and brittle deformation structures (rotational structures, marbled structures, fractures, crushed grains) were obvious in those deposits, proving a rather turbulent mass movement with pervasive pressure and stress and varying phases of deformation. In contrast, thin sections from Gailnau only provided very slight deformation structures, which lead to the assumption of a completely different and steadier type of movement with less pressure. Downslope, samples from all landslides showed accumulations of broken fragments with plasma filling out (parts of) the joints, while samples from the front areas (foot) revealed plasma-dominated, structureless, homogenized sediments with varying amounts of sand particles but with few fragments in it. This leads to the assumption of water-saturated plasma being squeezed out of the main accumulation body during its deposition, creating a flow-type movement in the foremost part of both landslides. The results significantly improved the understanding of the behavior of the landslides as several details in terms of processes and structures could be revealed. The micromorphological analyses also helped to validate presumptions gathered from geomorphological mapping and geophysical soundings. Although continuing research into the microstructure of landslide deposits is necessary, our investigations already illustrate the potential value of micromorphology in this environment. References - Bertran, P. & Texier, J.-P. (1999). Facies and microfacies of slope deposits. Catena 35: 99-121. - Maltman, A. J. (1988). The importance of shear zones in naturally deformed wet sediments. Tectonophysics 145: 163-175. - Menzies, J. (2000). Micromorphological analyses of microfabrics and microstructures, indicative of deformation processes. In: Maltman, A. J. Hubbard, B., Hambrey, M.J. (Eds.): Deformations of Glacial Materials. Geological Society, London, 245-258. - van der Meer, J. J. M. (1993). Microscopic evidence of subglacial deformation. Quaternary Science Reviews 12: 553-587. - van der Meer, J.J.M. (1996): Micromorphology. In: Menzies, J. (Ed.): Past Glacial Environments - Sediments, Forms and Techniques. Butterworth-Heinemann, Oxford, 335-356. - van der Meer, J. J. M. & Menzies, J. (2011). The micromorphology of unconsolidated sediments. Sedimentary Geology 238: 213-232. - van Fliet-Lanoe, B. (2010). Frost action. In: Stoops, G. Marcelino, V., Mees, F.: Interpretation of micromorphological features of soils and regoliths. Elsevier, Amsterdam, 81-108.
Sedimentary facies of the upper Cambrian (Furongian; Jiangshanian and Sunwaptan) Tunnel City Group, Upper Mississippi Valley: new insight on the old stormy debate

USGS Publications Warehouse

Eoff, Jennifer D.

2014-01-01

New data from detailed measured sections permit a comprehensive revision of the sedimentary facies of the Furongian (upper Cambrian; Jiangshanian and Sunwaptan stages) Tunnel City Group (Lone Rock Formation and Mazomanie Formation) of Wisconsin and Minnesota. Heterogeneous sandstones, comprising seven lithofacies along a depositional transect from shoreface to transitional-offshore environments, record sedimentation in a storm-dominated, shallow-marine epicontinental sea. The origin of glauconite in the Birkmose Member and Reno Member of the Lone Rock Formation was unclear, but its formation and preserved distribution are linked to inferred depositional energy rather than just net sedimentation rate. Flat-pebble conglomerate, abundant in lower Paleozoic strata, was associated with the formation of a condensed section during cratonic flooding. Hummocky cross-stratification was a valuable tool used to infer depositional settings and relative paleobathymetry, and the model describing formation of this bedform is expanded to address flow types dominant during its genesis, in particular the importance of an early unidirectional component of combined flow. The depositional model developed here for the Lone Rock Formation and Mazomanie Formation is broadly applicable to other strata common to the early Paleozoic that document sedimentation along flooded cratonic interiors or shallow shelves.
Sedimentation and occurrence and trends of selected nutrients, other chemical constituents, and cyanobacteria in bottom sediment, Clinton Lake, northeast Kansas, 1977-2009

USGS Publications Warehouse

Juracek, Kyle E.

2011-01-01

A combination of available bathymetric-survey information and bottom-sediment coring was used to investigate sedimentation and the occurrence of selected nutrients (total nitrogen and total phosphorus), organic and total carbon, 25 trace elements, cyanobacterial akinetes, and the radionuclide cesium-137 in the bottom sediment of Clinton Lake, northeast Kansas. The total estimated volume and mass of bottom sediment deposited from 1977 through 2009 in the conservation (multi-purpose) pool of the reservoir was 438 million cubic feet and 18 billion pounds, respectively. The estimated sediment volume occupied about 8 percent of the conservation-pool, water-storage capacity of the reservoir. Sedimentation in the conservation pool has occurred about 70 percent faster than originally projected at the time the reservoir was completed. Water-storage capacity in the conservation pool has been lost to sedimentation at a rate of about 0.25 percent annually. Mean annual net sediment deposition since 1977 in the conservation pool of the reservoir was estimated to be 563 million pounds per year. Mean annual net sediment yield from the Clinton Lake Basin was estimated to be 1.5 million pounds per square mile per year. Typically, the bottom sediment sampled in Clinton Lake was at least 99 percent silt and clay. The mean annual net loads of total nitrogen and total phosphorus deposited in the bottom sediment of Clinton Lake were estimated to be 1.29 million pounds per year and 556,000 pounds per year, respectively. The estimated mean annual net yields of total nitrogen and total phosphorus from the Clinton Lake Basin were 3,510 pounds per square mile per year and 1,510 pounds per square mile per year, respectively. Throughout the history of Clinton Lake, total nitrogen concentrations in the deposited sediment generally were uniform and indicated consistent inputs to the reservoir over time. Likewise, total phosphorus concentrations in the deposited sediment generally were uniform. Although, for two of three coring sites, a possible positive trend in phosphorus deposition was indicated. The Wakarusa River possibly was a larger contributor of nitrogen and phosphorus to Clinton Lake than was Rock Creek. As a principal limiting factor for primary production in most freshwater environments, phosphorus is of particular importance because increased inputs can contribute to accelerated reservoir eutrophication and the production of algal toxins and taste-and-odor compounds. Trace-element concentrations in the bottom sediment of Clinton Lake generally were uniform over time. As is typical for eastern Kansas reservoirs, arsenic, chromium, and nickel concentrations typically exceeded the threshold-effects guidelines, which represent the concentrations above which toxic biological effects occasionally occur. Zinc concentrations frequently exceeded the threshold-effects guideline. Trace-element concentrations did not exceed the probable-effects guidelines (available for eight trace elements), which represent the concentrations above which toxic biological effects usually or frequently occur. Cyanobacterial akinetes (cyanobacteria resting stage) in the bottom sediment of Clinton Lake, combined with historical water-quality data on chlorophyll-a and total phosphorus concentrations, indicated that the reservoir likely has been eutrophic throughout most of its history. A statistically significant increase in cyanobacterial akinetes in the bottom sediment indicated that Clinton Lake may have become more eutrophic over the life of the reservoir. The increase in cyanobacterial akinetes may, in part, be related to a possible increase in total phosphorus concentrations.
Gold and trace element zonation in pyrite using a laser imaging technique: Implications for the timing of gold in orogenic and carlin-style sediment-hosted deposits

USGS Publications Warehouse

Large, R.R.; Danyushevsky, L.; Hollit, C.; Maslennikov, V.; Meffre, S.; Gilbert, S.; Bull, S.; Scott, R.; Emsbo, P.; Thomas, H.; Singh, B.; Foster, J.

2009-01-01

Laser ablation ICP-MS imaging of gold and other trace elements in pyrite from four different sediment- hosted gold-arsenic deposits has revealed two distinct episodes of gold enrichment in each deposit: an early synsedimentary stage where invisible gold is concentrated in arsenian diagenetic pyrite along with other trace elements, in particular, As, Ni, Pb, Zn, Ag, Mo, Te, V, and Se; and a later hydrothermal stage where gold forms as either free gold grains in cracks in overgrowth metamorphic and/or hydrothermal pyrite or as narrow gold- arsenic rims on the outermost parts of the overgrowth hydrothermal pyrite. Compared to the diagenetic pyrites, the hydrothermal pyrites are commonly depleted in Ni, V, Zn, Pb, and Ag with cyclic zones of Co, Ni, and As concentration. The outermost hydrothermal pyrite rims are either As-Au rich, as in moderate- to high- grade deposits such as Carlin and Bendigo, or Co-Ni rich and As-Au poor as in moderate- to low-grade deposits such as Sukhoi Log and Spanish Mountain. The early enrichment of gold in arsenic-bearing syngenetic to diagenetic pyrite, within black shale facies of sedimentary basins, is proposed as a critical requirement for the later development of Carlin-style and orogenic gold deposits in sedimentary environments. The best grade sediment-hosted deposits appear to have the gold climax event, toward the final stages of deformation-related hydrothermal pyrite growth and fluid flow. ?? 2009 Society of Economic Geologists, Inc.
The Messinian erosional surface and early Pliocene reflooding in the Alboran Sea: New insights from the Boudinar basin, Morocco

NASA Astrophysics Data System (ADS)

Cornée, Jean-Jacques; Münch, Philippe; Achalhi, Mohammed; Merzeraud, Gilles; Azdimousa, Ali; Quillévéré, Frédéric; Melinte-Dobrinescu, Mihaela; Chaix, Christian; Moussa, Abdelkhalak Ben; Lofi, Johanna; Séranne, Michel; Moissette, Pierre

2016-03-01

New investigations in the Neogene Boudinar basin (Morocco) provide new information about the Messinian Salinity Crisis (MSC) and Zanclean reflooding in the southern part of the Alboran realm (westernmost Mediterranean). Based on a new field, sedimentological and palaeontological analyses, the age and the geometry of both the Messinian erosional surface (MES) and the overlying deposits have been determined. The MES is of late Messinian age and was emplaced in subaerial settings. In the Boudinar basin, a maximum of 200 m of Miocene sediments was eroded, including late Messinian gypsum blocks. The original geometry of the MES is preserved only when it is overlain by late Messinian continental deposits, conglomeratic alluvial fans or lacustrine marly sediments. These sediments are interpreted as indicators of the sea-level fall during the MSC. Elsewhere in the basin, the contact between late Messinian and early Pliocene deposits is a low-angle dipping, smooth surface that corresponds to the early Pliocene transgression surface that subsequently re-shaped the regressive MES. The early Pliocene deposits are characterized by: (i) their onlap onto either the basement of the Rif chain or the late Miocene deposits; (ii) lagoonal deposits at the base to offshore marls and sands at the top (earliest Pliocene; 5.33-5.04 Ma interval; foraminifer zone PL1); (iii) marine recovery occurring in the 5.32-5.26 Ma interval; and (iv) the change from lagoonal to offshore environments occurring within deposits tens of metres thick. This information indicates that at least the end of the reflooding period was progressive, not catastrophic as previously thought.

Landscape-Scale Analysis of Wetland Sediment Deposition from Four Tropical Cyclone Events

PubMed Central

Tweel, Andrew W.; Turner, R. Eugene

2012-01-01

Hurricanes Katrina, Rita, Gustav, and Ike deposited large quantities of sediment on coastal wetlands after making landfall in the northern Gulf of Mexico. We sampled sediments deposited on the wetland surface throughout the entire Louisiana and Texas depositional surfaces of Hurricanes Katrina, Rita, Gustav, and the Louisiana portion of Hurricane Ike. We used spatial interpolation to model the total amount and spatial distribution of inorganic sediment deposition from each storm. The sediment deposition on coastal wetlands was an estimated 68, 48, and 21 million metric tons from Hurricanes Katrina, Rita, and Gustav, respectively. The spatial distribution decreased in a similar manner with distance from the coast for all hurricanes, but the relationship with distance from the storm track was more variable between events. The southeast-facing Breton Sound estuary had significant storm-derived sediment deposition west of the storm track, whereas sediment deposition along the south-facing coastline occurred primarily east of the storm track. Sediment organic content, bulk density, and grain size also decreased significantly with distance from the coast, but were also more variable with respect to distance from the track. On average, eighty percent of the mineral deposition occurred within 20 km from the coast, and 58% was within 50 km of the track. These results highlight an important link between tropical cyclone events and coastal wetland sedimentation, and are useful in identifying a more complete sediment budget for coastal wetland soils. PMID:23185635
Photosynthetic microbial mats in the 3,416-Myr-old ocean.

PubMed

Tice, Michael M; Lowe, Donald R

2004-09-30

Recent re-evaluations of the geological record of the earliest life on Earth have led to the suggestion that some of the oldest putative microfossils and carbonaceous matter were formed through abiotic hydrothermal processes. Similarly, many early Archaean (more than 3,400-Myr-old) cherts have been reinterpreted as hydrothermal deposits rather than products of normal marine sedimentary processes. Here we present the results of a field, petrographic and geochemical study testing these hypotheses for the 3,416-Myr-old Buck Reef Chert, South Africa. From sedimentary structures and distributions of sand and mud, we infer that deposition occurred in normal open shallow to deep marine environments. The siderite enrichment that we observe in deep-water sediments is consistent with a stratified early ocean. We show that most carbonaceous matter was formed by photosynthetic mats within the euphotic zone and distributed as detrital matter by waves and currents to surrounding environments. We find no evidence that hydrothermal processes had any direct role in the deposition of either the carbonaceous matter or the enclosing sediments. Instead, we conclude that photosynthetic organisms had evolved and were living in a stratified ocean supersaturated in dissolved silica 3,416 Myr ago.
Photosynthetic microbial mats in the 3,416-Myr-old ocean

NASA Astrophysics Data System (ADS)

Tice, Michael M.; Lowe, Donald R.

2004-09-01

Recent re-evaluations of the geological record of the earliest life on Earth have led to the suggestion that some of the oldest putative microfossils and carbonaceous matter were formed through abiotic hydrothermal processes. Similarly, many early Archaean (more than 3,400-Myr-old) cherts have been reinterpreted as hydrothermal deposits rather than products of normal marine sedimentary processes. Here we present the results of a field, petrographic and geochemical study testing these hypotheses for the 3,416-Myr-old Buck Reef Chert, South Africa. From sedimentary structures and distributions of sand and mud, we infer that deposition occurred in normal open shallow to deep marine environments. The siderite enrichment that we observe in deep-water sediments is consistent with a stratified early ocean. We show that most carbonaceous matter was formed by photosynthetic mats within the euphotic zone and distributed as detrital matter by waves and currents to surrounding environments. We find no evidence that hydrothermal processes had any direct role in the deposition of either the carbonaceous matter or the enclosing sediments. Instead, we conclude that photosynthetic organisms had evolved and were living in a stratified ocean supersaturated in dissolved silica 3,416Myr ago.
Extended Kd distributions for freshwater environment.

PubMed

Boyer, Patrick; Wells, Claire; Howard, Brenda

2018-06-18

Many of the freshwater K d values required for quantifying radionuclide transfer in the environment (e.g. ERICA Tool, Symbiose modelling platform) are either poorly reported in the literature or not available. To partially address this deficiency, Working Group 4 of the IAEA program MODARIA (2012-2015) has completed an update of the freshwater K d databases and K d distributions given in TRS 472 (IAEA, 2010). Over 2300 new values for 27 new elements were added to the dataset and 270 new K d values were added for the 25 elements already included in TRS 472 (IAEA, 2010). For 49 chemical elements, the K d values have been classified according to three solid-liquid exchange conditions (adsorption, desorption and field) as was previously carried out in TRS 472. Additionally, the K d values were classified into two environmental components (suspended and deposited sediments). Each combination (radionuclide x component x condition) was associated with log-normal distributions when there was at least ten K d values in the dataset and to a geometric mean when there was less than ten values. The enhanced K d dataset shows that K d values for suspended sediments are significantly higher than for deposited sediments and that the variability of K d distributions are higher for deposited than for suspended sediments. For suspended sediments in field conditions, the variability of K d distributions can be significantly reduced as a function of the suspended load that explains more than 50% of the variability of the K d datasets of U, Si, Mo, Pb, S, Se, Cd, Ca, B, K, Ra and Po. The distinction between adsorption and desorption conditions is justified for deterministic calculations because the geometric means are systematically greater in desorption conditions. Conversely, this distinction is less relevant for probabilistic calculations due to systematic overlapping between the K d distributions of these two conditions. Copyright © 2018. Published by Elsevier Ltd.
Magma-sediment interactions in the Limagne trench (Massif Central, France): distinction between phreatomagmatic and stricto-sensu peperitic processes

NASA Astrophysics Data System (ADS)

Leibrandt, Sebastien; Bénard, Antoine; Brigaud, Benjamin

2013-04-01

Magma-sediment interactions provide important information to reconstruct paleo-eruption dynamics in hydromagmatic environments. The lithofacies resulting from these interactions are usually named "peperite" as first described on rocks from the Limagne area (Massif Central, France). Nevertheless, it is nowadays admitted that both fluidal and blocky peperite formation refers to mostly non-explosive, hydrodynamic disintegration of magma intruding and mingling with unconsolidated wet sediments (e.g. Skilling et al., 2002). Here we observe magma-limestones interactions (i.e. explosive and non-explosive) in phreatomagmatic vent-filling deposits, from outcrop scale to thin-section observations, with polarized, electronic and cathodoluminescence microscopy. Our field study is based on the comparison of selected localities from the Limagne trench that are mapped as peperites but which apparently only record phreatomagmatic processes leading to the deposit of sediment-rich maar diatreme material. Microscopic characterization mainly focuses on juvenile clasts and host carbonate sediment textural relationships, when mixed together and dispersed in the maar diatreme material. We deduce the mechanisms and timing of interaction of several generations of magmatic clasts with host pristine carbonate sediments or pre-existing volcaniclastic breccia. The extent of mixing and dispersion of the magmatic clasts is assessed in relation with the emplacement dynamics, magmatic cooling rates and host sediment properties. In this regard, cathodoluminescence microscopy allows us to deduce the properties of sediment before, during and after interaction, which also helps to reconstruct the paleo-environmental frame. As a first outcome of this study, we distinguish (1) early syn-eruptive fragmented material during phreatomagmatic magma-sediment interaction from (2) secondary, non-explosive, magmatic intrusions in poorly consolidated and water-saturated vent-filling deposits. This second process can solely give birth to the stricto-sensu fluidal to blocky peperite microtexture, which we clearly distinguish for the first time in the Limagne area. A second outcome emerges thanks to the several approaches we use for microscopic characterization, which possibly reveal high-grade, non-explosive mingling of liquefied sediment with magma at the sub-millimetre scale. These observations provide new insights into peperite formation processes in carbonate sediments, when both considering experiments (e.g. Zimanowski and Büttner, 2002) and worldwide field observations in contrasting environments (e.g. McClintock & White, 2002). McClintock, M.K., White, J.D.L., 2002. Granulation of weak rock as a precursor to peperite formation: coal peperite, Coombs Hill, Antartica. Journal of Volcanology and Geothermal Research, 114, 205-217. Skilling, I.P., White, J.D.L., McPhie, J., 2002. Peperite: a review of magma-sediment mingling. Journal of Volcanology and Geothermal Research, 114, 1-17. Zimanowski, B., Büttner, R., 2002. Dynamic mingling of magma and liquefied sediments. Journal of Volcanology and Geothermal Research, 114, 37-44.
Lithology and chemical analyses of core and cuttings from USGS drill hole near Gold Acres, Lander County, Nevada

USGS Publications Warehouse

Wrucke, Chester T.

1975-01-01

Upper Paleozoic to Mesozoic eolian blanket sandstones of the Colorado Plateau and the Rocky Mountains of Colorado and southern Wyoming are texturally complex. As petroleum reservoirs they commonly have poor performance histories. They contain the sediments of a depositional system comprised of three closely associated depositional subenvironments: dune, interdune, and extradune. Sediments of each subenvironment have different textural properties which resulted from different depositional processes. Dune sediments are usually more porous and permeable than interdune or extradune sediments and may be better quality reservoirs than interdune or extradune sediments. Interdune sediments are here restricted to those nondune sediments deposited in the relatively flat areas between dunes. Extradune sediments (a new term) include all deposits adjacent to a dune field and are mainly subaqueous deposits. Dune sediments may be enveloped by extradune sediments as the depositional system evolves resulting in a texturally inhomogeneous reservoir having poor fluid migration properties. This model of textural inhomogeneity in eolian blanket sandstones. was applied to the Weber (Tensleep) Sandstone in Brady, Wertz, and Lost Soldier fields, Sweetwater County, Wyoming. Data were obtained from both outcrop and subsurface and included environmental interpretation, textural analysis, and plotting of the distribution of depositional subenvironments. As predicted from the model, the texture of dune sediments in Brady field differed markedly from interdune and extradune sediments. The predicted geometric distribution of subenvironments was confirmed in Lost Soldier and Wertz fields. However, secondary cementation and fracturing there has obscured the original porosity and permeability contrasts. The porosity and permeability distribution, a characteristic depending partly on depositional processes, could impede fluid migration in the reservoir and significantly reduce recovery of hydrocarbons.
On the Isolation of Halophilic Microorganisms from Salt Deposits of Great Geological Age

NASA Technical Reports Server (NTRS)

Stan-Lotter, Helga; Denner, Ewald; Orans, Robin (Editor)

1993-01-01

From salt sediments of Triassic or Permian ace from various locations in the world halophilic microorganisms were isolated. Molecular characteristics of several of the isolates suggested they belong to the archaebacteriae. One group appears to represent novel strains; several properties or one such isolate, strain BIp, are described here. The existence of viable microorganisms in ancient sediments would have great implications with respect to our notions on evolution, the search for life in extraterrestrial environments and the long- term survival of functional biological structures. Of crucial importance is thus the question if these microorganisms existed in the salt since the time of deposition or invaded at some later date. Some suggestions to address these issues experimentally are discussed.
On the isolation of halophilic microorganisms from salt deposits of great geological age

NASA Technical Reports Server (NTRS)

Stan-Lotter, Helga; Denner, Ewald

1993-01-01

From salt sediments of Triassic or Permian age from various locations in the world halophilic microorganisms were isolated. Molecular characteristics of several of the isolates suggested they belong to the archaebacteria. One group appears to represent novel strains; several properties of one such isolate, strain BIp, are described here. The existence of viable microorganisms in ancient sediment would have great implications with respect to our notions on evolution, the research for life in extraterrestrial environments, and the longterm survival of functional biological structures. Of crucial importance is thus the question if these microorganisms existed in the salt since the time of deposition or invaded at some later date. Some suggestions to address these issues experimentally are discussed.
Geoligical outline of the Lower Cretaceous Bahia Supergroup, Brazil

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fonseca, J.I.

1966-01-01

The report area encompasses about 41,200 sq km covered by over 6,000 m of Lower Cretaceous sediments deposited in fresh to brackish water environment. These sediments, the Bahia Supergroup, represent most of the sedimentary section of the Almada, Reconcavo, Tucano and Jatoba basins. The Reconcavo basin is a half-graben filled with Lower Cretaceous rocks which tilt regionally to the SE. The sediments deposited in this basin were distorted by 2 major periods of deformation. As the result of the application of these systems of tensional forces, the sediments were broken into a complicated system of normal faults. Most of themore » oil production in Brazil, about 91,000 bpd, comes from the Reconcavo basin. During a great part of the Early Cretaceous the Reconcavo and Almada basins probably were connected with the Alagoas-Sergipe basin by the continental shelf. The continental drift theory may explain the presence of these fresh water sediments in the coast line and in the continental shelf of the Bahia and Alagoas-Sergipe states. This offshore area is very prospective and may contribute, in the future, with substantial quantities of hydrocarbons. (14 refs.)« less
Environmental mobility of (110m)Ag: lessons learnt from Fukushima accident (Japan) and potential use for tracking the dispersion of contamination within coastal catchments.

PubMed

Lepage, Hugo; Evrard, Olivier; Onda, Yuichi; Patin, Jeremy; Chartin, Caroline; Lefèvre, Irène; Bonté, Philippe; Ayrault, Sophie

2014-04-01

Silver-110 metastable ((110m)Ag) has been far less investigated than other anthropogenic radionuclides, although it has the potential to accumulate in plants and animal tissues. It is continuously produced by nuclear power plants in normal conditions, but emitted in much larger quantities in accidental conditions facilitating its detection, which allows the investigation of its behaviour in the environment. We analysed (110m)Ag in soil and river drape sediment (i.e., mud drapes deposited on channel-bed sand) collected within coastal catchments contaminated in Fukushima Prefecture (Japan) after the Fukushima Dai-ichi Nuclear Power Plant accident that occurred on 11 March 2011. Several field experiments were conducted to document radiosilver behaviour in the terrestrial environment, with a systematic comparison to the more documented radiocesium behaviour. Results show a similar and low mobility for both elements in soils and a strong affinity with the clay fraction. Measurements conducted on sediment sequences accumulated in reservoirs tend to confirm a comparable deposition of those radionuclides even after their redistribution due to erosion and deposition processes. Therefore, as the (110m)Ag:(137)Cs initial activity ratio varied in soils across the area, we justified the relevance of using this tool to track the dispersion of contaminated sediment from the main inland radioactive pollution plume generated by FDNPP accident. Copyright © 2014 Elsevier Ltd. All rights reserved.
Miocene tectono-stratigraphic history of La Mision basin, northwestern Baja California: implications for early tectonic development of southern California continental borderland

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ashby, J.R.; Minch, J.

1988-03-01

The middle Miocene La Mision basin in northwestern Baja California, Mexico, provides a rare opportunity to study an onshore portion of the southern California continental borderland. Stratigraphy, geometry of dispersal, and a variety of lithotypes within the volcanic and volcaniclastic sediments of the Rosarito Beach Formation provide clues to the nature of early tectonic evolution of this area during the Miocene. The elongated, trough-shaped La Mision basin formed in response to peninsular basement uplifts and the formation of volcanic highlands west of the present coastline. Lithologies and depositional environments represented within the basin sediments include: subaerial basalt flows and airfallmore » tuffs, submarine muddy- and sandy-matrix mudflow breccias, lapilli tuffs, crystal tuffs, tuffaceous sandstones,d diatomites, and conglomerates. The environments of deposition range from fluvatile to intertidal to shallow marine. Early basin infilling is characterized by sediments and basalts, with a western source terrane, that were deposited against the faulted seacliffs. progressive infilling against the seacliff resulted in the formation of an extensive eastward-sloping basaltic platform extending eastward to the foothill coastal belt of the Peninsular Ranges. Marine transgression and subsequent regression are recorded by diverse marine volcaniclastic lithologies. Abundant fossils, K-Ar dates, and paleomagnetic data obtained from the La Mision basin allow precise correlation with other areas in the continental borderland and provide conclusive evidence that this block of the borderland was formed and in its present position by 16-14 Ma.« less
Impacts of shore expansion and catchment characteristics on lacustrine thermokarst records in permafrost lowlands, Alaska Arctic Coastal Plain

USGS Publications Warehouse

Lenz, Josefine; Jones, Benjamin M.; Wetterich, Sebastian; Tjallingii, Rik; Fritz, Michael; Arp, Christopher D.; Rudaya, Natalia; Grosse, Guido

2016-01-01

Arctic lowland landscapes have been modified by thermokarst lake processes throughout the Holocene. Thermokarst lakes form as a result of ice-rich permafrost degradation, and they may expand over time through thermal and mechanical shoreline erosion. We studied proximal and distal sedimentary records from a thermokarst lake located on the Arctic Coastal Plain of northern Alaska to reconstruct the impact of catchment dynamics and morphology on the lacustrine depositional environment and to quantify carbon accumulation in thermokarst lake sediments. Short cores were collected for analysis of pollen, sedimentological, and geochemical proxies. Radiocarbon and 210Pb/137Cs dating, as well as extrapolation of measured historic lake expansion rates, were applied to estimate a minimum lake age of ~1400 calendar years BP. The pollen record is in agreement with the young lake age as it does not include evidence of the “alder high” that occurred in the region ~4000 cal yr BP. The lake most likely initiated from a remnant pond in a drained thermokarst lake basin (DTLB) and deepened rapidly as evidenced by accumulation of laminated sediments. Increasing oxygenation of the water column as shown by higher Fe/Ti and Fe/S ratios in the sediment indicate shifts in ice regime with increasing water depth. More recently, the sediment source changed as the thermokarst lake expanded through lateral permafrost degradation, alternating from redeposited DTLB sediments, to increased amounts of sediment from eroding, older upland deposits, followed by a more balanced combination of both DTLB and upland sources. The characterizing shifts in sediment sources and depositional regimes in expanding thermokarst lakes were, therefore, archived in the thermokarst lake sedimentary record. This study also highlights the potential for Arctic lakes to recycle old carbon from thawing permafrost and thermokarst processes.
Factors influencing organic carbon preservation in marine sediments

NASA Technical Reports Server (NTRS)

Canfield, D. E.

1994-01-01

The organic matter that escapes decomposition is buried and preserved in marine sediments, with much debate as to whether the amount depends on bottom-water O2 concentration. One group argues that decomposition is more efficient with O2, and hence, organic carbon will be preferentially oxidized in its presence, and preserved in its absence. Another group argues that the kinetics of organic matter decomposition are similar in the presence and absence of O2, and there should be no influence of O2 on preservation. A compilation of carbon preservation shows that both groups are right, depending on the circumstances of deposition. At high rates of deposition, such as near continental margins, little difference in preservation is found with varying bottom-water O2. It is important that most carbon in these sediments decomposes by anaerobic pathways regardless of bottom-water O2. Hence, little influence of bottom-water O2 on preservation would, in fact, be expected. As sedimentation rate drops, sediments deposited under oxygenated bottom water become progressively more aerobic, while euxinic sediments remain anaerobic. Under these circumstances, the relative efficiencies of aerobic and anaerobic decomposition could affect preservation. Indeed, enhanced preservation is observed in low-O2 and euxinic environments. To explore in detail the factors contributing to this enhanced carbon preservation, aspects of the biochemistries of the aerobic and anaerobic process are reviewed. Other potential influences on preservation are also explored. Finally, a new model for organic carbon decomposition, the "pseudo-G" model, is developed. This model couples the degradation of refractory organic matter to the overall metabolic activity of the sediment, and has consequences for carbon preservation due to the mixing together of labile and refractory organic matter by bioturbation.
Origin and emplacement of impactites in the Chesapeake Bay impact structure, Virginia, USA

USGS Publications Warehouse

Horton, J. Wright; Gohn, G.S.; Powars, D.S.; Edwards, L.E.

2007-01-01

The late Eocene Chesapeake Bay impact structure, located on the Atlantic margin of Virginia, may be Earth's best-preserved large impact structure formed in a shallow marine, siliciclastic, continental-shelf environment. It has the form of an inverted sombrero in which a central crater ???40 km in diameter is surrounded by a shallower brim, the annular trough, that extends the diameter to ???85 km. The annular trough is interpreted to have formed largely by the collapse and mobilization of weak sediments. Crystalline-clast suevite, found only in the central crater, contains clasts and blocks of shocked gneiss that likely were derived from the fragmentation of the central-uplift basement. The suevite and entrained megablocks are interpreted to have formed from impact-melt particles and crystalline-rock debris that never left the central crater, rather than as a fallback deposit. Impact-modified sediments in the annular trough include megablocks of Cretaceous nonmarine sediment disrupted by faults, fluidized sands, fractured clays, and mixed-sediment intercalations. These impact-modified sediments could have formed by a combination of processes, including ejection into and mixing of sediments in the water column, rarefaction-induced fragmentation and clastic injection, liquefaction and fluidization of sand in response to acoustic-wave vibrations, gravitational collapse, and inward lateral spreading. The Exmore beds, which blanket the entire crater and nearby areas, consist of a lower diamicton member overlain by an upper stratified member. They are interpreted as unstratified ocean-resurge deposits, having depositional cycles that may represent stages of inward resurge or outward anti-resurge flow, overlain by stratified fallout of suspended sediment from the water column. ?? 2008 The Geological Society of America. All rights reserved.
High sedimentation rates in the Early Triassic after latest Permian mass extinction: Carbonate production is main factor in non-Arctic regions

NASA Astrophysics Data System (ADS)

Horacek, Micha; Brandner, Rainer

2016-04-01

A substantial change in sedimentation rates towards higher values has been documented from the Late Permian to the Lower Triassic. Although it is assumed and also has been shown that the deposition of siliciclastic material increased in the Lower Triassic due to stronger erosion because of loss of land cover and increased chemical and physical weathering with extreme climate warming, the main sediment production occurred by marine carbonate production. Still, carbonate production might have been significantly influenced by weathering and erosion in the hinterland, as the transport of dust by storms into the ocean water probably was a main nutrient source for microbial carbonate producers, because "normal" nutrient supply by ocean circulation, i. e. upwelling was strongly reduced due to the elevated temperatures resulting in water-column stratification . Sediment accumulation was also clearly influenced by the paleo-geographic and latitudinal position, with lower carbonate production and sedimentation rates in moderate latitudes. The existence of a "boundary clay" and microbial carbonate mounds and layers in the immediate aftermath of the latest Permian mass extinction points towards a development from a short-timed acid ocean water - resulting in a carbonate production gap and the deposition of the boundary clay towards the deposition of the microbial mounds and layers due to the microbial production of micro-environments with higher alkalinity allowing the production of carbonate. After the return of the ocean water to normal alkalinity planktic production of carbonate resulted in a very high sedimentation rate, especially taking into account the absence of carbonate producing eukaryotic algae and animals.
Sedimentary processes on the Storfjorden trough-mouth fan during last deglaciation phase: the role of subglacial meltwater plumes on continental margin sedimentation

NASA Astrophysics Data System (ADS)

Lucchi, Renata G.; Camerlenghi, Angelo; Colmenero-Hidalgo, Elena; Sierro, Francisco J.; Bárcena, Maria Angeles; Flores, José-Abel; Urgeles, Roger; Macrı, Patrizia; Sagnotti, Leonardo; Caburlotto, Andrea

2010-05-01

The continental margin of the Southern Storfjorden trough-mouth fan was investigated within the SVAIS project (BIO Hesperides cruise, August 2007) as a Spanish contribution to IPY Activity N. 367 (Neogene ice streams and sedimentary processes on high- latitude continental margins - NICE STREAMS). The objectives were to investigate the glacially-dominated late-Neogene-Quaternary sedimentary architecture of the NW Barents Sea continental margin and reconstruct its sedimentary system in response to natural climate change. The paleo-ice streams in Storfjorden had a small catchment area draining ice from the southern Spitsbergen and Bear Island. The short distance from the ice source to the calving front produced a short residence time of ice, and therefore a rapid response to climatic changes. Here ground truthing recovered the last few thousands years sedimentary sequence thought to represent last deglaciation phase. Detailed palaeostratigraphic investigations together with paleomagnetic and rock magnetic analyses and AMS dating define the constraints for high-resolution inter-core correlation and dating. Most of the cores contain at the base gravity-mass deposits including debris flows and over-consolidated glacigenic diamicton. Mass deposits are overlain by an oxidized interval originated at the release and sink of fresh, cold and oxygenated melt-waters at the inception of the deglaciation phase. On the upper slope the oxidized interval is overlain by several meters of finely-stratified sediments composed of sandy-silt layers cyclically recurring within finer-grained laminated silty-clay sediments. Textural and compositional analyses suggest preferential deposition by settling from meltwater sediment-laden plumes (plumites) occurred during deglaciation with coarser layers representing episodes of subglacial meltwater discharge (glacial hyperpycnal flows) accompanying the ice streams retreat. The laminated sequence is truncated at uppermost part by a more recent gravity-mass deposit that possibly removed part of the younger sequence. In the deeper part of the slope the plumites consist of crudely laminated, terrigenous and almost barren sediments. Here the sedimentary sequence is topped by intensively bioturbated, bioclasts-bearing silty-clays representing the most recent interglacial sedimentation. On the continental shelf, the upper sedimentary sequence contains dispersed cm-thick bivalve's shells suggesting an oxygenated and nutrient-rich environment (interglacial) overlaying an interval of terrigenous, barren sediments (deglaciation). Here the short core's length suggests the presence of stiffer/coarser sediments at the base that could not be sampled. The seismic stratigraphy indicates that the slope is formed by alternating debris flow deposits and layered sediments corresponding into our cores to the fast-deposited, low-density, terrigenous plumites. Bathymetric and seismic data revealed the presence of widespread submarine landslides restricted to the southernmost part of Storfjorden continental slope. Geotechnical investigation are in progress in order to understand if such layered deposits can act on the slope as a possible preferential weak horizon favoring sediment failure.
The Examination of Exposures of Pleistocene Sediments in the Field: A Self-Paced Exercise.

ERIC Educational Resources Information Center

Keene, Peter

1982-01-01

Describes a self-paced field exercise which takes college geomorphology students through a step-by-step study of the origin and environment of pleistocene deposits. The exercise could also be adapted for use at the secondary level. (AM)
Depositional environment and sedimentary of the basinal sediments in the Eibiswalder Bucht (Radl Formation and Lower Eibiswald Beds), Miocene Western Styrian Basin, Austria

NASA Astrophysics Data System (ADS)

Stingl, K.

1994-12-01

The Eibiswald Bucht is a small subbasin of the Western Styrian Basin exposing sediments of Lower Miocene age. In the past the entire sequence exposed in the Eibiswalder Bucht has been interpreted as being of fluvial/lacustrine origin; here, results are presented of detailed sedimentological investigations that lead to a revision of this concept. The lowermost siliciclastic sedimentary unit of the Eibiswalder Bucht sequence is the Radl Formation. It is overlain by the Eibiswald Beds, which are subdivided into the Lower, Middle and Upper Eibiswald Beds. The Radl Formation and the Lower Eibiswald Beds are interpreted as a fan delta complex deposited along NNW-SSE striking faults. Based on the sedimentary facies this fan delta can be subdivided into a subaerial alluvial fan facies group, a proximal delta facies group and a distal delta/prodelta facies group. The Radl Formation comprises the alluvial fan and proximal delta facies groups, the Lower Eibiswald Beds the distal delta/prodelta facies group. The alluvial fan and the proximal delta consist of diverse deposits of gravelly flows. The distal delta/prodelta consists of wave-reworked, bioturbated, low density turbidites intercalated with minor gravelly mass flows. The prodelta can be regarded as as the basin facies of the small and shallow Eibiswalder Bucht, where marine conditions prevailed. The basin was probably in part connected with the Eastern Styrian Basin, the contemporary depositional environment of the Styrian Schlier (mainly turbiditic marine offshore sediments in the Eastern Styrian Basin). Analysis of the clast composition, in conjunction with the paleotransport direction of the coarse delta mass flows of the Radl Formation, shows that the source rocks were exclusively crystalline rocks ranging from greenschists to eclogites.
Evaluation of Deposited Sediment and Macroinvertebrate Metrics Used to Quantify Biological Response to Excessive Sedimentation in Agricultural Streams

NASA Astrophysics Data System (ADS)

Sutherland, Andrew B.; Culp, Joseph M.; Benoy, Glenn A.

2012-07-01

The objective of this study was to evaluate which macroinvertebrate and deposited sediment metrics are best for determining effects of excessive sedimentation on stream integrity. Fifteen instream sediment metrics, with the strongest relationship to land cover, were compared to riffle macroinvertebrate metrics in streams ranging across a gradient of land disturbance. Six deposited sediment metrics were strongly related to the relative abundance of Ephemeroptera, Plecoptera and Trichoptera and six were strongly related to the modified family biotic index (MFBI). Few functional feeding groups and habit groups were significantly related to deposited sediment, and this may be related to the focus on riffle, rather than reach-wide macroinvertebrates, as reach-wide sediment metrics were more closely related to human land use. Our results suggest that the coarse-level deposited sediment metric, visual estimate of fines, and the coarse-level biological index, MFBI, may be useful in biomonitoring efforts aimed at determining the impact of anthropogenic sedimentation on stream biotic integrity.
Evaluation of deposited sediment and macroinvertebrate metrics used to quantify biological response to excessive sedimentation in agricultural streams.

