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1

Observations of Barophilic Microbial Activity in Samples of Sediment and Intercepted Particulates from the Demerara Abyssal Plain  

PubMed Central

To better understand the ecological significance of pressure effects on bacteria in the abyssobenthic boundary layer, experimental suspensions of sediments and sinking particulates were prepared from samples collected in boxcore and bottom-moored sediment traps at two stations (depth, 4,470 and 4,850m) in the Demerara abyssal plain off the coast of Brazil. Replicate samples were incubated shipboard at 3°C and at both atmospheric and deep-sea pressures (440 or 480 atm [4.46 × 104 or 4.86 × 104 kPa]) following the addition of [14C]glutamic acid (<10 ?g liter?1) or yeast extract (0.025%) and the antibiotic nalidixic acid (0.002%). In seven of the eight samples supplemented with isotope, a barophilic microbial response was detected, i.e., substrate incorporation and respiration were greater under in situ pressure than at 1 atm (101.3 kPa). In the remaining sample, prepared from a sediment trap warmed to 24°C before recovery, pressure was observed to inhibit substrate utilization. Total bacterial counts by epifluorescence microscopy decreased with depth in each sediment core, as did utilization of glutamic acid. Significant percentages of the total bacterial populations in cold sediment trap samples (but not the prewarmed one or any boxcore sample) were abnormally enlarged and orange fluorescing after incubation with yeast extract and nalidixic acid under deep-sea conditions. Results indicated that in the deep sea, barophilic bacteria play a predominant role in the turnover of naturally low levels of glutamic acid, and the potential for intense microbial activity upon nutrient enrichment is more likely to occur in association with recently settled particulates, especially fecal pellets, than in buried sediments. PMID:16346897

Deming, Jody W.; Colwell, Rita R.

1985-01-01

2

Observations of barophilic microbial activity in samples of sediment and intercepted particulates from the demerara abyssal plain.  

PubMed

To better understand the ecological significance of pressure effects on bacteria in the abyssobenthic boundary layer, experimental suspensions of sediments and sinking particulates were prepared from samples collected in boxcore and bottom-moored sediment traps at two stations (depth, 4,470 and 4,850m) in the Demerara abyssal plain off the coast of Brazil. Replicate samples were incubated shipboard at 3 degrees C and at both atmospheric and deep-sea pressures (440 or 480 atm [4.46 x 10 or 4.86 x 10 kPa]) following the addition of [C]glutamic acid (<10 mug liter) or yeast extract (0.025%) and the antibiotic nalidixic acid (0.002%). In seven of the eight samples supplemented with isotope, a barophilic microbial response was detected, i.e., substrate incorporation and respiration were greater under in situ pressure than at 1 atm (101.3 kPa). In the remaining sample, prepared from a sediment trap warmed to 24 degrees C before recovery, pressure was observed to inhibit substrate utilization. Total bacterial counts by epifluorescence microscopy decreased with depth in each sediment core, as did utilization of glutamic acid. Significant percentages of the total bacterial populations in cold sediment trap samples (but not the prewarmed one or any boxcore sample) were abnormally enlarged and orange fluorescing after incubation with yeast extract and nalidixic acid under deep-sea conditions. Results indicated that in the deep sea, barophilic bacteria play a predominant role in the turnover of naturally low levels of glutamic acid, and the potential for intense microbial activity upon nutrient enrichment is more likely to occur in association with recently settled particulates, especially fecal pellets, than in buried sediments. PMID:16346897

Deming, J W; Colwell, R R

1985-10-01

3

Northwest African Continental Margin: History of sediment accumulation, landslide deposits, and hiatuses as revealed by drilling the Madeira Abyssal Plain  

NASA Astrophysics Data System (ADS)

ODP drill sites in the Madeira Abyssal Plain reveal sequences of organic-rich turbidites derived from the northwest African margin, in which each turbidite has a volume of tens to hundreds of cubic kilometers. The frequency of turbidite emplacement has been combined with core and seismic data to show the volume of redeposited sediment. The basin began to fill about 22 Ma with numerous small turbidites, up to 100 per million years, each with volumes of a few cubic kilometers. The total volume of turbidites deposited increased between 16 and 11 Ma, as did their individual volumes, and then declined to 7 Ma. At 7 Ma, there was a dramatic increase in the amount of turbidite input to 768 km3/Myr and a rise in the average volume of each unit to 59 km3. These high values have been maintained to the present day. The variations in the amount of redeposited sediment most likely reflect the rates of sedimentation on the northwest African margin since high sedimentation leads to oversteepening of the slopes and eventual mass wasting. The dramatic changes at about 7 Ma may be due to a large increase in upwelling off northwest Africa caused by circulation changes associated with increased glaciation of the poles. Up to 20% of sediment may be remobilized by landslides, with each event leaving a hiatus. Each of these hiatuses extends over an average area of ˜4800 km2 and represents removal of sediment layers several tens of meters thick and of several hundred thousand years duration.

Weaver, P. P. E.

2003-03-01

4

Mineralogical and rock magnetic provenance variation in Alaskan Abyssal Plain sediments, Gulf of Alaska  

NASA Astrophysics Data System (ADS)

The interplay between regional tectonic activity and climate is a fundamental issue in ocean and earth sciences. These interactions are greatest in areas of high topographic relief coupled with aggressive erosional agents. Focused erosion in uplifting glaciated regions generates a positive feedback loop, accelerating uplift (Tompkin, 2007) and depositing erosional products into adjacent basins. Gulf of Alaska (GoA) strata offer insight into erosional responses to shifts in climate, such as the intensification of Cordilleran glaciation at 2.6 Ma. This coincides with increased accumulation of terrigenous sediment and appearance of ice rafted debris in the adjacent mud-rich Surveyor Fan (SF). It is hypothesized that this change in sediment accumulation and lithology at 2.6 Ma between the Lower Fan Sequence (LFS) and Upper Fan Sequence (UFS) may represent intensification of glacial erosion along the windward side of coastal mountains in southern Alaska. Establishing a provenance record of the UFS and LFS would provide insight into the history of glaciation and subsequent erosion of this region. Determining provenance of fine-grained sediments of the SF requires tracers that not only uniquely differentiate the adjacent Chugach and Yakutat geologic terranes, but are also preserved in offshore muds. Preliminary quantitative powder XRD mineralogy suggests that muds from onshore terranes and UFS sediments can be largely characterized by their distribution as resolved clusters on cross-plots of quartz, feldspar, clinochlore, and muscovite abundance. Within these plots, UFS sediments predominantly occupy the same region as Yakutat-derived samples, suggesting the mineralogy of UFS fine-grained sediments reflects that of the Yakutat Terrane. Distinctive groupings of on- and offshore sediments can also be observed on a Day plot of coercivity of remnance (Hcr/Hc) versus magnetic grain size (Mr/Ms), where Chugach and Yakutat samples group into separate clusters in the multi-domain and pseudo-single-domain (PSD) regions, respectively. UFS sediments also form a cluster in the center of the PSD region. Magnetic data are consistent with previous provenance work in which Mr/Ms, Hcr/Hc, and mass susceptibility of the sand-sized fraction were used to distinguish between the Chugach and Yakutat terranes (Cowan et al., 2006). These preliminary data suggest that mineralogic and magnetic tracers exist in the mud fraction of onshore fluvial sediments and can be used to develop a provenance history of fine-grained marine muds on the Surveyor Fan.

Ullrich, A. D.; Jaeger, J. M.

2009-12-01

5

Comparative geoscience studies of the Madeira and Southern Nares Abyssal Plains: NEA/SWG preference location document  

SciTech Connect

This document summarizes the status of geoscience investigations in the two primary North Atlantic study locations Great Meteor East (GME) in the Madeira Abyssal Plain, and the Southern Nares Abyssal Plain (SNAP), and assesses the characteristics of these locations relative to the guidelines considered desirable and necessary for a potential subseabed high-level waste repository. These characteristics will be continually reevaluated as additional data become available and as our understanding of deep-sea sediment processes within abyssal plain environments improves. Initially, a number of areas of minimum size were identified in the ocean basins that appeared to comply with most of the stability and barrier guidelines. However, detailed studies in both GME and SNAP demonstrate that as our level of knowledge improves, and the degree of resolution increases, the number of 100 km/sup 2/ areas complying with these guidelines becomes much more limited. This observation may be characteristic of abyssal plain and abyssal hill environments in both the North Atlantic and North Pacific basins. Marked differences in geoscience characteristics exist between the Great Meteor East and the Southern Nares Abyssal Plain study locations. The significance of these differences, as they impact the selection of a single preferred site for a potential subseabed repository, can only be determined by using an integrated systems risk assessment modeling approach. The known geoscience characteristics can, however, be used in conjunction with the site assessment guidelines to draw conclusions concerning the geoscience suitability of these two locations. These conclusions will be modified as specific types of data from future expeditions become available.

Auffret, G.A.; Buckley, D.E.; Schuttenhelm, R.T.E.; Searle, R.C.; Shephard, L.E.; Cranston, R.E.

1986-01-01

6

Models of hydrothermal circulation within 106 Ma seafloor: Constraints on the vigor of fluid circulation and crustal properties, below the Madeira Abyssal Plain  

Microsoft Academic Search

Heat flow measurements colocated with seismic data across 106 Ma seafloor of the Madeira Abyssal Plain (MAP) reveal variations in seafloor heat flow of ±10–20% that are positively correlated with basement relief buried below thick sediments. Conductive finite element models of sediments and upper basement using reasonable thermal properties are capable of generating the observed positive correlation between basement relief

A. T. Fisher; R. P. Von Herzen

2005-01-01

7

Character, paleoenvironment, rate of accumulation, and evidence for seismic triggering of Holocene turbidites, Canada Abyssal Plain, Arctic Ocean  

USGS Publications Warehouse

Four box cores and one piston core show that Holocene sedimentation on the southern Canada Abyssal Plain for the last 8010??120 yr has consisted of a continuing rain of pelagic organic and ice-rafted elastic sediment with a net accumulation rate during the late Holocene of ???10 mm/1000 yr, and episodically emplaced turbidites 1-5 m thick deposited at intervals of 830 to 3450 yr (average 2000 yr). The average net accumulation rate of the mixed sequence of turbidites and thin pelagite interbeds in the cores is about 1.2 m/1000 yr. Physiography suggests that the turbidites originated on the Mackenzie Delta or its clinoform, and ??13C values of -27 to - 25??? in the turbidites are compatible with a provenance on a delta. Extant displaced neritic and lower slope to basin plain calcareous benthic foraminifers coexist in the turbidite units. Their joint occurence indicates that the turbidites originated on the modern continental shelf and entrained sediment from the slope and rise enroute to their final resting place on the Canada Abyssal Plain. The presence of Middle Pleistocene diatoms in the turbidites suggests, in addition, that the turbidites may have originated in shallow submarine slides beneath the upper slope or outer shelf. Small but consistent differences in organic carbon content and ??13C values between the turbidite units suggest that they did not share an identical provenance, which is at least compatible with an origin in slope failures. The primary provenance of the ice-rafted component of the pelagic beds was the glaciated terrane of northwestern Canada; and the provenance of the turbidite units was Pleistocene and Holocene sedimentary deposits on the outer continental shelf and upper slope of the Mackenzie Delta. Largely local derivation of the sediment of the Canada Abyssal Plain indicates that sediment accumulation rates in the Arctic Ocean are valid only for regions with similar depositional sources and processes, and that these rates cannot be extrapolated regionally. The location of an elliptical zone of active seismicity over the inferred provenance of the turbidites suggests that they were triggered by large earthquakes. Distal turbidite sediment accumulation rates were more than two orders of magnitude greater than pelagic sediment accumulation rates on the Canada Abyssal Plain during the last 8000 years. This disparity reconciles the discrepancy between the high accumulation rates assumed by some for the Arctic Ocean because of the numerous major rivers and large ice sheets that discharge into this small mediterranean basin and the low pelagic sedimentation rates that have been reported from the Arctic Ocean.

Grantz, A.; Phillips, R.L.; Mullen, M.W.; Starratt, S.W.; Jones, Glenn A.; Naidu, A.S.; Finney, B.P.

1996-01-01

8

Synchronous flows within the Seine Abyssal Plain, offshore NW Africa: A case for earthquake triggered turbidity currents  

NASA Astrophysics Data System (ADS)

Turbidites found in deep-water basins are derived from sediment accumulated on adjacent continental margins. In seismically active areas earthquakes can trigger submarine flows, which are potentially recorded within the basin stratigraphy. Thus a basin can potentially be used as a record of palaeoseismicity. Here we present a suite of shallow sediment cores, which penetrate turbidite stratigraphy down to ~225 ka across the Seine Abyssal Plain, offshore NW Africa. A robust chronostratigraphic framework is extended across the basin using coccolith biostratigraphy, stable oxygen isotope analysis, and carbon dating. From this individual turbidite beds are mapped out across the basin. From these correlations flow pathways into the Seine Abyssal Plain are identified, including the Agadir and El Jadida Canyons; two separate canyon systems that feed the basin from the West and East respectively. Three of the turbidite beds (ages ~15, ~60, and ~110 ka) have multiple fining trends, which originate from the mouths of the Agadir and El Jadida Canyons. The most likely explanation for these trends is that multiple flows passed through the canyons synchronously and entered the Seine Abyssal Plain forming individual beds composed of multiple flow events. The synchronous flows most likely originated from multiple simultaneous slope failures in the heads of each canyon. In turn, the most likely trigger for these simultaneous slope failures is an earthquake. Hence, we interpret these three turbidite beds as earthquake-triggered events. However, in historic times onshore Agadir has been subject to moderate seismic activity, yet no significant turbidites are recorded in the Seine Abyssal Plain. This study highlights the difficulties of using turbidites as a record of palaeoseismicity beyond historical records.

Stevenson, Chris; Talling, Peter; Sumner, Esther; Wynn, Russell; Kuhlmann, Holger; Hunt, James; Bender, Vera; Gibbs, Samantha

2013-04-01

9

Basin plains; Giant sedimentation events  

Microsoft Academic Search

The study of 13 modern basin plains ranging in size from the 200-km2 Navidad Basin up to the giant (> 100,000-km2) Hatteras and Sohm Abyssal Plains has reveaied that these features owe their existence to large-volume turbidity currents capable of covering the entire basin floor. Such convulsive events flatten out the topographic irregularities formed by the deposition of small flows

Orrin H. Pilkey

10

Long-term change in the megabenthos of the Porcupine Abyssal Plain (NE Atlantic)  

NASA Astrophysics Data System (ADS)

A radical change in the abundance of invertebrate megafauna on the Porcupine Abyssal Plain is reported over a period of 10 years (1989-1999). Actiniarians, annelids, pycnogonids, tunicates, ophiuroids and holothurians increased significantly in abundance. However, there was no significant change in wet weight biomass. Two holothurian species, Amperima rosea and Ellipinion molle, increased in abundance by more than two orders of magnitude. Samples from the Porcupine Abyssal Plain over a longer period (1977-1999) show that prior to 1996 these holothurian species were always a minor component of the megafauna. From 1996 to 1999 A. rosea was abundant over a wide area of the Porcupine Abyssal Plain indicating that the phenomenon was not a localised event. Several dominant holothurian species show a distinct trend in decreasing body size over the study period. The changes in megafauna abundance may be related to environmental forcing (food supply) rather than to localised stochastic population variations. Inter-annual variability and long-term trends in organic matter supply to the seabed may be responsible for the observed changes in abundance, species dominance and size distributions.

Billett, D. S. M.; Bett, B. J.; Rice, A. L.; Thurston, M. H.; Galéron, J.; Sibuet, M.; Wolff, G. A.

11

Evidences of intraplate deformation in the West Madeira Abyssal Plain (eastern North Atlantic) from seismic reflection and multibeam swath bathymetry data  

NASA Astrophysics Data System (ADS)

The West Madeira Abyssal Plain is located in the eastern North Atlantic off Madeira Islands, forming part of the Canary Basin and reaching a mean water depth of 5300 m. This region is also located within Africa plate at about 500 km southwards from the Açores-Gibraltar plate boundary, and for that reason lacks seismic activity. Although this region being located in an intraplate setting, the presence of faulted sediments was reported in several works published during the eighties of last century following a study conducted in late 1970s to evaluate the feasibility of disposal of high-level radioactive wastes in the ocean. According these works, the Madeira Abyssal Plain sediments are cut by many normal growth faults and this deformation is a result of compaction and dewatering of the sediments. Evidences of tectonic deformation of oceanic sediments in intraplate settings are uncommon, but folded sediments and reverse faults extending into the basement, were recognized in the equatorial Indian Ocean and in the West African continental margin. Recently, during 2006 multi-channel seismic reflection and multibeam swath bathymetry surveys were carried out in the West Madeira Abyssal Plain by EMEPC in order to prepare the Portuguese proposal for the extension of the continental shelf. The seismic lines were acquired onboard R/V Akademik Shatskiy using a source of 5720 cu in bolt gun array, cable length of 7950 m and shot interval of 50.00 m. The multibeam swath bathymetry was acquired onboard NRP Gago Coutinho, and allowed a high resolution mapping of the main geomorphological features. The multichannel seismic lines, oriented WNW-ESE, image the Madeira island lower slope located at about 4000 m water depth and the almost flat abyssal plain at about 5300 m water depth. These seismic lines show a thick sedimentary succession that reaches a maximum thickness of about 1.5 sec twt in the deepest parts of the West Madeira Abyssal Plain, overlying an irregular diffractive Late Cretaceous oceanic basement. This basement is outcropping in some places originating small highs, which top is placed at 4700-4800 m water depth, about 500 m above the surrounding flat abyssal plain. The acoustic facies shown by the sedimentary record suggests the presence of a great thickness of turbidites within the sedimentary succession. The sismostratigraphy interpretation allowed the identification of four distinctive seismic units named from bottom to top U1 to U4. A theoretical stratigraphic correlation model between these seismic units and the ODP 157 data (Sites 950, 951 and 952) is proposed in the present work. The oldest seismic units U1 and U2 rest above the oceanic basement and could be correlated with the Late Cretaceous to Early Miocene sediments drilled during ODP 157. The youngest seismic units U3 and U4 show a succession of very continuous and parallel reflections alternating between low and high amplitude. Such type of seismic facies could be correlated with alternating turbidites and pelagic sediments possibly of Middle-Upper Miocene to Pleistocene age considering the ODP 157 data. The Cenozoic sedimentary succession is cut by several normal faults, close spaced, possibly related to compaction and dewatering processes. The acoustic record suggests the occurrence of fluid circulation along these faults, which are rooted in the oceanic basement. In some places these faults cut though the entire sedimentary sequence, almost reaching the seafloor. Evidences of recent compressional deformation are shown by reverse faults that affected the sedimentary sequence and also deform the seafloor by buckling and high amplitude folding. A large pop-up structure is recognized, generating a seafloor high, suggesting the occurrence of recent compressional events in the West Madeira Abyssal Plain region.

Roque, C.; Simões, M.; Lourenço, N.; Pinto de Abreu, M.

2009-04-01

12

STUDY OF ABYSSAL SEAFLOOR ISOLATION OF CONTAMINATED SEDIMENTS CONCLUDED  

EPA Science Inventory

Recognizing the rapidly decreasing availability of disposal sites on land, in 1993 Congress directed the Department of Defense to assess the technical and scientific feasibility of isolating contaminated dredged material on the abyssal seafloor. The Naval Research Laboratory (NRL...

13

Neotectonic morphotructures in the junction zone of the Cape Verde Rise and Cape Verde Abyssal Plain, Central Atlantic  

Microsoft Academic Search

Acoustic profiling carried out with an Edgetech 3300 prophilograph in the junction zone of the Cape Verde Rise, Cape Verde Abyssal Plain, and Grimaldi and Bathymetrists seamounts in the Central Atlantic during Cruise 23 of the R\\/V Akademik Nikolaj Strakhov allowed us to obtain new data on neotectonic deformations in the ocean and to propose their interpretation. It has been

S. G. Skolotnev; S. Yu. Kolodyazhny; N. V. Tsukanov; N. P. Chamov; S. Yu. Sokolov

2009-01-01

14

Late Quaternary paleoenvironmental changes revealed by multi-proxy records from the Chukchi Abyssal Plain, western Arctic Ocean  

NASA Astrophysics Data System (ADS)

Late Quaternary paleoenvironmental changes in the western Arctic Ocean are revealed by multi-proxy records of core 03M03 from the Chukchi Abyssal Plain (CAP). Proxy parameters include lithology, grain size fractions, and mineralogy and petrology of ice-rafted detritus (IRD), element contents, biogenic components, ?18O, ?13C and Mg/Ca of planktonic foraminifera Neogloboquadrina pachyderma (sin.) (Nps). Seven IRD (> 250 ?m) peaks are interpreted as marking detrital input by rafting sea ice or icebergs during MIS 3 interstadials and early MIS 1. High MnO, CaO and MgO contents and high Ca/Al and Mg/Al ratios during MIS 3 and MIS 1 correspond to increases in ice-rafted detrital carbonates and the synchronous declines in siliciclastic elements (e.g., Al2O3, Fe2O3). Therefore, these warmer periods were characterized by a high detrital carbonate input entrained in icebergs from the Canadian Arctic Archipelago coeval with an increased input of Mn through rivers and/or coastal erosion. Relatively stable contents of siliciclastic elements and their ratios in the grayish sediment units are interpreted from turbid surface water plumes or nepheloid flows delivered by meltwater and/or brine rejection from ice-sheet margins at the Arctic Ocean periphery. Relatively stable clay- and silt-sized fractions were attributed mainly to sea ice entrainment over glacial-interglacial cycles. High foraminiferal abundances in the brown units during MIS 3 and 1 are related to enhanced calcareous plankton productivity under more open water conditions and/or the incremental input of Atlantic water masses. Relatively high TOC and opal contents in the grayish units of MIS 3 appear to have accumulated by lateral transport of organic matter from the Chukchi shelf to the deep abyssal plain. Lower contents of biogenic material in the brown units probably result from increased dilution by rapid IRD deposition, and from early diagenetic degradation. Depletions in Nps-?18O and -?13C concurrent with high foraminiferal abundances and IRD peaks within the brown units of MIS 3 and 1 are indicative of meltwater pulses, as previously documented across the Arctic Ocean. However, several Nps-?18O and -?13C depletions between the brown units B3 and B2 in MIS 3 could have resulted from enhanced sea ice formation. The Nps-Mg/Ca has the potential to record paleotemperature changes in the Arctic region, but still awaits a better calibration of the Nps-Mg/Ca-temperature relationship with results from core-tops, sediment traps, and plankton tows.

Wang, Rujian; Xiao, Wenshen; März, Christian; Li, Qianyu

2013-09-01

15

Organic matter accumulation, sulfate reduction, and methane generation in a turbidite sequence on the Iberia Abyssal Plain  

SciTech Connect

Organic matter can be transferred and redeposited from continental margins to the deep-sea by turbidity currents and slumps. An opportunity to investigate the consequences of turbidite deposition on sediment organic matter was provided by a transect of four closely spaced drill sites sampled during ODP Leg 149 in a Pliocene-Pleistocene distal turbidite sequence on the landward edge of the Iberia Abyssal Plain. Organic carbon concentrations average ca 0.7% in sediments from Sites 897 and 898 and ca 0.4% at Sites 899 and 900. Headspace concentrations of interstitial methane exceed 100,000 ppm in sediments from Sites 897 and 898 but are essentially zero in those from Sites 899 and 900. Methane concentrations do not rise until interstitial sulfate concentrations are virtually depleted, suggesting the presence of deep in situ methanogenic bacterial activity at Sites 897 and 898 and its absence at Sites 899 and 900. Two factors associated with the turbidity flows that created the sedimentary sequence evidently influenced post-depositional diagenesis at these sites. The principal factor is that the rapidly deposited turbidite sequences at Sites 897 and 898 protected organic matter from oxic, early degradation and thereby permitted anoxic, later degradation to proceed. In contrast, organic matter in the more slowly deposited turbidites at Sites 899 and 900 was oxidized soon after deposition and was therefore not available for later microbial utilization. A lesser factor is that the turbidity flows may have obtained their entrained organic matter from different environments and consequently delivered organic matter with different characteristics.

Meyers, P.A.; Silliman, J.E. [Univ. of Michigan, Ann Arbor, MI (United States); Shaw, T.J. [Univ. of South Carolina, Columbia, SC (United States)

1996-12-31

16

17. PETROGRAPHY AND GEOCHEMISTRY OF ORGANIC MATTER IN TRIASSIC AND CRETACEOUS DEEP-SEA SEDIMENTS FROM THE WOMBAT AND EXMOUTH PLATEAUS AND NEARBY ABYSSAL PLAINS OFF NORTHWEST AUSTRALIA1  

Microsoft Academic Search

Triassic (Carnian-Rhaetian) continental margin sediments from the Wombat Plateau off northwest Australia (Sites 759, 760, 761, and 764) contain mainly detrital organic matter of terrestrial higher plant origin. Although deposited in a nearshore deltaic environment, little liptinitic material was preserved. The dominant vitrinites and inertinites are hydrogen-lean, and the small quantities of extractable bitumen contain w-alkanes and bacterial hopanoid hydrocarbons

Jürgen Rullkötter; Ralf Littke; Matthias Radke; Ulrich Disko; Brian Horsfield; Jürgen Thurow

17

Neotectonic morphotructures in the junction zone of the Cape Verde Rise and Cape Verde Abyssal Plain, Central Atlantic  

Microsoft Academic Search

Acoustic profiling carried out with an Edgetech 3300 prophilograph in the junction zone of the Cape Verde Rise, Cape Verde\\u000a Abyssal Plain, and Grimaldi and Bathymetrists seamounts in the Central Atlantic during Cruise 23 of the R\\/V Akademik Nikolaj Strakhov allowed us to obtain new data on neotectonic deformations in the ocean and to propose their interpretation. It has been

S. G. Skolotnev; S. Yu. Kolodyazhny; N. V. Tsukanov; N. P. Chamov; S. Yu. Sokolov

2009-01-01

18

Seismic evidence of exhumed mantle rock basement at the Gorringe Bank and the adjacent Horseshoe and Tagus abyssal plains (SW Iberia)  

NASA Astrophysics Data System (ADS)

The Gorringe Bank is a gigantic seamount that separates the Horseshoe and Tagus abyssal plains offshore SW Iberia, in a zone that hosts the convergent boundary between the Africa and Eurasia plates. Although the region has been the focus of numerous investigations since the early 1970s, the lack of appropriate geophysical data makes the nature of the basement, and thus the origin of the structures, still debated. In this work, we present combined P-wave seismic velocity and gravity models along a transect that crosses the Gorringe Bank from the Tagus to the Horseshoe abyssal plains. The P-wave velocity structure of the basement is similar in the Tagus and Horseshoe plains. It shows a 2.5-3.0 km-thick top layer with a velocity gradient twice stronger than oceanic Layer 2 and an abrupt change to an underlying layer with a five-fold weaker gradient. Velocity and density is lower beneath the Gorringe Bank probably due to enhanced fracturing, that have led to rock disaggregation in the sediment-starved northern flank. In contrast to previous velocity models of this region, there is no evidence of a sharp crust-mantle boundary in any of the record sections. The modelling results indicate that the sediment overlays directly serpentinite rock, exhumed from the mantle with a degree of serpentinization decreasing from a maximum of 70-80% under the top of Gorringe Bank to less than 5% at a depth of ˜20 km. We propose that the three domains were originally part of a single serpentine rock band, of nature and possibly origin similar to the Iberia Abyssal Plain ocean-continent transition, which was probably generated during the earliest phase of the North Atlantic opening that followed continental crust breakup (Early Cretaceous). During the Miocene, the NW-SE trending Eurasia-Africa convergence resulted in thrusting of the southeastern segment of the exhumed serpentinite band over the northwestern one, forming the Gorringe Bank. The local deformation associated to plate convergence and uplift could have promoted pervasive rock fracturing of the overriding plate, leading eventually to rock disaggregation in the northern flank of the GB, which could be now a potential source of rock avalanches and tsunamis.

Sallarès, Valentí; Martínez-Loriente, Sara; Prada, Manel; Gràcia, Eulàlia; Ranero, César; Gutscher, Marc-André; Bartolome, Rafael; Gailler, Audrey; Dañobeitia, Juan José; Zitellini, Nevio

2013-03-01

19

Seismicity and seismotectonics of the diffusive Iberian/African plate boundary: Horseshoe Abyssal Plain and Gorringe Bank  

NASA Astrophysics Data System (ADS)

In the area to the west of the Gibraltar Arc the plate boundary between Africa and Iberia is poorly defined. The deformation in the area is forced by the slow NW-SE convergence of 4 mm/yr between the oceanic domains of Iberia/Eurasia and Africa and is accommodated over a 200 km broad tectonically-active deformation zone. The region, however, is also characterized by large earthquakes and tsunamis, such as the 1969 Mw=7.9 Horseshoe Abyssal Plain earthquake and the November 1, 1755 Great Lisbon earthquake with an estimated magnitude of Mw~8.5. The exact location of the source of the 1755 Lisbon earthquake is still unknown. Recent work may suggest that the event occurred in the vicinity of the Horseshoe fault, an oblique thrust fault. However, estimates of tsunami arrival times suggested a source near the Gorringe Bank, a ~180 km-long and ~70 km-wide ridge that has a relieve of ~5000 m. Deep Sea Drilling (DSDP) and rock samples indicated that the bank is mainly composed of serpentinized peridotites with gabbroic intrusions, perhaps being created by overthrusting of the Horseshoe Abyssal Plain onto the Tagus Abyssal Plain in NW direction. Further, the Horseshoe Abyssal Plain is marked by the presence of compressive structures with a roughly NE-SW orientation and E-W trending, segmented, crustal-scale, strike slip faults that extend from the Gorringe Bank to the Gibraltar Arc in the eastern Gulf of Cadiz, which were called "South West Iberian Margin" or SWIM faults. The fault system may mark a developing Eurasia-Africa plate boundary. Two local seismic networks were operated in the area. First, a network of 14 ocean-bottom seismometers (OBS) was operated between April and October 2012 in the vicinity of the Horseshoe fault between 10°W to 11°W, and 35°50'N to 36°10'N. From October 2013 to March 2014 a second network of 15 OBS monitored seismicity at the Gorringe Bank. Both networks benefitted from seismic stations operated in Portugal. The first network provided in the order of 100 locale earthquakes occurring with the network. Most earthquakes in the Horseshoe occurred at a depth of 40-60 km, either in oceanic or unroofed continental mantle. The large source depth of events observed in the Horseshoe Abyssal Plain supports the idea that large catastrophic earthquakes, like the Great Lisbon earthquake of 1755, may indeed occur in the area.

Grevemeyer, Ingo; Lange, Dietrich; Matias, Luis

2014-05-01

20

Miocene sedimentation in the Sigsbee Abyssal Plain, Gulf of Mexico  

E-print Network

, !, .', if;, ' I, W9 fl 91 / /j o 89 II ', i i' el l Ie r I U S 1 C / 1 I Jgl I|' P III co~o S Figure 1 -', cntl~pEG I 18 Bathymetric and Physiographic Province Map of the Gulf' of Mexico with Drill Gita Locations. Cross-section of the drill...

Kuzela, Robert Christian

1971-01-01

21

32. OXIDATION FRONTS IN MADEIRA ABYSSAL PLAIN TURBIDITES: PERSISTENCE OF EARLY DIAGENETIC TRACE-ELEMENT ENRICHMENTS DURING BURIAL, SITE 950 1  

Microsoft Academic Search

The emplacement of organic-rich turbidite units on abyssal plains is commonly followed by the early diagenetic redistribu- tion of redox-sensitive elements. This occurs only at the summit of the turbidite unit, where it is caused by the downward diff u- sion of seawater oxygen, which continues for as long as each turbidite is in diffusive contact with bottom waters. The

John Thomson; Ian Jarvis; Darryl R. H. Green; Damon Green

22

The response of Oneirophanta mutabilis (Holothuroidea) to the seasonal deposition of phytopigments at the Porcupine Abyssal Plain in the Northeast Atlantic  

NASA Astrophysics Data System (ADS)

The impact of seasonal pulses of phytodetritus on the grazing behaviour of Oneirophanta mutabilis was assessed on the Porcupine Abyssal Plain (PAP) in the NE Atlantic. Sediment and sediment trap samples were analysed by HPLC to estimate the quantity and quality of the organic material in terms of phytopigments and nucleic acids. Food selection by Oneirophanta was estimated by analysing these constituents in the gut contents. The study area is characterised by large interannual variations in the deposition of fresh organic material. The mass fluxes at 10 m above bottom (mab) varied from 0.25 g DW m -2 d -1 in September 1996 to <0.1 g DW m -2 d -1 in March 1997. The material caught in the sediment trap in September 1996 had a relative fresh signature with a chlorophyll -a:phaeophorbide ratio of 1.33. During the other seasons (March 1997, July 1997 and October 1997) the chlorophyll -a:phaeophorbide ratio remained low. In sediment cores this ratio showed a similar seasonal and inter-annual pattern, and again September 1996 was the period of maximum abundance of fresh organic material in the surficial sediment. The analyses of the gut contents of Oneirophanta mirrored exactly the seasonal variation of the phytopigments in both the sediment and the sediment trap material. Concentrations of pigments in the fore-gut were 5 to 15 times higher than in the sediment and the nucleic acid concentrations were up to 80 times higher. This discrepancy between pigments and nucleic acids concentrations suggests that the latter are “indigenous” to the gut of Oneirophanta, either because the gut contains high numbers of actively-dividing bacteria or as a result of cell lysis of the gut epithelium. The seasonal differences in the pigment concentration factor suggest that Oneirophanta does not actively search for hotspots where pigment concentrations are enriched. By using the degradation rate of chlorophyll- a in the PAP sediments, the minimum residence time of chlorophyll in the sediment within the gut of Oneirophanta was calculated. In combination with gut volume and density data it was estimated that each year the Oneirophanta population skims a third of the sediment surface at the PAP site.

Witbaard, R.; Duineveld, G. C. A.; Kok, A.; van der Weele, J.; Berghuis, E. M.

23

Response of a multi-domain continental margin to compression: Study from seismic reflection-refraction and numerical modelling in the Tagus Abyssal Plain  

NASA Astrophysics Data System (ADS)

The effects of the Miocene through Present compression in the Tagus Abyssal Plain are mapped using the most up to date available to scientific community multi-channel seismic reflection and refraction data. Correlation of the rift basin fault pattern with the deep crustal structure is presented along seismic line IAM-5. Four structural domains were recognized. In the oceanic realm mild deformation concentrates in Domain 1 adjacent to the Tore-Madeira Rise. Domain 2 is characterized by the absence of shortening structures, except near the ocean-continent transition (OCT), implying that Miocene deformation did not propagate into the Abyssal Plain. In Domain 3 we distinguish three sub-domains: Sub-domain 3A which coincides with the OCT, Sub-domain 3B which is a highly deformed adjacent continental segment, and Sub-domain 3C. The Miocene tectonic inversion is mainly accommodated in Domain 3 by oceanwards directed thrusting at the ocean-continent transition and continentwards on the continental slope. Domain 4 corresponds to the non-rifted continental margin where only minor extensional and shortening deformation structures are observed. Finite element numerical models address the response of the various domains to the Miocene compression, emphasizing the long-wavelength differential vertical movements and the role of possible rheologic contrasts. The concentration of the Miocene deformation in the transitional zone (TC), which is the addition of Sub-domain 3A and part of 3B, is a result of two main factors: (1) focusing of compression in an already stressed region due to plate curvature and sediment loading; and (2) rheological weakening. We estimate that the frictional strength in the TC is reduced in 30% relative to the surrounding regions. A model of compressive deformation propagation by means of horizontal impingement of the middle continental crust rift wedge and horizontal shearing on serpentinized mantle in the oceanic realm is presented. This model is consistent with both the geological interpretation of seismic data and the results of numerical modelling.

Neves, M. C.; Terrinha, P.; Afilhado, A.; Moulin, M.; Matias, L.; Rosas, F.

2009-04-01

24

Retention of Riverine Sediment and Nutrient Loads by Coastal Plain  

E-print Network

Retention of Riverine Sediment and Nutrient Loads by Coastal Plain Floodplains Gregory B. Noe floodplain ecosystems are important regulators of sediment, carbon, and nutrient transport in watersheds of the Chesapeake Bay. Key words: floodplain; sediment; nitrogen; phosphorus; retention; wetland; river

25

Neotectonic morphotructures in the junction zone of the Cape Verde Rise and Cape Verde Abyssal Plain, Central Atlantic  

NASA Astrophysics Data System (ADS)

Acoustic profiling carried out with an Edgetech 3300 prophilograph in the junction zone of the Cape Verde Rise, Cape Verde Abyssal Plain, and Grimaldi and Bathymetrists seamounts in the Central Atlantic during Cruise 23 of the R/V Akademik Nikolaj Strakhov allowed us to obtain new data on neotectonic deformations in the ocean and to propose their interpretation. It has been established that neotectonic movements occurred in the discrete manner: blocks of undeformed rocks alternate with linear zones of intense deformation spatially related to paleotransform fracture zones, where anticlines, horsts, diapir-like morphostructures, and grabens were formed. The Cape Verde Ridge is a large horst. Its sedimentary cover is disturbed by thrust (?), reverse, and normal faults, steeply dipping fracture zones, and folds. Three stages of tectonic movements—Oligocene-early Miocene, pre-Quaternary, and Holocene—are recognized. The tectonic deformations occurred largely under near-meridional compression. Extension setting was characteristic of the Cape Verde Ridge and the Carter Rise in the Holocene.

Skolotnev, S. G.; Kolodyazhny, S. Yu.; Tsukanov, N. V.; Chamov, N. P.; Sokolov, S. Yu.

2009-01-01

26

Heavy mineral dispersal patterns of the abyssal plain and Louisiana inner shelf of the Gulf of Mexico  

E-print Network

of the individual heavy minerals in the different size grades of a particular sample. Publications by Dryden (1932), on a study of the coastal plain of Maryland, and Hawkes and Smythe (1931), in a report dealing with garnetiferous sands of' the Northumberland... of heavy minerals in the South and East China Seas. Continental shelf of Texas and Louisiana. The heavy minerals of Gulf Coast sediments have been the subject of various earlier investigators: these include Bullard (1942), Goldstein (1942), Van Andel...

Moore, Walter Richard

1969-01-01

27

Iron-manganese nodules from nares abyssal plain: geochemistry and mineralogy.  

PubMed

Three nodules from a core taken north of Puerto Rico are composed chiefly of an x-ray amorphous, hydrated, iron-manganese oxide, with secondary goethite, and minor detrital silicates incorporated during growth of the nodules. No primary manganese mineral is apparent. The nodules are enriched in iron and depleted in manganese relative to Atlantic Ocean averages. The formation of these nodules appears to have been contemporary with sedimentation and related to volcanic activity. PMID:17802621

Smith, R E; Gassaway, J D; Giles, H N

1968-08-23

28

Temporal and depth-related differences in prokaryotic communities in abyssal sediments associated with particulate organic carbon flux  

NASA Astrophysics Data System (ADS)

Particulate organic carbon (POC) flux is hypothesized to be the most important parameter influencing activity and biomass of prokaryotic and faunal communities in the abyssal seafloor, but there is little evidence of POC-related changes in community composition of prokaryotes. This hypothesis was tested by 16S rRNA-gene-based analysis of prokaryotic DNA and RNA extracted from abyssal seafloor sediments during periods of low and high POC flux. Fingerprint analysis of prokaryotic communities indicated that approximately 50% of the phylotypes were identical at each sediment horizon, regardless of the temporal variations in POC flux. However, phylotypes were also detected that represented a relatively dynamic component of these communities and were probably strongly influenced by the prevalent POC flux regime. These patterns were also detected in deeper sediment horizons. DNA- and RNA-based community profiles differed, although both approaches had similar community dynamics. Crenarchaeota showed the strongest shift in community composition in response to availability of labile POC, indicating that POC flux may have a more pronounced impact on crenarchaeal communities than on bacterial communities. The high number of phylotypes common to each sample time suggests that both standing stock and active prokaryotic communities are stable.

Moeseneder, M. M.; Smith, K. L.; Ruhl, H. A.; Jones, D. O. B.; Witte, U.; Prosser, J. I.

2012-12-01

29

Controls on sediment delivery in coastal plain rivers.  

PubMed

Rivers crossing coastal plains are often inefficient conveyors of sediment, so that changes in upstream sediment dynamics are not evident at the river mouth. Extensive accommodation space and low stream power often result in extensive alluvial storage upstream of estuaries and correspondingly low sediment loads at the river mouth. However, gaging stations with sediment records are typically well upstream of the coast, and thus tend to overestimate sediment yields by under-representing the lower coastal plain and because there is often a net loss of sediment in lower coastal plain reaches. Studies of alluvial sediment storage have generally focused on accommodation space, but, using examples from Texas, we show that low transport capacity controlled largely by slope is a crucial factor. PMID:19892459

Slattery, Michael C; Phillips, Jonathan D

2011-02-01

30

Diatom flux reflects water-mass conditions on the southern Northwind Abyssal Plain, Arctic Ocean  

NASA Astrophysics Data System (ADS)

We studied time-series fluxes of diatom particles and their relationship to hydrographic variations from 4 October 2010 through 18 September 2012 using bottom-tethered sediment trap moorings deployed at Station NAP (75° N, 162° W; 1975 m water depth) in the western Arctic Ocean. We observed clear maxima of the diatom valve flux in November-December of both 2010 and 2011, and in August 2011. Diatoms in samples were categorized into 98 taxa. The diatom flux maxima were characterized by many resting spores in November-December and by the sea ice-associated diatom Fossula arctica in August 2011. These assemblages along with abundant clay minerals in the samples suggest a significant influence of shelf-origin materials transported by mesoscale eddies, which developed along the Chukchi Sea shelf break. In contrast, the fluxes of total mass and diatoms were reduced in summer 2012. We hypothesize that this suppression reflects the influx of oligotrophic water originating from the central Canada Basin. A physical oceanographic model demonstrated that oligotrophic surface water from the Beaufort Gyre was supplied to Station NAP from December 2011 to early half of 2012.

Onodera, J.; Watanabe, E.; Harada, N.; Honda, M. C.

2014-10-01

31

Diatom flux reflects water-mass conditions on the southern Northwind Abyssal Plain, Arctic Ocean  

NASA Astrophysics Data System (ADS)

We studied time-series fluxes of diatom particles from 4 October 2010 to 18 September 2012 using bottom-tethered moorings with two sediment traps deployed at 180 and 1300 m depths at Station NAP (75° N, 162° W; 1975 m water depth) in the western Arctic Ocean. This paper discusses on the relationship of time-series diatom fluxes to satellite-based sea-ice motion and simulated hydrographic variations. We observed clear maxima of the diatom valve flux in November-December of both 2010 and 2011, and in August 2011. Diatoms in samples were categorized into 98 taxa. The diatom flux maxima were characterized by many resting spores in November-December and by the sea-ice-associated diatom Fossula arctica in August 2011. These assemblages along with abundant clay minerals in the samples suggest a significant influence of shelf-origin materials transported by mesoscale eddies, which developed along the Chukchi Sea shelf break. In contrast, the fluxes of total mass and diatoms were reduced in summer 2012. We hypothesize that this suppression reflects the influx of oligotrophic water originating from the central Canada Basin. A physical oceanographic model demonstrated that oligotrophic surface water from the Beaufort Gyre was supplied to Station NAP from December 2011 to the early half of 2012.

Onodera, J.; Watanabe, E.; Harada, N.; Honda, M. C.

2015-03-01

32

SUBJECT INDEX abyssal plains  

E-print Network

:55 Albian, palynology, A:104 albite amphibolite, A:130­131 breccia, A:195 breccia clasts and matrix, A:193. magnesium oxide, A:199, 286 amphibole amphibolite, A:130­131 amphibolite clasts, A:190­191 breccia, A:188­189 breccia clasts and matrix, A:193­194 clasts, A:282­283 meta-anorthosite, A:131 metagabbro clasts, A:191

33

North Atlantic Deep Water and Antarctic Bottom Water variability during the last 200 ka recorded in an abyssal sediment core off South Africa  

Microsoft Academic Search

Benthic ?13C values (F. wuellerstorfi), kaolinite\\/chlorite ratios and sortable silt median grain sizes in sediments of a core from the abyssal Agulhas Basin record the varying impact of North Atlantic Deep Water (NADW) and Antarctic Bottom Water (AABW) during the last 200ka. The data indicate that NADW influence decreased during glacials and increased during interglacials, in concert with the global

S. Krueger; D. C. Leuschner; W. Ehrmann; G. Schmiedl; A. Mackensen

34

Chemistry and mineralogy of pyrite-enriched sediments at a passive margin sulfide brine seep: abyssal Gulf of Mexico  

NASA Astrophysics Data System (ADS)

Pyrite is rapidly accumulating at the contact between the Cretaceous limestones of the Florida Platform and the hemipelagic sediments of the abyssal Gulf of Mexico. Sediments sampled with the submersible "Alvin" in 3266 m of water are associated with a dense community of organisms that depend on chemosynthetic primary production as a food source. Analysis of the chemistry, mineralogy, and textural composition of these sediments indicate that iron sulfide mineralization is occurring at the seafloor within an anoxic micro-habitat sustained by the advection of hydrogen sulfide-charged saline brines from the adjacent platform. The chemosynthetic bacteria that directly overlie the sediments oxidize hydrogen sulfide for energy and provide elemental sulfur that reacts with iron monosulfide to form some of the pyrite. The sediments are mixtures of pyrite (˜ 30 wt.%), Ba sbnd Sr sulfates (˜ 4 wt.%), clays, and locally derived biogenic carbonates and are progressively being cemented by iron sulfides. Oxidation of hydrogen sulfide produces locally acidic conditions that corrode the adjacent limestones. Potential sources of S, H 2S, Fe, Ba, and Sr are discussed.

Commeau, Robert F.; Paull, Charles K.; Commeau, Judith A.; Poppe, Lawrence J.

1987-03-01

35

Chemistry and mineralogy of pyrite-enriched sediments at a passive margin sulfide brine seep: abyssal Gulf of Mexico  

USGS Publications Warehouse

Pyrite is rapidly accumulating at the contact between the Cretaceous limestones of the Florida Platform and the hemipelagic sediments of the abyssal Gulf of Mexico. Sediments sampled with the submersible "Alvin" in 3266 m of water are associated with a dense community of organisms that depend on chemosynthetic primary production as a food source. Analysis of the chemistry, mineralogy, and textural composition of these sediments indicate that iron sulfide mineralization is occurring at the seafloor within an anoxic micro-habitat sustained by the advection of hydrogen sulfide-charged saline brines from the adjacent platform. The chemosynthetic bacteria that directly overlie the sediments oxidize hydrogen sulfide for energy and provide elemental sulfur that reacts with iron monosulfide to form some of the pyrite. The sediments are mixtures of pyrite (??? 30 wt.%), BaSr sulfates (??? 4 wt.%), clays, and locally derived biogenic carbonates and are progressively being cemented by iron sulfides. Oxidation of hydrogen sulfide produces locally acidic conditions that corrode the adjacent limestones. Potential sources of S, H2S, Fe, Ba, and Sr are discussed. ?? 1987.

Commeau, R.F.; Paull, C.K.; Commeau, J.A.; Poppe, L.J.

1987-01-01

36

Lateral variability of overbank sedimentation on a Devon flood plain  

Microsoft Academic Search

Deployment of sediment traps over a 12-month period has enabled investigation of the lateral variability of overbank deposition rates and particle size composition of deposited sediment across a frequently inundated flood plain section of the River Culm, southeast Devon, UK. Although a general exponential decrease in deposition rate and grain size with distance from the channel occurs, significant deviations from

D. J. SIMM; D. E. WALLING

1999-01-01

37

Lateral variability of overbank sedimentation on a Devon flood plain  

Microsoft Academic Search

Deployment of sediment traps over a 12-month period has enabled investigation of the lateral variability of overbank deposition rates and particle size composition of deposited sediment across a frequently inundated flood plain section of the River Culm, southeast Devon, UK. Although a general exponential decrease in deposition rate and grain size with distance from the channel occurs, significant deviations from

D. J. SIMM; D. E. WALLING

1998-01-01

38

Geochemical indicators of subsidence in sediment, Terrebonne coastal plain, Louisiana  

SciTech Connect

Sediments comprising the Terrebonne Coastal Plain consist primarily of clays, silts, and peats that fill the depressions between alluvial ridges created by former Mississippi River courses. These sediments are subsiding at variable rates. Depositional history, sedimentation rates, and environment of deposition affect both the types and abundances of diagenetic products found in deltaic sediments. Early diagenesis influences the geotechnical properties of these coastal plain deposits and their local subsidence rates. Diagenetic mineralogy and elemental geochemistry therefore offer clues to understanding some of the variability associated with subsidence in the lower deltaic plain. Results show that diagenetic minerals consist of carbonates (siderite, calcite, dolomite, and rhodochrosite), iron sulfides, vivianite, and iron oxides. In general, siderite and other carbonates as well as pyrite are higher in the fine-grained swamp and lacustrine clays of the upper/middle deltaic plain environments where sediment compaction and subsidence rates are considerably lower than rapidly deposited lower delta and marine deposits. Prodelta clays, for example, contain fewer varieties and lower abundances of diagenetic inclusions than their freshwater fine-grained counterparts. Oxidized sediments of well-drained swamp and natural levee deposits that contain goethite, iron oxides, manganese oxides, and carbonates are stabilized early in their depositional history and therefore do not lend themselves to rapid volume reduction associated with dewatering and compaction. Elemental concentrations can also be interpreted to reflect relative diagenetic activity in the sediments. These preliminary results indicate that close examination of diagenetic mineralogical and geochemical features can provide valuable information concerning the subsidence history of delta plain areas.

Bailey, A.M. (Univ. of Southwestern Louisiana, Lafayette (USA)); Roberts, H.H. (Louisiana State Univ., Baton Rouge (USA))

1990-09-01

39

Sediments in Semi-arid Wetlands: US Southern High Plains  

Technology Transfer Automated Retrieval System (TEKTRAN)

Playas are ephemeral wetlands on the semi-arid U.S. Southern High Plains that serve as runoff catchment basins and are thought to be focal points of Ogallala aquifer recharge. Sediments in playas alter biodiversity and hydroperiods. The purpose of this study was to evaluate the effects of outerbas...

40

Sediment community oxygen consumption in the deep Gulf of Mexico  

Microsoft Academic Search

Sediment community oxygen consumption (SCOC) has been measured from the continental shelf out to the Sigsbee Abyssal Plain in the NE Gulf of Mexico (GoM). SCOC rates on the continental shelf were an order of magnitude higher than those on the adjacent continental slope (450–2750m depth) and two orders of magnitude higher than those on the abyssal plain at depths

Gilbert T. Rowe; John Morse; Clifton Nunnally; Gregory S. Boland

2008-01-01

41

Current-controlled, abyssal microtopography and sedimentation in Mozambique Basin, southwest Indian Ocean  

USGS Publications Warehouse

The Antarctic Bottom Water (AABW) activity and the variations in the abundance and grain size of the terrigenous sediments, derived from Africa and Madagascar land masses, are reflected in different types of microtopography in the Mozambique Basin. In southerly areas, where the sediment supply is much less, the bottom-current activity has resulted in the presence of manganese nodules, a thin veneer of sediments, and the absence of sediment waves. Farther north, along the marginal areas of the basin where the fine-grained sediments from the Africa-Madagascar source have been supplied in abundance, wavy bedforms have been generated by AABW. Wavy bedforms do not exist even in the northerly areas if coarse-grained, turbidite sediments are present on the sea floor. The continuation of acoustic reflectors from the zone of turbidites in the central areas of the basin into the zone of sediment waves along the margins, and the lithology and structures in sediment cores from these zones suggest that the turbidity-current-fed, fine-grained sediments were deposited as wavy bedforms by AABW flow. Thus, sediment waves formed readily during Pleistocene times. The enrichment of quartz and displaced Antarctic diatoms, and the relatively low kaolinite/chlorite ratios in the sediments, the north-pointing current lineations on the sea floor, the lack of any perceptible sedimentary fill in the troughs of waves, and the dense nepheloid layer in the westerly areas of the Mozambique Basin, attest to the current-controlled sedimentation and generation of wavy bedforms during Holocene time also. The formation of sediment waves in the Mozambique Basin can be modeled after a fluvial antidune mechanism. This model envisages that internal waves, focussed on a benthic boundary layer cap, have been locked in phase with sediment waves in the presence of an 8-10 cm/sec current in the Mozambique Basin. A density contrast of 2??10-6 g/cm3 appears to exist at the tops of benthic boundary layers in the Mozambique Basin and is quite sufficient for supporting the internal waves. The densiometric Froude number calculated for a 60-280 m thick boundary layer in the basin is close to unity or greater, and is compatible with the antidune model. ?? 1980.

Kolla, V.; Eittreim, S.; Sullivan, L.; Kostecki, J.A.; Burckle, L.H.

1980-01-01

42

Biogeochemical variations at the Porcupine Abyssal Plain Sustained Observatory (PAP-SO) in the northeast Atlantic Ocean, from weekly to inter-annual time scales  

NASA Astrophysics Data System (ADS)

We present high-resolution autonomous measurements of carbon dioxide partial pressure p(CO2) taken in situ at the Porcupine Abyssal Plain sustained observatory (PAP-SO) in the Northeast Atlantic (49° N, 16.5° W; water depth of 4850 m) for the period 2010 to 2012. Measurements of p(CO2) made at 30 m depth on a sensor frame are compared with other autonomous biogeochemical measurements at that depth (including chlorophyll a-fluorescence and nitrate concentration data) to analyse weekly to seasonal controls on p(CO2) flux in the inter-gyre region of the North Atlantic. Comparisons are also made with in situ regional time-series data from a ship of opportunity and mixed layer depth (MLD) measurements from profiling Argo floats. There is a persistent under saturation of CO2 in surface waters throughout the year which gives rise to a perennial CO2 sink. Comparison with an earlier dataset collected at the site (2003 to 2005) confirms seasonal and inter-annual changes in surface seawater chemistry. There is year-to-year variability in the timing of stratification and deep winter mixing. The 2010 to 2012 period shows an overall increase in p(CO2) values when compared to the 2003-2005 period. This is despite similar surface temperature, wind speed and MLD measurements between the two periods of time. Future work should incorporate daily CO2 flux measurements made using CO2 sensors at 1 m depth and the in situ wind speed data now available from the UK Met Office Buoy.

Hartman, S. E.; Jiang, Z.-P.; Turk, D.; Lampitt, R. S.; Frigstad, H.; Ostle, C.

2014-08-01

43

Biogeochemical variations at the Porcupine Abyssal Plain sustained Observatory in the northeast Atlantic Ocean, from weekly to inter-annual timescales  

NASA Astrophysics Data System (ADS)

We present high-resolution autonomous measurements of carbon dioxide partial pressure p(CO2) taken in situ at the Porcupine Abyssal Plain sustained Observatory (PAP-SO) in the northeast Atlantic (49° N, 16.5° W; water depth of 4850 m) for the period 2010-2012. Measurements of p(CO2) made at 30 m depth on a sensor frame are compared with other autonomous biogeochemical measurements at that depth (including chlorophyll a fluorescence and nitrate concentration data) to analyse weekly to seasonal controls on p(CO2) flux in the inter-gyre region of the North Atlantic. Comparisons are also made with in situ regional time series data from a ship of opportunity and mixed layer depth (MLD) measurements from profiling Argo floats. There is a persistent under-saturation of CO2 in surface waters throughout the year which gives rise to a perennial CO2 sink. Comparison with an earlier data set collected at the site (2003-2005) confirms seasonal and inter-annual changes in surface seawater chemistry. There is year-to-year variability in the timing of deep winter mixing and the intensity of the spring bloom. The 2010-2012 period shows an overall increase in p(CO2) values when compared to the 2003-2005 period as would be expected from increases due to anthropogenic CO2 emissions. The surface temperature, wind speed and MLD measurements are similar for both periods of time. Future work should incorporate daily CO2 flux measurements made using CO2 sensors at 1 m depth and the in situ wind speed data now available from the UK Met Office Buoy.

Hartman, S. E.; Jiang, Z.-P.; Turk, D.; Lampitt, R. S.; Frigstad, H.; Ostle, C.; Schuster, U.

2015-02-01

44

Amazonis Planitia: The role of geologically recent volcanism and sedimentation in the formation of the smoothest plains on Mars  

Microsoft Academic Search

Amazonis Planitia, located between the two main volcanic provinces on Mars (Tharsis and Elysium), is characterized by extremely smooth topography at several scale lengths, as smooth as oceanic abyssal plains topography on Earth. We use Mars Global Surveyor (MGS) data (primarily very high resolution Mars Orbiter Laser Altimeter (MOLA) topography and derivative slope maps, gradient maps, and detrended maps) to

Elizabeth R. Fuller; James W. Head

2002-01-01

45

Reproductive biology of porcellanasterid asteroids from three abyssal sites in the northeast Atlantic with contrasting food input  

Microsoft Academic Search

The reproductive biology of the abyssal asteroids Hyphalaster inermis, Styracaster chuni, and S. horridus from the Porcupine Abyssal Plain (PAP), the Madeira Abyssal Plain (MAP), and the northwest African slope (NWA) is described and compared. The most northern location (PAP) is subjected to a strong seasonal input of aggregated phytodetritus to the seabed. The site at MAP does not receive

E. Ramirez-Llodra; P. Tyler; D. Billett

2002-01-01

46

Spatial Distribution and Morphology of Sediments in Texas Southern High Plains Playa Wetlands  

Technology Transfer Automated Retrieval System (TEKTRAN)

Playas are depressional geomorphic features on the U.S. High Plains and about 20,000 Southern High Plains playa wetlands serve as runoff catchment basins, which are thought to be focal points of Ogallala aquifer recharge. Sediments in playas can alter biodiversity services, impede aquifer recharge,...

47

Spatial distribution and morphology of sediments in Texas Southern High Plains playa wetlands  

Technology Transfer Automated Retrieval System (TEKTRAN)

Playas are depressional geomorphic features on the U.S. High Plains. About 20,000 Southern High Plains playa wet¬lands serve as runoff catchment basins, which are thought to be focal points of Ogallala aquifer recharge. Sediments in playas can alter biodiversity services, impede aquifer recharge, an...

