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1

Quaternary stratigraphy, geochronology and carbon isotope geology of alluvial deposits in the Texas panhandle  

NASA Astrophysics Data System (ADS)

Sedimentology, stratigraphy, and stable carbon isotopy were used to reconstruct geologic and climatic events on the Texas southern High Plains from ca. 13,000 yr B.P. to the present. The alluvial sediments in Yellowhouse and Blackwater Draws were used to construct the geologic history. The oldest valley alluvium comprises more than 13,000 yr B.P. fluvial sediments that were incised and buried by fluvial and lacustrine mediments dating ca. 13,000 to 4900 yr B.P. Lucustrine waters changed from ologotrophic to eutrophic and finally calcalitrophic. Regional valley erosion at 4900 yr. B.P. developed a widespread disconformity within the Yellowhouse Draw formation, which separates lower fluvial and lacustrine sediments (ca. 13,000 to 4900 yr B.P.) from the overlying sediments dating 4900 yr B.P. to present. After 4900 yr B.P., intermittent streams and eolian processes deposited several meters of sand the length of each valley. Clenegas returned to downstream reaches of both draws after 1500 to 2000 yr B.P.

Stafford, T. W., Jr.

1984-06-01

2

Alluvial deposition and lake-level fluctuations forced by Late Quaternary climate change: the Dead Sea case example  

Microsoft Academic Search

Based on geomorphic observations, we discuss lake-level fluctuations, alluvial deposition and river entrenchment in the Dead Sea–Wadi Araba area. The bulk of alluvium in the northern Wadi Araba was probably deposited before the Lisan period of lake transgression that started at about 70 kyears B.P. The lake reached a maximum elevation about 150 m below sea level (b.s.l.), possibly around

Y. Klinger; J. P. Avouac; D. Bourles; N. Tisnerat

2003-01-01

3

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

4

Age and origin of alluvial sediments within and flanking the Mt Lofty Ranges, southern South Australia: a Late Quaternary archive of climate and environmental change  

Microsoft Academic Search

Quaternary alluvial sediments occur within and on the flanks of the Mt Lofty Ranges of southern South Australia. Within the ranges they occupy colluvium-filled bedrock depressions, alluvial-fan sequences at hill\\/plain junctions and river terraces that flank major streamlines in both locations. Sediments ranging in age throughout the Quaternary have been identified, but this paper focuses on those deposits of Late

R. P. Bourman; J. R. Prescott; D. Banerjee; N. F. Alley; S. Buckman

2010-01-01

5

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

6

Late Quaternary alluviation and offset along the eastern Big Pine fault, southern California  

NASA Astrophysics Data System (ADS)

Determining late Quaternary offset rates on specific faults within active mountain belts is not only a key component of seismic hazard analysis, but sheds light on regional tectonic development over geologic timescales. Here we report an estimate of dip slip rate on the eastern Big Pine oblique-reverse fault in the upper Cuyama Valley within the western Transverse Ranges of southern California, and its relation to local landscape development. Optically stimulated luminescence (OSL) dating of sandy beds within coarse-grained alluvial deposits indicates that deposition of alluvium shed from the Pine Mountain massif occurred near the southern margin of the Cuyama structural basin at the elevation of the Cuyama River between 25 and 14 ka. This alluvial deposit has been offset ˜ 10 m vertically by the eastern Big Pine fault, providing a latest Quaternary dip slip rate estimate of ˜ 0.9 m/ky based on a 50° fault dip. Incision of the adjacent Cuyama River has exposed a section of older Cuyama River sediments beneath the Pine Mountain alluvium that accumulated between 45 and 30 ka on the down-thrown footwall block of the eastern Big Pine fault. Corroborative evidence for Holocene reverse-slip on the eastern Big Pine fault is ˜ 1 m of incised bedrock that is characteristically exposed beneath 2 3.5 ka fill terraces in tributaries south of the fault. The eastern Big Pine fault in the Cuyama Valley area has no confirmed record of historic rupture; however, based on our results, we suggest the likelihood of multiple reverse-slip rupture events since 14 ka.

Delong, Stephen B.; Minor, Scott A.; Arnold, Lee J.

2007-10-01

7

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

8

Late Quaternary alluvial fans and paleosols of the Kangra basin, NW Himalaya: Tectonic and paleoclimatic implications  

Microsoft Academic Search

The paper describes Late Quaternary pedosedimentary sequences of the alluvial fans from the Kangra basin of NW Himalayas for tectonic and paleoclimatic implications. In the proximal part of the Kangra basin three coalescing alluvial fans, namely Rait-Rihlu fans (~65 km2), Kangra fans (~200 km2), and Palampur fans (~170 km2) from west to east evolved due to reactivation of longitudinal and transverse faults and

P. Srivastava; M. K. Rajak; L. P. Singh

2009-01-01

9

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

10

Alluvial Fans as Recorders of Landscape Development: Potential for Determining Depositional Chronologies Using Luminescence Dating  

NASA Astrophysics Data System (ADS)

Alluvial fans in both arid and humid environments provide a record of depositional events at the transition between mountain and lowland environments. Though complex in the detail of their depositional and erosional characteristics, they undoubtedly provide a valuable record of the highest erosion rate events in their upland catchments. Alluvial fans often also record tectonic activity; their mountain-front location is ideal to intersect bounding faults, and their characteristic geometry renders offsets easily recognisable. Dating of Quaternary alluvial fans can be accomplished using a number of techniques. These include radiocarbon dating where suitable organic materials are preserved; uranium series methods may be applied to provide a minimum age by dating carbonate inter-clast cements in some arid or semi-arid environments; terrestrial cosmogenic nuclide (TCN) methods work well in many dryland contexts though issues of inheritance in some catchments are significant. Optically stimulated luminescence (OSL) and infrared stimulated luminescence (IRSL) rely on light sensitive charge populations trapped at meta-stable centers associated with impurities in quartz and feldspar grains. When grains are exposed to light, charge is evicted from these traps, and is slowly re-tapped by interaction with environmental ionizing radiaton. These signals have the potential to date a range of Quaternary sediments including alluvial fans on timescales of one year to several hundred thousand years. The specific issues relating to alluvial fans are problems of incomplete signal zeroing caused by rapid deposition, as well as low sensitivity and poor signal characteristics for quartz OSL. In this presentation, we explore the relative importance of these issues in determining luminescence chronologies for alluvial fans in different locations, and the ways in which these chronologies may be used to help inform models of landscape evolution, both numerical and conceptual.

Lawson, M. J.; Rhodes, E. J.; Roder, B. J.; Antinao, J.; McDonald, E.

2011-12-01

11

Mt. Chambers Creek alluvial fan - a recorder for Late Quaternary flow regime changes along the eastern Flinders Ranges (South Australia)  

NASA Astrophysics Data System (ADS)

Climate is a primary control on Late Quaternary alluvial fan evolution and past hydrological changes should be sensitively recorded in alluvial fan stratigraphy. The Flinders Ranges (S Australia) are situated between tropical and extra-tropical (e.g. westerlies) elements of the atmospheric circulation. Numerous alluvial fans constitute the transition between the Flinders Ranges and the large salt lake system of Lake Frome to the east. Along the arid eastern margin of the Flinders Ranges, geomorphology and stratigraphy were investigated at Mt. Chambers Creek alluvial fan (31°S). The fan is connected to a ~380 km2 catchment via the Mt. Chambers gorge, which has incised into the uplifted range front. Upstream of the gorge, manifold exposures along valley fills provide evidence for a generally fining-upward sequence of fluvial gravels and (eolian?) silts, which are topped by thick layers of tufa that have subsequently incised. Downstream of the apex, the alluvial fan surface is characterized by relatively low slopes (~0.5° - 1.5°) and a complex pattern of desert pavements, overlain by several inactive feeder channels and/or floodouts. The modern channel drains into an active floodout approximately 13 km downstream of the fan apex, showing that significant quantities of coarse-grained sediment load do not currently reach the baselevel at Lake Frome. Mt. Chambers Creek has incised several meters into the fan body, exposing extensive outcrops of alluvial fan sediments and paleosols. Generally, the fan stratigraphy can be divided into six different units, each of them bounded by laterally continuous and mostly carbonaceous paleosol horizons. The lowermost four units are dominated by matrix- and clast supported gravels, indicating high-energy events such as hyperconcentrated and debris flows. Along the distal fan, the thickness of these units and grain size generally decreases, locally exposing a sequence of well-developed and buried desert pavements. In combination, these observations imply environmental conditions favourable of increased frequency and/or magnitude during the deposition of units 1-4 under wetter climatic conditions. In contrast, unit 5 consists of silts and carbonatic gravel deposits, containing numerous fragments of well-rounded carbonate nodules, likely indicating the onset of upstream erosion leading to reworking of paleosols and tufa deposits. The uppermost unit 6 is composed of mainly fluvial sands and pebbles and seems to be limited to the distal fan, where it corresponds to the currently observed floodout dynamics. In combination with new radiocarbon and OSL dates (currently in progress), the correlation of downstream alluvial fan stratigraphy and upstream catchment dynamics provides the base for a much more reliable reconstruction of alluvial fan history and flow regime changes over the Late Quaternary. Thereby, our results will provide an important link between existing regional paleoclimatic records from Lake Frome (lake level variations) and the Flinders Ranges (loessic valley fills), eventually helping to decipher the relative roles of the southern westerlies vs. tropical moisture sources over the Late Quaternary.

May, Jan-Hendrik; Larsen, Joshua; Cohen, Timothy; Nanson, Gerald

2010-05-01

12

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

13

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

14

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

SciTech Connect

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.

Donald S. Sweetkind; Ronald M. Drake II

2007-01-22

15

Characterizing avulsion stratigraphy in ancient alluvial deposits  

Microsoft Academic Search

Guidelines for identifying ancient avulsion deposits were set forth by Kraus and Wells [Kraus, M.J., Wells, T.M., 1999. Recognizing avulsion deposits in the ancient stratigraphical record. In: Smith, N.D., Rogers, J. (Eds.), Fluvial Sedimentology VI, Special Publication of the International Association of Sedimentologists, vol. 28, pp. 251–268], building on the study by Smith et al. [Smith, N.D., Cross, T.A., Dufficy,

H. L. Jones; E. A. Hajek

2007-01-01

16

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

17

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

18

GIS analysis of depositional slope change at alluvial-fan toes in Japan and the American Southwest  

Microsoft Academic Search

Slope change at alluvial-fan toes provides a clue to understanding differences between alluvial fans and other depositional landforms. This paper analyses topographic data for 430 alluvial fans and their adjacent lowlands in Japan and the American Southwest (ASW), typical humid and arid regions with abundant alluvial fans. Arcs showing fan toes were identified and representative areas above and below each

Akiko Hashimoto; Takashi Oguchi; Yuichi Hayakawa; Zhou Lin; Kyoji Saito; Thad A. Wasklewicz

2008-01-01

19

Hydrogeologic features of the alluvial deposits in the Greybull River valley, Bighorn Basin, Wyoming  

USGS Publications Warehouse

The alluvial aquifer along the Greybull River in Wyoming, consists principally of the Greybull terrace doposits and flood-plain alluvium but also includes Burlington terrace deposits east of Burlington, the McKinnie terrace, and the younger, generally undissected alluvial-fan deposits. Well-log data and 18 surface-resistivity measurements at four localities indicate that the thickness of the alluvial aquifer is as much as 60 feet thick only near Burlington and Otto. The most favorable area for development of ground water from the alluvial aquifer is near Burlington and Otto where relatively large amounts of water can be obtained from the Greybull terrace deposits and the flood-plain alluvium. Elsewhere, the deposits of the alluvial aquifer yield only small amounts of water to wells. (Woodard-USGS)

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

1979-01-01

20

Quaternary evolution of a large alluvial fan in a periglacial setting (Crau Plain, SE France) constrained by terrestrial cosmogenic nuclide (10Be)  

NASA Astrophysics Data System (ADS)

Located in the foreland of the Western Alps, the Crau Plain was the outlet of the Durance River in the Pleistocene. In order to constrain its geodynamic evolution in terms of chronology and denudation rates, the two main Quaternary deposits of this plain have been studied based on cosmogenic nuclide 10Be concentration measurements along depth profiles. The abandonment of the Miramas and Luquier alluvial surfaces occurred at the beginning of glacial periods, Würm (isotopic stage 4) and Riss (isotopic stage 6), respectively. Discrepancy in denudation rates under similar geomorphological and lithological conditions suggests different denudation processes during glacial and interglacial periods. The denudation rate has been estimated at about 25 mm ka? 1 for the interglacial period and about 60 mm ka? 1 for the glacial period. The abandonment of the Crau Plain as the outlet of the Durance River occurred sometime between 75 and 35 ka.

Molliex, Stéphane; Siame, Lionel L.; Bourlès, Didier L.; Bellier, Olivier; Braucher, Régis; Clauzon, Georges

2013-08-01

21

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

22

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  

Microsoft Academic Search

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

Lewis A. Owen; Robert C. Finkel; M. Haizhou; Patrick L. Barnard

2006-01-01

23

Digital data sets that describe aquifer characteristics of the alluvial and terrace deposits along the Cimarron River from Freedom to Guthrie in northwestern Oklahoma  

USGS Publications Warehouse

ARC/INFO export and nonproprietary format files This diskette contains digitized aquifer boundaries, maps of hydraulic conductivity, recharge, and ground-water level elevation contours for the alluvial and terrace deposits along the Cimarron River from Freedom to Guthrie in northwestern Oklahoma. Ground water in 1,305 square miles of Quaternary-age alluvial and terrace deposits along the the Cimarron River from Freedom to Guthrie is an important source of water for irrigation, industrial, municipal, stock, and domestic supplies. Alluvial and terrace deposits are composed of interfingering lenses of clay, sandy clay, and cross-bedded poorly sorted sand and gravel. The aquifer is composed of hydraulically connected alluvial and terrace deposits that unconformably overlie the Permian-age Formations. The aquifer boundaries are from a ground-water modeling report on the alluvial and terrace aquifer along the Cimarron River from Freedom to Guthrie in northwestern Oklahoma and published digital surficial geology data sets. The aquifer boundary data set was created from digital geologic data sets from maps published at a scale of 1:250,000. The hydraulic conductivity values, recharge rates, and ground-water level elevation contours are from the ground-water modeling report. Water-level elevation contours were digitized from a map at a scale of 1:250,000. The maps were published at a scale of 1:900,000. 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, Donna; Rea, Alan; Cederstrand, J. R.

1997-01-01

24

Fault-scarp morphology and amount of surface offset on late-Quaternary surficial deposits, eastern escarpment of the central Sierra Nevada, CA  

Microsoft Academic Search

Faults scarps, formed on glacial deposits and an alluvial fan near the east-central Sierra Nevada mountain front by late-Quaternary movement on the Hilton Creek (HCF), Wheeler Crest (WCFZ) and Coyote Warp (CWFZ) fault zones, were profiled to determine the amount and to estimate the recency of fault offset. Areas studied include McGee (N--near Lake Crowley), Pine, Mount Tom, Basin Mountain,

1992-01-01

25

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

26

Early Devonian synorogenic alluvial-fan deposits of the Maccullochs Range, western New South Wales  

Microsoft Academic Search

The Early Devonian, Maccullochs Range beds (new) of the Winduck Interval largely comprise non-marine fine-grained sheet-flood-deposited sandstones which lie in the southeast sector of the Darling Basin Conjugate Fault System. Deposition of the >2.5 km-thick sequence occurred on the Wilcannia, Towers and Coolabah Bore alluvial fans, that were sourced largely from lightly indurated sandstone caps overlying a large basement high lying

G. Neef

2007-01-01

27

Geological provenance of Quaternary deposits from the southeastern Brazilian coast  

NASA Astrophysics Data System (ADS)

Natural gamma radiation measurements of beach sand deposits were performed with the aim of understanding the provenance and transport processes of sediments along the coastal zone of three Brazilian States. The method employs thorium, uranium and potassium as tracers of the mineralogical properties of beach sand minerals, which reflect the geological history of transport and sorting processes. A considerable positive correlation with the geological evolution of these Quaternary coastal deposits was observed.

Anjos, R. M.; Veiga, R.; Carvalho, C.; Macario, K. D.; Gomes, P. R. S.

2007-05-01

28

Geotechnical mapping for alluvial fan deposits controlled by active faults: a case study in the Erzurum, NE Turkey  

NASA Astrophysics Data System (ADS)

Erzurum, the biggest city of Eastern Anatolia Region in the Turkey, is located in Karasu Plain. Karasu Plain, located on the central segment of the Erzurum Fault Zone, is an intermountain sedimentary basin with a Miocene-Quaternary volcanic basement, andesitic-basaltic lava flows and fissure eruptions of basaltic lava. It was filled in the early Quaternary by lacustrine fan-delta deposits. The basin is characterized by NNE-SSW trending sinistral wrench faults on its eastern margin and ENE-WSW trending reverse faults on its southern margin. Both systems of active faults intersect very near to Erzurum, which is considered to be the most likely site for the epicenter of a probable future large earthquake. Historical records of destructive earthquakes, morphotectonic features formed by paleo-seismic events and instrument seismic data of region indicate to a very high regional seismicity. The residential areas of Erzurum are located on thick alluvial fan deposits forming under the control of faults on the central segment of the Erzurum Fault Zone, which is one of the most active fault belts of the East Anatolian Region. Over time, the housing estates of city such as Yenisehir and Yildizkent have been expanded toward to the west and southwest part of Erzurum as a consequence of rapid and massive construction during the last 30 years. Geotechnical investigation has therefore been undertaken the residential areas of city in order to characterize geotechnical properties over the varied lithologies examine the potential for geotechnical mapping and assess the foundation conditions of the present and future settlement areas. The geological field observations and operations have been performed to make the soil sampling and characterize the lateral and vertical changes in thickness of the alluvial deposits in trenches, excavations and deep holes with 6-12 m sections. The soil samples have been subjected to a series of tests under laboratory conditions to obtain physical and mechanical properties. Furthermore, the standard penetration tests have been applied to the soils under field conditions. The geological field observations, geotechnical data and distribution of bearing capacity have been considered for the geotechnical mapping. Based on the geotechnical map, there are five geotechnical zones distinguished in the study area.

Yarbasi, Necmi; Kalkan, Ekrem

2009-08-01

29

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

30

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

31

An alluvial record of El Niño events from northern coastal Peru  

Microsoft Academic Search

Overbank flood deposits of northern coastal Peru provide the potential for the development of a late Quaternary chronology of El Niño events. Alluvial deposits from the 1982-1983 El Niño event are the basis for establishing a type El Niño deposit. Sedimentary structures suggesting depositional processes range from sheet flows to debris flows, with sheet flood deposits being the most common.

Lisa E. Wells

1987-01-01

32

Digital data sets that describe aquifer characteristics of the alluvial and terrace deposits along the North Canadian River from Canton Lake to Lake Overholser in Central 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 North Canadian River from Canton Lake to Lake Overholser in central Oklahoma. Ground water in approximately 400 square miles of Quaternary-age alluvial and terrace aquifer is an important source of water for irrigation, industrial, municipal, stock, and domestic supplies. The aquifer consists of clay, silt, sand, and gravel. Sand-sized sediments dominate the poorly sorted, fine to coarse, unconsolidated quartz grains in the aquifer. The hydraulically connected alluvial and terrace deposits unconformably overlie Permian-age formations. The aquifer is overlain by a layer of wind-blown sand in parts of the area. Most of the lines in the aquifer boundary, hydraulic conductivity, and recharge data sets were extracted from published digital surficial geology data sets 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. 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.; Rea, Alan; Runkle, D. L.

1997-01-01

33

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

NASA Astrophysics Data System (ADS)

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 µg/L to 191 µg/L with a mean concentration of 33 µg/L. Groundwater is mainly Ca-HCO3 type with high concentrations of dissolved As, Fe, and Mn, but low level of SO4. The uppermost aquifer occurs between 10 m and 80 m below the surface that has a mean arsenic concentration of 35 µg/L. Deeper aquifer (> 100 m depth) has a mean arsenic concentration of 18 µg/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.

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

2008-07-01

34

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

2008-04-10

35

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

36

Preservation of daily tidal cycles and stacked alluvial swamp deposits: Depositional response to early compaction of buried peat bodies  

SciTech Connect

The character of the clastic depositional environments represented in the lower Mary Lee coal zone of the Pennsylvanian Pottsville Formation in the Warrior basin Alabama (tidally influenced mud flats and alluvial swamps) was controlled by the compaction of buried peat bodies. The lowest mineable coal in the Mary Lee coal zone, the Jagger, is overlain by laminated shale and sandstone exhibiting pronounced cycle bedding. This bedding records daily tidal cyclicity in the form of sand-mud couplets. These correspond to flood-current deposition of the coarser fraction followed by fallout of the finer grained fraction during ensuing slack-water periods. These couplets are cyclically bundled-sandier bundles corresponding to spring tides and muddier bundles to neap tides (lamination counts suggest a 24-30-day cycle). The clastic sequence above the overlying Blue Creek coal is characterized by a series of stacked alluvial swamp horizons. These can be identified by autochthonous fossil plants and pedological features indicative of gleyed paleosols. Catastrophic flooding buried and preserved these horizons. The rapid, early compaction of the buried Jagger and Blue Creek peat bodies created accommodation space that allowed both the preservation of tidalites in the Jagger coal to Blue Creek coal interval and the stacking of alluvial swamp paleosols above the Blue Creek seam. Carboniferous peats were comprised of highly compressible plant parts and hence, were sensitive to sediment loading. Once the peat bodies had compressed to a certain extent, stability of the overlying sediment surface created conditions amenable to resumption of peat accumulation.

Demko, T.M.; Gastaldo, R.A. (Auburn Univ., AL (USA))

1990-05-01

37

High resolution sequence stratigraphy and reservoir architecture of proximal alluvial deposits: The Buntsandstein facies of central Spain  

SciTech Connect

The Buntsandstein facies outcrops along a 12 km long, 150 m thick cuesta near Ayllon (Central Spain). The outcrop study is based on vertical sedimentological sections and continuous photo paneling, and demonstrates the presence of two depositional systems: an alluvial fan system in the lower half of the outcrop, and a straight and braided river system in the upper part of the outcrop. This overall evolution is probably related to base-level fall to base-level rise cycle, in which the reservoir architecture is linked to genetic units stacking pattern: during the base-level fall, the alluvial fan is prograding over sand flat and sandy alluvial plain deposits. Coarse and pebbly proximal sandsheets are interbedded with finer reddish distal deposits. Reservoirs units are laterally continuous, but silty alluvial plain deposits constitute vertical permeability barriers, during base-level stillstand, erosive channels and sandsheets are vertically amalgamated. Reservoirs units are laterally continuous and vertically connected, during the base-level rise, alluvial fan deposits are overlapped by straight river deposits. Reservoirs units are laterally connected but silty argillaceous alluvial plain horizons are preserved, at the end of the base-level rise, braided and straight river deposits are amalgamated. Fully connected, these reservoirs units have a very large lateral extension. A lithofacies database is compiled on this outcrop, and variograms, horizontal and vertical proportion curves are completed. Each stage of the base-level cycle is then quantitatively characterized by a specific heterogeneity pattern. The outcrop study will improve the prediction of reservoir extension and architecture in subsurface gas storage of the Paris basin.

Oliver, L.; Desaubliaux, G. [Institut Francais du Petrole, Rueil-Malmaison (France); Verdier, F. [Gaz de France, Denis (France)] [and others

1995-08-01

38

Late Quaternary depositional history of the Albemarle Embayment, NC  

SciTech Connect

The depositional history of Albemarle Embayment documents deep fluvial incisement by the Roanoke River system during glacial episodes and subsequent infilling by fluvial-estuarine-barrier island sediment sequences during interglacial transgressions. Unraveling the Holocene time slice will help reconstruct complex Quaternary records of multiple incisement and backfilling. A network of drill holes, vibracores, and seismic data suggest a four-phase infill history over the last 12,000 years. (1) Lower Roanoke River: (a) Bedload-charged, braided fluvial systems deposited basal sequences of sand and gravel prior to [approximately]5,000 BP. (b) Aggradational, swamp-forest floodplains developed [approximately]5,000 BP and bound the modern incised channels characterized by minimal bedload sedimentation. (2) Albemarle sound: (a) In the central basin, the basal channel sand sequence is overlain by an open estuarine, highly interlaminated sand and mud sequence that accumulated between [approximately]12,000 BP and [approximately]2,000 BP. (b) Depositional patterns within this unit suggest multiple oscillations of Holocene sea level that caused channel reincisement and subsequent backfilling. (c) Present estuarine marsh sedimentation began in protected coastal areas [approximately]5,000 BP. (3) Outer banks: (a) Barrier islands first influenced sedimentation in the area after [approximately]5,000 BP producing a semi-enclosed Albemarle Sound. (b) Deposition within the central basin shifted to uniform organic-rich muds that grade eastward into overwash and inlet sands. (4) Modern man: (a) colonial development within the drainage basins in the early 1700's AD produced a wedge of orange mud in inner Albemarle Sound. (b) Dam construction in the 1950's terminated orange mud deposition and the central basin reverted to organic-rich mud sedimentation.

Riggs, S.R.; Klingman, C.R.; Wyrick, R.A. (East Carolina Univ., Greenville, NC (United States). Dept. of Geology)

1993-03-01

39

Rock magnetic properties of a soil developed on an alluvial deposit at Buttermilk Creek, Texas, USA  

NASA Astrophysics Data System (ADS)

The evolution of magnetization within a floodplain soil begins with initial deposition of magnetic particles during sedimentation and continues via subsequent alteration and growth of iron-bearing compounds by pedogenic and biologic processes. Measurements of soil magnetic properties capture information about the developmental history of the soil and are a convenient method by which to investigate environmental change and pedogenesis. Using a range of magnetic measurements, a comprehensive scenario for soil development was constructed for floodplain sediments at the Debra L. Friedkin site, an important archeological site near Buttermilk Creek, Texas. Floodplain deposits have traditionally been avoided for soil magnetism studies because it is thought that the episodic input of sediment would form soils characterized by discrete sedimentary units rather than a continuous record of pedogenesis. We demonstrate that alluvial deposits can sometimes carry a straightforwardly interpretable magnetic signal similar to those typically seen in loess deposits. Smooth variation of rock magnetic parameters as a function of depth also leads us to conclude that the soil at this site is largely undisturbed and that the age of lithic artifacts found within the soil may be interpreted within stratigraphic context.

Lindquist, Anna K.; Feinberg, Joshua M.; Waters, Michael R.

2011-12-01

40

Digital data sets that describe aquifer characteristics of the alluvial and terrace deposits along the North Canadian River from Oklahoma City to Eufaula Lake in east-central 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 North Canadian River from Oklahoma City to Eufaula Lake in east-central Oklahoma. Ground water in 710 square miles of Quaternary-age alluvial and terrace deposits along the North Canadian River is an important source of water for irrigation, industrial, municipal, stock, and domestic supplies. The aquifer, composed of alluvial and terrace deposits, consists of sand, silt, clay, and gravel. The aquifer is underlain and in hydraulic connection with the upper zone of the Permian-age Garber-Wellington aquifer and the Pennsylvanian-age Ada-Vamoosa aquifer. Most of the lines in the four digital data sets were digitized from a published ground-water modeling report but portions of the aquifer boundary data set was extracted from published digital geologic data sets. 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, Donna; Rea, Alan; Becker, C. J.

1997-01-01

41

Late Quaternary evolution of alluvial fans in the Playa, El Fresnal region, northern Chihuahua desert, Mexico: Palaeoclimatic implications  

Microsoft Academic Search

The Playa El Fresnal area is a tilted terrane characteristic of an extensional basin. It is a half graben\\/tilted-block system with a playa-lake on the basin floor flanked by piedmonts covered by alluvial fans. Structural heterogeneities within normal fault zones influenced the geomorphic expression of the uplifted footwall blocks of associated volcanism, and the downdropped hanging wall. The footwall area

J. Ortega-Ramírez; J. M. Maillol; W. Bandy; A. Valiente-Banuet; J. Urrutia Fucugauchi; J. Medina-Sánchez; G. J. Chacón-Cruz

2004-01-01

42

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

43

Geotechnical mapping for alluvial fan deposits controlled by active faults: a case study in the Erzurum, NE Turkey  

Microsoft Academic Search

Erzurum, the biggest city of Eastern Anatolia Region in the Turkey, is located in Karasu Plain. Karasu Plain, located on the\\u000a central segment of the Erzurum Fault Zone, is an intermountain sedimentary basin with a Miocene-Quaternary volcanic basement,\\u000a andesitic-basaltic lava flows and fissure eruptions of basaltic lava. It was filled in the early Quaternary by lacustrine\\u000a fan-delta deposits. The basin

Necmi Yarbasi; Ekrem Kalkan

2009-01-01

44

Geologically recent near-surface faulting in the Valley and Ridge Province: New exposures of extensional faults in alluvial deposits, Giles County, SW Virginia  

SciTech Connect

New excavations along the north side of the New River Valley between Pembroke and Pearisburg in Giles County, Virginia, have revealed two extensional faults cutting a series of alluvial terrace deposits composed of stratified, but unconsolidated, conglomerates, gravels and silts. Although the age of neither the faults nor the sediments is currently known, the unconsolidated nature of the alluvial deposits suggests that both are, geologically, relatively recent (tertiary or Quaternary). Both faults dip away from the New River valley and are marked by 15--20 cm wide zones of clay-rich gouge. Within these gouge zones, the basal planes of individual clay grains are oriented parallel to the planar gouge zones margins and define a macroscopic foliation. This foliation truncates stratification in both the adjacent hangingwall and footwall of each fault and is oriented at a high angle to stratification. No dragging over of stratification into the fault zones is observed. Foliation development is inferred to have involved recrystallization of clay minerals, probably in association with fluid flow along the fault zones. The authors currently interpret these features as indicating that the faults formed in response to tectonic rather than surficial processes. Seismic monitoring studies over the last twenty years in this part of the Valley and Ridge Province have indicated that earthquake foci are located within crystalline basement beneath the thrust zone detachment surface at depths greater than 5 km. No seismic or geological evidence for near-surface faulting appears to have previously been recorded in this area. Therefore, these faults are of considerable importance to both the assessment of seismic hazard and to the understanding of fault development in this area as they indicate the, at least local occurrence, of geologically recent near-surface faulting.

Bollinger, G.A.; Law, R.D.; Pope, M.C.; Wirgart, R.H.; Whitmarsh, R.S. (Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States). Dept. of Geological Sciences)

1992-01-01

45

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

Microsoft Academic Search

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

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

2007-01-01

46

Models of deposition of loess and loessoids in the upper quaternary of South America  

Microsoft Academic Search

Climatic changes occurred in South America during the Quaternary provoked deflation and deposition of large masses of silt, which formed loess and loessoid units of regional extension in several areas of the continent. An analysis of the most important Late Pleistocene and Holocene loess and loess-like deposits resulted in the identification of five types of transport and deposition of wind-blown

Martín H. Iriondo

1997-01-01

47

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

48

Quaternary Stratigraphy and Depositional Environments, Santa Monica Bay, Southern California.  

National Technical Information Service (NTIS)

High-resolution seismic-reflection profiles were used in conjunction with 51 vibracores to examine the Quaternary stratigraphy of the Santa Monica Shelf, southern California. Upper Pleistocene strata are confined to the central part of the shelf between t...

R. H. Osborne R. C. Scheidemann T. R. Nardin A. S. Harper

1980-01-01

49

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

50

Latest Quaternary outer shelf and slope deposits, northern Gulf of Mexico, USA: Industry research consortium  

Microsoft Academic Search

A consortium of oil companies is undertaking a multiyear shallow coring and high-resolution seismic investigation of the outer shelf-slope deposits of the northern Gulf of Mexico. The program's objective is to reconstruct the depositional, seismic stratigraphic, biostratigraphic, isotopic, and organic geochemical record of the latest Quaternary of a portion of the Gulf margin. Results will serve as an analog to

R. D. Jr

1991-01-01

51

Groundwater vulnerability map for the Ebro alluvial aquifer between Jalón and Ginel tributaries (Spain)  

Microsoft Academic Search

The Quaternary deposits of the Ebro Basin in the surroundings of Zaragoza (Spain) form an unconfined alluvial aquifer with a high degree of permeability and low thickness of unsaturated materials. This fact causes a high degree of vulnerability to contamination, which implies consequences for land-use decisions and the risk management of existing industrial facilities. In addition, in the last decades

M. T. Lamelas; O. Marinoni; A. Hoppe; J. de La Riva

2007-01-01

52

Glaciers and Late Quaternary glacial deposits of Turkey  

NASA Astrophysics Data System (ADS)

Turkish glaciers and Late Quaternary glacial deposits are observed in 3 regions: 1. The Taurus Mountain Range (Mediterranean coast and SE Turkey): Two thirds of the present day glaciers are concentrated in the SE part. Among these mountains, Mount Cilo (4168 m) alone supports more than ten glaciers, couple of them 4 km long. In the central part, Aladag (3756 m) and Bolkardag (3524 m) Mountains contain few small glaciers. Small ice caps developed on top of both mountains in Pleistocene. Several U-shaped valleys were carved by glaciers that formed different types of moraines. Even though there are signs of past glacial activity in Beydag (3086 m), Akdag (3016 m) and Sandiras Mountains (2295 m) no glaciers are present in the W Taurus Mountains today. 2. The Pontic Mountain Range (E Black Sea coast): The highest peak is Mount Kaçkar (3932 m) where five glaciers are developed. Several other mountains such as Verçenik (3710 m), Bulut (3562 m), Altiparmak (3353 m), Karagöl (3107 m) and Karadag (3331 m) also support various glaciers. Large U-shaped valleys containing terminal, lateral and ground moraines are observed although the present humid climatic conditions altered most of them. 3. Volcanoes and independent mountain chains scattered in the Anatolian Plateau: The volcanoes in the interior of the country support active glaciers and show signs of past glacial activity. Among them, Mount Agri (Ararat) (5165 m) is the only mountain on which a 10 km2 recent ice cap is developed. Eleven glaciers emerged from the summit, descending down to 3900 m on the N-facing slope and 4200 m on the S facing slope. The near absence of moraines can be explained by the lack of confining ridges to control valley glaciers, by insufficient debris load in the ice to form moraines and by volcanic eruptions that later covered the pre-existing moraines. Other important volcanoes, Mount Süphan (4058 m) and Mount Erciyes (3916 m) also contain active glaciers and well preserved moraines. Apart from the volcanoes, few other mountains in Central Anatolia, such as Uludag (2543 m), Mercan (3368 m) and Mescid (3239 m) bear signs of past glacial activity. The absence of dating of the morainic landforms makes it difficult to assign a precise age to the past glacial periods. However a project that aims to establish glacial chronlogies for the above mentioned mountains by using in situ cosmogenic 36Cl in the moraines, is recently developed. The data available on glaciers indicate that the most recent glacier retreat probably started at the beginning of the 20th century, becoming faster since the 1930's. This shrinkage trend is yet to be quantified by additional field observations in order to understand the glacier evolution of Turkey.

Çiner, A.

2003-04-01

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

Analysis of temperature effect on ceramic brick production from alluvial deposits, Tamilnadu, India  

Microsoft Academic Search

This study focuses on the thermal behaviour of alluvial clays in the production of ceramic brick industries, which are largely found on the bank of the Cauvery river, Tamilnadu, India. Clay bars were prepared which consisted of quartz, kaolinite, illite, chlorite, feldspars and iron oxides. The test samples were fired in the range of 700–1100°C and were examined with chemical

C. Manoharan; P. Sutharsan; S. Dhanapandian; R. Venkatachalapathy; R. Mohamed Asanulla

2011-01-01

55

Facies analysis of tertiary alluvial fan deposits in the Jundiaí region, São Paulo, southeastern Brazil  

Microsoft Academic Search

This article presents an analysis of facies of sedimentary sequences that occur as discontinuous bodies in the Jundiaí region, west of the main Tertiary continental basins of the southeastern Brazil continental rift. Nine identified sedimentary facies, grouped into four associations, suggest the existence of an ancient alluvial fan system whose source area was the Japi mountain range (Serra do Japi).

M. A. Neves; N. Morales; A. R. Saad

2005-01-01

56

Overlapping of pedogenesis and meteoric diagenesis in distal alluvial and shallow lacustrine deposits in the Madrid Miocene Basin, Spain  

NASA Astrophysics Data System (ADS)

The Miocene distal alluvial fan and palustrine deposits of the Madrid Basin (Paracuellos de Jarama area) were examined to establish the sequence of its pedogenic diagenetic processes and the main factors controlling them. In this area the diagenetic processes operated not only on carbonates, as commonly studied, but also in high magnesium clays and opaline cherts. This paper provides a dynamic model for saline alkaline lake margins that complements the existing freshwater palustrine model. Three sections (BER, PEL and UPC) containing limestones, sepiolite, dolostones and opaline cherts were examined; these represent the entire transition from alluvial fan deposit to lake environment. The alluvial fan deposits (PEL section) show the most complex sequence of processes. After a weak edaphic imprint, the primary mudstone and siltstones are affected by silicification (opaline levels formed mainly by selective replacement of sepiolites) and later dolomitization. Several types of dolomite are present, rounded crystals, spherules and globular bodies being the most characteristic. In the ponds situated at the foot of the alluvial fans or in interfan areas, sepiolite precipitated within free water bodies (BER section) and an intense pedogenesis led to the formation of palustrine sepiolite deposits. Later, the intense silicification of the sepiolite produced lenticular opaline levels that were locally transformed to quartz by aging. In the shallow lakes (UPC section), palustrine limestones and sepiolite were deposited. The carbonates are partially affected by silicification, the sepiolite becoming completely silicified. The opaline levels clearly preserve the structure of the limestones and sepiolite host rocks. All the opaline levels show local aging processes. The silicification processes were different in the three settings due to the interplay of groundwater with sedimentary environments and facies. In the distal alluvial fan sediments of the PEL section, the initial host rock affected by silicification is not preserved due to the later dolomitization that erased both it and its textures. The silicification environment was therefore not easy to determine. In the BER and UPC section, the main silicification took place in groundwater-influenced environments but evidence was seen of cements and silicifications in vadose environments. In all study settings, the overlapping of pedogenic, vadose and groundwater processes was controlled by changes in the position of the water table. Four stages were concluded to explain the transformation from the primary deposits to the later dolomitization process and the formation of vadose cements. The majority of the silicifications seen occurred as responses to changes in the water table position linked to the aggradation of this closed basin. In all the studied environments, the sepiolite deposits were preferentially silicified; their fibrous structure and high absorption capacity helping to retain interstitial fluids. Moreover sepiolite and opal are stable under relatively similar geochemical conditions in arid environments. The dissolution of the sepiolite caused an increase in silica in the interstitial fluids, favouring silicification and ruling out the need of a biogenic source. The replacement of limestones by silica is usually driven by variations in pH and salinity, which are very common in surface environments such as shallow lakes and soils.

Bustillo, M. A.; Alonso-Zarza, A. M.

2007-06-01

57

Elevated Mercury Concentrations in Alluvial Deposits of the Humid Tropics of South America: Natural vs. Anthropogenic Sources  

NASA Astrophysics Data System (ADS)

Mercury (Hg) amalgamation is extensively used throughout the humid tropics of South America for the extraction of fine-gold particles from secondary ore deposits. Early studies of water, sediments and fish generally concluded that these gold mining operations have extensively contaminated the aquatic environment. However, investigations along a 900-km reach of the Maderia River, Brazil suggest that while Hg values in sediments and water are above global averages, the high mercury levels are largely due to natural sources. Of primary significance is the inability to distinguish between Hg concentrations in upland soils (oxisols) and modern channel and floodplain deposits. Spatial trends in the data suggest that the impact of anthropogenically released Hg from mine sites is relatively localized. This conclusion is supported by other, independent studies in the Rio Negro basin where elevated Hg values were found in terrace deposits in spite of the fact that no modern mining activities are known to occur within the watershed. Moreover, Roulet and his colleagues have demonstrated using mass balance calculations that within the Tapajos River basin as much as 97 percent of Hg in the alluvial deposits is derived from Hg enriched oxisols eroded during deforestation. In a regional examination of Hg levels within alluvial deposits of Essequibo and Mazaruni Rivers of Guyana, we again found that Hg levels were above both regional background values (10 to 80 ppb) and global averages. However, deforestation within these watersheds is limited, reducing the influx of Hg from eroded upland soils. In addition, the spatial trends in Hg concentrations suggest a closer link between mining activities and Hg values than is found in Maderia River of Brazil. It is unclear at this time, however, whether the primary Hg source in Guyana is the direct input of Hg to the river during amalgamation, or to the influx of Hg enriched soils eroded during the dredging of channel bed sediments and hydraulic mining of floodplain materials.

Miller, J. R.; Lechler, P. J.

2001-12-01

58

Analysis and assessment on heavy metal sources in the coastal soils developed from alluvial deposits using multivariate statistical methods.  

PubMed

An investigation on heavy metal sources, i.e., Cu, Zn, Ni, Pb, Cr, and Cd in the coastal soils of Shanghai, China, was conducted using multivariate statistical methods (principal component analysis, clustering analysis, and correlation analysis). All the results of the multivariate analysis showed that: (i) Cu, Ni, Pb, and Cd had anthropogenic sources (e.g., overuse of chemical fertilizers and pesticides, industrial and municipal discharges, animal wastes, sewage irrigation, etc.); (ii) Zn and Cr were associated with parent materials and therefore had natural sources (e.g., the weathering process of parent materials and subsequent pedo-genesis due to the alluvial deposits). The effect of heavy metals in the soils was greatly affected by soil formation, atmospheric deposition, and human activities. These findings provided essential information on the possible sources of heavy metals, which would contribute to the monitoring and assessment process of agricultural soils in worldwide regions. PMID:18976857

Li, Jinling; He, Ming; Han, Wei; Gu, Yifan

2008-09-16

59

Pleistocene alluvial deposits dating along frontal thrust of Changhua Fault in western Taiwan: The cosmic ray exposure point of view  

NASA Astrophysics Data System (ADS)

To tackle the history of active thrusts, it is necessary to open the observation window on time scales on the order of 104-105 years by studying the surface morphologies resulting from their activities. Because fluvial systems are particularly sensitive to recent environmental changes, geomorphic features such as alluvial terraces are frequently used as markers to gauge tectonic deformation. Together with the measurement of cumulative displacements, the chronological framework of emplacement and abandonment of these geomorphic markers is thus fundamental to determine long-term fault slip-rates. In Taiwan, the geomorphic features associated with fault activity have been studied in detail with a high level of resolution; however, the use of deformed and partially preserved alluvial terraces is often hampered by the absence of well-documented ages. The purpose of this paper is two-fold. First, we take the opportunity to review the chronological constraints that have been published in Taiwan so far. Second, we present how the cosmogenic dating method (in situ-produced 10Be) can be used to constraint the chronological framework of alluvial deposits over a Pleistocene time scale. Thanks to a comparison of our cosmogenic-derived ages with existing data, we present a consistent regional chronological framework for the Pakua-Tadu area along the Changhua Fault, one of the most active frontal thrusts in the Western Foothills of the Taiwan mountain belt. We also discuss its relationships with global eustatism and its tectonic implications for the timing of propagation of the deformation front during the last 450 kyr.