PubMed

Sutherland, Andrew B; Culp, Joseph M; Benoy, Glenn A

2012-07-01

The objective of this study was to evaluate which macroinvertebrate and deposited sediment metrics are best for determining effects of excessive sedimentation on stream integrity. Fifteen instream sediment metrics, with the strongest relationship to land cover, were compared to riffle macroinvertebrate metrics in streams ranging across a gradient of land disturbance. Six deposited sediment metrics were strongly related to the relative abundance of Ephemeroptera, Plecoptera and Trichoptera and six were strongly related to the modified family biotic index (MFBI). Few functional feeding groups and habit groups were significantly related to deposited sediment, and this may be related to the focus on riffle, rather than reach-wide macroinvertebrates, as reach-wide sediment metrics were more closely related to human land use. Our results suggest that the coarse-level deposited sediment metric, visual estimate of fines, and the coarse-level biological index, MFBI, may be useful in biomonitoring efforts aimed at determining the impact of anthropogenic sedimentation on stream biotic integrity.

Miocene diagenetic and epigenetic strontium mineralization in calcareous series from Cyprus and the Arabian Gulf: Metallogenic perspective on sub- and suprasalt redox-controlled base metal deposits

NASA Astrophysics Data System (ADS)

Dill, Harald G.; Henjes-Kunst, Friedhelm; Berner, Zsolt; Stüben, Doris

2009-04-01

During the Neogene, celestite deposits evolved in the Neo-Tethys basins, in what is today called the Mediterranean Sea and the Arabian Gulf. Two evaporite deposits, in Cyprus and in Qatar have been investigated from the sedimentological and mineralogical point of view with emphasis placed on Sr, S and Ca isotopes of carbonate, gypsum and celestite. During the early Miocene shallow marine environments occurred in the Gulf region and in Cyprus both of which are abundant in syndiagenetic sulphate minerals. The calcareous environments had a strong impact on the fluid migration leading to the Sr mineralization. In the Gulf region algal biostromes favored the lateral migration of fluids but had a sealing effect so that any epigenetic mineralization based on vertical fluid flow was hampered. In contrast, the Cypriot depocentre overlying the Troodos ophiolite is dominated by patch and knoll reefs (bioherms) which provide enough porosity and permeability to be favorable for the circulation of fluids with a strong vertical component. Owing to these changes in the calcareous host series, epigenetic sulphate mineralization evolved in Cyprus during the late Miocene. This occurred as the Mediterranean Sea gradually became isolated from the open ocean and, as a precursor to the "Messinian salinity crisis" evaporitic brines circulated deep into the Meso-Cenozoic platform sediments and the underlying Troodos ophiolite where these fluids leached some base metals and sulphur for the celestite mineralization. The Red Sea Rifting was at full swing during the Late Miocene and its northern propagation into the Mediterranean Sea is assumed to have had a structural control on the positioning of the Sr deposits in Cyprus. In the Gulf area, the final closure of the Neo-Tethys and Zagros folding terminated deposition of marine calcareous rocks and alluvial-fluvial siliciclastic rocks were deposited across an unconformity. Missing circulation of highly saline brines was responsible for the absence of an epigenetic Sr mineralization of Cyprus-type in the Gulf area. Assemblages of light (e.g. zeolites) and heavy minerals (e.g. rutile, zoisite, clinopyroxene) and Ca isotope analyses support basic igneous rocks as the source for the detrital and dissolved matter in the depositional environments in Cyprus and the Arabian Gulf. The Ca isotope data imply formation of the sulphate and carbonate minerals in a marine environment without significant contributions of more radiogenic 40Ca coming from old continental crust, e.g., the Kyrenia Range or Mamonia Complex, both of which containing rocks as old as Permian. Cyprus-type (bioherm-type) and Gulf-type (biostrome-type) evaporites are potential progenitors of sediment-hosted mineral deposits (SHSCD) or base metal vein-type deposits. Syndiagenetic celestite-bearing evaporites of the Gulf-type are a model source and progenitor of base metal deposits of stratigraphically-controlled fixed or mobile reductants such as Kupferschiefer-type deposits. Is the Arabian Gulf a Kupferschiefer basin in the making? The epigenetic celestite-bearing mineralization of the Cyprus-type reflects an advanced stage of fluid migration relative to the celestite deposits along the Trucial coast but this brine mobilization failed to create a base metal deposit of its own mainly due to the absence of fixed or mobile reductants. These reductants were present in the western Mediterranean regions in Tunisia and Algeria, where evaporite-associated base metal deposits are going to be mined and in the Mesozoic through Cenozoic platform sediments in central Europe, where numerous suprasalt unconformity-related metal deposits were mined in the past.
The Antarctic dry valley lakes: Relevance to Mars

NASA Technical Reports Server (NTRS)

Wharton, R. A., Jr.; Mckay, Christopher P.; Mancinelli, Rocco L.; Clow, G. D.; Simmons, G. M., Jr.

1989-01-01

The similarity of the early environments of Mars and Earth, and the biological evolution which occurred on early Earth, motivates exobiologists to seriously consider the possiblity of an early Martian biota. Environments are being identified which could contain Martian life and areas which may presently contain evidence of this former life. Sediments which were thought to be deposited in large ice-covered lakes are present on Mars. Such localities were identified within some of the canyons of the Valles Marineris and more recently in the ancient terrain in the Southern Hemisphere. Perennially ice-covered Antarctic lakes are being studied in order to develop quantitative models that relate environmental factors to the nature of the biological community and sediment forming processes. These models will be applied to the Martian paleolakes to establish the scientific rationale for the exobiological study of ancient Martian sediments.
Huguangyan Maar Lake (SE China): A solid record of atmospheric mercury pollution history in a non-remote region

NASA Astrophysics Data System (ADS)

Zeng, Yan; Chen, Jingan; Yang, Yongqiong; Wang, Jianxu; Zhu, Zhengjie; Li, Jian

2017-10-01

Mercury is a highly toxic metal that can cause harm to environment and human health. As atmospheric deposition is the main source of total Hg input to aquatic system in remote and pristine regions, almost all the studies on atmospheric Hg pollution history concentrated in these areas, while the studies in non-remote areas are much limited, especially for the long history records. In this study, Huguangyan Maar Lake, an undisturbed lake system at low altitude in China, was selected to reconstruct the atmospheric mercury pollution history. Variation patterns of TOC, Hg and non-residual Sr in the sediment core indicated that, compared to the direct atmospheric Hg deposition, the effect of either Hg scavenging from water column by algae or the catchment inputs of previously deposited Hg on the Hg accumulation in the lake sediment was limited. The sediment Hg content in Huguangyan Lake was mainly controlled by the atmospheric Hg deposition, and thus accurately reflected the atmospheric Hg pollution history. The Hga (Hg content from atmospheric deposition) in Huguangyan Lake presented a comparable variation pattern to that in remote sites. It had the same variation trend as the global atmospheric Hg before 1950 CE, which could be attributed to the Industrial Revolution. After that, it was mainly controlled by Hg emissions from Asian countries. The variation of Hga also indicated that atmospheric Hg deposition accelerated significantly since 2000 CE. This study, along with other investigations in remote sites in China, showed that the sediment Hg in Huguangyan Lake responded to the atmospheric Hg pollution more sensitively than in the alpine regions. It should be noted that, the more intensive acceleration of Hg deposition in Huguangyan Lake may imply that the South of China suffered from much more serious atmospheric Hg pollution than previous studies revealed.
Tracking small mountainous river derived terrestrial organic carbon across the active margin marine environment

NASA Astrophysics Data System (ADS)

Childress, L. B.; Blair, N. E.; Orpin, A. R.

2015-12-01

Active margins are particularly efficient in the burial of organic carbon due to the close proximity of highland sources to marine sediment sinks and high sediment transport rates. Compared with passive margins, active margins are dominated by small mountainous river systems, and play a unique role in marine and global carbon cycles. Small mountainous rivers drain only approximately 20% of land, but deliver approximately 40% of the fluvial sediment to the global ocean. Unlike large passive margin systems where riverine organic carbon is efficiently incinerated on continental shelves, small mountainous river dominated systems are highly effective in the burial and preservation of organic carbon due to the rapid and episodic delivery of organic carbon sourced from vegetation, soil, and rock. To investigate the erosion, transport, and burial of organic carbon in active margin small mountainous river systems we use the Waipaoa River, New Zealand. The Waipaoa River, and adjacent marine depositional environment, is a system of interest due to a large sediment yield (6800 tons km-2 yr-1) and extensive characterization. Previous studies have considered the biogeochemistry of the watershed and tracked the transport of terrestrially derived sediment and organics to the continental shelf and slope by biogeochemical proxies including stable carbon isotopes, lignin phenols, n-alkanes, and n-fatty acids. In this work we expand the spatial extent of investigation to include deep sea sediments of the Hikurangi Trough. Located in approximately 3000 m water depth 120 km from the mouth of the Waipaoa River, the Hikurangi Trough is the southern extension of the Tonga-Kermadec-Hikurangi subduction system. Piston core sediments collected by the National Institute of Water and Atmospheric Research (NIWA, NZ) in the Hikurangi Trough indicate the presence of terrestrially derived material (lignin phenols), and suggest a continuum of deposition, resuspension, and transport across the margin. Based on tephra beds identified within the sediments, this material was likely transported by a series of turbidite events, delivered to the Hikurangi Trough through Poverty Canyon.
Massive sulfide metallogenesis at a late Mesozoic sediment-covered spreading axis: Evidence from the Franciscan complex and contemporary analogues

USGS Publications Warehouse

Koski, Randolph A.; Lamons, Roberta C.; Dumoulin, Julie A.; Bouse, Robin M.

1993-01-01

The Island Mountain deposit, an anomalous massive sulfide in the Central belt of the Franciscan subduction complex, northern California Coast Ranges, formed during hydrothermal activity in a sediment-dominated paleo-sea-floor environment. Although the base of the massive sulfide is juxtaposed against a 500-m-wide melange band, its gradational upper contact within a coherent sequence of sandstone, siltstone, and mudstone indicates that hydrothermal activity was concurrent with turbidite deposition. Accumulations of sulfide breccia and clastic sulfide were produced by mass wasting of the sulfide mound prior to burial by turbidites. The bulk composition of sulfide samples (pyrrhotite rich; high Cu, As, and Au contents; radiogenic Pb isotope ratios) is consistent with a hydrothermal system dominated by fluid-sediment interaction. On the basis of a comparison with possible contemporary tectonic analogues at the southern Gorda Ridge and the Chile margin triple junction, we propose that massive sulfide mineralization in the Central belt of the Franciscan complex resulted from hydrothermal activity at a late Mesozoic sediment-covered ridge axis prior to collision with the North American plate.
Massive sulfide metallogenesis at a late Mesozoic sediment-covered spreading axis: Evidence from the Franciscan complex and contemporary analogues

NASA Astrophysics Data System (ADS)

Koski, Randolph A.; Lamons, Roberta C.; Dumoulin, Julie A.; Bouse, Robin M.

1993-02-01

The Island Mountain deposit, an anomalous massive sulfide in the Central belt of the Franciscan subduction complex, northern California Coast Ranges, formed during hydrothermal activity in a sediment-dominated paleo-sea-floor environment. Although the base of the massive sulfide is juxtaposed against a 500-m-wide melange band, its gradational upper contact within a coherent sequence of sandstone, siltstone, and mudstone indicates that hydrothermal activity was concurrent with turbidite deposition. Accumulations of sulfide breccia and clastic sulfide were produced by mass wasting of the sulfide mound prior to burial by turbidites. The bulk composition of sulfide samples (pyrrhotite rich; high Cu, As, and Au contents; radiogenic Pb isotope ratios) is consistent with a hydrothermal system dominated by fluid-sediment interaction. On the basis of a comparison with possible contemporary tectonic analogues at the southern Gorda Ridge and the Chile margin triple junction, we propose that massive sulfide mineralization in the Central belt of the Franciscan complex resulted from hydrothermal activity at a late Mesozoic sediment-covered ridge axis prior to collision with the North American plate.
Depositional environments and controls of Juncal Formation, southern San Rafael Mountains, California

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thompson, T.J.

1987-05-01

The lower to middle Eocene Juncal Formation, north of the Santa Ynez fault in easternmost Santa Barbara County, represents the onset of marine sedimentation following an approximately 20-m.y. hiatus. The Juncal paraconformably overlies the upper Campanian Unnamed sandstone and is gradationally overlain by the middle Eocene Matilija Formation. Access to the Juncal exposures of this area was considerably enhanced by the Wheeler fire of July 1985. Facies analysis of both the vertical and lateral exposures of the Juncal Formation (approx. 1400 m thick) indicate that the Juncal represents coalescing outer-fan depositional lobes. This interpretation is based on the lateral continuitymore » of sandstone beds, presence of thickening-upward cycles, and high-concentration sediment gravity flows, bathyal fauna, and regional associations. Local channelization (to 10 m deep) represents the extension of a mid-fan channel over its associated depositional lobe. Outcrops are subparallel to depositional strike in the eastern part of the study area and form a broad syncline in the western part. Together, these exposures allow documentation of the depositional lobes vertically, laterally, and longitudinally. Outer-fan deposits of the Juncal Formation are part of a progradational basin-filling episode. The Juncal grades upward into the outer- to mid-fan depositions of the lower Matilija Formation. The upper Matilija Formation shoals upward into deltaic facies. This regressive sedimentary sequence was probably initiated by the major sea level fall which occurred near the early/middle Eocene boundary and coincides with the onset of fan sedimentation elsewhere along the California margin. Within the study area, depositional lobe activity was probably governed by either minor fluctuations in relative sea level or channel switching up-system.« less
Early Cambrian wave-formed shoreline deposits: the Hardeberga Formation, Bornholm, Denmark

NASA Astrophysics Data System (ADS)

Clemmensen, Lars B.; Glad, Aslaug C.; Pedersen, Gunver K.

2017-09-01

During the early Cambrian, the Danish island Bornholm was situated on the northern edge of the continent Baltica with palaeolatitudes of about 35°S. An early Cambrian (Terreneuvian) transgression inundated large areas of Baltica including Bornholm creating shallow marine and coastline environments. During this period, wave-formed shoreline sediments (the Vik Member, Hardeberga Formation) were deposited on Bornholm and are presently exposed at Strøby quarry. The sediments consist of fine- and medium-grained quartz-cemented arenites in association with a few silt-rich mudstones. The presence of well-preserved subaqueous dunes and wave ripples indicates deposition in a wave-dominated upper shoreface (littoral zone) environment, and the presence of interference ripples indicates that the littoral zone environment experienced water level fluctuations due to tides and/or changing meteorological conditions. Discoidal structures (medusoids) are present in the quarry, but due to the relative poor preservation of their fine-scale structures it is difficult to determine if the discoids represent true medusae imprints or inorganic structures. The preservation of the shallow-water bedforms as well as the possible medusae imprints is related to either the formation of thin mud layers, formed during a period of calm water when winds blew offshore for a longer period, or to the growth of bacterial mats. The orientation of the wave-formed bedforms indicates a local palaeoshoreline trending NE-SW and facing a large ocean to the north.
Brazilian continental cretaceous

NASA Astrophysics Data System (ADS)

Petri, Setembrino; Campanha, Vilma A.

1981-04-01

Cretaceous deposits in Brazil are very well developed, chiefly in continental facies and in thick sequences. Sedimentation occurred essentially in rift-valleys inland and along the coast. Three different sequences can be distinguished: (1) a lower clastic non-marine section, (2) a middle evaporitic section, (3) an upper marine section with non-marine regressive lithosomes. Continental deposits have been laid down chiefly between the latest Jurassic and Albian. The lower lithostratigraphic unit is represented by red shales with occasional evaporites and fresh-water limestones, dated by ostracods. A series of thick sandstone lithosomes accumulated in the inland rift-valleys. In the coastal basins these sequences are often incompletely preserved. Uplift in the beginning of the Aptian produced a widespread unconformity. In many of the inland rift-valleys sedimentation ceased at that time. A later transgression penetrated far into northeastern Brazil, but shortly after continental sedimentation continued, with the deposition of fluvial sandstones which once covered large areas of the country and which have been preserved in many places. The continental Cretaceous sediments have been laid down in fluvial and lacustrine environments, under warm climatic conditions which were dry from time to time. The fossil record is fairly rich, including besides plants and invertebrates, also reptiles and fishes. As faulting tectonism was rather strong, chiefly during the beginning of the Cretaceous, intercalations of igneous rocks are frequent in some places. Irregular uplift and erosion caused sediments belonging to the remainder of this period to be preserved only in tectonic basins scattered across the country.
Trawling-induced alterations of deep-sea sediment accumulation rates during the Anthropocene

NASA Astrophysics Data System (ADS)

Puig, P.; Paradis, S.; Masque, P.; Martin, J.; Juan, X.; Palanques, A.

2015-12-01

Commercial bottom trawling causes direct physical disturbance of the marine sedimentary environments by scraping and ploughing the seabed, generating periodic resuspension of surface sediments. However, the quantification of the sediment that is removed by trawling and exported across the continental margin remains largely unaddressed, and the preservation of the signal of such impacts in the geological record have been mostly overlooked. The analysis of sediment cores collected along the Catalan margin (NW Mediterranean) has allowed evaluating the contribution of this anthropogenic activity to the present-day sediment dynamics. Sediment cores at intensively trawled sites are characterized by over-consolidated sediments with lower 210Pb surface concentrations and inventories that indicate widespread erosion of recent sedimentary deposits. In turn, combined 210Pb and 137Cs chronologies indicate a significant increase of sediment accumulation rates within submarine canyon environments since the 1970s, coincidently with a strong impulse in the industrialization of the trawling fleets of this region. Two sampling sites that exhibited high sediment accumulation rates (0.6-0.7 cm/y) were reoccupied 1-2 decades after the first studies and revealed a second and even larger increase of sediment accumulation rates (>2 cm/y) occurring at the beginning of the XXI century. This recent change has been attributed to a preferential displacement of the trawling fleet towards fishing grounds surrounding submarine canyons and, also, to technical improvements in trawling vessels, presumably related to financial subsidies provided to the fishing sector. The alteration of sediment accumulation rates described in this continental margin may occur in many regions of the World's oceans given the wide geographical distribution of this human activity, and therefore, it could represent a potential marker of the Anthropocene in deep-sea environments.
Searching for the Source of Salt Marsh Buried Mercury.

NASA Astrophysics Data System (ADS)

Brooke, C. G.; Nelson, D. C.; Fleming, E. J.

2016-12-01

Salt marshes provide a barrier between upstream mercury contamination and coastal ecosystems. Mercury is sorbed, transported, and deposited in estuarine systems. Once the upstream mercury source has been remediated, the downstream mercury contaminated salt marsh sediments should become "capped" or buried by uncontaminated sediments preventing further ecosystem contamination. Downstream from a remediated mercury mine, an estuarine intertidal marsh in Tomales Bay, CA, USA, scavengers/predators (e.g. Pachygrapsus crassipes, Lined Shore Crab) have leg mercury concentrations as high as 5.5 ppm (dry wt./dry wt.), which increase significantly with crab size, a surrogate for trophic level. These elevated mercury concentrations suggests that "buried" mercury is rereleased into the environment. To locate possible sources of mercury release in Walker Marsh, we sampled a transect across the marsh that included diverse micro-environments (e.g. rhizoshere, stratified sediments, faunal burrows). From each location we determined the sediment structure, sediment color, total sediment mercury, total sediment iron, and microbial composition (n = 28). Where flora or fauna had perturbed the sediment, mercury concentrations were 10% less than undisturbed stratified sediments (1025 ppb vs. 1164 ppb, respectively). High-throughput SSU rRNA gene sequencing and subsequent co-occurrence network analysis genera indicated that in flora- or fauna- perturbed sediments there was an increased likelihood that microbial genera contained mercury mobilizing genes (94% vs 57%; in perturbed vs stratified sediments, respectively). Our observations are consistent with findings by others that in perturbed sites mercury mobility increased. We did however identify a microbial and geochemical profile with increased mercury mobility. For future work we plan to quantify the role these micro-environments have on mercury-efflux from salt marshes.
Sediment transport and resulting deposition in spawning gravels, north coastal California

Treesearch

Thomas E. Lisle

1989-01-01

Incubating salmonid eggs in streambeds are often threatened by deposition of fine sediment within the gravel. To relate sedimentation of spawning gravel beds to sediment transport, infiltration of fine sediment (
Sediment Transport and Deposition Resulting from a Dam-Removal Sediment Pulse: Milltown Dam, Clark Fork River, MT

NASA Astrophysics Data System (ADS)

Wilcox, A. C.

2010-12-01

The removal of Milltown Dam in 2008 from the Clark Fork River, Montana, USA, lowered base level at the dam site by 9 m and triggered erosion of nearly 600,000 metric tons of predominantly fine reservoir sediment. Bedload and bed-material sampling, repeat topographic surveys, sediment transport modeling, geochemical fingerprinting of downstream sediments, and Lidar analysis have all been applied to study the upstream and downstream effects of the dam removal. In the years since dam breaching, successive years with similar peak flows (3-year recurrence interval) were followed by a third year with below-average runoff. Nearly all of the documented reservoir erosion occurred in the first year, when sand and silt was eroded and transported downstream. In subsequent years, minimal reservoir erosion occurred, in part as a result of active management to prevent further reservoir erosion, but coarse material eroded from the reservoir has dispersed downstream. Upstream responses in this system have been strongly mediated by Superfund remediation activities in Milltown Reservoir, in which over two million metric tons of contaminated sediments have been mechanically excavated. Downstream aggradation has been limited in the main channel but was initially substantial in bars and side channels of a multi-thread reach 21 to 25 km downstream of the dam site, suggesting that channel change has been influenced far more by the antecedent depositional environment than by proximity to the source of the sediment pulse. Comparison of observed erosion with pre-removal modeling shows that reservoir erosion exceeded model predictions by two orders of magnitude in the unconfined Clark Fork arm of the reservoir. In addition, fine reservoir sediments predicted to move exclusively in suspension traveled as bedload at lower transport stages. The resulting fine sediment deposition in substrate interstices, on bars, and in side channels of the gravel- and cobble-bed Clark Fork River is the most significant and lasting change to downstream geomorphic and ecological systems.
Sources, fate, and effects of PAHs in shallow water environments: a review with special reference to small watercraft

USGS Publications Warehouse

Albers, P.H.; Kennish, Michael J.

2002-01-01

Polycyclic aromatic hydrocarbons (PAHs) are aromatic hydrocarbons with two to seven fused carbon (benzene) rings that can have substituted groups attached. Shallow coastal, estuarine, lake, and river environments receive PAHs from treated wastewater, stormwater runoff, petroleum spills and natural seeps, recreational and commercial boats, natural fires, volcanoes, and atmospheric deposition of combustion products. Abiotic degradation of PAHs is caused by photooxidation, photolysis in water, and chemical oxidation. Many aquatic microbes, plants, and animals can metabolize and excrete ingested PAHs; accumulation is associated with poor metabolic capabilities, high lipid content, and activity patterns or distributions that coincide with high concentrations of PAHs. Resistance to biological transformation increases with increasing number of carbon rings. Four- to seven-ring PAHs are the most difficult to metabolize and the most likely to accumulate in sediments. Disturbance by boating activity of sediments, shorelines, and the surface microlayer of water causes water column re-entry of recently deposited or concentrated PAHs. Residence time for PAHs in undisturbed sediment exceeds several decades. Toxicity of PAHs causes lethal and sublethal effects in plants and animals, whereas some substituted PAHs and metabolites of some PAHs cause mutations, developmental malformations, tumors, and cancer. Environmental concentrations of PAHs in water are usually several orders of magnitude below levels that are acutely toxic, but concentrations can be much higher in sediment. The best evidence for a link between environmental PAHs and induction of cancerous neoplasms is for demersal fish in areas with high concentrations of PAHs in the sediment.
Robustness of fossil fish teeth for seawater neodymium isotope reconstructions under variable redox conditions in an ancient shallow marine setting

NASA Astrophysics Data System (ADS)

Huck, Claire E.; van de Flierdt, Tina; Jiménez-Espejo, Francisco J.; Bohaty, Steven M.; Röhl, Ursula; Hammond, Samantha J.

2016-03-01

Fossil fish teeth from pelagic open ocean settings are considered a robust archive for preserving the neodymium (Nd) isotopic composition of ancient seawater. However, using fossil fish teeth as an archive to reconstruct seawater Nd isotopic compositions in different sedimentary redox environments and in terrigenous-dominated, shallow marine settings is less proven. To address these uncertainties, fish tooth and sediment samples from a middle Eocene section deposited proximal to the East Antarctic margin at Integrated Ocean Drilling Program Site U1356 were analyzed for major and trace element geochemistry, and Nd isotopes. Major and trace element analyses of the sediments reveal changing redox conditions throughout deposition in a shallow marine environment. However, variations in the Nd isotopic composition and rare earth element (REE) patterns of the associated fish teeth do not correspond to redox changes in the sediments. REE patterns in fish teeth at Site U1356 carry a typical mid-REE-enriched signature. However, a consistently positive Ce anomaly marks a deviation from a pure authigenic origin of REEs to the fish tooth. Neodymium isotopic compositions of cleaned and uncleaned fish teeth fall between modern seawater and local sediments and hence could be authigenic in nature, but could also be influenced by sedimentary fluxes. We conclude that the fossil fish tooth Nd isotope proxy is not sensitive to moderate changes in pore water oxygenation. However, combined studies on sediments, pore waters, fish teeth, and seawater are needed to fully understand processes driving the reconstructed signature from shallow marine sections in proximity to continental sources.
The Deposition and Accumulation of Microplastics in Marine Sediments and Bottom Water from the Irish Continental Shelf.

PubMed

Martin, Jake; Lusher, Amy; Thompson, Richard C; Morley, Audrey

2017-09-07

Microplastics are widely dispersed throughout the marine environment. An understanding of the distribution and accumulation of this form of pollution is crucial for gauging environmental risk. Presented here is the first record of plastic contamination, in the 5 mm-250 μm size range, of Irish continental shelf sediments. Sixty-two microplastics were recovered from 10 of 11 stations using box cores. 97% of recovered microplastics were found to reside shallower than 2.5 cm sediment depth, with the area of highest microplastic concentration being the water-sediment interface and top 0.5 cm of sediments (66%). Microplastics were not found deeper than 3.5 ± 0.5 cm. These findings demonstrate that microplastic contamination is ubiquitous within superficial sediments and bottom water along the western Irish continental shelf. Results highlight that cores need to be at least 4-5 cm deep to quantify the standing stock of microplastics within marine sediments. All recovered microplastics were classified as secondary microplastics as they appear to be remnants of larger items; fibres being the principal form of microplastic pollution (85%), followed by broken fragments (15%). The range of polymer types, colours and physical forms recovered suggests a variety of sources. Further research is needed to understand the mechanisms influencing microplastic transport, deposition, resuspension and subsequent interactions with biota.
Geologic Evidence of Earthquakes and Tsunamis in the Mexican Subduction zone - Guerrero

NASA Astrophysics Data System (ADS)

Ramirez-Herrera, M.; Lagos, M.; Hutchinson, I.; Ruiz-Fernández, A.; Machain, M.; Caballero, M.; Rangel, V.; Nava, H.; Corona, N.; Bautista, F.; Kostoglodov, V.; Goguitchaichrili, A.; Morales, J.; Quintana, P.

2010-12-01

A study of large historic and prehistoric earthquakes and their tsunamis using a multiproxy approach (geomorphic features, sediment deposits, microfossils, sediment geochemistry and more recently the use of magnetic properties) has provided valuable information in the assessment of earthquake and tsunami record. The Pacific coast of Mexico is located over the active subduction zone (~1000 km) that has experienced numerous large magnitude earthquakes in historical time (Mw>7.5), and more than 50 documented tsunamis since 1732. Geomorphic and stratigraphic studies through test pits at 13 sites on the Guerrero coast reveal distinct stratigraphic changes with depth, indicating clear rapid change in depositional environments over time. Microfossil ecology (diatoms and foraminifera), sediment geochemistry (concentration increment in elements such as Sr, Ba, Ca, P, Si, K), stratigraphy, sediment magnetic properties (magnetic susceptibility anisotropy for the first time applied in tsunami deposits identification) and other proxies are indicative of sudden changes in land level and tsunami deposits. Buried evidence of liquefaction confirms the occurrence of a large earthquake at Barra de Potosi and Ixtapa, Guerrero. Preliminary 210Pb analysis suggests a sedimentation rate of ca. 0.1±0.01 cm/year and an estimated minimum age of ~ 100 years (maximum age at ca. 450 years?) for the most recent earthquake. At least three large events can be recognized by sharp contacts and sand layers in the sedimentary record. Ongoing C14, OSL and 210Pb dating will constrain the timing of these events. Deposits from three marine inwash events (tsunamis) dating from the past 4600 years have been identified on the Guerrero coast. A near-surface sand bed with a sharp basal contact overlying soil at sites near Ixtapa and Barra de Potosi most probably marks the tsunami following the 1985 Mw 8.2 earthquake. Interviews with Barra de Potosi fishermen and locals corroborate that these sites were inundated by this tsunami.
Establishing a tracer-based sediment budget to preserve wetlands in Mediterranean mountain agroecosystems (NE Spain).

PubMed

Navas, Ana; López-Vicente, Manuel; Gaspar, Leticia; Palazón, Leticia; Quijano, Laura

2014-10-15

Mountain wetlands in Mediterranean regions are particularly threatened in agricultural environments due to anthropogenic activity. An integrated study of source-to-sink sediment fluxes was carried out in an agricultural catchment that holds a small permanent lake included in the European NATURA 2000 Network. More than 1000 yrs of human intervention and the variety of land uses pose a substantial challenge when attempting to estimate sediment fluxes which is the first requirement to protect fragile wetlands. To date, there have been few similar studies and those that have been carried out have not addressed such complex terrain. Geostatistical interpolation and GIS tools were used to derive the soil spatial redistribution from point (137)Cs inventories, and to establish the sediment budget in a catchment located in the Southern Pyrenees. The soil redistribution was intense and soil erosion predominated over soil deposition. On the areas that maintained natural vegetation the median soil erosion and deposition rates were moderate, ranging from 2.6 to 6 Mg ha yr(-1) and 1.5 to 2.1 Mg ha yr(-1), respectively. However, in cultivated fields both erosion and deposition were significantly higher (ca. 20 Mg ha yr(-1)), and the maximum rates were always associated with tillage practices. Farming activities in the last part of the 20th century intensified soil erosion, as evidenced by the 1963 (137)Cs peaks in the lake cores and estimates from the sediment budget indicated a net deposition of 671 Mg yr(-1). Results confirm a siltation risk for the lake and provide a foundation for designing management plans to preserve this threatened wetland. This comprehensive approach provides information useful for understanding processes that influence the patterns and rates of soil transfer and deposition within fragile Mediterranean mountain wetlands subjected to climate and anthropogenic stresses. Copyright © 2014 Elsevier B.V. All rights reserved.
Paleobiology of the Sand Beneath the Valders Diamicton at Valders, Wisconsin

NASA Astrophysics Data System (ADS)

Maher, Louis J.; Miller, Norton G.; Baker, Richard G.; Curry, B. Brandon; Mickelson, David M.

1998-03-01

Previously undescribed pollen, plant macrofossils, molluscs, and ostracodes were recovered from a 2.5-m-thick glaciolacustrine unit of silty sand and clay at Valders, Wisconsin. The interstadial sediment was deposited about 12,200 14C yr B.P. after retreat of the Green Bay lobe that deposited diamicton of the Horicon Formation, and before advance of the Lake Michigan lobe that deposited the red-brown diamicton of the Valders Member of the Kewaunee Formation. Fluctuations of abundance of Candona subtriangulata, Cytherissa lacustris,and three other species define four ostracode biozones in the lower 1.7 m, suggesting an open lake environment that oscillated in depth and proximity to glacial ice. Pollen is dominated by Piceaand Artemisia,but the low percentages of many other types of long-distance origin suggest that the terrestrial vegetation was open and far from the forest border. The upper part of the sediment, a massive sand deposited in either a shallow pond or a sluggish stream, contains a local concentration of plant macrofossils. The interpretation of a cold open environment is supported by the plant macrofossils of more than 20 species, dominated by those of open mineral soils ( Arenaria rubella, Cerastium alpinumtype, Silene acaulis, Sibbaldia procumbens, Dryas integrifolia, Vaccinium uliginosumvar. alpinum, Armeria maritima,etc.) that in North America occur largely in the tundra and open tundra-forest ecotone of northern Canada. Ice-wedge casts occur in the sand.
Geochemical and isotopic evidence for paleoredox conditions during deposition of the Devonian-Mississippian New Albany Shale, southern Indiana

NASA Technical Reports Server (NTRS)

Beier, J. A.; Hayes, J. M.

1989-01-01

The upper part of the New Albany Shale is divided into three members. In ascending order, these are (1) the Morgan Trail Member, a laminated brownish-black shale; (2) the Camp Run Member, an interbedded brownish-black and greenish-gray shale; and (3) the Clegg Creek Member, also a laminated brownish-black shale. The Morgan Trail and Camp Run Members contain 5% to 6% total organic carbon (TOC) and 2% sulfide sulfur. Isotopic composition of sulfide in these members ranges from -5.0% to -20.0%. C/S plots indicate linear relationships between abundances of these elements, with a zero intercept characteristic of sediments deposited in a non-euxinic marine environment. Formation of diagenetic pyrite was carbon limited in these members. The Clegg Creek Member contains 10% to 15% TOC and 2% to 6% sulfide sulfur. Isotopic compositions of sulfide range from -5.0% to -40%. The most negative values occur in the uppermost Clegg Creek Member and are characteristic of syngenetic pyrite, formed within an anoxic water column. Abundances of carbon and sulfur are greater and uncorrelated in this member, consistent with deposition in as euxinic environment. In addition, DOP (degree of pyritization) values suggest that formation of pyrite was generally iron limited throughout Clegg Creek deposition, but sulfur isotopes indicate that syngenetic (water-column) pyrite becomes an important component in the sediment only in the upper part of the member. At the top of the Clegg Creek Member, a zone of phosphate nodules and trace-metal enrichment coincides with maximal TOC values. During euxinic deposition, phosphate and trace metals accumulated below the chemocline because of limited vertical circulation in the water column. Increased productivity would have resulted in an increased flux of particulate organic matter to the sediment, providing an effective sink for trace metals in the water column. Phosphate and trace metals released from organic matter during early diagenesis resulted in precipitation of metal-rich phosphate nodules.

Sediment fingerprinting by using the Ag-110m: Cs-137 ratio along the main rivers draining the Fukushima radioactive pollution plume

NASA Astrophysics Data System (ADS)

Chartin, Caroline; Evrard, Olivier; Onda, Yuichi; Patin, Jeremy; Lefèvre, Irène; Ayrault, Sophie; Lepage, Hugo; Bonté, Philippe

2013-04-01

During the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident, large quantities of radionuclides were released into the environment between 12 and 19 March 2011. Even though about 80% of these emissions were transported offshore and out over the Pacific Ocean, 20% were deposited as wet and dry deposits on soils of Fukushima Prefecture on 15-16 March. In particular, 6.4 PBq of Cs-137 were modeled to have deposited on Japanese soils over a distance of 70 km to the northwest of the Fukushima Dai-ichi nuclear power plant. As most radionuclides are strongly sorbed by fine particles, and their mineralogical clay and organic matter fractions, they are likely to be redistributed within the landscape in association with soil and sediment particles transported by erosion processes and runoff. Based on a spatial analysis of the gamma-emitting radionuclides present in the environment respectively eight and thirteen months after the accident, we aim to provide a radioactive tracer to investigate the temporal evolution of the contaminant dispersion across Fukushima Prefecture. For this purpose, sediments were collected along rivers draining the main contamination plume in Fukushima Prefecture (i.e, Rivers Kutchibuto, Mano, Nitta and Ota) in November 2011 and April 2012.These campaigns directly followed the main hydro-sedimentary events that occurred in this region, i.e., the typhoon season (July and September-October) and the snowmelt (March 2012). The river sediment activities in gamma-emitting radionuclides were then compared to the initial activities measured in soils provided by the Japanese Ministry of Education, Culture, Sport, Science and Technology (MEXT). The initial fallout patterns in 110mAg appeared to differ from those of the main contamination plume defined mainly by radiocaesium fallout (i.e., Cs-134+137). The Ag-110m:Cs-137 ratio was then used to trace the spatial origin of contaminated sediment collected in rivers. Sediments collected within the coastal plain in November 2011 were locally composed of 50 to 100% of particles originated from inland mountains ranges that were exposed to the highest initial radionuclide fallout. Typhoons of the summer 2011 have then largely contributed to the dispersion of the contamination. In addition, the spatial analysis of river sediment contamination in April 2012 demonstrates that the spring snowmelt amplified significantly the flush of sediment deposited on the riverbed after the summer typhoons. Consequently, export of contaminated particles appears to be particularly fast in those mountainous catchments submitted to a very erosive climate. Our results have then important implications suggesting that coastal rivers may have become a perennial source of radioactive contaminants to the Pacific Ocean off Fukushima Prefecture.
Neogene Sediment Transport, Deposition, and Exhumation from the Southern Alaska Syntaxis to the Eastern Aleutian Subduction Zone

NASA Astrophysics Data System (ADS)

Ridgway, K. D.; Witmer, J. W.; Enkelmann, E.; Plafker, G.; Brennan, P. R.

2011-12-01

Over 5 km of Neogene sedimentary strata are well exposed in the Chugach-St. Elias Ranges within the southern Alaska syntaxis. This syntaxis forms where the Pacific-North America plate boundary changes from the northwest-trending Queen Charlotte-Fairweather transform system to the southwest-trending Alaska-Aleutian subduction zone. Active collision and subduction of the buoyant Yakutat microplate in the syntaxis results in a wide collisional zone defined by active mountain belts, extensive glaciation, and thick packages of synorogenic strata. New stratigraphic and U-Th/He thermochronologic data from Neogene synorogenic strata, named the Yakataga and Redwood Formations, provide insights on collisional tectonics, glacial erosion, and sediment transport, deposition, burial, and exhumation from the onshore Chugach and St. Elias Ranges to the exposed accretionary prism of the Aleutian trench. Stratigraphic analyses show that along the southeastern part of the syntaxis, Neogene strata are characterized by deposition in braid delta, shallow marine, and glaciomarine slope apron depositional systems that resulted in construction of a broad continental shelf. In the central part of the syntaxis, marine shelf and upper slope environments deposited thick-bedded sandstone and mudstone in a thrust belt/foreland basin system. Along the southwestern part of the syntaxis, Neogene strata were deposited in a regional submarine fan system that filled the easternmost part of the Aleutian trench. Geologic mapping of the contact between the Yakataga Formation and underlying strata along the syntaxis document an angular unconformity with maximum stratigraphic separation (> 5 km) in the central part of the syntaxis. Along strike, this unconformity becomes conformable along both the southwestern and southeastern parts of the syntaxis. The regional angular unconformity and facies transitions both point to the importance of the central part of the syntaxis in the generation and distribution of synorogenic sediment. Apatite and zircon U-Th/He thermochronologic data from granitoid and gneissic clasts in conglomerate suggest that Neogene sediments were buried no deeper than ~2 km in the central and southeastern parts of the syntaxis, and that burial temperatures did not exceed ~40-45°C. In contrast, Neogene sediment deposited by submarine fans in the Aleutian trench along the southwestern part of the syntaxis were buried at depths of 5 to 7.5 km and reached temperatures between ~120-160°C. These strata were subsequently exhumed as the trench fill was incorporated into the growing accretionary prism. Collectively, our data show that the first-order sediment pathway along a glaciated syntaxis is dynamically linked to tectonic uplift, focused glacial erosion, deposition of thick packages of glacial marine sediment, and rapid exhumation along thrust belts and accretionary prisms.
Glacial sediments and landforms of Holderness, eastern England: A glacial depositional model for the North Sea Lobe of the British-Irish Ice Sheet

NASA Astrophysics Data System (ADS)

Evans, David J. A.; Thomson, Stephen A.

