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1

Modern and ancient alluvial fan deposits  

SciTech Connect

Understanding the structure and depositional processes of alluvial fans (river outwash deposits) has a special interest for those involved with the exploration of petroleum and many minerals. This collection of facsimile reprints of significant and classical research papers sheds new light on the subject. This reference covers the stratigraphy, sedimentology, and depositional processes of modern and ancient alluvial fans. Geographical areas considered include Arctic Canada, the American Southwest, Australia, Wyoming, Norway, and Spain. It includes a state-of-the-art introduction by the editor along with commentaries on all the papers included, a master author citation index and a subject index, and a chronological listing of early studies of alluvial fans.

Nilsen, T.H.

1985-01-01

2

Late Quaternary eolian and alluvial response to paleoclimate, Canyonlands, southeastern Utah  

USGS Publications Warehouse

In upland areas of Canyonlands National Park, Utah, thin deposits and paleosols show late Quaternary episodes of eolian sedimentation, pedogenesis, and climate change. Interpretation of the stratigraphy and optically stimulated luminescence ages of eolian and nearby alluvial deposits, their pollen, and intercalated paleosols yields the following history: (1) Eolian deposition at ca. 46 ka, followed by several episodes of alluviation from some time before ca. 40 ka until after 16 ka (calibrated). (2) Eolian deposition from ca. 17 ka to 12 ka, interrupted by periods of pedogenesis, coinciding with late Pleistocene alluviation as local climate became warmer and wetter. (3) A wetter period from 12 to 8.5 ka corresponding to the peak of summer monsoon influence, during which soils formed relatively quickly by infiltration of eolian silt and clay, and trees and grasses were more abundant. (4) A drier period between ca. 8.5 and 6 ka during which sheetwash deposits accumulated and more desertlike vegetation was dominant; some dunes were reactivated at ca. 8 ka. (5) Episodic eolian and fluvial deposition during a wetter, cooler period that began at ca. 6 ka and ended by ca. 3-2 ka, followed by a shift to drier modern conditions; localized mobilization of dune sand has persisted to the present. These interpretations are similar to those of studies at the Chaco dune field, New Mexico, and the Tusayan dune field, Arizona, and are consistent with paleoclimate interpretations of pollen and packrat middens in the region. A period of rapid deposition and infiltration of eolian dust derived from distant igneous source terranes occurred between ca. 12 and 8 ka. Before ca. 17 ka, and apparently back to at least 45 ka, paleosols contain little or no such infiltrated dust. After ca. 8 ka, either the supply of dust was reduced or the more arid climate inhibited translocation of dust into the soils. ?? 2005 Geological Society of America.

Reheis, M. C.; Reynolds, R. L.; Goldstein, H.; Roberts, H. M.; Yount, J. C.; Axford, Y.; Cummings, L. S.; Shearin, N.

2005-01-01

3

Quaternary climate change and hillslope processes: What can we learn from alluvial fans?  

NASA Astrophysics Data System (ADS)

Examining the timing of sediment deposition on alluvial fans may clarify relationships among Quaternary changes in climate, sediment production, and sediment removal from uplifted mountain blocks. Deposition on fans indicates that (1) ample sediment is available for transport within contributing basins and (2) that stream power is adequate to move that sediment to the fan environment. Dating alluvial fan deposition clarifies relationships among climatically controlled factors (e.g. precipitation, vegetation, temperature), and hydrologic and geomorphic responses (e.g. weathering rates, frost action, glaciation, stream power) that influence landscape evolution. Numerous 2-5 km radius, low gradient alluvial fans head along the western side of the Lost River Range (LRR) in east-central Idaho. Timing of deposition on these fans is based on optically stimulated luminescence dating (OSL). In addition we described general deposit characteristics and mapped different aged fan surfaces to explore how fan deposition has changed over time. OSL results indicate that evacuation of sediment from contributing basins and deposition on fans was enhanced ~10-14 ka and ~40-50 ka. The younger episode is more robust in this record, with deposition recorded on all five studied fans despite differences in Quaternary glacial extent in contributing basins that varied from ~0-80%. Glacial chronologies from the nearby Sawtooth Range (Thackray, 2008) and Yellowstone-Teton region (Licciardi and Pierce, 2008; Gosse et al, 1995) suggest that this time period may have coincided with and followed the last glacial maxima in the northern Rocky Mountains. Deposition during the ~40-50 ka episode is recorded on the two largest studied fans, both with <10% glaciation in basin areas, as well as a ~40 m terrace of the East Fork Big Lost River that drains the Pioneer Range west of the LRR. A ~60-65 ka moraine in the northern LRR dated by U-series on pedogenic carbonate, an extensive glacio-fluvial terrace in the Wind River Basin (~200 km east of the LRR) dated to >55 ± 8.6 ka (Sharp et al, 2003), and substantial loess accumulation near the Teton Range at ~46-54 ka (Pierce et al, personal comm.) suggest that this episode of fan deposition was late- to post-glacial with respect to the MIS 4 glaciation and associated climatic conditions. Deposition on alluvial fans generally results from (1) increases in the sediment supply and/or (2) changes in stream power that alter the relative balance between sediment supply and stream power. In this region, sediment supply could increase following glacial conditions if reduced effective moisture decreases hillslope vegetation cover, freeing accumulated regolith for transport to fans, or greater temperature fluctuations increase the effectiveness of frost weathering. Stream power following a glacial maxima may have decreased in response to effectively drier climate, but may still have been adequate to transport sediment to fans. It’s also possible that stream power increased following glacial maxima with greater frequency of stochastic events such as rain on snow.

Kenworthy, M.; Pierce, J. L.; Rittenour, T. M.; Sharp, W. D.; Pierce, K. L.

2009-12-01

4

Climatic imprints in Quaternary valley fill deposits of the middle Teesta valley, Sikkim Himalaya  

Microsoft Academic Search

Quaternary alluvial sediments occur as distinct terrace and fan deposits in the middle Teesta valley in the belt between the Main Central Thrust and the Main Boundary Thrust in the Sikkim Himalaya. These sequences are characterized by lithofacies deposited by braided river channels, debris flows and hyperconcentrated flows. The channel flow deposits constitute relatively well sorted, well imbricated and clast-supported

Lukram I. Meetei; Sanjaya K. Pattanayak; Arun Bhaskar; Maharaj K. Pandit; Sampat K. Tandon

2007-01-01

5

Alluvial records of late Quaternary environmental change along the eastern Andes  

NASA Astrophysics Data System (ADS)

The piedmont in eastern Bolivia and northwestern Argentina is built from a series of coalescent alluvial fans and constitutes the transition between the Andean mountains and their foreland. As these alluvial fans receive their sediments from small local catchments in the Subandean ranges, past geomorphic and environmental changes are potentially stored in their alluvial stratigraphic record. The paleosol-sediment-sequences contained in these fans generally exhibit marked shifts between morphological activity with sedimentation and/or erosion, and periods of soil formation. Here, we present data from two different locations in eastern Bolivia and northwestern Argentina, and interpret them with regard to late Quaternary geomorphic, environmental and paleoclimatic changes in central South America. New chronological data (14C, OSL) from the laterally extensive exposures at Cabezas (eastern Bolivia) are combined with detailed sedimentological documentation of these sequences, and indicate important changes in sediment supply and transport capacities at least since Marine Isotope Stage (MIS) 3. In northwestern Argentina at Riacho Seco, piedmont stratigraphy is exposed in a profoundly incised stream valley, providing insights into downstream variations of paleosols, sediments and alluvial fan architecture. Interpretation of these data is complemented by new isotopic data from soil organic matter which contributes to an improved understanding of regional late Quaternary paleoenvironments. The comparison of both sites shows surprising similarities over the last 20-30 ka, but points to substantial differences during MIS 3, providing hints to potential changes in larger-scale circulation patterns and moisture sources. In summary, alluvial records contain valuable and largely unexplored regional archives for future application of a variety of methods. This way the investigation of the piedmont along the eastern Andes in Bolivia and Argentina can provide further data necessary for an improved understanding of the complex interplay between geological, geomorphic and environmental controls on landscape evolution over different late Quaternary timescales.

May, J.; Preusser, F.; Veit, H.

2010-12-01

6

Climatic, geomorphic, and archaeological implications of a late Quaternary alluvial chronology for the lower Salt River, Arizona, USA  

NASA Astrophysics Data System (ADS)

Recent archaeological excavations along the lower Salt River, Arizona resulted in the unexpected discovery of buried late Pleistocene soils and cultural features dating 5800-7100 cal YBP (Early Archaic), the latter representing the earliest evidence of human activity in the lower Salt River floodplain thus far identified. Because the lower Salt River floodplain has been heavily impacted by recent agriculture and urbanization and contains few stratigraphic exposures, our understanding of the river's geological history is limited. Here we present a late Quaternary alluvial chronology for a segment of the lower Salt River based on 19 accelerator mass spectrometry 14C and four optically stimulated luminescence ages obtained during two previous geoarchaeological investigations. Deposits are organized into allostratigraphic units and reveal a buried late Pleistocene terrace inset into middle-to-late Pleistocene terrace deposits. Holocene terrace fill deposits unconformably cap the late Pleistocene terrace tread in the site area, and the lower portion of this fill contains the Early Archaic archaeological features. Channel entrenchment and widening ~ 900 cal YBP eroded much of the older terrace deposits, leaving only a remnant of fill containing the buried latest Pleistocene and middle-to-late Holocene deposits preserved in the site area. Subsequent overbank deposition and channel filling associated with a braided channel system resulted in the burial of the site by a thin layer of flood sediments. Our study confirms that the lower Salt River is a complex mosaic of late Quaternary alluvium formed through vertical and lateral accretion, with isolated patches of buried soils preserved through channel avulsion. Although channel avulsion is linked to changes in sediment load and discharge and may have climatic linkages, intrinsic geomorphic and local base level controls limit direct correlations of lower Salt River stratigraphy to other large rivers in the North American Southwest.

Huckleberry, Gary; Onken, Jill; Graves, William M.; Wegener, Robert

2013-03-01

7

Late Quaternary alluvial processes in the north piedmont of Wutai Mountain in the graben system of north China and the influencing factors  

NASA Astrophysics Data System (ADS)

The alluvial processes in the piedmont may be controlled by tectonics, climate fluctuations and base level of erosion, etc. To distinguish the contributions of each factors is a hot field in fluvial geomorphology. The north piedmont of Wutai Mountain in Shanxi graben is an ideal area for this kind of study. The piedmont fault is very active with a slip rate of no less than 1 millimeter per year in late Quaternary. This semiarid region experienced significant climatic fluctuations in Quaternary time which is indicated by striking contrast in colors between loess and paleosoils in loess strata. The stratigraphic sequence of alluvial fans in late Pleistocene and Holocene is established through field surveying and trenching. Ages of the strata have been well constrained by the method of radiocarbon dating. It is discovered that the alluvial processes in front of the mountain were strong and weak alternately. The strong periods were from 32 ka to 29 ka B.P., from 7.5 ka to 4.7 ka B.P., and since 1 ka B.P., when coarse-grained sediments deposited and the sediment rate is relatively high. The other times are weak periods when fine-grained sediments deposited and the sediment rate is much lower. The three strong periods correspond either with the transform stages from warm to cool climates, or with the intense fluctuation stage after the maximum of warm climate. These three periods share a common feature of intense fluctuations of weather whose amplitudes are larger than other periods. According to former studies on Holocene paleoearthquakes about Wutai Mountain piedmont fault, two events happened in strong periods of alluvial processes, one event in weak period. Strong earthquakes may lead to landslides and rock-falls in mountain area, which increment the clastic provenance and contribute to alluvial processes, but the limited information of paleoearthquakes cannot support a salient effect of big earthquakes on alluvial processes in front of mountain. As our preliminary view, fault slips provided the space for deposition and slope of river bed, and climatic changes controlled the alternations of strong or weak alluvial processes. In the strongest fluctuations stage of climates, the vegetation degraded, physical weathering strengthened and storms easily led to flood, which contributed to erosions in mountain area and diluvium in front of mountain. This research deepens our understanding on the influencing factors of alluvial processes in semiarid area.

Zhang, S.; Gong, Z.; Ding, R.; Li, T.

2012-12-01

8

A Quaternary volcanic ash deposit in western Missouri  

SciTech Connect

Quaternary volcanic ash has been found in more than fifty localities in the midwest. The most widespread deposits originated from the Long Valley caldera, California; the Jemez calderas, New Mexico; or the Yellowstone caldera, Wyoming. Fission track dating has grouped the deposits into six separate ash falls ranging from 700,000--2,000,000 years old. A small volcanic ash deposit in western Missouri may be correlative with those found along the Kansas and Marais de Cygnes rivers in eastern Kansas. The ash deposit is in Northwest Bates County Missouri, exposed along a tributary to Miami Creek, four miles east of the Kansas state line. The ash layer is interbedded with alluvial terrace deposits and ranges from fifteen to thirty inches in thickness. It is inferred to have been deposited in a pond or oxbow lake. The color is white with a pale yellow tinge (Munsell 10YR 8/2). Shard examination shows that about 70% are flat bubble-wall types, about 20% have straight ridges, less than 10% are bubble-junction, and only a trace are vesicular. The closest known volcanic ash occurrence is an ash outcropping in a Kansas river terrace near DeSoto, KS, forty-five miles to the northwest. The DeSoto deposit has been identified as the .62 m.y. Lava Creek B ash from the Yellowstone caldera. A preliminary correlation of the Missouri ash with the DeSoto ash is based on similar shard morphology and color.

Emerson, J.W. (Central Missouri State Univ., Warrensburg, MO (United States))

1993-03-01

9

Geologic Characterization of Young Alluvial Basin-Fill Deposits from Drill-Hole Data in Yucca Flat, Nye County, Nevada  

USGS Publications Warehouse

Yucca Flat is a topographic and structural basin in the northeastern part of the Nevada Test Site in Nye County, Nevada, that has been the site of numerous underground nuclear tests; many of these tests occurred within the young alluvial basin-fill deposits. The migration of radionuclides to the Paleozoic carbonate aquifer involves passage through this thick, heterogeneous section of Tertiary and Quaternary rock. An understanding of the lateral and vertical changes in the material properties of young alluvial basin-fill deposits will aid in the further development of the hydrogeologic framework and the delineation of hydrostratigraphic units and hydraulic properties required for simulating ground-water flow in the Yucca Flat area. This report by the U.S. Geological Survey, in cooperation with the U.S. Department of Energy, presents data and interpretation regarding the three-dimensional variability of the shallow alluvial aquifers in areas of testing at Yucca Flat, data that are potentially useful in the understanding of the subsurface flow system. This report includes a summary and interpretation of alluvial basin-fill stratigraphy in the Yucca Flat area based on drill-hole data from 285 selected drill holes. Spatial variations in lithology and grain size of the Neogene basin-fill sediments can be established when data from numerous drill holes are considered together. Lithologic variations are related to different depositional environments within the basin such as alluvial fan, channel, basin axis, and playa deposits.

Sweetkind, Donald S.; Drake, Ronald M., II

2007-01-01

10

Geologic Characterization of Young Alluvial Basin-Fill Deposits from Drill Hole Data in Yucca Flat, Nye County, Nevada  

USGS Publications Warehouse

Yucca Flat is a topographic and structural basin in the northeastern part of the Nevada Test Site (NTS) in Nye County, Nevada, that has been the site of numerous underground nuclear tests; many of these tests occurred within the young alluvial basin-fill deposits. The migration of radionuclides to the Paleozoic carbonate aquifer involves passage through this thick, heterogeneous section of Tertiary and Quaternary rock. An understanding of the lateral and vertical changes in the material properties of young alluvial basin-fill deposits will aid in the further development of the hydrogeologic framework and the delineation of hydrostratigraphic units and hydraulic properties required for simulating ground-water flow in the Yucca Flat area. This report by the U.S. Geological Survey, in cooperation with the U.S. Department of Energy, presents data and interpretation regarding the three-dimensional variability of the shallow alluvial aquifers in areas of testing at Yucca Flat, data that are potentially useful in the understanding of the subsurface flow system. This report includes a summary and interpretation of alluvial basin-fill stratigraphy in the Yucca Flat area based on drill hole data from 285 selected drill holes. Spatial variations in lithology and grain size of the Neogene basin-fill sediments can be established when data from numerous drill holes are considered together. Lithologic variations are related to different depositional environments within the basin including alluvial fan, channel, basin axis, and playa deposits.

Sweetkind, Donald S.; Drake, Ronald M., II

2007-01-01

11

The Tabernas alluvial fan and lake system, southeast Spain: applications of mineral magnetic and pedogenic iron oxide analyses towards clarifying the Quaternary sediment sequences  

Microsoft Academic Search

Mineral magnetic and soil iron oxide data are applied to questions of relative age correlation of alluvial fans and lake sediments in the Tabernas basin, southeast Spain, within a context of interaction between tectonics and climatic change. Within the Tabernas basin, the sediment sequences and morphological evolution of late Quaternary alluvial fans suggest climatic change as the primary control. The

Adrian M Harvey; Gez Foster; Jack Hannam; Anne E Mather

2003-01-01

12

The impact of Quaternary sea-level and climatic change on coastal alluvial fans in the Cabo de Gata ranges, southeast Spain  

Microsoft Academic Search

Conventionally, a fall in base level is seen as stimulating incision into the distal zones of alluvial fans. In the Cabo de Gata ranges of southeast Spain evidence exists to the contrary. Two sets of Quaternary coastal alluvial fans demonstrate the interaction between climatically-driven variations in the supply of sediment and eustatically-driven changes in base level. The fans are supplied

Adrian M. Harvey; Pablo G. Silva; Anne E. Mather; Jose L. Goy; Martin Stokes; Cari Zazo

1999-01-01

13

SEDIMENTOLOGY AND GEOMORPHOLOGY OF QUATERNARY ALLUVIAL FANS WITH IMPLICATIONS TO GROWTH STRATA, LOST RIVER RANGE,  

E-print Network

The Wyoming Geological Association's J.D. Love Fellowship The Letters and Science Enhancement Award Hayley......................................................................................14 5. UPPER CEDAR CREEK ALLUVIAL FAN.............................................. 19 Surface 6. JONES CREEK ALLUVIAL FAN......................................................... 67 Surface

Lawrence, Rick L.

14

Development and lithogenesis of the palustrine and calcrete deposits of the Dibdibba Alluvial Fan, Kuwait  

NASA Astrophysics Data System (ADS)

A model is proposed for the development of the Quaternary palustrine carbonate-calcrete association, which occurs as hard crust capping low hills at a distal flood plain of Al Dibdibba alluvial fan located at southwestern Kuwait. Field occurrence, detailed petrographic investigation and geochemical analysis revealed that a single cycle of groundwater calcrete with vertical gradational maturity pattern was developed. This represents a continuous sedimentological cycle during which flood sheet conditions prevailed with intermittent periods of humid and arid conditions. Subsequently, calcitic micrite was continuously precipitated from small, shallow, local, isolated and short lived ponds fringed by freshwater marshes with abundant charophyte meadows. The latter were developed as a result of flooding scattered depressions by groundwater supersaturated with respect to calcite due to rise of groundwater table. The deposition of two facies of carbonate muds, namely; biomicrite and pelintraclasts skeletal micrites was followed by a drought phase which witnessed desiccation of the fresh water ponds and significant drop in groundwater level. A sequence of pedogenic and diagenetic processes acted on the deposited carbonate muds are manifested by: (a) desiccation cracks, (b) micrite neomorphism, (c) infilling of root burrows and some cracks by aeolian siliciclastics, (d) karstification, (e) marmorization, (f) calcretization of root burrow infill and development of pseudo-rhizocrete, (g) calcite cementation and mineral authigenesis, and (h) silcretization. These processes are responsible for the development of hard palustrine carbonate crust. At the advent of aridity, the whole system of Al Dibdibba alluvial fan was subjected to deflation. This resulted in reversing the paleotopography of the hard crusted palustrine depressions into carbonate capped domal hills.

AlShuaibi, Arafat A.; Khalaf, Fikry I.

2011-08-01

15

Rivers turned to rock: Late Quaternary alluvial induration influencing the behaviour and morphology of an anabranching river in the Australian monsoon tropics  

NASA Astrophysics Data System (ADS)

Late Quaternary alluvial induration has greatly influenced contemporary channel morphology on the anabranching Gilbert River in the monsoon tropics of the Gulf of Carpentaria. The Gilbert, one of a number of rivers in this region, has contributed to an extensive system of coalescing low-gradient and partly indurated riverine plains. Extensive channel sands were deposited by enhanced flow conditions during marine oxygen isotope (OI) Stage 5. Subsequent flow declined, probably associated with increased aridity, however, enhanced runoff recurred again in OI Stages 4-3 (˜65-50 ka). Aridity then capped these plains with 4-7 m of mud. A widespread network of sandy distributary channels was incised into this muddy surface from sometime after the Last Glacial Maximum (LGM) to the mid Holocene during a fluvial episode more active than the present but less so than those of OI Stages 5 and 3. This network is still partly active but with channel avulsion and abandonment now occurring largely proximal to the main Gilbert flow path. A tropical climate and reactive catchment lithology have enhanced chemical weathering and lithification of alluvium along the river resulting in the formation of small rapids, waterfalls and inset gorges, features characteristic more of bedrock than alluvial systems. Thermoluminescence (TL) and comparative optically stimulated luminescence (OSL) ages of the sediments are presented along with U/Th ages of pedogenic calcrete and Fe/Mn oxyhydroxide/ oxide accumulations. They show that calcrete precipitated during the Late Quaternary at times similar to those that favoured ferricrete formation, possibly because of an alternating wet-dry climate. Intense chemical alteration of the alluvium leading to induration appears to have prevailed for much of the Late Quaternary but, probably due to exceptional dryness, not during the LGM. The result has been restricted channel migration and a reduced capacity for the channel to adjust and accommodate sudden changes in bedload. Consequent avulsions have caused local stream powers to increase by an order of magnitude, inducing knickpoint erosion, local incision and the sudden influx of additional bedload that has triggered further avulsions. The Gilbert River, while less energetic than its Pleistocene ancestors, is clearly an avulsive system, and emphasizes the importance in some tropical rivers of alluvial induration for reinforcing the banks, generating nickpoints, reworking sediment and thereby developing and maintaining an indurated and anabranching river style.

Nanson, Gerald C.; Jones, Brian G.; Price, David M.; Pietsch, Timothy J.

2005-09-01

16

Late Quaternary landscape evolution in the Kunlun Mountains and Qaidam Basin, Northern Tibet: A framework for examining the links between glaciation, lake level changes and alluvial fan formation  

USGS Publications Warehouse

The Qaidam Basin in Northern Tibet is one of the largest hyper-arid intermontane basins on Earth. Alluvial fans, pediment surfaces, shorelines and a thick succession of sediments within the basin, coupled with moraines and associated landforms in the adjacent high mountain catchments of the Kunlun Mountains, record a complex history of Late Quaternary paleoenvironmental change and landscape evolution. The region provides an ideal natural laboratory to examine the interaction between tectonics and climate within a continent-continent collision zone, and to quantify rates of landscape evolution as controlled by climate and the associated glacial and hydrological changes in hyper-arid and adjacent high-altitude environments. Geomorphic mapping, analysis of landforms and sediments, and terrestrial cosmogenic radionuclide surface exposure and optically stimulated luminescence dating serve to define the timing of formation of Late Quaternary landforms along the southern and northwestern margins of the Qaidam Basin, and in the Burhan Budai Shan of the Kunlun Mountains adjacent to the basin on the south. These dates provide a framework that suggests links between climatic amelioration, deglaciation, lake desiccation and alluvial fan evolution. At least three glacial advances are defined in the Burham Budai Shan of the Kunlun Mountains. On the northern side of this range these occurred in the penultimate glacial cycle or early in the last glacial cycle, during the Last Glacial Maximum (LGM)/Lateglacial and during the Holocene. On the south side of the range, advances occurred during the penultimate glacial cycle, MIS-3, and possibly the LGM, Lateglacial or Holocene. Several distinct phases of alluvial fan sedimentation are likewise defined. Alluvial fans formed on the southern side of the Kunlun Mountains prior to 200 ka. Ice-contact alluvial fans formed during the penultimate glacial and during MIS-3. Extensive incised alluvial fans that form the main valley fills north of the Burham Budai and extend into the Qaidam Basin are dated to ???30 ka. These ages suggest that there was a period of alluvial fan aggradation and valley filling that persisted until desiccation of the large lakes in the Qaidam Basin post ???30 ka led to base level lowering and active incision of streams into the valley fills. The continued Lateglacial and Holocene desiccation likely led to further degradation of the valley fills. Ice wedge casts in the Qaidam Basin date to ???15 ka, indicating significant Lateglacial climatic amelioration, while Holocene loess deposits north of the Burham Bdudai suggest that aridity has increased in the region since the early Holocene. From these observations, we infer that the major landscape changes within high glaciated mountains and their adjacent hyper-arid intermontane basins, such as the Kunlun Mountains and Qaidam Basin, occur rapidly over millennial timescales during periods of climatic instability. ?? 2006 Elsevier Ltd and INQUA.

Owen, L.A.; Finkel, R.C.; Haizhou, M.; Barnard, P.L.

2006-01-01

17

Deposition and early hydrologic evolution of Westwater Canyon wet alluvial-fan system  

SciTech Connect

The Westwater Canyon Member is one of several large, low-gradient alluvial fans that compose the Morrison Formation in the Four Corners area. Morrison fans were deposited by major laterally migrating streams entering a broad basin bounded by highlands to the west and south. The Westwater Canyon sand framework consists of a downfan succession of 1) proximal braided channel, 2) straight bed-load channel, 3) sinuous mixed-load channel, and 4) distributary mixed-load-channel sand bodies. Regional sand distribution and facies patterns are highly digitate and radiate from a point source located northwest of Gallup, New Mexico. Early ground-water flow evolution within the Westwater Canyon fan aquifer system can be inferred by analogy with Quaternary wet-fan deposits and by the interpreted paragenetic sequence of diagenetic features present. Syndepositional flow was controlled by the downfan hydrodynamic gradient and the high horizontal and vertical transmissivity of the sand-rich fan aquifer. Dissolution and transport of soluble humate would be likely in earliest ground water, which was abundant, fresh, and slightly alkaline. With increasing confinement of the aquifer below less permeable tuffaceous Brushy Basin deposits and release of soluble constituents from volcanic ash, flow patterns stabilized, and relatively more saline, uranium-rich ground water permeated the aquifer. Uranium mineralization occurred during this early postdepositional, semiconfined flow phase. Development of overlying Dakota swamps suggests a shallow water table indicative of regional dischare or stagnation. In either event, only limited downward flux of acidic water is recorded by local, bleached, kaolinized zones where the Westwater Canyon directly underlies the Dakota swamps. Subsequent ground-water flow phases have further obscured primary alteration patterns and caused local oxidation and redistribution of uranium.

Galloway, W.E.

1980-01-01

18

Late Quaternary Upper Mississippi River alluvial episodes and their significance to the Lower Mississippi River system  

Microsoft Academic Search

The period in the Upper Mississippi Valley (UMV) from about 25 000 years B.P. until the time of strong human influence on the landscape beginning about 150–200 years ago can be characterized by three distinctly different alluvial episodes. The first episode is dominated by the direct and indirect effects of Late Wisconsin glacial ice in the basin headwaters. This period,

James C. Knox

1996-01-01

19

Alluvial deposits and plant distribution in an Amazonian lowland megafan  

NASA Astrophysics Data System (ADS)

A large volume of sandy alluvial deposits (> 1000 km2) characterizes a flat wetland in northern Amazonia. These have been recently described as the sedimentary record of a megafan system, which have a distinct triangular shape produced by highly migratory distributary rivers. The vegetation map suggests that this megafan is dominated by open vegetation in sharp contact with the surround rainforest. Understanding the relationship between geomorphological processes and vegetation distribution is crucial to decipher and conserve the biodiversity in this Amazonian ecosystem. In this study we interpret plant dynamics over time, and investigate its potential control by sedimentary processes during landscape evolution. The study area is located in the Viruá National Park. Two field campaigns were undertaken in the dry seasons of 2010 and 2011 and the sampling sites were selected by combining accessibility and representativeness. Vegetation contrasts were recorded along a transect in the medial section of the Viruá megafan. Due to the absence of outcrops, samples were extracted using a core device, which allowed sampling up to a depth of 7.5 m. All cores were opened and described in the field, with 5 cm3 samples collected at 20 cm intervals. The ?13C of organic matter was used as a proxy to distinguish between C3 and C4 plant communities. The chronology was established based on radiocarbon dating. The results suggest that the cores from forested areas show the most depleted values of ?13C, ranging from -32.16 to -27.28‰. The ?13C curve in these areas displays typical C3 land plant values for the entire record, which covers most of the Holocene. This finding indicates that either the vegetation remained stable over time or the sites were dominated by aquatic environments with freshwater plants before forest establishment. The cores from the open vegetation areas show a progressive upward enrichment in ?13C values, which range from -28.50 to -19.59‰. This trend is more pronounced after de mid-Holocene, suggesting that the open vegetation, represented mostly by C4 land plants, evolved only more recently. Based on our isotope data, a model is proposed taking into account the influence of sedimentary dynamics on the modern pattern of plan distribution. The establishment of open vegetation occurred at different times depending on location over the megafan area, varying from around 3,000 to 6,400 cal yrs BP. As sedimentation took place, areas located far from the surrounding rainforest were prone to inputs of organic matter derived from open vegetation, whereas the contribution of organic matter derived from arboreous vegetation increases toward the areas located closer to the rainforest. In general, open vegetation is constrained to depositional sites that remained active until relatively recent Holocene times, while surrounding areas with a relatively older geological history are covered by dense forest. The results presented here consist in a striking example of the influence of sedimentary processes during the Late Pleistocene-Holocene on the development of modern plants of this Amazonian lowland.

Zani, H.; Rossetti, D.; Cremon; Cohen, M.; Pessenda, L. C.

2012-12-01

20

Hydrogeologic features of the alluvial deposits in the Nowood River drainage area, Bighorn Basin, Wyoming  

USGS Publications Warehouse

In the Nowood River drainage area, Wyoming, the principal deposits comprising the alluvial aquifer include the flood-plain and younger (generally undissected) alluvial-fan deposits and a unique boulder-fan gravel. Other deposits mapped, but virtually nonwater yielding, are the older (dissected) alluvial-fan, pediment, and terrace deposits. Terraces are capped by gravel and form levels at 30-40, 45-100, 120-150, 200-260, and 280-330 feet above the Nowood River. The thickness of the alluvial aquifer indicated from the sparse well-log data and 42 surface resistivity measurements is between 25 and 50 feet along the Nowood River and more than 60 feet along Tensleep and Paint Rock Creeks. The resistivity measurements indicate a buried bedrock ridge below the boulder-fan gravel between Paint Rock and Medicine Lodge Creeks and a buried channel filled by alluvium along Tensleep Creek. Well yields from the alluvial aquifer are estimated to be low. The most favorable areas for ground-water development are from the flood-plain alluvium along Tensleep Creek and from the boulder-fan gravel and adjoining flood-plain alluvium along Paint Rock and Medicine Creeks. Along the Nowood River the flood-plain alluvium, although its yields are small, has the best potential for ground-water development. (Kosco-USGS)

Cooley, M.E.; Head, William J.

1979-01-01

21

Quaternary tilt of Death Valley determined from landform modelling of alluvial fans  

SciTech Connect

Alluvial fans along the east side of central Death Valley are being actively back-tilted along the Death Valley fault zone. Initial modelling of the Copper Canyon and Furnace Creek fans led to recognition of distinct segments. Field reconnaissance and aerial photo mapping were conducted to check model results and improve segment discrimination. Surface roughness, relative position, vegetation distribution, and drainage patterns provided independent evidence for segment discrimination. Subsequent modelling of individual segments produced a range of tilt values from 0.275[degree] to 0.559[degree] down to the northeast. Continued analysis of these fan segments is concentrated on: (1) assigning confidence and error values to the tilt values; and (2) dating individual segments. Further work will compare the tilt rates of east-side fans with those from the west. The mean squared error (MSE) is currently being used as a first order assessment of the quality of the model's fit to data digitized from 1:24,000 scale USGS topographic maps. MSE values of 1 m or less can be expected for relatively young or actively aggrading segments. Previous fan models have found the expected range of misfits to be between 2 m and 5 m. This seven parameter least squares model has produced fits with less than 2 m total range in misfits. Previous models have not accounted for tilt or have relied on simplifying assumptions to fix apex position.

West, R.B.; Wilson, D.S. (Univ. of California, Santa Barbara, CA (United States). Dept. of Geology)

1993-04-01

22

Resolving Structural Influences on Water-Retention Properties of Alluvial Deposits  

Microsoft Academic Search

With the goal of improving property-transfer model (PTM) predic- tions of unsaturated hydraulic properties, we investigated the influ- ence of sedimentary structure, defined as particle arrangement during deposition, on laboratory-measured water retention (water content vs. potential (u(c))) of 10 undisturbed core samples from alluvial deposits in the western Mojave Desert, California. The samples were classified as having fluvial or debris-flow

Kari A. Winfield; John R. Nimmo; John A. Izbicki; Peter M. Martin

2006-01-01

23

Hydrogeologic features of the alluvial deposits in the Owl Creek Valley, Bighorn Basin, Wyoming  

USGS Publications Warehouse

The alluvial acquifer principally of the flood-plain alluvium and part of the Arapahoe Ranch terrace deposits and consists subordinately of alluvial-fan deposits. Thickness of the alluvial aquifer is generally 20 to 40 feet. Dissolved-solids concentration of water in the alluvial aquifer ranges from about 500 to more than 3,000 milligrams per liter. The most favorable areas for groundwater development are the flood-plain alluvium and part of the Arapahoe Ranch terrace deposits; however, in much of these units, the water contains more than 2,000 milligrams per liter of dissolved solids. Measurements of specific conductance of the flow of Owl Creek indicate a progressive increase in the down stream direction and range between 15 and 355 micromhos per centimeter at 25C per mile. The increases are due to return flow of irrigation water, inflow from tributaries, and inflow from groundwater. Conspicuous terraces in Owl Creek Valley included an unnamed terrace at 500 feet above Owl Creek, the Embar Ranch terrace 160 to 120 feet above the creek, and the Arapahoe Ranch terrace 50 to 20 feet above the creek. (USGS)

Cooley, M.E.; Head, W.J.

1982-01-01

24

Soils developed from alluvial and proluvial deposits in the Gröndalselva River valley in West Spitsbergen  

NASA Astrophysics Data System (ADS)

The genetic characterization of soils developed from alluvial and proluvial deposits in the Gröndalselva River valley (West Spitsbergen) is presented. These soils are compared with analogous soils formed on marine terraces along the coasts of Isfjord and Grönfjord. Gray-humus (soddy) soils with an O-AY-C profile have been described on parent materials of different origins, including alluvial and proluvial sediments. The texture of the soils in the Gröndalselva River valley varies from medium to heavy loam and differs from the texture of the soils on other geomorphic positions in the higher content of fine particles. The soils developed from the alluvial deposits are characterized by their richer mineralogical and chemical composition in comparison with the soils developed from proluvial deposits, marine deposits, and bedrocks. All the deposits are impoverished in CaO. No differentiation of the chemical composition of the soils along the soil profiles has been found in the soils of the coastal areas and the river valley. Some accumulation of oxalate-soluble Al and Fe compounds takes place in the uppermost mineral horizon. The soils of all the geomorphic positions have a high humus content and a high exchange capacity.

Pereverzev, V. N.; Litvinova, T. I.

2012-05-01

25

Quaternary stratigraphy, sediment characteristics and geochemistry of arsenic-contaminated alluvial aquifers in the Ganges-Brahmaputra floodplain in central Bangladesh.  

PubMed

This study focuses on the Quaternary stratigraphy, sediment composition, mineralogy, and geochemistry of arsenic (As)-contaminated alluvial aquifers in the Ganges-Brahmaputra floodplain in the central Bangladesh. Arsenic concentrations in 85 tubewells in Manikganj area, 70 km northwest of Dhaka City, range from 0.25 microg/L to 191 microg/L with a mean concentration of 33 microg/L. Groundwater is mainly Ca-HCO(3) type with high concentrations of dissolved As, Fe, and Mn, but low level of SO(4). The uppermost aquifer occurs between 10 m and 80 m below the surface that has a mean arsenic concentration of 35 microg/L. Deeper aquifer (>100 m depth) has a mean arsenic concentration of 18 microg/L. Sediments in the upper aquifer are mostly gray to dark-gray, whereas sediments in the deep aquifer are mostly yellowing-gray to brown. Quartz, feldspar, mica, hornblende, garnet, kyanite, tourmaline, magnetite, ilmenite are the major minerals in sediments from both aquifers. Biotite and potassium feldspar are dominant in shallow aquifer, although plagioclase feldspar and garnet are abundant in deep aquifer sediments. Sediment composition suggests a mixed provenance with sediment supplies from both orogenic belts and cratons. High arsenic concentrations in sediments are found within the upper 50 m in drilled core samples. Statistical analysis shows that As, Fe, Mn, Ca, and P are strongly correlated in sediments. Concentrations of Cd, Cu, Ni, Zn, and Bi also show strong correlations with arsenic in the Manikganj sediment cores. Authigenic goethite concretions, possibly formed by bacteria, are found in the shallow sediments, which contain arsenic of a concentration as high as 8.8 mg/kg. High arsenic concentrations in aquifers are associated with fine-grained sediments that were derived mostly from the recycled orogens and relatively rapidly deposited mainly by meandering channels during the Early to Middle Holocene rising sea-level conditions. PMID:18502538

Shamsudduha, M; Uddin, A; Saunders, J A; Lee, M-K

2008-07-29

26

Quaternary landscape development, alluvial fan chronology and erosion of the Mecca Hills at the southern end of the San Andreas Fault zone  

NASA Astrophysics Data System (ADS)

Quantitative geomorphic analysis combined with cosmogenic nuclide 10Be-based geochronology and denudation rates have been used to further the understanding of the Quaternary landscape development of the Mecca Hills, a zone of transpressional uplift along the southern end of the San Andreas Fault, in southern California. The similar timing of convergent uplifts along the San Andreas Fault with the initiation of the sub-parallel San Jacinto Fault suggest a possible link between the two tectonic events. The ages of alluvial fans and the rates of catchment-wide denudation have been integrated to assess the relative influence of climate and tectonic uplift on the development of catchments within the Mecca Hills. Ages for major geomorphic surfaces based on 10Be surface exposure dating of boulders and 10Be depth profiles define the timing of surface stabilization to 2.6 +5.6/-1.3 ka (Qyf1 surface), 67.2 ± 5.3 ka (Qvof2 surface), and 280 ± 24 ka (Qvof1 surface). Comparison of 10Be measurements from active channel deposits (Qac) and fluvial terraces (Qt) illustrate a complex history of erosion, sediment storage, and sediment transport in this environment. Beryllium-10 catchment-wide denudation rates range from 19.9 ± 3.2 to 149 ± 22.5 m/Ma and demonstrate strong correlations with mean catchment slope and with total active fault length normalized by catchment area. The lack of strong correlation with other geomorphic variables suggests that tectonic uplift and rock weakening have the greatest control. The currently measured topography and denudation rates across the Mecca Hills may be most consistent with a model of radial topographic growth in contrast to a model based on the rapid uplift and advection of crust.

Gray, Harrison J.; Owen, Lewis A.; Dietsch, Craig; Beck, Richard A.; Caffee, Marc A.; Finkel, Robert C.; Mahan, Shannon A.

2014-12-01

27

Three-dimensional sedimentary architecture of Quaternary deposits; a case study of environmental sedimentology (Bam, Iran)  

NASA Astrophysics Data System (ADS)

Detailed 3-D analysis of the sedimentary structure and stratigraphy of these deposits allows for an accurate understand of sedimentary model of basin. This paper presents a case study in Bam (SE Iran) reconstructing the 3-D distribution of fluvial sediments based on a high resolution, process-orientated sedimentary facies classification and lithostratigraphy. We investigated the mean grain size with vertical and horizontal change of it, clay mineralogy, sediment texture, sedimentary structures, petrology and petrography and determination of paleo-environments and finally, we prepared two cross sections in S-N and W-E directions and a 3D block diagram for the situation of changes in subsurface sediments and compare them with the destruction rate map of earthquake in Bam city. Quaternary alluvial sediments are characterized by lithofacies deposited by braided river channels, debris flows and hyperconcentrated flows. The channel flow deposits constitute relatively well sorted, well imbricated and clast-supported gravels with coarse to medium sand matrix. Mostly poorly sorted, weakly imbricated to disorganized matrix supported pebble to boulder gravels with silty sand represent debris flow deposits. Hyperconcentrated flow deposits consist of clast-supported, poorly developed sorted polymodal gravel facies with poorly developed imbricated fabric, and generally occupy the lower parts of the terrace and fan sequences. The alternation from hyperconcentrated flow to channel flow deposits is predominant in the sequence, and is possibly the response to different climate modes. The high discharge and supply of sediments as well as the dispersal and deposition of these materials in the trunk stream is attributed to climatic perturbations during the Quaternary. These models allow quantifying the thickness and volume distribution of sandy gravel and clay deposits. We correlate these sedimentary units on the basis of lithofacies similarities, stratigraphic position. These relationships suggest that deformation had occured upward into the basin during time. According to our observations, a great number of recently constructed buildings were also damaged in city areas far from the faulted zones. These are areas where silty and clayey soils dominate, exhibiting very low electric resistivity and low wave velocity, together with high thickness, plasticity and compressibility. Rock samples are from volcanism stages in Eocene magmatism. The clay minerals have resulted from weathering of continental environments in upstream. Key Words: Bam, Sediment, facies, 3D sedimentary model, Earthquake.

Rezaei, K.; Guest, B.; Friedrich, A.; Fayazi, F.; Nakhaei, M.; Bakhtiari, H.; Nouri, L.

2009-04-01

28

Late Quaternary carbonate deposition at the bottom of the world  

NASA Astrophysics Data System (ADS)

Carbonate sediments on polar shelves hold great potential for improving understanding of climate and oceanography in regions of the globe that are particularly sensitive to global change. Such deposits have, however, not received much attention from sedimentologists and thus remain poorly understood. This study investigates the distribution, composition, diagenesis, and stratigraphic context of Late Quaternary calcareous sediments recovered in 15 piston cores from the Ross Sea shelf, Antarctica. Results are used to develop a depositional model for carbonate deposition on glaciated, polar shelves. The utility of the deposits as analogs for the ancient record is explored. In the Ross Sea, carbonate-rich lithofacies, consisting of poorly sorted skeletal sand and gravel, are concentrated in the west and along the outer reaches of the continental shelf and upper slope. Analysis of fossil assemblages shows that deposits were produced by numerous low-diversity benthic communities dominated locally by stylasterine hydrocorals, barnacles, or bryozoans. Radiocarbon dating indicates that carbonate sedimentation was episodic, corresponding to times of reduced siliciclastic deposition. Most accumulation occurred during a time of glacial expansion in the lead-up to the Last Glacial Maximum. A more recent interval of carbonate accumulation postdates the early Holocene sea level rise and the establishment of the modern grounding line for the Ross Ice Shelf. When carbonate factories were inactive, fossil debris was subjected to infestation by bioeroders, dissolution, fragmentation, and physical reworking. This study reveals the episodic nature of carbonate deposition in polar settings and a reciprocal relationship with processes that deliver and redistribute siliciclastic debris. Carbonate production is most active during colder periods of the glacial-interglacial cycle, a potential new sedimentological paradigm for polar carbonate systems. Low accumulation rates and long residence times on the seafloor leave sediments vulnerable to significant post-depositional modification, processes that profoundly affect the appearance of deposits as they enter the rock record. Comparison with other examples of polar carbonates highlights the utility of these Late Quaternary deposits as a well-constrained analog that can aid in the recognition and interpretation of similar deposits from the ancient record.

Frank, Tracy D.; James, Noel P.; Bone, Yvonne; Malcolm, Isabelle; Bobak, Lindsey E.

2014-05-01

29

The subfossil tree deposits from the Garonne Valley and their implications on Holocene alluvial plain dynamics  

NASA Astrophysics Data System (ADS)

Subfossil tree trunks deposits are common in large rivers, but their status as a source for dating alluvial sequences and palaeoenvironmental studies is still discussed. Particularly their origin and the process(es) of deposition as well as a possible remobilization were pointed as a limit to their use to document river alluvial changes. In this work we report the discovery of the largest subfossil trunks deposits in the Garonne valley. These new data are compared to the previous ones. A set of 17 tree trunks and more than 300 smaller wood fragments were collected. The xylologic study shows the prevalence of Quercus and a single occurrence of Ulmus. These two hardwood species are commonly associated with riparian forest. The 14C dating carried out on seven trunks and a single branch of Quercus on the outermost identified growth rings, indicates age ranging from 8400-8000 cal. BP for the oldest fragment (bough) to 4300-4000 cal. BP for the most recent tree trunk. Radiocarbon ages of the trunks are aggregated into two main periods: 5300-5600 cal. BP (four trunks) and 4300-4000 cal. BP (three trunks). The radiocarbon (charcoal) dating of the top of the alluvial sequence overlaying the trunks gives an age between 1965-1820 and 1570-1810 cal. BP, i.e. between the 2nd and the 5th c. AD. In addition, the discovery of two unpublished subfossil tree trunks deposits in Finhan are reported (six trunks). At the light of these results, we discuss previously proposed models for the Garonne floodplain building.

Carozza, Jean-Michel; Carozza, Laurent; Valette, Philippe; Llubes, Muriel; Py, Vanessa; Galop, Didier; Danu, Mihaela; Ferdinand, Laurie; David, Mélodie; Sévègnes, Laurent; Bruxelles, Laurent; Jarry, Marc; Duranthon, Francis

2014-01-01

30

Field Demonstrations of Five Geophysical Methods that Could Be Used to Characterize Deposits of Alluvial Aggregate  

USGS Publications Warehouse

Personnel from the U.S. Geological Survey and Martin Marietta Aggregates, Inc., conducted field demonstrations of five different geophysical methods to show how these methods could be used to characterize deposits of alluvial aggregate. The methods were time-domain electromagnetic sounding, electrical resistivity profiling, S-wave reflection profiling, S-wave refraction profiling, and P-wave refraction profiling. All demonstrations were conducted at one site within a river valley in central Indiana, where the stratigraphy consisted of 1 to 2 meters of clay-rich soil, 20 to 35 meters of alluvial sand and gravel, 1 to 6 meters of clay, and multiple layers of limestone and dolomite bedrock. All geophysical methods, except time-domain electromagnetic sounding, provided information about the alluvial aggregate that was consistent with the known geology. Although time-domain electromagnetic sounding did not work well at this site, it has worked well at other sites with different geology. All of these geophysical methods complement traditional methods of geologic characterization such as drilling.

Ellefsen, K. J.; Burton, B. L.; Lucius, J. E.; Haines, S. S.; Fitterman, D. V.; Witty, J. A.; Carlson, D.; Milburn, B.; Langer, W. H.

2007-01-01

31

The influence of time on the magnetic properties of late Quaternary periglacial and alluvial surface and buried soils along the Delaware River, USA  

NASA Astrophysics Data System (ADS)

Magnetic susceptibility of soils has been used as a proxy for rainfall, but other factors can contribute to magnetic enhancement in soils. Here we explore influence of century- to millennial-scale duration of soil formation on periglacial and alluvial soil magnetic properties by assessing three terraces with surface and buried soils ranging in exposure ages from <0.01 to ~16 kyrs along the Delaware River in northeastern USA. The A and B soil horizons have higher Xlf, Ms, and S-ratios compared to parent material, and these values increase in a non-linear fashion with increasing duration of soil formation. Magnetic remanence measurements show a mixed low- and high-coercivity mineral assemblage likely consisting of goethite, hematite and maghemite that contributes to the magnetic enhancement of the soil. Room-temperature and low-temperature field-cooled and zero field-cooled remanence curves confirm the presence of goethite and magnetite and show an increase in magnetization with increasing soil age. These data suggest that as the Delaware alluvial soils weather, the concentration of secondary ferrimagnetic minerals increase in the A and B soil horizons. We then compared the time-dependent Xlf from several age-constrained buried alluvial soils with known climate data for the region during the Quaternary. Contradictory to most studies that suggest a link between increases in magnetic susceptibility and high moisture, increased magnetic enhancement of Delaware alluvial soils coincides with dry climate intervals. Early Holocene enhanced soil Xlf (9.5 – 8.5 ka) corresponds with a well-documented cool-dry climate episode. This relationship is probably related to less frequent flooding during dry intervals allowing more time for low-coercive pedogenic magnetic minerals to form and accumulate, which resulted in increased Xlf. Middle Holocene enhanced Xlf (6.1 – 4.3 ka) corresponds with a transitional wet/dry phase and a previously documented incision event.......

Stinchcomb, Gary; Peppe, Daniel

2014-08-01

32

Late Quaternary (Weichselian) alluvial history and neotectonic control on fluvial landscape development in the southern Körös plain, Hungary  

Microsoft Academic Search

Four drill cores and a clay pit section have been examined in the southern part of the Körös plain to understand the history and controls on alluvial sedimentation for the last ~40ka. Four facies groups were identified, such as channel, channel margin, floodplain and floodbasin with seven distinctive facies. Magnetic susceptibility and mineralogy have further characterized the sedimentary facies indicating

Annamária Nádor; Rajiv Sinha; Árpád Magyari; Sampat K. Tandon; Zsófia Medzihradszky; Zoltán Unger; Ashish Singh

2011-01-01

33

Late Quaternary marginal marine deposits and palaeoenvironments from northeastern Buenos Aires Province, Argentina: A review  

Microsoft Academic Search

The late Quaternary marginal marine deposits along eastern Argentina (Southwestern Atlantic) are reviewed according to our present knowledge. In the northeastern coastal area of Buenos Aires Province they have been assigned to a series of transgressions and regressions ranging from the late Pliocene to the late Quaternary. The most widely accepted model is Frenguelli's (1957) classical chronostratigraphical scheme of: ‘Belgranense’,

M. L. Aguirre; R. C. Whatley

1995-01-01

34

The Tabernas alluvial fan and lake system, southeast Spain: applications of mineral magnetic and pedogenic iron oxide analyses towards clarifying the Quaternary sediment sequences  

NASA Astrophysics Data System (ADS)

Mineral magnetic and soil iron oxide data are applied to questions of relative age correlation of alluvial fans and lake sediments in the Tabernas basin, southeast Spain, within a context of interaction between tectonics and climatic change. Within the Tabernas basin, the sediment sequences and morphological evolution of late Quaternary alluvial fans suggest climatic change as the primary control. The fans toe out at the upper margins of a former lake, created in response to tectonic uplift. Magnetic and iron oxide data from soils, particularly dithionite-extractable iron (Fe d), and frequency-dependent magnetic susceptibility ( ?FD%) accord with the relative age relationships suggested by more conventional field-based geomorphic observations. Magnetic data from the lake sediments suggest the main provenance characteristics of the sediments, but also reveal a shift in sediment sources towards the end of the lake period (probably during the late Pleistocene) to sediment supplied from a more active fluvial system from soil erosion within the Sierra de los Filabres part of the catchment. Hence, although the locations of the fans and the existence of the lake relate primarily to tectonics, the fan sequences themselves appear to be primarily climatically controlled, and there is evidence of a climatic influence over the source of sediment input into the lake during the late Pleistocene.

Harvey, Adrian M.; Foster, Gez; Hannam, Jack; Mather, Anne E.

2003-02-01

35

Static and dynamic characterization of alluvial deposits in the Tiber River Valley: New data for assessing potential ground motion in the City of Rome  

Microsoft Academic Search

The paper presents the results of a case study conducted on the Holocene alluvial deposits of the Tiber River valley, in the city of Rome. The main test site selected for the study, Valco S. Paolo, is located about 2 km South of Rome's historical centre. The alluvial deposits were dynamically characterized in a comprehensive way via site investigations and

F. Bozzano; A. Caserta; A. Govoni; F. Marra; S. Martino

2008-01-01

36

Geologic Characterization of Young Alluvial Basin-Fill Deposits from Drill Hole Data in Yucca Flat, Nye County, Nevada  

Microsoft Academic Search

Yucca Flat is a topographic and structural basin in the northeastern part of the Nevada Test Site (NTS) in Nye County, Nevada, that has been the site of numerous underground nuclear tests; many of these tests occurred within the young alluvial basin-fill deposits. The migration of radionuclides to the Paleozoic carbonate aquifer involves passage through this thick, heterogeneous section of

Donald S. Sweetkind; Ronald M. Drake II

2007-01-01

37

Origin and depositional model of Wadi Al-Batin and its associated alluvial fan, Saudi Arabia and Kuwait  

Microsoft Academic Search

Wadi Al-Batin alluvial fan, which extends northeastward from Hafar Al-Batin in Saudi Arabia to cover parts of Kuwait and southwestern Iraq, represents the largest of several other non-active fans in central and south Arabia. Evidence put forward suggests that, like other comparable deposits of varying age in the Arabian Peninsula, the Al-Batin fan was deposited following downdip breaching of a

Jawad S. Al-Sulaimi; A. F. Pitty

1995-01-01

38

Unconfined alluvial flow processes: Recognition and interpretation of their deposits, and the significance for palaeogeographic reconstruction  

NASA Astrophysics Data System (ADS)

Palaeogeographic interpretation of the sedimentary rock record depends on correct recognition from the preserved evidence of the processes responsible for transporting and depositing the sediment. This in turn depends on robust knowledge transfer from previous workers, and the successful exchange of ideas between workers requires consistent use of a well-defined vocabulary. We have identified serious breakdowns in all these interpretation steps in the case of terrestrial unconfined flow and its deposits, and these failures are leading to unreliable environmental and climatic interpretation. This is significant because such alluvial deposits commonly form a majority of the rock record of continental environments. Working from the basic principles of geomorphology and fluid dynamics, we have undertaken a wide-ranging analysis of the nature of out-of-channel flow and from this make predictions about the characteristics of its deposits. We identify the range of possible locations and conditions that lead to the development of unconfined flow, review the processes operating in each case, and examine the range of lithological features that can be produced by these processes. This allows us to evaluate the reliability of the criteria claimed for identification of out-of-channel flow deposits, and examine how our new insights might alter palaeoclimatic and palaeogeographic reconstructions published previously by others. The sedimentary record of unconfined flows is much more diverse and complex than usually portrayed. The received wisdom that the record of unconfined flow consists solely of upwards-fining thin beds produced from shallow waning flows is shown to be flawed. A wide range of lithofacies are possible, and the variation in both flow steadiness and uniformity needs to be taken into account. The previously published criteria for recognition of flows of this type are not diagnostic of process or location; unconfined flow deposits cannot reliably be identified from grain size or bed thickness. Similar lithofacies may develop in a wide range of geomorphic and climatic settings because the deposits solely reflect the local flow conditions and sediment availability. We recommend that the terms 'sandflat' and 'sheetflood' should not be used in sedimentological accounts because there is no longer a safe informal usage for either; contradictory application of these terms, and lack of robust definitions, is leading to significant misunderstanding of palaeogeography and process. Our analysis should improve reconstruction of past terrestrial environments because it reveals more clearly the true variety of possibilities for the occurrence of unconfined flow and the resultant deposits. Enhanced understanding of the inherent uncertainties, and realisation of the wider range of plausible alternative explanations, should help resolve apparent contradictions with independent indicators of climate or geographic position.

North, Colin P.; Davidson, Stephanie K.

2012-02-01

39

Testing a model of alluvial deposition in the Middle Son Valley, Madhya Pradesh, India — IRSL dating of terraced alluvial sediments and implications for archaeological surveys and palaeoclimatic reconstructions  

NASA Astrophysics Data System (ADS)

Over the past three decades, the Middle Son Valley, Madhya Pradesh, India has been the focus of archaeological, geological, and palaeoenvironmental investigations that aim to reconstruct regional climate changes in the Late Pleistocene and to understand the effects of the ˜74 ka Toba super-eruption on ecosystems and human populations in northern India. The most recently published model of alluvial deposition for the Middle Son Valley subdivides its alluvium into five stratigraphic formations, each associated with a specific artefact assemblage. In this study, new cross-valley topographic profiles, field observations and infrared stimulated luminescence (IRSL) age estimates are used to refine this model south of the Rehi-Son River confluence. These data not only provide insights into the fluvial history of the Son River and its response to changes in palaeoclimate, but will also inform future archaeological surveys by constraining the geomorphic context of surficial and excavated artefacts in the area.

Neudorf, C. M.; Roberts, R. G.; Jacobs, Z.

2014-04-01

40

Palaeoenvironmental reconstruction of a middle Miocene alluvial fan to cyclic shallow lacustrine depositional system  

E-print Network

sandstone and mudstone, the latter exhibiting incipient pedogenic features; (2) distal alluvial fan facies. The development of the basin was constrained by gradual alluvial fan aggradation. Additional support a clear trend of d18 O Sedimentology (2003) 50, 211­236 � 2003 International Association

Utrecht, Universiteit

41

Hydrogeologic characteristics of the alluvial aquifer and adjacent deposits of the Fountain Creek valley, El Paso County, Colorado  

USGS Publications Warehouse

The alluvial aquifer in Fountain Creek Valley between Colorado Springs and Widefield is the source for several public-supply systems. Because of the importance of this aquifer, defining aquifer boundaries, areas where underflow occurs, and where Fountain Creek is hydraulically connected to the aquifer will greatly add to the understanding of the alluvial aquifer and management of the public- supply systems. Bedrock altitude, water-table altitude for October 1991, saturated thickness for October 1991, selected hydrogeologic sections in the alluvial aquifer and adjacent deposits of the Fountain Creek Valley, and estimated underflow rates are mapped or tabulated for the area between Colorado Springs and Widefield, Colorado. Results from test drilling indicate that the bedrock surface is highly irregular and that several ridges and buried channels exist in the study area. These features affect the direction of ground-water flow on a local scale. In places, a shale ridge prevents exchange of water between Fountain Creek and the aquifer. Generally, ground water flowed toward Fountain Creek during the study (June 1991 to September 1992) in response to relatively high hydraulic heads in the aquifer and the steep gradients on the boundaries of the study area. Water levels, which were measured monthly, varied little during the study, except in areas near pumping wells or adjacent to Fountain Creek. Hydraulic-conductivity values, estimated from 30 bail tests in wells completed in the alluvial aquifer, were used to determine underflow across the saturated boundaries of the alluvial aquifer. Estimated hydraulic-conductivity values range from 1 to about 1,300 feet per day; the larger values occur in the buried channel of the alluvial aquifer and the smaller values occur near the boundaries of the saturated alluvium. Estimated underflow into the study area exceeded underflow out of the study area by about 10 times. Gain-loss investigations along Fountain Creek indicated that the creek primarily was gaining during the study.

Radell, Mary Jo; Lewis, Michael E.; Watts, Kenneth R.

1994-01-01

42

Digital data sets that describe aquifer characteristics of the alluvial and terrace deposits along the Beaver-North Canadian River from the panhandle to Canton Lake in northwestern Oklahoma  

USGS Publications Warehouse

ARC/INFO export and nonproprietary format files This diskette contains digitized aquifer boundaries and maps of of hydraulic conductivity, recharge, and ground-water level elevation contours for the alluvial and terrace deposits along the alluvial and terrace deposits along the Beaver-North Canadian River from the panhandle to Canton Lake in northwestern Oklahoma. Ground water in 830 square miles of the Quaternary-age alluvial and terrace aquifer is an important source of water for irrigation, industrial, municipal, stock, and domestic supplies. The aquifer consists of poorly sorted, fine to coarse, unconsolidated quartz sand with minor amounts of clay, silt, and basal gravel. The hydraulically connected alluvial and terrace deposits unconformably overlie the Tertiary-age Ogallala Formation and Permian-age formations. Most of the lines in the aquifer boundary and recharge data sets and some of the lines in the hydraulic conductivity data set were extracted from a published digital surficial geology data set based on a scale of 1:250,000. The ground-water elevation contours and some of the lines for the aquifer boundary, hydraulic conductivity, and recharge data sets were digitized from a ground-water modeling report about the aquifer published at a scale of 1:250,000. The hydraulic conductivity values and recharge rates also are from the ground-water modeling report. The data sets are provided in both nonproprietary and ARC/INFO export file formats. Ground-water flow models are numerical representations that simplify and aggregate natural systems. Models are not unique; different combinations of aquifer characteristics may produce similar results. Therefore, values of hydraulic conductivity and recharge used in the model and presented in this data set are not precise, but are within a reasonable range when compared to independently collected data.