Siame, Lionel L.; Chen, Rou-Fei; Derrieux, Florence; Lee, Jian-Cheng; Chang, Kuo-Jen; Bourlès, Didier L.; Braucher, Régis; Léanni, Laetitia; Kang, Chu-Chun; Chang, Chung-Pai; Chu, Hao-Tsu

2012-06-01

60

A refined characterization of the alluvial geology of yucca flat and its effect on bulk hydraulic conductivity  

USGS Publications Warehouse

In Yucca Flat, on the Nevada National Security Site in southern Nevada, the migration of radionuclides from tests located in the alluvial deposits into the Paleozoic carbonate aquifer involves passage through a thick, heterogeneous section of late Tertiary and Quaternary alluvial sediments. An understanding of the lateral and vertical changes in the material properties of the alluvial sediments will aid in the further development of the hydrogeologic framework and the delineation of hydrostratigraphic units and hydraulic properties required for simulating groundwater flow in the Yucca Flat area. Previously published geologic models for the alluvial sediments within Yucca Flat are based on extensive examination and categorization of drill-hole data, combined with a simple, data-driven interpolation scheme. The U.S. Geological Survey, in collaboration with Stanford University, is researching improvements to the modeling of the alluvial section, incorporating prior knowledge of geologic structure into the interpolation method and estimating the uncertainty of the modeled hydrogeologic units.

Phelps, G.A.; Halford, K.J.

2011-01-01

61

Elevated marine deposits in Bermuda record a late Quaternary megatsunami  

NASA Astrophysics Data System (ADS)

Deposits of coral-bearing, marine shell conglomerate exposed at elevations higher than 20 m above present-day mean sea level (MSL) in Bermuda and the Bahamas have previously been interpreted as relict intertidal deposits formed during marine isotope stage (MIS) 11, ca. 360 420 ka before present. On the strength of this evidence, a sea level highstand more than 20 m higher than present-day MSL was inferred for the MIS 11 interglacial, despite a lack of clear supporting evidence in the oxygen-isotope records of deep-sea sediment cores. We have critically re-examined the elevated marine deposits in Bermuda, and find their geological setting, sedimentary relations, and microfaunal assemblages to be inconsistent with intertidal deposition over an extended period. Rather, these deposits, which comprise a poorly sorted mixture of reef, lagoon and shoreline sediments, appear to have been carried tens of meters inside karst caves, presumably by large waves, at some time earlier than ca. 310 360 ka before present (MIS 9 11). We hypothesize that these deposits are the result of a large tsunami during the mid-Pleistocene, in which Bermuda was impacted by a wave set that carried sediments from the surrounding reef platform and nearshore waters over the eolianite atoll. Likely causes for such a megatsunami are the flank collapse of an Atlantic island volcano, such as the roughly synchronous Julan or Orotava submarine landslides in the Canary Islands, or a giant submarine landslide on the Atlantic continental margin.

McMurtry, Gary M.; Tappin, David R.; Sedwick, Peter N.; Wilkinson, Ian; Fietzke, Jan; Sellwood, Bruce

2007-08-01

62

Elevated Marine Deposits in Bermuda Record a Late Quaternary Megatsunami  

NASA Astrophysics Data System (ADS)

Deposits of coral-bearing, marine shell conglomerate exposed at elevations higher than 20 m above present- day mean sea level (MSL) in Bermuda and the Bahamas have previously been interpreted as relict intertidal deposits formed during marine isotope stage (MIS) 11, ca. 360-420 ka before present. On the strength of this evidence, a sea level highstand more than 20 m higher than present-day MSL was inferred for the MIS 11 interglacial, despite a lack of clear supporting evidence in the oxygen-isotope records of deep-sea sediment cores. We have critically re-examined the elevated marine deposits in Bermuda, and find their geological setting, sedimentary relations, and microfaunal assemblages to be inconsistent with intertidal deposition over an extended period. Rather, these deposits, which comprise a graded and poorly sorted mixture of reef, lagoon and shoreline sediments, appear to have been carried tens of meters inside karst caves, presumably by large waves, at some time earlier than ca. 310-360 ka before present (MIS 9-11). Unlike earlier work, e.g. Hearty (1997) who found evidence for large waves impacting the Bahamas but could not distinguish between the competing mechanisms of a large storm or a tsunami, we have clear evidence that points to a tsunami as source, and by analysis of the deposit microfaunal diversity, an indication of the direction of the past waves, in this case from the east-southeast. We hypothesize that these deposits are the result of a large tsunami during the mid-Pleistocene, in which Bermuda was impacted by a wave set that carried sediments from the surrounding reef platform and nearshore waters over the eolianite atoll. Likely causes for such a megatsunami are the flank collapse of an Atlantic island volcano, such as the roughly synchronous Julan or Orotava submarine landslides in the Canary Islands, or a giant submarine landslide on the Atlantic continental margin.

McMurtry, G. M.; Tappin, D. R.; Sedwick, P. N.; Wilkinson, I. P.; Fietzke, J.; Sellwood, B. W.

2006-12-01

63

Provenance of alluvial fan deposits to constrain the mid-term offsets along a strike-slip active fault: the Elsinore fault in the Coyote Mountains, Imperial Valley, California.  

NASA Astrophysics Data System (ADS)

The lateral variation in rates along a fault and its constancy along time is a matter of discussion. To give light to this discussion, short, mid and long term offset distribution along a fault is needed. Many studies analyze the short-term offset distribution along a strike-slip fault that can be obtained by the analysis of offset features imprinted in the morphology of the near-fault area. We present an example on how to obtain the mid- to long-term offset values based on the composition of alluvial fans that are offset by the fault. The study area is on the southern tip of the Elsinore fault, which controls the mountain front of the Coyote Mountains (California). The Elsinore-Laguna Salada fault is part of the San Andreas fault (SAF) system, extending 250 km from the Los Angeles Basin southeastward into the Gulf of California, in Mexico. The slip-rate on the southern Elsinore fault is believed to be moderate based on recent InSAR observations, although a recent study near Fossil Canyon (southern Coyote Mountains) suggests a rate in the range of 1-2 mm/yr. For this study we processed the airborne LiDAR dataset (EarthScope Southern & Eastern California, SoCal) to map short to mid-term alluvial offsets. We reprocessed the point clouds to produce DEMs with 0.5m and 0.25m grids and we varied the insolation angles to illuminate the various fault strands and the offset features. We identified numerous offset features, such as rills, channel bars, channel walls, alluvial fans, beheaded channels and small erosional basins that varied in displacement from 1 to 350 m. For the mid- to long-term offsets of the alluvial fans we benefited from the diverse petrological composition of their sources. Moreover, we recognized that older alluvium, which is offset by greater amounts, is in some cases buried beneath younger alluvial fan deposits and separated by buried soils. To determine the source canyon of various alluvial elements, we quantified the clast assemblage of each source basin and each alluvial fan on both sides of the fault. To accomplish this, we used a portable grid and classified more than 300 clasts at each of more than 90 sites along the fault. We found a very good fit between displaced alluvial fan elements and their inferred source canyons, but a poor match with the alluvium from neighboring canyons, which allows us to resolve the long-term offset. Planned dating of the pedogenic carbonate associated with these buried soils will allow the resolution of the mid- to long-term slip rates over multiple time frames to test the constancy of fault slip rate during the late Quaternary, as well as to test the lateral variations in rate along the fault.

Masana, Eulalia; Stepancikova, Petra; Rockwell, Thomas

2013-04-01

64

A silicified bird from Quaternary hot spring deposits  

Microsoft Academic Search

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

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

2005-01-01

65

Depositional environments of quaternary peats, Yukon Delta, Alaska  

SciTech Connect

The stratigraphy and composition of the peats on the Yukon Delta are strongly affected by their formation in a high-latitude deltaic environment. These properties may be used to recognize coals formed under similar depositional and climatic conditions. 6 refs.

Klein, J.P.; Dupre, W.R.

1980-01-01

66

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

67

Geogene and anthropogenic controls on the mineralogy and geochemistry of modern alluvial–(fluvial) gold placer deposits in man-made landscapes in France, Switzerland and Germany  

Microsoft Academic Search

Five study areas in the Cévennes, France, the Gotthard Massif, Switzerland, and from the western edge of the Bohemian Massif, Germany, have been selected for an investigation of the natural and human impacts on modern alluvial–(fluvial) gold placer deposits. The current investigation involved the study of grain-related parameters such as morphology, grain size and accessory minerals in gold aggregates in

H. G. Dill

2008-01-01

68

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

69

Tectonic significance of Upper Cretaceous alluvial-fan deposits in the Peninsular Ranges forearc basin complex, Baja California (Mexico)  

SciTech Connect

Recent evidence suggests that forearc basins, previously depicted as broad downwarps, may experience syndepositional faulting and/or folding. The upper Campanian El Gallo Formation, which was deposited along the northern margin of the Rosario embayment of the peninsula Ranges forearc basin complex, records tilting of the underlying arc massif basement contemporaneous with dissection of the arc source terrane. The La Escarpa member at the base of the El Gallo Formation consists of a 100-180-m thick upward-fining sequence, interpreted as a retrogradational proximal to distal alluvial-fan deposit. Overlying the La Escarpa member is the 1,000-m thick El Disecado member, which lies at the top of the El Gallo Formation and consists of sandy fluvial deposits. Conglomerate clast counts from the La Escarpa member and point-count data from sandstones throughout the El Gallo Formation show an upsection increase in granitic and metasedimentary rock fragments relative to volcanic/metavolcanic rock fragments, reflecting unroofing and progressive headward erosion of the source terranes in the Peninsular Ranges. Paleocurrent data from the La Escarpa and El Disecado members suggest a rotation of approximately 110{degree} with time, from west-northwesterly to southerly, reflecting tilting of the basin floor. This may have been accomplished by downdropping along an east-west-trending fault that divided the Rosario embayment into separate subbasins during the Cretaceous.

Fulford, M.; Busby-Spera, C. (Univ. of California, Santa Barbara (USA))

1990-05-01

70

Saline-water contamination in Quaternary deposits and the Poplar River, East Poplar Oil Field, northeastern Montana  

USGS Publications Warehouse

The extent of saline-water contamination in Quaternary deposits in and near the East Poplar oil field may be as much as 12.4 square miles and appears to be present throughout the entire saturated zone. The saline-water contamination affects 9-60 billion gallons of ground water. Saline- contaminated water moves westward through Quaternary glacial deposits and merges with southward-flowing water in Quaternary alluvium in the Poplar River valley. Saline ground water discharges into the Poplar River, and increases the dissolved-solids and chloride concentrations of the river. The probable source of saline-water contamination in the Quaternary deposits is brine that is a byproduct of the production of crude oil in the East Poplar oil field study area.

Thamke, J. N.; Craigg, S. D.

1997-01-01

71

Slope Deposits and (Paleo)Soils as Geoarchives to Reconstruct Late Quaternary Environments of Southern Africa  

NASA Astrophysics Data System (ADS)

Although it is clear that large, rapid temperature changes have occurred during the last glacial-interglacial cycle and the Holocene in southern Africa, we have only limited, and often imprecise, knowledge of how the major moisture-bearing atmospheric circulation systems have reacted to these changes. Using slope deposits and soils as palaeoclimatic geoarchives we will overcome these constraints. The role of many geoarchives in the reconstruction of the Quaternary climate in southern Africa remains controversial, since the paleoclimate data are based on evidence from marine cores, lake sediments, speleothems and spring sinter, fluvial sediments, aeolian sands and dust, colluvium, and coastal sediments. To elucidate climate controls on Quaternary landscape evolution and to use these data for palaeoclimatic reconstructions, thus far slope deposits and soils have been investigated. Climatic controls on these cycles are incompletely known. The availability of results from earlier fieldwork, micromorphology, Optical Stimulated Luminescence (OSL), 14C dating and stable carbon isotope analysis will permit a thorough assessment of slope deposits and soils in terms of their palaeoenvironmental potential. The knowledge of suitable areas and sites in different climatic zones of southern Africa where slope deposits and soils have already been found document the late Quaternary climatic history and even climatic anomalies (e.g. Younger Dryas period at Eksteenfontein, 8.2 ka event at Tsumkwe, 4 ka event in the Auob valley, Little Ice Age in the Namib Desert). The findings will show the late Quaternary history of precipitation fluctuations, of the shifting of the ITCZ (and the ABF - Agulhas-Benguela Front), of wind intensities and directions, and of extreme precipitation events. The project will employ state-of-the-art geoscience methodology to interpret the record of precipitation changes of the late Quaternary, including the shifting of the summer and winter rain belts, the chronology of catastrophic floods, the wind intensity and direction, and the role climatic factors may have played for prehistoric cultures. We will use shallow geophysical surveys as ground penetrating radar, electrical resistivity tomography and seismic refraction to differentiate sediments and the layers within them. Drilling is needed to recover samples and cores. Remote sensing will basicly help to calculate the spreading of slope deposits in mountainous areas and escarpments. Sedimentological and pedogenetical lab analysis (XRF, XRA, element analysis etc.) is used to identify finger prints of special sediment units, their sources and transportation rates. OSL and other dating methods will give the needed chronostratigraphical informations. High resolution late Quaternary records are provided by analysing the interstratification of slope deposits and soils with fluvial, lacustrine and aeolian sediment sequences. Earlier research has shown that aeolian and fluvial processes were active at the same time in the southwestern Kalahari during the LGM, documented by sequences of alternate bedding of aeolian, colluvial and fluvial sediments. The interfingering of slope deposits with fluvial flood sediments (slackwater deposits) in Namib Desert valleys document extreme precipitation events in the upper highland catchments and rains at the same time in the desert itself. The program will generate space and time transgressive models of slope deposit formation and soil development and identify key parameters controlling slope processes. These results will provide a solid base for evaluation and assessment of precipitation conditions and erosion/sedimentation processes for southern Africa under global warming conditions.

Huerkamp, K.; Voelkel, J.; Heine, K.; Bens, O.

2009-04-01

72

Alluvial plains and earthquake recurrence at the Coalinga anticline  

SciTech Connect

Having approached 0.5 m during the May 2 earthquake, the uplift of Quaternary deposits on the Coalinga anticline may provide evidence of the average repeat time of similar earthquakes during the recent geologic past. Stein and King (1984) estimated the average late Quaternary repeat time to be 500 to 1,500 yr from the degree of folding in the upper Pliocene and Pleistocene Tulare Formation; in addition, they estimated the average Holocene repeat time to be at least 200 to 600 yr on the basis of an alluvial-plain profile near Los Gatos Creek, whose arroyo extends across the Coalinga anticline from the synclinal Pleasant Valley into the synclinal San Joaquin Valley. In this chapter, the authors estimate an average repeat time from the stratigraphy of Holocene alluvium exposed in the walls of that arroyo. Largely deposited overbank, this alluvium reveals the approximate configuration of former alluvial plains whose present configuration over the anticline should reflect the rate of anticlinal growth. Resulting constraints on the Holocene uplift rate, though made uncertain by possible differences in the initial configuration of the alluvial plains, suggest an average repeat time of at least 200 to 1,000 yr for major (M = 6-7) Coalinga-area earthquakes during the late Holocene.

Tucker, A.B. (San Jose State Univ., CA (USA)); Donahue, D.J.; Jull, A.J.T (Univ. of Arizona, Tucson (USA)); Payen, L.A. (Univ. of California, Riverside (USA)); Atwater, B.F.; Trumm, D.A.; Tinsley, J.C. III; Stein, R.S.

1990-01-01

73

Geomorphological and sedimentological features in Quaternary fluvial systems affected by solution-induced subsidence (Ebro Basin, NE-Spain)  

NASA Astrophysics Data System (ADS)

The Quaternary evolution and the morpho-sedimentary features of some of the most important rivers in Spain (Ebro and Tagus rivers among others) have been controlled by subsidence due to alluvial karstification of the evaporitic bedrock. The subsidence mechanism may range from catastrophic collapse to slow sagging of the alluvium by passive bending. In the Ebro Basin, the mechanisms and processes involved in karstic subsidence were studied through the analysis of present-day closed depressions as well as through old subsidence depressions (palaeocollapses and solution-induced basins) and associated deformations recorded in the Quaternary alluvial sediments. The Gállego-Ebro river system is presented as a case study of channel adjustments and geomorphic and sedimentary evolution of fluvial systems in dissolution-induced subsidence areas. In this fluvial system, evaporite dissolution during particular Quaternary time intervals (namely early and middle Pleistocene) have lead to the development of a solution-induced basin, approximately 30 km-long by 8 km-wide, filled by Quaternary deposits with a total thickness in excess of 190 m. The main river response to balance the subsidence in the alluvial plain was aggradation in the central reach of the subsiding area, and degradation both in the upstream reach and in the valley sides where alluvial fans and covered pediments may prograde over the fluvial sediments. The main sinking areas are recognized in the sedimentary record by anomalous thickenings in the alluvial deposits and fine-grained sediments deposited in backswamp and ponded areas.

Benito, Gerardo; Gutiérrez, Francisco; Pérez-González, Alfredo; Machado, Maria J.

2000-06-01

74

Late Quaternary incision and deposition in an active volcanic setting: The Volturno valley fill, southern Italy  

NASA Astrophysics Data System (ADS)

Extensive illustration of depositional facies, ostracod and foraminiferal assemblages, and Late Quaternary stratigraphic architecture is offered for the first time from beneath the modern coastal plain of Volturno River, the longest river in southern Italy. Proximity to an active volcanic district, including quiescent Vesuvius Volcano, provides an easily identifiable stratigraphic marker (Campania Grey Tuff or CGT), up to 55 m thick, emplaced 39 ky cal BP by a large-volume explosive pyroclastic eruption. Identification of top CGT to a maximum depth of 30 m allows tracing out the shape of a 15–20 km wide Late Quaternary palaeovalley incised by Volturno River into the thick ignimbritic unit immediately after its deposition. A terraced palaeotopography of the valley flanks is reconstructed on the basis of core data. Above the basal fluvial deposits, the early Holocene transgressive facies consist of a suite of estuarine (freshwater to brackish) deposits. These are separated from overlying transgressive barrier sands by a distinctive wave ravinement surface. Upwards, a distinctive shallowing-upward succession of middle–late Holocene age is interpreted to reflect initiation and subsequent progradation of a wave-dominated delta system, with flanking strandplains, in response to reduced rate of sea-level rise. The turnaround from transgressive to highstand conditions is identified on the basis of subtle changes in the meiofauna. These enable tracking of the maximum flooding surface into its updip (lagoonal/estuarine) counterpart, thus highlighting the role of refined palaeontological criteria as a powerful tool for high-resolution sequence-stratigraphic studies.

Amorosi, Alessandro; Pacifico, Annamaria; Rossi, Veronica; Ruberti, Daniela

2012-12-01

75

Debris-flow deposits in an alluvial-plain succession: The upper Triassic Callide coal measures of Queensland, Australia  

SciTech Connect

The Carnian-Rhaetian Callide Coal Measures are preserved in a small (22.5 km by 8 km), partially fault-bounded basin remnant in east-central Queensland, Australia. The <150 m thick coal-measure succession is interpreted to have accumulated during a phase of mild crustal extension that formed a series of discrete, intermontane basins in eastern Australia. The succession fines upward from a conglomerate-rich lower part into a finer-grained and coal-bearing upper section (including coal seams <34 m thick), and is interpreted as the deposits of an alluvial-plain environment. Anomalous, matrix-rich diamictites, breccias, and conglomerates have been recognized within the succession at several localities, in many cases interbedded with coals. These are interpreted as the product of debris flows. Two debris-flow lithofacies are recognized: (1) mixtures of fine carbonaceous material, clay, silt, sand, gravel, and volcaniclastic debris, and (2) breccias consisting principally of coal clasts in a coaly matrix with minor clastic and volcaniclastic debris. The distribution of debris flows in the Callide Coal Measures shows a coincidence with mapped faults and interpreted structural lineaments. The debris flows may have been triggered by fault movements, which formed rupture topography on the flat alluvial plain, and caused destabilization of water-saturated clastic and organic sediments. Some debris-flow bodies may have been mounded, such that subsequent peat formation was restricted until those bodies were buried. The preservation of debris-flow units at different stratigraphic levels along mapped structures suggests multiple paleoseismic events or multiple debris-flow units at different stratigraphic levels along mapped structures suggests multiple paleoseismic events or multiple debris-flow events along those structures. The mixing of volcaniclastic debris into debris-flow facies suggests that seismic events were coincident with (or perhaps caused by) nearby, explosive volcanic activity. The close relationship between debris-flow deposits and thick coal bodies on the inferred downthrown sides of faults at Callide further suggests that periodic, tectonic subsidence may have facilitated thick coal accumulation.

Jorgensen, P.J.; Fielding, C.R. [Univ. of Queensland, Brisbane (Australia). Dept. of Earth Sciences

1999-09-01

76

Groundwater vulnerability map for the Ebro alluvial aquifer between Jalón and Ginel tributaries (Spain)  

Microsoft Academic Search

The Quaternary deposits of the Ebro Basin in the surroundings of Zaragoza (Spain) form an unconfined alluvial aquifer with\\u000a a high degree of permeability and low thickness of unsaturated materials. This fact causes a high degree of vulnerability\\u000a to contamination, which implies consequences for land-use decisions and the risk management of existing industrial facilities.\\u000a In addition, in the last decades

M. T. Lamelas; O. Marinoni; A. Hoppe; J. de la Riva

2007-01-01

77

Sequence stratigraphy of the late Quaternary deposits in the central Yellow Sea  

NASA Astrophysics Data System (ADS)

High-resolution (Chirp and Sparker system) seismic profiles and piston core samples were analyzed to investigate the sequence stratigraphy of late Quaternary in the central Yellow Sea. Approximately 52,610 line-km data of chirp and sparker profiles was acquired. Along with seismic profiling, 16 piston core samples collected in 1998 and 1999. We also used a deep drill core to interpret the sedimentary sequences. In this study High-resolution seismic profiles and deep drill core show the complex sedimentary structure. The late Quaternary deposits in the study area can be divided into five sedimentary units (units CY1, CY2, CY3, CY4, and CY5 from the oldest to youngest) bounded by an erosional surface and internal seismic reflectors: (1) regressive estuarine/deltaic deposits (unis CY1), (2) transgressive incised channel fill (unit CY2), (3) transgressive sand sheet (unit CY3), (4) transgressive sand ridges (unit CY4), and (5) prodelta/recent mud (unit CY5). Based on the interpretation of high-resolution seismic records and correlation with the YSDP-105 and piston cores, lower sequence (DI) correspond to the falling stage systems tract regarded as regressive estuarine or deltaic deposits (unit CY1), whereas upper sequence (DII) consists of a set of the transgressive (units CY2, CY3, and CY4) and highstand systems tract (unit CY5) formed since the last-glacial period.

Bae, S.-H.; Kim, D.-C.; Lee, G.-S.; Yi, H.-I.; Cho, H.-G.

2012-04-01

78

Investigating Plant Patterns on Alluvial Fan Deposits of the Mojave Desert Using High Resolution Imagery  

NASA Astrophysics Data System (ADS)

Maps of desert vegetation derived from low-altitude, high-resolution imagery were combined with detailed geologic mapping to address how the spatial distribution of individual plants varies with fan position and mapped geologic unit. We collected Color Infrared (CIR) imagery along two proximal to distal fan transects in the Mojave Desert, CA from a helicopter platform; because of its small pixel size (3 cm to 20 cm) and sensitivity to vegetation, this imagery is ideal for analyzing spatial patterns of individual plants. Four band ratios were calculated from the CIR imagery; a three-band composite image of these ratios provides a base map that discriminates individual plants and is sensitive to the amount of photosynthetic material in the plant. An expert classifier was used to produce an automated, georeferenced vegetation map that includes both green vegetation and non-photosynthetic vegetation (NPV), from which percent cover and location of plants were derived. By analyzing the vegetation data in concert with detailed geologic mapping (e.g. 1:20, 1:500), we can address whether mapped geologic units influence plant location and density. Two plots along the CIR transects were compared in a preliminary analysis: one representing distal fan flora and geomorphology and one representing proximal fan flora and geomorphology. The georeferenced CIR imagery was used to map the discrete location of every plant in the two plots (3500 plants over 10000 m2). Because each plant has a georeferenced location, point pattern analysis can be used to determine 1) whether the plants exhibit spatial structure, and 2) whether any spatial structure can be attributed to alluvial fan position or mapped geologic unit. Several differences between the plots were observed. First, the proximal plot has more variety (11 species vs. 4), more individual plants (2000 vs. 1500), and denser cover (27 percent cover vs. 24) than the distal plot. Second, the two major species present in both plots, Larrea tridentata (LT) and Ambrosia dumosa (AD), exhibit spatial structure. AD exhibits strong clustering in both the proximal and distal plots; LT exhibits weak clustering between 5 and 10 m in the proximal plot and weak dispersion in the distal plot between 4 to 8 m. These plot scale patterns can then be compared to the spatial structure within individual geologic units.

Phelps, G. A.; Robinson, S.; Miller, D. M.

2005-12-01

79

Late Quaternary Deposition Rate In The Okinawa Trough And Climate Change  

NASA Astrophysics Data System (ADS)

The deposition rates in Okinawa Trough range about 10--30 cm/ka with 21.1 cm/ka in average based on the AMS14C datings of 11 cores. The patterns are that the sedimentation rates in continental slop and trough slop are higher than that in trough bottom, and the western slop are higher than the eastern side. The sedimentation rates gradually decrease from west to east, demonstrate that the sediment supply from the Chinese mainland is the major source. 2 depocenters with more than 40 m thick of the Yangtze River delta during Late Pleistocene were discovered in water depth of 80--100 m of the East China Sea. The deposition rate in OIS 2 is higher than that of the OIS 1 except the south Trough. During the LGM sea level fall 130--150 m and shoreline was close to the shelf edge, a great amount of sediments entered directly the Okinawa Trough leading to high deposition rate. As the sediments mainly consisting of continental matters, higher sedimentation rates generally corresponded to heavier ?18O values and some sudden coolings. The main factor of influencing the deposition rates in Okinawa Trough is climate change. Keywords: Late Quaternary, Okinawa Trough, deposition rate

Liu, Z.; Li, T.; Xiong, Y.; Liu, Y.

2003-04-01

80

Preliminary description of quaternary and late pliocene surficial deposits at Yucca Mountain and vicinity, Nye County, Nevada  

SciTech Connect

The Yucca Mountain area, in the south-central part of the Great Basin, is in the drainage basin of the Amargosa River. The mountain consists of several fault blocks of volcanic rocks that are typical of the Basin and Range province. Yucca Mountain is dissected by steep-sided valleys of consequent drainage systems that are tributary on the east side to Fortymile Wash and on the west side to an unnamed wash that drains Crater Flat. Most of the major washes near Yucca Mountain are not integrated with the Amargosa River, but have distributary channels on the piedmont above the river. Landforms in the Yucca Mountain area include rock pediments, ballenas, alluvial pediments, alluvial fans, stream terraces, and playas. Early Holocene and older alluvial fan deposits have been smoothed by pedimentation. The semiconical shape of alluvial fans is apparent at the junction of tributaries with major washes and where washes cross fault and terrace scarps. Playas are present in the eastern and southern ends of the Amargosa Desert. 39 refs., 9 figs., 1 tab.

Hoover, D.L.

1989-11-01

81

High-resolution sequence stratigraphy from piezocone tests: an example from the Late Quaternary deposits of the southeastern Po Plain  

Microsoft Academic Search

Cone penetration tests are traditionally regarded as a major tool for geotechnical investigations. This study, based upon interpretation of 234 cone penetration tests with pore-pressure measurements (piezocone tests or CPTU), carried out in the Late Quaternary deposits of the southeastern Po Plain, shows how CPTU tests can also be used for sedimentological purposes, including detailed facies characterization, subsurface stratigraphic correlations,

Alessandro Amorosi; Nazaria Marchi

1999-01-01

82

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

83

High-Resolution Subsurface Imaging and Stratigraphy of Quaternary Deposits, Marapanim Estuary, Northern Brazil  

NASA Astrophysics Data System (ADS)

The Marapanim estuary is situated in the Para Coastal Plain, North Brazil. It is characterized by an embayed coastline developed on Neogene and Quaternary sediments of the Barreiras and Pos-Barreiras Group. This system is strongly influenced by macrotidal regimes with semidiurnal tides and by humid tropical climate conditions. The interpretation of GPR-reflections presented in this paper is based on correlation of the GPR signal with stratigraphic data acquired on the coastal plain through five cores that were taken along GPR survey lines from the recent deposits and outcrops observed along to the coastal area. The profiles were obtained using a Geophysical Survey Systems Inc., Model YR-2 GPR, with monostatic 700 MHz antenna that permitted to get records of subsurface deposits at 20m depth. Were collected 54 radar sections completing a total of 4.360m. The field data were analyzed using a RADAN software and applying different filters. The interpretation of radar facies following the principles of seismic stratigraphy that permitted analyze the sedimentary facies and facies architecture in order to understand the lithology, depositional environments and stratigraphic evolution of this sedimentary succession as well as to leading to a more precise stratigraphic framework for the Neogene to Quaternary deposits at Marapanim coastal plain. Facies characteristics and sedimentologic analysis (i.e., texture, composition and structure aspects) were investigated from five cores collected through a Rammkernsonde system. The locations were determined using a Global Positioning System. Remote sensing images (Landsat-7 ETM+ and RADARSAT-1 Wide) and SRTM elevation data were used to identify and define the distribution of the different morphologic units. The Coastal Plain extends west-east of the mouth of the Marapanim River, where were identified six morphologic units: paleodune, strand plain, recent coastal dune, macrotidal sandy beach, mangrove and salt marsh. The integration of GPR profiles and stratigraphy data allowed for the recognition of paleochannel geometry, with width of 150m and depth of 20m, developed on Barreiras Group, two discontinuity surfaces and three facies associations organized into sedimentary facies: (i) Tidal channel with mottled sand, Conglomerate with clay pebble and Ophiomorpha/linear Skolithos, channel-fill and tabular cross-bedding sand and sand/mud interlayer facies. (ii) Dune/interdune with wavy bedding and cross-bedding sand and planar bedding and tabular cross-bedding sand facies. (iii) infilled tidal channel with mottled sand, planar/flaser bedding sand, lenticular bedding clay and sand/mud interlayer facies. The present study demonstrates that some facies associations occur restricts to tidal paleochannels and shows features well preserved that are very important to reconstruction of the relative sea-level history in the Marapanim Estuary.

Silva, C. A.; Souza Filho, P. M.; Gouvea Luiz, J.

2007-05-01

84

Impacts of Urban Development on Channel Slope, Erosion, and Depositional Processes  

Microsoft Academic Search

Watershed land uses, including urbanization, influence erosion and depositional processes in a tributary to the Navarro basin in north coastal California. The Robinson Creek subwatershed is deeply incised into easily erodible Quaternary alluvial river and terrace valley-fill deposits in the vicinity of the urbanizing town of Boonville. Remnant riparian forest vegetation exists at the top of the terrace. Detailed field

J. L. Florsheim

2007-01-01

85

Quaternary investigation  

SciTech Connect

The primary purpose of the Quaternary investigation is to provide information on the location and age of Quaternary deposits for use in evaluating the presence or absence of neotectonic deformation or paleoliquefaction features within the Savannah River Site (SRS) region. The investigation will provide a basis for evaluating the potential for capable faults and associated deformation in the SRS vicinity. Particular attention will be paid to the Pen Branch fault.

Stieve, A.

1991-05-15

86

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

87

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

88

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

89

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

90

Late Quaternary sedimentation on the Mid-Atlantic Reykjanes Ridge: clay mineral assemblages and depositional environment  

Microsoft Academic Search

Sediment samples from the Mid-Atlantic Reykjanes Ridge (59°N) were taken to get information about sediment genesis and to\\u000a identify different sources during the late Quaternary. Samples were investigated by X-ray diffraction and grain-size analyses.\\u000a The clay mineral assemblages in sediments of the Reykjanes Ridge reflect paleoceanographic changes during the late Quaternary.\\u000a Holocene sediments are characterized by high contents of smectite,

B. Gehrke; K. S. Lackschewitz; H.-J. Wallrabe-Adams

1996-01-01

91

OSL chronology of Quaternary terraced deposits outcropping between Mt. Etna volcano and the Catania Plain (Sicily, southern Italy)  

NASA Astrophysics Data System (ADS)

In this paper we tested the applicability of the Optically Stimulated Luminescence (OSL) technique through Single-Aliquot Regenerative-dose (SAR) protocol, on single grain quartz extracted from alluvial-coastal sediments. Five samples were collected from deposits belonging to a flight of seven orders of coastal-alluvial terraces outcropping in the area between Mt. Etna volcano and the Catania Plain (Sicily, southern Italy), at the front of the Sicilian fold and thrust system. After various performance tests, we obtained OSL ages ranging between 240 ± 12 and 80 ± 4 ka, consistent with the normal evolutionary model of a terraced sequence, moving from the highest to the lowest elevation. Obtained data allowed us to determine a mean uplift rate of 1.2 mm/year during the last 240 ka, mostly related to regional uplift processes coupled with sea-level changes. Moreover, terraces belonging to the two highest orders are folded, forming a large anticline. According to our results, the frontal thrust of the Sicilian chain was active between 236 and 197 ka ago, even though seismological and geodetic data suggest current activity to the back.

Ristuccia, Gloria M.; Di Stefano, Agata; Gueli, Anna M.; Monaco, Carmelo; Stella, Giuseppe; Troja, Sebastiano O.

92

Fault-scarp morphology and amount of surface offset on late-Quaternary surficial deposits, eastern escarpment of the central Sierra Nevada, CA  

SciTech Connect

Faults scarps, formed on glacial deposits and an alluvial fan near the east-central Sierra Nevada mountain front by late-Quaternary movement on the Hilton Creek (HCF), Wheeler Crest (WCFZ) and Coyote Warp (CWFZ) fault zones, were profiled to determine the amount and to estimate the recency of fault offset. Areas studied include McGee (N--near Lake Crowley), Pine, Mount Tom, Basin Mountain, McGee (S--near Bishop), and Bishop Creek drainages. The profile data indicate that movement of the range-front faults (HCF and WCFZ), which is characterized by normal slip, has offset Tioga-age deposits 6.5-26 m. Offset of Tahoe-age moraines cannot be measured directly because the landforms are buried at the mountain-front by moraines from later glaciations. However, the amount of offset is estimated at 52--130 m, based on crest-height differences between Tahoe and Tioga moraines. The rates of slip are highest on the northern end of the HCF, at McGee (N) Creek; the higher slip rates in this latter area may be related to its close proximity to the Long Valley caldera, where tectonic processes are complex and considered closely related to ongoing magmatic activity. The preservation of bevels on the fault scarps in both HCF and WCFZ, combined with the amounts of surface offset on the late-Pleistocene moraines, and AMS C-14 dates for charcoal found in fault-scarp colluvium, indicate that large ground-rupturing events have occurred on these faults during the Holocene. In contrast to the mountain-front faults, faults in the CWFZ, on a broad warp that separates the WCFZ from range-front faults to the south of Bishop, do not cross Tioga moraines, implying that surface rupture has not occurred in the CWFZ for at least 15,000-25,000 years. The degraded morphology of the fault scarps on adjacent Tahoe and pre-Tahoe moraines, which have been offset between 10.5 and 30 m, attests to the lack of late-Pleistocene and Holocene fault activity in this latter area.

Berry, M.E. (Southern Illinois Univ., Carbondale, IL (United States). Dept. of Geology)

1992-01-01

93

Surficial patterns of debris flow deposition on alluvial fans in Death Valley, CA using airborne laser swath mapping data  

Microsoft Academic Search

Debris flows are a common event in mountainous environments. They often possess the greatest potential for destruction of property and loss of lives in these regions. Delimiting the spatial extent of potential damage from debris flows relies on detailed studies of the location of depositional zones. Current research indicates debris flow fans have two distinct depositional zones. However, the two

Dennis M. Staley; Thad A. Wasklewicz; Jacek S. Blaszczynski

2006-01-01

94

Stratigraphy, sedimentology, chronology and palaeohydrology of Quaternary lacustrine deposits at Madigan Gulf, Lake Eyre, south Australia  

Microsoft Academic Search

Madigan Gulf is a large bay at the southern end of Lake Eyre North, a major ephemerally flooded playa in arid central Australia at the southwestern margin of a vast (1,300,000 km2) internal drainage basin. The stratigraphy and chronology of the Quaternary sequence in the gulf is described from 8 cores and a cliff exposure at the gulf margin. A

J. W. Magee; J. M. Bowler; G. H. Miller; D. L. G. Williams

1995-01-01

95

Quaternary deposits and soil formation in the Aragón Pyrenees (Spain) - First results from sedimentological studies  

Microsoft Academic Search

Within the scope of the research project Post LGM Pedogenesis and Geomorphodynamics in the Aragón Pyrenees funded by the DFG (Az RA 931\\/3-1) late Quaternary glacial, periglacial, fluvial and anthropogenic sediments are used to reconstruct the palaeoenvironment. The two research areas Gállego Valley and Aragón Valley are located in Aragón about 50 km northwest of Huesca which is a type

Florian Hirsch; Thomas Raab; Stefan Schuhart

2010-01-01

96

Late Quaternary Sedimentation and Erosion Rates Derived From Luminescence and Cosmogenic Nuclide Dating of Intermontane Basin Sediments, NW Argentine Cordillera  

Microsoft Academic Search

The easternmost basins of the central Andean cordillera (22o-25oS) are characterised by multiple Late Quaternary and Holocene alluvial fill-cut terraces. Humid phases in the central Andes, interpreted from cores of Late Pleistocene and Holocene lacustrine deposits, have been previously linked to periods of increased frequency of landsliding events. Large landslides lead to rapid increases in local base level and aggradation.

R. A. Robinson; J. Q. Spencer; W. M. Phillips; M. R. Strecker; R. N. Alonso; P. W. Kubik

2003-01-01

97

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

98

Carbonate deposition in an ephemeral siliciclastic alluvial system: Jurassic Shuttle Meadow Formation, Newark Supergroup, Hartford Basin, USA  

Microsoft Academic Search

Nonmarine carbonate accumulation, from a sedimentologic perspective, has multiple possible origins: clastic load, springs, groundwater discharge, soil development, biochemical seasonal changes, cave speleothems, and eolian influx. Many of these carbonates contain diagnostic textures from which origin is easy to ascertain. However, differentiating between clastic and spring\\/groundwater carbonates, especially in depositional systems dominated by siliciclastics, is not always simple; here criteria

E. H Gierlowski-Kordesch

1998-01-01

99

Frozen Quaternary Deposits of the Laptev Sea Region as a Reservoir of Organic Carbon: Total Content and Composition.  

NASA Astrophysics Data System (ADS)

Permafrost is a significant reservoir and potential source of ancient organic matter (OM) such as plant remains, humified organics, etc. and greenhouse gases. In according with different estimations 1 cubic meter of frozen deposits in this region consists up to 10 kg of Corg. Due to the degradation of permafrost under the both modern geological processes and global warming, this organic carbon is easily released into the present biogeochemical cycle Humus parameters, elementary and isotopic composition of OM, dissolved organic carbon content and some biomarkers in the following types of quaternary deposits were determined: Middle Pleistocene deposits contain 1-2% of TOC and characterised by the ratios of C/N 5-7,5 (syncryogenic) and 10-12 (epycryogenic). Late Pleistocene syncryogenic deposits composed by true syncryogenic deposits and buried soils. The former characterized by the 1-2% of TOC and C/N ratio 9-11 the later 4-16% of TOC and 12-16 C/N ratio. Late Pleistocene-Holocene taberal deposits. TOC - 1%, C/N - 10-12 Holocene alas deposits. TOC 4-6%, C/N - 10-12. Main part of total carbon is organic origin. Carbonates consist only 31 - 20 %. The following conclusions can be done: More transformed OM is in the buried soils and alas deposits. OM of syncryogenic deposits is a most labile. TOC and stage of organic matter transformation in the syncryogenic deposits depends on ratio of sedimentation and freezing rate. Decreasing of freezing rate leads to the more deposition and to deeper transformation of OM. Most transformed OM is in alas deposits and buried soils. About 20% of TOC presented by humus. Syncryogenic and taberal deposits are not so matured (humus content 15%). Content of organic matter potentially available to be dissolved in the water is low in the all investigated deposits. It consists approximately the 1-1,5% of TOC in Ice Complex deposits and 2-3% in alas and taberal deposits. Determination of biomarkers composition (n-alkanes, fatty acids and sterols) in alas and taberal deposits was carried out. Main part of organic matter in investigated deposits is presented by n-alkanes (37-74%, generally 55-60%). Fatty acids and sterols consist 13-22 and 2-7% correspondingly. On the base of the analyses conclusions about the main source of organic matter in the all investigated deposits can be done. Predomination of odd carbon-numbered long-chain n-alkanes (with 25-35 carbon atoms) and saturated fatty acids with long carbon chain (> C22) are character for terrestrial higher plants. There is a positive correlation of TOC and long-chain alkanes. All investigated deposits characterized by the low values of isotope C13 (from -24 to -24) what reflects the low decomposition of organic matter. Research was supported by RFBR (05-05-64062).

Kholodov, A.; Schirrmeister, L.; Shirshova, L.; Zolotareva, B.; Meyer, H.; Knoblauch, C.; Fahl, K.