48

Exchanges of sediment between the flood plain and channel of the Amazon River in Brazil  

USGS Publications Warehouse

Sediment transport through the Brazilian sector of the Amazon River valley, a distance of 2010 km, involves exchanges between the channel and the flood plain that in each direction exceed the annual flux of sediment out of the river at O??bidos (???1200 Mt yr-1). The exchanges occur through bank erosion, bar deposition, settling from diffuse overbank flow, and sedimentation in flood-plain channels. We estimated the magnitude of these exchanges for each of 10 reaches of the valley, and combined them with calculations of sediment transport into and out of the reaches based on sediment sampling and flow records to define a sediment budget for each reach. Residuals in the sediment budget of a reach include errors of estimation and erosion or deposition within the channel. The annual supply of sediment entering the channel from bank erosion was estimated to average 1570 Mt yr-1 (1.3 ?? the O??bidos flux) and the amount transferred from channel transport to the bars (380 Mt yr-1) and the flood plain (460 Mt yr-1 in channelized flow; 1230 Mt yr-1 in diffuse overbank flow) totaled 2070 Mt yr-1 (1.7 ?? the O??bidos flux). Thus, deposition on the bars and flood plain exceeded bank erosion by 500 Mt yr-1 over a 10-16 yr period. Sampling and calculation of sediment loads in the channel indicate a net accumulation in the valley floor of approximately 200 Mt yr-1 over 16 yr, crudely validating the process-based calculations of the sediment budget, which in turn illuminate the physical controls on each exchange process. Another 300-400 Mt yr-1 are deposited in a delta plain downstream of O??bidos. The components of the sediment budget reflect hydrologie characteristics of the valley floor and geomorphic characteristics of the channel and flood plain, which in turn are influenced by tectonic features of the Amazon structural trough.

Dunne, T.; Mertes, L.A.K.; Meade, R.H.; Richey, J.E.; Forsberg, B.R.

1998-01-01

49

Composite refraction-reflection stack sections: Tracing faults in the Atlantic coastal plain sediments  

SciTech Connect

Seismic data from the Atlantic Coastal Plain are reprocessed and composite refraction-reflection stack sections produced to investigate basement faults that penetrate upward into Atlantic Coastal Plain sediments in South Carolina. Reprocessing recovered reflections from within the deep crust to the Moho as well as from within thin veneer (300) of the Atlantic Coastal Plain sediments. One of the major objectives of this paper is to discuss the use of shallow refracted arrivals to construct a composite refraction- reflection stack that allows better imaging of the subsurface at shallow depths.

Stephenson, D.E. [Westinghouse Savannah River Co., Aiken, SC (United States); Coruh, C.; Costain, J.K. [Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States). Dept. of Geological Sciences

1993-05-01

50

Use of mining-contaminated sediment tracers to investigate the timing and rates of historical flood plain sedimentation  

Microsoft Academic Search

Changes in land use practices following European settlement in the 1830s produced accelerated sedimentation on virtually all valley floors in the Blue River Watershed, Wisconsin. The contamination of sediments by Pb and Zn mining allowed us to calculate cross-valley rates of flood plain sedimentation for three time periods: the pre-mining period (1830–1900), the mining period (1900–1920), and the post-mining period

Scott A. Lecce; Robert T. Pavlowsky

2001-01-01

51

Bacteria in deep coastal plain sediments of Maryland: A possible source of CO2 to groundwater  

Microsoft Academic Search

Nineteen cores of unconsolidated Coastal Plain sediments obtained from depths of 14 to 182 m below land surface near Waldorf, Maryland, were collected and examined for metabolically active bacteria. The age of the sediments cored range from Miocene to Early Cretaceous. Acridine orange direct counts of total (viable and nonviable) bacteria in core subsamples ranged from 108 to 104 bacteria\\/g

Francis H. Chapelle; Joseph L. Zelibor; D. Jay Grimes; LeRoy L. Knobel

1987-01-01

52

Geochemical signature of provenance, tectonics and chemical weathering in the Quaternary flood plain sediments of the Hindon River, Gangetic plain, India  

NASA Astrophysics Data System (ADS)

The Ganga basin in the Himalayan foreland is a part of the world's largest area of modern alluvial sedimentation. Flood plain sediments of the Hindon River of the Gangetic plain have been analyzed for sediment texture, major and trace elements including rare earth elements (REEs). The results have been used to characterize the source rock composition and to understand the intensity of chemical weathering, tectonics and their interplay in the Hindon flood plain. The sediments of the Hindon flood plain dominantly consist of sand sized particles with little silt and clay. The geochemistry of the Hindon sediments has been compared to the Siwalik mudstone of the Siwalik Group (Siwaliks). The Siwalik sedimentary rocks like sandstones, mudstones and conglomerates are the known source rocks for the Hindon flood plain sediments. Mudstone geochemistry has been considered best to represent the source rock characteristics. The UCC (Upper Continental Crust) normalized major and trace elements of the Hindon flood plain sediments are very similar to the Siwalik mudstone except for Th and Cr. Furthermore, the average chondrite normalized REE pattern of the Hindon flood plain sediments is similar to the Siwalik mudstone. Textural immaturity, K/Rb ratios and the average CIA (Chemical Index of Alteration) and PIA (Plagioclase Index of Alteration) values of the Hindon flood plain sediments indicate that the sediments have not been affected by chemical weathering. Our study suggests that the active tectonics of the Himalayas and monsoon climate enhances only physical erosion of the source rocks (Siwaliks) rather than the chemical alteration. These factors help the Hindon sediments to retain their parental and tectonic signature even after recycling.

Mondal, M. E. A.; Wani, H.; Mondal, Bulbul

2012-09-01

53

Retention of Riverine Sediment and Nutrient Loads by Coastal Plain Floodplains  

Microsoft Academic Search

Despite the frequent citation of wetlands as effective regulators of water quality, few quantitative estimates exist for their\\u000a cumulative retention of the annual river loads of nutrients or sediments. Here we report measurements of sediment accretion\\u000a and associated carbon, nitrogen, and phosphorus accumulation as sedimentation over feldspar marker horizons placed on floodplains\\u000a of the non-tidal, freshwater Coastal Plain reaches of

Gregory B. Noe; Cliff R. Hupp

2009-01-01

54

The Role of Lateral Fluid Flow in Off-Axis, Oceanic Hydrothermal Systems Under Abyssal Sedimentation Conditions  

NASA Astrophysics Data System (ADS)

Off-axis hydrothermal circulation is significant to the thermal and chemical evolution of the oceanic crust, to the chemical evolution of the oceans, and potentially to a deep biosphere within the upper crust. These off-axis hydrothermal systems are impacted by the type and distribution of sediment because sufficiently thick and contiguous sediment cover will limit the exchange of fluid between the ocean and the crust. It has been suggested that in off-axis settings lateral transport between sediment-poor regions, through the high permeability lavas, is the dominant geometry of fluid convection in igneous crust underlying thick sediment. To aid in understanding the role of sediment cover on seafloor hydrothermal systems, a numerical model of pelagic supply, post-depositional down-slope sediment redistribution (following [1]), and crustal hydrogeology has been developed. Synthetic seafloor bathymetry representative of crust formed at different spreading rates [2] is used as the initial bathymetry and seamounts are added randomly with a size and frequency distribution representative of the global ocean [3]. Other sedimentation variables are the diffusivity of sediment, the pelagic sediment supply rate and the sediment hydrological properties. From this, the model predicts the changing distribution of potential hydrothermal fluid recharge and discharge sites in response to sedimentation. These results are coupled with a two-dimensional model of fluid and heat transport to evaluate the conditions under which lateral fluid flow in the igneous oceanic crust are consistent with the global data set of seafloor heat flow measurements. Preliminary results suggest that, of the parameters investigated, the spatial density of model-predicted outcrops is most sensitive to the rate of pelagic sediment supply. In areas with lower than average seamount abundances crustal spreading rate is also important to the distribution of outcrops, with more outcrops predicted on crust formed at slow-spreading ridges. The model-predicted separation distance between potential fluid recharge and discharge sites is generally lower than previously estimated [4] implying that pressure gradients driving lateral fluid flow may be higher than predicted and upper crustal permeability may be lower than previously predicted. Results of this modeling will be presented, and the influences of the rate and nature of sedimentation on off-axis hydrothermal circulation will be discussed. [1] Webb and Jordan, JGR 2001, v106, p 30,433; [2] Goff and Jordan, JGR 1988, v93, p 13,589; [3] Hillier and Watts, Geophysical Research Letters 2007, v34, doi:10.1029/2007GL029874; [4] Fisher and Becker, Nature 2000, v403 p 71.

Anderson, B. W.; Coogan, L. A.; Gillis, K. M.

2010-12-01

55

Monsoon sedimentation on the ‘abandoned' tide-influenced Ganges-Brahmaputra delta plain  

NASA Astrophysics Data System (ADS)

Annual sediment delivery by the Ganges and Brahmaputra rivers to the Bengal margin has kept pace with sea level rise since the mid Holocene, sustaining subaerial growth of the delta. However, the Sundarbans region of the tidal delta is disconnected from major distributary sources of sediment and is often thought to be sediment starved, eroding, and susceptible to the meter of sea level rise predicted for the 21st century. Despite these assumptions, direct sedimentation measurements on the tidal delta plain reveal widespread mean annualized accretion rates of ?1.1 cm yr-1, although heterogeneous depositional patterns indicate that topography and internal creek networks influence local sediment distribution. Short-lived radioisotope inventories (7Be: t1/2 = 53.3 days) measured on the freshly accumulated sediments indicate that about ½ of the mass deposited on the lower delta was sourced directly from the seasonal flood pulse of the river; the remaining ½ is derived from older (?1 yr) reworked sediments. Net sedimentation on this part of the delta traps ?10% of annual Ganges-Brahmaputra sediment load, with accretion rates roughly equivalent to the mean regional rate of relative sea-level rise (RSLR) of ?1.0 cm yr-1. If these sedimentation rates are representative of longer-term trends and subsidence rates remain stable over the next century, the lower delta plain may continue to maintain its elevation and stability despite documented mangrove retreat around its seaward edges.

Rogers, Kimberly G.; Goodbred, Steven L.; Mondal, Dhiman R.

2013-10-01

56

Lineaments in coastal plain sediments as seen in ERTS imagery  

NASA Technical Reports Server (NTRS)

Examination of satellite imagery over the Atlantic Coastal Plain near Washington, D. C. shows numerous lineaments, which cannot be accounted for by any known cultural or natural features. At least some of these lineaments represent the surface expression of faults, for one of them has been correlated with the outcrop of a fault that had been traced for several miles in southern Prince Georges County, Maryland. If a substantial number of these lineaments do indeed represent fault traces, the fact that they show on the surface suggests that the geologic history of the Coastal Plain is much more complex than has previously been recognized, and that faulting may have occurred in the Holocene, much later than has generally been recognized. The importance that such recent movements could have on future development of the Coastal Plain should be emphasized.

Withington, C. F.

1973-01-01

57

Treatment of Mount St. Helens volcanic ash suspensions by plain sedimentation, coagulation, and flocculation  

Microsoft Academic Search

Aqueous suspensions made from Mount St. Helens volcanic ash, which fell in Pullman, Wash., on May 18,1980, were characterized in terms of pH, conductivity, alkalinity, acidity, turbidity, settleable solids, and fluoride content. Plain sedimentation followed by coaguiation-fioccuiation successfully reduced the turbidity and fluoride content of the ash suspensions at two alkalinity concentrations and two volcanic ash levels.

Ervin Hindin

1981-01-01

58

Volcanism and Sedimentation in Amazonis Planitia: The Origin of the Smoothest Plains on Mars  

Microsoft Academic Search

Data from the Mars Orbiting Laser Altimeter (MOLA) are used to investigate Amazonis Planitia, the region with the smoothest plains on Mars. Amazonis Planitia, located just west of Olympus Mons, shows evidence for several volcanic episodes as well as geologically recent water-borne sedimentation. When normalized for regional slope (\\

E. R. Fuller; J. W. Head; M. A. Kreslavsky; S. Pratt

2001-01-01

59

Sediment loss and runoff from cropland in a Southeast Atlantic Coastal Plain landscape  

Technology Transfer Automated Retrieval System (TEKTRAN)

Widespread implementation of conservation-tillage (CsT) systems during cotton and peanut production in the Atlantic Coastal Plain region (USA) has substantially reduced erosion and sediment loss. However, benefits of CsT in these cropping systems are being threatened by weather shifts that include i...

60

Holocene sediment fluxes in the northeast Atlantic from 230Thexcess and radiocarbon measurements  

Microsoft Academic Search

Radiocarbon and 230Thexcess data from six NE Atlantic box cores are considered. The cores form a transect from the Porcupine Abyssal Plain over the East Thulean Rise to the southern end of Feni Drift. The chronology for the cores is established from bulk sediment carbonate radiocarbon data and reveals that sections exhibiting constant accumulation rates can be identified in all

J. Thomson; S. Colley; R. Anderson; G. T. Cook; A. B. MacKenzie; D. D. Harkness

1993-01-01

61

Diversity of Thiosulfate-Oxidizing Bacteria from Marine Sediments and Hydrothermal Vents  

Microsoft Academic Search

Species diversity, phylogenetic affiliations, and environmental occurrence patterns of thiosulfate-oxidizing marine bacteria were investigated by using new isolates from serially diluted continental slope and deep-sea abyssal plain sediments collected off the coast of New England and strains cultured previously from Galapagos hydrothermal vent samples. The most frequently obtained new isolates, mostly from 10 3 - and 10 4 -fold dilutions

A. Teske; T. Brinkhoff; G. Muyzer; D. P. Moser; J. Rethmeier; H. W. Jannasch

2000-01-01

62

Seismic interpretation of pelagic sedimentation regimes in the 18–53 Ma eastern equatorial Pacific: Basin-scale sedimentation and infilling of abyssal valleys  

Microsoft Academic Search

Understanding how pelagic sediment has been eroded, transported, and deposited is critical to evaluating pelagic sediment records for paleoceanography. We use digital seismic reflection data from an Integrated Ocean Drilling Program site survey (AMAT03) to investigate pelagic sedimentation across the eastern-central equatorial Pacific, which represents the first comprehensive record published covering the 18–53 Ma eastern equatorial Pacific. Our goals are

Masako Tominaga; Mitchell Lyle; Neil C. Mitchell

2011-01-01

63

Arsenic fractionation and contamination assessment in sediments of thirteen lakes from the East Plain and Yungui Plateau Ecoregions, China.  

PubMed

Arsenic (As) fractions in the sediments of seven lakes from East Plain Ecoregion and six lakes from Yungui Plateau Ecoregion, China, were investigated. Results indicated that the total As concentrations in sediment samples of lakes of the East Plain Lake Ecoregion are higher than those of Yungui Plateau Lake Ecoregion. Residual As is the main fraction in sediment samples of lakes from both ecoregions, followed by reducible As and soluble or oxidizable As. The total As is correlated to oxidizable As and residual As in sediment samples from both lake ecoregions. As distribution in sediment samples of lakes of the East Plain Ecoregion appears to be affected by human activity, while the As origin mainly comes from natural sources in sediment samples of lakes in the Yungui Plateau Ecoregion. The potential ecological risk index and geoaccumulation index values suggest "low to moderate" risk degree and "unpolluted to moderately polluted" for As in the studied lake sediments. PMID:25288540

Zan, Fengyu; Huo, Shouliang; Zhang, Jingtian; Zhang, Li; Xi, Beidou; Zhang, Lieyu

2014-10-01

64

Abyssal undular vortices in the Eastern Mediterranean basin.  

PubMed

Abyssal temperature and velocity observations performed within the framework of the Neutrino Mediterranean Observatory, a project devoted to constructing a km(3)-scale underwater telescope for the detection of high-energy cosmic neutrinos, demonstrate cross-fertilization between subnuclear physics and experimental oceanography. Here we use data collected south of Sicily in the Ionian abyssal plain of the Eastern Mediterranean (EM) basin to show for the first time that abyssal vortices exist in the EM, at depths exceeding 2,500 m. The eddies consist of chains of near-inertially pulsating mesoscale cyclones/anticyclones. They are embedded in an abyssal current flowing towards North-Northwest. The paucity of existing data does not allow for an unambiguous determination of the vortex origin. A local generation mechanism seems probable, but a remote genesis cannot be excluded a priori. The presence of such eddies adds further complexity to the discussion of structure and evolution of water masses in the EM. PMID:22588296

Rubino, A; Falcini, F; Zanchettin, D; Bouche, V; Salusti, E; Bensi, M; Riccobene, G; De Bonis, G; Masullo, R; Simeone, F; Piattelli, P; Sapienza, P; Russo, S; Platania, G; Sedita, M; Reina, P; Avolio, R; Randazzo, N; Hainbucher, D; Capone, A

2012-01-01

65

Large-scale patterns in biodiversity of microbial eukaryotes from the abyssal sea floor  

PubMed Central

Eukaryotic microbial life at abyssal depths remains “uncharted territory” in eukaryotic microbiology. No phylogenetic surveys have focused on the largest benthic environment on this planet, the abyssal plains. Moreover, knowledge of the spatial patterns of deep-sea community structure is scanty, and what little is known originates primarily from morphology-based studies of foraminiferans. Here we report on the great phylogenetic diversity of microbial eukaryotic communities of all 3 abyssal plains of the southeastern Atlantic Ocean---the Angola, Cape, and Guinea Abyssal Plains---from depths of 5,000 m. A high percentage of retrieved clones had no close representatives in genetic databases. Many clones were affiliated with parasitic species. Furthermore, differences between the communities of the Cape Abyssal Plain and the other 2 abyssal plains point to environmental gradients apparently shaping community structure at the landscape level. On a regional scale, local species diversity showed much less variation. Our study provides insight into the community composition of microbial eukaryotes on larger scales from the wide abyssal sea floor realm and marks a direction for more detailed future studies aimed at improving our understanding of deep-sea microbes at the community and ecosystem levels, as well as the ecological principles at play. PMID:20007768

Scheckenbach, Frank; Hausmann, Klaus; Wylezich, Claudia; Weitere, Markus; Arndt, Hartmut

2009-01-01

66

Use of Chernobyl-der ived radiocaesium to investigate contemporary overbank sedimentation on the flood plains of Carpathian rivers  

Microsoft Academic Search

Evidence for recent incision is widespread along the channels of Carpathian rivers and because of the tendency for the relative height of the flood plain surface to increase, the contemporary importance of overbank sedimentation is uncertain. An attempt has been made to use measurements of Chernobyl-derived radiocaesium in flood plain cores to generate estimates of recent rates of overbank deposition

W. FROEHLICH; D. E. WALLING

1994-01-01

67

Sediment compaction rates and subsidence in deltaic plains: Numerical constraints and stratigraphic influences  

USGS Publications Warehouse

Natural sediment compaction in deltaic plains influences subsidence rates and the evolution of deltaic morphology. Determining compaction rates requires detailed knowledge of subsurface geotechnical properties and depositional history, neither of which is often readily available. To overcome this lack of knowledge, we numerically forward model the incremental sedimentation and compaction of stochastically generated stratigraphies with geotechnical properties typical of modern depositional environments in the Mississippi River delta plain. Using a Monte Carlo approach, the range of probable compaction rates for stratigraphies with compacted thicknesses ?1. The fastest compacting stratigraphies are composed primarily of peat and bar sand, whereas the slowest compacting stratigraphies are composed of prodelta mud and natural levee deposits. These results suggest that compaction rates can significantly influence vertical and lateral stratigraphic trends during deltaic evolution.

Meckel, T.A.; ten Brink, U.S.; Williams, S.J.

2007-01-01

68

Pathways for arsenic from sediments to groundwater to streams: Biogeochemical processes in the Inner Coastal Plain, New Jersey, USA  

Microsoft Academic Search

The Cretaceous and Tertiary sediments that underlie the Inner Coastal Plain of New Jersey contain the arsenic-rich mineral glauconite. Streambed sediments in two Inner Coastal Plain streams (Crosswicks and Raccoon Creeks) that traverse these glauconitic deposits are enriched in arsenic (15–25mg\\/kg), and groundwater discharging to the streams contains elevated levels of arsenic (>80?g\\/L at a site on Crosswicks Creek) with

Julia L. Barringer; Adam Mumford; Lily Y. Young; Pamela A. Reilly; Jennifer L. Bonin; Robert Rosman

2010-01-01

69

The IOSDL DEEPSEAS programme: introduction and photographic evidence for the presence and absence of a seasonal input of phytodetritus at contrasting abyssal sites in the northeastern atlantic  

NASA Astrophysics Data System (ADS)

This paper introduces the IOSDL DEEPSEAS programme. Two abyssal sites in the northeast Atlantic with presumed contrasting regimes of organic carbon supply have been studied. One of these sites, on the Porcupine Abyssal Plain (PAP), has an overlying water column with a winter mixed layer in excess of 500 m and was forecast to receive a highly seasonal organic input, a significant portion arriving in the form of rapidly sinking phytodetritus derived from the spring bloom. The winter mixed layer over the second site, on the Madeira Abyssal Plain (MAP), is much shallower, and the resulting flux to the benthos was expected to be quantitatively less and not in the form of aggregated phytodetritus. Recently published sediment-trap results from nearby localities indicate relatively similar total fluxes and widespread seasonality at depth, contrary to our expectations. However, benthic photographic data from the two stations seem to support the original hypothesis, at least in part. Transect photographs (and multiple-corer samples) at the PAP site in August 1989 and May 1991 revealed the presence of phytodetritus on the seafloor, relatively flocculent and evenly distributed in May and more granular and patchily distributed in August. Time-lapse photographs obtained between May 1991 and April 1992 recorded the sudden arrival of phytodetritus on 16 May and a further deposition at the beginning of June. In contrast, at the MAP site neither transect photographs in August 1990 nor time-lapse photographs obtained between August 1990 and July 1991 show evidence of the arrival of aggregated phytodetritus.

Rice, A. L.; Thurston, M. H.; Bett, B. J.

1994-09-01

70

Vertical distribution of bacterial communities in high arsenic sediments of Hetao Plain, Inner Mongolia.  

PubMed

Vertical distribution of bacterial communities was detected in high arsenic (As) sediments in a representative high As area in Inner Mongolia. Nineteen sediment samples were collected from a 30 m borehole and detected by geochemistry and molecular ecological approaches including polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE), 16S rRNA gene clone library and 454 pyrosequencing. As contents ranged from 42.1 to 111.3 mg kg(-1) which fluctuated with different depth and significantly high in clay and mild clay sediment samples at depth of 8, 20, 25 and 28 m respectively. The ratios of As(III) to total As generally increased with depth but As(V) dominated in all sediment samples. High concentrations of total As, sulfur, iron and total organic carbon were generally found in clay and low in sand samples. Both DGGE patterns and 454 pyrosequencing results indicated that bacterial communities dynamically diversified with increasing depth and were dominated by Firmicutes, Bacteroidetes, Proteobacteria and Chloroflexi. Most of the sediment samples were dominated by populations including Sporosarcina, Acinetobacter, Pseudomonas, Halomonas, Polaromonas, Paenibacillus and Flavobacterium. These populations were found with high similarities with those microbes capable of denitrification, sulfur oxidation, organic matter degradation and As resistance and reduction. These results implied that microbes might play an important role in As mobilization in the shallow aquifers of Hetao Plain, Inner Mongolia. PMID:25154458

Wang, Yanhong; Li, Ping; Jiang, Dawei; Li, Bing; Dai, Xinyue; Jiang, Zhou; Wang, Yanxin

2014-12-01

71

Linking suspended sediment transport metrics with fish functional traits in the Northwestern Great Plains (Invited)  

NASA Astrophysics Data System (ADS)

Loss of ecological integrity due to excessive suspended sediment in rivers and streams is a major cause of water quality impairment in the United States. Although 32 states have developed numeric criteria for turbidity or suspended solids, or both according to the USEPA (2006), criteria is typically written as a percent exceedance above background and what constitutes background is not well defined. Defining a background level is problematic considering suspended sediments and related turbidity levels change with flow stage and season, and limited scientific data exists on relationships between sediment exposure and biotic response. Current assessment protocols for development of sediment total maximum daily loads (TMDLs) lack a means to link temporally-variable sediment transport rates with specific losses of ecological functions as loads increase. This study, within the in Northwestern Great Plains Ecoregion, co-located 58 USGS gauging stations with existing flow and suspended sediment data, and fish data from federal and state agencies. Suspended sediment concentration (SSC) transport metrics were quantified into exceedance frequencies of a given magnitude, duration as the number of consecutive days a given concentration was equaled or exceeded, dosage as concentration x duration, and mean annual suspended sediment yields. A functional traits-based approach was used to correlate SSC transport metrics with site occurrences of 20 fish traits organized into four main groups: preferred rearing mesohabitat, trophic structure, feeding habits, and spawning behavior. Negative correlations between SSC metrics and trait occurrences were assumed to represent potential conditions for impairment, specifically identifying an ecological loss by functional trait. Potential impairment conditions were linked with presence of the following traits: habitat preferences for stream pool and river shallow waters; feeding generalists, omnivores, piscivores; and several spawning behaviors. Using these results, TMDL targets were proposed such as < 19 mg/l SSC and 1,500 mg/l-day dosage at the 95% recurrence frequency for feeding generalists and omnivores. In general, traits correlated with: 1) a broad range of SSC exceedance frequencies and flow stages, 2) exceedance frequencies near 90-95% occurring at moderate flow stages; and 3) exceedance frequencies near 0.01-10 % occurring during floods. Unstable channels were found to be greater in transported suspended sediment than stable channels over a range of concentration exceedance frequencies, and likely influence physical habitat quality. Pool-preference and gravel spawner traits were greater in stable channels than unstable channels. Overall, a functional traits-based approach utilizing concentration-duration-frequency characteristics of suspended sediment transport was successful in identifying potential “targets” for biological impairment due to excessive sediment, and will aid in developing sediment TMDLs.

Schwartz, J. S.; Simon, A.; Klimetz, L.

2009-12-01

72

Occurrence of arsenic in sediment pore waters in the central Kanto Plain, Japan  

NASA Astrophysics Data System (ADS)

The Kanto Plain is known as the largest plain in Japan, where marine sediments are widely developed because of cyclic iteration of global sea-level changes even 50 km or more inland from the present shoreline. In this area, dependence on groundwater for water requirements is relatively high; in particular, around 40 % of the municipal water supply is dependent on groundwater. Arsenic levels greater than that permitted by the environmental standards of Japan have been detected in groundwater in this area. Therefore, to evaluate occurrences of arsenic and other related elements in pore waters contained in natural sediment layers, we measured the levels of various inorganic chemical substances such as arsenic (As), iron (Fe), and sulfur (S) and major dissolved ions such as sulfate (SO42-), calcium (Ca2+), and sodium (Na+). Pore waters were collected from sediment samples that were obtained by a drilling from the river bottom down to 44 m depth; pore water samples were obtained immediately after extraction of sediments. The sedimentary facies in the vertical profile are continental, transitional, and marine, including two aquifers. The upper aquifer (15-20 m) contains fine to medium sand, whereas the lower aquifer (37-44 m) contains medium to coarse and gravelly sand. Arsenic and other inorganic elements were measured by an inductively coupled plasma mass spectrometer (ICP/MS) and an inductively coupled plasma atomic emission spectrometer (ICP/AES), and major dissolved ions were measured by an ion chromatograph analyzer. The total content of chemical elements was measured by X-ray fluorescence analysis using solid sediment samples. We obtained the following results. The arsenic concentrations in pore waters in marine silt and clay sediments (approximately 0.04 mg/L) were about five times higher than that in continental sediments (approximately 0.008 mg/L). The highest concentration of arsenic (0.074 mg/L) was detected at a depth of 13 m, which is immediately above the upper aquifer. Visual observations confirmed that this level is under oxidizing conditions. Thus, it regards that arsenic was adsorbed to iron hydroxide in the sediments. On the other hand, in the top part of the section, from the river bottom to a depth of approximately 3 m, arsenic concentrations in the pore waters were clearly high and decreased gradually and continuously with depth. This is considered to be the result of anthropogenic impact on the river.

Hachinohe, Shoichi; Hamamoto, Hideki; Ishiyama, Takashi; Hossain, Sushmita; Oguchi, Chiaki T.

2014-05-01

73

Sedimentation along the Eastern Chenier Plain Coast: Down Drift Impact of a Delta Complex Shift  

NASA Technical Reports Server (NTRS)

The Mississippi River Chenier Plain is a shore parallel landform (down-drift from the Atchafalaya distributary of the Mississippi River) consisting of an alternating series of transgressive sand-shell ridges and regressive, progradational mudflats. The late 1940s shift of 1/3 of the flow of the Mississippi to the newly developing Atchafalaya delta complex to the west has resulted in injection of the river waters and suspended sediment into the westward flowing currents of the coastal current system. This has reactivated the dormant processes of mud accumulation along this coast. These environmental circumstances have provided the opportunity to: (1) investigate the depositional processes of the prograding, fine grained, mud flat facies of the open Chenier main coast and (2) to test the hypothesis that the impacts of the frequent cold front passages of fall, winter and spring exceed those of the occasional and more localized hurricane in shaping the coast and powering the dominant sedimentary processes. We conducted field investigations with the benefit of multi - scale, time series environmental surveillance by remote sensing systems, including airborne and satellite sensors. These systems provided invaluable new information on areal geomorphic patterns and the behavior of the coastal waters. This is a classic case of weather impacting inner shelf waters and sediments and causing the development of a new landform. It is clear that mud flats of the eastern chenier plain are prograding seaward, as well as progressively growing in a westerly direction.

Huh, Oscar K.; Walker, Nan D.; Moeller, Christopher

2001-01-01

74

Source-To-Sink Perspectives On The Mississippi River System, Miocene To Present, Mountain To Abyss  

NASA Astrophysics Data System (ADS)

. The objective of this study is to present a synthesis of the Mississippi River source-to-sink system, from montane source to abyssal sink, to elucidate specific geomorphic components and boundaries in the system, controls on mass transfer, and resultant geomorphic and statigraphic development. The Mississippi River source-to-sink system constitutes one of the largest sources, conduits, and depocenters of sediment on Earth, extending from elevations of 3.7 km in the Rocky Mountains to the Gulf of Mexico abyssal plain. Despite being one of the most intensely studied fluvial-marine systems in the world, comprehensive understanding and management of the system's resources remain a challenge. The system is valuable in many ways: it provides navigation and water to the heart of North America, and sustains extensive marine fisheries. The river has built a delta that is home to millions of people and yet is subsiding rapidly. Ancestral Mississippi fluvial-marine deposits continue to yield high-value petroleum resources to exploration. To address the range of temporal and spatial scales over which the system has developed and continues to evolve, we will focus on three geological time spans that display contrasting geologic forcing and response: Miocene, Pleistocene, and late Holocene. The present configuration of source, conduit, and sink were established during the Miocene epoch, when tectonics (via the uplifting southern Rockies, and later the rejuvenated Appalachians) and climate (wet in the east and dry in the west) provided abundant water and sediment to prograde the shelf margin and initiate deep-sea fan growth. Pleistocene continental glaciation, eustasy, and catastrophic drainage events further sculpted the alluvial valley, and extended the shelf margin, and fan. Studies of Modern processes and Holocene delta development have provided keys to both the delta's past and future evolution, in terms of cyclic autogenic lobe-switching, mass-transport events, storm-driven sediment delivery to canyon heads, and allogenic/anthropogenic controls on sediment supply and subsidence.

Bentley, S. J.; Blum, M. D.

2013-12-01

75

Sediment-Basalt Architecture, Pliocene and Pleistocene Eastern and Central Snake River Plain  

NASA Astrophysics Data System (ADS)

This presentation is a synthesis of known stratigraphic studies of the Pliocene, Pleistocene and Holocene basalts and interbedded sedimentary beds on the Eastern Snake River Plain (ESRP). This information is important for understanding the post-caldera tectonic evolution of the ESRP, especially for tracking patterns of volcanic eruption and changes in topography. Geophysical surveys and existing well logs indicate the depth of the basalt sequence is usually 2 km or less, even near the axis of the Plain. An alteration horizon, the product of high heat-flow in the wake of the Yellowstone hot spot, moderated by cold-water recharge in the thick and highly-transmissive Snake River Aquifer, has variable depth. The surface and near-surface of the lava fields are mainly basalts less than a half a million years old, from Island Park to Twin Falls/Shoshone. Near the junction of the Eastern and Western Snake River Plains, these youngest late Pleistocene basalts, many less than 100,000 years old, overlie early Pleistocene basalts more than a million and a half years old. Most basalt flows have been erupted from NW-trending volcanic rift zones like the Great Rift of Idaho or from the Axial Volcanic High (AVH). The AVH is a constructional axial ridge formed by multiple volcanic vents, small shield volcanoes and rhyolitic domes which run the length of the ESRP. A combination of previous and new stratigraphic and geochronology studies, including U-Pb detrital-zircon geochronology on sediments, reveals several lake sequences, formed by the damming of rivers. These tend to be thickest in upstream, valley-mouth, and Plain-marginal locations where the rivers were trapped. The lake beds generally pinch out toward the AVH. The most notable of these are the Mid-Pleistocene Raft Formation, the Late Pleistocene American Falls Lake Beds, at least two mid-Pleistocene sequences of ponded sediment from the Big Lost River at its egress onto the ESRP, and a 2.5 to 1.6 Ma sequence in the Big Lost Trough (BLT). Argon-argon dating of intercalated basalts demonstrates that the Big Lost River was trapped in the BLT starting about ~2Ma. Egress was blocked by the AVH to the southeast and by constructional volcanic rift zones to the southwest. Channel deposits of the ancestral Big Lost River are present in well logs, with one 20 m thick sequence traceable to the southwest under the Craters of the Moon National Monument (COM) between 1430 and 1380 m MSL. Other lake sequences in the ESRP subsurface include two mid-Pleistocene 30 to 50m thick sequences of clayey sediments in the BLT, near the southeast corner of the Idaho National Laboratory at ~250 to ~300 m depths. Two other fine-grained sediment sequences of unknown age are found at similar depths south of COM. Lake Terreton and its predecessors can be traced from Howe to Menan in the northeastern ESRP. Fluvial sediments here are coarse-grained gravels and sands of the Snake River, exposed near Blackfoot and logged in many well logs. Other notable fluvial sediments include the southwest-trending channel deposits and the two previously-mentioned clay sequences south of COM may prove to be parts of a paleo-Big Lost River that flowed to the southwest before 2 Ma.

Helm-Clark, C. M.; Link, P. K.

2006-12-01

76

Sediment distribution, hydrolytic enzyme profiles and bacterial activities in the guts of Oneirophanta mutabilis, Psychropotes longicauda and Pseudostichopus villosus: what do they tell us about digestive strategies of abyssal holothurians?  

NASA Astrophysics Data System (ADS)

This paper describes inter-specific differences in the distribution of sediment in the gut compartments and in the enzyme and bacterial profiles along the gut of abyssal holothurian species - Oneirophanta mutabilis, Psychropotes longicauda and Pseudostichopus villosus sampled from a eutrophic site in the NE Atlantic at different times of the year. Proportions of sediments, relative to total gut contents, in the pharynx, oesophagus, anterior and posterior intestine differed significantly in all the inter-species comparisons, but not between inter-seasonal comparisons. Significant differences were also found between the relative proportions of sediments in both the rectum and cloaca of Psychropotes longicauda and Oneirophanta mutabilis. Nineteen enzymes were identified in either gut-tissue or gut-content samples of the holothurians studied. Concentrations of the enzymes in gut tissues and their contents were highly correlated. Greater concentrations of the enzymes were found in the gut tissues suggesting that they are the main source of the enzymes. The suites of enzymes recorded were broadly similar in each of the species sampled collected regardless of the time of the year, and they were similar to those described previously for shallow-water holothurians. Significant inter-specific differences in the gut tissue concentrations of some of the glycosidases suggest dietary differences. For example, Psychropotes longicauda and Pseudostichopus villosus contain higher levels of chitobiase than Oneirophanta mutabilis. There were no seasonal changes in bacterial activity profiles along the guts of O. mutabilis and Pseudostichopus villosus. In both these species bacterial activity and abundance declined between the pharynx/oesophagus and anterior intestine, but then increased along the gut and became greatest in the rectum/cloaca. Although the data sets were more limited for Psychropotes longicauda, bacterial activity increased from the anterior to the posterior intestine but then declined slightly to the rectum/cloaca. These changes in bacterial activity and densities probably reflect changes in the microbial environment along the guts of abyssal holothurians. Such changes suggest that there is potential for microbial breakdown of a broader range of substrates than could be otherwise be achieved by the holothurian itself. However, the present study found no evidence for sedimentary (microbial) sources of hydrolytic enzymes.

Roberts, D.; Moore, H. M.; Berges, J.; Patching, J. W.; Carton, M. W.; Eardly, D. F.

77

Geochemical Fractionations and Mobility of Arsenic, Lead and Cadmium in Sediments of the Kanto Plain, Japan.  

NASA Astrophysics Data System (ADS)

Lowland alluvial and floodplain sediment play a major role in transferring heavy metals and other elements to groundwater through sediment water interaction in changing environmental conditions. However identification of geochemical forms of toxic elements such as arsenic (As), lead (Pb) and cadmium (Cd) requires risk assessment of sediment and subsequent groundwater pollution. A four steps sequential extraction procedure was applied to characterize the geochemical fractionations of As, Pb and Cd for 44 sediment samples including one peat sample from middle basin area of the Nakagawa river in the central Kanto plain. The studied sediment profile extended from the bottom of the river to 44 m depth; sediment samples were collected at 1m intervals from a bored core. The existing sedimentary facies in vertical profile are continental, transitional and marine. There are two aquifers in vertical profile; the upper aquifer (15-20m) contains fine to medium sand whereas medium to coarse sand and gravelly sand contain in lower aquifer (37-44m). The total As and Pb contents were measured by the X-Ray Fluorescence analysis which ranged from 4 to 23 mg/kg of As and 10 to 27 mg/kg of Pb in sediment profile. The three trace elements and major heavy metals were determined by ICP/MS and ICP/AES, and major ions were measured by an ion chromatograph. The marine sediment is mainly Ca-SO4 type. The Geochemical analysis showed the order of mobility trends to be As > Pb > Cd for all the steps. The geochemical fractionations order was determined to be Fe-Mn oxide bound > carbonate bound > ion exchangeable > water soluble for As and Pb whereas the order for Cd is carbonate bound > Fe-Mn oxide bound > ion exchangeable > water soluble. The mobility tendency of Pb and Cd showed high in fine silty sediment of marine environment than for those from continental and transitional environments. In the case of As, the potential mobility is very high (>60%) in the riverbed sediments and clayey silt sediment at 13m depth which is just above the upper aquifer. This potential mobility may pose a threat to upper aquifer and riverbed aquatic system. The overall geochemical analysis revealed that the dissolution of Fe-Mn oxide is the most effective mechanism for As, Pb in groundwater however the mobility of Cd is mainly carbonate bound. In the present study, the pollution level is much below from leaching environmental standards (0.01 mg/L) for all three elements and the total content is within the natural abundance of As, Pb and Cd in sediment. The potential mobility of these elements in oxidized fine silty sediment and the possible further effect to the aquifer suggest that shallow groundwater abstraction should be restricted to protect seasonal groundwater fluctuation. Moreover marine sediment containing high total toxic element contents and mobility tendency at changing oxidation and reduction environments requires proper management when sediments are excavated for construction purpose.

Hossain, Sushmita; Oguchi, Chiaki T.; Hachinohe, Shoichi; Ishiyama, Takashi; Hamamoto, Hideki

2014-05-01

78

Organochlorine Pesticide Concentrations in Sediment and Amphibian Tissue in Playa Wetlands in the Southern High Plains, USA  

Microsoft Academic Search

Playa wetlands are critical habitat for wildlife in the Southern High Plains (SHP), a region dominated by agriculture. Little\\u000a information on pesticide levels exists for playas, and thus we measured organochlorine pesticide concentrations in sediment\\u000a and amphibians collected from playas in cropland and grassland watersheds. Heptachlor, ?- and ?-BHC, ?-chlordane, and dieldrin\\u000a were detected in sediment and\\/or tissue samples, typically

Louise S. Venne; Todd A. Anderson; Baohong Zhang; Loren M. Smith; Scott T. McMurry

2008-01-01

79

Is long-term change in the abyssal Northeast Atlantic driven by qualitative changes in export flux? Evidence from selective feeding in deep-sea holothurians  

NASA Astrophysics Data System (ADS)

The Porcupine Abyssal Plain (NE Atlantic) time-series has shown large, wide-scale, changes in the composition of the benthic community at 4800 m depth (48°50?N, 16°30?W). The abundance of holothurians has increased significantly since 1996 and one species in particular, Amperimarosea, has increased in abundance by three orders of magnitude. Environmental forcing in the form of phytodetrital food supply to the benthos is believed to be driving these changes. Chlorophyll and carotenoid pigments were determined from the gut sediments of seven species of abyssal holothurian, sampled from the Porcupine Abyssal Plain during Autumn 2000 and Spring 2002. These two samples fell either side of the main phytoplankton bloom in the NE Atlantic, providing an opportunity for seasonal comparisons. Significant inter-species differences in pigment profiles were observed among the seven species. Seasonal differences were noted among four species sampled in both time periods. All seven species were collected from the same geographical area and depth. As algal pigments cannot be synthesised by the holothurians, they provide good biomarkers for the composition of the phytodetritus. Differences in pigments from gut sediment profiles are indicative of selective feeding among the holothurians. A.rosea had a gut profile dominated by the pigments zeaxanthin, chlorophyll a/echineone and ?-carotene; these pigments were all present in significantly smaller quantities in the other species. The high quantities of these pigments are indicative of a diet rich in cyanobacteria. The gut sediments of A. rosea also lacked many chloropigments characteristic of other phytoplankton groups, which were observed in the guts of other holothurian species. Ovarian tissue for the five species taken in the pre-spring bloom 2002 sample were examined. All species showed similar carotenoid profiles, dominated by zeaxanthin, echinenone and ?-carotene, all of which are important compounds for reproductive success in echinoderms. The differences in gut pigment profiles highlight the potential for several species of deposit-feeding holothurians to partition the same phytodetrital food source, possibly providing a mechanism for maintaining the high diversity of deposit feeders at abyssal depths. The dominance of reproductively important carotenoids in the guts and gonads of A. rosea may highlight the ability of this species to rapidly utilise any change in the composition of the phytodetrital flux and translate that advantage into a successful reproductive and recruitment event. The results are discussed in relation to work on bathyal holothurians and the potential for food-driven regime shifts in both the abyssal and bathyal Northeast Atlantic.

Wigham, in deep-sea holothurians [review article] B. D.; Hudson, I. R.; Billett, D. S. M.; Wolff, G. A.

2003-12-01

80

Rates of overbank sedimentation on the flood plains of several British rivers during the past 100 years  

Microsoft Academic Search

The flood plains of lowland rivers frequently represent important sinks for suspended sediment transported through the river system. However, little is currently known about rates of overbank deposition by British rivers and, more particularly, whether such rates have increased in recent years in response to land use change. The fallout radionuclides 137Cs and 210Pb off ;r considerable potential for estimating

D. E. WALLING; Q. HE

81

Cadmium and associated metals in soils and sediments of wetlands across the Northern Plains, USA.  

PubMed

Cadmium, present locally in naturally high concentrations in the Northern Plains of the United States, is of concern because of its toxicity, carcinogenic properties, and potential for trophic transfer. Reports of natural concentrations in soils are dominated by dryland soils with agricultural land uses, but much less is known about cadmium in wetlands. Four wetland categories - prairie potholes, shallow lakes, riparian wetlands, and river sediments - were sampled comprising more than 300 wetlands across four states, the majority in North Dakota. Cd, Zn, P, and other elements were analyzed by ICP-MS, in addition to pH and organic matter (as loss-on-ignition). The overall cadmium content was similar to the general concentrations in the area's soils, but distinct patterns occurred within categories. Cd in wetland soils is associated with underlying geology and hydrology, but also strongly with concentrations of P and Zn, suggesting a link with agricultural land use surrounding the wetlands. PMID:23583941

Jacob, Donna L; Yellick, Alex H; Kissoon, La Toya T; Asgary, Aida; Wijeyaratne, Dimuthu N; Saini-Eidukat, Bernhardt; Otte, Marinus L

2013-07-01

82

Thermal, chemical, and mass-transport processes induced in abyssal sediments by the emplacement of nuclear waste: experimental and modeling results  

SciTech Connect

This paper discusses heat and mass transport studies of marine red clay sediments being considered as a nuclear waste isolation medium. Numerical models indicate that for a maximum allowable sediment/canister interface temperature of 200 to 250/sup 0/C, the sediment can absorb about 1.5 kW initial power from waste in a 3 m long by 0.3 m dia canister buried 30 m in the sediment. Fluid displacement due to convection is found to be less than 1 m. Laboratory studies of the geochemical effects induced by heating sediment/seawater mixtures indicate that the canister and waste form must be designed to resist a hot, acid (pH 3 to 4) oxidizing environment. Since the thermally altered sediment volume of about 5.5 m/sup 3/ is small relative to the sediment volume overlying the canister, the acid and oxidizing conditions are not anticipated to effect the properties of the far field. Using sorption coefficient correlations, the migration of four nuclides /sup 239/Pu, /sup 137/Cs, /sup 129/I, and /sup 99/Tc were computer for a canister buried 30 m deep in a 60 m thick red clay sediment layer. It was found that the /sup 239/Pu and /sup 137/Cs are essentially completely contained in the sediments, while /sup 129/I and /sup 99/Tc broke through the 30 m of sediment in about 5000 years. The resultant peak injection rates of 4.6 x 10/sup -5/ ..mu..Ci/year-m/sup 2/ for /sup 129/I and 1.6 x 10/sup -2/ ..mu..Ci/year-m/sup 2/ for /sup 99/Tc were less than the natural radioactive flux of /sup 226/Ra (3.5 to 8.8 x 10/sup -4/ ..mu..Ci/year-m/sup 2/) and /sup 222/Rn (0.26 to 0.88 ..mu..Ci/year-m/sup 2/).

McVey, D.F.; Erickson, K.L.; Seyfried, W.

1980-01-01

83

Ocean floor sediment as a repository barrier: comparative diffusion data for selected radionuclides in sediments from the Atlantic and Pacific Oceans  

SciTech Connect

Effective diffusion coefficients for selected radionuclides have been measured in ocean floor sediments to provide data for the assessment of barrier effectiveness in subseabed repositories for nuclear waste. The sediments tested include illite-rich and smectite-rich red clays from the mid plate gyre region of the Pacific Ocean, reducing sediment from the continental shelf of the northwest coast of North America, and Atlantic Ocean sediments from the Southern Nares Abyssal Plain and the Great Meteor East region. Results show extremely small effective diffusion coefficients with values less than 10/sup -14/ m/sup 2/s/sup -1/ for plutonium, americium, curium, thorium, and tin. Radionuclides with high diffusion coefficients of approximately 10/sup -10/ m/sup 2/s/sup -/ include the anionic species pertechnetate, TcO/sub 4//sup -/, iodide, I/sup -/, and selenite, SO/sub 3//sup -2/. Uranyl(VI) and neptunyl(V) ions, which are stable in solution, have diffusion coefficients around 10/sup -12/m/sup 2/s/sup -1/. The diffusion behavior of most radionuclides is similar in the oxygenated Pacific sediments and in the anoxic sediments from the Atlantic. An exception is neptunium, which is immobilized by Great Meteor East sediment, but has high mobility in Southern Nares Abyssal Plain sediment. Under stagnant conditions a 30 m thick sediment layer forms an effective geologic barrier isolating radionuclides in a subseabed repository from the biosphere.

Schreiner, F.; Sabau, C.; Friedman, A.; Fried, S.

1986-01-01

84

Extension controls Quaternary tectonics, geomorphology and sedimentation of the N-Appennies foothills and adjacent Po Plain (Italy)  

Microsoft Academic Search

In the middle Pleistocene, thrusting in the N-Apennine fold-and-thrust belt came to an end and foredeep sedimentation in the adjacent Po Plain basin ceased. A new tectono-sedimentary regime was installed. Extensional faults were activated in the foothills and are limited to the northeast by a major, SW-dipping normal fault, the Bologna fault for which a vertical displacement of >1000 m

G. V. Bertotti; R. Capozzi; V. Picotti

1997-01-01

85

Heavy Metals in Freshly Deposited Stream Sediments of Rivers Associated with Urbanisation of the Ganga Plain, India  

Microsoft Academic Search

Freshly deposited stream sediments from six urban centres of the Ganga Plain were collected and analysed for heavy metals\\u000a to obtain a general scenery of sediment quality. The concentrations of heavy metals varied within a wide range for Cr (115–817),\\u000a Mn (440–1 750), Fe (28 700–61 100), Co (11.7–29.0), Ni (35–538), Cu (33–1 204), Zn (90–1 974), Pb (14–856) and

Munendra Singh; German Müller; I. B. Singh

2002-01-01

86

Transparent layers in seismic reflection records from the central Ionian Sea (Mediterranean)—evidence for repeated catastrophic turbidite sedimentation during the Quaternary  

NASA Astrophysics Data System (ADS)

Echosounding and SCS records from the Ionian and Sirte Abyssal Plains show, below the Holocene Augias megaturbidite, two additional thick transparent layers which by analogy are interpreted as turbidites. Estimated thicknesses are 10 and 35 m (upper and lower) as a minimum (no consideration of presumable variations of acoustic velocities). The resulting sediment volumes are about 26 and about 200 km 3, respectively. Both layers occupy the entire abyssal plain basins similar to the Holocene Augias megaturbidite. A provenance of mobilized sediments from the Gulf of Sirte into the basins is assumed. The ages of the two turbidites have been estimated at 235,000 and 650,000 years, respectively. It is speculated that mobilization was triggered by tsunamis related to volcanic events or earthquakes in the southern Aegean region.

Hieke, W.

2000-09-01

87

Runoff and sediment responses to grazing native and introduced species on highly erodible Southern Great Plains soil  

NASA Astrophysics Data System (ADS)

SummaryOld World Bluestems, such as yellow bluestem (Bothriochloa ischaemum), have been seeded extensively in the Southern Great Plains because they are responsive to nitrogen fertilization and allow for higher stocking rates. From 1991 to 2005, we measured the effects of moderately grazing prairie species and heavily grazing fertilized yellow bluestem on runoff, sediment yield, leaf litter cover, and aboveground plant biomass for four adjacent watersheds located at the USDA-ARS Southern Plains Range Research Station in the sub-humid Rolling Red Plains of western Oklahoma. Here we show that factors other than leaf litter cover and biomass determine variation in runoff when leaf litter exceeds 70%. Runoff was related to grazing rate and storm size and inversely related to storm duration. Rainfall thresholds were similar between the moderately grazed prairie watersheds (15 mm) and the heavily grazed yellow bluestem watersheds (18 mm); however, the slope of the rainfall-runoff curve from heavily grazed yellow bluestem (0.242) was steeper than that of moderately grazed prairie (0.087). Slightly higher runoff from heavily grazed yellow bluestem relative to moderately grazed prairie may occur due to compaction of both the leaf litter and topsoil. Sediment yield was low from moderately grazed native prairie and heavily grazed yellow bluestem. Our findings indicate that both treatments assessed appear hydrologically sustainable.

Wine, Michael L.; Zou, Chris B.; Bradford, James A.; Gunter, Stacey A.

2012-07-01

88

Truncation and accretion of soil profiles on coastal plain croplands: implications for sediment redistribution  

NASA Astrophysics Data System (ADS)

Soil stratigraphy and morphology in a small agricultural watershed on the coastal plain at Clayroot, North Carolina, indicate long-term, decadal-scale patterns of the redistribution of sediment. The most dramatic truncation of the soil profile occurs on convex upper slopes, and suggests tillage and aeolian erosion as the major processes of soil loss. Thicker soils immediately downslope from convexities are consistent with redistribution by tillage, but significant aeolian soil loss also occurs from some fields. Thinner, apparently truncated soils were also associated with relatively steeper lower slope areas where contemporary rilling was observed. The presence of thicker, cumulic soils at toeslopes where small fans are observed at rill termini and about a half meter of alluvium in drainage ditches indicates that water erosion is also quite prominent. Distinctive soil stratigraphy is found in areas of aeolian deposition, where podzolization in sandy surface deposits has created compound soil profiles. On convex slopes, tillage and wind erosion result in net soil loss, with the former dominating on wetter soils and when plowing occurs, and aeolian processes dominating on drier hilltops and when no-till or minimum tillage practices are followed. Soils are thicker immediately downslope from convexities, with thinner soils and rill erosion on lower slopes. Thickened soils and colluvial deposition in the form of thin fan deposits occur at toeslopes and in depressions. The borders of fields often have thicker soils because of aeolian deposition. Water, wind, and tillage processes are all significant in soil redistribution at the Clayroot site, with relative importance in space and time controlled by topography, soil properties, seasonal moisture and vegetative cover, and tillage practices.

Phillips, Jonathan D.; Slattery, Michael C.; Gares, Paul A.

1999-05-01

89

Productivity of Ephemeral Headwater Riparian Forests Impacted by Sedimentation in the Southeastern United States Coastal Plain  

Microsoft Academic Search

ltering of sediments and nutrients from surface runoff . However, little is known about the impact of sediment deposition on productivity of riparian forests. Sediment inputs may act as a subsidy to forest productivity by providing additional nutrients for plant uptake or may act as a stress by creating anoxic soil conditions. Th is study determined how sediment deposition aff

Rachel L. Jolley; B. Graeme Lockaby; Guadalupe G. Cavalcanti

2009-01-01

90

Use of U-series nuclides to constrain sediments transfer-times in the alluvial plains: example of the Ganges and Bramaputra river system.  

NASA Astrophysics Data System (ADS)

U-series nuclides have the potential to bring important information on the transfer time of sediments in the alluvial plains. This is a consequence of the dual property of these nuclides 1) to be fractionated during physical denudation and chemical weathering processes and 2) to have radioactive decay periods of the same order of magnitude as the time-scales of these processes (e.g. Chabaux et al., 2003b, 2008). We have illustrated such a potential with the analysis of U-series disequilibria in sediments collected in the Ganges and Bramaputra river basin. The approach relies on the analysis of U-series in river sediments collected along the streams. Indeed, as illustrated in Granet et al. (2007), in large alluvial plains where sediments are only transferred and not affected by additional inputs of new weathering products from fresh rocks, the intensity of 238U-234U-230Th disequilibria in river sediments will only depend on two parameters: (a) the duration of the transfer including the time spent in soils and in the river, and (b) the nature and the intensity of U-Th fractionations occurring in sediments during their transfer into alluvial plains. Recovering time information from the variation of U-Th disequilibria in such sediments requires therefore the use of realistic models accounting for the U-Th fractionation of sediments during their transfers into the plain. From the data, it is proposed for the Ganges and Bramaputra river sediments, that the main U-Th fractionation process is connected with the sediment weathering during their transit and storage in the plain. In this case the U-Th variation in sediments along the two main rivers lead to quite long sediment transfer time in the alluvial plains, of 100-150 ky for Bramaputra plain and of 400 or 500 ky for the Ganges river. Chabaux F., Riotte J., Dequincey O. (2003) U-Th-Ra fractionation during weathering and river transport, Rev Mineral. Geochem. 52, 533-576. Chabaux, F., Bourdon, B., Riotte, J., 2008. U-series Geochemistry in weathering profiles, river waters and lakes. In : S. Krishnaswami and J.K. Cochran (Eds.), U/Th Series Radionuclides in Aquatic Systems, Elsevier, Radioactivity in the Environment, 13, 49-104 M. Granet, F. Chabaux, C. France-Lanord, P. Stille, E. Pelt (2007). Time-scales of sedimentary transfer and weathering processes from U-series nuclides: Clues from the Himalayan rivers, Earth and Planetary Science Letters, 261, 389-406.

Chabaux, François; Granet, Mathieu; Blaes, Estelle; Stille, Peter; France-Lanord, Christian; Dosseto, Antony

2010-05-01

91

Late Hesperian plains formation and degradation in a low sedimentation zone of the northern lowlands of Mars  

NASA Astrophysics Data System (ADS)

The plains materials that form the martian northern lowlands suggest large-scale sedimentation in this part of the planet. The general view is that these sedimentary materials were transported from zones of highland erosion via outflow channels and other fluvial systems. The study region, the northern circum-polar plains south of Gemini Scopuli on Planum Boreum, comprises the only extensive zone in the martian northern lowlands that does not include sub-basin floors nor is downstream from outflow channel systems. Therefore, within this zone, the ponding of fluids and fluidized sediments associated with outflow channel discharges is less likely to have taken place relative to sub-basin areas that form the other northern circum-polar plains surrounding Planum Boreum. Our findings indicate that during the Late Hesperian sedimentary deposits produced by the erosion of an ancient cratered landscape, as well as via sedimentary volcanism, were regionally emplaced to form extensive plains materials within the study region. The distribution and magnitude of surface degradation suggest that groundwater emergence from an aquifer that extended from the Arabia Terra cratered highlands to the northern lowlands took place non-catastrophically and regionally within the study region through faulted upper crustal materials. In our model the margin of the Utopia basin adjacent to the study region may have acted as a boundary to this aquifer. Partial destruction and dehydration of these Late Hesperian plains, perhaps induced by high thermal anomalies resulting from the low thermal conductivity of these materials, led to the formation of extensive knobby fields and pedestal craters. During the Early Amazonian, the rates of regional resurfacing within the study region decreased significantly; perhaps because the knobby ridges forming the eroded impact crater rims and contractional ridges consisted of thermally conductive indurated materials, thereby inducing freezing of the tectonically controlled waterways associated with these features. This hypothesis would explain why these features were not completely destroyed. During the Late Amazonian, high-obliquity conditions may have led to the removal of large volumes of volatiles and sediments being eroded from Planum Boreum, which then may have been re-deposited as thick, circum-polar plains. Transition into low obliquity ˜5 myr ago may have led to progressive destabilization of these materials leading to collapse and pedestal crater formation. Our model does not contraindicate possible large-scale ponding of fluids in the northern lowlands, such as for example the formation of water and/or mud oceans. In fact, it provides a complementary mechanism involving large-scale groundwater discharges within the northern lowlands for the emplacement of fluids and sediments, which could have potentially contributed to the formation of these bodies. Nevertheless, our model would spatially restrict to surrounding parts of the northern plain either the distribution of the oceans or the zones within these where significant sedimentary accumulation would have taken place.

Rodríguez, José Alexis Palmero; Tanaka, Kenneth L.; Berman, Daniel C.; Kargel, Jeffrey S.

2010-11-01

92

Invertebrate colonization of leaves and roots within sediments of intermittent coastal plain streams across hydrologic phases  

EPA Science Inventory

We compared benthic invertebrate assemblages colonizing three types of buried substrates (leaves, roots and plastic roots) among three intermittent Coastal Plain streams over a one year period. Invertebrate density was significantly lower in root litterbags than in plastic root l...