2010-08-01

Borehole records and exposures at coastal cliffs and inland quarries around Holderness are used in a critical assessment of the glacial depositional environments that operated at the margin of the North Sea lobe of the British-Irish Ice Sheet at the Last Glacial Maximum. Four lithofacies associations (LFA) are recognized in the area: LFAs 1 and 4 are laminated to massive diamictons, traditionally called the Skipsea and Withernsea tills/members, and display deformation structures indicative of stress from the NE, attenuated rafts of soft bedrock lithologies, ice-bed separation (canal fill) features and pseudo-stratification, and clast macrofabric data predominantly indicate deformation only to low strains. They are interpreted as subaqueous deposits subsequently deformed by glacier ice to create end products that lie on the glacitectonite continuum. Localized increases in strain signature are equated with the development of shear zones between onshore thickening wedges of deformed, pre-existing lake sediment. LFA 2 comprises cross-bedded clinoforms, locally steepening into foresets, at the core of linear hummocks along the central spine of Holderness (LFA 2a) and rhythmically laminated silts and sands with dropstones (LFA 2b). These sediments are interpreted as coalescent glacilacustrine subaqueous outwash fans, fining distally to lake bottom rhythmites and varves. Ice-contact deposition is evident in compressional folding, faulting and hydrofracture filling due to ice overriding, and extensional faulting associated with localized ice melt-out. Depressions produced by folding or sagging provided the accommodation space for the later deposition of LFA 2 and 3 through syntectonic sedimentation. LFA 3 comprises flat-lying beds of well to poorly sorted cross-stratified sands and gravels, interpreted as proximal proglacial braided outwash deposits laid down largely in ribbon sandar defined by the topography of abandoned ice-contact glacilacustrine depo-centres. Well developed ice wedge pseudomorphs in LFA 3 record permafrost conditions during ice sheet marginal recession, indicating that North Sea lobe oscillations may have been non-climatic or surge related. A depositional model is proposed in which "advance" and "retreat" phase tills/glacitectonites and associated ice-contact lake sediments are the geological imprint of a single glaciation. The initial advance of the North Sea lobe is recorded by a westerly thinning advance till (LFA 1). Later LFA 1 and 4 retreat "tills" are strictly glacitectonites, and are thicker depositional units because later ice readvances encroached upon and cannibalized more substantial sequences of deglacial lake sediment and subaqueous ice-contact fans (LFA 2). Similar regional till architectures will be manifest wherever the palaeogeography resulted in the onshore flow of ice and the concomitant production of glacitectonites from glacial lake sediments.
Chemical data and lead isotopic compositions of geochemical baseline samples from streambed sediments and smelter slag, lead isotopic compositions in fluvial tailings, and dendrochronology results from the Boulder River watershed, Jefferson County, Montana

USGS Publications Warehouse

Unruh, Daniel M.; Fey, David L.; Church, Stan E.

2000-01-01

IntroductionAs a part of the U.S. Geological Survey Abandoned Mine Lands Initiative, metal-mining related wastes in the Boulder River study area in northern Jefferson County, Montana, have been evaluated for their environmental effects. The study area includes a 24-km segment of the Boulder River in and around Basin, Montana and three principal tributaries to the Boulder River: Basin Creek, Cataract Creek, and High Ore Creek. Mine and prospect waste dumps and mill wastes are located throughout the drainage basins of these tributaries and in the Boulder River. Mine-waste material has been transported into and down streams, where it has mixed with and become incorporated into the streambed sediments. In some localities, mine waste material was placed directly in stream channels and was transported downstream forming fluvial tailings deposits along the stream banks. Water quality and aquatic habitat have been affected by trace-element-contaminated sediment that moves from mine wastes into and down streams during snowmelt and storm runoff events within the Boulder River watershed.Present-day trace element concentrations in the streambed sediments and fluvial tailings have been extensively studied. However, in order to accurately evaluate the impact of mining on the stream environments, it is also necessary to evaluate the pre-mining trace-element concentrations in the streambed sediments. Three types of samples have been collected for estimation of pre-mining concentrations: 1) streambed sediment samples from the Boulder River and its tributaries located upstream from historical mining activity, 2) stream terrace deposits located both upstream and downstream of the major tributaries along the Boulder River, and 3) cores through sediment in overbank deposits, in abandoned stream channels, or beneath fluvial tailings deposits. In this report, we present geochemical data for six stream-terrace samples and twelve sediment-core samples and lead isotopic data for six terrace and thirteen core samples. Sample localities are in table 1 and figures 1 and 2, and site and sample descriptions are in table 2.Geochemical data have been presented for cores through fluvial tailings on High Ore Creek, on upper Basin Creek, and on Jack Creek and Uncle Sam Gulch. Geochemical and lead isotopic data for modern streambed-sediment samples have been presented by Fey and others.Lead isotopic determinations in bed sediments have been shown to be an effective tool for evaluating the contributions from various sources to the metals in bed sediments. However, in order to make these calculations, the lead isotopic compositions of the contaminant sources must also be known. Consequently, we have determined the lead isotopic compositions of five streambed-sediment samples heavily contaminated with fluvial mine waste immediately downstream from large mines in the Boulder River watershed in order to determine the lead isotopic signatures of the contaminants. Summary geochemical data for the contaminants are presented here and geochemical data for the streambed-sediment samples are given by Fey and others.Downstream from the Katie mill site and Jib tailings, fluvial deposits of mill tailings are present on a 10-m by 50-m bar in the Boulder River below the confluence with Basin Creek. The source of these tailings is not known, but fluvial tailings are also present immediately downstream from the Katie mill site, which is immediately upstream from the confluence with Basin Creek. Nine cores of fluvial tailings from this bar were analyzed.Dendrochronology samples were taken at several stream terrace localities to provide age control on the stream terrace deposits. Trees growing on the surfaces of stream terraces provide a minimum age for the terrace deposits, although floods subsequent to the trees' growth could have deposited post-mining overbank deposits around the trees. Historical data were also used to provide estimates of minimum ages of cultural features and to bracket the age of events.
Estimating sediment budgets at the interface between rivers and estuaries with application to the Sacramento-San Joaquin River Delta

USGS Publications Warehouse

Wright, S.A.; Schoellhamer, D.H.

2005-01-01

[1] Where rivers encounter estuaries, a transition zone develops where riverine and tidal processes both affect sediment transport processes. One such transition zone is the Sacramento-San Joaquin River Delta, a large, complex system where several rivers meet to form an estuary (San Francisco Bay). Herein we present the results of a detailed sediment budget for this river/estuary transitional system. The primary regional goal of the study was to measure sediment transport rates and pathways in the delta in support of ecosystem restoration efforts. In addition to achieving this regional goal, the study has produced general methods to collect, edit, and analyze (including error analysis) sediment transport data at the interface of rivers and estuaries. Estimating sediment budgets for these systems is difficult because of the mixed nature of riverine versus tidal transport processes, the different timescales of transport in fluvial and tidal environments, and the sheer complexity and size of systems such as the Sacramento-San Joaquin River Delta. Sediment budgets also require error estimates in order to assess whether differences in inflows and outflows, which could be small compared to overall fluxes, are indeed distinguishable from zero. Over the 4 year period of this study, water years 1999-2002, 6.6 ?? 0.9 Mt of sediment entered the delta and 2.2 ?? 0.7 Mt exited, resulting in 4.4 ?? 1.1 Mt (67 ?? 17%) of deposition. The estimated deposition rate corresponding to this mass of sediment compares favorably with measured inorganic sediment accumulation on vegetated wetlands in the delta.
Landscapes, depositional environments and human occupation at Middle Paleolithic open-air sites in the southern Levant, with new insights from Nesher Ramla, Israel

NASA Astrophysics Data System (ADS)

Zaidner, Yossi; Frumkin, Amos; Friesem, David; Tsatskin, Alexander; Shahack-Gross, Ruth

2016-04-01

Middle Paleolithic human occupation in the Levant (250-50 ka ago) has been recorded in roofed (cave and rockshelter) and open-air sites. Research at these different types of sites yielded different perspectives on the Middle Paleolithic human behavior and evolution. Until recently, open-air Middle Paleolithic sites in the Levant were found in three major sedimentary environments: fluvial, lake-margin and spring. Here we describe a unique depositional environment and formation processes at the recently discovered open-air site of Nesher Ramla (Israel) and discuss their contribution to understanding site formation processes in open-air sites in the Levant. The site is 8-m-thick Middle Paleolithic sequence (OSL dated to 170-80 ka) that is located in a karst sinkhole formed by gravitational deformation and sagging into underground voids. The sedimentary sequence was shaped by gravitational collapse, cyclic colluviation of soil and gravel into the depression, waterlogging, in situ pedogenesis and human occupation. Original bedding and combustion features are well-preserved in the Lower archaeological sequence, a rare occurrence in comparison to other open-air archaeological sites. This phenomenon coincides with episodes of fast sedimentation/burial, which also allowed better preservation of microscopic remains such as ash. The Upper archaeological sequence does not exhibit bedding or preservation of ash, despite presence of heat-affected lithic artifacts, which makes it similar to other open-air sites in the Levant. We suggest that rate of burial is the major factor that caused the difference between the Upper and Lower sequences. The differences in the burial rate may be connected to environmental and vegetation changes at the end of MIS 6. We also identified an interplay between sediment in-wash and density of human activity remains, i.e. during episodes of low natural sediment input the density of artifacts is higher relative to episodes with high rate of sediment in-wash. The detailed analysis of natural and anthropogenic processes at Nesher Ramla suggests a much wider spectrum of processes than previously reported for southern Levantine Paleolithic sites. Nesher Ramla shares certain depositional and post-depositional characteristics with both cave and open-air sites and provides a better insight into processes which control both types of sites.
Eolian deposition cycles since AD 500 in Playa San Bartolo lunette dune, Sonora, Mexico: Paleoclimatic implications

NASA Astrophysics Data System (ADS)

Ortega, Beatriz; Schaaf, Peter; Murray, Andrew; Caballero, Margarita; Lozano, Socorro; Ramirez, Angel

2013-12-01

Records of past climatic changes in desert environments are scarce due to the poor preservation of biological proxies. To overcome this lack we consider the paleoenvironmental significance and age of a lunette dune at the eastern rim of Playa San Bartolo (PSB) in the Sonoran Desert (Mexico). Thermoluminescence and optical stimulated luminescence (TL and OSL) provide the chronology of lunette dune development. Mineralogical, geochemical (major, trace and REE element concentrations) and rock magnetic analyses allow for the assessment of sediment provenance and changes in the composition of the PSB dune over time. The upper 6 m of dune accumulation occurred over the past 1.5 ka, largely during AD 500-1200, a period that correlates with the Medieval climatic anomaly (AD 300-1300). Variability in composition of dune sediments is attributed to changes in sediment sources. Sand sized deposits are mainly eroded from granitoids from nearby outcrops. Sandy silt deposits, rich in evaporative minerals, resulted after the flooding of PSB, later deflation and accumulation of both detritic and authigenic components in the dune. These findings suggest that main dune accretion occurred during regionally extended drought conditions, disrupted by sporadic heavy rainfall.
Preliminary results of chronostratigraphic field work, OSL-dating and morphogenetic reconstruction of an alluvial apron at Alborz southern foothill, Damghan basin, Iran

NASA Astrophysics Data System (ADS)

Büdel, Christian; Fuchs, Markus; Majid Padashi, Seyed; Baumhauer, Roland

2014-05-01

Here we present preliminary results of a chronostratigraphic study of an alluvial fan in the Damghan Basin, northern Iran. The basin sediments date back to the Mio- and Pliocene and therefore represent the starting point of alluvial fan aggradation. Today, the still active alluvial fans prograde from the Albors Mountain ranges and sit on the older sediment bodies. In this study, our focus is on the late Pleistocene to Holocene alluvial fan sedimentation history. The upper stratigraphy of the alluvial fans and intercalated lake deposits is characterized by six individual layers of gravels and fines, representing six different stratigraphic units. These units are described and classified by detailed geomorphological and stratigraphic mapping. To establish an alluvial fan chronology, six profiles were sampled for OSL dating. As expected, due to the high-energy transport system of alluvial fan aggradation in semi-desert environments, OSL dating of these sediments is challenging due to the problem of insufficient bleaching. Consequently, most of the samples are interpreted as maximum ages. However, the measurements show a consistent internal age structure and the overall OSL-based chronology is in agreement with the age model derived from our geomorphological analysis. As a first interpretation, based on surveyed geomorphological features and chronological analysis, we could identify seven morphodynamic phases, leading to a genetic model of alluvial fan aggradation. The oldest Pleistocene age estimate is derived from a former lake terrace. The following ages represent ongoing lake sediment deposition and the development of a proximal and mid-fan gravel cover. After the youngest lake deposits were accumulated within the Holocene, the lake starts to retreat and small alluvial fans are filling up the former lake bottom. This last sedimentation phase can be divided in at least two sub-phases, probably coupled to a lateral shifting of the active depositional lobe and to the abandonment and shallow incision of mid fan surfaces.
Relationships between contourite deposition, climate and slope instability: new insights from the Demerara Plateau (French Guyana)

NASA Astrophysics Data System (ADS)

Tallobre, C.; Bassetti, M. A.; Loncke, L.; Giresse, P.; Bayon, G.; Buscail, R.

2015-12-01

A Contourite Depositional System (CDS) has been described at the Demerara Plateau (DP) based on seismic investigations, but little is known about the mechanisms of associated sediment deposition and its interaction with past deep ocean circulation patterns (e.g. bottom current velocity) and bottom morphology related to ancient event of slope instability. The new seismic and bathymetric data recently acquired allow describing in details the CDS on the DP. Erosional and syn-sedimentary features on the seafloor (comet tail, « longitudinal waves », contourite drifts and moats) have been observed, helping to constrain the sedimentary processes at the origin of the CDS construction. Also, the recovery and multi-proxy analysis of sediment cores allows the characterization of sedimentary environments and possible relation with climate forcing. These sediment cores are characterized by the presence of several beds rich in glauconite grains. Glauconite can form at the sediment/water interface by winnowing effect that prevent sediment deposition and increase the residence time at the seafloor. Under strong winnowing conditions, glauconite grains can develop at several stages of maturity. We observed that the residence time and hence the maturity of glauconite is reflected by the color changes (light to dark green), the presence of crack on grains, the formation of (secondary) glauconite lamellae and decrease of grain porosity. A chronological framework (based on radiocarbon dates and δ18O variations) of contourite sequences at the studied location indicates correlation with grain-size parameters (sortable silt) and allows one to further constrain their dynamics through time. The combination of these proxies allows us to estimate and understand the evolution and the impact of the bottom current on sedimentation on the DP during the last 80 ky. These results show the potentiality of the glauconite study to estimate the relative variation of bottom current velocity at margins.
The Middle Jurassic microflora from El Maghara N° 4 borehole, Northern Sinai, Egypt

NASA Astrophysics Data System (ADS)

Mohsen, Sayed Abdel

The coal bearing formation in El Maghara area, northern Sinai, yielded abundant, diverse and generally well preserved spores, pollen and marine microflora. The palynological analysis of the fine clastic sediments in this formation yielded (71) species related to (44) genera. Three different palynological assemblage zones can be distinguished. The sediments which contain lower and the upper assemblage zones bearing the coal seems, were deposited in non-marine (swamp) environment. In the middle assemblage zone few marine microflora can be identified, indicating a coastal near shore marine environment. Compared with other palynologic data obtained from Egypt and other countries, the three described assemblage zones belong to Middle Jurassic (Bathonian) age.
A plane-type soil sampler

USGS Publications Warehouse

Frey, Paul J.

1963-01-01

While studying the effects of pesticides on fish and their environment for the Bureau of Sport Fisheries and Wildlife, I have developed a soil sampler that will collect a thin uniform layer of sediment from pond and stream bottoms. As it is becoming increasingly important to analyze the residual deposits of pesticides in this shallow layer of soil in aquatic environments, it seems useful to describe the apparatus and compare it with other samplers.
Shallow stratigraphic control on pockmark distribution in north temperate estuaries

USGS Publications Warehouse

Brothers, Laura L.; Kelley, Joseph T.; Belknap, Daniel F.; Barnhardt, Walter A.; Andrews, Brian D.; Legere, Christine; Hughes-Clarke, John E.

2012-01-01

Pockmark fields occur throughout northern North American temperate estuaries despite the absence of extensive thermogenic hydrocarbon deposits typically associated with pockmarks. In such settings, the origins of the gas and triggering mechanism(s) responsible for pockmark formation are not obvious. Nor is it known why pockmarks proliferate in this region but do not occur south of the glacial terminus in eastern North America. This paper tests two hypotheses addressing these knowledge gaps: 1) the region's unique sea-level history provided a terrestrial deposit that sourced the gas responsible for pockmark formation; and 2) the region's physiography controls pockmarks distribution. This study integrates over 2500 km of high-resolution swath bathymetry, Chirp seismic reflection profiles and vibracore data acquired in three estuarine pockmark fields in the Gulf of Maine and Bay of Fundy. Vibracores sampled a hydric paleosol lacking the organic-rich upper horizons, indicating that an organic-rich terrestrial deposit was eroded prior to pockmark formation. This observation suggests that the gas, which is presumably responsible for the formation of the pockmarks, originated in Holocene estuarine sediments (loss on ignition 3.5–10%), not terrestrial deposits that were subsequently drowned and buried by mud. The 7470 pockmarks identified in this study are non-randomly clustered. Pockmark size and distribution relate to Holocene sediment thickness (r2 = 0.60), basin morphology and glacial deposits. The irregular underlying topography that dictates Holocene sediment thickness may ultimately play a more important role in temperate estuarine pockmark distribution than drowned terrestrial deposits. These results give insight into the conditions necessary for pockmark formation in nearshore coastal environments.
Morrowan sedimentation in the Orogrande basin, west Texas and south-central New Mexico

DOE Office of Scientific and Technical Information (OSTI.GOV)

Connolly, W.M.; Stanton, R.J. Jr.

1986-03-01

Morrowan strata in the Hueco and Franklin Mountains reflect deposition within a shallow, gradually subsiding, carbonate shelf lagoon. Postulated environments fluctuated between open shelf lagoon with localized shoaling, restricted inner shelf lagoon, and peritidal settings. Variations in depth were slight, probably not exceeding several tens of meters within the photic zone. The La Tuna Formation (Franklin Mountains) was deposited near the axis (center) of the Orogrande basin; the lower division of the Magdalena limestone (Hueco Mountains), 30 mi east, was deposited 20-30 mi west of the paleoshoreline. Physiographically, the Orogrande sea was a small gulf, offering a certain degree ofmore » protection from the Morrowan seaway to the south. Sedimentologically, it was a wide expanse of predominantly quiet-water carbonate sedimentation with subordinate argillaceous influex and coarser peripheral clastics. The Orogrande basin, a stratigraphic feature, corresponds to a blanket deposit of shallow epeiric carbonates. Climatic and orographic effects are invoked to explain the contrasting style of clastic sedimentation in the Delaware and orogrande basins, east and west of the Pedernal uplift. Analysis of Morrowan carbonates reveals no evidence of cyclicity, major transgressions or regressions, or local tectonic activity. Deposition was stable and in equilibrium with a gradually subsiding shallow basin. Based on lithologic, faunal, biostratigraphic, and paleogeographic criteria, the lower division is both laterally and temporally equivalent with the La Tuna Formation. Accordingly, the latter term is advocated in favor of the former, which lacks both priority and formal status.« less
Oasis deposits in the southern margin of the Taklimakan Desert and abrupt environmental changes during the last 30 ka

NASA Astrophysics Data System (ADS)

Shu, P.; Li, B.; Wang, H.; Cheng, P.; An, Z.; Zhou, W.; Zhang, D. D.

2017-12-01

Taklimakan Desert, the largest arid landform in the Eurasia, is one of the most important dust sources in the world. Growing evidences shows that millennial-scale abrupt climate changes during the last glacial period in the region. However, records on millennial-scale climate and environmental changes remain poorly understood because dating eolian, lacustrine, and fluvial sediments and establishing the reliable environmental proxies from these records are always challenging. Here, we present 32 AMS 14C dates of bulk sediments, grain size, and Rb/Sr ratio parameters from the oasis sequence and dates of bulk loess and charcoal from the upstream source regions to examine the significance of oasis sediments on millennial-scale environmental changes in the Taklimakan Desert. We found that substantial reversal of radiocarbon dates on total organic carbon (TOC) was controlled by source region organic carbon input. Loess hills, alpine meadow north of the study region provided fluvial deposits along drainage system and deflation in the river valleys further provide eolain materials. We argue that early oasis deposits experienced deflation and re-deposition less severe than the younger oasis deposits. After refining radiocarbon age-depth relationships for an age model by Bacon package, proxy records show substantial abrupt fluctuations in climate and environments during the last glacial period, among which three wet intervals, two dry periods are identified. The wetter and warmer conditions during the Holocene facilitated human to occupy the oasis.
Topography and Sedimentation Characteristics of the Squaw Creek National Wildlife Refuge, Holt County, Missouri, 1937-2002

USGS Publications Warehouse

Heimann, David C.; Richards, Joseph M.

2003-01-01

The Squaw Creek National Wildlife Refuge (hereafter referred to as the Refuge), located on the Missouri River floodplain in northwest Missouri, was established in 1935 to provide habitat for migratory birds and wildlife. Results of 1937 and 1964 topographic surveys indicate that sedimenta-tion, primarily from Squaw Creek and Davis Creek inflows, had substantially reduced Refuge pool volumes and depths. A study was undertaken by the U.S. Geological Survey, in cooperation with the U.S. Fish and Wildlife Service, to quantify and spatially analyze historic rates of sedimentation in the Refuge and determine the surface elevations, depths, and pool capacities for selected managed pools from a 2002 survey.The 1937 to 1964 mean total sediment depo-sition, in the area corresponding to the 2002 sur-veyed pool area (about 4,900 acres), was 1.26 ft (feet), or 0.047 ft/yr (foot per year). Mean annual rates of deposition, by pool, from 1937 to 1964 varied from 0.016 to 0.083 ft/yr. From 1964 to 2002, the mean total sediment deposition in the 2002 surveyed pools was 0.753 ft, or 0.020 ft/yr. Therefore, the mean rate of sediment-depth accu-mulation from 1964 to 2002 was about 42 percent of the mean 1937 to 1964 rate, or a 58 percent reduction. Mean annual rates of deposition by pool from 1964 to 2002 varied from 0.010 to 0.049 ft/yr. Despite a substantial reduction in the average sediment accumulation rate for the Refuge, 5 of the 15 separate pools for which annual rates were calculated for both periods showed a small increase in the deposition rates of up to 0.008 ft/yr. Sediment deposits have resulted in a sub-stantial cumulative loss of volume in the Refuge pools since 1937. The 1937 to 2002 total sediment volume deposited in the 2002 surveyed pool area was about 9,900 acre-ft (acre-feet), or 152 acre-ft/yr (acre-feet per year). The volume of sediment deposited from 1937 to 1964 for these pools was about 6,200 acre-ft, or 230 acre-ft/yr. The volume deposited from 1964 to 2002 was about 3,700 acre-ft, or 97.3 acre-ft/yr.Bulk density values were determined from sediment cores collected from 22 sites in the Ref-uge and the bulk densities, along with sediment volumes, allowed for the calculation of sediment mass contributions to the Refuge. From 1937 to 2002, about 10,300,000 tons of sediment were deposited in the 2002 surveyed area, or 32.4 tons/acre/yr (tons per acre per year). The total computed mass of sediment deposited between 1937 and 1964 was about 6,510,000 tons, or an average of 49.1 tons/acre/yr. The total mass depos-ited from 1964 to 2002 in surveyed pools was about 3,830,000 tons, or an average of 20.5 tons/acre/yr. As with sediment thickness compari-sons, the rate of sediment mass deposition between 1964 to 2002 was about 42 percent of that from 1937 to 1964, or a 58 percent reduction.The greatest amounts of sediment deposition in the Refuge for 1937 to 2002 have been near the Squaw Creek and Davis Creek inflow spillway locations. Sediment depths in some areas near former inflow locations have exceeded 8 ft. Relo-cation of an inflow spillway effectively reduced additional sediment deposition at the original loca-tion, and caused increased sedimentation at the new inflow location. This is most clearly depicted in a pool located in the north section of the Refuge that directly received Squaw Creek inflows from 1937 to 1964 and had a mean deposition rate of 0.081 ft/yr reduced to 0.012 ft/yr, from 1964 to 2002, after inflows were redirected and erosion-management plans were implemented in the con-tributing basins.
Loess and its geomorphic, stratigraphic and paleoclimatic significance in the Quaternary

USGS Publications Warehouse

Muhs, Daniel R.

2013-01-01

Loess is aeolian silt visible in the field as a sedimentary body. It covers a significant portion of the land surface of the Earth. Loess thickness, particle size, and carbonate content decrease downwind from sources, useful trends for paleowinds. Many loess sections consist of relatively thick deposits of mostly unaltered sediment with intercalated paleosols. Paleosols represent periods of landscape stability when loess deposition slowed significantly. Loess in most regions was deposited during glacial periods and paleosols formed during interglacial periods. Loess has the potential to record the timing and environment of glacial–interglacial cycles of the Quaternary on many continents.
Transfer of fallout radionuclides derived from Fukushima NPP accident: 1 year study on transfer of radionuclides through hydrological processes

NASA Astrophysics Data System (ADS)

Onda, Yuichi; Kato, Hiroaki; Patin, Jeremy; Yoshimura, Kazuya; Tsujimura, Maki; Wakahara, Taeko; Fukushima, Takehiko

2013-04-01

Previous experiences such as Chernobyl Nuclear Power Plant accident have confirmed that fallout radionuclides on the ground surface migrate through natural environment including soils and rivers. Therefore, in order to estimate future changes in radionuclide deposition, migration process of radionuclides in forests, soils, ground water, rivers should be monitored. However, such comprehensive studies on migration through forests, soils, ground water and rivers have not been conducted so far. Here, we present the following comprehensive investigation was conducted to confirm migration of radionuclides through natural environment including soils and rivers. 1)Study on depth distribution of radiocaesium in soils within forests, fields, and grassland 2)Confirmation of radionuclide distribution and investigation on migration in forests 3)Study on radionuclide migration due to soil erosion under different land use 4)Measurement of radionuclides entrained from natural environment including forests and soils 5)Investigation on radionuclide migration through soil water, ground water, stream water, spring water under different land use 6)Study on paddy-to-river transfer of radionuclides through suspended sediments 7)Study on river-to-ocean transfer of radionuclides via suspended sediments 8)Confirmation of radionuclide deposition in ponds and reservoirs
Sediment Dynamics Within Buffer Zone and Sinkhole Splay Areas Under Extreme Soil Disturbance Conditions.

PubMed

Schoonover, Jon E; Crim, Jackie F; Williard, Karl W J; Groninger, John W; Zaczek, James J; Pattumma, Klairoong

2015-09-01

Sedimentation dynamics were assessed in sinkholes within training areas at Ft. Knox Military Installation, a karst landscape subjected to decades of tracked vehicle use and extreme soil disturbance. Sinkholes sampled were sediment-laden and behaved as intermittent ponds. Dendrogeomorphic analyses were conducted using willow trees (Salix spp.) located around the edge of 18 sinkholes to estimate historical sedimentation rates, and buried bottles were installed in 20 sinkholes at the center, outer edge, and at the midpoint between the center and edge to estimate annual sedimentation rates. Sedimentation data were coupled with vegetation characteristics of sinkhole buffers to determine relationships among these variables. The dendrogeomorphic method estimated an average accumulation rate of 1.27 cm year(-1) translating to a sediment loss rate of 46.1 metric ton year(-1) from the training areas. However, sediment export to sinkholes was estimated to be much greater (118.6 metric ton year(-1)) via the bottle method. These data suggest that the latter method provided a more accurate estimate since accumulation was greater in the center of sinkholes compared to the periphery where dendrogeomorphic data were collected. Vegetation data were not tightly correlated with sedimentation rates, suggesting that further research is needed to identify a viable proxy for direct measures of sediment accumulation in this extreme deposition environment. Mitigation activities for the sinkholes at Ft. Knox's tank training area, and other heavily disturbed karst environments where extreme sedimentation exists, should consider focusing on flow path and splay area management.
Bacterially mediated diagenetic origin for chert-hosted manganese deposits in the Franciscan Complex, California Coast Ranges

NASA Astrophysics Data System (ADS)

Hein, James R.; Koski, Randolph A.

1987-08-01

Numerous manganese deposits in the Franciscan Complex, California, occur as conformable lenses within bedded radiolarian chert-argillite sequences that are, in turn, intercalated within thicker sections of sandstone and shale. The field relations, composition, and petro-graphic and isotopic characteristics indicate that the manganese was concentrated by diagenetic reconstitution of siliceous and hemipelagic sediment during burial. The ore lenses are Mn-rich and Fe-poor assemblages consisting largely of rhodochrosite, manganese silicates, opal-CT (disordered cristobalite-tridymite), and quartz. Highly negative δ13C values for the carbonate carbon in rhodochrosite indicate that CO2 likely originated from oxidation of methane; less negative values result from mixing of methanogenic carbon and CO2 derived from bacterial degradation of organic matter. The δ18O values for the carbonate of rhodochrosite indicate temperatures of formation between 12 and 100 °C. The oxidation of methane prior to carbonate precipitation may have used the minor (0.4% 0.5%) Mn and Fe oxyhydroxides and oxides deposited with the sediment. The mobilization of manganese from biogenic and terrigenous sources in the sediment column into discrete horizons and the fractioriation of manganese from iron reflect the presence of oxidation-reduction boundaries and gradients in the sediment column. Fluids derived from compaction and silica-dehydration reactions in the transformation of opal-A (X-ray amorphous biogenic silica) to quartz were involved in transportation of principal components. Sedimentary and geochemical attributes suggest that the deposits formed in a deep-water environment in a zone of oceanic upwelling near a continental margin.
Paleo-environments of Late Pliocene to Early Pleistocene Foreland-Basin Deposits in the Western Foothills of South-Central Taiwan

NASA Astrophysics Data System (ADS)

Chiu, Tzu-Hsuan; Tien-Shun Lin, Andrew; Chi, Wen-Rong; Wang, Shih-Wei

2017-04-01

Lithofacies and paleo-environmental analyses of the Pliocene-Pleistocene deposits of Taiwan provide a framework to understand the stratigraphic development of foreland basin to the west of the orogenic belt. In this study, we performed lithofacies analyses and biostratigraphic studies on calcareous nannofossils in two areas in south-central Taiwan, the Jhuoshuei River, and the Hushan Reservoir, respectively. The studied lithostratigraphic units are the Chinshui Shale, the Cholan Formation, and the Toukoshan Formation, in an ascending order, with a total stratigraphic thickness more than 3500 m in central Taiwan. Sixteen lithofacies and four lithofacies associations are identified, pertaining to tide-dominated deltaic systems bordering a shallow marine setting in the foreland basin. A few wide-spread layers of thickly-bedded sandstones featuring ball-and-pillow structures are interpreted as resulting from earthquake shaking (i.e., seismites). In addition, the vertical facies change shows a coarsening and shallowing-upward succession, indicating the gradually filling up of the foreland basin by sediment progradation. The progradation is interpreted to result from westward migrating orogenic belt and an increase in sediment supply. The top 2000-m thick foreland succession (i.e., the uppermost part of the Cholan Formation, and the Toukoshan Formation) is dominantly fluvial deposits with occasional intercalations of shoreface sediments, indicating an extremely rapid and balanced rate of basin subsidence and sediment supply for the past 1.5 Ma. Vertebrate fossils of deer and elephants are identified in the upper Cholan Formation deposited in coastal to fluvial settings. Keywords: Pliocene-Pleistocene Epoch, lithofacies, foreland basin, Taiwan

Forearc sedimentation in Terraba Trough, Costa Rica, Central America

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yuan, P.B.; Lowe, D.R.

1987-05-01

Sedimentary rocks of Terraba Trough, Costa Rica, were deposited in a forearc basin developed at an ocean-ocean convergent boundary. The basin developed in the middle to late Eocene when the Farallon plate began its subduction beneath the Caribbean plate. Shallow-water carbonates of the Brito Formation were deposited on shoals of basement blocks. These were surrounded by deeper marine areas in which volcaniclastics and carbonate debris accumulated. The Brito Formation consists of algal-foraminiferal packstone to grainstone, rudstone, and rare wackestone formed in fore-slope, carbonate buildup, and open platform environments in a warm, tropical sea. The Eocene Brito Formation is overlain bymore » rocks of the upper Oligocene Rio Claro Member of the Terraba Formation. It is composed of rhodolite and bioclastic grainstone deposited in shallow water. A combination of little subsidence, mild volcanism, and possible erosion at about 30 Ma during a global drop of sea level may be responsible for the absence of lower Oligocene rocks in the study area. After the deposition of the Rio Claro Member, the area subsided rapidly to become a trough possibly deeper than 2000 m. Sedimentation took place in deep water from sediment gravity flows. In the early to early middle Miocene, coarser sediments and thicker sand units containing coal fragments became more abundant, suggesting that the basin was gradually filled. This study indicates that the timing and degree of subsidence of the fore-arc basin and the vertical variation in lithology are closely related to the variation in convergence rate between lithospheric plates in this part of Central America and the eastern Pacific.« less
Periplatform carbonate flux in the northern Bahamas

NASA Astrophysics Data System (ADS)

Pilskaln, Cynthia H.; Neumann, A. Conrad; Bane, John M.

1989-09-01

In a preliminary effort to quantify the off-bank transport and vertical flux of shallow-water carbonates, a sediment trap was moored at 500 m in Northwest Providence Channel, northern, Bahamas. Two months of particulate flux data collected during a fair-weather, storm-free period revealed that the flux components differed significantly from that of the underlying sediments. Planktonic foraminifera tests, pteropod shells, fragments and coccoliths contributed 61% to the total flux of carbonate material, whereas bank-derived carbonates constituted 39%. Coccolith calcite represented half of the carbonate mass flux in the fine size fraction (< 63 μm) of the trap material. In contrast, the underlying periplatform ooze sediments consist of 80% bank-derived and 20% planktonic carbonate components. The results suggest that the flux and deposition of bank-derived carbonates in the periplatform environment are variable on a temporal scale, where a relatively minor proportion of bank-derived components is deposited during calm, storm-free periods, with the balance delivered during the passage of frequent, low-amplitude seasonal storms and occasional hurricanes.
Bryozoans from rio grande do sul continental shelf, southern Brazil.

PubMed

Ramalho, Laís V; Calliari, Lauro

2015-05-06

The continental shelf of Rio Grande do Sul (RS) is predominantly composed of unconsolidated sediments with a few hard substrates represented principally by beachrock. In this area there are elongate deposits of shell gravel material which are interpreted as indicators of the palaeo-shorelines. These Pleistocene deposits are overlapped by Holocene sediments (Recent), but are exposed during erosive events caused by extra-tropical cyclones, which provide the mixture of both sediments mainly during autumn and winter. The few studies on bryozoans made in this area previously recorded seven species, one fossil and the other six from Recent fluvial and marine environments. The aim of the present study was to describe the eight most abundant bryozoan species that occur in the inner RS shelf. Of these, four are new records for RS State (Arachnopusia aff. pusae, Hippomonavella brasiliensis, Turbicellepora pourtalesi, and Lifuella gorgonensis), and the other four are new to science (Chaperia taylori, Micropora nodimagna, Cellaria riograndensis, and Exochella moyani).
Cryofacies evidences of a Yedoma (?) development during the last glacial maximum in Yukon (Canada) along the current Alaska border

NASA Astrophysics Data System (ADS)

Stephani, E.; Fortier, D.; Shur, Y.

2012-12-01

In some areas that remained unglaciated during the Late Pleistocene, inorganic and organic sedimentation supported syngenetic upward permafrost development and the creation of so-called yedoma deposits (Ice Complex). This type of periglacial deposit is usually very ice-rich and is highly unstable upon thawing. As this deposit thaws, the landscape goes from a carbon sink to a carbon and inorganic sediment source. This carbon can be released into the environment or transformed to CH4. Yedoma deposits have been extensively studied in Russia and more recently in Alaska. However, very few studies have focused on yedomas of Yukon. With the objective to provide regional information on yedoma distribution in North America, we present here preliminary field evidences of a yedoma deposit near Beaver Creek, close to current Alaska border. 28 boreholes were core-drilled, and cores were described and analyzed in the laboratory. Well-developed microlenticular cryostructures in silt and numerous small rootlets are typical of yedoma deposit. Tiny ice lenses are formed in fine-grained sediment by cryosuction and rootlets gets incorporated into the permafrost as the table rises syngenetically in response to surface sedimentation. During sedimentary accumulation, when sedimentation slows down, peat layers can be formed at the surface. This change in material properties often lead to the development of belt-like cryostructures (thick ice lenses separated by reticulate ice veins). At Beaver Creek, the microlenticular and belt-like cryofacies with rootlets (typical of syngenetic ice-rich yedoma) were abundant in Units 2A and 2C. The average ice content of Units 2A and 2C was respectively 91 % and 109 %, and the organic matter content (loss on ignition) was 6 % and 8 %. Significant thaw strain was measured in Units 2A (50%) and 2C (35%). Interestingly Unit 2B was very ice-poor (gravimetric ice content: 47 %, thaw strain: 9 %) and showed only porous cryostructure (interstitial ice) in silt (3 % organic matter). This was interpreted as ice-rich fine-grained soils that thawed, drained, and refroze afterward. This ice-poor layer with sediment deformations (e.g. fold, fault, diapir) is called 'taberal deposit' in the Russian literature. This layer can be observed in yedoma deposit in areas which were affected by permafrost degradation. Yedoma deposits are usually characterized by the presence of tall and wide ice wedges. These wedges form continuously as the permafrost table rises in response to surface sedimentation and their size is thus a function of sedimentation rate and time. In our study, we observed ice wedges at least 8 m tall (tip of the wedge > maximum coring depth). The bottom of the ice wedges was located in lodgement till (> 11 m below surface). This deposit was covered by woody peat deposit up to 4.9 m thick and was thus interpreted to be older than MIS 3. We propose that frost cracking first occurred in the peat and the underlying diamicton after the last interglacial and that upward syngenetic ice wedge growth followed silt accumulation over thousands of years sometimes during the last glacial period. The top of the ice wedges were located at about 2.5 m depth in Unit 2B. This indicates that ice wedge growth was interrupted by an episode of permafrost degradation and resumed afterward during accumulation of unit 2A.
Magnetic fingerprint in marine sediments: clues from cultivated Magnetovibrio blakemorei and recent cores from Brazilian Coast

NASA Astrophysics Data System (ADS)

Jovane, L.; Florindo, F.; Bazylinski, D. A.; Pellizari, V. H.; Brandini, F. P.; de Almeida, L. A.; Carneiro, F. R.; Braga, E. D.; Lins, U.

2013-12-01

The magnetic properties (first order reversal curves, ferromagnetic resonance and decomposition of saturation remanent magnetization acquisition) of Magnetovibrio blakemorei strain MV-1, a marine magnetotactic bacterium, differ from those of other magnetotactic species from sediments deposited in lakes and marine habitats previously studied. This finding suggests that magnetite produced by some magnetotactic bacteria retains magnetic properties in relation to the crystallographic structure of the magnetic phase produced and thus might represent a 'magnetic fingerprint' for a specific magnetotactic bacterium. The technique used to determine this fingerprint is a non-destructive, new technology that might allow for the identification and presence of specific species or types of magnetotactic bacteria in certain environments such as sediment. We also show some preliminary results on the biogeochemical factors that control magnetotactic bacterial populations, documenting the environment and the preservation of bacterial magnetite, which dominates the palaeomagnetic signal throughout recent sediments from Brazilian Coast. We searched for magnetotactic bacteria in order to understand the ecosystems and environmental change related to their presence in sediments. We focused on studying the environmental conditions that allow for the presence of magnetotactic bacteria and magnetosomes in sediments including determining magnetotactic bacterial populations in marine settings, measuring crucial nutrient availability in the water column and in sediments, and examining particulate delivery to the seafloor.
Profiling bacterial diversity in a limestone cave of the western Loess Plateau of China

PubMed Central

Wu, Yucheng; Tan, Liangcheng; Liu, Wuxing; Wang, Baozhan; Wang, Jianjun; Cai, Yanjun; Lin, Xiangui

2015-01-01

Bacteria and archaea sustain subsurface cave ecosystems by dominating primary production and fueling biogeochemical cyclings, despite the permanent darkness and shortage of nutrients. However, the heterogeneity and underlying mechanism of microbial diversity in caves, in particular those well connect to surface environment are largely unexplored. In this study, we examined the bacterial abundance and composition in Jinjia Cave, a small and shallow limestone cave located on the western Loess Plateau of China, by enumerating and pyrosequencing small subunit rRNA genes. The results clearly reveal the contrasting bacterial community compositions in relation to cave habitat types, i.e., rock wall deposit, aquatic sediment, and sinkhole soil, which are differentially connected to the surface environment. The deposits on the cave walls were dominated by putative cave-specific bacterial lineages within the γ-Proteobacteria or Actinobacteria that are routinely found on cave rocks around the world. In addition, sequence identity with known functional groups suggests enrichments of chemolithotrophic bacteria potentially involved in autotrophic C fixation and inorganic N transformation on rock surfaces. By contrast, bacterial communities in aquatic sediments were more closely related to those in the overlying soils. This is consistent with the similarity in elemental composition between the cave sediment and the overlying soil, implicating the influence of mineral chemistry on cave microhabitat and bacterial composition. These findings provide compelling molecular evidence of the bacterial community heterogeneity in an East Asian cave, which might be controlled by both subsurface and surface environments. PMID:25870592
Profiling bacterial diversity in a limestone cave of the western Loess Plateau of China.