Adams, G.P.; Runkle, D.L.; Rea, Alan

1997-01-01

43

Resolving structural influences on water-retention properties of alluvial deposits  

USGS Publications Warehouse

With the goal of improving property-transfer model (PTM) predictions of unsaturated hydraulic properties, we investigated the influence of sedimentary structure, defined as particle arrangement during deposition, on laboratory-measured water retention (water content vs. potential [??(??)]) of 10 undisturbed core samples from alluvial deposits in the western Mojave Desert, California. The samples were classified as having fluvial or debris-flow structure based on observed stratification and measured spread of particle-size distribution. The ??(??) data were fit with the Rossi-Nimmo junction model, representing water retention with three parameters: the maximum water content (??max), the ??-scaling parameter (??o), and the shape parameter (??). We examined trends between these hydraulic parameters and bulk physical properties, both textural - geometric mean, Mg, and geometric standard deviation, ??g, of particle diameter - and structural - bulk density, ??b, the fraction of unfilled pore space at natural saturation, Ae, and porosity-based randomness index, ??s, defined as the excess of total porosity over 0.3. Structural parameters ??s and Ae were greater for fluvial samples, indicating greater structural pore space and a possibly broader pore-size distribution associated with a more systematic arrangement of particles. Multiple linear regression analysis and Mallow's Cp statistic identified combinations of textural and structural parameters for the most useful predictive models: for ??max, including Ae, ??s, and ??g, and for both ??o and ??, including only textural parameters, although use of Ae can somewhat improve ??o predictions. Textural properties can explain most of the sample-to-sample variation in ??(??) independent of deposit type, but inclusion of the simple structural indicators Ae and ??s can improve PTM predictions, especially for the wettest part of the ??(??) curve. ?? Soil Science Society of America.

Winfield, K. A.; Nimmo, J. R.; Izbicki, J. A.; Martin, P. M.

2006-01-01

44

Stratigraphy of the late Quaternary deposits of the northern Canterbury Plains, New Zealand  

Microsoft Academic Search

Stratigraphic correlations of late Quaternary subsurface deposits of the Canterbury Plains, New Zealand, are revised and defined using well logs, radiocarbon dates, and pollen analyses. Three new members—Bleak House, Riverview, and Courtenay—are proposed for the postglacial fluvial Springston Formation. Riccarton Gravel (last glaciation) and Bromley Formation (last interglaciation) are revised. Five new formations are defined for coastal subsurface deposits to

L. J. Brown; D. D. Wilson; N. T. Moar; D. C. Mildenhall

1988-01-01

45

Quaternary International 117 (2004) 2734 Chemical weathering of the loess deposits in the lower  

E-print Network

the last decade, chemical weathering and paleoclimatic changes recorded in Chinese Loess deposits duringQuaternary International 117 (2004) 27­34 Chemical weathering of the loess deposits in the lower, and considerable weathering of some silicate minerals, especially plagioclase. Chemical mobility of Ca

Yang, Shouye

46

Ground water in the alluvial deposits of Cottonwood Creek Basin, Oklahoma  

USGS Publications Warehouse

Cottonwood Creek basin is a 377 square mile area in central Oklahoma. The rim of the basin has altitudes as high as 1,300 feet, and the mouth is at an altitude of 910. Deposits of Quaternary age consist of alluvium along the stream courses and high terrace deposits along the southern rim of the basin. The alluvium contains a high percentage of clay and silt, ranges in thickness from a few inches to 40 feet, and underlies about 36 square miles of the basin. Sandstone, siltstone, and shale of Permian age, which form the bedrock, consist of the Garber sandstone along the eastern edge, the Hennessey shale through the central part, and Flowerpot shale along the western edge. Replenishment of water in the alluvium is from precipitation, lateral seepage and runoff from adjoining areas, and infiltration from the stream channels during high flows. The major use of ground water in the alluvium is transpiration by cottonwood and willow trees. Virtually no water is withdrawn from the alluvium by wells. (available as photostat copy only)

Stacy, B.L.

1960-01-01

47

Stratigraphy and the depositional environments of the Plio-Quaternary deposits of the Eastern Marmara Region, NW Turkey  

NASA Astrophysics Data System (ADS)

The study area is located along the western part of the North Anatolian Fault zone between the Gulf of Izmit and Adapazari and is represented by an east-west trending narrow depression. The depression is filled by Late Pliocene and younger deposits. Stratigraphy and depositional characteristics of this sedimentary fill shed light onto the geological evolution of North Anatolian Fault in the region. The sediments filling the Gulf of Izmit were examined mainly by seismic profiles and some borehole data. Seismic data were obtained by Sismik-1 vessel of General Directorate of Mineral Research and Exploration. Within the Gulf of Izmit; anoxic, brackish marine, brackish marine-deltaic and marine sediments have been deposited during the Late Pliocene, Early-Middle Pleistocene, Late Pleistocene and Late Pleistocene-Holocene periods respectively. In the onshore part to the east, Izmit-Adapazari depression, thick alluvial fan sediments (~400 m) have been deposited at the same time. These sediments consist of fluvial and alluvial fan deposits, mainly fed from the southern areas. Alluvial fan deposits can be separated into proximal, medial and distal parts from south to north. Coarse grained fanglomerates in the proximal parts and fine grained mudstones and local swamp and flood-plain deposits in the distal parts can be recognized. Fossils from the lower parts of these sediments indicate a late Pliocene-Pleistocene age. Palaeocurrent measurements and facies distribution of the fan deposits indicate that the depression started to form under the control of NE-SW and NW-SE trending faults having dominantly normal component since Late Pliocene. This period is characterized by the development of series of pull-apart basins. Recents sediments are still depositing in the Gulf of Izmit and the Izmit- Adapazari depression and cut by E-W trending active branches of the North Anatolian Fault.

Erturac, M. K.; Tari, U.; Tuysuz, O.; Kurt, H.; Demirbag, E.

2003-04-01

48

Reconnaissance investigation of the alluvial gold deposits in the North Takhar Area of Interest, Takhar Province, Afghanistan  

USGS Publications Warehouse

This study is a reconnaissance assessment of the alluvial gold deposits of the North Takhar Area of Interest (AOI) in Takhar Province, Afghanistan. Soviet and Afghan geologists collected data and calculated the gold deposit reserves in Takhar Province in the 1970s, prior to the development of satellite-based remote-sensing platforms and new methods of geomorphic mapping. The purpose of this study was to integrate new mapping techniques with previously collected borehole sampling and concentration sampling data and geomorphologic interpretations to reassess the alluvial gold placer deposits in the North Takhar AOI. Through a combination of historical borehole and cross-section data and digital terrain modeling, the Samti, Nooraba-Khasar-Anjir, and Kocha River placer deposits were reassessed. Resource estimates were calculated to be 20,927 kilograms (kg) for Samti, 7,626 kg for Nooraba-Khasar-Anjir, 160 kg for the mouth of the Kocha, 1,047 kg for the lower Kocha, 113 kg for the middle Kocha, and 168 kg for the upper Kocha. Previous resource estimates conducted by the Soviets for the Samti and Nooraba-Khasar-Anjir deposits estimated 30,062 kg and 802 kg of gold, respectively. This difference between the new estimates and previous estimates results from the higher resolution geomorphic model and the interpretation of areas outside of the initial work zone studied by Soviet and Afghan geologists.

Chirico, Peter G.; Malpeli, Katherine C.; Moran, Thomas W.

2013-01-01

49

Hierarchical dynamic stratigraphy in various Quaternary gravel deposits, Rhine glacier area (SW Germany): implications for hydrostratigraphy  

Microsoft Academic Search

The approach of ‘dynamic stratigraphy’ aims to understand genetic processes that form stratigraphic units in a hierarchy of spatial and temporal scales. This approach was used to investigate Quaternary gravel deposits in terms of their sedimentology and in order to characterize the various sedimentary units in terms of their hydrogeological properties. Facies analysis within 62 gravel pits, laboratory permeability measurements

Jürgen Heinz; Thomas Aigner

2003-01-01

50

Alluvial Fans on Mars  

NASA Technical Reports Server (NTRS)

Moore and Howard [1] reported the discovery of large alluvial fans in craters on Mars. Their initial survey from 0-30 S found that these fans clustered in three distinct regions and occurred at around the +1 km MOLA defined Mars datum. However, due to incomplete image coverage, Moore and Howard [1]could not conduct a comprehensive survey. They also recognized, though did not quantitatively address, gravity scaling issues. Here, we briefly discuss the identification of alluvial fans on Mars, then consider the general equations governing the deposition of alluvial fans and hypothesize a method for learning about grain size in alluvial fans on Mars.

Kraal, E. R.; Moore, J. M.; Howard, A. D.; Asphaug, E. A.

2005-01-01

51

Isotope geochemistry of Quaternary deposits from the arid lands in northern China  

Microsoft Academic Search

Quaternary deposits of various types (lacustrine, desert sand, river, loess and loess-like deposits) from the southwestern Tarim Basin, North Tianshan, northwest China and the central Loess Plateau exhibit an epsilonNd(0) range from -5 to -12.8 and a Sm-147\\/Nd-144 range from 0.110 to 0.140. Their Nd-depleted mantle model ages are between 1.50 and 1.92 Ga, with a mean value of 1.7

Cong-Qiang Liu; Akimasa Masuda; Akihiko Okada; Sadayo Yabuki; Zi-Li Fan

1994-01-01

52

Magnetic Properties of Quaternary Deposits, Kenai Peninsula, Alaska -- Implications for Aeromagnetic Anomalies of Upper Cook Inlet  

USGS Publications Warehouse

We measured magnetic susceptibilities of exposed Quaternary deposits on several beach cliffs and river banks on the Kenai Peninsula near Soldotna, Alaska. Data, descriptions, and photos from nine sites are included in this report. The mean susceptibility for Quaternary materials in this region is approximately 2.5 x 10-3 SI units. This is sufficiently magnetic to produce subtle aeromagnetic anomalies such as those observed to correlate with topographic features in the region of the measurements. The highest susceptibilities measured (greater than 20 x 10-3 SI units) may help, at least in part, to explain moderate amplitude aeromagnetic anomalies observed elsewhere in Cook Inlet, particularly those relating to structures showing Quaternary movement. Comparison of measured beach cliff susceptibility and susceptibility predicted from idealized formulas and two-dimensional cliff models suggests that measured susceptibilies underestimate true bulk susceptibility by 20 percent to 50 percent in this region.

Saltus, R. W.; Haeussler, P. J.

2004-01-01

53

Late Holocene Soil Stratigraphy and Geochronology of Alluvial Sedimentation in the Sonoran Desert, Arizona  

NASA Astrophysics Data System (ADS)

The integration of soil stratigraphic investigations and radiocarbon dating at two sites in combination with geomorphic mapping at scales of 1:50k and 1:5k offer insight to the timing and magnitude of alluvial sedimentation during the late Holocene within the Sonoran Desert near Yuma, Arizona. Mapping at 1:50k was performed over an area of 3400 km2 and alluvial landforms were labeled Qf1 to Qf5, from oldest to youngest, using 1- and 5-meter resolution satellite imagery within the U.S. Army Yuma Proving Ground (YPG). Approximately 70% of the identified landforms within YPG are Quaternary alluvial fans, alluvial plains, and active washes, whereas the other 30% consist of mountain highlands, pediments, and badlands. In the southwest portion of YPG near Muggins Mountains, alluvial fan terraces (Qf4) positioned 0.5 m above active washes are characterized as having moderate bar-and-swale microtopography, moderately developed desert pavement, and a Av/ Bw/ Cky/ Cky1/ Cky2/ Cky3 gravelly soil profile. A large piece of charcoalized Ironwood ( Olneya tesota) was recovered from a depth of 0.75 m and yielded three AMS 14C dates that range from 3330 to 2860 cal yr B.P. Geomorphic mapping at a scale of 1:5k indicates that in an area of 25 km2 at the site, the distribution of late Holocene alluvial fan terraces comprise 17% of the surrounding Quaternary alluvium. Similar aged alluvial features were observed about 70 km to the north near South Trigo Peak at YPG. Terraces of a broad and flat alluvial plain positioned 0.5 m above active channels are characterized as having moderate bar- and-swale microtopography, poorly developed desert pavement, and a AC/ C/ Bwkb1/ Bwk1b2/ Bwk2b2/ BCkb2/ Bwkb3 sandy soil profile. A terrestrial gastropod shell ( Lymnea sp.) fragment was recovered from a depth of 0.5 m and yielded an AMS 14C date of 2360-2310 cal yr B.P. Additional geomorphic mapping at 1:5k shows that in an area of 30 km2, the distribution of late Holocene alluvial plain terraces and equivalent alluvial fans include 35% of the surrounding Quaternary alluvium. Of the total Quaternary alluvium identified at 1:50k, 10% of the landforms consist of gravelly alluvial fans and sandy alluvial plains deposited between 3330 and 2310 cal yr B.P. The numerical ages and associated soil development provide evidence of regional alluvial sedimentation near Yuma, Arizona, and provides well constrained geomorphic data for paleoclimatic modeling in the Sonoran Desert during the late Holocene.

Bacon, S. N.; McDonald, E. V.; Dalldorf, G. K.; Caldwell, T. G.

2007-12-01

54

Infra-red stimulated luminescence ages from aeolian sand and alluvial fan deposits from the eastern Mojave Desert, California  

NASA Astrophysics Data System (ADS)

Infra-red stimulated luminescence (IRSL) from coarse-grained (180-212 ?m) potassium-rich feldspars has been used to date deposits associated with the western piedmont of the Providence Mountains in the eastern Mojave Desert. These deposits consist of alluvial fans, aeolian sand, which exists in the form of lenses within the fan matrices, and sand from the Kelso dune field which abuts the distal end of the fan sequence. Deposition and subsequent stabilisation of these sand units appears to have occurred in both aird and intermittent climates associated with pluvial phases during the Holocene and Late Pleistocene. Ages of 6600 ± 870 and 7840 ± 1790 years were obtained from dune sand bracketing the Mazama ash at Skull Creek Dunes, Oregon, giving an independent age control on the single aliquot IRSL method which was used on the Mojave samples.

Clarke, M. L.

55

Stratigraphy and Subaerial Exposure of Late Quaternary Tidal Deposits in Haenam Bay, Korea (South-eastern Yellow Sea)  

Microsoft Academic Search

Late Quaternary stratigraphy of the coastal deposits in Haenam Bay, south-western coast of Korea (south-eastern Yellow Sea) consists of two depositional units: a Holocene intertidal deposit (Unit I), and an underlying Late Pleistocene tidal deposit (Unit II), both of which are distinguished by distinct unconformity. The yellowish colour and more consolidated and oxidized nature are characteristics of the sediments in

Y. A. Park; D. I. Lim; B. K. Khim; J. Y. Choi; S. J. Doh

1998-01-01

56

Late Quaternary eolian dust in surficial deposits of a Colorado Plateau grassland: Controls on distribution and ecologic effects  

E-print Network

Late Quaternary eolian dust in surficial deposits of a Colorado Plateau grassland: Controls-arid grassland on the central Colorado Plateau, southwestern United States (Fig. 1). The current work builds

Ahmad, Sajjad

57

Evolution of late Quaternary deposits on the inner shelf of the South Sea of Korea  

Microsoft Academic Search

High-resolution (3.5 kHz) seismic profiles and sediment samples were analysed to delineate the shallow seismic stratigraphy of late Quaternary deposits in the central part of the Korean South Sea. The stratigraphy above the acoustic basement is represented by three distinct sedimentary sequences separated by erosional boundaries. The upper sequence (A) has an acoustically semi-transparent signature usually without distinct internal reflectors

Soo Chul Park; Seok Ku Hong; Dae Chul Kim

1996-01-01

58

A silicified bird from Quaternary hot spring deposits  

PubMed Central

The first avian fossil recovered from high-temperature hot spring deposits is a three-dimensional external body mould of an American coot (Fulica americana) from Holocene sinters of Yellowstone National Park, Wyoming, USA. Silica encrustation of the carcass, feathers and colonizing microbial communities occurred within days of death and before substantial soft tissue degradation, allowing preservation of gross body morphology, which is usually lost under other fossilization regimes. We hypothesize that the increased rate and extent of opal-A deposition, facilitated by either passive or active microbial mediation following carcass colonization, is required for exceptional preservation of relatively large, fleshy carcasses or soft-bodied organisms by mineral precipitate mould formation. We suggest physico-chemical parameters conducive to similar preservation in other vertebrate specimens, plus distinctive sinter macrofabric markers of hot spring subenvironments where these parameters are met. PMID:16024344

Channing, Alan; Schweitzer, Mary Higby; Horner, John R; McEneaney, Terry

2005-01-01

59

A silicified bird from Quaternary hot spring deposits.  

PubMed

The first avian fossil recovered from high-temperature hot spring deposits is a three-dimensional external body mould of an American coot (Fulica americana) from Holocene sinters of Yellowstone National Park, Wyoming, USA. Silica encrustation of the carcass, feathers and colonizing microbial communities occurred within days of death and before substantial soft tissue degradation, allowing preservation of gross body morphology, which is usually lost under other fossilization regimes. We hypothesize that the increased rate and extent of opal-A deposition, facilitated by either passive or active microbial mediation following carcass colonization, is required for exceptional preservation of relatively large, fleshy carcasses or soft-bodied organisms by mineral precipitate mould formation. We suggest physico-chemical parameters conducive to similar preservation in other vertebrate specimens, plus distinctive sinter macrofabric markers of hot spring subenvironments where these parameters are met. PMID:16024344

Channing, Alan; Schweitzer, Mary Higby; Horner, John R; McEneaney, Terry

2005-05-01

60

Soil Development and Relative Age Dating of Quaternary Landslide Deposits in the Boulder-Lyons Front Range area  

Microsoft Academic Search

An analysis of soil development on Quaternary landslide deposits provides a useful tool for estimating the age of the deposits. Certain requirements must be met for this approach to be successfully employed: 1. the analyzed soil must be one that has developed on material that was freshly exposed or deposited at the time the mass movement occurred; and, 2. soil

Matthew C. Larsen

61

Origin and depositional model of Wadi Al-Batin and its associated alluvial fan, Saudi Arabia and Kuwait  

NASA Astrophysics Data System (ADS)

Wadi Al-Batin alluvial fan, which extends northeastward from Hafar Al-Batin in Saudi Arabia to cover parts of Kuwait and southwestern Iraq, represents the largest of several other non-active fans in central and south Arabia. Evidence put forward suggests that, like other comparable deposits of varying age in the Arabian Peninsula, the Al-Batin fan was deposited following downdip breaching of a scarp barrier by a large paleoriver further to the west which once flowed southward down the full length of the Arabian Peninsula. The downdip breaching model offers an explanation of how the Dibdibba gravels were introduced into Kuwait. It is postulated that the present southeasterly course of Tigris-Euphrates rivers to the head of the Arabian Gulf was the last of the easterly diversions of the lower courses of the southward-flowing paleoriver, as its southern end shifted progressively by a sequence of lateral breaches through the Central Arabian scarplands. It is the postulated existence of this huge former drainage system which is seen as the fundamental explanation for the occurrence of the Dibdibba Formation in Kuwait and comparable gravels elsewhere on the eastern flank of the Arabian Peninsula. After the initial phases of deposition of Al-Batin alluvial fan, its surface was dissected by floods from a reduced catchment area, no longer carrying the same sediment load and, therefore, capable of eroding the fan. Dissection of the fan surface continued until the present Wadi AI-Batin became sufficiently incised into the underlying Tertiary bedrock to serve as a permanent outlet. This led to the transport and secondary concentration of post-dissection gravels along the perimeter of the ancient fan.

Al-Sulaimi, Jawad S.; Pitty, A. F.

1995-07-01

62

Quaternary silicic pyroclastic deposits of Atitla??n Caldera, Guatemala  

USGS Publications Warehouse

Atitla??n caldera has been the site of several silicic eruptions within the last 150,000 years, following a period of basalt/andesite volcanism. The silicic volcanism began with 5-10 km3 of rhyodacites, erupted as plinian fall and pyroclastic flows, about 126,000 yr. B.P. At 85,000 yr. B.P. 270-280 km3 of compositionally distinct rhyolite was erupted in the Los Chocoyos event which produced widely dispersed, plinian fall deposits and widespread, mobile pyroclastic flows. In the latter parts of this eruption rhyodacite and minor dacite were erupted which compositionally resembled the earliest silicic magmas of the Atitla??n center. As a result of this major eruption, the modern Atitla??n (III) caldera formed. Following this event, rhyodacites were again erupted in smaller (5-13 km3) volumes, partly through the lake, and mafic volcanism resumed, forming three composite volcanoes within the caldera. The bimodal mafic/silicic Atitla??n volcanism is similar to that which has occurred elsewhere in the Guatemalan Highlands, but is significantly more voluminous. Mafic lavas are thought to originate in the mantle, but rise, intrude and underplate the lower crust and partly escape to the surface. Eventually, silicic melts form in the crust, possibly partly derived from underplated basaltic material, rise, crystallize and erupt. The renewed mafic volcanism could reflect either regional magmato-tectonic adjustment after the large silicic eruption or the onset of a new cycle. ?? 1987.

Rose, W.I.; Newhall, C.G.; Bornhorst, T.J.; Self, S.

1987-01-01

63

Characteristics of ejecta and alluvial deposits at Meteor Crater, Arizona and Odessa Craters, Texas: Results from ground penetrating radar  

NASA Technical Reports Server (NTRS)

Previous ground penetrating radar (GRP) studies around 50,000 year old Meteor Crater revealed the potential for rapid, inexpensive, and non-destructive sub-surface investigations for deep reflectors (generally greater than 10 m). New GRP results are summarized focusing the shallow sub-surfaces (1-2 m) around Meteor Crater and the main crater at Odessa. The following subject areas are covered: (1) the thickness, distribution, and nature of the contact between surrounding alluvial deposits and distal ejecta; and (2) stratigraphic relationships between both the ejecta and alluvium derived from both pre and post crater drainages. These results support previous conclusions indicating limited vertical lowering (less than 1 m) of the distal ejecta at Meteor Crater and allow initial assessment of the gradational state if the Odessa craters.

Grant, J. A.; Schultz, P. H.

1991-01-01

64

Luminescence ages for alluvial-fan deposits in Southern Death Valley: Implications for climate-driven sedimentation along a tectonically active mountain front  

USGS Publications Warehouse

Controversy exists over whether alluvial-fan sedimentation along tectonically active mountain fronts is driven by climatic changes or tectonics. Knowing the age of sedimentation is the key to understanding the relationship between sedimentation and its cause. Alluvial-fan deposits in Death Valley and throughout the arid southwestern United States have long been the subjects of study, but their ages have generally eluded researchers until recently. Most mapping efforts have recognized at least four major relative-age groupings (Q1 (oldest), Q2, Q3, and Q4 (youngest)), using observed changes in surface soils and morphology, relation to the drainage net, and development of desert pavement. Obtaining numerical age determinations for these morphologic stages has proven challenging. We report the first optically stimulated luminescence (OSL) ages for three of these four stages deposited within alluvial-fans along the tectonically active Black Mountains of Death Valley. Deposits showing distinct, remnant bar and swale topography (Q3b) have OSL ages from 7 to 4 ka., whereas those with moderate to poorly developed desert pavement and located farther above the active channel (Q3a) have OSL ages from 17 to 11 ka. Geomorphically older deposits with well-developed desert pavement (Q2d) have OSL ages ???25 ka. Using this OSL-based chronology, we note that alluvial-fan deposition along this tectonically active mountain front corresponds to both wet-to-dry and dry-to-wet climate changes recorded globally and regionally. These findings underscore the influence of climate change on alluvial fan deposition in arid and semi-arid regions. ?? 2007 Elsevier Ltd and INQUA.

Sohn, M. F.; Mahan, S. A.; Knott, J. R.; Bowman, D. D.

2007-01-01

65

Survey of Martian Alluvial Fans  

NASA Astrophysics Data System (ADS)

Recent higher resolution images of the Martian surface reveal another complex geomorphic surface process - alluvial fans. Alluvial fans composed of water-transported, loose sediment deposited as the flow moves from steep, eroding terrain to low-gradient depositional basins. Martian alluvial fans are concentrated along crater rims where they erode into the higher surround topography depositing sediment into the crater interior. Initial work by Moore and Howard [2004] examined some of these fans in a band from 0-30 S. Their initial results included fan statistics, such as area and slope, and indicated that the fans were clustered in discrete areas. However, this survey was hampered by incomplete image coverage. We present the progress of our continuing, planet wide survey of alluvial fans. Specifically we focus on understanding if alluvial fans are indeed clustered in particular areas and if so, why. In addition, we expand fan statistics to include a comparison of fan volume to eroded area.

Kraal, E. R.; Moore, J.; Asphaug, E.; Howard, A.

2004-12-01

66

Late Quaternary depositional history, Holocene sea-level changes, and vertical crustal movement, southern San Francisco Bay, California  

USGS Publications Warehouse

Sediments collected for bridge foundation studies at southern San Francisco Bay, Calif., record estuaries that formed during Sangamon (100,000 years ago) and post-Wisconsin (less than 10,000 years ago) high stands of sea level. The estuarine deposits of Sangamon and post-Wisconsin ages are separated by alluvial and eolian deposits and by erosional unconformities and surfaces of nondeposition, features that indicate lowered base levels and oceanward migrations of the shoreline accompanying low stands of the sea. Estuarine deposits of mid-Wisconsin age appear to be absent, suggesting that sea level was not near its present height 30,000–40,000 years ago in central California. Holocene sea-level changes are measured from the elevations and apparent 14C ages of plant remains from 13 core samples. Uncertainties of ±2 to ±4 m in the elevations of the dated sea levels represent the sum of errors in determination of (1) sample elevation relative to present sea level, (2) sample elevation relative to sea level at the time of accumulation of the dated material, and (3) postdepositional subsidence of the sample due to compaction of underlying sediments. Sea level in the vicinity of southern San Francisco Bay rose about 2 cm/yr from 9,500 to 8,000 years ago. The rate of relative sea-level rise then declined about tenfold from 8,000 to 6,000 years ago, and it has averaged 0.1–0.2 cm/yr from 6,000 years ago to the present. This submergence history indicates that the rising sea entered the Golden Gate 10,000–11,000 years ago and spread across land areas as rapidly as 30 m/yr until 8,000 years ago. Subsequent shoreline changes were more gradual because of the decrease in rate of sea-level rise. Some of the sediments under southern San Francisco Bay appear to be below the level at which they initially accumulated. The vertical crustal movement suggested by these sediments may be summarized as follows: (1) Some Quaternary(?) sediments have sustained at least 100 m of tectonic subsidence in less than 1.5 million years (<0.07 mm/yr) relative to the likely elevation of the lowest Pleistocene land surface; (2) the deepest Sangamon estuarine deposits subsided tectonically about 20–40 m in about 0.1 million years (0.2±0.1–0.4±0.1 mm/yr) relative to the assumed initial elevations of the thalwegs buried by these sediments; and (3) Holocene salt-marsh deposits have undergone about 5 m of tectonic and possibly isostatic subsidence in about 6,000 years (0.8±.0.7 mm/yr) relative to elevations which might be expected from eustatic sea-level changes alone.

Atwater, Brian F.; Hedel, Charles W.; Helley, Edward J.

1977-01-01

67

Late Quaternary Spring-Fed Deposits of the Grand Canyon and Their Implication for Deep Lava-Dammed Lakes  

Microsoft Academic Search

One of the most intriguing episodes in the Quaternary evolution of the Grand Canyon of the Colorado River, Arizona, was the development of vast lakes that are thought to have backed up behind lava erupted into the gorge. Stratigraphic evidence for these deep lava-dammed lakes is expectedly sparse. Possible lacustrine deposits at six areas in the eastern canyon yielded no

Darrell S. Kaufman; Gary O'Brien; Jim I. Mead; Jordon Bright; Paul Umhoefer

2002-01-01

68

Maps of Quaternary Deposits and Liquefaction Susceptibility in the Central San Francisco Bay Region, California  

USGS Publications Warehouse

This report presents a map and database of Quaternary deposits and liquefaction susceptibility for the urban core of the San Francisco Bay region. It supercedes the equivalent area of U.S. Geological Survey Open-File Report 00-444 (Knudsen and others, 2000), which covers the larger 9-county San Francisco Bay region. The report consists of (1) a spatial database, (2) two small-scale colored maps (Quaternary deposits and liquefaction susceptibility), (3) a text describing the Quaternary map and liquefaction interpretation (part 3), and (4) a text introducing the report and describing the database (part 1). All parts of the report are digital; part 1 describes the database and digital files and how to obtain them by downloading across the internet. The nine counties surrounding San Francisco Bay straddle the San Andreas fault system, which exposes the region to serious earthquake hazard (Working Group on California Earthquake Probabilities, 1999). Much of the land adjacent to the Bay and the major rivers and streams is underlain by unconsolidated deposits that are particularly vulnerable to earthquake shaking and liquefaction of water-saturated granular sediment. This new map provides a consistent detailed treatment of the central part of the 9-county region in which much of the mapping of Open-File Report 00-444 was either at smaller (less detailed) scale or represented only preliminary revision of earlier work. Like Open-File Report 00-444, the current mapping uses geomorphic expression, pedogenic soils, inferred depositional environments, and geologic age to define and distinguish the map units. Further scrutiny of the factors controlling liquefaction susceptibility has led to some changes relative to Open-File Report 00-444: particularly the reclassification of San Francisco Bay mud (Qhbm) to have only MODERATE susceptibility and the rating of artificial fills according to the Quaternary map units inferred to underlie them (other than dams - adf). The two colored maps provide a regional summary of the new mapping at a scale of 1:200,000, a scale that is sufficient to show the general distribution and relationships of the map units but not to distinguish the more detailed elements that are present in the database. The report is the product of cooperative work by the National Earthquake Hazards Reduction Program (NEHRP) and National Cooperative Geologic Mapping Program of the U.S. Geological Survey, William Lettis and & Associates, Inc. (WLA), and the California Geological Survey. An earlier version was submitted to the U.S. Geological Survey by WLA as a final report for a NEHRP grant (Witter and others, 2005). The mapping has been carried out by WLA geologists under contract to the NEHRP Earthquake Program (Grant 99-HQ-GR-0095) and by the California Geological Survey.

Witter, Robert C.; Knudsen, Keith L.; Sowers, Janet M.; Wentworth, Carl M.; Koehler, Richard D.; Randolph, Carolyn E.; Brooks, Suzanna K.; Gans, Kathleen D.

2006-01-01

69

Depositional character of a dry-climate alluvial fan system from Palaeoproterozoic rift setting using facies architecture and palaeohydraulics: Example from the Par Formation, Gwalior Group, central India  

NASA Astrophysics Data System (ADS)

The ?20 m thick coarse-grained clastic succession in the basal part of Palaeoproterozoic Par Formation, Gwalior Group has been investigated using process-based sedimentology and deductive palaeohydraulics. Bounded between granitic basement at its base and shallow marine succession at the top, the studied stratigraphic interval represents products of an alluvial fan and its strike-wise co-existent braided river system that possibly acted as a tributary for the fan. Detailed facies, facies association analysis allowed identification of two anatomical parts for the fan system viz. proximal and mid fan. While thin proximal fan is represented by products of rock avalanche and hyperconcentrated flows with widely varying rheology, the mid fan is represented by products of sheet floods and flows within streamlets. The interpretation found support from palaeoslope estimation carried out on the fluvial part of the mid fan that plot dominantly within the alluvial fan field demarcated by Blair and McPherson (1994). Dry climatic condition suggested from dominance of stream flow over mass flow deposition within the Par alluvial fan. Strike-wise, the fan is discontinuous and juxtaposed with a braid plain system. In contrast to the fluvial part of fan system, the palaeoslope data from the braid plain system dominantly plot within the ‘natural depositional gap' defined by Blair and McPherson. A raised palaeoslope for the river systems, as suggested from Proterozoic braid plain deposits around the Globe, is found valid for the Par braid plain system as well. From preponderance of granular and sandy sediments within the alluvial fan and braid plain systems and a pervasive north-westward palaeocurrent pattern within the fluvial systems the present study infers a gently sloping bevelled source area in the south-southeast of the basin with occurrence of steep cliffs only locally.

Chakraborty, Partha Pratim; Paul, Pritam

2014-09-01

70

Episodic Late Quaternary slopewash deposition as recorded in colluvial aprons, Southeastern Wyoming  

NASA Astrophysics Data System (ADS)

Colluvial aprons found along fluvial terraces of the Laramie River and Sybille Creek in southeastern Wyoming are interpreted as late Quaternary slopewash deposits. Each apron studied contained multiple buried soils, interpreted to indicate that slopewash activity was episodic and short-lived, and was followed by relatively long periods of landscape stability and soil development. Apron deposits were described and subsequently correlated based on their internal stratigraphy and their relative degree of soil development. Optical dating was used to chronologically constrain periods of slopewash deposition, and based on 17 optical ages taken from five aprons, aggradation occurred at ˜65-56, 16.0, 12.9, 11.8, 8.1, 7.3, 5.0, and 1.7 ka. Several of these events correspond with climatic transitions such as the termination of Heinrich Event 1, the onset and termination of the Younger Dryas, and the 8.2 ka event, suggesting that apron aggradation was driven by changes in climatic regime. Although either increased aridity or a change in precipitation regime could result in increased erosion of terrace scarps, apron aggradation events do not correlate with regional records of aridity. Instead, periods of increased precipitation intensity and/or frequency that occur during climatic transitions most likely drive apron aggradation events.

Hanson, Paul R.; Mason, Joseph A.; Goble, Ronald J.

2004-09-01

71

Radiocarbon dating late Quaternary loess deposits using small terrestrial gastropod shells  

NASA Astrophysics Data System (ADS)

Constraining the ages and mass accumulation rates of late Quaternary loess deposits is often difficult because of the paucity of organic material typically available for 14C dating and the inherent limitations of luminescence techniques. Radiocarbon dating of small terrestrial gastropod shells may provide an alternative to these methods as fossil shells are common in loess and contain ˜12% carbon by weight. Terrestrial gastropod assemblages in loess have been used extensively to reconstruct past environmental conditions but have been largely ignored for dating purposes. Here, we present the results of a multi-faceted approach to understanding the potential for using small terrestrial gastropod shells to date loess deposits in North America. First, we compare highly resolved 14C ages of well-preserved wood and gastropod shells (Succineidae) recovered from a Holocene loess section in Alaska. Radiocarbon ages derived from the shells are nearly identical to wood and plant macrofossil ages throughout the section, which suggests that the shells behaved as closed systems with respect to carbon for at least the last 10 ka (thousands of calibrated 14C years before present). Second, we apply 14C dating of gastropod shells to late Pleistocene loess deposits in the Great Plains using stratigraphy and independent chronologies for comparison. The new shell ages require less interpretation than humic acid radiocarbon ages that are commonly used in loess studies, provide additional stratigraphic coverage to previous dating efforts, and are in correct stratigraphic order more often than their luminescence counterparts. Third, we show that Succineidae shells recovered from historic loess in the Matanuska River Valley, Alaska captured the 20th century 14C bomb spike, which suggests that the shells can be used to date late Holocene and historic-aged loess. Finally, results from Nebraska and western Iowa suggest that, similar to other materials, shell ages approaching ˜40 ka should be viewed with caution as they may reflect trace amounts of contamination. In sum, our results show that small terrestrial gastropod shells, especially from the Succineidae family, provide reliable ages for late Quaternary loess deposits in North America.

Pigati, Jeffrey S.; McGeehin, John P.; Muhs, Daniel R.; Bettis, E. Arthur

2013-09-01

72

Radiocarbon dating late Quaternary loess deposits using small terrestrial gastropod shells  

USGS Publications Warehouse

Constraining the ages and mass accumulation rates of late Quaternary loess deposits is often difficult because of the paucity of organic material typically available for 14C dating and the inherent limitations of luminescence techniques. Radiocarbon dating of small terrestrial gastropod shells may provide an alternative to these methods as fossil shells are common in loess and contain ?12% carbon by weight. Terrestrial gastropod assemblages in loess have been used extensively to reconstruct past environmental conditions but have been largely ignored for dating purposes. Here, we present the results of a multi-faceted approach to understanding the potential for using small terrestrial gastropod shells to date loess deposits in North America. First, we compare highly resolved 14C ages of well-preserved wood and gastropod shells (Succineidae) recovered from a Holocene loess section in Alaska. Radiocarbon ages derived from the shells are nearly identical to wood and plant macrofossil ages throughout the section, which suggests that the shells behaved as closed systems with respect to carbon for at least the last 10 ka (thousands of calibrated 14C years before present). Second, we apply 14C dating of gastropod shells to late Pleistocene loess deposits in the Great Plains using stratigraphy and independent chronologies for comparison. The new shell ages require less interpretation than humic acid radiocarbon ages that are commonly used in loess studies, provide additional stratigraphic coverage to previous dating efforts, and are in correct stratigraphic order more often than their luminescence counterparts. Third, we show that Succineidae shells recovered from historic loess in the Matanuska River Valley, Alaska captured the 20th century 14C bomb spike, which suggests that the shells can be used to date late Holocene and historic-aged loess. Finally, results from Nebraska and western Iowa suggest that, similar to other materials, shell ages approaching ?40 ka should be viewed with caution as they may reflect trace amounts of contamination. In sum, our results show that small terrestrial gastropod shells, especially from the Succineidae family, provide reliable ages for late Quaternary loess deposits in North America.

Pigati, Jeff S.; McGeehin, John P.; Muhs, Daniel R.; Bettis, E. Arthur, III

2013-01-01

73

Correlations between radiometric analysis of Quaternary deposits and the chronology of prehistoric settlements from the southeastern Brazilian coast.  

PubMed

Natural gamma radiation measurements of sand deposits were carried out in order to study the chronology of prehistoric colonization of the Brazilian coast during the Holocene. The method employs thorium, uranium and potassium as tracers of the geological provenance of Quaternary deposits, where artificial shellmounds are found. The so-called sambaquis are archaeological settlements, characteristic of fisher-gatherers, specialized in the exploitation of shellfish. Our results show a considerable positive correlation between the formation of coastal deposits, based on cross plots of eTh/eU and eTh/K, and the antiquity of its prehistoric human occupation. PMID:19800154

Anjos, R M; Macario, K D; Lima, T A; Veiga, R; Carvalho, C; Fernandes, P J F; Vezzone, M; Bastos, J

2010-01-01

74

Hydrogeologic controls on migration of an oil-spill plume in alluvial deposits near Fort Collins, Colorado  

Microsoft Academic Search

During 1979 a fuel oil spill of approximately 50,000 gallons resulted from leakage out of underground storage tanks directly into a shallow alluvial aquifer at an industrial site near Fort Collins, Colorado. When the spill was discovered and test holes drilled in November of 1979, the oil plume had a tear-drop shape and was approximately 300 feet in average diameter.

J. P. Waltz; R. E. Boyle

1985-01-01

75

Late Quaternary Spring-Fed Deposits of the Grand Canyon and Their Implication for Deep Lava-Dammed Lakes  

NASA Astrophysics Data System (ADS)

One of the most intriguing episodes in the Quaternary evolution of the Grand Canyon of the Colorado River, Arizona, was the development of vast lakes that are thought to have backed up behind lava erupted into the gorge. Stratigraphic evidence for these deep lava-dammed lakes is expectedly sparse. Possible lacustrine deposits at six areas in the eastern canyon yielded no compelling evidence for sediment deposited in a deep lake. At two of the sites the sediment was associated with late Quaternary spring-fed pools and marshes. Water-lain silt and sand at lower Havasu Creek was deposited ˜3000 cal yr ago. The deposit contains an ostracode assemblage similar to that living in the modern travertine-dammed pools adjacent to the outcrop. The second deposit, at Lees Ferry, formed in a spring-fed marsh ˜43,000 cal yr ago, as determined by 14C and amino acid geochronology. It contains abundant ostracode and mollusk fossils, the richest assemblages reported from the Grand Canyon to date. Our interpretation of these sediments as spring-fed deposits, and their relative youth, provides an alternative to the conventional view that deposits like these were formed in deep lava-dammed lakes that filled the Grand Canyon.

Kaufman, Darrell S.; O'Brien, Gary; Mead, Jim I.; Bright, Jordon; Umhoefer, Paul

2002-11-01

76

Static and dynamic characterization of alluvial deposits in the Tiber River Valley: New data for assessing potential ground motion in the City of Rome  

NASA Astrophysics Data System (ADS)

The paper presents the results of a case study conducted on the Holocene alluvial deposits of the Tiber River valley, in the city of Rome. The main test site selected for the study, Valco S. Paolo, is located about 2 km South of Rome's historical centre. The alluvial deposits were dynamically characterized in a comprehensive way via site investigations and geotechnical laboratory tests. Normalized shear modulus decay and damping curves (G/G0 and D/D0 vs ?) were obtained for the dominantly fine-grained levels. The curves demonstrate that these levels have a more marked shear stiffness decay if compared with the underlying Pliocene bedrock. Decay curves from laboratory tests for the Tiber alluvia correlated well with the trend of the function proposed by Hardin and Drnevich, making it possible to derive their specific interpolation function coefficients. Use was made of the extrapolation of the findings from the Valco S. Paolo test site to a large part of Rome's historical centre by means of two other test sites, supported by an engineering-geology model of the complex spatial distribution of the Tiber alluvia. The experimental Valco S. Paolo Vs profile was extrapolated to the other test sites on the basis of a stratigraphic criterion; the analysis of seismic noise measurements, obtained for the three test sites, validated the engineering-geology based extrapolation and showed that the main rigidity contrast occurs inside the alluvial body (at the contact with the underlying basal gravel-level G) and not between the alluvia and the Plio-Pleistocene bedrock, composed of highly consistent clay (Marne Vaticane). The 1D modeling of local seismic response to the maximum expected earthquakes in the city of Rome confirms that the deposits have one principal mode of vibration at about 1 Hz. However, the simulation also evidenced that the silty-clay deposits (level C), making up the most part of the Tiber alluvial body, play a key role in characterizing the soil column deformation profile since it can be affected by non linear effects induced by the maximum expected earthquake when some stratigraphic conditions are satisfied.

Bozzano, F.; Caserta, A.; Govoni, A.; Marra, F.; Martino, S.

2008-01-01

77

Nitrogen, sulfate, chloride, and manganese in ground water in the alluvial deposits of the South Platte River Valley near Greeley, Weld County, Colorado  

USGS Publications Warehouse

Ground water from the valley-fill deposits of the South Platte River Valley and its tributaries is used extensively for agriculture in the study area, about 10 miles east of Greeley and about 50 miles northeast of Denver, Colorado. The valley-fill deposits, which consist of alluvial and terrace deposits, are in a valley system eroded in Laramie Formation bedrock. Water samples collected from 53 wells during 1974 and 1980 were analyzed for nitrite plus nitrate nitrogen, sulfate, chloride, and manganese. Median concentrations changes in these constituents from 1974 to 1980 are as follows: 6.0 to 8.8 milligrams per liter for nitrite plus nitrate nitrogen, 850 to 900 milligrams per liter for sulfate, and 94 to 120 milligrams per liter for chloride. Manganese concentrations were greater than 1,000 micrograms per liter in both 1974 and 1980 in a small area at the mouth of Box Elder Creek. (USGS)

Gaggiani, N. G.

1984-01-01

78

Erosion and deposition on the eastern margin of the Bermuda Rise in the late Quaternary  

NASA Astrophysics Data System (ADS)

A near-bottom survey has been made on the Eastward Scarp (32°50'N, 57°30'W) of the Bermuda Rise, which rises 1150 m above the 5500-m deep Sohm Abyssal Plain in the western North Atlantic. The survey reveals evidence of erosion and deposition at present and in the late Quaternary by the deeper levels of the westward flowing Gulf Stream Return Flow. Four distinct regions of increasing bed gradient show increasing sediment smoothing and scour in the transition from plateau to abyssal plain. Bedforms observed are current crescents, crag and tail, triangular ripples, elongate mounds, transverse mud ripples, lineations, and furrows ranging from 10 to 1 m or less in depth, decreasing generally with bed gradient. Measured near-bottom current speeds are up to 20 cm s -1. Temperature structure on the lower, steep, slopes suggests that detachment of bottom mixed layers may occur there. Extensive net erosion appears to be confined to the lower steep slopes of the scarp. Reflection profiles (4 kHz) show that there has been erosion in areas thinly draped with recent sediments and in areas that show development of small scarps. The distribution of subsurface acoustic characteristics of the region corresponds broadly to the areas characterized by bed gradient and distinct sedimentation conditions. Subsurface hyperbolae, possibly caused by buried furrows, show furrow persistence through several tens of metres of deposition. Erosion occurs up to the top of the scarp during episodes of presumed stronger currents, which may correspond with intensified circulation during glacials.

McCave, I. N.; Hollister, C. D.; Laine, E. P.; Lonsdale, P. F.; Richardson, M. J.

1982-05-01

79

Preliminary maps of Quaternary deposits and liquefaction susceptibility, nine-county San Francisco Bay region, California: a digital database  

USGS Publications Warehouse

This report presents a preliminary map and database of Quaternary deposits and liquefaction susceptibility for the nine-county San Francisco Bay region, together with a digital compendium of ground effects associated with past earthquakes in the region. The report consists of (1) a spatial database of fivedata layers (Quaternary deposits, quadrangle index, and three ground effects layers) and two text layers (a labels and leaders layer for Quaternary deposits and for ground effects), (2) two small-scale colored maps (Quaternary deposits and liquefaction susceptibility), (3) a text describing the Quaternary map, liquefaction interpretation, and the ground effects compendium, and (4) the databse description pamphlet. The nine counties surrounding San Francisco Bay straddle the San Andreas fault system, which exposes the region to serious earthquake hazard (Working Group on California Earthquake Probabilities, 1999). Much of the land adjacent to the Bay and the major rivers and streams is underlain by unconsolidated deposits that are particularly vulnerable to earthquake shaking and liquefaction of water-saturated granular sediment. This new map provides a modern and regionally consistent treatment of Quaternary surficial deposits that builds on the pioneering mapping of Helley and Lajoie (Helley and others, 1979) and such intervening work as Atwater (1982), Helley and others (1994), and Helley and Graymer (1997a and b). Like these earlier studies, the current mapping uses geomorphic expression, pedogenic soils, and inferred depositional environments to define and distinguish the map units. In contrast to the twelve map units of Helley and Lajoie, however, this new map uses a complex stratigraphy of some forty units, which permits a more realistic portrayal of the Quaternary depositional system. The two colored maps provide a regional summary of the new mapping at a scale of 1:275,000, a scale that is sufficient to show the general distribution and relationships of the map units but cannot distinguish the more detailed elements that are present in the database. The report is the product of years of cooperative work by the USGS National Earthquake Hazards Reduction Program (NEHRP) and National Cooperative Geologic Mapping Program, William Lettis and & Associates, Inc. (WLA) and, more recently, by the California Division of Mines and Geology as well. An earlier version was submitted to the Geological Survey by WLA as a final report for a NEHRP grant (Knudsen and others, 2000). The mapping has been carried out by WLA geologists under contract to the NEHRP Earthquake Program (Grants #14-08-0001-G2129, 1434-94-G-2499, 1434-HQ-97-GR-03121, and 99-HQ-GR-0095) and with other limited support from the County of Napa, and recently also by the California Division of Mines and Geology. The current map consists of this new mapping and revisions of previous USGS mapping.

Knudsen, Keith L.; Sowers, Janet M.; Witter, Robert C.; Wentworth, Carl M.; Helley, Edward J.; Nicholson, Robert S.; Wright, Heather M.; Brown, Katherine H.

2000-01-01

80

The organic and mineral matter contents in deposits infilling floodplain basins: Holocene alluviation record from the K?odnica and Osob?oga river valleys, southern Poland  

NASA Astrophysics Data System (ADS)

The work examines the timing and environmental conditions of floodplain sedimentation in the valleys of the upland K?odnica and piedmont Osob?oga rivers in the Upper Odra River basin. A distribution of 52 14C-ages shows relatively high floodplain sedimentation at the Late Glacial-Holocene transition, more stable floodplain environments since the Early (in the K?odnica Valley) and Middle Holocene (in the Osob?oga Valley) and a gradual increase in floodplain deposition in the Late Holocene (since < 3.4 kyr BP). Organic matter [OM] and mineral matter [MM] fluctuations were correlated with variables responsible for the activation of erosion (i.e. vegetation changes, human impact and hydrological events) as well as factors affecting the local record of sedimentation (i.e. valley morphology, hydrologic conditions and episodes of local erosion). A clear relationship is shown between an increase in alluviation and climate- or human-induced extension of unforested areas. The deposition of mineral-rich sediments increases rapidly during periods characterized by non-arboreal pollen values exceeding approximately 8% in pollen diagrams. On the other hand, the results obtained do not confirm significant interactions between Holocene changes in forest composition and alluviation. Despite the settlement of agrarian groups, the sedimentary record of human activity in the Osob?oga catchment is very poor during the Neolithic and early Bronze Age. A large-scale alluviation of the Osob?oga and K?odnica valleys was initiated during the settlement of people of the Lusatian culture from the middle Bronze Age and escalated in the early Middle Ages and Modern Times. The deposition of products of soil erosion was limited to between ca. 1.9-1.2 kyr BP, probably due to demographic regression during the Migration Period. Comparison of OM/MM fluctuations with phases of increased fluvial activity does not show a relationship between Holocene wetter phases and catchment sediment yield. Sedimentary episodes in the Upper Odra basin also show a low degree of correlation with the probability density curve of the 14C-ages. The results obtained in the K?odnica and Osob?oga valleys indicate a strong to moderate correlation between the spatial distribution of the study sites and the origin of MM-rich deposits, but a weak correlation between the spatial distribution of the study sites and TOC content. Such a pattern suggests that OM/MM fluctuations relate predominantly to the changes in sediment yield, although morphological conditions have a significant impact on the capture potential of sedimentary basins during phases of alluviation. Additionally, high OM content is not a simple function of an increase in wetness of the sedimentary environment. On the other hand, hydrologically-conditioned hiatuses as well as erosion episodes impoverish the sedimentary record, complicating the consideration on the geochronology of deposits and making it difficult to calculate reliable accumulation rates. However, they do not reduce the value of OM/MM fluctuations as an indicator of alluviation events for a preserved series of sediments.

Wójcicki, K. J.; Marynowski, L.

2012-07-01

81

Late Quaternary stratigraphy of an alluvial valley along an active convergence front: Interactions of fluvial processes, tectonic channel steering, and sea level in the eastern Ganges-Brahmaputra-Meghna River delta  

NASA Astrophysics Data System (ADS)

Insights into how tectonics, alluvial channels, and sediment interact to build the stratigraphy in a tectonically active depositional basin can be discovered by studying the sediment record and the current geomorphology of a system. Tectonics is an influence on basins that often gets overlooked due to overriding controls such as sea level, climate, and sediment load. The area for this study is in the Ganges Brahmaputra Meghna Delta (GBMD) in close proximity to an active convergent thrust front. To investigate the stratigraphy, we drilled 48 cores along two approximately longitudinal transects, 25-60 km apart, each spanning ~100 km. The boreholes were drilled every 3-4 km to a maximum depth of 100 m. The transects are situated across an alluvial valley and are bounded to the west by a Pleistocene terrace (Madhupur Terrace) and to the east by a fold belt (Indo-Burman Fold Belt) that continues to deform due to active tectonics at the thrust front. A seismic cruise using a mini-GI gun was conducted in conjunction with this study along the current river channel and has shown evidence of folded sediment at depth, and field studies in the area have found outcropping anticlines thus aiding in the determination of transect location. Through analysis of aerial imagery and digital elevation models (DEMs) of the transects, abandoned channels once occupied by the alluvial channel are evidence of migration and avulsion occurring recently enough to be recorded on the land surface. Initial analysis of the sediment cores shows a dramatic contrast in the stratigraphy between the two transects despite lying along the same morphological reach of the GBMD. The northern transect is dominated by fine to medium sands throughout indicating a strong fluvial influence, while the southern transect is dominated by muds and finer sands at depth indicating a tidal estuarine influence. The stratigraphy and land surface are a consequence of the controls on the system and reflect channel behavior over time. The establishment of channel behavior, including avulsions, migration, and overbank processes, is the key to investigating how rivers and tectonics interact to shape the landscape and build stratigraphy, which will be discussed in detail based on these transect and seismic datasets.

Williams, L.; Goodbred, S. L.; Steckler, M. S.; Seeber, L.; Spiess, V.; Schwenk, T.; Palamenghi, L.; Akhter, S. H.; Mondal, D.; Hossain, S.

2012-12-01

82

Alluvial aquifer contamination: Exchangeable heavy metals and factors affecting their spatial distribution  

Microsoft Academic Search

The distributions of ammonium acetate — extracted (‘exchangeable’) Co, Ni, Cu, Zn, Cd and Pb were determined in alluvial sediments of the Sava River at Novi Beograd (Belgrade aquifer, Yugoslavia). Samples were taken from the river bottom and from three drill-holes in the alluvial formation (in increasing distance from the river-bed). The alluvial samples included the quaternary formation — humified

Predrag Poli?; Petar Pfendt

1994-01-01

83

Late Quaternary paleodune deposits in Abu Dhabi Emirate, UAF: Paleoclimatic implications  

SciTech Connect

Remnants of late Quaternary paleodunes are exposed near the coast of the Arabian Gulf and in large inland playas and interdunal areas in central and western Abu Dhabi Emirate over a distance of >45 km normal to the coast. Paleodunes occur south of Madinat Zayed (lat. 23[degree]35 N), which marks the northern limit of a modern dune field that grades into the mega-dune sand sea of the ar Rub al Khali, Saudi Arabia. Coastal paleodunes are composed of weakly cemented millolid foraminifers, ooids, and rounded biogenic grains, whereas inland and southward the paleodunes show a progressive increase in the proportion of eolian quartz sand. The paleodunes exhibit large-scale trough foresets in remnant exposures 0.5 to 10 m thick, indicating paleowind directions from 65[degree] to 184[degree] (dominantly southeast transport). Scattered paleoplaya remnants provide paleodune scale. Paleoplaya deposits form buttes 30--50 m high. If coeval with the Paleodunes, large-scale paleodune fields are implied (100+ m high), comparable to star dunes and sand mountains at the northwestern edge of the ar Rub al Khali. Based on U-Th isotopic analyses, the carbonate paleodune sands are >160ka and probably >250ka. The carbonate source was a shallow, nearly dry Arabian Gulf at a time when large areas were exposed during a low sea-level stand. Paleowind direction indicates that Pleistocene prevailing winds were northwesterly, the direction of the dominant (winter shamal) wind today. The geographic extend and implied magnitude of the paleodunes suggest large-scale eolian transport of carbonate sand during the Pleistocene disiccation, and admixed quartz sand identifies a youthful stage of contemporaneous evolution of the ar Rub al Khali. Wave-eroded paleodunes probably floor much of the present-day Gulf and extend beneath the modern dunes and sand mountains.

Brouwers, E.M.; Bown, T.M. (Geological Survey, Denver, CO (United States)); Hadley, D.G. (Geological Survey, Reston, VA (United States))

1993-04-01

84

Comparative study on Cu2ZnSnS4 thin films deposited by sputtering and pulsed laser deposition from a single quaternary sulfide target  

NASA Astrophysics Data System (ADS)

Cu2ZnSnS4 (CZTS) thin films were directly grown on the heating Mo-coated glass substrate by Sputtering and Pulsed Laser Deposition (PLD) with a single quaternary sulfide target. XRD and Raman scattering confirm that both CZTS films are of kesterite structure, although the composition of CZTS film deposited by Sputtering deviates from the stoichiometry of CZTS more significantly than that deposited by PLD. However, CZTS deposited by sputtering has poor crystallintiy and small grain-sizes in contrast with the sample deposited by PLD, due to severe compositional deviation. Reflection spectroscopy and spectroscopic ellipsometry demonstrate that these CZTS films have the ideal band gap (Eg?1.5 eV) and high absorption coefficient as the absorber layer of thin-film solar cells. This implies that the optical properties of CZTS film are tolerant to its compositional deviation.

Sun, Lin; He, Jun; Chen, Ye; Yue, Fangyu; Yang, Pingxiong; Chu, Junhao

2012-12-01

85

Fluvial deposits of Yellowstone tephras: Implications for late Cenozoic history of the Bighorn basin area, Wyoming and Montana  

USGS Publications Warehouse

Several deposits of tephra derived from eruptions in Yellowstone National Park occur in the northern Bighorn basin area of Wyoming and Montana. These tephra deposits are mixed and interbedded with fluvial gravel and sand deposited by several different rivers. The fluvial tephra deposits are used to calculate stream incision rates, to provide insight into drainage histories and Quaternary tectonics, to infer the timing of alluvial erosion-deposition cycles, and to calibrate rates of soil development. ?? 1992.

Reheis, M.C.

1992-01-01

86

A New Genus and Species of Buteonine Hawk from Quaternary Deposits in Bermuda (Aves: Accipitridae)  

Microsoft Academic Search

Bermuteo avivorus, new genus and species, is described from rare Quaternary fossils from the island of Bermuda. Although clearly referable to the Buteoninae, its relationships within that group are difficult to assess. Considerable size variation may be attributable to sexual dimorphism associated with bird-catching behavior. It is uncertain if the species survived into the historic period. Factors contributing to the

Storrs L. Olson

2008-01-01

87

Electrochemical deposition of quaternary Cu2ZnSnS4 thin films as potential solar cell material  

NASA Astrophysics Data System (ADS)

Quaternary compound semiconductor Cu2ZnSnS4 (CZTS), which appears to be a promising candidate for the absorber of a thin film type solar cell, was grown on polycrystalline Ag substrates by electrochemical epitaxial method. The elements were deposited in the following sequence: S/Sn/S/Cu/S/Zn/S/Cu… , the order being one cycle of SnS, one cycle of ZnS and two cycles of CuS. Morphology of the deposit has been characterized by field emission scanning electron microscopy (FE-SEM) with an energy dispersive X-ray (EDX) analyzer. X-ray diffraction (XRD) studies showed a (112) preferred orientation for the deposit. X-ray photoelectron spectroscopy (XPS) of the deposit indicated an approximate ratio 2:1:1:4 of Cu, Zn, Sn, and S, the expected stoichiometry for the deposit, and similar results have been obtained from EDX data. Near IR absorption measurements of the deposit at room temperature indicated a direct band gap of 1.5 eV, and open-circuit potential (OCP) studies indicated a good p-type property, both of which were suitable for fabricating a thin film solar cell.

Zhang, Xin; Shi, Xuezhao; Ye, Weichun; Ma, Chuanli; Wang, Chunming

2009-02-01

88

thin films deposited on different preferred oriented Mo back contact by RF sputtering from a quaternary target  

NASA Astrophysics Data System (ADS)

The Cu(In, Ga)Se2 (CIGS) thin films were deposited on bare glass and DC sputtered preferential oriented Mo-coated glass by RF sputtering from a single quaternary target. The structural and morphological properties of the films were characterized by X-ray diffraction (XRD), Raman spectroscope, energy dispersive X-ray spectrometer (EDS) and atomic force microscope (AFM). Preferred orientation of the Mo back contact was tuned between (110) and (211) plane by controlling the thickness. All the deposited CIGS thin films show (112) preferred oriented chalcopyrite structures. The films prepared on Mo-coated glass show higher quality crystallinity, better stoichiometry composition and more smooth surface morphology. Especially, the film on (211) oriented Mo-coated glass with the best integrated performance is expected to be a candidate absorber for high-efficiency CIGS solar cell device.

Tian, Jing; Peng, Lianqin; Chen, Jinwei; Wang, Gang; Wang, Xueqin; Kang, Hong; Wang, Ruilin

2014-09-01

89

Seismic stratigraphy of Late Quaternary deposits on the continental shelf of Antalya Bay, Northeastern Mediterranean  

Microsoft Academic Search

The Late Quaternary sedimentation and structural features of the continental shelf of Antalya Bay (SW Turkey) have been investigated using a single channel high-resolution shallow profiling system. Two seismic units denoted as unit 1 and unit 2 bounded by two major unconformities (R1 and R2) have been identified. R1 and R2 are type-1 sequence boundaries that formed under sub-aerial conditions

Devrim Tezcan; Mahmut Okyar

2006-01-01

90

Sequence stratigraphic interpretation methods for low-accommodation, alluvial depositional sequences: applications to reservoir characterization of Cut Bank field, Montana  

E-print Network

; and 3. identification of the bounding hiatal surfaces that separate genetic units and record significant interruptions in basin depositional history, such as shut-off of sediment supply or switch of sediment source, owing to avulsion on floodplain, a...; and 3. identification of the bounding hiatal surfaces that separate genetic units and record significant interruptions in basin depositional history, such as shut-off of sediment supply or switch of sediment source, owing to avulsion on floodplain, a...

Ramazanova, Rahila

2009-05-15

91

Erosion and deposition on the Pajarito Plateau, New Mexico, and implications for geomorphic responses to late Quaternary climatic changes  

SciTech Connect

The Pajarito Plateau of northern New Mexico contains a rich and diverse record of late Quaternary landscape changes in a variety of geomorphic settings that include gently-sloping mesa tops, steep canyon walls, and canyon bottoms. A broad range of investigations during the past decade, motivated by environmental and seismic hazard concerns, have resulted in examination of the characteristics, stratigraphy, and age of sediments and soils at numerous locations throughout the Plateau. Geochronologic control is provided by >140 radiocarbon dates supplemented by soil characterization and tephrochronology. In this paper we first summarize some of the results of recent and ongoing work on late Quaternary deposits on the Pajarito Plateau, illustrating both the complexity of the geomorphic record and some common elements that have been observed in multiple locations. We then use these observations, in combination with other work in the Southwest, to make some inferences about the local geomorphic response to regional climatic changes. Because the geomorphic and paleoclimatic records are fragmentary, and because the relations between large scale climate changes and local variations in precipitation, vegetation, and geomorphic processes are not fully understood, many uncertainties exist concerning the response of the local landscape to past climatic fluctuations. In addition, variations in local landscape sensitivity related to prior erosional history and spatial variations in vegetation, and the localized nature of many storms, probably contribute to the complexity of the geomorphic record. Nevertheless, the work discussed in this paper suggests a strong relation between regional climatic changes and local geomorphic history, and provides a framework for considering relations between modem processes, the record of past landscape changes, and future erosion and deposition on the Plateau and in surrounding areas.