93

Arsenic in sediments, groundwater, and streamwater of a glauconitic Coastal Plain terrain, New Jersey, USA—Chemical “fingerprints” for geogenic and anthropogenic sources  

Microsoft Academic Search

Glauconite-bearing deposits are found worldwide, but As levels have been determined for relatively few. The As content of glauconites in sediments of the Inner Coastal Plain of New Jersey can exceed 100mg\\/kg, and total As concentrations (up to 5.95?g\\/L) found historically and recently in streamwaters exceed the State standard. In a major watershed of the Inner Coastal Plain, chemical “fingerprints”

Julia L. Barringer; Pamela A. Reilly; Dennis D. Eberl; Alex E. Blum; Jennifer L. Bonin; Robert Rosman; Barbara Hirst; Marzooq Alebus; Kimberly Cenno; Miroslawa Gorska

2011-01-01

94

Pathways for arsenic from sediments to groundwater to streams: Biogeochemical processes in the Inner Coastal Plain, New Jersey, USA  

USGS Publications Warehouse

The Cretaceous and Tertiary sediments that underlie the Inner Coastal Plain of New Jersey contain the arsenic-rich mineral glauconite. Streambed sediments in two Inner Coastal Plain streams (Crosswicks and Raccoon Creeks) that traverse these glauconitic deposits are enriched in arsenic (15–25 mg/kg), and groundwater discharging to the streams contains elevated levels of arsenic (>80 ?g/L at a site on Crosswicks Creek) with arsenite generally the dominant species. Low dissolved oxygen, low or undetectable levels of nitrate and sulfate, detectable sulfide concentrations, and high concentrations of iron and dissolved organic carbon (DOC) in the groundwater indicate that reducing environments are present beneath the streambeds and that microbial activity, fueled by the DOC, is involved in releasing arsenic and iron from the geologic materials. In groundwater with the highest arsenic concentrations at Crosswicks Creek, arsenic respiratory reductase gene (arrA) indicated the presence of arsenic-reducing microbes. From extracted DNA, 16s rRNA gene sequences indicate the microbial community may include arsenic-reducing bacteria that have not yet been described. Once in the stream, iron is oxidized and precipitates as hydroxide coatings on the sediments. Arsenite also is oxidized and co-precipitates with or is sorbed to the iron hydroxides. Consequently, dissolved arsenic concentrations are lower in streamwater than in the groundwater, but the arsenic contributed by groundwater becomes part of the arsenic load in the stream when sediments are suspended during high flow. A strong positive relation between concentrations of arsenic and DOC in the groundwater samples indicates that any process—natural or anthropogenic—that increases the organic carbon concentration in the groundwater could stimulate microbial activity and thus increase the amount of arsenic that is released from the geologic materials.

Barringer, Julia L.; Mumford, Adam; Young, Lily Y.; Reilly, Pamela A.; Bonin, Jennifer L.; Rosman, Robert

2010-01-01

95

Sediment sources and sedimentation processes of 2011 Tohoku-oki tsunami deposits on the Sendai Plain, Japan — Insights from diatoms, nannoliths and grain size distribution  

NASA Astrophysics Data System (ADS)

The 11th March 2011 Tohoku-oki tsunami inundated the low-lying Sendai Plain (Japan) more than 5 km inland leaving sand and mud deposits over most of the area. In order to establish the sources of the tsunami deposits and interpret processes of their sedimentation, samples were collected from the deposits, underlying soils and the beach along a shore-perpendicular transect and analysed for grain size, diatom assemblages and nannoliths. The fining-inland tsunami deposits consisted of poorly to moderately sorted medium to coarse sand within 2 km of the coastline and very poorly to poorly sorted mud farther inland. More specifically, there was a slight fining of the coarse to medium sand mode within the sandy deposits and an increased contribution of the coarse and very coarse silt fraction in the mud deposits. The tsunami deposits also exhibited vertical changes including fining upward and coupled coarsening-fining upward trends. Few diatoms were present in beach sediments, soils and tsunami deposits within 1 km of the coastline, while diatoms were more abundant farther inland. Diatom assemblages in the soil and tsunami deposits were similar and dominated by species typical of freshwater-brackish habitats, while no typically marine species were encountered. Nannoliths were generally absent in the studied sediments, except for few specimens. Our data indicate that there was probably no or only a very minor component of marine sediments transported onland by the tsunami. The sandy tsunami deposits within ~ 1 km of the coastline were mostly derived from beach and dune erosion. From 1 to 2 km landward the contribution of these sources decreased, while sources comprising local soil erosion and the entrainment of sediments from the Teizan-bori canal increased. Farther inland, local soil erosion was the major sediment source for the mud deposits. The tsunami deposits were most likely deposited during at least two inundations, mostly out from suspension resulting in an upward grain size fining trend. However, bed load deposition was also important in the sandy deposits as suggested by a common grain size upward coarsening, position on C-M diagrams and frequent horizontal lamination. The present study reveals that even very large tsunamis may not transport marine sediments onland and thus many commonly applied indicators of tsunami deposits based on the assumption of their offshore origin (marine diatoms, foraminifera, nannoliths, marine sediments) may be of limited use.

Szczuci?ski, Witold; Kokoci?ski, Miko?aj; Rzeszewski, Micha?; Chagué-Goff, Catherine; Cachão, Mario; Goto, Kazuhisa; Sugawara, Daisuke

2012-12-01

96

Seasonal controls on sediment delivery in a small coastal plain watershed, North Carolina, USA  

E-print Network

variations in crop coverage and vegetation in drainage ditches influence sediment delivery. Following budget and relate seasonal variations in vegetation and the hydrological characteristics of storms to transport significant sediment loads. The maturation of field crops and ditch vegetation in spring produces

Lecce, Scott A.

97

Are Asymmetric Flow Fields Around Kilometer-Scale Topographic Seafloor Elevations Reflected in the Sediment?  

NASA Astrophysics Data System (ADS)

Kilometer-scale topographic seafloor elevations like abyssal hills, knolls and seamounts are ubiquitous and abundant features of the oceanic seafloor. Modeling and field studies in physical oceanography have indicated that there are asymmetric flow fields enfolding such seafloor elevations: On the northern hemisphere the lateral asymmetry in the flow exhibits an accelerated flow to the left of the elevation, looking downstream, and decelerated flow to the right. We expect this asymmetry to affect the near-bottom hydro- and particle dynamics and, thereby, the intensity of sediment deposition. To address the proposed effect on intensity of sediment deposition we assessed the spatial distribution of sedimentary excess 210Pb (210Pbxs) inventories using samples taken from the four major slopes and the summit of an abyssal knoll (rising up to ca 850m above the surrounding abyssal plain) in the NE Atlantic. Reference samples were obtained from an upstream far-field station on the abyssal plain (i.e. located southward as viewed from the knoll) not being profoundly influenced by any topographic elevations. Sediment inventories of 210Pbxs were compared to the expected 210Pb input from the water column. This comparison shows that on the summit and on the western slope 210Pbxs inventories are smaller than expected. There is also some evidence for 210Pbxs inventories on the northern and eastern slopes to be somewhat higher than expected. The spatial 210Pbxs pattern (low deposition on the summit and in the west, higher deposition in the northeast) coincides with the predicted pattern of flow intensity (high on the summit and in the west, lower in the northeast) around the topographic elevation. Other data (e.g. organic carbon, carbonate, uranium contents, grain size distribution) suggest an additional effect of the hydrodynamic asymmetry on the composition of the sedimentary deposit. Given the ubiquity of kilometer-scale topographic seafloor elevations, possible consequences of the described asymmetries for general pattern formation in the deep ocean are discussed.

Turnewitsch, R.; Lahajnar, N.; Thomson, J.; Croudace, I.

2002-12-01

98

Long-term change in the abyssal NE Atlantic: The ‘Amperima Event’ revisited  

NASA Astrophysics Data System (ADS)

The results from a time series study (1989-2005) at a depth of 4850 m on the Porcupine Abyssal Plain, NE Atlantic, are presented, showing radical changes in the density of large invertebrates (megafauna) over time. Major changes occurred in a number of different taxa between 1996 and 1999 and then again in 2002. One species of holothurian, Amperima rosea, was particularly important, increasing in density by over three orders of magnitude. There were no significant changes in total megafaunal biomass during the same period. Peaks in density were correlated to reductions in mean body size, indicating that the increases were related to large-scale recruitment events. The changes occurred over a wide area of the Porcupine Abyssal Plain. Comparisons made with changes in the density of protozoan and metazoan meiofauna, and with macrofauna, showed that major changes in community structure occurred in all size fractions of the benthic community at the same time. This suggests that the faunal changes were driven by environmental factors rather than being stochastic population imbalances of one or two species. Large-scale changes in the flux of organic matter to the abyssal seafloor have been noted in the time series, particularly in 2001, and may be related to the sudden mass occurrence of A. rosea the following year. Time-varying environmental factors are important in influencing the occurrence of megafauna on the abyssal seafloor.

Billett, D. S. M.; Bett, B. J.; Reid, W. D. K.; Boorman, B.; Priede, I. G.

2010-08-01

99

Arsenic in sediments, groundwater, and streamwater of a glauconitic Coastal Plain terrain, New Jersey, USA-Chemical " fingerprints" for geogenic and anthropogenic sources  

USGS Publications Warehouse

Glauconite-bearing deposits are found worldwide, but As levels have been determined for relatively few. The As content of glauconites in sediments of the Inner Coastal Plain of New Jersey can exceed 100mg/kg, and total As concentrations (up to 5.95??g/L) found historically and recently in streamwaters exceed the State standard. In a major watershed of the Inner Coastal Plain, chemical " fingerprints" were developed for streambed sediments and groundwater to identify contributions of As to the watershed from geologic and anthropogenic sources. The fingerprint for streambed sediments, which included Be, Cr, Fe and V, indicated that As was predominantly of geologic origin. High concentrations of dissolved organic C, nutrients (and Cl-) in shallow groundwater indicated anthropogenic inputs that provided an environment where microbial activity released As from minerals to groundwater discharging to the stream. Particulates in streamwater during high flow constituted most of the As load; the chemical patterns for these particulates resembled the geologic fingerprint of the streambed sediments. The As/Cr ratio of these suspended particles likely indicates they derived not only from runoff, but from groundwater inputs, because As contributed by groundwater is sequestered on streambed sediments. Agricultural inputs of As were not clearly identified, although chemical characteristics of some sediments indicated vehicle-related inputs of metals. Sediment sampling during dry and wet years showed that, under differing hydrologic conditions, local anthropogenic fingerprints could be obscured but the geologic fingerprint, indicating glauconitic sediments as an As source, was robust. ?? 2011.

Barringer, J.L.; Reilly, P.A.; Eberl, D.D.; Blum, A.E.; Bonin, J.L.; Rosman, R.; Hirst, B.; Alebus, M.; Cenno, K.; Gorska, M.

2011-01-01

100

Sediment Sources, Sedimentation Processes and Post-Depositional Changes of the 2011 Tohoku-Oki Tsunami Deposits on the Sendai Plain, Japan  

NASA Astrophysics Data System (ADS)

The 11th March 2011 Tohoku-oki tsunami inundated the low-lying Sendai Plain (Japan) more than 5 km inland leaving sand and mud deposits over most of the area. In order to establish the sources of the tsunami deposits and interpret processes of their sedimentation, samples were collected from the deposits, underlying soils and the beach along a shore-perpendicular transect and analysed for grain size, heavy minerals, diatom assemblages and nannoliths. Surveys were undertaken 2, 5 and 7 months after the tsunami to assess the importance of post-depositional changes in tsunami deposits. The last survey took place shortly after a major typhoon. The fining-inland tsunami deposits consisted of poorly to moderately sorted medium to coarse sand within 2 km of the coastline and very poorly to poorly sorted mud farther inland. The tsunami deposits also exhibited vertical changes including fining upward and coupled coarsening-fining upward trends. Heavy minerals comprised on average 35% of the tsunami deposit in the 0.125 - 0.25 mm grain size fraction. Heavy mineral concentrations and assemblages were similar in the tsunami deposits, beach and underlying soils. Diatoms were rare in beach sediments, soils and tsunami deposits within 1 km of the coastline, while they were more abundant farther inland. Diatom assemblages in the soil and tsunami deposits were similar and dominated by species typical of freshwater-brackish habitats, while no typically marine species were encountered. Nannoliths were generally absent in the studied sediments, except for few specimens. Our data indicate that there was probably no or only a very minor component of marine sediments transported onland by the tsunami. The sandy tsunami deposits within ~1 km of the coastline were mostly derived from beach and dune erosion. From 1 to 2 km landward the contribution of these sources decreased, while sources comprising local soil and inland canal sediments increased. Farther inland, mud deposits were mostly derived from local soil erosion. The tsunami deposits were most likely deposited during at least two inundations, mostly from suspension resulting in an upward grain size fining trend. However, bed load deposition was also important in the sandy deposits. The tsunami deposits were generally well preserved after 2 months but sandy sediments in exposed areas were redeposited by wind action. After 7 months, preservation was still good. On the coastal dune slopes there was limited redeposition of sediment by flowing water. Plant recolonisation was slow. The surface of the tsunami deposits was commonly stabilised by an algal mat cover. In places where the deposits were thinner than 1 cm their visual discrimination from the underlying soil was problematic, however, the deposits were still relatively well preserved for about 80% of their original extent. The study reveals that even very large tsunamis may not transport marine sediments onland and thus many commonly applied indicators of tsunami deposits based on the assumption of their offshore origin may be of limited use. Preservation of tsunami deposits in a coastal plain setting primarily depends on their thickness and land topography. Most erosion and redeposition of the deposits take place shortly after tsunami inundation and depend on climate (wind, rain) and topography.

Szczucinski, W.; Chague-Goff, C.; Goto, K.; Sugawara, D.; Jagodzinski, R.; Kokocinski, M.; Cachao, M.; Sternal, B.; Rzeszewski, M.; Goff, J. R.; Jaffe, B. E.

2012-12-01

101

Late Pleistocene to Holocene environmental changes as recorded in the sulfur geochemistry of coastal plain sediments, southwestern Taiwan  

USGS Publications Warehouse

A core, drilled at San-liao-wan in the southwestern coastal plain of Taiwan, has been analyzed for total sulfur contents, isotopic values, as well as ratios of pyritic sulfur to organic carbon. Our results demonstrate a close relationship between late Pleistocene sea-level change and the proxies generated in this study. The inorganic sulfur contents indicate that at our study site, the Holocene transgression started at ???11 ka and remained under seawater for thousands of years until the late Holocene, corresponding to a depth of 20 m in the study core. The uppermost 20 m of core shows relatively high total organic carbon (TOC) and ??34S of inorganic sulfur, suggesting a transitional environment such as muddy lagoon or marsh, before the site turned into a modern coastal plain. In the lower part of the core, at depths of 110-145 m (corresponding ages of ???12-30 ka), low sulfur contents are recorded, probably indicating fluvial sediments deposited during the oceanic isotope stage (OIS) 2, a sea-level lowstand. The lower part of the core, roughly within OIS 3, records at least two transgressions, although the transgressional signals may be somewhat obscured by subsequent weathering. The reworked origin of organic matter reported in previous studies is confirmed by our organic sulfur data; however, the marine organic source was periodically dominant. The modern high sulfate concentrations in pore water have no correlation to the other sulfur species in the sediments, probably indicating that the sulfate migrated into the site subsequent to early diagenesis. ?? 2003 Elsevier Ltd. All rights reserved.

Chen, Y.-G.; Liu, J.C.-L.; Shieh, Y.-N.; Liu, T.-K.

2004-01-01

102

Effects of agricultural tillage and sediment accumulation on emergent plant communities in playa wetlands of the U.S. High Plains.  

PubMed

Identifying community assembly filters is a primary ecological aim. The High Plains, a 30 million ha short-grass eco-region, is intensely cultivated. Cultivation disturbance, including plowing and eroded soil deposition down-slope of plowing, influences plant composition in depressional wetlands, such as playas, within croplands. We evaluated influences of wetland cultivation and sediment deposition on plant composition in playas embedded within croplands (46 plowed and 32 unplowed) and native grasslands (79) across 6 High Plains' states. Sediment accumulation ranged from 7 to 78 cm in cropland and 1 to 35 cm in grassland playas. Deeper sediments and plowing each decreased wetland plant richness, 28% and 70% respectively in cropland wetlands. Sediment depth reduced richness 37% in small grasslands playas while it increased richness 22% in larger ones, suggesting moderate disturbance increased richness when there were nearby propagule sources. Sediment depth was unrelated to species richness in plowed wetlands, probably because plowing was a strong disturbance. Plowing removed perennial plants from vegetation communities. Sediment accumulation also influenced species composition in cropland playas, e.g., probability of Eleocharis atropurpurea increased with sediment depth, while probability of Panicum capillare decreased. In grassland playas, observed lighter sediment depths did not influence species composition after accounting for wetland area. Sediment accumulation and plowing shift wetland plant communities toward annual species and decrease habitat connectivity for wetland-dependent organisms in cropland playas over 39,000 and 23,400 ha respectively. Conservation practices lessening sediment accumulation include short-grass buffer strips surrounding wetlands. Further, wetland tillage, allowed under federal agricultural conservation programs, should be eliminated. PMID:23500104

O'Connell, Jessica L; Johnson, Lacrecia A; Daniel, Dale W; McMurry, Scott T; Smith, Loren M; Haukos, David A

2013-05-15

103

Nile delta: extreme case of sediment entrapment on a delta plain and consequent coastal land loss  

Microsoft Academic Search

Accelerated erosion of Egypt's Nile delta coast during this century has generally been attributed to construction of two dams at Aswan, entrapment of sediment in Lake Nasser behind the High Dam, and effects of barrages and river control structures on River Nile deposition below Aswan. Also considered important are natural factors, including delta subsidence, rising sea level and strong coastal

Daniel Jean Stanley

1996-01-01

104

Sediment loading and controls in the grasslands of the Great Plains  

Technology Transfer Automated Retrieval System (TEKTRAN)

In this study, the effects of upstream conservation measures on sediment delivery to and half-life of the Fort Cobb Reservoir in West-Central Oklahoma are investigated. Few conservation practices were implemented on the Fort Cobb Reservoir watershed before the 1950s. In the second half of the 20th ...

105

An Abyssal Current in the Central Labrador Sea  

NASA Astrophysics Data System (ADS)

Lowered acoustic Doppler current profiler (LADCP) data collected along the repeat hydrographic section AR7W in the Labrador Sea has unveiled a new abyssal current, confined to a narrow trench extending from NW to SE over the entire abyssal basin and crossing AR7W in the center of the basin at about 57.8°N, 51.3°W. Maximum water depth in the trough is 75 - 100 m greater depth than the surrounding topography, and the current extends from about 160 m above the bottom to the bottom (3610 m), headed in a south to southeasterly direction. Maximum speeds of 10-20 cm s-1 occur in the deepest part of the current, implying a net transport of as much as 0.2 Sv of Denmark Strait Overflow Water (DSOW). Potential temperature and salinity in the bottom-intensified current tend to be well mixed below 3520 m, suggesting that the mixed bottom boundary layer is about 100 m thick. This V-shaped trench is part of the Northwest Atlantic Mid-Ocean Channel (NAMOC), which has been recognized as a turbidity current pathway by petrologists (Chough and Hesse, 1980; Chough et al., 1986). Another small trough intersects the main branch of the NAMOC where the abyssal current is observed, which may account for the varying direction of the current. This network of abyssal channels may provide a pathway for DSOW, entering the Labrador Sea around the southern tip of Greenland, to reach the central Labrador Sea with little delay. Indeed, Yashayaev and Dickson (2008) have noted the rapidity with which signals of hydrographic change in DSOW spread across the entire abyssal basin, reaching the central Labrador Sea within several months after their first appearance at the eastern boundary. Chough, S. K. and R. Hesse (1980). The Northwest Atlantic Mid-Ocean Channel of the Labrador Sea: III. Head spill vs. body spill deposits from turbidity currents on natural levees. J. of Sedimentary Petrology 50, 227-234. Chough, S. K., R. Hesse, and J. Muller (1987). The Northwest Atlantic Mid-Ocean Channel of the Labrador Sea. IV. Petrography and provenance of the sediments. Can. J. Earth Sci. 24, 731-740. Yashayaev, I., and R. R. Dickson (2008). Transformation and fate of overflows in the northern North Atlantic, in Arctic-Subarctic Ocean Fluxes: Defining the Role of the Northern Seas in Climate, edited by R. R. Dickson, J. Meincke, and P. Rhines, pp. 505- 526, Springer, New York.

Hall, M. M.; Yashayaev, I.; Torres, D. J.

2012-12-01

106

Sediment community oxygen consumption in the deep Gulf of Mexico  

NASA Astrophysics Data System (ADS)

Sediment community oxygen consumption (SCOC) has been measured from the continental shelf out to the Sigsbee Abyssal Plain in the NE Gulf of Mexico (GoM). SCOC rates on the continental shelf were an order of magnitude higher than those on the adjacent continental slope (450-2750 m depth) and two orders of magnitude higher than those on the abyssal plain at depths of 3.4-3.65 km. Oxygen penetration depth into the sediment was inversely correlated with SCOC measured within incubation chambers, but rates of SCOC calculated from either the gradient of the [O 2] profiles or the total oxygen penetration depth were generally lower than those derived from chamber incubations. SCOC rates seaward of the continental shelf were lower than at equivalent depths on most continental margins where similar studies have been conducted, and this is presumed to be related to the relatively low rates of pelagic production in the GoM. The SCOC, however, was considerably higher than the input of organic detritus from the surface-water plankton estimated from surface-water pigment concentrations, suggesting that a significant fraction of the organic matter nourishing the deep GoM biota is imported laterally down slope from the continental margin.

Rowe, Gilbert T.; Morse, John; Nunnally, Clifton; Boland, Gregory S.

2008-12-01

107

Aminostratigraphy of surface and subsurface Quaternary sediments, North Carolina coastal plain, USA  

USGS Publications Warehouse

The Quaternary stratigraphy and geochronology of the Albemarle Embayment of the North Carolina (NC) Coastal Plain is examined using amino acid racemization (AAR) in marine mollusks, in combination with geophysical, lithologic, and biostratigraphic analysis of 28 rotasonic cores drilled between 2002 and 2006. The Albemarle Embayment is bounded by structural highs to the north and south, and Quaternary strata thin westward toward the Suffolk paleoshoreline, frequently referred to as the Suffolk Scarp. The Quaternary section is up to ???90. m thick, consists of a variety of estuarine, shelf, back-barrier, and lagoonal deposits, and has been influenced by multiple sea-level cycles. The temporal resolution of the amino acid racemization method is tested statistically and with the stratigraphic control provided by this geologic framework, and it is then applied to the correlation and age estimation of subsurface units throughout the region. Over 500 specimens (primarily Mercenaria and Mulinia) from the subsurface section have been analyzed using either gas chromatographic (GC) or reverse-phase liquid chromatographic (RPLC) techniques. The subsurface stratigraphic data are compared with AAR results from numerous natural or excavated exposures from the surrounding region, as well as results from NC beach collections, to develop a comprehensive aminostratigraphic database for the entire Quaternary record within the NC coastal system. Age mixing, recognized in the beach collections, is also seen in subsurface sections, usually where major seismic reflections or core lithology indicate the presence of stratigraphic discontinuities. Kinetic models for racemization are tested within the regional stratigraphic framework, using either radiocarbon or U-series calibrations or comparison with regional biostratigraphy. Three major Pleistocene aminozones [AZ2, AZ3, and AZ4] are found throughout the region, all being found in superposition in several cores. Each can be subdivided, yielding a total of at least eight stratigraphically and statistically distinct aminozones. Kinetic modeling, supplemented with local calibration, indicates that these aminozones represent depositional events ranging from ???80. ka to nearly 2. Ma. Three prominent seismic reflections are interpreted to represent the base of the early, middle, and late Pleistocene, respectively, roughly 2. Ma, 800. ka, and 130. ka. The large number of samples and the available stratigraphic control provide new insights into the capabilities and limitations of aminostratigraphic methods in assessing relative and numerical ages of Atlantic Coastal Plain Quaternary deposits. ?? 2009 Elsevier B.V.

Wehmiller, J. F.; Thieler, E.R.; Miller, D.; Pellerito, V.; Bakeman, Keeney V.; Riggs, S.R.; Culver, S.; Mallinson, D.; Farrell, K.M.; York, L.L.; Pierson, J.; Parham, P.R.

2010-01-01

108

Black carbon's long trip to the abyssal plain  

NASA Astrophysics Data System (ADS)

Black carbon, or soot, is the second most important anthropogenic driver of global climate change, taking a backseat only to carbon dioxide. Whether from wood in a cookstove, coal in a power plant, or trees charred by a wildfire, black carbon is produced by the incomplete combustion of organic matter. Once it gets into the environment, black carbon lowers the albedo when it settles on land, increasing warming and enhancing snow and ice melt. In the atmosphere, black carbon both helps and inhibits the formation of clouds.

Schultz, Colin

2014-08-01

109

Algal pigments in Southern Ocean abyssal foraminiferans indicate pelagobenthic coupling  

NASA Astrophysics Data System (ADS)

The cytoplasm of four species of abyssal benthic foraminiferans from the Southern Ocean (around 51°S; 12°W and 50°S; 39°W) was analysed by High Performance Liquid Chromatography (HPLC) and found to contain large concentrations of algal pigments and their degradation products. The composition of the algal pigments in the foraminiferan cytoplasm reflected the plankton community at the surface. Some foraminiferans contained high ratios of chlorophyll a/degraded pigments because they were feeding on fresher phytodetritus. Other foraminiferans contained only degraded pigments which shows that they utilized degraded phytodetritus. The concentration of algal pigment and corresponding degradation products in the foraminiferan cytoplasm is much higher than in the surrounding sediment. It shows that the foraminiferans collect a diluted and sparse food resource and concentrate it as they build up their cytoplasm. This ability contributes to the understanding of the great quantitative success of foraminiferans in the deep sea. Benthic foraminiferans are a food source for many abyssal metazoans. They form a link between the degraded food resources, phytodetritus, back to the active metazoan food chains.

Cedhagen, Tomas; Cheah, Wee; Bracher, Astrid; Lejzerowicz, Franck

2014-10-01

110

Arsenic in New Jersey Coastal Plain streams, sediments, and shallow groundwater: effects from different geologic sources and anthropogenic inputs on biogeochemical and physical mobilization processes  

USGS Publications Warehouse

Arsenic (As) concentrations in New Jersey Coastal Plain streams generally exceed the State Surface Water Quality Standard (0.017 micrograms per liter (µg/L)), but concentrations seldom exceed 1 µg/L in filtered stream-water samples, regardless of geologic contributions or anthropogenic inputs. Nevertheless, As concentrations in unfiltered stream water indicate substantial variation because of particle inputs from soils and sediments with differing As contents, and because of discharges from groundwater of widely varying chemistry. In the Inner Coastal Plain, streams draining to lower reaches of the Delaware River traverse As-rich glauconitic sediments of marine origin in which As contents typically are about 20 milligrams per kilogram (mg/kg) or greater. In some of these sedimentary units, As concentrations exceed the New Jersey drinking-water maximum contaminant level (5 µg/L) in shallow groundwater that discharges to streams. Microbes, fueled by organic carbon beneath the streambed, reduce iron (Fe) and As, releasing As and Fe into solution in the shallow groundwater from geologic materials that likely include (in addition to glauconite) other phyllosilicates, apatite, and siderite. When the groundwater discharges to the stream, the dissolved Fe and As are oxidized, the Fe precipitates as a hydroxide, and the As sorbs or co-precipitates with the Fe. Because of the oxidation/precipitation process, dissolved As concentrations measured in filtered stream waters of the Inner Coastal Plain are about 1 µg/L, but the total As concentrations (and loads) are greater, substantially amplified by As-bearing suspended sediment in stormflows. In the Outer Coastal Plain, streams draining to the Atlantic Ocean traverse quartz-rich sediments of mainly deltaic origin where the As content generally is low ( With a history of agriculture in the New Jersey Coastal Plain, anthropogenic inputs of As, such as residues from former pesticide applications in soils, can amplify any geogenic As in runoff. Such inputs contribute to an increased total As load to a stream at high stages of flow. As a result of yet another anthropogenic influence, microbes that reduce and mobilize As beneath the streambeds are stimulated by inputs of dissolved organic carbon (DOC). Although DOC is naturally occurring, anthropogenic contributions from wastewater inputs may deliver increased levels of DOC to subsurface soils and ultimately groundwater. Arsenic concentrations may increase with the increases in pH of groundwater and stream water in developed areas receiving wastewater inputs, as As mobilization caused by pH-controlled sorption and desorption reactions are likely to occur in waters of neutral or alkaline pH (for example, Nimick and others, 1998; Barringer and others, 2007b). Because of the difference in As content of the geologic materials in the two sub-provinces of the Coastal Plain, the amount of As that is mobile in groundwater and stream water is, potentially, substantially greater in the Inner Coastal Plain than in the Outer Coastal Plain. In turn, streams within the Inner and Outer Coastal Plain can receive substantially more As in groundwater discharge from developed areas than from environments where DOC appears to be of natural origin.

Barringer, Julia L.; Reilly, Pamela A.; Eberl, Dennis D.; Mumford, Adam C.; Benzel, William M.; Szabo, Zoltan; Shourds, Jennifer L.; Young, Lily Y.

2013-01-01

111

Quantifying trace element disequilibria in mantle xenoliths and abyssal peridotites  

E-print Network

Quantifying trace element disequilibria in mantle xenoliths and abyssal peridotites Arnaud Agranier in mantle xenoliths and abyssal peridotites using in situ analytical tools. Even when only mineral cores in mantle xenoliths are closer to equilibrium than those in abyssal peridotites even though mantle xenoliths

Lee, Cin-Ty Aeolus

112

Importance of geomorphology and sedimentation processes for metal dispersion in sediments and soils of the Ganga Plain: identification of geochemical domains  

Microsoft Academic Search

The Ganga Plain, one of the largest alluvial plains of the earth is under severe environmental stress due to rapid industrial and urban development and exploding population growth. Disposal of industrial and urban wastes and the ignorance of their management have resulted severe environmental problems, especially metal pollution. In the present study, an attempt is made to understand the transport

A. A. Ansari; I. B. Singh; H. J. Tobschall

2000-01-01

113

Response of Late Cretaceous migrating deltaic facies systems to sea level, tectonics, and sediment supply changes, New Jersey Coastal Plain, U.S.A.  

USGS Publications Warehouse

Paleogeographic, isopach, and deltaic lithofacies mapping of thirteen depositional sequences establish a 35 myr high resolution (> 1 Myr) record of Late Cretaceous wave- and tide-influenced deltaic sedimentation. We integrate sequences defined on the basis of lithologic, biostratigraphic, and Sr-isotope stratigraphy from cores with geophysical log data from 28 wells to further develop and extend methods and calibrations of well-log recognition of sequences and facies variations. This study reveals the northeastward migration of depocenters from the Cenomanian (ca. 98 Ma) through the earliest Danian (ca. 64 Ma) and documents five primary phases of paleodeltaic evolution in response to long-term eustatic changes, variations in sediment supply, the location of two long-lived fluvial axes, and thermoflexural basement subsidence: (1) Cenomanian-early Turonian deltaic facies exhibit marine and nonmarine facies and are concentrated in the central coastal plain; (2) high sediment rates, low sea level, and high accommodation rates in the northern coastal plain resulted in thick, marginal to nonmarine mixed-influenced deltaic facies during the Turonign-Coniacian; (3) comparatively low sediment rates and high long-term sea level in the Santonian resulted in a sediment-starved margin with low deltaic influence; (4) well-developed Campanian deltaic sequences expand to the north and exhibit wave reworking and longshore transport of sands, and (5) low sedimentation rates and high long-term sea level during the Maastrichtian resulted in the deposition of a sediment-starved glauconitic shelf. Our study illustrates the widely known variability of mixed-influence deltaic systems, but also documents the relative stability of deltaic facies systems on the 106-107 yr scale, with long periods of cyclically repeating systems tracts controlled by eustasy. Results from the Late Cretaceous further show that although eustasy provides the template for sequences globally, regional tectonics (rates of subsidence and accommodation), changes in sediment supply, proximity to sediment input, and flexural subsidence from depocenter loading determines the regional to local preservation and facies expression of sequences. Copyright ?? 2008, SEPM (Society for Sedimentary Geology).

Kulpecz, A.A.; Miller, K.G.; Sugarman, P.J.; Browning, J.V.

2008-01-01

114

Relation of sediment load and flood-plain formation to climatic variability, Paria River drainage basin, Utah and Arizona  

USGS Publications Warehouse

Flood-plain alluviation began about 1940 at a time of decreasing magnitude and frequency of floods in winter, summer, and fall. No floods with stages high enough to inundate the flood plain have occurred since 1980, and thus no flood-plain alluviation has occurred since then. The decrease in magnitude and frequency of floods appears to have resulted from a decrease in frequency of large storms, particularly dissipating tropical cyclones, and not from a decrease in annual or seasonal precipitation. -from Authors

Graf, J.B.; Webb, R.H.; Hereford, R.

1991-01-01

115

Environmental factors affecting distribution and abundance of bacteria, fungi and protozoa in subsurface sediments of the Upper Atlantic Coastal Plain, USA  

SciTech Connect

Exploratory statistical analyses of microbiological, hydrological and geochemical data for samples from four boreholes drilled into Upper Atlantic Coastal Plain sediments near the Savannah River Site, SC, showed highly significant correlations between bacterial abundance (AODC and CFU) and hydraulic conductivity (K). Sediment texture variables (% sand (S), % silt, % clay (C), and S/C) were strongly interrelated with K and, therefore, also correlated with bacterial abundance. AODC did not correlate with the concentrations of dissolved inorganic nitrogen (DIN) or dissolved organic carbon (DOC) in pore water. CFU also did not correlate with DIN, but a negative relationship was found between the CFU and DOC for sandy sediments, suggesting that microbial activity may control pore water DOC concentration. In some, but not all boreholes, AODC and CFU correlated negatively with pore water concentrations of metals and positively with pH. Protozoan abundance correlated strongly with AODC and CFU in the two boreholes closest to the recharge areas for their major aquifers. It also correlated with sediment texture variables, but not with K. Fungal abundance did not correlate with the abundance of other microbial types when data from individual boreholes were considered; however it did correlate with both bacterial and protozoan abundance when data from all four boreholes were combined. There was no relationship between fungal abundance and either K or sediment texture.

Levine, S.N.; Ghiorse, W.C.

1990-12-31

116

Environmental factors affecting distribution and abundance of bacteria, fungi and protozoa in subsurface sediments of the Upper Atlantic Coastal Plain, USA  

SciTech Connect

Exploratory statistical analyses of microbiological, hydrological and geochemical data for samples from four boreholes drilled into Upper Atlantic Coastal Plain sediments near the Savannah River Site, SC, showed highly significant correlations between bacterial abundance (AODC and CFU) and hydraulic conductivity (K). Sediment texture variables (% sand (S), % silt, % clay (C), and S/C) were strongly interrelated with K and, therefore, also correlated with bacterial abundance. AODC did not correlate with the concentrations of dissolved inorganic nitrogen (DIN) or dissolved organic carbon (DOC) in pore water. CFU also did not correlate with DIN, but a negative relationship was found between the CFU and DOC for sandy sediments, suggesting that microbial activity may control pore water DOC concentration. In some, but not all boreholes, AODC and CFU correlated negatively with pore water concentrations of metals and positively with pH. Protozoan abundance correlated strongly with AODC and CFU in the two boreholes closest to the recharge areas for their major aquifers. It also correlated with sediment texture variables, but not with K. Fungal abundance did not correlate with the abundance of other microbial types when data from individual boreholes were considered; however it did correlate with both bacterial and protozoan abundance when data from all four boreholes were combined. There was no relationship between fungal abundance and either K or sediment texture.

Levine, S.N.; Ghiorse, W.C.

1990-01-01

117

A 200,000-year record of late Quaternary Aeolian sedimentation on the Southern High Plains and nearby Pecos River Valley, USA  

NASA Astrophysics Data System (ADS)

Presently stabilized Southern High Plains (SHP) dune systems have been repeatedly re-activated during the past 200,000 years, providing an archive of environmental and related climatic change for the late Quaternary. Our data set of 38 optically dated samples from four different localities identifies eolian activity from late-middle Pleistocene to the historic period. Oldest eolian sediments are from the Blackwater Draw Formation and indicate accretion during late-middle to late Pleistocene. Younger sediments dating from the later Pleistocene through the Holocene are found in the Muleshoe, Lea-Yoakum, Mescalero, and Monahans dunes that overlie the Blackwater Draw Formation. Muleshoe dunes accreted during the Late Pleistocene between 31 ± 3 and 27 ± 2 ka, while Holocene deposition transpired 7.5 ± 0.4, 4.0 ± 0.7 ka through 3.6 ± 0.4 ka, and between 1.3 ± 0.2 and 1.1 ± 0.1 ka. A period of dune building for Lea-Yoakum dune sediments occurred during the late Pleistocene (48 ± 5 ka), and the later Holocene (3.6 ± 0.4 ka). Mescalero and Monahans dunes were accreting during the later Pleistocene between 29 ± 3 and 22 ± 2 ka followed by a sequence of eolian sand deposited ca. 15 ka. Holocene eolian sedimentation for the Mescalero and Monahans dunes occurred 7.5 ± 0.8, 5.1 ± 0.5, 4.3 ± 0.4, and 2.0 ± 0.3 ka. Historic eolian deposition is identifiable in the dune chronology with multiple optical age estimates overlapping established drought events recorded ca. 1890, 1910, 1920, and during the 1930's when the North American "Dust Bowl" transpired. These Quaternary eolian deposits mantling the Southern High Plains are an important component of the surficial material of the region and provide a rich archive of past climatic change.

Rich, J.; Stokes, S.

2011-03-01

118

200,000 years of climate change recorded in eolian sediments of the High Plains of eastern Colorado and western Nebraska  

USGS Publications Warehouse

Loess and eolian sand cover vast areas of the western Great Plains of Nebraska, Kansas and Colorado (Fig. 1). In recent studies of Quaternary climate change, there has been a renewed interest in loess and eolian sand. Much of the attention now given to loess stems from new studies of long loess sequences that contain detailed records of Quaternary glacial-interglacial cycles, thought to be a terrestrial equivalent to the foraminiferal oxygen isotope record in deep-sea sediments (Fig. 2). Loess is also a direct record of atmospheric circulation, and identification of loess paleowinds in the geologic record can test atmospheric general circulation models. Until recently, eolian sand on the Great Plains had received little attention from Quaternary geologists. The past decade has seen a proliferation of studies of Great Plains dune sands, and many studies, summarized below, indicate that landscapes characterized by eolian sand have had dynamic histories. On this field trip, we will visit some key eolian sand and loess localities in eastern Colorado and southwestern Nebraska (Fig. 1). Stratigraphic studies at some of these localities have been conducted for more than 50 years, but others have been systematically studied only in the past few years. Many of the data which appear in this guidebook have been derived from previous studies (Swinehart and Diffendal, 1990; Madole, 1994; Loope and others, 1995; Maat and Johnson, 1996; Muhs and others, 1996, 1997a, 1999; Mason and others, 1997; Aleinikoff and others, 1999), but some are presented here for the first time.

Muhs, Daniel R.; Swinehart, James B.; Loope, David B.; Aleinikoff, John N.; Been, Josh

1999-01-01

119

Laboratory-Measured and Property-Transfer Modeled Saturated Hydraulic Conductivity of Snake River Plain Aquifer Sediments at the Idaho National Laboratory, Idaho  

USGS Publications Warehouse

Sediments are believed to comprise as much as 50 percent of the Snake River Plain aquifer thickness in some locations within the Idaho National Laboratory. However, the hydraulic properties of these deep sediments have not been well characterized and they are not represented explicitly in the current conceptual model of subregional scale ground-water flow. The purpose of this study is to evaluate the nature of the sedimentary material within the aquifer and to test the applicability of a site-specific property-transfer model developed for the sedimentary interbeds of the unsaturated zone. Saturated hydraulic conductivity (Ksat) was measured for 10 core samples from sedimentary interbeds within the Snake River Plain aquifer and also estimated using the property-transfer model. The property-transfer model for predicting Ksat was previously developed using a multiple linear-regression technique with bulk physical-property measurements (bulk density [pbulk], the median particle diameter, and the uniformity coefficient) as the explanatory variables. The model systematically underestimates Ksat,typically by about a factor of 10, which likely is due to higher bulk-density values for the aquifer samples compared to the samples from the unsaturated zone upon which the model was developed. Linear relations between the logarithm of Ksat and pbulk also were explored for comparison.

Perkins, Kim S.

2008-01-01

120

Sediment capture in flood plains of the Mississippi River: A case study in Cat Island National Wildlife Refuge, Louisiana  

NASA Astrophysics Data System (ADS)

To plan restoration of the Mississippi River Delta, it is imperative to know how much sediment the Mississippi River currently provides. Recent research has demonstrated that between Tarbert Landing and St Francisville on the Mississippi, as much as 67 million metric tons (Mt) per year is lost from river transport, of which ~16 Mt is muddy suspended sediment. So where does this sediment go? Two pathways for loss have been proposed: riverbed storage, and overbank deposition in regions that lack manmade levées. Cat Island National Wildlife Refuge, on the unleveed Mississippi River east bank near St Francisville, Louisiana, consists of undisturbed bottomland forest that is inundated most years by river flooding. To determine fluvial sediment accumulation rates (SAR) from flooding, pushcores 40-50 cm long were collected then dated by Pb-210 and Cs-137 geochronology. Preliminary data suggests that muddy sediment accumulation is 10-13% of muddy suspended sediment lost from river transport along this river reach.

Smith, M.; Bentley, S. J., Sr.

2015-03-01

121

Characterization on arsenic sorption and mobility of the sediments of Chia-Nan Plain, where Blackfoot disease occurred  

Microsoft Academic Search

Higher levels of arsenic in the aquifers of Chia-Nan Plain in southwestern Taiwan were attributed to the cause of Blackfoot\\u000a disease in the area half a century ago. Although extensive studies were conducted on the occurrence, speciation, mobility,\\u000a and transport of arsenic in the region, the relationship between arsenic adsorption by different aquifer materials and the\\u000a concentration and speciation of

Zhaohui Li; Hanlie Hong; Jiin-Shuh Jean; Andria J. Koski; Chia-Chuan Liu; Selim Reza; Jeffrey J. Randolph; Stephan R. Kurdas; Jonathan H. Friend; Sarah J. Antinucci

122

The Gulf Stream pathway and the impacts of the eddy-driven abyssal circulation and the Deep Western Boundary Current  

NASA Astrophysics Data System (ADS)

A hydrodynamic model of the subtropical Atlantic basin and the Intra-Americas Sea (9-47°N) is used to investigate the dynamics of Gulf Stream separation from the western boundary at Cape Hatteras and its mean pathway to the Grand Banks. The model has five isopycnal Lagrangian layers in the vertical and allows realistic boundary geometry, bathymetry, wind forcing, and a meridional overturning circulation (MOC), the latter specified via ports in the northern and southern boundaries. The northward upper ocean branch of the MOC (14 Sv) was always included but the southward Deep Western Boundary Current (DWBC) was excluded in some simulations, allowing investigation of the impacts of the DWBC and the eddy-driven mean abyssal circulation on Gulf Stream separation from the western boundary. The result is resolution dependent with the DWBC playing a crucial role in Gulf Stream separation at 1/16° resolution but with the eddy-driven abyssal circulation alone sufficient to obtain accurate separation at 1/32° resolution and a realistic pathway from Cape Hatteras to the Grand Banks with minimal DWBC impact except southeast of the Grand Banks. The separation from the western boundary is particularly sensitive to the strength of the eddy-driven abyssal circulation. Farther to the east, between 68°W and the Grand Banks, all of the 1/16° and 1/32° simulations with realistic topography (with or without a DWBC) gave similar generally realistic mean pathways with clear impacts of the topographically constrained eddy-driven abyssal circulation versus very unrealistic Gulf Stream pathways between Cape Hatteras and the Grand Banks from otherwise identical simulations run with a flat bottom, in reduced-gravity mode, or with 1/8° resolution and realistic topography. The model is realistic enough to allow detailed model-data comparisons and a detailed investigation of Gulf Stream dynamics. The corresponding linear solution with a Sverdrup interior and Munk viscous western boundary layers, including one from the northward branch of the MOC, yielded two unrealistic Gulf Stream pathways, a broad eastward pathway centered at the latitude of Cape Hatteras and a second wind plus MOC-driven pathway hugging the western boundary to the north. Thus, a high resolution model capable of simulating an inertial jet is required to obtain a single nonlinear Gulf Stream pathway as it separates from the coast. None of the simulations were sufficiently inertial to overcome the linear solution need for a boundary current north of Cape Hatteras without assistance from pathway advection by the abyssal circulation, even though the core speeds of the simulated currents were consistent with observations near separation. In the 1/16° simulation with no DWBC and a 1/32° simulation with high bottom friction and no DWBC the model Gulf Stream overshot the observed separation latitude. With abyssal current assistance the simulated (and the observed) mean Gulf Stream pathway between separation from the western boundary and ˜70°W agreed closely with a constant absolute vorticity (CAV) trajectory influenced by the angle of the coastline prior to separation. The key abyssal current crosses under the Gulf Stream at 68.5-69°W and advects the Gulf Stream pathway southward to the terminus of an escarpment in the continental slope. There the abyssal current crosses to deeper depths to conserve potential vorticity while passing under the downward-sloping thermocline of the stream and then immediately retroflects eastward onto the abyssal plain, preventing further southward pathway advection. Thus specific topographic features and feedback from the impact of the Gulf Stream on the abyssal current pathway determined the latitude of the stream at 68.5-69°W, a latitude verified by observations. The associated abyssal current was also verified by observations.

Hurlburt, Harley E.; Hogan, Patrick J.

2008-08-01

123

Sorption kinetics of Hg and HgCl[sub 2] on Kirkwood-Cohansey aquifer sediments from the New Jersey Coastal Plain  

SciTech Connect

Anomalously high Hg concentrations have been detected from domestic wells in the Kirkwood-Cohansey Aquifer System, New Jersey Coastal Plain. Mercury concentrations ranging from 0.2--83.0 [mu]g/l in relatively shallow wells ([lt] 100 feet) have been detected. Concentrations in excess of 2.0 [mu]g/l, (the USEPA Drinking Water Standard) have been detected in wells where the Cohansey Sand is overlain by the Bridgeton Formation; a fluvial iron-rich sand with some gravelly channel deposits containing goethite and gibbsite nodules. In this study, Bridgeton Fm. sediments were used to determine the sorption kinetics for solutions containing HgCl[sub 2] and for solutions containing dissolved elemental Hg in order to assess the potential for the Bridgeton sediments to act as a conduit for Hg mobilized from the surface. Results of batch equilibrium experiments suggest that dissolved elemental Hg sorbs to Bridgeton sediments by a risk-order kinetic process. Sorption of the Hg proceeded exponentially and equilibrium was reached within 14 hours. The sorption kinetics for the HgCl[sub 2] solutions, however, appear to be of a second or higher order. For this compound sorption to the sediments begins exponentially, but after 6 hours desorption into the water begins to predominate followed by a slower exponential sorption step that requires nearly 36 hours to reach equilibrium. These experiments illustrate the necessity of determining the distribution coefficients of possible source compounds when attempting to evaluate mobilization potential of a contaminant in the unsaturated zone. Moreover, these data also suggest that HgCl[sub 2], a seed dressing for corn, medial bacteriacide, and embalming fluid ingredient, is more mobile in the environment than dissolved elemental Hg. Consequently, the ground water contamination potential appears to be greater for HgCl[sub 2] than for elemental Hg.

MacLeod, C.; Peterson, J. (Princeton Univ., NJ (United States). Dept. of Geological and Geophysical Sciences)

1992-01-01

124

Surface sediments in the marsh-sandy land transitional area: sandification in the western Songnen Plain, China.  

PubMed

The development of sandification process was studied, by monitoring the changes of sediment characteristics, at marsh-sandy land intersections in China's Songnen region. A series of sediment collection plates were deployed in the region; after one year, sediments in these plates were analyzed for changes of mass and chemical characteristics. The sediment flux and the sand content of the sediments decreased with the increasing longitudinal distance between the sampling site and the centre line of a sand dune. The mean sediment flux was 29 ± 14 kg m(-2) yr(-1) and 0.6 ± 0.3 kg m(-2) yr(-1) in the sandy land and marsh, respectively. Strong, positive correlations were found between the concentrations of organic matter, total nitrogen, P, Fe, Ti, V and Zr, all of which were also negatively correlated with the sand content. The concentrations of organic matter, total nitrogen, P, Fe, Ti, V and Zr in the marsh sediment samples were all significantly greater than the corresponding concentrations of the sandy land (p<0.001). Sand content and Ti, V and Zr concentrations all proved to be valid indicators of sandification intensity, and they showed that the marsh could be divided into three distinct zones. Sand expansion extended about 88 m into the marsh. The mean sand content in the sediments of the sandy land was 91% and then 64% in the marsh, which in turn was higher than that of marshes outside the influence of sandification, suggesting that the marsh in the marsh-sandy land transitional area has already undergone extensive sandification in the past. The study results provide information on the wetland's function of indicating and buffering the sandification process. PMID:24932717

Yu, Xiaofei; Grace, Michael; Zou, Yuanchun; Yu, Xuefeng; Lu, Xianguo; Wang, Guoping

2014-01-01

125

Surface Sediments in the Marsh-Sandy Land Transitional Area: Sandification in the Western Songnen Plain, China  

PubMed Central

The development of sandification process was studied, by monitoring the changes of sediment characteristics, at marsh-sandy land intersections in China's Songnen region. A series of sediment collection plates were deployed in the region; after one year, sediments in these plates were analyzed for changes of mass and chemical characteristics. The sediment flux and the sand content of the sediments decreased with the increasing longitudinal distance between the sampling site and the centre line of a sand dune. The mean sediment flux was 29±14 kg m?2 yr?1 and 0.6±0.3 kg m?2 yr?1 in the sandy land and marsh, respectively. Strong, positive correlations were found between the concentrations of organic matter, total nitrogen, P, Fe, Ti, V and Zr, all of which were also negatively correlated with the sand content. The concentrations of organic matter, total nitrogen, P, Fe, Ti, V and Zr in the marsh sediment samples were all significantly greater than the corresponding concentrations of the sandy land (p<0.001). Sand content and Ti, V and Zr concentrations all proved to be valid indicators of sandification intensity, and they showed that the marsh could be divided into three distinct zones. Sand expansion extended about 88 m into the marsh. The mean sand content in the sediments of the sandy land was 91% and then 64% in the marsh, which in turn was higher than that of marshes outside the influence of sandification, suggesting that the marsh in the marsh-sandy land transitional area has already undergone extensive sandification in the past. The study results provide information on the wetland's function of indicating and buffering the sandification process. PMID:24932717

Yu, Xiaofei; Grace, Michael; Zou, Yuanchun; Yu, Xuefeng; Lu, Xianguo; Wang, Guoping

2014-01-01

126

Extreme 2002: Mission to the Abyss  

NSDL National Science Digital Library

This is the expedition page of the 2002 Mission to the Abyss. Developed by the University of Delaware Graduate College of Marine Studies, the site highlights the mission and crew, seafloor geology, creature features, and high-tech tools used in the study. This interactive website allows students to explore the submersible Alvin, find out how hydrothermal vents form, define the deep ocean, study plate tectonics, and meet hydrothermal vent organisms. The site includes extreme experiments, including: compression of a fluid vs. a gas, rising under pressure, my cup shrinks, soda squeeze, and plant pressure.

127

Results of rainfall simulation to estimate sediment-bound carbon and nitrogen loss from an Atlantic Coastal Plain (USDA) ultisol  

Technology Transfer Automated Retrieval System (TEKTRAN)

The impact of erosion on soil and carbon loss and redistribution within landscapes is an important component for developing estimates of carbon sequestration potential, management plans to maintain soil quality, and transport of sediment bound agrochemicals. Soils of the Southeastern U.S. Coastal Pl...

128

Strath terraces on the western High Plains indicate climatically-driven variations in sediment supply from source basins in the Colorado Front Range  

NASA Astrophysics Data System (ADS)

Large strath terraces adjacent to the Colorado Front Range record the local history of fluvial planation and incision into the erodible rocks of the Denver basin over the last 2 million years. Terrace surfaces have been correlated into ~6 alluvial units using elevation and soil development; each alluvial unit was thought to represent a fairly consistent elevation of the Denver basin during various stages of exhumation, driven by base-level fall of the South Platte River. Here we show instead that (1) strath terraces in the western High Plains cannot be correlated based on elevation alone and (2) exhumation of the Denver basin is likely spatially and temporally variable due to climatically-driven variations in sediment supply from the source basins. We collected samples for cosmogenic radionuclide (CRN) profiles (10Be and 26Al) and a soil chronosequence from three strath terraces adjacent to Lefthand Creek near Boulder, CO. 10Be profile data on the upper- and middle-elevation terraces yield dates of 95 ka and 91 ka; these dates are much younger than the correlative alluvial units to the south of Boulder, which date to 1.5 Ma and 250 ka, respectively. Soils on the upper and middle terraces are similar in soil development and clast weathering, consistent with the narrow time window obtained from CRN dating of the two units. 10Be-derived rates for catchment-wide paleo-denudation are ~8.0 cm/ka from the flat and broad upper-terrace gravels and ~3.5 cm/ka from the steeper and narrower middle-terrace gravels. Young terraces at Lefthand Canyon are more consistent with a model of fluvial incision and aggradation driven by climate-controlled variations in sediment production from source basins in the Front Range. High catchment-wide denudation rates generate a high sediment supply, leading to aggradation and lateral planation. Terrace sediments are likely deposited and eroded multiple times during periods of lateral planation; the most recent occupation is preserved in the gravel caps on strath terraces. Lower catchment-wide denudation rates, and thus low sediment supply, lead to vertical bedrock incision and abandonment of terrace surfaces. Our data indicate that Front Range rivers experience a complex and basin-specific history where long periods of aggradation and lateral planation are punctuated by brief episodes of rapid incision through the soft Cretaceous shale underlying the Boulder area.

Foster, M. A.; Dühnforth, M.; Anderson, R. S.

2013-12-01

129

Uranium-series dating of fossil corals from marine sediments of southeastern United States Atlantic Coastal Plain.  

USGS Publications Warehouse

The average 230Th ages of samples from the Norfolk Formation, and from later- and earlier-deposited sediments of the Wando Formation are 71 000, 87 000, and 129 000 yr, and they appear to correlate with oxygen isotope substages 5a, 5c and 5e, respectively. The average 230 Th age of samples from beds of the Rappahannock Rver, Ponzer, and Ten Mile Hill localities is 212 000 yr, and they correlate with oxygen isotope stage 7. The sediment of the Canepatch Formation is 460 000 yr old, and it is tentatively correlated with oxygen isotope stage 11. There is general agreement between uranium-series and uranium-trend dates and between the quantitative trends of the amino acid data and uranium-series dates. The amino acid values, however, are unacceptably high in at least two groups of samples, those from localities near Charleston, South Carolina, and from central Virginia. -from Author

Szabo, B. J.

1985-01-01

130

Role of naturally occurring gas hydrates in sediment transport  

SciTech Connect

Naturally occurring gas hydrates have the potential to store enormous volumes of both gas and water in semi-solid form in ocean-bottom sediments and then to release that gas and water when the hydrate's equilibrium condition are disturbed. Therefore, hydrates provide a potential mechanism for transporting large volumes of sediments. Under the combined low bottom-water temperatures and moderate hydrostatic pressures that exist over most of the continental slopes and all of the continental rises and abyssal plains, hydrocarbon gases at or near saturation in the interstitial waters of the near-bottom sediments will form hydrates. The gas can either be autochthonous, microbially produced gas, or allochthonous, catagenic gas from deeper sediments. Equilibrium conditions that stabilize hydrated sediments may be disturbed, for example, by continued sedimentation or by lowering of sea level. In either case, some of the solid gas-water matrix decomposes. Released gas and water volume exceeds the volume occupied by the hydrate, so the internal pressure rises - drastically if large volumes of hydrate are decomposed. Part of the once rigid sediment is converted to a gas- and water-rich, relatively low density mud. When the internal pressure, due to the presence of the compressed gas or to buoyancy, is sufficiently high, the overlying sediment may be lifted and/or breached, and the less dense, gas-cut mud may break through. Such hydrate-related phenomena can cause mud diapirs, mud volcanos, mud slides, or turbidite flows, depending on sediment configuration and bottom topography. 4 figures.

McIver, R.D.

1982-06-01

131

Analysis of the community structure of abyssal kinetoplastids revealed similar communities at larger spatial scales  

PubMed Central

Knowledge of the spatial scales of diversity is necessary to evaluate the mechanisms driving biodiversity and biogeography in the vast but poorly understood deep sea. The community structure of kinetoplastids, an important group of microbial eukaryotes belonging to the Euglenozoa, from all abyssal plains of the South Atlantic and two areas of the eastern Mediterranean was studied using partial small subunit ribosomal DNA gene clone libraries. A total of 1364 clones from 10 different regions were retrieved. The analysis revealed statistically not distinguishable communities from both the South-East Atlantic (Angola and Guinea Basin) and the South-West Atlantic (Angola and Brazil Basin) at spatial scales of 1000–3000?km, whereas all other communities were significantly differentiated from one another. It seems likely that multiple processes operate at the same time to shape communities of deep-sea kinetoplastids. Nevertheless, constant and homogenous environmental conditions over large spatial scales at abyssal depths, together with high dispersal capabilities of microbial eukaryotes, maintain best the results of statistically indistinguishable communities at larger spatial scales. PMID:22071346

Salani, Faezeh Shah; Arndt, Hartmut; Hausmann, Klaus; Nitsche, Frank; Scheckenbach, Frank

2012-01-01

132

Feeding rates of abyssal scavenging amphipods ( Eurythenes gryllus) determined in situ by time-lapse photography  

NASA Astrophysics Data System (ADS)

Bait (100 g of mackerel), moored 20 m above bottom at 5830 m in the Nares Abyssal Plain, northwest Atlantic Ocean and photographed at 10 min intervals, was completely consumed by scavenging lysianassid amphipods ( Eurythenes gryllus) within 38 h. An average feeding rate of 1.8 g amphipod -1 h -1 was calculated from the total number of amphipods counted in photographs and the time required for complete consumption of bait. Amphipods were present as single individuals during 12 h after the first animal arrived with an average residence time of 30± 10 min. Weight loss, calculated from changes in bait volume observed in photographs during this period, indicated an average consumption rate of 2.9 g amphipod -1. Amphipods of different sizes ingested from 30 to 60% of their body equivalent weight and then departed from the bait. These are the first in situ observations that permit calculation of feeding rate for any deep-sea animal.