PubMed

Wu, Yucheng; Tan, Liangcheng; Liu, Wuxing; Wang, Baozhan; Wang, Jianjun; Cai, Yanjun; Lin, Xiangui

2015-01-01

Bacteria and archaea sustain subsurface cave ecosystems by dominating primary production and fueling biogeochemical cyclings, despite the permanent darkness and shortage of nutrients. However, the heterogeneity and underlying mechanism of microbial diversity in caves, in particular those well connect to surface environment are largely unexplored. In this study, we examined the bacterial abundance and composition in Jinjia Cave, a small and shallow limestone cave located on the western Loess Plateau of China, by enumerating and pyrosequencing small subunit rRNA genes. The results clearly reveal the contrasting bacterial community compositions in relation to cave habitat types, i.e., rock wall deposit, aquatic sediment, and sinkhole soil, which are differentially connected to the surface environment. The deposits on the cave walls were dominated by putative cave-specific bacterial lineages within the γ-Proteobacteria or Actinobacteria that are routinely found on cave rocks around the world. In addition, sequence identity with known functional groups suggests enrichments of chemolithotrophic bacteria potentially involved in autotrophic C fixation and inorganic N transformation on rock surfaces. By contrast, bacterial communities in aquatic sediments were more closely related to those in the overlying soils. This is consistent with the similarity in elemental composition between the cave sediment and the overlying soil, implicating the influence of mineral chemistry on cave microhabitat and bacterial composition. These findings provide compelling molecular evidence of the bacterial community heterogeneity in an East Asian cave, which might be controlled by both subsurface and surface environments.
Dynamic modeling of environmental risk associated with drilling discharges to marine sediments.

PubMed

Durgut, İsmail; Rye, Henrik; Reed, Mark; Smit, Mathijs G D; Ditlevsen, May Kristin

2015-10-15

Drilling discharges are complex mixtures of base-fluids, chemicals and particulates, and may, after discharge to the marine environment, result in adverse effects on benthic communities. A numerical model was developed to estimate the fate of drilling discharges in the marine environment, and associated environmental risks. Environmental risk from deposited drilling waste in marine sediments is generally caused by four types of stressors: oxygen depletion, toxicity, burial and change of grain size. In order to properly model these stressors, natural burial, biodegradation and bioturbation processes were also included. Diagenetic equations provide the basis for quantifying environmental risk. These equations are solved numerically by an implicit-central differencing scheme. The sediment model described here is, together with a fate and risk model focusing on the water column, implemented in the DREAM and OSCAR models, both available within the Marine Environmental Modeling Workbench (MEMW) at SINTEF in Trondheim, Norway. Copyright © 2015 Elsevier Ltd. All rights reserved.
Sidescan-Sonar Imagery and Surficial Geologic Interpretations of the Sea Floor in Western Rhode Island Sound

USGS Publications Warehouse

McMullen, K.Y.; Poppe, L.J.; Haupt, T.A.; Crocker, J.M.

2009-01-01

The U.S. Geological Survey (USGS) and National Oceanic and Atmospheric Administration (NOAA) have been working together to interpret sea-floor geology along the northeastern coast of the United States. In 2004, the NOAA Ship RUDE completed survey H11322, a sidescan-sonar and bathymetric survey that covers about 60 square kilometers of the sea floor in western Rhode Island Sound. This report interprets sidescan-sonar and bathymetric data from NOAA survey H11322 to delineate sea-floor features and sedimentary environments in the study area. Paleozoic bedrock and Cretaceous Coastal Plain sediments in Rhode Island Sound underlie Pleistocene glacial drift that affects the distribution of surficial Holocene marine and transgressional sediments. The study area has three bathymetric highs separated by a channel system. Features and patterns in the sidescan-sonar imagery include low, moderate, and high backscatter; sand waves; scarps; erosional outliers; boulders; trawl marks; and dredge spoils. Four sedimentary environments in the study area, based on backscatter and bathymetric features, include those characterized by erosion or nondeposition, coarse-grained bedload transport, sorting and reworking, and deposition. Environments characterized by erosion or nondeposition and coarse-grained bedload transport are located in shallower areas and environments characterized by deposition are located in deeper areas; environments characterized by sorting and reworking processes are generally located at moderate depths.
Constraining Lipid Biomarker Paleoclimate Proxies in a Small Arctic Watershed

NASA Astrophysics Data System (ADS)

Dion-Kirschner, H.; McFarlin, J. M.; Axford, Y.; Osburn, M. R.

2017-12-01

Arctic amplification of climate change renders high-latitude environments unusually sensitive to changes in climatic conditions (Serreze and Barry, 2011). Lipid biomarkers, and their hydrogen and carbon isotopic compositions, can yield valuable paleoclimatic and paleoecological information. However, many variables affect the production and preservation of lipids and their constituent isotopes, including precipitation, plant growth conditions, biosynthesis mechanisms, and sediment depositional processes (Sachse et al., 2012). These variables are particularly poorly constrained for high-latitude environments, where trees are sparse or not present, and plants grow under continuous summer light and cool temperatures during a short growing season. Here we present a source-to-sink study of a single watershed from the Kangerlussuaq region of southwest Greenland. Our analytes from in and around `Little Sugarloaf Lake' (LSL) include terrestrial and aquatic plants, plankton, modern lake water, surface sediments, and a sediment core. This diverse sample set allows us to fulfill three goals: 1) We evaluate the production of lipids and isotopic signatures in the modern watershed in comparison to modern climate. Our data exhibit genus-level trends in leaf wax production and isotopic composition, and help clarify the difference between terrestrial and aquatic signals. 2) We evaluate the surface sediment of LSL to determine how lipid biomarkers from the watershed are incorporated into sediments. We constrain the relative contributions of terrestrial plants, aquatic plants, and other aquatic organisms to the sediment in this watershed. 3) We apply this modern source-to-sink calibration to the analysis of a 65 cm sediment core record. Our core is organic-rich, and relatively high deposition rates allow us to reconstruct paleoenvironmental changes with high resolution. Our work will help determine the veracity of these common paleoclimate proxies, specifically for research in southwest Greenland, and will enable an accurate, high-resolution watershed-level reconstruction of Holocene conditions. Serreze, M. and Barry, R. (2011). Global and Planetary Change, 77, 85-96. Sachse, D., et al. (2012). Annual Review of Earth and Planetary Sciences, 40, 221-249.
Syn-eruptive, soft-sediment deformation of dilute pyroclastic density current deposits: triggers from granular shear, dynamic pore pressure, ballistic impacts and shock waves

NASA Astrophysics Data System (ADS)

Douillet, G. A.; Taisne, B.; Tsang-Hin-Sun, È.; Müller, S. K.; Kueppers, U.; Dingwell, D. B.

2014-12-01

Soft-sediment deformation produces intriguing sedimentary structures and can occur in diverse environments and from a variety of triggers. From the observation of such structures and their interpretation in terms of trigger mechanisms, valuable information can be extracted about former conditions. Here we document examples of syn-eruptive deformation in dilute pyroclastic density current deposits. Outcrops from 6 different volcanoes have been compiled in order to provide a broad perspective on the variety of structures: Ubehebe craters (USA), Tungurahua (Ecuador), Soufrière Hills (Montserrat), Laacher See (Germany), Tower Hill and Purrumbete lake (both Australia). Isolated slumps as well as sinking pseudonodules are driven by their excess weight and occur after deposition but penecontemporaneous to the eruption. Isolated, cm-scale, overturned beds with vortex forms have been interpreted to be the signature of shear instabilities occurring at the boundary of two granular media. They may represent the frozen record of granular, pseudo Kelvin-Helmholtz instabilities. Their recognition can be a diagnostic for flows with a granular basal boundary layer. The occurrence of degassing pipes together with basal intrusive dikes suggest fluidization during flow stages, and can facilitate the development of Kelvin-Helmholtz structures. The occurrence at the base of flow units of injection dikes in some outcrops compared with suction-driven local uplifts in others indicates the role of dynamic pore pressure. Variations of the latter are possibly related to local changes between depletive and accumulative dynamics of flows. Ballistic impacts can trigger unconventional sags producing local displacement or liquefaction. Based on the deformation depth, these can yield precise insights into depositional unit boundaries. Such impact structures may also be at the origin of some of the steep truncation planes visible at the base of the so-called "chute and pool" structures. Finally, the passage of shock waves emanating from the vent may be preserved in the form of trains of isolated, fine-grained overturned beds which may disturb the surface bedding without occurrence of a sedimentation phase in the vicinity of a vent. Dilute pyroclastic density currents occur contemporaneously with seismogenic volcanic explosions. They are often deposited on steep slopes and can incorporate large amounts of water and gas in the sediment. They can experience extremely high sedimentation rates and may flow at the border between traction, granular and fluid-escape boundary zones. These are just some of the many possible triggers acting in a single environment, and reveal the potential for insights into the eruptive mechanisms of dilute pyroclastic density currents.
Sediment Retention Dynamics and Vegetation Along Three Tributaries of the Chesapeake Bay

NASA Astrophysics Data System (ADS)

Ross, K.; Ross, K.; Hupp, C.; Alexander, L.; Alexander, L.

2001-12-01

Coastal Plain riparian wetlands in the Mid-Atlantic United States are the last place for sediment and contaminant storage before reaching critical estuarine and marine environments. The deteriorating health of the Chesapeake Bay has been attributed in part to elevated sediment loads. The purpose of this study is to investigate the effects of channelization and urbanization on sediment deposition and geomorphic processes along the Pocomoke and Chickahominy Rivers and Dragon Run, three Coastal Plain tributaries. Floodplain microtopography was surveyed in 100 x 100 m grids at three characteristic reaches along each river and woody vegetation analyses were conducted. Floodplain suspended sediment concentrations and short and long-term sedimentation rates were estimated at each reach using single stage sediment sampler arrays, clay pads and dendrogeomorphic techniques, respectively. Site hydroperiod and flow characteristics were determined from USGS gaging station records, floodplain water level recorders, and field observations. Channelized floodplain reaches along the Pocomoke River are flooded less frequently, have lower mineral sedimentation rates (2 mm/yr to 6 mm/yr) and woody species diversity than the unchannelized reaches. Along the Chickahominy River, floodplain wetlands close to urban centers are flooded more frequently, but have shorter hydroperiods (3.5 days/yr compared to more than 45 days/yr), lower sedimentation rates (1.8 mm/yr to 6.8 mm/yr), and lower woody species diversity (0.51 to 1.95 on the Shannon-Weiner diversity index) than floodplains further downstream. Suspended sediment delivery and deposition rates are significantly influenced by floodplain hydroperiod duration and channel-floodplain connectivity. These results suggest that understanding floodplain sediment dynamics and geomorphic processes with respect to dominant watershed landuse patterns is critical for effective water quality management and restoration efforts.
Postglacial sedimentary record of the Southern California continental shelf and slope, Point Conception to Dana Point

USGS Publications Warehouse

Sommerfield, C.K.; Lee, H.J.; Normark, W.R.

2009-01-01

Sedimentary strata on the Southern California shelf and slope (Point Conception to Dana Point) display patterns and rates of sediment accumulation that convey information on sea-level inundation, sediment supply, and oceanic transport processes following the Last Glacial Maximum. In Santa Monica Bay and San Pedro Bay, postglacial transgression is recorded in shelf deposits by wave-ravinement surfaces dated at 13-11 ka and an upsection transition from coastal to shallow-marine sediment facies. Depositional conditions analogous to the modern environment were established in the bays by 8-9 ka. On the continental slope, transgression is evidenced in places by an increase in sediment grain size and accumulation rate ca. 15-10 ka, a consequence of coastal ravinement and downslope resedimentation, perhaps in conjunction with climatic increases in fluvial sediment delivery. Grain sizes and accumulation rates then decreased after 12-10 ka when the shelf flooded and backfilled under rising sea level. The Santa Barbara coastal cell contains the largest mass of postglacial sediment at 32-42 ?? 109 metric tons, most of which occurs between offshore Santa Barbara and Hueneme Canyon. The San Pedro cell contains the second largest quantity of sediment, 8-11 ?? 109 metric tons, much of which is present on the eastern Palos Verdes and outer San Pedro shelves. By comparison, the mass of sediment sequestered within the Santa Monica cell is smaller at ??6-8 ?? 109 metric tons. The postglacial sediment mass distribution among coastal cells reflects the size of local fluvial sediment sources, whereas intracell accumulation patterns reflect antecedent bathymetric features conducive for sediment bypass or trapping. ?? 2009 The Geological Society of America.
Carbonate Channel-Levee Systems Influenced by Mass-Transport Deposition, Browse Basin, Australia

NASA Astrophysics Data System (ADS)

Dunlap, D.; Janson, X.; Sanchez-Phelps, C.; Covault, J. A.

2017-12-01

Submarine channels are primary conduits for clastic sediment transport to deep-water basins, thereby controlling the location of marine depocenters and sediment bypass. The evolution and depositional character of submarine channels have broad implications to sediment dispersal, sediment quality, and hydrocarbon exploration potential. Siliciclastic channel systems have been extensively studied in modern environments, seismic and outcrop; however, carbonate channel-levee deposits have only recently been explored. Here we utilize newly released high-resolution (90 Hz) seismic-reflection data from the Australian Browse Basin to document the influence of mass-transport complex (MTC) deposition on the stratigraphic architecture of carbonate channel-levee systems. The 2014 vintage seismic survey is 2500 km2 and hosts numerous large Miocene-age carbonate channel-levee complexes basinward of the shelf edge. Regional horizons and individual channel forms were mapped. Channels range from 200-300 m wide and are bounded by high-relief levee-overbank wedges (>100 ms TWTT). These channels extend across the survey area >70 km. The leveed-channels were sourced from middle and late Miocene slope gullies linked to platform carbonates. Slope-attached and locally derived MTC's are evident throughout the Miocene section likely related to periods of basin inversion and shelf-edge gully incision. We interpret that regionally extensive (>1000 km2) slope-attached MTC's can shut down a channel-levee system and trigger the initiation of a new system, whereas more locally derived (<100 km2) MTC's can promote changes in channel map-view pattern, including avulsion in some cases. The stratigraphic architectures of the carbonate channel-levee systems and their interactions with MTC's are similar to siliciclastic analogs. The similarity in stratigraphic patterns between siliciclastic and carbonate depositional systems suggests similar formative processes related to submarine mass wasting and turbidity currents, which informs depositional models of carbonate slope systems and calls for re-evaluation of the controls on stratigraphic patterns in mixed siliciclastic-carbonate deep-water basins.
Impact of structural and autocyclic basin-floor topography on the depositional evolution of the deep-water Valparaiso forearc basin, central Chile

USGS Publications Warehouse

Laursen, J.; Normark, W.R.

2003-01-01

The Valparaiso Basin constitutes a unique and prominent deep-water forearc basin underlying a 40-km by 60-km mid-slope terrace at 2.5-km water depth on the central Chile margin. Seismic-reflection data, collected as part of the CONDOR investigation, image a 3-3.5-km thick sediment succession that fills a smoothly sagged, margin-parallel, elongated trough at the base of the upper slope. In response to underthrusting of the Juan Ferna??ndez Ridge on the Nazca plate, the basin fill is increasingly deformed in the seaward direction above seaward-vergent outer forearc compressional highs. Syn-depositional growth of a large, margin-parallel monoclinal high in conjunction with sagging of the inner trough of the basin created stratal geometries similar to those observed in forearc basins bordered by large accretionary prisms. Margin-parallel compressional ridges diverted turbidity currents along the basin axis and exerted a direct control on sediment depositional processes. As structural depressions became buried, transverse input from point sources on the adjacent upper slope formed complex fan systems with sediment waves characterising the overbank environment, common on many Pleistocene turbidite systems. Mass failure as a result of local topographic inversion formed a prominent mass-flow deposit, and ultimately resulted in canyon formation and hence a new focused point source feeding the basin. The Valparaiso Basin is presently filled to the spill point of the outer forearc highs, causing headward erosion of incipient canyons into the basin fill and allowing bypass of sediment to the Chile Trench. Age estimates that are constrained by subduction-related syn-depositional deformation of the upper 700-800m of the basin fill suggest that glacio-eustatic sea-level lowstands, in conjunction with accelerated denudation rates, within the past 350 ka may have contributed to the increase in simultaneously active point sources along the upper slope as well as an increased complexity of proximal depositional facies.
National Uranium Resource Evaluation: Palestine Quadrangle, Texas and Louisiana

DOE Office of Scientific and Technical Information (OSTI.GOV)

McGowen, M.; Basciano, J.; Fose, F.G. Jr.

1982-09-01

The uranium resource potential of the Palestine Quadrangle, Texas and Louisiana, was evaluated to a depth of 1500 m (5000 ft) using criteria established for the National Uranium Resource Evaluation program. Data derived from geochemical analyses of surface samples (substrate, soil, and stream sediment) in conjunction with hydrochemical data from water wells were used to evaluate geologic environments as being favorable or unfavorable for the occurrence of uranium deposits. Two favorable environments have been identified in the Palestine Quadrangle: potential deposits of modified Texas roll-type in fluvial channels and associated facies within the Yegua Formation, and potential occurrences along mineralizationmore » fronts associated with the Elkhart Graben and Mount Enterprise fault system. Unfavorable environments include: Cretaceous shales and limestones, Tertiary fine-grained marine sequences, Tertiary sandstone units that exhibit favorable host-rock characteristics but fail to show significant syngenetic or epigenetic mineralization, and Quaternary sands and gravels. Unevaluated units include the Woodbine Group (Upper Cretaceous), Jackson Group (Tertiary), and Catahoula Formation (Tertiary). The subsurface interval of the Jackson Group and Catahoula Formation contains depositional facies that may represent favorable environments; however, the evaluation of these units is inconclusive because of the general lack of shallow subsurface control and core material. The Woodbine Group, restricted to the subsurface except for a small exposure over Palestine Dome, occurs above 1500 m (5000 ft) in the northwest quarter of the quadrangle. The unit exhibits favorable host-rock characteristics, but the paucity of gamma logs and cores, as well as the lack of hydrogeochemical and stream-sediment reconnaissance data, makes evaluation of the unit difficult.« less
Holocene deposits in the Mangyshlak Peninsula, North Caspian Sea region

NASA Astrophysics Data System (ADS)

Bezrodnykh, Yu. P.; Deliya, S. V.; Romanyuk, B. F.; Fedorov, V. I.; Sorokin, V. M.; Luksha, V. L.

2014-07-01

Comprehensive analysis of the data of high-precision seismoacoustic profiling, drilling and sampling of deposits using seabed corers, biostratigraphic studies, and radiocarbon age data was performed for the first time for Mangyshlak sediments in several bottom sites of the North Caspian. It was found that the Mangyshlak sediments comprise numerous linearly stretched depressions of 5-10 m in depth (morphologically similar to modern substeppe ilmen areas in the Volga River delta), which are covered by the Novocaspian sedimentary cover, and river incisions (among them the largest Volga River valley). In addition, the Mangyshlak sediments comprise the deltaic alluvial fans of different sizes along the shelf zone of the North Caspian. Analysis of mollusks and biogenic remains indicates that accumulation of the Mangyshlak sediments occurred in freshwater and slightly salty water environments under various hydrodynamic and hydrochemical conditions. According to radiocarbon dating of organic matter, the Mangyshlak sediments formed during sea regression in the range of 10-8 ka (isotopic age) or 11.5-8.5 ka (calendar age). Several types of sediments are distinguished: clayey-carbonate sediments, enriched with organic matter up to the formation of sapropel and peat, accumulated at the lowest sea level; weakly calcareous silty-clayey silts, formed during the subsequent intense filling of paleodepressions with terrigenous material. The features of the mineral composition of sediments are as follows: polymineral composition of clayey material with a high proportion of hydromica and disordered mixed-layered formations, a high content of minerals of the epidote group, amphiboles, and other accessory minerals. All of this indicates a genetic relationship between the Mangyshlak sediments and the Volga terrigenous material.
Late Quaternary stratigraphy and sedimentation patterns in the western Arctic Ocean

USGS Publications Warehouse

Polyak, L.; Bischof, J.; Ortiz, J.D.; Darby, D.A.; Channell, J.E.T.; Xuan, C.; Kaufman, D.S.; Lovlie, R.; Schneider, D.A.; Eberl, D.D.; Adler, R.E.; Council, E.A.

2009-01-01

Sediment cores from the western Arctic Ocean obtained on the 2005 HOTRAX and some earlier expeditions have been analyzed to develop a stratigraphic correlation from the Alaskan Chukchi margin to the Northwind and Mendeleev-Alpha ridges. The correlation was primarily based on terrigenous sediment composition that is not affected by diagenetic processes as strongly as the biogenic component, and paleomagnetic inclination records. Chronostratigraphic control was provided by 14C dating and amino-acid racemization ages, as well as correlation to earlier established Arctic Ocean stratigraphies. Distribution of sedimentary units across the western Arctic indicates that sedimentation rates decrease from tens of centimeters per kyr on the Alaskan margin to a few centimeters on the southern ends of Northwind and Mendeleev ridges and just a few millimeters on the ridges in the interior of the Amerasia basin. This sedimentation pattern suggests that Late Quaternary sediment transport and deposition, except for turbidites at the basin bottom, were generally controlled by ice concentration (and thus melt-out rate) and transportation distance from sources, with local variances related to subsurface currents. In the long term, most sediment was probably delivered to the core sites by icebergs during glacial periods, with a significant contribution from sea ice. During glacial maxima very fine-grained sediment was deposited with sedimentation rates greatly reduced away from the margins to a hiatus of several kyr duration as shown for the Last Glacial Maximum. This sedimentary environment was possibly related to a very solid ice cover and reduced melt-out over a large part of the western Arctic Ocean.
Regional Big Injun (Price/Pocono) subsurface stratigraphy of West Virginia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Donaldson, A.C.; Zou, Xiangdong

1992-01-01

The lower Big Injun (Lower Mississippian) is the oil reservoir of the Granny Creek and Rock Creek fields and consists of multiple sandstones that were deposited in different fluvial-deltaic depositional environments. These multiple sandstones became amalgamated and now appear as a widespread blanket sandstone as a result of ancient cut and fill processes associated with river-channel sedimentation. The regional study of this Price Formation subsurface equivalent considers the continuity and thickness variations of the composite sandstones of the Big Injun mainly within western West Virginia. The major fluvial drainage system apparently flowed southward through Ohio (much of it later erodedmore » by the pre-Pottsville unconformity) during Big Injun time (and earlier) and part of the system was diverted into southwestern West Virginia as vertically stacked channel and river-mouth bar deposits (Rock Creek field). This ancient Ontario River system apparently drained a huge area including the northern craton as well as the orogenic belt. The emerging West Virginia Dome probably sourced the sediment transported by small rivers developing southwestward prograding deltas across Clay County (Granny Creek field). Sedimentation was affected by differential subsidence in the basin. Paleovalley fill was considered for areas with vertically stacked sandstones, but evidence for their origin is not convincing. Oil-reservoir sandstones are classified as dip-trending river channel (D1) and deltaic shoreline (D2) deposits.« less
New Insights into an Old Cycle: The Marine Phosphorus Cycle and the Formation of Critical Phosphate Rock Resources (Invited)

NASA Astrophysics Data System (ADS)

Filippelli, G. M.

2010-12-01

The cycling and geochemistry of phosphorus (P) in the marine environment is a critical component of biological productivity and of resource availability: P control the long-term carbon cycle via its role as a limiting nutrient, and the burial and concentration of P within marine sediments dictates the quality and availability of P as a fertilizer component from a resources standpoint. Given the projections of severe P fertilizer limitation over the next several centuries, understanding the controls on P geochemistry and concentration into a minable resource is critical in sustaining global populations. Several critical aspects of the marine P cycle have been uncovered over the past few decades which have clarified our understanding of P burial and concentration. First, the initial authigenic process of P mineralization within marine sediments, termed phosphogenesis, seems to occur regardless of marine setting. Phosphogenesis results from the release of P into sedimentary pore waters from organic and oxide-bound fractions, and the subsequent supersaturation with respect to carbonate fluorapatite. In sediment-starved basins with significant upwelling-driven productivity, the supply of P into sedimentary pore waters can be so high that visibly apparent layers of carbonate fluorapatite can be formed. Even in such environments, however, the mineral P content is too low to be of economic value unless it has undergone concentration via sediment reworking, a common occurrence in some dynamic continental margin environments. Thus, a combination of phosphogenesis in a high productivity setting plus sediment starvation plus condensation via reworking are necessary to produce phosphorites, sedimentary rocks with high P contents which are ideal as fertilizer-grade P resources. Given these special marine conditions, phosphorites are largely distributed along ancient marine environments (with the exception of the nearly-depleted atoll guano reserves). The largest currently-identified minable reservoirs of ore-grade P are found in the United States, in China, and in Morocco. Numerous less-economic sedimentary deposits exist, but these deposits are more dilute and represent former marine settings without the trifecta of productivity, geochemistry and sedimentology that makes phosphorites economically viable.

Heavy minerals in the 2011 Tohoku-oki tsunami deposits—insights into sediment sources and hydrodynamics

NASA Astrophysics Data System (ADS)

Jagodziński, Robert; Sternal, Beata; Szczuciński, Witold; Chagué-Goff, Catherine; Sugawara, Daisuke

2012-12-01

The 2011 Tohoku-oki tsunami left sand and mud deposits more than 4 km inland on the coastal plain of Sendai, Japan. The tsunami deposits, pre-tsunami soils and beach sediments were analysed for grain size, and heavy mineral content and assemblages to test the applicability of heavy mineral analyses in the identification of tsunami deposits and interpretation of associated sedimentation processes. Heavy minerals comprised on average 35% of the tsunami deposit in the 0.125-0.25 mm grain size fraction. The most common were orthopyroxenes, clinopyroxenes, amphiboles, limonites and opaque minerals. Heavy mineral concentrations and assemblages were similar in the tsunami deposits, beach and pre-tsunami soils and sediments and thus tsunami deposits could not simply be identified based on their heavy minerals. Sediment provenance analysis revealed that tsunami deposits left within 1.5 km of the shoreline were mostly eroded from the beach, dune and local soils, while deposits farther inland (> 1.5 km) were mostly derived from local soil erosion. No evidence was found for a significant contribution of offshore sediments. Detailed analyses revealed that the lowermost portion of tsunami deposits was mostly of local origin, while the sediment source of the upper portion was variable. A comparison with a previous study of heavy minerals in 2004 IOT deposits confirms that heavy minerals in tsunami deposits are mostly source-dependent and may represent a useful supplementary tool in studies of tsunami deposits. However, the interpretation must always be placed in the local geological context and corroborated with other "tsunami proxies".
Geologic framework of the regional ground-water flow system in the Upper Deschutes Basin, Oregon

USGS Publications Warehouse

Lite, Kenneth E.; Gannett, Marshall W.

2002-12-10

Geologic units in the Deschutes Basin were divided into several distinct hydrogeologic units. In some instances the units correspond to existing stratigraphic divisions. In other instances, hydrogeologic units correspond to different facies within a single stratigraphic unit or formation. The hydrogeologic units include Quaternary sediment, deposits of the Cascade Range and Newberry Volcano, four zones within the Deschutes Formation and age-equivalent rocks that roughly correspond with depositional environments, and pre-Deschutes-age strata.
DOE Office of Scientific and Technical Information (OSTI.GOV)

Cox, D.L.

The Berea Sandstone is a widely recognized producer of oil and gas in the Appalachian basin. Subsurface mapping, core analysis, and production data from producing wells have been evaluated in west-central West Virginia, where the Berea Sandstone represents a wide range of nearshore and coastal environments. Fluvial system deposits are found in southern Jackson County as channel sands (Gay-Fink) and adjacent deltaic facies. Coastal sediments were deposited to the north as intertidal shoals, tidal flats, and coarse-grained tidal-creek point bars. Marine shelf sands are found to the west.
Assessing the paradigm of mutually exclusive erosion and deposition of mud, with examples from upper Chesapeake Bay

USGS Publications Warehouse

Sanford, L.P.; Halka, J.P.

1993-01-01

A paradigm of cohesive sediment transport research is that erosion and deposition are mutually exclusive. Many laboratory studies have shown that there is a velocity/stress threshold below which erosion does not occur and a lower threshold above which deposition does not occur. In contrast, a deposition threshold is not included in standard noncohesive sediment transport models, allowing erosion and deposition to occur simultaneously. Several researchers have also modeled erosion and deposition of mud without a deposition threshold. This distinction can have important implications for suspended sediment transport predictions and for data interpretation. Model-data comparisons based on observations of in situ erosion and deposition of upper Chesapeake Bay mud indicate poor agreement when the sediments are modeled as a single resuspended particle class and mutually exclusive erosion and deposition is assumed. The total resuspended sediment load increases in conjunction with increasing bottom shear stress as anticipated, but deposition is initiated soon after the shear stress begins to decrease and long before the stress falls below the value at which erosion had previously begun. Models assuming no critical stress for deposition, with continuous deposition proportional to the near bottom resuspended sediment concentration, describe the data better. Empirical parameter values estimated from these model fits are similar to other published values for estuarine cohesive sediments, indicating significantly greater erodability for higher water content surface sediments and settling velocities appropriate for large estuarine flocs. The apparent failure of the cohesive paradigm when applied to in situ data does not mean that the concept of a critical stress for deposition is wrong. Two possibilities for explaining the observed discrepancies are that certain aspects of in situ conditions have not been replicated in the laboratory experiments underlying the cohesive paradigm, and that in situ sediment behavior is better described as a sequence of particle classes than as the single particle class modeled here. However, the in situ measurements needed to resolve these questions are very difficult and data generally are not available. For practical modeling purposes, allowing continuous deposition of a single resuspended particle class may often give quite satisfactory results. ?? 1993.
Distribution and tectonic implications of Cretaceous-Quaternary sedimentary facies in Solomon Islands

NASA Astrophysics Data System (ADS)

Turner, C. C.; Hughes, G. W.

1982-08-01

Sedimentary rocks of the Solomon Islands-Bougainville Arc are described in terms of nine widespread facies. Four facies associations are recognised by grouping facies which developed in broadly similar sedimentary environments. A marine pelagic association of Early Cretaceous to Miocene rocks comprises three facies. Facies Al: Early Cretaceous siliceous mudstone, found only on Malaita, is interpreted as deep marine siliceous ooze. Facies A2: Early Cretaceous to Eocene limestone with chert, overlies the siliceous mudstone facies, and is widespread in the central and eastern Solomons. It represents lithified calcareous ooze. Facies A3: Oligocene to Miocene calcisiltite with thin tuffaceous beds, overlies Facies A2 in most areas, and also occurs in the western Solomons. This represents similar, but less lithified calcareous ooze, and the deposits of periodic andesitic volcanism. An open marine detrital association of Oligocene to Recent age occurs throughout the Solomons. This comprises two facies. Facies B1 is variably calcareous siltstone, of hemipelagic origin; and Facies B2 consists of volcanogenic clastic deposits, laid down from submarine mass flows. A third association, of shallow marine carbonates, ranges in age from Late Oligocene to Recent. Facies C1 is biohermal limestone, and Facies C2 is biostromal calcarenite. The fourth association comprises areally restricted Pliocene to Recent paralic detrital deposits. Facies D1 includes nearshore clastic sediments, and Facies D2 comprises alluvial sands and gravels. Pre-Oligocene pelagic sediments were deposited contemporaneously with, and subsequent to, the extrusion of oceanic tholeiite. Island arc volcanism commenced along the length of the Solomons during the Oligocene, and greatly influenced sedimentation. Thick volcaniclastic sequences were deposited from submarine mass flows, and shallow marine carbonates accumulated locally. Fine grained graded tuffaceous beds within the marine pelagic association are interpreted as products of this volcanism, suggesting that the Santa Isabel-Malaita-Ulawa area, where these beds are prevalent, was relatively close to the main Solomons chain at this time. A subduction zone may have dipped towards the northeast beneath this volcanic chain. Pliocene to Pleistocene calcalkaline volcanism and tectonism resulted in the emergence of all large islands and led to deposition of clastic and carbonate facies in paralic, shallow and deep marine environments.
An Assessment of the Suitability of Cone Penetration Testing in Identifying the Late Quaternary Successions Formed in Tide-dominated Tnvironments: A Case Study from the Eastern China Coastal Plain

NASA Astrophysics Data System (ADS)

Zhang, X.; Lin, C. M., Sr.; Dalrymple, R. W.; Gao, S., Sr.

2017-12-01

Cone penetration testing (CPT) has proved to be as an effective method for sedimentological purposes in wave-dominated coastal environments. This study, based upon interpretation of 500 CPTs, carried out in the late Quaternary Qiantang River incised-valley fill over the eastern China coastal plain, shows how CPTs can also be used for detailed facies characterization and identification of the key surfaces for sequence-stratigraphic interpretation in tide-dominated systems based upon estimation of three major parameters: cone-tip resistance (qc), sleeve friction (fs), and the ratio of fs and qc (FR). Plotting of qc versus FR, in combination with the CPT curve shape and the relative depth in profile, is adopted as the major tool. The lithologic character which is controlled mainly by sediment supply and dynamics, and post-depositional diagenesis is respected as the main factor affecting how well the CPT technique works. Within this particular tide-dominated environment, dominated by non-cohesive sand and silt, the accumulation of the materials from fluid muds is rare. As a result, the tidal-channel deposits exhibit the nature of coarse-grained deposits, different from that of the other mud-dominated facies associations. On the other hand, a distinct layer of fine-grained deposit at the base of the Holocene sequences was subjected to early diagenesis during the last glacial maximum and early transgression, to become uniformly hard and over-consolidated, geotechnically distinct from the overlying softer sediments. Besides, due to the different sediment dynamics, the tidal-flat and salt-marsh deposits exhibit a distinct geotechnical behavior with the offshore shallow marine muddy deposits. All the above mentioned situations provide the basis for the recognition of facies association and the correlated key surfaces, even for the mapping of the incised-valley boundary. As a consequence, the CPT method has a potential to be a very attractive alternative to economically less convenient methods for the geological mapping in the tide-dominated coastal plain areas.
Changes of chromium concentration in alluvial sediments of the Obra river valley

NASA Astrophysics Data System (ADS)

Młynarczyk, Z.; Sobczyński, T.; Słowik, M.

2006-06-01

In this research work, changes in concentration of the chosen chemical element in alluvial sediments have been used to estimate the relative age of floodplain deposits. The research concerning changes of chromium concentration in alluvial deposits was done in the Obra river valley near Międzyrzecz (Western Poland). Chromium was chosen because of its low ability to migrate in groundwater environment. Moreover, this chemical element was used in the process of dyeing textures in Międzyrzecz between the sixteenth and the nineteenth century. Confrontation of changes in chromium concentration and age of alluvial sediments (age estimated in years BP using radiocarbon method) have shown that the sediments with higher chromium contents are much older than the period of development of the weaving industry in Międzyrzecz. Therefore, it is not possible to use changes in chromium concentration to estimate relative age of floodplain sediments. Despite information in the literature about low migration ability of this chemical component (Macioszczyk and Dobrzyński in Hydrogeochemia: strefy aktywnej wymiany wód podziemnych. PWN, Warszawa, 2002; Ball and Izbicki in Appl Geochem 19:1123 1135, 2004) migration of chromium is so intensive that distinct changes in its concentration are observed even before the period of increased human activity.
[Spatial change of the grain-size of aeolian sediments in Qira oasis-desert ecotone, Northwest China].

PubMed

Lin, Yong Chong; Xu, Li Shuai

2017-04-18

In order to understand the environmental influence of oasis-desert ecotone to oasis ecological system, we comparatively analyzed the grain size characteristics of various aeolian sediments, including the sediments in oasis-desert ecotone, shelterbelt and the inside oasis and in Qira River valley. The results showed that the grain size characteristics (including grain-size distribution curve, grain size parameters, and content of different size classes) of sediments in the oasis-desert ecotone were consistent along the prevailing wind direction with a grain-size range of 0.3-200 μm and modal size of 67 μm. All of the sediments were good sorting and mainly composed of suspension components and saltation components, but not denatured saltation and creeping components (>200 μm). They were typically aeolian deposits being short-range transported. The grain sizes of sediments in oasis-desert ecotone were smaller than that in the material sources of Qira River valley and desert (0.3-800 μm), but very similar to those of the modern aeolian deposits in oasis-desert ecotone, shelterbelt and the inside oasis. The denatured saltation and creep components (>200 μm) were suppressed to transport into oasis-desert ecotone because of the high vegetation cover in oasis-desert ecotone. Therefore, like the shelterbelts, the oasis-desert ecotone could also block the invasion of desert. They safeguarded the oasis ecological environment together.
Modelling potential landscape sediment delivery due to projected soybean expansion: a scenario study of the Balsas sub-basin, Cerrado, Maranhão state, Brazil.

PubMed

Barreto, Larissa; Schoorl, Jeroen M; Kok, Kasper; Veldkamp, Tom; Hass, Adriani

2013-01-30

In Brazil, agriculture expansion is taking place primarily in the Cerrado ecosystems. With the aim of supporting policy development and protecting the natural environment at relevant hotspots, a scenario study was conducted that concerned not only land-use change, but also the resulting effects on erosion and deposition. This coupled approach helped to evaluate potential landscape impacts of the land-use scenarios. In the study area, the Balsas sub-basin in Maranhão State, a model chain was used to model plausible future soybean expansion locations (CLUE-S model) and resulting sediment mobilization patterns (LAPSUS model) for a business-as-usual scenario. In the scenario, more erosion occurred in areas where the conversion of natural vegetation into soybean cultivation is likely to take place, but the generated sediments tended to accumulate mainly within the conversion areas, thus limiting the offsite effects of the increased erosion. These results indicated that when agricultural expansion is kept away from rivers, Cerrado conversion will have only a limited impact on the sediment loads of local rivers. Where land-use changes are most concentrated are coincident with areas where more new sediments are generated (higher erosion) and where more sediments are re-deposited. Crown Copyright © 2012. Published by Elsevier Ltd. All rights reserved.
Bathymetric and sediment facies maps for China Bend and Marcus Flats, Franklin D. Roosevelt Lake, Washington, 2008 and 2009

USGS Publications Warehouse

Weakland, Rhonda J.; Fosness, Ryan L.; Williams, Marshall L.; Barton, Gary J.