Reneau, S.L.; McDonald, E.V.; Gardner, J.N.; Longmire, P.A. [Los Alamos National Lab., NM (United States); Kolbe, T.R. [Woodward-Clyde Federal Services, Oakland, CA (United States); Carney, J.S. [Kent State Univ., OH (United States). Dept. of Geology; Watt, P.M. [New Mexico Univ., Albuquerque, NM (United States). Dept. of Earth and Planetary Sciences

1996-04-01

92

A monoclinic, pseudo-orthorhombic Au-Hg mineral of potential economic significance in Pleistocene Snake River alluvial deposits of southeastern Idaho  

USGS Publications Warehouse

A mineral with the approximate composition of Au94Hg6 - Au88Hg12 (atomic %) has been identified in Pleistocene Snake River alluvial deposits. The gold-mercury mineral occurs as very small grains or as polycrystalline masses composed of subhedral to nearly euhedral attached crystals. Vibratory cold-polishing techniques with 0.05-??m alumina abrasive for polished sections revealed a porous internal texture for most subhedral crystals after 48-72 hours of treatment. Thus, optical character (isotropic or anisotropic) could not be determined by reflected-light microscopy, and pore-free areas were too small for measurement of reflectance. X-ray-diffraction lines rather than individual reflections (spots), on powder camera X-ray films of unrotated spindles of single grains that morphologically appear to be single crystals, indicate that individual subhedral or euhedral crystals are composed of domains in random orientation. Thus, no material was found suitable for single-crystal X-ray diffraction studies. -from Authors

Desborough, G.A.; Foord, E.E.

1992-01-01

93

High-frequency cyclicity in quaternary fan-delta deposits of the Andean fore-arc: Relative sea level changes and aseismic ridge subduction  

SciTech Connect

The coast of northern Chile comprises Mesozoic magmatic rocks and Cenozoic-Holocene shallow-marine and alluvial fan/fan-delta sediments. The structure, landform development, and sedimentary response of the coast between Antofagasta in the south and Arica (600 km to the north) have been investigated to evaluate the influence of Nazca plate subduction on sea level changes over Quaternary to Holocene times. At Arica the coastal range is in net extension characterized by extensional normal faulting and subsidence, similar to much of Chile. South of Arica, uplift is recorded by marine terrace development and incision of alluvial fan surfaces; uplift reaches a maximum south of Iquiqui. The boundary between regions in net subsidence and net uplift is marked by north-facing neotectonic normal fault scarps. Variations in apparent uplift and subsidence are consistent with recently published oceanographic records on relative sea level changes over a 30 yr period. The authors data suggest that these regionally variable patterns of coastal uplift along the north Chilean coast are controlled by the subduction of an aseismic ridge, which overprints the effect of eustatic sea level fluctuations. Subduction of oceanic plate heterogeneities may provide a mechanism for producing cyclicity in sedimentary sequences at a frequency equal to or higher than glacio-eustacy in fore-arc and possibly back-arc sedimentary basins. These sequences will be neither of global extent nor of global synchroneity.

Flint, S. (Univ., of Liverpool (England)); Jolley, E.J.; Turner, P.; Williams, G.D.; Buddin, T. (Univ. of Birmingham (England))

1990-05-01

94

Episode(s) of intense alluvial deposition during an era of drought on Mars: Evidence from fans at Saheki (and Gale?)  

NASA Astrophysics Data System (ADS)

The martian alluvial fans of the Hesperian-Amazonian period [1,2] may represent a portion of the last widespread episode of large-scale fluvial modification on the red planet's surface. We undertook a detailed study of the fans in the western Terra Tyrrhena region, including geomorphic mapping, calculations of surface ages derived from crater density statistics, estimations of hydrology based on the morphologic parameters of the observed channels, and landform evolution modeling. Understanding the processes and prevalent climatic conditions during fan formation provides key insights into Mars' fluvial history, which continues to remain the premier focus of martian geologic study. The fans feature channel morphologies which indicate that they formed fluvially (as opposed to being debris flows), including the presence of scroll bars and meander bends. These are observed on the fan surface, meaning that the final flows responsible for forming the fan were fluvial. The lack of boulders greater than 0.5m (at which size they would be observed in HiRISE images), the presence of washed out portions of channels, and aeolian inversion of channel topography lead us to conclude that the channel beds are primarily made up of fine grained (sand to granule) sediment. Crater age statistics were computed using [3] software, using the chronology function of [4] and the production function of [5]. All of the fans in the area date to the Hesperian and in some cases as late as the early Amazonian, epochs that otherwise are generally characterized by a cool, dry Mars. This is at around same time period at which the alluvial deposits in Gale Crater may have formed. Natural levees observed on the fan were used to estimate paleochannel width. Channel depth is calculated from an assumed grain size and measured slope. Slopes were obtained from Digital Elevation Models (DEMs) that we have constructed from CTX and HiRISE stereo pairs. We use Manning and Darcy-Weisbach equations to obtain discharge estimates ranging from 2-6 m3/s, comparable with obtained values for similarly sized fans in the Atacama Desert [6]. In order to constrain climatic and geomorphic factors during the epoch of fan formation model we have been developing a numerical landform evolution model to simulate the aggradation of an alluvial fan. Output is statistically compared with our DEMs of the study area. References: [1]Moore, J.M., and A.D. Howard (2005), JGR, 110, E04005, doi:10.1029 / 2004JE002352 [2] Grant, J. A., Wilson, S.A. (2011) GRL, 38, L08201, doi:10.1029/2011- GL046844 [3]Michael G.G., Neukum G. (2010) Earth and Planetary Science Letters. doi: 10.1016/j.epsl.- 2009.12.041 [4]Hartmann, W.K., Neukum, G. (2001) Space Sci. Rev., v96, p. 165-194, doi: 10.1023/A:1011945222010 [5] Ivanov, B.A. (2001) Space Science Reviews 96, p. 87-104 [6] Haug, E.W., Kraal, E.R., Sewall, J.O., Van Dijk, M., Diaz, G.C. (2010) Geomorphology 121, 184-196, doi: 10.1016/j.geomorph.2010.04.005

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

2012-12-01

95

Processes of late Quaternary turbidity current flow and deposition on the Var deep sea fan, northwest Mediterranean sea  

SciTech Connect

Late Quaternary sedimentation patterns on the Var deep-sea fan are known from high-resolution seismic boomer profiles (vertical resolution < 1 m), piston cores, SAR side-scan sonargraphs, and submersible dives. Foram biostratigraphy and radiocarbon dating provide chronologic control that is seismically correlated across the fan. Regional erosional events correspond to the isotopic state 2 and 6 glacial maxima. A widespread surface sand layer was deposited from the 1979 turbidity current, which broke two submarine cables. Numerical modeling constrains its character. A small slide on the upper prodelta developed into an accelerating turbidity current, which eroded sand from the Var canyon. The current was 30 m thick in the upper valley, expanding downflow to >120 m, where it spilled over the eastern Var sedimentary ridge at a velocity of 2.5 ms[sup [minus]1]. Other Holocene turbidity currents (with a 103-yr recurrence interval) were muddier and thicker, but also deposited sand on middle fan-valley levees and are inferred to have had a similar slide-related origin. Late Pleistocene turbidity currents deposited on the high Var sedimentary ridge. The presence of sediment waves and the cross-flow slope inferred from levee asymmetry indicate that some flow were hundreds of meters thick, with velocities of 0.35 ms[sup [minus]1]. Estimated times for deposition of thick levee mud beds are many days or weeks. Late Pleistocene flows therefore are interpreted to result from hyperpycnal flow of glacial outwash in the Var River. Variation in late Pleistocene-Holocene turbidite sedimentation thus is controlled more by changes in sediment supply than by sea level.

Piper, D. (Atlantic Geoscience Centre, Dartmouth, Nova Scotia (Canada)); Savoye, B. (IFREMER, Plouzane (France))

1993-09-01

96

Mapping Neogene and Quaternary sedimentary deposits in northeastern Brazil by integrating geophysics, remote sensing and geological field data  

NASA Astrophysics Data System (ADS)

Neogene and late Quaternary sedimentary deposits corresponding respectively to the Barreiras Formation and Post-Barreiras Sediments are abundant along the Brazilian coast. Such deposits are valuable for reconstructing sea level fluctuations and recording tectonic reactivation along the passive margin of South America. Despite this relevance, much effort remains to be invested in discriminating these units in their various areas of occurrence. The main objective of this work is to develop and test a new methodology for semi-automated mapping of Neogene and late Quaternary sedimentary deposits in northeastern Brazil integrating geophysical and remote sensing data. The central onshore Paraíba Basin was selected due to the recent availability of a detailed map based on the integration of surface and subsurface geological data. We used airborne gamma-ray spectrometry (i.e., potassium-K and thorium-Th concentration) and morphometric data (i.e., relief-dissection, slope and elevation) extracted from the digital elevation model (DEM) generated by the Shuttle Radar Topography Mission (SRTM). The procedures included: (a) data integration using geographic information systems (GIS); (b) exploratory statistical analyses, including the definition of parameters and thresholds for class discrimination for a set of sample plots; and (c) development and application of a decision-tree classification. Data validation was based on: (i) statistical analysis of geochemical and airborne gamma-ray spectrometry data consisting of K and Th concentrations; and (ii) map validation with the support of a confusion matrix, overall accuracy, as well as quantity disagreement and allocation disagreement for accuracy assessment based on field points. The concentration of K successfully separated the sedimentary units of the basin from Precambrian basement rocks. The relief-dissection morphometric variable allowed the discrimination between the Barreiras Formation and the Post-Barreiras Sediments. In addition, two units of the latter (i.e., PB1 and PB2) previously mapped in the field were promptly separated based on Th concentration. A regression analysis indicated that the relationship between geophysical and geochemical values obtained for the PB1, PB2 and Barreiras Formation is significant (R-squared = 0.91; p-value <0.05). Map validation presented a high overall accuracy of 84%, with a coefficient of quantity disagreement of 12% and a coefficient of allocation disagreement of 8%. These results indicate that the methodology applied in the central onshore Paraíba Basin can be successfully used for mapping the Barreiras Formation and Post-Barreiras Sediments in other areas of the Brazilian coast. The ability to rapidly and precisely map these units using such methodology could reveal their geographic distribution along the northeastern coast of Brazil.

Andrades-Filho, Clódis de Oliveira; Rossetti, Dilce de Fátima; Bezerra, Francisco Hilario Rego; Medeiros, Walter Eugênio; Valeriano, Márcio de Morisson; Cremon, Édipo Henrique; Oliveira, Roberto Gusmão de

2014-12-01

97

Fracture networks and strike-slip deformation along reactivated normal faults in Quaternary travertine deposits, Denizli Basin, western Turkey  

NASA Astrophysics Data System (ADS)

The Denizli Basin in the West Anatolian Extensional Province in western Turkey is known for its numerous Quaternary travertine occurrences. Travertine morphology is often dependant on the relative position of the deposition with respect to basin-bounding faults. The travertine occurrences examined in this study are situated at the intersection of the locally E-W oriented Denizli Basin and the adjacent NE-SW oriented Baklan Graben in the NE. Based on an extensive field campaign, including LIDAR scanning, several high-resolution fault/fracture maps of five large quarries (> 300 m in length and > 60 m in height) are constructed in which this world-class travertine deposit is currently excavated. A structural analysis is performed in order to determine the tectonic overprinting of the travertine body and to derive the stress states of the basin after travertine deposition. The mostly open, non-stratabound joints are several tens of metres long and often bifurcate creating a dense fracture network. Minor infill of the joints resulted in the presence of a few colour-banded calcite veins. Based on the E-W, NE-SW and NW-SE orientation of three dominant joint sets it is concluded that the joint network is caused by local N-S extension, alternated by NW-SE and NE-SW extension exemplifying the presence of stress permutations in the Quaternary. High angle E-W to WNW-ESE faults cross-cut the quarries. Faults are filled with travertine debris and clastic infill of above lying sedimentary units indicative of the open nature of the faults. The specific E-W fault orientation in the locally E-W trending Denizli Basin indicates that they initiated as normal faults. A paleostress inversion analysis performed on kinematic indicators such as striations on the clayey fault infill and the sinistral displacement of paleosols shows that some of the normal faults were reactivated causing left-lateral deformation in a transient strike-slip stress field with a NE-SW oriented ?1.

Van Noten, Koen; Claes, Hannes; Soete, Jeroen; Foubert, Anneleen; Özkul, Mehmet; Swennen, Rudy

2013-03-01

98

The Effect of Shallow Quaternary Deposits on the Shape of the H/V Spectral Ratio  

NASA Astrophysics Data System (ADS)

In the last two decades, the horizontal-to-vertical (H/V) spectral ratio of seismic noise technique has been widely used for site-effect estimation and geophysical exploration through the soil fundamental frequency. Usually, only one peak is observed in the H/V spectral ratio, but in some cases, a second peak can also be obtained. Nevertheless, to date, the peaks at higher frequencies are rarely studied in detail. Geological and geophysical data are especially needed to better explain the presence of this second peak, which normally is neglected. An extensive survey of H/V measurements was conducted in the Llobregat river delta, located to the south of Barcelona. At most sites, two clear peaks were identified: one at low frequencies (<1 Hz) and the other at higher frequencies (>1 Hz). To understand this behaviour, a seismic noise array and active surface wave measurements have been conducted to obtain a shear-wave velocity profile (V s) up to the bedrock. Two impedance contrasts have been detected: the first one at a shallow depth and the second one between the soft sedimentary cover and the bedrock. During the modelling process, the theoretical H/V computed from the obtained V s models fits well with the experimental H/V peaks. The results from this study show that the structure of shallow quaternary layers can clearly change the shape of the H/V ratio, producing two clear peaks in some situations. In this case, the contact between the low-velocity clay layer and the gravels with a high seismic wave velocity produces a shallow impedance contrast related to the second peak observed in the H/V ratio. Comprehension of these secondary peaks could avoid a misreading of the soil fundamental frequency that could produce errors in a site-effect evaluation or in the calculation of the bedrock depth. Finally, we show that passive seismic techniques provide the quaternary overburden and bedrock geometry in urban areas and allow for the limitations of other geophysical techniques in these environments to be overcome.

Macau, A.; Benjumea, B.; Gabàs, A.; Figueras, S.; Vilà, M.

2014-09-01

99

Quaternary International 120 (2004) 2940 Late Pleistocene (Last Interglacial) terrace deposits, Bahia Coyote,  

E-print Network

in growth position and coral-rhodolith sands and marls. Beach sands and gravels and coastal dunes cap, Austin, TX, USA Abstract Late Pleistocene age terrace deposits are exposed in the narrow cliffed coastal

Banner, Jay L.

100

Clay-mineral assemblages from late Quaternary deposits on Vancouver Island, southwestern British Columbia, Canada  

NASA Astrophysics Data System (ADS)

On Vancouver Island, the Dashwood Drift, Cowichan Head Formation, Quadra Sand, and Vashon Drift were deposited during late Pleistocene glacial and interstadial periods and show large variations in clay-mineral contents partly related to changing climatic conditions. Glacial deposits are characterized by iron-rich chlorite, illite (both well crystallized), and smectite with a morphology reflecting rapid derivation from volcanic rocks. The clay mineralogy of nonglacial deposits is more complex, and is marked by the presence of vermiculite, kaolinite, halloysite, and irregular mixed-layer minerals. Nonglacial clay minerals are poorly preserved and show a higher state of alteration due to pedogenesis. Large variations in nonglacial deposits compared to glacial deposits are also due to secondary factors such as selective sorting, soil and rock source variations, differences in sedimentary environment, and diagenesis. These secondary factors do not seem to obliterate significantly the climatic imprint on the clay minerals. These studies also permit the recognition of glacially reworked sediments, the determination of relationships between two units in the same section, and the establishment of the conditions of clay-mineral formation.

Blaise, Bertrand

1989-01-01

101

Field evidence of seismites in Quaternary deposits of the Jijel (Eastern Algeria) coastal region  

NASA Astrophysics Data System (ADS)

Jijel has been hit by a strong earthquake in 1856 that triggered a destructive tsunami. Field geological investigations show that the marine terrace deposits (Tyrrhenian or likely Eutyrrhenian) exhibit several types of soft sediment deformation features including sismoslumps, thixotropic bowls, thixotropic wedges, and diapir-like structures. In addition, paleo-liquefaction features represented by neptunian and injection dikes have been observed in the sand dune deposits (Aterian or Würm). Furthermore, typical paleo-earthquake-induced ground failures including lateral spreading, paleo-landslides, and sand volcanoes have been observed in recent, likely, Holocene deposits. Such features, remarkably comparable to present-day earthquake-induced ground failures showing clearly repetitive occurrence of past events may constitute a precious material for future paleo-seismic investigation. The various features have been interpreted herein as seismites associated to strong earthquakes produced likely by the potentially active faults previously identified in the area.

Benhamouche, A.; Nedjari, A.; Bouhadad, Y.; Machane, D.; Oubaiche, E.; Sidi Said, N.

2014-04-01

102

Extreme Flood-Driven Dynamics of a mixed bedrock-alluvial Influenced Semi-Arid River  

NASA Astrophysics Data System (ADS)

Many of the large rivers draining southern Africa are characterised by incised bedrock ';macrochannels' cut 10-20 m into ancient planation surfaces but with variable amounts of unconsolidated sediment infill. Variations in lithology, structure, flow regime, sediment supply, and vegetation assemblages have created morphologically diverse river systems, many of which have been characterised by extended periods of alluviation on an historic timescale, thereby leading to the development of an increasingly alluviated set of channel types that commonly mask the underlying bedrock. However, cyclone-driven extreme flows are known to cause extensive erosion along these systems and may exert the primary control over their morphologic development. This paper reports on two significant cyclone events (2000 and 2012) that have impacted on the rivers of the Kruger National Park, with floods on the Sabie and Olifants estimated as among the largest documented Holocene floods for any South African river. Prior to the floods, both rivers displayed a diverse but well-ordered set of channel types (e.g. braided, anastomosed), with considerable lengths of both systems exhibiting fully alluvial conditions. Evaluation of post-flood aerial imagery has shown that the extreme flows have stripped this sediment, exposing and eroding the underlying weathered bedrock, particularly along the Olifants. This response suggests that although alluviation occurs over short timescales, the systems remain highly susceptible to alluvial and bedrock erosion during extreme floods. This is demonstrated by the results of a 2D hydraulic modelling study of the rivers. Simulation of the peak flood flow conditions shows that extreme shear stresses capable of eroding cohesive, well-vegetated sediments were predicted extensively within the macrochannels. Where remnant deposits remained from the 2000 floods, these areas were seen to be particularly vulnerable to erosion in the 2012 floods, due principally to their increased exposure to fluid forces. The ephemeral nature of the sediment infill is also supported by OSL dating, with preliminary ages from remnant bars, islands and floodplains suggesting that no deposits older than around 500 years can be found along the rivers. Together, the results imply that although periods of extensive alluviation may have been witnessed historically, on a longer (late Quaternary) timescale the alluvial morphologies are frequently reworked, with the geological setting and extreme climatic influence creating conditions conducive to the continuing erosion and development of the bedrock macrochannel template.

Entwistle, N. S.; Heritage, G. L.; Tooth, S.; Milan, D. J.

2013-12-01

103

Geophysical and Hydrological Characterization of Alluvial Fans in the Valle El Sauz Encinillas, Chihuahua, México.  

NASA Astrophysics Data System (ADS)

The Valle El Sauz Encinillas (VESE) is located 92 km north of Chihuahua City, México. Despite being the principal aquifer feeding Chihuahua City, and being flanked by two well studied geological features (Bloque Calera-Del Nido to the West, and the Sierra Peña Blanca to the East), a lack of available hydrogeological data prevails in the valley. The goals of this study are two: 1) geomorphometrical analysis of the sub-basins and alluvial fans, and 2) determination of the alluvial fan geoelectrical units via electrical-resistivity soundings. The Basin and Range system forms a closed sub-basin with a lacustrine basin system in extinction process. The aquifer is located in alluvial Quaternary sediments, with varying granulometry, reaching a thickness of 600 meters at the center of the valley. The biggest alluvial fan in the VESE is located at the Cañón de Santa Clara, and intersects the playa-lake deposits of the Laguna de Encinillas. This fan has a surface of 73.2 km2 and an average slope of 0.437°. The geomorphometrical analysis included the sub-basins, currents, and the fans in the area. These analyses allow a comparison between alluvial fans in the VESE and those in Death Valley, California, USA. The alluvial fans in both areas show a similar behavior in all plots. Twenty electrical resistivity soundings (Schlumberger array, AB/2 distance of 400 m) were performed in the alluvial fan. The basement and four other geoelectrical units were identified in the fan. The geophysical data, granulometric determinations, plus geochemical information of twelve wells in the area were analyzed. These data show how the decrease in granulometry, both frontally and laterally in the fan, results in a rise of the hydraulic conductivity and transmisivity values (water wells in Los Sauces and El Faro). However, both the permeability and the water quality in its distal portion, are affected by the playa lake deposits, the raising ratio of clay-size sediments (and evaporites) in the center of the valley, near to Laguna de Encinillas.

Villalobos-Aragón, A.; Chávez-Aguirre, R.; Osuna-Vizcarra, A.; Espejel-García, V. V.

2007-05-01

104

Three-dimensional sedimentary architecture of Quaternary deposits; a case study of environmental sedimentology (Bam, Iran)  

Microsoft Academic Search

Detailed 3-D analysis of the sedimentary structure and stratigraphy of these deposits allows for an accurate understand of sedimentary model of basin. This paper presents a case study in Bam (SE Iran) reconstructing the 3-D distribution of fluvial sediments based on a high resolution, process-orientated sedimentary facies classification and lithostratigraphy. We investigated the mean grain size with vertical and horizontal

K. Rezaei; B. Guest; A. Friedrich; F. Fayazi; M. Nakhaei; H. Bakhtiari; L. Nouri

2009-01-01

105

A New Fossil Bat (Chiroptera: Phyllostomidae) from a Quaternary Cave Deposit in Cuba  

Microsoft Academic Search

A new species of phyllostomid bat (Stenodermatinae: Stenodermatini) is described from a well preserved skull and two mandibular rami from a late Pleistocene cave deposit (derived from barn owl predation, Aves: Tyto) in Cueva El Abron, Pinar del Rõ ´o, western Cuba. This new taxon is the second fossil species described in the genus Phyllops, and it shares some features

WILLIAM SUAREZ; STEPHEN DIAZ-FRANCO

106

Quaternary deposits and landscape evolution of the central Blue Ridge of Virginia  

Microsoft Academic Search

A catastrophic storm that struck the central Virginia Blue Ridge Mountains in June 1995 delivered over 775 mm (30.5 in) of rain in 16 h. The deluge triggered more than 1000 slope failures; and stream channels and debris fans were deeply incised, exposing the stratigraphy of earlier mass movement and fluvial deposits. The synthesis of data obtained from detailed pollen

L. Scott Eaton; Benjamin A. Morgan; R. Craig Kochel; Alan D. Howard

2003-01-01

107

Ages of Quaternary Rio Grande terrace-fill deposits, Albuquerque area, New Mexico  

USGS Publications Warehouse

Results from luminescence dating on 13 samples from the Albuquerque area show that major-drainage fluvial deposits represent significant periods of aggradation that formed paired, correlatable terraces on the east and west margins of the Rio Grande valley . The youngest terrace fills (Primero Alto) formed during late Pleistocene as a result of streamflow variations with climate cooling during Marine Oxygen-Isotope Stage 3; our ages suggest aggradation of the upper part of the fill occurred at about 47–40 ka . Deposits of the second (Segundo Alto) terraces reached maximum height during climate cooling in the early part of Marine Oxygen-Isotope Stage 5 as late as 90–98 ka (based on dated basalt flows) . Our luminescence ages show considerable scatter and tend to be younger (range from 63 ka to 162 ka) . The third (Tercero Alto) and fourth (Cuarto Alto) terraces are dated on the basis of included volcanic tephra. Tercero Alto terrace-fill deposits contain the Lava Creek B tephra (639 ka), and Cuarto Alto terrace-fill deposits contain tephra of the younger Bandelier Tuff eruption (1 .22 Ma), the Cerro Toledo Rhyolite (1 .47 Ma), and the older Bandelier Tuff eruption (1 .61 Ma). These periods of aggradation culminated in fluvial terraces that are preserved at maximum heights of 360 ft (Cuarto Alto), 300 ft. (Tercero Alto), 140 ft (Segundo Alto), and 60 ft. (Primero Alto) above the modern floodplain. Despite lithologic differences related to local source-area contributions, these terracefill deposits can be correlated across the Rio Grande and up- and down-valley for tens of miles based on maximum height of the terrace above the modern floodplain.

James Channing Cole;Shannon A Mahan;Byron D Stone;Ralph R Shroba

2007-01-01

108

Ages of Quaternary Rio Grande terrace-fill deposits, Albuquerque area, New Mexico  

USGS Publications Warehouse

Results from luminescence dating on 13 samples from the Albuquerque area show that major-drainage fluvial deposits represent significant periods of aggradation that formed paired, correlatable terraces on the east and west margins of the Rio Grande valley. The youngest terrace fills (Primero Alto) formed during late Pleistocene as a result of streamflow variations with climate cooling during Marine Oxygen-Isotope Stage 3; our ages suggest aggradation of the upper part of the fill occurred at about 47-40 ka. Deposits of the second (Segundo Alto) terraces reached maximum height during climate cooling in the early part of Marine Oxygen-Isotope Stage 5 as late as 90-98 ka (based on dated basalt flows). Our luminescence ages show considerable scatter and tend to be younger (range from 63 ka to 162 ka). The third (Tercero Alto) and fourth (Cuarto Alto) terraces are dated on the basis of included volcanic tephra. Tercero Alto terrace-fill deposits contain the Lava Creek B tephra (639 ka), and Cuarto Alto terrace-fill deposits contain tephra of the younger Bandelier Tuff eruption (1.22 Ma), the Cerro Toledo Rhyolite (1.47 Ma), and the older Bandelier Tuff eruption (1.61 Ma). These periods of aggradation culminated in fluvial terraces that are preserved at maximum heights of 360 ft (Cuarto Alto), 300 ft (Tercero Alto), 140 ft (Segundo Alto), and 60 ft (Primero Alto) above the modern flood-plain. Despite lithologic differences related to local source-area contributions, these terracefill deposits can be correlated across the Rio Grande and up- and down-valley for tens of miles based on maximum height of the terrace above the modern floodplain.

Cole, J. C.; Mahan, S. A.; Stone, B. D.; Shroba, R. R.

2007-01-01

109

Mohawk Lake or Mohawk meadow Sedimentary facies and stratigraphy of Quaternary deposits in Mohawk Valley, upper Middle Fork of the Feather River, California  

Microsoft Academic Search

Mohawk Valley (MV) contain thick, well-exposed sections of Quaternary basin-fill sediments, with abundant interbedded tephra and a diverse assemblage of sedimentary facies. The eastern arm of MV, extending from Clio to Portola, contains as much as 100 m of trough cross-bedded cobble to pebble gravel and planar and trough cross-bedded coarse and medium sand, interpreted as braided stream deposits. Sections

J. C. Yount; D. S. Harwood; J. P. Bradbury

1993-01-01

110

75 FR 62137 - Notice of Public Meeting; Proposed Alluvial Valley Floor Coal Exchange Public Interest Factors...  

Federal Register 2010, 2011, 2012, 2013

...Public Meeting; Proposed Alluvial Valley Floor Coal Exchange Public Interest Factors; Montana...to consider a proposal to exchange Federal coal deposits for Alluvial Valley Floor (AVF) fee coal pursuant to the Federal Land Policy and...

2010-10-07

111

Temporal correlation of fluvial and alluvial sequences in the Makran Range, SE-Iran  

NASA Astrophysics Data System (ADS)

The Makran region of southeastern Iran is an active accretionary wedge with a partially subaerial component. New investigations have revealed a rather complex geodynamic evolution of the Makran active accretionary wedge that is not yet fully understood in its entity. Ongoing convergence between the Arabian and Eurasian plates and tectonic activity since the late Mesozoic has extended all trough the Quaternary. We focus here on fluvial and alluvial sequences in tectonically separated basins that have been deposited probably in the Pliocene/Quaternary, based on stratigraphic classification in official geological maps, in order to understand the climatic and tectonic forces occurring during the ongoing accretionary wegde formation. Specifically, we investigate the influence of Quaternary climate variations (Pleistocene cold period, monsoonal variations) on erosional and depositional processes in the (semi)arid Makran as well as local and regional tectonic forces in the Coastal and Central Makran Range region. Necessary for such an analysis is a temporal calibration of alluvial and fluvial terrace sequences that will allow an inter-basin correlation. We utilize the exposure age dating method using terrestrial cosmogenic nuclides (TCN) due to the lack of otherwise datatable material in the arid Makran region. Limited radiocarbon data are only available for marine terraces (wave-cut platforms). Our preliminary 21Ne and 10Be TCN-ages of amalgamated clast samples from (un)deformed terrace and alluvial sequences range from ~250 ky to present day (modern wash). These ages agree in relative terms with sequences previously assigned by other investigations through correlation of Quaternary sequences from Central and Western Iran regions. However, our minimum ages suggest that all age sequences are of middle to late Pleistocene age, compared to Pliocene age estimates previously assigned for the oldest units. Although often suggested, a genetical relation and connection of those fluvial sequences to coastal terraces and wave-cut platforms is problematic due to ambiguous ages and obscured stratigraphic linkage. Our data suggest that events of terrace formation are roughly coeval between basins, but do not indicate a distinct climate forcing, though there is some tendency that terraces were formed during interglacial periods. Preliminary incision rates derived from strath terraces are on the order of 0.1-3 mm/yr with non-steady intervals. This in turn is well in the range of uplift rates deduced from coastal terraces. Further investigations are on the way, especially resolving complex exposure histories based on combining cosmogenic radionuclides and 21Ne.

Kober, F.; Zeilinger, G.; Ivy-Ochs, S.; Dolati, A.; Smit, J.; Burg, J.-P.; Bahroudi, A.; Kubik, P. W.; Baur, H.; Wieler, R.; Haghipour, N.

2009-04-01

112

Lithology, mineralogy, and paleontology of Quaternary lake deposits in Long Valley Caldera, California  

USGS Publications Warehouse

Drill cores and cuttings from two drill holes, about 3 km apart, in Long Valley caldera, Mono County, California, were studied using x-ray diffraction and optical methods. A thick sequence of tuffs and lake sediments was encountered in LVCH-1 (1,000 ft deep) and Republic well 66-29 (6,920 ft deep), drilled in the southeast part of the Long Valley caldera. Ostracods, diatoms, and isotopic data indicate that the sediments and tuffs were deposited in a shallow caldera lake which changed in salinity over time. Conditions ranged from very saline in the older lake to fresh in the youngest. The sequence of secondary minerals from top to bottom is: clinoptilolite, mordenite, analcime, K-feldspar (and albite). In some geothermal systems, this sequence of secondary minerals is a function of temperature; however, the paleontological and isotopic data indicate that the change in secondary minerals with increasing depth is due to the older strata being deposited in a more saline environment. No mineralogical evidence of hydrothermal alteration is present, although the high lithium content of some clays and feldspars and the isotopic composition of some sulfate (gypsum) seems to require a hydrothermal source. (Lantz-PTT)

Fournier, R.B.

1989-01-01

113

Stratigraphy and U-series geochronology of Late Quaternary megatsunami deposits in Hawaii  

NASA Astrophysics Data System (ADS)

Our previous work on Kohala, Hawaii, established that the elevated marine basalt boulder conglomerates found there represent at least one, and probably two megatsunami events in the late Pleistocene. Together with the evidence for giant submarine landslides off western Hawaii island from contemporaneous flank failures of Mauna Loa volcano and identical sequences of submarine terraces off the NW coasts of the islands of Hawaii and Lanai, our hydrodynamic modeling indicates that all islands in the Hawaiian chain must have been affected by these giant waves. We present new dating of these deposits on Hawaii, Lanai and Maui islands together with stratigraphic interpretations of their impacts and origins. We used uranium-series dating of in situ coral clasts to constrain the age of the marine conglomerates, using multiple ion counting- inductively coupled plasma-mass spectrometry techniques, and used 87Sr/86Sr ratios of carbonates to help delineate their origins where marine fossils were absent. Southern Lanai records at least four megatsunami events: at 110 ka, 135 ka, 200 ka, and 240 ka, that likely correspond to the Alika phase 2, Alika phase 1, and two stages of the older South Kona giant submarine landslides. These event dates also correspond to O- isotopic stages 5d, 5e, 7a and 7b, and are in agreement with a changing-climate trigger mechanism for volcanic flank collapse proposed in previous work by ourselves and others. On southern Lanai, there is evidence for two megatsunami deposits in stratigraphic succession in the vicinity of Manele Bay, as well as higher-elevation deposits there containing reworked coral-bearing debris from two older megatsunami events. Coral clasts have been dated from all four events within the high-elevation gullies within Kaluakapo Crater on southern Lanai in this study and Moore and Moore (1988), indicating enormous runups to more than 626 m and wave heights of more than 240 m there that are in agreement with the latest hydrodynamic modeling. There is presently evidence for the 110 ka event on Hawaii, Lanai and West Maui, and for the 200 ka and 240 ka events on the islands of Lanai, Molokai and probably Hawaii. The 135 ka event has so far only been recorded on southern Lanai, but will likely turn up in future work elsewhere.

McMurtry, G. M.; Fryer, G. J.; Tappin, D. R.; Fietzke, J.

2008-12-01

114

Paleoclimatic significance of Late Quaternary eolian deposition on the Piedmont and High Plains, Central United States  

NASA Astrophysics Data System (ADS)

Presently stabilized dune systems on the piedmont of eastern Colorado and adjacent High Plains have been repeatedly re-activated during the past 20,000 years. Radiocarbon and thermoluminescence age estimates indicate eolian activity late in the last glacial cycle ca. 20,000-12,000 yr B.P. and subsequent episodes of dune reactivation at ca. 6000, 4500 and 1000 yr B.P. Pollen analysis from aggraded buried soil A horizons show a shift from grasses and shrubs to goosefoot, a disturbance indicator. The association of maximum goosefoot levels with the coarsest part of the buried A horizon immediately prior to burial by eolian sand indicates a substantial reduction in grass and dominance of shrubs with onset of eolian activity. The vegetation change and eolian depositional sequence indicates a reduction in plant coverage with regional drought, possibly augmented by bison grazing and surface heating effects. We infer an increase in summer monsoonal precipitation between 13,000 and 9000 yr B.P. reflecting a heightened land-to-sea temperature gradient associated with rising summer solar-insolation values and a meltwater cooled Gulf of Mexico. Dune reactivation in the middle and late Holocene appears to be independent of summer insolation values, but rather reflects a small (< 10°) easterly shift of the Bermuda High and western ridge aloft, difficult parameters to link to a cause and to resolve with climate models.

Forman, Steven L.; Oglesby, Robert; Markgraf, Vera; Stafford, Thomas

1995-06-01

115

Ochotona(Lagomorpha) from Late Quaternary Cave Deposits in Eastern North America  

NASA Astrophysics Data System (ADS)

Pikas ( Ochtona)—small gnawing mammals, related to rabbits—range today throughout parts of the Northern Hemisphere, but had a wider distribution during the Pleistocene. Nine caves from northeastern North America (a region not occupied by pikas today) have Pleistocene deposits containing remains of Ochotona.We examine 526 fossil specimens (ranging in age from approximately 850,000 to 8670 yr B.P.) from five of these caves. Two morphological forms of Ochotonalived in northeastern North America during the late Pleistocene—a large species (probably O. whartoni) and a small species (probably O. princeps). Ochotonaof glacial age are not necessarily indicative of talus slopes and mesic communities. O. princeps-like of the Irvingtonian of West Virginia were living with an amphibian-reptilian assemblage found in the area today, implying winters not much, if at all, colder than at present. Late glacial and postglacial change in climate south of the ice sheets in effect would have isolated Ochotonain eastern North America, where they were unable to retreat to the west or north. Whereas western pika had the option of moving up in elevation, into boreal islands, eastern forms became restricted to ever-diminishing habitats, culminating in extinction and extirpation. Radiocarbon ages imply that Ochotonalived in eastern North America during the late Pleistocene (late Rancholabrean) and into the earliest Holocene. We describe the youngest remains of Ochotonain eastern North America and the youngest for the extinct large form, O. whartoni.

Mead, Jim I.; Grady, Frederick

1996-01-01

116

Isopachs of Quaternary deposits, Fremont 1- by 2- degree Quadrangle and part of Omaha Quadrangle, Nebraska, digitized from a published 1:250,000-scale geologic map  

USGS Publications Warehouse

A geologic map showing the isopachs of Quaternary deposits in the Fremont and part of the Omaha, Nebraska, 1- by 2-degree quadrangles was published at a scale of 1:250,000 in 1975 (Burchett and others, 1975). This report describes the conversion of Quaternary thickness data into a digital geographic data set. A film separation of the published isopachs was scan-digitized and processed to produce digital geographic data. Geographic feature attributes and data-set documentation also are included in the digital data set. The digital data set are formatted for distribution with accordance with the Spatial Data Transfer Standard approved by the U.S. National Institute of Standards and Technology.

Zelt, R.B.; Patton, E.J.

1995-01-01

117

Geophysical Characterization of the Quaternary-Cretaceous Contact Using Surface Resistivity Methods in Franklin and Webster Counties, South-Central Nebraska  

USGS Publications Warehouse

To help manage and understand the Platte River system in Nebraska, the Platte River Cooperative Hydrology Study (COHYST), a group of state and local governmental agencies, developed a regional ground-water model. The southern boundary of this model lies along the Republican River, where an area with insufficient geologic data immediately north of the Republican River led to problems in the conceptualization of the simulated flow system and to potential problems with calibration of the simulation. Geologic descriptions from a group of test holes drilled in south-central Nebraska during 2001 and 2002 indicated a possible hydrologic disconnection between the Quaternary-age alluvial deposits in the uplands and those in the Republican River lowland. This disconnection was observed near a topographic high in the Cretaceous-age Niobrara Formation, which is the local bedrock. In 2003, the U.S. Geological Survey, in cooperation with the COHYST, collected surface geophysical data near these test holes to better define this discontinuity. Two-dimensional imaging methods for direct-current resistivity and capacitively coupled resistivity were used to define the subsurface distribution of resistivity along several county roads near Riverton and Inavale, Nebraska. The relation between the subsurface distribution of resistivity and geology was defined by comparing existing geologic descriptions of test holes to surface-geophysical resistivity data along two profiles and using the information gained from these comparisons to interpret the remaining four profiles. In all of the resistivity profile sections, there was generally a three-layer subsurface interpretation, with a resistor located between two conductors. Further comparison of geologic data with the geophysical data and with surficial features was used to identify a topographic high in the Niobrara Formation near the Franklin Canal which was coincident with a resistivity high. Electrical properties of the Niobrara Formation made accurate interpretation of the resistivity profile sections difficult and less confident because of similar resistivity of this formation and that of the coarser-grained sediment of the Quaternary-age deposits. However, distinct conductive features were identified within the resistivity profile sections that aided in delineating the contact between the resistive Quaternary-age deposits and the resistive Niobrara Formation. Using this information, an interpretive boundary was drawn on the resistivity profile sections to represent the contact between the Quaternary-age alluvial deposits and the Cretaceous-age Niobrara Formation. A digital elevation model (DEM) of the top of the Niobrara Formation was constructed using the altitudes from the interpreted contact lines. This DEM showed that the general trend of top of the Niobrara Formation dips to the southeast. At the north edge of the study site, the Niobrara Formation topographic high trends east-west with an altitude range of 559 meters in the west to 543 meters in the east. Based on the land-surface elevation and the Niobrara Formation DEM, the estimated thickness of the Quaternary-age alluvial deposits throughout the study area was mapped and showed a thinning of the Quaternary-age alluvial deposits to the north, approximately where the topographic high of the Niobrara Formation is located. This topographic high in the Niobrara Formation has the potential to act as a barrier to ground-water flow from the uplands alluvial aquifer to the Republican River alluvial aquifer as shown in the resistivity profile sections. The Quaternary-age alluvial deposits in the uplands and those in the Republican River Valley are not fully represented as disconnected because it is possible that there are ground-water flow paths that were not mapped during this study.

Teeple, Andrew P.; Kress, Wade H.; Cannia, James C.; Ball, Lyndsay B.

2009-01-01

118

Late Tertiary and Quaternary geology of the Tecopa basin, southeastern California  

SciTech Connect

Stratigraphic units in the Tecopa basin, located in southeastern California, provide a framework for interpreting Quaternary climatic change and tectonism along the present Amargosa River. During the late Pliocene and early Pleistocene, a climate that was appreciably wetter than today`s sustained a moderately deep lake in the Tecopa basin. Deposits associated with Lake Tecopa consists of lacustrine mudstone, conglomerate, volcanic ash, and shoreline accumulations of tufa. Age control within the lake deposits is provided by air-fall tephra that are correlated with two ash falls from the Yellowstone caldera and one from the Long Valley caldera. Lake Tecopa occupied a closed basin during the latter part, if not all, of its 2.5-million-year history. Sometime after 0.5 m.y. ago, the lake developed an outlet across Tertiary fanglomerates of the China Ranch Beds leading to the development of a deep canyon at the south end of the basin and establishing a hydrologic link between the northern Amargosa basins and Death Valley. After a period of rapid erosion, the remaining lake beds were covered by alluvial fans that coalesced to form a pediment in the central part of the basin. Holocene deposits consist of unconsolidated sand and gravel in the Amargosa River bed and its deeply incised tributaries, a small playa near Tecopa, alluvial fans without pavements, and small sand dunes. The pavement-capped fan remnants and the Holocene deposits are not faulted or tilted significantly, although basins to the west, such as Death Valley, were tectonically active during the Quaternary. Subsidence of the western basins strongly influenced late Quaternary rates of deposition and erosion in the Tecopa basin.

Hillhouse, J.W.

1987-12-31

119

Water-quality characteristics of quaternary unconsolidated-deposit aquifers and lower tertiary aquifers of the Bighorn Basin, Wyoming and Montana, 1999-2001  

USGS Publications Warehouse

As part of the Yellowstone River Basin National Water Quality Assessment study, ground-water samples were collected from Quaternary unconsolidated-deposit and lower Tertiary aquifers in the Bighorn Basin of Wyoming and Montana from 1999 to 2001. Samples from 54 wells were analyzed for physical characteristics, major ions, trace elements, nutrients, dissolved organic carbon, radionuclides, pesticide compounds, and volatile organic compounds (VOCs) to evaluate current water-quality conditions in both aquifers. Water-quality samples indicated that waters generally were suitable for most uses, and that natural conditions, rather than the effects of human activities, were more likely to limit uses of the waters. Waters in both types of aquifers generally were highly mineralized, and total dissolved-solids concentrations frequently exceeded the U.S. Environmental Protection Agency (USEPA) Secondary Maximum Contaminant Level (SMCL) of 500 milligrams per liter (mg/L). Because of generally high mineralization, waters from nearly one-half of the samples from Quaternary aquifers and more than one-half of the samples from lower Tertiary aquifers were not classified as fresh (dissolved-solids concentration were not less than 1,000 mg/L). The anions sulfate, fluoride, and chloride were measured in some ground-water samples at concentrations greater than SMCLs. Most waters from the Quaternary aquifers were classified as very hard (hardness greater than 180 mg/L), but hardness varied much more in waters from the lower Tertiary aquifers and ranged from soft (less than 60 mg/L) to very hard (greater than 180 mg/L). Major-ion chemistry varied with dissolved-solids concentrations. In both types of aquifers, the predominant anion changes from bicarbonate to sulfate with increasing dissolved-solids concentrations. Samples from Quaternary aquifers with fresh waters generally were calcium-bicarbonate, calcium-sodium-bicarbonate, and calcium-sodium-sulfate-bicarbonate type waters, whereas samples with larger concentrations generally were calcium-sodium-sulfate, calcium-sulfate, or sodium-sulfate-type waters. In the lower Tertiary aquifers, samples with fresh waters generally were sodium-bicarbonate or sodium-bicarbonate-sulfate type waters, whereas samples with larger concentrations were sodium-sulfate or calcium-sodium-sulfate types. Concentrations of most trace elements in both types of aquifers generally were small and most were less than applicable USEPA standards. The trace elements that most often did not meet USEPA secondary drinking-water standards were iron and manganese. In fact, the SMCL for manganese was the most frequently exceeded standard; 68 percent of the samples from the Quaternary aquifers and 31 percent of the samples from the lower Tertiary aquifers exceeded the manganese standard. Geochemical conditions may control manganese in both aquifers as concentrations in Quaternary aquifers were negatively correlated with dissolved oxygen concentrations and concentrations in lower Tertiary aquifers decreased with increasing pH. Elevated nitrate concentrations, in addition to detection of pesticides and VOCs in both aquifers, indicated some effects of human activities on ground-water quality. Nitrate concentrations in 36 percent of the wells in Quaternary aquifers and 28 percent of the wells in lower Tertiary aquifers were greater than 1 mg/L, which may indicate ground-water contamination from human sources. The USEPA drinking-water Maximum Contaminant Level (MCL) for nitrate, 10 mg/L, was exceeded in 8 percent of samples collected from Quaternary aquifers and 3 percent from lower Tertiary aquifers. Nitrate concentrations in Quaternary aquifers were positively correlated with the percentage of cropland and other agricultural land (non-cropland), and negatively correlated with rangeland and riparian land. In the lower Tertiary aquifers, nitrate concentrations only were correlated with the percentage of cropland. Concentratio

Bartos, Timothy T.; Eddy-Miller, Cheryl A.; Norris, Jody R.; Gamper, Merry E.; Hallberg, Laura L.

2004-01-01

120

Potential impacts of damming the Juba Valley, western Somalia: Insights from geomorphology and alluvial history  

NASA Astrophysics Data System (ADS)

In 1988 plans were well advanced to dam the Juba River in western Somalia. The aims of the Baardheere Dam Project were to generate hydroelectric power for the capital Mogadishu, and to provide water for irrigation in the Juba Valley. A reconnaissance survey on foot along 500 km of the river upstream of the proposed dam site at Baardheere and detailed geomorphic mapping from air photos provided a basis for reconstructing the late Quaternary alluvial history of the river and for assessing the potential impact of the proposed dam. The Juba River rises in the Ethiopian Highlands and is the only river in Somalia that flows to the sea. Its history reflects climatic events in Ethiopia, where the Rift Valley lakes were very low during the LGM (21±2 ka), and high for about 5, 000 years before and after then. Cave deposits in Somalia indicate wetter conditions at 13, 10, 7.5 and 1.5 ka. Alluvial terraces in the Juba Valley range in age from late Pleistocene to late Holocene but only attain a few metres above the present floodplain. This is because the dry tributary valleys contain limestone caves and fissures that divert any high flows from the parent river underground, a process not known when the project was first approved. The oldest preserved terrace was cemented by calcrete by 40 ka. Alluvial gravels were deposited at the outlet of dry tributary valleys during times of episodic high-energy flow between 26 ka and 28 ka. Finely laminated shelly sands accumulated at 10 ka to form the 5 m terrace. The 2 m terrace was laid down 3.2 ka ago as a slackwater deposit. The lack of high-level alluvial terraces raises doubts over plans to dam the river, since rapid leakage would occur from side valleys and the reservoir would not attain the height needed to generate hydroelectric power. It would submerge all existing arable land along the river. Finally, the presence in the late Holocene alluvium of the sub-fossil gastropods Bulinus truncatus and Biomphalaria pfeifferi, which are the two main vectors of schistosomiasis in northeast Africa, suggests that this parasitic disease could become endemic across the valley. Any future plans to manage the Juba River need to take proper account of alluvial history and geomorphic processes.

Williams, Martin

2014-05-01

121

Late Quaternary sediment deposition of core MA01 in the Mendeleev Ridge, the western Arctic Ocean: Preliminary results  

NASA Astrophysics Data System (ADS)

Late Quaternary deep marine sediments in the Arctic Ocean are characterized by brown layers intercalated with yellowish to olive gray layers (Poore et al., 1999; Polyak et al., 2004). Previous studies reported that the brown and gray layers were deposited during interglacial (or interstadial) and glacial (or stadial) periods, respectively. A 5.5-m long gravity core MA01 was obtained from the Mendeleev Ridge in the western Arctic Ocean by R/V Xue Long during scientific cruise CHINARE-V. Age (~450 ka) of core MA01 was tentatively estimated by correlation of brown layers with an adjacent core HLY0503-8JPC (Adler et al., 2009). A total of 22 brown layers characterized by low L* and b*, high Mn concentration, and abundant foraminifera were identified. Corresponding gray layers are characterized by high L* and b*, low Mn concentration, and few foraminiferal tests. Foraminifera abundance peaks are not well correlated to CaCO3 peaks which occurred with the coarse-grained (>0.063 mm) fractions (i.e., IRD) both in brown and gray layers. IRDs are transported presumably by sea ice for the deposition of brown layers and by iceberg for the deposition of gray layers (Polyak et al., 2004). A strong correlation coefficient (r2=0.89) between TOC content and C/N ratio indicates that the major source of organic matter is terrestrial. The good correlations of CaCO3 content to TOC (r2=0.56) and C/N ratio (r2=0.69) imply that IRDs contain detrital CaCO3 which mainly originated from the Canadian Arctic Archipelago. In addition, high kaolinite/chlorite (K/C) ratios mostly correspond to CaCO3 peaks, which suggests that the fine-grained particles in the Mendeleev Ridge are transported from the north coast Alaska and Canada where Mesozoic and Cenozoic strata are widely distributed. Thus, the Beaufort Gyre, the predominant surface current in the western Arctic Ocean, played an important role in the sediment delivery to the Mendeleev Ridge. It is worthy of note that the TOC and CaCO3 peaks are obviously distinct in the upper part of core MA01, whereas these peaks are reduced in the lower part of the core. More study on these contrasting features is in progress. References Adler, R.E., Polyak, L., Ortiz, J.D., Kaufman, D.S., Channell, J.E.T., Xuan, C., Grottoli, A.G., Sellén, E., and Crawford, K.A., 2009. Global and Planetary Change 68(1-2), 18-29. Polyak, L., Curry, W.B., Darby, D.A., Bischof, J., and Cronin, T.M., 2004. Palaeogeography, Palaeoclimatology, Palaeoecology 203, 73-93. Poore, R., Osterman, L., Curry, W., and Phillips, R., 1999. Geology 27, 759-762.

Park, Kwang-Kyu; Kim, Sunghan; Khim, Boo-Keun; Xiao, Wenshen; Wang, Rujian

2014-05-01

122

Increased storminess during MIS3 altered the late Quaternary basin-scale weathering, erosion, and deposition in Nahal Yael, hyperarid Negev, Israel  

NASA Astrophysics Data System (ADS)

A conceptual model for geomorphic response to Pleistocene to Holocene climate change (Bull and Schick, 1979, Quat. Res. 11: 153-171) was probably based on earlier observations in the southwestern US, but first applied to the hyperarid (<30 mm yr-1) Nahal Yael watershed, southern Negev desert. This influential model includes a chain of events following a climate change from semiarid late Pleistocene to hyperarid Holocene: reduced vegetation cover, increased yield of sediments from slopes, and accelerated aggradation of terraces and export of sediment from the basin to deposit an alluvial fan. The model is now >30 years old and during this time chronologic, paleoenvironmental and hydrogeomorphic research have all advanced but the discussions are still within the framework put forward then. The model is revaluated here by using data acquired in Nahal Yael over the 30 years since the original model was proposed. Recent studies indicate late Pleistocene climate was hyperarid and the transition from semiarid to hyperarid climates did not occur. The revised chronology reveals a 35-20 ka episode (probably already beginning at ~50 ka with lower rates) of accelerated weathering and sediment production and distinct talus accretion on slopes. Coeval with accretion on slopes, sediments were also transported and aggraded in fluvial terraces and alluvial fans, without noticeable lag time or a chain of discernable events. This intensified sediment production and delivery phase is unrelated to the Pleistocene-Holocene transition. The depositional landforms were rapidly incised during 20-18 ka; since this approximately LGM incision, sediment yield is from the storage in these depositional landforms and is not produced from bedrock in significant quantities. We propose that in such hyperarid environment, the main operators are individual extreme storms, and in this case specifically an episode of frequent storms and floods is the driver of change regardless the mean climatic conditions. It created a pulse of intense weathering due to numerous cycles of wetting and drying on slopes and sediment transport to fluvial terraces and alluvial fans; its impact continues all the way to the present. We suggest that even if aspects of the original conceptual model of Bull and Schick (1979) are correct, it has been applied too frequently, too generally, across very diverse arid climates and settings, and for too long in lieu of collecting new data at a full basin scale and testing the model.

Enzel, Y.; Amit, R.; Grodek, T.; Ayalon, A.; Lekach, J.; Porat, N.; Bierman, P. R.; Blum, J. D.; Erel, Y.

2012-12-01

123

Evidence of Quaternary rock avalanches in the central Apennines: new data and interpretation of the huge clastic deposit of the L'Aquila basin (central Apennines, Italy)  

NASA Astrophysics Data System (ADS)

Active extensional tectonics and widespread seismicity affect the axial zone of the central Apennines (Italy) and led to the formation of several plio-quaternary intermontane basins, whose morpho-evolution was controlled by the coupling of tectonic and climatic inputs. Common features of the Apennines intermontane basins as well as their general morpho-evolution are known. Nonetheless, the complex interaction among regional uplift, local fault displacements and morpho-climatic factors caused differences in the denudational processes of the single intermontane basins. Such a dynamic response left precious records in the landscape, which in some cases testify for the occurrence of huge, catastrophic rock slope failures. Several Quaternary rock avalanches have been identified in central Apennines, which are often associated with Deep Seated Gravitational Slope Deformation (DSGSD) and thus strictly related to the geological-structural setting as well as to the Quaternary morpho-structural evolution of the mountain chain. The L'Aquila basin is one of the intermontane tectonic depression aligned along the Middle Aterno River Valley and was the scene of strong historical earthquakes, among which the last destructive event occurred on April 6, 2009 (Mw 6.3). We present here the evidence that the huge clastic deposit on which the city of L'Aquila was built up is the body of a rock avalanche detached from the southern slope of the Gran Sasso Range. The clastic deposit elongates for 13 km to the SW, from the Assergi Plain to L'Aquila and is characterized by typical morphological features such as hummocky topography, compressional ridges and run-up on the opposite slope. Sedimentological characters of the deposit and grain size analyses on the matrix let us confirm the genetic interpretation, while borehole data and significant cross sections allowed us reconstructing the 3D shape and volume of the clastic body. Finally, morphometric analyses of the Gran Sasso Range southern slope evidenced the possible source area of the inferred rock avalanche, which is framed within a slope section characterized by the presence of DSGSD-related landforms. The estimated volume of this source area is coherent with the volume calculated for the outcropping landslide body, both in the order of magnitude of hundreds of millions of cubic meters. Such a study is framed within a wider research activity addressed to a better understanding of the role of gravity-induced processes in the Quaternary morpho-evolution of the Apennine chain, but also to assess the potential "residual risk" conditions affecting the slopes already involved in DSGSD and massive rock slope failure processes.

Esposito, Carlo; Scarascia Mugnozza, Gabriele; Tallini, Marco; Della Seta, Marta

2014-05-01

124

Mohawk Lake or Mohawk meadow Sedimentary facies and stratigraphy of Quaternary deposits in Mohawk Valley, upper Middle Fork of the Feather River, California  

SciTech Connect

Mohawk Valley (MV) contain thick, well-exposed sections of Quaternary basin-fill sediments, with abundant interbedded tephra and a diverse assemblage of sedimentary facies. The eastern arm of MV, extending from Clio to Portola, contains as much as 100 m of trough cross-bedded cobble to pebble gravel and planar and trough cross-bedded coarse and medium sand, interpreted as braided stream deposits. Sections exposed in the western arm of MV consist in their lower parts of massive organic-rich silt and clay interbedded with blocky to fissile peat beds up to 1 m thick. Diatom assemblages are dominated by benthic species indicating fresh marsh environments with very shallow water depths of one meter or less. Proglacial lacustrine deposits of limited lateral extent are present within the outwash complexes as evidenced by varved fine sand and silt couplets, poorly sorted quartz-rich silt beds containing dropstones, and contorted beds of diamict grading laterally into slump blocks surrounded by wood-bearing silt and silty sand. The Rockland Ash (400 ka) is a prominent marker in the middle or lower part of many sections throughout MV, indicating that at least half of the basin-fill sequence is Late Quaternary in age. A log buried in diamict slumped into a proglacial lake lying approximately 3 km downstream from the Tioga Stage ice termini in Jamison and Gray Eagle Creeks yields an age of 18,715 [+-]235 C[sup 14] years BP. Previous interpretations of MV deposits originating in a large, deep lake with water depths in excess of 150 m are untenable given the sedimentary facies and diatom floras that dominate the valley. Unexhumed valleys such as Sierra Valley to the east and Long Valley to the northwest which contain large meadows traversed by braided streams are probably good analogs for the conditions that existed during the accumulation of the Mohawk Valley deposits.

Yount, J.C. (Univ. of Nevada, Reno, NV (United States)); Harwood, D.S. (Geological Survey, Menlo Park, CA (United States)); Bradbury, J.P. (Geological Survey, Denver, CO (United States))

1993-04-01

125

VARIATION IN EROSION/DEPOSITION RATES OVER THE LAST FIFTTY YEARS ON ALLUVIAL FAN SURFACES OF L. PLEISTOCENE-MID HOLOCENE AGE, ESTIMATIONS USING 137CS SOIL PROFILE DATA, AMARGOSA VALLEY, NEVADA  

SciTech Connect

Variations in erosion and deposition for the last fifty years (based on estimates from 137Cs profiles) on surfaces (Late Pleistocene to Late Holocene in age) making up the Fortymile Wash alluvial fan south of Yucca Mountain, is a function of surface age and of desert pavement development or absence. For purposes of comparing erosion and deposition, the surfaces can be examined as three groups: (1) Late Pleistocene surfaces possess areas of desert pavement development with thin Av or sandy A horizons, formed by the trapping capabilities of the pavements. These zones of deposition are complemented by coppice dune formation on similar parts of the surface. Areas on the surface where no pavement development has occurred are erosional in nature with 0.0 +/- 0.0 cm to 1.5 +/- 0.5 cm of erosion occurring primarily by winds blowing across the surface. Overall these surfaces may show either a small net depositional gain or small erosional loss. (2) Early Holocene surfaces have no well-developed desert pavements, but may have residual gravel deposits in small areas on the surfaces. These surfaces show the most consistent erosional surface areas on which it ranges from 1.0 +/-.01 cm to 2.0+/- .01 cm. Fewer depositional forms are found on this age of surface so there is probably a net loss of 1.5 cm across these surfaces. (3) The Late Holocene surfaces show the greatest variability in erosion and deposition. Overbank deposition during floods cover many edges of these surfaces and coppice dune formation also creates depositional features. Erosion rates are highly variable and range from 0.0 +/- 0.0 to a maximum of 2.0+/-.01. Erosion occurs because of the lack of protection of the surface. However, the common areas of deposition probably result in the surface having a small net depositional gain across these surfaces. Thus, the interchannel surfaces of the Fortymile Wash fan show a variety of erosional styles as well as areas of deposition. The fan, therefore, is a dynamic system that primarily responds to the incising of the channels into the upper fan surface, and the development of protecting desert pavements with time.

C. Harrington; R. Kelly; K.T. Ebert

2005-08-26

126

Quaternary fluvial and eolian deposits on the Belan river, India: paleoclimatic setting of Paleolithic to Neolithic archeological sites over the past 85,000 years  

NASA Astrophysics Data System (ADS)

Archeological sites in the bedrock Belan Valley at the southern margin of the Ganga Plains of India have unearthed Paleolithic to Neolithic artifacts and the first known evidence for rice cultivation. We present a sedimentological and paleoclimatic analysis for Belan sections, incorporating new luminescence and radiocarbon dates and a compilation of previous research. Some 20 m of strata are exposed in fluvial terraces, commencing with pedogenic and channel calcretes linked to groundwater ponding on the underlying bedrock. Overlying alluvium deposited from mixed-load meandering rivers yields dates between 85±11 and 72±8 kyr before present (BP), implying sustained fluvial activity during Marine Isotope Stage 5 and later; these strata contain Middle Paleolithic artifacts. Thin reworked gravels with Upper Paleolithic artifacts are dated at ˜21-31 kyr BP, and may represent declining alluviation and floodplain gully erosion during reduced monsoonal activity around the Last Glacial Maximum (LGM). Younger channel fills contain shell-rich eolian sand, and mounds of shelly sand lie inland from the river. Five OSL dates from the sands span 14 to 7 kyr BP, corresponding to a period of climatic instability that includes the Younger Dryas as the monsoon intensified following the LGM. Although suggesting more arid phases, the source-bordering eolian material has a small volume and the grains are partially bleached, indicating local wind action. Overlying floodplain muds reflect renewed alluviation, after which the river incised during peak monsoon flow. The Mesolithic settlement of Chopani-Mando spans a period of reduced monsoon activity and climatic instability following the LGM. Subsequent Neolithic settlements were probably established under stronger monsoon conditions suitable for the development of agriculture. Mesolithic habitation may have ended when a nearby bedrock channel was abandoned as the reinvigorated Belan cut a new course, along which Neolithic settlements were later established.