2007-12-01

100

Biocompatible and mechanical properties of low temperature deposited quaternary (Ti, Al, V) N coatings on Ti6Al4V titanium alloy substrates  

Microsoft Academic Search

A series of quaternary (Ti, Al, V) N coating layers were obtained by low temperature reactive plasma sputtering in differing deposition conditions to improve the wear resistance and the biocompatibility of a titanium surgical alloy, specifically Ti-6Al-4V. Characterization of the mechanical properties, structure and the chemical composition of the coating layer was explored by microhardness test, ball against flat wear

D. M. Grant; W. J. Lo; K. G. Parker; T. L. Parker

1996-01-01

101

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

102

Geomorphology of Late Quaternary Mass Movement Deposits using a Decimetre-Resolution 3D Seismic Volume: Case Studies from Windermere, UK, and Trondheimsfjorden, Norway  

Microsoft Academic Search

We present results from decimetre resolution 3D seismic volumes acquired over Late Quaternary mass movement deposits in both Lake Windermere, UK, and the Trondheim Harbour area, central Norway. Both deposits were imaged using the 3D Chirp sub-bottom profiler, which combines the known, highly repeatable source waveform of Chirp profilers with the coherent processing and interpretation afforded by true 3D seismic

M. E. Vardy; J. K. Dix; T. Henstock; J. M. Bull; L. Pinson; J. L'Heureux; O. Longva; L. Hansen; S. Chand; M. Gutowski

2009-01-01

103

Alluvial aquifers in the Mzingwane catchment: Their distribution, properties, current usage and potential expansion  

Microsoft Academic Search

The Mzingwane River is a sand filled channel, with extensive alluvial aquifers distributed along its banks and bed in the lower catchment. LandSat TM imagery was used to identify alluvial deposits for potential groundwater resources for irrigation development. On the false colour composite band 3, band 4 and band 5 (FCC 345) the alluvial deposits stand out as white and

William Moyce; Pride Mangeya; Richard Owen; David Love

2006-01-01

104

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

105

Uranium-trend dating of quaternary deposits in the Nevada Test Site area, Nevada and California  

Microsoft Academic Search

The uranium-trend dating method has been used to estimate the ages of alluvium, colluvium, altered volcanic ash, and eolian deposits in the Nevada Test Site area. For dating of deposits of 5000 to 800,000 years age, the open-system technique consists of determining a linear trend from analyses of four to ten channel samples collected at different depths in a depositional

J. N. Rosholt; C. A. Bush; W. J. Carr; D. L. Hoover; W. C. Swadley; J. R. Jr. Dooley

1985-01-01

106

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

107

Organic and inorganic geochemical aspects of Mediterranean Late Quaternary sapropels and Messinian evaporitic deposits  

Microsoft Academic Search

This thesis describes the results of organic and inorganic geochemical\\u000ainvestigations obtained for samples collected from the eastern\\u000aMediterranean sea floor and from Italy. The samples vary in age from\\u000athe Late Miocene up to the Holocene. The environmental conditions\\u000aprevailing during deposition of the samples differ greatly. Sediment\\u000asamples deposited under both marine anoxic and oxic conditions were\\u000astudied

H. L. ten Haven

1986-01-01

108

Alluvial dolines in the central Ebro basin, Spain: a spatial and developmental hazard analysis  

Microsoft Academic Search

Alluvial dolines are abundant in Quaternary terraces and pediments overlying Neogene gypsum in the Zaragoza area (central Ebro basin). Spatial analysis and experimental simulation show that sulphate content in the groundwater, grain size of the detrital cover, topography of the Tertiary\\/Quaternary boundary, annual variation of the water table and thickness of the detrital cover are the main factors controlling their

María Asuncíon Soriano; JoséLuis Simón

1995-01-01

109

Influence of late Quaternary climatic changes on geomorphic and pedogenic processes on a desert piedmont, Eastern Mojave Desert, California  

USGS Publications Warehouse

Radiocarbon dating of late Quaternary deposits and shorelines of Lake Mojave and cation-ratio numerical age dating of stone pavements (Dorn, 1984) on the adjacent Soda Mountains piedmont provide age constraints for alluvial and eolian deposits. These deposits are associated with climatically controlled stands of Lake Mojave during the past 15,000 yr. Six alluvial fan units and three eolian stratigraphic units were assigned ages based on field relations with dated shorelines and piedmont surfaces, as well as on soil-geomorphic data. All but one of these stratigraphic units were deposited in response to time-transgressive climatic changes beginning approximately 10,000 yr ago. Increased eolian flux rates occurred in response to the lowering of Lake Mojave and a consequent increase in fine-sediment availability. Increased rates of deposition of eolian fines and associated salts influenced pedogenesis, stone-pavement development, and runoff-infiltration relations by (1) enhancing mechanical weathering of fan surfaces and hillslopes and (2) forming clay- and silt-rich surface horizons which decrease infiltration. Changes in alluvial-fan source areas from hillslopes to piedmonts during the Holocene reflect runoff reduction on hillslopes caused by colluvial mantle development and runoff enhancement on piedmonts caused by the development of less-permeable soils. Inferred increased in early to middle Holocene monsoonal activity resulted in high-magnitude paleo-sheetflood events on older fan pavements; this runoff triggered piedmont dissection which, in turn, caused increased sediment availability along channel walls. Thus, runoff-infiltration changes during the late Quaternary have occurred in response to eolian deposition of fines, pedogenesis, increased sheetflood activity in the Holocene, and vegetational changes which are related to many complicated linkages among climatic change, lake fluctuations, and eolian, hillslope, and alluvial-fan processes. ?? 1987.

Wells, S. G.; McFadden, L. D.; Dohrenwend, J. C.

1987-01-01

110

Alluvial Fan Flooding.  

National Technical Information Service (NTIS)

This report addresses a wide range of issues related to alluvial fan flooding. Chapter 1 presents an introduction to why identification of alluvial fan flooding hazards is controversial and the problems of definitions. Chapter 2 looks in more depth at fan...

1996-01-01

111

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

USGS Publications Warehouse

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 mineralogic and chemical disparities with local bedrock, but it is most readily shown by the abundance of titaniferous magnetite in the sandy deposits that is absent in local bedrock. Magnetite and some potential plant nutrients (especially, P, K, Na, Mn, and Zn) covary positively with depth (3-4 m) in dune-crest and dune-swale settings. Magnetite abundance also correlates strongly and positively with abundances of other elements (e.g., Ti, Li, As, Th, La, and Sc) that are geochemically stable in these environments. Soil-property variations with depth can be ascribed to three primary factors: (1) shifts in local geomorphic setting; (2) accumulation of relatively high amounts of atmospheric mineral dust inputs during periods of land-surface stability; and (3) variations in dust flux and composition that are likely related to changes in dust-source regions. Shifts in geomorphic setting are revealed by large variations in soil texture and are also expressed by changes in soil chemical and magnetic properties. Variable dust inputs are indicated by both changes in dust flux and changes in relations among magnetic, chemical, and textural properties. The largest of these changes is found in sediment that spans late Pleistocene to early Holocene time. Increased dust inputs to the central Colorado Plateau during this period may have been related to desiccation and shrinkage of large lakes from about 12 to 8 ka in western North America that exposed vast surfaces capable of emitting dust. Soil properties that result from variable dust accumulation and redistribution in these surficial deposits during the late Quaternary are important to modern ecosystem dynamics because some plants today utilize nutrients deposited as long ago as about 12-15 ky and because variations in fine-grained (silt) sediment, including eolian dust, influence soil-moisture capacity.

Reynolds, R. L.; Reheis, M. C.; Neff, J. C.; Goldstein, H.; Yount, J.

2006-01-01

112

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.

2013-07-01

113

Late Quaternary deposition and facies model for karstic Lake Estanya (North-eastern Spain)  

Microsoft Academic Search

Lake Estanya is a small (19 ha), freshwater to brackish, monomictic lake formed by the coalescence of two karstic sinkholes with maximum water depths of 12 and 20 m, located in the Pre-Pyrenean Ranges (North-eastern Spain). The lake is hydrologically closed and the water balance is controlled mostly by groundwater input and evaporation. Three main modern depositional sub-environments can be

Mario Morellón; Blas Valero-Garcés; Flavio Anselmetti; Daniel Ariztegui; Michael Schnellmann; Ana Moreno; Pilar Mata; Mayte Rico; Juan Pablo Corella

2009-01-01

114

Late Quaternary geoarchaeology and geochronology of stratified aeolian deposits, Tar River, North Carolina  

NASA Astrophysics Data System (ADS)

Recent geoarchaeological work on relict aeolian deposits in the North Carolina Coastal Plain has shown the potential for understanding prehistoric hunter-gatherer adaptations to changing environmental conditions likely related to Holocene climate change. Archaeological surveys and testing along the Tar River has revealed numerous sites with stratified Early Archaic through Woodland occupations. Geophysical, archeostratigraphic and sedimentological analysis along with chronometric dating (OSL and 14C) of source-bordering aeolian sediments along the Tar River in North Carolina indicate dune drapes (˜1 meter thick) accreted throughout much of the Holocene. Aeolian burial events along the Tar River appear to reflect Holocene millennial-scale climatic cyclicity (e.g., Bond Events) and its related effects on the fluvial system. These events likely influenced both hunter-gatherer adaptation and site preservation along the Tar River. Combined radiocarbon and OSL ages from lower paleo-braidplain sites, indicate incision of the lower paleo-braidplain and initiation of dune deposition just before or during the Younger Dryas stadial. The presence of stratified archaeological remains in these sediments preserves a record of both prehistoric human adaptations to local conditions and changes in depositional processes marking large-scale climatic change in the southeastern United States.

Moore, Christopher R.

115

Uranium and thorium series disequilibrium in quaternary carbonate deposits from the Serra da Bodoquena and Pantanal do Miranda, Mato Grosso do Sul State, central Brazil.  

PubMed

Activities of gamma-ray emitting members of the uranium (238U) and thorium (232Th) series were measured in a quaternary limestone deposit that outcrops in the southeastern Pantanal Matogrossense Basin and in quaternary tufas deposited at the drainage of the Serra da Bodoquena. It is a first step in a study of the mobilization of uranium and thorium series and its relation to surface hydrology, in a region where carbonate deposits are being continuously dissolved and reprecipitated. The obtained results show that all these deposits are characterized by very low concentrations of uranium and thorium. The 238U/226Ra and 228Th/228Ra activity ratios are significantly different than 1.0, indicating that both series are in radioactive disequilibrium. Although the Serra da Bodoquena deposits seem to be very recent, their very fine granulation and high porosity suggest that they behave as open systems for geochemical exchanges of uranium and thorium series members. The Pantanal do Miranda limestone has a radiocarbon age of 3900 yr BP. Since the thorium series is in disequilibrium it is also concluded that this deposit behaves as an open system for geochemical exchanges. PMID:11144246

Ribeiro, F B; Roque, A; Boggiani, P C; Flexor, J M

2001-01-01

116

Uranium-series dating of carbonate (tufa) deposits associated with quaternary fluctuations of Pyramid Lake, Nevada  

USGS Publications Warehouse

Uranium-series dating of dense tufa deposited in a small cave, at former lake margins, and in large tufa mounds clarifies the timing of lake-level variation during the past 400,000 yr in the Pyramid Lake basin. A moderate-sized lake occasionally overflowed the Emerson Pass sill at elevation of ???1207 m between ca. 400,000 and 170,000 and from ca. 60,000 to 20,000 yr B.P., as shown by 230Th/234U ages of the cave samples, 230Th-excess ages of tubular tufas, and average isochron-plot ages of shoreline-deposited tufas. (By comparison, modern Pyramid Lake is ???50 m below this sill). There is a lack of tufa record during the intervening period from ca. 170,000 to 60,000 yr B.P. After ca. 20,000 yr, Pyramid Lake underwent abrupt changes in level and, based on previous 14C ages, reached its highest elevation (ca 1335 m) at ca. 14,000 yr B.P. The youngest uranium-series ages are comparable with previously reported 14C ages. ?? 1996 University of Washington.

Szabo, B. J.; Bush, C. A.; Benson, L. V.

1996-01-01

117

Alluvial Fan in Icaria Planum, Mars  

NASA Astrophysics Data System (ADS)

The Mars Express HRSC data were used to study fluvial history of southern Claritas on Mars (1, 2). Volatiles, transported downslope to the basin, breached through a saddle valley and formed a channel towards Icaria Planum in the west. Along the channel, sapping provided additional water. The channel broke into a 30-km impact crater and formed a temporary lake. The crater rim has terraces and the floor has smooth deposits. A delta was formed in a standing water. After breaching the crater rim through a neck which is higher than the crater floor, water deposited onto Icaria Planum an alluvial fan. This fan was studied using the HRSC colour data by mapping deposit units of the Icaria lowlands in front of the channel. The flood deposits were made visible by the multichannel HRSC data classification. The alluvial structures reflect topography and regional slopes as well as the amount of available water. The hi-resolution HRSC image provides an additional view into the alluvial structures, erosion and sedimentation in the channel formation. These remote sensing approaches facilitate the mapping of characteristic phases in the fluvial development of the area studied. References. (1) Raitala et al., 2005. LPS XXXVI, #1307. (2) Korteniemi, J., Raitala, J., Aittola, M., Kostama V.-P., Hauber E., Kronberg P., Neukum G. and the HRSC Co-I Team, 2005. Fluvial channel resulted in alluvial fan formation in Icaria Planum, Mars. Submitted to 42nd Vernadsky-Brown Microsymposium, Moscow 9-12. 10. 2005.

Korteniemi, J.; Raitala, J.; Aittola, M.; Kostama, V.; Hauber, E.; Kronberg, P.; Neukum, G.; HRSC Co-I Team

2005-12-01

118

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

119

Alluvial terrace systems in Zhangjiajie of northwest Hunan, China: Implications for climatic change, tectonic uplift and geomorphic evolution  

Microsoft Academic Search

This paper reports the latest details from two comprehensive investigations of alluvial terrace sequences in Zhangjiajie, northwest Hunan Province, China. Seven alluvial terrace units along the Maoxi River and four terrace sequences along the Suoxi River record significant regional geomorphic history. Rates of regional Quaternary uplift and climate change are reconstructed using topographic and stratigraphic evidence from terrace and adjacent

Guifang Yang; Xujiao Zhang; Mingzhong Tian; Gary Brierley; Anze Chen; Yamin Ping; Zhiliang Ge; Zhiyun Ni; Zhen Yang

2011-01-01

120

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

121

Identifying late Quaternary coastal deposits in Kyonggi Bay, Korea, by their geotechnical properties  

NASA Astrophysics Data System (ADS)

Based on cone penetration tests with pore pressure measurements (CPTUs) and standard penetration tests (SPTs), the geotechnical properties of five lithostratigraphic units were determined during the construction of Incheon international airport on reclaimed macrotidal flats in Kyonggi Bay, Korea. Two late Pleistocene non-marine units (unit V and unit IV) display largest N values (cf. number of blows required to achieve a standard penetration), reflecting coarse-grained and overconsolidated sediments. Tidal channel and tidal flat facies (unit IIIb) consist of unweathered late Pleistocene tidal sand and mud. The tidal channel facies is characterized by upward-decreasing cone resistance ( q t) and sleeve friction ( f s) with negative pore pressures ( u bt), reflecting a fining-upward textural trend. The tidal flat facies, by contrast, is represented by uniformly low q t and f s values with high friction ratios (FRs), suggesting homogeneous muddy deposits. Two overconsolidated units, a weathered late Pleistocene tidal mud (unit IIIa) and an early Holocene organic-rich non-marine mud (unit II), are characterized by high q t, f s, FRs and N values, unit IIIa being much more consolidated than unit II. Holocene tidal sands and muds (unit I) show the smallest q t and f s values with positive u bt. These are slightly more consolidated than the tidal flat facies of unit IIIb. Two unconformable boundaries (a sequence boundary and a transgressive surface) have also been identified on some CPTU and SPT profiles. The boundaries are indicated by gradual but sharp increases in q t, f s and N values with an abrupt drop of u bt, which indicates the contact between two units showing contrasting rigidity. The regional pattern produced by the unconformable boundaries indicates the presence of late Pleistocene valleys which pass through the middle of study area. The location of the valleys seems to be controlled by the antecedent basement morphology.

Choi, Kyungsik; Kim, Ju Hyong

2006-06-01

122

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

123

The role of volcanic activity and climate in alluvial fan growth at volcanic areas: an example from southern Campania (Italy)  

Microsoft Academic Search

Volcaniclastic-rich alluvial fans developed in the southern Campanian Plain (Italy) during the late Pleistocene and Holocene in an area eastward of the Somma-Vesuvius and Campi Flegrei volcanoes. Meanwhile, bedrock-rich alluvial fans developed in areas unaffected by pyroclastic deposition. Late Pleistocene and Holocene volcaniclastic-rich alluvial fans show some important differences: (i) late Pleistocene alluvial fans were dominated by hyperconcentrated flow deposits,

G. Zanchetta; R. Sulpizio; M. A Di Vito

2004-01-01

124

Holocene flood plain soil formation in the lower Mississippi River Valley: Implications for the interpretation of alluvial paleosols  

SciTech Connect

Holocene Mississippi River flood soils representing different depositional environments and ages were sampled along three east-west transects between Vicksburg, MS and Baton Rouge, LA. Flood plain soil development is primarily controlled by episodic flood plain sedimentation and ground water table fluctuations as evidenced by relatively thick cumulative soil profiles with abundant mottles, nodules, and slickensides. Within flood plain deposits of similar age, profile, development is best expressed in moderately-drained silty and sandy soils in natural levee and point bar ridge environmental that occur within and adjacent to meander belts. Soils in natural levee and point bar ridge environments greater than 3 ka generally are acidic and have better-developed Bt horizons and brighter mottles than their younger counterparts. In addition to being acidic and brightly mottled, older back swamp soils have larger and more abundant slickensides and iron nodules. This study suggests that alluvial paleosols formed in aggradational settings may be better suited for interpreting flood plain depositional histories and paleohydrology than climate. Parameters such as solum thickness and clay and carbonate accumulations, routinely used to estimate relative time and climatic effects on soil development in Quaternary studies of stable geomorphic surfaces, may not be applicable to ancient alluvial deposits that reflect continuous sediment aggradation.

Aslan, A. (Univ. of Colorado, Boulder, CO (United States). Dept. of Geological Sciences); Autin, W.J. (Louisiana Geological Survey, Baton Rouge, LA (United States))

1992-01-01

125

Quaternary downcutting rate of the new river, Virginia, measured from differential decay of cosmogenic {sup 26}Al and {sup 10}Be in cave-deposited alluvium  

SciTech Connect

The concentrations of the cosmogenic radionuclides {sup 26}Al and {sup 10}Be in quartz can be used to date sediment burial. Here we use {sup 26} Al and {sup 10}Be in cave-deposited river sediment to infer the time of sediment emplacement. Sediment burial dates from a vertical sequence of caves along the New River constrain its Quaternary downcutting rate to 27.3{+-}4.5 m/m.y. and may provide evidence of regional tectonic tilt. 32 refs., 3 figs., 1 tab.

Granger, D.E.; Kirchner, J.W. [Univ. of California, Berkeley, CA (United States); Finkel, R.C. [Lawrence Livermore National Lab., CA (United States)

1997-02-01

126

Late Quaternary Sedimentation and Erosion Rates Derived From Luminescence and Cosmogenic Nuclide Dating of Intermontane Basin Sediments, NW Argentine Cordillera  

NASA Astrophysics Data System (ADS)

The easternmost basins of the central Andean cordillera (22o-25oS) are characterised by multiple Late Quaternary and Holocene alluvial fill-cut terraces. Humid phases in the central Andes, interpreted from cores of Late Pleistocene and Holocene lacustrine deposits, have been previously linked to periods of increased frequency of landsliding events. Large landslides lead to rapid increases in local base level and aggradation. Subsequent headward erosion propagates through the basin and produces a characteristic alluvial terrace, common to many active mountain belts. Although climate may be the predominant control on these events, small and young intra-basin faults could also be diverting fluvial systems and reorganising drainage basins and sediment pathways. We have integrated optically stimulated luminescence (OSL) with 10Be cosmogenic nuclide dating techniques to produce a chronology of three of these depositional and erosional sequences in the Quebrada de Humahuaca. From each sequence, multiple OSL samples were collected from the fluvial and (debris flow and stream dominated) alluvial fan deposits to quantify sedimentation rate; four cosmogenic samples were collected from a 1.5 m pit on each terrace surface to quantify surface exposure age, as well as basin-scale erosion rate. Integrating these two dating techniques allows us to test how episodic deposition-erosion events are linked to periods of pronounced climatic variability in the central Andes and to quantify landscape response time to incision events.

Robinson, R. A.; Spencer, J. Q.; Phillips, W. M.; Strecker, M. R.; Alonso, R. N.; Kubik, P. W.

2003-12-01

127

Fire, Holocene Climate Change, and Geomorphic Response Recorded in Alluvial Fan Sediments  

Microsoft Academic Search

Alluvial fan stratigraphic sequences record fire history in charcoal-rich deposits and buried burned soil surfaces. Deposit characteristics provide information about the magnitude of fire-related sedimentation events and severity of associated fires, and radiocarbon-dating of charcoal establishes the timing of fires. Unlike lakes, alluvial fans are ubiquitous in mountain environments. Although alluvial-fan fire records lack the annual resolution of tree-ring records,

J. L. Pierce; G. A. Meyer

2004-01-01

128

Analysis of deformation structures in Pliocene and Quaternary deposits of the Hyblean Plateaux (south-eastern Sicily)  

Microsoft Academic Search

A singular association of deformation structures that have disturbed terrains up to Quaternary age, has been detected along the rocky coast of Vendicari (south-eastern Sicily). These structures are soft sediment deformations consisting of autoclastic breccias, diapyr-like injections and thixotropic wedges, as well as fractures, generally opened and filled by sediments. Both soft and brittle deformations can be due either to

Claudia Pirrotta; Maria Serafina Barbano

2011-01-01

129

High-resolution 3D seismic reflection and coring techniques applied to late Quaternary deposits on the New Jersey shelf  

Microsoft Academic Search

Studies of variable, small-scale features typical of Quaternary glacimarine environments require an interdisciplinary approach: precisely navigated, high-resolution 3D seismic surveys nested within a regional 2D seismic framework and integrated with a precisely navigated coring program designed to sample specific shallow acoustic facies. We illustrate this approach with examples from continuing studies of sediments on the New Jersey continental shelf. Surficial

Thomas A. Davies; James A. Austin

1997-01-01

130

Facies architecture and depositional evolution of alluvial fan to fan-delta complexes in the tectonically active Miocene Köprüçay Basin, Isparta Angle, Turkey  

NASA Astrophysics Data System (ADS)

This paper provides the first general account of the facies associations that fill a Miocene fault bounded basin located in the central part of the Isparta Angle (Turkey), in order to define process-controlled sedimentary units reflecting environmental changes in a general tectonic and stratigraphic framework. The northern and western parts of the Köprüçay Basin are occupied by extensive conglomeratic successions belonging to three distinct alluvial fan fan delta systems (AFD), which pass laterally into pelagic mudstones in the deeper part of the basin. In spite of syn- and post-sedimentary tectonics, most of the sedimentary units still display their original relationships. This allows definition and interpretation of the conspicuous facies changes in the clastic successions according to their position along complete sections across the basin. The bulk of the paper is thus devoted to the description of 11 sub-facies types that have been identified in the three AFDs, and their environmental interpretation. As a result, the origin and sedimentary infill of the Köprüçay Basin appears primarily controlled from Langhian to Tortonian by the N S trending Kirkkavak Fault. After uplift and erosion of the western part of the basin, the final closure of the Isparta Angle resulted in a westward displacement of the Anatolian block during Upper Tortonian.

Deynoux, Max; Çiner, Attila; Monod, Olivier; Karab?y?koglu, Mustafa; Manatschal, Gianretto; Tuzcu, Sevim

2005-01-01

131

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

132

Giant landslide deposits in northwest Argentina  

SciTech Connect

Giant Quaternary landslide deposits occur along mountain fronts in the structural transition zone between the high-angle reverse-fault-bounded Sierras Pampeanas and the low-angle thrust belt of the Sierras Subandinas. There are two modes of occurrence: (1) chaotic masses without distinct geometry, and (2) masses with distinct lobate geometry similar to glacial moraines. Type (1) deposits occur where the moving rock mass followed a narrow valley and blocked the drainage. Many of these caused subsequent formation of lakes and changed the sedimentation processes on pediments at the mountain fronts. In type (2) deposits, lateral and frontal ridges are up to 10 m higher than the interior parts; in some places pressure ridges within the lobes are well preserved. Type (2) deposits show reverse grading and were deposited on relatively smooth pediments or alluvial fans. The lobate geometry strongly suggests that type (2) deposits are a product of flowage and are debris stream or sturzstrom deposits (sense of Heim, 1932 and Hsu, 1975). All investigated deposits occur in areas of demonstrated Quaternary faulting and are interpreted as the result of tectonic movements, although structural inhomogeneities in the source area may have been a significant factor for some of the landslides. No datable materials have yet been found associated with the deposits.

Fauque, L.; Strecker, M.R.; Bloom, A.L.

1985-01-01

133

Tectono-sedimentary characteristics of Late Miocene-Quaternary extensional basins of the Northern Apennines, Italy  

NASA Astrophysics Data System (ADS)

Extensional and compressional regimes exist at the same time in adjacent parts of the Northern Apennines (Italy), and the former regime succeeded the latter at the same place as the thrust mountain front moved eastward since Miocene times. Numerous extensional basins have developed west of the present mountain divide. The westernmost ones formed over attenuated continental crust since Late Miocene and have been subjected to several subsidence and uplift events, with rates of subsidence generally faster than rates of sedimentation. They contain continental deposits overlain by gypsum-bearing Upper Miocene marine sequences and siliciclastic, marine Pliocene deposits. These basins were affected by shallow magmatism and are still experiencing high geothermal gradient and late to post-magmatic activities, such as in the renowned thermal region of Larderello. To the east, closer to the present mountain divide, the extensional basins formed later, from Pliocene to Quaternary, contain continental (fluvial and lacustrine) deposits and have not experienced near-surface magmatic activities. The sedimentary fill architecture of the Apennine extensional basins is similar to that of other European, American and African extensional or transtensional systems. For instance, a common characteristic is the prevalence of large alluvial fan deposits at the hanging-wall shoulder of half-grabens, coarser, smaller, alluvial fans at the footwall shoulder, and some fluvial deposits introduced longitudinally. Unlike the African rifts though, the sedimentary facies distribution of extensional basins which developed in active orogenic zones such as in the Apennines, may be strongly affected by uplifting, steep mountain slopes and can have large, thick, coarse alluvial fans also on the footwall side of the half-grabens.

Martini, I. P.; Sagri, M.

1993-06-01

134

Climatic and Tectonic Controls on Alluvial Fan Evolution: The Lost River Range, Idaho  

NASA Astrophysics Data System (ADS)

In the northern Basin &Range, alluvial fans developed along the Lost River range-front consist of several distinct inset fan segments with concave-up radial profiles. Multiple large radius (>5 km), shallow (2- 3°), alluvial fans extend across and beyond the active, ~140-km-long, normal Lost River fault. These large fans are relict features, formed by major sheetfloods that occurred intermittently between ~15-180 ka. More recent deposition has been dominated by debris-flows that form small-radius (<2 km), steep (8- 17°), fans closely confined to the mountain front [1,2]. In order to determine the timing of fan surface stabilization, we have undertaken precise mass spectrometric 230Th/U dating of pedogenic carbonate from calcic soils that mantle fan surfaces on the Arco fault segment. Careful selection of mg-size samples of dense soil carbonate pebble coats, from within a trench that cuts through gravelly fan deposits, indicates that the fan soils are geochemically suitable for uranium-series dating (median U=7ppm, 232Th=0.09ppm, 232Th/230Th=154). 230Th/U analysis of these calcic soils can thus provide precise temporal constraints on intervals of surface stability and subsequent soil formation. The oldest fan surface (Qfo1, 178+/-8 ka), exposed within the footwall of the trench, suggests an interval of surface stability, indicating that the fan was likely abandoned due to incision early in MIS 6. Incision may have resulted from surface faulting along the Arco segment of the Lost River fault, but could relate to changes in stream power or sediment supply associated with climatic change or with auto-cyclic variations within the drainage basin. A younger incised and faulted fan surface (Qfo2, 69+/-6 ka), likely represents active alluviation at the beginning of MIS 4 and, since it formed as hanging-wall alluvial gravel, provides age limits on an episode of fault displacement between Qfo1 and Qfo2. In situ pedogenic carbonate coats on sub-angular gravels within the colluvial fault wedge date at 68+/-2 ka, suggesting that either faulting occurred soon after Qfo2 stabilized or that soil carbonate coats were recycled into the colluvial wedge from the faulted surface. Further studies in the Lost River Range will assess the timing of fan deposition, surface stabilization and fault activity since the late Pleistocene using coupled application of Optically Stimulated Thermoluminescence (OSL) dating of loess and fine-sands, and 230Th/U-dating of pedogenic carbonate formed within well- exposed fan stratigraphy. Defining intervals of erosion, deposition and stability within the context of regional records of Quaternary climate change will yield new insights into the interplay between faulting, climate change and alluvial fan deposition and incision in semi-arid environments. [1] Pierce, K.L., Scott, W.E., 1982. Idaho Mines &Geol. Bull. 26. [2] Patterson, S.J., 2006. M.S. Thesis, Montana State University

Phillips, R. J.; Pierce, J. L.; Sharp, W. D.; Pierce, K. L.

2006-12-01

135

Clinker deposits, Powder River Basin, Wyoming and Montana: A new source of high-fidelity paleomagnetic data for the Quaternary  

NASA Astrophysics Data System (ADS)

Clinker, rock baked and fused by in situ burning of underlying coal, posesses a thermoremanent and/or thermochemical magnetization that resides in magnetite, hematite, and goethite. Data from individual sites imply that clinker may provide a high resolution recording of the geomagnetic field (e.g., within-site virtual geomagnetic pole angular standard deviations are usually less than 10°) , but this is dependent on its thermal history and the time over which magnetic phases formed. Data from 17 sites in the Powder River Basin (13 normal polarity, 4 reverse) yield a mean of Decl. = 348°, Incl. = 62°, ?95 = 5°, k = 42 and a corresponding pole position of 81° lat., 158° long. with a virtual geomagnetic pole angular standard deviation of 17.3°. The mechanism of clinker formation, the wide geographic distribution, and the range of available fission-track ages suggest that clinker may contain a nearly complete geomagnetic field record for much of the Quaternary.

Jones, Alison H.; Geissman, John W.; Coates, Donald A.

1984-12-01

136

Inventory of sedimentary organic matter in modern wetland (Marais Vernier, Normandy, France) as source-indicative tools to study Holocene alluvial deposits (Lower Seine Valley, France)  

Microsoft Academic Search

Palynofacies' analysis was developed for petroleum exploration, but it is now commonly used to differentiate the major constituents of the sedimentary organic matter (SOM) in Postglacial deposits. Our work aimed at studying the SOM distribution in a present wetland of the Seine estuary (Vernier Marsh) in order to provide comparative elements to interpret the composition of SOM in the Lower

D. Sebag; C. Di Giovanni; S. Ogier; V. Mesnage; F. Laggoun-Défarge; A. Durand

2006-01-01

137

Issues associated with the distinction between climatic and tectonic controls on Permian alluvial fan deposits from the Kotzen and Barnim Basins (North German Basin)  

Microsoft Academic Search

Facies analysis focussing on coarse-grained sediments has been carried out on more than 2500m of drill cores from seven wells from southern margins of the North German Basin (NGB). The NGB forms a central element of the Southern Permian Basin (SPB). The wells exposed conglomerates and sandstones of the Rotliegend Grüneberg and Parchim Formations deposited in the Kotzen Basin and

Enrico Kallmeier; Christoph Breitkreuz; Hubert Kiersnowski; Marion Geißler

2010-01-01

138

Characterizing arid region alluvial fan surface roughness with airborne laser swath mapping digital topographic data  

Microsoft Academic Search

Range-front alluvial fan deposition in arid environments is episodic and results in multiple fan surfaces and ages. These distinct landforms are often defined by descriptions of their surface morphology, desert varnish accumulation, clast rubification, desert pavement formation, soil development, and stratigraphy. Although quantifying surface roughness differences between alluvial fan units has proven to be difficult in the past, high-resolution airborne

Kurt L. Frankel; James F. Dolan

2007-01-01

139

Spatial hydrochemical and isotopic variations within the alluvial aquifer of the Allier River (Massif Central, France)  

NASA Astrophysics Data System (ADS)

Hydrodynamic, hydrochemical (major ions, traces, pharmaceuticals and pesticides), isotopic (oxygen, hydrogen and carbon stable isotopes) and biological investigations were conducted every two weeks, since December 2010, to assess groundwater quality in the unconfined shallow alluvial aquifer of the Allier River (main tributary of the Loire River). The aquifer is mainly composed of unconsolidated alluvial deposits produced by the erosion of local crystalline rocks, the aquifer overlies impervious Oligocene marls; the surrounding hills are constituted with Quaternary deposits (early and old alluvial deposits on both sides of river), Oligocene limestones, marls and sandstones and Miocene volcano-sedimentary formations (Peperites). The study area is located in the east of the city of Clermont-Ferrand (France) where groundwater resources are used mainly for water supplies and then play an important socio-economic role as it is the major source of drinking water for about 100 000 inhabitants. This study aims at determining the factors and processes controlling shallow groundwater quality and groundwater origin by using the hydrochemical and hydrodynamical data collected on 87 water samples (71 boreholes, 13 piezometers and 4 surface waters) during a first field campaign carried out from the 9th to the 14th of December 2010. The Cournon Meteoric Water Line was determined according to 30 weekly rainfall samples. The results of this study show that spatial variations of physico-chemical parameters do exist in the study area, and the groundwater chemical composition is characterized by different water types with the predominance of the Ca-HCO3 type. Ionic concentration increases in boreholes far from the Allier River due to the increase of residence time or by a mixing with groundwater coming from the hills. The ð2H and ð18O signature of groundwater and surface water indicate that most of the boreholes close to the river are recharged by the Allier River, while boreholes far from the river exhibit isotopic contents close to the values of sampled springs of the hills, recharged by local precipitation. Nevertheless, some boreholes do not follow this simple scheme of functioning and present values attesting of a secondary process related to evaporation and/or mixing with deep groundwater from geothermal origin.

Mohammed, N.; Celle-Jeanton, H.; Huneau, F.; Le Coustumer, P.; Lavastre, V.; Bertrand, G.

2012-04-01

140

The "alluvial mesovoid shallow substratum", a new subterranean habitat.  

PubMed

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

Ortuño, Vicente M; Gilgado, José D; Jiménez-Valverde, Alberto; Sendra, Alberto; Pérez-Suárez, Gonzalo; Herrero-Borgoñón, Juan J

2013-10-04

141

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.

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

2013-01-01

142

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

143

Potentiometric Surface of the Alluvial Aquifer and Hydrologic Conditions in the Juana Diaz area, Puerto Rico, June 29 - July 1, 2005  

USGS Publications Warehouse

A synoptic survey of the hydrologic conditions in the Juana Diaz area, Puerto Rico, was conducted between June 29 and July 1, 2005, to define the spatial distribution of the potentiometric surface of the alluvial aquifer. The study area encompasses 21 square miles of the more extensive South Coastal Plain Alluvial Aquifer system and is bounded along the north by foothills of the Cordillera Central mountain chain, to the south by the Caribbean Sea, the east by the Rio Descalabrado and to the west by the Rio Inabon. Ground water in the Juana Diaz area is in the Quaternary-age alluvial deposits and the middle-Tertiary age Ponce Limestone and Juana Diaz Formation (Giusti, 1968). The hydraulic properties of the Ponce Limestone in the Juana Diaz area are unknown, and the Juana Diaz Formation is a unit of poor permeability due to its high clay content. Consequently, the Ponce Limestone and the Juana Diaz Formation are generally considered to be the base of the alluvial aquifer in the Juana Diaz area with ground-water flow occurring primarily within the alluvial deposits. The potentiometric-surface map of the alluvial aquifer was delineated using ground-water level measurements taken at existing wells. The water-level measurements were taken at wells that were either not pumping during the survey or were shut down for a brief period. In the latter case, a recovery period of 30 minutes was allowed for the drawdown in the wellbore to achieve a near static level position representative of the aquifer at the measurement point. Land-surface altitude from U.S. Geological Survey (USGS) 1:20,000 scale topographic maps (Playa de Ponce, Ponce, Rio Descalabrado, and Santa Isabel) were used to refer ground-water levels to mean sea level datum (National Geodetic Vertical Datum of 1929). In addition to the ground-water level measurements, the potentiometricsurface contours were delineated using hydrologic features, such as drainage ditches and saturated intermittent streams that were considered as aquifer drains and losing streams, respectively.

Rodriguez, Jose M.; Santigo-Rivera, Luis; Gomez-Gomez, Fernando

2006-01-01

144

Controls on alluvial fan long-profiles  

USGS Publications Warehouse

Water and debris flows exiting confined valleys have a tendency to deposit sediment on steep fans. On alluvial fans where water transport of gravel predominates, channel slopes tend to decrease downfan from ???0.10-0.04 to ???0.01 across wide ranges of climate and tectonism. Some have argued that this pattern reflects grain-size fining downfan such that higher threshold slopes are required just to entrain coarser particles in the waters of the upper fan, whereas lower slopes are required to entrain finer grains downfan (threshold hypothesis). An older hypothesis is that slope is adjusted to transport the supplied sediment load, which decreases downfan as deposition occurs (transport hypothesis). We have begun to test these hypotheses for alluvial fan long-profiles using detailed hydraulic and particle-size data in sediment transport models. On four alluvial fans in the western U.S., we find that channel hydraulic radiiare largely 0.5-0.9 m at fan heads, decreasing to 0.1-0.2 m at distal margins. We find that median gravel diameter does not change systematically along the upper 60%-80% of active fan channels as slope declines, so downstream gravel fining cannot explain most of the observed channel slope reduction. However, as slope declines, channel-bed sand cover increases systematically downfan from areal fractions of <20% above fan heads to distal fan values in excess of 70%. As a result, entrainment thresholds for bed material might decrease systematically downfan, leading to lower slopes. However, current models of this effect alone tend to underpredict downfan slope changes. This is likely due to off-channel gravel deposition. Calculations that match observed fan long-profiles require an exponential decline in gravel transport rate, so that on some fans approximately half of the load must be deposited off channel every -0.20-1.4 km downfan. This leads us to hypothesize that some alluvial fan long-proffies are statements about the rate of overbank deposition of coarse particles downfan, a process for which there is currently no mechanistic theory. ?? 2007 Geological Society of America.

Stock, J. D.; Schmidt, K. M.; Miller, D. M.

2008-01-01

145

High-resolution sequence stratigraphy of an alluvial fan–fan delta environment: stratigraphic and geodynamic implications – An example from the Keuper Chaunoy Sandstones, Paris Basin  

Microsoft Academic Search

Facies analysis of the Chaunoy Formation, conducted as the first stage of this study, reveals that the corresponding fluvial system essentially involved bedload deposition, 2-D and 3-D megaripple migration, and debris-flow deposition. Such processes are characteristic of alluvial fan depositional environments. These alluvial fan deposits pass laterally eastward into a shallow lacustrine environment. In stage 2 of the study, electrofacies

Sylvie Bourquin; Christophe Rigollet; Philippe Bourges

1998-01-01

146

Late Quaternary sea level and environmental changes from relic carbonate deposits of the western margin of India  

Microsoft Academic Search

Relic carbonate deposits along the western margin of India occur as dolomite crusts, aragonite sands (pelletal \\/ oolitic)\\u000a and aragonite-cemented limestones, oyster shells, corals, encrusted coralline algal and foraminiferal-dominated nodules. The\\u000a petrology and mineralogy of the deposits indicate that except for aragonite sands and foraminiferal nodules, the others were\\u000a formed in shallow marine conditions and serve as sea level indicators.

V. Purnachandra Rao; G. Rajagopalan; K. H. Vora; F. Almeida

2003-01-01

147

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

148

Preliminary U-series disequilibrium and thermoluminescence ages of surficial deposits and paleosols associated with Quaternary fault, Eastern Yucca Mountain  

SciTech Connect

Geochronological control is an essential component of paleoseismic evaluation of faults in the Yucca Mountain region. New U-series disequilibrium and thermoluminescence age estimates for pedogenic deposits that bracket surface-rupture events are presented from four sites exposing the Paintbrush Canyon, Bow Ridge and Stagecoach Road faults. Ages show an internal consistency with stratigraphic relationships as well as an overall concordancy between the two independent geochronometers. Age estimates are therefore interpreted to date depositional events or episodes of pedogenic carbonate mobility that can be used to establish a paleoseismic fault chronology. Ultimately, this type of chronological information will be used to evaluate seismic hazards at Yucca Mountain.

Paces, J.B.; Menges, C.M.; Bush, C.A.; Futa, K.; Millard, H.T.; Maat, P.B.; Whitney, J.W. [Geological Survey, Denver, CO (United States); Widmann, B. [Science Applications International Corp., Golden, CO (United States); Wesling, J.R. [Geomatrix Consultants, Inc., San Francisco, CA (United States)

1994-12-31

149

Soil genesis on the island of Bermuda in the Quaternary: The importance of African dust transport and deposition  

NASA Astrophysics Data System (ADS)

The origin of terra rossa, red or reddish-brown, clay-rich soils overlying high-purity carbonate substrates, has intrigued geologists and pedologists for decades. Terra rossa soils can form from accumulation of insoluble residues during dissolution of the host limestones, addition of volcanic ash, or addition of externally derived, long-range-transported (LRT) aeolian particles. We studied soils and paleosols on high-purity, carbonate aeolianites of Quaternary age on Bermuda, where terra rossa origins have been debated for more than a century. Potential soil parent materials on this island include sand-sized fragments of local volcanic bedrock, the LRT, fine-grained (<20?m) component of distal loess from the lower Mississippi River Valley, and LRT dust from Africa. These parent materials can be characterized geochemically using trace elements that are immobile in the soil-forming environment. Results indicate that local volcanic bedrock on Bermuda has Sc-Th-La, Cr-Ta-Nd, and Eu/Eu*, LaN/YbN, GdN/YbNthat can be distinguished from African dust and lower Mississippi River valley loess. Bermuda soils have Sc-Th-La, Cr-Ta-Nd, and Eu/Eu*, LaN/YbN, GdN/YbN that indicate derivation from a combination of LRT dust from Africa and local volcanic bedrock. Our results indicate that soils on islands in a very broad latitudinal belt of the western Atlantic margin have been influenced by African LRT dust inputs over much of the past ˜500 ka.

Muhs, Daniel R.; Budahn, James R.; Prospero, Joseph M.; Skipp, Gary; Herwitz, Stanley R.

2012-09-01

150

Flooding and flow path selection on alluvial fans and deltas  

Microsoft Academic Search

The surfaces of alluvial fans and river deltas (collectively fans) are often dissected by a small number of channels radiating from the fan apex. On long timescales, channels migrate via avulsion, the process of channel bed deposition and abandonment that often results in catastrophic flooding and loss of life on densely populated fans. We present results of an experimental fan

Meredith D. Reitz; Douglas J. Jerolmack; John B. Swenson

2010-01-01

151

Hydraulic processes on alluvial fans  

SciTech Connect

Alluvial fans are among the most prominent landscape features in the American Southwest and throughout the semi-arid and arid regions of the world. The importance of developing a qualitative and quantitative understanding of the hydraulic processes which formed, and which continue to modify, these features derives from their rapid and significant development over the past four decades. As unplanned urban sprawl moved from valley floors onto alluvial fans, the serious damage incurred from infrequent flow events has dramatically increased. This book presents a discussion of our current and rapidly expanding knowledge of hydraulic processes on alluvial fans. It addresses the subject from a multidisciplinary viewpoint, acquainting the reader with geological principles pertinent to the analysis of hydraulic processes on alluvial fans.