Hargrave, B. T.

1985-04-01

133

Variations in the invertebrate abyssal megafauna in the North Atlantic Ocean  

NASA Astrophysics Data System (ADS)

Epibenthic sledge and otter trawl samples of invertebrate megabenthos were collected from the abyss of the northeastern Atlantic Ocean. Stations were selected to have contrasting overlying water column structure. Strong seasonal pulses of phytodetritus on the sea floor have been recorded on the Porcupine Abyssal Plain (PAP) but not on the Madeira Abyssal Plain (MAP). Sledge-and trawl-derived abundances of 13.73 and 8.13 individuals 10 3 m -2 were found at PAP, with corresponding wet biomass values of 169.4 and 189.2 g 10 3 m -2. Data from sledge hauls taken at MAP gave an abundance of 7.48 individuals and 5.15g 10 3 m -2. Sledge and trawl abundances at Great Meteor East (GME) were 2.91 and 2.19 individuals 10 3 m -2 and 4.31 and 11.30 g 10 3 m -2. Holothurians dominated the invertebrate biomass at PAP while Astoroidea and Decapoda Natantia were important taxa at MAP and GME. Otter trawl samples demonstrated fish to be the major component of total megadaunal biomass and suggest that small fixed-frame trawls give gross underestimates of fish abundance and biomass. Size spectra based on abundance and biomass data indicated the megafauna to be a functional group at PAP stationl only. Here peak invertebrate biomass occurred in the 40-80 g wet wt size class. In contrast, no large invertebrates (>20 g wet wt) were found at MAP of GME. Concurrent photographic records indicate higher faunal densities than do net catches. Faunal differences between stations were examined, and a weak relationship between surface productivity and megafaunal abundance was established. Data are inadequate to detect a similar relationship with biomass. Biomass values at PAP of 16-39 times those of MAP and GME appear to be explained by the deposition of phytodetritus at PAP but not at MAP or, probably, at GME. Among invertebrates, detritivores form the dominant feeding guild at all localities, but carnivores are important at MAP and GME. Phytodetritus appears to support the abundant surface-grazing holothurians at PAP.

Thurston, M. H.; Bett, B. J.; Rice, A. L.; Jackson, P. A. B.

1994-09-01

134

2005 Nature Publishing Group In situ Os isotopes in abyssal peridotites bridge the  

E-print Network

© 2005 Nature Publishing Group In situ Os isotopes in abyssal peridotites bridge the isotopic gap Abyssal peridotites are assumed to represent the mantle residue of mid-ocean-ridge basalts (MORBs). However, the osmium isotopic compositions of abyssal peridotites and MORB do not appear

Demouchy, Sylvie

135

PhD position in igneous petrology Marie-Curie Initial Training Network ABYSS (ESR3)  

E-print Network

PhD position in igneous petrology Marie-Curie Initial Training Network ABYSS (ESR3) Training no later than November 1, 2014. It is funded by ABYSS, an EU Framework 7 Marie Curie Integrated Training) and Benoit Ildefonse (ildefonse@um2.fr) 1 ABYSS has received funding from the People programme (Marie Curie

Demouchy, Sylvie

136

Laboratory-Measured and Property-Transfer Modeled Saturated Hydraulic Conductivity of Snake River Plain  

E-print Network

Plain Aquifer Sediments at the Idaho National Laboratory, Idaho Scientific Investigations Report 2008 Conductivity of Snake River Plain Aquifer Sediments at the Idaho National Laboratory, Idaho By Kim S. Perkins saturated hydraulic conductivity of Snake River Plain aquifer sediments at the Idaho National Laboratory

137

Cross-equatorial flow through an abyssal channel under the complete Coriolis force: Two-dimensional solutions  

NASA Astrophysics Data System (ADS)

The component of the Coriolis force due to the locally horizontal component of the Earth's rotation vector is commonly neglected, under the so-called traditional approximation. We investigate the role of this "non-traditional" component of the Coriolis force in cross-equatorial flow of abyssal ocean currents. We focus on the Antarctic Bottom Water (AABW), which crosses from the southern to the northern hemisphere through the Ceara abyssal plain in the western Atlantic ocean. The bathymetry in this region resembles a northwestward channel, connecting the Brazil Basin in the south to the Guyana Basin in the north. South of the equator, the AABW leans against the western continental rise, consistent with a northward flow in approximate geostrophic balance. The AABW then crosses to the other side of the abyssal channel as it crosses the equator, and flows into the northern hemisphere leaning towards the east against the Mid-Atlantic Ridge. The non-traditional component of the Coriolis force is strongest close to the equator. The traditional component vanishes at the equator, being proportional to the locally vertical component of the Earth's rotation vector. The weak stratification of the abyssal ocean, and subsequent small internal deformation radius, defines a relatively short characteristic horizontal lengthscale that tends to make non-traditional effects more prominent. Additionally, the steep gradients of the channel bathymetry induce large vertical velocities, which are linked to zonal accelerations by the non-traditional components of the Coriolis force. We therefore expect non-traditional effects to play a substantial role in cross-equatorial transport of the AABW. We present asymptotic steady solutions for non-traditional shallow water flow through an idealised abyssal channel, oriented at an oblique angle to the equator. The current enters from the south, leaning up against the western side of the channel in approximate geostrophic balance, and crosses the channel as it crosses the equator. The "non-traditional" contribution to the planetary angular momentum must be balanced by stronger westward flow in the channel, which leads to an increased transport in a northwestward channel, and a reduced transport in a northeastward channel. Our results suggest that as much as 10-30% of the cross-equatorial flow of the AABW may be attributed to the non-traditional components of the Coriolis force.

Stewart, A. L.; Dellar, P. J.

138

Internal wave structures in abyssal cataract flows  

NASA Astrophysics Data System (ADS)

We discuss some theoretical approaches, experimental results and field data concerning wave phenomena in ocean near-bottom stratified flows. Such strong flows of cold water form everywhere in the Atlantic abyssal channels, and these currents play significant role in the global water exchange. Most interesting wave structures arise in a powerful cataract flows near orographic obstacles which disturb gravity currents by forced lee waves, attached hydraulic jumps, mixing layers etc. All these effects were observed by the authors in the Romanche and Chain fracture zones of Atlantic Ocean during recent cruises of the R/V Akademik Ioffe and R/V Akademik Sergei Vavilov (Morozov et al., Dokl. Earth Sci., 2012, 446(2)). In a general way, deep-water cataract flows down the slope are similar to the stratified flows examined in laboratory experiments. Strong mixing in the sill region leads to the splitting of the gravity current into the layers having the fluids with different densities. Another peculiarity is the presence of critical layers in shear flows sustained over the sill. In the case under consideration, this critical level separates the flow of near-bottom cold water from opposite overflow. In accordance with known theoretical models and laboratory measurements, the critical layer can absorb and reflect internal waves generated by the topography, so the upward propagation of these perturbations is blocked from above. High velocity gradients were registered downstream in the vicinity of cataract and it indicates the existence of developed wave structures beyond the sill formed by intense internal waves. This work was supported by RFBR (grants No 12-01-00671-a, 12-08-10001-k and 13-08-10001-k).

Makarenko, Nikolay; Liapidevskii, Valery; Morozov, Eugene; Tarakanov, Roman

2014-05-01

139

Abyssal benthos of the central Indian Ocean  

NASA Astrophysics Data System (ADS)

Quantitative studies of the abyssal benthos (3600 to 5300 m) of the central Indian Ocean show a rich fauna and high standing crops. Density of 3 meiofaunal and 12 macrofaunal taxa are large (2175 to 15233; x = 6441 m -2) Polychaetes (41.6%), peracarid crustaceans (31.7%), ophiuroids (12.2%), echiuroid-bryozoa (9.7%), molluscs (4.8%), and agglutinating rhizopod protozoans form the macrofauna. Meiofaunal taxa are nematodes (69.4%), harpacticoid copepods (26.6%), and ostracods (4%). Meiofauna abundances are positively correlated with distance from shore, whereas the distribution and abundance of macrofauna are independent of variations in depth and distance from the shore. Ratio of macro to meiofauna in the total population is 1 to 31. The benthic standing crop is uniformly high (0.54 to 13.73 g m -2; x = 2.70 g m -2) and many times larger than previously reported for comparable depths in other oceans and from the same region. Biomass values are significantly related to distance from shore and the type of substratum. Contribution of macro and meiofauna to the total standing crop was in the ratio of 31 to 1. High benthic biomass and rich fauna are consequences of high organic production in the euphotic zone. The correlation between biomass of the total oxidizable organic matter in the water column and the benthic standing crop is statistically significant ( r = -0.64) at the P < 0.05 level. Rich fauna and high standing crop were associated with the occurrence of polymetallic nodules.

Parulekar, A. H.; Harkantra, S. N.; Ansari, Z. A.; Matondkar, S. G. P.

1982-12-01

140

Abyssal ostracods from the South and Equatorial Atlantic Ocean: Biological and paleoceanographic implications  

USGS Publications Warehouse

We report the distribution of ostracods from ???5000 m depth from the Southeast and Equatorial Atlantic Ocean recovered from the uppermost 10 cm of minimally disturbed sediments taken by multiple-corer during the R/V Meteor DIVA2 expedition M63.2. Five cores yielded the following major deep-sea genera: Krithe, Henryhowella, Poseidonamicus, Legitimocythere, Pseudobosquetina, and Pennyella. All genera are widely distributed in abyssal depths in the world's oceans and common in Cenozoic deep-sea sediments. The total number of ostracod specimens is higher and ostracod shell preservation is better near the sediment-water interface, especially at the 0-1 cm core depths. Core slices from ???5 to 10 cm were barren or yielded a few poorly preserved specimens. The DIVA2 cores show that deep-sea ostracod species inhabit corrosive bottom water near the carbonate compensation depth (CCD) even though their calcareous valves are rarely preserved as fossils in sediment cores due to postmortem dissolution. Their occurrence at great water depths may partially explain the well-known global distributions of major deep-sea taxa in the world's oceans, although further expeditions using minimal-disturbance sampling devices are needed to fill geographic gaps. ?? 2008 Elsevier Ltd. All rights reserved.

Yasuhara, M.; Cronin, T. M.; Martinez, Arbizu P.

2008-01-01

141

The influence of vegetation and organic debris on flood-plain sediment dynamics: case study of a low-order stream in the New Forest, England  

Microsoft Academic Search

The presence of large woody debris (LWD) has important implications for the physical and ecological behaviour of rivers, and these aspects have been researched extensively in recent years. However, this research has so far focused primarily on interactions between LWD and in-channel processes, and the role of LWD in flood-plain genesis is still poorly understood. Established conceptual models of flood-plain

Richard Jeffries; Stephen E Darby; David A Sear

2003-01-01

142

Abyssal circulation of the southeastern Pacific and some geological implications  

Microsoft Academic Search

The abyssal circulation of the Pacific Ocean east of the East Pacific Rise is deduced from hydrographic data, supported by a few direct current measurements. Two main flow paths are recognized: across the Chile Rise into the Chile Basin, and thence northward into the Peru Basin and Panama Basin: and eastward across the East Pacific Rise into the Guatemala Basin

Peter Lonsdale

1976-01-01

143

Ontogeny of a flood plain  

USGS Publications Warehouse

The ontogeny of five flood-plain segments is described for a period of 18 yr following a major flood in 1978 on the Powder River in southeastern Montana. The flood plains developed on relatively elevated sand and gravel deposits left within the channel by the 1978 flood. In cross section, the flood plains resemble benches with well-developed natural levees. Flood-plain growth occurred as sediment was draped onto preexisting surfaces in layers of sand and mud a few centimeters to decimeters thick, resulting in some lateral, but mostly vertical accretion. Annual and biannual measurements indicated that, as the flood-plain segments grew upward, the annual rate of vertical accretion decreased as the partial duration recurrence interval for the threshold or bankfull discharge increased from 0.16 to 1.3 yr. It is clear that a constant recurrence interval for overbank flow cannot be meaningfully assigned to this type of flood-plain ontogeny. These flood plains did not grow on migrating point bars, and vertical accretion at least initially occurred within the channel, rather than across the valley flat during extensive overbank flows. Sediments of these flood plains define narrow, elongated stratigraphic units that border the active channel and onlap older flood-plain deposits. These characteristics are considerably different from those of many facies models for meandering river deposits. Facies similar to those described in this paper are likely to be preserved, thereby providing important evidence in the geologic record for episodes of periodic channel expansion by ancient rivers.

Moody, J.A.; Pizzuto, J.E.; Meade, R.H.

1999-01-01

144

Mercury in waters, soils, and sediments of the New Jersey Coastal Plain: A comparison of regional distribution and mobility with the mercury contamination at the William J. Hughes Technical Center, Atlantic County, New Jersey  

USGS Publications Warehouse

Mercury in soils, surface water, and groundwater at the William J. Hughes Technical Center , Atlantic County, New Jersey, has been found at levels that exceed established background concentrations in Coastal Plain waters, and, in some cases, New Jersey State standards for mercury in various media. As of 2012, it is not known whether this mercury is part of regional mercury contamination or whether it is related to former military activities. Regionally, groundwater supplying about 700 domestic wells in the New Jersey Coastal Plain is contaminated with mercury that appears to be derived from anthropogenic inputs, such as agricultural pesticide use and atmospheric deposition. High levels of mercury occasionally are found in Coastal Plain soils, but disturbance during residential development on former agricultural land is thought to have mobilized any mercury applied during farming, a hypothesis borne out by experiments leaching mercury from soils. In the unsewered residential areas with mercury-contaminated groundwater, septic-system effluent is believed to create reducing conditions in which mercury sorbed to subsoils is mobilized to groundwater. In comparing the levels of mercury found in soils, sediments, streamwater, and groundwater at the William J. Hughes Technical Center site with those found regionally, mercury concentrations in groundwater in the region are, in some cases, substantially higher than those found in groundwater at the William J. Hughes Technical Center site. Nevertheless, concentrations of mercury in streamwater at the site are, in some instances, higher than most found regionally. The mercury contents in soils and sediment at the William J. Hughes Technical Center site are substantially higher than those found to date (2012) in the region, indicating that a source other than regional sources may be present at the site.

Barringer, Julia L.; Szabo, Zoltan; Reilly, Pamela A.

2012-01-01

145

SUBSIDENCE OF THE NOBI PLAIN  

Microsoft Academic Search

The Nobi plain underlain by younger sediments is situated in the cent­ ral part of Japan and is about 1300 km2 in area. The yearly rates of sub­ sidence in this area were 1.4 - 1.8 mm before 1925, 2 - 5 mm during the period from 1925 to 1950, 10 - 20 mm during the period from 1950 to

K. Iida; Toyoda K. Sazanaini; T. Kuwahara; K. Ueshita

146

Estimated post-Messinian sediment supply and sedimentation rates on the Ebro continental margin, Spain  

USGS Publications Warehouse

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.

Nelson, C.H.

1990-01-01

147

Sedimental Reasons  

NSDL National Science Digital Library

Visitors to this site can view satellite imagery and read an account of how remote sensing was employed to evaluate the extent of flooding and sediment load in rivers on the coastal plain of North Carolina as a result of Hurricane Floyd in September, 1999. This feature is part of NASA's Earth Observatory, a publication that focuses on Earth's climate and environmental change.

148

Feeding Preferences of Abyssal Macrofauna Inferred from In Situ Pulse Chase Experiments  

PubMed Central

Climatic fluctuations may significantly alter the taxonomic and biochemical composition of phytoplankton blooms and subsequently phytodetritus, the food source for the majority of deep-sea communities. To examine the response of abyssal benthic communities to different food resources we simulated a food sedimentation event containing diatoms and coccolithophorids at Station M in the NE Pacific. In one set of experiments we measured incorporation of diatomC and coccoN into the macrofauna using isotopically enriched 13C-diatoms and 15N-coccolithophores. In a second experiment we measured incorporation of C and N from dual-labelled (13C and 15N) diatoms. The second experiment was repeated 2 months later to assess the effect of seasonality. The simulated food pulses represented additions of 650 – 800 mg C m?2 and 120 mg N m?2 to the seafloor. In all cases rapid incorporation of tracer was observed within 4 days, with between 20% and 52% of the macrofauna displaying evidence of enrichment. However, incorporation levels of both diatomC and coccoN were low (<0.05% and 0.005% of the added C and N). Incorporation of labelled diatoms was similar during both June and September suggesting that the community was not food limited during either period. We found no evidence for selective ingestion of the different food types in the metazoan fauna suggesting that macrofauna do not have strong preferences for diatom vs. coccolithophore dominated phytodetrital pulses. C?N ratios from both experiments suggest that the metazoan macrofauna community appear to have higher C demands and/or assimilation efficiencies compared to N. Concomitantly, the foraminifera preferentially selected for diatomN over coccoN, and we suggest that this may be related to foraminiferal requirements for intracellular nitrate. These experiments provide evidence that abyssal faunal feeding strategies are in part driven by an organism's internal stoichiometric budgets and biochemical requirements. PMID:24303022

Jeffreys, Rachel M.; Burke, Ciara; Jamieson, Alan J.; Narayanaswamy, Bhavani E.; Ruhl, Henry A.; Smith, Kenneth L.; Witte, Ursula

2013-01-01

149

Orphan strontium-87 in abyssal peridotites: daddy was a granite.  

PubMed

The (87)Sr/(86)Sr ratios in some bulk abyssal and alpine peridotites are too high to be binary mixtures of depleted mantle and seawater components. The apparent excess, or "orphan," (87)Sr appears to be separated from its radioactive parent. Such observations were widely held to be analytical artifacts. Study of several occurrences of orphan (87)Sr shows that the orphan component in abyssal peridotite is located in the alteration products of olivine and enstatite in the peridotite. The orphan (87)Sr is most likely introduced by infiltration of low-temperature (<200 degrees C) seawater bearing suspended detrital particulates. These particulates include grains of detrital clay that are partly derived from continental (that is, granitic) sources and thus are highly radiogenic. Orphan (87)Sr and other radiogenic isotopes may provide a tracer for low-temperature seawater penetrating into the oceanic crust. PMID:17829634

Snow, J E; Hart, S R; Dick, H J

1993-12-17

150

Trough-mouth-fan Evolution on the Pacific-Margin of the Antarctic Peninsula Outer Continental Shelf and its Relation to Sediment Drifts on the Adjacent Continental Rise  

NASA Astrophysics Data System (ADS)

Rebesco et al. (1998) propose a general depositional model that relates sediment drift evolution on the Antarctic Peninsula Pacific-margin abyssal plain to glacial processes on the continental shelf. In their model, the terrigenous sediment were directly delivered to the rise and contributed to the construction of large sediment drifts when grounded ice sheets extended to the shelf edge. In this scenario, large volumes of sediment by-passed the margin at the mouth of ice streams (i.e., fast flowing ice), whereas prograding slopes were constructed on those portions of the shelf margin between major ice streams. This model relies heavily on the modern geomorphology of the margin. In contrast, an evaluation of the subsurface stratigraphy suggested that there may have been significant lateral shifts of ice-stream locations and associated trough-mouth-fan depositional systems through time (Bart and Anderson, 1995). New seismic data acquired along the strike of the Antarctic Peninsula shelf during the 2002 season aboard the NBP R/VIB confirm that slope progradation between the modern troughs was indeed associated with large ice streams. Moreover, the data illustrate that the last several glacial cycles did not produce significant slope progradation anywhere along the margin which signifies a major change in the stratal-stacking pattern on the outer continental shelf. This change in stacking pattern is roughly coincident with a major reduction in sedimentation rates on at least two of the drifts (i.e., those drilled at ODP Sites 1095 and 1101).

Holloman, J.; Bart, P. J.

2002-12-01

151

Feasibility of disposal of high-level radioactive wastes into the seabed: Review of laboratory investigations of radionuclide migration through deep-sea sediments  

SciTech Connect

The Sediment Barrier Task Group (SBTG) coordinated laboratory studies of radionuclide migration through deep-sea sediments by investigators in six countries over a period of 12 years. The objectives of these studies were to evaluate the barrier properties of a variety of deep- sea sediments from study locations characterized by the Site Assessment Task Group (SATG), and to obtain site-specific data for use by the Radiological Assessment Task Group (RATG) in models of radionuclide transport through the sediments at the Great Meteor East (GME) and Southern Nares Abyssal Plain (SNAP) study locations in the North Atlantic Ocean. This volume presents a review of these laboratory investigations and the results obtained from them. Although the SBTG also participated in numerous geochemical investigations at the study locations characterized by the SATG, these field studies are not discussed here. For the convenience of the reader, however, this volume contains a brief description of the sediments from GME and SNAP, and the Mid-Plate Mid-Gyre I (MPG I) study location in the North Pacific Ocean. 130 refs., 48 figs., 11 tabs.

Brush, L.H.

1988-08-01

152

Abyssal recipes II: energetics of tidal and wind mixing  

Microsoft Academic Search

Without deep mixing, the ocean would turn, within a few thousand years, into a stagnant pool of cold salty water with equilibrium maintained locally by near-surface mixing and with very weak convectively driven surface-intensified circulation. (This result follows from Sandström’s theorem for a fluid heated and cooled at the surface.) In this context we revisit the 1966 “Abyssal Recipes”, which

Walter Munk; Carl Wunsch

1998-01-01

153

Plain Language  

Cancer.gov

The Plain Writing Act of 2010 requires federal agencies to write "clear Government communication that the public can understand and use." President Obama also emphasized the importance of establishing "a system of transparency, public participation, and collaboration" in his January 21, 2009, Memorandum on Transparency and Open Government.

154

Holocene Climate in the Northern Great Plains Inferred from Sediment Stratigraphy, Stable Isotopes, Carbonate Geochemistry, Diatoms, and Pollen at Moon Lake, North Dakota  

Microsoft Academic Search

Seismic stratigraphy, sedimentary facies, pollen stratigraphy, diatom-inferred salinity, stable isotope (?18O and ?13C), and chemical composition (Sr\\/Ca and Mg\\/Ca) of authigenic carbonates from Moon Lake cores provide a congruent Holocene record of effective moisture for the eastern Northern Great Plains. Between 11,700 and 950014C yr B.P., the climate was cool and moist. A gradual decrease in effective moisture occurred between

Blas L. Valero-Garcés; Kathleen R. Laird; Sherilyn C. Fritz; Kerry Kelts; Emi Ito; Eric C. Grimm

1997-01-01

155

Sorption kinetics of Hg and HgCl[sub 2] on Kirkwood-Cohansey aquifer sediments from the New Jersey Coastal Plain  

Microsoft Academic Search

Anomalously high Hg concentrations have been detected from domestic wells in the Kirkwood-Cohansey Aquifer System, New Jersey Coastal Plain. Mercury concentrations ranging from 0.2--83.0 [mu]g\\/l in relatively shallow wells ([lt] 100 feet) have been detected. Concentrations in excess of 2.0 [mu]g\\/l, (the USEPA Drinking Water Standard) have been detected in wells where the Cohansey Sand is overlain by the Bridgeton

C. MacLeod; J. Peterson

1992-01-01

156

Evaluation of Cross-Hole Seismic Tomography for Imaging Low Resistance Intervals and Associated Carbonate Sediments in Coastal Plain Sequences on the Savannah River Site, South Carolina  

SciTech Connect

The objectives of the pilot study were to investigate the limitations of the technique for imaging the presence, extent, and boundaries of the low-resistance intervals and associated carbonate sediments.

Cumbest, R. J.

1999-01-05

157

Suspended sediment sources and tributary effects in the lower reaches of a coastal plain stream as indicated by radionuclides, Loco Bayou, Texas  

Microsoft Academic Search

Characterizing the dynamics of fluvial sediment sources over space and time is often critical in identifying human impacts on fluvial systems. Upland interfluve and subsoil sources of suspended sediment at Loco Bayou, Texas, were distinguished using 226Ra\\/ 232Th, 226Ra\\/ 230Th and, 228Ra\\/ 232Th. Source contributions were apportioned at three stations during within-bank and flood flows. 137Cs and 210Pb xs (excess

K. M. Yeager; P. H. Santschi; J. D. Phillips; B. E. Herbert

2005-01-01

158

The fish fauna of Ampère Seamount (NE Atlantic) and the adjacent abyssal plain  

NASA Astrophysics Data System (ADS)

An inventory of benthic and benthopelagic fishes is presented as a result of two exploratory surveys around Ampère Seamount, between Madeira and the Portuguese mainland, covering water depths from 60 to 4,400 m. A total of 239 fishes were collected using different types of sampling gear. Three chondrichthyan species and 31 teleosts in 21 families were identified. The collections showed a vertical zonation with little overlap, but indications for an affinity of species to certain water masses were only vague. Although most of the species present new records for Ampère Seamount, all of them have been known for the NE Atlantic; endemic species were not found. The comparison with fish communities at other NE Atlantic seamounts indicates that despite a high ichthyofaunal similarity, which supports the "stepping stone" hypothesis of species dispersal, some differences can be attributed to the local features of the seamounts.

Christiansen, Bernd; Vieira, Rui P.; Christiansen, Sabine; Denda, Anneke; Oliveira, Frederico; Gonçalves, Jorge M. S.

2015-03-01

159

A ridgelet transform method for constraining tectonic models via abyssal-hill morphology  

E-print Network

, a relative of the two-dimensional wavelet transform. Our method is capable of locally estimating the width transform; abyssal hills. Index Terms: 0520 Computational Geophysics: Data analysis: algorithms., 1997]. [3] The shape of abyssal hills is controlled by the faulting process that occurs at oceanic

Clayton, Robert W.

160

Minor and trace element abundance of Cr-spinel from forearc mantle and abyssal peridotites  

E-print Network

Minor and trace element abundance of Cr-spinel from forearc mantle and abyssal peridotites 1 1 2-spinel in peridotites from several locations (fore arc mantle peridotites from the Marianas, Himalayas, Bay of Island). To characterize the spinel compositions from forearc mantle peridotites, spinel in abyssal peridotites from

161

Black carbon and ecological factors affect in situ biota to sediment accumulation factors for hydrophobic organic compounds in flood plain lakes.  

PubMed

Ecological factors may play an important role in the bioaccumulation of polychlorobiphenyls (PCBs) and polyaromatic hydrocarbons (PAHs). Geochemical and bioaccumulation behavior of these chemicals also appears to be related to the presence of black carbon (BC) in sediment. In situ PCB and PAH biota to sediment accumulation factors (BSAF) for benthic invertebrates, as well as 6h Tenax-extractable (fast-desorbing) concentrations and lake characteristics (including BC in sediment), were determined for different seasons in chemically similar but ecologically different lakes (fish-dominated turbid, algae-dominated turbid, and macrophyte-dominated). BSAFs could be explained with a model including a term for Freundlich sorption to BC and a term for uptake from fast-desorbing concentrations in ingested sediments. Freundlich coefficients for in situ sorption to BC (KF) were calculated from slow desorbing fractions and BC contents and agreed well with literature values for KF. Furthermore, in contrast to BSAFs based on total extracted concentrations, Tenax-based BSAF showed a strong positive correlation with log Kow. We therefore argue that BC caused slow desorption and limited BSAFs in these lakes. Seasonal and lake effects on BSAFs were detected, while the differences between oligochaetes and other invertebrates were small for PCBs and within a factor of 10 for PAHs. BSAFs for pyrogenic PAHs were much lower than for PCBs, which was explained by stronger sorption to BC and lesser uptake from ingested sediment. PMID:15926558

Moermond, Caroline T A; Zwolsman, John J G; Koelmans, Albert A

2005-05-01

162

The Late Pliocene Eltanin Impact: Documentation From Sediment Core Analyses  

NASA Technical Reports Server (NTRS)

The expeditions ANT-XII/4 (1995) and ANT-XVIII/5a (2001) of the RV POLARSTERN collected extensive bathymetric and seismic data sets as well as sediment cores from an area in the Bellingshausen Sea (eastern Pacific Southern Ocean) that allow the first comprehensive geoscientific documentation of an asteroid impact into a deep ocean (approx. 5 km) basin, named the Eltanin impact. Impact deposits have now been recovered from a total of more than 20 sediment cores collected in an area covering about 80,000 km2. Combined biomagnetostratigraphic dating places the impact event into the earliest Matuyama Chron, a period of enhanced climate variability. Sediment texture analyses and studies of sediment composition including grain size and microfossil distribution reveal the pattern of impact- related sediment disturbance and the sedimentary processes immediately following the impact event. The pattern is complicated by the San Martin Seamounts (approx. 57.5 S, 91 W), a large topographic elevation that rises up to 3000 m above the surrounding abyssal plain in the area affected by the Eltanin impact. The impact ripped up sediments as old as Eocene and probably Paleocene that have been redeposited in a chaotic assemblage. This is followed by a sequence sedimented from a turbulent flow at the sea floor, overprinted by fall-out of airborne meteoritic ejecta that settled trough the water column. Grain size distribution reveals the timing and interaction of the different sedimentary processes. The gathered estimate of ejecta mass deposited over the studied area, composed of shock-melted asteroidal material and unmelted meteorites including fragments up to 2.5 cm in diameter, point to an Eltanin asteroid larger than the 1 km in diameter size originally suggested as a minimum based on the ANT-XII/4 results. This places the energy released by the impact at the threshold of those considered to cause environmental disturbance at a global scale and it makes the impact a likely transport mechanism explaining the presence of extinct Cenozoic microfossils in the transantarctic Sirius Unit. Although a crater structure representing Eltanin ground zero has not been discovered, the distribution pattern of sediment disturbance and ejecta deposits now allows to better determine the central target area north of the San Martin Seamounts.

Gersonde, R.; Kyte, F.; Flores, J. A.; Becquey, S.

2002-01-01

163

A Deep Cabled Observatory: Biology and Physics in the Abyss  

NASA Astrophysics Data System (ADS)

The ALOHA Cabled Observatory (ACO) is the deepest operating observatory on the planet, providing power and communications to scientific instruments on the seafloor. In the future, ACO will add water column measurements, from the seafloor to the surface, using moorings and undersea vehicles. Recent results from video monitoring of deep-sea life and from temperature sensors illustrate the benefit of and need for long-term, sustained, continuous sampling in this abyssal context. The observatory is located at Station ALOHA (A Long-Term Oligotrophic Habitat Assessment), 100 kilometers north of Oahu, at 4728-meter water depth (Figure 1, top).

Howe, Bruce M.

2014-11-01

164

Abyssal Hill Segmentation: Quantitative analysis of the East Pacific Rise flanks 7°S-9°S  

NASA Astrophysics Data System (ADS)

The recent R/V Maurice Ewing EW9105 Hydrosweep survey of the East Pacific Rise (EPR) and adjacent flanks between 7°S and 9°S provides an excellent opportunity to explore the causal relationship between the ridge and the abyssal hills which form on its flanks. These data cover 100% of the flanking abyssal hills to 115 km on either side of the axis. We apply the methodology of Goff and Jordan (1988) for estimating statistical characteristics of abyssal hill morphology (rms height, characteristic lengths and widths, plan view aspect ratio, azimuthal orientation, and fractal dimension). Principal observations include the following: (1) the rms height of abyssal hill morphology is negatively correlated with the width of the 5- to 20-km-wide crestal high, consistent with the observations of Goff (1991) for northern EPR abyssal hill morphology; (2) the characteristic abyssal hill width displays no systematic variation with position relative to ridge segmentation within the EW9105 survey area, in contrast with observations of Goff (1991) for northern EPR abyssal hill morphology in which characteristic widths tend to be smallest at segment ends and largest toward the middle of segments; (3) abyssal hill rms heights and characteristic widths are very large just north of a counterclockwise rotating "nannoplate", suggesting that the overlap region is being pushed northward in response to microplate-style tectonics; and (4) within the 7°12'S-8°38'S segment, abyssal hill lineaments are generally parallel to the ridge axis, while south of this area, abyssal hill lineaments rotate with a larger "radius of curvature" than does the EPR axis approaching the EPR-Wilkes ridge-transform intersection.

Goff, John A.; Malinverno, Alberto; Fornari, Daniel J.; Cochran, James R.

1993-08-01

165

The use of environmental radionuclides in investigations of sediment sources and overbank sedimentation rates in the Himalaya Foreland, India  

Microsoft Academic Search

This paper presents some preliminary results from an investigation of overbank sedimentation rates on the flood plains of the Teesta and Brahmaputra Rivers in the Himalaya Foreland, India. The 210Pbex, 226 Ra and 137 Cs depth distributions in sediment cores have been used to derive estimates of overbank sedimentation rates. The estimated sedimentation rates for the flood plains of the

W. FROEHLICH; D. E. WALLING

166

Bacterial and Archaeal 16S rRNA Genes in Late Pleistocene to Holocene Muddy Sediments from the Kanto Plain of Japan  

Microsoft Academic Search

Microbial communities in ancient marine sediments composed of clay and silt obtained from the terrestrial subsurface were phylogenetically analyzed based on their 16S rRNA gene sequences. Chloroflexi and Miscellaneous Crenarchaeotic Group were predominant in bacterial and archaeal clone libraries, respectively. Of 44 operational taxonomic units (OTUs) that had close relatives in the database, 30 were close to sequences obtained from

Mio Takeuchi; Takeshi Komai; Satoshi Hanada; Hideyuki Tamaki; Susumu Tanabe; Yoshinori Miyachi; Mieko Uchiyama; Tsutomu Nakazawa; Katsumi Kimura; Yoichi Kamagata

2009-01-01

167

Utopia Plain  

NASA Technical Reports Server (NTRS)

5 March 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a dark-toned, cratered plain in southwest Utopia Planitia. Large, light-toned, windblown ripples reside on the floors of many of the depressions in the scene, including a long, linear, trough.

Location near: 30.3oN, 255.3oW Image width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Winter

2006-01-01

168

Abyssal ocean warming around Antarctica strengthens the Atlantic overturning circulation  

NASA Astrophysics Data System (ADS)

The abyssal warming around Antarctica is one of the most prominent multidecadal signals of change in the global ocean. Here we investigate its dynamical impacts on the Atlantic Meridional Overturning Circulation (AMOC) by performing a set of experiments with the ocean-sea ice model NEMO-LIM2 at ½° horizontal resolution. The simulations suggest that the ongoing warming of Antarctic Bottom Water (AABW), already affecting much of the Southern Hemisphere with a rate of up to 0.05°C decade-1, has important implications for the large-scale meridional overturning circulation in the Atlantic Ocean. While the abyssal northward flow of AABW is weakening, we find the upper AMOC cell to progressively strengthen by 5-10% in response to deep density changes in the South Atlantic. The simulations suggest that the AABW-induced strengthening of the AMOC is already extending into the subtropical North Atlantic, implying that the process may counteract the projected decrease of the AMOC in the next decades.

Patara, Lavinia; Böning, Claus W.

2014-06-01

169

Mercury net methylation in five tropical flood plain regions of Brazil: high in the root zone of floating macrophyte mats but low in surface sediments and flooded soils.  

PubMed

In aquatic systems, bottom sediments have often been considered as the main methylmercury (MeHg) production site. In tropical floodplain areas, however, floating meadows and flooded forests extend over large areas and can be important Hg methylating sites. We present here a cross-system comparison of the Hg net methylation capacity in surface sediments, flooded soils and roots of floating aquatic macrophytes, assayed by in situ incubation with 203Hg and extraction of formed Me203 Hg by acid leaching and toluene. The presence of mono-MeHg was confirmed by thin layer chromatography and other techniques. Study areas included floodplain lakes in the Amazon basin (Tapajós, Negro and Amazon rivers), the Pantanal floodplain (Paraguay river basin), freshwater coastal lagoons in Rio de Janeiro and oxbow lakes in the Mogi-Guaçú river, São Paulo state. Different Hg levels were added in assays performed in 1994-1998, but great care was taken to standardise all other test parameters, to allow data comparisons. Net MeHg production was one order of magnitude higher (mean 13.8%, range 0.28-35) in the living or decomposing roots of floating or rooted macrophyte mats (Eichhornia azurea, E. crassipes, Paspalum sp., Eleocharis sellowiana, Salvinia sp., S. rotundifolia and Scirpus cubensis) than in the surface layer of underlying lake sediments (mean 0.6%, range 0.022-2.5). Methylation in flooded soils presented a wide range and was in some cases similar to the one found in macrophyte roots but usually much lower. In a Tapajós floodplain lake, natural concentrations of MeHg in soil and sediment cores taken along a lake-forest transect agreed well with data on net methylation potentials in the same samples. E. azurea, E. crassipes and Salvinia presented the highest methylation potentials, up to 113 times higher than in sediments. Methylation in E. azurea from six lakes of the Paraguay and Cuiabá rivers, high Pantanal, was determined in the 1998 dry and wet seasons and ranged from 1.8 to 35%. Methylation was lower in washed roots than in untreated roots of E. azurea and methylation in solids isolated from the roots, was higher than in sediments but lower than in untreated roots. This indicates that the methylation in roots zones occurs mainly in the root-associated solids. Floating meadows are sites of intense production of biomass and of highly bioavailable MeHg and appear to be an essential link of the MeHg cycle in tropical aquatic systems. PMID:11036981

Guimarães, J R; Meili, M; Hylander, L D; de Castro e Silva, E; Roulet, M; Mauro, J B; de Lemos, R

2000-10-16

170

Relation of Mercury to Other Chemical Constituents in Ground Water in the Kirkwood-Cohansey Aquifer System, New Jersey Coastal Plain, and Mechanisms for Mobilization of Mercury from Sediments to Ground Water  

USGS Publications Warehouse

Water from 265 domestic wells that tap the unconfined Kirkwood-Cohansey aquifer system in the Coastal Plain of New Jersey contained concentrations of mercury that are equal to or exceed the U.S. Environmental Protection Agency maximum contaminant level (MCL) of 2 ug/L (micrograms per liter). The wells range in depth from 50 to 200 feet, and are located in 32 discrete, mostly residential, areas that were developed primarily on former agricultural land during the 1950?s through the 1970?s. Concentrations in two other areas exceeded 1 ug/L. Naturally occurring mercury concentrations in ground water from the Kirkwood-Cohansey aquifer system typically are less than 0.01 ug/L, but concentrations in water from some wells were as much as 42 ug/L. No evidence currently exists that conclusively links known point sources such as landfills, industrial operations, or commercial enterprises to most of the elevated concentrations of mercury in ground water in the residential areas. Possible sources of the mercury include pesticides and atmospheric deposition. Analysis of water from wells in 6 of the 34 areas for other constituents indicates that nitrate concentrations also commonly are elevated above background levels (which typically are undetectable at 0.01 milligrams per liter), and exceed the MCL of 10 milligrams per liter in some samples. Several volatile organic compounds (VOCs), including chloroform, also have been measured in water from wells at many of the 34 sites. Analytical results for water samples collected at several depths from boreholes at 2 of the 34 sites indicate elevated concentrations of calcium, magnesium, barium, strontium, nitrate, and chloride, which may be related to both agricultural chemical applications and septic-system effluent. Determinations of tritium and helium concentrations indicate that water containing elevated concentrations of mercury recharged the aquifer between 9.4 and 79 years ago, which includes the period during which many of the 34 sites were undergoing a change from agricultural or undeveloped to residential land use. Batch equilibrium experiments were used to measure adsorption of dissolved mercury, mercuric chloride, and phenylmercuric acetate by aquifer sediments at pH 3.5-4.0, 4.5-5.0, and 5.5-6.0. In nearly all cases, 55 to 95 percent of the mercury added to the sediments was adsorbed. Mercury mobilization from aquifer sediments inoculated with mercury was investigated by leaching the sediments with two concentrations of nitric acid (a component of acid rain), a sodium chloride solution (simulating road salt), and three fertilizer solutions. A solution of 20-20-20 (nitrogenphosphorous-potassium) fertilizer removed virtually all of the mercury with which the sediments had been inoculated. The sodium chloride solution was moderately effective in removing applied mercury from the sediments, as was a solution of nitric acid. A more dilute nitric acid solution and two sodium nitrate fertilizer solutions were less effective. Results of these experiments indicate that mercury adsorbs to aquifer sediments, but that varying amounts can be removed by infiltrating solutions, some of which can be related to specific land uses. Land-use history at the 34 sites generally indicates a change from agricultural or undeveloped settings to residential settings. Whatever the source of mercury to these sites, a change in the geochemical environment of the soil and aquifer brought about by land-use change probably provides mechanisms for mobilizing the mercury from soils and sediments to ground water.

Barringer, Julia L.; MacLeod, Cecilia L.

2001-01-01

171

Inter-annual dynamics of abyssal polychaete communities in the North East Pacific and North East Atlantic—A family-level study  

NASA Astrophysics Data System (ADS)

Characterising how deep-sea communities change on contemporary time-scales and understanding underlying ecosystem processes has become important under changing climate and the rise in the exploitation of deep-sea resources. However, little is known about these dynamics and processes. Long-term observations from which inter-annual variations can be detected are scarce in the deep sea. This study examines inter-annual changes in density, family richness and evenness, family and functional group rank abundance distributions of infaunal polychaetes at two abyssal stations in the North East Pacific (Station M, 1991 to 2005) and in the North East Atlantic (Porcupine Abyssal Plain, 1991 to 1999). The two long-term data sets were used to investigate not only if polychaete community structure and composition varied at inter-annual scales in terms of diversity and rank abundance distributions but also if any changes were related to previous observations in megafauna and environmental factors at each locality. The polychaete community structure at each locality was analysed using univariate statistics as well as multivariate ordination techniques based on Bray-Curtis similarity of the yearly family density. Sub-surface deposit feeders, such as Paraonidae, dominated the North East Pacific, whereas surface deposit feeders, such as Cirratulidae, dominated the North East Atlantic. Both stations showed inter-annual variations in density, family evenness and rank abundance distributions. The greatest changes occurred in 1998 in both time series when polychaete densities peaked, and switches in the rank abundance of the most abundant families and functional groups took place. Inter-annual variations in the polychaete community were correlated with a limited number of holothurian species changes, but no correlation was found with particulate organic matter flux or climate indices. Ecological and environmental factors behind the family-level changes remain elusive. Overall, changes in the dominance of functional groups imply changes in abyssal ecosystem functioning with potential consequences on carbon cycling at the seabed.

Laguionie-Marchais, C.; Billett, D. S. M.; Paterson, G. L. D.; Ruhl, H. A.; Soto, E. H.; Smith, K. L., Jr.; Thatje, S.

2013-05-01

172

Groundwater arsenic in the Chaco-Pampean Plain, Argentina  

Microsoft Academic Search

In large parts of rural Argentina people depend on groundwater whose As content exceeds the Argentine drinking water standards (0.05 mg l?1). The most affected areas are located in the Chaco-Pampean Plain, where aquifers comprise Tertiary loess deposits (in the Pampean Plain) and Tertiary and Quaternary fluvial and aeolian sediments (in the Chaco Plain). Robles county is located in the

J. Bundschuh; B. Farias; R. Martin; A. Storniolo; P. Bhattacharya; J. Cortes; G. Bonorino; R. Albouy

2004-01-01

173

Taphonomy and paleoecology of nonmarine mollusca: indicators of alluvial plain lacustrine sedimentation, upper part of the Tongue River Member, Fort Union Formation ( Paleocene), Northern Powder River Basin, Wyoming and Montana ( USA).  

USGS Publications Warehouse

The composition, species abundances, and spatial and temporal distributions of mollusc assemblages were controlled by the environments in which they lived and the depositional processes that affected the molluscs after death and before final burial. Post-mortem transport, reworking and concentration of shells, and mixing of faunal elements from discrete habitats produced a taphonomic 'overprint' on assemblage characteristics that directly reflects the processes of alluvial plain and floodbasin lacustrine sedimentation. The 'overprint' can be interpreted from outcrop analysis of molluscan biofabric, which consists of: 1) orientation, fragmentation, size-sorting, abrasion, density, and dispersion of shells, 2) the nature and extent of shell-infilling, and 3) ratio of articulated to disarticulated bivalves. Taphonomic characteristics were used with sedimentological properties to differentiate in-place, reworked, transported, and ecologically mixed mollusc assemblages. This study also defines the paleoecology of habitat preferences of mollusc species as a basis for recognition of the environments in which these assemblages were deposited: 1) large floodbasin lakes, 2) small floodbasin lakes, and 3) crevasse deltas and splays. Integration of sedimentology and paleoecology provides an interdisciplinary approach to the interpretation of alluvial environments through time in the Tongue River Member. -Authors

Hanley, J.H.; Flores, R.M.

1987-01-01

174

Peculiarities of Environment Pollution as a Special Type of Radioactive Waste: Field Means for Comprehensive Characterization of Soil and Bottom Sediments and their Application in the Survey at the Flood plain of Techa River - 13172  

SciTech Connect

Contamination of natural objects - zone alarm fallout, zones and flood plains near production sites (the result of technological accidents and resource extraction) occupy large areas. Large area and volume of contaminated matter, moderate specific activity (as low - medium-level wastes) make such objects specific types of radioactive waste. These objects exist for a long time, now they are characterized by a bound state of nuclides with the matrix. There is no cost-effective ways to remove these waste, the only solution for the rehabilitation of such areas is their isolation and regular monitoring through direct and indirect measurements. The complex of instruments was developed to field mapping of contamination. It consists of a portable spectrometric collimated detector, collimated spectrometric borehole detector, underwater spectrometer detector, spectrometer for field measurements of the specific activity of Sr-90, connected to a portable MCA 'Colibry (Hummingbird)'. The complex was used in settlements of Bryansk region, rivers Techa and Yenisei. The effectiveness of the developed complex considered by the example of characterization of the reservoir 10 (artificial lake) in Techinsky cascade containing a huge amount of radioactive waste. The developed field means for comprehensive characterization of soil and bottom sediments contamination are very effective for mapping and monitoring of environment contamination after accidents. Especially in case of high non-uniformity of fallout and may be very actual in Fukushima area. (authors)

Ivanov, Oleg; Danilovich, Alexey; Potapov, Victor; Stepanov, Vyacheslav; Smirnov, Sergey; Volkovich, Anatoly [National Research Centre - Kurchatov Institute, 1 Kurchatov Sq. (Russian Federation)] [National Research Centre - Kurchatov Institute, 1 Kurchatov Sq. (Russian Federation)

2013-07-01

175

Isotopic evidence for the source of lead in the North Pacific abyssal water  

E-print Network

The absence of accurate measurements of lead (Pb) isotopic composition in the pristine North Pacific abyssal water has made it difficult to assess the relative importance of what are believed to be the two major Pb sources: ...

Wu, Jingfeng

176

Saturation of the Internal Tides and Induced Mixing in the Abyssal Ocean  

E-print Network

As part of an ongoing effort to develop a parameterization of wave-induced abyssal mixing, the authors derive an heuristic model for nonlinear wave breaking and energy dissipation associated with internal tides. Then the ...

Bu?hler, Oliver

177

The role of the geothermal heat flux in driving the abyssal ocean circulation  

E-print Network

The results presented in this paper demonstrate that the geothermal heat flux (GHF) from the solid Earth into the ocean plays a non-negligible role in determining both abyssal stratification and circulation strength. Based ...

Mashayek, A.

178

Evidence for Pulsed Hydrothermal Venting from Young Abyssal Hills on the EPR Flank Suggests Frequent Seismic Pumping of Ridge Flank Fluid Flow  

NASA Astrophysics Data System (ADS)

Although measured heat flow suggests that 40-50% of oceanic hydrothermal heat and fluid flux is from young (0.1-5 Ma) abyssal hill terrain on MOR flanks, hydrothermal vents in this setting rarely have been found. On the EPR flanks, seafloor evidence of venting from abyssal hills has been discovered recently at two sites: on ˜0.1 Ma seafloor at 10° 20'N, 103° 33.2'W ("Tevnia Site") and on ˜0.5 Ma seafloor at 9° 27'N, 104° 32.3'W ("Macrobes Site"). Manifestations of venting at these sites include: fault scarp hydrothermal mineralization and macrofauna; fault scarp flocculations containing hyperthermophilic microbes; and hilltop sediment mounds and craters possibly created by fluid "blow-outs." Hydrothermal deposits recovered at the ˜0.1 Ma "Tevnia Site" are fault breccias that record many episodes of brecciation followed by hydrothermal cementation (Benjamin et al., this session). Tubeworm casings, live crabs, and "dandelions" observed at this site indicate that the most recent episode of venting was active during, or shortly before, this site was visited with Alvin in 1994. To create the 200 m-high axis-facing fault scarp at Tevnia Site in 100,000 years, an average uplift rate of at least 2 cm/y is required. Since off-axis earthquakes located on abyssal hill fault scarps typically are abyssal hills are uplifted on ridge flanks. Hyperthermophiles identified in microbial floc on the axis-facing fault scarp at the ˜0.5 Ma "Macrobes Site" are associated with chalcopyrite particles (Ehrhardt et al., this session). These observations indicate recent, transient venting of high-T (at least 250° C), Cu-rich fluids from the fault scarp. The hilltop here has many meter-scale sediment mounds and craters (macs). These appear to be small mud volcanoes that have formed at different times from fluids expelled episodically through the thin sediments blanketing the hilltop. Formation of macs may be triggered by frequent (decadal) seismic events that also produce transient bursts of high T fluid flow from the adjacent fault scarp. Hyperthermophiles in the subsurface may flush out and bloom on the fault scarp during these events, and then remain dormant until the next event. The combined evidence from the two EPR ridge flank sites points to seismic pumping of EPR abyssal hill hydrothermal pulses every few years-to-decades. These frequent hydrothermal pulses may be important in sustaining ridge flank biota. Monitoring of EPR abyssal hill fault scarps is needed to test these ideas.

Haymon, R. M.; MacDonald, K. C.; Benjamin, S. B.; Ehrhardt, C. J.

2004-12-01

179

A late Quaternary stratigraphic framework for the northeastern Ruapehu and eastern Tongariro ring plains, New Zealand  

Microsoft Academic Search

The northeastern Ruapehu and eastern Tongariro ring plains record a complex sequence of episodic lahar sedimentation. Andesitic and rhyolitic tephrostratigraphy reveals 15 lahar episodes in the northeastern Ruapehu ring?plain record ranging in age from >65 to 5 ka, and five in the Tongariro ring?plain record ranging in age from >23 to 14 ka. The most voluminous and widespread lahar deposition

Shane J. Cronin; Vincent E. Neall

1997-01-01

180

190Pt– 186Os and 187Re– 187Os systematics of abyssal peridotites  

Microsoft Academic Search

Abyssal peridotites are normally thought to be residues of melting of the mid-ocean ridge basalt (MORB) source and are presumably a record of processes affecting the upper mantle. Samples from a single section of abyssal peridotite from the Kane Transform area in the Atlantic Ocean were examined for 190Pt–186Os and 187Re–187Os systematics. They have uniform 186Os\\/188Os ratios with a mean

Alan D Brandon; Jonathan E Snow; Richard J Walker; John W Morgan; Timothy D Mock

2000-01-01

181

Organic-Carbon Sequestration in Soil/Sediment of the Mississippi River Deltaic Plain - Data; Landscape Distribution, Storage, and Inventory; Accumulation Rates; and Recent Loss, Including a Post-Katrina Preliminary Analysis (Chapter B)  

USGS Publications Warehouse

Soil/sediment of the Mississippi River deltaic plain (MRDP) in southeastern Louisiana is rich in organic carbon (OC). The MRDP contains about 2 percent of all OC in the surface meter of soil/sediment in the Mississippi River Basin (MRB). Environments within the MRDP differ in soil/sediment organic carbon (SOC) accumulation rate, storage, and inventory. The focus of this study was twofold: (1) develop a database for OC and bulk density for MRDP soil/sediment; and (2) estimate SOC storage, inventory, and accumulation rates for the dominant environments (brackish, intermediate, and fresh marsh; natural levee; distributary; backswamp; and swamp) in the MRDP. Comparative studies were conducted to determine which field and laboratory methods result in the most accurate and reproducible bulk-density values for each marsh environment. Sampling methods included push-core, vibracore, peat borer, and Hargis1 sampler. Bulk-density data for cores taken by the 'short push-core method' proved to be more internally consistent than data for samples collected by other methods. Laboratory methods to estimate OC concentration and inorganic-constituent concentration included mass spectrometry, coulometry, and loss-on-ignition. For the sampled MRDP environments, these methods were comparable. SOC storage was calculated for each core with adequate OC and bulk-density data. SOC inventory was calculated using core-specific data from this study and available published and unpublished pedon data linked to SSURGO2 map units. Sample age was estimated using isotopic cesium (137Cs), lead (210Pb), and carbon (14C), elemental Pb, palynomorphs, other stratigraphic markers, and written history. SOC accumulation rates were estimated for each core with adequate age data. Cesium-137 profiles for marsh soil/sediment are the least ambiguous. Levee and distributary 137Cs profiles show the effects of intermittent allochthonous input and/or sediment resuspension. Cesium-137 and 210Pb data gave the most consistent and interpretable information for age estimations of soil/sediment deposited during the 1900s. For several cores, isotopic 14C and 137Cs data allowed the 1963-64 nuclear weapons testing (NWT) peak-activity datum to be placed within a few-centimeter depth interval. In some cores, a too old 14C age (when compared to 137Cs and microstratigraphic-marker data) is the probable result of old carbon bound to clay minerals incorporated into the organic soil/sediment. Elemental Pb coupled with Pb source-function data allowed age estimation for soil/sediment that accumulated during the late 1920s through the 1980s. Exotic pollen (for example, Vigna unguiculata and Alternanthera philoxeroides) and other microstratigraphic indicators (for example, carbon spherules) allowed age estimations for marsh soil/sediment deposited during the settlement of New Orleans (1717-20) through the early 1900s. For this study, MRDP distributary and swamp environments were each represented by only one core, backswamp environment by two cores, all other environments by three or more cores. MRDP core data for the surface meter soil/sediment indicate that (1) coastal marshes, abandoned distributaries, and swamps have regional SOC-storage values >16 kg m-2; (2) swamps and abandoned distributaries have the highest SOC storage values (swamp, 44.8 kg m-2; abandoned distributary, 50.9 kg m-2); (3) fresh-to-brackish marsh environments have the second highest site-specific SOC-storage values; and (4) site-specific marsh SOC storage values decrease as the salinity of the environment increases (fresh-marsh, 36.2 kg m-2; intermediate marsh, 26.2 kg m-2; brackish marsh, 21.5 kg m-2). This inverse relation between salinity and SOC storage is opposite the regional systematic increase in SOC storage with increasing salinity that is evident when SOC storage is mapped by linking pedon data to SSURGO map units (fresh marsh, 47 kg m-2; intermediate marsh, 67 kg m-2; brackish marsh, 75 kg m-2; and salt marsh, 80 kg m-2). MRDP core data for this study also indicate that levees and backswamp have regional SOC-

Markewich, Helaine W.; Buell, Gary R.; Britsch, Louis D.; McGeehin, John P.; Robbins, John A.; Wrenn, John H.; Dillon, Douglas L.; Fries, Terry L.; Morehead, Nancy R.

2007-01-01

182

Stratigraphy of the Martian northern plains  

NASA Technical Reports Server (NTRS)

The northern plains of Mars are roughly defined as the large continuous region of lowlands that lies below Martian datum, plus higher areas within the region that were built up by volcanism, sedimentation, tectonism, and impacts. These northern lowlands span about 50 x 10(exp 6) km(sup 2) or 35 percent of the planet's surface. The age and origin of the lowlands continue to be debated by proponents of impact and tectonic explanations. Geologic mapping and topical studies indicate that volcanic, fluvial, and eolian deposition have played major roles in the infilling of this vast depression. Periglacial, glacial, fluvial, eolian, tectonic, and impact processes have locally modified the surface. Because of the northern plains' complex history of sedimentation and modification, much of their stratigraphy was obscured. Thus the stratigraphy developed is necessarily vague and provisional: it is based on various clues from within the lowlands as well as from highland areas within and bordering the plains. The results are summarized.

Tanaka, K. L.

1993-01-01

183

Stratigraphy of the Martian northern plains  

Microsoft Academic Search

The northern plains of Mars are roughly defined as the large continuous region of lowlands that lies below Martian datum, plus higher areas within the region that were built up by volcanism, sedimentation, tectonism, and impacts. These northern lowlands span about 50 x 106 km2 or 35 percent of the planet's surface. The age and origin of the lowlands continue

K. L. Tanaka

1993-01-01

184

The response of abyssal organisms to low pH conditions during a series of CO2-release experiments simulating deep-sea carbon sequestration  

NASA Astrophysics Data System (ADS)

The effects of low-pH, high-pCO2 conditions on deep-sea organisms were examined during four deep-sea CO2 release experiments simulating deep-ocean C sequestration by the direct injection of CO2 into the deep sea. We examined the survival of common deep-sea, benthic organisms (microbes; macrofauna, dominated by Polychaeta, Nematoda, Crustacea, Mollusca; megafauna, Echinodermata, Mollusca, Pisces) exposed to low-pH waters emanating as a dissolution plume from pools of liquid carbon dioxide released on the seabed during four abyssal CO2-release experiments. Microbial abundance in deep-sea sediments was unchanged in one experiment, but increased under environmental hypercapnia during another, where the microbial assemblage may have benefited indirectly from the negative impact of low-pH conditions on other taxa. Lower abyssal metazoans exhibited low survival rates near CO2 pools. No urchins or holothurians survived during 30-42 days of exposure to episodic, but severe environmental hypercapnia during one experiment (E1; pH reduced by as much as ca. 1.4 units). These large pH reductions also caused 75% mortality for the deep-sea amphipod, Haploops lodo, near CO2 pools. Survival under smaller pH reductions (?pH<0.4 units) in other experiments (E2, E3, E5) was higher for all taxa, including echinoderms. Gastropods, cephalopods, and fish were more tolerant than most other taxa. The gastropod Retimohnia sp. and octopus Benthoctopus sp. survived exposure to pH reductions that episodically reached -0.3 pH units. Ninety percent of abyssal zoarcids (Pachycara bulbiceps) survived exposure to pH changes reaching ca. -0.3 pH units during 30-42 day-long experiments.

Barry, J. P.; Buck, K. R.; Lovera, C.; Brewer, P. G.; Seibel, B. A.; Drazen, J. C.; Tamburri, M. N.; Whaling, P. J.; Kuhnz, L.; Pane, E. F.