Gibling, M. R.; Sinha, R.; Roy, N. G.; Tandon, S. K.; Jain, M.

2008-02-01

127

Vegetation ecology of Early Pennsylvanian alluvial fan and piedmont environments in southern New Brunswick, Canada  

Microsoft Academic Search

The vegetation ecology of Pennsylvanian upland\\/dryland regions is poorly known, despite its evolutionary significance. Here, fossil plant assemblages are described from well-drained alluvial fan\\/piedmont deposits in the uppermost Boss Point and Tynemouth Creek formations (late Yeadonian–Langsettian), southern New Brunswick. Beds record the northward building of a large alluvial fan complex over alluvial plain deposits in response to near-continuous sourceland uplift.

Howard J. Falcon-Lang

2006-01-01

128

Hydrogeologic Framework and Ground-Water Flow in Quaternary Deposits at the U.S. Army Atterbury Joint Maneuver Training Center near Edinburgh, Indiana, 2002-2003  

USGS Publications Warehouse

A hydrogeologic framework was developed for unconsolidated Quaternary deposits at the U.S. Army Atterbury Joint Maneuver Training Center. The framework describes the potential for the occurrence of ground water on the basis of physiography and the distribution of geologic materials within the study area. Four geologic units-the Jessup, Trafalgar, Atherton, and Martinsville Formations-were identified, and their distribution was mapped as four hydrogeologic regions. The Jessup and Trafalgar Formations are fine-grained, poorly sorted tills. At least two facies of the Atherton Formation, the lacustrine and outwash facies, are in the study area. The Martinsville Formation includes materials deposited or reworked since the glacial period. With the exception of the Atherton Formation outwash facies, the Quaternary deposits are primarily fine-grained, silt- and clay-rich sediments that function as confining layers or aquitards. The Atherton Formation out-wash facies includes sand and gravel deposits that constitute the primary aquifers in the study area. The four hydrogeologic regions mapped in this investigation are designated as the Bedrock, Jessup Till, Trafalgar Till, and Atherton Outwash Regions. Each region represents an area with a distinctive physiographic expression and vertical sequence of Quaternary deposits. The Bedrock Region in the western and southwestern part of the study area commonly is underlain by 0 to 15 feet of Martinsville Formation resting directly on bedrock. Potential ground-water yields are limited. The Jessup Till Region in the southeastern part of the study area includes the uplands on either side of the stream valleys. Sediments commonly range from 30 to 90 feet in thickness. This region includes clay-rich till of the Jessup Formation and sand and gravel deposits of the Atherton Formation outwash facies; the Atherton Formation outwash facies tends to be thin, and ground-water yields will be moderate. The Trafalgar Till Region in the north and northwest-central part of the study area commonly is underlain by 10 to 30 feet of Trafalgar till or Trafalgar till over 25 to 50 feet of Jessup till. Within, separating, and beneath these tills are deposits of the Atherton Formation outwash facies-the sand and gravel deposits with the best potential to support a water-supply well. Generally, the outwash facies in this region are thin sand and gravel lenses, except in a few locations that are in excess of 30 feet thick. The Atherton Outwash Region is the lowland area associated with the major valleys in all but the far southwestern part of the study area. This region has the greatest thickness of outwash facies sands and gravels (often in excess of 20 feet), which are the primary aquifers. In the Atterbury Joint Maneuver Training Center, the combined Atherton Outwash Region and the Trafalgar Till Region have the greatest potential as infiltration areas because of low topographic relief and(or) sandy soils. From water-level data collected in July and August 2003, horizontal ground-water flow was determined generally to be toward the Atherton Outwash Region and the valley of the Drift-wood River to the east. Vertical hydraulic gradients were documented at nested well pairs. At two sites, upwardly directed gradients are reflected by flowing wells. Ground-water discharge to surface water is likely in some eastern reaches of the valleys of Nineveh and Lick Creeks. In the valley of Nineveh Creek, potential for ground-water discharge is indicated by the presence of a flowing well, upwardly directed vertical hydraulic gradients, and ground-water heads that were higher than surface-water elevations. In the valley of Lick Creek, ground-water discharge also is indicated by the presence of flowing wells and ground-water heads that were higher than surface-water elevations.

Robinson, Bret A.; Risch, Martin R.

2006-01-01

129

Late Quaternary eolian dust in surficial deposits of a Colorado Plateau grassland: Controls on distribution and ecologic effects  

Microsoft Academic Search

In a semi-arid, upland setting on the Colorado Plateau that is underlain by nutrient-poor Paleozoic eolian sandstone, alternating episodes of dune activity and soil formation during the late Pleistocene and Holocene have produced dominantly sandy deposits that support grass and shrub communities. These deposits also contain eolian dust, especially in paleosols. Eolian dust in these deposits is indicated by several

Richard L. Reynolds; Marith C. Reheis; Jason C. Neff; Harland Goldstein; James Yount

2006-01-01

130

Provenance of the heavy mineral-enriched alluvial deposits at the west coast of the Red Sea. Implications for evolution of Arabian-Nubian crust  

NASA Astrophysics Data System (ADS)

Here we present the LA-ICP-MS U-Pb ages and Hf isotopic record of detrital zircons from the active alluvial fans at the west coast of the Red Sea. The Ras Manazal alluvial fan (primarily composed of zircon, magnetite with some rutile, ilmenite and monazite) yielded a relatively restricted age population ranges from 765 to 666 Ma. These ages and present-day drainage pattern is consistent that the sediments are primarily derived from erosion of nearby subduction related granitoids in the immediate west (i.e., not more than 50 km from the Red Sea coast) of the fan. In contrast, approximately 160 km south, at the Egypt-Sudan border, the Wadi Diit fan is relatively more enriched in ilmenite and REE-bearing phases (e.g., thorite, monazite, xenotime, garnet, etc.) and yielded five zircon age populations of (1) 824-733 Ma, (2) 730-705 Ma, (3) 646-608 Ma, (4) 516-500 Ma, and (5) 134-114 Ma. The age populations 1-3 if coupled with the present-day drainage pattern can be related to the earlier subduction related and later post collision granitoids in the southern part of the South Eastern Desert and Gebeit terrane of northern Sudan. Sparse Early Cretaceous zircons (134-114 Ma) are derived from the Mesozoic volcanic suits in the source region. However, the age group 516-500 Ma is enigmatic. Wadi Diit zircons are primarily derived from granitoids in the broad S-N directed Hamisana Shear Zone and its subordinate SW to NE directed Onib-Sol-Hamed Suture Zone. These shear zones provided pathways for the present-day drainage system for sediment transportation to the Wadi Diit and adjacent coastal region. We infer that the ca. 500 Ma late-stage magmatic zircons represent a hitherto unknown magmatic event, possibly related to the shear heating associated with the crustal scale shear zones. This implies that the shear zones in the South Eastern Desert and northern Sudan remained thermally active as late as ?500 Ma. The time resolved hafnium composition (?Hf (t)) of both fans varies from +3.5 to +13.5. Our new U-Pb ages and Hf isotopic composition suggests that the detrital zircons were derived from the Neoproterozoic juvenile crust. This is consistent with the Neoproterozoic juvenile igneous and metamorphic rocks in the Eastern Desert and northern Sudan.

Mahar, Munazzam Ali; Ibrahim, Tarek M. M.; Goodell, Philip C.

2014-12-01

131

Shallow subsurface stratigraphy and alluvial architecture of the Kosi and Gandak megafans in the Himalayan foreland basin, India  

NASA Astrophysics Data System (ADS)

The Kosi and the Gandak are two major Himalayan tributaries of the Ganga River in the north Bihar plains India. With a large hinterland in the Nepal Himalaya, both these rivers have generated megafans in the plains over the Quaternary time scale. Both these rivers are known to be highly dynamic and sediment-charged. A few conceptual models and limited field data suggested that these megafans have produced thick sand sheets over Late Quaternary period but these ideas have remained speculative and there is no data on the size and dimension of these sand bodies. This paper attempts to reconstruct the subsurface stratigraphy and alluvial architecture for the upper ~ 100 m of the megafans based on electrical resistivity soundings, borehole data and drill cores. Alluvial architecture of the Kosi megafan shows significant variability from proximal to medial parts of the fan in terms of sediment grain size and layer thicknesses. While the medial part shows ~ 20-30 m thick medium to coarse sand sheets which are laterally stacked, the proximal part of the fan has a dominantly gravel unit below ~ 15 m depth that is underlain and overlain by medium to coarse sand units. Further, the medial fan also shows significant vertical and lateral variability in alluvial stratigraphy. The near-surface (< 20 m depth) deposits from the Kosi megafan have pockets of clay and silt within large amalgamated sand bodies whereas the shallow sub-surface (50-100 m depth) sediments are largely sandy and devoid of clay and silt pockets. Alluvial architecture of the Gandak megafan shows two major lithounits; the upper fan succession has a higher stacking density of smaller sand bodies perhaps reflecting the migratory behavior of the river whereas the lower succession shows narrow but thick sand fills reflecting incised channels. The western part of the Gandak megafan has more abundant sand bodies compared to the eastern side of the river along both transects. There are no significant differences between proximal and medial transects across the Gandak megafan. The absence of gravel deposits in the shallow subsurface of the Gandak megafan may be attributed to the presence of a prominent intermontane valley in the hinterland of the Gandak river which has acted as a 'sediment filter' thereby trapping most of the coarser fraction. On the other hand, the Kosi river exits directly through the mountain front, and therefore, has been able to transport gravels into the plains in pre-historic times. Our study thus suggests significant variability in subsurface stratigraphy of the Kosi and the Gandak megafans even though they are located in similar geographic region. Such differences are attributed to the geomorphic diversity of the mountain exits of these megafans and their sediment transport history.

Sinha, Rajiv; Ahmad, Jawed; Gaurav, Kumar; Morin, Guillaume

2014-03-01

132

Sedimentology and paleogeographic evolution of the intermontane Kathmandu basin, Nepal, during the Pliocene and Quaternary. Implications for formation of deposits of economic interest  

NASA Astrophysics Data System (ADS)

The Kathmandu Valley is an intermontane basin in the center of a large syncline of the Lesser Himalayas. The sedimentary basin fill comprises three units of Plio-Pleistocene to Holocene age. The study aimed at modeling the paleogeographic evolution of the basin, with emphasis on sedimentary series of fossil fuels and non-metallic deposits. The lithological setting of the basin and the tectonic framework were instrumental to basin subsidence. Alluvial through lacustrine sedimentation during incipient stages is a direct response to uplift in the hinge zone of the synclinorium. Axial parallel sediment dispersal gave way to fluviodeltaic sedimentation mainly from the limbs of the synclinorium. Ongoing compression and renewed uplift in the core zone of the synclinorium drove the uplift of a NW-SE running divide and a subdivision of the mono-lake into two basins. This ridge blocked the flow of transverse rivers and the northern subbasin became gradually choked. Ongoing uplift of the entire basin during the recent geological history caused a reorganization of the drainage pattern and triggered linear erosion in the southern mountain range. Step-by-step the remaining lacustrine basins disappeared. Fan aggradation coincide with cold dry or warm seasons, fluvial dissection and discharge increased during warmer and more humid periods. High lake levels exist during phases of increased humidity. The results of this basin analysis may be used predictively in the exploration for coal, natural gas, diatomaceous earths and quarrying for sand or clay. The gas potential is at its maximum in the lacustrine facies, sand and clay for construction purposes may be quarried economically from various fluvial and deltaic deposits. Diatomaceous earths predominantly accumulated in marginal parts of the lake and some landslide-dammed ponds. Lignitic brown coal can be mined together with combustible shales from poorly drained swamps.

Dill, H. G.; Kharel, B. D.; Singh, V. K.; Piya, B.; Busch, K.; Geyh, M.

2001-10-01

133

Late Quaternary extraglacial cold-climate deposits in low and mid-altitude Tasmania and their climatic implications  

NASA Astrophysics Data System (ADS)

Many Tasmanian deposits previously described as 'periglacial' have been described in more detail, re-interpreted and dated. We suggest that 'periglacial' has little meaning when applied locally and the term 'relict cold-climate deposits' is more appropriate. In this paper we examine the origin and age of relict cold-climate slope deposits, fan alluvium and aeolian sediments in Tasmania, and infer the conditions under which they accumulated. Fan alluvium dating from the penultimate Glacial (OIS 6) and capped by a prominent palaeosol deduced to date to the Last Interglacial (OIS 5e) is present at Woodstock, south of Hobart. Many fan deposits formed before 40 ka or in a period c. 30-23 ka; only a few deposits date to the Last Glacial Maximum in Tasmania, which is defined as spanning the period 23.5-17.5 ka. Slope deposits indicate widespread instability down to present-day sea level throughout the Last Glacial, probably as a result of freeze-thaw in a sparsely vegetated landscape. Layered fine gravel and coarse sand colluvial deposits resembling grèzes litées, produced both by dry deposition and by the action of water, are locally common where jointed siltstone bedrock outcrops. These deposits occur from altitudes of 500 m to near sea level and also in caves and must have formed under sparse vegetation cover, probably by freeze-thaw in extremely dry conditions. They have been radiocarbon dated from 35 to 17.5 cal. ka. Relict dunes and sandsheets are widespread at the margin of the Bassian Plain that once provided a land bridge between Tasmania and the mainland. They are also found in western Tasmania and in areas of inland southern Tasmania that now support wet eucalypt forest and rainforest and receive mean annual rainfall > 1500 mm. In the south they have been dated > 87.5-19 ka and attest to a long period of semi-arid climate in an area extending well to the west and south of the present semiarid zone. We deduce that during most of the Last Glacial anticyclones dominated Tasmania's climate and rain-bearing depressions generally passed south of the land mass. However in the east prominent palaeosols in aeolian deposits, dated between 26.4 ka and 16 ka at different locations, and palaeosols with morphology indicating formation under humid conditions, indicate periods of wetter climate in eastern Tasmania during or close to the LGM, deduced to be the result of easterlies associated with near-coastal depressions in the western Tasman Sea. Such easterlies may also be responsible for short Last Glacial wet periods noted at mainland coastal sites. A plot of ages of all dated deposits reveals an increase of erosion and deposition between 35 and 20 ka, and greater prevalence of aeolian deposits in the 35-15 ka period than earlier in the Last Glacial. There are two possible explanations for this pattern: (1) that aeolian activity increased as the result of climatic effects (e.g. increased windiness); or (2) that shrubland biomass increased after the megafauna were hunted to extinction following human arrival c. 40 ka, causing increased fire frequency, and in the cold dry climate of the late Last Glacial such fires caused increased erosion and increased aeolian accumulation.

McIntosh, P. D.; Eberhard, R.; Slee, A.; Moss, P.; Price, D. M.; Donaldson, P.; Doyle, R.; Martins, J.

2012-12-01

134

Alluvial Fan Records of Climatically Driven Changes in Hillslope Eerosion Rates: Successes, Limitations, and Future Directions  

NASA Astrophysics Data System (ADS)

The erosional response of semi-arid landscapes to changes in the frequency and intensity of precipitation is poorly understood. Some have argued that hillslope erosion rates are greater when precipitation is dominated by short-duration, high-intensity events that generate intense overland flow on poorly vegetated hillslopes, whereas others have suggested that hillslope erosion and sediment transport rates are greater when precipitation is dominated by long-duration, low-intensity events due to higher rates of sediment production on hillslopes and sustained stream discharge. Both of these models suggest that hillslope erosion rates will vary as a function of the relative balance of low-intensity, long-duration (e.g., winter frontal storms) to high-intensity, short-duration (e.g., monsoons and convective storms) precipitation. Variations in hillslope erosion rates should affect sediment supply to alluvial fan heads, and so the timing and magnitude of fan head depositional events may provide a record of temporal changes in the style of precipitation. Preliminary depositional ages, interpreted from new cosmogenic 10Be measurements, are combined with existing soils, sedimentologic, and existing 10Be data from an alluvial fan head in the semi-arid Providence Mountains, eastern Mojave Desert, CA, to test this hypothesis. The Providence Mountains expose Proterozoic gneisses and Mesozoic granites and show no evidence of Quaternary faulting, indicating that Pleistocene fan complexes exposed at the mountain front are primarily climatically driven. Erosion rates determined from 10Be concentrations in active wash sediments vary from 33.27 ± 1.20 to 62.40 ± 1.40 m/My and show no apparent relation to grain size. Additionally, soil stratigraphic observations from a 5.5 m thick alluvial package exposed in the fan head include a ~70 cm thick stage IV calcic horizon that is cross cut by a ~3 m deep paleochannel, which contains at least four separate soils. The paleochannel is overlain by a laterally continuous deposit possessing a Bt horizon, a capping Av, and moderately developed pavement that, based on microlamination stratigraphy, is at least 56 ky old. These observations, combined with preliminary 10Be interpretations, indicate that the top of the older alluvial sequence, which contains the stage IV calcic horizon, is at least 375 ka. Using this limiting age, two end-member models for the depositional history of the alluvial sequence, and our observations of soil development elsewhere in the region, we can use several different methods to arrive at the paleoerosion rates at the time of deposition of the oldest stratigraphic interval. These rates are between ~25 and ~135 m/My or between ~30 and ~850 m/My, depending on the preferred age model and interpretive method. Although the lack of tighter age control does not allow us to establish whether faster paleoerosion rates are the result of periods of dominantly more or less intense precipitation, our results do demonstrate that erosion rates may have varied by up to an order of magnitude through time. Perhaps more importantly, even though the results are broadly similar in this case, it appears that it is possible for one to arrive at completely different answers to the same question depending on how the cosmogenic nuclide data are interpreted.

Cyr, A. J.; Miller, D. M.; Reheis, M. C.

2012-12-01

135

A debris flow deposit in alluvial, coal-bearing facies, Bighorn Basin, Wyoming, USA: Evidence for catastrophic termination of a mire  

USGS Publications Warehouse

Coal and clastic facies investigations of a Paleocene coal-bearing succession in the Grass Creek coal mine, southwestern Bighorn Basin, Wyoming, USA, suggest that disruption of peat accumulation in recurrent mires was caused by the repetitive progradation of crevasse splays and, ultimately, by a catastrophic mass movement. The mass movement, represented by deposits of debris flow, marked the termination of significant peat accumulation in the Grass Creek coal mine area. Megascopic and microscopic analyses of coal beds exposed along the mine highwalls suggest that these deposits developed in low-lying mires, as evidenced primarily by their ash yields and maceral composition. Disruption of peat accumulation in successive mires was caused by incursions of sediment into the mire environments. Termination by crevasse splay progradation is represented by coarsening-upward successions of mudrock and tabular, rooted sandstone, which overlie coal beds in the lower part of the coal-bearing interval. A more rapid process of mire termination by mass movement is exemplified by a debris flow deposit of diamictite, which overlies the uppermost coal bed at the top of the coal-bearing interval. The diamictite consists of a poorly sorted, unstratified mixture of quartzite cobbles and pebbles embedded in a claystone-rich or sandy mudstone matrix. Deposition of the diamictite may have taken place over a matter of weeks, days, or perhaps even hours, by catastrophic flood, thus reflecting an instantaneous process of mire termination. Coarse clastics and mud were transported from the southwest some 20-40 km as a viscous debris flow along stream courses from the ancestral Washakie Range to the Grass Creek area, where the flow overrode a low-lying mire and effectively terminated peat accumulation. ?? 1994.

Roberts, S.B.; Stanton, R.W.; Flores, R.M.

1994-01-01

136

Effect of post-sulfurization on the composition, structure and optical properties of Cu2ZnSnS4 thin films deposited by sputtering from a single quaternary target  

NASA Astrophysics Data System (ADS)

Quaternary Cu2ZnSnS4 (CZTS) thin films were deposited on heated glass substrates directly from a non-stoichiometric quaternary CZTS target by radio-frequency (RF) magnetron sputtering process, followed by post-sulfurization in atmosphere of Ar + H2S(5%). The results of X-ray diffraction (XRD), Raman spectra, and scanning electron microscope (SEM) show that post-annealed process can improve the crystallinity of CZTS thin films. Both XRD and Raman spectra analysis indicate the internal compressive stress relaxes in post-annealed CZTS thin films. Further transmission spectra demonstrate that the band gaps of post-annealed CZTS thin films are smaller than those of as-deposited due to the relaxation of internal compressive stress and the increase of Cu content in the post-annealed CZTS films.

He, Jun; Sun, Lin; Zhang, Kezhi; Wang, Weijun; Jiang, Jinchun; Chen, Ye; Yang, Pingxiong; Chu, Junhao

2013-01-01

137

Microbial activity, organic C accumulation and 13C abundance in soils under alley cropping systems after 9 years of recultivation of quaternary deposits  

NASA Astrophysics Data System (ADS)

The impact of alley cropping on post lignite mine soils developing from quaternary deposits after 9 years of recultivation was evaluated on the basis of microbial indicators, organic C and total N contents, and the isotope characteristics of soil C. Soils were sampled at the 0 to 3, 3 to 10 and 10 to 30 cm depths under black locust (Robinia pseudoacacia L.), poplar clone (Populus spp.), the transition zone and in the middle of alley under rye (Secale cereale). There was no significant effect of vegetation on microbial properties presumably, due to the high spatial variability, whereas organic C and total N contents at the 0 to 3 cm layer were significantly higher under black locust and poplar than in the transition zone and rye field. Organic C total N contents, and basal respiration, microbial biomass and microbial quotient decreased with soil depth. Soil organic C and total N contents were more than doubled after 9 years of recultivation, with annual C and N accretion rate of 162 g Corg m-2 yr-1 and 6 g Nt m-2 yr-1. Microbial properties indicated that the soils are in early stages of development; the C isotope characteristics confirmed that the sequestered C was predominantly from C3 plants of the alley cropping.

Nii-Annang, S.; Grünewald, H.; Freese, D.; Hüttl, R. F.; Dilly, O.

2009-04-01

138

High Resolution Particle Size Analyses Applied to Late Quaternary Loess Deposits at Orkutsay, Uzbekistan, Western Tien-Shan  

NASA Astrophysics Data System (ADS)

The loess deposits in the proximity of Tashkent (Uzbekistan) are one of the most promising widespread terrestrial climate and environmental archives of the Pleistocene in Central Asia, in addition to the loess of southern Tajikistan and the loess in the region of Almaty (Kazakhstan). In this paper we present high resolution particle-size data from the upper part of the long-studied loess record at Orkutsay (Uzbekistan). During the fieldwork samples for grain size and magnetic susceptibility were taken at 2 cm and 5 cm intervals from the loess. Particle size measurements of all samples were made on a Beckman Coulter LS 13320 PIDS laser sizer with auto-prep station to provide a dynamic range that spans from 0.04 to 2000 ?m and ensure accuracy and reproducibility. The granulometric results show a maximum in the fine and middle silt fraction and allow a clear distinction between cold and dry, and warm cycles. They show an important coherence between the type of dust sedimentation and the prevailing climate. Loess layers, which are associated with cold climate conditions, are dominated by the deposition of coarser dust particles. In contrast, finer airborne material has been deposited within the pedocomplexes that represent temperate interstadial or interglacial environments. Our results demonstrate the potential of the aeolian dust record at Orkutsay to decipher impacts of past climatic changes on terrestrial ecosystems and to understand climate feedback processes in continental interiors such as Central Asia.

Mavlyanova, N. G.; Machalett, B.; Rakhmatullaev, H.

2011-12-01

139

High-resolution particle size analyses applied to late Quaternary loess deposits at Orkutsay, Uzbekistan, Western Tien-Shan  

NASA Astrophysics Data System (ADS)

The loess deposits in the proximity of Tashkent (Uzbekistan) are one of the most promising widespread terrestrial climate and environmental archives of the Pleistocene in Central Asia, in addition to the loess of southern Tajikistan and the loess in the region of Almaty (Kazakhstan). In this paper we present high resolution particle-size data from the upper part of the long-studied loess record at Orkutsay (Uzbekistan). During the fieldwork samples for grain size and magnetic susceptibility were taken at 2 cm and 5 cm intervals from the loess. Particle size measurements of all samples were made on a Beckman Coulter LS 13320 PIDS laser sizer with auto-prep station to provide a dynamic range that spans from 0.04 to 2000 µm and ensure accuracy and reproducibility. The granulometric results show a maximum in the fine and middle silt fraction and allow a clear distinction between cold and dry, and warm cycles. They show an important coherence between the type of dust sedimentation and the prevailing climate. Loess layers, which are associated with cold climate conditions, are dominated by the deposition of coarser dust particles. In contrast, finer airborne material has been deposited within the pedocomplexes that represent temperate interstadial or interglacial environments. Our results demonstrate the potential of the aeolian dust record at Orkutsay to decipher impacts of past climatic changes on terrestrial ecosystems and to understand climate feedback processes in continental interiors such as Central Asia.

Mavlyanova, Nadira G.; Machalett, Bjoern; Rakhmatullaev, Hirojilla L.

2013-04-01

140

The "Alluvial Mesovoid Shallow Substratum", a New Subterranean Habitat  

PubMed Central

In this paper we describe a new type of subterranean habitat associated with dry watercourses in the Eastern Iberian Peninsula, the “Alluvial Mesovoid Shallow Substratum” (alluvial MSS). Historical observations and data from field sampling specially designed to study MSS fauna in the streambeds of temporary watercourses support the description of this new habitat. To conduct the sampling, 16 subterranean sampling devices were placed in a region of Eastern Spain. The traps were operated for 12 months and temperature and relative humidity data were recorded to characterise the habitat. A large number of species was captured, many of which belonged to the arthropod group, with marked hygrophilous, geophilic, lucifugous and mesothermal habits. In addition, there was also a substantial number of species showing markedly ripicolous traits. The results confirm that the network of spaces which forms in alluvial deposits of temporary watercourses merits the category of habitat, and here we propose the name of “alluvial MSS”. The “alluvial MSS” may be covered or not by a layer of soil, is extremely damp, provides a buffer against above ground temperatures and is aphotic. In addition, compared to other types of MSS, it is a very unstable habitat. It is possible that the “alluvial MSS” may be found in other areas of the world with strongly seasonal climatic regimes, and could play an important role as a biogeographic corridor and as a refuge from climatic changes. PMID:24124544

Ortuno, Vicente M.; Gilgado, Jose D.; Jimenez-Valverde, Alberto; Sendra, Alberto; Perez-Suarez, Gonzalo; Herrero-Borgonon, Juan J.

2013-01-01

141

Interpreting alluvial archives: sedimentological factors in the British Holocene fluvial record  

Microsoft Academic Search

A Holocene alluvial archive of 506 dated units for Great Britain is analysed in terms of the sedimentation styles involved. The database is classified by sedimentation unit (channel sediments, palaeochannel fills, floodplain surface sediments, floodbasins and colluvial deposits) and alluvial ensemble (fans and cones, upland gullies and streams, braided systems and active\\/inactive meandering and anastomosing systems).Floodplain, palaeochannel and floodbasin sediments

J. Lewin; M. G. Macklin; E. Johnstone

2005-01-01

142

Bedrock versus alluvial channel geometry  

NASA Astrophysics Data System (ADS)

We present observations of channel geometry obtained on a 524 km long continuous traverse of Fraser River, British Columbia, Canada, as it passes through the Fraser canyons. The channel alternates between gravel-bedded reaches that are incised into semi-consolidated glacial deposits and bedrock-bound reaches (7.7% of the reach above Hope). We obtained data of 71 cross-sections using 600 kHz and 1200 kHz aDcp and, in addition, obtained measures of channel width from Google® imagery at 0.5 km spacing throughout the traverse. To homogenize the data of sectional geometry along the river (to compensate increasing flows at tributary junctions), we computed w/Q^1/2 and d/Q^1/3, following commonly observed scaling relations. For the sounded cross sections Q is the recorded flow at the time of the survey; for the map measurements, Q is mean annual flood for the reach, leading to some difference between the two sets of statistics. From the more abundant map data, alluvial reaches are 2.3x wider than and, from soundings, 0.60 as deep as rock-bound reaches, implying that mean velocity is accelerated in rock reaches by 38%. These data are based on section averages: extremes of depth and velocity in rock canyons are substantially greater. There is also variation from reach to reach along the river controlled by variation in rock lithologies, with the narrowest canyons occurring in Fraser Canyon proper (w/Q^1/2 = 0.083 compared with 1.4 elsewhere). The uppermost ('Marguerite') and lowermost ('Agassiz') alluvial reaches are considerably wider (w/Q^1/2 = 3.9 and 7.1 respectively) than intervening ones (~2.35). These reaches have lower gradients and exhibit wandering channels. Because of lithological control, the downstream hydraulic geometry of the river does not, in fact, conform with the common pattern, even when sections are analyzed according to boundary material. However, river gradient is well correlated with scaled width, inversely for gravel reaches and directly, but with little sensitivity for rock-bound reaches. We show distributions of channel width and depth along the river.

Church, M. A.; Venditti, J. G.; Rennie, C. D.

2012-12-01

143

Comparison of planform multi-channel network characteristics of alluvial and bedrock constrained large rivers  

NASA Astrophysics Data System (ADS)

The Mekong River in northern Cambodia is an multi-channel mixed bedrock-alluvial river but it was poorly researched until present. Preliminary study of the Mekong geomorphology was conducted by gathering existing knowledge of its geological and tectonic settings, specific riparian vegetation and ancient alluvial terraces in which the river has incised since the Holocene. Altogether this process has allowed a geomorphological portrait of the river to be composed within the Quaternary context. Following this outline, the planform characteristics of the Mekong River network are compared, using analysis of channel network and islands configurations, with the fluvial patterns of the Orange River (South Africa), Upper Columbia River (Canada) and the Ganga River (India, Bangladesh). These rivers are selected as examples of multi-channel mixed bedrock alluvial, anastomosed alluvial and braided alluvial rivers respectively. Network parameters such as channel bifurcation angles asymmetry, sinuosity, braid intensity and island morphometric shape metrics are compared and contrasted between bedrock and alluvial systems. In addition, regional and local topographic trend surfaces produced for each river planform help explain the local changes in river direction and the degree of anastomosis, and distinguish the bedrock-alluvial rivers from the alluvial rivers. Variations between planform characteristics are to be explained by channel forming processes and in the case of mixed bedrock-alluvial rivers mediated by structural control. Channel metrics (derived at the reach-scale) provide some discrimination between different multi-channel patterns but are not always robust when considered singly. In contrast, island shape metrics (obtained at subreach-scale) allow robust discrimination between alluvial and bedrock systems.

Carling, P. A.; Meshkova, L.; Robinson, R. A.

2011-12-01

144

Late Quaternary tectonics in the inner Northern Apennines (Siena Basin, southern Tuscany, Italy) and their seismotectonic implication  

NASA Astrophysics Data System (ADS)

Defining the most recent Quaternary tectonics represents a challenging task for neotectonic, palaeoseismological and seismotectonic studies. This paper focuses on an integrated approach to reconstructing the latest Quaternary deformation affecting the northern part of the Siena Basin (inner Northern Apennines, i.e., southern Tuscany, Italy) near the town of Siena, and to discuss the seismological implications. Field work and structural and stratigraphic analyses, coupled with the interpretation of reflection seismic lines, have been combined to define the geometry, kinematics and age of mesoscopic to map-scale faults which have affected the mainly Quaternary continental and Pliocene marine deposits. The resulting dataset describes a tectonic setting characterized by coeval SW- and NW-trending transtensional and normal faults, respectively, dissecting alluvial sediments younger than 23.9 ± 0.23 ka. Seismic interpretation sheds light on the geometrical setting of the faults at deeper levels, down to 1-2 km, and provides support for the presence of a wide brittle shear zone defined by conjugated fault segments, locally giving rise to an asymmetrical negative flower-like structure. Faults and their damage zones have controlled (and still control) the discharge of gas vents (mainly CO2 and H2S) and hydrothermal circulation (which deposits travertine) since at least 23.216 ± 0.124 ka. The resulting complete data set provides support for our description of the Neogene-Quaternary tectonics which were active until the late Quaternary, providing additional information about the seismotectonic framework of an area characterized by low seismicity and generally low-magnitude earthquakes (M < 4), but having experienced significant seismic events over the last few centuries.

Brogi, Andrea; Capezzuoli, Enrico; Martini, Ivan; Picozzi, Matteo; Sandrelli, Fabio

2014-05-01

145

Age and significance of the Quaternary cemented deposits of the Duje Valley (Picos de Europa, Northern Spain)  

NASA Astrophysics Data System (ADS)

Cemented calcareous breccias appear in the Picos de Europa (Cantabrian Mountains, Spain) resting on glacially abraded surfaces and covered by moraines. U/Th dating of the calcite coating the clasts was successful in two samples, the oldest one indicating that the breccias accumulated during or prior to Marine Isotope Stage (MIS) 11, and the youngest indicating later cementation during MIS 8. The former introduces a limit for the age of the glaciation preceding the breccias, which cannot correspond to an event younger than MIS 12. This is the oldest absolute age so far obtained for intercalated glacial/interglacial deposits of the Iberian Peninsula.

Villa, Elisa; Stoll, Heather; Farias, Pedro; Adrados, Luna; Edwards, R. Lawrence; Cheng, Hai

2013-01-01

146

Late Quaternary depositional history of the Reuss delta, Switzerland: constraints from high-resolution seismic reflection and georadar surveys  

NASA Astrophysics Data System (ADS)

Glacial erosion has caused overdeepening of many alpine valleys. After retreat of the ice, they were filled with heterogeneous deposits of glacial, lacustrine and fluvial sediments. A typical example of such a valley segment and its infill is the Reuss delta on the southern shore of Lake Lucerne in Switzerland. To obtain a detailed three-dimensional image of this valley segment, the ETH Institute of Geophysics has acquired several two-dimensional, high-resolution seismic and georadar profiles, and conducted a three-dimensional georadar survey. Interpretations of these geophysical data were constrained by a geological core extracted from a borehole 300 m deep near the investigation site. The seismic profiles imaged ca. 600 m of sediment infill above bedrock. Based on their reflection characteristics, five different deposition units were distinguished. These units were interpreted as a succession of clay/silt at the base, followed by different sand units with variable but generally increasing amounts of gravel. This succession represented a prograding delta that filled the southern part of Lake Lucerne. The latest fluvial development of the region is best represented by the georadar data. In particular, the three-dimensional georadar data set provides a detailed view of an ancient braided river channel

Nitsche, Frank O.; Green, Alan G.; Horstmeyer, Heinrich; Büker, Frank

2002-02-01

147

Stable isotope variations in the Quaternary epithermal calcite-fluorite deposit at Monte delle Fate near Cerveteri (Latium, central Italy)  

USGS Publications Warehouse

Carbon, oxygen and hydrogen isotope variations have been measured in samples from the epithermal fluorite vein deposit at Monte delle Fate, Latium. The ranges in ?? 13C and ??18O of calcite are -1.3 to 3.4 and 9.5 to 17.3, respectively. ??D values of water extracted from fluid inclusions are -49 to -39 for calcite and -41 to -34 for fluorite. Fluid inclusion filling temperatures (225??-240??C) and salinites (3.75) are nearly the same for both fluorite and sparry calcite. An elongated form of calcite, of minor abundance, precipitated at lower temperatures. The data indicate that (1) the CO2 involved in the mineralization was provided by the local marine limestones, (2) the waters were meteoric in origin and underwent an 18O shift of ??? 10 permil by exchange with marine country rocks, and (3) all geochemical features can be explained by the action of two hydrothermal fluids. Hot brines recently discovered in the Cesano geothermal area, 30 km to the east, have temperatures and some chemical characteristics similar to the hydrothermal fluids at Monte delle Fate. ?? 1980 Springer-Verlag.

Masi, U.; O'Neil, J.R.

1980-01-01

148

Significance of relic carbonate deposits along the central and southwestern margin of India for late Quaternary environmental and sea level changes  

NASA Astrophysics Data System (ADS)

Environmental and sea level indicators were investigated using dredge samples from late Quaternary carbonate deposits along the shelf break between Goa and Cape Comorin, India. Geomorphic features in the area were identified from sonar profiles and included isolated patch reefs with a relief of up to 10 m, and linear reefs with reliefs between 2 and 15 m. The main clast types recovered from these features include fragmented corals and carbonate nodules dominated by either encrusted foraminifera or coralline algae. Some of these clast types are clearly of shallow-water origin. Fragments of reef-forming Poritid corals, for example, were collected off Mangalore at depths of 110-105 m and dated between 11,520 and 12,610 14C years BP (13.42-14.77 ka). Nodules of similar age dominated by Lithothamnium and capped by foraminiferal veneers were also collected at -90 m off Cape Comorin. Their altered algal tissues are consistent with formation in shallow water, high-energy conditions. In contrast, nodules recovered off Kochi and Mangalore-Goa are of deeper water origin, younger in age (10,980-7350 14C years BP), and are dominated by Gypsina encrustations with volumetrically less algal encrustation. They show cyclic succession of foraminiferal-algal, or foraminiferal-algal-coral laminations in which the algal species are typical of deeper waters. The age and elevation of corals and shallow-water nodules are both consistent with published glacio-eustatic sea-level curves. In addition, the alternate micro-encrustations of foraminifera, algae and encrusting corals could indicate changing conditions from nutrient-rich and turbid to nutrient-poor and clear water that may be attributable to seasonal variations in sediment flux caused by monsoons.

Rao, V. Purnachandra; Montaggioni, L.; Vora, K. H.; Almeida, F.; Rao, K. M.; Rajagopalan, G.

149

Quaternary Geologic Map of Connecticut and Long Island Sound Basin  

USGS Publications Warehouse

The Quaternary geologic map (sheet 1) and explanatory figures and cross sections (sheet 2) portray the geologic features formed in Connecticut during the Quaternary Period, which includes the Pleistocene (glacial) and Holocene (postglacial) Epochs. The Quaternary Period has been a time of development of many details of the landscape and of all the surficial deposits. At least twice in the late Pleistocene, continental ice sheets swept across Connecticut. Their effects are of pervasive importance to the present occupants of the land. The Quaternary geologic map illustrates the geologic history and the distribution of depositional environments during the emplacement of glacial and postglacial surficial deposits and the landforms resulting from those events.

Stone, Janet Radway; Schafer, John P.; London, Elizabeth Haley; DiGiacomo-Cohen, Mary L.; Lewis, Ralph S.; Thompson, Woodrow B.

2005-01-01

150

Rapid migration of heavy metals and 137 Cs in alluvial sediments, Upper Odra River valley, Poland  

Microsoft Academic Search

The studies presented explore post-depositional changes of zinc, cadmium, lead, manganese and 137Cs distribution in alluvial sediments accumulated in the upper Odra River valley in southern Poland. The rate of these changes\\u000a was estimated by comparing metal and 137Cs distributions in four vertical alluvial profiles with a history of river pollution and sediment deposition. The untypical\\u000a 137Cs distribution with peaks

Dariusz Ciszewski; Agnieszka Czajka; Sylwia B?a?ej

2008-01-01

151

Neogene and Quaternary development of the Turiec Basin and landscape in its catchment: a tentative mass balance model  

NASA Astrophysics Data System (ADS)

The development of the Turiec Basin and landscape evolution in its catchment has been reconstructed by methods of geological research (structural geology, sedimentology, paleoecology, and geochronological data) as well as by geophysics and geomorphology. The basin and its surrounding mountains were a subject of a mass balance study during periods of tectonic activity, accompanied by considerable altitudinal differentiation of relief and also during quiet periods, characterized by a development of planation surfaces in the mountains. The coarse clastic alluvial fans deposited beneath the offshore pelitic sediments document the rapid Middle Miocene uplift of mountains on the margin of the Turiec Basin. The Late Miocene finegrained sedimentation represents the main fill of this basin and its origin was associated with the formation of planation surfaces in the surrounding mountains. The rapid uplift of the western and northern parts of the catchment area during the latest Miocene and Early Pliocene times further generated the deposition of coarse-grained alluvial fans. The Late Pliocene basin inversion, due to uplift of the whole Western Carpathians mountain chain, was associated with the formation of the Early Quaternary pediment and ultimately with the formation of the Turiec river terrace systems.

Ková?, Michal; Hók, Jozef; Minár, Jozef; Vojtko, Rastislav; Bielik, Miroslav; Pipík, Radovan; Rakús, Miloš; Krá?, Ján; Šujan, Martin; Králiková, Silvia

2011-08-01

152

The use of O, H and Sr isotopes and carbamazepine to identify the origin of water bodies supplying a shallow alluvial aquifer  

NASA Astrophysics Data System (ADS)

Alluvial aquifers are of great socio-economic importance in France since they supply 82% of drinking water production, though they reveal to be very vulnerable to pesticides and emerging organic contaminants. The aim of this work is to identify the origin of water bodies which contribute to the recharge of an alluvial aquifer for a better understanding of its hydrochemistry and transfer of contaminants therein. The study is based on an isotopic and geochemical tracers approach, including major elements, trace elements (Br, Sr),and isotopes (?18O, ?2H, 87Sr/86Sr), as well as organic molecules. Indeed, organic molecules such as pharmaceutical compounds, more precisely carbamazepine and caffeine, have shown their use as indicators of surface water in groundwater. The study area is a partially-confined shallow alluvial aquifer, the so-called Vistrenque aquifer, located at 15 km from the Mediterranean Sea, in the Quaternary alluviums deposited by an ancient arm of the Rhône River, in Southern France. This aquifer constitutes a shallow alluvial layer in a NE-SW graben structure. It is situated between a karst aquifer in lower Cretaceous limestones, on the NW border, and the Costières Plateau, on the SE border, having a similar geology as the Vistrenque. The alluvial plain is crossed by a surface water network with the Vistre as the main stream, and a canal used for irrigation essentially, the BRL canal, which is fed by the Rhône River. ?18O and ?2H allowed to differentiate the BRL canal water, depleted in heavy isotopes (?2H = -71.5o vs V-SMOW), and the more enriched local rainwater (?2H = -35.5o vs V-SMOW). In the Vistre surface water a binary mixing were evidenced with the BRL canal water and the rainwater, as end members. Then, in the Vistrenque groundwater both the BRL and the Vistre contributions could be identified, as they still show contrasting signature with local recharge. This allows to highlight the surface water contribution to a heavily exploited alluvial aquifer. These mixing processes are confirmed by comparing O and H isotopes to major elements composition. Furthermore, organic compound concentrations such as carbamazepine which show relatively high concentrations in surface waters, was also detected in groundwater especially in those influenced by the BRL canal water, and hence may be used as a tracer of surface water contribution. On the other hand, 87Sr/86Sr allowed highlighting this time a mixing process between groundwater bodies contributing to the recharge of the alluvial aquifer. The 87Sr/86Sr vs 1/Sr plot showed a locale influence on the Vistrenque groundwater by the karst limestone aquifer (87Sr/86Sr ?0.7076; [Sr] =1540 ?g/L), and the Costières Plateau water (87Sr/86Sr ?0.7090; [Sr] =320 ?g/L). In conclusion, 18O and 2H isotopes allowed to highlight the influence of surface waters on the quality of a shallow vulnerable alluvial aquifer, by determining the relationship between the two water bodies. While 87Sr/86Sr were useful to identify mixing processes between groundwater bodies from aquifers of different geology, the limestone karst and alluvial sediments. A multi-isotope approach proved useful to understand the origin of water bodies and contaminants.

Sassine, Lara; Le Gal La Salle, Corinne; Lancelot, Joël; Verdoux, Patrick

2014-05-01

153

Constraining Quaternary offset of the Cady fault, eastern California shear zone, southern California, with geologic mapping, luminescence dating, and geophysics  

NASA Astrophysics Data System (ADS)

We interpreted bedrock and surficial geologic mapping in conjunction with potential-field anomalies and recently acquired luminescence dates of alluvial sediment to constrain offset along the east-striking sinistral Cady fault within the Mojave block of the eastern California shear zone. Previous research, new field mapping of Quaternary deposits, and analysis of aeromagnetic data indicate that the Cady fault forms a significant structural boundary separating northwest-striking dextral faults to the south, from east-northeast-striking faults to the north. We estimated total sinistral offset of ~6 km along the Cady fault based upon reconstruction of displaced bedrock outcrops and magnetic anomalies. Assuming extensional strain in the region began ~10 Ma, as recorded by interbedded sediments and volcanics of the Ricardo Group exposed along the Garlock fault, the long-term offset rate is ~0.6 mm/yr. Assuming that onset of strain is dated by the opening of the Gulf of California to marine incursions by rifting associated with the San Andreas fault system at ~ 6 Ma, the long-term offset rate is roughly 1 mm/yr. Time-averaged sinistral offset rates through the Quaternary, estimated from field mapping of displaced alluvial deposits and from regional age constraints obtained through luminescence and radiocarbon dating techniques, decrease with older deposit age. Deposits from the late Pleistocene/Holocene transition yield rates exceeding 1 mm/yr whereas minimum rates for middle to early Pleistocene deposits may be as low as 0.02 mm/yr, assuming this time-averaged fault offset ensued immediately following deposit formation. At one Holocene-Pleistocene deposit beheaded by the Cady fault, we dated two horizons below the Bk horizon to preclude sampling of illuviated post-deposition fines. New infrared-stimulated luminescence (IRSL) dates were used to estimate numeric ages of alluvial sediment and an aggradation rate. For illustration purposes, we assumed that sediment aggradation was constant to extrapolate a ground-surface age. IRSL ages from K-feldspar of 10,660 (0.52 m) and 12,940 years (1.15 m) were used to infer an aggradation rate of almost 0.3 mm/yr. If characteristic, the extrapolated ground-surface age pre-dating fault displacement is ~8,780 years. Supporting this inferred deposit age is the deduction that Holocene-aged alluvial fans along the Cady fault are typically friction-dominated granular media, composed primarily of sand and gravel, and consequently are poor candidates for tectonic scarp preservation. Earthquake-induced surface rupture is likely better preserved in deposits older than mid-Holocene, such as the dated deposit, because of the greater proportion of fine-grained, more cohesive sediment derived from pedogenesis. Adopting the extrapolated deposit age of ~8,780 years, and a measured offset of ~7 m, results in a time-averaged sinistral offset rate of 0.8 mm/yr. Therefore the tectonic block-bounding Cady fault is an active feature that may have similar offset rates using short- and long-term slip indicators.

Schmidt, K. M.; Mahan, S.; Langenheim, V. E.

2012-12-01

154

Water-Quality Characteristics of Quaternary Unconsolidated-Deposit Aquifers and Lower Tertiary Aquifers of the Bighorn Basin, Wyoming and Montana, 1999-2001.  

National Technical Information Service (NTIS)

This report describes current (1999-2001) ground-water quality characteristics in Quaternary and lower Tertiary aquifers in the Bighorn Basin part of the Yellowstone River Basin NAWQA study unit. Results are presented for samples from 24 new wells and one...

T. T. Bartos, C. A. Eddy-Miller, J. R. Norris, M. E. Gamper, L. L. Hallberg

2005-01-01

155

Investigation of Quaternary slip rates along the Banning strand of the southern San Andreas Fault near San Gorgonio Pass  

NASA Astrophysics Data System (ADS)

Present-day Pacific-North American relative plate motion in southern California is shared primarily between the San Jacinto and San Andreas faults. At the north end of the Coachella Valley, the San Andreas fault splits into the Banning and Mission Creek strands, which are sub-parallel to each other within the Indio Hills. Northwest of the Indio Hills, the Mission Creek fault diverges from the Banning and continues northwest toward the southeastern San Bernardino Mountains, but loses surface expression beneath Quaternary alluvial deposits in Morongo Wash. The Banning fault, upon exiting the Indio Hills, is deflected toward the west and transitions into a structurally complex fault zone at San Gorgonio Pass, where it is delineated by thrust scarps in Holocene alluvium. The slip rates of the Banning and Mission Creek fault strands northwest of the Indio Hills and southeast of San Gorgonio Pass are presently unconstrained, but understanding how slip is partitioned between these two strands is critical to southern California earthquake forecasting efforts. Here we present preliminary slip rate data for the Banning fault ~2 km southeast of San Gorgonio Pass at Devers Hill. Using the B4 LiDAR as a base, we have mapped the extents of three truncated and offset alluvial fan deposits, which we have differentiated based on both field and remote (LiDAR- and air photo-based) observations of texture: in particular, the distribution of different clast sizes, pavement and soil development, and color and appearance. To confirm across-fault correlation of the displaced deposits, we have measured 26 cosmogenic Be-10 ages from boulders and cobble samples taken from each of the three fan surfaces on both sides of the fault. One debris flow deposit (Q2a) has been dated to ~80 ka, and appears to be offset 1.6-2.2 km, though confirming this reconstruction will depend on future excavations and uranium-series dating of soil carbonate. A second debris flow deposit (Q2b), for which ages are pending, has been displaced 1-1.6 km. Together, these measurements suggest a late Quaternary slip rate for the Banning strand of the San Andreas fault of about 12-24 mm/yr. Our preliminary slip rate measurement for the Banning strand just southeast of San Gorgonio Pass is consistent with the slip rate of the San Bernardino section of the San Andreas fault to the northwest, and suggests that averaged over late Quaternary timescales (~80 ka), displacement along the San Andreas south of San Gorgonio Pass may be more focused on the Banning strand than the Mission Creek strand.

Gold, P. O.; Behr, W. M.; Rood, D.; Kendrick, K. J.; Rockwell, T. K.; Sharp, W. D.

2013-12-01

156

Reconciling Holocene Alluvial Records in Buckskin Wash, Utah--Where do Arroyo Cycles end and Paleofloods Begin?  

Microsoft Academic Search

Drainages that undergo arroyo cut-and-fill cycles clearly change their grade over time, probably in response to climatic forcing. Reconstructions of this behavior are usually based on alluvial records found in broad alluvial valleys. Conversely, paleoflood hydrologists have constructed flood records by studying slackwater deposits preserved in nearby bedrock canyons, typically assuming a constant grade over millennial timescales. These contrasting approaches

J. E. Harvey; J. Pederson; T. Rittenour

2008-01-01

157

Quaternary Geochronology, Paleontology, and Archaeology of the Upper San Pedro River Valley, Sonora, Mexico  

NASA Astrophysics Data System (ADS)

This poster presents the results of multi-disciplinary investigations of the preservation and extent of Quaternary fossil-bearing strata in the San Pedro River Valley in Sonora, Mexico. Geologic deposits in the portions of the San Pedro Valley in southern Arizona contain one of the best late Cenozoic fossil records known in North America and the best record of early humans and extinct mammals on the continent. The basin in the U.S. is one of the type locations for the Blancan Land Mammal Age. Hemiphilian and Irvingtonian fossils are common. Rancholabrean remains are widespread. Strata in the valley adjacent to the international border with Mexico have yielded the densest concentration of archaeological mammoth-kill sites known in the western hemisphere. Despite more than 60 years of research in the U.S., however, and the fact that over one third of the San Pedro River lies south of the international boundary, little has been known about the late Cenozoic geology of the valley in Mexico. The study reported here utilized extensive field survey, archaeological documentation, paleontological excavations, stratigraphic mapping and alluvial geochronology to determine the nature and extent of Quaternary fossil-bearing deposits in the portions of the San Pedro Valley in Sonora, Mexico. The results demonstrate that the Plio-Pleistocene fossil -bearing formations known from the valley in Arizona extend into the uppermost reaches of the valley in Mexico. Several new fossil sites were discovered that yielded the remains of Camelids, Equus, Mammuthus, and other Proboscidean species. Late Pleistocene archaeological remains were found on the surface of the surrounding uplands. AMS radiocarbon dating demonstrates the widespread preservation of middle- to late- Holocene deposits. However, the late Pleistocene deposits that contain the archaeological mammoth-kill sites in Arizona are absent in the valley in Mexico, and are now known to be restricted to relatively small portions of the valley immediately north of the international border.

Gaines, E. P.

2013-12-01

158

Infilling of the Younger Kathmandu-Banepa intermontane lake basin during the Late Quaternary (Lesser Himalaya, Nepal): a sedimentological study  

NASA Astrophysics Data System (ADS)

The Kathmandu and Banepa Basins, Central Nepal, are located in a large syncline of the Lesser Himalayas. The Older Kathmandu Lake evolved during the Pliocene and early Pleistocene; the Younger Kathmandu Lake, which is the focus of this study, is infilled with late Quaternary sediments. Three formations, arranged in stratigraphical order, the Kalimati, Gokarna and Thoka Formations formed during the infilling stage of this lacustrine basin. Structural and textural sedimentological analyses, a chemical survey across the basin and mineralogical investigations of fine-grained sediments form the basis of this palaeogeographical study. The basin under investigation was covered by a perennial freshwater lake before 30 000 yr BP. The lake was infilled with alluvial and fluvial sediments delivered mainly from the mountains north of the basin. A fairly low gradient was favourable for the formation of diatomaceous earths, carbonaceous mudstones and siltstones, which were laid down in the centre of the lake and in small ponds. Towards the basin edge, lacustrine sediments gave way to deltaic deposits spread across the delta plain. Crevasse splays and anastomosing rivers mainly delivered suspended load for the widespread siltstones and mudstones. The proximal parts of the alluvial-fluvial sedimentary wedge contain debris flows that interfinger with fine-grained floodplain deposits. Three highstands of the water-level (>30 000 yr BP, 28 000-19 000 yr BP, 11 000-4000 yr BP (?)) have been recognised in the sedimentary record of the younger Kathmandu Lake in the Late Quaternary. Second-order water-level fluctuations are assumed to be triggered by local processes (damming by tectonically induced landslides). First-order water-level fluctuations are the result of climatic changes.

Dill, H. G.; Khadka, D. R.; Khanal, R.; Dohrmann, R.; Melcher, F.; Busch, K.

2003-01-01

159

Morphodynamic equilibrium of alluvial estuaries  

NASA Astrophysics Data System (ADS)

The evolution of the longitudinal bed profile of an estuary, with given plan-form configuration, subject to given tidal forcing at the mouth and prescribed values of water and sediment supply from the river is investigated numerically. Our main goal is to ascertain whether, starting from some initial condition, the bed evolution tends to reach a unique equilibrium configuration asymptotically in time. Also, we investigate the morphological response of an alluvial estuary to changes in the tidal range and hydrologic forcing (flow and sediment supply). Finally, the solution helps characterizing the transition between the fluvially dominated region and the tidally dominated region of the estuary. All these issues play an important role also in interpreting how the facies changes along the estuary, thus helping to make correct paleo-environmental and sequence-stratigraphic interpretations of sedimentary successions (Dalrymple and Choi, 2007). Results show that the model is able to describe a wide class of settings ranging from tidally dominated estuaries to fluvially dominated estuaries. In the latter case, the solution is found to compare satisfactory with the analytical asymptotic solution recently derived by Seminara et al. (2012), under the hypothesis of fairly 'small' tidal oscillations. Simulations indicate that the system always moves toward an equilibrium configuration in which the net sediment flux in a tidal cycle is constant throughout the estuary and equal to the constant sediment flux discharged from the river. For constant width, the bed equilibrium profile of the estuarine channel is characterized by two distinct regions: a steeper reach seaward, dominated by the tide, and a less steep upstream reach, dominated by the river and characterized by the undisturbed bed slope. Although the latter reach, at equilibrium, is not directly affected by the tidal wave, however starting from an initial uniform stream with the constant 'fluvial' slope, the final equilibrium state is reached through an erosional wave, which leads to bed degradation of the upstream 'fluvial reach'. For a given river discharge, the length of the tidal reach increases quite rapidly with tidal amplitude, up to some threshold value of the tidal amplitude above which the length of the estuary becomes comparable with the length of the tidal wave. When the channel plan-form is convergent, deposition of sediments of fluvial origin in the funnel-shaped region drastically changes the equilibrium configuration. The effect of an increasing channel convergence is thus to induce bed aggradation close to the inlet. Nevertheless, tidal forcing only slightly changes the non-tidal profile. The effect of increasing tidal oscillations again leads to an increase of the bed slope at the inlet and to a general bed degradation upstream. The effects of varying sediment supply, flow discharge and river width in the upstream reach have also been investigated and play an important role. Further geomorphological implications of these results will be discussed at the meeting. References Dalrymple, R. W., and K. Choi (2007), Morphologic and facies trends through the fluvialmarine transition in tide-dominated depositional systems: A schematic framework for environmental and sequence-stratigraphic interpretation, Earth-Science Reviews, 81(3-4), 135-174, doi:10.1016/j.earscirev.2006.10.002. Seminara, G., M. Bolla Pittaluga, and N. Tambroni (2012), Morphodynamic equilibrium of tidal channels, Environmental Fluid Mechanics: Memorial Volume in Honour of Prof. Gerhard H. Jirka, 153-174

Tambroni, Nicoletta; Bolla Pittaluga, Michele; Canestrelli, Alberto; Lanzoni, Stefano; Seminara, Giovanni

2014-05-01

160

Ancient and modern sites of natural CO2 leakage: Geochemistry and geochronology of Quaternary and modern travertine deposits on the Colorado Plateau, USA, and implications for CO2 sequestration  

NASA Astrophysics Data System (ADS)

Travertine-precipitating springs and travertine deposits of the Colorado Plateau serve as natural analogues for evaluating potential leakage associated with geologic sequestration of carbon dioxide (CO2). Extensive Quaternary and modern travertine deposits occur along the Jemez lineament and Rio Grande rift in New Mexico and Arizona, and in the Paradox Basin in Utah, along the Little Grand Wash Fault and the Salt Wash Graben. These groundwater discharge deposits are interpreted to be sites of persistent and significant CO2 degassing along faults and above magmatic systems. Analysis of the geochemical and isotopic composition of U-series dated travertine deposits and modern travertine-precipitating waters allows evaluation of the flow paths of CO2-charged waters. Initial results from New Mexico and Arizona travertine deposits show characteristic rare earth element (REE) signatures for individual travertine deposits and yet generally overlap in concentrations of other trace elements such as Al, As, B, Ba, K, and Si. We report stable oxygen and carbon isotopes of the travertines in New Mexico, Arizona, and Utah. Different travertine deposits have different carbon-oxygen isotope variation patterns suggesting that these stable isotopes are tracers that have the ability to identify distinctive groundwater sources within and between spring groups based on the travertine record. Stable isotope analyses of travertine deposits in New Mexico and Arizona overlap substantially between deposits and cluster around -10‰ to -6‰ for ?18O and around 3.5‰ to 6.5‰ for ?13C. Travertine deposits in Utah show a distinctly different range of stable isotope values: ?18O values cluster around -14‰ to -10.5‰ and ?13C around 4.5‰ to 6.5‰. U-series dating of travertine deposits shows episodic travertine formation in New Mexico and Arizona over the last 700,000 years, and travertine accumulation over the last 400,000 years in Utah. We use U-series dating and volumetric analysis of the travertine deposits to estimate the minimum CO2 flux that was necessary to form the deposits and compare it to modern flux measurements in order to assess the extent of former and modern CO2 leakage. In addition, the thickness of dated travertine sections provides information about the longevity of travertine mound or spring systems that may be controlled by, e. g., sealing of faults, alternating wet/ dry paleohydrologic conditions, and/or rates of magmatic CO2 supply to springs. Understanding travertine deposition is important for the assessment of the long-term performance of a potential CO2 sequestration site because travertine deposits give insight into the complexities of CO2 pathways and leakage rates over timescales necessary for CO2 sequestration.

Priewisch, A.; Crossey, L. J.; Karlstrom, K. E.; McPherson, B. J.; Mozley, P.

2013-12-01

161

Unbalanced sediment budgets in the catchment-alluvial fan system of the Kuitun River (northern Tian Shan, China): Implications for mass-balance estimates, denudation and sedimentation rates in orogenic systems  

NASA Astrophysics Data System (ADS)

Mass balances are often used to calculate sediment fluxes in foreland basins and denudation rates in adjacent mountain ranges on intermediate to long timescales (from a few tens of thousand to a million years). Here, we study the simple Quaternary catchment-alluvial fan system of the Kuitun River, in northern Tian Shan, to discuss some ideas about sediment storage, release, and bypass in relatively short (100 km long) sediment routing systems. This study shows that the Kuitun catchment and piedmont areas clearly present evidence of a significant and temporary storage of sediments during the Pleistocene. These sediments were then excavated and delivered farther into the foreland basin during the Holocene. The difference between the volumes of materials released from the catchment and piedmont areas (5.5 ± 1.7 km3) and the volume stored in a contemporaneous fan downstream (2.6 ± 0.6 km3) indicates that the latter did not trap the whole sediment load transported by the river. The alluvial fan was bypassed by 27 to 78% of this load toward its distal alluvial plain. If this value is well estimated, it implies a major volumetric partitioning of the deposits between the fan and the alluvial plain, with a very high sedimentation rate in the fan (1.97 ± 0.52 mm·y- 1) and a much lower one downstream (0.11 ± 0.11 mm·y- 1). However, this volumetric partitioning might only occur during periods with a very specific hydrological regime such as the Holocene deglaciation. Eventually, the peculiar sediment storage and release pattern within the Kuitun catchment and piedmont areas during the Pleistocene and Holocene complicates the calculation of mean paleodenudation rates using either sediment budgets or in situ produced cosmogenic nuclides.