French, R.H.

1987-01-01

152

Frozen Quaternary Deposits of the Laptev Sea Region as a Reservoir of Organic Carbon: Total Content and Composition  

Microsoft Academic Search

Permafrost is a significant reservoir and potential source of ancient organic matter (OM) such as plant remains, humified organics, etc. and greenhouse gases. In according with different estimations 1 cubic meter of frozen deposits in this region consists up to 10 kg of Corg. Due to the degradation of permafrost under the both modern geological processes and global warming, this

A. Kholodov; L. Schirrmeister; L. Shirshova; B. Zolotareva; H. Meyer; C. Knoblauch; K. Fahl

2007-01-01

153

Comparison of the Quaternary travertine sites in the Denizli extensional basin based on their depositional and geochemical data  

NASA Astrophysics Data System (ADS)

In the Denizli Basin (Turkey), located in the western Anatolian extensional province, travertine and tufa deposition has been an ongoing process for at least 600,000 years. Travertine bodies, which are 30 to 75 m thick and each covers areas of 1 to 34 km2, are up to 1 km3 in volume.

Özkul, Mehmet; Kele, Sándor; Gökgöz, Ali; Shen, Chuan-Chou; Jones, Brian; Baykara, Mehmet Oruç; F?rizs, István; Németh, Tibor; Chang, Yu-Wei; Alçiçek, Mehmet Cihat

2013-08-01

154

A Measure of Intense in West and Central Java Through Manifestation of River Basin Morphometry Development on Quaternary Volcanic Deposits  

Microsoft Academic Search

Indications exhibiting active tectonic movements in Java occur in many places, characterized by unstable regions, such as active faults, earthquakes, volcanic eruptions, etc. The results of researches conducted at several areas in West and Central Java on tectonic morphometry developments of river basins both in Qua- ternary deposits and Tertiary sediments exhibit a degree of active tectonic intensity. Such the

Febri Hirnawan

2009-01-01

155

Quaternary history of the northeastern Bighorn Basin based on a climatically-controlled process-response model  

SciTech Connect

The highest surfaces and oldest Pleistocene sediments in the northeastern Bighorn Basin are associated with the 600 kya North Kane Ash. Subsequent climatically-induced periods of aggradation and incision produced the remaining geomorphic elements. Processes associated with a typical interglacial-glacial cycle include: (1) interglacial stability with Bighorn River alluviation, pedimentation, and eolian deposition; (2) late-interglacial to early-glacial incision; (3) alluvial fan extension and increased landslide development during glacial intervals; and (4) an early-interglacial return to more stable conditions. Frequent stream captures during interglacial times were caused by the out-of-phase relationships between the Bighorn River and its tributaries. Quaternary climates of a given type have not been of equal magnitude or duration in the northeastern Bighorn Basin. The most intense glacial climates from which sediments are preserved are believed to have occurred ca. 600 kya, 440 kya an d140 kya. An abnormally dry climate existed between 400 kya and 275 kya, while extremely wet interglacial conditions prevailed about 100 kya. The last complete climatic cycle was the Bull Lake. The subsequent Holocene interglacial has been unusually dry. Thus not all Pleistocene climates have been capable of generating terraces of extensive alluvial fans.

Birdseye, R.U.

1985-01-01

156

Large alluvial fans on Mars  

Microsoft Academic Search

Several dozen distinct alluvial fans, 10 to ?40 km long downslope, have been observed in highlands craters. Within a search region between 0° and 30°S, alluvial fan-containing craters were found only between 18° and 29°S, and they all occur at around ±1 km of the MOLA-defined Martian datum. Within the study area they are not randomly distributed but instead form

Jeffrey M. Moore; Alan D. Howard

2005-01-01

157

Modified High-resolution Sequence Stratigraphy of Alluvial Sediments Based on Modern Geomorphology  

Microsoft Academic Search

The short-term base level cycle was subdivided into two types in the established high-resolution sequence stratigraphic model of alluvial deposits, namely deepening-upward unsymmetrical type and symmetrical type, which all stress that the common \\

Lan Chaoli; Zhang Junfeng; Tao Weixiang

2010-01-01

158

Late Quaternary geomorphology and soils in Crater Flat, Yucca mountain area, southern Nevada  

SciTech Connect

Crater Flat is an alluvium-filled structural basin on the west side of Yucca Mountain, Nevada, which is under consideration for a high-level nuclear waste repository. North-trending, late Quaternary faults offset alluvium in Crater Flat both along the canyons of the western flanks of Yucca Mountain and out on the piedmont slope. We believe the initial lack of young offsets at Yucca Mountain was in part due to unrecognized late Quaternary stratigraphy. We hypothesize that alluviation in the Yucca Mountain region was more active during the late Quaternary than previously thought. Several techniques were tried to test this hypothesis. Results are compared with previous soils and surface-exposure dating studies, and correlated to stratigraphy of other late Quaternary units in the southern Nevada, Death Valley, and Mojave Desert areas, and provide new stratigraphic data relevant to understanding climatic-alluvial processes in the Basin and Range Province during the late Quaternary. 76 refs., 7 figs., 6 tabs.

Peterson, F.F.; Bell, J.W.; Ramelli, A.R. [Univ. of Nevada, Reno, NV (United States); Dorn, R.I. [Arizona State Univ., Tempe, AZ (United States); Ku, T.L. [Univ. of Southern California, Los Angeles, CA (United States)

1995-04-01

159

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

160

A late quaternary record of eolian silt deposition in a maar lake, St. Michael Island, western Alaska  

USGS Publications Warehouse

Recent stratigraphic studies in central Alaska have yielded the unexpected finding that there is little evidence for full-glacial (late Wisconsin) loess deposition. Because the loess record of western Alaska is poorly exposed and not well known, we analyzed a core from Zagoskin Lake, a maar lake on St. Michael Island, to determine if a full-glacial eolian record could be found in that region. Particle size and geochemical data indicate that the mineral fraction of the lake sediments is not derived from the local basalt and is probably eolian. Silt deposition took place from at least the latter part of the mid-Wisconsin interstadial period through the Holocene, based on radiocarbon dating. Based on the locations of likely loess sources, eolian silt in western Alaska was probably deflated by northeasterly winds from glaciofluvial sediments. If last-glacial winds that deposited loess were indeed from the northeast, this reconstruction is in conflict with a model-derived reconstruction of paleowinds in Alaska. Mass accumulation rates in Zagoskin Lake were higher during the Pleistocene than during the Holocene. In addition, more eolian sediment is recorded in the lake sediments than as loess on the adjacent landscape. The thinner loess record on land may be due to the sparse, herb tundra vegetation that dominated the landscape in full-glacial time. Herb tundra would have been an inefficient loess trap compared to forest or even shrub tundra due to its low roughness height. The lack of abundant, full-glacial, eolian silt deposition in the loess stratigraphic record of central Alaska may be due, therefore, to a mimimal ability of the landscape to trap loess, rather than a lack of available eolian sediment. ?? 2003 University of Washington. Published by Elsevier Inc. All rights reserved.

Muhs, D. R.; Ager, T. A.; Been, J.; Bradbury, J. P.; Dean, W. E.

2003-01-01

161

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

162

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

163

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

164

Groundwater vulnerability map for the Ebro alluvial aquifer between Jalón and Ginel tributaries (Spain)  

NASA Astrophysics Data System (ADS)

The Quaternary deposits of the Ebro Basin in the surroundings of Zaragoza (Spain) form an unconfined alluvial aquifer with a high degree of permeability and low thickness of unsaturated materials. This fact causes a high degree of vulnerability to contamination, which implies consequences for land-use decisions and the risk management of existing industrial facilities. In addition, in the last decades the intense irrigation and the use of pesticides is threatening the quality of the groundwater and as a consequence the amount of usable groundwater at a low cost. Thus, the development of groundwater vulnerability maps has great importance in a regional planning process. Consequently, groundwater vulnerability maps have been developed following a method proposed by the German State Geological Surveys. In this paper the methodology developed within ArcGIS and Gocad, a two- and three-dimensional software, respectively, is presented. Although the results obtained within GIS (Geographical Information System) are acceptable it is to say that the 3D-model improves considerably the final product.

Lamelas, M. T.; Marinoni, O.; Hoppe, A.; de La Riva, J.

2007-12-01

165

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

166

Experimental study of alluvial fans  

NASA Astrophysics Data System (ADS)

The role of geomorphic thresholds in the short term operation and long term evolution of alluvial fans was examined. A theoretical, cyclic pattern of alluvial fan evolution, involving apex sedimentation, followed by channel incision and a longer period of lateral channel migration and backfilling, was confirmed. The regularity and predictability of cyclic changes in spatial sedimentation patterns increased as mudflows became more important. When mudflows were the primary agent, apex slopes were steep and unstable under intervening streamflow conditions. It is suggested that the alluvial fans of an area will display a myriad of contrasting morphologic forms, even if they were not subject to a change in external conditions. Incongruous morphologic responses of fans in Idaho imply differing levels of landform stability existed at the last major change in conditions. Changes in external variables may affect the stability of alluvial fans by either physically altering the landform relative to an unchanging threshold value or by modifying the threshold value of one of the variables which controls fan response. Instead of controlling landform behavior, external stimuli act within the cyclic framework of landform development to merely hasten or delay the conclusion of one cycle and the initiation of the next.

Weaver, W. E.

167

Uranium-series comminution ages of continental sediments: Case study of a Pleistocene alluvial fan  

SciTech Connect

Obtaining quantitative information about the timescales associated with sediment transport, storage, and deposition in continental settings is important but challenging. The uranium-series comminution age method potentially provides a universal approach for direct dating of Quaternary detrital sediments, and can also provide estimates of the sediment transport and storage timescales. (The word"comminution" means"to reduce to powder," reflecting the start of the comminution age clock as reduction of lithic parent material below a critical grain size threshold of ~;;50 mu m.) To test the comminution age method as a means to date continental sediments, we applied the method to drill-core samples of the glacially-derived Kings River Fan alluvial deposits in central California. Sediments from the 45 m core have independently-estimated depositional ages of up to ~;;800 ka, based on paleomagnetism and correlations to nearby dated sediments. We characterized sequentially-leached core samples (both bulk sediment and grain size separates) for U, Nd, and Sr isotopes, grain size, surface texture, and mineralogy. In accordance with the comminution age model, where 234U is partially lost from small sediment grains due to alpha recoil, we found that (234U/238U) activity ratios generally decrease with age, depth, and specific surface area, with depletions of up to 9percent relative to radioactive equilibrium. The resulting calculated comminution ages are reasonable, although they do not exactly match age estimates from previous studies and also depend on assumptions about 234U loss rates. The results indicate that the method may be a significant addition to the sparse set of available tools for dating detrital continental sediments, following further refinement. Improving the accuracy of the method requires more advanced models or measurements for both the recoil loss factor fa and weathering effects. We discuss several independent methods for obtaining fa on individual samples that may be useful for future studies.

Lee, Victoria E.; DePaolo, Donald J.; Christensen, John N.

2010-04-30

168

Late Quaternary river drainage and fish evolution, Southland, New Zealand  

NASA Astrophysics Data System (ADS)

Late Quaternary to Holocene landscape evolution in southern New Zealand was dominated by glacial outwash processes. Evolution of the drainage network on a regional scale was punctuated by numerous river capture events associated with outwash transport and deposition. River capture events can be inferred from geological and topographic observations throughout the region. Independent evidence for river capture and drainage reorientation can be obtained from genetic studies of a freshwater-limited fish (Galaxias ‘southern’, informal name). Regionally extensive interlinking of principal rivers (Mataura, Oreti, Aparima) via coalescence of alluvial plains onshore, and offshore at sea level lowstands, has resulted in a widespread genetic homogenisation of fish populations (< 0.9% mtDNA divergence). Genetically similar populations of G. ‘southern’ are present in an adjacent catchment (Von) that was captured episodically by the neighbouring major river system (Clutha). The low degree of genetic divergence between Oreti and Von catchments (< 0.15% mtDNA divergence) demonstrates that genetic interaction between fish populations was severed recently, probably during the early Holocene. This is in accord with radiocarbon dating (11 13 ka) of the youngest gravel level within the intervening divide. In contrast, morphologically similar fish in another adjacent major river (Waiau) have a minimum mtDNA divergence of 2.4% from the fish in the Mataura, Oreti, and Aparima Rivers. This genetic separation occurred at ca. 145 240 ka, based on the late Quaternary outwash terrace dating, in agreement with “molecular clock” estimates. Geological and genetic data in combination provide powerful tools for the elucidation of local and regional geomorphic evolution where river capture is an important process. The potential is strong for genetic data alone to provide information on the relative and absolute timing of river capture events, but must be interpreted in the context of severance of water connections between catchments and subsequent isolation of freshwater-limited populations.

Craw, D.; Burridge, C.; Anderson, L.; Waters, J. M.

2007-02-01

169

The Alaska Quaternary Center  

NSDL National Science Digital Library

This website illustrates the Alaska Quaternary Center's (at the University of Alaska, Fairbanks) commitment "to the promotion of interdisciplinary research and the enhancement of interdisciplinary instruction in Quaternary sciences." Users can view images of the field work and learn how to obtain quaternary data from the AQC Quaternary Research Geodatabase.

1969-12-31

170

Irish Quaternary Association (IQUA)  

NSDL National Science Digital Library

The Irish Quaternary Association (IQUA) website publicizes its aim "to promote Quaternary studies in Ireland through its publications, and the organization of field meetings and conferences." Visitors can learn about the importance of quaternary studies, find out the latest news and upcoming meetings, and find links to Quaternary studies journals.

1969-12-31

171

Beryllium-10 terrestrial cosmogenic nuclide surface exposure dating of Quaternary landforms in Death Valley  

NASA Astrophysics Data System (ADS)

Quaternary alluvial fans, and shorelines, spits and beach bars were dated using 10Be terrestrial cosmogenic nuclide (TCN) surface exposure methods in Death Valley. The 10Be TCN ages show considerable variance on individual surfaces. Samples collected in the active channels date from ~ 6 ka to ~ 93 ka, showing that there is significant 10Be TCN inheritance within cobbles and boulders. This suggests that the predominantly bedrock hillslopes erode very slowly and sediment is transferred very gradually in most regions within Death Valley. Comparisons of 10Be TCN ages on alluvial fan surfaces with chronostratigraphies based on soil development and optically stimulated luminescence dating show that minimum 10Be TCN ages within sample sets on individual surfaces most closely approximate to the age of landforms that are younger than ~ 70 ka. Alluvial fan surfaces older than ~ 70 ka have begun to undergo sufficient erosion such that the majority of 10Be TCN ages for datasets on individual surfaces probably underestimate the true age of the surface due to erosion and exhumation of fresh cobbles and boulders. The spread of 10Be TCN ages for beach bars near Beatty Junction and shorelines ~ 8 km south of Furnace Creek is large, ranging from ~ 119 ka to ~ 385 ka and ~ 109 ka to ~ 465 ka, respectively. New and previously published luminescence ages and soil development suggest that these landforms may have formed during marine isotope stage (MIS) 2 (~ 22-18 ka), but these younger ages may reflect elluviation of material into the bar deposit long after deposition, and hence the younger ages do not record the true antiquity of the landforms. This disparity between dates determined by different dating methods and the large spread of TCN ages suggests that the cobbles and boulders have considerable inherited 10Be concentrations, suggesting that the clasts have been derived from older shorelines or associated landforms. These results highlight the problems associated with using surface cobbles and boulders to date Quaternary surfaces in Death Valley and emphasizes the need to combine multiple, different dating methods to accurately date landforms in similar dryland regions elsewhere in the world. However, these results highlight the potential to use TCN methods, when used in combination with other dating techniques, to examine and quantify processes such as sediment transfer and denudation in drylands.

Owen, Lewis A.; Frankel, Kurt L.; Knott, Jeffrey R.; Reynhout, Scott; Finkel, Robert C.; Dolan, James F.; Lee, Jeffrey

2011-02-01

172

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

Microsoft Academic Search

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

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

2008-01-01

173

The Holocene Alluvial Delta Relief Complex and Hydrological Regime of the Lena River Delta  

Microsoft Academic Search

Summary: This study presents the geological-geomorphologic characreristics of the Holocene alluvial-delta relief complex of the Lena River delta and deposits comprising it. A complex of the Holocene alluvial-delta relief is represented by a set of channel forrns ancl a low floodplain of modern age, a high floodplain fonning from the end of the Early-Late Holocene and the first above- the

Elena Yu; Marina V. Dorozhkina

174

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

175

Rates of late Quaternary normal faulting in central Tibet from U-series dating of pedogenic carbonate in displaced fluvial gravel deposits  

NASA Astrophysics Data System (ADS)

Along the main boundary fault of the central Tibetan Shuang Hu graben, two well-preserved fluvial terrace surfaces are vertically offset by ~1.3 m (terrace I) and ~14.8 m (terrace II). Using thermal ionization mass spectrometry (TIMS), we have determined 48 230Th-234U-238U ages of small (10-40 mg) samples from pedogenic carbonate rinds on clasts in the terrace deposits. Based on textural, microstratigraphic and geochemical criteria, we conclude that the U-series ages of innermost-rind samples provide reliable ages of 16.4+/-1.9 ka for terrace I, and 233.1+/-9.3 ka for terrace II. This constrains the average rate of vertical displacement along the normal fault to be 0.079+/-0.011 mm/yr during the past ~16 kyr, and 0.064+/-0.007 mm/yr during the past ~233 kyr. Combining these results with slip-rate estimates for other normal faults along the graben margins indicates that the cumulative vertical displacement on all normal faults did not exceed ~0.3 mm/yr during the late Quaternary. This new rate from central Tibet is distinctly lower than the rate of 1.9+/-0.6 mm/yr inferred for normal faults bounding the Yadong-Gulu graben system in southern Tibet, consistent with more pronounced and common graben development in southern Tibet. We therefore suggest that normal faulting in southern Tibet is largely controlled by local processes, and that the age of its initiation is not a valid proxy for uplift of the Tibetan plateau, as has been widely assumed. Our data also place chronologic constraints on the termination of periglacial conditions in central Tibet during the last three interglaciations. Rind formation appears to have been relatively continuous on clasts in terrace I from ~16 ka. Clast rinds from terrace II, in contrast, are characterized by three main episodes of rind growth that are widely separated in time. The earliest and least well-preserved episode started at 233.1+/-9.3 ka, a second episode occurred at 131.8+/-7.8 ka, and a third episode was approximately coeval with rind formation in terrace I after 16.4+/-1.9 ka. In each case, the age of onset of carbonate rind accumulation coincides with independently estimated ages of global deglaciation. Accordingly, we conclude that periglacial conditions in the central Tibetan plateau terminated synchronously with early stages of global warming following the last three glacial maxima, and that fluvial aggradation, terrace formation, and pedogenic carbonate accumulation in terrace soils ensued rapidly.

Blisniuk, Peter M.; Sharp, Warren D.

2003-10-01

176

The modern environments of Molluscs in southern Mesopotamia, Iraq: A guide to paleogeographical reconstructions of Quaternary fluvial, palustrine and marine deposits  

Microsoft Academic Search

The Quaternary, mainly freshwater sediments of the Lower Mesopotamian plain include a thin transgressive marine unit which extends inland some 250 km from the present coastline, the Hammar Formation. The identity and respective areal extent of continental and transgressive units are based mainly on their molluscan faunas. Those faunas reflect the several environments of the Middle Eastern biogeographic province: fluviatile,

Jean-Claude PLAZIAT; Woujdan R. YOUNIS

2005-01-01

177

Modified High-resolution Sequence Stratigraphy of Alluvial Sediments Based on Modern Geomorphology  

NASA Astrophysics Data System (ADS)

The short-term base level cycle was subdivided into two types in the established high-resolution sequence stratigraphic model of alluvial deposits, namely deepening-upward unsymmetrical type and symmetrical type, which all stress that the common "dualistic structure" of fluvial vertical profile in alluvial environments was deposited in a deepening-upward base level half-cycle. However, according to observation about modern fluvial geomorphology, it is found that fluvial deposits always behave as characteristics of shoaling-upward sedimentary successions. On the basis of redefinition of base level and accommodation in alluvial settings, rise and fall of base level and their sedimentological responses were investigated that sediments are piled up in a descending base level half-cycle in this environment, while show eroding-downward or lateral erosion in a rising base level half-cycle with coarse bed lags perhaps. On the principle of base level rise-fall process and sedimentation response, it is suggested an improved division proposal for short-term base level cycle of alluvial deposits that includes two types, consisting of shoaling-upward unsymmetrical type and symmetrical type mainly on shoaling-upward cycle. The most difference between the recommended and the existed is that the former put emphasis on alluvial sediments deposited during period of base level fall. Although reliability of the suggested plan needs to be testified further, it at least reduces arbitrariness in ascertaining transformation surface between short term rise and fall half-cycle of base level.

Chaoli, Lan; Junfeng, Zhang; Weixiang, Tao

2010-05-01

178

Quaternary Geologic History of the Rio Tambo, Southern Peru: Repeated Mass-Wasting Events in Western Cordillera Drainages  

NASA Astrophysics Data System (ADS)

The amount and timing of river incision along the western margin of the Altiplano can provide insight into the climatic, volcanic, and tectonic history of this region. While many studies have focused on the Tertiary geologic history of the western margin of the Altiplano, the Quaternary geologic history of this margin remains largely unstudied. The Pacific draining Rio Tambo river valley in the forearc of southern Peru is one of the large drainages of the western margin. While much of this river is presently cutting bedrock, many locations within the main and tributary channels contain lacustrian, landslide, and volcanic ash deposits of Quaternary age (?). While geomorphologic features such as active and abandoned alluvial fans, fluvial terraces (strath and fill), and pediment surfaces exist along multiple segments of this drainage current geologic maps of the area lack the spatial resolution to effectively use these deposits for constructing the geomorphic evolution of the area. Thus, we have mapped the Quaternary (?) features through field measurements using a theodolite, as well as from remotely sensed data including SRTM DEMs, stereo-pair aerial photos, and ASTER images. Using cosmogenic 10Be to date the surfaces, we are able to place bounds on the age of terrace, lacustrian, and landslide deposits. Although fluvial incision is an important erosive process, which has resulted in this high-relief landscape, we find extensive evidence that mass-wasting is here extremely effective at facilitating the rapid movement of large amounts of material. At numerous times throughout the Quaternary, huge debris flows have dammed the steep fluvial valleys producing vast lakes and thick (up to ~100m ) lacustrian deposits upstream of the landslide deposits. At present, the landslide and lacustrian deposits have been re-incised, in many cases, to bedrock, and only stranded lake and landslide deposits remain high on valley walls. Thus, a large amount of material has been transported out of this drainage basin through first mass-wasting followed by river incision. As the Rio Tambo is located in the hyperarid climatic zone and thus receives very little annual precipitation, landsliding might result from over steepened valley walls associated with nick-point migration or possibly as a result of groundwater sapping. Further, we observe this type of rapid landscape modification in many of the bedrock-rivers in both northern and southern Peru and indeed throughout the western margin of the Peruvian Andes. While previous authors have described the late Cenozoic-present as a period of canyon cutting throughout the western margin, we suggest that mass-wasting and re-incision is the dominant process facilitating the degradation of the high topography of this portion of the the Andes.

Davis, M. W.; Hall, S. R.; Farber, D. L.; Audin, L.; Finkel, R.

2007-12-01

179

Sedimentology of Holocene debris flow-dominated alluvial fans, northwest Wyoming: Contributions to alluvial fan facies models  

SciTech Connect

Facies models for debris flow-dominated alluvial fans are based exclusively upon studies of relatively few fans in the arid American southwest. Detailed geomorphic, stratigraphic, and sedimentologic analyses of several highly-active, debris flow-dominated alluvial fans in northern Yellowstone National Park, WY (temperature, semi-arid) serve to diversify and increase the usefulness of alluvial fan facies models. These fans display an intricate distributary pattern of incised active (0--6 m deep; 700--900 m long) and abandoned channels (1--4 m deep; 400 m long) with levees/levee complexes (<3 m high; <20 m wide; <750 m long) and lobes constructed by pseudoplastic to plastic debris flows. The complex pattern of debris flow deposits is due to repeated channel back filling and overtopping by debris flows behind in-channel obstructions which subsequently lead to channel abandonment. Debris-flow deposition is dominant due to: (1) small, steep (up to 35 degrees) source area catchments, (2) extensive mud rock outcrops in the source area, and (3) episodic summer rainfall events. Proximal to distal fan surfaces exhibit sheetflood deposits several cm thick and up to 70 m in lateral extent. Vertical lithofacies profiles reveal: (1) massive, matrix- and clast-supported gravel units (1--2 m thick) deposited by clast-poor and clast-rich debris flows respectively, with reworked; scoured tops overlain by thin (<0.25 m) trough cross-bedded gravel and ripple cross-laminated sand intervals, and (2) volumetrically less significant 1--2 m thick intervals comprising fining-upward sequences of interbedded cm-scale trough cross-bedded pebbly gravel, massive sand, horizontally stratified sand, and mud rock deposited by hyperconcentrated flow and stream flow during decelerating sheetflood events. Organic rich layers record periods of non-deposition. Channelized stream flow is restricted to minor reworking of in-channel debris flow and hyperconcentrated flow deposits.

Cechovic, M.T.; Schmitt, J.G. (Montana State Univ., Bozeman, MT (United States). Dept. of Earth Sciences)

1993-04-01

180

Paleomagnetic Stratigraphy and Time in Sediments: Studies in Alluvial Siwalik Rocks of Pakistan  

Microsoft Academic Search

Sediments may acquire magnetic remanence upon deposition and shortly after deposition. Hence, the paleomagnetic record of sedimentary rocks may provide a chronostratigraphic framework for rates and patterns of depositional and post-depositional processes over time scales intermediate between those of modern observation and those of the dated geologic record. Two applications of high-resolution magneto-stratigraphy in Miocene, alluvial rocks of Pakistan illustrate

Catherine Badgley; Lisa Tauxe

1990-01-01

181

Alluvial aquifers in the Mzingwane catchment: Their distribution, properties, current usage and potential expansion  

NASA Astrophysics Data System (ADS)

The Mzingwane River is a sand filled channel, with extensive alluvial aquifers distributed along its banks and bed in the lower catchment. LandSat TM imagery was used to identify alluvial deposits for potential groundwater resources for irrigation development. On the false colour composite band 3, band 4 and band 5 (FCC 345) the alluvial deposits stand out as white and dense actively growing vegetation stands out as green making it possible to mark out the lateral extent of the saturated alluvial plain deposits using the riverine fringe and vegetation . The alluvial aquifers form ribbon shaped aquifers extending along the channel and reaching over 20 km in length in some localities and are enhanced at lithological boundaries. These alluvial aquifers extend laterally outside the active channel, and individual alluvial aquifers have been measured with area ranging from 45 ha to 723 ha in the channels and 75 ha to 2196 ha on the plains. The alluvial aquifers are more pronounced in the Lower Mzingwane, where the slopes are gentler and allow for more sediment accumulation. Estimated water resources potential ranges between 175,000 m3 and 5,430,000 m3 in the channels and between 80,000 m3 and 6,920,000 m3 in the plains. Such a water resource potential can support irrigation ranging from 18 ha to 543 ha for channels alluvial aquifers and 8 ha to 692 ha for plain alluvial aquifers. Currently, some of these aquifers are being used to provide water for domestic use, livestock watering and dip tanks, commercial irrigation and market gardening. The water quality of the aquifers in general is fairly good due to regular recharge and flushing out of the aquifers by annual river flows and floodwater. Water salinity was found to increase significantly in the end of the dry season, and this effect was more pronounced in water abstracted from wells on the alluvial plains. During drought years, recharge is expected to be less and if the drought is extended water levels in the aquifers may drop substantially, increasing salinity problems.

Moyce, William; Mangeya, Pride; Owen, Richard; Love, David

182

Climatic controls on late Pleistocene alluvial fans, Cyprus  

NASA Astrophysics Data System (ADS)

Alluvial fans are commonly associated with tectonically active mountain ranges and tectonism is frequently held responsible for abrupt coarsening and cyclical sedimentation of alluvial fan sequences. Whilst it is accepted that tectonism provides the opportunity for alluvial fan development through the creation of topography, increasing gradients of fluvial systems supplying sediments, and creating accommodation for the storage of sediment flux, the role of climate in fan development is frequently neglected. The hypothesis that climatically controlled events can produce recognisable sedimentary signatures in alluvial fan deposits is tested in the active supra-subduction zone setting of the late Pleistocene of southern Cyprus. This study demonstrates through architectural analysis and the reconstruction of palaeoflood hydrology a recorded pattern of increasing and decreasing palaeoflow dynamics, with switches from a wetter to drier mode, clearly exhibited by changes in the sedimentology of the fan. At the present day Cyprus has a semi-arid climate and is influenced by a strongly seasonal rainfall pattern, largely restricted to the winter months (plus rare occurrences of summer cyclones). However at precession minima increased activity of western Mediterranean depressions produces wetter summers. Using inference we propose that longer-term increases in rainfall increased river discharge as recorded in the fan palaeoflood hydrology and occurred at minima in the precession. These periods correlate with the deposition of conglomeratic channels and open framework gravels. Drier periods are exhibited by sandier braided fluvial deposits. Shorter term or seasonal change is recorded in the form of 2nd and 3rd low order bounding surfaces. This increased activity of Mediterranean summer depressions increased precipitation to the wider Levantine area and was coincident with increased intensity of the north African and Indian Ocean (SW) monsoons. The resultant increase in river discharges at precession minima from both the Nile (and the wider Levant) resulted in the formation of sapropels in the eastern Mediterranean and is recorded as wet periods in speleothem deposits in the Soreq and Peqiin Caves of Israel. The predominant control of sedimentation on the late Pleistocene alluvial fans of southern Cyprus was climate.

Waters, J. V.; Jones, S. J.; Armstrong, H. A.

2010-03-01

183

Developing a Geophysical Approach to the Study of Climatic Change Markers in Quaternary Formations of the Fresnal Valley, North Chihuahuan Desert, Mexico  

NASA Astrophysics Data System (ADS)

In the context of an ongoing multidisciplinary investigation of the El Fresnal valley, Chihuahua (31\\deg05'N and 107\\deg30'W), a multi-method geophysical survey program has been initiated. Its initial objective is the establishment of the best approach to assess and complement the geomorphological and geological study of the deposits characteristic of varying climatic conditions. The valley is a N-S oriented half-graben/tilted-block system with a playa-lake on the basin floor, and bordered by piedmonts classified as alluvial fans. Fan development appears to coincide with a proposed late Quaternary climatic shift that may have increased sediment flux. Three alluvial fans located on the footwall slopes were formed during this time and are consistent with the main climatic changes registered in the paleolake stratigraphy of Northern Mexico and the American Southwest. These alluvial fans consist mainly of debris flow deposits formed by flash floods probably triggered by a change from relatively moist to arid conditions. To investigate these formations, a combination of standard electrical resistivity sounding, 2-D resistivity imaging and ground penetrating radar is used. Most of the survey lines are confined to a long traverse crossing the basin from East to West, roughly perpendicular to the structural axis. The two main challenges encountered are the difficulty of access and the high electrical conductivities found at very shallow depths in most areas. The worst affected method is GPR, which will most likely prove of limited use except for very detailed work. Electrical surveys yield more useful results and allow the main units of the fan deposits to be resolved. At this point the best geophysical approach seems to be a combination of fast, relatively deep vertical soundings for determining the overall geoelectrical structure and high-resolution 2-D imaging profiles that provide information on lateral variations.

Maillol, J.; Ortega-Ramirez, J.; Fortier, G.; Bandy, W. L.; Valiente-Banuet, A.; Urrutia-Fucugauchi, J.; Anderson, L.; Martinez-Estrella, F.

2001-12-01

184

Early Cretaceous stratigraphy, paleontology, and sedimentary tectonics in Paris overthrust foredeep (western Wyoming and southeastern Idaho) compared with Quaternary features of indo-gangetic plain  

SciTech Connect

Fluviatile clastics of the nonmarine, early Cretaceous Gannett and Wayan groups were deposited on wet alluvial megafans and on intervening interfan piedmont slopes which declined eastward into more poorly drained lowlands from a western highland source area uplifted episodically by movements of the Paris overthrust. Lacustrine episodes of deposition intercalated Peterson and Draney limestones with Gannett fluvial clastics. Westward marine transgressions (Skull Creek, Mowry) intercalated mixed lacustrine and brackish facies (Smiths and Cokedale formations) into Wayan fluviatile clastics. Newly discovered fossil vertebrate and invertebrate materials (all fragmentary but identifiable) include: Gannett Group - large reptiles including turtles; Thomas Fork Formation - freshwater gastropods and unionid pelecypods, gastroliths, two types of turtles, large reptilian fragments (dinosaur), and abundant dinosaur eggshell fragments; Wayan Formation - perennially aquatic snails, turtles, unidentifiable large reptiles, two types of crocodilians, an iguanodontid dinosaur (Tenontosaurus), an ankylosaurian dinosaur, a large ornithopod dinosaur, gastroliths, abundant and ubiquitous dinosaur eggshell fragments (numerous types and sizes), and miscellaneous unidentifiable small vertebrate bone fragments. A census of analogous modern reptile reproductive behaviors supports the conclusion that the Wayan, and probably also the Gannett, alluvial fan environments were used as upland breeding grounds by dinosaurs and perhaps other reptiles. Comparison of these Early Cretaceous data with observations on the tectonic setting, sedimentology, and biology of the Quaternary indo-gangetic plain suggests many close analogies between the two sedimentary tectonic settings.

Dorr, J.A. Jr.

1983-08-01

185

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

186

Uplift of quaternary shorelines in eastern Patagonia: Darwin revisited  

Microsoft Academic Search

During his journey on the Beagle, Darwin observed the uniformity in the elevation of coastal Eastern Patagonia along more than 2000km. More than one century later, the sequences of Quaternary shorelines of eastern Patagonia have been described and their deposits dated but not yet interpreted in terms of geodynamics. Consequently, we i) mapped the repartition of the Quaternary coastal sequences

Kevin Pedoja; Vincent Regard; Laurent Husson; Joseph Martinod; Benjamin Guillaume; Enrique Fucks; Maximiliano Iglesias; Pierre Weill

2011-01-01

187

Geochemistry of carbonate cements in surficial alluvial conglomerates and their paleoclimatic implications, Sultanate of Oman  

SciTech Connect

Early diagenetic carbonate cements are a common feature of Quaternary alluvial conglomerates in Oman. Cements are formed in the vadose and, more commonly, phreatic zones from near-surface groundwaters. In drainage areas underlain by the Semail Ophiolite, groundwaters have Mg{sup 2+}/Ca{sup 2+} ratios greater than two, and cements are often dolomite or high-magnesium calcite in addition to low-magnesium calcite. In drainage areas underlain by limestone, groundwaters have Mg{sup 2+}/Ca{sup 2+} ratios of around one or less and cement mineralogy is nearly always low-magnesium calcite. The oxygen and carbon stable isotopic ratios of the cements vary widely, from {minus}10.6{per_thousand} to +3.0{per_thousand} PDB and from {minus}10.0{per_thousand} to +0.7{per_thousand} PDB, respectively. Cement {delta}{sup 18}O values principally reflect variation in rainfall {delta}{sup 18}O over a time scale of several thousand years. Rainfall and cement {delta}{sup 18}O values probably are inversely correlated with the amount of rainfall, which is related to the frequency and intensity of the Indian Ocean monsoon. Thus, cement {delta}{sup 18}O is potentially a proxy indicator of relative rainfall and monsoon activity. For each of three sampling areas, {delta}{sup 13}C is positively correlated to {delta}{sup 18}O. Cement {delta}{sup 13}C values are also related to rainfall amount because rainfall controls the plant population. Greater plant respiration of isotopically depleted CO{sub 2} to shallow groundwaters and burial of organic material in conglomerate deposits results in lower cement {delta}{sup 13}C values compared to periods of lesser plant activity.

Burns, S.J.; Matter, A. [Univ. Bern (Switzerland). Geologisches Inst.

1995-01-02

188

Morphologic expression of Quaternary deformation in the northwestern foothills of the Ysyk-Köl basin, Tien Shan  

Microsoft Academic Search

The Tien Shan is one of the most active intracontinental mountain belts exhibiting numerous examples of Quaternary fault-related folding. To provide insight into the deformation of the Quaternary intermontane basins, the territory of the northwestern Ysyk-Köl region, where the growing Ak-Teke Anticline divided the piedmont apron of alluvial fans, is studied. It is shown that the Ak-Teke Hills are a

A. M. Korjenkov; I. E. Povolotskaya; E. Mamyrov

2007-01-01

189

Convex bar formation in an alluvial-bedrock stream channel  

NASA Astrophysics Data System (ADS)

Bar formation in the Guadalupe River occurs at a variety of spatial and temporal scales. The Guadalupe River is a mixed alluvial-bedrock river in central Texas which is characterized by the presence of an alluvial macro channel and a bedrock active channel that is shallowly incised. The flow regime in the Guadalupe and other rivers in the Balcones Escarpment region are punctuated by frequent high-magnitude flooding. The combination of low infiltration capacity upland soils, steep highly dissected watersheds, and dryland vegetation, creates conditions for rapid runoff and large volume sediment loads during floods. The processes controlling bar formation in the Guadalupe River are unlike those in alluvial rivers and is dominated by the process of convex bar formation. Convex bar formation has been documented in a large width to depth ratio river in eastern Wyoming where large volumes of sediment were deposited during floods and then re-worked by the active channel scale longitudinal processes at lower flows. This poster illustrates convex bar formation in the Guadalupe River at the macro and active channel scales as part of the hierarchical classification of channel boundary type in mixed rivers.

Keen-Zebert, A.; Curran, J. C.

2006-12-01

190

The paradox of large alluvial rivers (Invited)  

NASA Astrophysics Data System (ADS)

Large alluvial rivers exhibit large floodplains, very gentle slopes, a good selection of bed materials (generally sand), low specific stream power, and could represent the ultimate examples of “dynamic equilibrium” in fluvial systems. However, equilibrium can be discussed at different temporal scales. Base level changes by tectonic or climatic effects, modifications in sediment and water supply or different kinds of human impacts are the traditional causes that could trigger “disequilibrium” and changes in the longitudinal profile. Simultaneously, adjustments of longitudinal profiles were thought to be evolving from downstream to upstream by several processes, being the most common receding erosion. Some authors,have demonstrated that when changes in base level happen, a variety of adjustments can be reached in the lower course in function of the available sediment and water discharge, slopes articulations between the fluvial reach and the continental shelve, among others, and that the adjustments can be transferred upstream significantly in small rivers but not far upstream along large fluvial systems. When analyzing the Quaternary fluvial belts of large rivers in the millennium scale, paleohydrological changes and modifications in floodplain constructional processes or erosion, are associated normally to late Quaternary climatic changes. The study of several of the largest rivers demonstrates that climatic changes and fluvial responses are not always working totally in phase and those direct cause-consequences relations are not a rule. This paper describes floodplain evolution and the lagged geomorphic responses of some large river system to recent climatic changes. Information from some of the largest rivers of the world such as the Amazon, Parana, several tributaries of the Amazon (Negro, Xingú, Tapajos) as well as some large Siberian Rivers was used. Since the last deglaciation, these large fluvial systems have not had enough time to reach equilibrium conditions along whole the river and present several stages of “incomplete floodplains”. Furthermore, minor climatic changes during the Holocene have possibly also affected their fluvial style, producing additional and partial adjustments. A main concept presented here is that large rivers achieved equilibrium conditions mainly from upstream to downstream by partially filling up their valleys and local sedimentary basins/sediment sinks (e.g. wide valleys, flood basins and permanent water saturated floodplains, tectonic sunken blocks, among others) with a variety of morpho-sedimentological processes, and transferring equilibrium conditions from upstream to downstream. When the “available space” (sedimentary sink) becomes as full of sediments as possible, the rivers adjust on a more efficient corridor of channels in quasi-equilibrium conditions. Valley infilling processes progress downstream as a prograding system on areas of the channel-floodplain system that have not yet reached quasi-equilibrium conditions Because most results in the literature are focused on small to medium size rivers, these results intend to open a new discussion about floodplain mechanisms of construction, demystifying some traditional concepts relating floodplains and equilibrium, and climatic changes and river responses in large rivers.

Latrubesse, E. M.

2010-12-01

191

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

192

Are North Slope surface alluvial fans pre-Holocene relicts?  

USGS Publications Warehouse

The surface morphology of the northern slope of the Brooks Range (North Slope) from the Canning River, Alaska, eastward is dominated by a series of large alluvial fans and braided streams floored by coarse alluvium. On the basis of our studies, we conclude that the fans are not prograding now nor have they been prograding at any time during the Holocene. During the latest transgression and the following sea-level highstand, the North Slope depositional environment and climate probably differed greatly from the present ones.

Reimnitz, Erk; Wolf, Stephen C.

1998-01-01

193

Characterizing arid region alluvial fan surface roughness with airborne laser swath mapping digital topographic data  

NASA Astrophysics Data System (ADS)

Range-front alluvial fan deposition in arid environments is episodic and results in multiple fan surfaces and ages. These distinct landforms are often defined by descriptions of their surface morphology, desert varnish accumulation, clast rubification, desert pavement formation, soil development, and stratigraphy. Although quantifying surface roughness differences between alluvial fan units has proven to be difficult in the past, high-resolution airborne laser swath mapping (ALSM) digital topographic data are now providing researchers with an opportunity to study topography in unprecedented detail. Here we use ALSM data to calculate surface roughness on two alluvial fans in northern Death Valley, California. We define surface roughness as the standard deviation of slope in a 5-m by 5-m moving window. Comparison of surface roughness values between mapped fan surfaces shows that each unit is statistically unique at the 99% confidence level. Furthermore, there is an obvious smoothing trend from the presently active channel to a deposit with cosmogenic 10Be and 36Cl surface exposure ages of ˜70 ka. Beyond 70 ka, alluvial landforms become progressively rougher with age. These data suggest that alluvial fans in arid regions smooth out with time until a threshold is crossed where roughness increases at greater wavelength with age as a result of surface runoff and headward tributary incision into the oldest surfaces.

Frankel, Kurt L.; Dolan, James F.