2013-08-01

185

Holocene fluvial processes in Troy plain  

NASA Astrophysics Data System (ADS)

The Troy plain is the lower part of Scamander (Karamenderes) River basin before its mouth in the Dardanelle straits. The fluvial processes of the deltaic progradation and floodplain aggradation have changed the landscape of the plain during the past 10,000 years. They transformed a sheltered gulf reaching the Ancient Troy into an extensive plain. Ancient Troy is today 7 km inland while Simois (Dumrek) River is a tributary of Scamander (Karamenderes) River. A detailed geomorphological survey with high resolution topographical measurements was carried out using of a TOPCON FC100 differential GPS. This survey took place not only along the Troy plain but further southwards in Araplar gorge and Ezine basin. The morphological analysis of the data showed that the graded channel profile of the Scamander River is lower than its alluvial plain. The channel incision ranging from 2 to 5 meters is responsible for the formation of a pair of alluvial terraces along the channel. These aggradational terraces formed into the resent alluvial sandy deposits of the basin. The channel morphology of an alluvial river like Scamander is highly sensitive in changes concerning the discharge and the sediment load at downstream points. Active tectonics, climate change and sea level rise are the main causes of changes in the channel equilibrium. Ten sediment samples, from the alluvial terraces in Araplar gorge, were dated with OSL technique. The sample ages allowed the time estimation of the channel changes.

Vouvalidis, Konstantinos; Ates, Ozkan; Syrides, George; Pavlides, Spyros; Tutkun, Zeki; Chatzipetros, Alexandros; Ozden, Suha; Mavroudis, Petros; Sboras, Sotirios; Kurcer, Akin; Valkaniotis, S.

2010-05-01

186

Thermal history of deep-sea sediments as a record of recent changes in the deep circulation of the eastern Mediterranean  

NASA Astrophysics Data System (ADS)

During three cruises of the MEDRIFF project in 1993 and 1994, 154 geothermal heat flow measurements and seven CTD profiles in the water column have been collected along a 300 km SW-NE oriented transect traversing the Mediterranean Ridge accretionary complex. The original goal of the measurements was to identify areas of anomalous heat flow that could be interpreted as possible sites for fluid outflow. Contrary to expectations, the upper few meters of the temperature profiles in the sediments showed decreasing temperature from the seafloor down to 3 to 6 m depth indicating consistently transient temperature regimes. The only exception (positive heat flow) was found in the Sirte abyssal plain. Measurements collected in the same area at different times indicated that the thermal structure in the bottom water and sediments had changed significantly at weekly, monthly, and interannual timescales. One-dimensional forward modeling of the conductive heat propagation into the sediment explains the observed thermal anomalies, assuming up to 0.5 K warming of the bottom waters that propagated south westward from the Matapan Trench to the crestal area of the Mediterranean Ridge. Analysis of nonsteady state thermal profiles in the upper sediment provided time information on the onset of bottom water warming, by what is now called the Eastern Mediterranean Transient (EMT). The sediment warming started in the Matapan Trench, between spring 1992 and spring 1993, and reached the Mediterranean Ridge crest in spring-summer 1993. The average propagation velocity of the thermal perturbation along the profile is about 0.5-1.6 km d-1 (0.6-1.8 cm s-1).

Della Vedova, B.; Pellis, G.; Camerlenghi, A.; Foucher, J. P.; Harmegnies, F.

2003-09-01

187

Z .Earth and Planetary Science Letters 152 1997 251265 The origin of abyssal peridotites: a new perspective  

E-print Network

Z .Earth and Planetary Science Letters 152 1997 251­265 The origin of abyssal peridotites: a new peridotites have been interpreted to be residues of mantle melting beneath ocean ridges. Recent experimental that abyssal peridotites are not purely melting residues. Their modal proportions and whole-rock compositions

Langmuir, Charles H.

188

Edwardsia sojabio sp. n. (Cnidaria: Anthozoa: Actiniaria: Edwardsiidae), a new abyssal sea anemone from the Sea ofJapan  

NASA Astrophysics Data System (ADS)

The paper describes new deep-water edwardsiid sea anemone Edwardsia sojabio sp. n. which is very common on soft muddy bottoms at lower bathyal and upper abyssal depths in the Sea of Japan. It was recorded in high quantity in depths between 2545 and 3550 m and is the second abyssal species of the genus Edwardsia.

Sanamyan, Nadya; Sanamyan, Karen

2013-02-01

189

Postdoctoral fellowship in ore-deposit geology/igneous geochemistry Marie-Curie Initial Training Network ABYSS (ER1)  

E-print Network

Postdoctoral fellowship in ore-deposit geology/igneous geochemistry Marie-Curie Initial Training Network ABYSS (ER1) Training network on reactive geological systems from the mantle to the abyssal sub-Cu-PGE deposits Requirements: Candidates must hold PhD in geology/geochemistry This fellowship is for a period

Demouchy, Sylvie

190

Clay mineral distribution in surface sediments of the South Atlantic: sources, transport, and relation to oceanography  

Microsoft Academic Search

Surface samples, mostly from abyssal sediments of the South Atlantic, from parts of the equatorial Atlantic, and of the Antarctic Ocean, were investigated for clay content and clay mineral composition. Maps of relative clay mineral content were compiled, which improve previous maps by showing more details, especially at high latitudes. Large-scale relations regarding the origin and transport paths of detrital

Rainer Petschick; Gerhard Kuhn; Franz Gingele

1996-01-01

191

Preliminary Flood Plain Characterization Appendix A  

E-print Network

Appendix A Preliminary Flood Plain Characterization #12;Appendix A Preliminary Flood Plain ................................................................................................................................. 1 1.1 Flood Plain Preliminary Characterization Objectives.......................................................................1 2 Flood Plain Preliminary Characterization Activities

192

Sources and controls for the mobility of arsenic in oxidizing groundwaters from loess-type sediments in arid/semi-arid dry climates - evidence from the Chaco-Pampean plain (Argentina).  

PubMed

In oxidizing aquifers, arsenic (As) mobilization from sediments into groundwater is controlled by pH-dependent As desorption from and dissolution of mineral phases. If climate is dry, then the process of evaporative concentration contributes further to the total concentration of dissolved As. In this paper the principal As mobility controls under these conditions have been demonstrated for Salí River alluvial basin in NW Argentina (Tucumán Province; 7000 km(2)), which is representative for other basins or areas of the predominantly semi-arid Chaco-Pampean plain (1,000,000 km(2)) which is one of the world's largest regions affected by high As concentrations in groundwater. Detailed hydrogeochemical studies have been performed in the Salí River basin where 85 groundwater samples from shallow aquifers (42 samples), deep samples (26 samples) and artesian aquifers (17 samples) have been collected. Arsenic concentrations range from 11.4 to 1660 ?g L(-1) leaving 100% of the investigated waters above the provisional WHO guideline value of 10 ?g L(-1). A strong positive correlation among As, F, and V in shallow groundwaters was found. The correlations among those trace elements and U, B and Mo have less significance. High pH (up to 9.2) and high bicarbonate (HCO(3)) concentrations favour leaching from pyroclastic materials, including volcanic glass which is present to 20-25% in the loess-type aquifer sediments and yield higher trace element concentrations in groundwater from shallow aquifers compared to deep and artesian aquifers. The significant increase in minor and trace element concentrations and salinity in shallow aquifers is related to strong evaporation under semi-arid climatic conditions. Sorption of As and associated minor and trace elements (F, U, B, Mo and V) onto the surface of Fe-, Al- and Mn-oxides and oxi-hydroxides, restricts the mobilization of these elements into groundwater. Nevertheless, this does not hold in the case of the shallow unconfined groundwaters with high pH and high concentrations of potential competitors for adsorption sites (HCO(3), V, P, etc.). Under these geochemical conditions, desorption of the above mentioned anions and oxyanions occurs as a key process for As mobilization, resulting in an increase of minor and trace element concentrations. These geochemical processes that control the concentrations of dissolved As and other trace elements and which determine the groundwater quality especially in the shallow aquifers, are comparable to other areas with high As concentrations in groundwater of oxidizing aquifers and semi-arid or arid climate, which are found in many parts of the world, such as the western sectors of the USA, Mexico, northern Chile, Turkey, Mongolia, central and northern China, and central and northwestern Argentina. PMID:21035830

Nicolli, Hugo B; Bundschuh, Jochen; García, Jorge W; Falcón, Carlos M; Jean, Jiin-Shuh

2010-11-01

193

A comparative study on arsenic and humic substances in alluvial aquifers of Bengal delta plain (NW Bangladesh), Chianan plain (SW Taiwan) and Lanyang plain (NE Taiwan): implication of arsenic mobilization mechanisms.  

PubMed

Humic substances in groundwater and aquifer sediments from the arsenicosis and Blackfoot disease (BFD) affected areas in Bangladesh (Bengal delta plain) and Taiwan (Lanyang plain and Chianan plain) were characterized using fluorescence spectrophotometry and Fourier transform infrared (FT-IR) spectroscopy. The results demonstrate that the mean concentration of As and relative intensity of fluorescent humic substances are higher in the Chianan plain groundwater than those in the Lanyang plain and Bengal delta plain groundwater. The mean As concentrations in Bengal delta plain, Chianan plain, and Lanyang plain are 50.65 ?g/l (2.8-170.8 ?g/l, n=20), 393 ?g/l (9-704 ?g/l, n=5), and 104.5 ?g/l (2.51-543 ?g/l, n = 6), respectively. Average concentrations and relative fluorescent intensity of humic substances in groundwater are 25.381 QSU (quinine standard unit) and 17.78 in the Bengal delta plain, 184.032 QSU and 128.41 in the Chianan plain, and 77.56 QSU and 53.43 in the Lanyang plain. Moreover, FT-IR analysis shows that the humic substances extracted from the Chianan plain groundwater contain phenolic, alkanes, aromatic ring and amine groups, which tend to form metal carbon bonds with As and other trace elements. By contrast, the spectra show that humic substances are largely absent from sediments and groundwater in the Bengal delta plain and Lanyang plain. The data suggest that the reductive dissolution of As-adsorbed Mn oxyhydroxides is the most probable mechanism for mobilization of As in the Bengal delta plain. However, in the Chianan plain and Lanyang plain, microbially mediated reductive dissolution of As-adsorbed amorphous/crystalline Fe oxyhydroxides in organic-rich sediments is the primary mechanism for releasing As to groundwater. High levels of As and humic substances possibly play a critical role in causing the unique BFD in the Chianan plain of SW Taiwan. PMID:20706862

Selim Reza, A H M; Jean, Jiin-Shuh; Yang, Huai-Jen; Lee, Ming-Kuo; Hsu, Hua-Fen; Liu, Chia-Chuan; Lee, Yao-Chang; Bundschuh, Jochen; Lin, Kao-Hong; Lee, Chi-Yu

2011-06-01

194

Phylogenetic identification of marine bacteria isolated from deep-sea sediments of the eastern South Atlantic Ocean.  

PubMed

The deep-sea environments of the South Atlantic Ocean are less studied in comparison to the North Atlantic and Pacific Oceans. With the aim of identifying the deep-sea bacteria in this less known ocean, 70 strains were isolated from eight sediment samples (depth range between 1905 to 5560 m) collected in the eastern part of the South Atlantic, from the equatorial region to the Cape Abyssal Plain, using three different culture media. The strains were classified into three phylogenetic groups, Gammaproteobacteria, Firmicutes and Actinobacteria, by the analysis of 16s rRNA gene sequences. Gammaproteobacteria and Firmicutes were the most frequently identified groups, with Halomonas the most frequent genus among the strains. Microorganisms belonging to Firmicutes were the only ones observed in all samples. Sixteen of the 41 identified operational taxonomic units probably represent new species. The presence of potentially new species reinforces the need for new studies in the deep-sea environments of the South Atlantic. PMID:23565357

da Silva, Marcus Adonai Castro; Cavalett, Angélica; Spinner, Ananda; Rosa, Daniele Cristina; Jasper, Regina Beltrame; Quecine, Maria Carolina; Bonatelli, Maria Letícia; Pizzirani-Kleiner, Aline; Corção, Gertrudes; Lima, André Oliveira de Souza

2013-12-01

195

Recent changes in the deep circulation of the eastern Mediterranean recorded in the thermal history of deep sea sediments  

NASA Astrophysics Data System (ADS)

We present an exceptional data set of 154 anomalous geothermal heat flow measurements collected in deep sea sediments of the Ionian Sea and several CTD temperature profiles in the above water column, which document the thermal forcing of the Eastern Mediterranean Transient (EMT) on the undisturbed sediment temperature distribution. The data were collected during three cruises of the MEDRIFF project in 1993 and 1994, along a 300 km transect traversing the Mediterranean Ridge accretionary complex and adjacent Matapan Trench, to possibly identify areas of anomalous heat flow that could be related to fluid outflow. Contrary to expectations, the upper few meters of sediment revealed decreasing temperatures with depth, showing an inversion at systematically variable depths in the range of 6 to 3 m, from the NE to the SW along the corridor, respectively. The temperature profiles in the sediment were found strongly related to the thermal structure in the above bottom-waters. The space and time variability of the thermal anomalies, both in the sediment and in the water masses, indicates that they are all related to a single regional process, identified as the progressive spreading of warm and dense saline Aegean waters, filling the Matapan Trench and rising onto the Mediterranean Ridge (EMT). The only exception (positive heat flow) was found to the west of the Mediterranean Ridge, in the Sirte abyssal plain. Measurements collected in the same area at different times indicated that the thermal structure in the bottom-water and sediments had changed significantly at weekly, monthly, and inter annual time-scales. One-dimensional forward modeling of the conductive heat propagation into the sediment explains the observed sea bottom warming of up to +0.5 K and provides time information on the onset of sediment warming, as well as on the undisturbed thermal gradients. These parameters, combined with the oceanographic data in the area, make it possible to reconstruct the early history of the EMT: the sea bottom warming started in the Matapan Trench, between spring 1992 and spring 1993, postdating earlier estimates of the onset of the EMT. The transient reached the Mediterranean Ridge Crest in spring-summer 1993, with an average propagation velocity at the seafloor ranging between 0.5 and 1.6 km/day.

della Vedova, B.; Pellis, G.; Camerlenghi, A.; Foucher, J.-P.

2003-04-01

196

Sediment chemistry and magnetic properties in an anomalously reducing core from the eastern Mediterranean Sea  

Microsoft Academic Search

In Core KC19C (19.6 m long), recovered in the abyssal plain between Crete and Cyprus in the eastern Mediterranean, a large number of organic-rich layers (sapropels) occur, which correlate to maxima in the insolation curve. In contrast to other sites in the eastern Mediterranean, porewaters contain sulfide below a few meters below seafloor (mbsf). Geochemical analyses were performed on the

Hilde F. Passier; Mark J. Dekkers; Gert J. de Lange

1998-01-01

197

South African Association of Geomorphologists, Johannesburg, South Africa, 2000 Flood plain formation in semi-arid central Australia.  

E-print Network

of sediment waves and the close succession of a series of high-energy overbank flows contribute, the paleoflood formations exert a major influence on flood plain sediment texture and morphostratigraphy. The residence time of sediment storages associated with the modern channel is related to the sediment transport

Bourke, Mary C.

198

Assessment and estimation of streambank erosion rates in the Southeastern Plains ecoregion of Mississippi  

Technology Transfer Automated Retrieval System (TEKTRAN)

Sediment loads from watersheds located in the Southeastern Plain Ecoregion can have contributions from stream channel degradation as large as 90%. Monitoring and modeling techniques to assess the contribution of channel sediment to overall sediment load are needed to determine the reductions necessa...

199

Using Eulerian and Lagrangian Approaches to Investigate Wind-Driven Changes in the Southern Ocean Abyssal Circulation  

NASA Astrophysics Data System (ADS)

This study uses a global ocean eddy-permitting climate model to explore the export of abyssal water from the Southern Ocean and its sensitivity to projected twenty-first-century poleward-intensifying Southern Ocean wind stress. The authors investigate the abyssal flow pathways and transport using a combination of Lagrangian and Eulerian techniques. In an Eulerian format, the equator- and poleward flows within similar abyssal density classes are increased by the wind stress changes, making it difficult to explicitly diagnose changes in the abyssal export in a meridional overturning circulation framework. Lagrangian particle analyses are used to identify the major export pathways of Southern Ocean abyssal waters and reveal an increase in the number of particles exported to the subtropics from source regions around Antarctica in response to the wind forcing. Both the Lagrangian particle and Eulerian analyses identify transients as playing a key role in the abyssal export of water from the Southern Ocean. Wind-driven modifications to the potential energy component of the vorticity balance in the abyss are also found to impact the Southern Ocean barotropic circulation.

Spence, Paul; van Sebille, Erik; Saenko, Oleg; England, Matthew

2014-05-01

200

Crystallization and differentiation in abyssal tholeiites and gabbros from mid-oceanic ridges  

Microsoft Academic Search

Tholeiitic gabbros from the Mid-Atlantic Ridge near 24°N were found to show remarkable differentiation, producing high-iron, high-titanium gabbros and aplite in later stages. Crystallization of olivine and plagioclase from abyssal tholeiite magma approximately follows cotectic relation in the system olivine-plagioclase-pyroxene.

Akiho Miyashiro; Fumiko Shido; Maurice Ewing

1970-01-01

201

An association between komokiacean foraminifers (Protozoa) and paludicelline ctenostomes (Bryozoa) from the abyssal Northeast Atlantic  

Microsoft Academic Search

Large collections of komokiacean foraminifers have been obtained from epibenthic sledge samples taken at bathyal and abyssal depths in the north-east Atlantic. Eight of the 32 species so far recognized have been found to form an association with paludicelline bryozoans. Approximately 4% of the > 12000 komokiaceans studied were involved in the association. The bryozoan colonies intergrow as networks with

A. J. Gooday; P. L. Cook

1984-01-01

202

Os isotopic systematics of the MORB mantle: results from altered abyssal peridotites  

Microsoft Academic Search

Abyssal peridotites are fragments of the oceanic upper mantle. Previous studies have indicated that their Os isotopic compositions span a wide range, including values more radiogenic than most estimates of the average bulk Earth 187Os188Os ratio. This is difficult to reconcile with their derivation as residues of MORB partial melting. We present results that suggest that some of this variation,

Jonathan E. Snow; Laurie Reisberg

1995-01-01

203

The origin of abyssal peridotites: a reinterpretation of constraints based on primary bulk compositions  

Microsoft Academic Search

We calculated primary bulk compositions for a global suite of abyssal peridotites using primary mineral modes and either analyzed or calculated phase compositions. The latter were obtained through correlations between reported mineral compositions and modal olivine contents. Both the modal data and the mineral compositions were averaged by dredge site, drill hole, or fracture zone (FZ) depending on the amount

Michael B. Baker; John R. Beckett

1999-01-01

204

Tectonic types of oceanic abyssal basins and related potentially economic fields of ferromanganese nodules  

NASA Astrophysics Data System (ADS)

Tectonic typification of the abyssal basins of the Atlantic, Indian, and Pacific oceans is proposed. Six types of basins are recognized: perispreading, pericontinental, central thalassogenic, intermontane abyssal, interfault, and thalassosyneclise. The tectonic diversity of the basins and their systems reflects significant regional tectono-geodynamic features of the oceanic lithosphere. Basins of the first type are inherent to the Atlantic Ocean; of the second and third types, to the Indian Ocean; and of the fourth to sixth types, to the Pacific. In the Atlantic Ocean, the basins are spatially and paragenetically conjugated with the mid-oceanic ridge. Beyond the Atlantic, a similar situation is characteristic of the southern Indian Ocean only. Hence, differentiated energetic models of deep geospheres are required. The relations of potentially economic fields of ferromanganese nodules to tectonic types of abyssal basins are discussed. The largest fields with respect to both dimensions and reserves are confined to interfault and intermontane abyssal basins. The fields localized in central thalassogenic basins are second in importance. The perispreading and pericontinental basins are the least promising in this respect. Along with other criteria, tectonic analysis should be taken into consideration in the future development of these valuable mineral resources.

Pushcharovsky, Yu. M.

2008-07-01

205

Research paper Behavior of fluid-mobile elements in serpentines from abyssal to subduction  

E-print Network

Research paper Behavior of fluid-mobile elements in serpentines from abyssal to subduction. In order to constrain geochemical behavior of fluid-mobile elements hosted by serpentine phases during indicating extensive fluid­rock interaction. In situ analyses allow distinction of three types of serpentines

206

Internal tide generation by abyssal hills using analytical theory Angelique Melet,1  

E-print Network

Internal tide generation by abyssal hills using analytical theory Angelique Melet,1 Maxim 2013. [1] Internal tide driven mixing plays a key role in sustaining the deep ocean stratification and meridional overturning circulation. Internal tides can be generated by topographic horizontal scales ranging

Nycander, Jonas

207

Carbon dioxide release from the North Pacific abyss during the last deglaciation  

E-print Network

LETTERS Carbon dioxide release from the North Pacific abyss during the last deglaciation Eric D , John R. Southon6 & Roger Francois1 Atmospheric carbon dioxide concentrations were significantly lower the surface waters above but only a small increase in atmospheric carbon dioxide concentration8 . We speculate

Gilli, Adrian

208

Monologue or Dialogue? Stepping Away from the Abyss in Higher Education  

ERIC Educational Resources Information Center

This paper investigates the possibilities of the use of dialogue, and the dangers of the use of monologue, in higher education in the early twenty-first century, in a period facing a number of smaller- and larger-scale crises--each interpreted as an "abyss" of some kind. How does higher education contribute, positively or negatively, to personal…

Stern, Julian

2009-01-01

209

Abyssal erosion and scarp retreat: Deep Tow observations of the Blake Escarpment and Blake Spur  

Microsoft Academic Search

Deep Tow surveys conducted at two sites at the base of the Blake Spur and Blake Escarpment serve to delineate the contact between Mesozoic platform carbonates of the Blake Plateau and adjacent abyssal strata. The continental margin in the surveyed areas consists of steep limestone cliffs and headlands with over 2 km of relief. This extreme topography distorts the hydrographic

Lewis A Land; Charles K Paull; Fred N Spiess

1999-01-01

210

Eddy-induced variability in Southern Ocean abyssal mixing on climatic timescales  

NASA Astrophysics Data System (ADS)

The Southern Ocean plays a pivotal role in the global ocean circulation and climate. There, the deep water masses of the world ocean upwell to the surface and subsequently sink to intermediate and abyssal depths, forming two overturning cells that exchange substantial quantities of heat and carbon with the atmosphere. The sensitivity of the upper cell to climatic changes in forcing is relatively well established. However, little is known about how the lower cell responds, and in particular whether small-scale mixing in the abyssal Southern Ocean, an important controlling process of the lower cell, is influenced by atmospheric forcing. Here, we present observational evidence that relates changes in abyssal mixing to oceanic eddy variability on timescales of months to decades. Observational estimates of mixing rates, obtained along a repeat hydrographic transect across Drake Passage, are shown to be dependent on local oceanic eddy energy, derived from moored current meter and altimetric measurements. As the intensity of the regional eddy field is regulated by the Southern Hemisphere westerly winds, our findings suggest that Southern Ocean abyssal mixing and overturning are sensitive to climatic perturbations in wind forcing.

Sheen, K. L.; Naveira Garabato, A. C.; Brearley, J. A.; Meredith, M. P.; Polzin, K. L.; Smeed, D. A.; Forryan, A.; King, B. A.; Sallée, J.-B.; St. Laurent, L.; Thurnherr, A. M.; Toole, J. M.; Waterman, S. N.; Watson, A. J.

2014-08-01

211

Geology, geochemistry, and tectonostratigraphic relations of the crystalline basement beneath the coastal plain of New Jersey and contiguous areas  

USGS Publications Warehouse

Coastal plain sediments are underlain by pre-Mesozoic crystalline rocks. The inner coastal plain is underlain by schist that is correlated with the Potomac Terrane, as well as by mafic rocks probably equivalent to the Wilmington or Bel Air-Rising Sun terranes. The northern and central outer coastal plain is underlain by metasedimentary rocks similar to the Brompton-Cameron Terrane. Rocks beneath the southern coastal plain probably correlate with those of the Chopawamsic and Roanoke Rapids terranes.

Volkert, Richard A.; Drake, Avery Ala, Jr.; Sugarman, Peter J.

1996-01-01

212

The Plains City Story  

ERIC Educational Resources Information Center

This case study portrays a contemporary phenomenon that affects many U.S. school districts. Specifically, the authors address the challenges that the superintendent of the Plains City school district faced as a result of a change in the demographic distribution of his district. The gradual development of the pig farming industry in Plains City…

van Olphen, Marcela; Rios, Francisco; Berube, William; Dexter, Robin; McCarthy, Robert

2006-01-01

213

Abundance, diversity, and latitudinal gradients of southeastern Atlantic and Antarctic abyssal gastropods  

NASA Astrophysics Data System (ADS)

Mollusca are widely used for deriving concepts on deep-sea biology and biodiversity, yet abyssal collections are limited to only a few regions of the world ocean and biased toward the northern Atlantic. The present study compares gastropod molluscs sampled along a transect through the southern Atlantic from the equator to Antarctica. The DIVA I and II expeditions concentrated on the hardly explored Guinea, Angola, and Cape Basins. Of the 145 deep-sea deployments (5025-5656 m depth) analyzed to date, 20 have yielded 68 specimens of benthic gastropods, representing 27 species. Only five abyssal species were previously known, four of them from the northern Atlantic deep sea; the remainder appear to be undescribed. Interestingly, there is no faunal overlap with the nearby Antarctic deep-sea. Most of these DIVA species (63%) are represented by single individuals, or limited to one or two stations. The rarity (i.e. 0.55 specimens m -2 calculated from quantitative corers) and still undetectable patchiness of southeastern Atlantic abyssal gastropods may indicate "source-sink" dynamics, but comparison is needed with thus far hardly explored regional bathyal faunas. The BRENKE-epibenthic sledge (EBS) may be efficient at surveying the abyssal gastropod species richness, but is shown to drastically underestimate true abundances. Low diversity values throughout the three southern Atlantic ocean basins do further challenge earlier estimates of a hyperdiverse global abyssal macrofauna. Comparative EBS data available from the southern hemisphere indicate a gradient from the equatorial Guinea Basin towards higher gastropod abundances and diversity in Antarctica. This is in clear contrast to the paradigm of a globally strongly decreasing marine diversity from lower to higher latitudes, highlighting the importance of further exploring the southern fauna from the tropics to Antarctica.

Schrödl, M.; Bohn, J. M.; Brenke, N.; Rolán, E.; Schwabe, E.

2011-03-01

214

Observation of the abyssal western boundary current in the Philippine Sea  

NASA Astrophysics Data System (ADS)

Mooring observations were conducted from July 16, 2011 to March 30, 2012 east of Mindanao, Philippines (127°2.8'E, 8°0.3'N) to observe the abyssal current at about 5 600 m deep and 500 m above the ocean bottom. Several features were revealed: 1) the observed abyssal current was highly variable with standard deviations of 57.3 mm/s and 34.0 mm/s, larger than the mean values of -31.9 and 16.6 mm/s for the zonal and meridional components, respectively; 2) low-frequency current longer than 6 days exhibited strong seasonal variation, flowing southeastward (mean flow direction of 119.0° clockwise from north) before about October 1, 2011 and northwestward (mean flow direction of 60.5° counter-clockwise from north) thereafter; 3) the high-frequency flow bands were dominated by tidal currents O1, K1, M2, and S2, and near-inertial currents, whose frequencies were higher than the local inertial frequency. The two diurnal tidal constituents were much stronger than the two semidiurnal ones. This study provides for the first time an observational insight into the abyssal western boundary current east of Mindanao based on long-term observations at one site. It is meaningful for further research into the deep and abyssal circulation over the whole Philippine Sea and the 3D structure of the western boundary current system in this region. More observational and high-resolution model studies are needed to examine the spatial structure and temporal variation of the abyssal current over a much larger space and longer period, their relation to the upper-layer circulation, and the underlying dynamics.

Zhai, Fangguo; Wang, Qingye; Hu, Dunxin; Guo, Xiaogang

2014-09-01

215

Radiocarbon and stable carbon isotope compositions of organic compound classes in sediments from the NE Pacific and Southern Oceans  

Microsoft Academic Search

Radiocarbon (?14C) abundance and stable carbon isotope (?13C) compositions were measured for total lipid, total hydrolyzable amino acids (THAA), total carbohydrates (TCHO), and acid-insoluble organic fractions separated from phytoplankton, zooplankton, and sediment cores collected from two abyssal sites, one in the northeast (NE) Pacific Ocean and one in the Southern Ocean. These results are compared with those obtained for a

Xu-Chen Wang; Ellen R. M Druffel

2001-01-01

216

Channel morphodynamics on a small proglacial braid plain (Fagge River, Gepatschferner, Austria)  

NASA Astrophysics Data System (ADS)

Braid plains are important sediment stores in high mountains, particularly in the glacier forefields of Alpine glaciers. Proglacial braid plains receive sediment input from glacial meltwater and proglacial sediment sources like moraines and glacio-fluvial deposits. The channel morphodynamics on the braid plains are strongly related to the sediment transport and flow regime of the proglacial river. This study deals with channel morphodynamics on a small proglacial braid plain in the European Alps. It focuses on two different time scales. Decadal channel planform changes were assessed by remote sensing approaches. The recent channel bed changes were investigated by cross-sectional surveys and particle counts in 2013. This study is part of the DFG/FWF funded interdisciplinary research project PROSA (High-resolution measurements of morphodynamics in rapidly changing PROglacial Systems of the Alps).

Morche, D.; Schuchardt, A.; Dubberke, K.; Baewert, H.

2015-03-01

217

Early India-Australia spreading history revealed by newly detected Mesozoic magnetic anomalies in the Perth Abyssal Plain  

E-print Network

Early India-Australia spreading history revealed by newly detected Mesozoic magnetic anomalies the early spreading history between India and Australia during the Mesozoic breakup of Gondwana. However from Australia with Greater India during initial breakup at ~130 Ma, then rifted from India following

Granot, Roi

218

Geomorphic characterization and diversity of the fluvial systems of the Gangetic Plains  

NASA Astrophysics Data System (ADS)

The extensive Gangetic alluvial plains are drained by rivers which differ strongly in terms of hydrological and sediment transport characteristics. These differences are manifested in the geomorphic diversity of the plains. The Western Gangetic Plains (WGP) are marked by a degradational topography with incised channels and extensive badland development in some parts, while the Eastern Gangetic Plains (EGP) are characterized by shallow, aggrading channels with frequent avulsions and extensive flooding. We interpret such geomorphic diversity in terms of differences in stream power and sediment supply from the catchment areas. The rivers draining the western plains are marked by higher stream power and lower sediment yield that result in degradation. In comparison, the rivers draining the eastern Gangetic Plains have lower stream power and higher sediment yield that result in aggradation. The variation of stream power, a function of channel slope and high sediment yield, is attributed to differences in rainfall and rate of uplift in the hinterland. It is suggested that such differences have resulted in a marked geomorphic diversity across the plains. It is also suggested that such diversity has existed for a fairly long time because of climatic and tectonic variance.

Sinha, R.; Jain, Vikrant; Babu, G. Prasad; Ghosh, S.

2005-09-01

219

Salt Plains Microbial Observatory  

NSDL National Science Digital Library

This site is home of the Salt Plains Microbial Observatory, located in the Salt Plains National Wildlife Refuge in northern Oklahoma. This area has permitted the first extensive study of a non-marine, terrestrial, hypersaline environment. The web site offers information about the extreme environment, images and video clips of its microbial inhabitants, an image-rich summary of research activities, information about summer courses and research opportunities, a list of publications, and links to other informative resources pertaining to hypersaline environments.

Mark Buchheim

220

Stratigraphic investigations of selected sediments, southwest Gulf of Mexico  

E-print Network

. Circles cor re pondl to eo& e. number show- on th. ad j scen . . li. ne. Tectoni. c map of Lhe Republic of Mexico (Af tcr Ing. Manucl Alvarez, Jr. , 1948). Physiograp'hic Provinces of Lhc Gulf of Mexico showing tie shelf & slope, abyssal plain... were placed in a 250 27 mi llili tcr bottle with 15 milli liters of 60 gtams/300 n i! li li t c s of ca! agon-w ter solution and 200 mi! li liters of w; tcr. The bottle was then capped and placed !n sn electric baker for four hours or until...

Morton, William Thomas

1969-01-01

221

The Plains of Venus  

NASA Astrophysics Data System (ADS)

Volcanic plains units of various types comprise at least 80% of the surface of Venus. Though devoid of topographic splendor and, therefore often overlooked, these plains units house a spectacular array of volcanic, tectonic, and impact features. Here I propose that the plains hold the keys to understanding the resurfacing history of Venus and resolving the global stratigraphy debate. The quasi-random distribution of impact craters and the small number that have been conspicuously modified from the outside by plains-forming volcanism have led some to propose that Venus was catastrophically resurfaced around 725×375 Ma with little volcanism since. Challenges, however, hinge on interpretations of certain morphological characteristics of impact craters: For instance, Venusian impact craters exhibit either radar dark (smooth) floor deposits or bright, blocky floors. Bright floor craters (BFC) are typically 100-400 m deeper than dark floor craters (DFC). Furthermore, all 58 impact craters with ephemeral bright ejecta rays and/or distal parabolic ejecta patterns have bright floor deposits. This suggests that BFCs are younger, on average, than DFCs. These observations suggest that DFCs could be partially filled with lava during plains emplacement and, therefore, are not strictly younger than the plains units as widely held. Because the DFC group comprises ~80% of the total crater population on Venus the recalculated emplacement age of the plains would be ~145 Ma if DFCs are indeed volcanically modified during plains formation. Improved image and topographic data are required to measure stratigraphic and morphometric relationships and resolve this issue. Plains units are also home to an abundant and diverse set of volcanic features including steep-sided domes, shield fields, isolated volcanoes, collapse features and lava channels, some of which extend for 1000s of kilometers. The inferred viscosity range of plains-forming lavas, therefore, is immense, ranging from the extremely fluid flows (i.e., channel formers), to viscous, possibly felsic lavas of steep-sided domes. Wrinkle ridges deform many plains units and this has been taken to indicate that these ridges essentially form an early stratigraphic marker that limits subsequent volcanism to a minimum. However, subtle backscatter variations within many ridged plains units suggest (but do not prove) that some plains volcanism continued well after local ridge deformation ended. Furthermore, many of volcanic sources show little, if any, indications of tectonic modification and detailed analyses have concluded that resurfacing rates could be similar to those on Earth. Improving constraints on the rates and styles of volcanism within the plains could lend valuable insights into the evolution of Venus's internal heat budget and the transition from thin-lid to thick-lid tectonic regimes. Improved spatial and radiometric resolution of radar images would greatly improve abilities to construct the complex local stratigraphy of ridged plains. Constraining the resurfacing history of Venus is central to understanding how Earth-sized planets evolve and whether or not their evolutionary pathways lead to habitability. This goal can only be adequately addressed if broad coverage is added to the implementation strategies of any future mapping missions to Venus.

Sharpton, V. L.

2013-12-01

222

Species composition and distribution of bivalves in bathyal and abyssal depths of the Sea of Japan  

NASA Astrophysics Data System (ADS)

Twenty-six bivalve species collected by four Russian (1972, 1976, 1985, 2005) and Russian-German (2010) expeditions in the bathyal and abyssal depths of the Sea of Japan (465-3435 m) are listed with the material examined and illustrated. Taxonomic decisions herein: Robaia habei Scarlato, 1981 is synonymized with Nuculana (Robaia) robai (Kuroda, 1929); following Scarlato (1981) and Coan et al. (2000)Dacrydium nipponicum Okutani, 1975 and Dacrydium minimum Okutani and Izumidate, 1992 are synonymized with Dacrydium vitreum (Möller, 1842); Maorithyas yamatotaensis Okutani and Izumidate, 1992 is synonymized with Adontorhina cyclia Berry, 1947; Axinopsida rubiginosa Okutani and Izumidate, 1992 is synonymized with Mendicula ferruginosa (Forbes, 1844); Cardiomya lindbergi batialis Scarlato, 1972 is synonymized with Cardiomya tosaensis (Kuroda, 1948); Cuspidaria sadoensis Okutani and Ito, 1983 is synonymized with Cuspidaria ascoldica Scarlato, 1972; Cyclocardia rjabininae (Scarlato, 1955) recognized as valid and distinct from Cyclocardia ovata (Rjabinina, 1952). The deep-water bivalve fauna of the Sea of Japan is characterized by an impoverished shelf fauna and consists of eurybathic species that extend from the shelf to the bathyal and abyssal zones. Most of them have a wide geographic distribution and inhabit cold water regions of the Northern Atlantic, Northern Pacific, and Arctic Ocean. Only five species are endemic to the Sea of Japan. With increase in depth, the species richness of bivalves decreases. In the depth range from 200 to 1600 m, all species (26) found in the deep Sea of Japan were recorded, while only 10 species were recorded in the lower bathyal slope (1700-3000 m). At depths below 3000 m, only D. vitreum, Delectopecten vancouverensis (Whiteaves, 1893), and Thyasira (Parathyasira) sp. were found. The lack of typical abyssal species of bivalves in the deep Sea of Japan is probably connected with the isolation of this body of water from the Pacific abyssal depths.

Kamenev, Gennady M.

2013-02-01

223

Spatially heterogeneous diapycnal mixing in the abyssal ocean: A comparison of two parameterizations to observations  

NASA Astrophysics Data System (ADS)

The spatial distributions of the diapycnal diffusivity predicted by two abyssal mixing schemes are compared to each other and to observational estimates based on microstructure surveys and large-scale hydrographic inversions. The parameterizations considered are the tidal mixing scheme by Jayne, St. Laurent and co-authors (JSL01) and the Roughness Diffusivity Model (RDM) by Decloedt and Luther. Comparison to microstructure surveys shows that both parameterizations are conservative in estimating the vertical extent to which bottom-intensified mixing penetrates into the stratified water column. In particular, the JSL01 exponential vertical structure function with fixed scale height decays to background values much nearer topography than observed. JSL01 and RDM yield dramatically different horizontal spatial distributions of diapycnal diffusivity, which would lead to quite different circulations in OGCMs, yet they produce similar basin-averaged diffusivity profiles. Both parameterizations are shown to yield smaller basin-mean diffusivity profiles than hydrographic inverse estimates for the major ocean basins, by factors ranging from 3 up to over an order of magnitude. The canonical 10-4 m2 s-1abyssal diffusivity is reached by the parameterizations only at depths below 3 km. Power consumption by diapycnal mixing below 1 km of depth, between roughly 32°S and 48°N, for the RDM and JSL01 parameterizations is 0.40 TW & 0.28 TW, respectively. The results presented here suggest that present-day mixing parameterizations significantly underestimate abyssal mixing. In conjunction with other recently published studies, a plausible interpretation is that parameterizing the dissipation of bottom-generated internal waves is not sufficient to approximate the global spatial distribution of diapycnal mixing in the abyssal ocean.

Decloedt, Thomas; Luther, Douglas S.

2012-11-01

224

A glimpse into the deep of the Antarctic Polar Front - Diversity and abundance of abyssal molluscs  

NASA Astrophysics Data System (ADS)

Our knowledge of the biodiversity and distribution patterns of benthic deep-sea faunas is still limited, with large parts of the world's abyss unexplored, lacking ?-taxonomic data across oceans basins and especially of biogeographic transition zones between oceans. The Antarctic Polar Frontal Zone has been discussed as major biogeographic barrier hindering faunal exchange between Subantarctic and Antarctic provinces and conserving high rates of endemism in the Southern Ocean benthos. In the present study we report first, exploratory ?-taxonomy on the malacofauna sampled by means of an epibenthic sledge from four bathyal respectively abyssal stations (2732-4327 m depth) in the vicinity of the Antarctic Polar Front during the SYSTCO II expedition (SYSTem COupling in the Southern Ocean, RV Polarstern cruise ANT XXVIII/3). We identified 58 distinct molluscan taxa based on external morphology ('morphospecies'); of the 33 taxa successfully assigned to described species 94% were previously reported from the Southern Ocean, but 24% exhibit distribution ranges crossing the Polar Front. One North Atlantic scaphopod is reported for the first time in Antarctic waters. Our study supports that the Antarctic Polar Front does not serve as effective barrier preventing gene flow in deep-sea molluscs. The present dataset shows the general characteristics of deep-sea sampling: patchiness in distribution and a high degree of singletons. Overall molluscan abundances were generally low ranging between 3.60 and 24.65 ind./1000 m², but in comparison with equatorial and subtropic abyssal basins, gastropod species richness and abundance were reaching high values similar to high Antarctic stations. Comparison between high productivity and low productivity zones along the Polar Front suggests increased abundances and species richness in high productivity zones. Intensified sampling is needed, however, to outweigh stochastic errors and to evaluate the influence of carbon flux as driving factor to faunal composition and abundances of abyssal molluscs.

Jörger, K. M.; Schrödl, M.; Schwabe, E.; Würzberg, L.

2014-10-01

225

Size–frequency dynamics of NE Pacific abyssal ophiuroids (Echinodermata: Ophiuroidea)  

Microsoft Academic Search

The 17-year time-series study at Station M in the NE Pacific has provided one of the longest datasets on deep-sea ophiuroids\\u000a to date. Station M is an abyssal site characterized by low topographical relief and seasonal and interannual variation in\\u000a surface-derived food inputs. From 1989 to 2005, over 31,000 ophiuroid specimens were collected. Size–frequency distributions\\u000a of the four dominant species,

J. Ashley T. Booth; Henry A. Ruhl; Lawrence L. Lovell; David M. Bailey; Kenneth L. Smith

2008-01-01

226

Hydrologic impacts of strip tillage for a Coastal Plain soil  

Technology Transfer Automated Retrieval System (TEKTRAN)

Strip till is a growing practice among many Coastal Plain cotton growers which can lead to reduced surface runoff and reduced transport of sediment and agrichemicals. This research examines nine years of rainfall-runoff data from a paired conventional till / strip till research site. Annual water ...

227

Abyssal Scavenging Communities attracted to Sargassum and fish in the Sargasso Sea  

NASA Astrophysics Data System (ADS)

Deep-sea communities rely on epipelagic surface production as a primary source of energy and food. The flux of phytodetritus drives many abyssal ecological processes but the flux of large particles such as nekton carcasses, macroalgae, and wood may also be important. Recent baited camera experiments noted that some abyssal fish consumed spinach and phytoplankton placed on the seafloor. To evaluate if fish or other scavengers would consume natural plant or macroalgal material falling to the deep-sea floor we conducted camera experiments using Sargassum or mackerel bait in the Sargasso Sea. A benthic community of invertebrates was attracted to Sargassum, which naturally falls to the seafloor in this area. In five instances it was observed that an isopod Bathyopsurus sp. removed a piece of Sargassum from the main clump and left the field of view with it. An ophiuroid is also observed handling a piece of Sargassum. The group of scavengers attracted to mackerel bait was very different and was dominated by large ophidiid fish. In contrast to studies elsewhere in the abyssal North Atlantic, only a small number of rattails are observed, which could be related to water depth or an ichthyofaunal zonal change between oligotrophic and eutrophic regions.

Fleury, Aharon G.; Drazen, Jeffrey C.

2013-02-01

228

Turbulent mixing and hydraulic control of abyssal water in the Samoan Passage  

NASA Astrophysics Data System (ADS)

We report the first direct turbulence observations in the Samoan Passage (SP), a 40 km wide notch in the South Pacific bathymetry through which flows most of the water supplying the North Pacific abyssal circulation. The observed turbulence is 1000 to 10,000 times typical abyssal levels —strong enough to completely mix away the densest water entering the passage—confirming inferences from previous coarser temperature and salinity sections. Accompanying towed measurements of velocity and temperature with horizontal resolution of about 250 m indicate the dominant processes responsible for the turbulence. Specifically, the flow accelerates substantially at the primary sill within the passage, reaching speeds as great as 0.55 m s-1. A strong hydraulic response is seen, with layers first rising to clear the sill and then plunging hundreds of meters downward. Turbulence results from high shear at the interface above the densest fluid as it descends and from hydraulic jumps that form downstream of the sill. In addition to the primary sill, other locations along the multiple interconnected channels through the Samoan Passage also have an effect on the mixing of the dense water. In fact, quite different hydraulic responses and turbulence levels are observed at seafloor features separated laterally by a few kilometers, suggesting that abyssal mixing depends sensitively on bathymetric details on small scales.

Alford, Matthew H.; Girton, James B.; Voet, Gunnar; Carter, Glenn S.; Mickett, John B.; Klymak, Jody M.

2013-09-01

229

Arsenic Levels in Groundwater from Quaternary Alluvium in the Ganga Plain and the Bengal Basin, Indian Subcontinent: Insights into Influence of Stratigraphy  

Microsoft Academic Search

Late Quaternary stratigraphy and sedimentation in the Ganga Alluvial Plain and the Bengal Basin have influenced arsenic contamination of groundwater. Arsenic contaminated aquifers are pervasive within lowland organic rich, clayey deltaic sediments in the Bengal Basin and locally within similar facies in narrow, entrenched river valleys within the Ganga Alluvial Plain. These were mainly deposited during early-mid Holocene sea level

S. K. Acharyya

2005-01-01

230

Spatial and temporal variations in the grain-size characteristics of historical flood plain deposits, Blue River, Wisconsin, USA  

E-print Network

of suspended sediment during overbank flooding (Lewin, 1978; Nanson and Young, 1981; Magilli- gan, 1992; Lecce, 1997a). In these systems, the storage of overbank sediment on flood plains rep- resents a significant-size characteristics of overbank deposits, however, may vary in response to the dynamic nature of sediment transport

Lecce, Scott A.

231

Northern Plains Scene  

NASA Technical Reports Server (NTRS)

30 January 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a typical view of the martian northern plains during northern summer. In spring and summer, dust devils crisscross the plains, creating dark, filamentary streaks such as those shown here. MOC has rarely observed actual active dust devils on the northern plains, suggesting that these probably occur at a time of day that is different than the 2 p.m. local time when MGS flies over these surfaces. As with high latitudes on Earth, daytime lasts longer in summer than at lower latitudes; thus, dust devils might occur earlier or later in the afternoon than is common in equatorial settings.

Location near: 69.5oN, 66.5oW Image width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Summer

2006-01-01

232

Quantitative analysis of abyssal hills in the Atlantic Ocean: A correlation between inferred crustal thickness and extensional faulting  

NASA Astrophysics Data System (ADS)

A recent cruise to the Office of Naval Research Atlantic Natural Laboratory obtained ˜100% Hydrosweep bathymetrie coverage, >200% Hawaii MRl (HMRl) side scan coverage, gravity and magnetics over an area spanning three ridge segments along axis (˜25°25'N to ˜27°10'N), and crustal ages from 0 to 26-30 Ma (˜400 km) on the west flank of the Mid-Atlantic Ridge. This data set represents a first opportunity for an extensive regional analysis of abyssal hill morphology created at a slow spreading ridge. The primary purpose of this work is to investigate the relationship between abyssal hill morphology and the properties of the ridge crest at which they were formed. We apply the method of Goff and Jordan [1988] for the estimation of two-dimensional statistical properties of abyssal hill morphology from the gridded Hydrosweep bathymetry. Important abyssal hill parameters derived from this analysis include root-mean-square (rms) height, characteristic width, and plan view aspect ratio. The analysis is partitioned into two substudies: (1) analysis of near-axis (< 7 Ma) abyssal hills for each of the three segments and (2) analysis of temporal variations (˜2-29 Ma) in abyssal hill morphology along the run of the south segment. The results of this analysis are compared and correlated with analysis of the gravity data and preliminary determination of faulting characteristics based on HMRl side scan data. Principal results of this study are: (1) Abyssal hill morphology within the study region is strongly influenced by the inside-outside corner geometry of the mid-ocean ridge segments; abyssal hills originating at inside corners have larger rms height and characteristic width and smaller plan view aspect ratio than those originating at outside corners. (2) The residual mantle Bouguer gravity anomaly is positively correlated with intersegment and along-flow-line variations in rms height and characteristic width, and it is negatively correlated with plan view aspect ratio. From this result, we infer that lower-relief, narrower, and more elongated abyssal hills are produced when the crust being generated is thicker. (3) Intersegment variations in near-axis rms height negatively correlate with average fault density as determined from analysis of HMRl side scan imagery.

Goff, John A.; Tucholke, Brian E.; Lin, Jian; Jaroslow, Gary E.; Kleinrock, Martin C.

1995-11-01

233

Origin of late Quaternary dune fields on the Southern High Plains of Texas and New Mexico  

Microsoft Academic Search

Mostly stabilized late Holocene eolian sands on the Southern High Plains of the United States were studied to determine their origins and to assess whether present dune stability depends more strongly on sediment supply, sediment availability, or transport limitations. Geomorphic, sedi- mentological, and geochemical trends indi- cate that late Holocene dunes formed under westerly paleowinds, broadly similar to those of

Daniel R. Muhs; Vance T. Holliday

2001-01-01

234

Coastal Plain Near Kalapana  

USGS Multimedia Gallery

This composite image of the coastal plain near Kalapana combines a thermal image and a conventional photograph. The majority of lava is traveling through the lava tube system to the ocean and is not easily detectable in the image. Sometimes, however, the lava tubes do show a clear thermal sign...

235

Geochemistry of abyssal peridotites (Mid-Atlantic Ridge, 1520N, ODP Leg 209): Implications for fluid/rock interaction in slow  

E-print Network

Geochemistry of abyssal peridotites (Mid-Atlantic Ridge, 15°20N, ODP Leg 209): Implications form 20 April 2006; accepted 27 April 2006 Abstract Abyssal peridotite from the 15°20N area of the Mid-altered, highly refractory, peridotite with strong depletion in LREE and shows a gradual increase in the intensity

Demouchy, Sylvie

236

PhD position within the topic of magnetic petrology/mineralogy and crustal Marie-Curie Initial Training Network ABYSS (ESR12)  

E-print Network

PhD position within the topic of magnetic petrology/mineralogy and crustal magnetism Marie-Curie Marie Curie Integrated Training Network1 starting on March 1, 2014. ABYSS brings together 10 European. Suzanne McEnroe (Suzanne.mcenroe@ntnu.no). 1 ABYSS has received funding from the People programme (Marie

Demouchy, Sylvie

237

ROLE OF LAND USE AND BMPS IN REDUCING THE EFFECT OF EXTREME MAGNITUDE EVENTS ON SEDIMENT AND POLLUTANT TRANSPORT IN THE SE US COASTAL PLAIN AND MISSISSIPPI ALLUVIAL VALLEY  

EPA Science Inventory

Suspended sediment is a major non-point source pollutant of surface waters. Best management practices (BMPs) and current landuse decisions may not be sufficient to protect water quality in a changing climate, as a result of a loss of efficiency at reducing suspended sedimen...

238

Carbon dioxide release from the North Pacific abyss during the last deglaciation.  

PubMed

Atmospheric carbon dioxide concentrations were significantly lower during glacial periods than during intervening interglacial periods, but the mechanisms responsible for this difference remain uncertain. Many recent explanations call on greater carbon storage in a poorly ventilated deep ocean during glacial periods, but direct evidence regarding the ventilation and respired carbon content of the glacial deep ocean is sparse and often equivocal. Here we present sedimentary geochemical records from sites spanning the deep subarctic Pacific that--together with previously published results--show that a poorly ventilated water mass containing a high concentration of respired carbon dioxide occupied the North Pacific abyss during the Last Glacial Maximum. Despite an inferred increase in deep Southern Ocean ventilation during the first step of the deglaciation (18,000-15,000 years ago), we find no evidence for improved ventilation in the abyssal subarctic Pacific until a rapid transition approximately 14,600 years ago: this change was accompanied by an acceleration of export production from the surface waters above but only a small increase in atmospheric carbon dioxide concentration. We speculate that these changes were mechanistically linked to a roughly coeval increase in deep water formation in the North Atlantic, which flushed respired carbon dioxide from northern abyssal waters, but also increased the supply of nutrients to the upper ocean, leading to greater carbon dioxide sequestration at mid-depths and stalling the rise of atmospheric carbon dioxide concentrations. Our findings are qualitatively consistent with hypotheses invoking a deglacial flushing of respired carbon dioxide from an isolated, deep ocean reservoir, but suggest that the reservoir may have been released in stages, as vigorous deep water ventilation switched between North Atlantic and Southern Ocean source regions. PMID:17943127

Galbraith, Eric D; Jaccard, Samuel L; Pedersen, Thomas F; Sigman, Daniel M; Haug, Gerald H; Cook, Mea; Southon, John R; Francois, Roger

2007-10-18

239

Global Variations in Abyssal Peridotite Compositions II: What Determines the Major Element MORB Composition  

NASA Astrophysics Data System (ADS)

Large scale global variability of abyssal basalts and peridotites was discovered over 20 years ago, with increasingly depleted peridotites correlating to increasingly enriched MORB that carries a major element signature of higher degrees of mantle melting (Dick et al., 1984; Klein & Langmuir, 1987). While time and further analysis shows that these correlations do not hold for the Pacific, they remain largely valid for the Atlantic, Arctic and Indian Oceans. Given the large variability in abyssal peridotite compositions at local and regional scales this is remarkable. Nearly the full range of mantle major, trace and isotopic composition can be found in peridotites dredged from a single fracture zone or ridge segment. Detailed analysis of large peridotite suites from the Gakkel Ridge (Dick, Hellebrand & Snow, unpub. data), and in the central Atlantic from 14° to 16°N also show large magma starved regions with highly depleted mantle compositions that must be inherited from prior melting events. Our recent investigations of SW Indian Ridge Peridotites also lead us to believe that much of the local peridotite variability at the scale of a single dredge could be inherited from an early melting event. All this leaves one wondering what, if anything the "global" (actually regional) variability of MORB and abyssal peridotites defined by Dick et al. (1984) and Klein and Langmuir (1987) means. For abyssal peridotites the correlations only show up when the mineral and modal compositions of large numbers of samples are averaged by locality. Moreover, the sample source on which the correlations are based was almost exclusively fracture zones. Thus, the samples come from the same geodynamic environment, with the same P-T-Melt Flux history, and therefore do not reflect the full variability produced beneath a ridge segment, but only the melting history at the distal end of a magmatic segment. We would contend, therefore, that the correlations found by the cited authors remain valid and show that MORB aggregates from large regions and therefore the melt aggregation process averages out the variability seen in the source at segment scales. As the previously analyzed peridotites are from fracture zone walls 0.5 to 14 m.y. old, and the 'spatially associated basalts' are largely from the modern ridge axis, this argues for a long-term stability in magma composition and therefore mantle composition as well. There remains the question, however, to what degree the lateral variability of MORB major element compositions reflect varying degrees of mantle melting of a uniform source, and to what degree this is a function of varying mantle composition. It is certainly the case that trace and isotopic composition vary, and we suggest that it is equally likely that mantle major element composition varies significantly as well.

Dick, H. J.; Warren, J. M.; Shimizu, N.

2007-12-01

240

Cracked Plain, Buried Craters  

NASA Technical Reports Server (NTRS)

4 September 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a cracked plain in western Utopia Planitia. The three circular crack patterns indicate the location of three buried meteor impact craters. These landforms are located near 41.9oN, 275.9oW. The image covers an area approximately 3 km (1.9 mi) across. Sunlight illuminates this scene from the lower left.

2004-01-01

241

SEDIMENT REMOVAL  

EPA Science Inventory

When properly conducted, sediment removal is an effective lake management technique. This chapter describes: (1) purposes of sediment removal, (2) environmental concerns, (3) appropriate depth of sediment removal, (4) sediment removal techniques, (5) suitable lake conditions, (6)...

242

The absence of sharks from abyssal regions of the world's oceans  

PubMed Central

The oceanic abyss (depths greater than 3000?m), one of the largest environments on the planet, is characterized by absence of solar light, high pressures and remoteness from surface food supply necessitating special molecular, physiological, behavioural and ecological adaptations of organisms that live there. Sampling by trawl, baited hooks and cameras we show that the Chondrichthyes (sharks, rays and chimaeras) are absent from, or very rare in this region. Analysis of a global data set shows a trend of rapid disappearance of chondrichthyan species with depth when compared with bony fishes. Sharks, apparently well adapted to life at high pressures are conspicuous on slopes down to 2000?m including scavenging at food falls such as dead whales. We propose that they are excluded from the abyss by high-energy demand, including an oil-rich liver for buoyancy, which cannot be sustained in extreme oligotrophic conditions. Sharks are apparently confined to ca 30% of the total ocean and distribution of many species is fragmented around sea mounts, ocean ridges and ocean margins. All populations are therefore within reach of human fisheries, and there is no hidden reserve of chondrichthyan biomass or biodiversity in the deep sea. Sharks may be more vulnerable to over-exploitation than previously thought. PMID:16777734

Priede, Imants G; Froese, Rainer; Bailey, David M; Bergstad, Odd Aksel; Collins, Martin A; Dyb, Jan Erik; Henriques, Camila; Jones, Emma G; King, Nicola

2006-01-01

243

"First" abyssal record of Stenosemus exaratus (G.O. Sars, 1878) (Mollusca, Polyplacophora) in the North-Atlantic Ocean.  

PubMed

The first proven abyssal record of Stenosemus exaratus (G.O. Sars, 1878) is presented on the basis of an ROV study in the Irish Sea. For the first time in situ images of the species and data on the environmental parameters are provided. PMID:23794838

Allcock, Louise; Schwabe, Enrico

2013-01-01

244

EDITORIAL -BASED ON MIR INVESTIGATIONS IN LAKE GENEVA Into the abyss of Lake Geneva: the elemo interdisciplinary field  

E-print Network

EDITORIAL - BASED ON MIR INVESTIGATIONS IN LAKE GENEVA Into the abyss of Lake Geneva: the elemo interdisciplinary field investigation using the MIR submersibles Alfred Wu¨est · Flavio S. Anselmetti · J. Samuel 2014 Abstract In summer 2011, the two Russian MIR sub- mersibles were brought to Switzerland to perform

Gilli, Adrian

245

EDITORIAL -BASED ON MIR INVESTIGATIONS IN LAKE GENEVA Into the abyss of Lake Geneva: the elemo interdisciplinary field  

E-print Network

EDITORIAL - BASED ON MIR INVESTIGATIONS IN LAKE GENEVA Into the abyss of Lake Geneva: the elemo interdisciplinary field investigation using the MIR submersibles Alfred Wu¨est · Flavio S. Anselmetti · J. Samuel May 2014 � Springer Basel 2014 Abstract In summer 2011, the two Russian MIR sub- mersibles were

Wehrli, Bernhard

246

“First” abyssal record of Stenosemus exaratus (G.O. Sars, 1878) (Mollusca, Polyplacophora) in the North-Atlantic Ocean  

PubMed Central

Abstract The first proven abyssal record of Stenosemus exaratus (G.O. Sars, 1878) is presented on the basis of an ROV study in the Irish Sea. For the first time in situ images of the species and data on the environmental parameters are provided. PMID:23794838

Allcock, Louise; Schwabe, Enrico

2013-01-01

247

High Plains Regional Climate Center  

NSDL National Science Digital Library

The mission of the High Plains Regional Climate Center is to increase the use and availability of climate data in the High Plains region. This site contains a variety of climatic and hydrologic data from High Plains research projects. Data types include automated weather data, interactive climate summary maps, historical weather data, and an interactive climate atlas. Research projects include Nebraska soil moisture, crop phenology, and wind energy on the High Plains. This website also features relevant publications and a variety of weather and climate links.