Jolivet, Marc; Barrier, Laurie; Dominguez, Stéphane; Guerit, Laure; Heilbronn, Gloria; Fu, Bihong

2014-06-01

162

Contaminated Alluvial Ground Water in the Butte Summit Valley  

Microsoft Academic Search

.  Ground water in alluvial sediments of upper Silver Bow Creek is chronically contaminated with heavy metals, including Cd,\\u000a Cu, Fe, Mn, and Zn. Most of this contamination stems from slag, mill tailings, and waste rock from the Butte mining district\\u000a that had been deposited along the ancestral Silver Bow Creek floodplain. Much of this mine waste is now buried by

Christopher H. Gammons; James P. Madison

2006-01-01

163

Radiocarbon dating of minute gastropods and new constraints on the timing of late Quaternary spring-discharge deposits in southern Arizona, USA  

Microsoft Academic Search

Gastropod shells are commonly preserved in Quaternary sediments, but are often avoided for radiocarbon dating because some taxa incorporate 14C-deficient carbon during shell formation. Recently, Brennan and Quade [(1997) Quat. Res. 47, 329–336] found that some minute taxa (Vallonia, Pupilla, and Succineidae) appear to yield reliable 14C ages for late Pleistocene samples. A more rigorous evaluation of the 14C inventory

Jeffrey S Pigati; Jay Quade; Timothy M Shahanan; C. Vance Haynes

2004-01-01

164

Variation in sedimentology and architecture of Eocene alluvial strata, Wind River and Washakie basins, Wyoming  

SciTech Connect

Eocene continental, alluvial strata of the Wind River Formation (Wind River Basin) and the Cathedral Bluffs Member of the Wasatch Formation (Washakie basin) provide two examples of Laramide intermontane basin aggradation. These alluvial sediments primarily represent overbank flood deposits marginal to channel complexes. Their sedimentology and architecture, although grossly similar, appear to vary somewhat with proximity to Laramide uplifts. In both cases, repetitive sedimentation on the floodplain produced a succession of depositional couplets, each composed of a light-gray sand overlain by a red clay-rich silt or sand. The lower sands are tabular bodies that, near their distal margins, taper discernibly. They commonly display planar and ripple-drift laminations. Upper clay-rich layers, which are laminated, are also generally tabular. Those floodplain strata depositional proximal to Laramide uplifts show little evidence of scouring prior to deposition of the next, overlying couplet. Most of these sedimentary layers, therefore, are laterally continuous (up to 2 km). This alluvial architecture results in relatively uniform porosity laterally within depositional units but variable porosity stratigraphically through the sequence. In contrast, alluvial sediments deposited farther from the Laramide uplifts have undergone sporadic incision (either during rising flood stage or subsequently) followed by aggradation. As a result, many of these floodplain couplets are discontinuous laterally and, hence, exhibit large-scale lateral variability in porosity. Both alluvial sequences have undergone similar types and extents of burial diagenesis.

Patterson, P.E.; Larson, E.E. (Univ. of Colorado, Boulder (United States))

1991-03-01

165

Loess sedimentation in Tibet: provenance, processes, and link with Quaternary glaciations  

USGS Publications Warehouse

Well-preserved loess deposits are found on the foothills of mountains along the middle reaches of the Yarlung Zangbo River in southern Tibet. Optically stimulated luminescence (OSL) dating is used to determine loess ages by applying the single-aliquot regeneration technique. Geochemical, mineralogical, and granulometric measurements were carried out to allow a comparison between loess from Tibet and the Chinese Loess Plateau. Our results demonstrate that (i) the loess deposits have a basal age of 13-11 ka, suggesting they accumulated after the last deglaciation, (ii) loess in southern Tibet has a "glacial" origin, resulting from eolian sorting of glaciofluvial outwash deposits from braided river channels or alluvial fans by local near-surface winds, and (iii) the present loess in the interior of Tibet has accumulated since the last deglaciation when increased monsoonal circulation provided an increased vegetation cover that was sufficient for trapping eolian silt. The lack of full-glacial loess is either due to minimal vegetation cover or possibly due to the erosion of loess as glaciofluvial outwash during the beginning of each interglacial. Such processes would have been repeated during each glacial-interglacial cycle of the Quaternary. ?? 2007 Elsevier Ltd. All rights reserved.

Sun, J.; Li, S.-H.; Muhs, D.R.; Li, B.

2007-01-01

166

A comparison and integration of tree-ring and alluvial records of fire history at the Missionary Ridge Fire, Durango, Colorado, USA  

Microsoft Academic Search

We used tree-ring and alluvial sediment methods to reconstruct past fire regimes for a mixed conifer forest within a 1 km2 drainage basin which was severely burned by a wildfire near Durango, Colorado. Post-fire debris flow events incised the valley-filling alluvial sediments in the lower basin, and created exposures of fire-related of deposits of late-Holocene age. Tree-ring and alluvial sediment

Erica Bigio; Thomas W. Swetnam; Christopher H. Baisan

2010-01-01

167

The morphology of alluvial rivers  

NASA Astrophysics Data System (ADS)

Alluvial rivers form their channel in the material they transport, producing a varied collection of bed shapes, from deep single-thread channels to wide and shallow braids. Laboratory flumes produce similar morphologies at the centimeter scale, while braided rivers can spread over a few kilometers, suggesting that the same basic phenomena express themselves across scales. We conjecture that the competition between gravity and diffusion, at the scale of a sediment grain, controls the morphology of alluvial rivers. The classical threshold theory, which neglects diffusion, explains the relationship between river width and discharge [1]. However, it is valid only when bedload transport vanishes. When the river transports sediments, gravity pulls the grains towards the center of the channel, precluding equilibrium within this theoretical framework [2]. Based on laboratory experiments, we suggest that each bedload grain follows a random walk in the transverse direction. Consequently, sediments diffuse towards the less active areas of the bed, thus counteracting gravity by continuously rebuilding the river's bank. As the sediment discharge increases, this balance requires a wider and narrower channel, until the river becomes unstable. [1] R.E. Glover and Q.L. Florey, Stable channel profiles, US Bur. Reclamation, Hydr., 325, 1951. [2] G. Parker, Self-formed straight rivers with equilibrium banks and mobile bed. Part 2. The gravel river, J. Fluid Mech., 89, 1, 1978.

Devauchelle, O.; Seizilles, G.; Lajeunesse, E.; Bak, M. T.; Marc, O.; Metivier, F.

2012-12-01

168

Quaternary deformation mapping with ground penetrating radar  

Microsoft Academic Search

Ground penetrating radar (GPR) was used in a programme of geological and hydrogeological investigations into the Quaternary of west Cumbria, UK. The investigations were part of an extensive programme to determine the suitability of the area for a deep radioactive waste repository. The hydrogeological characteristics of the drift deposits are important since they affect both recharge and discharge. The glacially

J. P Busby; J. W Merritt

1999-01-01

169

Radiocarbon dates and late-Quaternary stratigraphy from Mamontova Gora, unglaciated central Yakutia, Siberia, U.S.S.R.  

USGS Publications Warehouse

A fine exposure of perennially frozen ice-rich silt and associated flora and vertebrate fauna of late-Quaternary age exists at Mamontova Gora along the Aldan River in central Yakutia, Siberia, U.S.S.R. The silt deposit caps a 50-m-high terrace and consists of three units. An upper layer 1-2 m thick overlies a 10-15-m-thick brownish to black silt layer. The lower silt layer is greenish to gray and about 15 m thick. All the silt is well sorted with 60% of the particles falling between 0.005 and 0.5 mm in diameter and is generally chemically and mineralogically homogeneous. The middle unit contains may extinct vertebrate mammal remains and ice wedges. The lower unit contains little vegetation and no ice wedges. The silt is widespread and exists as a loamy blanket on terraces at various elevations on both sides of the lower Aldan River. The origin of the silt blanket of late-Quaternary age in central Yakutia has long been controversial. Various hypotheses have been suggested, including lacustrine and alluvial, as well as frost-action origins. It is sometimes referred to as loess-like loam. Pe??we?? believes the silt at Mamontova Gora is loess, some of which has been retransported very short distances by water. The silt probably was blown from wide, braided, unvegetated flood plains of rivers draining nearby glaciers. The silt deposits are late Quaternary in age and probably associated with the Maximum glaciation (Samarov) and Sartan and Syryan glaciations of Wisconsinan age. On the basis of biostratigraphy, 10 radiocarbon dates, and their relation to the nearby glacial record, it is felt that the upper unit at Mamontova Gora is Holocene and the middle unit is Wisconsinan. The youngest date available from the middle unit at this particular location is 26,000 years. Dates greater than 56,000 years were obtained in the lower part of the middle unit. The lower unit is definitely beyond the range of radiocarbon dating and probably is older than the last interglacial. The sediment, fauna, ice wedges, stratigraphy, and age of perennially frozen slit deposits in central Alaska are remarkably similar to those of the deposits exposed in central Yakutia. Both areas consist of unglaciated rolling lowlands and river terraces surrounded by high mountains that were extensively glaciated in Pleistocene time. The glaciers extended from the high mountains to the edges of the ranges. In both regions, extensively braided, silt-charged rivers drained the mountains and flowed through the lowlands on their way to the sea. It follows that there should be a similar late-Quaternary history. ?? 1977.

Pewe, T.L.; Journaux, A.; Stuckenrath, R.

1977-01-01

170

Quaternary geology and geomorphology of the Sacramento-San Joaquin Delta, California: evolution and processes  

NASA Astrophysics Data System (ADS)

The Sacramento-San Joaquin Delta (~1,400 km2) is a combination of tidal marsh, islands and agricultural lands at the confluence of the Sacramento and the San Joaquin Rivers, in northern California. Most of the Delta islands are now 3 to 8 m below sea-level and must be protected by levees from inundation. Because of the Delta's crucial role in conveying fresh water to the State, levee failures can cause substantial economic loss by disrupting this supply. Understanding the evolution of the Delta is fundamental to assess the vulnerability of the Delta islands to seismically-induced levee failure. The modern Delta is a young geological feature that began forming during the middle Holocene. Preceding versions of the Delta hosted a variety of depositional environments as sea level fluctuated, responding to climatically-controlled changes. The rising sea reached the Delta about 8,000 years ago, and modern deltaic evolution continued into Holocene time until present. More accurate stratigraphic studies incorporating depositional ages are required to i) better understand the late Quaternary evolution of the Delta, ii) trace the base of Holocene deposits, iii) identify potentially active faults, and iv) evaluate liquefaction hazard for the Delta . This study uses the large amount of data available on the Delta (collected by the California Department of Water Resources and others during the past 30 years) and merges them into a unified dataset. We have produced a database that includes historic and surficial maps, aerial photographs, boreholes, and CPT data, for the purpose of clarifying the nature of the Quaternary deposits and the evolution of the Late Quaternary Delta. Additionally, we have identified recently discovered Pleistocene tephra as the Rockland ash, ~0.575 Ma, and the Loleta ash, ~0.40-0.37 Ma, which have improved stratigraphic correlations and assessment of subsidence rates. Delta sediments include sequences of glacial and interglacial deposits. Borehole logs reveal sequences of incision and backfilling corresponding to major climatic fluctuations: incised channels, sand-filling channels, gravel alluvial fans and eolian dunes during glacial periods, and fine-grained alluvial floodplains, mud flats deposits, marshes and peat during warmer interglacials. The evolution of the Delta is likely the result of three processes: subsidence (based on tephra ages, between ~0.004 cm/yr and 0.007 cm/yr in the Northern Delta, ~0.01 cm/yr in the central Delta, ~0.06 cm/yr in the Eastern Delta), compaction due to organic soil oxidation (3.6-6.1 cm/yr), and tectonic control. The thickness of the organic soils (>20 m) suggests that the Holocene sea-level rise was the major factor controlling the Delta's morphology before agricultural drainage began in the 1850's. Because the patterns suggest that sea-level rise was the major cause of changes in the Delta, it is likely that once the organic soil is all oxidized by anthropogenic processes within a few centuries, the major controlling factor will become anthropogenic sea-level rise.

Gatti, E.; Maier, K. L.; Holzer, T. L.; Knudsen, K. L.; Olson, H.; Pagenknopp, M.; Ponti, D. J.; Rosa, C.; Tinsley, J. C.; Wan, E.

2013-12-01

171

Cambrian to Devonian evolution of alluvial systems: The sedimentological impact of the earliest land plants  

NASA Astrophysics Data System (ADS)

In present-day alluvial environments, the impact of vegetation on sedimentological processes and deposits is well known. A vegetated catchment may decrease sediment yield, sediment erodibility, Hortonian overland flow, aeolian winnowing of fines, the proportion of sediment transported as bedload, and may increase bank stability, infiltration into substrates, and bed roughness. Vegetation also promotes the production of chemically-weathered clays and soils and the adoption of a meandering style. It is generally understood that, prior to the evolution of terrestrial vegetation during the Early Palaeozoic, ancient alluvial systems were markedly different from modern systems, with many systems adopting a "sheet-braided" style. This understanding has previously informed the interpretations of many Precambrian pre-vegetation alluvial successions, but there has been relatively little work regarding Early Palaeozoic alluvial successions laid down prior to and during the initial colonization of the Earth's surface by plants. A comprehensive review of 144 Cambrian to Devonian alluvial successions documented in published literature was combined with original field data from 34 alluvial successions across Europe and North America. The study was designed to identify changes in alluvial style during the period that vegetation was evolving and first colonizing alluvial environments. An increase in mudrock proportion and sandstone maturity is apparent, along with a decrease in overall sand grain size through the Early Palaeozoic. These trends suggest that primitive vegetation cover promoted the production and preservation of muds from the mid Ordovician onwards and increased the residence time of sand-grade sediment in alluvial systems. The compilation also enables the first stratigraphic occurrence of certain vegetation-dependent sedimentary features to be pinpointed and related to the evolution of specific palaeobotanical adaptations. The first markedly heterolithic alluvial sequences appeared at about the same time as the most primitive terrestrial vegetation in the Ordovician, and prolific pedogenic calcite, charcoal and bioturbated floodplain fines first appeared in the rock record at about the same time as vascular-plant macrofossils became abundant in the late Silurian. Lateral accretion sets in channel deposits appeared near the Silurian-Devonian boundary, at or shortly before the appearance of underground rooting systems, and become progressively more abundant in the record during the Devonian, implying a major expansion of meandering rivers as rooted plants stabilized river banks. Coals become abundant after the development of plant arborescence. The analysis suggests that the evolution of embryophytes had a profound effect on fluvial processes and deposits, and this period of landscape evolution must be considered amongst the most significant environmental and geomorphological changes in Earth history, with profound consequences for all aspects of the Earth system.

Davies, Neil S.; Gibling, Martin R.

2010-02-01

172

Bedload transport in alluvial channels  

USGS Publications Warehouse

Hydraulic, sediment, land-use, and rock-erosivity data of 22 alluvial streams were used to evaluate conditions of bedload transport and the performance of selected bedload-transport equations. Transport categories of transport-limited (TL), partially transport-limited (PTL), and supply-limited (SL) were identified by a semiquantitative approach that considers hydraulic constraints on sediment movement and the processes that control sediment availability at the basin scale. Equations by Parker et al. in 1982, Schoklitsch in 1962, and Meyer-Peter and Muller in 1948 adequately predicted sediment transport in channels with TL condition, whereas the equations of Bagnold in 1980, and Schoklitsch, in 1962, performed well for PTL and SL conditions. Overall, the equation of Schoklitsch predicted well the measured bedload data for eight of 22 streams, and the Bagnold equation predicted the measured data in seven streams.

Bravo-Espinosa, M.; Osterkamp, W.R.; Lopes, V.L.

2003-01-01

173

Flow resistance in alluvial and mountain rivers  

NASA Astrophysics Data System (ADS)

Open channel flow resistance has been fruitfully studied in alluvial rivers. However, due to the complex dynamics of shallow water flow, there remains difficulties in the flow resistance study of mountain rivers. Most of studies about resistance in mountain rivers inherit the modifications of resistance relations in alluvial rivers despite significant differences existing in the mechanisms of flow resistance. Resistance relationships of mountain rivers are almost semi-experienced relying on field data. To the author's best knowledge, there is no unified description of the resistance relation covering both mountain and alluvial rivers. In this study, we aim to propose the first attempt on the uniform of the resistance relation. Fluid resistance is partitioned into skin friction and bed form drag through the partitioning of hydraulic radius. Corresponding to the skin friction and the bed form drag, the grain roughness and the bed form roughness are considered separately. We formulate the equations of the energy losses due to bed form drag in mountain rivers e.g. step-pool structures, considering its consistency with bed form drag of alluvial rivers. Thus bed form roughness of mountain rivers could be estimated referring to those of alluvial rivers. The consistent expression of bed form roughness allows a unified form drag formula suitable to both alluvial and mountain rivers by a modified Einstein flow intensity parameter. The formula agrees with the field survey data very well, demonstrating the inherent uniformity in the resistance relations of mountain and alluvial rivers to some extent.

Fu, X.; Zhang, L.; Ma, H.; Li, T.; Guo, D.

2013-12-01

174

Shapefile of the Elevation of the Bedrock Surface Beneath the Rocky Flats Alluvial Fan, Boulder and Jefferson Counties, Colorado  

USGS Publications Warehouse

The Rocky Flats alluvial fan is a large early Pleistocene gravel deposit at the mouth of Coal Creek Canyon along the eastern flank of the Colorado Front Range in Jefferson and Boulder Counties, Colorado. Elevations of the bedrock surface beneath the alluvial fan gravels have been compiled at selected points from a variety of sources and recorded in a digital dataset suitable for importing into commonly used GIS and image processing software packages.

Knepper, Daniel H., Jr.

2003-01-01

175

Diatoms from the Quaternary sediments of the Nile Delta, Egypt, and their palaeoecological significance  

Microsoft Academic Search

This study represents the first contribution describing diatom taxa from the Quaternary sediments of the Nile Delta, Egypt. A total of 99 diatom species and varieties belonging to 28 genera were identified. The palaeoecological conditions during the time of deposition (pH salinity, eutrophication and dissolved silica concentration) are discussed. Deposition of the Quaternary Nile Delta sediments occurred in slightly alkaline,

Abdelfattah A. Zalat

1995-01-01

176

Quaternary dust sources on the Chinese Loess Plateau: a view from single zircon grains, heavy minerals and quartz luminescence  

NASA Astrophysics Data System (ADS)

The origin of loess deposits on the Chinese Loess Plateau (CLP), one of the most valuable Cenozoic climate archives on land, is the subject of considerable debate. A large number of sources have been proposed for the vast quantity of dust that forms the up to 400 m thick loess sequences that cover the c. 640,000 km2 the CLP, including deserts, alluvial fans and mountain regions. There is also debate over whether sources shift across the CLP, within loess units, between units and across the Quaternary/Pliocene boundary. Furthermore, the role of river systems in sediment supply to the CLP has not previously been substantively addressed. Geochemical analysis of bulk sediment from loess is limited by mixing of different source influences and so here we apply a variety of techniques to Quaternary sequences on the CLP. We use single-grain based techniques on zircons and heavy mineral analyses in an attempt to discriminate between potential multiple sources and to test the influence of proximal deserts and major rivers on CLP dust. In addition, we utilise information from detailed optically stimulated luminescence dating of quartz from loess to identify rapid shifts in source region on the CLP. Provenance signatures from samples from the eastern Mu Us and the Tengger deserts can be explained by local sources and recycling of the underlying Cretaceous rock. However, the western Mu Us desert as well as Quaternary loess shows different zircon U-Pb age spectra and heavy mineral distributions, indicative of strong influence from northeastern Tibet. Further, samples from the Yellow River are close to identical to these western Mu Us samples and crucially, also to Quaternary samples from the Loess Plateau. This suggests that the Tibetan-derived sediments are unlikely to have been transported from Tibet by wind, but rather may have been delivered by the Yellow River. This provides the first evidence of a possible genetic link between the Yellow River and the CLP. However, there is also an abrupt shift to an apparently more local aeolian source during the last glacial period at one site on the CLP, potentially indicating activation of proximal aeolian dust sources. The Quaternary source signatures appear to contrast to those of the underlying Pliocene/Miocene red clay, which suggest more western, distal sources.

Stevens, T.; Carter, A.; Vermeesch, P.; Bird, A.; Rittner, M.; Lu, H.; Andò, S.; Garzanti, E.; Nie, J.; Adamiec, G.; Zeng, L.; Zhang, H.; Xu, Z.

2013-12-01

177

Geomorphic Processes and Remote Sensing Signatures of Alluvial Fans in the Kun Lun Mountains, China  

NASA Technical Reports Server (NTRS)

The timing of alluvial deposition in arid and semiarid areas is tied to land-surface instability caused by regional climate changes. The distribution pattern of dated deposits provides maps of regional land-surface response to past climate change. Sensitivity to differences in surface roughness and composition makes remote sensing techniques useful for regional mapping of alluvial deposits. Radar images from the Spaceborne Radar Laboratory and visible wavelength images from the French SPOT satellite were used to determine remote sensing signatures of alluvial fan units for an area in the Kun Lun Mountains of northwestern China. These data were combined with field observations to compare surface processes and their effects on remote sensing signatures in northwestern China and the southwestern United States. Geomorphic processes affecting alluvial fans in the two areas include aeolian deposition, desert varnish, and fluvial dissection. However, salt weathering is a much more important process in the Kun Lun than in the southwestern United States. This slows the formation of desert varnish and prevents desert pavement from forming. Thus the Kun Lun signatures are characteristic of the dominance of salt weathering, while signatures from the southwestern United States are characteristic of the dominance of desert varnish and pavement processes. Remote sensing signatures are consistent enough in these two regions to be used for mapping fan units over large areas.

Farr, Tom G.; Chadwick, Oliver A.

1996-01-01

178

Depositional sequences controlled by high rates of sediment supply, sea-level variations, and growth faulting: the Quaternary Baram Delta of northwestern Borneo  

Microsoft Academic Search

The shelf off the Baram Delta is 50–70km wide, and is underlain by 8–9km of post-Eocene upper slope, prodelta, delta-front, fluvial, shelf–shoreface, and estuarine (incised-valley and tidal-embayment) deposits. The shelf break is defined by a prominent fault scarp ?130m below sea level. Beyond, the seabed descends at an average of 2–3° to the Borneo Trough at >2750m depth. The outer-shelf

R. N. Hiscott

2001-01-01

179

Quaternary Faults and Basin-fill Sediments of the Las Vegas Basin, Southern Nevada  

NASA Astrophysics Data System (ADS)

The N-S elongated extensional Las Vegas basin, southern Nevada, contains 100's of meters of Cenozoic basin-fill sediments that are cut by several Quaternary (Q) faults. These faults define or influence the basin geometry. The basin is generally an asymmetrical half graben defined by the W-dipping, Q Frenchman Mountain fault (FMF) along its E side and a series of smaller offset E-dipping faults to the W. The N terminus of the basin is controlled by the Las Vegas Valley shear zone, along which the majority of the offset occurred prior to the Q. Here, we asses the influence of the Q faults on the distribution of the sedimentary units. Well, exposure, seismic reflection and seismic refraction data show that sedimentary units of different grain sizes or seismic velocity dominate different parts of the basin. Sections dominated by coarse clastic deposits occupy a narrow area along the E side of the basin. Coarse clastic sediments are mixed with finer grained sediments in a broader area along the W side of the basin. Based on provenance and alluvial fan distribution, the coarse deposits along the E side of the basin appear to be trapped in close proximity to the W-dipping FMF. The coarse-grained deposits along the opposite, W side of the basin, are sourced from the nearby Spring Mountains. Because of the structural asymmetry of the basin, these sediments traveled farther from their source area than those on the E side. Some of these E-dipping faults influence the depth to Paleozoic bedrock and some faults form small sub-basins filled with finer grained sediments. Along a WNW trend near the center of the basin and near the present-day Las Vegas Wash, a change in the grain size distribution occurs up stratgraphic section: continuous clay layers are less common and coarse-grained deposits are more common. This difference may reflect a change from internal drainage early in the basin history to external drainage through the Las Vegas Wash in the latter history of the basin-fill sedimentation. This interpretation implies that the FMF was breached by a wash connected to the Colorado River drainage system during basin development. The basin fill deposits suggest an early history of alluvial fan dominated deposits showing internal drainage. That depositional system was followed by E- and W-sloping alluvial fans cut by a NW-trending external drainage system that probably flowed to the Colorado River. The greatest structural influence on sediment distribution was from the Q FMF on the E side of the basin and the dominantly Miocene Las Vegas Valley shear zone on the north, but the structural influence is reduced as Colorado River system and base level imposes on the basin up section.

Taylor, W. J.; Fossett, E.; Luke, B.; Snelson, C.; Rasmussen, T.; McCallen, D.; Rodgers, A.; Louie, J.

2003-12-01

180

Lower Palaeozoic Alluvial Systems: The Sedimentological Impact of Evolving Vegetation in Terrestrial Environments  

NASA Astrophysics Data System (ADS)

In present-day alluvial environments, the impact of vegetation on sedimentological processes and deposits is well known. A vegetated catchment may decrease sediment yield, sediment erodability, Hortonian overland flow, aeolian winnowing of fines, the proportion of sediment transported as bedload, may increase bank stability, infiltration into substrates, bed roughness, and can promote the production of chemically-weathered clays and soils and the adoption of a meandering style. It is generally understood that, prior to the evolution of terrestrial vegetation during the Lower Palaeozoic, ancient alluvial systems were markedly different from modern systems, with many systems adopting a "sheet-braided" style. This understanding has previously informed the interpretations of many Precambrian pre-vegetation alluvial successions, but there has been relatively little work regarding Lower Palaeozoic alluvial successions that existed during the active terrestrialization of plants. In this study, a comprehensive review of 141 Cambrian to Devonian alluvial successions documented in published literature was combined with original field data from 20 alluvial successions from across Europe and North America, in order to identify changes in the sedimentary style of alluvial strata while vegetation was evolving and colonizing alluvial environments. This approach has established clear trends indicating an increase in mudrocks and sandstone maturity and a decrease in overall sand grain size through the Lower Palaeozoic, suggesting that primitive vegetation cover was able to promote the production and preservation of muds and increase the residence time of sand-grade sediment (and thus sediment reworking) in alluvial systems. It has also enabled the first stratigraphic occurrence of certain vegetation-dependent sedimentary features to be pinpointed and tied directly to the onset of specific evolutionary adaptations recorded in the palaeobotanical fossil record. As such, the first markedly heterolithic alluvial sequences can be shown to first appear at the same time as the most primitive terrestrial vegetation in the Lower Ordovician, whilst pedogenic calcite first appears in the rock record at the same time as vascular plants in the Lower Silurian. Vertisols, coal, and certain indicators of meandering fluvial style (lateral accretion surfaces) only appear after the development of plant arborescence and deep rooting in the Devonian.

Davies, N. S.; Gibling, M. R.

2009-04-01

181

Geometry and evolution of a syntectonic alluvial fan, Southern Pyrenees  

SciTech Connect

Syntectonic alluvial fans formed on the northern margin of the Ebro Foreland Basin along the South Pyrenean thrust front during late orogenic thrust movements in the late Oligocene/early Miocene. The present-day geometry, structural relations and sedimentology of one of these fans, the Aguero fan in the province of Huesca, Spain, were studied. Field observations of the architecture of depositional facies and the geometries of syn-tectonic folds and unconformities indicate that the Aguero fan formed as the result of several phases of sedimentation which were primarily controlled by periods of tectonic activity and quiescence. The syntectonic unconformities and growth folds in the fan deposits provide a detailed record of the evolution of a fan adjacent to an active thrust front. Using a computer program to simulate sedimentation and deformation of an alluvial fan it is possible to constrain rates of both sedimentary and tectonic processes by modeling the evolution of the fan body. A facies model for the fan phases indicates that the facies change from proximal (coarse-grained, amalgamated) to distal (finger grained, stacked fining up cycles) in less than 1 km across a fan of radius estimated to be about 2 km.

Arminio, J.F. (Maraven S.A., Caracas (Venezuela)); Nichols, G.J. (Univ. of London, Egham, Surrey (United Kingdom))

1993-02-01

182

Geologically based model of heterogeneous hydraulic conductivity in an alluvial setting  

Microsoft Academic Search

Information on sediment texture and spatial continuity are inherent to sedimentary depositional facies descriptions, which\\u000a are therefore potentially good predictors of spatially varying hydraulic conductivity (K). Analysis of complex alluvial heterogeneity\\u000a in Livermore Valley, California, USA, using relatively abundant core descriptions and field pumping-test data, demonstrates\\u000a a depositional-facies approach to characterization of subsurface heterogeneity. Conventional textural classifications of the\\u000a core

Graham E. Fogg; Charles D. Noyes; Steven F. Carle

1998-01-01

183

Fossil spring deposits in the southern Great Basin and their implications for changes in water-table levels near Yucca Mountain, Nevada, during quaternary time  

SciTech Connect

The proposed high-level nuclear waste repository at Yucca Mountain will be located nearly 200-400 m above the modern water table. Water tables will rise in response to a future return to glacial climates, but the magnitude of the change - and the consequences for radionuclide travel times and overall repository integrity - are key uncertainties. Increased recharge during past pluvial periods in the Spring Mountains and Sheep Range caused water tables to rise and ground water to discharge over broad expanses of the Las Vegas Valley system, and in nearby Pahrump, Sandy, and Coyote Springs Valleys. The change in water-table levels since the last full glacial period varies between and within valleys, from as little as 10 m in several areas to 95 m in the Coyote Springs Valley. At Yucca Mountain, the water table has probably changed by {le}115 m in response to climate change. The spring deposits and the mollusk faunas found with them, often misinterpreted as lacustrine in origin, share many essential features with active spring systems in northeast Nevada. Deposits associated with discharge mainly consist of pale brown silt and sand that is entrapped by dense stands of phreatophytes covering valley bottoms when water tables are high. 81 refs., 13 figs., 6 tabs.

Quade, J. [Univ. of Arizona, Tucson, AZ (United States)] [Univ. of Arizona, Tucson, AZ (United States); Mifflin, M.D. [Mifflin and Associates, Inc., Las Vegas, NV (United States)] [Mifflin and Associates, Inc., Las Vegas, NV (United States); Pratt, W.L. [Univ. of Nevada, Las Vegas, NV (United States)] [Univ. of Nevada, Las Vegas, NV (United States); McCoy, W. [Univ. of Massachusetts, Amherst, MA (United States)] [Univ. of Massachusetts, Amherst, MA (United States); Burckle, L. [Lamont-Doherty Geological Observatory, Pallisades, NY (United States)] [Lamont-Doherty Geological Observatory, Pallisades, NY (United States)

1995-02-01

184

Magnitude of late Quaternary left-lateral displacements along the north edge of Tibet  

Microsoft Academic Search

Images taken by the earth observation satellite SPOT of the Quaternary morphology at 18 sites on the 2000-kilometer-long Altyn Tagh fault at the north edge of Tibet demonstrate that it is outstandingly active. Long-term, left-lateral strike-slip offsets of stream channels, alluvial terrace edges, and glacial moraines along the fault cluster between 100 and 400 meters. The high elevation of the

Gilles Peltzer; Paul Tapponnier; Rolando Armijo

1989-01-01

185

Concentrations of selected metals in Quaternary-age fluvial deposits along the lower Cheyenne and middle Belle Fourche Rivers, western South Dakota, 2009-10  

USGS Publications Warehouse

The headwaters of the Cheyenne and Belle Fourche Rivers drain the Black Hills of South Dakota and Wyoming, an area that has been affected by mining and ore-milling operations since the discovery of gold in 1875. A tributary to the Belle Fourche River is Whitewood Creek, which drains the area of the Homestake Mine, a gold mine that operated from 1876 to 2001. Tailings discharged into Whitewood Creek contained arsenopyrite, an arsenic-rich variety of pyrite associated with gold ore, and mercury used as an amalgam during the gold-extraction process. Approximately 18 percent of the tailings that were discharged remain in fluvial deposits on the flood plain along Whitewood Creek, and approximately 25 percent remain in fluvial deposits on the flood plain along the Belle Fourche River, downstream from Whitewood Creek. In 1983, a 29-kilometer (18-mile) reach of Whitewood Creek and the adjacent flood plain was included in the U.S. Environmental Protection Agency's National Priority List of the Comprehensive Environmental Response, Compensation, and Liability Act of 1980, commonly referred to as a "Superfund site." Listing of this reach of Whitewood Creek was primarily in response to arsenic toxicity of fluvial deposits on the flood plain. Lands along the lower Cheyenne River were transferred to adjoining States and Tribes in response to the Water Resources Development Act (WRDA) of 1999. An amendment in 2000 to WRDA required a study of sediment contamination of the Cheyenne River. In response to the WRDA amendment, the U.S. Geological Survey completed field sampling of reference sites (not affected by mine-tailing disposal) along the lower Belle Fourche and lower Cheyenne Rivers. Reference sites were located on stream terraces that were elevated well above historical stream stages to ensure no contamination from historical mining activity. Sampling of potentially contaminated sites was performed on transects of the active flood plain and adjacent terraces that could potentially be inundated during high-flow events. Sampling began in 2009 and was completed in 2010. A total of 74 geochemical samples were collected from fluvial deposits at reference sites, and 473 samples were collected from potentially contaminated sites. Sediment samples collected were analyzed for 23 metals, including arsenic and mercury. Sequential replicate, split duplicate, and field quality-control samples were analyzed for quality assurance of data-collection methods. The metal concentrations in sediment samples and location information are presented in this report in electronic format (Microsoft Excel), along with non-parametric summary statistics of those data. Cross-sectional topography is graphed with arsenic and mercury concentrations on transects at the potentially contaminated sites. The mean arsenic concentration in reference sediment samples was 8 milligrams per kilogram (mg/kg), compared to 250, 650, and 76 mg/kg for potentially contaminated sediment samples at the surface of the middle Belle Fourche River site, the subsurface of the middle Belle Fourche River site, and the surface of the lower Cheyenne River site, respectively. The mean mercury concentration in reference sediment samples was 16 micrograms per kilogram (?g/kg), compared to 130, 370, and 71 ?g/kg for potentially contaminated sediment samples at the surface of the middle Belle Fourche River site, the subsurface of the middle Belle Fourche River site, and the surface of the lower Cheyenne River site, respectively.

Stamm, John F.; Hoogestraat, Galen K.

2012-01-01

186

Quaternary Research Center  

NSDL National Science Digital Library

"The Quaternary Research Center (QRC) fosters interdisciplinary research on the last two million years of the global environment: a time which encompasses massive, abrupt changes of climate, sea level, global biota and ice extent, as well the evolution of humans and the advent of civilization." Divided into six laboratories, the University of Washington's Center studies Cosmogenic Isotopes, Stable Isotopes, Old Quaternary Isotopes, Periglacial environments, quaternary ecology, paleoecology, and remote sensing. Researchers can find a tremendous amount of isotope, carbon dioxide, and chemistry data on the Taylor Dome, a part of the East Antarctic ice sheet. Students and educators can read papers by the center covering topics such as interactions among climate, surface, and tectonics; and glaciations and climate variations in the Pacific Northwest.

187

Preliminary results of chronostratigraphic field work, OSL-dating and morphogenetic reconstruction of an alluvial apron at Alborz southern foothill, Damghan basin, Iran  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

188

Tertiary and Quaternary Research with Remote Sensing Methods  

NASA Technical Reports Server (NTRS)

Problems encountered in mapping the Quaternary section of the Wind River Region using remote sensing methods are discussed. Analysis of the stratigraphic section is a fundamental aspect of the geologic study of sedimentary basins. Stratigraphic analysis of post-Cretaceous rocks in the Wind River Basin encounters problems of a distinctly different character from those involved in studying the pre-Cretaceous section. The interior of the basin is predominantly covered by Tertiary and Quaternary sediments. These rocks, except on the basin margin to the north, are mostly flat lying or gently dipping. The Tertiary section consists of sandstones, siltstones, and tuffaceous sediments, some variegated, but in general poorly bedded and of great lithologic similarity. The Quaternary sediments consist of terrace, fan, and debris tongue deposits, unconsolidated alluvium occupying the bottoms of modern watercourses, deposits of eolian origin and tufa. Terrace and fan deposits are compositionally diverse and reflect the lithologic diversity of the source terranes.

Conel, J. E.

1985-01-01

189

Quaternary Faunal Environments  

NSDL National Science Digital Library

Students collect information the environments associated with a list of presently living mammals. Students use FAUNMAP to explore the spatial patterns associated with these living mammals during the late Quaternary. They compare these distributions for living mammals to the distribution patterns for a set of extinct mammals. Students answer a set of questions that provide a basis for a summary report.

Hill, Christopher

190

Hydrogeology and simulation of flow between the alluvial and bedrock aquifers in the upper Black Squirrel Creek basin, El Paso County, Colorado  

USGS Publications Warehouse

Anticipated increases in pumping from the bedrock aquifers in El Paso County potentially could affect the direction and rate of flow between the alluvial and bedrock aquifers and lower water levels in the overlying alluvial aquifer. The alluvial aquifer underlies about 90 square miles in the upper Black Squirrel Creek Basin of eastern El Paso County. The alluvial aquifer consists of unconsolidated alluvial deposits that unconformably overlie siltstones, sandstones, and conglomerate (bedrock aquifers) and claystone, shale, and coal (bedrock confining units) of the Denver Basin. The bedrock aquifers (Dawson, Denver, Arapahoe, and Laramie-Fox Hills aquifers) are separated by confining units (upper and lower Denver and the Laramie confining units) and overlie a relatively thick and impermeable Pierre confining unit. The Pierre confining unit is assumed to be a no-flow boundary at the base of the alluvial/ bedrock aquifer system. During 1949-90, substantial water-level declines, as large as 50 feet, in the alluvial aquifer resulted from withdrawals from the alluvial aquifer for irrigation and municipal supplies. Average recharge to the alluvial aquifer from infiltration of precipitation and surface water was an estimated 11.97 cubic feet per second and from the underlying bedrock aquifers was an estimated 0.87 cubic foot per second. Water-level data from eight bedrock observation wells and eight nearby alluvial wells indicate that, locally, the alluvial and bedrock aquifers probably are hydraulically connected and that the alluvial aquifer in the upper Black Squirrel Creek Basin receives recharge from the Denver and Arapahoe aquifers but-locally recharges the Laramie-Fox Hills aquifer. Subsurface-temperature profiles were evaluated as a means of estimating specific discharge across the bedrock surface (the base of the alluvial aquifer). However, assumptions of the analytical method were not met by field conditions and, thus, analyses of subsurface-temperature profiles did not reliably estimate specific discharge across the bedrock surface. The vertical hydraulic diffusivity of a siltstone and sandstone in the lower Denver confining unit was estimated, by an aquifer test, to be about 8 x 10'4 square foot per day. Physical and chemical characteristics of water from the bedrock aquifers in the study area generally differ from the physical and chemical characteristics of water from the alluvial aquifer, except for the physical and chemical characteristics of water from one bedrock well, which is completed in the Laramie-Fox Hills aquifer. In the southern part of the study area, physical and chemical characteristics of ground water indicate downward flow of water from the alluvial aquifer to the Laramie-Fox Hills aquifer. A three-dimensional numerical model was used to evaluate flow of water between the alluvial aquifer and underlying bedrock. Simulation of steady-state conditions indicates that flow from the bedrock aquifers to the alluvial aquifer was about 7 percent of recharge to the alluvial aquifer, about 0.87 cubic foot per second. The potential effects of withdrawal from the alluvial and bedrock aquifers at estimated (October 1989 to September 1990) rates and from the bedrock aquifers at two larger hypothetical rates were simulated for a 50-year projection period. The model simulations indicate that water levels in the alluvial aquifer will decline an average of 8.6 feet after 50 years of pumping at estimated October 1989 to September 1990 rates. Increases in withdrawals from the bedrock aquifers in El Paso County were simulated to: (1) Capture flow that currently discharges from the bedrock aquifers to springs and streams in upland areas and to the alluvial aquifer, (2) induce flow downward from the alluvial aquifer, and (3) accelerate the rate of waterlevel decline in the alluvial aquifer.

Watts, K.R.

1995-01-01

191

The transition on North America from the warm humid Pliocene to the glaciated Quaternary traced by eolian dust deposition at a benchmark North Atlantic Ocean drill site  

NASA Astrophysics Data System (ADS)

We present Plio-Pleistocene records of sediment color, %CaCO3, foraminifer fragmentation, benthic carbon isotopes (?13C) and radiogenic isotopes (Sr, Nd, Pb) of the terrigenous component from IODP Site U1313, a reoccupation of benchmark subtropical North Atlantic Ocean DSDP Site 607. We show that (inter)glacial cycles in sediment color and %CaCO3 pre-date major northern hemisphere glaciation and are unambiguously and consistently correlated to benthic oxygen isotopes back to 3.3 million years ago (Ma) and intermittently so probably back to the Miocene/Pliocene boundary. We show these lithological cycles to be driven by enhanced glacial fluxes of terrigenous material (eolian dust), not carbonate dissolution (the classic interpretation). Our radiogenic isotope data indicate a North American source for this dust (˜3.3-2.4 Ma) in keeping with the interpreted source of terrestrial plant wax-derived biomarkers deposited at Site U1313. Yet our data indicate a mid latitude provenance regardless of (inter)glacial state, a finding that is inconsistent with the biomarker-inferred importance of glaciogenic mechanisms of dust production and transport. Moreover, we find that the relation between the biomarker and lithogenic components of dust accumulation is distinctly non-linear. Both records show a jump in glacial rates of accumulation from Marine Isotope Stage, MIS, G6 (2.72 Ma) onwards but the amplitude of this signal is about 3-8 times greater for biomarkers than for dust and particularly extreme during MIS 100 (2.52 Ma). We conclude that North America shifted abruptly to a distinctly more arid glacial regime from MIS G6, but major shifts in glacial North American vegetation biomes and regional wind fields (exacerbated by the growth of a large Laurentide Ice Sheet during MIS 100) likely explain amplification of this signal in the biomarker records. Our findings are consistent with wetter-than-modern reconstructions of North American continental climate under the warm high CO2 conditions of the Early Pliocene but contrast with most model predictions for the response of the hydrological cycle to anthropogenic warming over the coming 50 years (poleward expansion of the subtropical dry zones).

Lang, David C.; Bailey, Ian; Wilson, Paul A.; Beer, Christopher J.; Bolton, Clara T.; Friedrich, Oliver; Newsam, Cherry; Spencer, Megan R.; Gutjahr, Marcus; Foster, Gavin L.; Cooper, Matthew J.; Milton, J. Andrew

2014-06-01

192

Late quaternary sequence stratigraphy, South Florida margin  

SciTech Connect

Late Quaternary sea-level change and the Florida Current have combined to produce a progradational shelf-slope margin along the western portion of the south Florida Platform facing the Straits of Florida. Analysis of high resolution seismic reflection profiles suggest at least eight 5th order late Quaternary sequences downlap onto the Pourtales Terrace at 250 m water depth. Along most of the south Florida margin, this Late Quaternary section is very thin, and only where significant accumulations occur can the stratigraphic patterns produced by sea-level change be clearly observed. Recognition of systems tracts and their boundaries from high-resolution seismic data is important for prediction of sedimentary facies and stratigraphic development of margins. Many south Florida seismic boundaries can be fit to the Exxon sequence stratigraphy model. Others appear to reflect the added effect of bottom-current erosion that complicates the signal produced by sea-level change. Overall, the sea-level signal appears to dominate the stratigraphic record, especially from the 2-dimensional perspective of dip-oriented seismic profiles. However, the 3-dimensional geometry of deposits are strongly influenced by along slope accumulation patterns controlled by the Florida Current. This study provides new insight on the importance of both geostrophic boundary currents and sea-level change in controlling stratigraphic development of a carbonate platform margin. Similar anomalously thick slope deposits in ancient sequences may indicate similar controls on accumulation and could lend to predictions of related paleo-platform configurations.

Locker, S.D.; Hine, A.C. [Univ. of South Florida, St. Petersburg, FL (United States). Dept. of Marine Science

1995-12-01

193

Simulating Fine grained Alluvial Fan Sedimentation on Mars  

NASA Astrophysics Data System (ADS)

The alluvial fans on Mars date to as late as the Hesperian Period and may be representative of the last major episode of widespread fluvial modification to the red planet's surface. These fans lie within enclosed crater basins, and are characterized by their large size (tens of km in length) and gentle gradient (less than 1-3°). The fans generally feature a network of channel distributaries floored with coarser sediment and what we have interpreted to be fine grained overbank deposits that comprise the bulk of the fan material [1]. We have developed a landform evolution model based on the approach of [2] to simulate the growth of these fans in order to answer several questions about their formation, including: (1) what are the characteristics of water discharge (flow magnitude and duration) and sediment supply (quantity and grain size); and (2) what are the associated implications for the responsible climatic environment (e.g. amount and frequency of precipitation sourcing the fans). The model combines discharge and sediment deposition with channel avulsion and abandonment, allowing for an analysis of both the micro and macro scale processes concerning fan formation. Water and sediment is routed through a distributary network that can branch, recombine, and avulse. The model simulates deposition of both coarse-grained bedload and a fine-grained suspended load material that can be deposited overbank during flood events. The model records the stratigraphy of the deposited material in terms of the relative proportions of coarse and fine-grained sediment. Using measures such as channel width, relative proportions of channel versus overbank deposited sediment, and frequency of channel branching, output is statistically compared with digital elevation models that have been produced from high-resolution CTX and HiRISE stereo pairs. Initial results suggest fans formed from hundreds of flow events over many thousands of years. Fan formation processes appear to be similar to those active in terrestrial fans in northern Chile's Atacama Desert. Additional model runs will simulate fan development under different patterns of precipitation (uniform over the fan versus an orographic pattern of greater precipitation on upper crater walls) and variations in sediment size distribution. References: [1] Morgan, A. M., Howard, A. D., Hobley, D. E. J., Moore, J. M., Dietrich, W. E., Williams, R. M. E., Burr, D. M., Grant, J. A., Wilson, S. A., and Matsubara, Y. (in review) Sedimentology and Climatic Environment of Alluvial Fans in the Martian Saheki Crater and a Comparison with Terrestrial Fans in the Atacama Desert [2] Sun, T., C. Paola, G. Parker, and P. Meakin (2002), Water Resour. Res., 38, no.8, 10.

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

2013-12-01

194

Geomorphological evolution of the Tilcara alluvial fan (Jujuy Province, NW Argentina): Tectonic implications and palaeoenvironmental considerations  

NASA Astrophysics Data System (ADS)

The development and evolution of the Tilcara alluvial fan, in the Quebrada de Humahuaca (Andean Eastern Cordillera, NW Argentina), has been analysed by using geomorphological mapping techniques, sedimentological characterisation of the deposits and OSL chronological methods. It is a complex segmented alluvial fan made up of five evolutionary stages (units Qf1, Qf2, Qf3, Qf4 and Qf5) developed under arid climatic environments as well as compressive tectonic conditions. Segmentation processes, including aggradation/entrenchment cycles and changes in the location of the depositional lobe, are mainly controlled by climatic and/or tectonic changes as well as channel piracy processes in the drainage system. Alluvial fan deposits include debris flows, sheet flows and braided channel facies associated with high water discharge events in an arid environment. The best mean OSL age estimated for stage Qf2 is 84.5 ± 7 ka BP. In addition, a thrust fault affecting these deposits has been recognized and, as a consequence, the compressive tectonics must date from the Upper Pleistocene in this area of the Andean Eastern Cordillera.

Sancho, Carlos; Peña, José Luis; Rivelli, Felipe; Rhodes, Ed; Muñoz, Arsenio

2008-07-01

195

Late Quaternary faulting along the southern Lemhi fault, southeastern Idaho: A complex segmentation history  

SciTech Connect

The Lemhi fault is a 140-km-long range-bounding normal fault in the northern Basin and Range province, north of the eastern Snake River Plain (ESRP). The authors investigation of the southern two (proposed) rupture segments, the Howe and the Fallert Springs, to the north, identified multiple large late Quaternary, surface-faulting events, some of which occurred in temporal clusters. Geologic evidence suggest that the history of the late Pleistocene activity along the northern part of the Fallert Springs segment differs from that along the southern part of the segment. The distribution and timing of surface ruptures, suggest that the Howe segment has ruptured together with at least the southern half of the Fallert Springs segment during the late Pleistocene faulting events. They propose that the Howe-Fallert Springs segment boundary has had little, if any, influence on the propagation of coseismic ruptures for some events, but appears to have effectively arrested others. Their data imply that the central portion of the Fallert-Springs segment has ruptured independent of the southern part of the segment, and that a non-persistent boundary exists within the segment. Paleoseismic activity of the southern Lemhi fault was evaluated in five trenches, two excavated on the Howe segment and three on the Fallert Springs segment; all trenches were excavated in mapped Pinedale-aged alluvial fan deposits (Pierce, 1982). At the southern site on the Howe segment, the most-recent-event colluvial wedge is interbedded with reworked loess, probably derived from the ESRP, that was deposited from about 25 to 15 ka. Thermoluminescence (TL) dates on loess bracket the event between 19 and 15 ka. TL dates indicate the penultimate event occurred before 27--25 ka. TL dates on a probable colluvial wedge, partly exposed in a trench on the southern Fallert Springs segment, suggests that the first of three faulting events occurred about 75 ka.

Hemphill-Haley, M.A.; Sawyer, T.L.; Wong, I.G. (Woodward-Clyde Federal Services, Oakland, CA (United States)); Knuepfer, P.L.K. (State Univ. of New York, Binghamton, NY (United States)); Forman, S.L. (Ohio State Univ., Columbus, OH (United States). Byrd Polar Research Center); Smith, R.P. (EG G Idaho, Inc., Idaho Falls, ID (United States). Idaho National Engineering Lab.)

1993-04-01

196

Analysis of the Sediment Hydrograph of the alluvial deltas in the Apalachicola River, Florida  

NASA Astrophysics Data System (ADS)

Channel and alluvial characteristics in lowlands are the products of boundary conditions and driving forces. The boundary conditions normally include materials and land cover types, such as soil type and vegetation cover. General driving forces include discharge rate, sediment loadings, tides and waves. Deltas built up of river-transported sediment occur in depositional zones of the river mouth in flat terrains and slow currents. Total sediment load depends on two major abilities of the river, the river shear stress and capacity. The shear stress determines transport of a given sediment grain size, normally expressed as tractive force. The river capacity determines the total load or quantity of total sediments transported across a section of the river, generally expressed as the sediment loading rate. The shear stress and sediment loading rate are relatively easy to measure in the headwater and transfer zones where streams form a v-shape valley and the river begins to form defined banks compared to the deposition zone where rivers broaden across lower elevation landscapes creating alluvial forms such as deltas. Determinations of deposition and re-suspension of sediment in fluvial systems are complicated due to exerting tidal, wind, and wave forces. Cyclic forces of tides and waves repeatedly change the sediment transport and deposition rate spatially and temporally in alluvial fans. However, the influence decreases with water depth. Understanding the transport, deposition, and re-suspension of sediments in the fluvial zone would provide a better understanding of the morphology of landscape in lowland estuaries such as the Apalachicola Bay and its estuary systems. The Apalachicola River system is located in the Florida Panhandle. Shelf sedimentation process is not a strong influence in this region because it is protected by barrier islands from direct ocean forces of the Gulf of Mexico. This research explores the characteristic of suspended sediment loadings in fluvial zones of the Apalachicola River and its distributaries through field investigation and laboratory analysis of a series of total suspended solid (TSS) samples. Time-series TSS samples are collected at the alluvial zone. TSS and particle-size distribution analyses are performed to determine the TSS hydrograph and particle-size distribution of suspended solids. Relationships between the TSS hydrograph, discharge hydrograph, and tidal data provide a better understanding of the deposition and re-suspension of the fluvial system in the region. Total suspended particle-size distribution data are used to determine the deposition rate or diminishing rate of alluvial landform in the estuarine system. This dataset and analysis provide excellent information for future modeling work and wetland morphologic studies in the Apalachicola River and similar systems.

Daranpob, A.; Hagen, S.; Passeri, D.; Smar, D. E.

2011-12-01

197

Late Miocene to Plio-Pleistocene fluvio-lacustrine system in the Karacasu Basin (SW Anatolia, Turkey): Depositional, paleogeographic and paleoclimatic implications  

NASA Astrophysics Data System (ADS)

The sedimentary record of the late Cenozoic Karacasu Basin, a long-lived continental half-graben from southwestern Turkey, is characterized by siliciclastic and carbonate deposits. Sedimentation was controlled by an active NW-SE trending major normal fault along the basin's southern margin and by climatically-induced lake-level changes. Detailed facies analysis subdivides the entire Neogene-Quaternary basin-fill into three distinct litostratigraphic units representing paleogeographic changes and sedimentation patterns throughout the basin evolution. Sedimentation commenced in the late Miocene with the deposition of proximal-medial alluvial fan and fluvial facies (Damdere Formation; FA1). At this stage, alluvial fans developed in elevated areas to the south, prograding towards the basin center. At the beginning of the Pliocene, fresh to slightly alkaline, shallow lake deposits (FA2a) of the Karacaören Formation formed. The lake became open and meromictic conditions developed (FA2b). Pollen data from the FA2b facies show that climate was arid to humid. Climate probably changed cyclically through time producing alternation of Artemisia steppe (cold and dry periods) and more forested vegetation (warm and wet). The open lake facies passes upwards into lake margin facies (FA2c), but it was still dominated by alkaline to slightly saline lake conditions. Sedimentation was almost continuous from the late Miocene to Pleistocene. In the early Quaternary, the basin was dissected by the re-activation of basin bounding faults. The unconformable base of the overlying Quaternary deposits (Karacasu Formation; FA3) reflected the basin's transformation from a half-graben into a full-graben system. Oxygen isotope data from carbonates show an alternation of humid climatic periods, when freshwater settings predominated, and semiarid/arid periods in which the basin hosted alkaline and saline water lakes. Neotectonic activity has rejuvenated many of the basin-bounding faults, causing development of talus aprons and local alluvial fans. The basin was progressively incised by modern rivers that have largely smoothed out the topographic relief of the graben margins. id="ab0010" The study highlights to the paleo-geography/-climatology in the east Mediterranean.

Alçiçek, Hülya; Jiménez-Moreno, Gonzalo

2013-06-01

198

Downstream effects of dams on alluvial rivers  

Microsoft Academic Search

This study describes changes in mean channel-bed elevation, channel width, bed-material sizes, vegetation, water discharges, and sediment loads downstream from 21 dams constructed on alluvial rivers. Most of the studied channels are in the semiarid western US. Flood peaks generally were decreased by the dams, but in other respects the post-dam water-discharge characteristics varied from river to river. Sediment concentrations

G. P. Williams; M. G. Wolman

1985-01-01

199

Fertilizers mobilization in alluvial aquifer: laboratory experiments  

Microsoft Academic Search

In alluvial plains, intensive farming with conspicuous use of agrochemicals, can cause land pollution and groundwater contamination.\\u000a In central Po River plain, paleo-channels are important links between arable lands and the underlaying aquifer, since the\\u000a latter is often confined by clay sediments that act as a barrier against contaminants migration. Therefore, paleo-channels\\u000a are recharge zones of particular interest that have

M. Mastrocicco; N. Colombani; S. Palpacelli

2009-01-01

200

ALLUVIAL SCRUB VEGETATION IN COASTAL SOUTHERN CALIFORNIA1 Ted L. Hanes, Richard D. Friesen, and Kathy Keane2  

E-print Network

coastal and desert dunes, coastal val- leys and foothills, interior mountains and desert flats. HollandALLUVIAL SCRUB VEGETATION IN COASTAL SOUTHERN CALIFORNIA1 Ted L. Hanes, Richard D. Friesen deposits along the coastal side of major mountains of southern California. This vegetation type is adapted

Standiford, Richard B.

201

Quaternary Research Association Educational Resources  

NSDL National Science Digital Library

The Quaternary Research Association (QRA) is an organization comprising archaeologists, botanists, civil engineers, geographers, geologists, soil scientists, zoologists and others interested in research into the problems of the Quaternary. This site describes their activities and organization. This direct link to the educational teaching resources provides access to glacier and glaciation resources.

202

Evidence for syntectonic activity during alluvial deposition, Yucca Flat, Nevada  

Microsoft Academic Search

Downhole movies in four large diameter drillholes show a shallowing of bedding dip with increasing distance above the alluvium-tuff contact. The holes are located on the downthrown side of an east dipping normal fault. In each hole the dip of the strata decreases from 20° to 30° at total depth to nearly horizontal at a depth of 150 to 200m.

R. Elwood; H. L. McKague; J. Wagoner

1985-01-01

203

Groundwater geochemistry and microbial community structure in the aquifer transition from volcanic to alluvial areas.  

PubMed

Groundwaters may act as sinks or sources of organic and inorganic solutes, depending on the relative magnitude of biochemical mobilizing processes and groundwater-surface water exchanges. The objective of this study was to link the lithological and hydrogeological gradients to the aquatic microbial community structure in the transition from aquifer recharge (volcanic formations) to discharge areas (alluvial deposits). A field-scale analysis was performed along a water table aquifer in which volcanic products decreased in thickness and areal extension, while alluvial deposits became increasingly important. We measured the main groundwater physical parameters and the concentrations of major and trace elements. In addition, the microbial community structure was assessed by estimating the occurrence of total coliforms and Escherichia coli, the prokaryotic abundance, the cytometric and phylogenetic community composition. The overall biogeochemical asset differed along the aquifer flow path. The concentration of total and live prokaryotic cells significantly increased in alluvial waters, together with the percentages of Beta- and Delta-Proteobacteria. The microbial propagation over a theoretical groundwater travel time allowed for the identification of microbial groups shifting significantly in the transition between the two different hydrogeochemical facies. The microbial community structure was intimately associated with geochemical changes, thus it should be further considered in view of a better understanding of groundwater ecology and sustainable management strategies. PMID:25165005

Amalfitano, S; Del Bon, A; Zoppini, A; Ghergo, S; Fazi, S; Parrone, D; Casella, P; Stano, F; Preziosi, E

2014-11-15

204

A multiple quantum well integrated with a selectively grown quaternary layer  

NASA Astrophysics Data System (ADS)

The multiple quantum well is an important backbone to a number of advanced III-V optoelectronic devices. These include semiconductor lasers, detectors and modulators. Increased device functionality can be achieved by monolithically integrating a multiple quantum well with a selectively grown bulk quaternary. We report on a method for fabricating a selectively deposited quaternary film integrated with a multiple quantum well in an MOCVD reactor. Selective area epitaxy is known to cause a composition shift in the deposited quaternary. Quantitative modelling of the selective area epitaxy process is used to determine the nominal group-III composition required to deposit a quaternary film such that the peak strain induced by the composition shift is minimized. Measurements using spatially resolved photoluminescence and surface profiling are reported to demonstrate the validity and usefulness of the model.

Greenspan, J. E.; Campbell, S.; Shih, I.

2006-07-01

205

Quaternary GIS Laboratory  

NSDL National Science Digital Library

This is the home page of the Quaternary Geographic Information System (GIS) Laboratory at the Institute of Arctic and Alpine Research (INSTAAR) at the University of Colorado. The laboratory supports quantitative spatial analysis of glacier, climate, coastal, and other environmental relationships at high latitudes. Users can access a collection of climate animations for the State of Alaska which show seasonal variation in monthly temperature and precipitation. There is also a set of high-resolution imagery and terrain models for Barrow, Alaska, an animation of the land bridge between Asia and North America, an atlas of paleoglaciation for the state, and links to a variety of other projects involving climatology, paleoclimatology, and glacial geomorphology in the Sate of Alaska.

2007-02-27

206

Fertilizers mobilization in alluvial aquifer: laboratory experiments  

NASA Astrophysics Data System (ADS)

In alluvial plains, intensive farming with conspicuous use of agrochemicals, can cause land pollution and groundwater contamination. In central Po River plain, paleo-channels are important links between arable lands and the underlaying aquifer, since the latter is often confined by clay sediments that act as a barrier against contaminants migration. Therefore, paleo-channels are recharge zones of particular interest that have to be protected from pollution as they are commonly used for water supply. This paper focuses on fertilizer mobilization next to a sand pit excavated in a paleo-channel near Ferrara (Italy). The problem is approached via batch test leaking and columns elution of alluvial sediments. Results from batch experiments showed fast increase in all major cations and anions, suggesting equilibrium control of dissolution reactions, limited availability of solid phases and geochemical homogeneity of samples. In column experiments, early elution and tailing of all ions breakthrough was recorded due to preferential flow paths. For sediments investigated in this study, dispersion, dilution and chemical reactions can reduce fertilizers at concentration below drinking standards in a reasonable time frame, provided fertilizer loading is halted or, at least, reduced. Thus, the definition of a corridor along paleo-channels is recommended to preserve groundwater quality.

Mastrocicco, M.; Colombani, N.; Palpacelli, S.

2009-02-01

207

Using hydrochemical data and modelling to enhance the knowledge of groundwater flow and quality in an alluvial aquifer of Zagreb, Croatia.  