2007-06-01

194

Avulsion Clusters in Alluvial Systems: An Example of Large-Scale Self-Organization in Ancient and Experimental Basins  

Microsoft Academic Search

The stratigraphic record of at least some alluvial basins exhibits a spatial structure that may reflect long time- scale (103-105 yr in natural basins) autogenic organization of river avulsions. Current models of avulsion-dominated alluvial sequences emphasize the spatial and temporal distribution of coarse-grained channel-belt deposits amid fine-grained floodplain materials. These models typically assume that individual avulsions move, either randomly or

E. Hajek; P. Heller; S. Huzurbazar; B. Sheets; C. Paola

2006-01-01

195

Alluvial sedimentology of the Upper Pleistocene Hinuera formation, Hamilton Basin, New Zealand  

Microsoft Academic Search

The Upper Pleistocene HinueraFormation is an unconsolidated alluvial deposit, up to 90 m thick, underlying some 2000 km of the plains of the Hamilton Basin and the southern half of the Hauraki Lowland. The sediments have been studied in detail at 19 widely-spaced sections in Hamilton Basin. The most striking lithological features are their coarseness, acid volcanic composition, and abundant

Terry M. Hume; Alan M. Sherwood; Campbell S. Nelson

1975-01-01

196

Evidence for episodic alluvial fan formation in far western Terra Tyrrhena, Mars  

Microsoft Academic Search

A Late Noachian-aged alluvial fan complex within Harris Crater in far western Terra Tyrrhena, Mars, is comprised of two well-defined source regions and associated discrete depositional lobes. Three fan units were recognized based on common morphological characteristics, thermal properties and spectral signatures. Although the entire fan complex has been subjected to extensive erosional degradation, the preserved morphologies record episodic fan

Rebecca M. E. Williams; A. Deanne Rogers; Matthew Chojnacki; Joseph Boyce; Kimberly D. Seelos; Craig Hardgrove; Frank Chuang

2011-01-01

197

Climatically controlled Late Quaternary terrace staircase development in the fold- and -thrust belt of the Sub Himalaya  

Microsoft Academic Search

The alluviation and incision history of Late Quaternary terrace staircases of Yamuna River and its tributaries in the Sub Himalaya, between the Main Boundary Thrust (MBT) and the Himalayan Frontal Thrust (HFT), were studied to understand interlinkages between tectonics and climate in their genesis. We documented five levels of terraces (T1 to T5), cutting across numerous tectonic plains, ranging in

Sharat Dutta; N. Suresh; Rohtash Kumar

198

Geomorphological and sedimentological features in Quaternary fluvial systems affected by solution-induced subsidence (Ebro Basin, NE-Spain)  

Microsoft Academic Search

The Quaternary evolution and the morpho-sedimentary features of some of the most important rivers in Spain (Ebro and Tagus rivers among others) have been controlled by subsidence due to alluvial karstification of the evaporitic bedrock. The subsidence mechanism may range from catastrophic collapse to slow sagging of the alluvium by passive bending. In the Ebro Basin, the mechanisms and processes

Gerardo Benito; Francisco Gutiérrez; Alfredo Pérez-González; Maria J Machado

2000-01-01

199

OSL dating without sand lenses: Late Pleistocene alluvial fan aggradation in the Lost River Range, Idaho  

NASA Astrophysics Data System (ADS)

Along the western front of the Lost River Range (LRR) in Idaho, USA, numerous sheetflood-dominated alluvial fans extend 2-6 km from the mountain front. Despite their geomorphic significance within the basin, these fans are largely inactive under modern conditions and are hypothesized to be remnants of glacial climate (e.g. Pierce and Scott, 1982). To investigate climate and glaciation as potential drivers of fan aggradation, the first goal of this study was determining how best to apply optically stimulated luminescence (OSL) dating as deposits lacked sand lenses and were predominately clast-supported sheetflood gravels with a sandy matrix. The second goal of the study was to investigate the Quaternary climate conditions that promote alluvial fan aggradation, including the importance of glacial activity vs. general glacial climate conditions as drivers of sedimentation. Five fans that represent the variation in late Pleistocene glaciation within contributing basins (0-80% of basin area) were selected for dating and geomorphic mapping. Samples for OSL dating were largely collected by excavating material from under light-safe tarps or at night, with samples for equivalent dose estimates sieved to retain the <2mm portion. Sediment chemistry for dose rate (DR) estimation was analyzed for numerous grain sizes. Sand grain size fractions (<2 mm and 0.15-2.0 mm) produced the highest DR estimates, pebbles (>5 mm) the lowest, with results from bulk samples generally in between. Bulk sample DR estimates were preferred, likely providing the best estimate of the average dose from the sediment. Partial bleaching is not suggested by equivalent dose distributions, but overdispersion values of >20% for some samples may result from the heterogeneity in the sediment DR. Despite potential DR problems, resulting ages are consistent with fan morphology and multiple ages from single surfaces show good agreement. Ages from 31 OSL samples ranged from ~4-60 ka and with mapped fan surfaces suggest aggradation during four distinct intervals: 0-10 ka, 10-20 ka, 20-35 ka and 35-60 ka. Surprisingly, the timing of deposition is similar for all fans, regardless of past glacial extent within contributing basins. The majority of fan aggradation occurred during the late Pleistocene, with deposition during the Holocene limited to ~10% of total fan surface area. The greater extent of late Pleistocene surfaces, steeper slopes and dominance of coarser sheetflood facies suggests greater transport capacity of streams and sediment delivery to fans between 10-60 ka. Regional climate records indicate generally cold climate in the LRR throughout 10-60 ka, but more variable moisture delivery. Cold conditions may have increased transport capacity with greater effective moisture and higher spring discharges in response to increased winter snowpacks . Concurrently, sediment delivery may have increased by mobilization of stored hillslope sediment, decreased vegetation cover or increased sediment production by glaciation, enhanced weathering rates and more effective frost weathering. Overall, this research shows that glacial climate conditions, not necessarily glaciation, enhance hillslope sediment supply and fan aggradation in the LRR of Idaho.

Kenworthy, M.; Rittenour, T. M.; Pierce, J. L.

2011-12-01

200

Using airborne geophysics to define the 3D distribution and landscape evolution of Quaternary valley-fill deposits around the Jamestown area, South Australia  

Microsoft Academic Search

The combined analysis of airborne electromagnetics, airborne gamma-ray spectrometry, magnetics and a digital elevation model with ground-based calibration has enabled construction of a 3D architectural and landscape evolution model of valley-fill deposits around the township of Jamestown in South Australia. The valley-fill sediments consist of traction, suspension and debris-flow deposits that range in age (optically stimulated luminescence dating) from 102 ± 12

J. Wilford

2009-01-01

201

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

202

Geomorphological facies reconstruction of Late Quaternary alluvia by the application of fluvial architecture concepts  

NASA Astrophysics Data System (ADS)

This paper investigates the methodical implications, the benefits, and the constraints of applying the fluvial architecture concept to Late Quaternary shallow-subsurface alluvial deposits. The focus is upon a typical small- to mesoscale valley floor of the temperate zone. The studied reach is part of the river Wetter catchment (517 km2) in central Germany. A large number of studies on Late Quaternary terrestrial paleoenvironmental change of the temperate zone refer to such small- to mesoscale catchments, which are mostly occupied by mixed- to suspended-load rivers. As in many cases mostly coring-based evidence is available, the observation and measurement is limited to lithology and lithofacies boundaries; facies geometry must be inferred. Moreover, in those environments differences in lithofacies are obscured by a significantly reduced range of grain size distributions. An example of an ancient channel belt of Late Glacial to Holocene age serves to delineate the methodical practice and utility of the fluvial architecture approach. Field evidence is obtained from detailed cross-sectional surveys and comprises descriptions of lithofacies, structural, pedogenetical, biotic features, Munsell color, and total organic carbon magnetic volume susceptibility. Cross-sectional lithofacies information is represented by spatially attributed, scaled borehole logs. The example also accentuates the need for applying additional stratigraphical methods such as physical age determination, macrofossil analysis, and tephrological stratigraphy. These methods form the basis to discern stacked channel facies and derive a diachrony of channel forms. Thus, the adapted architecture approach provides a significant surplus of information on channel dimensions, ages, and channel floodplain interconnectedness. Distinct fluvial landforms such as channels, levees, abandoned channels, swamps, and floodplain flats can be highlighted. A number of methodical constraints are discussed in detail, e.g., the sharpness of channel element geometry and the underlying ordering of bounding surfaces. Moreover, it is shown that the analytical process resembles an iterative looping process that is led by deduction. Many geomorphologists and multi-disciplinary floodplain researchers collect sedimentary data but still neglect utilizing the potential of architectural analysis. The study makes clear that sedimentological approaches used in 'big river' floodplains also apply to small valleys; in fact, the procedures for facies reconstruction need to be adjusted to each individual case study. Alluvial architecture analysis provides the tools to reveal interconnectedness (or disconnectedness) of channel, near-channel, and overbank fluvial landforms, which is essential for a geomorphological understanding of floodplain evolution.

Houben, Peter

2007-04-01

203

Alluvial Diamond Resource Potential and Production Capacity Assessment of Ghana  

USGS Publications Warehouse

In May of 2000, a meeting was convened in Kimberley, South Africa, and attended by representatives of the diamond industry and leaders of African governments to develop a certification process intended to assure that rough, exported diamonds were free of conflictual concerns. This meeting was supported later in 2000 by the United Nations in a resolution adopted by the General Assembly. By 2002, the Kimberley Process Certification Scheme (KPCS) was ratified and signed by both diamond-producing and diamond-importing countries. Over 70 countries were included as members at the end of 2007. To prevent trade in 'conflict' diamonds while protecting legitimate trade, the KPCS requires that each country set up an internal system of controls to prevent conflict diamonds from entering any imported or exported shipments of rough diamonds. Every diamond or diamond shipment must be accompanied by a Kimberley Process (KP) certificate and be contained in tamper-proof packaging. The objective of this study was to assess the alluvial diamond resource endowment and current production capacity of the alluvial diamond-mining sector in Ghana. A modified volume and grade methodology was used to estimate the remaining diamond reserves within the Birim and Bonsa diamond fields. The production capacity of the sector was estimated using a formulaic expression of the number of workers reported in the sector, their productivity, and the average grade of deposits mined. This study estimates that there are approximately 91,600,000 carats of alluvial diamonds remaining in both the Birim and Bonsa diamond fields: 89,000,000 carats in the Birim and 2,600,000 carats in the Bonsa. Production capacity is calculated to be 765,000 carats per year, based on the formula used and available data on the number of workers and worker productivity. Annual production is highly dependent on the international diamond market and prices, the numbers of seasonal workers actively mining in the sector, and environmental conditions, which influence seasonal farming.

Chirico, Peter G.; Malpeli, Katherine C.; Anum, Solomon; Phillips, Emily C.

2010-01-01

204

Large Alluvial Fans in the Araba Valley (Jordan) as a Record of Tectonic Deformation of the Southern Dead Sea Fault and Regional Paleoclimates  

NASA Astrophysics Data System (ADS)

The Dead Sea fault is the 1000 km-long strike-slip fault that accommodates northward motion of Arabia relative to Sinai at a rate of about 5 mm/yr. This study focuses on the southern segment of this fault, the Wadi Araba fault. From the Dead Sea basin to the Gulf of Aqaba, the fault runs along an axial valley, about 20 km wide and 150 km long, bounded to the east by the Jordanian Plateau, reaching 1500 m in elevation and to the west by the Negev Plateau, lower in elevation (500-700 m). The Araba valley is floored with Plio-Quaternary deposits and in particular with large alluvial fans that are cut by the fault and offset relative to their feeding channel. We mapped the valley floor in details and dated some of these fans first to assess their lateral offset and further constrain the slip rate on the fault, and secondly to try to correlate alluvial fan aggradation periods in this arid/semi-arid environment to paleoclimatic variations at the regional and global scales. To identify the possible sources of the large alluvial fans, we analyzed the drainage network and the catchment basins on the valley rims based on SRTM3 topography. Previous study suggested that these fans were Pliocene and underwent offsets of 15 to 30 km. Ages as young as 50 to 350 kyr derived from 10Be exposure dating of 33 samples from the surface of some of these fans indicate that such offsets are very unlikely. Actual offsets have to be smaller. Preliminary reconstructions suggest offsets of 700-1300 m and 1600-2000 m for fans dated at 160 +/- 20 kyr and 330 +/- 22 kyr respectively, and offsets of 2.5-3.5 and 4.4-5.4 km for older fans that have not been dated yet. Consistent ages at different sites suggest simultaneous fan emplacement controlled by some external controlling factor such as climate variations. The correlation between these aggradation episodes and paleoclimatic variations would allow us to draw hypotheses on the age of these older surfaces. These preliminary results provide new constraints on the slip rate of the fault of 4-9 mm/yr since the Middle to Late Pleistocene.

Le Beon, M.; Klinger, Y.; Al-Qaryouti, M.; Meriaux, A.; Finkel, R. C.; Mayyas, O.; Ryerson, F. J.; Tapponnier, P.

2007-12-01

205

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

206

Second Quaternary dating workshop.  

National Technical Information Service (NTIS)

The second Quaternary dating methods workshop was held at Lucas Heights and sponsored by ANSTO and AINSE. Topics covered include, isotope and thermoluminescence dating, usage of accelerator and thermal ionisation mass spectrometry in environmental studies...

1999-01-01

207

Reservoir Characterization, Production Characteristics, and Research Needs for Fluvial/Alluvial Reservoirs in the United States  

SciTech Connect

The Department of Energy's (DOE's) Oil Recovery Field Demonstration Program was initiated in 1992 to maximize the economically and environmentally sound recovery of oil from known domestic reservoirs and to preserve access to this resource. Cost-shared field demonstration projects are being initiated in geology defined reservoir classes which have been prioritized by their potential for incremental recovery and their risk of abandonment. This document defines the characteristics of the fifth geological reservoir class in the series, fluvial/alluvial reservoirs. The reservoirs of Class 5 include deposits of alluvial fans, braided streams, and meandering streams. Deposit morphologies vary as a complex function of climate and tectonics and are characterized by a high degree of heterogeneity to fluid flow as a result of extreme variations in water energy as the deposits formed.

Cole, E.L.; Fowler, M.L.; Jackson, S.R.; Madden, M.P.; Raw-Schatzinger, V.; Salamy, S.P.; Sarathi, P.; Young, M.A.

1999-04-28

208

Late Quaternary high resolution sequence stratigraphy of an active rift, the Sperchios Basin, Greece: An analogue for subtle stratigraphic plays  

SciTech Connect

The Sperchios Basin is an active asymmetric graben, bounded to the south by a major border fault system with major fault segments typically 20-30 km long. The basin is dominated by a major axial fluvio-deltaic system which enters the partially enclosed Maliakos Gulf to the east. Lateral sourced depositional systems within the basin comprise hanging-wall and footwall-derived alluvial fans and a narrow coastal plain along the footwall scarp bordering the Maliakos Gulf. High resolution seismic data from the Maliakos Gulf reveals three late Quaternary progradational parasequences sourced from axial and lateral depositional systems, with a regional late-Pleistocene transgressive surface dated at circa. 10 ka BP within the Maliakos Gulf. Differential subsidence of the late Pleistocene transgressive surface indicates marked variation in subsidence from 2.4 m ka[sup -1] at fault segment centers to 0.8 m ka[sup -1] at segment boundaries. The geometry and internal variability of each parasequence is controlled by the interplay of the local accommodation development and fluctuations in sediment supply and climatic conditions. The Sperchios Rift provides a modem analogue for subtle stratigraphic plays within ancient extensional basins. The study of controls on sediment source and transport patterns within active rifts has refined our appreciation of the controls on potential reservoir distribution and geometries.

Eliet, P.P. (Total Oil Marine, Aberdeen (United Kingdom)); Gawthorpe, R.L. (Univ. of Manchester, Manchester (United Kingdom))

1996-01-01

209

Quaternary sediment in the Yichang area: Implications for the formation of the Three Gorges of the Yangtze River  

NASA Astrophysics Data System (ADS)

Sediment data from the Yichang area in the Jianghan Basin of Hubei Province in China suggest deposition in a lacustrine environment prior to 0.75 Ma, B.P., followed by incision of the Yangtze River. The earliest Quaternary Yunchi Formation accumulated in an alluvial fan to fan-delta environment. The subsequent Shanxiyao Formation was deposited in an environment that changed from fan-delta to lacustrine. The distribution of sedimentary facies suggests the presence of a lake in the Yichang area prior to 0.75 Ma, B.P. The lack of sediments contemporaneous with the Yunchi and Shanxiyao Formations in other areas of the Jianghan Basin, suggests that this ancient lake was limited to the Yichang area. This lake predates the present Yangtze River in the Yichang area and the Jianghan basin. Provenance studies of gravels in the Yunchi and Shanxiyao Formations, as well as gravels in terraces and the channel of the Yangtze River indicate a variety of sediment sources, but suggest that no material from the area west of the Three Gorges had been carried into the Yichang area prior to 0.75 Ma, B.P. The Yangtze River cut through Three Gorges area only after 0.75 Ma, B.P.

Xiang, Fang; Zhu, Lidong; Wang, Chengshan; Zhao, Xixi; Chen, Hongde; Yang, Wenguang

2007-03-01

210

Late Quaternary slip rate of the Owl Lake fault and maximum age of the latest event on the easternmost Garlock fault, S. California  

SciTech Connect

The Owl Lake fault is an active, left-lateral oblique-slip fault in the southwestern Basin and Range province. It intersects the left-lateral Garlock fault in the Quail Mountains and extends about 19 km northeastern toward southern Death Valley. The eastern wall of a channel incised into Late Tertiary or Quaternary fanglomerate north of the fault and into Late Quaternary alluvial fan deposits south of the fault has been offset at least 43 meters left-laterally. This slip estimate is a minimum because of possible erosion of the channel wall upstream from (north of) the fault. If the upstream channel prior to offset was of comparable width to the modern channel, the offset is no more than about 80 m. Organic matter entombed beneath rock varnish on two boulders on the alluvial fan surface into which the channel incised has conventional radiocarbon ages of 29,470 [+-] 270 and 30,820 [+-] 280 years B.P. Abandonment of the fan surface was probably caused by incision of the offset channel, so the channel wall probably has a similar age. This suggests a preliminary left-lateral slip rate of about 1--3 mm/yr for the Owl Lake fault. Fault scarp heights suggest relative uplift of the northwestern side of the fault by at least 1--2 meters and possibly more since deposition of the Late Quaternary fan. At a site in the Avawatz Mountains, within 2 km of the eastern end of the Garlock fault (Leach Lake strand), a terrace riser has been offset 2.7 [+-] 0.6 m left-laterally and 0.2 m south-side-up. This offset probably occurred during the most recent large earthquake on this part of the fault. Organic matter beneath varnish on two cobbles on the upper terrace has conventional radiocarbon ages of 1,583 [+-] 90 and 1,656 [+-] 88 years B.P. This suggests the most recent slip event occurred after a date of A.D. 150--590. This is significantly older than the maximum age (AD 1490) of the most recent slip event on the central Garlock fault in Searles Valley.

McGill, S.F. (California State Univ., San Bernardino, CA (United States). Dept. of Geological Sciences)

1993-04-01

211

Observations on Alluvial Fans with Relevance to Recent Sediment Transport  

NASA Astrophysics Data System (ADS)

Steep (slope > 0.01) alluvial fans are widely written about, but there are almost no quantitative field studies of the fluvial channels moving water and sediment across them. For this reason, it is difficult to apply existing mechanistic models of fan evolution (e.g., Parker et al., 1998). It follows that we have little ability to quantitatively predict the effects of regional changes in water flux, sediment supply, or vegetation from ongoing anthropogenic and climatic changes on fans, particularly in arid lands. We have begun a field program to quantify fluvial sediment transport across alluvial fans by measuring the hydraulic geometry and bed texture of channels. The goal of the measurements is to parameterize sediment transport in a way that predicts the observed pattern of slope reduction, often from ~0.07 at fan heads to ~0.02 at downfan margins. In the Mojave Desert of California, we find that alluvial fan channel bankfull depths are largely 0.4-1.0 m at fan heads, decreasing to 0.1-0.2 m at distal fan margins. Contrary to many previous studies, we find that median gravel diameter does not change systematically along the upper 60-80% of active fan channels, and thus downstream gravel fining cannot explain most of the observed channel slope reduction. However, as slope declines, surface sand cover increases systematically downfan from values of <20% above fan heads to distal fan values in excess of 70%. Plots of reach gradient versus sand content from these channels agree with experimental flume data from Ikeda and Iseya (1988) with similar hydraulic geometries, suggesting a general relation where similar loads can be transported at lower slopes because of the role that increased fines play in reducing the threshold for sediment transport. However, our attempts to model this role using reduced nondimensional critical shear stress values at higher sand concentrations (Wilcock & Crowe, 2003) with conventional excess shear stress sediment transport formulas result in underpredictions of the observed downfan slope decline. Although the relation between reach slope and sand cover suggests a strong role for sand cover in reducing fan slope, calculations indicate a strong component of bedload deposition is also necessary to match observed slope patterns. These uncertainties about the relative roles of sediment load and grainsize illustrate that much remains to be understood about alluvial fans before we can predict even first-order responses to climatic or anthropogenic change.

Stock, J. D.; Schmidt, K. M.; Miller, D. M.

2004-12-01

212

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

1995-02-01

213

Quaternary Glacial Mapping in Western Wisconsin Using Soil Survey Information  

ERIC Educational Resources Information Center

The majority of soils in the western Wisconsin have developed from glacial sediments deposited during the Quaternary Period (2.6 million years before present). In many regions, multiple advances and retreats have left a complex landscape of diverse glacial sediments and landforms. The soils that have developed on these deposits reflect the nature…

Oehlke, Betsy M.; Dolliver, Holly A. S.

2011-01-01

214

Quaternary Glacial Mapping in Western Wisconsin Using Soil Survey Information  

ERIC Educational Resources Information Center

|The majority of soils in the western Wisconsin have developed from glacial sediments deposited during the Quaternary Period (2.6 million years before present). In many regions, multiple advances and retreats have left a complex landscape of diverse glacial sediments and landforms. The soils that have developed on these deposits reflect the nature…

Oehlke, Betsy M.; Dolliver, Holly A. S.

2011-01-01

215

Design of canals in alluvial soils  

Microsoft Academic Search

Conclusions 1.The morphometric method of estimating the geometry of stable canal channels, as based on a deeper physical nature and using the fluvial process theory principle, has become most popular in solving the problem of designing canals in alluvial soil. It can be considered that sufficiently reliable relations have presently been obtained which can be used in practice with consideration

E. K. Rabkova

1991-01-01

216

Characterization and modeling of spatial variability in a complex alluvial aquifer: Implications on solute transport  

NASA Astrophysics Data System (ADS)

Field investigations of stratified alluvial deposits suggest that they can give rise to a hierarchy of permeability modes across scales, corresponding to a hierarchy of sedimentary unit types and thus may lead to enhanced plume spread in such media. In this work, we model the sedimentary architecture of the alluvium deposits in Fortymile Wash, Nevada, using a hierarchical transition probability geostatistical approach. The alluvial aquifer comprises a segment of the groundwater flow pathway from the potential high-level nuclear waste repository at Yucca Mountain, Nevada to the downstream accessible environment and may be a natural barrier to radionuclide migration. Thus our main goal is to quantify the impact of spatial variability in the alluvium on solute transport. The alluvial aquifer is a gravel-dominated braid-belt deposit, having lower-permeability paleosols interstratified with higher-permeability gravel-bar deposits. A three-dimensional hierarchical hydrofacies model is developed through fusion of multiple geologic data types and sources. Markov chain models of transition probabilities are employed to represent complex patterns of spatial variability at each hierarchical level in a geostatistical fashion and to impose realistic constraints to such variations through conditioning on existing data. The link between the alluvium spatial variability and solute dispersion at different spatiotemporal scales is demonstrated using the stochastic-Lagrangian transport theory. We show that the longitudinal macrodispersivity can be on the order of hundreds to thousands of meters, and it may not reach its asymptotic value until after 1,000 years of traveltime.

Sun, Alexander Y.; Ritzi, Robert W.; Sims, Darrell W.

2008-04-01

217

Gulf coastal plain evolution in West Louisiana: Heavy mineral provenance and Pleistocene alluvial chronology  

NASA Astrophysics Data System (ADS)

High Resolution Heavy Mineral Analysis (HRHMA) of late Pleistocene terrace samples, their Tertiary source rocks, and modern river sediments provided an effective tool for reconstructing sediment provenance and mapping heavy mineral provinces in southwest Louisiana. Each province, linked to a discrete source region, represents Pleistocene fluvial channel belts within which depositional activity was controlled by periods of climate, sediment supply, and sea level changes. Four coastal heavy mineral provinces have been identified. The Northern Province (NP), drained by the lower reaches of the Sabine and Calcasieu Rivers underlies level mid- and late Pleistocene coastal terrace surfaces and is distinguished by high-grade metamorphic assemblages (kyanite, staurolite, sillimanite) and abundant zircon, probably of Ouachita Mts. derivation. Transporting eroded Cretaceous, Tertiary, and Pleistocene coastal plain deposits, the modern Calcasieu and Sabine River sands in west-central and southwest Louisiana and east Texas, display identical heavy mineral composition to that of the NP. Level Late Pleistocene coastal terrace areas in the east represent the Red River Province (RRP) with dominant epidote, tourmaline, garnet, and zircon. Its mineralogy is influenced significantly by Paleozoic Mesozoic sedimentary units that frame the drainage basin upstream. Modern Red River sands differ in their spectra both from Red River Pleistocene coastal terrace and valley terrace deposits, interpreted by temporal fluctuations in sediment supply initiating a variable contribution of detritus from different sources. Tributaries that drain formations with high concentrations of high-grade metamorphic minerals also affected Red River valley Pleistocene terrace deposits in west-central Louisiana, enriching them in kyanite and staurolite. The Mississippi Province (MP) occupies the eastern-southeastern area of the low, flat, gently seaward-sloping Prairie coastal terrace. Whereas modern Mississippi alluvium is dominated by hornblende, pyroxenes, and epidote, as the result of post-depositional dissolution, pyroxenes are rare in the MP. The Mixed Suite Province (MSP) reflects MP, RRP, and to a lesser degree, NP signatures and forms the Prairie fluvial coastal plain surface closer to the Texas state line. Raw data of the principal heavy minerals were used for statistical analysis. Statistical parameters proved consistent with mineralogy-derived reconstruction of sediment provenance and provinciality of heavy mineral suites, thus providing an independent and objective support to data interpretation. Optical and thermal luminescence dating at other Gulf locations [Otvos, E.G. (2005). Numerical chronology of Pleistocene coastal plain and valley development; extensive aggradation during glacial low sea levels. Quaternary Internat., 135 91 113.] supports the pre-Sangamon ages of the Intermediate Pleistocene terraces in the NP area. Sangamon (135 116 ka), Eowisconsin (114 76 ka), and Wisconsin (74 36 ka) dates characterize the four provinces in the low, level northern Gulf Prairie coastal plain. Refuting earlier assumptions that coastal plain aggradation occurred only during marine highstand phases, thermal and optical luminescence dates indicated that, despite the low Eowisconsin and Wisconsin eustatic sea levels of several preglacial and glacial stages and substages, coastal plain alluviation, paradoxically, recurred between 106 and 35 ka BP. An interesting outcome of our heavy mineral study is the recognition and dating of a previously undocumented, rare ash-fall event that originated in Caribbean andesitic volcanoes. It was identified by the presence of a volcanogenic heavy mineral suite, composed of pristine euhedral clinopyroxene, sphene, zircon, apatite, and hexagonal biotite. Unaffected by fluvial reworking, this suite was recovered from a MP sample, dated ca. 86 ka BP.

Mange, Maria A.; Otvos, Ervin G.

2005-12-01

218

Simplified process modeling of river avulsion and alluvial architecture: Connecting models and field data  

NASA Astrophysics Data System (ADS)

Modeling is an invaluable tool for studying sedimentary basin filling and for understanding depositional processes with long recurrence intervals, including channel avulsion. Simplified modeling approaches, such as cellular models and process-analogue experiments, are particularly useful for efficiently exploring alternative hypotheses and evaluating first-order controls on river avulsion and alluvial architecture. Here we review the history and current state of the art in simplified avulsion and alluvial architecture models, with a particular focus on how results and insights from these models can be incorporated into field and subsurface studies, and vice versa. Simplified avulsion and alluvial architecture models have proliferated in the past decade, providing a wide variety of models to serve as a basis for future coupled field-modeling studies. We compare features of leading models and discuss avenues for effectively pairing model capabilities with hypotheses and field data. Outstanding questions highlighted by recent modeling efforts include 1) What thresholds control avulsion initiation in different systems? 2) How do floodplain processes and topography influence avulsion dynamics and alluvial architecture? 3) What factors determine where avulsion channels stabilize? Answering these questions will require targeted modeling efforts coupled to data from ancient systems. Hence our model comparison emphasizes features that can be used to choose or design fit-for-purpose models, and we outline how quantitative data useful for model selection and validation can be obtained from modern systems and ancient deposits. Matching model goals with targeted questions, and model parameters and predictions with quantitative field data, will help tighten communication between field- and model-oriented sedimentary geologists, facilitating advances in our understanding of river avulsion and alluvial architecture.

Hajek, Elizabeth A.; Wolinsky, Matthew A.

2012-06-01

219

Gravel-Sand Transition in a Large, Lowland Alluvial Channel.  

NASA Astrophysics Data System (ADS)

The beds of alluvial river channels become finer grained moving downstream and often exhibit an abrupt transition from gravel to sand-bedded conditions. Most previous work documenting this phenomenon have focused on small upland streams where sediment supply to the channel is strongly connected to sediment delivery from hillslopes. Fewer studies have focused on the gravel-sand transition in large alluvial channels and none have documented the spatial variability through reaches where transitions occur. The downstream fining pattern observed in the Fraser River is widely cited as a classic example of an abrupt gravel-sand transition in a large alluvial channel. However, important questions regarding the exact current location of the transition, its morphology, and what controls its location remain unanswered. Here, we present detailed observations of bed material grain-size and river bed topography through the reach where the transition is widely thought to occur in the Fraser River. Bed topography was measured using a multibeam echo- sounding system (Reson 8101 Seabat) at high flow (11,000 m3s-1) when all fractions of the bed material were mobile. Some limited bed material sampling was done at high flow with more detailed sampling at low flows (~1000 m3s-1). These observations indicate that there is little gravel material on the active channel bed downstream of Yaalstrick Bar, the last bar along the river dominated by gravel (> 75% of the bar material > 2 mm). However, sorting patterns caused by the superior mobility of gravel over sand have lead to gravel patches on the upstream sides and surfaces of sand bars. There are also gravel patches along the thalweg through the apex of some river bends, but whether this is topographically induced sorting or a lag deposit exposed by high flow is not clear. Bedforms associated with sand-gravel mixtures appear on the river bed immediately downstream of Yaalstrick Bar in a sequence (sand ribbons, barchans, dunes) suggesting sand deposition from suspension. There is also a dramatic increase in bar amplitude downstream of Yaalstrick Bar, suggesting greater sand composition. Our observations suggest the gravel- sand transition in the Fraser River is somewhat more diffuse than is observed in smaller scale channels. Yet, for all practical purposes, Yaalstrick Bar is the end of the gravel-bedded reach of the Fraser River.

Venditti, J. G.; Humphies, R. P.; Allison, M. A.; Nittrouer, J. A.; Church, M.

2008-12-01

220

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

221

Holocene dune-sourced alluvial fans in the Nebraska Sand Hills  

Microsoft Academic Search

The large, stabilized dunes of the Nebraska Sand Hills are in a phase of degradation. The deposition of small-scale alluvial fans composed of well-sorted, fine- to medium-grained sand occurs when sand is transported via gullies on the lee side of large barchanoid-ridge dunes during infrequent, intense summer rain storms (>5 cm\\/h). The hydraulic conductivity of the dune sand itself is

Mark R. Sweeney; David B. Loope

2001-01-01

222

A Quaternary paleolake in a sinkhole at Cassis (SE France) : a geomorphology and geophysical study  

NASA Astrophysics Data System (ADS)

The Lower Provence and the Massif des Calanques, near Marseille, are a key area in understanding the mechanisms of evolution of the Mediterranean climate and the study of human impact on the local environment during the Quaternary. However, a continuous continental record of paleoenvironment in coastal Provence was not previously available. Looking for such a record, we discovered in a coastal alluvial plain a small paleolake filling a sinkhole that occurred in a marl sequence topping pure limestones at an altitude of 80 m, and a distance to the sea of 2 km. The sinkhole is close to the outlet of a small catchment area of about 8 km2. Limestone is massive but much fractured and therefore suitable for the development of karst. The drilling sedimentary sequence of 50 meters is mainly resulting from the weathering of Cretaceous marls. It consists of 5 meters of oxidized brown clay deposit which covers 45 meters of laminated lacustrine gray clay with sandy past. Cretaceous marls are at the base of the sequence. The presence of marls pebbles in the last meters of the sequence reflects the collapse of the sinkhole. The lacustrine clay was probably deposed during stages isotope 2 to 4 (48 ± 3 ka C14 date at 23 meters depth), whereas brown clay deposit was interpreted as Holocene paleosol. Combination of surface observation, drilling and geophysical studies (gravimetry and Electrical Resistivity Tomography) allows to constraint the geometry of the paleo-polje that formed during glacial period. Lake diameter was likely of the order of 200 m. It evolved from a deep lake to a swamp (probably Holocene, dating in progress) and it was drained in roman times for agriculture. Locally, this discovery has implications for the understanding of karst processes and water resources. The relationship between the sinkhole, rooted at circa 100 m below surface according to gravimetric modeling and the underground karstic river of Bestouan is strongly suggested by underwater exploration and hydrogeologic investigations.

Romey, C.; Rochette, P.; Vella, C.; Arfib, B.; Champollion, C.; Dussouillez, P.; Hermitte, D.; Parisot, J.-C.

2012-04-01

223

Changes in vegetation and drainage density as controlling factors in the episodicity of Quaternary sediment flux: southwestern United States and Bolivian Eastern Cordillera  

NASA Astrophysics Data System (ADS)

Piedmont geomorphic surfaces in the southwestern U.S. primarily represent cut-and-fill cycles resulting from variations in sediment supply from adjacent mountain catchments. Although sparse, precise age control supports the hypothesis that sediment supply in the southwestern U.S. can increase by an order of magnitude during Quaternary humid-to-arid transitions recognized in high-resolution paleoclimatic proxies. As an example, this episodicity is quantified with a time series of sediment flux for the central Gila Mountains, southwestern Arizona, where paleosurfaces outcrop in the modern channel bank, permitting an estimate of deposit volume in conjunction with high-resolution photogrammetric DEMs. Age control is provided by a new method of surface exposure dating based on 3D hillslope diffusion adjacent to gullies penetrating the surface. We propose that episodes of piedmont alluviation result from an increase in drainage density resulting from climatically-induced vegetative successions from mature woodland vegetation to desert shrubs that excavate large amounts of hillslope colluvium stored during the previous humid interval. Analogous vegetative shifts occur in the Bolivian Eastern Cordillera (EC). Field observations and analyses of topographic maps and LANDSAT images suggest that the longitudinal profiles of the major rivers of the EC are dominated by an order-of-magnitude increase in Plio-Quaternary hillslope erosion in the elevation zone between approximately 2.5 and 3.5 kilometers above sea level corresponding to glacial-interglacial vegetational successions from Andean forest (glacial) to Paramo grasslands (interglacial). These vegetation changes resulted in rapid fluctuations in drainage density responsible for a large increase in transport rates that alluviated major valleys and enhanced bedrock incision rates downstream. Areas above and below this elevation have perennial grassland and forest, respectively, whose long-term vegetational stability has resulted in low erosion rates compared with the intermediate elevation zone. These studies suggest that fluctuations in drainage density driven by vegetative shifts between glacial and interglacial times may be the dominant mechanism of Quaternary sediment production in unglaciated terrain.

Barnes, J.; Pelletier, J. D.

2001-12-01

224

Quaternary palaeoenvironments in Namibia: new records from optically stimulated dating of Kalahari linear dune accumulation and northern Namib Sand Sea interdune deposits.  

NASA Astrophysics Data System (ADS)

In this study we consider new linear dune accumulation records from the west of the southern Kalahari linear dunefield (~24o S 18oE) and a new chronology for three sites along the former course of the Tsondab River in the northern Namib Sand Sea (23o49'15'S, 14o57'30'E, 23o48'39'S, 15o02'21'E and 23o56'11'S, 15o17'89'E) from Namibia, southern Africa. Optically stimulated luminescence dating (OSL) has been applied to both sites in order to: (i) provide a chronology for linear dune accumulation in a previously unstudied region of the southern Kalahari linear dunefield and (ii) to provide a chronological reassessment for water-lain units from the Namib Sand Sea, previously dated using radiocarbon applied to inorganic carbonate sediments. The 48 OSL ages from the linear dunes include the oldest linear dune sediment ages recorded in the southern Kalahari and also reveal that the dunefield has been partially active throughout much of the past 120 ka. These ages are considered alongside the net accumulation record for the entire southern Kalahari linear dunefield (141 optical ages) and we make some important observations about the influence of sampling strategy. We attempt to isolate a rigorous signal that does not depend on sampling strategy by removing cores and comparing the net accumulation record from different parts of the dataset. We consider the young bias resulting from the predominance of shallow sampling in the total dataset. The bracketing OSL ages (from sand units that inter-bed water-lain calcareous rich sediments) in the northern Namib Sand Sea suggest that the series of seven mud units at Narabeb (23o49'15'S, 14o57'30'E) are substantially older than the existing radiocarbon chronology from the mud units themselves. Twelve of the thirteen OSL ages fall within MIS 5. By contrast, at Ancient Tracks (23o56'11'S, 15o17'89'E) the OSL-based chronological reassessment suggests the water-lain units were 1 to 2 ka younger than the existing radiocarbon ages, with deposition between 12.8 ± 0.8 ka and 12.0 ± 0.8 ka and between 11.5 ± 0.6 ka and 10.5 ± 0.5 ka. Together the three sites provide a new estimate for the timing of the progressive desiccation of the Tsondab River. We conclude that larger datasets of linear dune accumulation (1000s not 100s of OSL ages) are needed, and also to demonstrate that altering sampling strategy within this dataset does not bias the combined-core results, before we have a reliable dataset of dune accumulation in this region. This is before tackling the additional issue of interpreting the palaeoenvironmental significance of the dune accumulation record. For the Namib Sand Sea we conclude that the revised timing for increased moisture availability to the catchment of the Tsondab River still reinforces the idea that changes in moisture availability are driven by precipitation changes over the catchments in the Great Escarpment and further inland. Finally, we make some brief observations regarding how these two new records compare with the current regional palaeoclimatic syntheses.

Stone, Abigail; Thomas, David; Viles, Heather; Bailey, Richard

2010-05-01

225

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

NASA Astrophysics Data System (ADS)

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 to interpreting alluvium from a single drainage must be reconciled, as many drainages feature both reach types along their length. This OSL/radiocarbon-based chronostratigraphic investigation has the goal of linking these alluvial records in Buckskin Wash, a major tributary of the Paria River, south-central Utah, where a broad alluvial reach drains into a severely constricted slot canyon. We are testing the hypothesis that the same floods that cut arroyos in the alluvial reach are preserved as depositional packages in the constricted reach downstream. OSL dating in this setting is challenging, partly due to the partial bleaching of sand grains during transport. However, initial results indicate that fine-grained alluvium stored within the unconstricted reach consists of aggradational packages as old as late Pleistocene--much older than previously thought. Conversely, the constricted-reach sediments are latest Holocene in age. Sedimentology also appears to be controlled by reach geometry. The upstream alluvial reach is a complex series of interfingering tributary and mainstem facies; heavily bioturbated and penetrated by a series of filled paleochannels. Depositional units in the slot canyon are thicker, less bioturbated, and instead preserve mostly high-stage mainstem floods. Observations from the modern wash suggest that the grade of the constricted reach is not static over millennial timescales. Ongoing work includes hydraulic modeling to identify a transition zone between the two end-member geomorphic reaches.

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

2008-12-01

226

Aquifer characteristics, water availability, and water quality of the Quaternary aquifer, Osage County, northeastern Oklahoma, 2001-2002  

USGS Publications Warehouse

Additional sources of water are needed on the Osage Reservation for future growth and development. The Quaternary aquifer along the Arkansas River in the Osage Reservation may represent a substantial water resource, but limited amounts of hydrogeologic data were available for the aquifer. The study area is about 116 square miles of the Quaternary aquifer in the Arkansas River valley and the nearby upland areas along the Osage Reservation. The study area included the Arkansas River reach downstream from Kaw Lake near Ponca City, Oklahoma to upstream from Keystone Lake near Cleveland, Oklahoma. Electrical conductivity logs were produced for 103 test holes. Water levels were determined for 49 test holes, and 105 water samples were collected for water-quality field analyses at 46 test holes. Water-quality data included field measurements of specific conductance, pH, water temperature, dissolved oxygen, and nitrate (nitrite plus nitrate as nitrogen). Sediment cores were extracted from 20 of the 103 test holes. The Quaternary aquifer consists of alluvial and terrace deposits of sand, silt, clay, and gravel. The measured thickness of the alluvium ranged from 13.7 to 49.8 feet. The measured thickness of the terrace sediments ranged from 7 to 93.8 feet. The saturated thickness of all sediments ranged from 0 to 38.2 feet with a median of 24.8 feet. The weighted-mean grain size for cores from the alluvium ranged from 3.69 to 0.64 f, (0.08- 0.64 millimeter), and ranged from 4.02 to 2.01 f (0.06-0.25 millimeter) for the cores from terrace deposits. The mean of the weighted-mean grain sizes for cores from the alluvium was 1.67 f (0.31 millimeter), and the terrace deposits was 2.73 f (0.15 millimeter). The hydraulic conductivity calculated from grain size of the alluvium ranged from 2.9 to 6,000 feet per day and of the terrace deposits ranged from 2.9 to 430 feet per day. The calculated transmissivity of the alluvium ranged from 2,000 to 26,000 feet squared per day with a median of 5,100 feet squared per day. Water in storage in the alluvium was estimated to be approximately 200,000 acre-feet. The amount of water annually recharging the aquifer was estimated to be approximately 4,800 acre-feet. Specific conductance for all water samples ranged from 161 to 6,650 microsiemens per centimeter. Median specific conductance for the alluvium was 683 microsiemens per centimeter and for the terrace deposits was 263 microsiemens per centimeter. Dissolved-solids concentrations, estimated from specific conductance, for water samples from the aquifer ranged from 88 to 3,658 milligrams per liter. Estimated median dissolved- solids concentration for the alluvium was 376 milligrams per liter and for the terrace deposits was 145 milligrams per liter. More than half of the samples from the Quaternary aquifer were estimated to contain less than 500 milligrams per liter dissolved solids. Field-screened nitrate concentrations for the sampling in December 2001-August 2002 ranged from 0 to 15 milligrams per liter. The field-screened nitrate concentrations for the second sampling in September 2002 were less than corresponding laboratory reported values.