School of Natural Resources

248

Distinctive upper mantle anisotropy beneath the High Lava Plains and Eastern Snake River Plain,  

E-print Network

Distinctive upper mantle anisotropy beneath the High Lava Plains and Eastern Snake River Plain and continuing with the still- ongoing volcanism in the High Lava Plains (HLP) and eastern Snake River Plain (SRP waves; shear wave splitting; high lava plains; Snake River Plain; Yellowstone. Index Terms: 8137

249

Wet coastal plain tundra  

SciTech Connect

This years's census data for the wet coastal plain tundra in Alaska; North Slope Borough, 3 km SSW of Naval Arctic Research Laboratory, Barrow; 71/sup 0/ 18'N, 156/sup 0/ 43'W; Barrow Quadrangle, USGS, reflect an increase in breeding species of 31% over the 5-year average, while breeding density was up 22%. Ten species increased and only 4 decreased. There was a total of 17 species; 61.5 territorial males or females (171/km/sup 2/, 69/100 acres).

Myers, J.P.; McCaffery, B.J.; Pitelka, F.A.

1980-01-01

250

Implications of spinel compositions for the petrotectonic history of abyssal peridotite from Southwest Indian Ridge (SWIR)  

NASA Astrophysics Data System (ADS)

Abyssal peridotites generate at mid-ocean ridges. Lherzolite and harzburgite are the main rock types of peridotites in the uppermost mantle. The lherzolite subtype, less depleted and less common in ophiolites, characterizes mantle diapirs and slow-spreading ridges. Along the Earth's mid-ocean ridges, abyssal peridotites undergo hydration reactions to become serpentinite minerals, especially in slow to ultraslow spreading mid-ocean ridges. Spinel is common in small quantities in peridotites, and its compositions have often been used as petrogenetic indicators [1]. The Southwest Indian Ridge (SWIR) is one of the two ultraslow spreading ridges in the world. The studied serpentinized peridotite sample was collected by the 21st Voyage of the Chinese oceanic research ship Dayang Yihao (aka Ocean No. 1) from a hydrothermal field (63.5°E, 28.0°S, and 3660 m deep) in SWIR. The studied spinels in serpentinized lherzolite have four zones with different compositions: relic, unaltered core is magmatic Al-spinels; micro- to nano- sized ferrichromite zoned particles; narrow and discontinuous magnetite rim; and chlorite aureoles. The values Cr# of the primary Al-spinels indicate the range of melting for abyssal peridotites from SWIR extends from ~4% to ~7% [2]. The alteration rims of ferrichromite have a chemical composition characterized by Fe enrichment and Cr# increase indicating chromite altered under greenschist-amphibolite facies. Magnetites formed in syn- and post- serpentinization. Chlorite (clinochlore) formed at the boundary and crack of spinel indicating it had undergone with low-temperature MgO- and SiO2-rich hydrothermal fluids [3]. It suggests that serpentinized lherzolite from SWIR had undergone poly-stage hydration reactions with a wide range of temperature. Acknowledgments: EMPA experiment was carried out by Xihao Zhu and Shu Zheng in The Second Institute of Oceanography and China University of Geosciences, respectively. The work was supported by NSFC. References [1] Dick, H.J.B., et al., Contrib Mineral Petr., 86:54, 1984. [2] Hellebrand et al., Nature, 410: 677, 2001. [3] Hamdy, M.M. , et al., JGMR, 3(9): 232, 2011.

Chen, T.; Jin, Z.; Wang, Y.; Tao, C.

2012-12-01

251

Rich and rare—First insights into species diversity and abundance of Antarctic abyssal Gastropoda (Mollusca)  

NASA Astrophysics Data System (ADS)

The abyssal depths of the polar oceans are thought to be low in diversity compared with the shallower polar shelves and temperate and tropical deep-sea basins. Our recent study on the gastropod fauna of the deep Southern Ocean gives evidence of the existence of a rich gastropod assemblage at abyssal depths. During the ANDEEP I and II expeditions to the southern Drake Passage, Northwestern Weddell Sea, and South Sandwich Trench, gastropods were collected by bottom and Agassiz trawls, epibenthic sledge, and multicorer, at 40 stations in depths between 127 and 5194 m. On the whole, 473 specimens, corresponding to 93 species of 36 families, were obtained. Of those, 414 specimens were caught below 750 m depth and refer to 84 (90%) benthic species of 32 (89%) families. Most families were represented by a single species only. The numerically dominant families were Skeneidae and Buccinidae (with 10 and 11 species, respectively), Eulimidae and Trochidae (with 9 species each), and Turridae (6 species). Thirty-Seven benthic deep-sea species (44%) were represented by a single specimen, and another 20 species (24%) were found at a single station, suggesting that more than two thirds of Antarctic deep-sea gastropod species are very rare or have a very scattered distribution. Of the 27 species occurring at two or more deep-sea stations, 14 were collected with different gear. Approximately half of the deep-water species are new to science or have been recently described. The present investigation increases the total number of recorded benthic Antarctic deep-sea gastropods (below 750 m) from 115 to 177. The previously known depth ranges have been extended, often considerably, for 31 species. The collected deep-sea gastropods comprise both eurybathic shelf species (29%) and apparently true deep-sea species (58%); some of the latter may belong to a so far unknown Antarctic abyssal fauna. Geographical ranges of the collected Antarctic benthic deep-sea gastropod species appear limited, and all these 84 species seem endemic to Antarctica south of the Polar Front. Comparing diversity and abundances based on epibenthic sledge samples, there is no clear relationship between Antarctic deep-sea gastropod abundance and species richness with depth. However, both Antarctic and adjacent deep-sea areas are still far from being adequately sampled to allow more comprehensive conclusions.

Schwabe, Enrico; Michael Bohn, Jens; Engl, Winfried; Linse, Katrin; Schrödl, Michael

2007-08-01

252

49 CFR 229.64 - Plain bearings.  

Code of Federal Regulations, 2013 CFR

... 2013-10-01 2013-10-01 false Plain bearings. 229.64 Section 229.64 Transportation...Requirements Suspension System § 229.64 Plain bearings. A plain bearing box shall contain visible free oil and may not...

2013-10-01

253

49 CFR 229.64 - Plain bearings.  

Code of Federal Regulations, 2014 CFR

... 2014-10-01 2014-10-01 false Plain bearings. 229.64 Section 229.64 Transportation...Requirements Suspension System § 229.64 Plain bearings. A plain bearing box shall contain visible free oil and may not...

2014-10-01

254

49 CFR 229.64 - Plain bearings.  

Code of Federal Regulations, 2010 CFR

... 2010-10-01 2010-10-01 false Plain bearings. 229.64 Section 229.64 Transportation...Requirements Suspension System § 229.64 Plain bearings. A plain bearing box shall contain visible free oil and may not...

2010-10-01

255

49 CFR 229.64 - Plain bearings.  

Code of Federal Regulations, 2011 CFR

... 2011-10-01 2011-10-01 false Plain bearings. 229.64 Section 229.64 Transportation...Requirements Suspension System § 229.64 Plain bearings. A plain bearing box shall contain visible free oil and may not...

2011-10-01

256

49 CFR 229.64 - Plain bearings.  

Code of Federal Regulations, 2012 CFR

... 2012-10-01 2012-10-01 false Plain bearings. 229.64 Section 229.64 Transportation...Requirements Suspension System § 229.64 Plain bearings. A plain bearing box shall contain visible free oil and may not...

2012-10-01

257

Quails on the High Plains  

Technology Transfer Automated Retrieval System (TEKTRAN)

The Southern High Plains of Texas are on the southern end of the North American Great Plains and occupy about 20 million acres. The climate is semi-arid, with long-term (90-year) average annual precipitation at Lubbock of 18.9 inches. Two species of quail, northern bobwhite (Colinus virginianus) and...

258

Flood plain and channel dynamics of the Quinault and Queets Rivers, Washington, USA  

USGS Publications Warehouse

Comparison of historic channel migration rates, modern planform conditions, and overall sediment, wood, and flow conditions and interactions for the Quinault River and Queets River in the western Olympic Peninsula, Washington, reveals decadal- to century-scale interactions between gravel-bed channels and forested flood plains in temperate maritime environments. The downstream alluvial portions of these two rivers can be divided into three reaches of different slope, flow, sediment, and wood regimes: (i) the upper Quinault River is aggrading behind Lake Quinault, a natural lake that traps most sediment and wood transported from the Olympic Mountain headwaters. (ii) The lower Quinault River, downstream of Lake Quinault, transports only sediment and wood derived from reworking of flood-plain deposits and contributed from valley margins. (iii) The Queets River has unimpeded movement of sediment and water from the mountainous headwaters to the Pacific Ocean. Measurements of channel planform characteristics and historic migration rates and patterns show that these three reaches have correspondingly distinct channel and flood-plain morphologies and dynamics. The aggrading and sediment-rich upper Quinault River has the widest flood plain, widest active channel, greatest number of low-flow channels and flanking gravel bars, and an average channel migration rate of 12.7??3.3 m/year between 1900 and 1994. The comparatively sediment-poor lower Quinault River has the narrowest flood plain, narrowest active channel, and lowest channel migration rate (4.0??1.2 m/year); and most flow is through a single channel with few adjacent gravel bars. The Queets River has attributes intermediate between the lower and upper Quinault Rivers, including an average channel migration rate of 7.5??2.9 m/year. Flood-plain turnover rates are similar for all three reaches, with channels eroding the flood plain at the rate of about 0.2% of the flood-plain area per year, and with corresponding flood-plain half-lives of 300 to 500 years. Observations from this study and previous studies on the Queets River show that channel and flood-plain dynamics and morphology are affected by interactions between flow, sediment, and standing and entrained wood, some of which likely involve time frames similar to 200-500-year flood-plain half-lives. On the upper Quinault River and Queets River, log jams promote bar growth and consequent channel shifting, short-distance avulsions, and meander cutoffs, resulting in mobile and wide active channels. On the lower Quinault River, large portions of the channel are stable and flow within vegetated flood plains. However, locally, channel-spanning log jams have caused channel avulsions within reaches that have been subsequently mobile for several decades. In all three reaches, log jams appear to be areas of conifer germination and growth that may later further influence channel and flood-plain conditions on long time scales by forming flood-plain areas resistant to channel migration and by providing key members of future log jams. Appreciation of these processes and dynamics and associated temporal and spatial scales is necessary to formulate effective long-term approaches to managing fluvial ecosystems in forested environments. Published by Elsevier Science B.V.

O'Connor, J. E.; Jones, M.A.; Haluska, T.L.

2003-01-01

259

Aerosols Over Yellow Sea Sediments  

NASA Technical Reports Server (NTRS)

This SeaWiFS image shows complex phytoplankton distribution patterns in the Bohai and Yellow seas. A wide band of brownish water along the coast north and south of the mouth of the Yangtze River indicates a heavy load of suspended sediment. The air over eastern central China and the Yellow Sea is thick with aerosols. Farther north over the Manchurian Plain and Greater Khingan Range, the air is much clearer.

2002-01-01

260

Hidden in Plain Sight  

NSDL National Science Digital Library

Steganography is the science and art of hiding messages in plain sight so only the sender and intended recipient know the existence of a message. Steganography can be characterized as security through obscurity. Through this lesson, students experience a portion of the engineering design process as they research steganography and steganographic methods; identify problems, criteria and constraints; brainstorm possible solutions; and generate ideas. These are the critical first steps in the engineering design process, often overlooked by students who want to get to the "doing" phases—designing, building and testing. In computer science, a thorough design phase makes program implementation much easier and more effective. Students obtain practice with a portion of the design process that may be less exciting, but is just as important as the other steps in the process.

IMPART RET Program, College of Information Science & Technology,

261

Cracked and Pitted Plain  

NASA Technical Reports Server (NTRS)

MGS MOC Release No. MOC2-536, 6 November 2003

This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a typical view--at 1.5 meters (5 feet) per pixel--of surfaces in far western Utopia Planitia. In this region, the plains have developed cracks and pit chains arranged in a polygonal pattern. The pits form by collapse along the trend of a previously-formed crack. This picture is located near 45.0oN, 275.4oW. This April 2003 image covers an area 3 km (1.9 mi) wide and is illuminated by sunlight from the lower left.

2003-01-01

262

The Kansas Plains  

E-print Network

The Kansas Plains An Exhibit from the Kansas Collection UNIVERSITY OF KANSAS LIBRARIES T R A V E L L I N G ACROSS KANSAS f r o m e a s t to west , one is a w a r e of a t rans i t ion f r o m the ta l l g r a s s P r a i r i e P l a i n... and faunal c o m m u n i t i e s which have adapted to it ; man in his turn has a l s o had to contend with this e n v i r o n ­ m e n t . According to Waldo R . Wedel in P r e h i s t o r i c Man on the Grea t P l a i n s , man had devised b a s i c s u b...

Zimmerman, Karen P.

1973-01-01

263

Quantifying variable rainfall intensity events on runoff and sediment losses  

Technology Transfer Automated Retrieval System (TEKTRAN)

Coastal Plain soils in Georgia are susceptible to runoff, sediment, and chemical losses from short duration-high intensity, runoff producing storms at critical times during the growing season. We quantified runoff and sediment losses from a Tifton loamy sand managed under conventional- (CT) and stri...

264

Sediment flux and the Anthropocene.  

PubMed

Data and computer simulations are reviewed to help better define the timing and magnitude of human influence on sediment flux--the Anthropocene epoch. Impacts on the Earth surface processes are not spatially or temporally homogeneous. Human influences on this sediment flux have a secondary effect on floodplain and delta-plain functions and sediment dispersal into the coastal ocean. Human impact on sediment production began 3000 years ago but accelerated more widely 1000 years ago. By the sixteenth century, societies were already engineering their environment. Early twentieth century mechanization has led to global signals of increased sediment flux in most large rivers. By the 1950s, this sediment disturbance signal reversed for many rivers owing to the proliferation of dams, and sediment load reduction below pristine conditions is the dominant signal today. A delta subsidence signal began in the 1930s and is now a dominant signal in terms of sea level for many coastal environments, overwhelming even the global warming imprint on sea level. Humans have engineered how most water and sediment are discharged into the coastal ocean. Hyperpycnal flow events have become more common for some rivers, and less common for other rivers. Bottom trawling is now widespread, suggesting that even continental shelves have received a significant but as yet quantified Anthropocene impact. The Anthropocene attains the level of a geological climate event, such as that seen in the transition between the Pleistocene and the Holocene. PMID:21282156

Syvitski, James P M; Kettner, Albert

2011-03-13

265

Geologic map of the northern plains of Mars  

USGS Publications Warehouse

The northern plains of Mars cover nearly a third of the planet and constitute the planet's broadest region of lowlands. Apparently formed early in Mars' history, the northern lowlands served as a repository both for sediments shed from the adjacent ancient highlands and for volcanic flows and deposits from sources within and near the lowlands. Geomorphic evidence for extensive tectonic deformation and reworking of surface materials through release of volatiles occurs throughout the northern plains. In the polar region, Planum Boreum contains evidence for the accumulation of ice and dust, and surrounding dune fields suggest widespread aeolian transport and erosion. The most recent regional- and global-scale maps describing the geology of the northern plains are largely based on Viking Orbiter image data (Dial, 1984; Witbeck and Underwood, 1984; Scott and Tanaka, 1986; Greeley and Guest, 1987; Tanaka and Scott, 1987; Tanaka and others, 1992a; Rotto and Tanaka, 1995; Crumpler and others, 2001; McGill, 2002). These maps reveal highland, plains, volcanic, and polar units based on morphologic character, albedo, and relative ages using local stratigraphic relations and crater counts. This geologic map of the northern plains is the first published map that covers a significant part of Mars using topography and image data from both the Mars Global Surveyor and Mars Odyssey missions. The new data provide a fresh perspective on the geology of the region that reveals many previously unrecognizable units, features, and temporal relations. In addition, we adapted and instituted terrestrial mapping methods and stratigraphic conventions that we think result in a clearer and more objective map. We focus on mapping with the intent of reconstructing the history of geologic activity within the northern plains, including deposition, volcanism, erosion, tectonism, impact cratering, and other processes with the aid of comprehensive crater-density determinations. Mapped areas include all plains regions within the northern hemisphere of Mars, as well as an approximately 300-km-wide strip of cratered highland and volcanic regions, which border the plains. Note that not all of the contiguous northern plains are mapped, because some minor parts of Elysium and Amazonis Planitiae lie south of the equator.

Tanaka, Kenneth L.; Skinner, James A.; Hare, Trent M.

2005-01-01

266

GREAT PLAINS INTERSTATE FOREST FIRE COOPERATIVE  

E-print Network

GREAT PLAINS INTERSTATE FOREST FIRE COMPACT COOPERATIVE ANNUAL OPERATING PLAN 2011 #12;Great Plains Interstate Forest Fire Compact Page 2 of 31 2011 Great Plains Forest Fire Compact AOP Table of Contents I. Intentionally Left Blank 28 K. Public Law 110-79 29 #12;Great Plains Interstate Forest Fire Compact Page 3 of 31

267

Sediment Retention Dynamics and Vegetation Along Three Tributaries of the Chesapeake Bay  

Microsoft Academic Search

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

K. Ross; C. Hupp; L. Alexander

2001-01-01

268

Paleoenvironmental interpretation of an ancient Arctic coastal plain: Integrated paleopedology and palynology from the Late Cretaceous (Maastrichtian) Prince Creek Formation, North Slope, Alaska, USA  

Microsoft Academic Search

The Cretaceous (Early Maastrichtian), dinosaur-bearing Prince Creek Formation, North Slope, Alaska, records high-latitude, alluvial sedimentation and soil formation on a low-lying, coastal plain during a greenhouse phase in Earth history. This study combines outcrop observations, micromorphology, geochemistry, and palynological analyses of paleosols in order to reconstruct local paleoenvironments of weakly developed, high-latitude coastal plain soils. Sediments of the Prince Creek

P. J. McCarthy; P. P. Flaig; A. R. Fiorillo

2010-01-01

269

Ages of Lunar Light Plains  

NASA Astrophysics Data System (ADS)

Light plains are characterized by their relative smoothness and lower crater densities (compared to the highlands), and their occurrence as crater fills. They also exhibit highland-like characteristics, such as high albedos (in comparison to mare basalts) and their geological and stratigraphic setting. Despite the long history of investigating light plains, there are still numerous open questions concerning their mode of emplacement, their mineralogical composition, their ages, and their origin. We dated 16 light plains with crater size-frequency distribution (CSFD) measurements. All dated regions were previously identified as light plains in the geologic maps [1-5] and either mapped as smooth light plains (Ip) or light plains with undulatory surfaces (INp). The studied light plains occur both inside and outside the South Pole-Aitken (SPA) basin within a latitudinal band between ~-36° and ~-75°. In particular, we investigated the following smooth light plains: Janssen (40.82°E, -44.96°; Ip [1]), Nishina (-170.8°E, -44.57°; Ip [2]), South of Nishina (Ip [2]), Obruchev (162.43°E, -38.67°; Ip [2]), Oresme (169.22°E, -42.61°, Ip [2]), Schrödinger (132.93°E, -74.73°; Ip [3]), Nearch (39.01°E, -58.58°; Ip [3]), Nasmyth (-56.39°E, -50.49°; Ip [3]), Manzinus (26.37°E, -67.51°; Ip [3]), Klaproth (-26.26°E, -69.85°; Ip [3]), Phocylides (-57.31°E, -52.79°, Ip [3]), Buffon (-133.53°E, -40.64°; Ip [4]), Roche (136.54°E, -42.37°; Ip [5]). We also dated the following light plains with undulatory surfaces: Koch (150.33°E, -42.13°; INp [2]), Garavito (156.78°E, -47.21°; INp [2]), Eötvös (134.43°E, -35.61°; INp [5]). Our CSFD measurements resulted in absolute model ages of 3.71 to 4.02 Ga for all investigated light plains, thus confirming the Imbrian and/or Nectarian ages of the geologic maps [1-5]. We only dated three INp light plains, but they appear to have ages that are close to the upper limit, i.e., 3.96-4.02 Ga. However, further CSFDs of INp light plains are necessary to corroborate this preliminary observation. In general, our new absolute model ages are similar to model ages derived for light plains north of Mare Frigoris (3.65-4.0 Ga) [6], light plains within the SPA basin (3.43-3.81 Ga) [7], and light plains in the surroundings of the Orientale and Imbrium basins (3.8-4.3 Ga) [8]. The ages are not only similar, but also show similar ranges. While our model ages vary by about 300 Ma, model ages of [6,7] exhibit ranges of ~350 Ma and ~380 Ma, respectively. Ages of [8] show a somewhat wider range of ~500 Ma. From this wide range in ages it has been concluded that a formation of the light plains by a single event (i.e., Orientale or Imbrium) is unlikely [6-8]. References: [1] Wilhelms and McCauley (1971), USGS I-703; [2] Stuart-Alexander (1978), USGS I-1047; [3] Wilhelms et al. (1979), USGS I-1162; [4] Scott et al. (1977), USGS I-1034; [5] Wilhelms and El-Baz (1977), USGS I-948; [6] Köhler et al. (2000), LPSC 31, #1822; [7] Thiessen et al. (2012), LPSC 43, #2060; [8] Neukum (1977b), Moon 17, 383-393.

Hiesinger, Harald; Howes van der Bogert, Carolyn; Thiessen, Fiona; Robinson, Mark

2013-04-01

270

Investigating the effects of abyssal peridotite alteration on Si, Mg and Zn isotopes  

NASA Astrophysics Data System (ADS)

Around 1/3 of Earth's divergent ridge system is now classified as "slow" spreading [1], exposing ultramafic rocks (abyssal peridotites) at the seafloor. Such material is often highly altered by serpentinisation and steatisation (talc formation). It is crucial to understand such processes in order to access the original composition of the mantle, and to quantify any impact on ocean composition. Here we examine the effect of both serpentinisation and steatisation on Si, Mg and Zn isotopes. Hydrothermal alteration and seafloor weathering are both sources of oceanic Si [2] and weathering of abyssal peridotites is a source of oceanic Mg [3]; hence isotopic fractionation as a result of seafloor alteration could affect oceanic Si and Mg isotope composition. Zinc isotopes can provide complimentary information; the magnitude and direction of fractionation is highly dependent on complexing ligand [4] and can provide compositional information on the fluids driving metasomatism. For this study, two cores from the well-characterised abyssal peridotites recovered on ODP Leg 209 were examined [5]. Hole 1274a peridotites exhibit variable serpentinisation at ~200°C, whereas samples from Hole 1268a have been comprehensively serpentinised and then subsequently steatised to talc facies at ~350°C, by a low Mg/Si, low pH fluid. The Si, Mg and Zn isotope compositions of 1274a samples are extremely homogeneous, identical to that of pristine mantle rocks (BSE) i.e., serpentinisation at this locality was predominantly isochemical [5]. In contrast, samples from 1268a show greater isotopic variability. In all samples, Mg is enriched in the heavier isotopes relative to BSE, consistent with formation of isotopically heavy secondary phases [6]. For Si, serpentinised samples are slightly enriched in the lighter isotopes compared to BSE, again consistent with the behaviour of Si during formation of secondary phases [7]. Within the steatised samples, some exhibit enrichments in the lighter Si isotopes (similar to the serpentinites), however, some are isotopically heavy, relative to BSE. Such samples were found to have abundant chlorite, whose formation requires fluid with high Al activity, likely sourced from late-emplaced gabbroic dykes. The Zn of all 1268a samples are enriched in the lighter isotopes, implying the involvement of isotopically light sulfide precipitation during metasomatism [4]. The consistently heavy Mg isotope data suggest that seafloor alteration of peridotites can input an isotopically light Mg-bearing fluid to the ocean. Fluid composition is less easy to determine from the more complex behaviour observed in Si isotopes, although it is unlikely to substantially deviate from BSE, consistent with previous observations [8]. Finally, the strong enrichment in the lighter isotopes of Zn confirms that this isotope system could be used as a tracer of recycled serpentinised material at arc settings, as suggested in [4]. [1] Dick et al. (2003) Nature 426, 405-412; [2] Treguer and De La Rocha (2013) Ann. Rev. Mar. Sci. 5, 477-501; [3] Snow & Dick (1995) GCA, 59, 4219-4235; [4] Pons et al. (2011) PNAS 108(43) 17639-17643; [5] Bach et al., (2004) G3 5; [6] Tipper et al. (2006) EPSL 247, 267-279; [7] Opfergelt et al. (2012) Chem. Geol. 326, 113-122; [8] De La Rocha et al. (2000) GCA 64, 2467-2477.

Savage, P. S.; Wimpenny, J.; Harvey, J.; Yin, Q.; Moynier, F.

2013-12-01

271

The Oceanic Lithosphere as Reactive Filter: Implications for MORB and Abyssal Peridotite Compositions  

NASA Astrophysics Data System (ADS)

Melt-rock reaction in the lithosphere is, as suggested by textural observations and compositional data, a ubiquitous phenomenon capable of generating locally diverse peridotite series, such as those observed at oceanic spreading centers and transform faults, and may represent an important mechanism of creating compositional diversity in MORBs [1]. Whereas our understanding of the principles governing reactive melt transport is supported by basic theories and models, studies that attempt to quantify the physical conditions and mechanisms creating heterogeneities in the oceanic lithosphere are still limited in number [e.g. 2]. Using Adiabat_1ph 3.0 [3] in combination with the pMELTS algorithm [4], we have previously shown that reactive percolation of basaltic melts through depleted harzburgites can generate the dunite-(wehrlite)-harzburgite-lherzolite spectrum observed in the abyssal mantle and ophiolites, and that the amplitude of transformations is a function of thermal boundary layer thickness and amount of available melt [5]. To gain further insight into how melt-rock reactions shape the oceanic lithosphere, here we extend our study to show that the major and trace element variability in the oceanic mantle and rising melts are also significantly influenced by the mechanism of melt transport. If associated with cooling, distributed porous melt percolation (simulated by incremental addition of the same amount of melt) more efficiently converts harzburgites into fertile lherzolites and creates more pronounced compositional gradients in the abyssal mantle than imparted during channelized melt influx (simulated as batch addition of large amounts of melt) under otherwise identical circumstances. To remain within the tholeiitic trend observed in MORB, reacted melts must be released before clinopyroxene precipitation peaks. Further reaction with harzburgite causes liquids to evolve toward boninite-like compositions. As reaction progresses with decreasing temperature, the chance of such liquids to erupt diminishes rapidly, because reactive melt productivity declines rapidly after the point of clinopyroxene precipitation maximum. We speculate that decreasing melt productivity associated with decreasing temperature, which promotes crystallization, are major factors that prevent such boninite-like liquids to become globally important MORB components. [1] Collier & Kelemen (2010) J Pet. 51/1913; [2] Kelemen (1990), J Pet. 31/51; [3] Antoshechkina et al. ED11-AGU Fall 2010; [4] Ghiorso et al. (2002), G-cubed 3/1030; [5] Luffi & Lee (2009), V33A-2025 AGU Fall 2009.

Luffi, P. I.; Lee, C.; Antoshechkina, P. M.

2010-12-01

272

Southern Ocean abyssal heat uptake in fine and coarse resolution climate model simulations  

NASA Astrophysics Data System (ADS)

The recently observed warming of Antarctic Bottom Water (AABW) represents an important component of accumulated sea level rise and global ocean heat uptake. Yet in simulations of greenhouse warming with coarse resolution climate models (which parameterize ocean eddies), Southern Ocean heat uptake dominantly occurs within near-surface waters, which are subsequently transported northward and subducted at mid-latitudes. Here, we examine the response of the abyssal Southern Ocean to greenhouse forcing within a global climate model run with a fine resolution (eddy-resolving) ocean component, which more faithfully simulates AABW formation than its coarse resolution counterparts. We argue that AABW warming may play a more important role in Southern Ocean heat uptake than is suggested by the CMIP5 ensemble of coarse resolution models. We examine the heat uptake in the Southern Ocean using the Community Climate System Model version 3.5 (CCSM 3.5). The model was run at two resolutions in the ocean and sea ice components: coarse (1 degree), which is a standard resolution of many CMIP5 models, and fine (.1 degree), in which sea ice and AABW is formed more realistically. The atmosphere and land components were fixed throughout at .5 degrees resolution. Each version was forced identically with a 1% ramping of CO2 for 150 years. The fine resolution simulation produces more dense water in the control climate, which sinks to a more realistic depth. We attribute this to the improved simulation of sea ice formation regions granted by increasing the ocean model resolution. The reduction of AABW formation as the climate warms leads to a larger response at depth at fine resolution; below 2000 meters, the fine resolution simulation takes up two orders of magnitude more heat than at coarse resolution. We further propose a framework to weigh the amount of heat taken up at depth in the Southern Ocean by the timescale at which it is sequestered, giving more value to heating of regions with long ventilation timescales. Using this framework, the degree of deep ocean heating emerges as a key difference between fine and course resolution, and an important component of the total heat sequestered in the Southern Ocean. Our work suggests that realistic abyssal ocean heat uptake may be an important component missing from many standard resolution models, and may play an important role in the observed decrease in sea surface temperatures around Antarctica in recent decades.

Newsom, E. R.; Singh, H.; Bitz, C. M.

2013-12-01

273

Can Geothermal Abyssal Heating be a Trigger of Abrupt Climate Change?  

NASA Astrophysics Data System (ADS)

There are observational data and numerical models suggesting that geothermal heating of ocean bottom waters may play an important role in the large-scale oceanic circulation. However, the role of abyssal geothermal heating in abrupt climate change has not been evaluated. Energy is continuously escaping the interior of Earth at a rate of 47 TW (1012 W), mostly through the ocean floors. Geothermal heat flow density varies from about 40 mWm-2 over the oldest oceanic crust to greater than 200 mWm-2 over the young mid-ocean ridges, with a mean of around 100 mWm-2. In general, this geothermal energy flux is capable of warming a 1000 m thick water layer by 0.0008 °C a year, or around 1.5 °C in two thousand years. Deep ocean waters are layered and rich in minerals and greenhouse gases. When the temperature of a static abyssal water parcel increases, it becomes more buoyant. There must be a buoyancy threshold when deep water starts upwelling due to geothermal heating. Small scale upwelling may not have a significant climate impact. But a basin-wide eruption of upwelling could perhaps interrupt global thermohaline and meridional overturning circulation. Most existing hypotheses on abrupt climate change rely on climate-dependent processes such as albedo feedback, fresh water influx, and wind-driven circulation. However, paleoclimate records indicate that abrupt changes in climate occurred during both glacial and interglacial periods. Geothermal-driven deep ocean water upwelling is a climate-independent hypothesis given that geothermal heat flow is a persistent energy source from below the ocean floor. This conceptual model is consistent with the recent report that the rise in atmospheric CO2 during the last deglaciation was preceded by deep water warming [Stott, et al., 2007, Nature, 466, 1093-1097] and the evidence that the abrupt ending of the last ice age was associated with the release of very old (14C-depleted) CO2 from the deep ocean to the atmosphere on a cross ocean scale [Rose, et al., 2010, Nature, 466, 1093-1097]. We are searching more paleoclimate records to identify abrupt changes that might carry evidence of a geothermal trigger.

Huang, S.

2010-12-01

274

Structure and evolution of the abyssal jet in the Vema Channel of the South Atlantic  

NASA Astrophysics Data System (ADS)

The Vema Channel represents the only major conduit through which the deepest and coldest (<0.2 °C potential temperature) Antarctic Bottom Water (AABW) flows from the Argentine into the Brazil Basin. From 2003 to 2007 two current meter moorings were present on each side of the Vema Sill, close to the narrowest spot of the Vema Channel. The data from the moorings are compared with earlier current and temperature observations. On average the maximum current core lies ˜100 m above the bottom of the sill with a mean northward speed of 0.3 m s-1. Farther up in the water column where Lower Circumpolar Deep Water and North Atlantic Deep Water prevail, one finds a level of sluggish currents with a southward tendency in the sub-centimeter-per-second range. The lower boundary of a layer of 'no' motion was observed at ˜3700 m depth where the mean potential temperature amounts to 1.5 °C. The evolution of the abyssal warming phenomenon over the last decades with notable fluctuations at the choke point between the Argentine and the Brazil Basin differs from the more stable attitude of deep horizontal currents. Starting with CTD observations in 1972 we find a steady increase of temperatures of the coldest AABW in the Vema Channel. This general trend of rising abyssal potential temperatures of almost 2 mKelvin per year is based on mostly annual CTD observations. The overall warming trend is fully compatible with our three-year moored temperature series in agreement with earlier records with high temporal resolution. Distinct frequently fluctuating horizontal current shear between the western and eastern sides of the Vema Sill may be explained by two different catchment areas for AABW at the mouth of the Vema Channel. One pathway originates at the American continental rise and advects bottom water in form of the deep western boundary current. A second pathway is supplied by an eastern boundary current along the Mid Atlantic Ridge in the Argentine Basin. Both source waters merge at the channel entrance, mix, and their respective strengths can alternate within the sill area.

Zenk, Walter; Visbeck, Martin

2013-01-01

275

Rocky Martian Plain  

NASA Technical Reports Server (NTRS)

The rocky Martian plain surrounding Viking 2 is seen in high resolution in this 85-degree panorama sweeping from north at the left to east at right during the Martian afternoon on September 5. Large blocks litter the surface. Some are porous, sponge-like rocks like the one at the left edge (size estimate: 1 1/2 to 2 feet); others are dense and fine-grained, such as the very bright rounded block (1 to 1 1/2 feet across) toward lower right. Pebbled surface between the rocks is covered in places by small drifts of very fine material similar to drifts seen at the Viking 1 landing site some 4600 miles to the southwest. The fine-grained material is banked up behind some rocks, but wind tails seen by Viking 1 are not well-developed here. On the right horizon, flat-topped ridges or hills are illuminated by the afternoon sun. Slope of the horizon is due to the 8-degree tilt of the spacecraft.

1976-01-01

276

Impact of dredging on dissolved phosphorus transport in agricultural drainage ditches of the Atlantic Coastal Plain  

Technology Transfer Automated Retrieval System (TEKTRAN)

Drainage ditches can be a key conduit of phosphorus (P) between agricultural soils of the Atlantic coastal plain and local surface waters, including the Chesapeake Bay. This study sought to quantify the effect of a common ditch management practice, sediment dredging, on fate of P in drainage ditches...

277

Sedimentological and morphological characteristics of some nabkha deposits in the northern coastal plain of Kuwait, Arabia  

Microsoft Academic Search

Nabkhas in the sabkha flat of the northern coastal plain of Kuwait are generallylocated in areas slightly higher than the evaporitic sabkha pans, and facing the alluvium fans descending from the bordering cliffs and slopes. They are developed by the deposition of wind-driven sediments around Nitraria retusa shrubs. The nabkhas vary in shape and size. However, they mostly have an

F. I. Khalaf; R. Misak; A. Al-Dousari

1995-01-01

278

TECTONIC STRUCTURE AND OIL AND GAS POTENTIAL OF THE KOLKHIDA PLAIN AND ADJACENT REGIONS  

Microsoft Academic Search

Western Georgia is in the eastern part of the Riono-Black Sea intermontane oil and gas reservoir. Coastal Abkhaziya and the Colchis Plain is favorable for oil and gas prospecting as Mesozoic sediments are here overlain by a series of Tertiary and Quaternary rocks. From the Recent tectonic pattern, evolution, age, and composition of the present complexes the authors could outline

V. B. Olenin; B. A. Sokolov

1960-01-01

279

Freshwater and marine coupling in estuaries of the Mississippi River deltaic plain  

Microsoft Academic Search

The estuaries of Louisiana's Mississippi River deltaic plain (MRDP) exhibit sharp physical and biological contrasts due to their different successional stages in delta development. The Atchafalaya- Fourleague Bay complex is a young deltaic system with high freshwater and sediment inputs. The area has been undergoing rapid land building since 1973. The Barataria Basin estuary occupies a deltaic land mass which

CHRISTOPHER J. MADDEN; JOHN W. DAY; JOHN M. RANDALL

1988-01-01

280

Geology and Wine 11. Terroir of the Western Snake River Plain, Idaho, USA  

Technology Transfer Automated Retrieval System (TEKTRAN)

This article explores unique factors that shape the terroir of Idaho’s principal wine grape-growing district. Most Idaho wine grape vineyards are located in the Western Snake River Plain (WSRP) rift basin (~43°N, ~114°W) on soils derived from lake, river, or wind-blown sediments, volcanic events, a...

281

Human Responses to Middle Holocene (Altithermal) Climates on the North American Great Plains  

Microsoft Academic Search

The climate of the Great Plains during the middle Holocene varied considerably, but overall it was marked by a north–south gradient of increasingly warmer and drier conditions, with a reduction in effective moisture, surface water, and resource abundance, and an increase in resource patchiness, sediment weathering, erosion, and aeolian activity. Pronounced drought conditions were most evident on the Southern High

David J. Meltzer

1999-01-01

282

Genetic and Morphological Divergences in the Cosmopolitan Deep-Sea Amphipod Eurythenes gryllus Reveal a Diverse Abyss and a Bipolar Species  

PubMed Central

Eurythenes gryllus is one of the most widespread amphipod species, occurring in every ocean with a depth range covering the bathyal, abyssal and hadal zones. Previous studies, however, indicated the existence of several genetically and morphologically divergent lineages, questioning the assumption of its cosmopolitan and eurybathic distribution. For the first time, its genetic diversity was explored at the global scale (Arctic, Atlantic, Pacific and Southern oceans) by analyzing nuclear (28S rDNA) and mitochondrial (COI, 16S rDNA) sequence data using various species delimitation methods in a phylogeographic context. Nine putative species-level clades were identified within E. gryllus. A clear distinction was observed between samples collected at bathyal versus abyssal depths, with a genetic break occurring around 3,000 m. Two bathyal and two abyssal lineages showed a widespread distribution, while five other abyssal lineages each seemed to be restricted to a single ocean basin. The observed higher diversity in the abyss compared to the bathyal zone stands in contrast to the depth-differentiation hypothesis. Our results indicate that, despite the more uniform environment of the abyss and its presumed lack of obvious isolating barriers, abyssal populations might be more likely to show population differentiation and undergo speciation events than previously assumed. Potential factors influencing species’ origins and distributions, such as hydrostatic pressure, are discussed. In addition, morphological findings coincided with the molecular clades. Of all specimens available for examination, those of the bipolar bathyal clade seemed the most similar to the ‘true’ E. gryllus. We present the first molecular evidence for a bipolar distribution in a macro-benthic deep-sea organism. PMID:24086322

Havermans, Charlotte; Sonet, Gontran; d’Udekem d’Acoz, Cédric; Nagy, Zoltán T.; Martin, Patrick; Brix, Saskia; Riehl, Torben; Agrawal, Shobhit; Held, Christoph

2013-01-01

283

Hydrocarbon traps along Louisiana offshore  

SciTech Connect

A compilation of potential hydrocarbon trap types has been assembled for the Louisiana offshore, from coastal plain to abyssal plain. These potential traps are listed according to paleophysiographic provinces: coastal plain, shelf, shelf break, upper slope, middle slope, lower slope, and abyssal plain. Characteristics of each trap type are tabulated. The characteristics include tectonics, regional and local sedimentation rates and types, position within an evolving sequence as determined by sequence stratigraphy, duration of reservoir and/or trap creation, and sea level position. Regional geologic processes, such as salt tectonics, and approximate rates at which they operate are also listed.

Lowrie, A.; Sullivan, N.

1989-03-01

284

Mineralogy of the mid-ocean-ridge basalt source from neodymium isotopic composition of abyssal peridotites.  

PubMed

Inferring the melting process at mid-ocean ridges, and the physical conditions under which melting takes place, usually relies on the assumption of compositional similarity between all mid-ocean-ridge basalt sources. Models of mantle melting therefore tend to be restricted to those that consider the presence of only one lithology in the mantle, peridotite. Evidence from xenoliths and peridotite massifs show that after peridotite, pyroxenite and eclogite are the most abundant rock types in the mantle. But at mid-ocean ridges, where most of the melting takes place, and in ophiolites, pyroxenite is rarely found. Here we present neodymium isotopic compositions of abyssal peridotites to investigate whether peridotite can indeed be the sole source for mid-ocean-ridge basalts. By comparing the isotopic compositions of basalts and peridotites at two segments of the southwest Indian ridge, we show that a component other than peridotite is required to explain the low end of the (143)Nd/(144)Nd variations of the basalts. This component is likely to have a lower melting temperature than peridotite, such as pyroxenite or eclogite, which could explain why it is not observed at mid-ocean ridges. PMID:12097907

Salters, Vincent J M; Dick, Henry J B

2002-07-01

285

Photo-real rendering of bioluminescence and iridescence in creatures from the abyss  

NASA Astrophysics Data System (ADS)

The generation of photo-real renderings of bioluminescence is developed for creatures from the abyss. Bioluminescence results from a chemical reaction with examples found in deep-sea marine environments including: algae, copepods, jellyfish, squid, and fish. In bioluminescence, the excitation energy is supplied by a chemical reaction, not by a source of light. The greatest transparency window in seawater is in the blue region of the visible spectrum. From small creatures like single-cell algae, to large species of siphonophore Praya dubia (40m), luminescent phenomena can be produced by mechanical excitement from disturbances of objects passing by. Deep sea fish, like the Pacific Black Dragonfish are covered with photophores along the upper and lower surfaces which emits light when disturbed. Other animals like small squids have several different types of light organs oscillating at different rates. Custom shaders and material phenomena incorporate indirect lighting like: global illumination, final gathering, ambient occlusion and subsurface scattering to provide photo real images. Species like the Hydomedusae jellyfish, produce colors that are also generated by iridescence of thin tissues. The modeling and rendering of these tissues requires thin film multilayer stacks. These phenomena are simulated by semi-rigid body dynamics in a procedural animation environment. These techniques have been applied to develop spectral rendering of scenes outside the normal visible window in typical computer animation render engines.

Prusten, Mark

2008-08-01

286

Evidence for enhanced mixing over rough topography in the abyssal ocean  

PubMed

The overturning circulation of the ocean plays an important role in modulating the Earth's climate. But whereas the mechanisms for the vertical transport of water into the deep ocean--deep water formation at high latitudes--and horizontal transport in ocean currents have been largely identified, it is not clear how the compensating vertical transport of water from the depths to the surface is accomplished. Turbulent mixing across surfaces of constant density is the only viable mechanism for reducing the density of the water and enabling it to rise. However, measurements of the internal wave field, the main source of energy for mixing, and of turbulent dissipation rates, have typically implied diffusivities across surfaces of equal density of only approximately 0.1 cm2 s(-1), too small to account for the return flow. Here we report measurements of tracer dispersion and turbulent energy dissipation in the Brazil basin that reveal diffusivities of 2-4 cm2 s(-1) at a depth of 500 m above abyssal hills on the flank of the Mid-Atlantic Ridge, and approximately 10 cm2 s(-1) nearer the bottom. This amount of mixing, probably driven by breaking internal waves that are generated by tidal currents flowing over the rough bathymetry, may be large enough to close the buoyancy budget for the Brazil basin and suggests a mechanism for closing the global overturning circulation. PMID:10646599

Ledwell; Montgomery; Polzin; St. Laurent LC; Schmitt; Toole

2000-01-13

287

Basin dynamics in the Pampas Plain, Argentina  

NASA Astrophysics Data System (ADS)

The Argentine Pampean foreland or Pampas Plain, located at leading edge of the modern flat slab of the south-central Andes between 31°-33° SL, is examined in order to understand the large-scale subsidence using flexural and gravity studies together with computations of dynamic topography. At scales <300 km, Bouguer anomalies and flexural analysis predicts a foredeep of ~250 km width and a peripheral bulge amplitude of ~25 m, which match the regional morphologies of the modern Plain. These calculations assume a tectonic loading placed at the easternmost Sierras Pampeanas broken foreland (considered as the modern analogue of the North American Laramide). These results, however, do not account for the subsurface Miocene-Quaternary basin preservation, represented by an accumulated sedimentary thickness ~400 m and with depocenters >400 km eastward with respect to flexural models. The discrepancy suggests that two mechanisms, acting at different wavelengths, might have influenced in the formation of the Argentine Pampas. The basin preservation, generated by the subduction dynamics of this segment of the Andes, is likely the result of large-scale dragging forces. Models of mantle flow, driven by realistic subducting slab geometries and density contrasts, reproduced the depocenter location and the wavelength of subsidence as well as most of the remaining amplitude. However, while the net dynamic subsidence across the Pampas was ~200-100 m during the early Miocene normal-dipping subduction stage of the Andes, the Pliocene to Holocene slab flattening, in contrast to expected, reproduced very small negative dynamic topography values (<20 m). Consequently, the net change of dynamic topography from Miocene to Present would tend to zero or even to positive signals, suggesting a minor control of the subduction on the Quaternary sediment accommodation. These results agree reasonably well with the subsurface Pampas stratigraphy.

Davila, F. M.; Lithgow-Bertelloni, C.

2012-04-01

288

A sediment budget for Town Creek watershed: Suspended sediment transport analysis  

Technology Transfer Automated Retrieval System (TEKTRAN)

The Town Creek watershed is located in the Southeastern Plains Ecoregion in Mississippi. Its total area covers 1,769 km2 and represents approximately 50% of the upper Tombigbee River basin area contributing to the Aberdeen Pool on the Tennessee-Tombigbee Waterway. The sediment yield from the watersh...

289

Northern Plains Of Mars  

NASA Technical Reports Server (NTRS)

This rocky panoramic scene is the second picture of the Martian surface that was taken by Viking Lander 2 shortly after touchdown on September 3 at 3:58 PM PDT (Earth received time). The site is on a northern plain of Mars, at about 48 N. Lat., 226 W. Long., known as Utopia Planitia. The picture sweeps around 330 degrees in azimuth, starting from northwest at the left through north (above the sampler arm housing) past east, where the sky is bright at the center, and southeast toward the right above the radioisotope thermoelectric generator cover. The surface is strewn with rocks out to the horizon, ranging in size up to several meters across. Some pitted rocks resemble fragments of porous volcanic lava. Other rocks have grooves that may have been eroded by windblown sand and dust. Although fine-grained material is seen between the boulders, no sand dunes are evident. The dip in the eastern horizon at the center is an illusion caused by an 8-degree tilt of the Lander toward the west. Actually, the terrain is more level than that at the Viking 1 site. The horizon toward the left of the panorama (northwest) appears featureless, indicating that it may be several kilometers distant. The sky at the center (east) is bright because the sun was above but out of the picture at 10 AM Mars time. Toward the right (southeast), the rocks that are silhouetted against the skyline indicate that the horizon is much nearer, probably because of a slight rise in that area of the terrain. The circular high-gain antenna at the right has clots of fine-grained material adhering to the lower half, some of which appeared to have been sliding downward while the camera was scanning the area. At the extreme right, the banded appearance resulted because the camera continued to scan while it was no longer moving in azimuth. Any motion or other variation in the scene would show up as a change in successive lines.

1976-01-01

290

Tectonic control of Eocene arkosic sediment deposition, Oregon and Washington  

Microsoft Academic Search

Chronostratigraphic and geographic studies of Eocene arkosic sandstones suggest deposition during a volcanically quiet interval resulting from the westward jump of the Farallon-Kula plate subduction zone in Oregon and Washington. The Eocene arkosic sandstones were deposited as part of a broad fluvial plain-coastal plain-shelf margin basin complex extending throughout Oregon and Washington between uplands of Mesozoic rocks. Feldspathic-quartzose sediments were

J. M. Armentrout; A. R. Ulrich

1983-01-01

291

Two abyssal sites in the Southern Ocean influenced by different organic matter inputs: Environmental characterization and preliminary observations on the benthic foraminifera  

NASA Astrophysics Data System (ADS)

The abundance and diversity of the deep-sea benthos are intimately linked to inputs of organic matter from the euphotic zone. However, it is often difficult to isolate the influence of surface productivity on benthic ecosystems from other environmental factors. To this end, two abyssal sites (˜4200 m water depth) located under contrasting productivity regimes around the Crozet Plateau, in the Indian Ocean sector of the Southern Ocean, were sampled during the austral summer of 2004/2005. One site (M5), east of the Crozet Isles, was located beneath an area where there was an enduring seasonal phytoplankton bloom. The second site (M6) was located in an oligotrophic high-nutrient low-chlorophyll (HNLC) region to the south of the islands. Organic fluxes to the seafloor at these sites are thought to reflect the overlying productivities, so that the benthic environment to the east of the islands was more eutrophic than at the southerly station. All other environmental variables were similar at the two sites, which are located just 460 km apart. The concentrations of chlorophyll- a and total organic carbon in the surficial sediments were significantly greater at the relatively eutrophic site, east of the islands (M5), than at the southerly site (M6). Total nitrogen, however, was similar at both sites. Significantly higher phytopigment concentrations were observed in the surficial sediments at the eutrophic site; in particular, the concentration of chlorophyll- a was 3 times greater than at the southern site, although the freshness of the labile component, as measured by chlorophyll- a to pheophorbide ratio, was not different between sites. These results confirm that fluxes of organic matter to the seafloor were higher at the site located beneath the bloom region. This was reflected in the abundance and diversity of live (stained) and dead benthic foraminifera (>125 ?m), which were greater at the eutrophic site. The species composition of the dead foraminiferal assemblages were similar at both sites, however, and were dominated by Nuttallides umbonifera, Pullenia bulloides, and Melonis pompiloides. An exception was the "phytodetritus species" Epistominella exigua, which was more abundant at the eutrophic site, indicating a larger seasonal component to the export under the bloom region. Differences in the organic matter input regimes at the two sites appear to influence the abundance and diversity, but not the overall species composition, of the foraminiferal assemblages.

Hughes, J. A.; Smith, T.; Chaillan, F.; Bett, B. J.; Billett, D. S. M.; Boorman, B.; Fisher, E. H.; Frenz, M.; Wolff, G. A.

2007-09-01

292

Aquatic Sediments.  

ERIC Educational Resources Information Center

Presents a literature review of aquatic sediments and its effect upon water quality, covering publications of 1976-77. This review includes: (1) sediment water interchange; (2) chemical and physical characterization; and (3) heavy water in sediments. A list of 129 references is also presented. (HM)

Sanville, W. D.; And Others

1978-01-01

293

AQUATIC SEDIMENTS  

EPA Science Inventory

One hundred seventeen literature references in the area of freshwater sediments were abstracted and synthesized to produce a review of sediment-related research for the period November, 1975 through October, 1976. Research areas covered included sediment-water interchange, sampli...

294

Heterogeneity in the Upper Mantle From Nd Isotopic Composition of the Abyssal Peridotites  

NASA Astrophysics Data System (ADS)

We have determined trace element concentrations, Sr and Nd isotopic composition of clinopyroxene separates from abyssal peridotites from the South West Indian Ridge (SWIR) and from the Mid Cayman Rise (MCR). The SWIR peridotites from three different dredges all show LREE (light rare earth elements) depletions, however the samples from the three dredges have distinct Nd-isotopic characteristics. The six peridotites analyzed from dredge VAN-7-85 have high Nd-isotope ratios (0.513086-0.513320) all higher than the Nd- isotope ratios of the associated basalts. The cpx from these peridotites are also some of the most depleted in terms of REE with CeN being less than 0.1 times the chondritic value and YbN less than 10 times chondritic. Basalts from this area range from LREE depleted to LREE enriched and the cpx are not in equilibrium with the associated basalts. Nd-isotope ratios of the dredge VAN 7-78 is more homogeneous (0.513003-0.513046) and overlapping with the associated basalts. The LREE are less depleted (CeN 2-5 times chondritic) than dredge 85. The least depleted cpx could be in equilibrium with associated basalts. In contrast to these two dredges, cpx from the VAN 7-96 are most enriched in Nd-isotope ratios (0.512885-0.512933). LREE concentrations in the cpx are more enriched (8 times chondritic) than those at the two other locations and show highest normalized concentrations for the middle REE (Sm-Eu-Gd, up to 11 times chondritic). However, these cpx are too depleted in the HREE Ho to Lu to be in equilibrium with the associated basalts. MCR peridotites dredged from two different locations show extreme LREE depletion pattern with CeN less than 0.1 times chondritic and YbN less than 10 times chondritic, and are not in equilibrium with the associated basalts. Nd-isotope ratios of these two locations have a restricted range (0.513111 to 0.513278) which overlaps with the basalt (0.513115-0.513190) and extends to higher ratios. At both SWIR and MCR, peridotites are on average more depleted in Nd-isotope ratios than the associated basalts. This systematic depletion requires an enriched component with lower solidus. Lack of correlation between isotopic composition and degree of major element depletion in the abyssal peridotite indicates that this enriched component is not peridotitic. Although the range in Nd-isotopic composition of a single dredge is significant, the range is smaller than observed at peridotite massifs over a similar lengthscale. However, the range in trace element compositions observed in a single dredge is larger than can be explained by variations in degree of melting as a single dredge is often less then a few kilometers in length. This indicates that the MORB mantle exhibits significant heterogeneity in the peridotitic component.

Mallick, S.; Salters, V. J.

2006-12-01

295

A Reverse Taxonomic Approach to Assess Macrofaunal Distribution Patterns in Abyssal Pacific Polymetallic Nodule Fields  

PubMed Central

Heightened interest in the exploitation of deep seafloor minerals is raising questions on the consequences for the resident fauna. Assessing species ranges and determination of processes underlying current species distributions are prerequisites to conservation planning and predicting faunal responses to changing environmental conditions. The abyssal central Pacific nodule belt, located between the Clarion and Clipperton Fracture Zones (CCZ), is an area prospected for mining of polymetallic nodules. We examined variations in genetic diversity and broad-scale connectivity of isopods and polychaetes across the CCZ. Faunal assemblages were studied from two mining claims (the eastern German and French license areas) located 1300 km apart and influenced by different productivity regimes. Using a reverse taxonomy approach based on DNA barcoding, we tested to what extent distance and large-scale changes in environmental parameters lead to differentiation in two macrofaunal taxa exhibiting different functions and life-history patterns. A fragment of the mitochondrial gene Cytochrome Oxidase Subunit 1 (COI) was analyzed. At a 97% threshold the molecular operational taxonomic units (MOTUs) corresponded well to morphological species. Molecular analyses indicated high local and regional diversity mostly because of large numbers of singletons in the samples. Consequently, variation in composition of genotypic clusters between sites was exceedingly large partly due to paucity of deep-sea sampling and faunal patchiness. A higher proportion of wide-ranging species in polychaetes was contrasted with mostly restricted distributions in isopods. Remarkably, several cryptic lineages appeared to be sympatric and occurred in taxa with putatively good dispersal abilities, whereas some brooding lineages revealed broad distributions across the CCZ. Geographic distance could explain variation in faunal connectivity between regions and sites to some extent, while assumed dispersal capabilities were not as important. PMID:25671322

Janssen, Annika; Kaiser, Stefanie; Meißner, Karin; Brenke, Nils; Menot, Lenaick; Martínez Arbizu, Pedro

2015-01-01

296

A reverse taxonomic approach to assess macrofaunal distribution patterns in abyssal pacific polymetallic nodule fields.  

PubMed

Heightened interest in the exploitation of deep seafloor minerals is raising questions on the consequences for the resident fauna. Assessing species ranges and determination of processes underlying current species distributions are prerequisites to conservation planning and predicting faunal responses to changing environmental conditions. The abyssal central Pacific nodule belt, located between the Clarion and Clipperton Fracture Zones (CCZ), is an area prospected for mining of polymetallic nodules. We examined variations in genetic diversity and broad-scale connectivity of isopods and polychaetes across the CCZ. Faunal assemblages were studied from two mining claims (the eastern German and French license areas) located 1300 km apart and influenced by different productivity regimes. Using a reverse taxonomy approach based on DNA barcoding, we tested to what extent distance and large-scale changes in environmental parameters lead to differentiation in two macrofaunal taxa exhibiting different functions and life-history patterns. A fragment of the mitochondrial gene Cytochrome Oxidase Subunit 1 (COI) was analyzed. At a 97% threshold the molecular operational taxonomic units (MOTUs) corresponded well to morphological species. Molecular analyses indicated high local and regional diversity mostly because of large numbers of singletons in the samples. Consequently, variation in composition of genotypic clusters between sites was exceedingly large partly due to paucity of deep-sea sampling and faunal patchiness. A higher proportion of wide-ranging species in polychaetes was contrasted with mostly restricted distributions in isopods. Remarkably, several cryptic lineages appeared to be sympatric and occurred in taxa with putatively good dispersal abilities, whereas some brooding lineages revealed broad distributions across the CCZ. Geographic distance could explain variation in faunal connectivity between regions and sites to some extent, while assumed dispersal capabilities were not as important. PMID:25671322

Janssen, Annika; Kaiser, Stefanie; Meißner, Karin; Brenke, Nils; Menot, Lenaick; Martínez Arbizu, Pedro

2015-01-01

297

Uplifted Sediments in the Northern Plains of Mars?  

NASA Astrophysics Data System (ADS)

We present a compositional analysis of a set of impact craters in the Northern Lowlands and morphologic evidence that sedimentary material (phyllosilicates) were uplifted from great depth, showing striking similarities to southern highland material.

Gross, C.; Carter, J.; Sowe, M.; Bishop, J. L.