PubMed

The Zagreb alluvial aquifer system is located in the southwest of the Pannonian Basin in the Sava Valley in Croatia. It is composed of Quaternary unconsolidated deposits and is highly utilised, primarily as a water supply for the more than one million inhabitants of the capital city of Croatia. To determine the origin and dynamics of the groundwater and to enhance the knowledge of groundwater flow and the interactions between the groundwater and surface water, extensive hydrogeological and hydrochemical investigations have been completed. The groundwater levels monitored in nested observation wells and the lithological profile indicate that the aquifer is a single hydrogeologic unit, but the geochemical characteristics of the aquifer indicate stratification. The weathering of carbonate and silicate minerals has an important role in groundwater chemistry, especially in the area where old meanders of the Sava River existed. Groundwater quality was observed to be better in the deeper parts of the aquifer than in the shallower parts. Furthermore, deterioration of the groundwater quality was observed in the area under the influence of the landfill. The stable isotopic composition of all sampled waters indicates meteoric origin. NETPATH-WIN was used to calculate the mixing proportions between initial waters (water from the Sava River and groundwater from "regional" flow) in the final water (groundwater sampled from observation wells). According to the results, the mixing proportions of "regional" flow and the river water depend on hydrological conditions, the duration of certain hydrological conditions and the vicinity of the Sava River. Moreover, although the aquifer system behaves as a single hydrogeologic unit from a hydraulic point of view, it still clearly demonstrates geochemical stratification, which could be a decisive factor in future utilisation strategies for the aquifer system. PMID:23707721

Markovi?, Tamara; Brki?, Željka; Larva, Ozren

2013-08-01

208

Synthesis of Quaternary Heterocyclic Salts  

PubMed Central

The microwave synthesis of twenty quaternary ammonium salts is described. The syntheses feature comparable yields to conventional synthetic methods reported in the current literature with reduced reaction times and the absence of solvent or minimal solvent. PMID:24256924

Winstead, Angela J.; Nyambura, Grace; Matthews, Rachael; Toney, Deveine; Oyaghire, Stanley

2014-01-01

209

Morpho-sedimentary characteristics of the Quaternary Matiali fan and associated river terraces, Jalpaiguri, India: Implications for climatic controls  

NASA Astrophysics Data System (ADS)

The Matiali fan is a coarse-grained, small alluvial fan in the eastern Himalayan foothills. It co-exists side by side with the large Tista megafan and other Quaternary fluvial deposits, and has been affected by a number of young thrust faults. It is generally believed that tectonics is the main control in the deposition of these proximal fan-terrace systems. In this paper, geomorphologic and sedimentologic study of the Matiali fan and associated river terraces are combined with five OSL dates from these deposits to understand the succession of events and the forcing mechanism that shaped the geomorphology in the study area during late Quaternary time. Two aggradational terraces (T1 and T2; T2 > T1) occur within the river valleys incised on the Matiali fan. Three E-W scarps cross the fan surface, and they represent the steeper limb of the asymmetric fault-propagation folds formed over blind thrusts. These folds have deformed the fan (T3) and T2 terrace sediments, but the youngest T1 terrace deposits have remained undeformed. Sedimentological studies indicate continuous gradation from the coarsening-upwards mass-flow megagravel in the proximal part to the traction transported finer sheetflood gravels in the distal part, implying a continuous sedimentation history across the fan, uninterrupted by any evidence of syn-depositional tectonic movement. Poorly consolidated sandy gravels of the terraces indicate deposition through braided fluvial processes during a later period of sediment aggradation that filled up the incised river valleys. Previously published 14C dates indicate that deposition of the Matiali fan started around 34 ka coinciding with a period of the intensified Indian summer monsoon of MIS-3. It is suggested that the fan was abandoned and river valleys incised during the LGM between 24 and 18 ka when the discharge decreased substantially. Increased rainfall and sediment supply, with their inherent fluctuations, during wetter periods of MIS-2 and MIS-1 since 12 ka probably resulted in the aggradation of T2 and T1 as shown by our OSL dates. OSL dates from the top of deformed T2 and base of undeformed T1 indicate that the Chalsa fold formed between ~ 11 and ~ 6 ka. Succession of geomorphic and deformational events reconstructed from this study and available age data indicate that the Matiali fan and terrace aggradation coincides with periods of increased monsoonal precipitation, whereas tectonic movements along blind thrusts of Chalsa and Matiali took place later, deforming the fan and older terrace deposits. The evidence unequivocally indicates, contrary to the prevalent notion of tectonic control of geomorphic features in the proximal mountain-front setting, that the deposition of the fan-terrace system was primarily controlled by the fluctuation of the Asian summer monsoon rather than Himalayan tectonics.

Kar, Rimpal; Chakraborty, Tapan; Chakraborty, Chandan; Ghosh, Parthsarathi; Tyagi, Anil K.; Singhvi, Ashok K.

2014-12-01

210

Large Well-exposed Alluvial Fans in Deep Late-Noachian Craters  

NASA Technical Reports Server (NTRS)

Large, fresh-appearing alluvial fans (typically greater than 10 km long) have been identified during a systematic search of 100 m/pixel low-sun daylight THEMIS IR imaging in deep late-Noachian or early- Hesperian craters. Our study of these fans was augmented with MOLA-derived topography and high-resolution MOC and THEMIS VIS images where available. The influence of alluvial fan deposition on the topography of crater floors has been recognized in previous topographic studies. Recent Mars Odyssey-era studies have also identified and described in detail a fluvial delta or fan of approximately the same age as the alluvial fans of this study. Our results, at the time of this writing, indicate that these fans are only found in less than 5% of all craters = 70 km in diameter within a large study region. In every case the fan-containing craters were restricted to a latitude belt between 20 deg S and 30 deg S. All of which had significant topographic relief and appeared morphologically younger than typical mid-Noachian craters in the size range. However, large fans were not found in the most pristine (and presumably youngest) craters in this size range. Most Martian fans have morphologies consistent with terrestrial debris-flow-dominated fans.

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

2004-01-01

211

Large Well-Exposed Alluvial Fans in Deep Late-Noachian Craters  

NASA Technical Reports Server (NTRS)

Large, fresh-appearing alluvial fans (typically greater than 10 km long) have been identified during a systematic search of 100 m/pixel low-sun daylight THEMIS IR imaging in deep late-Noachian or early-Hesperian craters. Our study of these fans was augmented with MOLA-derived topography and high-resolution MOC and THEMIS VIS images where available. The influence of alluvial fan deposition on the topography of crater floors has been recognized in previous topographic studies. Recent Mars Odyssey-era studies have also identified and described in detail a fluvial delta or fan of approximately the same age as the alluvial fans of this study. Our results, at the time of this writing, indicate that these fans are only found in less than 5% of all craters greater than or equal to 70 kilometers in diameter within a large study region. In every case the fan-containing craters were restricted to a latitude belt between 20 degrees S and 30 degrees S. All of which had significant topographic relief and appeared morphologically younger than typical mid-Noachian craters in the size range. However, large fans were not found in the most pristine (and presumably youngest) craters in this size range. Most Martian fans have morphologies consistent with terrestrial debris-flow-dominated fans.

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

2004-01-01

212

Fault-sourced alluvial fans and their interaction with axial fluvial drainage: An example from the Plio-Pleistocene Upper Valdarno Basin (Tuscany, Italy)  

NASA Astrophysics Data System (ADS)

The present study deals with the fault-sourced, alluvial-fan deposits of the Plio-Pleistocene Upper Valdarno Basin (Northern Apennines, Italy). Different phases of alluvial fan aggradation, progradation and backstep are discussed as possible effects of the interaction among fault-generated accommodation space, sediment supply and discharge variations affecting the axial fluvial drainage. The Upper Valdarno Basin, located about 35 km SE of Florence, is filled with 550 m palustrine, lacustrine and alluvial deposits forming four main unconformity-bounded units (i.e. synthems). The study alluvial-fan deposits belong to the two uppermost synthems (Montevarchi and Torrente Ciuffenna synthems) and are Early to Middle Pleistocene in age. These deposits are sourced from the fault-bounded, NE margin of the basin and interfinger with axial fluvial deposits. Alluvial fan deposits of the Montevarchi Synthem consist of three main intervals: i) a lower interval, which lacks any evidence of a depositional trend and testify balance between the subsidence rate (i.e. fault activity) and the amount of sediment provided from the margin; ii) a coarsening-upward middle interval, pointing to a decrease in subsidence rate associated with an augment in sediment supply; iii) a fining-upward, upper interval (locally preserved), documenting a phase of tectonic quiescence associated with a progressive re-equilibration of the tectonically-induced morphological profile. The basin-scale unconformity, which separates the Montevarchi and Torrente Ciuffenna synthems was due to the entrance of the Arno River into the basin as consequence of a piracy. This event caused a dramatic increase in water discharge of the axial fluvial system, and its consequent embanking. Such an erosional surface started to develop in the axial areas, and propagated along the main tributaries, triggering erosion of the alluvial fan deposits. Alluvial-fan deposits of the Torrente Ciuffenna Synthem accumulated above the unconformity during a phase of tectonic quiescence, and show a fining-upward depositional trend. This trend was generated by a progressive decrease in sediment supply stemming out from upstream migration of the knickpoints developed during the embanking of the axial system.

Fidolini, Francesco; Ghinassi, Massimiliano; Aldinucci, Mauro; Billi, Paolo; Boaga, Jacopo; Deiana, Rita; Brivio, Lara

2013-05-01

213

Fire, climate, and alluvial system dynamics: A Holocene record from Yellowstone National Park  

SciTech Connect

Many large debris-flow, hyperconcentrated-flow, and flood-streamflow sediment transport events have been produced in steep basins that were burned in the 1988 fires in northeaster Yellowstone National Park. The charcoal- and fines-rich character of fire-related debris-flow deposits and the abundance of similar facies in Holocene fan sections have allowed them to construct a [sup 14]C-dated chronology of fire-related sedimentation in the Soda Butte and Slough Creek drainages for the last 3500 years. Major periods of fire-related alluvial fan aggradation are interpreted as drought-dominated with the support of local paleoenvironmental data and statistical analyses of historical climate-fire relations; however, some fire-related events may occur due to high climatic variability and severe short-term drought within generally moist intervals. The last major episode of fire-related debris-flow activity encompasses the Medieval Warm Period of 900--1300 AD and peaks ca. 1150 AD; a prior episode culminates ca. 350--100 BC. Wetter periods contain minimal fire-related fan sedimentation; however, floodplain broadening and aggradation occurs along axial streams. Higher average snowmelt runoff discharges are probably involved, such that the dominant alluvial activity shifts to removal of sediment from alluvial fan storage and transport to downstream floodplains. The Little Ice Age (ca. 1300--1900 AD) contains minimal fire-related debris0flow activity and is associated with floodplain aggradation of the T4 terrace, and independent evidence suggests substantially wetter conditions during T3 aggradation ca. 350--650 AD. Thus, small-scale climate changes of the late Holocene effectively control the dominant mode of alluvial activity.

Meyer, G.A. (Univ. of New Mexico, Albuquerque, NM (United States). Dept. of Geology); Wells, S.G. (Univ. of California, Riverside, CA (United States). Dept. of Earth Sciences); Jull, A.J. (Univ. of Arizona, Tucson, AZ (United States). NSF-Arizona Accelerator Facility For Isotope Dating)

1992-01-01

214

Efficient extraction of fine heavy minerals from alluvial and ground ores  

SciTech Connect

A new extraction method which includes a combination of gravity and alternating electromagnetic fields with interfriction of mineral particles was proposed and tested in lab conditions at Mineral Processing Department of St. Petersburg Mining Institute. At the beginning of the work the main goal was to find an efficient alternative to traditional extraction methods (like shaking table, etc.) used for concentration of fine alluvial gold particles. After the method and a series of gradually improved lab separators were positively tested for gold, the efficiency of the method was also proved for extraction of platinum and other heavy minerals from alluvial and ground ores in experimental work at the St. Petersburg Mining institute. The fine heavy minerals were separated to concentrates with high technological indices. In parallel a semi-industrial gravi-electromagnetic separator was made and several technological flowsheets were designed for testing the method in industrial conditions. A series of industrial tests accompanied with complete sampling and standard technological measurements were performed at several alluvial deposits, with good technological indices. Thus the method and the flowsheets displayed high additional recovery of fine alluvial gold particles during elaborated industrial experiments in Siberia (Aldan province). At higher concentrate grade this method, even in one-stage operation, increased gold recovery more than by 25% compared with shaking table (for particles < 0.10 mm gold recovery was 82% vs. 55% by shaking table, for particles < 0.25 mm the recovery was 97.5% vs. 61.8%). Experiments were performed by joint team of St. Petersburg Mining institute and the Irkutsk Institute of Rare Metals.

Tikhonov, O.N. [St. Petersburg Mining Inst. (Russian Federation)

1995-12-31

215

Ground-water quality in alluvial basins that have minimal urban development, south-central Arizona  

USGS Publications Warehouse

Ground-water quality data (1917-96) from 772 wells in 16 alluvial basins that have minimal urban development were used to determine the effect of nonurban factors on ground-water quality in south- central Arizona. Characterization of the spatial variability of ground-water quality within and among alluvial basins that have minimal urban development will provide a baseline to which water- quality problems associated with urbanization can be compared. Four water-type categories--calcium carbonate, calcium mixed anion, sodium carbonate, and sodium chloride--were used to classify the 13 alluvial basins for which adequate data were available. Ground-water quality was compared to U.S. Environmental Protaection Agency maximum contaminant levels for drinking water, depth of well, and depth to top of perforated interval for five alluvial basins that represented the four water-type categories. Exceedances of maximum contaminant levels for fluoride and nitrate occurred in three and four basins, respectively, of the five selected basins. Specific-conductance values for ground water in the five selected basins tend to increase in a northwesterly direction toward the central part of Arizona as the extent of evaporite deposits increases. The results of this study, which are part of the U.S. Geological Survey's National Water-Quality Assessment Program, can be used to determine the effects of urban land-use activities on ground-water quality in similar hydrogeologic conditions and may be the best indicator available for nonurban ground-water quality in the region.

Gellenbeck, Dorinda J.; Coes, Alissa L.

1999-01-01

216

Alluvial Bars of the Obed Wild and Scenic River, Tennessee  

USGS Publications Warehouse

In 2004, the U.S. Geological Survey (USGS) and the National Park Service (NPS) initiated a reconnaissance study of alluvial bars along the Obed Wild and Scenic River (Obed WSR), in Cumberland and Morgan Counties, Tennessee. The study was partly driven by concern that trapping of sand by upstream impoundments might threaten rare, threatened, or endangered plant habitat by reducing the supply of sediment to the alluvial bars. The objectives of the study were to: (1) develop a preliminary understanding of the distribution, morphology, composition, stability, and vegetation structure of alluvial bars along the Obed WSR, and (2) determine whether evidence of human alteration of sediment dynamics in the Obed WSR warrants further, more detailed examination. This report presents the results of the reconnaissance study of alluvial bars along the Obed River, Clear Creek, and Daddys Creek in the Obed WSR. The report is based on: (1) field-reconnaissance visits by boat to 56 alluvial bars along selected reaches of the Obed River and Clear Creek; (2) analysis of aerial photographs, topographic and geologic maps, and other geographic data to assess the distribution of alluvial bars in the Obed WSR; (3) surveys of topography, surface particle size, vegetation structure, and ground cover on three selected alluvial bars; and (4) analysis of hydrologic records.

Wolfe, W.J.; Fitch, K.C.; Ladd, D.E.

2007-01-01

217

Geomorphology and regional stratigraphic model of Cenozoic deposits from "Continental to Marine" of Western Peninsular Malaysia and Strait of Malacca.  

NASA Astrophysics Data System (ADS)

Coastal basins have been greatly influenced worldwide by their geological heritage (lithology, structural control) and eustatic sea-level fluctuations. Along the western side of Peninsular Malaysia, both the structures of the tertiary-quaternary basement and the geomorphology are poorly known. The coast is characterized landward by an absence of tertiary deposits on the alluvial and coastal plains and seaward by numerous deeply incised valleys although the incision potential is low. Offshore, in the Strait of Malacca, the thickness of sediments increases drastically, particularly at the apex of some N-S elongated basins (> 2 Km), and in the central part of the Strait of Malacca. Onshore, the geomorphology of the Western Peninsular Malaysia is controlled mostly by climatic effects on an old (Indosinian) orogen affected by transtensional brittle tectonics during the Tertiary. We investigate the effects of Tertiary extension and associated vertical motions on the Cenozoic geomorphology and stratigraphy. The study is based on a combined morphobathymetric approach of based on GEBCO data, supported by low and recent high resolution offshore seismic data, and DTM data from ASTER and SRTM. The main results are the followings: (1) the structural control appears to be responsible of the positioning and preservation of the Tertiary deposits; while the Quaternary (marine) deposits thinner, drowned the western Malaysia Peninsular coast, independently of the geomorphological and structural context; (2) The offshore Tertiary deposits seem disconnected from the modern drainage network, suggesting probable uplift during the late Tertiary period, which reactivated NW-SE trending faults and fractures; (3) The orientation, the shape and the depth of the ancient and modern incised valleys (Perak, Kerian , Kinta rivers) are controlled by the structural context and lithological contrast; (4) Finally, from a landward to a seaward directions, the Cenozoic deposits seems to have transited via incised valleys, therefore by-passing the platform.

Menier, David; Mansor, Yazid; Sautter, Benjamin; Pubellier, Manuel; Estournes, Guilhem; Meng Choong, Chee; Ghosh Deva, Prasad; Proust, Jean-Noel; Goubert, Evelyne

2014-05-01

218

Distribution and Orientation of Alluvial Fans in Martian Craters  

NASA Technical Reports Server (NTRS)

We present the results of the complete survey of Martian alluvial fans from 0-30 S, initiated by Moore and Howard. Nineteen impact craters contain alluvial fans. They are regionally grouped into three distinct areas. We present our initial results regarding their distribution and orientation in order to understand what controls their formation. Since alluvial fans are formed by water transport of sediment, these features record wetter episodes of Martian climate. In addition, their enigmatic distribution (in regional groups and in some craters, but not similar adjacent ones) needs to be understood, to see how regional geology, topographic characteristics, and/or climate influence their formation and distribution.

Kraal, E. R.; Moore, J. M.; Howard, A. D.; Asphaug, E. I.

2005-01-01

219

Design of flood protection for transportation alignments on alluvial fans  

SciTech Connect

The method of floodplain delineation on alluvial fans developed for the national flood insurance program is modified to provide estimates of peak flood flows at transportation alignments crossing an alluvial fan. The modified methodology divides the total alignment length into drainage design segments and estimates the peak flows that drainage structures would be required to convey as a function of the length of the drainage design segment, the return period of the event, and the location of the alignment on the alluvial fan. An example of the application of the methodology is provided. 16 refs., 5 figs.

French, R.H.

1991-01-01

220

Relative Age Dating Techniques and a Late Quaternary Chronology, Arikaree Cirque, Colorado  

Microsoft Academic Search

Late Quaternary deposits in Arikaree Cirque are re-examined, using eight relative age dating methods including lichenometry. If snowkill of lichens is unrecognized, an erroneously young age may be assigned to Neoglacial deposits if only lichenometric methods are employed. The data were entered into two clustering programs, which were used to group sample sites according to age. The results of this

Tom Carroll

1974-01-01

221

Quaternary and pre-Quaternary( ) materials and processes of southeast Ohio: Overview, speculations, and recommendations  

SciTech Connect

Investigations and mapping of surficial deposits in Ohio have focused largely on the glacial deposits which cover nearly two-thirds of the state. Research on Quaternary deposits beyond the glacial border has been done by Foster, Hildreth, Andrews, Leverett, Tight, Stout, Goldthwait, Forsyth, Lessig, White, Totten, Hoyer, and Noltimier. However, growing human interaction with surficial materials of southeast Ohio now requires much more detailed mapping and characterization of these deposits. Recognition of periglacial, proglacial, and preglacial processes and materials in eastern and southern states has led to the search for similar processes and materials in southeast Ohio. Evidence for gelifraction, gelifluction, cryoturbation, and considerable periglacial colluviation is more extensive than previously thought. Proglacial deposits are also much more extensive, outwash and glaciolacustrine deposits cover large areas in southeast Ohio and are poorly mapped and characterized, or not mapped at all. Preglacial processes including a long span of profound weathering and formation of saprolite have been given little or no attention in southeast Ohio. The signature of protracted preglacial weathering still remains in this part of the state, and should change prevailing views of the terrain upon which periglacial processes worked. Mapping and characterization of these materials are urgently needed as citizens make important land-use decisions such as locating landfills and new developments.

Berg, T.M. (Ohio Geological Survey, Columbus, OH (United States))

1992-01-01

222

Evaluating the controls of shear stress, sediment supply, alluvial cover, and channel morphology on experimental bedrock incision rate  

NASA Astrophysics Data System (ADS)

We explored the dependence of experimental bedrock erosion rate on shear stress, bed load sediment flux, alluvial bed cover, and evolving channel morphology. We isolated these variables experimentally by systematically varying gravel sediment flux Qs and water discharge Qw in a laboratory flume, gradually abrading weak concrete "bedrock." All else held constant, we found that (1) erosion rate was insensitive to flume-averaged shear stress, (2) erosion rate increased linearly with sediment flux, (3) erosion rate decreased linearly with the extent of alluvial bed cover, and (4) the spatial distribution of bed cover was sensitive to local bed topography, but the extent of cover increased with Qs/Qt (where Qt is flume-averaged transport capacity) once critical values of bed roughness and sediment flux were exceeded. Starting from a planar geometry, erosion increased bed roughness due to feedbacks between preferential sediment transport through interconnected topographic lows, focused erosion along these zones of preferential bed load transport, and local shear stresses that depended on the evolving bed morphology. Finally, continued growth of bed roughness was inhibited by imposed variability in discharge and sediment flux, due to changes in spatial patterns of alluvial deposition and impact wear. Erosion was preferentially focused at lower bed elevations when the bed was cover-free, but was focused at higher bed elevations when static alluvial cover filled topographic lows. Natural variations in discharge and sediment flux may thus stabilize and limit the growth of roughness in bedrock channels due to the effects of partial bed cover.

Johnson, Joel P. L.; Whipple, Kelin X.

2010-06-01

223

INTRODUCTION Mesopotamia is the broad, flat alluvial plain  

E-print Network

INTRODUCTION Mesopotamia is the broad, flat alluvial plain between the Tigris and Euphrates Rivers to the headwaters of the Tigris and Euphrates Rivers from ca. 4300 to 4200 B.P. Particularly important

deMenocal, Peter B.

224

The Shape of Trail Canyon Alluvial Fan, Death Valley  

NASA Technical Reports Server (NTRS)

A modified conic equation has been fit to high-resolution digital topographic data for Trail Canyon alluvial fan in Death Valley, California. Fits were accomplished for 3 individual fan units of different age.

Farr, Tom G.; Dohrenwend, John C.

1993-01-01

225

Kinematic wave model of bed profiles in alluvial channels  

E-print Network

A mathematical model, based on the kinematic wave (KW) theory, is developed for describing the evolution and movement of bed profiles in alluvial channels. The model employs a functional relation between sediment transport rate and concentration, a...

Tayfur, Gokmen; Singh, Vijay P.

2006-06-21

226

Alluvial Fans as a Record of Late Precipitation on Mars  

NASA Astrophysics Data System (ADS)

Alluvial Fans on Mars provide a record of late activity likely driven by synoptic precipitation as snowfall. Snowfall may have been concentrated into topography around craters, thereby facilitating weathering and enabling runoff during melting.

Grant, J. A.; Wilson, S. A.

2014-07-01

227

The Quaternary History of Scandinavia  

NASA Astrophysics Data System (ADS)

During the Quaternary Period, Scandinavia's mountains were the source for repeated glaciation that covered much of eastern, central and western Europe. With a particular emphasis on Denmark, Norway, Sweden and Finland, this text describes how these glaciations, and their intervening warmer stages, affected Scandinavia and the surrounding areas. In particular, this account focuses on the last cold stage, the Weichselian, with its extensive Late Weichselian glaciation and the subsequent deglaciation, and on the last 10,000 years, the Holocene, with its well documented environmental changes. The Quaternary History of Scandinavia provides a cross-frontier synthesis of how the glaciation affected this vast region.

Donner, Joakim

2005-08-01

228

SOILS, SEC 1 SOIL ORGANIC MATTER DYNAMICS AND NUTRIENT CYCLING RESEARCH ARTICLE Soil carbon and nitrogen storage in alluvial wet meadows  

E-print Network

Purpose Wet meadows formed on alluvial deposits potentially store large amounts of soil carbon (C) but its and characterize soil organic carbon (SOC) and nitrogen (N) in mountain wet meadows across ranges of meadow Mountains representing a range of wetness and livestock utilization levels were selected for soil sampling

Norton, Jay B.

229

Braidplain, floodplain and playa lake, alluvial-fan, aeolian and palaeosol facies composing a diversified lithogenetical sequence in the permian and triassic of South Devon (England)  

Microsoft Academic Search

The Permian and Triassic of South Devon (England) are a continental red bed sequence of very diversified lithogenetical composition. Within the thick series, the distribution of the main depositional environments being fluvial braidplain, fluvial floodplain and playa lake, alluvial fan, aeolian dune and calcrete palaeosol changes repeatedly in both horizontal and vertical direction. Significant sedimentary milieus such as aeolian dunes

Detlef Mader

1985-01-01

230

Braidplain, floodplain and playa lake, alluvial-fan, aeolian and palaeosol facies composing a diversified lithogenetical sequence in the permian and triassic of South Devon (England)  

Microsoft Academic Search

The Permian and Triassic of South Devon (England) are a continental red bed sequence of very diversified lithogenetical composition. Within the thick series, the distribution of the main depositional environments being fluvial braidplain, fluvial floodplain and playa lake, alluvial fan, aeolian dune and calcrete palaeosol changes repeatedly in both horizontal and vertical direction. Significant sedimentary milieus such as aeolian dunes

Detlef Mader

231

Geomorphologic flood-hazard assessment of alluvial fans and piedmonts  

USGS Publications Warehouse

Geomorphologic studies are an excellent means of flood-hazard assessment on alluvial fans and piedmonts in the southwestern United States. Inactive, flood-free, alluvial fans display well developed soils, desert pavement, rock varnish, and tributary drainage networks. These areas are easily distinguished from flood-prone active alluvial fans on aerial photographs and in the field. The distribution of flood-prone areas associated with alluvial fans is strongly controlled by fanhead trenches dissecting the surface. Where fanhead trenches are permanent features cut in response to long-term conditions such as tectonic quiescence, flood-prone surfaces are situated down-slope from the mountain front and their positions are stable for thousands of years. Since the length and permanency of fanhead trenches can vary greatly between adjacent drainages, it is not appropriate to use regional generalizations to evaluate the distribution and stability of flood-hazard zones. Site-specific geomorphologic studies must be carried out if piedmont areas with a high risk of flooding are to be correctly identified and losses due to alluvial-fan flooding minimized. To meet the growing demand for trained professionals to complete geomorphologic maps of desert piedmonts, undergraduate and graduate geomorphology courses should adopt an instructional unit on alluvial-fan flood hazards that includes: 1) a review of geomorphologic characteristics that vary with surface age; 2) a basic mapping exercise; and 3) a discussion of the causes of fanhead trenching.

Field, J.J.; Pearthree, P.A.

1997-01-01

232

The linkage between hillslope vegetation changes and late-Quaternary fluvial-system aggradation in the Mojave Desert revisited  

NASA Astrophysics Data System (ADS)

Valley-floor-channel and alluvial-fan deposits and terraces in the southwestern US record multiple episodes of late Quaternary fluvial aggradation and incision. Perhaps the most well constrained of these episodes took place from the latest Pleistocene to the present in the Mojave Desert. One hypothesis for this episode, i.e. the paleo-vegetation change hypothesis (PVCH), posits that a reduction in hillslope vegetation cover associated with the transition from Pleistocene woodlands to Holocene desert scrub generated a pulse of sediment that triggered a primary phase of aggradation downstream, followed by channel incision, terrace abandonment, and initiation of a secondary phase of aggradation further downstream. A second hypothesis, i.e. the extreme-storm hypothesis, attributes episodes of aggradation and incision to changes in the frequency and/or intensity of extreme storms. In the past decade a growing number of studies has advocated the extreme-storm hypothesis and challenged the PVCH on the basis of inconsistencies in both timing and process. Here I show that in eight out of nine sites where the timing of fluvial-system aggradation in the Mojave Desert is reasonably well constrained, measured ages of primary aggradation and/or incision are consistent with the predictions of the PVCH if the time-transgressive nature of paleo-vegetation changes with elevation is fully taken into account. I also present an alternative process model for PVCH that is more consistent with available data and produces sediment pulses primarily via an increase in drainage density (i.e. a transformation of hillslopes into low-order channels) rather than solely via an increase in sediment yield from hillslopes. This paper further documents the likely important role of changes in upland vegetation cover and drainage density in driving fluvial-system response during semiarid-to-arid climatic changes.

Pelletier, J. D.

2014-03-01

233

Age and origin of the Gezira alluvial fan between the Blue and White Nile rivers  

NASA Astrophysics Data System (ADS)

The Gezira is a low-angle alluvial fan bounded by the Blue Nile to the east and the White Nile to the west. It is the main agricultural region of Sudan and produces high quality long-staple cotton for export. Dark cracking clays (vertisols) cover much of the Gezira and range in age from 50 kyr to Holocene. The Gezira is traversed by a series of defunct sandy channels that originate between Sennar and Wad Medani on the present-day Blue Nile. With a radius of 300 km and an area of 40,000 km2 the Gezira is a mega-fan. The younger channels range in age from early Holocene to 100 kyr, while near surface channels filled with rolled quartz and carbonate gravels have ages back to >250 kyr. Boreholes in the Gezira reveal coarse alluvial sands and gravels in now buried channels overlain by alluvial clays, forming a repetitive sequence of fining-upwards alluvial units. that probably extend back to Pliocene times. The fan is up to 180 m thick with a volume of ~1,800 km3. The sandy or gravelly bed-load channels coincide with colder drier climates and sparse vegetation in the Ethiopian headwaters of the Blue Nile and the alluvial clays denote widespread flooding during times of stronger summer monsoon. The early stages of such flood events were often accompanied by mass burial of Nile oyster (Etheria elliptica) beds, such as the 45-50 kyr floods that deposited up to 5 m of clay in the northern Gezira. A unique feature of the eastern Gezira is a former Blue Nile channel at least 80 km long running parallel to the present river and entirely filled with volcanic ash. The channel was only 3-4 m deep and 20-30 m wide. Very fine laminations and cross-beds, together with locally abundant phytoliths and sponge spicules, suggest slow-moving water, with flow dispersed across many distributary channels. The ash geochemistry is similar to that in the lower part of the Kibish Formation in the lower Omo valley of southern Ethiopia and points to a minimum age of 100 kyr and a maximum age of 190 kyr. The Ethiopian volcano that provided the ash was located on the interfluve between the upper Omo and the upper Blue Nile. Although the Blue Nile has frequently changed course in the last 250 kyr, it has flowed close to its present channel at least three times in that time.

Williams, martin

2014-05-01

234

Quaternary alkaloids of Argemone mexicana.  

PubMed

Four quaternary isoquinoline alkaloids, dehydrocorydalmine, jatrorrhizine, columbamine, and oxyberberine, have been isolated from the whole plant of Argemone mexicana Linn. (Papaveraceae) and their structures established by spectral evidence. This is the first report of these alkaloids (dehydrocorydalmine, jatrorrhizine, columbamine, and oxyberberine) from Argemone mexicana and the Argemone genus. PMID:20645832

Singh, Sarita; Singh, Tryambak Deo; Singh, Virendra Pratap; Pandey, Vidya Bhushan

2010-02-01

235

Quaternary uplift of southern Italy  

Microsoft Academic Search

Dramatic coastline changes demonstrate rapid Quaternary uplift of Calabria in southern Italy. Because most of the west (Tyrrhenian Sea) coast is normal fault bounded, previous work has asserted that its uplift is local footwall uplift related to extension. However, the east (Ionian Sea) coast is also uplifting but is not normal fault bounded. This reanalysis, based on original field work

Rob Westaway

1993-01-01

236

Modern alluvial fan and deltaic sedimentation in a foreland tectonic setting: the Lower Mesopotamian Plain and the Arabian Gulf  

NASA Astrophysics Data System (ADS)

The Arabo-Persian Gulf, generally considered as a classical carbonate basin, in fact also includes important terrigenous systems whose nature and geometry are related closely to the tectonic framework. The Gulf is bordered along its northeastern periphery by an active alpine system which constitutes a major source of both siliceous and calcareous detritus. There are four types of terrigenous discharge which are classified according to their structural relationships. Numerous alluvial fans terminate ephemeral consequent streams draining the flanks of anticlines forming the external parts of the Zagros Mountain belt. Alluvial-fan deltas studied in detail in southeastern Iran terminate semi-permanent streams which flow along major synclinal axis. They are composed mainly of fine carbonate detritus, part of which accumulates as spectacular marine mud banks. Two major types of delta occur. Relatively small marine deltas, associated with permanent antecedent streams which cross the Zagros fold system, are scattered along the Persian shoreline. The other is the a major deltaic complex which is associated with the Tigris-Euphrates Rivers. This system has prograded along the main axis of the Gulf, the resulting Mesopotamian Plain filling at least half of the original basin which, in early Quaternary times, extended from Hormuz to Syria.

Baltzer, Frédéric; Purser, Bruce H.

1990-05-01

237

Holocene alluvial stratigraphy and response to climate change in the Roaring River valley, Front Range, Colorado, USA  

NASA Astrophysics Data System (ADS)

Stratigraphic analyses and radiocarbon geochronology of alluvial deposits exposed along the Roaring River, Colorado, lead to three principal conclusions: (1) the opinion that stream channels in the higher parts of the Front Range are relics of the Pleistocene and nonalluvial under the present climate, as argued in a water-rights trial USA v. Colorado, is untenable, (2) beds of clast-supported gravel alternate in vertical succession with beds of fine-grained sediment (sand, mud, and peat) in response to centennial-scale changes in snowmelt-driven peak discharges, and (3) alluvial strata provide information about Holocene climate history that complements the history provided by cirque moraines, periglacial deposits, and paleontological data. Most alluvial strata are of late Holocene age and record, among other things, that: (1) the largest peak flows since the end of the Pleistocene occurred during the late Holocene; (2) the occurrence of a mid- to late Holocene interval (~ 2450-1630(?) cal yr BP) of warmer climate, which is not clearly identified in palynological records; and (3) the Little Ice Age climate seems to have had little impact on stream channels, except perhaps for minor (~ 1 m) incision.

Madole, Richard F.

2012-09-01

238

Holocene alluvial stratigraphy and response to climate change in the Roaring River valley, Front Range, Colorado, USA  

USGS Publications Warehouse

Stratigraphic analyses and radiocarbon geochronology of alluvial deposits exposed along the Roaring River, Colorado, lead to three principal conclusions: (1) the opinion that stream channels in the higher parts of the Front Range are relics of the Pleistocene and nonalluvial under the present climate, as argued in a water-rights trial USA v. Colorado, is untenable, (2) beds of clast-supported gravel alternate in vertical succession with beds of fine-grained sediment (sand, mud, and peat) in response to centennial-scale changes in snowmelt-driven peak discharges, and (3) alluvial strata provide information about Holocene climate history that complements the history provided by cirque moraines, periglacial deposits, and paleontological data. Most alluvial strata are of late Holocene age and record, among other things, that: (1) the largest peak flows since the end of the Pleistocene occurred during the late Holocene; (2) the occurrence of a mid- to late Holocene interval (~2450–1630(?) cal yr BP) of warmer climate, which is not clearly identified in palynological records; and (3) the Little Ice Age climate seems to have had little impact on stream channels, except perhaps for minor (~1 m) incision. Published

Madole, Richard F.

2012-01-01

239

Paleosol architecture of a late Quaternary basin-margin sequence and its implications for high-resolution, non-marine sequence stratigraphy  

NASA Astrophysics Data System (ADS)

Paleosol stratigraphy, a technique commonly applied in basin-margin settings to depict cyclic alluvial architecture on time scales of 10-100 ky, can be consistent with regional accommodation trends at even higher temporal resolution (1-10 ky), having strong implications for the sequence stratigraphy of late Quaternary, non-marine deposits. Three closely-spaced late Pleistocene paleosols (P1-P3), dating back approximately to 42-39, 35-31, and 29-26 cal kyr BP, respectively, form prominent stratigraphic markers across a lithologically homogeneous interfluve succession in the subsurface of Bologna, close to the Apenninic foothills. These paleosols are weakly developed (Inceptisols) and can be tracked continuously for 6 km across the triangle-shaped interchannel zone between two gravel/sand-filled channel systems (Reno and Savena rivers). In particular, the thickest paleosol (P3) is a distinctive stiff horizon that can be traced into laterally extensive, erosional-based fluvial bodies. We infer the correlation between (P3) soil development (and channel downcutting) and the final stage of the stepwise Late Pleistocene sea-level fall that culminated at the marine isotope stage 3/2 transition around 29 cal kyr BP (low accommodation systems tract). A fourth laterally extensive Inceptisol, encompassing the Pleistocene-Holocene boundary (PH), represents the major phase of soil development since the Last Glacial Maximum and is inferred to be related to channel entrenchment at the onset of the Younger Dryas. With the exception of the Iron Age-Roman paleosol, which reflects a predominantly anthropogenic control, the Holocene paleosols are laterally discontinuous and invariably more immature (Entisols) than their Pleistocene counterparts. This trend of decreasing paleosol development (and correlatability) upsection is interpreted to reflect increasing (transgressive-equivalent) accommodation during sea-level rise, thus confirming the possible extension of models used to interpret the ancient rock record to short-term depositional cycles.

Amorosi, Alessandro; Bruno, Luigi; Rossi, Veronica; Severi, Paolo; Hajdas, Irka

2014-01-01

240

Heavy metals in Ratnapura alluvial gem sediments, Sri Lanka  

NASA Astrophysics Data System (ADS)

The valuable gems in Sri Lanka are found from the sedimentary gem deposits in Ratnapura District, which are found as alluvial deposits some are about >50 m deep. Gem bearing gravel layer is taken out from the mine, washed by panning to recover the gem minerals in the heavy mineral fraction, is a common practice in the gem mining area. Gem bearing sediment layer is associated with different heavy minerals in which different trace metals as Co, Cr, Cu, Al, Zr, Pb and As also can be present. During panning, the sediment is washed away and the heavy metals attached to the sediments are released into the environment. Hence we studied the lability and bioavailability of arsenic and other heavy metals from the gem sediments. Sediment samples were collected from 15 small scale gem mines (3 soil layers- top, gem mineral layer and layer below gem bearing gravel layer), air dried and sieved to obtain <63?m fraction. Bioavailable, exchangeable and residual fractions were 0.01M CaCl2, 1M NaOAc, pH 8.2 and microwave digestion using HF, HNO3 and HClO4. Filtered samples were analyzed for As, Co, Zn, Mn, Cu, Ni, Pb and Fe using atomic absorption spectrophotometer (GBC 933AA). Total digestion results in different layers indicated that heavy metals show an increasing pattern with depth. About 4 gem bearing gravel layers were consist of high concentrations of Ni (>150 mg/kg), Cu (>150 mg/kg), Pb (>400 mg/kg), Zn (>600 mg/kg) and Co ions (>100 mg/kg). Arsenite in the gem sediments were low and recorded as <5mg/kg. Total arsenic analysis is under investigation. Highest concentrations for bioavailable and exchangeable (leach to water) metals were Fe>Co>Zn>Mn>Ni>Cu>Pb. Sediments from few gem pits showed considerably high concentrations of metals analyzed. In some places Fe, Ni, Cu, Zn reported high in bioavailable fractions 70, 25, 20, 10 mg/kg respectively. Mobilization of these metals may increase due to changes in the pH and the presence of other ions in the environment. High concentrations of toxic metals in exchangeable and bioavailable fractions indicate the risk on plant and animals as well as the open water bodies and groundwater sources.

Vithanage, M. S.; Hettiarachchi, J. K.; Rajapaksha, A. U.; Wijesekara, H.; Hewawasam, T.

2011-12-01

241

Quaternary fluvial archives: achievements of the Fluvial Archives Group  

NASA Astrophysics Data System (ADS)

In their geomorphological and sedimentary records, rivers provide valuable archives of environments and environmental change, at local to global scales. In particular, fluvial sediments represent databanks of palaeoenvironment and palaeoclimatic (for example) of fossils (micro- and macro-), sedimentary and post-depositional features and buried soils. Well-dated sequences are of the most value, with dating provided by a wide range of methods, from radiometric (numerical) techniques to included fossils (biostratigraphy) and/or archaeological material. Thus Quaternary fluvial archives can also provide important data for studies of Quaternary biotic evolution and early human occupation. In addition, the physical disposition of fluvial sequences, be it as fragmented terrace remnants or as stacked basin-fills, provides valuable information about geomorphological and crustal evolution. Since rivers are long-term persistent features in the landscape, their sedimentary archives can represent important frameworks for regional Quaternary stratigraphy. Fluvial archives are distributed globally, being represented on all continents and across all climatic zones, with the exception of the frozen polar regions and the driest deserts. In 1999 the Fluvial Archives Group (FLAG) was established, as a working group of the Quaternary Research Association (UK), aimed at bringing together those interested in such archives. This has evolved into an informal organization that has held regular biennial combined conference and field-trip meetings, has co-sponsored other meetings and conference sessions, and has presided over two International Geoscience Programme (IGCP) projects: IGCP 449 (2000-2004) 'Global Correlation of Late Cenozoic Fluvial Deposits' and IGCP 518 (2005-2007) 'Fluvial sequences as evidence for landscape and climatic evolution in the Late Cenozoic'. Through these various activities a sequence of FLAG publications has appeared, including special issues in a variety of journals, amassing a substantial volume of information on fluvial archives worldwide. This presentation will highlight some of these data and will describe important patterns observed and interpretations arising therefrom.

Bridgland, David; Cordier, Stephane; Herget, Juergen; Mather, Ann; Vandenberghe, Jef; Maddy, Darrel

2013-04-01

242

Developing a post-fire flood chronology and recurrence probability from alluvial stratigraphy in the Buffalo Creek watershed, Colorado, USA  

USGS Publications Warehouse

Stratigraphic and geomorphic evidence indicate floods that occur soon after forest fires have been intermittent but common events in many mountainous areas during the past several thousand years. The magnitude and recurrence of these post-fire flood events reflects the joint probability between the recurrence of fires and the recurrence of subsequent rainfall events of varying magnitude and intensity. Following the May 1996 Buffalo Creek, Colorado, forest fire, precipitation amounts and intensities that generated very little surface runoff outside of the burned area resulted in severe hillslope erosion, floods, and streambed sediment entrainment in the rugged, severely burned, 48 km2 area. These floods added sediment to many existing alluvial fans, while simultaneously incising other fans and alluvial deposits. Incision of older fans revealed multiple sequences of fluvially transported sandy gravel that grade upward into charcoal-rich, loamy horizons. We interpret these sequences to represent periods of high sediment transport and aggradation during floods, followed by intervals of quiescence and relative stability in the watershed until a subsequent fire occurred. An alluvial sequence near the mouth of a tributary draining a 0??82 km2 area indicated several previous post-fire flood cycles in the watershed. Dendrochronologic and radiocarbon ages of material in this deposit span approximately 2900 years, and define three aggradational periods. The three general aggradational periods are separated by intervals of approximately nine to ten centuries and reflect a 'millennium-scale' geomorphic response to a closely timed sequence of events: severe and intense, watershed-scale, stand-replacing fires and subsequent rainstorms and flooding. Millennium-scale aggradational units at the study site may have resulted from a scenario in which the initial runoff from the burned watershed transported and deposited large volumes of sediment on downstream alluvial surfaces and tributary fans. Subsequent storm runoff may have produced localized incision and channelization, preventing additional vertical aggradation on the sampled alluvial deposit for several centuries. Two of the millennium-scale aggradational periods at the study site consist of multiple gravel and loam sequences with similar radiocarbon ages. These closely dated sequences may reflect a 'multidecade-scale' geomorphic response to more frequent, but aerially limited and less severe fires, followed by rainstorms of relatively common recurrence. Published in 2001 by John Wiley and Sons, Ltd.

Elliott, J. G.; Parker, R. S.

2001-01-01

243

Andrei Sher and Quaternary science  

NASA Astrophysics Data System (ADS)

Andrei Sher (1939-2008) was a key individual in Beringian studies who made substantial and original contributions, but also, importantly, built bridges between western and eastern Beringian scientists spanning some five decades of research. He is perhaps best known as a Quaternary palaeontologist, specializing in large mammals, and mammoths in particular, but his field of his scientific research was much broader, encompassing Quaternary geology, stratigraphy, geocryology, and paleoenvironmental reconstructions. He worked mainly in Siberia, in the Kolyma and Indigirka lowlands, and Chukotka, but also completed fieldwork in Alaska and Yukon through joint projects with American and Canadian scientists. Andrei was an active scientist until the last days of his life. He was involved in many different research projects ranging from mammoth evolution, fossil insects and environmental changes and ancient DNA. Without Andrei's connections between researchers, many unique discoveries would likely be unknown.

Kuzmina, Svetlana; Lister, Adrian M.; Edwards, Mary E.

2011-08-01

244

Quaternary ecology: A paleoecological perspective  

SciTech Connect

This book considers issues and problems in ecology which may be illuminated, if not solved, by considering paleoecology. The five central chapters include a discussion of application of Quaternary ecology to future global climate change, including global warming. Other areas presented include: population dispersal, invasions, expansions, and migrations; plant successions; ecotones; factors in community structure; ecosystem patterns and processes. Published case studies are numerous. The role played by continuing climatic change in vegetation change is acknowledged but not stressed.

Delcourt, H.R.; Delcourt, P.A.

1991-01-01

245

Quaternary glaciation of Mount Everest  

Microsoft Academic Search

The Quaternary glacial history of the Rongbuk valley on the northern slopes of Mount Everest is examined using field mapping, geomorphic and sedimentological methods, and optically stimulated luminescence (OSL) and 10Be terrestrial cosmogenic nuclide (TCN) dating. Six major sets of moraines are present representing significant glacier advances or still-stands. These date to >330ka (Tingri moraine), >41ka (Dzakar moraine), 24–27ka (Jilong

Lewis A. Owen; Ruth Robinson; Douglas I. Benn; Robert C. Finkel; Nicole K. Davis; Chaolu Yi; Jaakko Putkonen; Dewen Li; Andrew S. Murray

2009-01-01

246

Latest Quaternary stratigraphic framework of the Mississippi River delta region  

USGS Publications Warehouse

Previous researchers separated the uppermost Quaternary stratigraphy of the Mississippi River delta region into two major lithofacies. The stratigraphically lower of these, "substratum," primarily consists of coarse-grained sediment deposited within lowstand-incised stream valleys. Relatively finer-grained "topstratum" overlies substratum; above interfluves, topstratum directly overlies weathered late Pleistocene sediments. However, the onshore to offshore distribution and architecture of these lithofacies was not well constrained. This study integrates published and unpublished lithostratigraphic data with high-resolution seismic profiles from the continental shelf to aid in mapping the regional distribution of major substratum deposits and thickness of topstratum sediments. A transgressive sand sheet commonly marks the base of the topstratum deposits, providing a stratigraphic marker to aid in regional lithostratigraphic correlations. Radiocarbondated deposits and boreholes tied to oxygen isotope chronologies provide chronostratigraphic control. Excellent correlation between these multiple datasets has been found to exist, enabling construction of regional isopachous and structural elevation maps and cross sections detailing elements of the Late Quaternary stratigraphy.

Kulp, Mark; Howell, Paul; Adiau, Sandra; Penland, Shea; Kindinger, Jack; Williams, S. Jeffress

2002-01-01

247

A multiple-point geostatistical method for characterizing uncertainty of subsurface alluvial units and its effects on flow and transport  

USGS Publications Warehouse

This report provides a proof-of-concept to demonstrate the potential application of multiple-point geostatistics for characterizing geologic heterogeneity and its effect on flow and transport simulation. The study presented in this report is the result of collaboration between the U.S. Geological Survey (USGS) and Stanford University. This collaboration focused on improving the characterization of alluvial deposits by incorporating prior knowledge of geologic structure and estimating the uncertainty of the modeled geologic units. In this study, geologic heterogeneity of alluvial units is characterized as a set of stochastic realizations, and uncertainty is indicated by variability in the results of flow and transport simulations for this set of realizations. This approach is tested on a hypothetical geologic scenario developed using data from the alluvial deposits in Yucca Flat, Nevada. Yucca Flat was chosen as a data source for this test case because it includes both complex geologic and hydrologic characteristics and also contains a substantial amount of both surface and subsurface geologic data. Multiple-point geostatistics is used to model geologic heterogeneity in the subsurface. A three-dimensional (3D) model of spatial variability is developed by integrating alluvial units mapped at the surface with vertical drill-hole data. The SNESIM (Single Normal Equation Simulation) algorithm is used to represent geologic heterogeneity stochastically by generating 20 realizations, each of which represents an equally probable geologic scenario. A 3D numerical model is used to simulate groundwater flow and contaminant transport for each realization, producing a distribution of flow and transport responses to the geologic heterogeneity. From this distribution of flow and transport responses, the frequency of exceeding a given contaminant concentration threshold can be used as an indicator of uncertainty about the location of the contaminant plume boundary.

Cronkite-Ratcliff, C.; Phelps, G.A.; Boucher, A.

2012-01-01

248

Determinants of quaternary association in legume lectins  

PubMed Central

It is well known that the sequence of amino acids in proteins code for its tertiary structure. It is also known that there exists a relationship between sequence and the quaternary structure of proteins. The question addressed here is whether the nature of quaternary association can be predicted from the sequence, similar to the three-dimensional structure prediction from the sequence. The class of proteins called legume lectins is an interesting model system to investigate this problem, because they have very high sequence and tertiary structure homology, with diverse forms of quaternary association. Hence, we have used legume lectins as a probe in this paper to (1) gain novel insights about the relationship between sequence and quaternary structure; (2) identify the sequence motifs that are characteristic of a given type of quaternary association; and (3) predict the quaternary association from the sequence motif. PMID:15215518

Brinda, K.V.; Mitra, Nivedita; Surolia, Avadhesha; Vishveshwara, Saraswathi

2004-01-01

249

Fluvial sedimentation following Quaternary eruptions of Mount St. Helens, Washington  

SciTech Connect

Depositional records of convulsive volcanic events at Mount St. Helens are in many places obscured by rapid fluvial erosion and deposition close to the volcano. Some major eruptions are recorded primarily by lahars and alluvium deposited tens of kilometers away. About 35 percent of the distinctive hummocky topography of the 1980 North Fork Toutle debris avalanche deposit now resembles an alluvial fan or a braided glacial outwash plain covered with 10 m or more of alluvium. Deposits of small (20 x 10/sup 6/m/sup 3/) but damaging lahars, such as those generated in the afternoon of 18 May 1980 and on 19 March 1982, have been largely eroded away. Rivers draining rapidly eroding areas surrounding Mount St. Helens presently have sediment yields that are among the highest in the world for nonglaciated streams of comparable size. These sediment loads are capable of causing aggradation-induced flooding in populated areas along the lower Toutle and Cowlitz Rivers. Sediment retention structures and dredging have prevented such flooding. Immediately following prehistoric eruptions, however, coarse-grained volcanic alluvium was deposited in the Cowlitz River to levels more than 1 m above the 1980 mud flow inundation level. Post-1980 rapid landscape modifications and high sediment yields are noteworthy because the eruption-impact area has not yet had a major regional storm and potentially catastrophic breachings of avalanche-impounded lakes have been prevented through engineering measures.

Janda, R.J.; Meyer, D.F

1985-01-01

250

Late quaternary geomorphology and geoarchaeology of a segment of the Central Mimbres River Valley, Grant County, New Mexico  

E-print Network

Two terraces, a modem floodplain, and alluvial fans were identified along a segment of the central Mimbres River Valley in Grant County, New Mexico. The oldest terrace, T2, is composed of one major depositional unit (1) and is capped by a...

Fitch, Michael Anthony

2012-06-07

251

Geomorphic, sedimentary, and potential palaeoenvironmental significance of peat blocks in alluvial river systems  

NASA Astrophysics Data System (ADS)

Fluvial erosion of peat deposits occurs in many environmental settings; however, the erosion and transport of large peat blocks by river channels has received relatively little attention. This paper describes the sedimentary significance and potential palaeoenvironmental interpretation of peat blocks in alluvial river systems. Evidence is presented from a number of field studies of upland river systems in northern England that illustrate a range of peat block forms and sedimentary features that are briefly compared with examples of peat blocks preserved in gravel stratigraphy. We show that peat blocks are an important geomorphological and sedimentological component of upland rivers draining eroding peatland catchments. They are of widespread occurrence and contribute significantly to river channel roughness and channel sedimentation. A variety of common sedimentary features can be observed including, shadow, crescent, perched, armoured, drape, embedded (part buried), cluster, and step forms. Peat blocks tend to be deposited on channel margins and bar tops and can be used as “maximum” stage indicator for major floods. The role of peat blocks in controlling sedimentation varies with channel width. In narrow channels where the size of the peat block approximates the channel width, blocks become jammed in the channel and exert a primary control on channel sedimentation. In wider channels, blocks tend to occur in isolation or in small clusters and are of only secondary importance in controlling sedimentation. Residence times of peat blocks varies from short periods of temporary deposition (days to months) to much longer timescales (months to years) with some blocks becoming permanently incorporated into the sedimentary record. The sedimentary characteristics of contemporary buried peat blocks have much in common with blocks preserved in alluvial gravel stratigraphy. This offers the potential for using these features for palaeoenvironmental reconstruction. Peat blocks in many ways are analogous to other low density geological materials (ice blocks, woody debris, and some volcanic sediments), and recognising the special sedimentological characteristics of this suite of materials is important as they are not always adequately characterised using conventional hydraulic relationships.

Warburton, Jeff; Evans, Martin

2011-07-01

252

Characteristics of bedrock-alluvial anastomosed rivers: the Mekong River in Cambodia  

NASA Astrophysics Data System (ADS)

The Mekong River is the 12th largest river in the world in terms of its length and mean annual discharge and yet it is poorly investigated. In the north eastern regions of Cambodia the Mekong River develops a multichannel pattern. It is characterised by a complex of intersecting bedrock channels, well vegetated alluvial and seasonally inundated islands, various types of sand bars, numerous bedrock exposures, rapids, waterfalls and deep bedrock pools which can be classified as a large mixed bedrock-alluvial anastomosed river of a tropical monsoonal climate zone. In order to complete a portrait of the river at the high level of details new data on morphology, geology and sediments were obtained during field surveys of a 120 km river section in Cambodia and combined with information from published literature and interpretation of available remote sensing images. This process has enabled to update and clarify knowledge on morphology of observed islands and floodplain, comprehensive geology and tectonic structures, hydrological regime and land cover. Complex analyses of the collected data have distinguished several geomorphological zones accordingly to frequency of morphological elements, the planview configuration of channels and vertical profile characteristics. The occurrence of each zone is a subject of variable controlling factors such as local topography, channel gradient, structural and tectonic elements and intercalating geological units. Evolution of the channel pattern has been considered at both short- and long term time scales. Historical cartographic and remote sensing materials were applied to determine planform channel changes over the last 50 years revealing the channels stability and cases of occasional, local erosion and deposition. The channel network was extracted from vector layers to examine channels and islands width and length parameters, bifurcation angles at the upstream end of islands and to obtain main channel network indices such as braiding intensity and channel sinuosity. In addition, luminescence dating of the sediments from a palaeochannel and the sediments constituting the surfaces of alluvial islands and an adjacent plain elucidate paleo-the development of the Mekong in this region. Finally, the description of the channel planform and the network metrics provide a quantitative means to describe the distinctive character of the Mekong in comparison with other well known large alluvial anastomosed river systems in similar environmental settings.

Meshkova, Liubov. V.; Carling, Paul. A.

2010-05-01

253

Impact of the alluvial style on the geoarcheology of stream valleys  

NASA Astrophysics Data System (ADS)

The extensive archeological record within river valleys provides an environment long favored for study by the archeologic community. This record of human occupation varies with the alluvial style of the river, resulting in each river valley having a unique archeological record controlled by three factors; location of occupation sites, preservation of those sites, and recognition of the sites. If problems of site preservation and recognition in a river valley can be recognized and addressed, a better insight into settlement patterns and complex human-environment interactions can result. This study represents a synthesis of extensive published and secondary data sets pertaining to archaeology and alluvial geomorphology of the lower Missouri, Red, and Mississippi Rivers, to examine the relationship of prehistoric site distribution with fluvial geomorphology. The archeologic data are from published literature and government agencies. The geomorphic data are from a variety of published and unpublished investigations, including maps of alluvial geomorphology, digital elevation models, aerial photographs, and topographic maps. The data were input into spreadsheets and a GIS for qualitative and quantitative analysis. Prehistoric human occupation of the narrow Missouri valley floor is limited, with only 0.061 recorded sites/km 2. Additional sites are likely buried by thick vertical accretion sediment on the limited prehistoric portions of the floodplain and within alluvial/colluvial fans along the valley margin. Non-random preservation patterns, such as the absence of sites from the youngest cultural period, are attributed to shifts in settlement patterns. In comparison to the lower Missouri River valley, prehistoric occupation of the lower Red and Mississippi rivers was much more extensive and the density of occupation was 0.274 sites/km 2 and 0.277 sites/km 2 respectively. Significant differences do exist in the age of sites and their relationship to different floodplain depositional environments. Many sites along the active meander belt of the Red River were likely lost due to high rates of channel migration. Nevertheless, intense occupation of Paleo-Indian through Caddoan groups assures that many significant sites have been preserved. The wide valley and high rates of sedimentation suggest that many sites are likely buried, particularly along natural levees flanking an older meander belt. Recorded sites are also present along streams that incise the terrace, along the terrace margin, and along small channels that cross the backswamp. The spatial and temporal site distribution along the lower Mississippi valley is distinct in comparison with the Red River because the Mississippi valley is wider, the terraces are younger and less dissected, and the floodplain has more relief and is not broadly inundated by floodwater with relatively low sediment concentrations. Most of the significant Archaic through Mississippian period floodplain sites are located along the surfaces of abandoned Mississippi and distributary meander belts which aggraded above the adjacent backswamp and have rarely been influenced by flood sedimentation since abandonment. Abundant Paleo-Indian through Mississippian period sites are also widely distributed across undissected terraces. Only a few significant Mississippian sites are present along the active meander belt and in the backswamp where flooding was common. In comparison with the Red River, the archaeological record of the floodplain is less likely to be influenced by burial or erosion due to the Mississippi River having lower rates of overbank sedimentation and channel migration, respectively. The variable alluvial styles of the lower Missouri River, lower Red River, and the lower Mississippi River valleys presented varying opportunities and constraints to occupation and sustained settlement, and resulted in widely varying archaeological patterns that are partly dependent upon the alluvial geomorphology.

Guccione, Margaret J.

2008-10-01

254

Multiple sources of alkanes in Quaternary oceanic sediment of Antarctica  

USGS Publications Warehouse

Normal alkanes (n-C13n-C36), isoprenoid hydrocarbons (i-C15, i-C16, i-C18, i-C19, and i-C20) triterpanes (C27C32), and (C27C29) are present in low concentrations offshore Antarctica in near-surface, Quaternary sediment of the Wilkes Land continental margin and of the western Ross Sea. The distributions of these hydrocarbons are interpreted relative to possible sources and processes. The hydrocarbons appear to be mixtures of primary and recycled material from marine and terrigenous sources. The n-alkanes are most abundant and are characterized by two distinct populations, one of probable marine origin and the other likely from terrigenous, vascular plant sources. Because the continent of Antarctica today is devoid of higher plants, the plant-derived hydrocarbons in these offshore sediments probably came from wind-blown material and recycled Antarctic sediment that contains land-plant remains from an earlier period of time. Isoprenoid hydrocarbons are partially recycled and mainly of marine origin; the dominance of pristane over phytane suggests oxic paleoenvironmental conditions. Both modern and ancient triterpanes and steranes are present, and the distribution of these indicates a mixture of primary and recycled bacterial, algal, and possible higher-plant materials. Although the sampled sediments were deposited during the Quaternary, they apparently contain a significant component of hydrocarbons of pre-Quaternary age. ?? 1987.

Kvenvolden, K.A.; Rapp, J.B.; Golan-Bac, M.; Hostettler, F.D.

1987-01-01

255

The transition from wave-dominated estuary to wave-dominated delta: The Late Quaternary stratigraphic architecture of Tiber River deltaic succession (Italy)  

NASA Astrophysics Data System (ADS)

This paper presents a detailed description of the stratigraphic architecture of the Late Pleistocene/Holocene Tiber delta succession in order to document the passage from wave-dominated estuary to wave-dominated delta in the broader context of Late Quaternary sea level fluctuations. This succession constitutes a sequence-stratigraphic unit known as Tiber Depositional Sequence (TDS), which was deposited during the last glacial-interglacial cycle (last 120 ka). Our study is based on the examination of an enormous amount of data derived from the stratigraphy of about 300 wells, petrographical and paleontological data (foraminifera, ostracoda, pollen, and plant macrofossils), 14C dating, and from the integration of geomorphological and geoarcheological data. Recently a 100 m deep core (Pesce Luna well) was studied through a multidisciplinary approach and a detailed description of sedimentary facies, foraminifer and ostracod assemblages, pollen and 14C dating is presented in this paper. The new data allowed to produce three new correlation panels and to describe in more detail, with respect to previous interpretations, the stratigraphic-depositional architecture of the TDS, which internally shows the preservation of sediment deposited during the early and late lowstand, the transgressive and the highstand systems tracts. Alluvial and coastal depositional systems characterize the early lowstand phase of the TDS, which developed during the eustatic sea-level fall between about 120 and 30-26 yr BP. During the late lowstand phase, which is characterized by stillstand and slow eustatic sea-level rise a prograding delta and an aggrading incised-valley fluvial fill developed. The Tiber incised valley was transformed into a wave-dominated estuary during the transgressive phase (TST), whereas a coastal-shelf sedimentation took place during the subsequent highstand phase (HST). This study confirms the lithofacies distribution resulting from transgression and infilling of the wave-dominated estuaries, but also shows how the transition to a wave-dominated delta, prograding at the time of sea-level highstand occurred. Changes in sediment input, climatic variations and, more recently, human activities played a major role in the development of the Tiber delta during the last 20,000 yr BP. In the last 3000 years a relationship between progradational phases of the delta and flood events of the Tiber river has been highlighted, suggesting also the formation and merging of barrier-spits to the mainland.