2011-01-01

The U.S. Geological Survey (USGS) created bathymetric and sediment facies maps for portions of two reaches of Lake Roosevelt in support of an interdisciplinary study of white sturgeon (Acipenser transmontanus) and their habitat areas within Franklin D. Roosevelt Lake, Washington. In October 2008, scientists from the USGS used a boat-mounted multibeam echo sounder (MBES) to describe bathymetric data to characterize surface relief at China Bend and Marcus Flats, between Northport and Kettle Falls, Washington. In March 2009, an underwater video camera was used to view and record sediment facies that were then characterized by sediment type, grain size, and areas of sand deposition. Smelter slag has been identified as having the characteristics of sand-sized black particles; the two non-invasive surveys attempted to identify areas containing black-colored particulate matter that may be elements and minerals, organic material, or slag. The white sturgeon population in Lake Roosevelt is threatened by the failure of natural recruitment, resulting in a native population that consists primarily of aging fish and that is gradually declining as fish die and are not replaced by nonhatchery reared juvenile fish. These fish spawn and rear in the riverine and upper reservoir reaches where smelter slag is present in the sediment of the river lake bed. Effects of slag on the white sturgeon population in Lake Roosevelt are largely unknown. Two recent studies demonstrated that copper and other metals are mobilized from slag in aqueous environments with concentrations of copper and zinc in bed sediments reaching levels of 10,000 and 30,000 mg/kg due to the presence of smelter slag. Copper was found to be highly toxic to 30-day-old white sturgeon with 96-h LC50 concentrations ranging from 3 to 5 (u or mu)g copper per liter. Older juvenile and adult sturgeons commonly ingest substantial amounts of sediment while foraging. Future study efforts in Lake Roosevelt should include sampling of bottom material to confirm the presence or absence of slag material indicated on the map. In addition, follow-up acoustic work to determine stream velocities at varying discharges, in conjunction with sediment mapping, would be helpful to more accurately identify areas of scour and areas of sediment deposition where slag deposits may accumulate within the Marcus Flats and China Bend reaches. MBES mapping could also be used to determine changes in bed elevation and sedimentation in the study reaches and could help evaluate annual deposition and provide estimates on fine-sediment thickness.
Trace element storage capacity of sediments in dead Posidonia oceanica mat from a chronically contaminated marine ecosystem.

PubMed

Di Leonardo, Rossella; Mazzola, Antonio; Cundy, Andrew B; Tramati, Cecilia Doriana; Vizzini, Salvatrice

2017-01-01

Posidonia oceanica mat is considered a long-term bioindicator of contamination. Storage and sequestration of trace elements and organic carbon (C org ) were assessed in dead P. oceanica mat and bare sediments from a highly polluted coastal marine area (Augusta Bay, central Mediterranean). Sediment elemental composition and sources of organic matter have been altered since the 1950s. Dead P. oceanica mat displayed a greater ability to bury and store trace elements and C org than nearby bare sediments, acting as a long-term contaminant sink over the past 120 yr. Trace elements, probably associated with the mineral fraction, were stabilized and trapped despite die-off of the overlying P. oceanica meadow. Mat deposits registered historic contamination phases well, confirming their role as natural archives for recording trace element trends in marine coastal environments. This sediment typology is enriched with seagrass-derived refractory organic matter, which acts mainly as a diluent of trace elements. Bare sediments showed evidence of inwash of contaminated sediments via reworking; more rapid and irregular sediment accumulation; and, because of the high proportions of labile organic matter, a greater capacity to store trace elements. Through different processes, both sediment typologies represent a repository for chemicals and may pose a risk to the marine ecosystem as a secondary source of contaminants in the case of sediment dredging or erosion. Environ Toxicol Chem 2017;36:49-58. © 2016 SETAC. © 2016 SETAC.
Immediate and delayed signal of slab breakoff in Oligo/Miocene Molasse deposits from the European Alps

PubMed Central

Schlunegger, Fritz; Castelltort, Sébastien

2016-01-01

High-resolution 32–20 Ma-old stratigraphic records from the Molasse foreland basin situated north of the Alps, and Gonfolite Lombarda conglomerates deposited on the southern Alpine margin, document two consecutive sedimentary responses - an immediate and delayed response - to slab breakoff beneath the central Alps c. 32–30 Ma ago. The first signal, which occurred due to rebound and surface uplift in the Alps, was a regional and simultaneous switch from basin underfill to overfill at 30 Ma paired with shifts to coarse-grained depositional environments in the foreland basin. The second signal, however, arrived several million years after slab breakoff and was marked by larger contributions of crystalline clasts in the conglomerates, larger clast sizes, larger sediment fluxes and shifts to more proximal facies. We propose that this secondary pulse reflects a delayed whiplash-type erosional response to surface uplift, where erosion and sediment flux became amplified through positive feedbacks once larger erosional thresholds of crystalline bedrock were exceeded. PMID:27510939
Paleolakes and life on early Mars

NASA Technical Reports Server (NTRS)

Meyer, M. A.; Wharton, Robert A., Jr.; Mckay, C. P.

1991-01-01

Two distinct directions have begun to elucidate key parameters in the search for extinct life on Mars. Carbonate sediments, deposited about 10,000 years ago in association with biological activity, have been sampled from the paleolake beds of Lake Vanda and Meirs in the McMurdo Dry Valleys in Antarctica. These samples are being analyzed for simple biological signatures that remain in cold and dry paleolake sediments, namely microfossils, percent carbonate, and total organic carbon. Our second initiative is the study of Colour Lake, in the Canadian Arctic, that periodically maintains a perennial ice cover. Physical measurements started this year will be used to determine one end point for ice covered lake environments and will be compared to continuous measurements from Antarctic lakes started in November 1985. Interestingly, Colour Lake also supports benthic mat communities, but the low pH precludes carbonate deposition. This research will broaden our knowledge base for what conditions are necessary for ice covered lake formation and what biological signatures will remain in paleolake deposits.
Constant Flux Proxies and Pleistocene Sediment Accumulation Rates on the Juan de Fuca Ridge in the Northeast Pacific

NASA Astrophysics Data System (ADS)

Middleton, J. L.; Mukhopadhyay, S.; Langmuir, C. H.; Costa, K.; McManus, J. F.; d'Almeida, M.; Huybers, P. J.; Winckler, G.

2016-12-01

Mass accumulation rates of marine sediments are often employed to constrain deposition rates of important proxies such as terrigenous dust, carbonate, and biogenic opal to quantitatively examine variations in continental aridity, atmospheric transport, and biologic productivity across changing climatic conditions. However, deposition rates that are estimated using traditional mass accumulation rates calculated from sediment core age models can be subject to bias from lateral sediment transport and limited age model resolution. Constant flux proxies, such as extraterrestrial helium-3 (3HeET) and excess thorium-230 (230ThXS), can be used to calculate vertical sediment accumulation rates that are independent of age model uncertainties and the effects of lateral sediment transport. While a short half-life limits analyses of 230ThXS to the past 500 ka, 3HeET is stable and could be used to constrain sedimentary fluxes during much of the Cenozoic. Despite the vast paleoceanographic potential of constant flux proxies, few studies have directly compared the behavior of 230ThXS and 3HeET using measurements from the same samples. Sediment grain size fractionation and local scavenging effects may differentially bias one or both proxy systems and complicate the interpretation of 230ThXS or 3HeET data. We will present a new record of vertical sediment accumulation rates spanning the past 600 ka in the Northeast Pacific constrained using analyses of both 3HeET and 230ThXS in two sediment cores from cruise AT26-19 on the Juan de Fuca Ridge. Such a record allows for intercomparison of both constant flux proxies in the mid-ocean ridge environment and examination of sedimentary behavior across multiple glacial cycles. The 230ThXS-derived accumulation rates typically range from 0.5 to 2 g cm-2 ka-1 over the past 450 ka, with periods of maximum deposition coinciding with glacial maxima. Preliminary results of samples analyzed with both 3HeET and 230ThXS indicate relative consistency between vertical sediment accumulation rates computed from each proxy and encourage the use of these constant flux proxies in other sedimentary records.
AMS radiocarbon analyses from Lake Baikal, Siberia: Challenges of dating sediments from a large, oligotrophic lake

USGS Publications Warehouse

Colman, Steven M.; Jones, Glenn A.; Rubin, M.; King, J.W.; Peck, J.A.; Orem, W.H.

1996-01-01

A suite of 146 new accelerator-mass spectrometer (AMS) radiocarbon ages provides the first reliable chronology for late Quaternary sediments in Lake Baikal. In this large, highly oligotrophic lake, biogenic and authigenic carbonate are absent, and plant macrofossils are extremely rare. Total organic carbon is therefore the primary material available for dating. Several problems are associated with the TOC ages. One is the mixture of carbon sources in TOC, not all of which are syndepositional in age. This problem manifests itself in apparent ages for the sediment surface that are greater than zero. However, because most of the organic carbon in Lake Baikal sediments is algal (autochthonous) in origin, this effect is limited to about 1000+500 years, which can be corrected, at least for young deposits. The other major problem with dating Lake Baikal sediments is the very low carbon contents of glacial-age deposits, which makes them extremely susceptible to contamination with modern carbon. This problem can be minimized by careful sampling and handling procedures. The ages show almost an order of magnitude difference in sediment-accumulation rates among different sedimentary environments in Lake Baikal, from about 0.04 mm/year on isolated banks such as Academician Ridge, to nearly 0.3 mm/year in the turbidite depositional areas beneath the deep basin floors, such as the Central Basin. The new AMS ages clearly indicate that the dramatic increase in diatom productivity in the lake, as evidenced by increases in biogenic silica and organic carbon, began about 13 ka, in contrast to previous estimates of 7 ka for the age of this transition. Holocene net sedimentation rates may be less than, equal to, or greater than those in the late Pleistocene, depending on the site. This variability reflects the balance between variable terrigenous sedimentation and increased biogenic sedimentation during interglaciations. The ages reported here, and the temporal and spatial variation in sedimentation rates that they imply, provide opportunities for paleoenvironmental reconstructions at different time scales and resolutions.
Paleobiological implications of dinosaur egg-bearing deposits in the Cretaceous Gyeongsang Supergroup of Korea

NASA Astrophysics Data System (ADS)

Paik, In Sung; Kim, Hyun Joo; Huh, Min

2010-05-01

Dinosaur egg-bearing deposits in the Cretaceous Gyeongsang Basin in Korea is described in taphonomic aspect, their paleoenvironments are interpreted, and geobiological implications of dinosaur egg-bearing deposits in the world and Korea are analyzed in geographic occurrences, geological ages, paleoenvironments, and lithology. Dinosaur eggs with spheroolithids, faveoloolithid, and elongatoolithid structural types occur in several stratigraphic formations of the Cretaceous Gyeongsang Basin in South Korea, and most of the egg-bearing formations are the Late Cretaceous. The dinosaur eggs usually occur as clutches in purple sandy mudstone of floodplain deposits preserved as calcic paleosol with association of vertic paleosol features in places. Most of the eggs are top-broken and filled with surrounding sediments. The general depositional environment of dinosaur egg deposits in the Gyeongsang Supergroup are interpreted as a dried floodplain where volcanic activity occurred intermittently in the vicinity of the nesting sites. Their depositional settings on which floodplains developed are diverse from fluvial plain with meandering rivers to alluvial plain with episodic sheet flooding. The nesting areas in the Gyeongsang Basin are deemed to have been under semi-arid climate, which resulted in formation of calcic soils facilitating preservation of the dinosaur eggs. The geochronologic occurrences of dinosaur egg-bearing deposits are mostly restricted to the Late Cretaceous in the world as well as in Korea. If it has not been resulted from biased discoveries and reports of dinosaur eggs, biological rather than physical and chemical conditions for preservation of dinosaur eggs might be related with the restricted occurrences in the Late Cretaceous. Two hypotheses are suggested for probable biological causes to the geochronologically restricted occurrences of dinosaur egg-bearing deposits. One is related with the appearance of angiosperms in the Late Jurassic and the spreading of angiosperm trees in ecological range through swamps and floodplains during the Late Cretaceous and subsequent change of herbivorous dinosaurs' dietary habit and the increase of volcanic activity in the Cretaceous. The other is related with the nesting behaviour in the Cretaceous. By contrast to the geochronologically restricted occurrence of dinosaur eggs, paleoenvironments of nesting areas of dinosaurs are varying from inland areas (alluvial fan, fluvial plain, desert, lake, etc.) to coastal areas (coastal plain, beach, lagoon), suggesting that dinosaurs avoided competition in sharing nesting areas. Little change in lithology from nested deposits to subsequent burying sediments indicates that dinosaurs preferred stable environment in terms of sedimentation as nesting sites. Key words: Dinosaur eggs, Cretaceous, Paleobiological occurrence, Korea
Modern sedimentary facies, depositional environments, and major controlling processes on an arid siliciclastic coast, Al qahmah, SE Red Sea, Saudi Arabia

NASA Astrophysics Data System (ADS)

Nabhan, Abdullah I.; Yang, Wan

2018-04-01

The facies and environments along the arid siliciclastic coast of Red Sea in Al Qahmah, Saudi Arabia are studied to establish a depositional model for interpretation of ancient rocks deposited in rift settings. Field and petrographic studies of 151 sediment samples in an area of 20 km2 define seven main facies types: beach, washover fan, tidal channel, dune, sabkha, delta, and wadi (seasonal stream). The wadi and delta facies are composed of poorly to moderately well-sorted, gravelly, medium-to-fine sands. Delta-front sands are redistributed by southward longshore currents to form a beach. Beach facies is composed of well-to-moderately sorted fine sands with minor gravels, which contain high concentrations of magnetite, ilmenite, garnet, pyroxene, amphibole, epidote, titanite, and apatite grains, indicating strong winnowing. Crabs and other burrowers destroy primary sedimentary structures and mix sediments in foreshore and backshore of the beaches. Wind and storm surge rework foreshore and backshore sediments to form washover fans. Sabkha facies occurs extensively in supratidal depressions behind beach, are flooded by rainstorms and spring tide, and capped by a 5-cm-thick crust composed of interlaminated halite, quartz, albite, minor gypsum and biotite, and rarely calcium carbonate. Halite occurs as thin sheets and gypsum as nodules with a chicken-wire structure. Clastic fraction in sabkha sediments ranges from coarse silt to coarse sand with moderate sorting, and is transported by currents and wind. Tidal inlets and tidal creeks assume abandoned wadis and are filled by muddy sand. Sand dunes and sand sheets are 1-7 m high and widely distributed due to variable wind directions. Fine-grained dune sands are moderately well sorted, whereas sheet sands are coarser and poorly sorted due to vegetation baffling. Most eolian sands are sourced from beach deposits. This suite of complex riverine, wave, tidal, wind, chemical, and biological processes form the facies mosaic along the arid Al Qahmah coast, which is strongly affected by climate-driven evaporation and wind action.
The investigation of terrestrial analogs for the paleoclimate of Mars

NASA Astrophysics Data System (ADS)

Thorpe, M.; Hurowitz, J.; Dehouck, E.

2016-12-01

The paleoclimate of Mars is recorded in sedimentary rocks and deposits, with geochemical and mineralogical lines of evidence illustrating an active hydrologic cycle and aqueous weathering environment. The nature of this paleoclimate remains a debatable subject, with several competing hypothesis existing from warm and wet to cold and icy. However, sedimentary processes in basaltic terrains are understudied, leading to an inadequate reference frame for the sedimentary record of Mars. Therefore, investigating the effects of climate on basaltic terrestrial analogs will help in establishing a context for understanding the ancient conditions of Mars. The Columbia River Basalts in Idaho, USA will serve as conditions in a warm and wet climate, while the weathering of Icelandic Basalts in southwestern Iceland will provide a cold and wet climate scenario. In the warm and wet conditions of Idaho, Miocene basaltic source rock is broken down by physical and chemical weathering, transported by streams and deposited locally as small deltas. The sediment that accumulates preserves the basaltic provenance mineralogy in grain sizes as small as silt. The major elemental geochemistry displays chemical weathering trends that are consistent with decreasing grain size, and interpreted as mafic mineral dissolution (i.e., olivine and pyroxenes). Clay mineral phases are separated into the finest grain size fraction during the sedimentation process and are identified as smectite clays. A similar story of preserving basaltic mineralogy is illustrated by Icelandic deposits, except mechanical breakdown of the sediment appears to have a larger impact. Primary mafic minerals are identified in even the clay size fraction of the Icelandic fluvial delta deposits. Additionally, there are limited abundances of clay mineral phases, with more obvious contributions of poorly crystalline phases in the less than 2 micron fraction. The preservation of basaltic provenance in the mineralogy of sediments generated in two contrasting climates is important to Mars were sedimentary rocks display a primary igneous mineralogy. Weathering trends and the formation of secondary clay and(or) poorly crystalline phases may be the defining tracers for climatic influence on sedimentary processes in basaltic environments.
Carbonate Formation And Diagenesis In Pastos Grandes Laguna (Bolivia): Modern Analog For The South Atlantic Cretaceous Presalt Travertinoid Deposits

NASA Astrophysics Data System (ADS)

Muller, E.; Ader, M.; Gérard, E.; Virgone, A.; Gaucher, E.; Bougeault, C.; Durlet, C.; Moreira, M. A.; Virgile, R.; Vennin, E.; Agogué, H.; Hugoni, M.

2017-12-01

The Cretaceous Presalt travertinoid deposits of the South Atlantic are usually considered as "strange deposits" having poor equivalents in modern environments. Pastos Grandes Laguna, which is located in a 2.9 Ma caldera on the andean-bolivian Altiplano (at 4450 m), is intersected by active faults with hydrothermal fluids and presents a spherulitic plateform with similar sedimentological facies to the Presalt: halite and bedded evaporites, shrub-shaped calcites, ooids, pisolites and various stromatolites. Pastos Grandes Laguna is certainly one of the best modern analog of the Presalt for investigating the on going processes of carbonate deposition and diagenesis and the influence of biology. During two expeditions, we recovered samples of gas, water and microbial mats from the hydrothermal sources to the evaporating zones on the spherulitic plateform. These samples are being analyzed to determine 1) the influence of the gases emitted at the hydrothermal sources (chemical and isotopic composition) on the chemistry of the Laguna and the mineralogy of its sediments and 2) the role of ecosystems that develop in this environment on carbonate formation. Preliminary results on gas composition, corrected for the atmospheric contribution, indicates a magmatic source of CO2 partly mantellic associated with a small crustal contribution. Other initial results have so far indicated that CO2 gas emissions, evaporation, as well as photosynthesis and respiration play a role on water chemistry and carbonate precipitation. This study will contribute to the overall understanding of the role of organisms in sedimentation and the predictive diagenetic evolution of hydrothermal and lacustrine deposits.
Spatial distributions and deposition chronology of short chain chlorinated paraffins in marine sediments across the Chinese Bohai and Yellow Seas.

PubMed

Zeng, Lixi; Chen, Ru; Zhao, Zongshan; Wang, Thanh; Gao, Yan; Li, An; Wang, Yawei; Jiang, Guibin; Sun, Liguang

2013-10-15

As the most complex halogenated contaminants, short chain chlorinated paraffins (SCCPs) are scarcely reported in marine environments. In this work, a total of 117 surficial sediment (0-3 cm) samples and two sediment cores were collected from the Chinese Bohai and Yellow Seas to systematically study the spatial and temporal trends of SCCPs at a large scale in the Chinese marine environment. Total SCCP concentrations in the surficial sediments were in the range of 14.5-85.2 ng g(-1) (dry weight, d.w.) with an average level of 38.4 ng g(-1) d.w. Spatial distribution showed a decreasing trend with the distance from the coast to the open waters. Compositional pattern analysis suggested that C10 was the most predominant homologue group, followed by C11, C12, and C13 homologue groups. The concentrations of total SCCPs in sediment cores ranged from 11.6 to 94.7 ng g(-1) d.w. for YS1 and from 14.7 to 195.6 ng g(-1) d.w. for YS2, with sharp rise from the early 1950s to present based on (210)Pb dating technique. The historical records in cores correspond well to the production and usage changes of CPs in China. Multivariate regression statistics indicate TOC, latitude and longitude are the major factors influencing surficial SCCP levels in the Chinese East Seas by combining analysis with the data from the East China Sea (R(2) = 0.332, p < 0.01). These findings indicated that the sources of SCCPs were mainly from river outflows via ocean current and partly from atmospheric depositions by East Asian monsoon in the sampling areas.

Diatoms as Proxies for a Fluctuating Ice Cap Margin, Hvitarvatn, Iceland

NASA Astrophysics Data System (ADS)

Black, J. L.; Miller, G. H.; Geirsdottir, A.

2005-12-01

There are no complete records of terrestrial environmental change for the Holocene (11,000yrs) in Iceland and the status of Icelandic glaciers in the early Holocene remains unclear. It is not even known whether Iceland's large ice caps disappeared in the early Holocene, and if they did, when they re-grew. Icelandic lakes are particularly well suited to address these uncertainties as: 1) Glacial erosion and soft bedrock result in high lacustrine sedimentation rates, 2) Diagnostic tephras aid the geochronology, 3) Iceland's sensitivity to changes in North Atlantic circulation should produce clear signals in key environmental proxies (diatoms) preserved in lacustrine sequences, and 4) Ice-cap profiles are relatively flat so small changes in the equilibrium line altitude result in large changes in accumulation area. Hence, large changes in ice-sheet margins during the Holocene will impact sedimentation in glacier-dominated lakes and the diatom assemblages at those times. Hvitarvatn is a glacier dominated lake located on the eastern margin of Langjokull Ice Cap in central-western Iceland. The uppermost Hvitarvatn sediments reflect a glacially dominated system with planktonic, silica-demanding diatom taxa that suggest a high dissolved silica and turbid water environment consistent with high fluxes of glacial flour. Below this are Neoglacial sediments deposited when Langjokull was active, but outlet glaciers were not in contact with Hvitarvatn. The diatom assemblage here shows a small increase in abundance, but is still dominated by planktic, silica-demanding taxa. A distinct shift in lake conditions is reflected in the lowermost sediments, composed of predominantly benthic diatoms and deposited in clear water conditions with long growing seasons likely found in an environment with warmer summers than present and with no glacial erosion. Langjokull must have disappeared in the early Holocene for such a diverse, benthic dominated diatom assemblage to flourish.
Sediment-hosted Pb-Zn Deposits: a global perspective

USGS Publications Warehouse

Leach, David L.; Sangster, Donald F.; Kelley, Karen D.; Large, R; Garven, G.; Allen, Craig R.

2005-01-01

Sediment-hosted Pb-Zn deposits contain the world's greatest lead and zinc resources and dominate world production of these metals. They are a chverse group of ore deposits hosted by a wide variety of carbonate and siliciclastic roch that have no obviolls genetic association with igneous activity. A nmge of ore-fortl1ing processes in a vmiety of geologic and tectonic environments created these deposits over at least two billion years of Earth history. The metals were precipitated by basinal brines in synsedimentary and early diagenetic to low-grade metamorphic environments. The deposits display a broad range of relationships to enclosing host rocks that includes stratiform, strata-bound, and discordant ores. These ores are divided into two broad subt)1Jes: Mississippi Valley-type (MVT) and sedimentmy exhalative (SEDEX), Despite the "exhalative" component inherent in the term "SEDEX," in this manusclipt, direct evidence of an exhalite in the ore or alteration component is not essential for a deposit to be classified as SEDEX. The presence of laminated sulfides parallel to bedding is assumed to be permissive evidence for exhalative ores. The chstinction between some SEDEX and MVT depOSits can be quite subjective because some SEDEX ores replaced carbonate, whereas some MVT depOSits formed in an early diagenetic environment and display laminated ore textures. Geologic and resource information are presented for 248 depositS that provide a framework to describe ,mel compare these deposits. Nine of tlle 10 largest sediment-hosted Pb-Zn deposits are SEDEX, Of the deposits that contain at least 2.5 million metric tons (Mt), there are 35 SEDEX (excluding Broken Hill-type) deposits and 15 MVT (excluding Iris-type) deposits. Despite the skewed distribution of the deposit size, the two deposits types have an excellent correlation between total tonnage and tonnage of contained metal (Pb + Zn), with a fairly consistent ratio of about lO/l, regardless of the size of the deposit or district. Zinc grades are approximately the same for both, whereas Pb and Ag grades are about 25 percent greater for SEDEX deposits. The largest difference between SEDEX and MVT deposits is their Cu content. Three times as many SEDEX deposits have reported Cu contents, and the median Cu value of SEDEX deposits is nearly double that of MVT deposits. Furthermore, grade-tonnage values for MVT deposits compared to a subset of SEDEX deposits hosted in carbonate rocks are virtually indistinguishable. The distribution of MVT deposits through geologic time shows that they are mainly a Phanerozoic phenomenon. The ages of SEDEX deposits are grouped into two major groups, one in the Proterozoic and another in the Phanerozoic, MVT deposits dominantly formed in platform carbonate sequences typically located within extensional zones inboard of orogenic belts, whereas SEDEX deposits formed in intracontinental or failed rifts, and rifted continental margins. The ages of MVT ores are generally tens of millions of years younger than their host rocks; however, a few are close <~5 m.y.) to the age of their host rocks. In the absence of direct dates for SEDEX deposits, their age of formation is generally constnuned by relationships to sedimentary or diagenetic features in the rocks. These studies suggest that deposition of SEDEX ores was coeval with sedimentation or early diagenesis, whereas some deposits formed at least 20 m.y. after sedimentation. Fluid inclusion, isotopic studies, and deposit modeling suggest that MVf and SEDEX deposits formed from basin brines with similar temperatures of mainly 90° to 200°C and lO to 30 wt percent NaCI equiv. Lead isotope compositions for MVT and SEDEX deposits show that Pb was mainly derived from a variety of crustal sources. Lead isotope compositions do not provide critelia that distinguish MVT from SEDEX subtypes. However, sulfur isotope compositions for sphalerite and galena show an apparent difference. SEDEX and MVf sulfur isotope compositions extend over a large range; however, most data for SEDEX ores have mainly positive isotopic compositions from 0 to 20 per mil. Isotopic values for MVf ores extend over a wider range and include more data with negative isotopic values. Given that there are relatively small differences between the metal character of MVT and SEDEX deposits and the fluids that deposited them, perhaps the most significant difference between these deposits is their depositional environment, which is determined by their respective tectonic settings. The contrasting tectonic setting also dictates the fundamental deposit attributes that generally set them apart, such as host-rock lithology, deposit morphology, and ore textures. Blief discussions are also presented on two controversial sets of deposits: Broken Hill-type deposits and a subset of deposits in the MVT group located in the Irish Midlands, considered by some authors to be a distinct ore type (Irish type). There are no Significant differences in grade tonnage values between MVT deposits and the subset that is described as Irish type. Most features of the Irish deposits are not distinct from the family of MVT deposits; however, the age of mineralization that is the same as or close to the age of the host rocks and the anomalously high fluid inclusion temperatures (up to 250°C) stand out as distinctly different from typical MVT ores. The dominance of bacteriogenic sulfur in the hish ores commonly ascribed as uniquely hish type is in fact no different from several MVT deposits or districts. A comparison of SEDEX and Broken Hill-type deposits shows that the latter deposits contain signiflcantly higher contents of Ag and Pb relative to SEDEX deposits. In terms of median values, Broken Hill-type deposits are almost three times more ellliched in Ag and one and a half times more enriched in Pb compared to other SEDEX deposits. Metamorphism is a charactelisoc feature but not a prerequisite for inclusion in the Broken Hill-type category, and IGlown Broken Hill-type examples appear to occur in Paleo- to Mesoproterozoic terranes. Broken Hill-type deposits remain an enigmatic grouping; however, there is sufficient evidence to support their inclusion as a separate category of SEDEX deposits.
Formation of fine sediment deposit from a flash flood river in the Mediterranean Sea

USGS Publications Warehouse

Grifoll, Manel; Gracia, Vicenç; Aretxabaleta, Alfredo L.; Guillén, Jorge; Espino, Manuel; Warner, John C.

2014-01-01

We identify the mechanisms controlling fine deposits on the inner-shelf in front of the Besòs River, in the northwestern Mediterranean Sea. This river is characterized by a flash flood regime discharging large amounts of water (more than 20 times the mean water discharge) and sediment in very short periods lasting from hours to few days. Numerical model output was compared with bottom sediment observations and used to characterize the multiple spatial and temporal scales involved in offshore sediment deposit formation. A high-resolution (50 m grid size) coupled hydrodynamic-wave-sediment transport model was applied to the initial stages of the sediment dispersal after a storm-related flood event. After the flood, sediment accumulation was predominantly confined to an area near the coastline as a result of preferential deposition during the final stage of the storm. Subsequent reworking occurred due to wave-induced bottom shear stress that resuspended fine materials, with seaward flow exporting them toward the midshelf. Wave characteristics, sediment availability, and shelf circulation determined the transport after the reworking and the final sediment deposition location. One year simulations of the regional area revealed a prevalent southwestward average flow with increased intensity downstream. The circulation pattern was consistent with the observed fine deposit depocenter being shifted southward from the river mouth. At the southern edge, bathymetry controlled the fine deposition by inducing near-bottom flow convergence enhancing bottom shear stress. According to the short-term and long-term analyses, a seasonal pattern in the fine deposit formation is expected.
Constraints on Environmental Conditions on Mars during Periods of Alluvial Fan Formation: Results from Landform Evolution Modeling

NASA Astrophysics Data System (ADS)

Morgan, A. M.; Howard, A. D.; Moore, J. M.

2015-12-01

As depositional systems forming within enclosed crater basins, the Late Noachian and Hesperian -aged [1] alluvial fans on Mars (including the Peace Vallis fan in Gale crater) may be representative of the last vestiges of widespread fluvial activity on the planet's surface, an era during which the climate transitioned from a wetter early Mars to the cold and dry planet we observe today. We have constructed a landform evolution model that combines sediment transport with channel avulsion to study the evolution of a fan-forming channel network over timescales of decades to hundreds of thousands of years. We aim to address two related questions: (1) what were the characteristics of water discharge (flow magnitude and duration); and (2) what are the associated implications for the responsible climatic environment (e.g. amount and frequency of precipitation sourcing the fans). The model uses a cellular network with a grid spacing set equal to the channel width. Two end-members of sediment are transported through the channel network: gravel bedload and fine grained material that is deposited overbank as a function of distance and elevation difference from an active channel. Overbank deposition creates channel levees, which must be overtopped for the channel to undergo an avulsion. By recording the relative amounts of bedload and overbank deposition, the 3-D stratigraphy is recorded as the fan is constructed. Using measures such as channel width, relative proportions of channel versus overbank deposited sediment, and frequency of channel branching, output is statistically compared with digital elevation models that we been produced from high-resolution CTX and HiRISE stereo pairs. Our modeling suggests that the fans formed from many flow events over many thousands of years, in agreement with estimations based on geomorphological observations by [2]. We are continuing to refine the model to test for varying patterns of precipitation, duricrusts, and limits on sediment supply in the source basin catchments. [1] Grant, J.A., Wilson, S.A., 2011. Late alluvial fan formation in southern Margaritifer Terra, Mars. Geophys. Res. Lett. 38 [3] Morgan, A.M., et al., 2014. Sedimentology and climatic environment of alluvial Fans in the martian Saheki crater and a comparison with terrestrial fans in the Atacama Desert. Icarus 229
Fluvial depositional environment evolving into deltaic setting with marine influences in the buntsandstein of northern vosges (France)

NASA Astrophysics Data System (ADS)

Gall, Jean-Claude

The Buntsandstein in the Northern Vosges (France) originates mainly in an inland braidplain fluvial environment which passes in the upper part of the sequence into deltaic milieu in the coastal plain along the border of the sea, with the continental environment finally being drowned with the transgression of the shallow sea. The fluvial sedimentation is characterized by the presence of two facies throughout the Buntsandstein : channel facies and overbank plain facies. The channel facies comprises sandy and conglomeratic deposits forming within active streams by strong currents, whereas the overbank plain facies is built up of silty-clayey sandstones or silt/clay originating in stagnant water in abandoned watercourses, ponds, pools and puddles. The significance of particularly the floodplain sediments is subjected to considerable changes throughout the Buntsandstein sequence. There are all stages of transition between overbank plain deposits being only preserved in ghost-like facies as reworked clasts due to effective secondary removal of primarily occasionally formed suspension fines, and an abundance of autochthonous floodplain sediments in the depositional record resulting from favourable conditions of primary origin and secondary preservation. Reworked ventifacts within fluvial channel sediments testify to subordinate aeolian influences in the alluvial plain, with reasonable reworking, however, having removed all in situ traces of wind activity. Declining aridity of palaeoclimate towards the top is indicated by the appearance of violet horizon palaeosols in the Zone-Limite-Violette and the Couches intermédiaires being accompanied by Bröckelbank carbonate breccias originating from concentration of reworked fragments of pedogenic carbonate nodules. Biogenic traces are in the lower part of the sequence mainly present as Planolites burrows in the finer-grained sediments. Palaeosalinities as revealed from boron contents indicate progressively increasing supersaturation of stagnant waters with time. The fluvial environment persists up to the lower part of the Grès à Voltzia where the progression of the sea towards the west gives rise to a close intertonguing of fluvial and marine influences in a deltaic setting. Lenticular sandstone bodies are laid down as stream mouth bars at the end of the distributary channels and as river bars in the watercourses during both normal and flood discharge. Silty-clayey sediments settle out in stagnant water in restricted ponds, pools and puddles as well as in extensive veneers of shallow water in the overbank plain between the streams. Carbonate-bearing deposits originate in the coastal littoral mud flat, marsh seam, beach belt and tidal flat. The Grès à Voltzia has the greatest palaeoenvironmental and palaeoecological significance in the Buntsandstein of the Northern Vosges due to the occurrence of a wealth of extraordinarily well-preserved plant and animal fossils (having been recovered by Louis Grauvogel during almost 50 years and since abt. 25 years by Jean-Claude Gall). The rich suite of faunal and floral elements includes aquatic invertebrates, terrestrial animals and continental plants. The aquatic invertebrate fauna lives in fresh lakes and brackish ponds in the overbank plain and in brackish lagoons in the coastal seam as well as in hypersaline and euhaline marginal marine waters. The terrestrial plants colonize both dry and wet substrates, and the continental fauna consists of mainly arthropods, amphibians and reptiles inhabiting the levee zones of standing and flowing waters and strolling across the desiccated flats. The marine euryhaline association of invertebrates is with time replaced by a stenohaline community, and the deltaic plain of the Grès à Voltzia is finally inundated by a pellicular transgression representing the first stage of the Muschelkalk sea setting an end to Buntsandstein continental deposition.
Influence of Cougar Reservoir Drawdown on Sediment and DDT Transport and Deposition in the McKenzie River Basin, Oregon, Water Years 2002-04

USGS Publications Warehouse

Anderson, Chauncey W.

2007-01-01

Construction of a selective withdrawal tower at Cougar Reservoir in the South Fork McKenzie River, Oregon, during 2002-05 resulted in a prolonged release of sediment and high-turbidity water to downstream reaches throughout the summer of 2002, with additional episodic releases during storms in the following winters. Suspended-sediment concentrations and loads at five continuously monitored turbidity and discharge gaging stations were estimated using regression methods. Deposition in salmonid spawning beds was measured using infiltration bags. Stations were located upstream and downstream of Cougar Reservoir in the South Fork McKenzie River, in the mainstem of the McKenzie River upstream of the South Fork and downstream of Blue River, and in Blue River downstream of Blue River Reservoir. During 2002, Cougar Reservoir released approximately 17,000 tons of suspended sediment into the South Fork McKenzie River, or more than twice the incoming load from the South Fork upstream of the reservoir. In 2003 and 2004, the release of sediment from Cougar Reservoir decreased to 10,900 and 4,100 tons, respectively. Although Cougar Reservoir likely was a substantial source of sediment to the lower reaches during water years 2002 and 2003, the lack of continuous turbidity monitoring at stations other than the South Fork McKenzie River prior to January 2003 prevents quantification of the actual contribution to the mainstem. During water year 2004, the only year with complete records at all sites, Cougar Reservoir released about 24 percent (4,100 tons) of the sediment load estimated on the mainstem near Vida (16,900 tons); however, the relative contribution of Cougar Reservoir is expected to have been substantially larger during 2002 and 2003 when the newly exposed river channel in the upper reaches of the reservoir was actively eroding and migrating. Deposition of fine (less than 0.063-millimeter diameter) sediment into spawning beds, measured with the use of deployed infiltration bags, was greatest downstream of Cougar and Blue River Reservoirs (1.0 and 1.2 percent of total sediments, respectively). Deposition was least in the high-energy, unregulated environments (about 0.25 percent) of the South Fork McKenzie River above Cougar Reservoir and in the mainstem above the South Fork, and intermediate near Vida, the most downstream site on the mainstem. DDT, applied throughout much of the upper McKenzie River drainage basin to control spruce budworm during the 1950s, was detected in the South Fork near Rainbow in the form of its metabolites DDD and DDE in fine sediment captured in the infiltration bags. DDE also was detected in infiltration bags deployed in the McKenzie River near Vida, downstream of the South Fork. All concentrations of DDD and DDE were less than the aquatic-life criterion for bed sediment. DDT species were not detected in water samples, including samples collected during large storms. The reservoir apparently acted as a trap for sediment and DDT throughout the course of its existence, facilitating degradation of the trapped DDT, and may have been a source for both during the construction period in 2002-05, but the lack of detections during storms indicates that DDT transport was small. Transport of detectable amounts of DDT likely was limited to periods of high suspended-sediment concentrations (greater than 75-100 milligrams per liter). Infiltration bags were deployed during August 2003-July 2004 and were a useful device for measuring fine-sediment deposition and for chemical analysis of the deposited material. Deposition of fine-grained sediment downstream of the flood-control dams may be reduced if bed-moving events can be periodically reintroduced to those reaches.
Empirical models for predicting volumes of sediment deposited by debris flows and sediment-laden floods in the transverse ranges of southern California

USGS Publications Warehouse

Gartner, Joseph E.; Cannon, Susan H.; Santi, Paul M

2014-01-01

Debris flows and sediment-laden floods in the Transverse Ranges of southern California pose severe hazards to nearby communities and infrastructure. Frequent wildfires denude hillslopes and increase the likelihood of these hazardous events. Debris-retention basins protect communities and infrastructure from the impacts of debris flows and sediment-laden floods and also provide critical data for volumes of sediment deposited at watershed outlets. In this study, we supplement existing data for the volumes of sediment deposited at watershed outlets with newly acquired data to develop new empirical models for predicting volumes of sediment produced by watersheds located in the Transverse Ranges of southern California. The sediment volume data represent a broad sample of conditions found in Ventura, Los Angeles and San Bernardino Counties, California. The measured volumes of sediment, watershed morphology, distributions of burn severity within each watershed, the time since the most recent fire, triggering storm rainfall conditions, and engineering soil properties were analyzed using multiple linear regressions to develop two models. A “long-term model” was developed for predicting volumes of sediment deposited by both debris flows and floods at various times since the most recent fire from a database of volumes of sediment deposited by a combination of debris flows and sediment-laden floods with no time limit since the most recent fire (n = 344). A subset of this database was used to develop an “emergency assessment model” for predicting volumes of sediment deposited by debris flows within two years of a fire (n = 92). Prior to developing the models, 32 volumes of sediment, and related parameters for watershed morphology, burn severity and rainfall conditions were retained to independently validate the long-term model. Ten of these volumes of sediment were deposited by debris flows within two years of a fire and were used to validate the emergency assessment model. The models were validated by comparing predicted and measured volumes of sediment. These validations were also performed for previously developed models and identify that the models developed here best predict volumes of sediment for burned watersheds in comparison to previously developed models.
Establishing a sediment budget in the newly created "Kleine Noordwaard" wetland area in the Rhine-Meuse delta

NASA Astrophysics Data System (ADS)

Christien van der Deijl, Eveline; van der Perk, Marcel; Middelkoop, Hans

2018-03-01

Many deltas are threatened by accelerated soil subsidence, sea-level rise, increasing river discharge, and sediment starvation. Effective delta restoration and effective river management require a thorough understanding of the mechanisms of sediment deposition, erosion, and their controls. Sediment dynamics has been studied at floodplains and marshes, but little is known about the sediment dynamics and budget of newly created wetlands. Here we take advantage of a recently opened tidal freshwater system to study both the mechanisms and controls of sediment deposition and erosion in newly created wetlands. We quantified both the magnitude and spatial patterns of sedimentation and erosion in a former polder area in which water and sediment have been reintroduced since 2008. Based on terrestrial and bathymetric elevation data, supplemented with field observations of the location and height of cut banks and the thickness of the newly deposited layer of sediment, we determined the sediment budget of the study area for the period 2008-2015. Deposition primarily took place in channels in the central part of the former polder area, whereas channels near the inlet and outlet of the area experienced considerable erosion. In the intertidal area, sand deposition especially takes place at low-lying locations close to the channels. Mud deposition typically occurs further away from the channels, but sediment is in general uniformly distributed over the intertidal area, due to the presence of topographic irregularities and micro-topographic flow paths. Marsh erosion does not significantly contribute to the total sediment budget, because wind wave formation is limited by the length of the fetch. Consecutive measurements of channel bathymetry show a decrease in erosion and deposition rates over time, but the overall results of this study indicate that the area functions as a sediment trap. The total contemporary sediment budget of the study area amounts to 35.7×103 m3 year-1, which corresponds to a net area-averaged deposition rate of 6.1 mm year-1. This is enough to compensate for the actual rates of sea-level rise and soil subsidence in the Netherlands.
Source-to-Sink: An implicit and O(n) landscape evolution model and its application to the Ogooue Delta, Gabon

NASA Astrophysics Data System (ADS)

Yuan, X.; Braun, J.; Guerit, L.; Simon, B.