Mashburn, Shana L.; Cope, Caleb C.; Abbott, Marvin M.

2003-01-01

227

Quaternary dichotomous voting rules  

Microsoft Academic Search

In this article, we provide a general model of “quaternary” dichotomous voting rules (QVRs), namely, voting rules for making\\u000a collective dichotomous decisions (to accept or reject a proposal), based on vote profiles in which four options are available\\u000a to each voter: voting (“yes”, “no”, or “abstaining”) or staying home and not turning out. The model covers most of actual\\u000a real-world

Annick Laruelle; Federico Valenciano

2010-01-01

228

Turkana Grits - a Cretaceous braided alluvial system in northern Kenya  

SciTech Connect

Rather spotty but excellent exposures of the Cretaceous-age Turkana Grits occur near the western shore of Lake Turkana, northern Kenya. These very coarse to pebbly arkosic sandstones and sandy conglomerates were derived from and rest unconformably upon Precambrian metamorphic basement; they are overlain by late Tertiary basaltic flows that comprise much of the volcanics in the East African Rift Zone. The formation ranges up to 2000 ft thick in the Laburr Range. Several outcrops contain sauropod, crocodile, and tortoise remains as well as abundant trunks of petrified wood (Dryoxylon). Five major facies make up the Turkana Grits and record a major episode of continental fluvial deposition in basins flanked by Precambrian basement. Facies 1 is crudely stratified, cobble and boulder conglomerate (clast-supported); Facies 2 is crudely stratified pebble-cobble conglomerate and pebbly sandstone; Facies 3 is trough cross-bedded, very coarse sandstones containing fossils wood and vertebrate remains; Facies 4 is crudely stratified to massive sandstones with ironstone nodules; and Facies 5 is red, purple, and gray mudstone and mud shale with carbonate nodules. Facies 1 through 3 record deposition in proximal to medial braided-stream channel, longitudinal bar and dune complexes. Facies 4 is a lowland, hydromorphic paleosol, and Facies 5 represents overbank and abandoned channel-fill sedimentation in an alluvial plain.

Handford, C.R.

1987-05-01

229

CHANNEL EVOLUTION IN MODIFIED ALLUVIAL STREAMS.  

USGS Publications Warehouse

This study (a) assesses the channel changes and network trends of bed level response after modifications between 1959 and 1972 of alluvial channels in western Tennessee and (b) develops a conceptual model of bank slope development to qualitatively assess bank stability and potential channel widening. A six-step, semiquantitative model of channel evolution in disturbed channels was developed by quantifying bed level trends and recognizing qualitative stages of bank slope development. Development of the bank profile is defined in terms of three dynamic and observable surfaces: (a) vertical face (70 to 90 degrees), (b) upper bank (25 to 50 degrees), and (c) slough line (20 to 25 degrees).

Simon, Andrew; Hupp, Cliff, R.

1987-01-01

230

Effects of Quaternary Sea Level Cycles on Strontium in Seawater  

Microsoft Academic Search

The effects of Quaternary sea level changes on the Sr budget of the ocean are investigated using coupled numerical models of the seawater Sr and Ca budgets. Glacial\\/interglacial sea level cycles influence the Sr concentration of seawater directly through the periodic exposure and weathering of aragonite on continental shelves and indirectly by modulating the location and extent of carbonate deposition

Heather M Stoll; Daniel P Schrag

1998-01-01

231

Late Quaternary history of southern Chesapeake Bay  

SciTech Connect

More than 700 km of high-resolution, seismic-reflection profiles and sidescan-sonar images provide new information about the late Quaternary history of southern Chesapeake Bay. Sidescan-sonar images show that, excluding the nearshore zone, most of the bay bottom has a monotonously smooth surface, except that sand waves, ripples, and other bedforms occur in local areas affected by tidal currents. Seismic-reflection data show that the Quaternary stratigraphy of the southern part of the Bay is related primarily to the last cycle of sea-level change. The Quaternary section overlies an erosion surface cut deeply into gently seaward-dipping marine beds of Neogene age. Fluvial paleochannels, related to the last major low sea-level stand, are characterized by as much as 55 m of incision and by thin, irregular, terrace and channel-bottom deposits. Marine and estuarine deposits related to the Holocene transgression partially or fully bury the fluvial valleys and overlie the interfluves. A prominent feature of the Bay-mouth area is a wedge of sediment that has prograded into the Bay from the inner shelf. The common assumption--that the Chesapeake Bay is the drowned valley of the Pleistocene Susquehanna River--is only partially valid for the southern part of the Bay. The Bay mouth area, in general, is relatively young. The axial channel of the Bay is a modern tidal channel that is actively eroding Tertiary deposits and migrating toward the south and west; it is unrelated to older fluvial channels. Also, the positions of the modern axial channel and the last two fluvial paleochannels indicate long-term southward migration of the Bay mouth.

Colman, S.M.; Hobbs, C.H. III; Halka, J.P.

1985-01-01

232

Climatic, eustatic, and tectnoic controls on Quarternary deposits and landforms, Red Sea coast, Egypt  

NASA Astrophysics Data System (ADS)

The degree to which local climatic variations, eustatic sea level fluctuations, and tectonic uplift have influenced the development of Quaternary marine and fluvial landforms and deposits along the Red Sea coast, Eastern Desert, was investigated using a combination of remote sensing and field data, age determinations of corals, and numerical simulations. False color composites generated from Landsat Thematic Mapper and SPOT image data, digital elevation models derived from sterophotogrammetric analysis of SPOT data, and field observations document that a approximately 10-km wide swath inland from the coast is covered in many places with coalescing alluvial fans of Quaternary age. Wadis cutting through the fans exhibit several pairs of fluvial terraces, and wadi walls expose alluvium interbedded with corraline limestone deposits Further, three distinct coral terraces are evident along the coatline. Climatic, eustatic, and tectonic uplift controls on the overall system were simulated using a cellular automata algorithm with the following characteristics: (1) uplift as a function of position and time, as defined by the elevations and ages of corals; (2) climatic variations driven by insolation changes associated with Milankovitch cycles; (3) sea level fluctuations based on U/Th ages of coral terraces and eustatic data; and (4) parametrized fluvial erosion and deposition. Results imply that the fans and coralline limestones were generated in a setting in which the tectonic uplift rate decreased over the Quarternary to negligible values at present. Coralline limestones formed furing eustatic highstands when alluvium was trapped uspstream and wadis filled with debris. During lowstands, wadis cut into sedimentary deposits; coupled with continuing uplift, fans were dissected, leaving remnant surfaces, and wadi-related terraces were generated by down cutting. Only landforms from the past three to four eustatic sea level cycles (i.e., approximately 300 to 400 kyr) are likely to have survived erosion and deposition associated with fluvial processes.

Arvidson, Raymond; Becker, Richard; Shanabrook, Amy; Luo, Wei; Sturchio, Neil; Sultan, Mohamed; Lofty, Zakaria; Mahmood, Abdel Moneim; El Alfy, Zeinhom

1994-06-01

233

Monti Martani (umbria, Italy) Alluvial Fans: Hazards Sites and Occurrence  

NASA Astrophysics Data System (ADS)

In this paper we proposed modeling and simulation approaches for testing the debris flows occurrence hypothesis. The approach is an empirically and process based, and use multiple physically-based simulations to evaluate hazard down-slope from initiation sites in alluvial fans of the Terni basin-northern area (Umbria, Italy). The northern part of the area is bounded by the M. Martani normal fault that controls the drainage network where produces a large debris piedimont deposition. The main fault scarp is cut by narrow streams that represents the dominant constructional process by three alluvial fans generations. Field-based and remote sensing observations from the area will be used to provide a sound empirical evaluation of the new landslide occurrence hypothesis. In humid, soil-mantled environments in particular, debris flow always originate in fine-scale valleys in steep, rhythmically dissected terrain. Concave planform contours define topographic swales, referred to as "hollows" in the nomenclature, that typically contain colluvial soils significantly thicker than those found on adjacent slope. Areas underlain by massive, resistant bedrock, show that the majority of debris flows originated in colluvium-filled hollows. Hollows consequently define a mappable debris flow hazard. The association of debris flow with hollows is governed by relations between sediment transport, hillslope hydrology and slope stability. Consequently, colluvial deposits in hollows are particularly susceptible to landsliding. Furthermore topographic converge also focuses subsurface runoff into hollows, so high intensity rainfall cells indicate that a lack of historic landsliding from specific hollow is by no means an indicator of future stability. The strong likelihood that the 25m resolution DEM can be used in this project means that we will have the topographic control to do more detailed modeling of hill slope hydrology to account for spatial and temporal variability in groundwater saturation on hillslopes, and the consequences for slope failure. We will use a software tools for multiflow routing of runoff given a precipitation model, a DEM, and a probabilistic model of finding pockets of colluvium on hillslopes which is demonstrated for the synthetic hillslope.

Taramelli, A.; Melelli, L.

234

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

235

Influences of Alluvial Fans on Upland Watersheds in Central Nevada  

Microsoft Academic Search

Geomorphic, hydrologic, and vegetation processes of upland watersheds in central Nevada are influenced by side-valley alluvial fans. Discontinuous longitudinal stream profiles and spatial variation in stream channel incision are often associated with the alluvial fans. In many cases, groundwater flow is restricted immediately upstream of side-valley fans resulting in elevated water tables and the occurrence of springs and seeps. Riparian

John L. Korfmacher; Jeanne C. Chambers

236

Detectability of minerals on desert alluvial fans using reflectance spectra  

Microsoft Academic Search

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;

Hugh Shipman; John B. Adams

1987-01-01

237

Alluvial fans as an effect of long-term man-landscape interactions and moist climatic conditions: A case study from the Glubczyce Plateau, SW Poland  

NASA Astrophysics Data System (ADS)

At the mouth of periodically drained valleys in the loess Glubczyce Plateau (SW Poland), favorable conditions for deposition of alluvial fan sediments occur, so these forms are very common in the investigated area. The origin of the forms analyzed is related to long-term human-landscape interactions, because deforestation and land-use changes started in the Neolithic, ca. 5.5 ka BC, causing intensification of soil erosion processes. Willful and continuous interference by man into natural environment began at that time. Thus, human impact is responsible for acceleration of runoff and mobilization of sediment which formed alluvial fans at the mouths of episodically drained valleys. The objectives of this study are (1) to measure the morphological and topographical characteristics of the fans, (2) to describe and analyze the inner structures of the alluvial fans analyzed and (3) to date the alluvial fan deposition. The alluvial fans are mainly formed of silty-clayey massive sediments. The gravel-sand layers occurring in two exposures indicate the incision of the valleys in the older Pleistocene sediments underlying the loess upland deposits and intensive phases of erosion in the course of which coarser material could have been transported. Radiocarbon dating of the peat filling the bottoms of the valleys and underlying the mineral deposits of the fans indicates that sediment transfer from cultivated valley slopes and its deposition at the mouth of the valleys was recorded in alluvial fan sediments by the Neolithic (6895 ± 140 BP). During this period, erosion was probably intensified by a moister climate. Radiocarbon dating of organic layers, which were discovered inside the sediments of two fans, show that the youngest dated stage of intensified erosion took place in Early Medieval Times, when the Glubczyce Plateau was colonized again by Slavs after the "settlement depression" during the Migration Period.

Zygmunt, Edyta

2009-07-01

238

Late Quaternary faulting in Clayton Valley, Nevada: Implications for distributed deformation in the eastern California shear zone-Walker Lane  

NASA Astrophysics Data System (ADS)

The Walker Lane is a key component of the Pacific-North America plate boundary. This transtensional region of right lateral strike-slip and normal faulting accommodates ~25% of the total relative motion between the Pacific and North American plates. Recent studies indicate a discrepancy between short- and long-term rates of right-lateral shear in the Walker Lane with geodetic measurements of ~9.3 mm/yr being more than double the late Pleistocene geologic rate of <3.5 mm/yr. The Walker Lane, therefore, provides an excellent natural laboratory in which to address one of the major unresolved questions in active tectonics: are rates of strain accumulation and release along active plate boundaries constant through space and time or are significant temporal and spatial variations common? The Clayton Valley fault system of the Silver Peak-Lone Mountain extensional complex (SPLM) is a prime candidate to account for part of the “missing” strain in the Walker Lane due to its dominantly down-to-the-NW orientation, which ultimately accommodates right lateral shear in the region. The distribution of late Quaternary faults and alluvial fan deposits in Clayton Valley was determined through detailed geologic mapping (1:10,000 scale), which resulted in eight individual units that are consistent with the well-established western U.S. alluvial stratigraphy. Differential GPS was used to survey the prominent normal fault scarps displacing the fan deposits and cosmogenic nuclide (TCN) geochronology depth profile samples were collected from four units (Q2b, Q2c, Q2d, and Q3a). Displacement measured from the scarp profiles combined with TCN ages of the deformed fans will allow us to determine extension rates over multiple late Pleistocene time scales. Analysis of the Clayton Valley extension rates coupled with those from nearby structures, such as the Lone Mountain and Lida faults, will help determine if slip along these extensional faults can account for the observed discrepancy between short- and long-term rates of deformation along this important component of the Pacific-North America plate boundary.

Foy, T. A.; Lifton, Z. M.; Frankel, K. L.; Johnson, C.

2010-12-01

239

Chronology and Archeology of Holocene Alluvial Archives in the Wadi Sbeïtla Basin, Central Tunisia  

NASA Astrophysics Data System (ADS)

A multidisciplinary study of Holocene alluvial archives in the Wadi Sbeïtla Basin revealed several phases of increased geomorphic activity, each followed by a stable environment and a soil formation phase. The alternate dynamic and stable phases are due to the past climatic fluctuations, superimposed by human activities. Using radiocarbon dating and archaeological study, we established a detailed chronostratigraphy of the Holocene alluvial records in the study area. Four important phases of deposition were dated: an early-Holocene phase (10-7 ka cal BP), a mid-Holocene phase (6-4 ka cal BP), a late Roman phase (1.6-1.4 ka cal BP) and a recent medieval phase (1-0.5 ka cal BP). A peak of fluvial activity took place during the Pleistocene-Holocene transition and in the late Roman crisis (around 1.6 ka cal BP). Two long periods of soil forming process were dated around the Capsian epoch (7 ka cal BP) and in the second half of the mid-Holocene (5-4 ka cal BP). Finally, immature alluvial soils were developed around 1.1 ka cal BP.

Zerai, K.

2009-04-01

240

Abo Formation alluvial facies and Associated Basin Fill, Sacramento Mountains, New Mexico  

SciTech Connect

Outcrops of the Abo Formation (Wolfcampian to early Leonardian age) in the Sacramento Mountains of south-central New Mexico record the evolution of a dry alluvial fan system as it was deposited off the pedernal uplift into the Orogrande basin. The location and orientation of present-day outcrops allow us to observe an inferred east-to-west transverse facies tract consisting of: (1) proximal alluvial fans (lower Abo), which are contiguous in places with underlying Laborcita Formation fan-deltaic sediments; (2) medial anastomosed streams (middle Abo); and (3) distal low-gradient mud-dominated flood basins characterized by either distributary streams (upper Abo) or clastic tidal flats (Lee Ranch Tongue of the Abo) with associated marine carbonates (Pendejo Tongue of the Hueco Formation). Tectonism in the Pedernal highlands, which climaxed during the Late Pennsylvanian, apparently continued well into the Wolfcampian in this region, as evidenced by a major basal Abo unconformity and distinct stacked megasequences of lower Abo alluvial fan lithofacies. However, by the middle Abo, tectonic activity had quiesced and the uplift began eroding and retreating to the north and east. By the late Abo, a pediment surface had formed that was subsequently onlapped by upper Abo and eventually Yeso Formation sediments.

Speer, S.W.

1986-03-01

241

Alluvial-fan and lacustrine fan-delta sedimentation in west-central California during the Middle Tertiary transition from subduction to transform tectonics  

Microsoft Academic Search

The Plush Ranch (PR) Formation was deposited in one of several sedimentary basins in west-central California. The PR consists of more than 1,800 m of nonmarine sedimentary rocks and interbedded basaltic volcanic rocks that together record a complicated history of synsedimentary faulting, volcanism, and deposition in alluvial-fan, fan-delta, and lacustrine depositional settings. The sedimentological analysis indicates that both the northern

R. B. Cole; R. G. Stanley

1992-01-01

242

Morphology and stratigraphy of the late Quaternary lower Brazos valley: Implications for paleo-climate, discharge and sediment delivery  

NASA Astrophysics Data System (ADS)

A shallow coring and geophysical logging program has recorded the sedimentary fill of the Brazos River valley in the Texas Gulf Coastal Plain. Thermoluminescence dates together with new and recalibrated published radiocarbon dates show the valley fill to include extensive, sandy, buried falling stage and lowstand Oxygen Isotope Stage (OIS) 3 and 2 deposits. These alluvial deposits are punctuated by numerous paleosoil horizons that record alternating periods of cutting, bypass and accumulation. Maximum valley incision and two periods of terrace formation preceded marine lowstand conditions, suggesting significant discordance between preserved fluvial and classical marine system tracts. The latest Pleistocene incision and fill history appears related to cycles of increased discharge and incision, followed by system equilibration and terrace formation. Analysis of the Brazos River incised valley and its contained paleochannels indicates that latest Pleistocene mean annual discharge was as much as four times greater than that of today. This magnitude of discharge in the Brazos would require a two-fold increase in precipitation across the drainage basin. Such an increase is comparable to the present day measured positive El Niño winter precipitation anomaly across the region. Paleochannel geometries and the stratigraphic and sedimentologic data from this investigation support the hypothesis that periods of high-amplitude, El Niño-like climatic perturbations characterized the late Quaternary climate of the south-central and southwestern U.S. This period of high discharge coincides, at least in part, with late OIS 3 progradation of the Brazos delta to the shelf margin, OIS 3 and 2 valley incision across the Texas shelf, and concomitant sand bypass to intraslope basins beyond the shelf edge.

Sylvia, Dennis A.; Galloway, William E.

2006-08-01

243

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

244

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

245

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

246

Numerical Simulation of Sediment Plug Formation in Alluvial Channels  

NASA Astrophysics Data System (ADS)

A sediment plug is the aggregation of sediment in a river reach that completely blocks the original channel resulting in plug growth upstream by accretion and flooding in surrounding areas. Sediment plugs historically form over relatively short periods, in many cases a matter of weeks. Although sediment plugs are much more common in reach constrictions associated with large woody debris, the mouths of tributaries, and along coastal regions, this investigation focuses on sediment plug formation in an alluvial river. During high flows in the years 1991, 1995, 2005, and 2008, a sediment plug formed in the San Marcial reach of the Middle Rio Grande. The Bureau of Reclamation has had to spend millions of dollars dredging the channel to restore flows to Elephant Butte Reservoir. The hydrodynamic and sediment transport processes, associated with plug formation, occurring in this reach are driven by 1) a flow constriction associated with a rock outcrop, 2) a railroad bridge, and 3) the water level of the downstream reservoir. The three-dimensional hydrodynamic model, Delft3D, was implemented to determine the hydrodynamic and sediment transport parameters and variables required to simulate plug formation in an effort to identify hydro- and morphodynamic thresholds. Several variables were identified by previous studies as metrics for plug formation. These variables were used in our investigation to detect the relative magnitude of each process. Both duration and degree of high flow events were simulated, along with extent of cohesive sediment deposits, reservoir level, and percent of fines in suspended sediment distribution. Results of this analysis illustrate that this model is able to reproduce the sediment plug formation. Model calibration was based on measured water levels and changes in bathymetry using both sediment transport and morphologic change parameters. Changes to hydraulic and sediment parameters are not proportional to morphologic changes and are asymptotic in their response. These results suggest that there are thresholds to predict plug formation and that the contribution of specific variables to plug formation is not uniform. Sediment plug formation is a costly and dangerous phenomenon, especially in large alluvial rivers. This investigation yielded specific insights into the hydrodynamic and morphologic processes occurring during sediment plug formation. These insights can be used to reduce the risk of plug formation and predict the locations and times of other sediment plugs.

Posner, A. J.; Duan, J. G.

2011-12-01

247

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

248

ROLES OF NATURAL LEVEES ON THE ARA RIVER ALLUVIAL FAN  

NASA Astrophysics Data System (ADS)

For the comprehensive flood control measures for alluvial fans, it is required to understand the effects of natural levees and micro-topography on reducing flood damages. We investigate the role of natural levees in the flood control measures for the alluvial fan of the Ara River by mapping historical community development and using the hazard maps.As a result, it is clarified that many communities have been developed on natural levees, and that natural levees are resistant to spreading of flood waters. The above indicates the significance of researches on natural levees and micro-topography as control measures on alluvial fans.

Saito, Shigeru; Fukuoka, Shoji

249

Liquefaction potential of Quaternary alluvium in Bolu settlement area, Turkey  

NASA Astrophysics Data System (ADS)

Groundwater bearing alluvial units in the seismically active settlement areas may bring out probable damage on the urban and built environment due to liquefaction. Bolu settlement area and surroundings are located in the North Anatolian Fault Zone. Geotechnical boreholes were drilled in order to determine the distribution of the geological units, to obtain representative soil samples and to measure groundwater level. Quaternary aged alluvium is the main geological unit in the South of study area. Stiffness and consistency of the soils were determined by Standart penetration test. P and S wave velocities of soil have been measured along the seismic profiles. The index and physical properties of the samples have also been tested in the laboratory. Liquefaction potential and safety factor of the sandy levels in Quaternary aged alluvium were investigated by different methods based on SPT and V s. Liquefaction seems to be a significant risk in case of an earthquake with a max = 0.48 g and M w = 7.5 at different levels of the boreholes. This situation may bring out environmental problems in the future.

Ulamis, Koray; Kilic, Recep

2008-09-01

250

Quaternary seismo-tectonic activity of the Polochic Fault, Guatemala  

NASA Astrophysics Data System (ADS)

The Polochic-Motagua fault system is part of the sinistral transform boundary between the North American and Caribbean plates in Guatemala and the associated seismic activity poses a threat to ˜70% of the country's population. The aim of this study is to constrain the Late Quaternary activity of the Polochic fault by determining the active structure geometry and quantifying recent displacement rates as well as paleo-seismic events. Slip rates have been estimated from offsets of Quaternary volcanic markers and alluvial fan using in situ cosmogenic 36Cl exposure dating. Holocene left-lateral slip rate and Mid-Pleistocene vertical slip rate have been estimated to 4.8 ± 2.3 mm/y and 0.3 ± 0.06 mm/y, respectively, on the central part of the Polochic fault. The horizontal slip rate is within the range of longer-term geological slip rates and short-term GPS-based estimates. In addition, the non-negligible vertical motion participates in the uplift of the block north of the fault and seems to be a manifestation of the regional, far-field stress regime. We excavated the first trench for paleo-seismological study on the Polochic fault in which we distinguish four large paleo-seismic events since 17 ky during which the Polochic fault ruptured the ground surface.

Authemayou, Christine; Brocard, Gilles; Teyssier, Christian; Suski, Barbara; Cosenza, Beatriz; MoráN-Ical, Sergio; GonzáLez-VéLiz, Claussen Walther; Aguilar-Hengstenberg, Miguel Angel; Holliger, Klaus

2012-07-01

251

Characterization of alluvial sources in the Owens Valley of eastern California using Fourier shape analysis  

SciTech Connect

Two-dimensional quartz grain shape was used to characterize sand grains from different source areas in the Owens Valley of eastern California. Combining a mathematical description of the grain outline and multivariate discriminant analysis, we have shown that quartz from clastic source rocks has a distinctive imprint when compared to samples from granitic, volcanic, or mixed fluvial source areas. Alternatively, quartz provided by a granitic source could equally well have been interpreted as if it were derived from any of the other sources considered. This study provides a standard of comparison for further analysis of sediment deposited in arid alluvial environments.

Wagoner, J.L.; Younker, J.L.

1982-03-01

252

Short-term sediment accumulation rates determined from Eocene alluvial paleosols  

NASA Astrophysics Data System (ADS)

A new method uses alluvial paleosols to calculate sediment accumulation rates for thin (25 m) stratigraphic intervals and allows the reliable interpolation of ages for stratigraphic levels within a thick stratigraphic interval bounded by established dates. Sediment accumulation rates calculated for a 650 m composite section in the Eocene Willwood Formation of Wyoming span time intervals ranging from only 0.05 to 0.25 m.y. Important sedimentologic changes coincide with changes in accumulation rate and indicate close and direct relations between the history of basin subsidence and depositional patterns.

Kraus, Mary J.; Bown, Thomas M.

1993-08-01

253

Sedimentology and progressive tectonic unconformities of the sheetflood-dominated Hell's Gate alluvial fan, Death Valley, California  

Microsoft Academic Search

The Hell's Gate alluvial fan of northern Death Valley has an area of 49.5km2, a radius of 11.8km, and a smooth 5–3° sloping surface interrupted by shallow (<0.5m), radially aligned gullies 1–4m wide. Facies analysis of 1–14m high exposures at 45 sites reveals that the fan is built almost entirely by water-flow processes. Two facies deposited by sheetflooding dominate the

T. C. Blair

2000-01-01

254

Successional changes in soil and hyporheic nitrogen fertility on an alluvial flood plain: implications for riparian vegetation  

Microsoft Academic Search

In floodplain primary succession, vegetation colonizes nitrogen-poor alluvial deposits and fertility improves as soil nitrogen\\u000a accumulates over time. It is generally assumed that vegetation assimilates the vast majority of its nitrogen from the soil;\\u000a however, recent studies have suggested that the hyporheic zone also may be an important nitrogen source. We investigated the\\u000a potential relative importance of hyporheic nitrogen by

Michael R. Morris; Brook O. Brouwer; Jeremy K. Caves; Mary J. Harner; Jack A. Stanford

2010-01-01

255

Characterization of hydrogeologic properties for a multi-layered alluvial aquifer using hydraulic and tracer tests and electrical resistivity survey  

Microsoft Academic Search

A multi-layered aquifer, typical of riverbank alluvial deposits in Korea, was studied to determine the hydrologic properties.\\u000a The geologic logging showed that the subsurface of the study site was comprised of four distinctive hydrogeologic units: silt,\\u000a sand, highly weathered and fresh bedrock layers. The electrical resistivity survey supplied information on lateral extension\\u000a of hydrogeologic strata only partially identified by a

Jeong-Woo Kim; Heechul Choi; Jin-Yong Lee

2005-01-01

256

Fragmented Landscapes in the San Gorgonio Pass Region: Insights into Quaternary Strain History of the Southern San Andreas Fault System  

NASA Astrophysics Data System (ADS)

The San Gorgonio Pass (SGP) region is a zone of structural complexity within the southern San Andreas Fault system that is characterized by (1) multiple strands of the San Andreas Fault (SAF), (2) intense and diverse microseismicity, (3) contraction within the SGP fault zone (SGPfz), and (4) complex and diverse landforms - all a consequence of structural complications in the vicinity of the southeastern San Bernardino Mountains (SBM). Multiple strands of the SAF zone in the SGP region partition the landscape into discrete geomorphic/geologic domains, including: San Gorgonio Mountain (SGM), Yucaipa Ridge (YR), Kitching Peak (KP), Pisgah Peak (PP), and Coachella Valley (CV) domains. The morphology of each domain reflects the tectonic history unique to that region. Development of the SGP knot in the Mission Creek strand of the SAF (SAFmi) led to westward deflection of the SAFmi, juxtaposition of the KP, PP, and SGM domains, initiation of uplift of YR domain along thrust faults in headwaters of San Gorgonio River, and development of the San Jacinto Fault. Slip on the SAF diminished as a result, thereby allowing integrated drainage systems to develop in the greater SGP region. San Gorgonio River, Whitewater River, and Mission Creek are discrete drainages that transport sediment across the SGM, YR, PP, KP, and CV domains into alluvial systems peripheral to the SGP region. There, depositional units (San Timoteo Formation, upper member, deformed gravels of Whitewater River) all contain clasts of SBM-type and San Gabriel Mountain-type basement, thus constraining slip on the SAF in the SGP region. Middle and late Pleistocene slip on the Mill Creek strand of the SAF (SAFm) in the SGP region has attempted to bypass the SGP knot, and has disrupted landscapes established during SAFmi quiescence. Restoration of right-slip on the SAFm is key to deciphering landscape history. Matti and others (1985, 1992) proposed that a bi-lobed alluvial deposit in the Raywood Flats area has been displaced by 8-10 km from entrenched bedrock drainages north of the SAFm (North Fork Whitewater River and Hell-For-Sure Canyon). This restoration, along with restoration of 3-4 km of dextral-slip along SAFmi, leads to an integrated drainage network that extended from San Gorgonio Peak southward across the SAFm and SAFmi, through the San Timoteo drainage basin and ultimately to the Santa Ana River drainage. Following final slip on the SAFmi, which occurred between approximately 1.2 and 0.5 Ma, the 8-10 km dextral-slip reconstruction on the SAFm can be used to restore the ancestral Mission Creek drainage system, which has always flowed southeast. A large alluvial-fan complex that overlies the SAFmi strand developed where the ancestral Mission Creek River debouched into the Coachella Valley. Analysis of cosmogenic radionuclides (21Ne from quartz) from surface boulders indicates that oldest deposits in the fan complex are about 400ka old, compatible with pedogenic development on the oldest surface. Approximately 2-4 km dextral slip on the youngest strands of the SAF (Banning and Garnet Hill) represents the latest bypass of the SGP structural knot. Cumulative displacement on all strands of the SAF in the greater SGP region appears to have been no more than ~18 km since inception of the left step in the SAFmi. Regional evidence suggests that this event initiated at ~1.2Ma, leading to a Quaternary slip rate on the SAF at SGP of no more than 10-15 mm/yr.

Kendrick, K. J.; Matti, J. C.; Landis, G. P.; Alvarez, R. M.

2006-12-01

257

RESERVOIR ARCHITECTURE IN A TERMINAL ALLUVIAL PLAIN: AN OUTCROP ANALOGUE STUDY (UPPER TRIASSIC, SOUTHERN GERMANY) PART II: CYCLICITY, CONTROLS AND MODELS  

Microsoft Academic Search

This outcrop analogue study investigates Triassic fluvial sandstones of the Stubensandstein Formation which were deposited on a terminal alluvial plain under semi- arid to sub-humid climatic conditions in the land-locked South German Keuper Basin. The Stubensandstein may serve as an analogue for reservoir units in comparable continental basins. Data came from studies of 13 large sandpits, together with a subsurface

J. Hornung; T. Aigner

2002-01-01

258

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

259

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

260

Microbial communities of alluvial soils in the Volga River delta  

NASA Astrophysics Data System (ADS)

The number and biomass of the microbial community in the upper humus horizon (0-20 cm) were determined in the main types of alluvial soils (mucky gley, desertified soddy calcareous, hydrometamorphic dark-humus soils) in the Volga River delta. Fungal mycelium and alga cells predominate in the biomass of the microorganisms (35-50% and 30-47%, respectively). The proportion of prokaryotes in the microbial biomass of the alluvial soils amounts to 2-6%. No significant seasonal dynamics in the number and biomass of microorganisms were revealed in the alluvial soils. The share of carbon of the microbial biomass in the total carbon content of the soil organic matter is 1.4-2.3% in the spring. High coefficients of microbial mineralization and oligotrophy characterize the processes of organic matter decomposition in the alluvial soils of the mucky gley, desertified soddy calcareous, and hydrometamorphic dark humus soil types.

Sal'Nikova, N. A.; Polyanskaya, L. M.; Tyugai, Z. N.; Sal'Nikov, A. N.; Egorov, M. A.

2009-01-01

261

Late alluvial fan formation in southern Margaritifer Terra, Mars  

Microsoft Academic Search

Crater statistics show alluvial fans are much younger than previously thoughtFans formed in the Amazonian to near the Hesperian-Amazonian boundaryFan distribution requires a late period of regional water-driven degradation

John A. Grant; Sharon A. Wilson

2011-01-01

262

The Role of Climatic Change in Alluvial Fan Development  

Microsoft Academic Search

Alluvial fans develop at the base of drainages where feeder channels release their solid load (Blair and McPherson, 2009;\\u000a Leeder et al., 1998; Harvey et al., 2005). A classic fan-shape forms where there is a well-defined topographic apex. Multiple\\u000a feeder channels, however, often blur the fan-shape resulting in a merged bajada. Alluvial fans can be found in almost all\\u000a terrestrial

Ronald I. Dorn

263

[Quaternary prevention in the elderly].  

PubMed

Quaternary prevention is a group of measures taken to prevent, decrease and/or alleviate the harm caused by health activities. Health activities not only generally produce benefits, but also harm. That is to say, although medical intervention is mainly favourable, there is a dynamic balance that requires continuous assessment of the clinical situation as naturally only those health activities that achieve more benefit than harm at the end are justified. Quaternary prevention is the avoidance of unnecessary medical activity, such as "check-ups". In another example, quaternary prevention is the recommendation of preventive measures of proven efficacy. As regards diagnosis, quaternary prevention is, for example, the avoidance of screening without foundation, such as in prostate cancer. The appropriate use of antibiotics in upper respiratory tract infections serves as an example of quaternary prevention in the field of treatment. Another example is the application of the correct rehabilitation techniques in non-specific low back pain, such as swimming and maintaining an active life as much as possible. Not to forget other important "non-classic" aspects in the elderly, such as to limit the harm that can be caused by physical movement restriction devices. These and other examples in daily practice are considered in this article to encourage the continual assessment of quaternary prevention, the classic primum non nocere "first, do no harm". PMID:23062686

Gérvas, Juan

2012-10-11

264

Ion-probe U-Pb dating of authigenic and detrital opal from Neogene-Quaternary alluvium  

NASA Astrophysics Data System (ADS)

Knowing depositional ages of alluvial fans is essential for many tectonic, paleoclimatic, and geomorphic studies in arid environments. The use of U-Pb dating on secondary silica to establish the age of Neogene-Quaternary clastic sediments was tested on samples of authigenic and detrital opal and chalcedony from depths of ˜25 to 53 m in boreholes at Midway Valley, Nevada. Dating of authigenic opal present as rinds on rock clasts and in calcite/silica cements establishes minimum ages of alluvium deposition; dating of detrital opal or chalcedony derived from the source volcanic rocks gives the maximum age of sediment deposition. Materials analyzed included 12 samples of authigenic opal, one sample of fracture-coating opal from bedrock, one sample of detrital opal, and two samples of detrital chalcedony. Uranium-lead isotope data were obtained by both thermal ionization mass spectrometry and ion-microprobe. Uranium concentrations ranged from tens to hundreds of ?g/g. Relatively large U/Pb allowed calculation of 206Pb/238U ages that ranged from 1.64±0.36 (2?) to 6.16±0.50 Ma for authigenic opal and from 8.34±0.28 to 11.2±1.3 Ma for detrital opal/chalcedony. Three samples with the most radiogenic Pb isotope compositions also allowed calculation of 207Pb/235U ages, which were concordant with 206Pb/238U ages from the same samples. These results indicate that basin development at Midway Valley was initiated between about 8 and 6 Ma, and that the basin was filled at long-term average deposition rates of less than 1 cm/ka. Because alluvium in Midway Valley was derived from adjacent highlands at Yucca Mountain, the low rates of deposition determined in this study may imply a slow rate of erosion of Yucca Mountain. Volcanic strata underlying the basin are offset by a number of buried faults to a greater degree than the relatively smooth-sloping bedrock/alluvium contact. These geologic relations indicate that movement on most faults ceased prior to erosional planation and burial. Therefore, ages of the authigenic opal from basal alluvium indicate that the last movement on buried faults was older than about 6 Ma.

Neymark, L. A.; Paces, J. B.

2013-01-01

265

Seismic facies analysis of shallowly buried channels, New Jersey continental shelf: understanding late Quaternary paleoenvironments during the last transgression  

NASA Astrophysics Data System (ADS)

We are investigating the late Quaternary sedimentary record of the New Jersey mid-outer continental shelf using deep-towed chirp sonar (1-4 kHz and 1-15 kHz) profiles, coupled with lithologic and chronostratigraphic control from long sediment cores collected using the DOSECC AHC-800 drilling system. We have seismically mapped extensive, shallowly buried, dendritic drainage systems. Observed seismic facies distributions suggest the complex nature of channel fills, and synthetic seismograms derived from MST logs enable us to correlate the chirp data to changes in lithology and physical properties of the cored samples, including channel fills, confirming that fine-grained material is transparent seismically, while interbedded sand and mud produce laminated reflections. We suggest that these channels probably formed during shelfal exposure coincident with the last glacial lowstand along this margin. Observed seismic facies superposition within valley fills is in part consistent with a tripartite zonation derived from wave-dominated estuary models. We have mapped four main facies within these dendritic incised valleys: (1) The lower facies, SF1, consists of a high-amplitude chaotic configuration. We interpret this facies as lowstand fluvial fill; (2) Overlying facies SF2 is generally a thin layer (<1-2m) of stratified, high amplitude reflectors in valley axes. This facies is characterized by small wedges along channel flanks, with a generally transparent acoustic response, but occasionally also by internal clinoforms. This facies could have been deposited as transgression began, by backfilling of valleys (bayhead delta? aggradational alluvial deposits?); (3) SF3 is generally transparent; subtle horizontal and parallel reflectors onlap channel flanks. We interpret this facies as representing central basin/bay deposits, a low-energy zones during the transgression, perhaps related to turbidity maxima; (4) SF4 is observed only in the seaward end of the valley. This facies is more variable in amplitude and configuration, and includes a laminated acoustic response, small erosional surfaces, and some wavy reflections. We think the complexity of this facies likely reflects deposition of an estuary mouth complex in a dynamic environment, including frequent lateral variations in sedimentary facies from tidal inlets, washovers, tidal-deltas and barriers. A seismic transition upward from chaotic to flat-lying reflections and a more transparent acoustic response indicates less depositional energy, suggesting replacement of fluvial systems by tidal/estuarine environments. This has been confirmed by vibra-coring of one channel. Our paleo-flow reconstructions also yield velocities in the range of 0.5-1.5 m/s, which are reasonable estimates for flows in estuarine environments.

Nordfjord, S.; Goff, J. A.; Austin, J. A.; Gulick, S. P.; Sommerfield, C.; Alexander, C.; Schock, S.

2004-12-01

266

Calcrete ‘fossilisation’ of alluvial fans in SE Spain: The roles of groundwater, pedogenic processes and fan dynamics in calcrete development  

NASA Astrophysics Data System (ADS)

Dryland alluvial fans developed along the northern flanks of the Sierra Lisbona in the north-western Vera basin (Almería region, southeast Spain) display negligible amounts of incision despite distal base-level lowering of > 30 m by the modern drainage network. The fans are of early-middle Quaternary age and are graded to a coeval river terrace, now isolated from the modern drainage network. The negligible incision is due to the encasement and ‘fossilisation’ of the alluvial fans by calcrete. This paper explores the reasons for such fossilisation and assesses the relative importance of pedogenic and groundwater mechanisms for calcrete formation within an alluvial fan setting. A single fan was selected for detailed examination. The geomorphological and sedimentological features of the fan, its catchment area and their relationship to the distal river terrace were documented. Qualitative and semi-quantitative petrographic and scanning electron microscope analyses of calcrete samples collected from transects across the fan surface, and within its distal top river terrace surface, enabled the style, pattern and relative timing of calcrete development to be assessed. Calcrete fabrics comprised initial micritic grain-coating cements, pellets and glaebular carbonate nodules, with interstitial spaces infilled by equant sparite and microsparite mosaics. It is proposed that the early phases of calcrete development were dominated by pedogenic processes with increasing groundwater calcretisation over time. Point count data indicated increased quantities of interstitial sparite and microsparite cement within near-surface proximal fan calcretes and at depth across the fan, suggesting that groundwater processes played a more important role in calcrete formation in these locations. The contribution of groundwater to calcrete development can be best explained by the intrinsic funnelling of groundwater from the catchment through the proximal fan head area, a zone where the fan gravels are thinnest. Calcrete ‘fossilisation’ appears to have followed a reduction in the fan catchment area as a result of rockfalls and watershed stream capture, which reduced water and sediment supply to the fan and enabled surface stabilization and calcrete development to take place. The reduced sediment/water supply, combined with calcrete fossilisation, appears to have protected the alluvial fans from regional base-level lowering. The implications of these results for existing pedostratigraphic models of calcrete development in alluvial fans are subsequently explored.

Stokes, Martin; Nash, David J.; Harvey, Adrian M.

2007-03-01

267

Modeling Baseflow from an Alluvial Aquifer Using Hydraulic-Conductivity Data Obtained from a Derived Relation with Apparent Electrical Resistivity  

NASA Astrophysics Data System (ADS)

In order to accurately quantify the water flux entering the Netherlands from Belgium via the Meuse River and its alluvial plain, the Belgian Ministry of Public Works has supported hydrological and hydrogeological studies in the area between the city of Liège (Belgium) and the Dutch border. The groundwater fluxes from the Albert Canal to the Meuse River and those passing around the weir-lock systems within the alluvial gravel deposits are not measured by the existing surface-water gauging system; therefore, detailed quantitative hydrogeological studies of the groundwater fluxes in these alluvial deposits were needed. A detailed three-dimensional finite-element numerical model was used to compute these fluxes. Previous hydrogeological studies involving piezometers, pumped wells, and electrical soundings provided, respectively, data for potentiometric maps, local values of hydraulic condictivity, and more than 200 measurements of the apparent geoelectrical resistivity of the gravel deposits. From this data set, a new correlation between geoelectrical resistivity and hydraulic conductivity was used to define a spatially distributed set of hydraulic-conductivity values to be entered in the model. Maps and measured potentiometric heads were used as references for the calibration of the model, and features of the model, such as layer geometry, external sink and source terms, and boundary conditions, were selected on the basis of all available information. Four non-horizontal layers were discretized as 2,356 elements. On the basis of the model, the additional flow crossing to the Netherlands via the alluvial aquifer and the Meuse River is about 5.4 3/s during the summer.

Dassargues, A.