Milli, Salvatore; D'Ambrogi, Chiara; Bellotti, Piero; Calderoni, Gilberto; Carboni, Maria Gabriella; Celant, Alessandra; Di Bella, Letizia; Di Rita, Federico; Frezza, Virgilio; Magri, Donatella; Pichezzi, Rita Maria; Ricci, Valeria

2013-02-01

256

Late Quaternary paleoceanography of the South China Sea: surface circulation and carbonate cycles  

Microsoft Academic Search

Paleoceanographic information from 34 sediment cores is summarized to investigate the glacial-interglacial variations in sea surface circulation and late Quaternary carbonate cycles in the South China Sea. Judging from the distribution pattern of deposition rates, the enormous terrigenous supply by rivers is responsible for the high rate of hemipelagic sedimentation which was even higher during glacial periods.Paleotemperature maps based on

Pinxian Wang; Luejiang Wang; Yunhua Bian; Zhimi Jian

1995-01-01

257

Late Quaternary megaturbidites of the Indus Fan: Origin and stratigraphic significance  

E-print Network

-to-sink" systems of the Quaternary and extends over 106 km2 offshore. It is characterized by a complex tectonic.g., incised valley formation) on the timing of sedimentary transfer and sediment distribution at the basin their depositional patterns and their evolution through time. Large mud-rich fans are typically associated

Nicolas, Chamot-Rooke

258

On Earthquake Ground Motion and Structural Response in Alluvial Valleys  

E-print Network

On Earthquake Ground Motion and Structural Response in Alluvial Valleys By Jacobo Bielak 1 , Member amplification and structural dam­ age due to local site conditions in sedimentary valleys during earthquakes the 1988 Armenia Earthquake. A more realistic two­dimensional finite element analysis is performed herein

Shewchuk, Jonathan

259

MAP OF ECOREGIONS OF THE MISSISSIPPI ALLUVIAL PLAIN  

EPA Science Inventory

The ecoregions of The Mississippi Alluvial Plain (73) have been identified, mapped, and described and provide a geographic structure for environmental resources research, assessment, monitoring, and management. This project is part of a larger effort by the U.S. EPA to create a ...

260

Bed Material Transport and the Morphology of Alluvial River  

E-print Network

Bed Material Transport and the Morphology of Alluvial River Channels Michael Church DepartmentUniversityofBritishColumbiaLibraryon12/27/06.Forpersonaluseonly. #12;Bed material: material that forms the bed and lower banks of the river and chiefly determines the morphology of the channel Wash material: material that, once entrained

Jellinek, Mark

261

Bed Material Transport and the Morphology of Alluvial River  

E-print Network

Bed Material Transport and the Morphology of Alluvial River Channels Michael Church DepartmentSimonFraserUniversityon08/10/06.Forpersonaluseonly. #12;Bed material: material that forms the bed and lower banks of the river and chiefly determines the morphology of the channel Wash material: material that, once entrained

Venditti, Jeremy G.

262

Engineering geologic studies of the Austin Chalk, Taylor Marl, and Quaternary alluvium Ellis County, Texas  

E-print Network

to determine the electrical and radioactive properties of the material. Surface seismic refraction yielded information on the thickness and sonic characteristics of alluvial terrace deposits and geological mapping delineated outcropping units... ~ RAYS ~ /. DETECTOR Figure l2. The natural gamma tool. It is used in a cased or uncased, fluid-filled or dry borehole. isotopes in the surrounding rock. The most common radioactive isotope present in earth materials is potassium-40 (k ) which...

Westerfield, John Gayden

2012-06-07

263

Ancient biomolecules in Quaternary palaeoecology  

NASA Astrophysics Data System (ADS)

The last few years have seen an enormous proliferation of ancient biomolecules research, especially in the field of ancient DNA. Ancient DNA studies have been transformed by the advent of next generation sequencing, with the first Pleistocene sample being analysed in 2005, and several complete and draft genomes that have been compiled from ancient DNA to date. At the same time, although less conspicuous, research on ancient proteins has also seen advances, with the time limit for research on ancient biomolecules now extending to over 1 million years. Here we review which effects these developments have on research in Quaternary science. We identify several lines of research that have the potential to profit substantially from these recent developments in ancient biomolecules research. First, the identification of taxa can be made using ancient biomolecules, and in the case of ancient DNA, specimens can even be assigned to specific populations within a species. Second, increasingly large DNA data sets from Pleistocene animals allow the elucidation of ever more precise pictures of the population dynamic processes whereby organisms respond to climate and environmental change. With the accompanying better understanding of process in the Quaternary, past ecologies can also more realistically be interpreted from proxy data sets. The dominant message from this research so far is that the Quaternary saw a great deal more dynamism in populations than had been forecast by conventional palaeoecology. This suggests that reconstructions of past environmental conditions need to be done with caution. Third, ancient DNA can also now be obtained directly from sediments to elucidate the presence of both plant and animal species in an area even in the absence of identifiable fossils, be it macro- or micro-fossils. Finally, the analysis of proteins enables the identification of bone remains to genus and sometimes species level far beyond the survival time of DNA, at least in temperate regions, illustrating that precise data is now forthcoming from seemingly unlikely sources. Together, these approaches allow the study of environmental dynamics throughout a substantial part, and perhaps even the entire Quaternary (the last 2.6 million years).

Hofreiter, Michael; Collins, Matthew; Stewart, John R.

2012-02-01

264

Hydrogeology and simulation of ground-water flow in the Ohio River alluvial aquifer near Carrollton, Kentucky  

USGS Publications Warehouse

The alluvial aquifer near Carrollton, Kentucky, lies in a valley eroded by glacial meltwater that was later part filled with outwash sand and gravel deposits. The aquifer is unconfined, and ground water flows from the adjacent bedrock-valley wall toward the Ohio River and ground-water withdrawal wells. Ground-water-level and Ohio River stage data indicate the alluvial aquifer was at or near steady-state condition in November 1995. A two-dimensional, steady-state ground-water-flow model was developed to estimate the hydraulic properties, the rate of recharge, and the contributing areas to discharge boundaries for the Ohio River alluvial aquifer at Carrollton and the surrounding area. Results from previous investigations, available hydrogeologic data, and observations of water levels from area ground-water wells were compiled to conceptualize the ground-water-flow system and construct the numerical model. Ground water enters the modeled area by induced infiltration from the Ohio River and smaller streams, flow from the bedrock-valley wall, and infiltration of precipitation. Ground water exits the modeled area primarily through withdrawal wells and flow to the Ohio River. A sensitivity analysis of the model indicates that it is most sensitive to changes in the stage of the Ohio River and conductance values for the riverbed material. A particle-tracking simulation was used to delineate recharge and discharge boundaries of the flow system and contributing areas for withdrawal wells, and to estimate time of travel through the flow system.

Unthank, Michael D.

1999-01-01

265

Stereoselective Synthesis of Quaternary Proline Analogues  

PubMed Central

This review describes available methods for the diastereoselective and asymmetric synthesis of quaternary prolines. The focus is on the preparation of ?-functionalized prolines with the pyrrolidine moiety not embedded in a polycyclic frame. The diverse synthetic approaches are classified according to the bond which is formed to complete the quaternary skeleton. PMID:19655047

Calaza, M. Isabel

2009-01-01

266

Quaternary glaciation of the Himalayan-Tibetan  

Microsoft Academic Search

Glacial geological evidence from throughout the Himalayan-Tibetan orogen is examined to determine the timing and extent of late Quaternary glaciation in this region and its relation to similar changes on a global scale. The evidence summarised here supports the existence of expanded ice caps and extensive valley glacier systems throughout the region during the late Quaternary. However, it cannot yet

LEWIS A. OWEN; MARC W. CAFFEE; ROBERT C. FINKEL; YEONG BAE SEONG

267

Transport of Escherichia coli and solutes during waste water infiltration in an urban alluvial aquifer  

NASA Astrophysics Data System (ADS)

Recharge of waste water in an unconsolidated poorly sorted alluvial aquifer is a complex process, both physically and hydrochemically. The aim of this paper is to analyse and conceptualise vertical transport mechanisms taking place in an urban area of extensive wastewater infiltration by analysing and combining the water balance, the microbial ( Escherichia coli) mass balance, and the mass balance for dissolved solutes. For this, data on sediment characteristics (grain size, organic carbon, reactive iron, and calcite), groundwater levels, and concentrations of E. coli in groundwater and waste water were collected. In the laboratory, data on E. coli decay rate coefficients, and on bacteria retention characteristics of the sediment were collected via column experiments. The results indicated that shallow groundwater, at depths of 50 m below the surface, was contaminated with E. coli concentrations as high as 10 6 CFU/100 mL. In general, E. coli concentrations decreased only 3 log units from the point of infiltration to shallow groundwater. Concentrations were lower at greater depths in the aquifer. In laboratory columns of disturbed sediments, bacteria removal was 2-5 log units/0.5 cm column sediment. Because of the relatively high E. coli concentrations in the shallow aquifer, transport had likely taken place via a connected network of pores with a diameter large enough to allow bacterial transport instead of via the sediment matrix, which was inaccessible for bacteria, as was clear from the column experiments. The decay rate coefficient was determined from laboratory microcosms to be 0.15 d - 1 . Assuming that decay in the aquifer was similar to decay in the laboratory, then the pore water flow velocity between the point of infiltration and shallow groundwater, coinciding with a concentration decrease of 3 log units, was 0.38 m/d, and therefore, transport in this connected network of pores was fast. According to the water balance of the alluvial aquifer, determined from transient groundwater modelling, groundwater flow in the aquifer was mainly in vertical downward direction, and therefore, the mass balance for dissolved solutes was simulated using a 1D transport model of a 200 m column of the Quaternary Alluvium aquifer. The model, constructed with PHREEQC, included dual porosity, and was able to adequately simulate removal of E. coli, cation-exchange, and nitrification. The added value of the use of E. coli in this study was the recognition of relatively fast transport velocities occurring in the aquifer, and the necessity to use the dual porosity concept to investigate vertical transport mechanisms. Therefore, in general and if possible, microbial mass balances should be considered more systematically as an integral part of transport studies.

Foppen, J. W. A.; van Herwerden, M.; Kebtie, M.; Noman, A.; Schijven, J. F.; Stuyfzand, P. J.; Uhlenbrook, S.

2008-01-01

268

Hypogene and supergene alteration of the zeolite-bearing pyroclastic deposits at Tell Rimah, Jordan, and rift-related processes along the Dead-Sea-Transform Fault System during the Quaternary  

NASA Astrophysics Data System (ADS)

The boundary between the Arabian and African plates, is marked in the Middle East by one of the most prominent deep-seated lineamentary structures, called the Dead-Sea-Transform Fault System (DSTFS). Structural and mineralogical processes related to the DSTFS were correlated with equivalent processes leading to the alteration of pyroclastic deposits of alkali-olivine basaltic to nepheline basaltic composition which formed during a time span of less than 0.5 Ma. The large deposit of Tell Rimah, Jordan, is operated for the exploitation of zeolites, tuffs, and as pozzolana raw material. Four discrete stages of mineralizations have been distinguished from each other within these volcanic-hosted mineral deposits. (1) Hypogene syneruptive alteration of pyroclastic rocks produced siliceous gels ("allophane"), smectite, analcime, and phillipsite in vesicles when the groundwater level was low in the rift basin of the DSTFS. The lake-level lowstand caused the fluid system in the pyroclastic cone to become self-sufficient and it has been considered as a closed hydrothermal system. (2) Periods of tectonic and magmatic quiescence grinded the detrital sedimentation in the rift basin to a halt, while triggering a supergene alteration in the eruptive cones on the adjacent Arabian Plate. (3) Epigenetic alteration affected the pyroclastic rocks in the distal part of the DSTFS as a result of a rising water level. The water gradually filled the pore space of the permeable pyroclastic deposits almost to completeness and caused meniscus and blocky cements of calcite, phillipsite and chabazite to develop. In the rift basin, contemporaneously with the alteration of the pyroclastic rocks, freshwater limestones formed on calcareous bedrocks. Ba and Mn minerals in these freshwater limestones were supplied by subaquatic brines. Subsequently, a drastic lowering of the lake water level in the DSTFS converted the system of subaquatic freshwater limestones into subaerial tufa and travertine. As long as the basal parts of the pyroclastic units at Tell Rimah were in the reaches of the saline groundwaters, calcite and faujasite developed in the pyroclastic host rocks. (4) Another lake level lowstand within the rift basin caused the pyroclastic host rocks to get emerged and forced zeolite-carbonate mineralization in the tuffs to a complete stillstand. Hypogene and supergene alteration in these phreatomagmatic-strombolian pyroclastic cones of the Pleistocene x were correlated with lake high- and lowstands in the adjacent rift basin along the DSTFS. The results obtained by current tectono-morphological studies of the rift-related alteration of pyroclastic rocks along the DSTFS may also be applied to basin-and-swell-topographies elsewhere in the world. The current studies involved microscopy supplemented by SEM-EDX, X-ray diffraction analysis, mid (MIR) and far (FIR) infrared spectroscopy. Major and trace elements were analyzed by X-ray fluorescence spectrometry (XRF). C- and O isotope analyses were conducted on carbonate minerals, which were also targeted on by radiocarbon dating.

Dill, H. G.; Techmer, A.; Botz, R.; Dohrmann, R.; Kaufhold, S.

2012-09-01

269

43 CFR 3436.2-2 - Federal coal deposits subject to disposal by exchange.  

Code of Federal Regulations, 2013 CFR

... 2013-10-01 2013-10-01 false Federal coal deposits subject to disposal by exchange. 3436...MINERALS MANAGEMENT (3000) NONCOMPETITIVE LEASES Coal Lease and Coal Land Exchanges: Alluvial Valley Floors §...

2013-10-01

270

43 CFR 3436.2-2 - Federal coal deposits subject to disposal by exchange.  

Code of Federal Regulations, 2012 CFR

... 2012-10-01 2012-10-01 false Federal coal deposits subject to disposal by exchange. 3436...MINERALS MANAGEMENT (3000) NONCOMPETITIVE LEASES Coal Lease and Coal Land Exchanges: Alluvial Valley Floors §...

2012-10-01

271

43 CFR 3436.1-2 - Federal coal deposits subject to lease by exchange.  

Code of Federal Regulations, 2013 CFR

... 2013-10-01 2013-10-01 false Federal coal deposits subject to lease by exchange. 3436.1-2...MINERALS MANAGEMENT (3000) NONCOMPETITIVE LEASES Coal Lease and Coal Land Exchanges: Alluvial Valley Floors §...

2013-10-01

272

43 CFR 3436.2-2 - Federal coal deposits subject to disposal by exchange.  

Code of Federal Regulations, 2011 CFR

... 2011-10-01 2011-10-01 false Federal coal deposits subject to disposal by exchange. 3436...MINERALS MANAGEMENT (3000) NONCOMPETITIVE LEASES Coal Lease and Coal Land Exchanges: Alluvial Valley Floors §...

2011-10-01

273

43 CFR 3436.1-2 - Federal coal deposits subject to lease by exchange.  

Code of Federal Regulations, 2012 CFR

... 2012-10-01 2012-10-01 false Federal coal deposits subject to lease by exchange. 3436.1-2...MINERALS MANAGEMENT (3000) NONCOMPETITIVE LEASES Coal Lease and Coal Land Exchanges: Alluvial Valley Floors §...

2012-10-01

274

43 CFR 3436.1-2 - Federal coal deposits subject to lease by exchange.  

Code of Federal Regulations, 2011 CFR

... 2011-10-01 2011-10-01 false Federal coal deposits subject to lease by exchange. 3436.1-2...MINERALS MANAGEMENT (3000) NONCOMPETITIVE LEASES Coal Lease and Coal Land Exchanges: Alluvial Valley Floors §...

2011-10-01

275

Magnitude of late Quaternary left-lateral displacements along the north edge of Tibet  

NASA Technical Reports Server (NTRS)

Images taken by the earth observation satellite SPOT of the Quaternary morphology at 18 sites on the 2000-kilometer-long Altyn Tagh fault at the north edge of Tibet demonstrate that it is outstandingly active. Long-term, left-lateral strike-slip offsets of stream channels, alluvial terrace edges, and glacial moraines along the fault cluster between 100 and 400 meters. The high elevation of the sites, mostly above 4000 meters in the periglacial zone, suggests that most offsets resulted from slip on the fault since the beginning of the Holocene. These data imply that slip rates are 2 to 3 centimeters per year along much of the fault length and support the hypothesis that the continuing penetration of India into Asia forces Tibet rapidly toward the east.

Peltzer, Gilles; Tapponnier, Paul; Armijo, Rolando

1989-01-01

276

A Pleistocene coastal alluvial fan complex produced by Middle Pleistocene glacio-fluvial processes  

NASA Astrophysics Data System (ADS)

A coarse-grained alluvial fan sequence at Lipci, Kotor Bay, in western Montenegro, provides a sedimentary record of meltwater streams draining from the Orjen Massif (1,894 m a.s.l.) to the coastal zone. At Lipci sedimentary evidence and U-series ages have been used alongside offshore bathymetric imagery and seismic profiles to establish the size of the fan and constrain the nature and timing of its formation. Establishing the depositional history of such coastal fans is important for our understanding of cold stage sediment flux from glaciated uplands to the offshore zone, and for exploring the impact of sea level change on fan reworking. There is evidence of at least four phases of Pleistocene glaciation on the Orjen massif, which have been U-series dated and correlated to MIS 12, MIS 6, MIS 5d-2 and the Younger Dryas. A series of meltwater channels delivered large volumes of coarse- and fine-grained limestone sediment from the glaciated uplands into the Bay of Kotor. At the southern margin of the Orjen massif, a series of large (>700 m long) alluvial fans has developed. Some of these extend offshore for up to 600 m. Lipci fan lies downstream of end moraines in the valley immediately above, which were formed by an extensive outlet glacier of the Orjen ice cap during MIS 12. The terrestrial deposits are part of the fan apex (50 m a.s.l.) that lies at the foot of a steep bedrock channel, but the majority of the fan is now more than 25 m below sea level. The terrestrial fan sediments are strongly cemented by multiple generations of calcite precipitates: the oldest U-series ages are infinite indicating that the fan is >350 ka in age. These ages are in agreement with alluvial sedimentary evidence and U-series ages from other fluvial units on Mount Orjen. The terrestrial portion of the Lipci fan surface contains several channels. These are well preserved due to cementation with calcium carbonate. Submarine imagery indicates that the now submerged portion of the fan also contains deeply incised (up to 10 m) channels which are similar in morphology to those exposed onshore. It is likely that strong cementation of the fan sediments, and associated channel forms, has protected them from coastal erosion during several regression-transgression cycles. These records provide important opportunities to correlate the Pleistocene terrestrial glacial and fluvial records with the marine archive.

Adamson, Kathryn; Woodward, Jamie; Hughes, Philip; Giglio, Federico; Del Bianco, Fabrizio

2014-05-01

277

The linkages among hillslope-vegetation changes, elevation, and the timing of late-Quaternary fluvial-system aggradation in the Mojave Desert revisited  

NASA Astrophysics Data System (ADS)

Valley-floor-channel and alluvial-fan deposits and terraces in the southwestern US record multiple episodes of late-Quaternary fluvial-system aggradation and incision. Perhaps the most well-constrained of these episodes took place from the latest Pleistocene to the present in the Mojave Desert. One hypothesis for this episode - i.e., the paleovegetation-change hypothesis (PVCH) - posits that a reduction in hillslope vegetation cover associated with the transition from Pleistocene woodlands to Holocene desert scrub generated a pulse of sediment that triggered a primary phase of aggradation downstream, followed by channel incision, terrace abandonment, and initiation of a secondary phase of aggradation further downstream. A second hypothesis - i.e., the extreme-storm hypothesis - attributes episodes of aggradation and incision to changes in the frequency and/or intensity of extreme storms. In the past decade a growing number of studies has advocated the extreme-storm hypothesis and challenged the PVCH on the basis of inconsistencies in both timing and process. Here I show that in eight out of nine sites where the timing of fluvial-system aggradation in the Mojave Desert is reasonably well constrained, measured ages of primary aggradation are consistent with the predictions of the PVCH if the time-transgressive nature of paleovegetation changes with elevation is fully taken into account. I also present an alternative process model for PVCH that is more consistent with available data and produces sediment pulses primarily via an increase in drainage density (i.e., a transformation of hillslopes into low-order channels) rather than solely via an increase in sediment yield from hillslopes. This paper further documents the likely important role of changes in upland vegetation cover and drainage density in driving fluvial-system response during semiarid-to-arid climatic changes.

Pelletier, J. D.

2014-08-01

278

An index of ecological integrity for the Mississippi alluvial plain ecoregion: index development and relations to selected landscape variables  

USGS Publications Warehouse

Macroinvertebrate community, fish community, water-quality, and habitat data collected from 36 sites in the Mississippi Alluvial Plain Ecoregion during 1996-98 by the U.S. Geological Survey were considered for a multimetric test of ecological integrity. Test metrics were correlated to site scores of a Detrended Correspondence Analysis of the fish community (the biological community that was the most statistically significant for indicating ecological conditions in the ecoregion) and six metrics--four fish metrics, one chemical metric (total ammonia plus organic nitrogen) and one physical metric (turbidity)--having the highest correlations were selected for the index. Index results indicate that sites in the northern half of the study unit (in Arkansas and Missouri) were less degraded than sites in the southern half of the study unit (in Louisiana and Mississippi). Of 148 landscape variables evaluated, the percentage of Holocene deposits and cotton insecticide rates had the highest correlations to index of ecological integrity results. sites having the highest (best) index scores had the lowest percentages of Holocene deposits and the lowest cotton insecticide use rates, indicating that factors relating to the amount of Holocene deposits and cotton insecticide use rates partially explain differences in ecological conditions throughout the Mississippi Alluvial Plain Ecoregion.

Justus, B.G.

2003-01-01

279

Simulation of the transfer of organochlorine pollutants in an alluvial aquifer in an alpine valley: the case of tetrachloroethene  

NASA Astrophysics Data System (ADS)

During a series of environmental analysis carried out in soil and groundwater in the Alpine Valley (Rhone valley Western Switzerland), were identified high levels of chlorinated solvents, particularly the tetrachloroethene. The leakage of this pollutant originates from industry. The geological substratum in this part of the valley is mainly composed of alluvial deposits and the deposit of a large rock avalanche. The sediments are composed of sandy silt, sandy clay, sand and gravel. The rock avalanche deposit which is the wall of the alluvial aquifer consists of fine materials, stones and large debris mainly of limestone. The investigations developed in this area have shown the presence of a contaminant plume of 60 m long and 35 m wide approximately. Thus the technique of venting / sparging was proposed as remediation measure. Despite the effectiveness of this technique, it turns out that there are still some pockets of contamination of groundwater in the area. In order to assess the potential pollution, a numerical modeling was developed by using the Visual Modflow software. The stages of this modeling are: • Selecting the parameters of the models; • Developing conceptual and numerical models; • Calibration and validation of the model; • Reproducing the observed concentrations; • Sensitivity analysis; • Making a parametric study to see at different stages the tetrachloroethene plume. The first results of the simulation show a slow leakage of the pollutant forming a pocket in the water flow direction.

Kouamé, A. A.; Jaboyedoff, M.; Tacher, L.; Derron, M.-H.

2012-04-01

280

An aminostratigraphy for the British Quaternary based on Bithynia opercula  

PubMed Central

Aminostratigraphies of Quaternary non-marine deposits in Europe have been previously based on the racemization of a single amino acid in aragonitic shells from land and freshwater molluscs. The value of analysing multiple amino acids from the opercula of the freshwater gastropod Bithynia, which are composed of calcite, has been demonstrated. The protocol used for the isolation of intra-crystalline proteins from shells has been applied to these calcitic opercula, which have been shown to more closely approximate a closed system for indigenous protein residues. Original amino acids are even preserved in bithyniid opercula from the Eocene, showing persistence of indigenous organics for over 30 million years. Geochronological data from opercula are superior to those from shells in two respects: first, in showing less natural variability, and second, in the far better preservation of the intra-crystalline proteins, possibly resulting from the greater stability of calcite. These features allow greater temporal resolution and an extension of the dating range beyond the early Middle Pleistocene. Here we provide full details of the analyses for 480 samples from 100 horizons (75 sites), ranging from Late Pliocene to modern. These show that the dating technique is applicable to the entire Quaternary. Data are provided from all the stratotypes from British stages to have yielded opercula, which are shown to be clearly separable using this revised method. Further checks on the data are provided by reference to other type-sites for different stages (including some not formally defined). Additional tests are provided by sites with independent geochronology, or which can be associated with a terrace stratigraphy or biostratigraphy. This new aminostratigraphy for the non-marine Quaternary deposits of southern Britain provides a framework for understanding the regional geological and archaeological record. Comparison with reference to sites yielding independent geochronology, in combination with other lines of evidence, allows tentative correlation with the marine oxygen isotope record. PMID:23396683

Penkman, Kirsty E.H.; Preece, Richard C.; Bridgland, David R.; Keen, David H.; Meijer, Tom; Parfitt, Simon A.; White, Tom S.; Collins, Matthew J.

2013-01-01

281

A Quaternary Geomagnetic Instability Time Scale  

NASA Astrophysics Data System (ADS)

Reversals and excursions of Earth's geomagnetic field create marker horizons that are readily detected in sedimentary and volcanic rocks worldwide. An accurate and precise chronology of these geomagnetic field instabilities is fundamental to understanding several aspects of Quaternary climate, dynamo processes, and surface processes. For example, stratigraphic correlation between marine sediment and polar ice records of climate change across the cryospheres benefits from a highly resolved record of reversals and excursions. The temporal patterns of dynamo behavior may reflect physical interactions between the molten outer core and the solid inner core or lowermost mantle. These interactions may control reversal frequency and shape the weak magnetic fields that arise during successive dynamo instabilities. Moreover, weakening of the axial dipole during reversals and excursions enhances the production of cosmogenic isotopes that are used in sediment and ice core stratigraphy and surface exposure dating. The Geomagnetic Instability Time Scale (GITS) is based on the direct dating of transitional polarity states recorded by lava flows using the 40Ar/39Ar method, in parallel with astrochronologic age models of marine sediments in which O isotope and magnetic records have been obtained. A review of data from Quaternary lava flows and sediments yields a GITS comprising 10 polarity reversals and 27 excursions during the past 2.6 million years. Nine of the ten reversals bounding chrons and subchrons are associated with 40Ar/39Ar ages of transitionally-magnetized lava flows. The tenth, the Guass-Matuyama chron boundary, is tightly bracketed by 40Ar/39Ar dated ash deposits. Of the 27 well-documented excursions, 14 occurred during the Matuyama chron and 13 during the Brunhes chron; 19 have been dated directly using the 40Ar/39Ar method on transitionally-magnetized volcanic rocks and form the backbone of the GITS. Excursions are clearly not the rare phenomena once thought. Rather, during the Quaternary period, they occur nearly three times as often as full polarity reversals. I will address analytical issues, including the size and consistency of system blanks, that have led to the recognition of minor (1%) discrepencies between the 40Ar/39Ar age for a particular reversal or excursion and the best astrochronologic estimates from ODP sediment cores. For example, re-analysis of lava flows from Haleakala volcano, Maui that record in detail the Matuyama-Brunhes polarity reversal have been undertaken with blanks an order of magntitude smaller and more stable than was common a decade ago. Using the modern astrochronologic calibration of 28.201 Ma for the age of the Fish Canyon sanidine standard, results thus far yield an 40Ar/39Ar age of 772 × 11 ka for the reversal that is identical to the most precise and accurate astrochronologic age of 773 × 2 ka for this reversal from ODP cores. Similarly, new dating of sanidine in the Cerro Santa Rosa I rhyolite dome, New Mexico reveals an age of 932 × 5 ka for the excursion it records, in perfect agreement with astrochronologically dated ODP core records. Work underway aims at refining the 40Ar/39Ar ages that underpin the entire GITS by further eliminating the bias between the radioisotopic and astrochronologically determined ages for several reversals and excursions.

Singer, B. S.

2013-12-01

282

Detectability of minerals on desert alluvial fans using reflectance spectra  

NASA Technical Reports Server (NTRS)

The visible and near-infrared reflectance spectra of soil samples collected from desert alluvial and colluvial surfaces in the Cuprite mining district, Nevada, were analyzed. These surfaces are downslope from hydrothermally altered volcanic rocks that contain spectrally characteristic minerals such as alunite and kaolinite. Coarse fractions of the soils on the alluvial fans are mineralogically variable and express the upslope lithologies; fine fractions are remarkably similar mineralogically and spectrally in all samples because of dilution of local mineral components by regionally derived windblown dust. Theoretical models for spectral mixing and for particle-size effects were used to model the observed spectral variations. Diagnostic mineral absorption bands in the spectra of fan materials were enhanced by computationally removing the spectrum of the homogeneous fine-soil component. Results show that spectral mixing models are useful for analyzing data with high spectral resolution obtained by field and aircraft spectrometers.

Shipman, Hugh; Adams, John B.

1987-01-01

283

Ground-Water Geology and Hydrology of the Kern River Alluvial-Fan Area, California  

USGS Publications Warehouse

The Kern River alluvial fan is the southernmost major alluvial fan built by the streams which drain the west side of the Sierra Nevada. The climate is semiarid with rainfall near 5 inches per year. Agricultural development within the area uses over half the 700,000 acre-feet per year flow of the Kern River, plus a considerable amount drawn from the ground-water reservoir particularly during periods of low flow. The area overlies a deep structural trough between crystalline rocks of the Sierra Nevada and the marine rocks of Tertiary age of the Coast Ranges. The top horizon of the marine rocks that lap on the Sierra Nevada block underlies the report area at an average depth of 2,000 feet. The overlying continental deposits that form the groundwater reservoir consist of alluvial-fan and lacustrine deposits. The continental deposits are subdivided into three lithologic units on the basis of grain size and sorting. The gravel and clay unit consists of older alluvial-fan material, of both Sierra Nevada and Coast Range provenance, that shows extremely poor sorting with some diagenetic decomposition through chemical weathering. The fine sand to clay unit consists principally of fine sand, silt, and clay deposited in a lacustrine environment, although some of the unit is of alluvial-fan origin derived from poorly consolidated marine shale of the Coast Ranges. Within the fine sand to clay unit three distinct clays, which affect ground-water conditions, can be recognized. The gravel to medium sand unit consists of unweathered alluvial-fan material that shows much better sorting than the gravel and clay unit. In the eastern part of the area the basal part of this unit is a gravel lentil that can be traced in the subsurface more than 250 square miles. The overlying deposits consist principally of medium sand. In the western part of the area the unit is a heterogeneous gravel and sand unit. Permeability in Meinzer units of the gravel and clay unit ranges between 10 and 100 with specific yield about 5 percent. For the fine sand to clay unit the permeability ranges between 0.0001 and 100 with about 10 percent specific yield. The gravel to medium sand unit has permeabilities between 100 and 10,000, and specific yield is about 15 percent. For the period 1955-59 the annual gross surface-water supply was estimated at 421,000 acre-feet and pumpage was 664,000 acre-feet, giving a rounded total supply of 1,100,000 acre-feet. Annual consumptive use was estimated at 750,000 acre-feet and annual infiltration at 350,000 acre-feet. The approximate 300,000 acre-feet difference between 664,000 acre-feet pumped and 350,000 acre-feet infiltrated has caused an annual decline in water levels of up to 7 feet. Ground water occurs under both unconfined and confined conditions within the report area. In general, the gravel to medium sand unit contains unconfined water, and the other two units contain confined water. Pumping is less intense in the Kern River fan area than in the adjoining areas to the north or south. This fact, plus infiltration from the Kern River, results in ground-water movement being principally out of the area. There is a ground-water divide that approximately underlies the Kern River. South of the river the flow spreads out semicircularly from the river, and north of the river the flow is linear to the northwest. Based on chemical quality the ground water has been divided areally into (1) east side, (2) west side, and (3) axial water. With the exception of two areas of comparable size northwest of Bakersfield and a much smaller area southeast of that city where ground water is somewhat saline, east-side ground water is generally of the calcium bicarbonate and calcium sodium bicarbonate type of low to medium salinity. The chemical character of east-side ground water is necessarily related to that of Kern River water, the principal source of recharge, and water of intermittent streams which drain the dissected upland

Dale, R. H.; French, James J.; Gordon, G. V.

1966-01-01

284

A Numerical Model of Retreating Alluvial Fan Coasts  

Microsoft Academic Search

A numerical model has been developed that simulates the wave-driven retreat of partially-consolidated alluvial- fan shores over millennium time-scales. It has been developed to reproduce the shore profiles and coastal erosion rates observed along the Pleistocene glacial-outwash fan built by the Waitaki River on the east coast of New Zealand's South Island. This cliffed shore is currently fronted by a

M. Hicks; M. Dickson; G. Coco

2006-01-01

285

A model of channel response in disturbed alluvial channels  

USGS Publications Warehouse

Dredging and straightening of alluvial channels between 1959 and 1978 in West Tennessee caused a series of morphologic changes along modified reaches and tributary streams. Degradation occurred for 10 to 15 years at sites upstream of the area of maximum disturbance and lowered bed-levels by as much as 6.1 m. Following degradation, reaches upstream of the area of maximum disturbance experienced a secondary aggradation phase in response to excessive incision and gradient reduction. -from Author

Simon, A.

1989-01-01

286

DC Electrical Resitivity constraints on hydrostratigraphy in the lower South Platte River alluvial aquifer in northeastern Colorado  

NASA Astrophysics Data System (ADS)

This study uses DC Electrical Resistivity Tomography (ERT) to delineate hydrostratigraphic units within the lower South Platte River alluvial aquifer. The geophysical investigation was conducted at Tamarack Ranch State Wildlife Area in northeastern Colorado, where the South Platte River is artificially recharged via pumping to surface recharge ponds and groundwater flow through the underlying unconfined alluvial aquifer system. Twenty-seven ERT profiles collected within a 4.2 km2 study area on the south bank of the South Platte River define 3 different electrostratigraphic units. The ERT data was correlated with drilling logs and laboratory resistivity measurements to develop a hydrostratigraphic model and confining bedrock surface map. Results indicate 7-25 m thick eolian sand deposits (50-800 ohm-m) serve as infiltration zones and do not readily store groundwater. These eolian deposits form up to 15 m high sand hills in the southern half of the study area, and underlie recharge ponds that are used as water sources for artificial recharge of the river. The underlying alluvium (20-3890 ohm-m) varies from 10-70 m thick and functions as the primary groundwater storage unit. A 10-20 m thick intermittent conductive zone (25-80 ohm-m) occurs within the upper part of the alluvial layer that underlies the sand hills, and is interpreted to be caused by clay deposits that potentially influence initial groundwater flow paths emanating from the recharge ponds. The alluvium is underlain by highly conductive siltstone and claystone bedrock formations (1-60 ohm-m) that confine the aquifer system. The bedrock surface is complexly eroded (1055-1110 m.a.s.l.) and is characterized by prominent large-scale paleo-topographic lows (at typical scales of 700 m wide, 35-40 m deep and 700 m wide, 20-25 m deep) that occur on the northern bank of an incised paleo-channel. These features are interpreted to represent a paleo-topographic surface formed by groundwater outflow in the form of piping and sapping networks. The rugged bedrock topography establishes a previously unrecognized first order control on groundwater flowpaths within the unconfined alluvial aquifer.

Lonsert, Reece

287

Evidence of Late Quaternary Faulting along the Northeastern Segment of the Stagner Creek Fault in the Northwestern Wind River Basin, Wyoming  

NASA Astrophysics Data System (ADS)

The Stagner Creek fault, located along the southern margin of the Owl Creek Mountains in central Wyoming, is one of several east-west striking Quaternary faults that may correspond with scattered, present-day, intraplate seismicity in the region. These Quaternary faults are peculiar in that they strike nearly orthogonal to the Basin and Range faults observed in western Wyoming, and their orientation may reflect the influence of inherited, Laramide structures. These east-west striking faults are inferred to be predominantly normal faults. Previous studies have documented the Quaternary activity of the Stagner Creek fault affecting 6 distinct alluvial fan southeast of the Boysen Reservoir. This study aims to expand on these prior efforts using geomorphic and geophysical analyses. In this area, the Stagner Creek fault is expressed as a prominent scarp, visible in air photos and satellite imagery. Microtopographic mapping was accomplished using a real-time kinematic GPS surveying. The resulting DEM provides detailed scarp morphology, as well as documenting possible knick points within the alluvial surfaces upstream from the scarp. The alluvial surface has a regional slope of 2-3 degrees, and the scarp face has a relatively shallow slope of 6-12 degrees. Scarp heights range from 0.4 to 2 meters. The minimum scarp may reflect a single faulting event, corresponding with a magnitude 6.5 - 6.7. These surfaces are believed to be Late Pleistocene and younger, and geochronological constraints are pending. A shallow seismic reflection profile acquired across the scarp imaged structure to depths of about 500 meters. The profile suggests a steep fault coincident with the surface scarp that offsets Tertiary reflectors several 10s of meters in the subsurface. The steep dip is similar to Laradmide structures. These results suggest that the Stagner Creek fault is capable of generating moderate magnitude earthquakes in this low-strain tectonic environment.

Abousaif, A.; Wang, H.; Cochran, W. J.; Hinrichs, N.; Gomez, F.; Sandvol, E. A.

2012-12-01

288

Geophysical approach to delineate arsenic hot spots in the alluvial aquifers of Bhagalpur district, Bihar (India) in the central Gangetic plains  

NASA Astrophysics Data System (ADS)

A combined study of the geophysical survey and hydro-geochemistry in the Quaternary alluvial aquifers of Bhagalpur district from Bihar state in central Gangetic plain of India was carried out with the objective of identifying the geochemical processes and their relation with lithological profile. Results of resistivity survey validated with borehole lithology gave us a clear picture of the geological signature of the aquifers, which support the reducing nature of the aquifer where concentration of arsenic was high. Reducing nature of the aquifer environment was shown by water samples having relatively negative Eh value. From XRD study of the soil samples, it was found that goethite, dolomite, calcite, quartz and feldspar are the major minerals for most of the samples. Output of this work concludes that resistivity survey is an economically feasible tool which can be successfully used to target arsenic-safe aquifers on wide scale.

Kumar, Pankaj; Avtar, Ram; Kumar, Alok; Singh, Chander Kumar; Tripathi, Parijat; Senthil Kumar, G.; Ramanathan, A. L.

2014-06-01

289

The role of base-level change in the dissection of alluvial fans: case studies from southeast Spain and Nevada  

NASA Astrophysics Data System (ADS)

Tectonics, climate and base level are the underlying controls of alluvial fan development. On many fans base level is stable, but where base-level change occurs it may itself be a response to tectonics or climatic change. Tectonically induced base-level change will be temporally independent of climatic change, and will show spatial variability depending on the rate of propagation of tectonically induced regional dissection. This is illustrated by the Tabernas fans, southeast Spain. The timing of climatically induced base-level change follows the timing of climatic change itself, and will show more consistency of spatial relationships within groups of fans affected. Alluvial fans which toe out in coastal zones or at lake shorelines may be influenced by climatically controlled base-level changes. Conventionally, a fall in base level would be expected to cause dissection of the distal fan zone. However, the reverse may occur, with fan progradation taking place in response to a base-level fall, and dissection occurring in response to a base-level rise. Two contrasted case studies are considered, based in part on previously published work, from dry-region alluvial fan zones, the coastal Cabo de Gata fans in southeast Spain and the Stillwater and Cold Springs fans in Nevada, USA. In these areas, base-level changes occurred in response to late Quaternary eustatic changes of sea level, and changes in the levels of pluvial lakes, respectively. Within both areas there are fans not affected by base-level change (Cabo de Gata, west-coast and inland fans; Cold Springs fans), and others where base-level change has been important in fan evolution (Cabo de Gata, east-coast fans; Stillwater fans). The differences in geomorphic regime between those fans influenced by base-level changes and those not are expressed in morphometric contrasts and different fan profile and plan characteristics. Within those fans influenced by base-level changes, the different mechanisms have influenced the location and elevation of the zone of incision. The differences can be attributed in part to the temporal interactions of base-level change with climatically induced changes in sediment supply, and in part to differences in gradients of the foreshore exposed by the falling sea or lake base levels.

Harvey, A. M.

2002-06-01

290

Enantioselective Construction of Remote Quaternary Stereocenters  

PubMed Central

Summary Molecules containing all-carbon quaternary stereocenters – carbon atoms bonded to four distinct carbon substituents – are prevalent in Nature. However, the construction of such compounds in an enantioselective fashion remains a long-standing challenge to synthetic organic chemists. In particular, methods for forging quaternary stereocenters that are remote from other functional groups are underdeveloped. Herein we report a catalytic and enantioselective intermolecular Heck-type reaction of trisubstituted-alkenyl alcohols with aryl boronic acids. The reported method allows direct access to quaternary all-carbon-substituted ?-, ?-, ?-, ?- or ? aryl carbonyl compounds, as the unsaturation of the alkene is relayed to the alcohol resulting in the formation of a carbonyl group. The scope of the process also includes incorporation of pre-existing stereocenters along the alkyl chain, which links the alkene and the alcohol, wherein the stereocenter is preserved. The described method is flexible, allowing access to diverse building blocks containing an enantiomerically enriched, quaternary center. PMID:24717439

Mei, Tian-Sheng; Patel, Harshkumar H.; Sigman, Matthew S.

2014-01-01

291

Correlation characteristics of surficial deposits with a description of surficial stratigraphy in the Nevada test site region  

SciTech Connect

Surficial deposits in the Nevada Test Site region have been correlated between valleys using correlation characteristics. Correlation characteristics include topography, drainage, topographic relationships, soils, desert pavement, depositional environment, and lithology. Stratigraphic units include Pliocene or Pleistocene debris flows, Pliocene or Pleistocene lakebeds, bedded gravels, and spring deposits, and two Quaternary fluvial and eolian units. The Pliocene or Pleistocene debris flows and the two Quaternary units are separated by regional unconformities. Each of the Quaternary units contains five subunits. The Bishop ash and several radiometric dates have been used to determine the age of the Quaternary units.

Hoover, D.L.; Swadley, W.C.; Gordon, A.J.

1981-12-31

292

Bedrock erosion surface beneath the rocky flats alluvial fan, Jefferson and Boulder counties, Colorado  

USGS Publications Warehouse

The early Pleistocene Rocky Flats alluvial fan formed at the mouth of unglaciated Coal Creek Canyon along the eastern flank of the Colorado Front Range. The fan consists of boulder, cobble, and pebble gravel deposited on an erosional surface cut on tilted Mesozoic sedimentary strata. A north-trending hogback of steeply dipping Cretaceous Laramie Formation and Fox Hills Sandstone is exposed through the gravel across the central portion of the fan. Elevations on the gravel-bedrock contact were used in a GIS to reconstruct the bedrock surface at the base of the gravel, providing a glimpse of the geomorphology of the early Pleistocene Colorado Piedmont. The reconstructed erosional bedrock surface portrays a landscape carved by a series of easterly flowing streams that eroded headward to the resistant hogback units, creating a bedrock step up to 37 m high. East-trending ridges on the bedrock surface are remnants of drainage divides between the Pleistocene streams. Water gaps in the bedrock step allowed the streams access to the upper surface of the step. This entire surface, except the hogback, was covered by gravel about 1.35 to 1.5 Ma ago. Subsequent erosion of the alluvial fan has been by headward (westward) erosion of easterly flowing streams incising into the eastern portion of the fan. Because the gravel is more resistant than the underlying bedrock, modern streams are established over the Pleistocene drainage divides, where the gravel was thinnest. Thicker gravel in the Pleistocene paleovalleys now caps modern drainage divides, producing an inverted topography.

Knepper, D.H., Jr.

2005-01-01

293

The nature, timing and controls of the Quaternary development of the Rio Bergantes, Ebro basin, northeast Spain  

NASA Astrophysics Data System (ADS)

Geomorphological, sedimentological and geochronological analyses have been undertaken to decipher the effects of Quaternary environmental change on the development of the Rio Bergantes, Ebro basin, northeast Spain. Field mapping and profiling using aerial photography and airborne LiDAR data have identified a sequence of six river terraces. Age control, provided by luminescence dating, has revealed two major phases of valley floor aggradation that appear to have occurred at ~ 183-130 ka (Terrace BT1, elevated ~ 25 m above the modern river channel) and ~ 111-26.8 ka (BT2, ~ 18-20 m above the modern river channel), punctuated by ~ 20 m of incision in the intervening period. Following these two phases of large-scale aggradation, the Bergantes river system appears to have adjusted to a relatively sediment-limited regime and responded to environmental changes through a series of smaller cut and fill cycles. This resulted in four lower elevation terraces (BT3-BT6) that are inset within the older (BT1 and BT2) valley fills. These lower terraces have been temporally constrained to ~ 24.5-14.2 ka (BT3); 10.6-9.8 ka (BT4); 8.3-6.2 ka (BT5) and ~ 3 ka (BT6). Field sedimentological and stratigraphic analyses of the alluvial fills indicate the influence of tributary and hill slope derived sediment supply during the aggradation of BT1 and, to a lesser extent BT2. This contrasts with the predominantly trunk river derived deposits which make up the fill of BT3-BT6, when the hillslopes and tributaries in the study area appear to have been relatively de-coupled from the trunk river. Data presented in this paper suggest that the Bergantes river system has responded to, and has preserved, a record of environmental changes operating both in synchrony with, and at a higher frequency than, Milankovitch-driven glacial-interglacial cycles. Major net aggradation phases (those associated with relatively large amounts of fluvial sediment e.g. BT1 and BT2) appear to coincide with Pleistocene glacial conditions in MIS 6, and parts of MIS 5 and MIS 4, when the climate on the Iberian Peninsula was cool and dry. Intervening phases of net valley incision appear to coincide with warmer and moister climates in Pleistocene interglacials. The younger terraces (BT3-BT6) are characterised by much smaller amounts of fluvial sediment supply. Dating control places their development during stadial (aggradation) and interstadial (incision) events of the Late Pleistocene and Holocene. Some phases of aggradation appear to coincide with North Atlantic Heinrich Events, and also with other securely dated phases of aggradation elsewhere in the Mediterranean basin.

Whitfield, R. Greg; Macklin, Mark G.; Brewer, Paul A.; Lang, Andreas; Mauz, Barbara; Whitfield (née Maher), Elizabeth

2013-08-01

294

The distinction of submarine mass failure deposits from tsunami backwash deposits - an example from Hornitos, Northern Chile  

NASA Astrophysics Data System (ADS)

Sedimentary features of onshore tsunami deposits were studied in great detail within the last decade. While the characteristics of such onshore deposits are well documented, the associated marine tsunami effects, such as sediment dispersion, re-deposition, and sediment bypassing during runup and backwash are scarcely reported. The knowledge of the appearance of submarine tsunami features is important, not only to understand the hydrodynamic processes involved, but also because pre-Quaternary sediments tend to be of marine origin when extending the geological record farther into the past. In this study we challenge the former interpretation of a backwash tsunami origin of a Pliocene coarse clast unit at Hornitos that was previously linked to the Eltanin impact tsunami. The respective unit contains several tens of meters long rock slabs and components from both the shallow marine basin and onshore environments, such as alluvial fans, beaches, cliffs and the local basement rocks. It is intercalated into breccia layers of smaller scale that represent the likewise energetic background sedimentation. The unit was most likely emplaced by a high-density flow with possible hydroplaning at its base and front. This is underlined by soft-sediment deformation and sand dykes. The comparison to recent submarine tsunami sediments shows that there are hardly any similarities, most notably because the unit at Hornitos was deposited en masse without any obvious trends. Our re-interpretation considers the local synsedimentary tectonic background and a comparison to recent submarine tsunami sediments caused by tsunamis with similar onshore wave heights. We show that a relation to the Eltanin impact can be excluded because enhanced models that include a shoaling effect as soon as the tsunami approaches shallow shelf regions prove that such an impact did not entail large onshore wave heights at Hornitos. Additionally, the biostratigraphic age of the La Portada formation is not overlapping with the age of the Eltanin impact. Instead, we argue for an earthquake-triggered debris flow origin of the unit. Its emplacement occurred a phase of increased uplift during the Pliocene that entailed the oversteepening of the coastal scarp. Contemporaneous increase in the frequency of seismic events caused slope failures and cliff collapses. Hence, the megabreccia unit at Hornitos represents an extraordinary event that is intercalated into mass wasting deposits of smaller scale, but is not linked to a tsunami.

Spiske, M.; Bahlburg, H.; Weiss, R.

2013-12-01

295

Quaternary geologic map of Minnesota  

NASA Technical Reports Server (NTRS)

The Quaternary Geologic Map of Minnesota is a compilation based both on the unique characteristics of satellite imagery and on the results of previous field investigations, both published and unpublished. The use of satellite imagery has made possible the timely and economical construction of this map. LANDSAT imagery interpretation proved more useful than expected. Most of the geologic units could be identified by extrapolating from specific sites where the geology had been investigated into areas where little was known. The excellent geographic registry coupled with the multi-spectral record of these images served to identify places where the geologic materials responded to their ecological environment and where the ecology responded to the geologic materials. Units were well located on the map at the scale selected for the study. Contacts between till units could be placed with reasonable accuracy. The reference points that were used to project delineations between units (rivers, lakes, hills, roads and other features), which had not been accurately located on early maps, could be accurately located with the help of the imagery. The tonal and color contrasts, the patterns reflecting geologic change and the resolution of the images permitted focusing attention on features which could be represented at the final scale of the map without distraction by other interesting but site-specific details.

Goebel, J. E.

1977-01-01

296

Quaternary glaciation of Mount Everest  

NASA Astrophysics Data System (ADS)

The Quaternary glacial history of the Rongbuk valley on the northern slopes of Mount Everest is examined using field mapping, geomorphic and sedimentological methods, and optically stimulated luminescence (OSL) and 10Be terrestrial cosmogenic nuclide (TCN) dating. Six major sets of moraines are present representing significant glacier advances or still-stands. These date to >330 ka (Tingri moraine), >41 ka (Dzakar moraine), 24-27 ka (Jilong moraine), 14-17 ka (Rongbuk moraine), 8-2 ka (Samdupo moraines) and ˜1.6 ka (Xarlungnama moraine), and each is assigned to a distinct glacial stage named after the moraine. The Samdupo glacial stage is subdivided into Samdupo I (6.8-7.7 ka) and Samdupo II (˜2.4 ka). Comparison with OSL and TCN defined ages on moraines on the southern slopes of Mount Everest in the Khumbu Himal show that glaciations across the Everest massif were broadly synchronous. However, unlike the Khumbu Himal, no early Holocene glacier advance is recognized in the Rongbuk valley. This suggests that the Khumbu Himal may have received increased monsoon precipitation in the early Holocene to help increase positive glacier mass balances, while the Rongbuk valley was too sheltered to receive monsoon moisture during this time and glaciers could not advance. Comparison of equilibrium-line altitude depressions for glacial stages across Mount Everest reveals asymmetric patterns of glacier retreat that likely reflects greater glacier sensitivity to climate change on the northern slopes, possibly due to precipitation starvation.

Owen, Lewis A.; Robinson, Ruth; Benn, Douglas I.; Finkel, Robert C.; Davis, Nicole K.; Yi, Chaolu; Putkonen, Jaakko; Li, Dewen; Murray, Andrew S.

2009-07-01

297

Extended stratigraphy, palynology and depositional environments record the initiation of the Himalayan Gyirong Basin (Neogene China)  

E-print Network

Extended stratigraphy, palynology and depositional environments record the initiation, a basin induced by east­west extension in the Himalayas of south- ern Tibet. We document the conglomeratic, have revealed three depositional environ- ments for the deposition of the studied section. (1) Alluvial

Utrecht, Universiteit

298

Attributes of an alluvial river and their relation to water policy and management  

PubMed Central

Rivers around the world are being regulated by dams to accommodate the needs of a rapidly growing global population. These regulatory efforts usually oppose the natural tendency of rivers to flood, move sediment, and migrate. Although an economic benefit, river regulation has come at unforeseen and unevaluated cumulative ecological costs. Historic and contemporary approaches to remedy environmental losses have largely ignored hydrologic, geomorphic, and biotic processes that form and maintain healthy alluvial river ecosystems. Several commonly known concepts that govern how alluvial channels work have been compiled into a set of “attributes” for alluvial river integrity. These attributes provide a minimum checklist of critical geomorphic and ecological processes derived from field observation and experimentation, a set of hypotheses to chart and evaluate strategies for restoring and preserving alluvial river ecosystems. They can guide how to (i) restore alluvial processes below an existing dam without necessarily resorting to extreme measures such as demolishing one, and (ii) preserve alluvial river integrity below proposed dams. Once altered by dam construction, a regulated alluvial river will never function as before. But a scaled-down morphology could retain much of a river's original integrity if key processes addressed in the attributes are explicitly provided. Although such a restoration strategy is an experiment, it may be the most practical solution for recovering regulated alluvial river ecosystems and the species that inhabit them. Preservation or restoration of the alluvial river attributes is a logical policy direction for river management in the future. PMID:11050220

Trush, William J.; McBain, Scott M.; Leopold, Luna B.

2000-01-01

299

Ice Age refugia and Quaternary extinctions: An issue of Quaternary evolutionary palaeoecology  

NASA Astrophysics Data System (ADS)

Quaternary palaeoecology, as a discipline, involves the analysis of a large range of fossil organisms from the last ca. 2 million years. This paper considers the role that these Quaternary records can take in better understanding the evolution of those organisms. We also discuss the surprisingly low uptake of evolutionary biology in Quaternary palaeoecological studies. This leads us to encourage an advance on both these fronts with a greater degree of collaboration with phylogeographic and ancient DNA researchers. These discussions accompany a summary of a special issue of Quaternary Science Reviews representing the proceedings of the XVII INQUA held in Cairns Australia in 2007. This special issue includes papers on a wide variety of Quaternary evolutionary palaeoecological and population dynamic subjects including extinct Pacific Island palm trees, Beringian beetles, Scandinavian trees, and the effects on human and animal populations of an extraterrestrial impact event in the Late Glacial of North America.

Stewart, John R.; Cooper, Alan

2008-12-01

300

Groundwater research in the alluvial of river Sitnica, Kosova  

NASA Astrophysics Data System (ADS)

In the today's world, the problems of too much, too little or too polluted water are increasing at a rapid rate. Water resources in Kosova are relatively small, the average of annual runoff is 3.61miliard m3, relatively 113m3/s. Territory of Kosova is divided in four river basins: Drini i Bardhë, Ibri, Morava e Binqës and Lepenci. Sitnica River belongs to the river basin Ibri. The total surface of in this river is 2.861km2, the average of the annual rainfalls is 686mm, from which around 93mm (13.6%) flows on the surface and around 593mm (84.6%) infiltrates. In this case study are applied different methods for groundwater research and calculations of hydro-geological parameters in the alluvial of river Sitnica. Geophysics researches carried out with geo-electrical sounding and geo-electrical profile line. The goal of the geophysics researches is to identify hydrogeological collector and to determine the best position for placement of the piezometers. The geophysics research are done in aquifer area, in which 10 profiles line with different lengths and placed in distance from 30 m between each other are done. After finishing of the geophysics works, seven drilling wells with general length from 95.5 m are completed. Based to the testing results of two drilling wells we have concluded that the quantity of 27.4(l/sec) water can be exploited. The achieved results from application of those methods in this case study show that alluvial of river Sitnica are rich with groundwater. Based to the statistics the population is increasing in Kosova also water needs will be increasing too, so it is necessary to explore the existing groundwater for improving drinking water supply, industrial waters, agriculture etc. Key works: river, alluvial, geophysics researches, drilling wells, hydrogeological collector, water

Avdullahi, S.; Fejza, I.; Osmani, L.

2009-04-01

301

Thermal tracer tests for characterizing a shallow alluvial aquifer  

NASA Astrophysics Data System (ADS)

Using heat as an active tracer in different types of aquifers is a topic of increasing interest [e.g. Vandenbohede et al.; 2008, Wagner et al., 2013; Read et al., 2013]. In this study, we investigate the potential interest of coupling heat and solute tracer tests for characterization of a shallow alluvial aquifer. A thermal tracer test was conducted in the alluvial aquifer of the Meuse River, Belgium. The tracing experiment consisted in simultaneously injecting heated water and a dye tracer in a piezometer and monitoring the evolution of groundwater temperature and tracer concentration in the recovery well and in nine monitoring wells located according to three transects with regards to the main groundwater flow direction. The breakthrough curves measured in the recovery well showed that heat transfer in the alluvial aquifer is slower and more dispersive than solute transport. Recovery is very low for heat while in the same time it is measured as relatively high for the solute tracer. This is due to the fact that heat diffusion is larger than molecular diffusion, implying that exchange between groundwater and the porous medium matrix is far more significant for heat than for solute tracers. Temperature and concentrations in the recovery well are then used for estimating the specific heat capacity with the energy balance approach and the estimated value is found to be consistent with those found in the literature. Temperature breakthrough curves in other piezometers are contrasted with what would be expected in an ideal layered aquifer. They reveal strongly unequal lateral and vertical components of the transport mechanisms. By means of a numerical heat transport model, we provide a preliminary interpretation of these temperature breakthrough curves. Furthermore, these data could be included in the calibration of a complex heat transfer model for estimating the entire set of heat transfer parameters and their spatial distribution by inverse modeling.

Wildemeersch, Samuel; Klepikova, Maria; Jamin, Pierre; Orban, Philippe; Hermans, Thomas; Brouyère, Serge; Dassargues, Alain

2014-05-01

302

Co-contamination of As and F in alluvial aquifer  

NASA Astrophysics Data System (ADS)

Co-contamination of As and F is frequently observed in alluvial aquifers of many countries including Argentina, Mexico, China, and Pakistan. However, processes causing this phenomenon are still poorly understood. In arid or semi-arid areas, the aquifers are generally under oxidizing condition and As and F show a good correlation. In contrast, groundwaters under reducing condition generally show a poorer correlation. In this study, we explored the geochemical mechanisms causing the co-contamination of As and F and their poorer correlation in the reducing environment by investigating alluvial groundwaters of the Mankyeong River floodplain, Korea. For this study, we collected 72 groundwater samples from 42 shallow wells placed into the alluvial aquifer. Desorption experiments using soils collected from the study area were also performed. Groundwater chemistry data showed that waters are under strong reducing condition and the reductive dissolution of Fe oxides was the main process increasing As concentration in groundwaters. The co-contamination was also observed in the study area and F did not show a good correlation with As. F showed concentrations increasing with pH. Desorption experiments also showed the dependences of As and F on pH. The experiments using soils treated with Na citrate-NaHCO3-dithonite solution indicated that iron oxides were the main phases hosting both As and F in soils. In our study area, pH of groundwaters increases due to a series of reduction reactions, and which increased F concentration by desorption from iron oxides. This result suggests that sharing the same adsorption hosts and the pH increased by reduction reactions are the main reason for the co-occurrence of As and F in alluvial groundwater under reducing environments. The lack of correlation between As and F was derived by the precipitation of As as sulfides in sulfate reducing condition. However, the correlation could be much better in the oxidizing condition because As released from iron oxides by pH increase cannot be removed as sulfides.

Kim, S.; Kim, K.; Kim, B.; Zhu, W.; Lee, E.; Ko, K.

2010-12-01

303

Pliocene-Quaternary evolution of the continental shelf of central Vietnam based on high resolution seismic data  

NASA Astrophysics Data System (ADS)

The continental shelf of central Vietnam is characterized by complex geological structures in a strike-slip setting and thus by unique morphology compared to other parts of the Vietnam shelf. Studying the Pliocene-Quaternary sediments in this area allows the processes that control the stratigraphic evolution to be highlighted. In this paper, we present new results derived from high resolution seismic data that reveal the geological evolution of the continental shelf of central Vietnam during the Pliocene-Quaternary. Our results demonstrate that the continental shelf of central Vietnam is narrow relatively to other parts of the Vietnam shelf. The evolution of the shelf during the Pliocene-Quaternary was controlled by the pre-Pliocene rifting process. However, fault systems below the present shelf were not strongly active during the Pliocene-Quaternary period, except for several listric faults in the slope. Nonetheless, Quaternary volcanic activities occurred widely both offshore and onshore, especially near the major faults. The Pliocene-Quaternary sedimentary deposits were subdivided into 7 units based on unconformities as result of marine regression corresponding to glacial cycles. Sedimentary environments during this period consist of coastal plain, fluvial, nearshore and shelf environments. Most of the Holocene sediments were trapped nearshore while the outer shelf is characterized by abundant lag gravels as a result of rapid sea level rise between ˜20 and 8 ka.