2017-12-01

Limited attention has been given to linking continental erosion to transport and deposition of sediments in the marine environment in large-scale landscape evolution models. Although both environments have been thoroughly investigated, the details of how erosional or climatic events are recorded in the sedimentary and stratigraphic records have not been studied in a consistent quantitative manner. Here we propose a new numerical model for marine multi-lithology (sand and silt) coupling transport and deposition that is directly coupled to FastScape, a landscape evolution model that solves the continental stream power law and hillslope diffusion equation using implicit and O(n) algorithms. Marine transport and deposition is simulated by a nonlinear 2D diffusion model that incorporates a dual lithology (sand and slit) and where source terms represent the sediment flux from continental river erosion. Sediment compaction effects are also incorporated, taking into account the dual lithology, and are important to properly compute the details of the synthetic stratigraphic record. The algorithm used to represent marine transport and deposition is also implicit and O(n). The main purpose of our work is to invert stratigraphic data from offshore marginal basins to provide constraints on the tectonic, climatic and sea-level conditions that have affected the adjacent continental areas. In order to do so, we have incorporated the new model into a Bayesian inversion and optimisation scheme and tested and validated the approach with synthetic data. This is made possible due to the high efficient of the forward model. We are in the process of applying the inversion scheme to stratigraphic data from the Ogooue Delta (Gabon). By comparing real and synthetic stratigraphic geometries along cross-section of the delta, the shape and slope of seismic/time markers, and the sand to silt fraction in wells, we hope to obtain good constraints, not only of the value of the transport coefficients for sand and silt in the marine environment, but also of the uplift, erosional and climate history of the adjacent continental areas, as well as the amplitude of sea level variations.
Contamination of short-chain chlorinated paraffins to the biotic and abiotic environments in the Bohai Sea.

PubMed

Jiang, Wanyanhan; Huang, Tao; Chen, Han; Lian, Lulu; Liang, Xiaoxue; Jia, Chenhui; Gao, Hong; Mao, Xiaoxuan; Zhao, Yuan; Ma, Jianmin

2018-02-01

Short-chain chlorinated paraffins (SCCPs) have been produced and emitted intensively around the Bohai Sea, potentially causing risks to this unique ecosystem and one of primary fishery resources in China and busiest seaways in the world. Little is known about fate, cycling, and sources of SCCPs in the Bohai Sea biotic and abiotic environment. In this study, we combined a marine food web model with a comprehensive atmospheric transport-multiple phase exchange model to quantify SCCPs in the biotic and abiotic environment in the Bohai Sea. We performed multiple modeling scenario investigations to examine SCCP levels in water, sediment, and phytoplankton. We assessed numerically dry and wet depositions, biomagnification and bioaccumulation of SCCPs in the Bohai Sea marine food web. Results showed declining SCCP levels in water and sediment with increasing distance from the coastline, and so do dry and wet depositions. The net deposition overwhelmed the water-air exchange of SCCPs due to their current use in China, though the diffusive gas deposition fluctuated monthly subject to mean wind speed and temperature. A risk assessment manifests that SCCPs levels in the Bohai Sea fish species are at present not posing risks to the residents in the Bohai Sea Rim region. We identified that the SCCP emission sources in the south of the Bohai Sea made a primary contribution to its loadings to the seawater and fish contamination associated with the East Asian summer monsoon. In contrast, the SCCP emissions from the north and northwest regions of the Bohai Sea were major sources contributing to their loading and contamination to Bohai Sea food web during the wintertime, potentially driven by the East Asian winter monsoon. Copyright © 2017 Elsevier Ltd. All rights reserved.
Thin terrestrial sediment deposits on intertidal sandflats: effects on pore-water solutes and juvenile bivalve burial behaviour

NASA Astrophysics Data System (ADS)

Hohaia, A.; Vopel, K.; Pilditch, C. A.

2014-04-01

Nearshore zones experience increased sedimentation due to coastal development and enhanced loads of fine terrestrial sediment (hereafter, TS) in river waters. Deposition of TS can alter seabed biogeochemical processes but the effects on benthic ecosystem functioning are unknown. The results of a past experiment with defaunated, intertidal sediment suggest that a decrease in the oxygenation of this sediment by a thin (mm) TS deposit causes substrate rejection (refusal to bury) by post-settlement juvenile recruits of the tellinid bivalve Macomona liliana. We further examined this behaviour, asking if such deposits negatively affect burial when applied to intertidal sediment that is oxygenated by bioturbation (C) or depleted of dead and living organic matter (D). We observed recruits on the surface of four treatments: C, D, and the same sediments to which we added a 1.7-1.9 mm layer of TS (CTS, DTS). The TS deposit decreased the oxygenation and the pH of the underlying intertidal sediment (CTS) confirming previous results, but significantly increased but not decreased the probability of burial, irrespectively of treatment. Juveniles more likely buried into C than into D. The mechanism that caused previously observed substrate rejection by post-settlement juvenile M. liliana remains unclear but our results suggest that contact of the recruits with the TS deposit does not cause substrate rejection. We now hypothesise that conditioning of sediment by bioturbation can mediate negative effects of TS deposits on the recruits' burial behaviour.
Dispersal of suspended sediments in the turbid and highly stratified Red River plume

NASA Astrophysics Data System (ADS)

van Maren, D. S.; Hoekstra, P.

2005-03-01

The Red River, annually transporting 100 million tons of sediment, flows into a shallow shelf sea where it rapidly deposits most of its sediment on a prograding delta front. Oceanographic cruises were carried out in February-March and July-August 2000 to determine the vertical structure of the Ba Lat river plume and sediment transport patterns on the delta front. The surface waters in the coastal zone were strongly stratified with a low density and high sediment concentration during the larger part of the wet season, caused by low mixing rates of river plumes with ambient water. The river plume is advected to the south by a well-developed coastal current which originates from the river plumes that enter the Gulf of Tonkin North of the Ba Lat and are deflected southward by the Coriolis force. Sediment predominantly leaves the surface plume by settling from suspension and less by mixing of fresh and marine water. A one-dimensional model for plume deposition valid for fair weather conditions indicates that most sediment is deposited within 10 km and southward of the river mouth. Of prime importance for this depositional pattern is the phase relation between river outflow and tidal currents, in combination with the southward surface flow; alongshore advection is very low during outflow of the turbid river plume. The agreement of modeled plume sedimentation patterns with long-term bathymetric changes strongly suggests that fair weather depositional processes determine delta front development. This may be related to the fact that reworking of sediment mainly occurs several months after the peak deposition period; in the meantime sediment compaction and consolidation have increased the shear strength of deposited sediments.
Tidal oscillation of sediment between a river and a bay: A conceptual model

USGS Publications Warehouse

Ganju, N.K.; Schoellhamer, D.H.; Warner, J.C.; Barad, M.F.; Schladow, S.G.

2004-01-01

A conceptual model of fine sediment transport between a river and a bay is proposed, based on observations at two rivers feeding the same bay. The conceptual model consists of river, transitional, and bay regimes. Within the transitional regime, resuspension, advection, and deposition create a mass of sediment that oscillates landward and seaward. While suspended, this sediment mass forms an estuarine turbidity maximum. At slack tides this sediment mass temporarily deposits on the bed, creating landward and seaward deposits. Tidal excursion and slack tide deposition limit the range of the sediment mass. To verify this conceptual model, data from two small tributary rivers of San Pablo Bay are presented. Tidal variability of suspended-sediment concentration markedly differs between the landward and seaward deposits, allowing interpretation of the intratidal movement of the oscillating sediment mass. Application of this model in suitable estuaries will assist in numerical model calibration as well as in data interpretation. A similar model has been applied to some larger-scale European estuaries, which bear a geometric resemblance to the systems analyzed in this study. ?? 2004 Elsevier Ltd. All rights reserved.
Gas hydrates in the ocean environment

USGS Publications Warehouse

Dillon, William P.

2002-01-01

A GAS HYDRATE, also known as a gas clathrate, is a gas-bearing, icelike material. It occurs in abundance in marine sediments and stores immense amounts of methane, with major implications for future energy resources and global climate change. Furthermore, gas hydrate controls some of the physical properties of sedimentary deposits and thereby influences seafloor stability.
Cretaceous shales from the western interior of North America: sulfur/carbon ratios and sulfur-isotope composition.

USGS Publications Warehouse

Gautier, D.L.

1986-01-01

Sulphur/carbon ratios in cores of selected Cretaceous marine shales average 0.67, a value greater than that observed in recent marine sediments and much higher than global values calculated for the Cretaceous. This may be ascribed to generally low levels of bioturbation and enhanced efficiency of sulphate reduction due to low oxygen levels in Cretaceous seaways. Isotopic compositions of pyrite sulphur vary systematically with level of oxygenation of the depositional environment and therefore with organic carbon abundance and type of organic matter. Samples with >4% organic carbon are extremely depleted in 34S (mean delta 34S -31per mille) and contain hydrogen-rich organic matter. Samples containing <1.5% organic carbon display relatively 'heavy' but wide-ranging delta 34S values (-34.6 to +16.8per mille) and contain hydrogen-poor organic matter. Samples with intermediate amounts of organic carbon have average delta 34S of -25.9per mille and contain both types of organic matter. Relations between the nature of these shales, and their sedimentation rate and depositional environment are discussed.-L.C.H.
Decoupling flood and interflood deposits for delta island formation and channel bifurcation

NASA Astrophysics Data System (ADS)

Daniller-Varghese, M. S.; Kim, W.

2016-12-01

Channel islands' size and organization dictate delta networks' morphology. To understand their complex network organization, a single channel island node within that network should be investigated first as the fundamental building block. When a sediment-laden flow enters slack water, it loses momentum and carrying capacity, depositing its sediment. As sediment accumulates, flow moves around it and a mouth bar island develops. We present an experimental investigation of island formation and channel bifurcation using the Sediment Transport and Earth-surface Processes (STEP) basin. We made mouth bar deposits and flow bifurcations in transport-limited turbulent conditions. Time-lapse images, elevation scans on the deltaic surface, and a low-cost particle imaging velocimetry system allow us to characterize the flow and depositional evolution of our experimental islands. Using two flow discharges (0.355 l/s, 6 l/s) and uniform sediment, our experiments have two characteristic advection lengths and corresponding deposit types. One, associated with interflood bedload transport, and the other with flood-suspended transport: proximal low-angle deposits and distal steep deposits, respectively. By varying the frequency of floods (one every 20s-20 mins) while keeping sediment and water mass constant across experiments, we are able to control the time and spatial organization of these two deposit types and examine the effect on bifurcation length and bifurcation incidence time. As the interflood flow deposit and flood deposit accumulate sediment over time, the interflood deposit encroaches onto the flood deposit. Flow is routed from the interflood deposit to the flood deposit but does not have the momentum to uniformly cover it. The flow becomes unsteady, and bifurcates around an island. After the bifurcation, the island's vertical aggradation rate also increases. The experiments suggest that the interaction between deposits stemming from different particle advection lengths is a sufficient condition for island formation and flow bifurcation.
Cyanobacterial diversity and related sedimentary facies as a function of water flow conditions: Example from the Monasterio de Piedra Natural Park (Spain)

NASA Astrophysics Data System (ADS)

Berrendero, Esther; Arenas, Concha; Mateo, Pilar; Jones, Brian

2016-05-01

The River Piedra in the Monasterio de Piedra Natural Park (NE Spain) is a modern tufa-depositing river that encompasses various depositional environments that are inhabited by different cyanobacterial populations. Molecular (16S rDNA) and morphological analyses of the cyanobacteria from different facies showed that Phormidium incrustatum dominates in the fast-flowing water areas where the mean depositional rate is 1.6 cm/year. Stromatolites in these areas are formed of palisades of hollow calcite tubes (inner diameter of 6.0-7.5 μm, walls 2-12 μm thick) that formed through calcite encrustation around the filaments followed by decay of the trichomes. In contrast, in slow-flowing water areas with lower depositional rates (mean depositional rate of 0.3 cm/year), Phormidium aerugineo-caeruleum is the dominant species. In these areas, randomly oriented calcite tubes (inner diameter of 5-6 μm, walls 3-8 μm thick) formed by calcite encrustation, are found in thin and uneven laminae and as scattered tubes in the loose lime mud and sand-sized carbonate sediment. Although this species did not build laminated deposits, it gave cohesiveness to the loose sediment. In the stepped and low waterfalls, with intermediate deposition rates (mean depositional rate of 0.9 cm/year), both species of Phormidium are found in association with spongy moss and algal boundstones, which is consistent with the variable flow conditions in this setting. The calcite encrustations on the cyanobacteria from different environments exhibit irregular patterns that may be linked to changes in the calcite saturation index. The physicochemical conditions associated with extracellular polymeric substances may be more significant to CaCO3 precipitation in microbial mats in slow-flowing water conditions than in fast-flowing water conditions. These results show that flow conditions may influence the distribution of different cyanobacteria that, in turn, leads to the development of different sedimentary facies and structures in fluvial carbonate systems.
Fate and Transport of Mercury in Environmental Media and Human Exposure

PubMed Central

Kim, Moon-Kyung

2012-01-01

Mercury is emitted to the atmosphere from various natural and anthropogenic sources, and degrades with difficulty in the environment. Mercury exists as various species, mainly elemental (Hg0) and divalent (Hg2+) mercury depending on its oxidation states in air and water. Mercury emitted to the atmosphere can be deposited into aqueous environments by wet and dry depositions, and some can be re-emitted into the atmosphere. The deposited mercury species, mainly Hg2+, can react with various organic compounds in water and sediment by biotic reactions mediated by sulfur-reducing bacteria, and abiotic reactions mediated by sunlight photolysis, resulting in conversion into organic mercury such as methylmercury (MeHg). MeHg can be bioaccumulated through the food web in the ecosystem, finally exposing humans who consume fish. For a better understanding of how humans are exposed to mercury in the environment, this review paper summarizes the mechanisms of emission, fate and transport, speciation chemistry, bioaccumulation, levels of contamination in environmental media, and finally exposure assessment of humans. PMID:23230463
Microplastic ingestion decreases energy reserves in marine worms.

PubMed

Wright, Stephanie L; Rowe, Darren; Thompson, Richard C; Galloway, Tamara S

2013-12-02

The indiscriminate disposal of plastic to the environment is of concern. Microscopic plastic litter (<5 mm diameter; 'microplastic') is increasing in abundance in the marine environment, originating from the fragmentation of plastic items and from industry and personal-care products [1]. On highly impacted beaches, microplastic concentrations (<1mm) can reach 3% by weight, presenting a global conservation issue [2]. Microplastics are a novel substrate for the adherence of hydrophobic contaminants [1], deposition of eggs [3], and colonization by unique bacterial assemblages [4]. Ingestion by indiscriminate deposit-feeders has been reported, yet physical impacts remain understudied [1]. Here, we show that deposit-feeding marine worms maintained in sediments spiked with microscopic unplasticised polyvinylchloride (UPVC) at concentrations overlapping those in the environment had significantly depleted energy reserves by up to 50% (Figure 1). Our results suggest that depleted energy reserves arise from a combination of reduced feeding activity, longer gut residence times of ingested material and inflammation. Copyright © 2013 Elsevier Ltd. All rights reserved.
Paleobiology of the Sand Beneath the Valders Diamicton at Valders, Wisconsin

USGS Publications Warehouse

Maher, L.J.; Miller, N.G.; Baker, R.G.; Curry, B. Brandon; Mickelson, D.M.

1998-01-01

Previously undescribed pollen, plant macrofossils, molluscs, and ostracodes were recovered from a 2.5-m-thick glaciolacustrine unit of silty sand and clay at Valders, Wisconsin. The interstadial sediment was deposited about 12,200 14C yr B.P. after retreat of the Green Bay lobe that deposited diamicton of the Horicon Formation, and before advance of the Lake Michigan lobe that deposited the red-brown diamicton of the Valders Member of the Kewaunee Formation. Fluctuations of abundance of Candona subtriangulata, Cytherissa lacustris, and three other species define four ostracode biozones in the lower 1.7 m, suggesting an open lake environment that oscillated in depth and proximity to glacial ice. Pollen is dominated by Picea and Artemisia, but the low percentages of many other types of longdistance origin suggest that the terrestrial vegetation was open and far from the forest border. The upper part of the sediment, a massive sand deposited in either a shallow pond or a sluggish stream, contains a local concentration of plant macrofossils. The interpretation of a cold open environment is supported by the plant macrofossils of more than 20 species, dominated by those of open mineral soils (Arenaria rubella, Cerastium alpinum type, Silene acaulis, Sibbaldia procumbens, Dryas integrifolia, Vaccinium uliginosum var. alpinum, Armeria maritima, etc.) that in North America occur largely in the tundra and open tundra-forest ecotone of northern Canada. Ice-wedge casts occur in the sand. ?? 1998 University of Washington.

Geochemistry and exploration criteria for epithermal cinnabar and stibnite vein deposits in the Kuskokwim River region, southwestern Alaska

USGS Publications Warehouse

Gray, J.E.; Goldfarb, R.J.; Detra, D.E.; Slaughter, K.E.

1991-01-01

Cinnabar- and stibnite-bearing epithermal vein deposits are found throughout the Kuskokwim River region of southwestern Alaska. A geochemical orientation survey was carried out around several of these epithermal lodes to obtain information for planning regional geochemical surveys and to develop procedures which maximize the anomaly: threshold contrast of the deposits. Stream sediment, heavy-mineral concentrate, stream water, and vegetation samples were collected in drainages surrounding the Red Devil, Cinnabar Creek, White Mountain, Rhyolite, and Mountain Top deposits. Three sediment size fractions; nonmagnetic, paramagnetic and magnetic splits of the concentrate samples; stream waters; and the vegetation samples were analyzed for multi-element suites by a number of different chemical procedures. Nonmagnetic, heavy-mineral concentrates were also examined microscopically to identify their mineralogy. Results confirm Hg, Sb and As concentrations in minus-80-mesh stream sediments as effective pathfinder elements in exploration for epithermal cinnabar and stibnite deposits. Coarser-grained sediments are much less effective in the exploration for these deposits. Concentrations greater than 3 ppm Hg, 1 ppm Sb, and 15 ppm As in the minus-80-mesh stream sediment, regardless of the host lithology, are indicative of upstream cinnabar-stibnite deposits. Gold, Ag and base metals in the stream sediments are ineffective pathfinders for this epithermal deposit type. Collection of heavy-mineral concentrates provides little advantage in the exploration for these mineral deposits. Antimony and As dispersion patterns downstream from mineralized areas are generally more restricted in the concentrates than those in the stream sediments. Anomalous placer cinnabar observed in the concentrates has a similar spatial distribution pattern as anomalous Hg and Sb in corresponding sediments. Stream waters are less effective than the stream sediments or heavy-mineral concentrates, and vegetation is an ineffective geochemical sample medium in exploration for this deposit type. ?? 1991.
Depositional environments, provenance and paleoclimatic implications of Ordovician siliciclastic rocks of the Thango Formation, Spiti Valley, Tethys Himalaya, northern India

NASA Astrophysics Data System (ADS)

Rashid, Shaik A.; Ganai, Javid A.

2018-05-01

Recently published findings indicate that the Ordovician period has been much more dynamic than previously anticipated thus making this period significant in geological time. The Ordovician of India can best be studied in the Spiti region because the Spiti basin records the complete uninterrupted history of excellent marine sedimentary rocks starting from Cambrian to Paleogene which were deposited along the northern margin of India. Due to these reasons the geochemical data on the Ordovician rocks from the Spiti region is uncommon. The present geochemical study on the Ordovician Thango Formation (Sanugba Group) is mainly aimed to understand the provenance and the paleoclimatic conditions. The sandstones are the dominant lithology of the Thango Formation with intercalations of minor amount of shales. Detailed petrographic and sedimentological analysis of these rocks suggest that three major depositional environments, viz., fluvial, transitional and marine prevailed in the basin representing transgressive and regressive phases. The major and trace element ratios such as SiO2/Al2O3, K2O/Na2O and La-Th- Sc discrimination diagram suggest that these rocks were deposited in passive margin tectonic settings. Various geochemical discriminants and elemental ratios such as K2O/Na2O, Al2O3/TiO2, La/Sc, Th/Sc, Cr/Th, Zr/Sc, (Gd/Yb)N and pronounced negative Eu anomalies indicate the rocks to be the product of weathering of post-Archean granites. The striking similarities of the multi-elemental spider diagrams of the studied sediments and the Himalayan granitoids indicate that sediments are sourced from the Proterozoic orogenic belts of the Himalayan region. Chemical index of alteration (CIA) values of the studied sediments (55-72) suggest that the source rocks underwent low to moderate degree of chemical weathering. The span of the CIA values (55-72) recorded in the sediments from the Spiti region may have resulted from varying degrees of weathering conditions in the source area. This, in turn, reflects variable climatic conditions prevailing during the Ordovician period, which is consistent with the global studies. The high CIA values observed by numerous studies on siliciclastic sediments may imply warm paleoclimate attributed to an increase in atmospheric carbon dioxide and/or methane levels inducing an acidic weathering environment and enhanced silicate weathering. While the low CIA values indicates prevalence of arid-glacial conditions where negligible chemical alteration is possible. This study documents the noteworthy events like fluctuating (rise and fall) atmospheric CO2 and sea levels during the Ordovician period, a conclusion which is consistent with the other such studies on the Phanerozoic glaciation (or mass extinction) events on Gondwana supercontinent.
The Geologic History of Lake of the Woods, Minnesota, Reconstructed Using Seismic-Reflection Imaging and Sediment Core Analysis

NASA Astrophysics Data System (ADS)

Hougardy, Devin D.

The history of glacial Lake Agassiz is complex and has intrigued researchers for over a century. Over the course of its ˜5,000 year existence, the size, shape, and location of Lake Agassiz changed dramatically depending on the location of the southern margin of the Laurentide Ice Sheet (LIS), the location and elevation of outflow channels, and differential isostatic rebound. Some of the best-preserved sequences of Lake Agassiz sediments are found in remnant lake basins where erosional processes are less pronounced than in adjacent higher-elevation regions. Lake of the Woods (LOTW), Minnesota, is among the largest of the Lake Agassiz remnant lakes and is an ideal location for Lake Agassiz sediment accumulation. High-resolution seismic-reflection (CHIRP) data collected from the southern basin of LOTW reveal up to 28 m of stratified lacustrine sediment deposited on top of glacial diamicton and bedrock. Five seismic units (SU A-E) were identified and described based on their reflection character, reflection configuration, and external geometries. Three prominent erosional unconformities (UNCF 1-3) underlie the upper three seismic units and indicate that deposition at LOTW was interrupted by a series of relatively large fluctuations in lake level. The lowermost unconformity (UNCF-1) truncates uniformly draped reflections within SU-B at the margins of the basin, where as much as four meters of sediment were eroded. The drop in lake level is interpreted to be contemporaneous with the onset of the low-stand Moorhead phase of Lake Agassiz identified from subaerial deposits in the Red River Valley, Rainy River basin, and Lake Winnipeg. A rise in lake level, indicated by onlapping reflections within SU-C onto UNCF-1, shifted the wave base outwards and as much as 11 m of sediment were deposited (SU-C) in the middle of the basin before a second drop, and subsequent rise, in lake level resulted in the formation of UNCF-2. Reflections in the lower part of SU-D onlap onto UNCF-2 only near the margins of the basin, suggesting that water occupied much of the middle of the southern basin after lake level drawdown. The reflection character and configuration of SU-C and SU-D are genetically different indicating that the depositional environment had changed following the formation of UNCF-2. Piston-type sediment cores collected from the southern basin of LOTW at depths that correspond to the middle of SU-D contain high amounts of organic material and charcoal fragments and sediment that are probably not related to Lake Agassiz. Instead, they were likely deposited during a transitional phase between when Lake Agassiz left the LOTW basin (UNCF-2) and inundation of LOTW from the northern basin due to differential isostatic rebound (UNCF-3). All sediment cores collected from the southern basin of LOTW record the uppermost unconformity, analogous in depth to UNCF-3 in the seismic images, which separates modern sediments from mid to late-Holocene sediments. The lithology of sediments below this unconformity varies across the basin from gray clay to laminated silt and clay. Radiocarbon ages from two peat layers immediately below the unconformity indicate that subaerial conditions had existed prior to the formation of UNCF-1, at about 7.75 ka cal BP. The timing correlates well with other lakes in the upper Midwest that record a prolonged dry climate during the mid-Holocene. UNCF-3 is planar and erosional across the entire survey area but erosion is greatest in the northern part of the basin as the result of a southward transgressing wave base driven by differential isostatic rebound. Deposition in the southern basin probably resumed around 3.3 ka cal BP, though no radiocarbon dates were collected directly above UNCF-3. The lithology of sediment above UNCF-3 is highly uniform across the basin and represents modern sedimentation. Late-Holocene sedimentation rates were calculated at about 0.9 mm year-1 and are roughly double the sedimentation rates in the NW Angle basin, suggesting that erosion of the southern shoreline contributes significantly to deposition in the southern basin.
Functional trait responses to sediment deposition reduce macrofauna-mediated ecosystem functioning in an estuarine mudflat

NASA Astrophysics Data System (ADS)

Mestdagh, Sebastiaan; Bagaço, Leila; Braeckman, Ulrike; Ysebaert, Tom; De Smet, Bart; Moens, Tom; Van Colen, Carl

2018-05-01

Human activities, among which dredging and land use change in river basins, are altering estuarine ecosystems. These activities may result in changes in sedimentary processes, affecting biodiversity of sediment macrofauna. As macrofauna controls sediment chemistry and fluxes of energy and matter between water column and sediment, changes in the structure of macrobenthic communities could affect the functioning of an entire ecosystem. We assessed the impact of sediment deposition on intertidal macrobenthic communities and on rates of an important ecosystem function, i.e. sediment community oxygen consumption (SCOC). An experiment was performed with undisturbed sediment samples from the Scheldt river estuary (SW Netherlands). The samples were subjected to four sedimentation regimes: one control and three with a deposited sediment layer of 1, 2 or 5 cm. Oxygen consumption was measured during incubation at ambient temperature. Luminophores applied at the surface, and a seawater-bromide mixture, served as tracers for bioturbation and bio-irrigation, respectively. After incubation, the macrofauna was extracted, identified, and counted and then classified into functional groups based on motility and sediment reworking capacity. Total macrofaunal densities dropped already under the thinnest deposits. The most affected fauna were surficial and low-motility animals, occurring at high densities in the control. Their mortality resulted in a drop in SCOC, which decreased steadily with increasing deposit thickness, while bio-irrigation and bioturbation activity showed increases in the lower sediment deposition regimes but decreases in the more extreme treatments. The initial increased activity likely counteracted the effects of the drop in low-motility, surficial fauna densities, resulting in a steady rather than sudden fall in oxygen consumption. We conclude that the functional identity in terms of motility and sediment reworking can be crucial in our understanding of the regulation of ecosystem functioning and the impact of habitat alterations such as sediment deposition.
A buried marine depositional sequence (Presumpscot FM. ) N. of the marine limit, Waterboro, Maine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morency, R.E.

Subsurface investigations conducted in Waterboro, ME (York Co.) in connection with studies of two hazardous waste sites and a municipal water supply exploration project, have demonstrated that a laterally extensive sequence of marine deposits underlies surficial sediments mapped as non-esker ice contact glacio-fluvial deposits. The marine deposits consist of a fining-downwards sequence of grey, micaceous sands (fine to medium, grading down to a silty-fine sand), which grade downward into a thick ([plus minus] 30 feet) grey silt/clay unit, which itself shows a fining-downward trend. The stratigraphy is likely correlative to the Presumpscot Formation, as described by Bloom (1963). The bottommore » of the regressive marine sequence is marked at several locations by a thin layer of sand-sized biotite mica. Lodgement till was encountered only at scattered localities (in boreholes) at each site. The bedrock surface is of considerable relief, with changes of 200--300 feet over short distances detected. The sequence appears to be the record of a rapidly transgressing sea which inundated a valley where outwash had been deposited by meltwater ahead of retreating ice. As the sea retreated, up to 70 feet of sediment was deposited in a continuous, coarsening-upwards sequence. Subsequent to the marine regression, the sediments were reworked in a subaerial (braided stream) environment. The Surficial Geologic Map of Maine shows that the inland limit of late-glacial marine submergence is located approximately 8 miles southwest of Waterboro, in Alfred, Maine. The marine limit in Alfred takes the form of a NNE trending, blunt-ended embayment. The results of this study suggest that the marine embayment once extended northward from Alfred, and is now a buried feature, possibly representing a preglacial valley, which hosted an estuary in late Wisconsonian time.« less
Palaeo-tsunami in the southern Caribbean: clarity through new geological archives?

NASA Astrophysics Data System (ADS)

Engel, M.; Brückner, H.; Messenzehl, K.; Frenzel, P.; Wennrich, V.; May, S. M.; Daut, G.; Willershäuser, T.; Scheffers, A.; Scheffers, S.; Vött, A.; Kelletat, D.

2010-12-01

A general lack of accounts of palaeo-tsunami deposits in back barrier environments throughout the Caribbean and diverging and conflicting interpretation of onshore coarse-clast deposits and landforms on the Leeward Netherlands Antilles (Bonaire, Curaçao, Aruba) encouraged the investigation of coastal stratigraphies along the coast of Bonaire. This work was conducted in order to (i) identify overwash deposits and reconstruct the regional history of high-energy wave events and (ii) provide a scientific basis for local hazard assessment. Vibracores and push cores at the windward (Playa Grandi, Lagun) and leeward coast (Saliña Tam, Klein Bonaire) were analyzed in terms of sedimentary characteristics, geochemical composition and fossil content. The coring sites in exposure to wave energy, foreshore morphology, sediment budgets, relief gradient and vegetation cover. Accordingly the pattern of subsurface overwash deposits varies significantly from site to site depending on exposure direction. For instance, although a prominent layer of sand and shell debris identified at the Lagun embayment (2000-1700 BP) has a counterpart at the sheltered lagoon of Saliña Tam, it is obviously absent at the northern coast. Along the entire island major layers of extreme wave deposits were radiocarbon dated to around 3300 BP, 2000-1700 BP and >500 BP. Sedimentary characteristics, bedforms and geochemical signatures did not provide unequivocal evidence for either tsunami or hurricane storm surge. However, evidence from the taphonomic characteristics of mollusc shells (articulation, fragmentation, rounding, encrustations, abrasion/dissolution) found within candidate coarse sediment layers and by comparison with the marginal sediment input of recent category 4/5 hurricane storm surges, the deposits were classified as representatives for palaeo-tsunami events.
210Pb dating

USGS Publications Warehouse

Swarzenski, Peter W.

2014-01-01

Roughly fifty years ago, a small group of scientists from Belgium and the United States, trying to better constrain ice sheet accumulation rates, attempted to apply what was then know about environmental lead as a potential geochronometer. Thus Goldberg (1963) developed the first principles of the 210Pb dating method, which was soon followed by a paper by Crozaz et al. (1964), who examined accumulation history of Antarctic snow using 210Pb. Shortly thereafter, Koide et al. (1972, 1973) adapted this technique to unravel sediment deposition and accumulation records in deep-sea environments. Serendipitously, they chose to work in a deep basin off California, where an independent and robust age model had already been developed. Krishanswami et al. (1971) extended the use of this technique to lacustrine deposits to reconstruct depositional histories of lake sediment, and maybe more importantly, contaminant inputs and burial. Thus, the powerful tool for dating recent (up to about one century old) sediment deposits was established and soon widely adopted. Today almost all oceanographic or limnologic studies that address recent depositional reconstructions employ 210Pb as one of several possible geochronometers (Andrews et al., 2009; Gale, 2009; Baskaran, 2011; Persson and Helms, 2011). This paper presents a short overview of the principles of 210Pb dating and provides a few examples that illustrate the utility of this tracer in contrasting depositional systems. Potential caveats and uncertainties (Appleby et al., 1986; Binford, 1990; Binford et al., 1993; Smith, 2001; Hancock et al., 2002) inherent to the use and interpretation of 210Pb-derived age-models are also introduced. Recommendations as to best practices for most reliable uses and reporting are presented in the summary.
Dynamics of Braided Channels, Bars, and Associated Deposits Under Experimental Density Currents

NASA Astrophysics Data System (ADS)

Limaye, A. B. S.; Jean-Louis, G.; Paola, C.

2015-12-01

Turbidity currents are the principal agents that transfer clastic sediment from continental margins to the deep ocean. The extensive sedimentary deposits that result can record influences from fluvial transport, ocean currents, and seafloor bathymetry; decoding these controls is key to understanding long-term continental denudation and the formation of hydrocarbon reservoirs. Experimental turbidity currents often use pre-formed, single-thread channels, but more recent experiments and seafloor observations suggest that braided channels also develop in submarine environments. Yet controls on the formation of submarine braided channels and relationships between these channels and stratigraphic evolution remain largely untested. We have conducted a series of experiments to determine the conditions conducive to forming braided submarine channels, and to relate channel geometry and kinematics to deposit architecture. Dissolved salt supplies the excess density of the experimental turbidity currents, which transport plastic, sand-sized sediment as bedload across a test section two meters long and one meter wide. Our experiments indicate that braided channels can form as constructional features without prior erosion for a range of input water and sediment fluxes. Channel migration, avulsion, and aggradation construct sedimentary deposits with bars at a variety of scales. Bar geometry and channel kinematics are qualitatively similar under subaerial and subaqueous experiments with other parameters fixed. We will present quantitative analyses of the relationships between channel geometry and mobility and deposit architecture, at scales from individual bars to the entire deposit, and compare these results to control experiments with subaerial braiding. These experimental results suggest parallels between subaerial and subaqueous braiding, and help to constrain forward models for stratigraphic evolution and inverse methods for estimating flow conditions from turbidites.
Effects of Emergent Vegetation on Sediment Dynamics within a Retreating Coastal Marshland

NASA Astrophysics Data System (ADS)

Stellern, C.; Grossman, E.; Fuller, R.; Wallin, D.; Linneman, S. R.

2015-12-01

Coastal emergent vegetation in estuaries physically interrupts flow within the water column, reduces wave energy and increases sediment deposition. Previous workers conclude that wave attenuation rates decrease exponentially with distance from the marsh edge and are dependent on site and species-specific plant characteristics (Yang et al., 2011). Sediment deposition may exhibit similar patterns; however, sediment, geomorphic and habitat models seldom integrate site-specific biophysical plant parameters into change analyses. We paired vegetation and sediment dynamic studies to: (1) characterize vegetation structure, (2) estimate sediment available for deposition, (3) estimate rate, distribution and composition of sediment deposits, (4) determine sediment accumulation on vegetation, (5) compare sediment deposition within dense tidal wetland relative to non-vegetated tidal flat. These studies integrate a variety of monitoring methods, including the use of sediment traps, turbidity sensors, side-on photographs of vegetation and remote sensing image analysis. We compared sedimentation data with vegetation characteristics and spatial distribution data to examine the relative role of vegetation morphologic traits (species, stem density, biomass, distribution, tidal channels, etc.) on sediment dynamics. Our study is focused on Port Susan Bay of Washington State; a protected delta that has experienced up to 1 kilometer of marsh retreat (loss) over the past fifty years. Preliminary results show that the highest winter deposition occurred in the high marsh/mid-marsh boundary, up to 300m inland of the marsh edge, where bulrush species are most dense. These results will inform restoration efforts aimed at reestablishing sediment supply to the retreating marshland. This research is necessary to understand the vulnerability and adaptability of coastal marshlands to climate change related stressors such as, increased water levels (sea-level rise) and wave energy.
Sedimentation in small reservoirs on the San Rafael Swell, Utah

USGS Publications Warehouse

King, Norman Julius; Mace, Mervyn M.

1953-01-01

Movement of sediment from upland areas and eventually into main drainages and rivers is by no means through continuous transportation of material from the source to the delta. Instead it consists of a series of intermittent erosional and depositional phases that present a pulsating movement. Hence, sediment carried off upland areas may be deposited in lower reaches or along main drainages if an existing combination of factors tend to effect deposition. During this period actual sediment movement out of the basin may be relatively small. Following any change in existing conditions, however, these unconsolidated alluvial fills may be subjected to rapid removal; thus, for a limited time, abnormally high sediment production rates occur until the deposits are either removed or another cycle of deposition is started.
Swept Away: Resuspension of Bacterial Mats Regulates Benthic-Pelagic Exchange of Sulfur

NASA Astrophysics Data System (ADS)

Grant, Jonathan; Bathmann, Ulrich V.

1987-06-01

Filaments and extracellular material from colorless sulfur bacteria (Beggiatoa spp.) form extensive white sulfur mats on surface sediments of coastal, oceanic, and even deep-sea environments. These chemoautotrophic bacteria oxidize soluble reduced sulfur compounds and deposit elemental sulfur, enriching the sulfur content of surface sediment fivefold over that of deeper sediments. Laboratory flume experiments with Beggiatoa mats from an intertidal sandflat (Nova Scotia) demonstrated that even slight erosion of sediment causes a flux of 160 millimoles of sulfur per square meter per hour, two orders of magnitude greater than the flux produced by sulfur transformations involving either sulfate reduction or sulfide oxidation by benthic bacteria. These experiments indicate that resuspension of sulfur bacterial mats by waves and currents is a rapid mechanism by which sediment sulfur is recycled to the water column. Benthic communities thus lose an important storage intermediate for reduced sulfur as well as a high-quality bacterial food source for benthic grazers.
Simulation of the fate of faecal bacteria in estuarine and coastal waters based on a fractionated sediment transport model

NASA Astrophysics Data System (ADS)

Yang, Chen; Liu, Ying

2017-08-01

A two-dimensional depth-integrated numerical model is refined in this paper to simulate the hydrodynamics, graded sediment transport process and the fate of faecal bacteria in estuarine and coastal waters. The sediment mixture is divided into several fractions according to the grain size. A bed evolution model is adopted to simulate the processes of the bed elevation change and sediment grain size sorting. The faecal bacteria transport equation includes enhanced source and sink terms to represent bacterial kinetic transformation and disappearance or reappearance due to sediment deposition or re-suspension. A novel partition ratio and dynamic decay rates of faecal bacteria are adopted in the numerical model. The model has been applied to the turbid water environment in the Bristol Channel and Severn estuary, UK. The predictions by the present model are compared with field data and those by non-fractionated model.
Fate, bioavailability and toxicity of silver in estuarine environments

USGS Publications Warehouse

Luoma, S.N.; Ho, Y.B.; Bryan, G.W.