2014-07-01

298

Suspended-sediment and fresh-water discharges in the Ob and Yenisey rivers, 1960-1988  

Microsoft Academic Search

Of the world's great rivers, the Ob and Yenisey rank among the largest suppliers of fresh water and among the smallest suppliers of suspended sediment to the coastal ocean. Sediment in the middle reaches of the rivers is mobilized from bordering terraces and exchanged between channels and flood plains. Sediment in the lower reaches of these great rivers is deposited

R. H. Meade; N. N. Bobrovitskaya; V. I. Babkin

2000-01-01

299

Geochemistry and mineralogy of shallow alluvial aquifers in Daudkandi upazila in the Meghna flood plain, Bangladesh  

NASA Astrophysics Data System (ADS)

The shallow alluvial aquifers of the delta plains and flood plains of Bangladesh, comprises about 70% of total land area are mostly affected by elevated concentrations of arsenic (As) in groundwater exposing a population of more than 35 million to As toxicity. Geochemical studies of shallow alluvial aquifer in the Meghna flood plain show that the uppermost yellowish grey sediment is low in As (1.03 mg/kg) compared to the lower dark grey to black sediment (5.24 mg/kg) rich in mica and organic matter. Sequential extraction data show that solid phase As bound to poorly crystalline and amorphous metal (Fe, Mn, Al)-oxyhydroxides is dominant in the grey to dark grey sediment and reaches its maximum level (3.05 mg/kg) in the mica rich layers. Amount of As bound to sulphides and organic matter also peaks in the dark grey to black sediment. Vertical distributions of major elements determined by X-ray fluorescence (XRF) show that iron (Fe2O3), aluminum (Al2O3) and manganese (MnO) follow the general trend of distribution of As in the sediments. Concentrations of As, Mn, Fe, HCO3 -, SO4 2- and NO3 - in groundwater reflect the redox status of the aquifer and are consistent with solid phase geochemistry. Mineralogical analysis by X-ray diffraction (XRD) and scanning electron microscopy (SEM) fitted with energy dispersive X-ray spectrometer (EDS) revealed dominance of crystalline iron oxides and hydroxides like magnetite, hematite and goethite in the oxidised yellowish grey sediment. Amorphous Fe-oxyhydroxides identified as grain coating in the mica and organic matter rich sediment suggests weathering of biotite is playing a critical role as the source of Fe(III)-oxyhydroxides which in turn act as sink for As. Presence of authigenic pyrite in the dark grey sediment indicates active reduction in the aquifer.

Hasan, M. Aziz; von Brömssen, Mattias; Bhattacharya, Prosun; Ahmed, Kazi Matin; Sikder, Arif Mohiuddin; Jacks, Gunnar; Sracek, Ondra

2009-04-01

300

The Texas High Plains Evapotranspiration (TXHPET) network  

Technology Transfer Automated Retrieval System (TEKTRAN)

The newly developed Texas High Plains Evapotranspiration (TXHPET) network is comprised of the North Plains and South Plains evapotranspiration (ET) networks. The TXHPET network currently entails the operation of 18 meteorological stations located in 15 Texas counties and regional coverage is estima...

301

Expanded Plain TEX Steven Smith  

E-print Network

Expanded Plain TEX Sept 2004 2.8.4 Karl Berry Steven Smith #12;This manual documents the Eplain Berry. Steven Smith wrote the documentation for the commutative diagram macros. (He also wrote the macros.) Some additions/corrections by Adam Lewenberg. Permission is granted to make and distribute

Mintmire, John W.

302

Lava Flow on Coastal Plain  

USGS Multimedia Gallery

Lava flows remain active within the Royal Gardens subdivision and onto the coastal plain below. The number of surface flows has decreased however, due in part to a probable decrease in activity related to the ongoing deflation of Pu`u `? `?, and because the new lava tube branch...

303

White Plains MetARs  

NSDL National Science Digital Library

In this activity, students use METeorological Aerodome Reports (METARs) to view changes in temperature, dew point, air pressure, sky condition, wind, and visibility at White Plains, New York. After studying the reports, they answer a series of questions related to radiation and insolation, radiative balance, and meteorological processes.

Steve Kluge

304

Lava Flows on Coastal Plain  

USGS Multimedia Gallery

The lava flows on the coastal plain, which show up as the light colored flows in the foreground, are erupted into the TEB tube system from the D fissure which first opened up in July 2007. This vent is faintly visible as a fuming source in the background near the upper left corner of the photo. Smal...

305

Carrisa Plains solar power plant  

Microsoft Academic Search

A 30-MWe solar central receiver power plant is being designed for installation at Carrisa Plains in California. This second-generation system is to be built using private venture capital funding with power generation scheduled for late 1986. Liquid sodium is used in the heat transfer system. Proven or tested components are used throughout.

Johnson

1984-01-01

306

Tuffaceous ephemeral lake deposits on an alluvial plain, Middle Tertiary of central California  

USGS Publications Warehouse

The Oligocene and Miocene Valley Springs Formation represents a large fluvial depositional system that extended westward from sediment-filled palaeovalleys in the high Sierra Nevada to a piedmont alluvial plain under the present Central Valley. The Valley Springs Formation consists largely of tuffaceous mudrocks, tuffaceous sandstone, polymict conglomerate and rhyodacitic tuff. The tuffaceous mudrock lithofacies probably represents a complex of ephemeral lake and marsh environments on a low gradient alluvial plain. The inferred abundance of shallow lakes, ponds and marshes implies a climate that was wetter than the semi-arid climate of the region today. -from Author

Bartow, J.A.

1994-01-01

307

Natural oil and gas seeps on the Black Sea floor  

Microsoft Academic Search

Migration of hydrocarbons to the seafloor in the Black Sea occurs via direct seepages, mud volcanoes, and development of fluidized sediment flows (e.g., diapers). Gas migration occurs on the shelf, continental slope, and abyssal plain. Gas hydrates are spatially related to gas accumulations and are present in shallow subsurface sediment layers. Their distribution is controlled by the activity of mud

R. P. Kruglyakova; Y. A. Byakov; M. V. Kruglyakova; L. A. Chalenko; N. T. Shevtsova

2004-01-01

308

Middle and upper jurassic depositional environments at outer shelf and slope of Baltimore Canyon Trough  

Microsoft Academic Search

New CDP data acquired in the Baltimore Canyon Trough during project LASE made it possible to map a continuous Jurassic sedimentary sequence from the continental margin to the abyssal plain without interruption by basement structures. Intense carbonate sedimentation is inferred at the outer shelf during the Middle and Late Jurassic. Carbonate sedimentation probably started during the Middle Jurassic with a

L. A. Gamboa; P. L. Stoffa; M. Truchan

1985-01-01

309

Progressive deformation of an evaporite-bearing accretionary complex: SeaMARC I, SeaBeam and piston-core observations from the Mediterranean Ridge  

Microsoft Academic Search

The Mediterranean Ridge is an arcuate ridge of deformed sediment caught up in the convergent plate margin between the African plate and the Aegean. An intensive campaign of SeaMARC I and SeaBeam surveys followed by piston coring has been conducted along the contact between undeformed turbidites of the Sirte Abyssal Plain and folded and faulted sediments of the Mediterranean Ridge.

Kim A. Kastens; Nancy A. Breen; Maria B. Cita

1992-01-01

310

Influence of the Atchafalaya River on recent evolution of the chenier-plain inner continental shelf, northern Gulf of Mexico  

USGS Publications Warehouse

This study examines the influence of the Atchafalaya River, a major distributary of the Mississippi River, on stratigraphic evolution of the inner continental shelf in the northern Gulf of Mexico. Sedimentary, geochemical, and shallow acoustic data are used to identify the western limit of the distal Atchafalaya subaqueous delta, and to estimate the proportion of the Atchafalaya River's sediment load that accumulates on the inner shelf seaward of Louisiana's chenier-plain coast. The results demonstrate a link between sedimentary facies distribution on the inner shelf and patterns of shoreline accretion and retreat on the chenier plain. Mudflat progradation on the eastern chenier-plain coast corresponds to the location of deltaic mud accumulation on the inner shelf. On the central chenier-plain shelf, west of the subaqueous delta, relict sediment is exposed that was originally deposited between ???1200 and 600 years BP during activity of the Lafourche lobe of the Mississippi Delta complex. Mass-balance calculations indicate that the eastern chenier-plain inner shelf and coastal zone form a sink for 7??2% of the sediment load carried by the Atchafalaya River. ?? 2004 Elsevier Ltd. All rights reserved.

Draut, A.E.; Kineke, G.C.; Velasco, D.W.; Allison, M.A.; Prime, R.J.

2005-01-01

311

The Arctic Coastal Plain, Alaska  

NSDL National Science Digital Library

This tutorial is about the Arctic tundra biome; the plants and animals found there; and the amount of sunlight, temperatures, seasons and permafrost. Examples of Arctic ecosystem interactions, food chains, and biological adaptations to the Arctic Coastal Plain are given. There are photographs of wolves, caribou, arctic hares, minks, lemmings, arctic foxes, polar bears, seals, walruses, ptarmigans, hawks, and owls. Definitions of ecosystem terms can be found by clicking on the term within the tutorial.

312

Warming of Global Abyssal and Deep Southern Ocean Waters between the 1990s and 2000s: Contributions to Global Heat and Sea Level Rise Budgets*  

E-print Network

Warming of Global Abyssal and Deep Southern Ocean Waters between the 1990s and 2000s: Contributions of recent warming of these regions in global heat and sea level budgets. The authors 1) compute warming produces a 0.053 (60.017) mm yr21 increase in global average sea level and the deep warming south

Johnson, Gregory C.

313

History of plains resurfacing in the Scandia region of Mars  

USGS Publications Warehouse

We present a preliminary photogeologic map of the Scandia region of Mars with the objective of reconstructing its resurfacing history. The Scandia region includes the lower section of the regional lowland slope of Vastitas Borealis extending about 500–1800 km away from Alba Mons into the Scandia sub-basin below ?4800 m elevation. Twenty mapped geologic units express the diverse stratigraphy of the region. We particularly focus on the materials making up the Vastitas Borealis plains and its Scandia sub-region, where erosional processes have obscured stratigraphic relations and made the reconstruction of the resurfacing history particularly challenging. Geologic mapping implicates the deposition, erosion, and deformation/degradation of geologic units predominantly during Late Hesperian and Early Amazonian time (~3.6–3.3 Ga). During this time, Alba Mons was active, outflow channels were debouching sediments into the northern plains, and basal ice layers of the north polar plateau were accumulating. We identify zones of regional tectonic contraction and extension as well as gradation and mantling. Depressions and scarps within these zones indicate collapse and gradation of Scandia outcrops and surfaces at scales of meters to hundreds of meters. We find that Scandia Tholi display concentric ridges, rugged peaks, irregular depressions, and moats that suggest uplift and tilting of layered plains material by diapirs and extrusion, erosion, and deflation of viscous, sedimentary slurries as previously suggested. These appear to be long-lived features that both pre-date and post-date impact craters. Mesa-forming features may have similar origins and occur along the southern margin of the Scandia region, including near the Phoenix Mars Lander site. Distinctive lobate materials associated with local impact craters suggest impact-induced mobilization of surface materials. We suggest that the formation of the Scandia region features potentially resulted from crustal heating related to Alba Mons volcanism, which acted upon a sequence of lavas, outflow channel sediments, and polar ice deposits centered within the Scandia region. These volatile-enriched sediments may have been in a state of partial volatile melt, resulting in the mobilization of deeply buried ancient materials and their ascent and emergence as sediment and mud breccia diapirs to form tholi features. Similar subsurface instabilities proximal to Alba Mons may have led to surface disruption, as suggested by local and regional scarps, mesas, moats, and knob fields.

Tanaka, Kenneth L.; Fortezzo, Corey M.; Hayward, Rosalyn K.; Rodriguez, J. Alexis P.; Skinner, James A.

2011-01-01

314

Fluvial sediments a summary of source, transportation, deposition, and measurement of sediment discharge  

USGS Publications Warehouse

This paper presents a broad but undetailed picture of fluvial sediments in streams, reservoirs, and lakes and includes a discussion of the processes involved in the movement of sediment by flowing water. Sediment is fragmental material that originates from the chemical or physical disintegration of rocks. The disintegration products may have many different shapes and may range in size from large boulders to colloidal particles. In general, they retain about the same mineral composition as the parent rocks. Rock fragments become fluvial sediment when they are entrained in a stream of water. The entrainment may occur as sheet erosion from land surfaces, particularly for the fine particles, or as channel erosion after the surface runoff has accumulated in streams. Fluvial sediments move in streams as bedload (particles moving within a few particle diameters of the streambed) or as suspended sediment in the turbulent flow. The discharge of bedload varies with several factors, which may include particle size and a type of effective shear on the surface of the streambed. The discharge of suspended sediment depends partly on concentration of moving sediment near the streambed and hence on discharge of bedload. However, the concentration of fine sediment near the streambed varies widely, even for equal flows, and, therefore, the discharge of fine sediment normally cannot be computed theoretically. The discharge of suspended sediment also depends on velocity, turbulence, depth of flow, and fall velocity of the particles. In general, the coarse sediment transported by a stream moves intermittently and is discharged at a rate that depends on properties of the flow and of the sediment. If an ample supply of coarse sediment is available at the surface of the streambed, the discharge of the coarse sediment, such as sand, can be roughly computed from properties of the available sediment and of the flow. On the other hand, much of the fine sediment in a stream usually moves nearly continuously at about the velocity of the flow, and even low flows can transport large amounts of fine sediment. Hence, the discharge of fine sediments, being largely dependent on the availability of fine sediment upstream rather than on the properties of the sediment and of the flow at a cross section, can seldom be computed from properties, other than concentrations based directly on samples, that can be observed at the cross section. Sediment particles continually change their positions in the flow; some fall to the streambed, and others are removed from the bed. Sediment deposits form locally or over large areas if the volume rate at which particles settle to the bed exceeds the volume rate at which particles are removed from the bed. In general, large particles are deposited more readily than small particles, whether the point of deposition is behind a rock, on a flood plain, within a stream channel, or at the entrance to a reservoir, a lake, or the ocean. Most samplers used for sediment observations collect a water-sediment mixture from the water surface to within a few tenths of a foot of the streambed. They thus sample most of the suspended sediment, especially if the flow is deep or if the sediment is mostly fine; but they exclude the bedload and some of the suspended sediment in a layer near the streambed where the suspended-sediment concentrations are highest. Measured sediment discharges are usually based on concentrations that are averages of several individual sediment samples for a cross section. If enough average concentrations for a cross section have been determined, the measured sediment discharge can be computed by interpolating sediment concentrations between sampling times. If only occasional samples were collected, an average relation between sediment discharge and flow can be used with a flow-duration curve to compute roughly the average or the total sediment discharges for any periods of time for which the flow-duration c

Colby, B.R.

1963-01-01

315

MOVEMENT OF TRACTIVE SEDIMENT FROM DISTURBED LANDS.  

USGS Publications Warehouse

The Smoky Creek basin of the coal area of northeastern Tennessee shows extensive evidence of tractive movement of coarse sediment from mined tributary basins into the main channel. Coal-rich gravel bars and flood-plain debris are common below tributaries. Using a combination of techniques including channel-geometry and bar measurements, sediment sampling for rock-debris and coal size distributions, and botanical dating of flood events and geomorphic features, an average annual yield of 65 metric tons per square kilometer (187 tons per square mile) for tractively moved sediment has been calculated for the period 1977 to 1982. This value, 8 percent of the total sediment load, is probably an underestimate owing to the method of calculation. Slightly more than half of the traction load is coal, which moves through the basin within a few years. Rock debris, however, appears to require years to decades to move similar distances.

Osterkamp, W.R.; Carey, W.P.; Hupp, C.R.; Bryan, B.A.

1984-01-01

316

A qualitative assessment of the influence of bioturbation in Lake Baikal sediments  

NASA Astrophysics Data System (ADS)

The impact of bioturbation in Lake Baikal sediments, particularly on rhythmic layering and mixing, was assessed by studying the actual vertical distribution of benthic animals in continuous accumulation zones selected by seismic survey (Vydrino Shoulder, Posolskoe Bank, Continent Ridge). To assess the influence of the bioturbation, animals were extracted from short cores and identified at the relevant taxonomic level. The faunal distribution is examined in parallel with the bioturbation tracks observed in thin section. Oligochaeta, Nematoda, Ostracoda, Copepoda, Gammaridae, Chironomidae and Hydrachnidia were found inhabiting the sediment. Among them, only oligochaete worms were assumed to have a significant impact on sediment mixing because of their "conveyor belt" feeding. The other two most abundantly sampled groups, nematods and copepods, belong to the interstitial fauna that has no significant impact on the vertical displacement of sediment particles and do not ingest the sediment. The presence of a benthic fauna as deep as 15 cm in the sediment indicates that the possibility of sediment disturbance by invertebrate activity cannot be dismissed in Lake Baikal. The effect of biological mixing is more limited in the deepest stations because the number of potential bioturbators is reduced, qualitatively as well as quantitatively. Located in the abyssal zone, Continent and Vydrino (but outside turbidites) deep stations appear to be most promising sediment records for tracking climate signal at high resolution.

Martin, Patrick; Boes, Xavier; Goddeeris, Boudewijn; Fagel, Nathalie

2005-04-01

317

Shift in detrital sedimentation in the eastern Bay of Bengal during the late Quaternary  

NASA Astrophysics Data System (ADS)

Down-core variations of granulometric, geochemical and mineral magnetism of a 70-cm long sediment core retrieved from the eastern Bay of Bengal abyssal region were studied to understand sedimentation pattern and sediment provenance during the last ˜12 kyr BP. Based on down-core physical and elemental variations, three units were identified: unit 3 (70-43 cm) is a ˜30 cm thick clayey silt organic carbon-rich (0.5-0.92%) turbidite probably delivered by the Brahmaputra River during the late Quaternary period. Units 2 (43-24 cm) and 1 (24-0 cm) represent enhanced and reduced supply of coarse-grained detrital sediments from the Ganges River during early and late Holocene period, respectively. Increased terrigenous supply dilutes calcium carbonate (CaCO3) and biogenic elements (P, Ba and Cu) in units 3 and 2. On the contrary, a reduction in detrital input enhances CaCO3 and biogenic elements in unit 1. Lithogenic elements (Ti, Al, K and Rb) and shale-normalized REE patterns in all three units suggest terrigenous source. The shift in provenance from the Brahmaputra to the Ganges derived sediments is evident by a sharp increase in sediment grain size, increased concentration and grain size assemblages of magnetic minerals, lithogenic elements concentration and Lan/Ybn ratio. This study highlights terrigenous dilution on biogenic sedimentation in the eastern Bay of Bengal sediments.

Prakash Babu, C.; Pattan, J. N.; Dutta, K.; Basavaiah, N.; Ravi Prasad, G. V.; Ray, D. K.; Govil, P.

2010-06-01

318

Aquatic sediments  

SciTech Connect

The authors present a literature review concerning sediment properties, interactions, and conditions. Topics of discussion include the following: biological activity and toxicity; nutrients; metals; organic compounds; dredging; radionuclides; oxygen demand and organic carbon; mathematical modeling; sediment transport and suspension; and paleolimnology.

Bonner, J.S.; Autenrieth, R.L.; Schreiber, L. (Texas A and M Univ., College Station (United States))

1990-06-01

319

A conceptual model to facilitate amphibian conservation in the northern Great Plains  

USGS Publications Warehouse

As pressures on agricultural landscapes to meet worldwide resource needs increase, amphibian populations face numerous threats including habitat destruction, chemical contaminants, disease outbreaks, wetland sedimentation, and synergistic effects of these perturbations. To facilitate conservation planning, we developed a conceptual model depicting elements critical for amphibian conservation in the northern Great Plains. First, we linked upland, wetland, and landscape features to specific ecological attributes. Ecological attributes included adult survival; reproduction and survival to metamorphosis; and successful dispersal and recolonization. Second, we linked ecosystem drivers, ecosystem stressors, and ecological effects of the region to each ecological attribute. Lastly, we summarized information on these ecological attributes and the drivers, stressors, and effects that work in concert to influence the maintenance of viable and genetically diverse amphibian populations in the northern Great Plains. While our focus was on the northern Great Plains, our conceptual model can be tailored to other geographic regions and taxa.

Mushnet, David M.; Euliss, Ned H.; Stockwell, Craig A.

2012-01-01

320

A Budget of Carbonate Framework and Sediment Production, Kailua Bay, Oahu, Hawaii  

Microsoft Academic Search

Sediments of the bay and coastal plain of Kailua (Oahu, Hawaii) are . 90% biogenic carbonate produced by destruction of primary reef framework (coral and encrusting coralline algae) and by direct sedimentation through the biological activity of calcifying or- ganisms (the green alga Halimeda, the branching coralline alga Poro- lithion gardineri, molluscs, and benthic foraminifera). Field measure- ments of benthic

J. N. Harney; C. H. Fletcher

2003-01-01

321

Holocene delta evolution and sediment discharge of the Mekong River southern Vietnam  

Microsoft Academic Search

Evolutionary changes, delta progradation, and sediment discharge of the Mekong River Delta, southern Vietnam, during the late Holocene are presented based on detailed analyses of samples from six boreholes on the lower delta plain. Sedimentological and chronostratigraphic analyses indicate clearly that the last 3 kyr were characterized by delta progradation under increasing wave influence, southeastward sediment dispersal, decreasing progradation rates,

Thi Kim Oanh Ta; Van Lap Nguyen; Masaaki Tateishi; Iwao Kobayashi; Susumu Tanabe; Yoshiki Saito

2002-01-01

322

Disequilibria in the uranium decay series in sedimentary deposits at Allen's cave, nullarbor plain, Australia: Implications for dose rate determinations  

Microsoft Academic Search

Disequilibrium in the uranium decay series can cause a time-dependent variation in the radiation dose received by deposited sediments. In luminescence and ESR dating studies, the observation of disequilibrium usually requires modelling of the variation in dose rate as a function of burial time. In this paper, we report on radionuclide data collected from Allen's Cave on the Nullarbor Plain,

Jon M. Olley; Richard G. Roberts; Andrew S. Murray

1997-01-01

323

Numerical chronology of Pleistocene coastal plain and valley development; extensive aggradation during glacial low sea-levels  

Microsoft Academic Search

Based on more than 60 newly acquired luminescence ages, field information, and sediment granulometry data, a comprehensive chronostratigraphic framework is presented for Pleistocene alluvial coastal plain and valley terraces and coastal barrier trends on the northern Gulf of Mexico between Texas and NW Florida. Luminescence ages 216–188ka from the second youngest coastal terrace coincide with the highstand during the second

Ervin G. Otvos

2005-01-01

324

Stochastic analysis of seafloor morphology on the flank of the Southeast Indian Ridge: The influence of ridge morphology on the formation of abyssal hills  

NASA Astrophysics Data System (ADS)

In this study we estimate the statistical properties of abyssal hill morphology adjacent to the Southeast Indian Ridge in a region where the axial morphology changes from axial high to axial valley without a corresponding change in spreading rate. We explore the influence of axial morphology on abyssal hills and place these results within the context of response to spreading rate. Two cruises aboard the R/V Melville collected Sea Beam 2000 multibeam data along the Southeast Indian Ridge, providing continuous multibeam coverage of the axis from ˜89°W to ˜118°W, and ˜100% coverage within four survey regions extending out to ˜45 km (˜1.2 Ma) from the axis [Sempéré et al., 1997; Cochran et al., 1997]. We apply the statistical modeling method of Goff and Jordan [1988] to gridded data from the four survey areas, examining in particular estimates of abyssal hill rms height, characteristic width and length, aspect ratio, and skewness. Two analyses are performed: (1) comparison of the along-axis variation in abyssal hill characteristics to ridge segmentation, and (2) a calculation of population statistics within axial high, intermediate, and axial valley data populations of this study, and comparison of these results to population statistics derived from studies adjacent to the Mid-Atlantic Ridge and East Pacific Rise. We find that abyssal hills generated along axial high mid-ocean ridges are very different from those generated along axial valley mid-ocean ridges, not only with respect to size and shape, but also in their response to such factors as spreading rate and segmentation.

Goff, John A.; Ma, Ying; Shah, Anjana; Cochran, James R.; SempéRé, Jean-Christophe

1997-07-01

325

Late Pleistocene braided rivers of the Atlantic Coastal Plain, USA  

NASA Astrophysics Data System (ADS)

Infrared Landsat imagery (band 4) clearly reveals braided river patterns on late Pleistocene terraces of unglaciated rivers in the Atlantic Coastal Plain of the southeastern United States, a region that presently exhibits meandering patterns that have existed throughout the Holocene. These Pleistocene braided patterns provide a unique global example of river responses to late Quaternary climate changes in an unglaciated humid subtropical region at 30-35° north latitude. Detailed morphological and chronological results are given for the Oconee-Altamaha River valley in Georgia and for the Pee Dee River valley in South Carolina, including 15 optically stimulated luminescence (OSL) dates and four radiocarbon dates. Correlative examples are drawn from additional small to large rivers in South- and North Carolina. OSL and radiocarbon ( 14C) dates indicate distinct braiding at 17-30 ka, within oxygen isotope stage 2 (OIS 2), and braiding probably existed at least during parts of OIS 3 and possibly OIS 4 back to ca 70 ka. The chronology suggests that braiding is the more common pattern for the late Quaternary in the southeastern United States. Braided terraces appear to have been graded to lower sea-levels and are onlapped by Holocene floodplain deposits up to 10-60 km from the coast. The braiding probably reflects the response of discharge and sediment yield to generally cooler and drier paleoclimates, which may have had a pronounced runoff season. Sedimentation of eolian dunes on the braid plains is coeval with braiding and supports the conclusion of dry soils and thin vegetation cover during the late Pleistocene. Our chronological data contribute to a body of literature indicating that reliable OSL age estimates can be obtained from quartz-rich bed load sand from braided rivers, based on good correlations with both radiocarbon dates from braided fluvial sediment and OSL dates from stratigraphically correlative eolian sand.

Leigh, David S.; Srivastava, Pradeep; Brook, George A.

2004-01-01

326

Managing Cotton Insects in the High Plains, Rolling Plains and Trans Pecos Areas of Texas--2008  

E-print Network

E-6 5-08 Managing Cotton Insects in the High Plains, Rolling Plains and Trans Pecos Areas of Texas 2008 Contents Page Pest Management Principles ......................................................................... 3 Insecticide... ..................................................................................... 6 Management Decisions ................................................................................... 7 Scouting Decisions .......................................................................................... 7 Early-Season Pests...

Siders, Kerry; Baugh, Brant A.; Sansone, Chris; Kerns, David L.

2008-04-29

327

Production of Virginia Peanuts in the Rolling Plains and Southern High Plains of Texas  

E-print Network

-5140 Production of Virginia Peanuts in the Rolling Plains and Southern High Plains of Texas Robert G. Lemon and Thomas A. Lee* *Extension Agronomist and Extension Plant Pathologist, The Texas A&M University System. Texas Agricultural Extension Service...

Lemon, Robert G.; Lee, Thomas A.

1995-08-01

328

Coastal Mudflat Accretion under Energetic Conditions, Louisiana Chenier-Plain Coast, USA  

NASA Technical Reports Server (NTRS)

Mudflat accretion on the chenier-plain coast of Louisiana, northern Gulf of Mexico, is anomalous in an area that otherwise experiences widespread land loss due to rapid relative sea level rise. Accretion is shown to be related to energetic events (Winta cold fronts and occasional tropical-dcprrssion srmms) using a 17-year record of meteorological conditions and aerial surveys The results indicate substantial differences between the behavior of sand- and mud-dominated coastal systems under energetic conditions. Comparison of the Louisiana chenier plain to other mud-rich coasts indicates that certain conditions are necessary for mudflat accretion to occur during energetic atmospheric activity. These include an abundant supply of fine-grained fluvial sediment and resuspension events that maintain an unconsolidated sea floor, dominant onshore wind direction during energetic conditions, particularly when onshore winds coincide with high fluvial sediment input to the coastal ocean, and a low tidal range.

Draut, Amy E.; Kineke, Gail C.; Huh, Oscar K.; Grymes, John M., III; Westphal, Karen A.; Moeller, Christopher C.

2005-01-01

329

Water Management Studies in the Rolling Plains.  

E-print Network

patterns at Chillicothe and Iowa Park showed that irrigation often is not needed for production of 30 to 50 bushels of wheat per acre. Water Management Studies In the Rolling Plains C. J. GERARD, D. G. BORDOVSKY, AND L. E. CLARK* Crop production... in the Rolling Plains is dependent upon the effective utilization of rainfall and, sometimes, supplemental irrigation. Although irrigation is practiced on only a small percentage of the area in the Rolling Plains, the amount is significant. For example...

Gerard, C.J.; Bordovsky, D.G.; Clark, L.E.

1980-01-01

330

Assessing the sedimentation deficit problem in Louisiana's coastal salt marshes  

Microsoft Academic Search

The imbalance between relative sea-level rise and vertical marsh accretion is frequently cited as a major factor in the problem of wetland loss in coastal Louisiana. Relative sea-level rise rates are high, compared to the rest of the Gulf coast, owing to subsidence of Holocene Mississippi deltaic plain sediments, and although marsh accretion rates are also high, in comparison with

Reed

1990-01-01

331

Discharge, Sediment, and Channel Characteristics of the Río Pánuco, Mexico  

Microsoft Academic Search

Spatial and temporal variations in watershed characteristics provide insight into the controls on discharge, sediment transport, and channel morphology for the Río Panuco, Mexico, the sixth largest (98,227 km2) river flowing into the Gulf of Mexico. Although there has been considerable study of Gulf Coastal Plain river systems within the United States, there have been very few studies of rivers

Paul F. Hudson

332

Environmental studies in Western Europe using overbank sediment  

Microsoft Academic Search

There is particular concern in Western Europe about the environmental problems, and urgent and concerted international action is warranted. An evaluation of the present state of pollution requires systematic, compatible data on the present distribution as well as the preindustrial, natural distribution of chemical elements in surface environments. The appliance of overbank sediments from river plains as a sampling medium

J. BOGEN

333

What can we learn about the history of oceanic shield volcanoes from deep marine sediments? Example from La Reunion volcanoes.  

NASA Astrophysics Data System (ADS)

The discovery in 2006, during the oceanographic survey FOREVER, of large volcaniclastic sedimentary systems off La Réunion Island (western Indian ocean) revealed a new image of the evolution of oceanic shield volcanoes and their dismantling. Marine data obtained from 2006 to 2011 during the oceanographic surveys ERODER 1 to ERODER 4 included bathymetry, acoustic imagery, echosounding profiles, dredging and coring. Six major turbidite systems were mapped and described on the submarine flanks of La Reunion volcanic edifice and the surrounding oceanic plate. The interpretation of sediment cores enable us to characterise the processes of gravity-driven sediment transfer from land to deep sea and also to revisit the history of the volcanoes of La Réunion Island. Turbidite systems constitute a major component of the transfer of volcanic materials to the abyssal plain (Saint-Ange et al., 2011; 2013; Sisavath et al., 2011; 2012; Babonneau et al., 2013). These systems are superimposed on other dismantling processes (slow deformation such as gravity sliding or spreading, and huge landslides causing debris avalanches). Turbidite systems mainly develop in connection with the hydrographic network of the island, and especially at the mouths of large rivers. They show varying degrees of maturity, with canyons incising the submarine slope of the island and feeding depositional areas, channels and lobes extending over 150 km from the coast. The cores collected in turbidite systems show successions of thin and thick turbidites alternating with hemipelagic sedimentation. Sedimentological and stratigraphic analysis of sediment cores yielded a chronology of submarine gravity events. First-order information was obtained on the explosive activity of these volcanoes by identifying tephra layers in the cores (glass shards and pumice). In addition, major events of the volcanic and tectonic history of the island can be identified and dated. In this contribution, we focus most attention on the southernmost turbidite system (St-Joseph system). Sedimentary records allow us to establish a link between two major landslides affecting the flanks of Piton de la Fournaise volcano and the triggering of major turbidity currents. Thus, the age of these events could be obtained; their chronology being far too difficult to establish otherwise. In short: a beautiful example of the contribution of sedimentology to the study of the structural evolution of the volcanoes. References Babonneau N., Delacourt C., Cancouet R., Sisavath E., Bachelery P., Deschamps A., Mazuel A., Ammann J., Jorry S.J., Villeneuve N., 2013, Marine Geology, 346, 47-57. Saint-Ange F., Bachèlery P., Babonneau N., Michon, L., Jorry S.J., 2013, Marine Geology. 337, 35-52. Saint-Ange, F., Savoye, B., Michon, L., Bachelery, P., Deplus, C., De Voogd, B., Dyment, J., Le Drezen, E., Voisset, M., Le Friant, A., and Boudon, G., 2011. Geology, 39, 271-274, doi: 10.1130/G31478.1. Sisavath, E., Mazuel, A., Jorry, S., Babonneau, N., Bachèlery P., De Voogd, B., Salpin, M., Emmanuel, L., Beaufort, L., Toucanne, S., 2012, Sedimentary Geology, 281, p. 180-193, doi :10.1016/j.sedgeo.2012.09.010. Sisavath, E., Babonneau N., Saint-Ange F., Bachèlery P., Jorry S., Deplus C., De Voogd B., Savoye B., 2011, Marine Geology, v. 288, p. 1-17, doi:10.1016/j.margeo.2011.06.011.

Bachelery, Patrick; Babonneau, Nathalie; Jorry, Stephan; Mazuel, Aude

2014-05-01

334

Correlation of Miocene sequences and hydrogeologic units, New Jersey Coastal Plain  

Microsoft Academic Search

We have developed a Miocene sequence stratigraphic framework using data from recently drilled boreholes in the New Jersey Coastal Plain. Sequences are shallowing upward, unconformity-bounded units; fine-grained shelf and prodelta sediments grade upward to delta front and shallow-marine sands, corresponding to confining bed—aquifer couplets. By dating Miocene sequences using Sr-isotope stratigraphy, and mapping with borehole data and geophysical logs, we

Peter J. Sugarman; Kenneth G. Miller

1997-01-01

335

Petrological, magnetic and chemical properties of basalt dredged from an abyssal hill in the North-east pacific  

USGS Publications Warehouse

OVER the years, samples of basalt from the oceanic crust have been taken mainly from seamounts, fracture zones and ridge and rise crests1-6, and rarely from the vast fields of abyssal hills which cover a large part of the deep-sea floor. The basalt sampled from the deeper regions of the oceanic crust (for example, on fault scarps) is a distinct variety of tholeiitic basalt, while alkali basalt is restricted to the volcanic edifices4. Oceanic tholeiitic basalt differs from alkali basalt and continental tholeiite chiefly in having a relatively low percentage of K2O (0.2 weight per cent)4. Some authors have speculated that this type of tholeiitic basalt is the major extrusion from the upper mantle and constitutes the predominant rock type in the upper oceanic crust. ?? 1969 Nature Publishing Group.

Luyendyk, B.P.; Engel, C.G.

1969-01-01

336

Geomorphic evidence for an eolian contribution to the formation of the Martian northern plains  

NASA Technical Reports Server (NTRS)

The northern plains of Mars have many morphologic characteristics that are uncommon or absent on the rest of the planet. Mariner 9 and Viking images obtained north of latitude 30 deg N revealed 'smooth' and 'mottled' plains of an uncertain origin. Some or all of the northern plains were interpreted to consist of lava plains intermixed with eolian and volcanic materials thick eolian mantles that buried portions of the mid latitudes periglacial deposits resulting from the presence of ground ice and as water-transported sediments derived from fluvial runoff, lacustrine deposition in standing bodies of water, or glacial runoff. The highest-resolution Viking images show many intriguing details that may provide clues to the origin of this complex and distinctive terrain. Some of the informative features present in the best Viking images, comparing the observations to what may be expected from various hypotheses of formation, are reviewed. While the results are not conclusive for any single hypothesis, eolian processes have played a major role in the erosion (and possibly deposition) of the materials that make up the surface exposures in the Martian northern plains.

Zimbelman, J. R.

1993-01-01

337

Descending into the abyss: Bathymetric patterns of diversity in decapod crustaceans shift with taxonomic level and life strategies  

NASA Astrophysics Data System (ADS)

The aim of this study was to examine the depth-related changes in the diversity of decapod crustaceans from the intertidal to abyssal zones off Madeira Archipelago, a chain of islands in the subtropical North East Atlantic Ocean. The bathymetric gradient in species richness was evaluated using the reported ranges of 175 out of approximately 186 decapod species known in this archipelago. The depth-related changes at different taxonomic (order, sub-orders and families) and life strategy (pelagic, benthopelagic and benthic) levels were investigated and different ecological hypotheses (species-energy, mid-domain and Rapoport's effects) were tested to explain the observed patterns. No unimodal trend of Decapoda diversity was revealed and, instead, a monotonic decrease towards the abyss was observed, mainly as a consequence of the depth-related changes in the benthic diversity of the suborder Pleocyemata. Nonetheless, all bathymetric gradients of pelagic diversity (at order and suborder levels) displayed parabolic trends. There was also a general increase in bathymetric range towards greater depth, and the major faunal break was identified within the continental shelf area. All species richness-depth patterns were significantly nested, but there was a clear increasing trend in randomness from the benthic to the pelagic realm. The present study shows for the first time that even within the same taxonomic group and geographic region different bathymetric patterns of diversity can be observed, depending on the taxonomic level and, more importantly, on the group's life strategies. Moreover, our analysis supports the species-energy hypothesis, implicating a combination of temperature and food availability as the main causal predictors explaining diversity variation.

Rosa, Rui; Boavida-Portugal, Joana; Trübenbach, Katja; Baptista, Miguel; Araújo, Ricardo; Calado, Ricardo

2012-06-01

338

Wet coastal plain tundra III  

SciTech Connect

This year's census data for the wet coastal plain tundra in Alaska; North Slope Borough, 3 km SSE of Naval Arctic Research Laboratory, Barrow; 71/sup 0/ 18'N, 156/sup 0/ 38'W; Barrow Quadrangle, USGS reflect a decrease in the total number of species breeding. However, total breeding density rose by 82%. Lapland Longspurs (up 105%) accounted for half of this increase while the rest was spread among many species. There was a total of 8 species; 40.5 territorial males or females (162/km/sup 2/, 66/100 acres).

Myers, J.P.; Gellman, S.T.; Pitelka, F.A.

1980-01-01

339

Rates of Microbial Metabolism in Deep Coastal Plain Aquifers  

PubMed Central

Rates of microbial metabolism in deep anaerobic aquifers of the Atlantic coastal plain of South Carolina were investigated by both microbiological and geochemical techniques. Rates of [2-14C]acetate and [U-14C]glucose oxidation as well as geochemical evidence indicated that metabolic rates were faster in the sandy sediments composing the aquifers than in the clayey sediments of the confining layers. In the sandy aquifer sediments, estimates of the rates of CO2 production (millimoles of CO2 per liter per year) based on the oxidation of [2-14C] acetate were 9.4 × 10?3 to 2.4 × 10?1 for the Black Creek aquifer, 1.1 × 10?2 for the Middendorf aquifer, and <7 × 10?5 for the Cape Fear aquifer. These estimates were at least 2 orders of magnitude lower than previously published estimates that were based on the accumulation of CO2 in laboratory incubations of similar deep subsurface sediments. In contrast, geochemical modeling of groundwater chemistry changes along aquifer flowpaths gave rate estimates that ranged from 10?4 to 10?6 mmol of CO2 per liter per year. The age of these sediments (ca. 80 million years) and their organic carbon content suggest that average rates of CO2 production could have been no more than 10?4 mmol per liter per year. Thus, laboratory incubations may greatly overestimate the in situ rates of microbial metabolism in deep subsurface environments. This has important implications for the use of laboratory incubations in attempts to estimate biorestoration capacities of deep aquifers. The rate estimates from geochemical modeling indicate that deep aquifers are among the most oligotrophic aquatic environments in which there is ongoing microbial metabolism. PMID:16348227

Chapelle, Francis H.; Lovley, Derek R.

1990-01-01

340

Hydrologic Controls On Methylmercury Availability In Coastal Plain Rivers  

NASA Astrophysics Data System (ADS)

Methylmercury (MeHg) in streams is often attributed to methylation in up-gradient wetland areas, with episodic flood events maximizing wetland-stream hydrologic connectivity and dominating MeHg supply to the stream habitat. A number of studies have demonstrated that Coastal Plain streams in the southeastern United States are particularly vulnerable to high MeHg bioaccumulation and have attributed this vulnerability to wetland abundance and strong hydrologic connectivity between wetland areas and adjacent stream aquatic habitat. Because characteristically coarse-grained Coastal Plain sediments favor vertical infiltration with little surface runoff, flood events attributable to Coastal Plain precipitation are driven by rising groundwater, promoting efficient transport of MeHg from wetland/floodplain source areas to the stream habitat and increasing in-stream availability. Several observations at McTier Creek, South Carolina, however, suggest that good hydrologic connectivity and efficient MeHg transport in Coastal Plain systems are not limited to flood conditions. Close correspondence between stream and shallow-groundwater water levels at McTier indicate good hydrologic connectivity exists prior to flood conditions. Dissolved MeHg concentrations do not increase under flood conditions. Thus, we assessed the flux of water and dissolved mercury (Hg) species (FMeHg and total Hg (FTHg)) from surface water and groundwater sources in a short reach at McTier Creek during separate events in April and July 2009, to determine the importance of shallow groundwater Hg transport from floodplain areas to the stream under non-flood conditions. Mass balance assessments indicated that, under non-flood conditions, the primary supply of water, FMeHg, and FTHg within the reach (excluding upstream surface-water influx) was groundwater discharge, rather than tributary transport from wetlands, in-stream MeHg production, or atmospheric deposition. The results indicate efficient transport of MeHg from out-of-channel (wetland and riparian floodplain) areas to the stream aquatic habitat in Coastal Plain streams of the southeastern United States, even under non-flood conditions.

Bradley, P. M.; Brigham, M. E.; Burns, D. A.; Button, D. T.; Lutz, M. A.; Marvin-DiPasquale, M. C.; Riva-Murray, K.; Journey, C.

2011-12-01

341

Modelling radioactive waste disposal by penetrator experiments in the abyssal Atlantic Ocean  

Microsoft Academic Search

The use of streamlined projectiles is a possible method of disposing of high-level radioactive waste in oceanic sediments1-3. But there is little information about the manner in which freely-falling projectiles impact on the ocean floor4-5. To correct this situation, the Engineering Studies Task Group of the OECD's Nuclear Energy Agency (NEA) Seabed Working Group, through which research into the feasibility

T. J. Freeman; C. N. Murray; T. J. G. Francis; S. D. McPhail; P. J. Schultheiss

1984-01-01

342

Contrasting lithofacies architecture in ring-plain deposits related to edifice construction and destruction, the Quaternary Stratford and Opunake Formations, Egmont Volcano, New Zealand  

NASA Astrophysics Data System (ADS)

The early constructional and destructional history of ancestral Egmont Volcano is recorded by variations in lithofacies assemblages and architecture in volcaniclastic deposits making up the southern ring plain. Eruptive periods and edifice construction are recorded by aggradational sequences of debris-flow deposits on the ring plain and numerous tephra deposits preserved on the lower flanks of the volcano. The aggradational sequences represent fairly long-term periods of accumulation when a succession of lahars delivered coarse-grained sediment to the ring plain. Edifice destruction is recorded on the ring plain by deposits of debris-avalanches and associated debris flows. Individual deposits represent rapid (as much as 2.6 km 3), but episodic, sedimentation over large areas (up to 500 km 2) of the ring plain. Sedimentation following these events was slow, with reworked tephra and lignite accumulating over most of the ring plain. Episodes of edifice destruction usually marked the beginning of long-term quiescent intervals or periods of low-frequency eruptive activity. Tephra deposits on the flanks of the volcano are not as abundant as in stratigraphic intervals representing periods of edifice construction.

Palmer, Beth A.; Neall, Vincent E.

1991-11-01

343

Sediment Transport  

NSDL National Science Digital Library

Each student reviews a recent USGS publication detailing sediment transport data collection and reduction on the Yellowstone River. Using that report, they answer a series of questions about sediment transport and make some basic hydrologic and hydraulic calculations using data in the report. They also use USGS software to analyze cross-sections on the Yellowstone in a real world application. Designed for a geomorphology course

Karen Williams

344

12 CFR 611.1217 - Plain language requirements.  

Code of Federal Regulations, 2011 CFR

...2011-01-01 2011-01-01 false Plain language requirements. 611.1217 Section 611...System Institution Status § 611.1217 Plain language requirements. (a) Plain language presentation. All communications to...

2011-01-01

345

49 CFR 230.102 - Tender plain bearing journal boxes.  

Code of Federal Regulations, 2010 CFR

...4 2010-10-01 2010-10-01 false Tender plain bearing journal boxes. 230.102 Section...MAINTENANCE STANDARDS Steam Locomotives and Tenders Running Gear § 230.102 Tender plain bearing journal boxes. Plain...

2010-10-01

346

49 CFR 230.102 - Tender plain bearing journal boxes.  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Tender plain bearing journal boxes. 230.102 Section 230.102...Tenders Running Gear § 230.102 Tender plain bearing journal boxes. Plain bearing journal boxes with the following defects...

2013-10-01

347

49 CFR 230.102 - Tender plain bearing journal boxes.  

Code of Federal Regulations, 2014 CFR

...2014-10-01 2014-10-01 false Tender plain bearing journal boxes. 230.102 Section 230.102...Tenders Running Gear § 230.102 Tender plain bearing journal boxes. Plain bearing journal boxes with the following defects...

2014-10-01

348

49 CFR 230.102 - Tender plain bearing journal boxes.  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Tender plain bearing journal boxes. 230.102 Section 230.102...Tenders Running Gear § 230.102 Tender plain bearing journal boxes. Plain bearing journal boxes with the following defects...

2012-10-01

349

49 CFR 230.102 - Tender plain bearing journal boxes.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Tender plain bearing journal boxes. 230.102 Section 230.102...Tenders Running Gear § 230.102 Tender plain bearing journal boxes. Plain bearing journal boxes with the following defects...

2011-10-01

350

HIGH PLAINS INTEGRATED PEST MANAGEMENT GUIDE  

Technology Transfer Automated Retrieval System (TEKTRAN)

Many diseases affect crops grown in the High Plains region. This guide is intended to provide current effective management options for plant diseases affecting all major field crops grown in the High Plains region. Chemical and non-chemical control practices, when available, are described in detai...

351

Second chance for the plains bison  

Microsoft Academic Search

Before European settlement the plains bison (Bison bison bison) numbered in the tens of millions across most of the temperate region of North America. Within the span of a few decades during the mid- to late-1800s its numbers were reduced by hunting and other factors to a few hundred. The plight of the plains bison led to one of the

Curtis H. Freese; Keith E. Aune; Delaney P. Boyd; James N. Derr; Steve C. Forrest; C. Cormack Gates; Peter J. P. Gogan; Shaun M. Grassel; Natalie D. Halbert; Kyran Kunkel; Kent H. Redford

2007-01-01

352

JAPANESE BROME IMPACTS NORTHERN GREAT PLAINS RANGELAND  

Technology Transfer Automated Retrieval System (TEKTRAN)

Japanese brome (Bromus japonicus Thunb.) is an annual grass that has invaded thousands of hectares of Northern Great Plains rangelands. We studied the effect of Japanese brome on the current year's increase in biomass in a plant community in the Northern Great Plains dominated by western wheatgrass...

353

Ohio Conservation Plan: Plains gartersnake, Thamnophis radix  

Microsoft Academic Search

This plan outlines strategies and methods used in an ongoing study initiated in 1999 to restore a selfsustaining population of the Plains gartersnake (Thamnophis radix) in Ohio. Restoring a self-sustaining population would require increases in the current population to where the ratios of T. radix to T. sirtalis are approximately 1:1 in multiple locations in Killdeer Plains Wildlife Area (KPWA).

Norman Reichenbach; M. Barrie; K. Becka; G. Burghardt; S. Butterworth; C. Caldwell; F. Dierkes; P. Johantgen; K. Stanford; D. Wynn

2010-01-01

354

Second chance for the plains bison  

Microsoft Academic Search

Before European settlement the plains bison (Bison bison bison) numbered in the tens of mil- lions across most of the temperate region of North America. Within the span of a few dec- ades during the mid- to late-1800s its numbers were reduced by hunting and other factors to a few hundred. The plight of the plains bison led to one

Curtis H. Freesea; Keith E. Auneb; Delaney P. Boydc; James N. Derrd; Steve C. Forresta; C. Cormack Gatese; Peter J. P. Goganf; Shaun M. Grasselg; Natalie D. Halbertd; Kyran Kunkelh; Kent H. Redfordi

355

Comparison of bioturbation rates determined by lead-210 and plutonium in abyssal cores  

E-print Network

, 1981) 50 LIST OF FIGURES Figure Page 1. The natural uranium series 2. Potential sources of Pb-210 in marine sediments (as described by Bruland, 1974) 3. Core locations 18 Plot. s of isotope data for core 76-G-4-9. A. Radium-226 and lead-210.... Radium-226 and lead-210 profiles. B. Excess lead-210 profile and theoretical curves calculated using lead-210 derived 2 mixing rat. e (80 cm /kyr) and plutonium derived mixing rate (190 cm /kyr). C. Plutonium profile. . 2 32 6. Plots of isotope data...

Stordal, Mary Christine

1981-01-01

356

Low sea-level stand emplacement of megaturbidites in the western and eastern Mediterranean Sea  

NASA Astrophysics Data System (ADS)

Piston cores from the Balearic and Herodotus Abyssal Plains in the Mediterranean Sea show that the Late Pleistocene to Holocene sedimentary sequence is dominated by turbidite muds. On each plain, one turbidite bed is conspicuous by its thickness, and this bed can be correlated basinwide on the basis of geochemical compositional analysis and its apparent correspondence with a distinct acoustically transparent layer on high-resolution seismic records. These megabeds on the two plains represent megaturbidites of very large volume (300-600 km 3 each) and are shown by AMS radiocarbon dating to have been emplaced during the last low stand of sea-level at the height of the last glacial maximum. The megabed on the Balearic Abyssal Plain is derived from the southern European margin and is the main sedimentation event over the last 120 ka. It emplaced as much material as was deposited by smaller flows during the previous 25 ka. Sedimentation rate curves for the Balearic Abyssal Plain show that falling sea-level correlates with increased terrigenous deposition, and that gross sedimentation rates in the basin increased as sea level fell from 120-18 ka due to more frequent emplacement of distal turbidites. The Herodotus Abyssal Plain megabed is derived from the Libyan-Egyptian continental shelf west of the Nile Delta and was the dominant sedimentation event in this basin during the past 60 kyr. High-resolution seismic profiles from the Ionian and Sirte Abyssal Plains in the central Mediterranean also suggest possible low sea-level emplacement of megabeds in these regions. Available evidence suggests widespread emplacement of megaturbidites throughout the Mediterranean at the last glacial maximum. Although the triggering mechanisms for these events remain speculative, catastrophic destabilisation of the margin after a long period of accumulation with an increased rate of sediment supply is suggested.

Rothwell, R. G.; Reeder, M. S.; Anastasakis, G.; Stow, D. A. V.; Thomson, J.; Kähler, G.

2000-09-01

357

Flood Plain Lakes Along the Elbe River - a Forgotten Risk  

NASA Astrophysics Data System (ADS)

Flood Plain Lakes Along the Elbe River - a Forgotten Risk Introduction: Along the German part of the Elbe River, more than 1000 "side structures" form potential sinks of contaminated sediment. They are mostly remains of previous river courses which have been cut off by natural causes or anthropogenic alterations of the river (oxbow lakes), or are floodplain lakes that were formed during high water conditions. These water bodies sometimes have a small opening towards the Elbe, or are hydrodynamically connected only in situations of high discharges. High discharges in the Elbe River, however, are mainly responsible for transporting historic contaminants along with suspended matter from former historic sources in the middle Elbe downstream. As these may settle when the current dies down at the end of a high discharge period, side structures have been under suspicion to have accumulated contaminated material over the last decades. Until this study was conducted, nothing was known about erodibility and contamination of sediment in these lakes even though they could have a large impact on the Elbe River itself: A preliminary investigation showed that the total surface of side structures in the Elbe floodplain adds up to about 50 km2. In case that deposited sediment is contaminated and only the upper 20 cm are prone to resuspension and transport during flooding, 10 Mio m3 of contaminated sediment could potentially be added to the contaminant load during a high water event. This study was carried out to evaluate the risk from these side structures for the environmental quality of the Elbe River. Methods: 15 side structures were investigated. Sediment cores were taken on 1 to 3 locations per water body in order to obtain the following information: • Depth of sediment layer • Erodibility of surface sediment, measured immediately after sampling - using the "Gust Microcosm", • Eroded mass at over-critical shear stress, measured in the lab by eroding a sediment core for one hour and collecting the suspended sediment matter. • Chemical contamination • Ecotoxicological effects Results and Discussion All side structures that were sampled exceeded the national quality guidelines for sediments which have been set by the International Commission for the Protection of the Elbe. In some cases very high concentrations were reached such as 1300 µg/kg dw for p,p-DDD, up to 61 mg/kg for Hg and 39 mg/kg for Cd. Erodibility varied a lot with critical shear stresses of less than 1 cm/s to more than 2 cm/s. Ecotoxicological data were also very different between side structures and sampling locations, but partly indicating very high inhibitions. Methanol extracts of sediments on all locations were screened using the luminescence bacteria test with Vibrio fischeri. Selected sediemt samples were tested applying the sediment contact test with Arthrobacter globiformes and the algae growth inhibition test with Pseudokirchneriella subcapitata. An integrated evaluation of all information led to a classification of 7 sites out of 15 to be of high risk, 7 to be of medium risk and only one site to be of low risk for the environmental quality of the Elbe River.

Heise, Susanne

2014-05-01

358

Planetary plains: subsidence and warping  

NASA Astrophysics Data System (ADS)

A common feature of all celestial bodies is their tectonic dichotomy best studied, naturally, at Earth [1]. Here there is an opposition of the eastern continental hemisphere and the western oceanic one. The first one is uplifted and cracked, the second one subsided, squeezed and warped. The next excellent example of dichotomy is at Mars where the subsided northern hemisphere is opposed by the highly uplifted southern one. The enigmatic two-face Iapetus now with help of Cassini SC presents a more clear picture: the leading dark hemisphere is opposed by the trailing light one. The light hemisphere is built mainly of water ice, the dark one of some more dense material. Bean-shaped asteroids with one convex and another concave hemispheres are best exemplified by Ida. Examples of dichotomic asteroids, satellites, planets and stars could be extended. Ubiquity of this phenomenon was expressed as the 1st theorem of the planetary wave tectonics [2 & others]: "Celestial bodies are dichotomic". A reason of this phenomenon is in action of inertia-gravity waves occurring in any celestial body because of its movement in non-round but elliptical (parabolic) orbit with periodically changing accelerations. The inertia-gravity standing waves warp rotating bodies (but all bodies rotate !) in 4 ortho- and diagonal interfering directions and in several harmonic wave-lengths. The fundamental wave1 produces ubiquitous tectonic dichotomy (2?R-structure): an opposition of two hemispheres with different planetary radii. To keep angular momenta of two hemispheres equal (otherwise a body will fall apart) the lower subsiding one is constructed of denser material than the higher one. Normally in terrestrial planets lowlands are filled with dense basalts, highlands are built by lighter lithologies. A subsidence means diminishing radius, otherwise, the larger surface must be fit into a smaller space. It is possible only if an original infilling is warped. At Earth cosmic altimetry shows complex fabric of oceanic floors. Short, medium wave undulations of Pacific's floor (A. Cazenave et al., 1992; D. McAdoo & K. Marks, 1992) present lineations underlining its whole shape. NE lineations predominate on its northern sub-basin, NW lineations on its southern one. They cross at the equatorial zone and together with some other directions give a pattern resembling that observed on the venusian surface. The venusian regional plains typically deformed by wrinkle ridges show interesting similarities to volcanic plains on the Moon and Mars [3]. A subsidence along with warpings can squeeze out some "superfluous" material to surface through planetary scale fissures. This material builds mid-oceanic ridges and huge Hawaii volcano. The Cassini Regio on Iapetus is crossed in the equatorial plain by the dark ridge in some places high 20 km. References: [1] Kochemasov G. G. (2004) Mars and Earth: two dichotomies - one cause. In Workshop on "Hemispheres 1 apart: the origin and modification of the martian crustal dichotomy", LPI Contribution # 1203, Lunar and Planetary Institute, Houston, p. 37. [2] Kochemasov G.G.(1999) Theorems of wave planetary tectonics // Geophys. Res. Abstr. v.1, #3, p.700 . [3] Basilevsky A.T., Head J.W. (2006) Impact craters on regional plains in Venus: Age relations with wrinkle ridges and implications for the geological evolution of Venus // JGR, v.111, EO3006, doi: 10.1029/2005JE002473, 2006. 2

Kochemasov, G.

359

PLAINS CO2 REDUCTION PARTNERSHIP  

SciTech Connect

The Plains Co{sub 2} Reduction (PCOR) Partnership continues to make great progress. Task 2 (Technology Deployment) activities have focused on developing information on deployment issues to support Task 5 activities by providing information to be used to assess CO{sub 2} sequestration opportunities in the PCOR Partnership region. Task 3 (Public Outreach) activities have focused on developing an informational video about CO{sub 2} sequestration. Progress in Task 4 (Sources, Sinks, and Infrastructure) has included the continued collection of data regarding CO{sub 2} sources and sinks and data on the performance and costs for CO{sub 2} separation, capture, treatment, and compression for pipeline transportation. Task 5 (Modeling and Phase II Action Plans) activities have focused on screening and qualitatively assessing sequestration options. Task 5 activities also continue to be useful in structuring data collection and other activities in Tasks 2, 3, and 5.

Edward N. Steadman

2004-07-01

360

PLAINS CO2 REDUCTION PARTNERSHIP  

SciTech Connect

The Plains CO{sub 2} Reduction (PCOR) Partnership continues to make great progress. Task 2 (Technology Deployment) focused on developing information regarding deployment issues to support Task 5 (Modeling and Phase II Action Plans) by providing information to be used to assess CO{sub 2} sequestration opportunities in the PCOR Partnership region. Task 3 (Public Outreach) focused on developing an informational video about CO{sub 2} sequestration. Progress in Task 4 (Sources, Sinks, and Infrastructure) included the continued collection of data regarding CO{sub 2} sources and sinks and data on the performance and costs for CO{sub 2} separation, capture, treatment, and compression for pipeline transportation. Task 5 focused on screening and qualitatively assessing sequestration options. Task 5 activities also continue to be useful in structuring data collection and other activities in Tasks 2, 3, and 5.

Edward N. Steadman; John A. Harju; Erin M. O'Leary; James A. Sorensen; Daniel J. Daly; Melanie D. Jensen; Thea E. Reikoff

2004-10-01

361

PLAINS CO2 REDUCTION PARTNERSHIP  

SciTech Connect

The Plains CO{sub 2} Reduction (PCOR) Partnership continues to make great progress. Task 2 (Technology Deployment) focused on developing information regarding deployment issues to support Task 5 (Modeling and Phase II Action Plans) by providing information to be used to assess CO{sub 2} sequestration opportunities in the PCOR Partnership region. Task 3 (Public Outreach) focused on developing an informational video about CO{sub 2} sequestration. Progress in Task 4 (Sources, Sinks, and Infrastructure) included the continued collection of data regarding CO{sub 2} sources and sinks and data on the performance and costs for CO{sub 2} separation, capture, treatment, and compression for pipeline transportation. Task 5 focused on screening and qualitatively assessing sequestration options. Task 5 activities also continue to be useful in structuring data collection and other activities in Tasks 2, 3, and 5.