Tan, Mai Thanh; Dung, Le Van; Bach, Le Duy; Bieu, Nguyen; Nghi, Tran; Long, Hoang Van; Huong, Phan Thien

2014-01-01

304

Geomorphologic, stratigraphic and sedimentologic evidences of tectonic activity in Sone-Ganga alluvial tract in Middle Ganga Plain, India  

NASA Astrophysics Data System (ADS)

The basement of the Ganga basin in the Himalayan foreland is criss-crossed by several faults, dividing the basin into several sub-blocks forming horsts, grabens, or half-grabens. Tectonic perturbations along basement faults have affected the fluvial regime and extent of sediment fill in different parts of the basin during Late Quaternary. The East Patna Fault (EPF) and the West Patna Fault (WPF), located in Sone-Ganga alluvial tract in the southern marginal parts of Middle Ganga Plain (MGP), have remained tectonically active. The EPF particularly has acted significantly and influenced in evolving the geomorphological landscape and the stratigraphic architecture of the area. The block bounded by the two faults has earlier been considered as a single entity, constituting a half-graben. The present investigation (by morpho-stratigraphic and sedimentologic means) has revealed the existence of yet another fault within the half-graben, referred to as Bishunpur-Khagaul Fault (BKF). Many of the long profile morphological characters (e.g., knick-zone, low width-depth ratio) of the Sone River at its lower reaches can be ascribed to local structural deformation along BKF. These basement faults in MGP lie parallel to each other in NE-SW direction.

Sahu, Sudarsan; Saha, Dipankar

2014-08-01

305

Quaternary landscape evolution of the Turkey River Valley, northeastern Iowa  

SciTech Connect

The Turkey River Valley, a major Mississippi tributary in northeastern Iowa, provides a more complete and accessible Quaternary record than the Upper Mississippi Valley. This project, using 3-dimensional reconstructions of both valley and upland deposits, revealed at least 13 important depositional, erosional, and soil-forming events. From oldest to youngest these events are: (1) deposition of pre-Illinoian till; (2) erosion of till and bedrock as the Turkey River cut down; (3) deposition of fluvial and colluvial sediments in the valley; (4) development of a Sangamon soil(s) on both the pre-Illinoian (upland) till and valley sediments; (5) truncation of the Sangamon soil(s) relatively high in the valley as bedrock entrenchment proceeded to its deepest point; (6) deposition of coarse fluvial and colluvial sediments in the valley prior to 32,000 yr. B.P.; (7) aggradation of mostly loess-derived alluvium until approximately 16,000 yr. B.P.; (8) large-scale colluviation between approximately 32,000 and 13,000 yr., B.P.; (9) major downcutting between 16,000 and 14,000 yr. B.P.; (10) aggradation of coarse to medium alluvium from approximately 14,000 to 13,000 yr. B.P.; (11) overall downcutting during several intervals of the late Wisconsinan and early Holocene; (12) aggradation of mid to late Holocene alluvium starting by 5000 yr. B.P.; (13) lateral erosion and deposition during the past 200 yr. B.P. Turkey River Valley deposits previously interpreted as pre-Illinoian are now recognized as late Wisconsinan or early Holocene, as indicated by /sup 14/C dates and molluscan fossils. The Paleozoic Plateau landform region (formerly part of the Driftless Area) is herein interpreted as a rugged, although complex, extension of the Iowan Erosion Surface.

Hudak, C.M.

1987-01-01

306

Geomorphic Characterization of the FortyMile Wash Alluvial Fan, Nye County, Nevada, In Support of the Yucca Mountain Project  

SciTech Connect

In the event of an unlikely volcanic eruption through the proposed high-level radioactive waste repository at Yucca Mountain, contaminated ash would be deposited in portions of the Fortymile Wash drainage basin and would subsequently be redistributed to the Fortymile Wash alluvial fan by fluvial processes. As part of an effort to quantify the transport of contaminated ash throughout the fluvial system, characterization of the Fortymile Wash alluvial fan is required, especially the spatial distribution of fluvial activity over time scales of repository operation, and the rates of radionuclide migration into different soils on the fan. The Fortymile Wash alluvial fan consists of extremely low relief terraces as old as 70 ka. By conducting soils-geomorphic mapping and correlating relative surface ages with available geochronology from the Fortymile Wash fan and adjacent piedmonts, we identified 4 distinct surfaces on the fan. Surface ages are used to predict the relative stability of different areas of the fan to fluvial activity. Pleistocene-aged surfaces are assumed to be fluvially inactive over the 10 kyr time scale, for example. Our mapping and correlation provides a map of the depozone for contaminated ash that takes into account long-term channel migration the time scales of repository operation, and it provides a geomorphic framework for predicting radionuclide dispersion rates into different soils across the fan. The standard model for vertical migration of radionuclides in soil is diffusion; therefore we used diffusion profiles derived from {sup 137}Cs fallout to determine infiltration rates on the various geomorphic surfaces. The results show a strong inverse correlation of the geomorphic surface age and diffusivity values inferred from the {sup 137}Cs profiles collected on the different surfaces of the fan.

Cline; De Long; Pelletier; Harrington

2005-09-06

307

Internal structure and evolution of the Late Quaternary sequence in a shallow embayment: The Amvrakikos Gulf, NW Greece  

Microsoft Academic Search

The Late Quaternary stratigraphic pattern of the Amvrakikos Gulf in the eastern Mediterranean has been studied on the basis of the analysis of high-resolution seismic profiles and short sediment cores. Lowstand, transgressive and highstand systems tracts have been identified that are configured in a major depositional sequence of a fifth-order sea level cycle. During the last glaciation, when the sea

Vasilios Kapsimalis; Petros Pavlakis; Serafim E. Poulos; Stamatina Alexandri; Christos Tziavos; Andreas Sioulas; Dimitrios Filippas; Vasilios Lykousis

2005-01-01

308

Paleomagnetism of Quaternary sediments from Lomonosov Ridge and Yermak Plateau: implications for age models in the Arctic Ocean  

E-print Network

for age models in the Arctic Ocean Chuang Xuan a,*, James E.T. Channell a , Leonid Polyak b , Dennis A magnetization (NRM) in Quaternary sediment cores from the Arctic Ocean have been widely used for stratigraphic deposited during the Brunhes Chron in the Arctic Ocean appear to have a partly diagenetic origin. Rock

Stoner, Joseph

309

Onshore Quaternary geological surveys in the 21st century—a perspective from the British Geological Survey  

Microsoft Academic Search

At the turn of the century the British Geological Survey has embarked on a major programme to construct a 3-dimensional geological model of the UK. The reassessment of methodologies used to investigate Quaternary deposits and processes forms an important part of this programme. Surveys of user requirements indicate that the collation of new data and the generation of new output

Andrew A McMillan

2002-01-01

310

Late Quaternary deformation and slip rates in the northern San Andreas fault zone at Olema Valley, Marin County, California  

Microsoft Academic Search

Quaternary sedimentary deposits along the structural depression of the San Andreas fault (SAF) zone north of San Francisco in Marin County provide an excellent record of rates and styles of neotectonic deformation in a location near where the greatest amount of horizontal offset was measured after the great 1906 San Francisco earthquake. A high-resolution gravity survey in the Olema Valley

Karen Grove; Tina M. Niemi

2005-01-01

311

Electrical and Optical Properties of Stannite-Type Quaternary Semiconductor Thin Films  

Microsoft Academic Search

Quaternary stannite-type semiconductor films of Cu2CdSnS4 and Cu2ZnSnS4 with (112) orientation were deposited on heated glass substrates using atom beam sputtering. These p-type films showed resistivities which were decreasing functions of the substrate temperature up to 240°C. The films had an absorption coefficient larger than 1 × 104 cm-1 in the visible wavelength range. The direct optical band gaps of

Kentaro Ito; Tatsuo Nakazawa

1988-01-01

312

Mediterranean Quaternary sapropels, an immediate response of the African monsoon to variation of insolation  

Microsoft Academic Search

Rossignol-Strick, M., 1985. Mediterranean Quaternary sapropels, an immediate response of the African monsoon to variation of insolation. Palaeogeogr., Palaeoclimatol., Palaeoecol., 49: 237--263. In the subsurface of the East Mediterranean Sea, eleven discrete basin-wide, organic- rich, black sapropels were deposited during the last 465 000 years. They are dated by oxygen isotopic chronostratigraphy. The too.st recent sapropel has been shown to

MARTINE ROSSIGNOL-STRICK

1985-01-01

313

Herbicide interchange between a stream and the adjacent alluvial aquifer  

USGS Publications Warehouse

Herbicide interchange between a stream and the adjacent alluvial aquifer and quantification of herbicide bank storage during high streamflow were investigated at a research site on the Cedar River flood plain, 10 km southeast of Cedar Rapids, Iowa. During high streamflow in March 1990, alachlor, atrazine, and metolachlor were detected at concentrations above background in water from wells as distant as 20, 50, and 10 m from the river's edge, respectively. During high streamflow in May 1990, alachlor, atrazine, cyanazine, and metolachlor were detected at concentrations above background as distant as 20, 50, 10, and 20 m from the river's edge, respectively. Herbicide bank storage took place during high streamflow when hydraulic gradients were from the river to the alluvial aquifer and the laterally infiltrating river water contained herbicide concentrations larger than background concentrations in the aquifer. The herbicide bank storage can be quantified by multiplying herbicide concentration by the "effective area" that a well represented and an assumed porosity of 0.25. During March 1990, herbicide bank storage values were calculated to be 1.7,79, and 4.0 mg/m for alachlor, atrazine, and metolachlor, respectively. During May 1990, values were 7.1, 54, 11, and 19 mg/m for alachlor, atrazine, cyanazine, and metolachlor, respectively. ?? 1994 American Chemical Society.

Wang, W.; Squillace, P.

1994-01-01

314

Surface processes on a mud-dominated Mars analogue alluvial fan, Atacama Desert, northern Chile  

NASA Astrophysics Data System (ADS)

We characterize surface processes on highly unusual terrestrial alluvial fans, which we interpret as a strong analogue for large fans on Mars. The Mars fans date to post-Noachian periods when the martian climate was dominated by cold, hyperarid conditions. Some of the martian fans are differentially eroded to leave their distributary channels in positive relief. This inversion, along with the lack of boulders visible on most fan surfaces, reveals that the dominant grain size of the fans is fine enough for the overbank deposits to be stripped by wind. Degradation, image resolution, and lack of ground truthing all act to obscure the nature of the past flow processes. The fans in the Pampa de Tamarugal of the Atacama Desert of northern Chile are excellent potential Mars analogues for a number of reasons: 1. Hyperaridity, with ~2 mm/y rainfall over the fans themselves, resulting in 2. very little vegetation, 3. no fluvial erosion on the fans themselves, and 4. wind-driven erosion of the fan surfaces; 5. equivalent fan scale (tens of km); 6. similar fan gradient (low); 7. low channel branching density; 8. runoff fed from adjacent, much steeper terrain receiving more precipitation (~500 km2 drainages receiving 0.1-1 m/y precipitation in the High Andes, crater walls and interpreted orographic effects on Mars). Both the modern channels and the preserved stratigraphy are dominated by debris flow-like sheetflow mud deposits. Channels are leveed by concrete-like mass-supported deposits of granules and sand suspended in a silt and clay matrix, often overtopping the channel margins and forming up to 150 m wide levees and km-length sheet flows. This leveeing strongly constrains the aggrading channel, which is typically dominated by better sorted and imbricated fluvial deposits. We infer that the wetter tail of mudlfows sorts the deposits, keeping the central channel unblocked by mud. Relatively few channels are active at any time, but aggradation triggers occasional avulsions. The older, inactive parts of the Atacama fan surface develop partially inverted topography, leaving paleochannels in positive relief. Lack of direct rainfall onto the fan itself means the fan surface is not locally fluvially incised, and the dominant degradation process is aeolian stripping of overbank deposits. Low granular ripples with ~1 m spacing are common on the low surfaces, presumably moving by reptation, and part of a partially mobile desert pavement derived primarily from the channel deposits and channel-marginal overbank sediments. Both development of a coarse grain lag on paleochannel ridge crests and cementation of ridge flanks by halite produce the erodability contrast necessary for inversion.

Hobley, D. E.; Howard, A. D.; Morgan, A. M.; Matsubara, Y.; Moore, J. M.; Parsons, R.; Williams, R. M.; Burr, D. M.; Hayes, A. G.; Dietrich, W.

2012-12-01

315

RIVER TRANSPORT - INDUCED CHANGES IN CHEMICAL COMPOSITION OF ALLUVIAL GOLD (DOCUMENTED ON LOCALITIES THE WESTERN CARPATHIANS)  

Microsoft Academic Search

Alluvial gold is influenced by various physical, chemical and biological factors. As type- localities for study of changes in chemical composition of alluvial gold we chose Pukanec (Central Slovakia Neovolcanic Field) and Magurka and Ni?ná Boca (Nízke Tatry Mts). The most distinctive are morphological and chemical changes (dissolution and precipitation), the latter is most commonly represented by the formation of

B. BAHNA; A. SMIRNOV; M. CHOVAN; F. BAKOS

316

A. Reservoir Effects of Stream Channels DAM IMPACTS ON AND RESTORATION OF AN ALLUVIAL RIVER  

E-print Network

A. Reservoir Effects of Stream Channels DAM IMPACTS ON AND RESTORATION OF AN ALLUVIAL RIVER ­ RIO and reservoirs on alluvial rivers extends both upstream and downstream of the dam. Downstream of dams, both and sediment retention. Prior to dam construction, the Rio Grande was a wide, sandy braided river. Following

Julien, Pierre Y.

317

The lower Mzingwane alluvial aquifer: managed releases, groundwater - surface water interactions and the challenge of salinity  

Microsoft Academic Search

The alluvial aquifers of the Mzingwane Catchments are the most extensive of any tributaries in the Limpopo Basin and are present in the lower reaches of most of the larger rivers. The alluvial aquifers form ribbon shapes covering over 20 km in length, generally less than 1 km in width and areal extents ranging from 100 ha to 255 ha

David Love; Richard Owen; Stefan Uhlenbrook; Pieter van der Zaag; William Moyce

2007-01-01

318

Geomorphology and morphometric characteristics of alluvial fans, Guadalupe Mountains National Park and adjacent areas, west Texas and New Mexico  

E-print Network

analysis indicate that the morphometric relationships that exist between the alluvial fans of the GMR and their contributory drainage basins are comparably to those of alluvial fans of the western United States. Morphologic and morphometric differences...

Given, Jeffrey Lyle

2004-09-30

319

The rio caliente ignimbrite: Analysis of a compound intraplinian ignimbrite from a major late quaternary Mexican eruption  

Microsoft Academic Search

The Rio Caliente ignimbrite is a multi-flow unit orcompound ignimbrite formed during a major late Quaternary explosive rhyolitic eruption of La Primavera volcano, Mexico. The eruption\\u000a sequence of the ignimbrite is complex and it occurs between lower and upper plinian air-fall deposits. It is, therefore, anintraplinian ignimbrite. Air-fall layers, pyroclastic surge, mudflow and fluviatile reworked pumice deposits also occur interbedded

J. V. Wright

1981-01-01

320

Multiple submarine-cemented grainstone sequences along leeward carbonate margins: examples from late Quaternary of Little and Great Bahama Banks  

Microsoft Academic Search

Coarse-grained, leeward-margin sand shoals, developed during the late Quaternary along the western edges of Little and Great Bahama Bank, have been deposited and preserved in response to regional sediment-transport process and local physicochemical conditions. These sand bodies are fundamental depositional sequences, chronostratigraphically bounded by subaerial exposure crusts, and thus are of major importance in determining rates of bank-margin growth and

W. R. Jude; A. C. Hine; C. Neumann

1985-01-01

321

Summary of Quaternary Stratigraphy and history, Eastern Canada  

NASA Astrophysics Data System (ADS)

Deposits of three Wisconsinan substages, Sangamonian Stage, and older Quaternary stratigraphic units are recognized in Eastern Canada. The age assignment of these units is based on radiocarbon dating and correlation of events. Quaternary deposits older than Sangamonian are recognized locally in Eastern Canada. In southern Ontario glacial deposits directly underlie Sangamonian sediments and are referred to as Illinoian in age. In other areas the ages of older sediments are largely unknown. Offshore core stratigraphy suggests that a major glaciation took place about 436 ka and that the Illinoian (oxygen isotope stage 6) was also a time of extensive glaciation. In this report Sangamonian is used as the name for the chronostratigraphic stage that includes all of deep-sea oxygen isotope stage 5 and consequently, on a regional basis, it includes warm interglacial deposits, glacial deposits and cool interglacial deposits. In southern Ontario the warm interglacial deposits are represented by the Don Formation, the stadial deposits by the Scarborough Formation and the cool interglacial deposits by the Pottery Road Formation. Warm interglacial deposits have not been recognized in Quebec (unless they are part of the pre-Johnville Sediments); the Bécancour Till is included as glacial Sangamonian sediments, and the St. Pierre Sediments are recognized as cool interglacial sediments. The Early Wisconsinan appears to have been the time of maximum Wisconsinan glaciation in Eastern Canada with ice moving south of the International Boundary and well out onto the continental shelf. The Middle Wisconsinan was primarily a nonglacial period in southern Ontario and a glacial stade elsewhere in Eastern Canada. In southern Ontario the Middle Wisconsinan record has been subdivided into two interstades (Port Talbot and Plum Point), separated by a stade (Cherrytree). The Port Talbot Interstade began before the limit of radiocarbon dating (before 48 ka) and ended about 40 ka; glacial or near glacial conditions of the Cherrytree Stage lasted from about 40 to 35 ka ago, and the Plum Point Interstade was from about 35 to 23 ka ago. Central St. Lawrence Lowland was occupied by ice throughout the Middle Wisconsinan, but southeastern Quebec and the Montreal area were briefly deglaciated. Scattered evidence in Atlantic Canada suggests local deglaciation of coastal areas during Middle Wisconsinan but extensive ice remained on the continental shelf and ice from centres located on the shelf flowed onto land in at least two areas. Glacial conditions predominated throughout Eastern Canada during the Late Wisconsinan. At the Late Wisconsinan maximum, through-moving ice deposited the Catfish Creek Drift in southern Ontario but ice lobes, which developed in the basins of the Great Lakes after 15.5 ka, controlled ice flow during a period of ice margin oscillation and retreat. A calving bay developed in lower St. Lawrence valley, after the Late Wisconsinan maximum, causing a reversal of flow on the south shore of the St. Lawrence and replacing ice in the valley with the Champlain Sea about 12 ka. Late Wisconsinan glaciers were largely limited to land areas in Atlantic Canada. Local ice caps dominated with complicated patterns of flow and retreat developing as centres of accumulation shifted and competing ice centres achieved dominance. The period of Late Wisconsinan retreat in Atlantic Canada appears to have lasted from about 14 to 10 ka.

Fulton, R. J.; Karrow, P. F.; LaSalle, P.; Grant, D. R.

322

Effects of Climate-Induced Hydrologic Modifications on Biogeochemical Cycling of Trace Metals in Alluvial and Coastal Watersheds  

NASA Astrophysics Data System (ADS)

Assessing the impacts of climate changes on water quality requires an understanding of the biogeochemical cycling of trace metals. Evidence from research on alluvial aquifers and coastal watersheds shows direct impacts of climate change on the fate and transformation of trace metals in natural environments. This study employs field data and numerical modeling techniques to test assumptions about the effects of climate change on natural arsenic contamination of groundwater in alluvial aquifers and mercury bioaccumulation in coastal saltmarshes. The results show that the rises of sea level and river base during the warm Holocene period has led to an overall increase in groundwater arsenic concentration due to the development of reducing geochemical conditions and sluggish groundwater movement. Modeling results indicate that the intrusion of seawater occurring during high sea-level stand may lead to desorption of arsenic from the surfaces of hydrous oxides due to pH effects and ionic competition for mineral sorbing sites. Our results also show that contamination and bioaccumulation of Hg and other metals in estuarine and coastal ecosystems may be influenced by climate-induced hydrologic modifications (atmospheric deposition, riverine input, salinity level, etc.). An integrated research framework consisting of numerical modeling, long-term monitoring, laboratory experiments will be necessary for building a comprehensive understanding of the complex response of biogeochemical cycling of trace metals to climate change.

Lee, M.; Natter, M. G.; Keevan, J. P.; Guerra, K.; Saunders, J.; Uddin, A.; Humayun, M.; Wang, Y.; Keimowitz, A. R.

2013-12-01

323

Late Quaternary history of Washington Land, North Greenland OLE BENNIKE  

E-print Network

Late Quaternary history of Washington Land, North Greenland OLE BENNIKE Bennike, O. 2002 (September): Late Quaternary history of Washington Land, North Greenland. Boreas, Vol. 31, 260­272. Oslo. ISSN 0300 Quaternary history of the region. The lack of data re ects the inaccessibility of this remote region

Ingólfsson, �lafur

324

Ground-Water Resource Assessment in the Rio Grande de Manati Alluvial Plain, Rio Arriba Saliente Area, Puerto Rico  

USGS Publications Warehouse

The alluvial aquifer within a 160-acre area of the Rio Grande de Manati alluvial plain was investigated to evaluate its potential as a water-supply source for the Barrios Rio Arriba Saliente and Pugnado Afuera, municipio of Manati, Puerto Rico. Analysis of well boring samples and the results of electric resistivity surveys indicate that the average thickness of the unconsolidated alluvial deposits in the study area is about 100 to 110 feet. The alluvium is a mixture of sand and gravel, which generally has a porosity of 0.2 to 0.35. Short-duration pump tests in small-diameter piezometers indicate that the alluvial aquifer has a hydraulic conductivity of about 200 feet per day and a transmissivity of about 7,900 feet squared per day. Analyses of water levels in piezometers, combined with stage measurements at a series of surveyed reference points along the Rio Grande de Manati channel, indicate that the water-table gradient in the alluvial aquifer is about 0.001, and that ground-water flow is generally from south to north, in the general direction of river flow. The water-table data indicate that the Rio Grande de Manati is the principal source of ground-water recharge to the alluvial aquifer in the study area. Because base flow for the Rio Grande de Manati is usually greater than 44 cubic feet per second, a continuous withdrawal rate of 0.5 to 1.0 cubic foot per second (225 to 450 gallons per minute) from a production well is possible. Chemical analysis of a ground-water sample indicates that the alluvial aquifer water meets U.S. Environmental Protection Agency secondary standards for selected constituents. Bacteriological analysis of ground-water samples indicates that the ground water contains little or no fecal coliform or fecal streptococcus bacteria. Although long-term data from upstream of the study area indicate high levels of fecal coliform and fecal streptococcus prior to 1996, bacteriological analyses of Rio Grande de Manati water samples obtained during the present study indicate that fecal coliform and fecal streptococcus concentrations are within the standards for surface water intended for use (or with the potential for use) as a raw source of public water supply in Puerto Rico. If a production well were constructed in the study area, it would be located close to the river channel (within 500 to 800 feet). Pumping from the porous and permeable alluvial aquifer close to the river channel could substantially enhance recharge from the Rio Grande de Manati channel to the aquifer. Enhanced recharge could shorten travel times for ground water in the aquifer, which might not allow sufficient time to attenuate bacteria and viruses. Travel times for bacteria moving from the river channel to a hypothetical production well were estimated using the numerical transport model MODFLOW/MT3DMS with an uncalibrated model of the alluvial aquifer. The model assumes a well pumping at 1 cubic foot per second. The transport of particles from the river to the well is most sensitive to the porosity of the aquifer and the pumping rate of the well. Sensitivity analysis indicates that a decrease in pumpage will increase the time of travel for particles to move from the river to the pumping well. The model indicates that the leading edge of a plume would reach the production well in about 40 days assuming a porosity of 0.20, 60 days assuming a porosity of 0.275, and about 70 days assuming a porosity of 0.35. If the well were moved 50 feet further from the river, the leading edge of the plume would reach the well in about 50 days assuming a porosity of 0.20 and about 70 days assuming a porosity of 0.275. These estimates are considered worse case estimates because no decay rate was included in the simulation, and because the hypothetical well was located in the center of the alluvial plain rather than further eastward, away from the river channel.

Torres-Gonzalez, Sigfredo; Gomez-Gomez, Fernando; Warne, Andrew G.

2002-01-01

325

Quaternary tectonic movements in the Argentine Puna, 24/sup 0/ to 27/sup 0/ s latitude  

SciTech Connect

The Puna of NW Argentina, one of the highest plateaus in the world, is the southern continuation of the Andean Altiplano geomorphic province of Peru and Bolivia. The region is not seismically active and reports of neotectonic movements are scarce. However, the areas of Salar de los Pastos Grandes, Salar del Hombre Muerto and Sierra Calalaste clearly have experienced Quaternary tectonic movements. At Salar de los Pastos Grandes, early Pleistocene lake sediments are offset by reverse faulting. At Salar del Hombre Muerto, Quaternary pyroclastic and debris-flow deposits are unconformable over sediments 5.86 m.y. old that were folded during the Pliocene-Pleistocene Diaguita deformation. Within the Quaternary sediments two separate deformational phases with reverse faulting and shallow thrusting are recognized. The timing of movement is well defined since the deformed strata are covered by a basalt flow 0.75 m.y. old. The flow in turn is affected by normal faulting. Similar normal faults associated with basalt flows were found at Sierra Calalaste. These observations are in accord with pronounced extensional movements and basaltic volcanism at the Calama-Olacapato-Toro Lineament (0.2 m.y. old flows) and might document the Quaternary transition from a compressive to an extensional tectonic regime in the southern Puna.

Strecker, M.R.; Alonso, R.; Rivelli, F.; Mon, R.

1985-01-01

326

Geologic map of Late Cenozoic deposits, Santa Clara County, California  

USGS Publications Warehouse

This map is the first of several in the San Francisco Bay region showing the distribution and differentiation of the late Cenozoic alluvial, estuarine, and volcanic deposits. The sedimentary deposits of gravel, sand, silt, and clay were separated into geologic map units on the basis of their post-depositional soil development, texture, and geomorphology. Some of the geologic units are associated with different landforms having recognizable topographic expression such as alluvial fans, natural stream terraces, levees, and interfluvial basins. The relative ages of these unites were established on the basis of intensity of soil profile development, stratigraphic position, and geomorphic expression. The older deposits exhibit strongly developed soil profiles with strong horizon differentiation whereas younger deposits display minimal soil profile development, consisting primarily of organic matter accumulations near the land surface. Geomorphic expression and degree of erosion and dissection were additional criteria used to aid in the age determinations. For example, younger deposits form well-defined morphologic features such as levees, terraces, and broad, undissected alluvial fans along the margin of the bay basin and are related to present drainage patterns. The oldest deposits shown on this map (QTs) are structurally deformed by folding and faulting and therefore exhibit no original depositional geomorphic features. These deposits are not related to present drainage patterns but suggest earlier patterns much different from those existing today.

Helley, E.J.; Brabb, E.E.

1971-01-01

327

Sedimentology and climatic environment of alluvial fans in the martian Saheki crater and a comparison with terrestrial fans in the Atacama Desert  

NASA Astrophysics Data System (ADS)

The deflated surfaces of the alluvial fans in Saheki crater reveal the most detailed record of fan stratigraphy and evolution found, to date, on Mars. During deposition of at least the uppermost 100 m of fan deposits, discharges from the source basin consisted of channelized flows transporting sediment (which we infer to be primarily sand- and gravel-sized) as bedload coupled with extensive overbank mud-rich flows depositing planar beds of sand-sized or finer sediment. Flow events are inferred to have been of modest magnitude (probably less than ?60 m3/s), of short duration, and probably occupied only a few distributaries during any individual flow event. Occasional channel avulsions resulted in the distribution of sediment across the entire fan. A comparison with fine-grained alluvial fans in Chile’s Atacama Desert provides insights into the processes responsible for constructing the Saheki crater fans: sediment is deposited by channelized flows (transporting sand through boulder-sized material) and overbank mudflows (sand size and finer) and wind erosion leaves channels expressed in inverted topographic relief. The most likely source of water was snowmelt released after annual or epochal accumulation of snow in the headwater source basin on the interior crater rim during the Hesperian to Amazonian periods. We infer the Saheki fans to have been constructed by many hundreds of separate flow events, and accumulation of the necessary snow and release of meltwater may have required favorable orbital configurations or transient global warming.

Morgan, A. M.; Howard, A. D.; Hobley, D. E. J.; Moore, J. M.; Dietrich, W. E.; Williams, R. M. E.; Burr, D. M.; Grant, J. A.; Wilson, S. A.; Matsubara, Y.

2014-02-01

328

Synoptic snowfall as a possible source of water for late alluvial fan activity in southern Margaritifer Terra, Mars  

NASA Astrophysics Data System (ADS)

Alluvial deposits on Mars provide an important record of the environmental conditions enabling their formation. A recent study of alluvial fans within large craters in southern Margaritifer Terra showed that deposition of exposed surfaces occurred late in Martian history, within the latest Hesperian or well into the early Amazonian. These fans typically display well developed alcoves and fan surfaces preserve distributary channels standing ~10-15 m in relief (via inversion of topography). Understanding whether the water responsible for fan emplacement was related to a local source (e.g., impact-related melting of ground ice) versus regional or global synoptic climatic events has implications for the nature of late water activity and potential habitability of Mars. Water released during and after impact events may be sufficient to cause runoff within and around newly formed craters and could contribute to late valley and fan formation without requiring changes in climate. For example, the impact forming the Amazonian-aged Hale crater (35.7S, 323.6E) produced valleys, but was not likely responsible for the alluvial fans because 1) alluvial fans occur in craters up to 700-800 km away from Hale; 2) craters with fans occur at a range of azimuths from Hale (and may not be consistent with downwind transport of volatiles under prevailing winds); and 3) many craters bearing older floor deposits and mantling deposits are closer to Hale than those containing fans. The impact forming the Hesperian-aged Holden crater (26.1S, 326E) is another possible local source of water, but like Hale, craters hosting fans occur at a range of azimuths and up to hundreds of km away from Holden. Moreover, at least six degraded craters on the relatively high relief rim of Holden suggest a gap in time between the Holden impact and the fluvial modification of these near-rim craters and the simultaneous fan activity within Holden. Fans within Holden also record evidence for multiple periods of formation, supporting the contention that crater formation was followed by an even later period of fan emplacement. A latest Hesperian or Amazonian emplacement age for the surface materials in such widely distributed fans likely requires late-occurring synoptic precipitation. Precipitation, possibly occurring as snow, may have been locally influenced by topography and (or) orbital variations. It is not known how much of the total sediment inventory in the fans relates to this late activity versus possible earlier events that may have had alternate (e.g., local) sources of water. Winds may have concentrated late precipitation in the form of snow into existing relief and (or) preexisting alcoves that facilitated physical weathering to produce fine sediments later incorporated into fans. Two of the craters containing fan deposits, Holden and Eberswalde, were finalists for the Mars Science Laboratory (MSL) landing site. Results suggest that exposed and accessible fan sediments at both crater sites may record late occurring, relatively colder, drier, and less sustained conditions relative to earlier periods on Mars.

Grant, J. A.; Wilson, S. A.

2012-12-01

329

Late quaternary slip-rate variations along the Warm Springs Valley fault system, northern Walker Lane, California-Nevada border  

USGS Publications Warehouse

The extent to which faults exhibit temporally varying slip rates has important consequences for models of fault mechanics and probabilistic seismic hazard. Here, we explore the temporal behavior of the dextral?slip Warm Springs Valley fault system, which is part of a network of closely spaced (10–20 km) faults in the northern Walker Lane (California–Nevada border). We develop a late Quaternary slip record for the fault using Quaternary mapping and high?resolution topographic data from airborne Light Distance and Ranging (LiDAR). The faulted Fort Sage alluvial fan (40.06° N, 119.99° W) is dextrally displaced 98+42/-43 m, and we estimate the age of the alluvial fan to be 41.4+10.0/-4.8 to 55.7±9.2??ka, based on a terrestrial cosmogenic 10Be depth profile and 36Cl analyses on basalt boulders, respectively. The displacement and age constraints for the fan yield a slip rate of 1.8 +0.8/-0.8 mm/yr to 2.4 +1.2/-1.1 mm/yr (2?) along the northern Warm Springs Valley fault system for the past 41.4–55.7 ka. In contrast to this longer?term slip rate, shorelines associated with the Sehoo highstand of Lake Lahontan (~15.8??ka) adjacent to the Fort Sage fan are dextrally faulted at most 3 m, which limits a maximum post?15.8 ka slip rate to 0.2??mm/yr. These relations indicate that the post?Lahontan slip rate on the fault is only about one?tenth the longer?term (41–56 ka) average slip rate. This apparent slip?rate variation may be related to co?dependent interaction with the nearby Honey Lake fault system, which shows evidence of an accelerated period of mid?Holocene earthquakes.

Gold, Ryan; dePolo, Craig; Briggs, Richard; Crone, Anthony

2013-01-01

330

Late Quaternary glaciation of the Upper Soc??a River Region (Southern Julian Alps, NW Slovenia)  

USGS Publications Warehouse

Extent of Late Quaternary glaciers in the Upper Soc??a River Region (Southern Julian Alps, SE Europe) has been analyzed using a combination of geological mapping, glaciological modeling, and sediment dating (radiocarbon, U/Th series and Infrared Stimulated Luminescence-IRSL). Field investigations focused mainly on relatively well preserved Quaternary sequences in the Bovec Basin, an intramontane basin located SW of the Mediterranean/Black Sea divide and surrounded by mountain peaks reaching from approximately 2100 up to 2587 m a.s.l. Within the Basin we recognized two Late Quaternary sedimentary assemblages, which consist of the same facies association of diamictons, laminated lacustrine deposits and sorted fluvial sediments. Radiocarbon dating of the upper part of the lake sediments sequence (between 12790??85 and 5885??60 14C years b.p.) indicates that the younger sedimentary assemblage was deposited during the last glacial maximum and through early Holocene (Marine Isotope Stage 21, MIS 2-1). Sediment ages obtained for the older assemblage with U/Th and IRSL techniques (between 154.74??22.88 and 129.93??7.90 ka b.p. for selected samples) have large errors but both methods yield results consistent with deposition during the penultimate glacial-interglacial transition (MIS 6-5). Based on analyses of field data combined with glaciological modeling, we argue that both sediment complexes formed due to high sediment productivity spurred by paraglacial conditions with glaciers present in the uplands around the Bovec Basin but not extending down to the basin floor. Our study shows that the extent and intensity of direct glacial sedimentation by Late Quaternary glaciers in the region was previously significantly overestimated. ?? 2004 Elsevier B.V. All rights reserved.

Bavec, M.; Tulaczyk, S.M.; Mahan, S.A.; Stock, G.M.

2004-01-01

331

Micropaleontologic record of Quaternary paleoenvironments in the Central Albemarle Embayment, North Carolina, U.S.A.  

USGS Publications Warehouse

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

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

2011-01-01

332

Petrological comparison of some tertiary and quaternary sands from Brazos and adjourning counties, Texas  

E-print Network

, Sparta sands, and Quaternary high level terrace deposits from northeastern and western Burleson County (Blankenship, 1955, p. 48; Foster, 1956, p. 52; and Napp, 1956' pp. 4549) suggested coarser sands for the terrace deposits as compared to Queen City... of muscovite in the Queen City and Sparta sands. Napp discovered no dii'ference in the degree of rounding of the various sends studied. Kelly made similar textural analyses of the Queen City and Sparta formations (1953, p. 110). He reported that the sands...

Elsik, William Clinton

2012-06-07

333

Seismic Response of Alluvial Valleys to SH Waves  

SciTech Connect

This paper presents a theoretical study on the seismic response of alluvial valleys. The considered model consists of a two-dimensional elastic inclusion of arbitrary shape embedded in a stiffer half-plane excited by vertically or obliquely incident SH waves. Computations are conducted using a procedure based on the boundary element method. As known, this numerical technique is well suited to deal with wave propagation in infinite media as it avoids the introduction of fictitious boundaries and reduces by one the dimensions of the problem. This provides significant advantages from a computational point of view. A one-dimensional closed form solution is also used for comparison, and the most significant differences between the results obtained using the two methods are highlighted.

Ausilio, Ernesto; Conte, Enrico; Dente, Giovanni [Dipartimento di Difesa del Suolo, Universit della Calabria (Italy)

2008-07-08

334

The measurement of total sediment load in alluvial streams  

USGS Publications Warehouse

The measurement of the total sediment load transported by streams that flow in alluvial channels has been a perplexing problem to engineers and geologists for over a century. Until the last decade the development of equipment to measure bed load and suspended load was carried on almost independently, and without primary consideration of the fundamental laws governing the transportation of fluvial sediments. French investigators during the nineteenth century described methods of measurement and a mathematical approach for computing the rate of bed-load movement. The comprehensive laboratory investigations by Gilbert early in this century provided data that are still being used for studies of sediment transport. Detailed laboratory investigations of bed-load movement conducted during the last two decades by a number of investigators have resulted in the development of additional mathematical formulas for computing rates of bed-load movement. Likewise, studies of turbulent flow have provided the turbulence suspension theory for suspended sediment as it is known today.

Benedict, P.C.; Matejka, D.Q.

1953-01-01

335

Estimating contaminant attenuation half-lives in alluvial groundwater systems  

SciTech Connect

One aspect of describing contamination in an alluvial aquifer is estimating changes in concentrations over time. A variety of statistical methods are available for assessing trends in contaminant concentrations. We present a method that extends trend analysis to include estimating the coefficients for the exponential decay equation and calculating contaminant attenuation half-lives. The conceptual model for this approach assumes that the rate of decline is proportional to the contaminant concentration in an aquifer. Consequently, the amount of time to remove a unit quantity of the contaminant inventory from an aquifer lengthens as the concentration decreases. Support for this conceptual model is demonstrated empirically with log-transformed time series of contaminant data. Equations are provided for calculating system attenuation half-lives for non-radioactive contaminants.

Tardiff, Mark F.; Katzman, Danny

2007-03-13

336

Methodologies for hydraulic hazard mapping in alluvial fan areas  

NASA Astrophysics Data System (ADS)

Hydraulic hazards in alluvial fan areas are mainly related to torrential floods and debris flows. These processes are characterized by their fast time evolution and relevant sediment load. Rational approaches for the estimation of hazard levels in flood-prone areas make use of the maps of depth and velocity, which are provided by numerical simulations of the event. This paper focuses on national regulations regarding quantitative debris-flow hazard mapping and compares them to a simple conceptual model for the quantification of the hazard levels on the basis of human stability in a flood. In particular, the proposed method takes into account, in a conceptual fashion, both the local slope and the density of the fluid, that are crucial aspects affecting stability for processes in mountain environments. Physically-based hazard criteria provide more comprehensible and objective maps, increasing awareness among stakeholders and providing more acceptable constraints for land planning.

Milanesi, L.; Pilotti, M.; Ranzi, R.; Valerio, G.

2014-09-01

337

Enantioselective construction of remote quaternary stereocentres  

NASA Astrophysics Data System (ADS)

Small molecules that contain all-carbon quaternary stereocentres--carbon atoms bonded to four distinct carbon substituents--are found in many secondary metabolites and some pharmaceutical agents. The construction of such compounds in an enantioselective fashion remains a long-standing challenge to synthetic organic chemists. In particular, methods for synthesizing quaternary stereocentres that are remote from other functional groups are underdeveloped. Here we report a catalytic and enantioselective intermolecular Heck-type reaction of trisubstituted-alkenyl alcohols with aryl boronic acids. This method provides direct access to quaternary all-carbon-substituted ?-, ?-, ?-, ?- or ?-aryl carbonyl compounds, because the unsaturation of the alkene is relayed to the alcohol, resulting in the formation of a carbonyl group. The scope of the process also includes incorporation of pre-existing stereocentres along the alkyl chain, which links the alkene and the alcohol, in which the stereocentre is preserved. The method described allows access to diverse molecular building blocks containing an enantiomerically enriched quaternary centre.

Mei, Tian-Sheng; Patel, Harshkumar H.; Sigman, Matthew S.

2014-04-01

338

Quaternary International 138139 (2005) 14 In Memorium  

E-print Network

awards include being named a fellow of the Geological Society of America in 2004. Geoff's major galvanizing efforts to apply surface exposure dating methods to date moraines in Peru and Bolivia. Results, Geology, Quaternary Research, and GSA Bulletin. Geoff was blessed with a combination of keen intellectual

Howat, Ian M.

339

Late Quaternary fire regimes of Australasia  

Microsoft Academic Search

We have compiled 223 sedimentary charcoal records from Australasia in order to examine the temporal and spatial variability of fire regimes during the Late Quaternary. While some of these records cover more than a full glacial cycle, here we focus on the last 70,000 years when the number of individual records in the compilation allows more robust conclusions. On orbital

S. D. Mooney; S. P. Harrison; P. J. Bartlein; A.-L. Daniau; J. Stevenson; K. C. Brownlie; S. Buckman; M. Cupper; J. Luly; M. Black; E. Colhoun; D. D’Costa; J. Dodson; S. Haberle; G. S. Hope; P. Kershaw; C. Kenyon; M. McKenzie; N. Williams

2011-01-01

340

Late Quaternary land-sea correlations, northern Labrador, Canada  

SciTech Connect

Late Quaternary glacial and postglacial units in the Torngat Mountains, northern Labrador, are correlated with units identified on the adjacent continental shelf. The late Wisconsinan Laurentide Ice Sheet drained through major valleys of the Torngat Mountains as outlet glaciers, depositing the Saglek Moraines. These are of regional extent and have been mapped from Saglek Fiord north to Noodleook Fiord. A C-14 date of 18,210 +/- 1900 BP on total organic matter (TOM) from lake sediment dammed by a segment of the Saglek Moraines is interpreted as a maximum date for deposition of the Saglek Moraine system because of possible contamination. Glacial sediments comprising the Saglek Moraines are correlated with upper till mapped in troughs and saddles on the continental shelf. Outlet glaciers depositing a late Wisconsinan unit flowed through Labrador fiords and onto the shelf at low basal shear stresses, particularly on the shelf where, although grounded, they were hydrostatically buoyed up and moved principally by sliding. A glaciomarine unit conformably overlies late Wisconsinan till on the shelf and on the land. This unit is a gravelly clayey silt, contains abundant foraminifera, and has up to 60% limestone in the pebble fraction. C-14 dates suggest deposition of this unit began ca. 10,000 BP on the shelf and 9000 BP on the land, an ended by 8000 BP. Limestone pebbles in this unit suggest a source in part from sediment-laden icebergs and pack-ice from the north. Marine deposition from ca. 8000-0 BP is characterize by basinal sedimentation.

Clark, P.; Josenhans, H.

1985-01-01

341

Numerical Modeling of the co-Evolution of Alluvial Rivers and Vegetated Floodplains  

NASA Astrophysics Data System (ADS)

We are developing a model to simulate the evolution of alluvial rivers and their adjacent, vegetated floodplains. Our model consists of simplified 2-d vertically averaged equations of momentum and continuity, with depth and unit discharge as the dependent variables. Advection and diffusion terms have been omitted, leaving only gravitational acceleration, friction, and time dependent terms. The hydrodynamics model is thus a 2-d wave equation that can represent floodplain inundation in its simplest form. The effect of vegetation on the flow is represented using a spatially variable friction factor that includes momentum losses caused by the vegetation itself. The effect of vegetation can vary with time to represent growth and decay of riparian plants. Bedload and suspended sediment transport are represented by simplified semi-empirical transport equations. Suspended sediment includes both wash load and suspended bed material load. Wash load is only deposited when fluid stresses are less than a critical value. The effects of lateral slopes on bedload transport are also included. Vegetation effects transport directly by increasing critical shear stresses for erosion. Even though the hydrodynamic model does not include lateral shear, steeply sloping banks are included in the computation of friction terms. If friction on the banks exceeds threshold stresses required for erosion, bank erosion can occur.

Allmendinger, N. E.; Pizzuto, J. E.

2002-12-01

342

Extent and source of saltwater intrusion into the alluvial aquifer near Brinkley, Arkansas, 1984  

USGS Publications Warehouse

An approximate area of 56 sq mi of the alluvial aquifer just north of Brinkley, Arkansas, has been contaminated by saltwater (chloride concentration > or = 50 mg/L) intruded from underlying aquifers. The contamination was mapped from water quality data for 217 wells. Saltwater problems appear to have spread rapidly in the alluvial aquifer since the late 1940's. Chemical comparisons indicate that the alluvial aquifer was contaminated by water from the Sparta aquifer which in turn was contaminated by the underlying Nacatoch aquifer. The possibility of intrusion into the alluvial aquifer through abandoned oil and gas test wells was investigated but no evidence could be found to support this possibility. Upward movement into the alluvial aquifer from the underlying Sparta aquifer through the thinned or absent Jackson confining unit appears to be the principal reason for saltwater in the alluvial aquifer. Increased withdrawals of water from the alluvial aquifer for irrigation and public supply appear to have contributed to this upward movement. (Author 's abstract)

Morris, E. E.; Bush, W. V.

1986-01-01

343

Debris-flow dominance of alluvial fans masked by runoff reworking and weathering  

NASA Astrophysics Data System (ADS)

Arid alluvial fan aggradation is highly episodic and fans often comprise active and inactive sectors. Hence the morphology and texture of fan surfaces are partly determined by secondary processes of weathering and erosion in addition to primary processes of aggradation. This introduces considerable uncertainty in the identification of formative processes of terrestrial and Martian fans from aerial and satellite imagery. The objectives of this study are (i) to develop a model to describe the sedimentological and morphological evolution of inactive fan surfaces in arid settings, and (ii) to assess the relative importance of primary processes of aggradation and secondary processes of weathering and reworking for surface morphology and sedimentology and for the stratigraphic record. We studied an alluvial fan characterized by a recently active sector and a long-abandoned, inactive sector along the coast of the hyperarid Atacama Desert. Here, rates of primary geomorphic activity are exceptionally low because of extreme aridity, while weathering rates are relatively high because of the effects of coastal fogs. Long-term processes of fan aggradation and reworking were determined through sedimentological facies analysis of stratigraphic sections. Ground surveys for textural and morphological patterns at the fan surface were integrated with remote-sensing by an Unmanned Airborne Vehicle (UAV). Discharges and sediment-transport capacities were calculated to estimate the efficiency of secondary runoff in reshaping the inactive fan sector. Stratigraphic sections reveal that the fan was dominantly aggraded by debris flows, whereas surface morphology is dominated by debris-flow signatures in the active sector and by weathering and runoff on the inactive sector. On the latter, rapid particle breakdown prevents the formation of a coarse desert pavement. Furthermore, relatively frequent local runoff events erode proximal debris-flow channels on the inactive sector to form local lag deposits and accumulate fine sediment in low-gradient distal channels, forming a well-developed drainage pattern that would suggest a runoff origin from aerial images. Nevertheless, reworking is very superficial and barely preserved in the stratigraphic record. This implies that fans on Earth and Mars that formed dominantly by sporadic mass flows may be masked by a surface morphology related to other processes.

de Haas, Tjalling; Ventra, Dario; Carbonneau, Patrice E.; Kleinhans, Maarten G.

2014-07-01

344

Combining sedimentological and geophysical data for high-resolution 3-D mapping of fluvial architectural elements in the Quaternary Po plain (Italy)  

NASA Astrophysics Data System (ADS)

Current approaches to the reconstruction of the geometry of fluvial sediments of Quaternary alluvial plains and the characterization of their internal architecture are strongly dependent on core data (1-D). Accurate 2-D and 3-D reconstructions and maps of the subsurface are needed in hydrostratigraphy, hydrogeology and geotechnical studies. The present study aims to: 1) improve current methods for geophysical imaging of the subsurface by means of VES, ERGI and GPR data, and calibration with geomorphological and geological reconstructions, 2) optimize the horizontal and vertical resolution of subsurface imaging in order to resolve sedimentary heterogeneity, and 3) check the reliability/uncertainty of the results (maps and architectural reconstructions) by comparison with exposed analogues. The method was applied to shallow (0 to 15 m) aquifers of the fluvial plain of southern Lombardy (Northern Italy). At two sites we studied fluvial sediments of meandering systems of the Last Glacial Maximum and post-glacial historical age. These sediments comprise juxtaposed and superimposed gravel-sand units with fining-upward sequences (channel-bar depositional elements), which are separated by thin and laterally discontinuous silty and sandy clay units (overbank and flood plain deposits). The sedimentary architecture has been studied at different scales in the two areas. At the scale of the depositional system, we reconstructed the subsurface over an area of 4 km 2 to a depth of 18 m (study site 1). Reconstructed sequences based on 10 boreholes and water-well stratigraphic logs were integrated with the interpretation of 10 vertical electrical soundings (VES) with Schlumberger arrays and 1570 m long dipole-dipole electrical resistivity ground imaging profiles (ERGI). In unsaturated sediments, vertical and horizontal transitions between gravel-sand units and fine-grained sediments could be mapped respectively at the meter- to decameter scale after calibration of the VES with borehole data. Similar information could be obtained in waterlogged sediments, in which the largest units could be portrayed and the lateral continuity of major hydrostratigraphic units could be assessed. Maps of apparent resistivity were combined with sand-to-clay ratio maps obtained from stratigraphic data, which substantially increased their quality. ERGI profiles added substantial information about the horizontal transitions between fine- and coarse-grained units. At the scale of depositional elements (channel-bar systems) we studied quarry exposures, over an area of about 4000 m 2, down to 8 m below ground level (study site 2). In this case, facies analysis was performed on progressing quarry faces and integrated with a network of 165 m long ERGI profiles and 1100 m long ground-penetrating radar (GPR) profiles. Channel boundaries and accretion surfaces of point bars were resolved by both GPR and ERGI, which permitted 3-D mapping of these surfaces. Comparison between the results obtained for the two study sites demonstrates that integration of sedimentological data with geophysical imaging (ERGI and VES) enables the identification of stratigraphic units at the scale of depositional elements. Moreover, fining-upward trends and other internal features of the deposits, such as the transitions from coarse to fine-grained sediments within channel-bar complexes, could be resolved. Hence, the combination of sedimentological and geophysical methods provides a more accurate 3-D reconstruction of hydrostratigraphically significant sedimentary units compared to reconstructions based solely on borehole/point data.

Bersezio, R.; Giudici, M.; Mele, M.

2007-11-01

345

Mapping the late Quaternary evolution of the lower Mississippi Valley  

NASA Astrophysics Data System (ADS)

The lower Mississippi Valley (LMV) extends from Cape Girardeau to Natchez and from Little Rock to Memphis. Extensive Quaternary terraces within the LMV have been considered to reflect downstream changes in base level (global sea level) and (or) upstream changes in water and sediment input because of glaciation. We suggest that the first-order control on terrace development was glacial-isostatic adjustment (GIA). Observed variation in heights of Quaternary alluvial surfaces at Memphis is 50 m (Rittenour et al., 2007). GIA modeling by Clark et al. (1994) predicted vertical displacement of as much as 130 m at Memphis over the last 18,000 years. ICE-5G models predict smaller displacement and reinforce the viability of GIA as the primary cause of LMV aggradation and incision. Existing analyses of LMV terraces are built on geomorphic maps by Saucier and colleagues (1974, 1994; Autin et al., 1991) that were interpreted from aerial photographs and inch-to-the-mile contour maps. Geomorphic mapping from high-resolution DEMs is more accurate, more rapid, and more reproducible than mapping from aerial photography and intermediate-resolution contours. Working from lidar DEMs (1-5 m XY resolution) and the 10 m National Elevation Dataset (NED) DEM largely derived from 1:24,000 scale contours, Haugerud is mapping the geomorphology of the LMV at ~1:500,000 scale. Goals are to explore the GIA-terrace hypothesis and improve the geomorphic and stratigraphic context for studies of New Madrid seismicity. Mapping leads to several observations: 1. The Holocene floodplain of the Mississippi River onlaps older surfaces. The river appears to be filling a hole created by collapse of the Laurentide forebulge. Continued filling of this accommodation space will, barring human intervention, enable the river to abandon its course through Thebes Gap in favor of a lower-elevation route through Oran Gap. 2. Within Holocene meander belts, younger levee crests are higher than older levee crests. The belts are aggrading, their substrates are compacting, or both. 3. Pleistocene braid plains step downward and merge downstream. Evidently there was up-to-the-north tilting as the braid plains formed. 4. Anomalous landforms suggest Holocene faulting or folding. Greater sinuosity and more-extensive wetlands along the St Francis River immediately upstream of Crowleys Ridge and pronounced incision where the river crosses the ridge indicate uplift of the ridge relative to the Western Lowlands. Unusual inset terraces along the L'Anguille River south of Forrest City, AR may record local uplift. Ten km southeast of Monroe, LA, N-S scarps dissect a meander belt; to the east, a subtle NE-SW scarp truncates braid plain. These are probably fault scarps. 5. Much of the LMV has been surveyed with lidar. Surveys have been at the behest of NRCS, FEMA, USACE, state agencies, and USGS-NEHRP. Improved coordination among survey efforts would reduce overlap and costs, could ease data access, and might lead to greater use of the data.

Haugerud, R. A.; Simon, K. M.; James, T. S.

2013-12-01

346

New perspectives on quaternary faulting in the southern Walker Lane, Nevada and California  

SciTech Connect

A preliminary survey of aerial photographs of the southern Walker Lane began in late 1986. The purpose of this survey is to determine the nature and scope of future studies required to ascertain whether the apparent concentration of Quaternary faults in and near the Nevada Test Site is real or is simply a result of the greater effort invested in mapping Quaternary deposits in that area, and determine whether faults in the southern Walker Lane are active and could produce significant earthquakes. The survey is focused on the area extending south from Lone Mountain to Pahrump Valley and east from the Furnace Creek fault zone to an irregular line passing through the Cactus Range and Pahute Mesa. Lineaments and scraps were identified on stereopairs of black-and-white aerial photographs at scales of 1:80,000 or 1:60,000. The lineaments and and scarps were plotted on 1:24,000- and 1:62,500-scale topographic maps using a PG-2 plotter, and were color-coded according to distinctness and occurrence in Quaternary or Tertiary deposits (age assignments based on appearance in aerial photographs and on existing geologic maps). Additional lineaments identified on the topographic maps were also plotted. Areas of particular interest were selected for more detailed study using larger-scale aerial photographs. Most of the lineaments and scraps identified in the survey, although referred to as faults in this paper, have not been checked in the field. 11 refs., 1 fig.

Reheis, M.C.; Noller, J.S.

1987-12-31

347

Origin of Bermuda's clay-rich Quaternary paleosols and their paleoclimatic significance  

USGS Publications Warehouse

Red clayey paleosols that are chiefly the product of aerosolic dust deposition are interbedded in the Quaternary carbonate formations of the Bermuda oceanic island system. These paleosols provide a basis for reconstructing Quaternary atmospheric circulation patterns in the northwestern Atlantic. Geochemical analyses were performed on representative paleosol samples to identify their parent dust source. Fine-grained fractions were analyzed by energy-dispersive X ray fluorescence to determine trace element (Zr, Y, La, Ti, and Nb) concentrations and to derive geochemical signatures based on immobile element ratios. These ratios were compared with geochemical signatures determined for three possible sources of airborne dust: (1) Great Plains loess, (2) Mississippi River Valley loess, and (3) Saharan dust. The Zr/Y and Zr/La ratios provided the clearest distinction between the hypothesized dust sources. The low ratios in the paleosol B horizons most closely resemble Saharan dust in the <2-??m size class fraction. Contributions from the two North American loessial source areas could not be clearly detected. Thus Bermuda paleosols have a predominantly Saharan aerosolic dust signature. Saharan dust deposition on Bermuda during successive Quaternary glacial periods is consistent with patterns of general circulation models, which indicate that during glacial maxima the northeast summer trade winds were stronger than at present and reached latitudes higher than 30 ?? N despite lower-than-present sea surface temperatures in the North Atlantic.

Herwitz, S.R.; Muhs, D.R.; Prospero, J.M.; Mahan, S.; Vaughn, B.

1996-01-01

348

Alluvial architecture and predictive modeling of the Late Cretaceous John Henry member, Straight Cliffs formation, southern Utah  

NASA Astrophysics Data System (ADS)

Five detailed measured sections (each >175 m), two outcrop gamma ray logs, 2100 paleocurrent measurements, and detailed facies interpretation of high-resolution composite photographs were used to document the vertical and lateral variations of the alluvial architecture of the John Henry Member of the Upper Cretaceous Straight Cliffs Formation (southwest Kaiparowits Plateau, southern Utah). These data interpretations correlate to 24 measured sections and logged cores from previous work in fluvial and paralic facies in the John Henry Member and complement previous correlation to marginal marine facies ˜60 km basinward of the study area. The proximal fluvial strata of the ˜230 m-thick member is divided into seven depositional units (DU) from stratigraphic base to top: DU-0, tidally-influenced channel belts; DU-1, highly amalgamated, laterally accreting channel belts with tidally-influenced channel belts in the upper section; DU-2, laterally extensive (>1.2 km wide), laterally accreting channel belts; DU-3, isolated channel belts (<150 m) embedded within thick floodplain muds; DU-4, clusters of laterally restricted (<500 m), laterally accreting channel belts and isolated channel belts; DU-5, laterally extensive, locally amalgamated, downstream accreting channel belts; and DU-6, highly amalgamated, downstream accreting channel belts. An unconformable surface at the base of DU-1 demonstrates a basinward shift in facies and is interpreted to represent erosion during base level fall. DU-0 correlates basinward to tidally-influenced channel belts and coastal coal mires in the south-central Kaiparowits Plateau that are coeval with the landward extensive, net progradational shoreface sandstones. An unconformity bound, fining upward trend limited to DU-1 through DU-3 in the western plateau is broadly consistent with previous interpretations of a northeast trending incised valley system and fill, which is correlative with a basinward shift and subsequent net transgression of shoreface sandstones. A coarsening upward trend from DU-4 through the overlying Drip Tank Member is consistent throughout alluvial facies of the entire John Henry Member and corresponds to net progradation of landward extensive shoreface sandstones. Reservoir characterization based on grain size, average porosity, net to gross estimates, channel belt size, internal connectivity (heterogeneity) and channel belt connectivity show that these defining trends in fluvial architecture (fining upward and coarsening upward) correspond to trends in reservoir analog quality (upward decreasing and upward increasing) and demonstrate that revised depositional models of alluvial architecture may be used to predict reservoir quality.

Gooley, Jared Thomas

349

230Th/U dating of a late Pleistocene alluvial fan along the southern San Andreas fault  

USGS Publications Warehouse

U-series dating of pedogenic carbonate-clast coatings provides a reliable, precise minimum age of 45.1 ± 0.6 ka (2?) for the T2 geomorphic surface of the Biskra Palms alluvial fan, Coachella Valley, California. Concordant ages for multiple subsamples from individual carbonate coatings provide evidence that the 238U-234U-230Th system has remained closed since carbonate formation. The U-series minimum age is used to assess previously published 10Be exposure ages of cobbles and boulders. All but one cobble age and some boulder 10Be ages are younger than the U-series minimum age, indicating that surface cobbles and some boulders were partially shielded after deposition of the fan and have been subsequently exhumed by erosion of fine-grained matrix to expose them on the present fan surface. A comparison of U-series and 10Be ages indicates that the interval between final alluvial deposition on the T2 fan surface and accumulation of dateable carbonate is not well resolved at Biskra Palms; however, the “time lag” inherent to dating via U-series on pedogenic carbonate can be no larger than ?10 k.y., the uncertainty of the 10Be-derived age of the T2 fan surface. Dating of the T2 fan surface via U-series on pedogenic carbonate (minimum age, 45.1 ± 0.6 ka) and 10Be on boulder-top samples using forward modeling (preferred age, 50 ± 5 ka) provides broadly consistent constraints on the age of the fan surface and helps to elucidate its postdepositional development.

Fletcher, Kathryn E. K.; Sharp, Warren D.; Kendrick, Katherine J.; Behr, Whitney M.; Hudnut, Kenneth W.; Hanks, Thomas C.

2010-01-01

350

Digital data sets that describe aquifer characteristics of the Tillman terrace and alluvial aquifer in southwestern Oklahoma  

USGS Publications Warehouse

ARC/INFO export and nonproprietary format files This diskette contains digitized aquifer boundaries and maps of hydraulic conductivity, recharge, and ground-water level elevation contours for the Tillman terrace and alluvial aquifer in southwestern Oklahoma. The Tillman terrace aquifer encompasses the unconsolidated terrace deposits and alluvium associated with the North Fork of the Red River and the Red River in the western half of Tillman County. These sediments consist of discontinuous layers of clay, sandy clay, sand, and gravel. The aquifer extends over an area of 285 square miles and is used for irrigation and domestic purposes. Granite and the Hennessey Formation outcrop in northern parts of the aquifer where alluvial deposits are absent. These outcrops were included as part of the aquifer in a thesis that modeled the ground-water flow in the aquifer. Most of the aquifer boundaries and some of the lines in the hydraulic conductivity and recharge data sets were extracted from a published digital surficial geology data set based on a scale of 1:250,000. Most of the lines in the hydraulic conductivity, recharge, and 1969 water-level elevation contour data sets, and one line in the aquifer boundary data set were digitized from a paper map published at a scale of 1:249,695 in a thesis in which the ground-water flow in the aquifer was modeled. Ground-water flow models are numerical representations that simplify and aggregate natural systems. Models are not unique; different combinations of aquifer characteristics may produce similar results. Therefore, values of hydraulic conductivity and recharge used in the model and presented in this data set are not precise, but are within a reasonable range when compared to independently collected data.

Becker, C. J.; Runkle, D. L.; Rea, Alan

1997-01-01