1997-03-01

268

Long term trend in groundwater levels and watershed condition in the Kurobe River alluvial fan in Japan  

Microsoft Academic Search

The Kurobe River alluvial fan is one of the most popular alluvial fans in Japan. The difference in elevation from Aimoto where is the top of the alluvial fan to seashore is approximately 130m, and the slope of the alluvial fan is approximately 10 degrees. The Kurobe River alluvial fan is consisted of conglomerate layers and has had many flowing

T. Tebakari

2010-01-01

269

Radiogenic 3He/4He Estimates and Their Effect on Calculating Plio-Pleistocene Cosmogenic 3He Ages of Alluvial-Fan Terraces in the Lower Colorado River Basin, USA  

NASA Astrophysics Data System (ADS)

Several alluvial-fan terraces near Topock, AZ were created by successive entrenchment of Pliocene and Pleistocene alluvial-fan gravels shed from the adjacent Black Mountains along the lower Colorado River corridor below Hoover Dam. These fans interfinger with and overlie main-stem Colorado River sands and gravels and grade to terrace levels that correspond with pre-existing elevations of the Colorado River. Absolute dates for the ages of Quaternary deposits on the lower Colorado River are rare and cosmogenic 3He age estimates of these surfaces would help constrain the timing of aggradation and incision in the lower Colorado River corridor. We analyzed individual basalt boulders from several terrace surfaces for total 3He/4He concentrations to calculate cosmogenic 3He ages of each fan terrace; 3He/4He values, expressed as R/Ra where Ra is the 3He/4He of air, range from 0.29 to 590. Black Mountain volcanic rocks have reported K-Ar ages between 15 and 30 Ma and basalt samples from adjacent alluvial fans contain 0.42 to 47× 1012 at/g of 4He, which has likely accumulated due to nuclear processes. The amount of radiogenic 3He/4He can be significant in old rocks with young exposure ages and can complicate determination of cosmogenic 3 He content. Alpha-decay of U, Th, and their daughter isotopes produces large amounts of 4He, whereas significant amounts of radiogenic 3He are only produced through the neutron bombardment of Li and subsequent beta-decay of tritium. We measured Li, U, Th, major and rare-earth element concentrations in whole-rock basalts and mineral separates. These concentrations are used to estimate the ratio of radiogenic helium contributed to the total helium system in our samples. Li concentrations typically range from 6 to 17 ppm, with one outlier of 62 ppm. U contents range from <0.1 to 2.7 ppm and Th contents range from 0.4 to 15.3 ppm. Based on these values, our calculations predict that the average radiogenic helium (R/Ra) contributed to the total helium in Black Mountain basalt samples is 0.011. Other noble gas studies have shown that radiogenic 3He/4He is independent of the U content, nearly independent of the Th content, and strongly influenced by the Li content of a rock; we find the same results. It is assumed that mantle gases are released when the sample is crushed into a fine powder before melting in a furnace under vacuum. To correct for the possible presence of mantle gases in our age-calculations, we crushed two samples under vacuum to measure the R/Ra value (7.9 and 16.03) of mantle helium trapped in fluid inclusions in olivines and pyroxenes. Based on our 3He corrections and calculations, boulders on these alluvial fans range in age from 10 ka to 2.7 Ma.

Fenton, C.; Pelletier, J.

2005-12-01

270

Mass balance from alluvial fan isopachs: a case study from the Chinese Tian Shan  

NASA Astrophysics Data System (ADS)

Continental surfaces are incessantly reworked through erosion and sedimentation. Markers of erosion within drainage areas are often scarce and temporary, but at the outlet of mountain belts, more continuous and perennial records of deposition can be found in alluvial fans. These fans are constructed by the deposition through time of the coarse part of sediments transported by rivers. Volume of sediments trapped in alluvial fans can then be used in order to reconstruct sediment fluxes coming out from their catchment areas and the associated erosion rates. Quantifying such erosion rates is of great interest for the study of mass transfer. It is also necessary to understand relief dynamics, as well as the influence of tectonic and climate on this dynamics. We propose here a complete method to estimate erosion fluxes from alluvial fans in a specific area, the northern piedmont of the Tian Shan in China. Along the piedmont of this range, series of fans of different ages are clearly identified. In particular, abandoned fans (which were active before 10 000 years ago) are well preserved in the landscape, and easily identifiable on satellite images. These fans have been deeply incised during the last deglaciation (about 10 000 years ago), and therefore, their basal surface can be observed. In this specific area, it is then possible to obtain field constraints on the real fan thickness. First, we draw a morpho-sedimentary map of the fans and their drainage basins. Then, we went on the field to estimate the fan thickness wherever it is possible. Finally, based on this data set, and on geometrical considerations, we built isopach maps of the fans and calculate their volumes. These 3D reconstructions can then be compared to the geometrical relationships classically used to assess alluvial fan volumes from their upper surface only. Erosion rates of ten drainage basins can be derived from these volumes, allowing a sink to source investigation, for the period of fan activity. In north Tian Shan, these erosion rates can be compared with other values calculated from bedload measurements and cosmogenic data, providing thus an opportunity to discuss results coming from different methods

Guerit, Laure; Barrier, Laurie; Métivier, François; Jolivet, Marc; Fu, Bihong

2013-04-01

271

Variability in alluvial rocks, determined from TM analysis, and its tectonic significance  

NASA Astrophysics Data System (ADS)

This study demonstrates that images generated from Thematic Mapper data are valuable for sedimentologic analysis of a depositional basin. A ratio composite color image was used to identify and regionally map large-scale lithologic packages in the alluvial Willwood Formation. The facies were further distinguished using field sedimentologic criteria. The spatial distribution of facies demonstrates that east-west trending lineaments extend from the Bighorn Mountains westward into the Bighorn Basin, Wyoming and were active faults during early Eocene time. The lithologic heterogeneity is attributed to differential crustal subsidence on either side of the lineaments. This caused topographic gradients and variability in local moisture regimes, which influenced the location of major stream channels and the types of paleosols that formed. Temporal changes in lithology record a regional change to increase dryness followed by a return to moister conditions, culminating in the development of lacustrine deposits.

Kraus, Mary J.

272

Tufa and travertine of the Lesser Caucasus: a light on the Quaternary palaeoenvironment of the Circumcaspian regions  

NASA Astrophysics Data System (ADS)

In the course of the International Associated Laboratory HEMHA (Humans and Environment in Mountainous Habitats : the case of Armenia), the French Foreign Affair Ministry Caucasus Mission (CNRS-UMR 5133 Archéorient, Lyon University) and the French-German research program Ancient Kura (CNRS-UMR 7192 PrOCauLAC, Paris, France, Deutsches Archäologisches Institut, Eurasien-Abteilung, Berlin, Germany with ANR-CNRS and DFG funding) numerous sites of the Lesser Caucasus territory are under geomorphological, palaeoenvironmental and archaeological investigations. Through comparisons between the tufa/travertine system and the detrital formation morphosedimentary evolution, one of our research interests is to define the Late Quaternary landscape mutations as well as the origin and rhythmicity of the major morphogenic trends reversals. The impacts of the environmental changes highlighted on the human occupation modes are also debated. A total of 14 travertine and tufa formations were studied (8 Pleistocene and 6 Postglacial formations) on a Northwest-Southeast transect of more than 300 km across the Lesser Caucasus. Each of these carbonated system development are correlated with high global relative sea levels and interstadial climates on a range between the Marine Isotopic Stage 11 and 1 (ca. 335 to 1.5 Ky BP). The absolute chronology is constrained by a series of U/Th and 14C dating. A total of 24 dating was performed (6 radiocarbon and 18 U/Th datings), allowing a high quality overview of the travertinization process over the time at a regional scale. Jointly with the measurement of the late Quaternary interglacial series impact on the tufas development in the Caucasus, the geomorphological position of some travertinous formations and their absolute dating gives some clues about the neotectonic evolution of the studied valleys. In some area, the uplift rate has been determined (ca. 8 mm/year) and discretized from the alluvial incision signal. The analysis of the carbonated deposits (faciological determinations, palaeobotanical and palynological identifications of leave imprints and pollens), which are the expression of specific climatic conditions, and the comparative approach with the general morphosedimentary evolution, give a complete reading grid of the regional landscape mutation expressions and origins (Caspian Sea eustatism or exclusive climatic impact), necessary to understand the magnitude of the changes and their influence on the Circumcaspian societies.

Ollivier, V.; Roiron, P.; Nahapetyan, S.; Joannin, S.; Chataigner, C.

2012-04-01

273

Evolution Of Quaternary Stream Fan Deposits At The Confluences Of Turung Khola And Bembung Khola Of Middle Teesta Basin In Sikkim-Darjeeling Himalaya,India: A Tectonic - Climate Response  

Microsoft Academic Search

Tributary fan deposits are well preserved on either side of the Teesta river in the non-glaciated middle part of the Himalayan valley lying in a tectonic region bounded by the MCT and MBT. The lithofacies characteristics and assemblage patterns of these deposits bear testimony to the effects of tectonic and climatic activities on the sedimentation process in the basin. Two

I. M. Lukram

2007-01-01

274

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

275

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

276

Stratigraphic architecture of alluvial–aeolian systems developed on active karst terrains: An Early Pleistocene example from the Ebro Basin (NE Spain)  

NASA Astrophysics Data System (ADS)

During the Early Pleistocene, fluvial, alluvial and aeolian depositional systems interacted in the central Ebro Basin, Spain, constructing wide alluvial plains over a Neogene evaporite substratum. Fluvial sediments, mainly longitudinal gravel bars and channels, are interdigitated with gravel mass flow and distal mudflat deposits. Aeolian sedimentation is registered as aeolian dunes and sand sheets. Episodes of fluvial deposition alternated with periods of alluvial fan progradation and aeolian deposition. These changes are related to climate-driven water availability. Stratigraphic units and deformation structures show synsedimentary karstification of the evaporite substratum that, although karst was not restricted to any particular climate scenario, was probably favoured during periods of high water availability. Karstification conditioned the development of local sedimentary depocentres which, in turn, influenced the distribution of sedimentary subenvironments as well as the accumulation and preservation of aeolian dunes and lacustrine–palustrine deposits. Stratigraphic architecture shows that thickening of the series due to karst subsidence did not occur homogeneously, but was controlled by diachronous subsidence resulting in numerous angular unconformities. In subsiding karst areas transport capacity was reduced and sediment preservation increased.

Gil, H.; Luzón, A.; Soriano, M. A.; Casado, I.; Pérez, A.; Yuste, A.; Pueyo, E.; Pocoví, A.

2013-10-01

277

Avulsion Clusters in Alluvial Systems: An Example of Large-Scale Self-Organization in Ancient and Experimental Basins  

NASA Astrophysics Data System (ADS)

The stratigraphic record of at least some alluvial basins exhibits a spatial structure that may reflect long time- scale (103-105 yr in natural basins) autogenic organization of river avulsions. Current models of avulsion-dominated alluvial sequences emphasize the spatial and temporal distribution of coarse-grained channel-belt deposits amid fine-grained floodplain materials. These models typically assume that individual avulsions move, either randomly or deterministically, to low spots distributed throughout the model space. However, our observations of ancient deposits and experimental stratigraphy indicate a previously unrecognized pattern of channel-belt organization, where clusters of closely-spaced channel-belt deposits are separated from each other by extensive intervals of overbank deposits. We explore potential causes of and controls on avulsion clustering with outcrop and subsurface data from Late Cretaceous/Early Paleogene fluvial deposits in the Rocky Mountains (including the Ferris, Lance, and Fort Union formations of Wyoming) and results of physical stratigraphy experiments from the St. Anthony Falls Lab, University of Minnesota. We use Ripley's K-function to determine the degree and scales of clustering in these basins with results that show moderate statistical clustering in experimental deposits and strong clustering in the Ferris Formation (Hanna Basin, Wyoming). External controls (base level, subsidence rate, and sediment/water supplies) were not varied during the experiment, and therefore not factors in cluster formation. Likewise, the stratigraphic context of the ancient system (including the absence of incised valleys and lack of faulting) suggests that obvious extrinsic controls, such as base level change and local tectonics, were not major influences on the development of clusters. We propose that avulsion clusters, as seen in this study, reflect a scale of self-organization in alluvial basins that is not usually recognized in stratigraphy. However cursory examination of other ancient systems suggests that such structure may be common in the rock record. Understanding mechanisms driving avulsion clustering will shed light on the dominant processes in alluvial basins over long time scales. Furthermore, characterizing autogenic avulsion clusters will be an important factor to consider when interpreting allogenic signals in ancient basin fills.

Hajek, E.; Heller, P.; Huzurbazar, S.; Sheets, B.; Paola, C.

2006-12-01

278

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

279

Quaternary Studies: An Interdisciplinary Program  

NSDL National Science Digital Library

Rutgers University promotes its Graduate Certificate in Quaternary Studies where students take part in geology, geography, meteorology, and other disciplines interested in the last couple of million years of Earth's history. Students and educators can find information on the researchers involved with the program and the necessary course work.

1969-12-31

280

Corrosion inhibition by quaternary amines  

Microsoft Academic Search

Quaternary ammonium compounds are excellent inhibitors of acid corroison, and seem to influence the anodic partial reaction more than the cathodic. This behavior is not readily interpreted in terms of physical vs. chemical adsorption, since these compounds do not possess bonding for chemisorption. Increasing the hydrogen bulk in the inhibitor molecule markedly increases the inhibition efficiency, which is to be

R. M. Hurd; H. Raiszadeh

1970-01-01

281

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

282

Paleomagnetic stratigraphy and time in sediments: Studies in alluvial Siwalik rocks of Pakistan  

SciTech Connect

Sediments may acquire magnetic remanence upon deposition and shortly after deposition. Hence, the paleomagnetic record of sedimentary rocks may provide a chronostratigraphic framework for rates and patterns of depositional and post-depositional processes over time scales intermediate between those of modern observation and those of the dated geologic record. Two applications of high-resolution magneto-stratigraphy in Miocene, alluvial rocks of Pakistan illustrate this point. (1) Transition stratigraphy-the dense sampling of a magnetic reversal-of correlated sections in the Dhok Pathan Formation revealed high variability in sediment accumulation rates (over several thousand to 10,000 yr), time-transgressive strata representing a paleosol and a floodplain marsh, and a pervasive post-depositional record mainly from pedogenesis. (2) Lateral tracing of paleomagnetic reversal boundaries in the Chinji Formation revealed a secular change in sediment accumulation rate and evidence for increased accumulation rate associated with extensive sandstones and the time-transgressive nature of certain sandstone units. Both studies demonstrate the significant lateral component to accumulation of lithological units, indicating that individual strata may embody considerably greater time spans in their lateral extent than in any vertical transect. Hence, stratigraphic completeness should be evaluated in the lateral as well as the vertical dimension.

Badgley, C. (Univ. of Michigan, Ann Arbor (USA)); Tauxe, L. (Scripps Institution of Oceanography, La Jolla, CA (USA))

1990-07-01

283

Early Cretaceous stratigraphy, paleontology, and sedimentary tectonics in Paris overthrust foredeep (western Wyoming and southeastern Idaho) compared with Quaternary features of indo-gangetic plain  

Microsoft Academic Search

Fluviatile clastics of the nonmarine, early Cretaceous Gannett and Wayan groups were deposited on wet alluvial megafans and on intervening interfan piedmont slopes which declined eastward into more poorly drained lowlands from a western highland source area uplifted episodically by movements of the Paris overthrust. Lacustrine episodes of deposition intercalated Peterson and Draney limestones with Gannett fluvial clastics. Westward marine

J. A. Jr

1983-01-01

284

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

285

Tectonic controls on the geomorphic evolution of alluvial fans in the Piedmont Zone of Ganga Plain, Uttarakhand, India  

NASA Astrophysics Data System (ADS)

The Piedmont Zone is the least studied part of the Ganga Plain. The northern limit of the Piedmont Zone is defined by the Himalayan Frontal Thrust (HFT) along which the Himalaya is being thrust over the alluvium of the Ganga Plain. Interpretation of satellite imagery, Digital Terrain Models (DTMs) and field data has helped in the identification and mapping of various morphotectonic features in the densely forested and cultivated Piedmont Zone in the Kumaun region of the Uttarakhand state of India. The Piedmont Zone has formed as a result of coalescing alluvial fans, alluvial aprons and talus deposits. The fans have differential morphologies and aggradation processes within a common climatic zone and similar litho-tectonic setting of the catchment area. Morphotectonic analysis reveals that the fan morphologies and aggradation processes in the area are mainly controlled by the ongoing tectonic activities. Such activities along the HFT and transverse faults have controlled the accommodation space by causing differential subsidence of the basin, and aggradation processes by causing channel migration, channel incision and shifting of depocentres. The active tectonic movements have further modified the landscape of the area in the form of tilted alluvial fan, gravel ridges, terraces and uplifted gravels.

Goswami, Pradeep K.; Pant, Charu C.; Pandey, Shefali

2009-06-01

286

The legacy of Pleistocene glaciation and the organization of lowland alluvial process domains in the Puget Sound region  

NASA Astrophysics Data System (ADS)

Alluvial rivers of the eastern Puget lowland, a landscape shaped by scour and fill from the Cordilleran ice sheet, continue to respond to patterns of deposition and scour by the last-glacial-age ice sheet 18,000 years after deglaciation. Topography revealed by valley cross sections created from high resolution LIDAR digital elevation models shows that rivers are aggrading in valleys eroded by subglacial runoff and degrading in valleys incised by rivers post-glaciation. Slope-area analysis of river profiles shows that profile concavity varies systematically between river segments in the two valley contexts. Concavity indices ( ?) in mountain headwaters (0.3 < ? < 0.9) compare to those of many world rivers (0.2 < ? < 1.0), but in the lowlands these indices differ between valleys created by subglacial fluvial erosion (5 < ? < 45) and post-glacially incised river valleys that grade to base levels set by these relict glacial valleys or by post-glacial sea levels (1 < ? < 7). Dramatic differences in river pattern, landforms, and dynamics occur in valleys having contrasting (aggrading vs. degrading) and incomplete responses to Pleistocene glaciation, creating discrete valley-scale heterogeneities in fluvial process domains along and between rivers. These results point to the importance of valley-scale organization of alluvial process domains along and between rivers having profiles remaining in disequilibrium from Pleistocene glaciation. They also point to the potential usefulness of slope-area analysis of longitudinal profiles in distinguishing among different river valley process domains in lowland alluvial landscapes.

Collins, Brian D.; Montgomery, David R.

2011-03-01

287

HYDRAULIC ANALYSIS OF BASEFLOW AND BANK STORAGE IN ALLUVIAL STREAMS  

EPA Science Inventory

This paper presents analytical solutions, which describe the effect of time-variable net recharge (net accretion to water table) and bank storage in alluvial aquifers on the sustenance of stream flows during storm and inter-storm events. The solutions relate the stream discharge,...

288

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 ...

289

Catalogue of large alluvial fans in martian impact craters  

Microsoft Academic Search

We conducted a systematic, global survey using Thermal Emission Imaging System Infrared (THEMIS IR) coverage (?100 m\\/pixel) to search for large alluvial fans in impact craters on Mars. Our survey has focused on large fans (apron areas greater than ?40 km2, usually located in craters greater than 20 km in diameter) due to the resolution of the THEMIS images and

Erin R. Kraal; Erik Asphaug; Jeffery M. Moore; Alan Howard; Adam Bredt

2008-01-01

290

Microbial contamination of alluvial gravel aquifers by septic tank effluent  

Microsoft Academic Search

The effects of two methods of septic tank effluent disposal on the microbial quality of alluvial gravel aquifers were investigated at an experimental site in the Canterbury Plains, New Zealand. The movement of faecal coliform bacteria 9 m from a 5.5 m deep soakage pit into an unconfined aquifer, and 42 m from an 18 m deep injection bore into

L. W. Sinton

1986-01-01

291

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

292

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

293

Quaternary History of the Northern Cumberland Peninsula, Baffin Island, N.W.T. Part III. The Late Glacial Deposits of Sulung and Itidlirn Valleys and Adjacent Parts of the Maktak-Narpaing Trough.  

National Technical Information Service (NTIS)

Four moraine systems are recognized within the area. The oldest was deposited at the margin of a major outlet glacier about 600 m a.s.l. Local corrie glaciers in the Sulung and Itidlirn Valleys show three and two moraine systems respectively, which in par...

R. E. Dugdale

1972-01-01

294

Charcoal and the Record of Fire-related Sedimentation in Holocene Alluvial Sediments  

NASA Astrophysics Data System (ADS)

Over the last few decades, rising temperatures and ensuing severe wildfires in the western USA cordillera have provided the opportunity to examine processes and deposits of postfire sedimentation on alluvial fans and floodplains. Most events are generated by widespread surface runoff from intense convective-storm precipitation on severely burned slopes. Flow processes range from debris flow to sediment-charged water floods. Muddy debris flows best preserve coarse charcoal in fan deposits, whereas gravelly debris flows often comminute charcoal into fine particles. As charcoal remains suspended in high-energy hyperconcentrated and water floods, only their fine-grained deposits typically contain much charcoal. Charcoal is locally concentrated in low-energy fluvial deposits, but displays increasing evidence for reworking with distance from source. Charred vegetation and litter marking burned soil surfaces may be preserved under postfire fan and fluvial sediments. Modern deposits provide models for identification of Holocene fire-related sediments and estimates of paleofire severity. AMS 14C dating of discrete charcoal fragments allows sample selection to minimize errors of sample age > fire age. Fires are incompletely recorded in the event stratigraphy of one fan, but larger populations of 14C ages from numerous fans permit composite probability distributions that represent centennial- to millennial-scale changes in fire-related sedimentation across a study area. Records from Yellowstone and central Idaho indicate the large role of fire in episodic erosion across a range of conifer forests, most strongly during severe, multidecadal droughts in warmer periods (e.g. in Medieval time 900-1300 AD). In central Idaho, identification of charcoal macrofossils indicates broadly similar, aspect-controlled forest compositions over the last 3000 yr. Emerging data from the Sacramento Mountains, New Mexico, show rapid fan aggradation due to fire-related events in the warm middle Holocene. Charcoal macrofossils provide a test for the hypothesis that Gambel oak shrubfields in the Sacramentos were initiated and maintained by severe fires that destroyed conifer stands. Charcoal in alluvial deposits allows examination of Holocene fire-climate- geomorphic relations in diverse environments, aiding in assessment of the potential impacts of future climatic change.

Meyer, G. A.

2006-12-01

295

Behavior of Late Quaternary and historical faults in the western Basin and Range province  

SciTech Connect

Quaternary stratigraphic relations and exploratory trenching in zones of historical surface faulting in the western Basin and Range Province suggest that faults with historical surface ruptures have similar, and in some cases lower, long-term (late Quaternary) and short-term (Holocene) slip rates than other adjacent and regional non-historical Quaternary faults. In the 1954 Dixie Valley earthquake (M6.8) zone, the range-front and piedmont faults collectively record a late Quaternary (200 ka) slip rate on the order of 0.2 mm/yr and a Holocene (7--12 ka) slip rate of 0.5--0.8 mm/yr. The principal segment of the 1932 Cedar Mountain earthquake (M7.2) zone has an estimated latest Quaternary (25--35 ka) slip rate of 0.2--0.7 mm/yr and a Holocene (6--13 ka) slip rate of 0.3--0.7 mm/yr. The 1954 Rainbow Mountain earthquakes (M6.6 and M6.8) and 1954 Fairview Peak earthquake (M7.1) zones have late Quaternary slip rates that are lower (< 0.1 mm/yr), and although there are adjacent Holocene faults, neither zone shows surficial evidence of a previous Holocene event as do the first two zones. The 13 ka Lahontan shoreline at Rainbow Mountain is displaced only by the 1954 faulting, and the main segment of the Fairview Peak zone is overlain by a late Pleistocene (60--120 ka) alluvial fan which is offset by only the 1954 event. An important observation its that the central Nevada seismic belt is not unique based on slip rates. The greatest slip rates in the central and western Nevada region are associated with the Sierra Nevada frontal fault zone and the northern Walker Lane (Pyramid Lake) fault zone where Holocene slip rates are [>=] 1 mm/yr. Based on a comparison of Holocene and late Quaternary rates, many, but not all, historical and non-historical zones show evidence of temporal clustering.

Bell, J.W. (Univ. of Nevada, Reno, NV (United States). Nevada Bureau of Mines and Geology)

1993-04-01

296

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

297

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

298

Geostatistical simulations of alluvial sandbodies in the Triassic series of the Chaunoy field, France  

SciTech Connect

Chaunoy field, the largest oil field of the Paris basin, is exploiting heterogeneous reservoirs deposited during the Triassic in a large alluvial fan/lacustrine complex. The construction of a realistic reservoir model is difficult in such a setting because of the highly complex architecture of single reservoir units. Geostatistical simulations therefore have been performed to take into account the reservoir heterogeneities in the fluid flow modeling. A first layering has been determined from sedimentological and sequence stratigraphic analysis. The series was deposited in an alluvial outer fan environment. A lower siliciclastic member shows four heterogeneous sand sheets (7 m thick), which have been correlated across the field. Each of them is made up of stacked single channel sequences. The sand sheets are separated by extensive lacustrine and flood plain mudstone layers acting as permeability barriers. An upper siliciclastic/dolomitic member has been divided into two units with porous conglomeratic channels interfingered with cemented lagoonal dolomites. Proportional curves in lithofacies have confirmed this layering, showing the continuity of the permeability barriers, and the variogram analysis has shown that the well spacing is larger than the channel width. Simulations in lithofacies have been performed with the Heresim software using three different variogram ranges (small, medium, and large values). Because a good correlation exists between the lithofacies and the petrophysical attributes, a transcription of the lithofacies simulations into petrophysical attributes therefore was easy and realistic. Scaling-up techniques have given fluid-flow models corresponding to the three correlation ranges. Comparison of the global results of the fluid flow simulations with the observed production history enabled us to choose the more relevant case. The the model using the selected correlation range helped determine optimum well spacing.

Eschard, R.; Desaubliaux, G.; Eemouzy, P. (Institut Francais du Petrole, Rueil Malmaison (France)); Bacchiana, C.; Parpant, J.; Chautru, J.M.

1993-09-01

299

Neotectonic impact and Palaeohydrology of Gaxun Nur Basin (NW China) during the Late Quaternary  

NASA Astrophysics Data System (ADS)

The Gaxun Nur Basin - enclosed by the Tibetan Plateau in the south and the Gobi Altay in the north - has continuously evolved as a strong continental endorheic depositional environment for the last 250,000 years. The Hei River drainage system originates in the Qilian Shan (>5,000 m a.s.l.) fed a crescent-shaped series of terminal lakes at its far end (Gaxun Nur, Sogo Nur and Juyanze). Large scale geomorphological mapping from Landsat-data, Corona-Images and SRTM - elevation data shows widespread features of faults within the whole basin (Hartmann 2003). Main lineaments have been proved by geophysical investigations (Hoelz et al. 2007). Geomorphological discontinuities (e.g. inverted channels, concave alluvial fans,..) in order of their underlying processes of fluvial, aeolian and lacustrine origin allow a stratigraphic placement. Dating of lake deposits within and between geomorphological units yield the chronological frame of tectonic movement and environmental change as well. The 230m long core D100 in the centre of the basin (ca. 28,000 km²) shows the start-up of more or less continuous lacustrine deposition at ca. 250,000 yrs BP. A large set of radiocarbon datings of the upper ca. 90m suggests an increasing subsidence rate since MIS 4 within the whole basin. (Wünnemann et al. 2007) A 26 m high cliff section of gravel-covered lake sediments within the Juyanze Palaeolake indicates a strong subsidence of the lake bottom of 3.6m/1000yrs since 18 kyrs BP. Geophysical investigation indicates a lowering of the western basin along a fault system as a continuation of a duplex structure developed further south at Gurinai depression (Hoelz et al. 2007). The rhombic shape of the modern dry Gaxun Nur, fossil cliffs, well preserved beach ridges and gravel covered top-sets of lacustrine sediments indicate local displacements of morphological features. Flat flower structures along a WNW-trending fault indicate young tectonic movements related to the Tian Shan fault system. The displacements of lake sediments at the southern margin of the modern Gaxun Nur basin imply a subsidence of at least 0.81m/1000 yrs since 25 kyr as a result of a pull-apart development due to the left stepping faults in a sinistral system. Frequently lakes are of tectonic origin. Their sediments and nearby catchment topography provide an excellent archive for reconstructing young tectonic movement. In this respect palaeohydrological reconstruction of lake catchments has to consider the occurrence of tectonic. In classical proxies of hydrological changes, both signals in the same archive interfere with each other. Complex system variables derived from large datasets by multivariate approaches are able to dissolve the processes (Hartmann & Wünnemann 2007). References Hartmann, K. (2003): Spätpleistozäne und holozäne Morphodynamik im nördlichen Gaxun Nur Becken, Innere Mongolei, NW China. Ph D-Thesis, Dept. of Geosciences, Freie Universitaet Berlin. Hartmann, K. & B. Wünnemann (2009): Hydrological changes and Holocene climate variations in NW China, inferred from lake sediments of Juyanze palaeolake by factor analyses. Quaternary International 194, 28-44. Hölz, S., Polag, D., Becken, M. Fiedler-Volmer, R., Zhang, HC., Hartmann,K., Burkhardt, H. (2007): Electromagnetic and Geoelectric Investigation of the Gurinai Structure, Inner Mongolia, NW China. Tectonophysics 445, (Issues 1-2): 26-48. Wünnemann, B., Hartmann, K., Altmann, N., Pachur, H.-J., Hambach, U. (2007): Glacial and Interglacial fingerprints from lake deposits in the Gobi Desert, NW China. In: Siroko, F., Clausen & M. Sanchez-Goni (Editors): The Climate of the Past Interglacials, pp. 323-348, Elevier, Amsterdam, N.Y..

Hartmann, K.; Wünnemann, B.; Zhang, H.

2009-04-01

300

Interaction of climate and tectonics upon alluvial architecture: Late Carboniferous-Early Permian sequences at the southern margin of the Pennine Basin, UK  

Microsoft Academic Search

Late Carboniferous (mid to late Westphalian D) to Early Permian strata of south Staffordshire, English Midlands were deposited on the margins of a foreland basin (Pennine Basin) during a period of increasing climatic aridity. Approximately 300–500 m of grey and red-bed alluvial sediments contain five vertically stacked facies associations, each with characteristic stratal architecture and palaeosols.The succession exhibits three orders

Brian W. Glover; John H. Powell

1996-01-01

301

Rapid subsidence in the Nile delta and the effects of a mobile depositional surface on stratigraphic facies development  

SciTech Connect

Radiocarbon-data late Quaternary sedimentary sections serve as a base to quantify high rates of subsidence in the northern Nile delta of Egypt. Measurements of recent vertical shifts of land relative to the sea, coupled with eustatic changes, are used to interpret temporal and spatial facies distribution patterns and delta lobe migration in the major recent depocenter in the eastern Mediterranean. The study is based largely on cores, collected during two drilling expeditions, which recovered material deposited during the past 30,000 years. These borings, plus an additional 50 core logs, allow good correlation for the region around Lake Manzala. There, variable thicknesses of Holocene marine and fluvio-marine units lie above transgressive coastal sands (upper Pleistocene to lower Holocene) and older alluvial delta-plain deposits. Mapping of these facies shows that the top of the transgressive sand becomes younger (to /approximately/ 7000 years ago) and shallower toward the south of the present coastline. Progradation of delta lobes began about 8000 years ago, and the coastline has advanced northward at a rate of approximately 1 km/100 years.

Stanley, D.J.

1988-02-01

302

Holocene vegetation changes along the southeastern coast of the Argentinean Pampa grasslands in relation to sea-level fluctuations and climatic variability: Palynological analysis of alluvial sequences from Arroyo Claromecó  

Microsoft Academic Search

Here we present palynological records from alluvial deposits in four outcrop sequences along the lower reaches of Arroyo Claromecó, Buenos Aires Province, Argentina (38° 50? S latitude, 60° 05? W longitude). These data indicate development of soils and grasslands with associated halophytic vegetation in the higher elevations of the floodplains between ca. 7200 and 600014C yr BP (ca. 8000 and

Isabel Vilanova; Aldo R. Prieto; Silvina Stutz; E. Arthur Bettis

2010-01-01

303

Effects of saccharin and quaternary ammonium chlorides on the electrodeposition of nickel from a Watts-type electrolyte  

Microsoft Academic Search

The effect of the presence of quaternary ammonium chlorides (QACl) and saccharin on various electrodeposition parameters for nickel deposition on a stainless steel cathode from a Watts-type plating bath was investigated. The parameters included cathodic current efficiency, throwing power of the bath, cathodic polarization, crystal orientation, and quality of the deposit. The following additives were investigated: saccharin, 1-alkyloxymethyl 3-benzyl imidazolium

Aleksander Ciszewski; Szymon Posluszny; Grzegorz Milczarek; Marek Baraniak

2004-01-01

304

OSL Ages Of Quaternary Sediments In The Luzow-Holm Bay Region, East Antarctica, And Their Implications  

Microsoft Academic Search

The fluctuation of both hemisphere ice sheets during the Late Quaternary has given great impacts on global sea-level changes and climatic variations. We have been studied the stratigraphic relationship between raised beach deposits including in situ fossil shells and glacial deposits in the Lutzow-Holm Bay region, East Antarctica, clarifying the Antarctic ice sheet, unlike the northern hemisphere ice sheet, was

M. Takada; H. Miura; H. Maemoku; Y. Yokoyama; S. Iwasaki

2005-01-01

305

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

306

Quaternary Sea-level Fluctuations and Environmental Change Indicated by Foraminiferal Assemblages, Outer Banks, North Carolina  

Microsoft Academic Search

A 155-ft. drillcore at the site of a former inlet penetrates several Quaternary depositional sequences previously recognized in seismic records and shorter cores. Several foraminiferal assemblages from the early Pleistocene to the Recent reflect changing environmental conditions that correspond to several high frequency sea-level fluctuations previously described for this region. At the base of the core, low energy, low oxygen,

S. J. Culver; S. R. Riggs; R. E. Thieler; J. F. Wehmiller; S. W. Snyder; D. A. Mallinson; J. Bratton

2002-01-01

307

Gas venting and late Quaternary sedimentation in the Persian (Arabian) Gulf  

Microsoft Academic Search

High resolution 3.5 kHz echo sounding profiles and piston cores were used to reconstruct the microtopography and late Quaternary depositional history of the Persian Gulf. Perversive throughout the seafloor of the Gulf is an extensive network of pockmarks formed by seepages of thermogenic gas. These gas seeps and bottom water exiting the Gulf via the Strait of Hormuz are the

Elazar Uchupi; S. A. Swift; D. A. Ross

1996-01-01

308

Whole-Rock Aminostratigraphy and Quaternary Sea-Level History of the Bahamas  

Microsoft Academic Search

The surficial geology of the tectonically stable Bahamian archipelago preserves one of the most complete records of middle to late Quaternary sea-level-highstand cycles in the world. However, with the exception of deposits from marine isotope substage (MIS) 5e, fossil corals for radiometric dating of this rich stratigraphic sequence are rare. This study utilizes the previously published, independent lithostratigraphic framework as

Paul J. Hearty; Darrell S. Kaufman

2000-01-01

309

Geochemical evidence for the origin of late Quaternary loess in central Alaska  

Microsoft Academic Search

Loess is extensive in central Alaska, but there are uncertainties about its source and the direction of paleo- winds that deposited it. Both northerly and southerly winds have been inferred. The most likely sources of loess are the Tanana River (south), the Nenana River (southeast), and the Yukon River (north). Late Quaternary loess in central Alaska has immobile trace-element compositions

Daniel R. Muhs; James R. Budahn

2006-01-01

310

Late Quaternary vegetation and climate dynamics in the Serra da Bocaina, southeastern Brazil  

Microsoft Academic Search

Late Quaternary vegetation, fire and climate dynamics were studied by pollen and charcoal analysis in the Serra da Bocaina, in the coastal ranges of southeastern Brazil, Rio de Janeiro and São Paulo States. Samples were taken from two cores, Serra da Bocaina 1 and 2. Seven radiocarbon dates indicate deposits of Late Pleistocene to Holocene age. During the period between

Hermann Behling; Lydie Dupont; Hugh DeForest Safford; Gerold Wefer

2007-01-01

311

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

312

Submarine slides during relative sea level rise: three late-Quaternary examples from the Central Mediterranean  

Microsoft Academic Search

Sea level lowering is commonly invoked as an important predisposing factor or potential trigger for sediment failure of unconsolidated sediment deposited during previous highstand conditions on continental shelves and slopes. However, studies from Quaternary continental margins increasingly document sediment failure during times of relative sea level rise and hint to a more complex relation between changing sea level and mass

F. Trincardi; A. Asioli; M. Canu; A. Cattaneo; A. Correggiari

2003-01-01

313

Late Quaternary slip rate gradient defined using high-resolution topography and 10Be dating of offset landforms on the southern San Jacinto Fault zone, California  

NASA Astrophysics Data System (ADS)

Recent studies suggest the San Jacinto fault zone may be the dominant structure accommodating PA-NA relative plate motion. However, because the late Quaternary slip history of the southern San Andreas fault system is insufficiently understood, it is difficult to evaluate the partitioning of deformation across the plate boundary and its evolution. Landforms displaced by the Clark fault of the southern San Jacinto fault zone were mapped using high-resolution airborne laser-swath topography and selected offset landforms were dated using cosmogenic 10Be. Beheaded channels at Rockhouse Canyon, displaced by 500 ± 70 m and 220 ± 70 m, have been dated to 47 ± 8 ka and 28 ± 9 ka, respectively. Farther south, near the southern Santa Rosa Mountains, an alluvial deposit displaced by 51 ± 9 m has been dated to 35 ± 7 ka. From these sites, the slip rate of the Clark fault is determined to diminish southward from 8.9 ± 2.0 to 1.5 ± 0.4 mm/yr. This implies a slip-rate decrease along the Clark fault from Anza southeastward to its surface termination near the Salton Trough, where slip is transferred to the Coyote Creek fault, and additional deformation is compensated by folding and thrusting in the basin. These data suggest that since ˜30 to 50 ka, the slip rate along the southern San Jacinto fault zone has been lower than, or equivalent to, the rate along the southernmost San Andreas fault. Accordingly, either the slip rate of the San Jacinto fault has substantially decreased since fault initiation, or fault slip began earlier than previously suggested.

Blisniuk, Kimberly; Rockwell, Thomas; Owen, Lewis A.; Oskin, Michael; Lippincott, Caitlin; Caffee, Marc W.; Dortch, Jason

2010-08-01

314

Late Quaternary sedimentation on the North Aegean continental margin, Greece  

SciTech Connect

The late Quaternary seismic stratigraphy of the North Aegean continental shelf and adjacent basins has been interpreted from boomer and 3.5-kHz seismic profiles. Ages derived from shallow cores and offshore wells, and relative offsets on small synsedimentary faults, provide chronological control. Sea level history inferred from seismic stratigraphy correlates with the global eustatic sea level record based on oxygen isotopic curves. The present depth of the delta plain formed on the outer shelf during the late stage 6 lowstand provides a dated and originally horizontal marker for estimating rates of tectonic subsidence. Gross distribution of sediment facies is similar in both tectonically stable and active areas. The shell break formed by delta progradation, but is marked by faults in most places because of the accommodation provided by graben subsidence rates of 0.3-1.5 mm/yr. Standard sequence stratigraphic analysis can be applied to these sediments deposited during high-amplitude Quaternary sea level oscillations. High rates of subsidence result in the preservation an unusually complete record of sea level change. Major lowstand progradation is dependent on the duration, rather than the magnitude, of sea level lowstand. The long glaciations in isotopic stages 6, 12, 16, and 22 resulted in the most prominent seaward progradation on the margin. Sandy lowstand turbidite deposits formed only when there was rapid fall in sea level; otherwise sand was trapped on delta tops and silty muds were deposited in deep water.

Piper, D.J.W. (Bedford Inst. of Oceanography, Dartmouth, Nova Scotia (Canada)); Perissoratis, C. (Inst. of Geology and Mineral Research, Athens (Greece))

1991-01-01

315

Efficient upscaling of hydraulic conductivity in heterogeneous alluvial aquifers  

Microsoft Academic Search

An efficient method to upscale hydraulic conductivity (K) from detailed three-dimensional geostatistical models of hydrofacies heterogeneity to a coarser model grid is presented.\\u000a Geologic heterogeneity of an alluvial fan system was characterized using transition-probability-based geostatistical simulations\\u000a of hydrofacies distributions. For comparison of different hydrofacies architecture, two alternative models with different\\u000a hydrofacies structures and geometries and a multi-Gaussian model, all with

Jan H. Fleckenstein; Graham E. Fogg

2008-01-01

316

Monti Martani (umbria, Italy) Alluvial Fans: Hazards Sites and Occurrence  

Microsoft Academic Search

In this paper we proposed modeling and simulation approaches for testing the debris flows occurrence hypothesis. The approach is an empirically and process based, and use multiple physically-based simulations to evaluate hazard down-slope from initiation sites in alluvial fans of the Terni basin-northern area (Umbria, Italy). The northern part of the area is bounded by the M. Martani normal fault

A. Taramelli; L. Melelli

2002-01-01

317

Evolution of Devonian alluvial systems in an oblique-slip mobile zone—an example from the Broken River Province, northeastern Australia  

NASA Astrophysics Data System (ADS)

The lower 1500 m of the Late Devonian Bulgeri Formation was deposited in a tectonically active foreland basin in response to a major Late Devonian orogeny in the Broken River Province, northeastern Australia. The basin was bounded to the east by an uplifted belt of Palaeozoic sedimentary and volcanic rocks that was deformed east of an active thrust zone (Gray Creek Fault). To the south, the basin was bounded by igneous and metamorphic basement rocks, uplifted along a major oblique-slip fault zone (Clarke River Fault). Facies analysis and mapping of alluvial stratigraphy has resulted in the recognition of compositionally distinct, coalescing, axial and transverse alluvial drainage systems.The axial drainage system flowed to the northeast, approximately parallel to the Gray Creek Fault and away from the Clarke River Fault. The system drained the cratonic basement to the south and west, and accumulated mainly feldspathic and quartzose sediments. A lower, fine-grained succession, and an upper coarse-grained succession are recognised. The lower succession (‘Rockfields’ alluvial system) was deposited in broad, sandy, low-sinuosity channels and semi-permanent floodplain lakes. These rivers drained ultimately northward into a retreating coastal plain and shallow sea that lay over the Georgetown Province. The upper succession (‘Bulgeri’ alluvial system) was deposited in gravelly and sandy braided rivers emanating from south of the Clarke River Fault. The transverse distributary system (‘Stopem Blockem’ alluvial system), accumulated mainly lithic, coarse-grained sediments deposited in gravelly braided rivers sourced from the uplifted orogenic belt to the east. These rivers flowed towards the northwest before coalescing with the axial drainage system where they changed to a northerly orientation. Uplifted fault blocks of Devonian limestone within the basin locally contributed limestone gravel to these rivers. Between the coalescing axial and transverse river systems lay extensive floodplains, which received a slow, but compositionally mixed supply of mainly fine-grained sediments. Long periods of weathering resulted in the development of reddened palaeosols, with well developed calcrete horizons. The palaeogeography and fluvial style of the lower Bulgeri Formation is compared to the Gulf of Carpentaria in northeastern Australia.Analysis of the architecture of these alluvial systems has led to recognition of at least three, subsidence-driven, tectonic cyclothems and this is supported by simple quantitative modelling. The lower part of each cycle begins with a thin conglomeratic succession above an unconformity, and is overlain by thick, relatively fine-grained, syn-tectonic alluvial facies deposited during maximum subsidence. The upper part of each cycle is marked by increasingly coarse-grained, post-tectonic alluvial facies. These were deposited by gravel progradation following cessation of uplift or thrusting in the source areas and concomitant slowing of subsidence rates.