Edward N. Steadman; John A. Harju; Erin M. O'Leary; James A. Sorensen; Daniel J. Daly; Melanie D. Jensen; Thea E. Reikoff

2005-01-01

362

Control on sediment and organic carbon delivery to the Arctic Ocean revealed with space-borne synthetic aperture radar: Ob' River, Siberia  

Microsoft Academic Search

An important control on river biogeochemistry and sediment load is the process of water exchange between primary channels and the flood plain, particularly in low-relief areas containing lakes, ephemeral channels, and other aquatic ecosystems. Flood-plain exchange may be a dominant process on the lowland rivers of Arctic Russia, which are among the world's largest in water discharge yet are strikingly

Laurence C. Smith; Douglas E. Alsdorf

1998-01-01

363

Ice-walled-lake plains: Implications for the origin of hummocky glacial topography in middle North America  

USGS Publications Warehouse

Ice-walled-lake plains are prominent in many areas of hummocky-till topography left behind as the Laurentide Ice Sheet melted from middle North America. The formation of the hummocky-till topography has been explained by: (1) erosion by subglacial floods; (2) squeezing of subglacial till up into holes in stagnant glacial ice; or (3) slumping of supraglacial till. The geomorphology and stratigraphy of ice-walled-lake plains provide evidence that neither the lake plains nor the adjacent hummocks are of subglacial origin. These flat lake plains, up to a few kilometers in diameter, are perched as much as a few tens of meters above surrounding depressions. They typically are underlain by laminated, fine-grained suspended-load lake sediment. Many ice-walled-lake plains are surrounded by a low rim ridge of coarser-grained shore sediment or by a steeper rim ridge of debris that slumped off the surrounding ice slopes. The ice-walled lakes persisted for hundreds to thousands of years following glacial stagnation. Shells of aquatic molluscs from several deposits of ice-walled-lake sediment in south-central North Dakota have been dated from about 13 500 to 10 500??B.P. (calibrated radiocarbon ages), indicating a climate only slightly cooler than present. This is confirmed by recent palaeoecological studies in nearby non-glacial sites. To survive so long, the stagnant glacial ice had to be well-insulated by a thick cover of supraglacial sediment, and the associated till hummocks must be composed primarily of collapsed supraglacial till. ?? 2007 Elsevier B.V. All rights reserved.

Clayton, L.; Attig, J.W.; Ham, N.R.; Johnson, M.D.; Jennings, C.E.; Syverson, K.M.

2008-01-01

364

Bait-attending fauna of the Kermadec Trench, SW Pacific Ocean: Evidence for an ecotone across the abyssal-hadal transition zone  

NASA Astrophysics Data System (ADS)

The bait-attending fauna of the abyssal-hadal transition zone of the Kermadec Trench, SW Pacific Ocean (4329-7966 m), was investigated using a baited camera and a trap lander. The abyssal stations (4329-6007 m) revealed a typical scavenging fish community comprising macrourids and synaphobranchid eels, as well as natantian decapods. At the hadal depths of 7199 and 7561 m, the endemic liparid Notoliparis kermadecensis was observed aggregating at the bait reaching surprisingly high numbers of 5 and 13, respectively. A total of 3183 invertebrate samples were collected (mean deployment time=16 h) of which 97.8% were of the order Amphipoda (nine families, 16 species). Ten of the amphipod species represent new distributional records for the Kermadec Trench and the New Zealand Exclusive Economic Zone; this includes the shallowest known record of the endemic hadal amphipod Hirondellea dubia (6000, 6007 m). Using amphipods to statistically examine the compositional change across the abyssal-hadal boundary, an ecotone between depths <6007 and >6890 m was found, indicating that there is an ecologically distinct bait-attending fauna in this trench.

Jamieson, A. J.; Kilgallen, N. M.; Rowden, A. A.; Fujii, T.; Horton, T.; Lörz, A.-N.; Kitazawa, K.; Priede, I. G.

2011-01-01

365

A reconnaissance study of the effect of irrigated agriculture on water quality in the Ogallala Formation, Central High Plains Aquifer  

USGS Publications Warehouse

In 1998, the U.S. Geological Survey's National Water-Quality Assessment (NAWQA) Program began a regional study of water quality in the High Plains aquifer. The High Plains aquifer underlies an area of about 174,000 square miles in parts of eight States. Because of its large size, the High Plains aquifer has been divided into three regions: the Southern High Plains, Central High Plains, and Northern High Plains (fig. 1A). Although an assessment of water quality in each of the three regions is planned, the initial focus will be the Central High Plains aquifer. Anyone who has flown over the Central High Plains in the summer and has seen the large green circles associated with center pivot sprinklers (fig. 2) knows that irrigated agriculture is a widespread land use. Pesticides and fertilizers applied on those irrigated fields will not degrade ground-water quality if they remain in or above the root zone (fig. 3). However, if those chemicals move downward through the unsaturated zone to the water table, they may degrade the quality of the ground water. Water is the principal agent for transporting chemicals from land surface to the water table, and in the semiarid Central High Plains, irrigation often represents the most abundant source of water during the growing season. One objective of NAWQA's High Plains Regional Ground-Water study is to evaluate the effect of irrigated agriculture on the quality of recently recharged water in the Ogallala Formation of the Central High Plains aquifer (figs. 1A and 1B). The Ogallala Formation is the principal geologic unit in the Central High Plains aquifer, and it consists of poorly sorted clay, silt, sand, and gravel that generally is unconsolidated (Gutentag and others, 1984). Approximately 23 percent of the cropland overlying the Ogallala Formation is irrigated (U.S. Department of Agriculture, 1999). The NAWQA Program generally defines recently recharged ground water to be water recharged in the last 50 years. The water table in the Ogallala Formation is separated from overlying land-use practices by as much as 400 feet of unsaturated sediments. Consequently, one may hypothesize that recently recharged water is not present in the formation. The U.S. Geological Survey conducted a reconnaissance study in 1999 to establish (a) if recently recharged water was present in the Ogallala Formation underlying irrigated cropland and (b) if agricultural land-use practices affect water quality. Results from the reconnaissance study will be used to determine whether a full-scale land-use study is warranted.

McMahon, Peter B.

2000-01-01

366

Mapping Titan’s Undifferentiated Plains (“Blandlands”) to infer their origin  

NASA Astrophysics Data System (ADS)

The undifferentiated plains first mapped by Lopes et al. (2010, Icarus, 205) are vast expanses of terrains that appear bland in Cassini RADAR Synthetic Aperture Radar images, hence the designation “blandlands”. While the interpretation of several other geologic units on Titan, such as dunes and well-preserved impact craters, has been relatively straightforward, the origin of the “blandlands” has remained mysterious. SAR images show that the “blandlands” are mostly found at mid-latitudes and appear relatively featureless at radar wavelengths, with no significant topographic variations. Their gradational boundaries and paucity of features in SAR data make geologic interpretation particularly challenging. We have mapped the distribution of these terrains using SAR swaths up to T92 (July 2013), which cover > 50% of Titan’s surface. We compared SAR images with their de-noised counterparts, the topography using the SARTopo method (Stiles et al., 2009, Icarus 202) and, where possible, the response from radiometry. We examined and evaluated different formation mechanisms. Plains may be sedimentary in origin, resulting from fluvial or lacustrine deposition or accumulation of photolysis products created in the upper atmosphere. Alternatively, the plains may be cryovolcanic, consisting of overlapping flows of low relief, obscured by accumulation of sediments. In this paper, we use SAR, radiometry, and SARTopo data to examine the characteristics of the plains and compare them with other geologic units. The results from our analysis suggest that the sedimentary origin is the most likely, and that plain materials are similar or the same as dune materials. Plains occur mostly at mid-latitudes, while dunes occur mostly at low latitudes. This may be a result of wind patterns, decrease in sand supply, or changes in properties of sand, perhaps moisture content, all of which would inhibit the formation of large dunes.

Lopes, Rosaly M.; Malaska, Michael J.; Schoenfeld, Ashley M.; LeGall, Alice; Hayes, Alexander G.; Birch, Samuel P.; Solomonidou, Anezina

2014-11-01

367

THE TEXAS HIGH PLAINS EVAPOTRANSPIRATION NETWORK (TXHPET) USER MANUAL  

Technology Transfer Automated Retrieval System (TEKTRAN)

The Texas High Plains Evapotranspiration (TXHPET) network is comprised of two evapotranspiration (ET) networks, namely the North Plains ET and the South Plains ET networks within the Texas High Plains region. The TXHPET network entails the operation of 18 meteorological stations located in 15 Texas...

368

Property Rights and Groundwater Management in the High Plains Aquifer  

E-print Network

of western Kansas that overlies the High Plains (Ogallala) Aquifer. An area with a relatively wellProperty Rights and Groundwater Management in the High Plains Aquifer Lisa Pfeiffer 7600 Sand Point of the High Plains Aquifer system, located in the Midwestern plains of the United States, began in the late

Lin, C.-Y. Cynthia

369

CORN BELT PLAIN RIVER AND STREAMS PROJECT - 3 BIOCRITERIA PRODUCTS  

EPA Science Inventory

This effort resulted in eight products, as follows: 1) Development of Index of Biotic Integrity Expectations for the Ecoregions of Indiana I. Central Corn Belt Plain; 2) Ibid. II. Huron-Erie Lake Plain; 3) Ibid III. Northern Indiana Till Plain; 4) Ibid .IV.Eastern Corn Belt Plain...

370

Trend analyses of sediment data for the DEC project  

USGS Publications Warehouse

Daily stream discharge, suspended-sediment concentration, and suspended-sediment discharge data were collected at eight sites in six watersheds of the Demonstration Erosion Control project in the Yazoo River Basin in north-central Mississippi during the period July 1985 through September 1991. The project is part of an ongoing interagency program of planning, design, construction, monitoring, and evaluation to alleviate flooding, erosion, sedimentation, and water-quality problems for watersheds located in the bluff hills upstream of the Mississippi River alluvial plain. This paper presents preliminary results of trend analyses for stream discharge and sediment data for the eight project sites. More than 550 stream discharge measurements and 20,000 suspended-sediment samples have been collected at the eight sites since 1985.

Rebich, Richard Allen

1995-01-01

371

Plain Language Thesauruses | accrualnet.cancer.gov  

Cancer.gov

These resources offer plain language equivalents to medical terms, phrases, and references frequently used in clinical trials. They are helpful when developing informed consent forms and other patient information text.

372

Ages of plains volcanism on Mars  

Microsoft Academic Search

Plain-style volcanism [1] is widespread in the Tharsis and Elysium volcanic provinces on Mars, [2,3]. Detailed images and topographic data reveal the morphology and topography of clusters of low shields and associated lava flows. The landforms of plains volcanism on Mars have all well-known terrestrial analogues in basaltic volcanic regions, such as Hawaii, Iceland, and in particular the Snake River

Ernst Hauber; Felix Jagert; Petr Broz

2010-01-01

373

Light Plains in the South-Pole Aitken Basin: Surface Ages and Mineralogical Composition  

NASA Astrophysics Data System (ADS)

We studied light plains in the north-eastern South-Pole Aitken basin to investigate their origin, ages, and mineralogical composition. Light plains, also known as the Cayley Formation, occur on the near- and farside of the Moon. Due to their smooth texture, lower crater densities, and occurrence as crater fills, they were thought to be of volcanic origin [e.g., 1]. However, Apollo 16 samples of light plains deposits were in fact highly brecciated rocks [2]. Therefore, the Imbrium and Orientale impacts were thought to have formed light plains because they reshaped the surface thousands of kilometers from their impact sites. Subsequent studies revealed varying surface ages of light plains [e.g., 3] and different mineralogical compositions, which are in some cases more highland-like and in others more mare-like. Hence, an origin solely from the Imbrium and/or Orientale impacts is unlikely. Thus, the question whether light plains formed due to large impacts or regional cratering, or through endogenic processes remains open. We performed crater size-frequency measurements [e.g., 4] on Lunar Reconnaissance Orbiter Wide Angle Camera images and obtained absolute model ages between 3.43 and 3.81 Ga. We observed neither a distinctive peak of light plains ages nor clustering of similar ages in any specific regions of the studied area. Due to the fact that the derived ages vary as much as 380 Ma, an origin by a single event seems unlikely. Moreover, some ages even post-date the Imbrium and Orientale impacts, and thus an origin related to those impacts is not likely. Examination of multispectral data from Clementine [5] shows that the Ti abundances vary between 0.2 and 3 wt % and Fe abundances between 12.5 and 19 wt %. We observed a regional difference in distribution: light plains units within the Apollo basin have lower Fe and Ti values and are more highland-like, whereas light plains outside the Apollo basin show higher Fe and Ti values and are more mare-like. Furthermore, M3 spectra from small impact craters on light plains show characteristic absorption bands for pyroxene. We conclude that light plains are unlikely to have formed by the Imbrium and Orientale impacts due to the range of surface ages and the compositional differences. Nevertheless, these impacts together with secondary cratering and sedimentation from regional and local impacts may have played an important role in forming these plains. An endogenic origin can still not be excluded due to the mare-like composition of some light plains. [1] Wilhelms D.E. (1970) Astrogeol. Stud. Ann. Prog. Report, 13-28. [2] Young J.W. (1972) NASA Apollo 16 Prelim. Sci. Rep., 5-1-5-6. [3] Neukum, G. (1977) The Moon 17, 383-393. [4] Neukum G. et al. (1975) The Moon 12, 201-229. [5] Lucey P.G. et al. (2000) J. Geophys. Res. 105, 20,297-20,305.

Thiessen, F.; Hiesinger, H.; van der Bogert, C. H.; Pasckert, J. H.; Robinson, M. S.

2012-04-01

374

Age determinations and Earth-based multispectral observations of lunar light plains  

NASA Technical Reports Server (NTRS)

The history of light plains still remains doubtful, but there are good arguments - mainly obtained by age determinations and supported by multispectral observations - for an endogenic (magmatic) instead of an (exclusively) impact related origin. Light plains are characterized by smooth areas with an albedo lower than the surrounding highlands (12 - 13 percent), but significantly higher than maria (5 - 6 percent). Before Apollo 16 a volcanic source has been supposed, but analysis of returned samples (highly brecciated and metamorphosed rocks) favored an impact ejecta related origin. Among the currently discussed models are formation by ejecta sedimentation from multi-ringed basins, formation by secondary and tertiary cratering action of ballistically ejected material during the formation of multi-ringed basins, in situ formation by impact melt of large events, and premare (crypto-) volcanism basalts covered by a thin ejecta cover; younger impacts penetrated the ejecta surface to create the dark haloed craters. To find arguments in favor or against these ideas the chronology of light plains is of major importance. Obviously a genetic relationship between the evolution of light plains and the basin forming impacts can be possible only if the events of emplacement features happened simultaneously.

Koehler, U.; Jaumann, R.; Neukum, G.

1993-01-01

375

Geogenic arsenic in groundwaters from Terai Alluvial Plain of Nepal  

NASA Astrophysics Data System (ADS)

The origin and mobility of arsenic (As) in the groundwater environment has received serious attention in recent years. Recent studies have reported naturally occurring As in groundwaters of the Terai Alluvial Plains (TAP) in southern Nepal, where groundwater exploitation has increased since the 1960s. The source of As in TAP is geogenic and leached primarily due to weathering of As bearing rocks and sediments in the Himalayas. In our present study, we have investigated the groundwater chemistry in the central part of the TAP in Nawalparasi district. TAP groundwaters are near-neutral to alkaline, with predominantly reducing character and high HCO3^- low SO^{2-}_4 and NO3^- concentrations. Elevated HCO3 levels possibly result due to the oxidation of organic matter, low SO4^{2-} levels reflect sulfate reduction. Elevated NH4^+ concentrations in these groundwaters suggest dissimilatory nitrate reduction in the aquifers. Total arsenic (Astot) levels in groundwater varied from 1.7 ?g/L to as high as 404 ?g/L with dominance of As (III) species and elevated levels of dissolved Fe and Mn. Arsenic is mobilized in groundwaters as a result of desorption of As-oxyanions adsorbed onto Fe-and Mnoxides as well as reductive dissolution of these surface reactive phases from the sediments along with release ouf as in anoxie groundwaters.

Bhattacharya, P.; Tandukar, N.; Nekul, A.; Valero, A. A.; Mukherjee, A. B.; Jacks, G.

2003-05-01

376

Global calcite cycling constrained by sediment preservation controls  

NASA Astrophysics Data System (ADS)

We assess the global balance of calcite export through the water column and burial in sediments as it varies regionally. We first drive a comprehensive 1-D model for sediment calcite preservation with globally gridded field observations and satellite-based syntheses. We then reformulate this model into a simpler five-parameter box model, and combine it with algorithms for surface calcite export and water column dissolution for a single expression for the vertical calcite balance. The resulting metamodel is optimized to fit the observed distributions of calcite burial flux. We quantify the degree to which calcite export, saturation state, organic carbon respiration, and lithogenic sedimentation modulate the burial of calcite. We find that 46% of burial and 88% of dissolution occurs in sediments overlain by undersaturated bottom water with sediment calcite burial strongly modulated by surface export. Relative to organic carbon export, we find surface calcite export skewed geographically toward relatively warm, oligotrophic areas dominated by small, prokaryotic phytoplankton. We assess century-scale projected impacts of warming and acidification on calcite export, finding high sensitive to inferred saturation state controls. With respect to long-term glacial cycling, our analysis supports the hypothesis that strong glacial abyssal stratification drives the lysocline toward much closer correspondence with the saturation horizon. Our analysis suggests that, over the transition from interglacial to glacial ocean, a resulting ˜0.029 PgC a-1decrease in deep Atlantic, Indian and Southern Ocean calcite burial leads to slow increase in ocean alkalinity until Pacific mid-depth calcite burial increases to compensate.

Dunne, John P.; Hales, Burke; Toggweiler, J. R.

2012-09-01

377

PLAINS CO2 REDUCTION PARTNERSHIP  

SciTech Connect

The Plains CO{sub 2} Reduction (PCOR) Partnership continues to make great progress. Task 2 (Technology Deployment) focused on developing information regarding deployment issues to support Task 5 (Modeling and Phase II Action Plans) and provided information to be used to assess CO{sub 2} sequestration opportunities in the PCOR Partnership region. Task 2 efforts also included preparation of a draft topical report entitled ''Deployment Issues Related to Geologic CO{sub 2} Sequestration in the PCOR Partnership Region'', which is nearing completion. Task 3 (Public Outreach) focused on developing an informational video about CO{sub 2} sequestration. The video will be completed and aired on Prairie Public Television in the next quarter. Progress in Task 4 (Sources, Sinks, and Infrastructure) included the continued collection of data regarding CO{sub 2} sources and sinks and data on the performance and costs for CO{sub 2} separation, capture, treatment, and compression for pipeline transportation. The addition of the Canadian province of Alberta to the PCOR Partnership region expanded the decision support system (DSS) geographic information system database. Task 5 screened and qualitatively assessed sequestration options. Task 5 activities also continue to be useful in structuring data collection and other activities in Tasks 2, 3, and 5.

Edward N. Steadman; John A. Harju; Erin M. O'Leary; James A. Sorensen; Daniel J. Daly; Melanie D. Jensen; Thea E. Reikoff

2005-04-01

378

PLAINS CO2 REDUCTION PARTNERSHIP  

SciTech Connect

The Plains CO{sub 2} Reduction (PCOR) Partnership characterization work is nearing completion, and most remaining efforts are related to finalizing work products. Task 2 (Technology Deployment) has developed a Topical Report entitled ''Deployment Issues Related to Geologic CO{sub 2} Sequestration in the PCOR Partnership Region''. Task 3 (Public Outreach) has developed an informational Public Television program entitled ''Nature in the Balance'', about CO{sub 2} sequestration. The program was completed and aired on Prairie Public Television in this quarter. Task 4 (Sources, Sinks, and Infrastructure) efforts are nearing completion, and data regarding CO{sub 2} sources and sinks and data on the performance and costs for CO{sub 2} separation, capture, treatment, and compression for pipeline transportation are being incorporated into a series of topical reports. The expansion of the Decision Support System Geographic Information System database has continued with the development of a ''save bookmark'' feature that allows users to save a map from the system easily. A feature that allows users to develop a report that summarizes CO{sub 2} sequestration parameters was also developed. Task 5 (Modeling and Phase II Action Plans) focused on screening and qualitatively assessing sequestration options and developing economic estimates for important regional CO{sub 2} sequestration strategies.

Edward N. Steadman; John A. Harju; Erin M. O'Leary; James A. Sorensen; Daniel J. Daly; Melanie D. Jensen; Lisa S. Botnen

2005-07-01

379

Surface erosion, sediment transport, and reservoir sedimentation  

Microsoft Academic Search

Systematic plans and policies are needed to reduce adverse impacts of sedimentation and prolong the useful life of reservoirs. The ability to estimate the rate of watershed surface erosion, sediment transport, scour and deposition in a river system, and sediment deposition and distribution in a reservoir is essential to the development of sound sediment management plans and policies. The empirical

CHIH TED YANG; TIMOTHY J. RANDLE; SHIANG-KUEEN HSU

1998-01-01

380

Long and short-term episodic storage and removal of sediment in watersheds of southwestern Wisconsin and northwestern Illinois  

Microsoft Academic Search

Average annual rates of erosion and sedimentation commonly are used to evaluate long-term movement and storage of sediment in watersheds. Use of average rates often poorly represent actual rates because changing environmental factors may dramatically alter surface runoff, flooding, and channel stability. Dating of historical, Holocene (post-glacial), and Late-Wisconsin (late glacial) hillslope and flood plain sediments in southwestern Wisconsin and

James C. Knox

1989-01-01

381

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  

Microsoft Academic Search

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

Matthieu Ghilardi; Stéphane Kunesch; Mixalis Styllas; Eric Fouache

2008-01-01

382

Sequence stratigraphy of the Upper Cretaceous (Cenomanian and Turonian) Tuscaloosa Group in the subsurface of the eastern Gulf Coastal plain area  

Microsoft Academic Search

In the subsurface of the eastern Gulf Coastal plain area, the Tuscaloosa Group consists of approximately 1,000 ft of nonmarine, marginal marine, and marine terrigenous clastic sediments. Based on regional stratigraphical, sedimentological, petrophysical, and paleontological data, three unconformity bounded depositional sequences reflecting relative changes in sea level and coastal onlap during the Late Cretaceous (Cenomanian and Turonian) are recognized for

E. A. Mancini; B. H. Tew; R. M. Mink

1990-01-01

383

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)

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.

Ghilardi, Matthieu; Kunesch, Stéphane; Styllas, Mixalis; Fouache, Eric

2008-05-01

384

Control on sediment and organic carbon delivery to the Arctic Ocean revealed with space-borne synthetic aperture radar: Ob' River, Siberia  

NASA Astrophysics Data System (ADS)

An important control on river biogeochemistry and sediment load is the process of water exchange between primary channels and the flood plain, particularly in low-relief areas containing lakes, ephemeral channels, and other aquatic ecosystems. Flood-plain exchange may be a dominant process on the lowland rivers of Arctic Russia, which are among the world's largest in water discharge yet are strikingly deficient in their delivery of sediment to the Arctic shelf. Temporal synthetic aperture radar (SAR) amplitude and interferometric images of the Ob' River, Siberia, reveal a time-varying limnological network controlling water, sediment, and nutrient exchange between flood-plain wetlands and the main channel. The amount of hydrologic exchange decreases by one order of magnitude from June to September, enhancing sedimentation over as much as 90% of the flood plain and enriching channel waters with colloidal organic carbon. This observation, combined with Russian field measurements of water discharge and sediment load, indicates that a major sediment sink on the lower Ob' flood plain may be responsible for the low amount of sediment delivery by the Ob' River to its estuary and the Kara Sea.

Smith, Laurence C.; Alsdorf, Douglas E.

1998-05-01

385

2009 High Plains and Northern Rolling Plains Cotton Harvest-Aid Guide  

E-print Network

2009 High Plains and Northern Rolling Plains Cotton Harvest-Aid Guide Dr. Randy Boman, Extension Agronomist-Cotton, Dr. Mark Kelley, Extension Program Specialist-Cotton, Texas AgriLife Extension Service; Dr, and to reduce potential preharvest losses of lint yield and fiber quality. Proper use of harvest aids can result

Behmer, Spencer T.

386

2010 High Plains and Northern Rolling Plains Cotton Harvest-Aid Guide  

E-print Network

2010 High Plains and Northern Rolling Plains Cotton Harvest-Aid Guide Dr. Randy Boman, Extension Agronomist-Cotton, Dr. Mark Kelley, Extension Program Specialist-Cotton, Texas AgriLife Extension Service; Dr, and to reduce potential preharvest losses of lint yield and fiber quality. Proper use of harvest aids can result

Mukhtar, Saqib

387

Mineral resources of Cactus Plain and East Cactus Plain Wilderness Study Areas, La Paz County, Arizona  

SciTech Connect

This paper reports on geologic, geochemical, and geophysical studies in the Cactus Plain and East Cactus Plain Wilderness Study Areas outlined in areas with moderate to high potential for gold, silver, copper, lead, zinc, barite, fluorite, manganese, and sand suitable for foundry, fracturing, and abrasive uses and low resource potential for beryllium, uranium and bentonitic clays.

Tosdal, R.M.; Eppinger, R.G.; Erdman, J.A.; Hanna, W.F.; Pitkin, J.A.; Blank, H.R. Jr.; O'Leary, R.M.; Watterson, J.R. (US Geological Survey (US)); Kreidler, T.J. (US Bureau of Mines (US))

1990-01-01

388

Holocene flood plain soil formation in the lower Mississippi River Valley: Implications for the interpretation of alluvial paleosols  

SciTech Connect

Holocene Mississippi River flood soils representing different depositional environments and ages were sampled along three east-west transects between Vicksburg, MS and Baton Rouge, LA. Flood plain soil development is primarily controlled by episodic flood plain sedimentation and ground water table fluctuations as evidenced by relatively thick cumulative soil profiles with abundant mottles, nodules, and slickensides. Within flood plain deposits of similar age, profile, development is best expressed in moderately-drained silty and sandy soils in natural levee and point bar ridge environmental that occur within and adjacent to meander belts. Soils in natural levee and point bar ridge environments greater than 3 ka generally are acidic and have better-developed Bt horizons and brighter mottles than their younger counterparts. In addition to being acidic and brightly mottled, older back swamp soils have larger and more abundant slickensides and iron nodules. This study suggests that alluvial paleosols formed in aggradational settings may be better suited for interpreting flood plain depositional histories and paleohydrology than climate. Parameters such as solum thickness and clay and carbonate accumulations, routinely used to estimate relative time and climatic effects on soil development in Quaternary studies of stable geomorphic surfaces, may not be applicable to ancient alluvial deposits that reflect continuous sediment aggradation.

Aslan, A. (Univ. of Colorado, Boulder, CO (United States). Dept. of Geological Sciences); Autin, W.J. (Louisiana Geological Survey, Baton Rouge, LA (United States))

1992-01-01

389

Contrasting soils and landscapes of the Piedmont and Coastal Plain, eastern United States  

USGS Publications Warehouse

The Piedmont and Coastal Plain physiographic provinces comprise 80 percent of the Atlantic Coastal states from New Jersey to Georgia. The provinces are climatically similar. The soil moisture regime is udic. The soil temperature regime is typically thermic from Virginia through Georgia, although it is mesic at altitudes above 400 m in Georgia and above 320 m in Virginia. The soil temperature regime is mesic for the Piedmont and Coastal Plain from Maryland through New Jersey. The tightly folded, structurally complex crystalline rocks of the Piedmont and the gently dipping "layer-cake" clastic sedimentary rocks and sediments of the Coastal Plain respond differently to weathering, pedogenesis, and erosion. The different responses result in two physiographically contrasting terrains; each has distinctive near-surface hydrology, regolith, drainage morphology, and morphometry. The Piedmont is predominantly an erosional terrain. Interfluves are as narrow as 0.5 to 2 km, and are convex upward. Valleys are as narrow as 0.1 to 0.5 km and generally V-shaped in cross section. Alluvial terraces are rare and discontinuous. Soils in the Piedmont are typically less than 1 m thick, have less sand and more clay than Coastal Plain soils, and generally have not developed sandy epipedons. Infiltration rates for Piedmont soils are low at 6-15 cm/h. The soil/saprolite, soil/rock, and saprolite/rock boundaries are distinct (can be placed within 10 cm) and are characterized by ponding and/or lateral movement of water. Water movement through soil into saprolite, and from saprolite into rock, is along joints, foliation, bedding planes and faults. Soils and isotopic data indicate residence times consistent with a Pleistocene age for most Piedmont soils. The Coastal Plain is both an erosional and a constructional terrain. Interfluves commonly are broader than 2 km and are flat. Valleys are commonly as wide as 1 km to greater than 10 km, and contain numerous alluvial and estuarine terrace sequences that can be correlated along valleys for tens of kilometers. Coastal Plain soils are typically as thick as 2 to 8 m, have high sand content throughout, and have sandy epipedons. These epipedons consist of both A and E horizons and are 1 to 4 m thick. In Coastal Plain soils, the boundaries are transitional between the solum and the underlying parent material and between weathered and unweathered parent material. Infiltration rates for Coastal Plain soils are typically higher at 13-28 cm/h, than are those for Piedmont soils. Indeed, for unconsolidated quartz sand, rates may exceed 50 cm/h. Water moves directly from the soil into the parent material through intergranularpores with only minor channelization along macropores, joints, and fractures. The comparatively high infiltration capacity results in relatively low surface runoff, and correspondingly less erosion than on the Piedmont uplands. Due to differences in Piedmont and Coastal Plain erosion rates, topographic inversion is common along the Fall Zone; surfaces on Cenozoic sedimentary deposits of the Coastal Plain are higher than erosional surfaces on regolith weathered from late Precambrian to early Paleozoic crystalline rocks of the Piedmont. Isotopic, paleontologic, and soil data indicate that Coastal Plain surficial deposits are post-middle Miocene to Holocene in age, but most are from 5 to 2 Ma. Thus, the relatively uneroded surfaces comprise a Pliocene landscape. In the eastern third of the Coastal Plain, deposits that are less than 3.5 Ma include alluvial terraces, marine terraces and barrier/back-barrier complexes as morphostratigraphic units that cover thousands of square kilometers. Isotopic and soil data indicate that eastern Piedmont soils range from late Pliocene to Pleistocene in age, but are predominantly less than 2 Ma old. Thus, the eroded uplands of the Piedmont "peneplain" comprise a Pleistocene landscape. ?? 1990.

Markewich, H.W.; Pavich, M.J.; Buell, G.R.

1990-01-01

390

Saline systems of the Great Plains of western Canada: an overview of the limnogeology and paleolimnology  

PubMed Central

In much of the northern Great Plains, saline and hypersaline lacustrine brines are the only surface waters present. As a group, the lakes of this region are unique: there is no other area in the world that can match the concentration and diversity of saline lake environments exhibited in the prairie region of Canada and northern United States. The immense number of individual salt lakes and saline wetlands in this region of North America is staggering. Estimates vary from about one million to greater than 10 million, with densities in some areas being as high as 120 lakes/km2. Despite over a century of scientific investigation of these salt lakes, we have only in the last twenty years advanced far enough to appreciate the wide spectrum of lake types, water chemistries, and limnological processes that are operating in the modern settings. Hydrochemical data are available for about 800 of the lake brines in the region. Composition, textural, and geochemical information on the modern bottom sediments has been collected for just over 150 of these lakes. Characterization of the biological and ecological features of these lakes is based on even fewer investigations, and the stratigraphic records of only twenty basins have been examined. The lake waters show a considerable range in ionic composition and concentration. Early investigators, concentrating on the most saline brines, emphasized a strong predominance of Na+ and SO4-2 in the lakes. It is now realized, however, that not only is there a complete spectrum of salinities from less than 1 ppt TDS to nearly 400 ppt, but also virtually every water chemistry type is represented in lakes of the region. With such a vast array of compositions, it is difficult to generalize. Nonetheless, the paucity of Cl-rich lakes makes the northern Great Plains basins somewhat unusual compared with salt lakes in many other areas of the world (e.g., Australia, western United States). Compilations of the lake water chemistries show distinct spatial trends and regional variations controlled by groundwater input, climate, and geomorphology. Short-term temporal variations in the brine composition, which can have significant effects on the composition of the modern sediments, have also been well documented in several individual basins. From a sedimentological and mineralogical perspective, the wide range of water chemistries exhibited by the lakes leads to an unusually large diversity of modern sediment composition. Over 40 species of endogenic precipitates and authigenic minerals have been identified in the lacustrine sediments. The most common non-detrital components of the modern sediments include: calcium and calcium-magnesium carbonates (magnesian calcite, aragonite, dolomite), and sodium, magnesium, and sodium-magnesium sulfates (mirabilite, thenardite, bloedite, epsomite). Many of the basins whose brines have very high Mg/Ca ratios also have hydromagnesite, magnesite, and nesquehonite. Unlike salt lakes in many other areas of the world, halite, gypsum, and calcite are relatively rare endogenic precipitates in the Great Plains lakes. The detrital fraction of the lacustrine sediments is normally dominated by clay minerals, carbonate minerals, quartz, and feldspars. Sediment accumulation in these salt lakes is controlled and modified by a wide variety of physical, chemical, and biological processes. Although the details of these modern sedimentary processes can be exceedingly complex and difficult to discuss in isolation, in broad terms, the processes operating in the salt lakes of the Great Plains are ultimately controlled by three basic factors or conditions of the basin: (a) basin morphology; (b) basin hydrology; and (c) water salinity and composition. Combinations of these parameters interact to control nearly all aspects of modern sedimentation in these salt lakes and give rise to four 'end member' types of modern saline lacustrine settings in the Great Plains: (a) clastics-dominated playas; (b) salt-dominated playas; (c) deep water, non-stratified lakes; and (d) deep water, "permanently" st

Last, William M; Ginn, Fawn M

2005-01-01

391

Fire Cycles on the Northern Great Plains and Their Relation to Prairie Drought  

NASA Astrophysics Data System (ADS)

Drought is a naturally occurring, recurrent phenomenon that has historically gripped large regions of the United States, often with catastrophic consequences. Human insight into the duration, frequency, and dynamics of drought is largely limited to short-term observation. For example, the "Dust Bowl" of the 1930's in the central plains is one of the most vivid cases of prolonged drought in the USA and yet it persisted for less than a decade. To circumnavigate this limited perspective, we employed a paleoenvironmental approach to better characterize landscape response to prairie droughts and specifically document fire response to droughts. Two long sediment cores were collected from Kettle and Brush lakes in the Northern Great Plains (NGP) and age-depth models were developed for the cores by fitting locally weighted loess curves to AMS radiocarbon dates. The cores were continuously sub-sampled at high resolution (1 cm) for particulate charcoal, pollen, sediment mineralogy, and loss-on-ignition. In contrast to recent human observation, spectral and wavelet analyses reveal that multi-decadal to centennial drought cycles have persisted on the northern plains for much of the last ca. 10,000 years, though there were intervals where the cycles were muted, further compounding the dynamics of climate on the plains. In the latest Holocene interval, 160-year fire and drought cycles are clearly denoted. Fires are more common during the wet phases of the drought cycles because moist conditions foster increased grass productivity, resulting in greater fuel loads. In contrast, forbs expanded during the drier periods, limiting fuel loads which resulted in less fire. The charcoal data reveal three general Holocene fire intervals on the NGP associated with millennial-scale changes in climate. In general, the incidence of fire was greater in the early- and late-Holocene with less fire during the warm dry mid-Holocene.

Brown, K. J.; Clark, J. S.; Grimm, E. C.; Donovan, J. J.; Mueller, P.

2004-12-01

392

Do abyssal scavengers use phytodetritus as a food resource? Video and biochemical evidence from the Atlantic and Mediterranean  

NASA Astrophysics Data System (ADS)

Deep-sea benthic communities derive their energetic requirements from overlying surface water production, which is deposited at the seafloor as phytodetritus. Benthic invertebrates are the primary consumers of this food source, with deep-sea fish at the top of the trophic hierarchy. Recently, we demonstrated with the use of baited cameras that macrourid fish rapidly respond to and feed vigorously on large plant food falls mimicked by spinach ( Jeffreys et al., 2010). Since higher plant remains are scarce in the deep-sea, with the exception of canyons, where terrestrial material has been observed, these results led us to ask if a more commonly documented plant material i.e. phytodetritus might form a food source for deep-sea fish and mobile scavenging megafauna. We simulated a phytodetritus dump at the seafloor in two contrasting environments (1) the NE Atlantic where carpets of phytodetritus have been previously observed and (2) the oligotrophic western Mediterranean, where the deposition of phytodetritus at the seafloor is a rare occurrence. We recorded the response of the scavenging fauna using an in situ benthic lander equipped with baited time-lapse cameras. In the NE Atlantic at 3000 m, abyssal macrourids and cusk-eels were observed ingesting the phytodetritus. The phytodetrital patch was significantly diminished within 2 h. Abundance estimates calculated from first arrival times of macrourids at the phytodetrital patch in the Atlantic corresponded with abundance estimates from video-transect indicating that fish were attracted to the scent of phytodetrital bait. In contrast to this, in the western Mediterranean at 2800 m a single macrourid was observed investigating the phytodetrital patch but did not feed from it. The phytodetrital patch was significantly diminished within 6.5 h as a result of mainly invertebrate activity. At 1900 m, Lepidion lepidion was observed near the lander and the bait, but did not feed. The phytodetrital patch remained intact until the end of the experiment. In the deployments in the Mediterranean abundance estimates from first arrival times at the bait, corrected for their body size, were lower than estimates obtained from video-transects and trawl catches. This suggests that the Mediterranean fish were not readily attracted to this food source. In contrast, invertebrates in the Balearic Sea were observed ingesting the phytodetritus bait despite the rare occurrence of phytodetritus dumps in the Mediterranean. Stable isotope values of the fish at both study sites, set within the context of the benthic food web, did not demonstrate a strong trophic link to phytodetritus. Fatty acid profiles of these fish indicated a strong link between their lipid pool and primary producers i.e. phytoplankton, which may be attributed to trophic transfer. The usefulness of fatty acid biomarkers in ascertaining deep-sea fish diets is discussed. Our study suggests that the abyssal grenadier C. armatus on the Atlantic Iberian margin is attracted to phytodetritus. However the exact contribution of this food source to the diet of macrourids in this area remains unresolved.

Jeffreys, Rachel M.; Lavaleye, Marc S. S.; Bergman, Magda J. N.; Duineveld, Gerard C. A.; Witbaard, Rob

2011-04-01

393

Satellite-Based Assessment of Sediment Transport, Distribution and Resuspension Associated with the Atchafalaya River Discharge Plume  

NASA Technical Reports Server (NTRS)

Tbe Atchafalaya River discharges over 80 x 10(exp 6) tons of sediment annually onto the broad shallow continental shelf of central and western Louisiana. Satellite imagery from the NOAA AVHRR and Terra MODIS are used in this paper to quantify suspended sediment concentrations and to assess sediment transport processes along the Louisiana shelf under varying conditions of river discharge and wind forcing. The image data reveal the maim sources of sediment, direction of transport amd regional extent of wind-wave resuspension. The prevailing easterly winds transport much of the suspended sediments westward toward the Chernier Plain in a well-defined mud stream. Westerly flow rates of 25-50 cm/s (21-43 km per day) have been measured, yielding a transit time of about 1.5-2.5 days from the mouth of Atchafalaya Bay to the Chernier Plain. Progradation rates along the Chernier Plain coast reach 50 m per year. The westward-flowing Atchafalaya "mud stream" is rapidly disrupted by westerly winds and northerly winds, which accompany frequent winter storms and less frequent tropical storms or hurricanes. During these events, the coastal current reverses and sediments are rapidly transported out of Atchafalaya Bay and offshore where substantial sedimentary deposits can also be found. Offshore sediment fluxes during storm events, in combination with wind-wave resuspension, can result in surface sediment "plumes" extending 70 km offshore and 150 km alongshore. Field measurements of suspended sediment concentrations, current and wind velocities, and directions are used to assess sediment transport processes on the shelf. These combined processes are extending the pro-delta deposits of the Atchafalaya-Wax Lake delta complex far onto the continental shelf and supplying sediments for a renewal era of progradation along tbe downdrift Chernier Plain coast.

Walker, Nan; Roberts, Harry; Stone, Gregory; Bentley, Samuel; Huh, Oscar; Sheremet, Alexandru; Rouse, Larry; Inoue, Masamichi; Welsh, Susan; Hsu, S. A.

2002-01-01

394

Sources and chemistry of atmospheric aerosol in the Southern High Plains of west Texas, USA  

NASA Astrophysics Data System (ADS)

The Southern High Plains area of west Texas is an important source of mineral dust aerosols in North America. Fugitive dust events in this region have been extensively studied with regard to their climatology and the effect of soil properties on dust production via wind erosion. However, less research has been done with regard to mineral dust chemistry and the presence of other types of aerosols in the Southern High Plains. Aerosol filter samples were collected on a daily basis in various size fractions (TSP, PM10, and/or PM2.5) at several sites in the region (Lubbock, Reese Center, and/or Big Spring, Texas) since 1996. This unique archive of samples provided the opportunity to better understand the variations in concentration and chemistry of Southern High Plains aerosols. A suite of these filter samples was analyzed for their elemental composition by PIXE in a preliminary reconnaissance of aerosol event types, sites and size ranges. The results provide chemical profiles of mineral dust within a regionally-significant source region, useful for source apportionment studies of particles transported downwind to receptor sites and/or mixed with other aerosol types. Elemental compositions and elemental ratios of Southern High Plains dust aerosols in several size ranges generally match those of local sands and carbonate deposits closest to the dust monitoring sites, reflecting wind erosion of local sediments. Iron is enriched in the finer fraction of the aerosols and during the most vigorous wind erosion events, suggesting the abrasion of clay coatings on sands as a mineral aerosol source. The impact of relatively fine smoke aerosols transported long distances from the south in spring 1998 is also documented. Finally, the data illustrate that during infrequent but annual summertime haze events, sulfate aerosols from points east can invade the Southern High Plains.

Gill, T. E.; Stout, J. E.

2001-12-01

395

Hydrogeology and geochemistry of the Ogallala aquifer, Southern High Plains  

NASA Astrophysics Data System (ADS)

The Ogallala aquifer, which underlies the Southern High Plains, consists of saturated sediments of the Ogallala Formation (Neogene) that are deposited mainly as a set of humid-type alluvial fans derived from the Rocky Mountains. The Ogallala aquifer, the main source of water for the High Plains of Texas and New Mexico, has been severely depleted by extensive pumpage. The hydrology and geochemistry of the aquifer are controlled by the surface topography of the underlying formations and by the thickness and permeability of the alluvial-fan deposits. Axes of three major alluvial fans trend from northwest to southeast; the fans have increased thickness and permeability compared with interfan areas. Flow lines follow the orientation of the alluvial fans. Along these major axes, the saturated section is thick and the chemical composition is relatively constant (Ca?HCO 3 to mixed-cation?HCO 3 water, depleted in ? 18O, ?D and tritium). External effects on the chemical composition are less pronounced. The aquifer is thinner and less permeable in areas between major fan axes and along the Caprock Escarpment. In these areas, groundwater can discharge from aquifers in the Cretaceous, Triassic and Permian formations into the Ogallala Formation. Cross-formational movement of water and low permeabilities in the Ogallala Formation result in varying hydrochemical facies and in isotopic compositions that differ from those of the major depositional areas. Areas where upward cross-formational flow occurs are evident by the presence of permeable contacts between the Ogallala and the underlying formations, water-level head differences and chemical and isotopic similarities. Secondary factors that locally affect the chemical composition of Ogallala Formation groundwater include contamination from evaporating saline lakes, agricultural chemicals and fertilizers and oil field brines. Impact of chemicals and brines may increase in the future because much of these contaminants may still be moving through the unsaturated zone toward the water table.

Nativ, Ronit; Smith, D. Anderson

1987-06-01

396

Serpentinization of abyssal peridotites from the MARK area, Mid-Atlantic Ridge: Sulfur geochemistry and reaction modeling  

USGS Publications Warehouse

The opaque mineralogy and the contents and isotope compositions of sulfur in serpentinized peridotites from the MARK (Mid-Atlantic Ridge, Kane Fracture Zone) area were examined to understand the conditions of serpentinization and evaluate this process as a sink for seawater sulfur. The serpentinites contain a sulfur-rich secondary mineral assemblage and have high sulfur contents (up to 1 wt.%) and elevated ??34Ssulfide (3.7 to 12.7???). Geochemical reaction modeling indicates that seawater-peridotite interaction at 300 to 400??C alone cannot account for both the high sulfur contents and high ??34Ssulfide. These require a multistage reaction with leaching of sulfide from subjacent gabbro during higher temperature (???400??C) reactions with seawater and subsequent deposition of sulfide during serpentinization of peridotite at ???300??C. Serpentinization produces highly reducing conditions and significant amounts of H2 and results in the partial reduction of seawater carbonate to methane. The latter is documented by formation of carbonate veins enriched in 13C (up to 4.5???) at temperatures above 250??C. Although different processes produce variable sulfur isotope effects in other oceanic serpentinites, sulfur is consistently added to abyssal peridotites during serpentinization. Data for serpentinites drilled and dredged from oceanic crust and from ophiolites indicate that oceanic peridotites are a sink for up to 0.4 to 6.0 ?? 1012 g seawater S yr-1. This is comparable to sulfur exchange that occurs in hydrothermal systems in mafic oceanic crust at midocean ridges and on ridge flanks and amounts to 2 to 30% of the riverine sulfate source and sedimentary sulfide sink in the oceans. The high concentrations and modified isotope compositions of sulfur in serpentinites could be important for mantle metasomatism during subduction of crust generated at slow spreading rates. ?? 2003 Elsevier Science Ltd.

Alt, J.C.; Shanks, W. C., III

2003-01-01

397

North-south compression, active uplift, and abyssal mantle exhumation of the Saint Peter and Saint Paul Rock, Equatorial Atlantic Ocean  

NASA Astrophysics Data System (ADS)

This article presents near N-S compression, active uplift tectonism, and the consequent abyssal mantle exhumation of the Saint Peter and Saint Paul Rock, Equatorial Atlantic Ocean. The mantle peridotite ridge is about 80 km long, 25 km wide, 3800 m high, and of near E-W direction. The ridge flanks are extremely steep with sub-vertical scarps of about 2000 m of relative height. The Flandrian wave-cut and the 14C datings for the carbonaceous algae of the Saint Peter and Saint Paul Rock indicate active uplift of 1.5 mm/year. The tectonic factures shows conjugated system of N-S compression tending slightly to NW-ES. Close to the peridotite ridge, the earthquakes with near N-S compression focal mechanism take place. The southern half of the peridotite ridge is constituted by undeformed peridotite. The existence of corrugation morphology indicates that the mantle rocks are originated from old megamullion. On the other hand, the northern half is composed of strongly deformed mylonitic peridotite suggesting that the ultramafic rocks are possibly originated from sub-crustal abyssal mantle of old transform fault. The mylonite structure is intensely perturbed indicating the tectonic events which disturbed the original parallel structure. The Saint Paul transform fault zone is characterized by E-W trend right lateral movement and the near N-S compression is unlikely. Therefore, an unusual local geotectonic process is expected. This tectonism was originated from the plate boundary jump at about 8 Ma, caused by the emergence of a new ridge segment, and the new transform fault is oblique to the relative plate movement. This angular discrepancy causes the compression perpendicular to the oblique transform fault, of near N-S direction, which squeeze out the sub-crustal abyssal mantle up to sea level. Therefore, the peridotite Ridge is considered to be a pressure ridge of the strike-slip movement of the Saint Paul transform fault.

Motoki, A.; Sichel, S. E.; Campos, T. F.; Motoki, K. F.; Szatmari, P.; Poseidon-Colmeia

2013-05-01

398

Sediment facies and Late Holocene progradation of the Mekong River Delta in Bentre Province, southern Vietnam: an example of evolution from a tide-dominated to a tide- and wave-dominated delta  

Microsoft Academic Search

The Mekong River Delta, southern Vietnam, is a typical mixed tide and wave energy delta with a wide delta plain formed during the last 6 ka and is one of the largest deltas in the world, Three cores were taken from Bentre Province in the lower delta plain, with the objective to describe the sediment facies and to clarify the

Thi Kim Oanh Ta; Van Lap Nguyen; Masaaki Tateishi; Iwao Kobayashi; Yoshiki Saito; Toshio Nakamura

2002-01-01

399

Project HOTSPOT: Borehole geophysics log interpretation from the Snake River Plain, Idaho  

NASA Astrophysics Data System (ADS)

The Snake River Plain (SRP), Idaho, hosts potential geothermal resources due to elevated groundwater temperatures associated with the thermal anomaly Yellowstone-Snake River hotspot. Project HOTSPOT has coordinated international institutions and organizations to understand subsurface stratigraphy and assess geothermal potential. Over 5.9km of core were drilled from three boreholes within the SRP in an attempt to acquire continuous core documenting the volcanic and sedimentary record of the hotspot: (1) Kimama, (2) Kimberely, and (3) Mountain Home. The most eastern drill hole is Kimama located along the central volcanic axis of the SRP and documents basaltic volcanism. The Kimberely drill hole was selected to document continuous volcanism when analysed in conjunction with the Kimama drill hole and is located near the margin of the plain. The Mountain Home drill hole is located along the western plain and documents older basalts overlain by sediment. A suite of ground and borehole geophysical surveys were carried out within the SRP between 2010 and 2012. The borehole geophysics logs included gamma ray (spectral and natural), neutron hydrogen index, electrical resistivity, magnetic susceptibility, ultrasonic borehole televiewer imaging, full waveform sonic, and vertical seismic profile. The borehole geophysics logs were qualitatively assessed through visual interpretation of lithological horizons and quantitatively through physical property specialized software and digital signal processing automated filtering process to identify step functions and high frequency anomalies. Preliminary results were published by Schmitt et al. (2012), Potter et al. (2012), and Shervais et al. (2013). The results are continuously being enhanced as more information is qualitatively and quantitatively delineated from the borehole geophysics logs. Each drill hole encounters three principal units: massive basalt flows, rhyolite, and sediments. Basalt has a low to moderate porosity and is low in the natural gamma ray isotopes uranium, thorium, and potassium, while rhyolites produce high total gamma ray responses. Sediment interbeds become apparent as the radioactivity associated with fine grained minerals is significantly higher than that of the host rock (e.g. basalt) due to high hydrogen concentration within the crystal structure of clays. Basalt lacks conductive minerals and results in high resistivity but moderate magnetic susceptibility. The sediments on the other hand are highly conductive and have a low magnetic susceptibility. The basalt and rhyolite units are relatively massive except for fractures which become apparent in the ultrasonic borehole televiewer. Signal is lost in soft sediments resulting in dark regions when full amplitude is displayed for the ultrasonic borehole televiewer. The massive basalt shows short P- and S-wave travel times and therefore a high sonic velocity, while the sediments display only P-wave first arrivals.

Lee, M. D.; Schmitt, D. R.; Chen, X.; Shervais, J. W.; Liberty, L. M.; Potter, K. E.; Kessler, J. A.

2013-12-01

400

Mechanisms of Basalt-plains Ridge Formation  

NASA Technical Reports Server (NTRS)

The morphologic similarities between the Columbia Plateau ridges and ridges on the Moon, Mercury and Mars form a strong basis for the interpretation of basalt-plains ridges as compressional folds. The basalt-plains ridges appear to have formed on competent flood basalt units deformed at the surface with essentially no confining pressure. Estimates of compressive strain for planetary ridges range from a few tenths of a percent on the Moon to up to 0.4% on Mars, to as high as 35% for Columbia Plateau folds with associated thrust faults. Such values have strong implications for both deformational mechanisms as well as for the source of stress. Deformational mechanisms that will attempt to account for the morphology, fold geometry, possible associated thrust faulting and regular spacing of the basalt-plains ridges on the terrestrial planets are under investigation.

Watters, T. R.; Maxwell, T. A.

1985-01-01

401

Late Quaternary climatic influences on river geomorphology on the Alberta Plains, Canada  

NASA Astrophysics Data System (ADS)

The most obvious geomorphic aberrations on the flat Alberta plains, incised river valleys partly refilled with alluvium, are indirect products of changing climate in latest Pleistocene and early Holocene time. The valley bottoms lie 15 to 120 m below the general plains surface and cut through till-bedrock contacts, indicating that rivers established their present courses following deglaciation. Previous hypotheses for incision invoked post-glacial isostatic rebound, but rebound models show that base levels rose downstream during and after deglaciation, a situation not conducive to incision. We hypothesize that large quantities of meltwater from the retreating Cordilleran Ice Sheet generated rapid incision for a period of about 2 000 years following the retreat of the ice sheets (14-12ka.) In this study, a combined ice sheet-climate model is used to estimate the amount of water derived from the melting Cordilleran Ice Sheet between 14 and 12ka; resulting annual discharges allocated to each basin indicate that major rivers were approximately 3 times greater in discharge than their modern counterparts. Experiments with the bedrock equation suggest these discharges are capable of causing the dramatic incision of Alberta rivers. Uncertainty concerning the duration and magnitude of large floods operating during deglaciation creates large variations in results; however, even the most conservatively estimated discharges are shown to be capable of causing incision of rivers to depths greater than indicated by field observations. Very soon after incision, rivers on the Alberta plains began aggrading, and deposited fills up to 35 m thick. Radiocarbon ages of bone fragments indicate filling was in progress ca. 13-12 ka. Previous work on paraglacial sedimentation is suggestive of an indirect climate-change trigger for aggradation: debris-laden valley walls in the Canadian Rockies began shedding sediment into the major rivers as the valley became progressively more ice-free. Hence plains evolution in latest Pleistocene and early Holocene time was mainly a consequence of changes in sediment/water balance in rivers, generated by changing climate. During the Holocene the major rivers proceeded to episodically reincise into their own alluvial fills, leaving terraces behind. Holocene degradation may merely be a continuation of long-term downcutting, which resumed when major sediment sources dried up. But presently there are no robust hypotheses tying terrace development to climatic (or tectonic) drivers.

Malowany, K.; Osborn, G.

2013-12-01

402

Coastal geomorphology of the Martian northern plains  

NASA Technical Reports Server (NTRS)

The paper considers the question of the formation of the outflow channels and valley networks discovered on the Martian northern plains during the Mariner 9 mission. Parker and Saunders (1987) and Parker et al. (1987, 1989) data are used to describe key features common both in the lower reaches of the outflow channels and within and along the margins of the entire northern plains. It is suggested, that of the geological processes capable of producing similar morphologies on earth, lacustrine or marine deposition and subsequent periglacial modification offer the simplest and most consistent explanation for the suit of features found on Mars.

Parker, Timothy J.; Gorsline, Donn S.; Saunders, Stephen R.; Pieri, David C.; Schneeberger, Dale M.

1993-01-01

403

Plain radiograph assessment of spinal hardware.  

PubMed

The frequency and variety of spinal instrumentation has increased tremendously over the past 100 years, and imaging plays an important role in evaluating the postoperative spine. Although assessment of spinal hardware often involves a multimodality approach, plain radiographs are the most commonly used modality, given accessibility, cost, relatively low radiation dose compared with computed tomography, and provision of positional information. An approach to assessment of plain radiographs of the postoperative spine is discussed, and examples of common postoperative complications are provided, including infection, hardware failure, incomplete fusion, and junctional failure. PMID:21500135

Venu, Vicnays; Vertinsky, Alexandra Talia; Malfair, David; Chew, Jason B; Shewchuk, Jason; Heran, Manraj K S; Graeb, Douglas A; Street, John T

2011-04-01

404

Geophysical Constraints on Sediment Dispersal Systems  

NASA Astrophysics Data System (ADS)

Geophysical and geological approaches were employed to understand sediment dispersal systems and their response to various forcing functions (i.e., sea level fluctuations, tectonic deformation, sediment supply, and climate change). Two end member marine environments were studied; one with high precipitation and sediment discharge (Gulf of Papua, Papua New Guinea) and the other with low precipitation and sediment discharge (Oceanside Littoral Cell). The high-sedimentation rate in the Gulf of Papua (GoP) yields high-fidelity records of Earth history. As part of the NSF Margins Source-to-Sink (S2S) program, we acquired CHIRP and core data across the GoP continental shelf that complemented onshore and offshore research in the region. CHIRP seismic data imaged three Holocene sedimentary lobes. The older Central lobe is downlapped by two younger lobes to the north and south. Sediment analysis showed that the older Central lobe has an elemental signature similar to the younger Northern lobe with both sourced from the Purari River watershed and lobe migration appears to be climatically controlled. The Southern lobe has elemental signatures more consistent with the Fly River watershed. Our results suggest the northern rivers began depositing sediments on the shelf during the Holocene sea level rise in the central region of the GoP and migrated abruptly north at ~2 kybp. Conversely, during the early Holocene transgression, sediments in the Fly drainage system were sequestered onshore infilling accommodation created in the large low-relief coastal plain during the sea level rise. Upon infilling the onshore accommodation, the Fly River delivered sediment to the ocean and formed the Southern lobe. Such differences in onshore storage capacity may introduce a lag between low-gradient rivers (Type I) with a large coastal plain versus high-gradient river systems (Type II) with small coastal plains. The second study site is in the sediment-starved Oceanside Littoral Cell (OCL) of Southern California. Terrestrial Laser scanning was performed seasonally using Light Detection and Ranging (LiDAR) technology to perform time series modeling of sea cliff erosion. We established a repeatable and reliable protocol for efficiently conducting coastal sea cliff mapping. Changes in geomorphology were quantified to determine the forcing mechanisms controlling erosion. Results from our investigations provide insight into "hot spots" of erosion along the coast and the controlling processes. Subaerial and marine erosion are predominantly controlled by precipitation and wave energy, respectively. Beach elevation, a seasonally dependent variable, is the most important physical factor controlling whether a sea cliff is vulnerable to marine-based or subaerial erosion. Due to the heavy coastal development and important state revenue from beach tourism, it is critical to continue this type of time series research to understand fully these relationships. This study provides a baseline from which future change due to the rapid sea level rise (>3 mm/yr) and climate change can be assessed.

Johnstone, Elizabeth Anne Carruthers

405

18 CFR 801.8 - Flood plain management and protection.  

Code of Federal Regulations, 2014 CFR

...2014-04-01 2014-04-01 false Flood plain management and protection. 801...COMMISSION GENERAL POLICIES § 801.8 Flood plain management and protection. ...waterways has not discouraged development of flood hazards areas. Major floods cause...

2014-04-01

406

18 CFR 801.8 - Flood plain management and protection.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 2012-04-01 true Flood plain management and protection. 801...COMMISSION GENERAL POLICIES § 801.8 Flood plain management and protection. ...waterways has not discouraged development of flood hazards areas. Major floods cause...