1995-01-01

The chemistry and bioavailability of Ag contribute to its high toxicity in marine and estuarine waters. Silver is unusual, in that both the dominant speciation reaction in seawater and the processes important in sorbing Ag in sediments favour enhanced bioavailability. Formation of a stable chloro complex favours dispersal of dissolved Ag, and the abundant chloro complex is available to biota. Sequestration by sediments also occurs, but with relatively slow kinetics. Amorphous aggregated coatings enhance Ag accumulation in sediments, as well as Ag uptake from sediments by deposit feeders. In estuaries, the bioaccumulation of Ag increases 56-fold with each unit of increased Ag concentration in sediments. Toxicity for sensitive marine species occurs at absolute concentrations as low as those observed for any nonalkylated metal, partly because bioaccumulation increases so steeply with contamination. The environmental window of tolerance to Ag in estuaries could be narrower than for many elements.
Sedimentary architecture of a sub-lacustrine debris fan: Eocene Dongying Depression, Bohai Bay Basin, east China

NASA Astrophysics Data System (ADS)

Liu, Jianping; Xian, Benzhong; Wang, Junhui; Ji, Youliang; Lu, Zhiyong; Liu, Saijun

2017-12-01

The sedimentary architectures of submarine/sublacustrine fans are controlled by sedimentary processes, geomorphology and sediment composition in sediment gravity flows. To advance understanding of sedimentary architecture of debris fans formed predominantly by debris flows in deep-water environments, a sub-lacustrine fan (Y11 fan) within a lacustrine succession has been identified and studied through the integration of core data, well logging data and 3D seismic data in the Eocene Dongying Depression, Bohai Bay Basin, east China. Six types of resedimented lithofacies can be recognized, which are further grouped into five broad lithofacies associations. Quantification of gravity flow processes on the Y11 fan is suggested by quantitative lithofacies analysis, which demonstrates that the fan is dominated by debris flows, while turbidity currents and sandy slumps are less important. The distribution, geometry and sedimentary architecture are documented using well data and 3D seismic data. A well-developed depositional lobe with a high aspect ratio is identified based on a sandstone isopach map. Canyons and/or channels are absent, which is probably due to the unsteady sediment supply from delta-front collapse. Distributary tongue-shaped debris flow deposits can be observed at different stages of fan growth, suggesting a lobe constructed by debrite tongue complexes. Within each stage of the tongue complexes, architectural elements are interpreted by wireline log motifs showing amalgamated debrite tongues, which constitute the primary fan elements. Based on lateral lithofacies distribution and vertical sequence analysis, it is proposed that lakefloor erosion, entrainment and dilution in the flow direction lead to an organized distribution of sandy debrites, muddy debrites and turbidites on individual debrite tongues. Plastic rheology of debris flows combined with fault-related topography are considered the major factors that control sediment distribution and fan architecture. An important implication of this study is that a deep-water depositional model for debrite-dominated systems was proposed, which may be applicable to other similar deep-water environments.
Millennial-scale record of overwash deposits preserved within lagoon sediments from the Arabian Peninsula

NASA Astrophysics Data System (ADS)

Griffis, A. M.; Jessica, P.; Reinhardt, E. G.; Kosciuch, T. J.; Kovacs, S. E.; Hoffmann, G.

2017-12-01

Coastlines along the Arabian Sea are susceptible to tsunami-related inundation due to their proximity to the Makran Subduction Zone (MSZ). This subduction zone has seen decades of low intensity events, but has historically produced large tsunamigenic-earthquakes that have impacted the 100 million people living along the Arabian Sea. One major problem in assessing the seismic risk of the MSZ is that the historical record of events are spatially and temporally limited and rely heavily on eye witness accounts. This hinders our ability to forecast the potential magnitude and recurrence intervals of earthquakes and tsunamis that can be expected in the future. Sediments deposited by paleotsunamis are useful as they expand the decadal record of events to include millennial timescales that more accurately capture the full range of magnitudes and recurrence intervals. On November 28, 1945 a 8.1 Mw earthquake originating from the MSZ generated a tsunami inundating coastlines along the Arabian Sea with wave heights up to 13m. At Sur, a small village on the northeastern coastline of Oman, the tsunami deposited a laterally continuous shell-rich layer within a 12 km2 lagoon. This layer contained distinctive taphonomic assemblages of foraminifera and bivalves. Below the 1945 shelly deposit at Sur Lagoon, seven anomalous sand layers were found preserved within fine-grained lagoonal sediment. These layers of medium-coarse sands range in thickness from 5 to 35 cm and are separated by sandy-mud sediment. Grain size analysis shows that these anomalously coarse layers are followed by an abrupt return to lagoonal mud. The sand layers have features consistent with the 1945 tsunami deposit such as fining upward trends, sharp basal contact, and marine foraminifera (e.g., Amphistegina sp., planktics). In contrast, the surrounding lagoon deposits are generally massive, finer in grain size, and contain foraminiferal species typically found in shallow quiescent coastal environments (e.g., Ammonia tepida, miliolids). We have attributed these seven marine sand layers to tsunami overwash deposition. Preliminary radiocarbon dating of articulated bivalve shells establish a late Holocene age range for the tsunami sand layers with ongoing analyses further constraining timings leading to assessing relative magnitudes of past events.
A new seepage site south of Svalbard? Results from Eurofleets-2 BURSTER cruise

NASA Astrophysics Data System (ADS)

Giulia Lucchi, Renata; Morigi, Caterina; Sabbatini, Anna; Mazzini, Adriano; Krueger, Martin; de Vittor, Cinzia; Kovacevic, Vedrana; Deponte, Davide; Stefano, Graziani; Bensi, Manuel; Langone, Leonardo; Eurofleets2-Burster*, Scientific Party Of

2017-04-01

The oceanographic and environmental characteristics of the Kveithola Glacial Trough, located south of Svalbard, have been investigated during the Eurofleets2-BURSTER project onboard the German icebreaker Polarstern (expedition PS99-1a, June, 19-20, 2016). The inner part of the glacial trough contains a complex sediment drift that deposited under persistent bottom currents, active in the area after Last Glacial Maximum. Notwithstanding the highly dynamic environment depicted from the morphological and structural characteristics of the Kveithola sediment drift, previous studies indicated the presence of an apparently "stagnant" environment with black anoxic sediments and absence of bottom current related sediment features. We present the preliminary results from the new dataset that includes micropaleontological, geochemical and microbial analyses of multi-core sediments; morphological analyses of sea floor sediments with benthic camera (Ocean Floor Observatory System); acoustic analyses of the sub-bottom record, and oceanographic analyses of CTD-Rosette sampling, all together indicating the possible presence of a new seepage site in the Arctic area south of 75°N Latitude. *Bazzaro, M., Biebow, N., Carbonara, K., Caridi, F., Dominiczak, A., Gamboa Sojo, V.M., Laterza R., Le Gall, C., Musco, M.E., Povea, P., Relitti, F., Ruggiero, L., Rui, L., Sánchez Guillamón, O., Tagliaferro, M., Topchiy, M., Wiberg, D., Zoch, D.
Metal contamination in urban street sediment in Pisa (Italy) can affect the production of antioxidant metabolites in Taraxacum officinale Weber.

PubMed

Bretzel, Francesca; Benvenuti, Stefano; Pistelli, Laura

2014-02-01

Taraxacum officinale Weber (dandelion) is a very ubiquitous species, and it can grow in urban environments on metal-polluted sediments deposited in the gutters. This study represents a preliminary step to verify the presence of metals in sediments collected in urban streets in Pisa and to assess the alteration in dandelion metabolites in order to understand its adaptation to polluted environments. The soil and sediments were collected at three urban streets and analyzed for total and extractable Cr, Pb, Cu, Ni, and Zn. The total values of Pb and Zn in street sediments exceeded the limits for residential areas of soils. Zn was the most mobile of the metals analyzed. Floating cultivations trials were set up with dandelion seedlings and street sediments. The metals were analyzed in roots and leaves. Antioxidant power, anthocyanins, polyphenols, non-protein thiols (NP-TH) and chlorophylls were measured in dandelion leaves. The first two parameters (anthocyanins and antioxidant power) were higher in the polluted samples compared to the control; chlorophyll content was lower in the treated samples, whereas NP-TH showed no differences. NP-TH groups determined in roots were associated with the root content of Zn and Pb. These results indicate that dandelion can tolerate plant stress by altering its metabolite content.
Critical elements in sediment-hosted deposits (clastic-dominated Zn-Pb-Ag, Mississippi Valley-type Zn-Pb, sedimentary rock-hosted Stratiform Cu, and carbonate-hosted Polymetallic Deposits): A review: Chapter 12

USGS Publications Warehouse

Marsh, Erin; Hitzman, Murray W.; Leach, David L.

2016-01-01

Some sediment-hosted base metal deposits, specifically the clastic-dominated (CD) Zn-Pb deposits, carbonate-hosted Mississippi Valley-type (MVT) deposits, sedimentary-rock hosted stratiform copper deposits, and carbonate-hosted polymetallic (“Kipushi type”) deposits, are or have been important sources of critical elements including Co, Ga, Ge, and Re. The generally poor data concerning trace element concentrations in these types of sediment-hosted ores suggest that there may be economically important concentrations of critical elements yet to be recognized.
Welded slump-graded sand couplets: evidence for slide generated turbidity currents

NASA Astrophysics Data System (ADS)

Stanley, Daniel Jean

1982-09-01

Some massive channelized strata preserved in the rock record are characterized by a lower slump member which evolves upward to a turbidite. This merging is indicative of probable generation of sediment gravity flows from submarine sliding. Conditions essential for deposition of such sequences are short transport distance between point of failure and depositional site, and an environment likely to retain both facies. Fan valleys are a likely setting for welded couplets: flowing sand, initiated by the sliding event, comes to rest at nearly the same time and position as the slump mass deposited near the base of the valley wall and in the axis proper.
Sediment Transport at River Lima Estuary: Developing a Sound Methodology to Assess Sediment River Basin Input to an Erosion Prone Coast (NW Iberian Peninsula)

NASA Astrophysics Data System (ADS)

Pinho, J.; Costa, N.; Venâncio, S.; Martins, M.; Vieira, J.; Granja, H.

2016-12-01

The NW coast of Iberian Peninsula is mainly formed by rocky cliffs northern of the river Minho mouth and by narrow sandy beaches south of this river. These beaches are mainly in a sedimentary deficit status resulting from the north-south longitudinal drift driven by the dominant wave climate that acts from the NW direction. In this scenario understand and quantify river sediment inputs to the coast is crucial in order to follow a sustainable management policy to mitigate erosion impacts both in the natural and social environments. This work will present results from research conducted at rive Lima Estuary, one of the rivers flowing to the NW Iberian coast, based on both numerical modeling and field data acquisition. A hydrological model of the river basin and a detailed morphodynamic model of the estuary were implemented. Instrumentation of the estuary that is being conducted comprises traditional sensor pressures and new ones that are being designed and assembled to be installed at different measurement stations within the estuary. Modelling results for flood events showed that the river is capable of remove all the sediments that are deposited in the narrow estuarine canal located near the river mouth. Some of these sediments are immediately deposited downstream, within the interior of the harbor. Here, there is a strong possibility of silting of the river mouth and the central area of the harbor. Since the river flows during extreme events are controlled by an upstream reservoir, the capacity of the river to transport sediments to the coast was lowered during the last decades, which, moreover, requires dredging works over the years to maintain navigation depth requirements. Dredging sediments should be correctly deposited at the coast in order to properly feed the longitudinal drift, otherwise they will be out of the system, which aggravate the installed erosion tendency.

Freshwater sediments and sludges: two important terrestrial sinks for emissions from damaged NPPs

NASA Astrophysics Data System (ADS)

Fischer, Helmut W.; Evangelia Souti, Maria; Ulbrich, Susanne; Hormann, Volker

2013-04-01

Surface deposition of radionuclides released from the damaged Fukushima NPPs is well documented and emissions to the Pacific Ocean and their distribution with time and space are also subject to monitoring and research. In both cases, solid matter (soil and sea sediment, respectively) acts as a sink for radioisotopes after their transport through air and water. The possible hazards from direct irradiation of workers and public and from entry of radionuclides into food chains are well recognized. Apart from direct deposition onto soil, plants, building roofs etc., aerosols and contaminated rainwater will reach surface waters, leading to long-term deposition in freshwater sediments (and possibly to interim contamination of drinking water). In populated and industrial areas, drained rainwater will enter the wastewater collection and treatment chain if a combined rain and wastewater sewer is used. Depending on the processes in the wastewater treatment plant and chemical element and speciation, the isotopes will either concentrate in treatment sludge or be released with the effluent to rivers and lakes and their sediments. The mentioned media may act as long-term storage for radioisotopes when disposed of properly, but can also contribute to direct irradiation of workers or public, lead to continuous releases to the environment and possibly enter the food chain in the same way as soil and sea sediments. It appears therefore essential to monitor these environmental compartments as well. However, very few data on Fukushima-related radioisotope concentration in sludges and freshwater sediments have been published to date. We will therefore compare data for regional surface deposition and related concentrations in surface water, river sediments and sewage sludge obtained in Europe during 1986 to published data from Japan in 2011 for the most important common short-lived (I-131, half-life = 8.02 d) and long-lived (Cs-137, half-life = 30.17 yr) isotopes. As in central Europe the Chernobyl fallout was not accompanied by other catastrophic events, well documented time series of data exist. It might become possible to estimate sludge and sediment isotope concentrations in Japan by proportionality considerations and by application of transport models when no or insufficient current data exist. Additional insight into transport processes can be obtained from ongoing investigations of medically used I-131 in wastewater and rivers. The results might help in identification and remediation of possibly emerging hazards.
Utilizing of 2-D resistivity with geotechnical method for sediment mapping in Sungai Batu, Kedah

NASA Astrophysics Data System (ADS)

Taqiuddin, Z. M.; Rosli, S.; Nordiana, M. M.; Azwin, I. N.; Mokhtar, S.

2017-07-01

Sungai Batu is Lembah Bujang subdistrict, located at northern region of Peninsular Malaysia, recognized as an international cultural and commercial crossroad for 2000 years ago, and recorded as the oldest archaeological site in southeast Asia. The discovering of iron smelting area (1st-4th century) shows the evidence of important iron industry in Malay Peninsular to others civilization. Nowadays, a lot of interdisciplinary research was conducted in this area including geophysical prospect to understand the subsurface profile for this locality. Geophysical approach such as 2-D resistivity was performed with the main objective is to identify sediment deposit for this area. Three 2-D resistivity survey lines were design across borehole and data acquired using ABEM SAS4000 system with Pole-dipole array using 2.5 m minimum electrode spacing. The data obtained was process using Res2Dinv software to produce inversion model and Surfer10 software used for interpretation and correlation with respective borehole record. The 2-D resistivity inversion model shows that, the area dominated by clay soil with resistivity values of <50 Ωm while high resistivity values of >500 Ωm interpreted as hard layer. The saturated zone (<100 Ωm) were identified at depth of >25 m which consider large volume of soil deposit during sedimentation process. The correlation with the borehole record shows that clay profile distributed at depth of >20 m. The present of shale in certain borehole record indicate that the environment deposit is clam/stagnant water condition during the formation process which suspected controlled by the deposition process from the land deposit.
Sedimentary Signatures of Submarine Earthquakes: Deciphering the Extent of Sediment Remobilization from the 2011 Tohoku Earthquake and Tsunami and 2010 Haiti Earthquake

NASA Astrophysics Data System (ADS)

McHugh, C. M.; Seeber, L.; Moernaut, J.; Strasser, M.; Kanamatsu, T.; Ikehara, K.; Bopp, R.; Mustaque, S.; Usami, K.; Schwestermann, T.; Kioka, A.; Moore, L. M.

2017-12-01

The 2004 Sumatra-Andaman Mw9.3 and the 2011 Tohoku (Japan) Mw9.0 earthquakes and tsunamis were huge geological events with major societal consequences. Both were along subduction boundaries and ruptured portions of these boundaries that had been deemed incapable of such events. Submarine strike-slip earthquakes, such as the 2010 Mw7.0 in Haiti, are smaller but may be closer to population centers and can be similarly catastrophic. Both classes of earthquakes remobilize sediment and leave distinct signatures in the geologic record by a wide range of processes that depends on both environment and earthquake characteristics. Understanding them has the potential of greatly expanding the record of past earthquakes, which is critical for geohazard analysis. Recent events offer precious ground truth about the earthquakes and short-lived radioisotopes offer invaluable tools to identify sediments they remobilized. In the 2011 Mw9 Japan earthquake they document the spatial extent of remobilized sediment from water depths of 626m in the forearc slope to trench depths of 8000m. Subbottom profiles, multibeam bathymetry and 40 piston cores collected by the R/V Natsushima and R/V Sonne expeditions to the Japan Trench document multiple turbidites and high-density flows. Core tops enriched in xs210Pb,137Cs and 134Cs reveal sediment deposited by the 2011 Tohoku earthquake and tsunami. The thickest deposits (2m) were documented on a mid-slope terrace and trench (4000-8000m). Sediment was deposited on some terraces (600-3000m), but shed from the steep forearc slope (3000-4000m). The 2010 Haiti mainshock ruptured along the southern flank of Canal du Sud and triggered multiple nearshore sediment failures, generated turbidity currents and stirred fine sediment into suspension throughout this basin. A tsunami was modeled to stem from both sediment failures and tectonics. Remobilized sediment was tracked with short-lived radioisotopes from the nearshore, slope, in fault basins including the deepest, offering a comprehensive characterization of sediment remobilization by a transform earthquake. These and other modern case studies will improve our ability to recognize earthquake-related sedimentation events, to differentiate them from other causes, and to decipher in them important characteristics of the earthquakes.
A Regional Survey of River-plume Sedimentation on the Mississippi River Delta Front

NASA Astrophysics Data System (ADS)

Courtois, A. J.; Bentley, S. J.; Xu, K.; Georgiou, I. Y.; Maloney, J. M.; Miner, M. D.; Chaytor, J. D.; Smith, J.

2017-12-01

Many studies of the Mississippi River and Delta (MRD) have shown historic declines in sediment load reaching the main river distributaries over the last few decades. Recent studies also reported that 50% of the suspended load during floods is sequestered within the delta. While the impact of declining sediment load on wetland loss is well documented, submarine sedimentary processes on the delta front during this recent period of declining sediment load are understudied. To better understand modern sediment dispersal and deposition across the Mississippi River Delta Front, 31 multicores were collected in June 2017 from locations extending offshore from Southwest Pass, South Pass, and Pass a Loutre (the main river outlets) in water depths of 25-280 m. Core locations were selected based on multibeam bathymetry and morphology collected by the USGS in May 2017; the timing of collection coincided with the end of annual peak discharge on the Mississippi River. This multi-agency survey is the first to study delta-front sedimentary processes regionally with such a wide suite of tools. Target locations for coring included the dominant depositional environments: mudflow lobes, gullies, and undisturbed prodelta. Cores were subsampled at 2 cm intervals and analyzed for Beryllium-7 activity via gamma spectrometry; in such settings, Be-7 can be used as a tracer of sediment recently delivered from fluvial origin. Results indicate a general trend of declining Be-7 activity with increasing distance from source, and in deeper water. Inshore samples near Southwest Pass show the deepest penetration depth of Be-7 into the sediment (24-26 cm), which is a preliminary indicator of rapid seasonal sedimentation. Nearshore samples from South Pass exhibited similar Be-7 penetration depths, with results near Pass a Loutre to 14-16 cm depth. Be-7 remains detectable to 2 cm in water 206 m deep, approximately 20 km from South Pass. Sediment dispersal remains impressive offshore from all three major river outlets, despite overall decline of sediment load in recent decades, and pronounced declines for South Pass and Pass a Loutre. Future research will focus on relationships among changing sediment loads, dispersal patterns, and sediment transport by mudflows, which are an important process for dispersal after initial deposition.
The role of extreme floods in estuary-coastal behaviour: contrasts between river- and tide-dominated microtidal estuaries

NASA Astrophysics Data System (ADS)

Cooper, J. A. G.

2002-06-01

Contrasting modes of sedimentation and facies arrangement in tide- and river-dominated microtidal estuaries arise from the degree to which river or tidal discharge and sediment supply influences an estuary. A distinct facies gradation exists in tide-dominated systems from sandy, barrier/tidal delta-associated environments at the coast through deep mud-dominated middle reaches to fluvial sediment in the upper reaches. In river-dominated systems, fluvial sediment extends to the barrier and flood-tidal deltas are poorly developed or absent from the estuary. A number of independent observations during extreme floods on the South African coast indicate that these types of estuary respond differently to extreme river floods and that the mode of response corresponds to estuary type. Tide-dominated systems exhibit preferential erosion of noncohesive barrier and tidal delta sediments during river floods while the middle reaches remain little modified. River-dominated systems experience consistent erosion throughout their channel length during extreme floods. The increased cohesion of riverine sediments and stabilisation of bars by vegetation in river-dominated channels means that higher magnitude floods are necessary to effect significant morphological change. Barrier erosion, including the tidal delta, results in deposition of an ephemeral delta composed almost entirely of sands from these deposits in tide-dominated estuaries. In river-dominated systems, eroded channel sediments and material from the river catchment may augment barrier sediments in the ephemeral delta deposit. Post-flood, wave-reworking of ephemeral delta sediments acts to restore barriers to pre-flood morphology within a few years; however, in river-dominated systems, the additional sediment volume may produce significant coastal progradation that requires several years or decades to redistribute. These different modes of flood response mediated by the nature of the estuary have implications for coastal behaviour at the time scale of months to several decades. Estuary-coastal behaviour at river-dominated estuaries may be influenced for several decades by post-flood morphological adjustment. Tide-dominated estuaries, however, respond more rapidly in reworking flood-eroded sediment and are typically fully adjusted to modal wave and tidal conditions within a few months to a few years. In addition, the facies arrangement within the two estuary types renders tide-dominated estuaries more responsive to minor floods, while river-dominated estuaries, by virtue of more cohesive channel sediments, require greater discharges to effect significant morphological change.
Wave Glider Monitoring of Sediment Transport and Dredge Plumes in a Shallow Marine Sandbank Environment.

PubMed

Van Lancker, Vera; Baeye, Matthias

2015-01-01

As human pressure on the marine environment increases, safeguarding healthy and productive seas increasingly necessitates integrated, time- and cost-effective environmental monitoring. Employment of a Wave Glider proved very useful for the study of sediment transport in a shallow sandbank area in the Belgian part of the North Sea. During 22 days, data on surface and water-column currents and turbidity were recorded along 39 loops around an aggregate-extraction site. Correlation with wave and tidal-amplitude data allowed the quantification of current- and wave-induced advection and resuspension, important background information to assess dredging impacts. Important anomalies in suspended particulate matter concentrations in the water column suggested dredging-induced overflow of sediments in the near field (i.e., dynamic plume), and settling of finer-grained material in the far field (i.e., passive plume). Capturing the latter is a successful outcome to this experiment, since the location of dispersion and settling of a passive plume is highly dependent on the ruling hydro-meteorological conditions and thus difficult to predict. Deposition of the observed sediment plumes may cause habitat changes in the long-term.
A suture delta: the co-evolution of tectonics and sedimentology as a remnant ocean basin closes; the Indo Burman ranges, northeast India and Bangladesh

NASA Astrophysics Data System (ADS)

Sincavage, R.; Betka, P. M.; Seeber, L.; Steckler, M. S.; Zoramthara, C.

2017-12-01

The closure of an ocean basin involves the interplay of tectonics and sedimentology, whereby thick successions of fluvio-deltaic and shallow marine sediment accumulate in the closing gap between the subduction zone and passive margin. The transition from subduction to collision involves processes that are inherently time-transgressive and co-evolve to influence the nature of the developing tectonic wedge. The Indo-Burman Ranges (IBR) of eastern India present a unique opportunity to examine this scenario on a variety of spatial (10-2-105 m2) and temporal (1 a-10 Ma) scales. Recent field mapping campaigns in the IBR have illuminated analogous depositional environments expressed in the Neogene outcrops of the IBR and the Holocene sediment archive of the Ganges-Brahmaputra-Meghna delta (GBMD). Six distinct lithofacies are present in shallow-marine to fluvial strata of the IBR, containing sedimentary structures that reflect depositional environments correlative with the modern delta. Cyclical alternations of fine sands and silts in packages on the order of 15-20 cm thick define part of the shallow-marine section (M2 facies) that we interpret to represent the foreset beds of the ancient subaqueous delta. The overall scale and sedimentary structures of M2 compare favorably with modern foreset deposits in the Bay of Bengal. Tan-orange medium-grained, well sorted fluvial sandstone that contain large scale (1-10 m) tabular and trough cross bedding represent large-river channel deposits (F2 facies) that overlie the shallow marine strata. F2 deposits bear a striking resemblance in scale and character to bar deposits along the modern Jamuna River. Preliminary grain size analyses on the F2 facies yield grain size distributions that are remarkably consistent with Brahmaputra-sourced mid-Holocene sediments from Sylhet basin within the GBMD. Current research on the GBMD has revealed quantifiable trends in bed thicknesses, downstream fining, and grain size within fluvial deposits. These data will be coupled with ongoing structural and geo- and thermochronology field studies of the IBR that aim to continue to reveal the structural and stratigraphic evolution of this geologically active and densely populated region.
Use of the Cone Penetration Testing (CPT) method to interpret late Quaternary tide-dominated successions: A case study from the eastern China coastal plain

NASA Astrophysics Data System (ADS)

Zhang, Xia; Lin, Chun-Ming; Dalrymple, Robert W.; Gao, Shu; Canas, Daniel T.

2018-06-01

We evaluate the applicability of cone penetration testing (CPT), calibrated using adjacent cores, as a tool for the sedimentological and stratigraphic examination of late Quaternary tide-dominated successions in the eastern China coastal plain. The results indicate that the sedimentary facies and sequence-stratigraphic surfaces can be readily distinguished using CPT profiles in the Qiantang River incised-valley system because of their distinctive mechanical behavior. The lithologic character of the various facies, which is controlled mainly by sediment supply, dynamic processes and post-depositional diagenesis, is the key factor affecting how well the CPT technique works. Within this particular macrotidal environment, which is dominated by non-cohesive sand and silt in the tidal channels, the accumulation of fluid mud is rare. Consequently, the tidal-channel deposits exhibit the geotechnical properties of coarse-grained sediments, and can be easily distinguished from the mud-dominated facies. However, in the nearby Changjiang delta system which is characterized by very high suspended-sediment concentrations and an abundance of fine-grained cohesive sediments, the presence of channel-bottom fluid muds makes it difficult to recognize channel deposits, because of the lack of a sharp lithologic contrast at their base. Consequently, the CPT method might not be as universally effective in tide-dominated systems as it appears to be in wave-dominated settings. Care is needed in the interpretation of the results from tide-dominated successions because of the widespread presence of fluid muds, the heterolithic nature of tidal deposits, the rheological similarity between adjacent facies, and the averaging of geotechnical properties between the alternating finer and coarser layers.
Properties of small instream wood as a logjam clogging agent: Implications for clogging dynamics based on wood density, water content, and depositional environment

NASA Astrophysics Data System (ADS)

Haga, Hirokazu; Moriishida, Takuya; Morishita, Naoya; Fujimoto, Takaaki

2017-11-01

In cooperation with large instream wood (LW) within logjams, small instream wood (SW) can control downstream flux of sediment and particulate organic matter and can play an important role for stream ecosystems. However, information regarding the density and moisture content of SW-which affects wood transport, wood decay, and mass loading-is limited. Here we investigated the SW properties, i.e., density under field conditions (in situ density), basic density, volumetric water content, and depositional environment of SW sampled from five logjams and their backwater areas in two headwater streams (second- and third-order streams) surrounded by mixed broadleaf-conifer forests in western Japan. The in situ density ranged from 0.49 to 1.25 g cm- 3, and pieces with densities > 1.0 g cm- 3 accounted for 45% of all samples. Additionally, the in situ density of SW closely related to the volumetric water content (r2 = 0.76) rather than the basic density as an index of solidity or decay condition of wood. The SW that was partially submerged in water had a higher volumetric water content than SW exposed to air. These results indicate that a nonfloating transport cannot be ignored as an important mechanism for SW movement and that in situ density depends not on the solidity of the wood but on water sorption by SW. However, waterlogged SW should be well decayed because it has a lower basic density than air-exposed and sediment-buried SW. We conclude that the moisture conditions of the depositional environment can affect subsequent transport and decay processes of SW. Moreover, most waterlogged and sediment-buried SW, because of its high in situ density (> 1.0 g cm- 3), may contribute to clogging between the channel bed and LW that initiate a logjam during future movements.
Unraveling signatures of biogeochemical processes and the depositional setting in the molecular composition of pore water DOM across different marine environments

NASA Astrophysics Data System (ADS)

Schmidt, Frauke; Koch, Boris P.; Goldhammer, Tobias; Elvert, Marcus; Witt, Matthias; Lin, Yu-Shih; Wendt, Jenny; Zabel, Matthias; Heuer, Verena B.; Hinrichs, Kai-Uwe

2017-06-01

Dissolved organic matter (DOM) in marine sediment pore waters derives largely from decomposition of particulate organic matter and its composition is influenced by various biogeochemical and oceanographic processes in yet undetermined ways. Here, we determine the molecular inventory of pore water DOM in marine sediments of contrasting depositional regimes with ultrahigh-resolution mass spectrometry and complementary bulk chemical analyses in order to elucidate the factors that shape DOM composition. Our sample sets from the Mediterranean, Marmara and Black Seas covered different sediment depths, ages and a range of marine environments with different (i) organic matter sources, (ii) balances of organic matter production and preservation, and (iii) geochemical conditions in sediment and water column including anoxic, sulfidic and hypersaline conditions. Pore water DOM had a higher molecular formula richness than overlying water with up to 11,295 vs. 2114 different molecular formulas in the mass range of 299-600 Da and covered a broader range of element ratios (H/C = 0.35-2.19, O/C = 0.03-1.19 vs. H/C = 0.56-2.13, O/C = 0.15-1.14). Formula richness was independent of concentrations of DOC and TOC. Near-surface pore water DOM was more similar to water column DOM than to deep pore water DOM from the same core with respect to formula richness and the molecular composition, suggesting exchange at the sediment-water interface. The DOM composition in the deeper sediments was controlled by organic matter source, selective decomposition of specific DOM fractions and early diagenetic molecule transformations. Compounds in pelagic sediment pore waters were predominantly highly unsaturated and N-bearing formulas, whereas oxygen-rich CHO-formulas and aromatic compounds were more abundant in pore water DOM from terrigenous sediments. The increase of S-bearing molecular formulas in the water column and pore waters of the Black Sea and the Mediterranean Discovery Basin was consistent with elevated HS- concentrations reflecting the incorporation of sulfur into biomolecules during early diagenesis. Sulfurization resulted in an increased average molecular mass of DOM and higher formula richness (up to 5899 formulas per sample). In sediments from the methanogenic zone in the Black Sea, the DOM pool was distinctly more reduced than overlying sediments from the sulfate-reducing zone. Bottom and pore water DOM from the Discovery Basin contained the highest abundances of aliphatic compounds in the entire dataset; a large fraction of abundant N-bearing formulas possibly represented peptide and nucleotide formulas suggesting preservation of these molecules in the life inhibiting environment of the Discovery Basin. Our unique data set provides the basis for a comprehensive understanding of the molecular signatures in pore water DOM and the turnover of sedimentary organic matter in marine sediments.
Quantifying grain shape with MorpheoLV: A case study using Holocene glacial marine sediments

NASA Astrophysics Data System (ADS)

Charpentier, Isabelle; Staszyc, Alicia B.; Wellner, Julia S.; Alejandro, Vanessa

2017-06-01

As demonstrated in earlier works, quantitative grain shape analysis has revealed to be a strong proxy for determining sediment transport history and depositional environments. MorpheoLV, devoted to the calculation of roughness coefficients from pictures of unique clastic sediment grains using Fourier analysis, drives computations for a collection of samples of grain images. This process may be applied to sedimentary deposits assuming core/interval/image archives for the storage of samples collected along depth. This study uses a 25.8 m jumbo piston core, NBP1203 JPC36, taken from a 100 m thick sedimentary drift deposit from Perseverance Drift on the northern Antarctic Peninsula continental shelf. Changes in ocean and ice conditions throughout the Holocene recorded in this sedimentary archive can be assessed by studying grain shape, grain texture, and other proxies. Ninety six intervals were sampled and a total of 2319 individual particle images were used. Microtextures of individual grains observed by SEM show a very high abundance of authigenically precipitated silica that obscures the original grain shape. Grain roughness, computed along depth with MorpheoLV, only shows small variation confirming the qualitative observation deduced from the SEM. Despite this, trends can be seen confirming the reliability of MorpheoLV as a tool for quantitative grain shape analysis.
Middle Miocene Rosarito Beach Formation, northwest Baja California, Mexico

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ledesma-Vasquez, J.

1988-03-01

The Rosarito Beach Formation was deposited on the continental borderland adjacent to the Peninsular Range province. This formation provides an insight to the paleo-oceanographic characteristics that are representative of marine sediments. The La Mision Member consists largely of basalts more than 150 m thick, which thin to the east. There are no pillow lavas or water-laid textures associated with this member. The Los Indios Member, which overlies the La Mision, consists of a wide variety of volcaniclastic marine sediments (tuffs, lapilli tuffs, tuffaceous sandstones) and 4-m thick diatomaceous layers. Basalts were emplaced through a series of fissures in the Mesozoicmore » basement while the area was uplifted to the west. At the same time, the coastline receded to the east. The basalt flows that comprise the La Mision Member and the overlying pyroclastics were deposited at the same time that the coastline was moving east and the entire area was being faulted, building horst and graben structures (continental borderland). The diatomaceous sediments were deposited on this new shallow area associated with upwelling and an oxygen minimum layer, and were reinforced by the presence of grabens, which acted as silled basins. The silicic microfossils indicate a mixed environment of outer and inner shelves on a shallow platform no deeper than 200 m.« less
Widespread Weathered Glass on the Surface of Mars

NASA Technical Reports Server (NTRS)

Horgan, Briony; Bell, James F., III

2012-01-01

Low albedo sediments cover >10(exp 7) sq km in the northern lowlands of Mars, but the composition and origin of these widespread deposits have remained ambiguous despite many previous investigations. Here we use near-infrared spectra acquired by the Mars Express OMEGA (Observatoire pour la Mineralogie, l'Eau, les Glaces, et l'Activite') imaging spectrometer to show that these sediments exhibit spectral characteristics that are consistent with both high abundances of iron-bearing glass and silica-enriched leached rinds on glass. This interpretation is supported by observations of low-albedo soil grains with possible rinds at the Phoenix Mars Lander landing site in the northern lowlands. By comparison with the extensive glass-rich dune fields and sand sheets of Iceland, we propose an explosive volcanic origin for these glass-rich sediments. We also propose that the glassy remnant rinds on the sediments are the result of post-depositional alteration, as these rinds are commonly formed in arid terrestrial volcanic environments during water-limited, moderately acidic leaching. These weathered, glass-rich deposits in the northern lowlands are also colocated with the strongest concentrations of a major global compositional surface type previously identified in mid-infrared spectra, suggesting that they may be representative of global processes. Our results provide potential confirmation of models suggesting that explosive volcanism has been widespread on Mars, and also raise the possibilities that glass-rich volcaniclastics are a major source of eolian sand on Mars and that widespread surficial aqueous alteration has occurred under Amazonian climatic conditions.
The Atmospheric Supply of Terrestrial Authigenic Phosphate Minerals to Open Marine Sediments

NASA Astrophysics Data System (ADS)

Flaum, J. A.; Jacobson, A. D.; Sageman, B. B.

2007-12-01

Authigenic P-bearing minerals (Pauth), such as carbonate fluorapatite, form within shallow marine sediments as biological processes degrade organic matter and release associated phosphate to the dissolved pool during early diagenesis. Thus, Pauth is commonly used as a proxy for productivity in modern and ancient marine depositional environments. To help refine this proxy and further improve understanding of the marine P cycle, we investigated if dust deposition could supply terrestrially derived Pauth and other P-bearing phases to modern marine sediments. We used the SEDEX sequential extraction procedure to quantify the occurrence of P in ten samples of loess from the Chinese Loess Plateau, a major source of dust to the North Pacific Ocean (NPO). On average, 40% of the total P within Chinese Loess occurs as Pauth, 33% as detrital apatite (Pdet), 17% in organic matter (Porg), and 10% bound to Fe-Al oxides (Pox). Using eolian dust and total P accumulation rates reported for core LL44-GC3 taken from the central NPO, we find that ~86% of the total P accumulation within the central NPO could originate from the atmospheric deposition of Pauth and Pdet. Hence, productivity estimates based upon total P accumulation for this site are likely lower than previously estimated. Our findings suggest that marine productivity studies predicated on the measurement of Pauth need to quantify the fraction of Pauth supplied from terrestrial sources. This may be even more significant along continental margins where rivers can supply sediments with high concentrations of Pauth minerals.
Evidence of synsedimentary microbial activity and iron deposition in ferruginous crusts of the Late Cenomanian Utrillas Formation (Iberian Basin, central Spain)

NASA Astrophysics Data System (ADS)

García-Hidalgo, José F.; Elorza, Javier; Gil-Gil, Javier; Herrero, José M.; Segura, Manuel

2018-02-01

Ferruginous sandstones and crusts are prominent sedimentary features throughout the continental (braided)-coastal siliciclastic (estuarine-tidal) wedges of the Late Cenomanian Utrillas Formation in the Iberian Basin. Crust types recognized are: Ferruginous sandy crusts (Fsc) with oxides-oxyhydroxides (hematite and goethite) concentrated on sandstone tops presenting a fibro-radial internal structure reminding organic structures that penetrate different mineral phases, suggesting the existence of bacterial activity in crust development; Ferruginous muddy crusts (Fmc) consisting of wavy, laminated, microbial mats, being composed mainly of hematite. On the other hand, a more dispersed and broader mineralization included as Ferruginous sandstones with iron oxides and oxyhydroxides (hematite and goethite) representing a limited cement phase on these sediments. The presence of microbial remains, ferruginous minerals, Microbially-induced sedimentary structures, microbial laminites and vertebrate tracks preserved due to the presence of biofilms suggest firstly a direct evidence of syn-depositional microbial activity in these sediments; and, secondly, that iron accumulation and ferruginous crusts development occurred immediately after deposition of the host, still soft sediments. Ferruginous crusts cap sedimentary cycles and they represent the gradual development of hard substrate conditions, and the development of a discontinuity surface at the top of the parasequence sets, related to very low sedimentary rates; the overlying sediments record subsequent flooding of underlying shallower environments; crusts are, consequently, interpreted as boundaries for these higher-order cycles in the Iberian Basin.
Sedimentation and bathymetric change in San Pablo Bay, 1856-1983

USGS Publications Warehouse

Jaffe, Bruce E.; Smith, Richard E.; Torresan, Laura Zink

1998-01-01

A long-term perspective of erosion and deposition in San Francisco Bay is vital to understanding and managing wetland change, harbor and channel siltation, and other sediment-related phenomena such as particle and particle-associated substance (pollutants, trace metals, etc.) transport and deposition. A quantitative comparison of historical hydrographic surveys provides this perspective. This report presents results of such a comparison for San Pablo Bay, California. Six hydrographic surveys from 1856 to 1983 were analyzed to determine long-term changes in the sediment system of San Pablo Bay. Each survey was gridded using surface modeling software. Changes between survey periods were computed by differencing grids. Patterns and volumes of erosion and deposition in the Bay are derived from difference grids. More than 350 million cubic meters of sediment was deposited in San Pablo Bay from 1856 to 1983. This is equivalent to a Baywide accumulation rate of approximately 1 cm/yr. However, sediment deposition was not constant over time or throughout the Bay. Over two-thirds of that sediment was debris from hydraulic mining that accumulated from 1856 to 1887. During this period, deposition occurred in nearly the entire Bay. In contrast, from 1951 to 1983 much of the Bay changed from being depositional to erosional as sediment supply diminished and currents and waves continued to remove sediment from the Bay. The decrease in sediment supply is likely the result of upstream flood-control and water-distribution projects that have reduced peak flows, which are responsible for the greatest sediment transport. One consequence of the change in sedimentation was a loss of about half of the tidal flat areas from the late 1800's to the 1980's. Change in sedimentation must also have affected flow in the Bay, areas where polluted sediments were deposited, exchange of sediment between the nearshore and wetlands, and wave energy reaching the shoreline that was available to erode wetlands. Further work is needed. Studies of historical wetland change and the relationship between change and man-made and natural influences would be valuable for developing sound wetland management plans. Additionally, extending the historical hydrographic and wetland change analyses eastward into Suisun Bay will improve the understanding of the North Bay sediment system.
Sea-level responses to sediment transport over the last ice age cycle

NASA Astrophysics Data System (ADS)

Ferrier, K.; Mitrovica, J. X.

2013-12-01

Sea-level changes over the last ice age cycle were instrumental in steering Earth's topographic evolution. These sea-level variations were driven by changes in surface mass loads, including not only ice and ocean mass variations but also the transfer of rock from eroding mountains to sedimentary deposits. Here we use an extended numerical model of ice age sea level (Dalca et al., 2013) to explore how sediment erosion and deposition affected global sea-level variations over the last ice age cycle. The model takes histories of ice and sediment loads as inputs, and it computes gravitationally self-consistent sea level responses by accounting for the deformational, gravitational, and rotational perturbations in the Earth's viscoelastic form. In these model simulations, we use published estimates of erosion rates, sedimentation rates, and ice sheet variations to constrain sediment and ice loading since the Last Interglacial. We explore sea-level responses to several erosional and depositional scenarios, and in each we quantify the relative contributions of crustal deformation and gravitational perturbation to the computed sea-level change. We also present a case study to illustrate the effects that sediment transfer can have on sea level at the regional scale. In particular, we focus on the region surrounding the Indus River, where fluvial sediment fluxes are among the highest on Earth. Preliminary model results suggest that sediment fluxes from Asia to the ocean are large enough to produce a significant response in sea level along the northeastern coast of the Arabian Sea. Moreover, they suggest that modeled sea-level histories are sensitive to the timing and spatial distribution of sediment erosion and deposition. For instance, sediment deposition along the continental shelf - which may have been the primary site of Indus River sediment deposition during the Holocene - produces a different sea-level response than sediment deposition on the deep-sea Indus Fan, where most of the Indus sediment may have been deposited during the glacial period preceding the Holocene. These simulations highlight the role that massive continent-to-ocean sediment fluxes can play in driving sea-level patterns over thousands of years. References: Dalca A.V., Ferrier K.L., Mitrovica J.X., Perron J.T., Milne G.A., Creveling J.R., 2013. On postglacial sea level - III: Incorporating sediment redistribution. Geophys. J. Int., doi: 10.1093/gji/ggt089.
Textural Maturity Analysis and Sedimentary Environment Discrimination Based on Grain Shape Data

NASA Astrophysics Data System (ADS)

Tunwal, M.; Mulchrone, K. F.; Meere, P. A.

2017-12-01

Morphological analysis of clastic sedimentary grains is an important source of information regarding the processes involved in their formation, transportation and deposition. However, a standardised approach for quantitative grain shape analysis is generally lacking. In this contribution we report on a study where fully automated image analysis techniques were applied to loose sediment samples collected from glacial, aeolian, beach and fluvial environments. A range of shape parameters are evaluated for their usefulness in textural characterisation of populations of grains. The utility of grain shape data in ranking textural maturity of samples within a given sedimentary environment is evaluated. Furthermore, discrimination of sedimentary environment on the basis of grain shape information is explored. The data gathered demonstrates a clear progression in textural maturity in terms of roundness, angularity, irregularity, fractal dimension, convexity, solidity and rectangularity. Textural maturity can be readily categorised using automated grain shape parameter analysis. However, absolute discrimination between different depositional environments on the basis of shape parameters alone is less certain. For example, the aeolian environment is quite distinct whereas fluvial, glacial and beach samples are inherently variable and tend to overlap each other in terms of textural maturity. This is most likely due to a collection of similar processes and sources operating within these environments. This study strongly demonstrates the merit of quantitative population-based shape parameter analysis of texture and indicates that it can play a key role in characterising both loose and consolidated sediments. This project is funded by the Irish Petroleum Infrastructure Programme (www.pip.ie)
Sediment dispersal in the northwestern Adriatic Sea

USGS Publications Warehouse

Harris, C.K.; Sherwood, C.R.; Signell, R.P.; Bever, A.J.; Warner, J.C.

2008-01-01

Sediment dispersal in the Adriatic Sea was evaluated using coupled three-dimensional circulation and sediment transport models, representing conditions from autumn 2002 through spring 2003. The calculations accounted for fluvial sources, resuspension by waves and currents, and suspended transport. Sediment fluxes peaked during southwestward Bora wind conditions that produced energetic waves and strengthened the Western Adriatic Coastal Current. Transport along the western Adriatic continental shelf was nearly always to the south, except during brief periods when northward Sirocco winds reduced the coastal current. Much of the modeled fluvial sediment deposition was near river mouths, such as the Po subaqueous delta. Nearly all Po sediment remained in the northern Adriatic. Material from rivers that drain the Apennine Mountains traveled farther before deposition than Po sediment, because it was modeled with a lower settling velocity. Fluvial sediment delivered to areas with high average bed shear stress was more highly dispersed than material delivered to more quiescent areas. Modeled depositional patterns were similar to observed patterns that have developed over longer timescales. Specifically, modeled Po sediment accumulation was thickest near the river mouth with a very thin deposit extending to the northeast, consistent with patterns of modern sediment texture in the northern Adriatic. Sediment resuspended from the bed and delivered by Apennine Rivers was preferentially deposited on the northern side of the Gargano Peninsula, in the location of thick Holocene accumulation. Deposition here was highest during Bora winds when convergences in current velocities and off-shelf flux enhanced delivery of material to the midshelf. Copyright 2008 by the American Geophysical Union.
Atmospheric deposition, water-quality, and sediment data for selected lakes in Mount Rainer, North Cascades, and Olympic National Parks, Washington, 2008-10

USGS Publications Warehouse

Sheibley, Rich W.; Foreman, James R.; Moran, Patrick W.; Swarzenski, Peter W.

2012-01-01

To evaluate the potential effect from atmospheric deposition of nitrogen to high-elevation lakes, the U.S. Geological Survey partnered with the National Park Service to develop a "critical load" of nitrogen for sediment diatoms. A critical load is defined as the level of a given pollutant (in this case, nitrogen) at which detrimental effects to a target endpoint (sediment diatoms) result. Because sediment diatoms are considered one of the "first responders" to ecosystem changes from nitrogen, they are a sensitive indicator for nitrogen deposition changes in natural areas. This report presents atmospheric deposition, water quality, sediment geochronology, and sediment diatom data collected from July 2008 through August 2010 in support of this effort.

Controlling factors of recent clastic coastal sediments (Viransehir, Mersin bay, S Turkey)

NASA Astrophysics Data System (ADS)

Gül, Murat; Özbek, Ahmet; Kurt, Mehmet Ali; Zorlu, Kemal

2009-04-01

The Plio-Quaternary conglomeratic sets within the marine environment of the Viranşehir coast (W Mersin, S Turkey) are responsible for the evolution of sandy and gravely beaches due to their control on various factors such as sea floor irregularity, wave energy, and organic activity. The conglomeratic sets close to the shoreline (50-150 cm) act as wave breakers, creating hard substratum and high energy, well-oxygenated environment for organisms like Patella sp., Phoronida worms and Brachidontes pharaonis (Fischer P. 1870). The boring activities of these organisms have disintegrated the sandy matrix of these sets. Finer-grained matrix sediments have been transported to the interset and open sea, while cobble-pebbles have been carried landwards and have created imbricated gravely beach deposits without matrix. Sandy beach is evolving where the conglomeratic sets away from the shoreline (5.0-10.0 m). In this example, sets form a bar; causing fivefold division as backshore, berm, surf zone, bar and offshore from land to sea. Poorly sorted, cobbles-pebbles cobbles and pebbles are found associated with the high-energy environments of bars, whilst well-sorted sands are observed in low energetic environments on shore. The sets and recent shell fragments are the main sources of coastal sediments in Viranşehir. However, the amount of shell fragments decrease towards the active river mouth. This is due to sediment and fresh water influx from the river causing deteriorated temperature, salinity and light penetration of the marine environment resulting in less organic diversity.
Morphology and stratal geometry of the Antarctic continental shelf: Insights from models

USGS Publications Warehouse

Cooper, Alan K.; Barker, Peter F.; Brancolini, Giuliano

1997-01-01

Reconstruction of past ice-sheet fluctuations from the stratigraphy of glaciated continental shelves requires understanding of the relationships among the stratal geometry, glacial and marine sedimentary processes, and ice dynamics. We investigate the formation of the morphology and the broad stratal geometry of topsets on the Antarctic continental shelf with numerical models. Our models assume that the stratal geometry and morphology are principally the results of time-integrated effects of glacial erosion and sedimentation related to the location of the seaward edge of the grounded ice. The location of the grounding line varies with time almost randomly across the shelf. With these simple assumptions, the models can successfully mimic salient features of the morphology and the stratal geometry. The models suggest that the current shelf has gradually evolved to its present geometry by many glacial advances and retreats of the grounding line to different locations across the shelf. The locations of the grounding line do not appear to be linearly correlated with either fluctuations in the 5 l s O record (which presumably represents changes in the global ice volume) or with the global sea-level curve, suggesting that either a more complex relationship exists or local effects dominate. The models suggest that erosion of preglacial sediments is confined to the inner shelf, and erosion decreases and deposition increases toward the shelf edge. Some of the deposited glacial sediments must be derived from continental erosion. The sediments probably undergo extensive transport and reworking obliterating much of the evidence for their original depositional environment. The flexural rigidity and the tectonic subsidence of the underlying lithosphere modify the bathymetry of the shelf, but probably have little effect on the stratal geometry. Our models provide several guidelines for the interpretation of unconformities, the nature of preserved topset deposits, and the significance of progradation versus aggradation of shelf sediments.
Fluxes and burial of particulate organic carbon along the Adriatic mud-wedge (Mediterranean Sea)

NASA Astrophysics Data System (ADS)

Tesi, T.; Langone, L.; Giani, M.; Ravaioli, M.; Miserocchi, S.

2012-04-01

Clinoform-shaped deposits are ubiquitous sedimentological bodies of modern continental margins, including both carbonate and silicoclastic platforms. They formed after the attainment of the modern sea level high-stand (mid-late Holocene) when river outlets and shoreline migrated landward. As clinoform-shape deposits are essential building blocks of the infill of sedimentary basins, they are sites of intense organic carbon (OC) deposition and account for a significant fraction of OC burial in the ocean during interglacial periods. In this study, we focused on sigmoid clinoforms that are generally associated with low-energy environments. In particular, we characterized the modern accumulation and burial of OC along the late-Holocene sigmoid in the Western Adriatic Sea (Mediterranean Sea). This sedimentary body consists of a mud wedge recognizable on seismic profiles as a progradational unit lying on top the maximum flooding surface that marks the time of maximum landward shift of the shoreline attained around 5.5 kyr cal BP. In the last two decades, several projects have investigated sediment dynamics and organic geochemistry along the Adriatic mud wedge (e.g., PRISMA, EURODELTA, EuroSTRATAFORM, PASTA, CIPE, VECTOR). All these studies increased our understanding of strata formation and organic matter cycling in this epicontinental margin. The overarching goal of this study was to combine the results gained during these projects with newly acquired data to assess fluxes to seabed and burial efficiency of organic carbon along the uppermost strata of the Adriatic mud-wedge. Our study benefited of an extensive number of radionuclide-based (Pb-210, and Cs-137) sediment accumulation rates and numerous biogeochemical data of surface sediments and sediment cores (organic carbon, total nitrogen, radiocarbon measurements, carbon stable isotopes, and biomarkers). In addition, because the accumulation of river-borne sediment may or may not be linked to a specific source, another important goal of this study was to characterize the spatial distribution of OC deposition/burial along the Adriatic mud wedge.
Compositions, ages, and diagenetic histories of the carbonate, sulfide, oxide, and phosphatic concretions at Gay Head, Massachusetts

USGS Publications Warehouse

Poppe, L.J.; Commeau, R.F.; O'Leary, Dennis W.

1988-01-01

The calcite/ankerite concretions were formed in a hot, seasonally arid, caliche-prone environment of early Raritan age; the pyrite, marcasite, and siderite concretions precipitated in sediments deposited in low-energy, marshy, estuarine environments of late Raritan age. The phosphate concretions formed in a middle to inner shelf environment. The goethite and lepidocrocite concretions are secondary oxidation or alteration products of the prexistent Cretaceous concretions that were excavated during the Pleistocene and incorporated into the glacial drift. -from Authors
Deposition of sedimentary organic matter in black shale facies indicated by the geochemistry and petrography of high-resolution samples, blake nose, western North Atlantic

USGS Publications Warehouse

Barker, C.E.; Pawlewicz, M.; Cobabe, E.A.

2001-01-01

A transect of three holes drilled across the Blake Nose, western North Atlantic Ocean, retrieved cores of black shale facies related to the Albian Oceanic Anoxic Events (OAE) lb and ld. Sedimentary organic matter (SOM) recovered from Ocean Drilling Program Hole 1049A from the eastern end of the transect showed that before black shale facies deposition organic matter preservation was a Type III-IV SOM. Petrography reveals that this SOM is composed mostly of degraded algal debris, amorphous SOM and a minor component of Type III-IV terrestrial SOM, mostly detroinertinite. When black shale facies deposition commenced, the geochemical character of the SOM changed from a relatively oxygen-rich Type III-IV to relatively hydrogen-rich Type II. Petrography, biomarker and organic carbon isotopic data indicate marine and terrestrial SOM sources that do not appear to change during the transition from light-grey calcareous ooze to the black shale facies. Black shale subfacies layers alternate from laminated to homogeneous. Some of the laminated and the poorly laminated to homogeneous layers are organic carbon and hydrogen rich as well, suggesting that at least two SOM depositional processes are influencing the black shale facies. The laminated beds reflect deposition in a low sedimentation rate (6m Ma-1) environment with SOM derived mostly from gravity settling from the overlying water into sometimes dysoxic bottom water. The source of this high hydrogen content SOM is problematic because before black shale deposition, the marine SOM supplied to the site is geochemically a Type III-IV. A clue to the source of the H-rich SOM may be the interlayering of relatively homogeneous ooze layers that have a widely variable SOM content and quality. These relatively thick, sometimes subtly graded, sediment layers are thought to be deposited from a Type II SOM-enriched sediment suspension generated by turbidities or direct turbidite deposition.
The role of impoundments in the sediment budget of the conterminous United States

USGS Publications Warehouse

Renwick, W.H.; Smith, S.V.; Bartley, J.D.; Buddemeier, R.W.

2005-01-01

Previous work on sediment budgets for U.S. agricultural regions has concluded that most sediment derived from accelerated erosion is still on the landscape, primarily in colluvial and alluvial deposits. Here we examine the role of small impoundments in the subcontinental sediment budget. A recent inventory based on a 30-m satellite imagery reveals approximately 2.6 million ponds, while extrapolation from a sample of 1:24,000 topographic quadrangles suggests the total may be as large as 8-9 million. These ponds capture an estimated 21% of the total drainage area of the conterminous U.S., representing 25% of total sheet and rill erosion. We estimate the total sedimentation in these small impoundments using three different methods; these estimates range from 0.43 to 1.78 ?? 109 m3 yr-1. Total sedimentation in ???43,000 reservoirs from the National Inventory of Dams is estimated at 1.67 ?? 109 m3 yr-1. Total USLE erosion in 1992 was 2.4 ?? 109 m3 yr-1, and export to coastal areas is estimated at 0.6 ?? 109 m3 yr-1. Total sedimentation in impoundments is large in relation to upland erosion, in apparent contradiction to previous studies that have identified colluvial and alluvial deposition as the primary sinks. Several alternative hypotheses that could help explain this result are proposed. Regardless of which of these alternatives may prove to be the most significant in any given setting, it is clear that most sedimentation is now taking place in subaqueous rather than subaerial environments, and that small impoundments are a major sediment sink. ?? 2005 Elsevier B.V. All rights reserved.
Late Pleistocene and Holocene aeolian sedimentation in Gonghe Basin, northeastern Qinghai-Tibetan Plateau: Variability, processes, and climatic implications

NASA Astrophysics Data System (ADS)

Qiang, Mingrui; Jin, Yanxiang; Liu, Xingxing; Song, Lei; Li, Hao; Li, Fengshan; Chen, Fahu

2016-01-01

Although stratigraphic sequences of aeolian deposits in dryland areas have long been recognized as providing information about past environments, the exact nature of the environmental processes they reflect remains unclear. Here, we report the results of a detailed investigation of eight outcrop sections in the Gonghe Basin, northeastern Qinghai-Tibetan Plateau. Measurements of sediment grain-size and chemical composition indicate that the deposits are primarily of aeolian origin, consisting of interbedded, well-sorted sand, silty sand, loess and/or palaeosol; however, their occurrence varies from site to site. Fossil dune sands mainly occur in or close to the currently stabilized or semi-stabilized dune fields, whereas loess is distributed along the downwind marginal areas. This pattern of basin-scale differentiation was controlled mainly by spatial variability of sediment supply due to the antecedent sedimentary patterns within the basin. Together with previously-published optically stimulated luminescence (OSL) ages, 24 new OSL dates are used to elucidate the history of aeolian activity and its relationship to climatic changes. There is no apparent relationship between past dune activity and downwind loess deposits. Deposition of silty sand probably occurred during past phases of windy, dry and cold climate in the Late Pleistocene. However, climatic factors alone cannot explain the occurrence of silty sand deposition. This is because the deposition of silty sand was always preceded by episodes of fluvial deposition prior to river incision, thereby indicating the importance of an 'activated' sediment supply associated with fluvial processes. Deposition of well-sorted sand occurred episodically, not only during the Late Pleistocene, but also during the early- to mid-Holocene. Vegetation conditions, controlled either by the occurrence of intervals of moisture deficit during the Late Pleistocene or by changes in the balance between precipitation and evapotranspiration at a local scale, played an important role in sand mobility and deposition. The effect of vegetation on sand mobility is also suggested by independent evidence of aeolian activity from Genggahai Lake in the Gonghe Basin. Here, the deposition of aeolian sand in the basin during the early- to mid-Holocene indicates a low level of effective moisture caused by high evaporation induced by higher summer insolation, despite the coeval increased regional precipitation recorded by lacustrine sediments. In contrast, late Holocene palaeosols represent a high level of effective moisture, and their formation did not necessarily require increased regional precipitation. Overall, our results suggest that the relationship between aeolian activity and regional climate change is complex, and that sand accumulations do not represent the consistent action of surface processes that are related to climatic changes.
Suspended sediment in tidal currents: an often-neglected pollutant that aggravates mangrove degradation.

PubMed

Fu, Weiguo; Liu, Daomin; Yin, Qilin; Wu, Yanyou; Li, Pingping

2014-07-15

In this study, the influence of sediments deposited on the leaves of different mangrove species due to tidal movements on photosynthetic characteristics and chlorophyll fluorescence of the species was explored. The degree of accelerated degradation among different mangrove species was also obtained. Results show that the leaves of mangrove species have varying degrees of sediment deposition. Sediment deposition leads to photosynthetic reduction and physiological stress among Kandelia candel, Aegiceras corniculatum, and Avicennia marina in the Quanzhou Bay. Thus, the deposition of suspended sediments from tidal currents is an important environmental factor that accelerates the degradation of some mangrove species. Copyright © 2014 Elsevier Ltd. All rights reserved.
X-Ray Diffraction on Mars: Scientific Discoveries Made by the CheMin Instrument

NASA Technical Reports Server (NTRS)

Rampe, E. B.; Blake, D. F.; Ming, D. W.; Bristow, T. F.

2017-01-01

The Mars Science Laboratory Curiosity landed in Gale crater in August 2012 with the goal to identify and characterize habitable environments on Mars. Curiosity has been studying a series of sedimentary rocks primarily deposited in fluviolacustrine environments approximately 3.5 Ga. Minerals in the rocks and soils on Mars can help place further constraints on these ancient aqueous environments, including pH, salinity, and relative duration of liquid water. The Chemistry and Mineralogy (CheMin) X-ray diffraction and X-ray fluorescence instrument on Curiosity uses a Co X-ray source and charge-coupled device detector in transmission geometry to collect 2D Debye-Scherrer ring patterns of the less than 150 micron size fraction of drilled rock powders or scooped sediments. With an angular range of approximately 2.52deg 20 and a 20 resolution of approximately 0.3deg, mineral abundances can be quantified with a detection limit of approximately 1-2 wt. %. CheMin has returned quantitative mineral abundances from 16 mudstone, sandstone, and aeolian sand samples so far. The mineralogy of these samples is incredibly diverse, suggesting a variety of depositional and diagenetic environments and different source regions for the sediments. Results from CheMin have been essential for reconstructing the geologic history of Gale crater and addressing the question of habitability on ancient Mars.
Litho- and biofacies of Early Cretaceous rudist-bearing carbonate sediments in northeastern Japan

NASA Astrophysics Data System (ADS)

Sano, Shin-ichi

1995-11-01

Carbonate blocks of late Aptian (Lower Cretaceous) age occur in the Lower Yezo Group of central Hokkaido in northeast Japan. The shallow-water carbonates were emplaced by gravity sliding and rock fall into a deep-water flysch basin. Various lithofacies can be distinguished within the blocks including massive wackestone, bedded packstone and micro-oncoid grainstone, containing corals, rudists, an oyster, gastropods, calcareous algae and an orbitolinid foraminifer. Facies and palaeoecological analyses suggest deposition of low-energy biostromes and sand banks in open lagoonal and restricted environments with local higher-energy shoals and beaches. The presence of calcareous sandstones and abundant insoluble residues in limestones suggest deposition in an attached carbonate platform close to a supply of terrigenous material, rather than deposition upon seamounts within an oceanic setting. A narrow rimmed shelf in tropical-subtropical conditions would have been the depositional environment for these carbonates, which were subsequently deformed into blocks and transported into deep water as a result of the tectonic collapse of the platform.
Increased sediment load during a large-scale dam removal changes nearshore subtidal communities

PubMed Central

Foley, Melissa M.; Berry, Helen D.; Duda, Jeffrey J.; Hudson, Benjamin; Elder, Nancy E.; Beirne, Matthew M.; Warrick, Jonathan A.; McHenry, Michael L.; Stevens, Andrew W.; Eidam, Emily F.; Ogston, Andrea S.; Gelfenbaum, Guy; Pedersen, Rob

2017-01-01

The coastal marine ecosystem near the Elwha River was altered by a massive sediment influx—over 10 million tonnes—during the staged three-year removal of two hydropower dams. We used time series of bathymetry, substrate grain size, remotely sensed turbidity, scuba dive surveys, and towed video observations collected before and during dam removal to assess responses of the nearshore subtidal community (3 m to 17 m depth). Biological changes were primarily driven by sediment deposition and elevated suspended sediment concentrations. Macroalgae, predominantly kelp and foliose red algae, were abundant before dam removal with combined cover levels greater than 50%. Where persistent sediment deposits formed, macroalgae decreased greatly or were eliminated. In areas lacking deposition, macroalgae cover decreased inversely to suspended sediment concentration, suggesting impacts from light reduction or scour. Densities of most invertebrate and fish taxa decreased in areas with persistent sediment deposition; however, bivalve densities increased where mud deposited over sand, and flatfish and Pacific sand lance densities increased where sand deposited over gravel. In areas without sediment deposition, most invertebrate and fish taxa were unaffected by increased suspended sediment or the loss of algae cover associated with it; however, densities of tubeworms and flatfish, and primary cover of sessile invertebrates increased suggesting benefits of increased particulate matter or relaxed competition with macroalgae for space. As dam removal neared completion, we saw evidence of macroalgal recovery that likely owed to water column clearing, indicating that long-term recovery from dam removal effects may be starting. Our results are relevant to future dam removal projects in coastal areas and more generally to understanding effects of increased sedimentation on nearshore subtidal benthic communities. PMID:29220368
Increased sediment load during a large-scale dam removal changes nearshore subtidal communities.

PubMed

Rubin, Stephen P; Miller, Ian M; Foley, Melissa M; Berry, Helen D; Duda, Jeffrey J; Hudson, Benjamin; Elder, Nancy E; Beirne, Matthew M; Warrick, Jonathan A; McHenry, Michael L; Stevens, Andrew W; Eidam, Emily F; Ogston, Andrea S; Gelfenbaum, Guy; Pedersen, Rob

2017-01-01

The coastal marine ecosystem near the Elwha River was altered by a massive sediment influx-over 10 million tonnes-during the staged three-year removal of two hydropower dams. We used time series of bathymetry, substrate grain size, remotely sensed turbidity, scuba dive surveys, and towed video observations collected before and during dam removal to assess responses of the nearshore subtidal community (3 m to 17 m depth). Biological changes were primarily driven by sediment deposition and elevated suspended sediment concentrations. Macroalgae, predominantly kelp and foliose red algae, were abundant before dam removal with combined cover levels greater than 50%. Where persistent sediment deposits formed, macroalgae decreased greatly or were eliminated. In areas lacking deposition, macroalgae cover decreased inversely to suspended sediment concentration, suggesting impacts from light reduction or scour. Densities of most invertebrate and fish taxa decreased in areas with persistent sediment deposition; however, bivalve densities increased where mud deposited over sand, and flatfish and Pacific sand lance densities increased where sand deposited over gravel. In areas without sediment deposition, most invertebrate and fish taxa were unaffected by increased suspended sediment or the loss of algae cover associated with it; however, densities of tubeworms and flatfish, and primary cover of sessile invertebrates increased suggesting benefits of increased particulate matter or relaxed competition with macroalgae for space. As dam removal neared completion, we saw evidence of macroalgal recovery that likely owed to water column clearing, indicating that long-term recovery from dam removal effects may be starting. Our results are relevant to future dam removal projects in coastal areas and more generally to understanding effects of increased sedimentation on nearshore subtidal benthic communities.
Increased sediment load during a large-scale dam removal changes nearshore subtidal communities

USGS Publications Warehouse

Rubin, Stephen P.; Miller, Ian M.; Foley, Melissa M.; Berry, Helen D.; Duda, Jeffrey J.; Hudson, Benjamin; Elder, Nancy E.; Beirne, Matthew M.; Warrick, Jonathan; McHenry, Michael L.; Stevens, Andrew; Eidam, Emily; Ogston, Andrea; Gelfenbaum, Guy R.; Pedersen, Rob

2017-01-01

The coastal marine ecosystem near the Elwha River was altered by a massive sediment influx—over 10 million tonnes—during the staged three-year removal of two hydropower dams. We used time series of bathymetry, substrate grain size, remotely sensed turbidity, scuba dive surveys, and towed video observations collected before and during dam removal to assess responses of the nearshore subtidal community (3 m to 17 m depth). Biological changes were primarily driven by sediment deposition and elevated suspended sediment concentrations. Macroalgae, predominantly kelp and foliose red algae, were abundant before dam removal with combined cover levels greater than 50%. Where persistent sediment deposits formed, macroalgae decreased greatly or were eliminated. In areas lacking deposition, macroalgae cover decreased inversely to suspended sediment concentration, suggesting impacts from light reduction or scour. Densities of most invertebrate and fish taxa decreased in areas with persistent sediment deposition; however, bivalve densities increased where mud deposited over sand, and flatfish and Pacific sand lance densities increased where sand deposited over gravel. In areas without sediment deposition, most invertebrate and fish taxa were unaffected by increased suspended sediment or the loss of algae cover associated with it; however, densities of tubeworms and flatfish, and primary cover of sessile invertebrates increased suggesting benefits of increased particulate matter or relaxed competition with macroalgae for space. As dam removal neared completion, we saw evidence of macroalgal recovery that likely owed to water column clearing, indicating that long-term recovery from dam removal effects may be starting. Our results are relevant to future dam removal projects in coastal areas and more generally to understanding effects of increased sedimentation on nearshore subtidal benthic communities.
Sediment budget as affected by construction of a sequence of dams in the lower Red River, Viet Nam

NASA Astrophysics Data System (ADS)

Lu, Xi Xi; Oeurng, Chantha; Le, Thi Phuong Quynh; Thuy, Duong Thi

2015-11-01

Dam construction is one of the main factors resulting in riverine sediment changes, which in turn cause river degradation or aggradation downstream. The main objective of this work is to examine the sediment budget affected by a sequence of dams constructed upstream in the lower reach of the Red River. The study is based on the longer-term annual data (1960-2010) with a complementary daily water and sediment data set (2008-2010). The results showed that the stretch of the river changed from sediment surplus (suggesting possible deposition processes) into sediment deficit (possible erosion processes) after the first dam (Thac Ba Dam) was constructed in 1972 and changed back to deposition after the second dam (Hoa Binh Dam) was constructed in 1985. The annual sediment deposition varied between 1.9 Mt/y and 46.7 Mt/y with an annual mean value of 22.9 Mt/y (1985-2010). The sediment deposition at the lower reach of the Red River would accelerate river aggradation which would change river channel capacity in the downstream of the Red River. The depositional processes could be sustained or changed back to erosional processes after more dams (the amount of sediment deposit was much less after the latest two dams Tuyen Quang Dam in 2009 and Sonla Dam in 2010) are constructed, depending on the water and sediment dynamics. This study revealed that the erosional and depositional processes could be shifted for the same stretch of river as affected by a sequence of dams and provides useful insights in river management in order to reduce flood frequency along the lower reach of the Red River.
Linking fluvial and aeolian morphodynamics in the Grand Canyon, USA

USGS Publications Warehouse

Kasprak, Alan; Bangen, Sara G.; Buscombe, Daniel; Caster, Joshua; East, Amy; Grams, Paul E.; Sankey, Joel B.

2017-01-01

In river valleys, fluvial and upland landscapes are intrinsically linked through sediment exchange between the active channel, near-channel fluvial deposits, and higher elevation upland deposits. During floods, sediment is transferred from channels to low-elevation nearchannel deposits [Schmidt and Rubin, 1995]. Particularly in dryland river valleys, subsequent aeolian reworking of these flood deposits redistributes sediment to higher elevation upland sites, thus maintaining naturallyoccurring aeolian landscapes [Draut, 2012].
Reconstruction of Mid-Holocene sedimentary environments in the central part of the Thessaloniki Plain (Greece), based on microfaunal identification, magnetic susceptibility and grain-size analyses

NASA Astrophysics Data System (ADS)

Ghilardi, Matthieu; Kunesch, Stéphane; Styllas, Mixalis; Fouache, Eric

2008-05-01

The study aims to estimate the relative contributions of the two drainage basins of the Aliakmon and Axios rivers which, since the Mid-Holocene, have been responsible for building the largest deltaic area in Greece. Sediments from five cores located in the central part of the Thessaloniki Plain have been studied for their environmental changes using paleontological and sedimentological methods. Chronostratigraphical evidence was obtained from 14C AMS dating of marine shells, peat and organic sediment samples. During the Holocene marine transgression, this large coastal plain was a shallow marine bay reaching approx. 35 km inland circa the 4th millennium BC, from which the sea subsequently regressed to the east. Around the middle of the 3rd millennium BC, strong fluvial deposition of Aliakmon, to the east, and of Axios, to the north, occurred and was responsible of a gradual change to lagoonal and limnic environmental conditions. Around the 5th Century BC, a freshwater lake occupied the westernmost part of the plain. Microfaunal identification, together with magnetic susceptibility measurements, and grain-size analysis reveal three main environments of sediment deposition that reflect combinations of both concentrated and dispersed sources of magnetic/source minerals. Using remote sensing and a combination of spectral bands (LANDSAT TM imagery), we identify former fluvial levees and a freshwater lake, and give a spatial interpretation of the rivers' influences in building this deltaic complex. The mechanisms of edification of the plain as well as the roles played by Aliakmon and Axios sedimentation are described.
Palaeoenvironments and palaeotectonics of the arid to hyperarid intracontinental latest Permian- late Triassic Solway basin (U.K.)

NASA Astrophysics Data System (ADS)

Brookfield, Michael E.

2008-10-01

The late Permian to late Triassic sediments of the Solway Basin consist of an originally flat-lying, laterally persistent and consistent succession of mature, dominantly fine-grained red clastics laid down in part of a very large intracontinental basin. The complete absence of body or trace fossils or palaeosols indicates a very arid (hyperarid) depositional environment for most of the sediments. At the base of the succession, thin regolith breccias and sandstones rest unconformably on basement and early Permian rift clastics. Overlying gypsiferous red silty mudstones, very fine sandstones and thick gypsum were deposited in either a playa lake or in a hypersaline estuary, and their margins. These pass upwards into thick-bedded, multi-storied, fine- to very fine-grained red quartzo-felspathic and sublithic arenites in which even medium sand is rare despite channels with clay pebbles up to 30 cm in diameter. Above, thick trough cross-bedded and parallel laminated fine-grained aeolian sandstones (deposited in extensive barchanoid dune complexes) pass up into very thick, multicoloured mudstones, and gypsum deposited in marginal marine or lacustrine sabkha environments. The latter pass up into marine Lower Jurassic shales and limestones. Thirteen non-marine clastic lithofacies are arranged into five main lithofacies associations whose facies architecture is reconstructed where possible by analysis of large exposures. The five associations can be compared with the desert pavement, arid ephemeral stream, sabkha, saline lake and aeolian sand dune environments of the arid to hyperarid areas of existing intracontinental basins such as Lake Eyre and Lake Chad. The accommodation space in such basins is controlled by gradual tectonic subsidence moderated by large fluctuations in shallow lake extent (caused by climatic change and local variation) and this promotes a large-scale layer-cake stratigraphy as exemplified in the Solway basin. Here, the dominant fine-grained mature sandstones above the local basal reg breccias suggest water-reworking of wind-transported sediment, as in the northern part of the Lake Chad basin. Growth faulting occurs in places in the Solway basin, caused by underlying evaporite movement, but these faults did not significantly affect pre-late Triassic sedimentation and did not expose pre-Permian units above the basal breccias. There is no evidence of post-early Permian rifting anywhere during deposition of the late Permian to middle Triassic British succession although the succession is often interpreted with a rift-basin model. The arid to hyperarid palaeoclimate changed little during deposition of the Solway basin succession, in contrast to Lakes Eyre and Chad: and this is attributed to tectonic and palaeolatitude stability. Unlike the later Mesozoic- Cenozoic, only limited plate movements took place during the Triassic in western Europe, palaeolatitude changed little, and the Solway Basin remained in the northern latitudinal desert belt from early to mid-Triassic times. However, the influence of the early Triassic impoverished biota on environmental interpretations needs further study.
Palaeoflood evidence on the River Nore, South East Ireland

NASA Astrophysics Data System (ADS)

Fleming, Ciara; Turner, Jonathan; Bourke, Mary

2017-04-01

Past geomorphic changes can be detected in sediment sinks, through the investigation of natural sediment archives. Since the advent of palaeoflood hydrology in the 1980s, numerous authors have demonstrated that such sediment deposits record valuable evidence of past flooding events. Many of these studies have focussed on fluvial systems in arid environments, with bedrock channels proving to be particularly successful field sites. In some districts, the collected datasets are now routinely employed to augment analyses of flood frequency and magnitude, which have traditionally relied on extrapolation of short hydrometric datasets. This study targets river reaches in a temperate humid environment, with a predominantly alluvial channel. The River Nore is one of the largest catchments draining South East Ireland. It is situated in a valley with an inherited glacial legacy and is principally a lowland river catchment. Specific morphological zones have been targeted which are optimal for flood deposit preservation, including palaeochannels, tributary junctions and floodplain overbank settings.There are a variety of anthropogenic pressures evident in this landscape. Among them are channelisation of select tributaries, a legacy of coal mining in the upland Carboniferous limestones, and the installation of man-made obstacles or modifications along the length of the river channel such as sluices and weirs. Regarding land-use, the majority of the catchment is dominated by agriculture, mainly pasture with some tillage. This study investigates palaeoflood evidence in the River Nore catchment and examines the development of the river floodplain using a variety of complementary field and desk-based methods. The sub-surface and micro-topography of river reaches are investigated using Ground Penetrating Radar (GPR) and Unmanned Aerial Vehicle (UAV) technology. Flood deposits have been characterised by examination of bank exposures and sediment cores. Installation of sediment traps at discrete locations will enable quantification of sedimentation rates of individual flood events over the winter period 2016/17. Historical Ordnance Survey maps, aerial and satellite imagery have been digitised in a GIS (Geographic Information System) to document channel change over time. Previous authors have noted a paucity of research in fluvial geomorphology in Ireland, particularly in lowland catchments, and this study endeavours to start addressing that gap. Furthermore, in terms of developments in palaeoflood hydrology, this is the first study of its kind in Ireland, attempting to understand and utilise geomorphic evidence of previous flood events in an Irish river catchment.
Interactions between fauna and environment in recent alluvial soils (Dunajec River, SE Poland)

NASA Astrophysics Data System (ADS)

Mikuś, Paweł; Uchman, Alfred

2017-04-01

Recent riverine system is a particular place for interactions between fauna and the deposited sediments containing young and old alluvial soils. It is characterized by large energy gradients in relatively short time, which forces special adaptations of burrowing animals recorded in bioturbation structures. Predators produce mainly shelter burrows (interpreted as domichnia), and saprofags, especially earthworms, produce locomotion and feeding structures (pascichnia). Such structures have been studied in non- or poorly vegetated, sandy or muddy Holocene alluvia in the lower reach of the Dunajec River flowing through the Carpathian Foredeep in SE Poland. The observed burrows are mostly produced by a variety of organisms, including the European mole (Talpa europaea), common earthworm (Lumbricus terrestris), ground beetles (Carabidae), solitary bees (Ammophila), red fox (Vulpes vulpes), European beaver (Castor fiber), shrews (Soricidae), European otter (Lutra lutra), several species of mice (Muridae), voles (Myodae, Microtae), and the swallow sand martin (Riparia riparia). Burrows of a few species of ground beetles have been subjected to more detailed studies. Fertile deposits of older (early to middle Holocene) terraces, formed with many long-term interruptions in sedimentation processes, have a well-developed soil levels, more vulnerable to burrowing than recently deposited sediments. The terraces contain layers of sands and muds, which primary sedimentary structures and layer boundaries are completely or partly disturbed by bioturbation. Organic-rich muds have been moved up and down and mixed with sand. Moreover, sediments have been leached into open burrows during floods or rainfalls. In the natural levee sediments, mostly fine to medium sands, are horizontally burrowed, foremost by earthworms (Lumbricidae). Vertical, long (over 2 m deep) burrows of larger earthworms cross cut the natural levee sediments and enter buried soils. They were formed during a long period between flooding events reaching into the soil profile. Not rarely, the vertical burrows follow living or dead roots. As the European mole feed on earthworms, their burrows commonly co-occur. Diversity and abundance of burrowing animals in the riverine environment are mainly controlled by water-level fluctuations, foremost these which cause floods or droughts. The highest biodiversity of infauna occurs under moderate level of river disturbances. With low level of disturbances, larger, long-living species dominate, whereas with high-level disturbances small, short-living forms prevail.
Insights into site formation at Rose Cottage Cave, South Africa, based on the analysis of sediment peels

NASA Astrophysics Data System (ADS)

Kloos, Peter; Miller, Christopher E.; Kritikakis, Panagiotis; Wadley, Lyn

2016-04-01

Rose Cottage Cave (RCC), in South Africa, has been a key site for explaining the origins of modern human behaviour and movement of early modern humans out of Africa. Nine sediment peels were made previously from the profile sections, preserving original materials that provide a record of cultural and environmental change during the late Pleistocene and Holocene. Here, we present the preliminary results of the study of the RCC sediment peels which aims to investigate site formation processes and the implications for site interpretation. Methods used include micromorphology and Fourier Transform Infrared spectroscopy coupled with detailed observations of the peels. The predominance of geogenic processes is demonstrated by the abundance of silt- and sand-sized quartz grains, which entered the site primarily through a crevice at the back of the cave. RCC lacks rich anthropogenic deposits as noted at other Middle Stone Age sites in southern Africa, but anthropogenic input to the sediment is indicated by the presence of charcoal, burnt bone, lithic fragments, fat-derived char and ashes. Clay coating fragments and chaotic microstructures demonstrate that bioturbation and colluvial reworking homogenised much of the deposit and may explain the absence of preserved bedding and rarity of combustion features. Downward movement of water through the sequence, indicated by clay coatings, is the likely cause for poor bone preservation and near lack of ashes at the site, as well as fluctuations in dose rate that have complicated luminescence dating studies. Evidence for diagenesis at the site is in the form of secondary apatite and gypsum. Sedimentary structures such as channel lag deposits and (silt and sand) laminae observed in peels dating between 60 and 35 ka BP suggest a high-energy sedimentary environment, which experienced flooding events that eroded underlying deposits and deposited large volumes of sediment. This explains why some of the post-Howiesons Poort layers contain few artefacts and implies that there may have been more human activity at the site during this time than has previously been suggested.

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