Lang, Simon C.

1993-05-01

318

21 CFR 172.165 - Quaternary ammonium chloride combination.  

Code of Federal Regulations, 2013 CFR

...FOOD ADDITIVES PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN CONSUMPTION Food Preservatives § 172.165 Quaternary ammonium chloride combination. The food additive, quaternary ammonium chloride...

2013-04-01

319

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

320

Neogene-Quaternary evolution of the Manisa Basin: Evidence for variation in the stress pattern of the ?zmir-Balikesir Transfer Zone, western Anatolia  

NASA Astrophysics Data System (ADS)

In this paper, we aim to identify the Neogene-Quaternary evolution of the Manisa Basin located in the ?zmir-Balikesir Transfer Zone (?BTZ) which lies between the normal-fault-dominated West Anatolian Extensional Province (WAEP) and the strike-slip-dominated North Aegean Region (NAR). The Manisa Basin, which forms a connection with the Gediz Graben, underwent two-stage basin evolution, distinguished by an ancient and modern graben-fill. The ancient basin-fill is made up of a folded and normal-to-reverse faulted and strike-slip-faulted Miocene volcano-sedimentary sequence. The younger modern basin-fill is represented by the Quaternary Bahadir Formation comprising fluvial terrace deposits, early-middle Pleistocene continental clastics of the Turgutlu Formation, alluvial/colluvial sediments of late Pleistocene-early Holocene Emlakdere Formation, and Holocene alluvium.Structural and stratigraphical data reveal that the basin was initially formed as a lacustrine basin bounded by a volcanic ridge from the west; it was subsequently uplifted and deformed probably as a result of Pliocene wrench-dominated strike-slip tectonics, which is characterised by NNW-SSE horizontal ?3 and vertical ?2. Post-Miocene strike-slip faulting along the ?BTZ occurred along a right-lateral shear zone in the Manisa Basin. This suggests that some branches of the right-lateral movement of the North Anatolian Fault Zone may continue into the WAEP. The youngest stage shows an extension-dominated transtension with a NE-SW trending ?3 and a vertical ?1. These results are consistent with progressive deformation developed during late Pliocene and onwards wherein the axis of minimum horizontal stress remained in the horizontal plane but the intermediate and maximum horizontal stress axes switched position in the vertical plane. In addition, available palaeostress data for the Gediz Graben are consistent with the pure extension in the eastern and middle part of the graben and with the wrench-to-extension-dominated transtension in the western part, where the Manisa Basin is located. This indicates a NE-SW trending segment boundary zone forming the western end of the E-W trending Gediz Graben.

Özkaymak, Ça?lar; Sözbilir, Hasan; Uzel, Bora

2013-04-01

321

Sequence stratigraphy and composition of late quaternary shelf-margin deltas, Northern Gulf of Mexico  

Microsoft Academic Search

High-resolution seismic profiles and foundation borings from the northwestern Gulf of Mexico record the physical attributes and depositional histories of several late Quaternary sequences that were deposited by wave-modified, river-dominated shelf-margin deltas during successive periods of lowered sea level. Each progressively younger deltaic sequence is thinner and exhibits a systematic decrease in the abundance and concentration of sand, which is

R. A. Morton; J. R. Suter

1996-01-01

322

Late Quaternary seismic stratigraphy and structure of the western insular shelf margin of Puerto Rico  

NASA Astrophysics Data System (ADS)

725 km of high-resolution seismic data were collected over the insular shelf of western Puerto Rico to better understand its late Quaternary depositional and structural history. Due to low tectonic uplift rates of onshore areas in this region, well dated late Quaternary sediments and corals have only been identified in a few scattered onland localities around Puerto Rico. Seismic data from the Rio Anasco delta area of western Puerto Rico reveals four main units with characteristic stratal reflection terminations that total about 25 m in thickness. Because of a lack of well information, age estimates of these late Quaternary units are based on correlations with sea level curves derived from dated coral samples from Puerto Rico, St. Croix, and Antigua. Units include: Unit 1 - a gently folded and faulted basal section correlated to the Oliogene-early Pliocene? carbonate shelf of Puerto Rico; deeper penetration, industry MCS lines show that these rocks are deformed in a broad EW-trenching arch; Unit 2 - chaotic channel fill deposits in incisions related to the lowstand equivalent of the Rio Anasco likely formed during the Last Glacial Maximum about 25-15 ka; Unit 3 - roughly stratified deposits onlapping the top of Unit 2; these are interpreted as an estuarine facies deposited during Holocene sea level transgression; Unit 4 - highly stratified deposits related to progradation of the Anasco delta during sea level rise. The base of unit 4 is a downlap surface interpreted as a maximum flooding surface likely formed about 6 ka. East-northeast-striking faults are observed breaking the younger late Quaternary units in three separate zones off the west coast of Puerto Rico. Onland continuations of these faults have not been identified likely due to cultural overprint of natural scarps on late Quaternary floodplains.

Hanzlik, M.; Mann, P.; Abrams, L.; Grindlay, N.

2005-12-01

323

Quaternary geochronology and distribution of Mammuthus on the Colorado Plateau  

SciTech Connect

There are 41 known localities containing mammoth remains from the Colorado Plateau: 24 in Arizona, 12 in Utah, 3 in New Mexico, and 2 in Colorado. Of the 41 localities, 13 (32%; Arizona and Utah only) have yielded radiometric dates ({sup 14}C and U/Th); 10 (77%) of these have been the result of the authors' investigations. The four youngest radiocarbon dates produce a weighted average date of approximately 11,270 {plus minus}65 yr B.P., the youngest directly aged mammoth remains on the Colorado Plateau. Mammoth remains are recovered predominantly in alluvial regimes, in addition to alcove, cave, and spring deposits. No direct association of Mammuthus and the Clovis hunters has been reported from the Colorado Plateau. Dietary intake, recorded in dung remains, included predominantly graminoids, in addition to various woody shrubs and trees that currently grow at higher elevations on the Colorado Plateau.

Agenbroad, L.D.; Mead, J.I. (Northern Arizona Univ., Flagstaff (USA))

1989-09-01

324

Quaternary geochronology and distribution of Mammuthus on the Colorado Plateau  

NASA Astrophysics Data System (ADS)

There are 41 known localities containing mammoth remains from the Colorado Plateau: 24 in Arizona, 12 in Utah, 3 in New Mexico, and 2 in Colorado. Of the 41 localities, 13 (32%; Arizona and Utah only) have yielded radiometric dates (14C and U/Th); 10 (77%) of these have been the result of our investigations. The four youngest radiocarbon dates produce a weighted average date of approximately 11,270 ±65 yr B.P., the youngest directly aged mammoth remains on the Colorado Plateau. Mammoth remains are recovered predominantly in alluvial regimes, in addition to alcove, cave, and spring deposits. No direct association of Mammuthus and the Clovis hunters has been reported from the Colorado Plateau. Dietary intake, recorded in dung remains, included predominantly graminoids, in addition to various woody shrubs and trees that currently grow at higher elevations on the Colorado Plateau.

Agenbroad, Larry D.; Mead, Jim I.

1989-09-01

325

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

326

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.

Calaza, M. Isabel

2009-01-01

327

Quaternary alluvial terraces in an active tectonic region: the San Juan River Valley, Andean Ranges, San Juan Province, Argentina  

Microsoft Academic Search

The San Juan River, located in San Juan Province (Argentina), crosses the Precordillera and other geologic units including the Ullum tectonic valley and the La Laja Zone between latitudes 31°S and 32°S. The San Juan River is antecedent as is suggested by its two perpendicular segments linked by an almost parallel segment to the main structural trend. Along the Precordillera,

F. Colombo; P. Busquets; E. Ramos; J. Vergés; D. Ragona

2000-01-01

328

Avalanche sedimentation in seas and oceans, paper 4: sedimentogenesis stages at the second global level (preparation, transport, and accumulation). Models of submarine alluvial cones  

SciTech Connect

This paper demonstrates that, in the terminal discharge basins, the ordinary sedimentogenesis stages are combined with gravity effects. The models of submerged alluvial cones--fans--are considered, which are constructed on the basis of studies of recent and ancient fans of different sizes. An important feature of the sedimentary process in this case is the relationship between the influx of the bulk of sedimentary matter and the repeated variations of the ocean level in the past (up to 8-12 times within the Quaternary alone), leading to massive discharges of sedimentary matter from upper (recent, short-lived) levels of avalanche sedimentation (in river mouths) to a lower level (to sites of constant storage of the material at the base of the continental slope).

Lisitsyn, A.P.

1986-07-01

329

The Quaternary Silver Creek Fault Beneath the Santa Clara Valley, California  

USGS Publications Warehouse

The northwest-trending Silver Creek Fault is a 40-km-long strike-slip fault in the eastern Santa Clara Valley, California, that has exhibited different behaviors within a changing San Andreas Fault system over the past 10-15 Ma. Quaternary alluvium several hundred meters thick that buries the northern half of the Silver Creek Fault, and that has been sampled by drilling and imaged in a detailed seismic reflection profile, provides a record of the Quaternary history of the fault. We assemble evidence from areal geology, stratigraphy, paleomagnetics, ground-water hydrology, potential-field geophysics, and reflection and earthquake seismology to determine the long history of the fault in order to evaluate its current behavior. The fault formed in the Miocene more than 100 km to the southeast, as the southwestern fault in a 5-km-wide right step to the Hayward Fault, within which the 40-km-long Evergreen pull-apart basin formed. Later, this basin was obliquely cut by the newly recognized Mt. Misery Fault to form a more direct connection to the Hayward Fault, although continued growth of the basin was sufficient to accommodate at least some late Pliocene alluvium. Large offset along the San Andreas-Calaveras-Mt Misery-Hayward Faults carried the basin northwestward almost to its present position when, about 2 Ma, the fault system was reorganized. This led to near abandonment of the faults bounding the pull-apart basin in favor of right slip extending the Calaveras Fault farther north before stepping west to the Hayward Fault, as it does today. Despite these changes, the Silver Creek Fault experienced a further 200 m of dip slip in the early Quaternary, from which we infer an associated 1.6 km or so of right slip, based on the ratio of the 40-km length of the strike-slip fault to a 5-km depth of the Evergreen Basin. This dip slip ends at a mid-Quaternary unconformity, above which the upper 300 m of alluvial cover exhibits a structural sag at the fault that we interpret as a negative flower structure. This structure implies some continuing strike slip on the Silver Creek Fault in the late Quaternary as well, with a transtensional component but no dip slip. Our only basis for estimating the rate of this later Quaternary strike slip on the Silver Creek Fault is to assume continuation of the inferred early Quaternary rate of less than 2 mm/yr. Faulting evident in a detailed seismic reflection profile across the Silver Creek Fault extends up to the limit of data at a depth of 50 m and age of about 140 ka, and the course of Coyote Creek suggests Holocene capture in a structural depression along the fault. No surface trace is evident on the alluvial plain, however, and convincing evidence of Holocene offset is lacking. Few instrumentally recorded earthquakes are located near the fault, and those that are near its southern end represent cross-fault shortening, not strike slip. The fault might have been responsible, however, for two poorly located moderate earthquakes that occurred in the area in 1903. Its southeastern end does mark an abrupt change in the pattern of abundant instrumentally recorded earthquakes along the Calaveras Fault-in both its strike and in the depth distribution of hypocenters-that could indicate continuing influence by the Silver Creek Fault. In the absence of convincing evidence to the contrary, and as a conservative estimate, we presume that the Silver Creek Fault has continued its strike-slip movement through the Holocene, but at a very slow rate. Such a slow rate would, at most, yield very infrequent damaging earthquakes. If the 1903 earthquakes did, in fact, occur on the Silver Creek Fault, they would have greatly reduced the short-term future potential for large earthquakes on the fault.

Wentworth, Carl M.; Williams, Robert A.; Jachens, Robert C.; Graymer, Russell W.; Stephenson, William J.

2010-01-01

330

Late Quaternary paleosols and climate change in southern New Mexico  

SciTech Connect

A climate change toward more arid conditions in the southwest US has been postulated for a period around 7 ka. In southern NM, deposition of the youngest generation of alluvial fans surrounding arid mountains began around 7 ka based on radiocarbon dates of charcoal. The deposition of these fans has been interpreted as evidence for aridity because plant cover would have declined, thus making the landscape more susceptible to erosion and sedimentation. Isotopes of pedogenic calcite and pollen content in well-preserved paleosols associated with alluvial fans provide additional evidence for testing the aridity hypothesis. Buried paleosols, ranging from 23,070 [+-] 190 to 9,070 [+-] 70 yr BP, contain pedogenic calcite that is isotopically heavier in carbon than calcite in soils younger than 7 ka. The buried paleosols have a mean delta C-13 values of [minus]2.2 [+-] 0.8 [per thousand] (PDP). In contrast, soils younger than 7 ka have a man delta C-13 value of [minus]7.8 [+-] 1.3 [per thousand]. The higher delta C-13 values in buried paleosols may reflect the presence of abundant C[sub 4] grasses, similar to the present vegetation in the southern High Plains, which would have curtailed erosion. Pollen analysis reveals that buried paleosols contain more grass pollen than soils younger than 7 ka, which contain high proportions of desertscrub pollen taxa. delta O-18 values of pedogenic calcite are similar for the buried paleosols ([minus]5.2 [+-] 0.3 [per thousand] PDB) and soils younger than 7 ka ([minus]5.1 [+-] 0.6 [per thousand]). These values indicate a relatively constant mean annual temperature of approximately 14C, which prevailed throughout late Pleistocene and Holocene time.

Monger, H.C. (New Mexico State Univ., Las Cruces, NM (United States). Agronomy Dept.); Cole, D.R. (Oak Ridge National Lab., TN (United States)); Gish, J.W. (Quaternary Palynology Research, Flagstaff, AZ (United States))

1992-01-01

331

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.

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

2000-01-01

332

An aminostratigraphy for the British Quaternary based on Bithynia opercula.  

PubMed

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

2013-02-01

333

Evidence for episodic alluvial fan formation in far western Terra Tyrrhena, Mars  

NASA Astrophysics Data System (ADS)

A Late Noachian-aged alluvial fan complex within Harris Crater in far western Terra Tyrrhena, Mars, is comprised of two well-defined source regions and associated discrete depositional lobes. Three fan units were recognized based on common morphological characteristics, thermal properties and spectral signatures. Although the entire fan complex has been subjected to extensive erosional degradation, the preserved morphologies record episodic fan formation and indicate the type of flow processes that occurred; the bulk of the fan surface has morphology consistent with fluvial emplacement while one fan unit exhibits a rugged surface texture with boulders consistent with a debris flow. This transition from fluvial to late-stage debris flow(s) suggests a decline in available water and/or change in sediment supply. The thermal inertia values obtained for all three fan surface units (mean values ranged from 318 to 344 J m-2 K-1 s-1/2) are typical for coarse-grained and/or well-indurated materials on Mars, but subtle variations point to important distinctions. Variations in aeolian bedform coverage as well as the density of ridges (inferred inverted channels) and boulders contribute to these subtle fan thermophysical differences and likely reflect changes in the fan depositional mechanisms and variations in post-depositional modification histories. The majority of the alluvial fan surface has a spectral signature that is broadly similar to TES “Surface Type 2” (ST2), with some important exceptions at long wavelengths. However, a unique spectral component was identified in one of the fan units (unit 3), that likely reflects lithological differences from other fan materials. This spectral attribute of unit 3 matched locations within the western catchment providing confirmation of provenance and supporting the contention that sediment supply changed over time as the fan developed. Finally, we applied simple modeling to a well preserved subsection of the fan complex to quantify the developmental history. Using the computed eastern fan volume (32 km3), significant water, likely from precipitation, was involved in fan construction (>50 km3) and an extensive period of fan formation occurred over millennia or longer.

Williams, Rebecca M. E.; Deanne Rogers, A.; Chojnacki, Matthew; Boyce, Joseph; Seelos, Kimberly D.; Hardgrove, Craig; Chuang, Frank

2011-01-01

334

Morphometry of Alluvial Fans in a Polar Desert (Svalbard, Norway): Implications for Interpreting Martian Fans  

NASA Astrophysics Data System (ADS)

Alluvial fan-like landforms have been identified on Mars [e.g., 1-3]. Alluvial fans contain information on several controlling factors (tectonism, climate, lithology/geology), and therefore the investigation of possible Martian fans can reveal information about the planet`s climate. In lieu of direct observations of active depositional processes on Martian fans, comparisons with terrestrial analogues can constrain models of Martian fan formation derived from remote sensing data. Since present-day Mars is cold and dry, alluvial fans formed in cold deserts should be considered as useful analogues. The probably closest climatic analogue to Mars on Earth are the Antarctic Dry Valleys [5], but polar deserts can also be found in the Arctic. We report on our field work in summer 2008 and a simultaneous flight campaign with an airborne version (HRSC-AX) of the High Resolution Stereo Camera (HRSC) onboard Mars Express [6]. The results are compared with measurements of Martian fans, based on HRSC DEM. Our study area is in Svalbard near Longyearbyen (78°13'0"N, 15°38'0"E), around mountains of Mesozoic layered sandstones and shales) on the northern side of Adventfjorden. Climate data are available from the nearby Longyearbyen airport (just a few km from the study area). The present climate is arctic [7], with low mean annual air temperatures and very low precipitation, mostly as snow. Stereo images acquired in July 2008 (at the end of the snow melting season) were processed to orthoimages with a spatial resolution of 20 cm/pixel, and corresponding Digital Elevation Models (DEM) with a grid spacing of 50 cm/pixel. Simultaneous field measurements focused on channels and levees (widths, depths, heights), which were determined at vertical increments of 10 m, together with the local slope. Alluvial fans in the study area are present on slopes of all orientations. They typically coalesce into bajadas. Basically all alluvial fans in the study area are characterized by sinuous channels, many of which display well-developed lateral levees, and debris tongues. Boulder-sized (>1 m) rocks are present, but rare. Where a vertical section of the fan can be observed (typically at the toe, where braided rivers cut the fans), it appears poorly sorted. Following the reasoning of, e.g., [8,9], we conclude that the fans in our study area are dominated by debris flows. However, fluvial processes might also have been involved, and the complex interplay between fluvial incision and debris flows on alluvial fans is well known also from fans in different climatic environments [e.g., 10]. Topographic profiles along 55 fans were measured in HRSC-AX DEM. Fan length ranges between 80 m and about 800 m, with heights between 9 and 140 m (from apex to toe). The profiles of the Svalbard fans can be approximated very well with a power law function. Overall gradients vary between 0.11 and 0.43, with a peak at 0.18-0.2. Several measures have been suggested to quantify the concavity of river and fan profiles [e.g., 1, 11]. We use a simple method, which was suggested by Langbein [12] and is still widely used [e.g., 9, 13,14]. The Langbein-concavity of the fan profiles shows a continous range between 0 and 0.53. The topography of Martian fan-like features [2,3] is studied on the basis of DEM derived from HRSC stereo data [15,16], with a grid spacing of 50-100 m. An example of a profile along a Martian fan in Holden crater exhibits a Langbein-concavity of 0.194 and a gradient of 0.069. While the concavity falls in the range observed on Svalbard, the gradient is less. Another major difference is the fan dimension, with the fan in Holden Crater being much larger. We also produced a HRSC DEM of Mojave Crater on Mars, which displays a number of fans with dimensions similar to those on Svalbard [3], and discuss the relationship between local slopes and fans in Mojave Crater. Alluvial fans form by one or a combination of the following mechanisms: avulsing channelized rivers, sheet flows, and debris flows [17]. Previous studies comparing Martian and terrestrial fa

Hauber, E.; Preusker, F.; Trauthan, F.; Reiss, D.; Zanetti, M.; Jaumann, R.; Hiesinger, H.

2009-04-01

335

Sedimentation model of gravel-dominated alluvial piedmont fan, Ganga Plain, India  

NASA Astrophysics Data System (ADS)

The Piedmont Zone of the Indo-Gangetic Plain contains numerous, laterally coalescing small alluvial fans. The Latest Pleistocene-Holocene 30 km long Gaula Fan can be divided into gravelly proximal fan (0-14 km down-stream), gravel-sand rich mid fan (14-22 km) and sand-mud dominated distal fan (22-30 km). The fan succession is composed of two fan expansion cycles A and B. Separated by an undulatory erosional contact of regional extent, cycle A is characterized by river borne clast-supported gravelly deposits, and the overlying fan expansion cycle B by matrix-supported gravely debris flows. The main process behind fan development has been lateral migration of channels over the fan surface probably due to rapid sedimentation caused by increased sediment supply, and the fluctuating water budget in response to changing climate. The water laid expansion cycle A represents a humid phase. The debris flow deposits of expansion cycle B suggest a dry phase. Approximately between 8 and 3 Ka, cycle B also indicates a phase of tectonic instability in the Siwalik Hills forming the mountain front. The tectonic activity caused incision of rivers into the fan surface, and in turn resulted in reduced fan-building activity. At present the fan surface is accreting by sheet flow processes.

Shukla, U. K.

2009-03-01

336

Lignin Degradation and Humus Formation in Alluvial Soils and Sediments  

PubMed Central

The contribution of lignin to the formation of humic compounds was examined in different environments of the terrestrial-aquatic interface in the Garonne River valley in southwestern France. Alluvial soils and submerged or nonsubmerged river and pond sediments containing alder, poplar, or willow [14C-lignin]ligno-celluloses were incubated. After a 49-day incubation period, 10 to 15% of labeled lignins in alluvial soils was recovered as evolved 14CO2. In nonsubmerged sediments, 10% of the applied activity was released as 14CO2, and in submerged sediments, only 5% was released after 60 days of incubation. In the different alluvial soils and sediments, the bulk of residual activity (70 to 85%) remained in the two coarsest-grain fractions (2,000 to 100 and 100 to 50 ?m). Only 2 to 6% of the residual activity of these two coarse fractions was recovered as humic and fulvic acids, except in the case of alder [14C-lignin]lignocellulose, which had decomposed in a soil collected beneath alders. In this one 55% of the residual activity was extracted as humic substances from the 2,000- to 100-?m fraction. Humic and fulvic acids represented from 6 to 50% of the residual activity in the finest-grain fractions (50 to 20 and 20 to 0 ?m). The highest percentages were obtained in soil collected beneath alders and in submerged pond sediment. The contribution of different groups of microorganisms, as well as nutrients and clay content, may influence humic-substance formation in such environments. Physical stability also may be an important factor for complex microbial activity involved in this process.

Fustec, Eliane; Chauvet, Eric; Gas, Gilbert

1989-01-01

337

Late Quaternary fault activity in the Western Carpathians: evidence from the Vikartovce Fault (Slovakia)  

NASA Astrophysics Data System (ADS)

The Cenozoic structure of the Western Carpathians is strongly controlled by faults. The E-W striking Vikartovce fault is one of the most distinctive dislocations in the region, evident by its geological structure and terrain morphology. This feature has been assumed to be a Quaternary reactivated fault according to many attributes such as its perfect linearity, faceted slopes, the distribution of travertines along the fault, and also its apparent prominent influence on the drainage network. The neotectonic character of the fault is documented herein by morphotectonic studies, longitudinal and transverse valley profile analyses, terrace system analysis, and mountain front sinuosity. Late Pleistocene activity of the Vikartovce fault is now proven by luminescence dating of fault-cut and uplifted alluvial sediments, presently located on the crest of the tilted block. These sediments must slightly pre-date the age of river redirection. Considering the results of both luminescence dating and palynological analyses, the change of river course probably occurred during the final phase of the Riss Glaciation (135 ± 14 ka). The normal displacement along the fault during the Late Quaternary has been estimated to about 105-135 m, resulting in an average slip rate of at least 0.8-1.0 mm · yr-1. The present results identify the Vikartovce fault as one of the youngest active faults in the Central Western Carpathians.

Vojtko, Rastislav; Marko, František; Preusser, Frank; Madarás, Ján; Ková?ová, Marianna

2011-12-01

338

Late Quaternary Range-Front Fault Scarps in the Western Sierra El Mayor, Baja California, Mexico: A Geomorphologic Expression of Slip Across an Active Low-Angle Normal Fault  

NASA Astrophysics Data System (ADS)

The western margin of the Sierra El Mayor (SEM), in northeastern Baja California, is controlled by an active, top-to-the-west, low-angle normal fault named the Canada David detachment (CDD) that accommodates part of the extensional component of shearing between the Pacific and North American plates. The CDD has a length of 60 km and shows a curvilinear trace with two major antiformal and synformal megamullion pairs. Late Quaternary slip has produced a broad array of Quaternary scarps cutting alluvial fans along nearly the entire length of the CDD. Detailed mapping reveals eight regional strath terraces distinguished by surface weathering characteristics, soil profile development and relative elevation. Relative height between terraces increases in domains where the CDD and basin deposits are being uplifted due to either the basinward migration of faulting (e.g., rolling hinge) or flexural uplift in antiformal megamullion domains. Linear diffusion analysis of 46 synthetic fault scarps, with a calculated angle of repose ?o = 28.75°, reveal fault scarp domains exhibiting both multi-modal and unimodal distribution of diffusion ages (kt). Uni-modal domains are typically younger, but there is no systematic variation in scarp age with distance along the CDD. Scarps yielding negative kt ages (i.e. scarps steeper than ?o) are common in the north, near inferred locations of important historic seismic events. Microseismicity drops off significantly adjacent to these very young scarp arrays, which likely reflects a recent post-seismic stress drop. Domains of high seismic risk are identified by high microseismicity and lack of young scarps. Minimum estimates of the diffusivity constant (k) are calculated by coupling scarp diffusion ages and 10Be surface exposure ages of the faulted deposits. In the southernmost SEM a Q6 terrace with a minimum surface exposure age t = 233±6.6 ky (weighted mean of six rock samples) is cut by scarps with an average kt = 11.25±9.31 m2, which yields a minimum k = 0.05±0.04 m2/ky. Scarps cutting Q4 terraces yield diffusion ages (kt = 0.16±0.04 m2) consistent with the inferred post-glacial age of the four youngest terraces.

Spelz, R. M.; Fletcher, J.; Owen, L.

2006-12-01

339

Dynamic classification of alluvial gold placers in the northeast of Russia  

NASA Astrophysics Data System (ADS)

The comprehensive study of alluvial gold placers, fluvial sediments, and river valleys allowed division of these placers into subtypes, categories, and varieties on the basis of genetic principles. The comparison of observation results with reconstructions of placer-forming fluvial processes demonstrates the distinct dependence of all basic properties of placers on the dynamics of their formation, i.e., on the hydraulic size of gold grains, the dimensions of streams, and the phase of the elementary erosion cycle (PEC). Four PECs are distinguished: erosion, abrasion, equilibrium, and aggradation. A lithodynamic alluvial complex (LDAC) of the same name corresponds to each PEC. Any fractions of free gold can be transported by streams, and the mode of transportation depends on the PEC. Placers of eight dynamic categories, brush, erosion, perluvial, apron, bar, equilibrium, aggradational, and gravitational, are syngenetic to certain lithofacies belonging to different LDACs. The first four categories are combined into the channel-line subtype, which embraces all traditional placers. The nontraditional bar and equilibrium (beach subtype) and aggradational and gravitational categories (representing two subtypes of the same name (?)) are so far poorly studied but may be regarded as highly promising. The size, morphology, thickness, structure, and localization of placers; average and modal values of size and roundness of gold grains; degree of their sorting and concentration; three-dimensional distribution of gold; composition of alluvium; relationships of placers with alluvium and the gutter, river valleys of various sizes, and types of morphostructures; and other features are distinct for placers pertaining to specific categories and make up natural groups individualized for each category. The correlation of placer properties in each category makes these properties predictable at the early stages of geological exploration and enhances the efficiency of forecasting and prospecting. In high-grade gold clusters, closely spaced placers group into composite deposits. The subdivision of these placers into categories makes it possible to apply rational methods and tools of exploration and mining of placers; to estimate the character, volume, and location of previous losses of gold; and to select targets for their remining. The dynamic analysis of recently formed and ancient placers is helpful for implementation of panning and interpretation of the results obtained in the context of prospecting for gold. The proposed classification may be used not only in the study of stream gold but also in the exploration of some other placer deposits.

Goldfarb, Yu. I.

2007-08-01

340

Alluvial Fan in Icaria Planum, Mars: a MEX HRSC Study  

NASA Astrophysics Data System (ADS)

Numerous channels of the Claritas-Thaumasia area, such as Warrego Valles, indicate previous water flow activities. At some point, the wide basin (Raitala et al., 2005) of southern Claritas Fossae was filled by water transported from the uplands. After the paleolake reached the level of the lowest barrier valley floor it broke through this western saddle valley and formed a channel from the paleolake into the direction of Icaria Planum. The paleolake and adjoining formations were studied using the Mars Express HRSC data sets. Additional sapping channels connected into the channel from the direction of an old impact crater on the northern side of the saddle valley. In the west, close to Icaria Planum, the channel reached an impact crater and the water broke into it. This temporary crater lake has a delta at the channel mouth. The flow continued further through the western crater rim. The crater floor is lower than the channel neck out of the crater and indicates a paleolake phase. Water was led out from the impact crater into the lowlands of Icaria Planum where it formed an alluvial fan. The flow structures and the alluvial fan units in Icaria Planum are visible in the Mars Express HRSC color data. Reference: Raitala, J., Aittola, M., Korteniemi, J., Kostama, V.-P., Hauber, E., Kronberg, P., Neukum, G. and the HRSC Co-Investigator Team, 2005. Claritas paleolake studied from the MEX MEX HRSC data. LPS XXXVI, #1307.

Korteniemi, J.; Raitala, J.; Aittola, M.; Kostama, V.-P.; Hauber, E.; Kronberg, P.; Neukum, G.; HRSC Co-Investigator Team

2005-08-01

341

Catalogue of large alluvial fans in martian impact craters  

NASA Astrophysics Data System (ADS)

We conducted a systematic, global survey using Thermal Emission Imaging System Infrared (THEMIS IR) coverage (˜100 m/pixel) to search for large alluvial fans in impact craters on Mars. Our survey has focused on large fans (apron areas greater than ˜40 km 2, usually located in craters greater than 20 km in diameter) due to the resolution of the THEMIS images and Mars Orbiter Laser Altimeter (MOLA) coverage. We find that the host craters are found to have a distinctive diameter range from 30-150 km. The fans generally cluster in three geographic areas—southern Margaritifer Terra, southwestern Terra Sabaea, and southwestern Tyrrhena Terra, however several outliers do exist. The alluvial fans do not form in a particular orientation along the crater rim nor are they associated with the location of current high rim topography. Fan area magnitude and variability increase with crater diameter while fan concavity magnitude and variability increase with decreasing crater diameter. Smaller fan aprons in general have higher, more variable concavity. The source of the water forming these fans is uncertain given the challenges of accommodating the global distribution pattern and formation patterns within the craters.

Kraal, Erin R.; Asphaug, Erik; Moore, Jeffery M.; Howard, Alan; Bredt, Adam

2008-03-01

342

Mineralogy of lode and alluvial gold from the western Capricorn Orogen, Western Australia  

Microsoft Academic Search

There are significant differences in the mineralogy of lode and alluvial gold from the Egerton Mining Centre (EMC) compared with that of gold from the Bangemall Mining Centre (BMC) in the western Capricorn Orogen of Western Australia. In contrast, within each mining centre, lode and alluvial gold are very similar, with minor differences being due to weathering and transport processes.

E. A. Hancock; A. M. Thorne

2011-01-01

343

Precambrian alluvial fan and braidplain sedimentation patterns: Example from the Mesoproterozoic Rjukan Rift Basin, southern Norway  

Microsoft Academic Search

An integrated approach of facies analysis, geochemistry and paleohydrology provides new insight into the sedimentology and paleogeography of alluvial sediments in the Precambrian. Here, alluvial fan and braidplain sedimentation patterns are documented in a Mesoproterozoic rift basin, called (known as) the Rjukan Rift Basin in southern Norway. The studied formation (Heddersvatnet Formation) consists of volcanoclastic breccias and conglomerates, cross-bedded sandstones

Juha Köykkä

2011-01-01

344

Hydrogeochemistry of alluvial groundwaters in an agricultural area: an implication for groundwater contamination susceptibility  

Microsoft Academic Search

Alluvial groundwaters in the area where intensive agricultural activity takes place were geochemically investigated to evaluate factors regulating groundwater quality of alluvial aquifers. For this study, 55 groundwater samples were taken from the uniformly distributed irrigation wells and were classified into three distinct groups according to their geochemical characteristics. This study reveals that the groundwater quality and the geochemical characteristics

Gi-Tak Chae; Kangjoo Kim; Seong-Taek Yun; Kyoung-Ho Kim; Soon-Oh Kim; Byoung-Young Choi; Hyoung-Soo Kim; Chul Woo Rhee

2004-01-01

345

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

346

Hydrogeology, model description, and flow analysis of the Mississippi River alluvial aquifer in northwestern Mississippi  

USGS Publications Warehouse

The Mississippi River alluvial aquifer underlies a 7,000-square-mile area of the Mississippi River alluvial plain in northwestern Mississippi, an area locally known as the Delta. The alluvial aquifer is the most heavily pumped aquifer in Mississippi, and wells yielding more than 2,000 gallons per minute are common. About 98 percent of the pumpage from the alluvial aquifer is for agriculture. The sand and gravel that form the alluvial aquifer averages about 110 feet in thickness. The aquifer is confined over most of the Delta, and the upper confining unit averages about 25 feet in thickness. The average depth to water in the alluvial aquifer during fall 1999 was about 25 feet. The alluvial aquifer receives lateral recharge at the western boundary from the Mississippi River and at the eastern boundary from aquifers that directly underlie the Bluff Hills. The alluvial aquifer receives water vertically from precipitation, internal streams and lakes, and locally from the Cockfield and Sparta aquifers where they directly underlie the alluvial aquifer. The alluvial aquifer also discharges water to the underlying aquifers, and during extended periods with no surface runoff, to the Mississippi River and to the internal streams and lakes. The magnitude of recharge from the Mississippi River, precipitation, and internal lakes and streams can vary greatly depending upon hydrologic and climatic conditions. The U.S. Geological Survey modular threedimensional finite-difference ground-water flow model, MODFLOW, was used to simulate the Mississippi River alluvial aquifer flow system in northwestern Mississippi. The model uses one layer with a rectangular-grid and 1-mile square cells to represent the alluvial aquifer. The model was calibrated and verified by using spring and fall water-level measurements from January 1988 through December 1996. The values of selected model calibration-derived parameters for the alluvial aquifer are hydraulic conductivity, 425 feet per day; specific yield, 0.32; and storage coefficient, 0.016. The model showed that the aquifer lost water from storage at an average rate of 404 cubic feet per second during the 9-year simulation period. During this period, the average pumpage rate was 1,270 million gallons per day (1,980 cubic feet per second). Simulated areal recharge from precipitation averaged 2.6 inches per year (1,360 cubic feet per second). Vertical recharge from the internal streams and lakes and lateral recharge from aquifers underlying the Bluff Hills averaged 113 and 108 cubic feet per second, respectively. Model results indicated that net recharge from the Mississippi River and from aquifers directly underlying the alluvial aquifer was small.

Arthur, J. K.

2001-01-01

347

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

348

Quantities and associations of lead, zinc, cadmium, manganese, chromium, nickel, vanadium, and copper in fresh Mississippi delta alluvium and New Orleans alluvial soils.  

PubMed

The topic of this study is the effect of anthropogenic metals on the geochemical quality of urban soils. This is accomplished by comparing the metal contents and associations between two alluvial soils of the lower Mississippi River Delta, freshly deposited alluvial parent materials and alluvial soils collected from a nearby urban environment. Fresh alluvium samples (n = 97) were collected from the Bonnet Carré Spillway. The urban alluvial soil samples (n = 4026) were collected from New Orleans and stratified by census tracts (n = 286). The Spillway samples tend to have less Pb and Zn than generally noted for the baseline of natural soils. Except for Mn and V, Spillway alluvium contains significantly less metal than urban soils. For Spillway samples, the median metal content (in microg g(-1)) is 4.7 Pb, 11.1 Zn, 0.7 Cd, 164 Mn, 0.8 Cr, 3.9 Ni, 3.2 V, and 3.9 Cu. For urban soils, the median metal content (in microg g(-1)) is 120 Pb, 130 Zn, 3.2 Cd, 138 Mn, 2.1 Cr, 9.8 Ni, 3.8 V, and 12.7 Cu. Metal associations also differ between Spillway alluvium and urban alluvial soils. Fresh alluvium correlation coefficients between individual metals vary from 0.87 to 0.99 (P < 10(-13)) except for Cr which ranges from 0.57 to 0.68 (P < 10(-7)). The urban soil correlation coefficients for metals and the index value are 0.40-0.98. In urban soils, Pb, Zn, Cr, and Cu are dominant metals and highly associated, with a correlation coefficient ranging from 0.83 to 0.98 (P < 10(-25)). Their strong association justifies the use of GIS to map the integrated soil metal index (sum of the medians of metals by census tract) of New Orleans. Although also positively correlated (0.40-0.68, P < 10(-10)), Cd, Mn, Ni and V differ in their distribution in the city compared to Pb, Zn, Cr and Cu. Overall, significantly higher metal values occur in the inner city and lower values occur in outlying areas. The human health impact of the mixture of metals is not well understood. This study provides empirical data about the mixture and distribution of metals in New Orleans alluvial soils. Given common technical development, especially of traffic flows in cities, similar patterns of soil metals are expected for all US cities and probably international cities as well. Primary prevention of urban metal accumulations is necessary to enhance and sustain the development of urban culture. PMID:10696726

Mielke, H W; Gonzales, C R; Smith, M K; Mielke, P W

2000-02-10

349

Large to intermediate-scale aquifer heterogeneity in fine-grain dominated alluvial fans (Cenozoic As Pontes Basin, northwestern Spain): insight based on three-dimensional geostatistical reconstruction  

NASA Astrophysics Data System (ADS)

Facies reconstructions are used in hydrogeology to improve the interpretation of aquifer permeability distribution. In the absence of sufficient data to define the heterogeneity due to geological processes, uncertainties in the distribution of aquifer hydrofacies and characteristics may appear. Geometric and geostatistical methods are used to understand and model aquifer hydrofacies distribution, providing models to improve comprehension and development of aquifers. However, these models require some input statistical parameters that can be difficult to infer from the study site. A three-dimensional reconstruction of a kilometer scale fine-grain dominated Cenozoic alluvial fan derived from more than 200 continuously cored, closely spaced, and regularly distributed wells is presented. The facies distributions were reconstructed using a genetic stratigraphic subdivision and a deterministic geostatistical algorithm. The reconstruction is only slightly affected by variations in the geostatistical input parameters because of the high-density data set. Analysis of the reconstruction allowed identification in the proximal to medial alluvial fan zones of several laterally extensive sand bodies with relatively higher permeability; these sand bodies were quantified in terms of volume, mean thickness, maximum area, and maximum equivalent diameter. These quantifications provide trends and geological scenarios for input statistical parameters to model aquifer systems in similar alluvial fan depositional settings.

Falivene, O.; Cabrera, L.; Sáez, A.

2007-08-01

350

Quaternary tectonics of the southeastern coastal area, Korea: subsidence of marine terrace and late Quaternary faults  

Microsoft Academic Search

Strong earthquake has rarely occurred in Korean peninsula and a few events were recorded since 27 A.D. Historical and recent earthquakes are concentrated in the southeastern area of Korean peninsula, where more than 30 Quaternary fault exposures have recently been founded. The southern tip of the southeastern coastal area has been known as a stable block: quaternary fault and micro-earthquakes

S.-J. Choi; Y. Ota; U. Chwae

2003-01-01

351

New Quaternary slip-rate estimates for the central Garlock fault in SE California - Evidence for large transient slip-rates  

NASA Astrophysics Data System (ADS)

Significant short-term fluctuations in a mature fault’s slip rate are enigmatic. Work over the last decade in southern California has demonstrated this behavior on the San Andreas Fault (SAF) in the LA basin and the Eastern California shear zone (ECSZ) (e.g., Peltzer, Oskin and Dolan). We report here new slip-rate data for the central Garlock fault in the Pilot Knob Valley area that suggests that it also shows an irregular late Quaternary slip-rate history. An abandoned drainage containing an estimated 3-4 k.y. debris flow is faulted against a 47-m-long shutter ridge (UTM 481630E, 3935170N), implying a 11.8 - 15.6 mm/yr slip rate. Well-preserved bar-and-swale morphology on the surface of the debris flow abuts the shutter ridge perpendicularly, indicating that the debris flow predates slip. Surface clasts have only incipient development of varnish and rubification. A 140-cm-deep hand-dug trench displays incipient Av- and Bw-horizon soil development typical of late-Holocene alluvial deposits in the Mojave Desert. A silt lens in the deposit was sampled ~200 m upstream and has been submitted for OSL dating. Terrestrial-based LiDAR scanning will be performed to map the site’s surface morphology at mm-scale resolution. Two possible implications of this data are (1) that the GF now acts as a conjugate to the SAF and that faster slip on the GF is correlated with fast slip on the Big Bend section of the SAF and on faults within the LA basin, while the ECSZ is quiescent; or (2) that the GF is near the end of its current earthquake cycle. Faster slip on the GF in the past 3-4 k.y., coupled with a more active SAF and a quieter ECSZ, may help explain how the GF can cut across the ECSZ without itself being cut by the ECSZ. In addition, the lack of resolvable sinistral shear across the GF in the geodetic record suggests that either the GF has come out of its transient high slip-rate period, or conversely, it is near the end of its earthquake cycle.

Rittase, W. M.; Walker, D.; Kirby, E.; McDonald, E.

2009-12-01

352

Initial Results on the Pliocene and Quaternary Evolution of the Western Arctic from the Deep Drilling in 2008/09 at Lake Elgygytgyn, Chukotka (Invited)  

NASA Astrophysics Data System (ADS)

Lake Elgygytgyn, located 100 km to the north of the Arctic Circle (67°30' N, 172°05' E) in a crater of 18 km diameter, was formed 3.6 Ma ago by a meteorite impact event. From Oct. 2008 until May 2009 an ICDP drilling campaign was conducted at Lake Elgygytgyn, achieving its three major objectives. First, drilling from the ice cover in the lake center penetrated the entire, 315 m thick lake sediment succession in 170 m water depth. The sediments show no indications for hiatuses due to glaciation or desiccation. Hence, their temporal length and geologic significance is absolutely unprecedented, for the first time providing deep and widely continuous insights into the climatic and environmental evolution of the terrestrial Arctic since Pliocene times. This is particularly true for the lowermost 40 m and uppermost 140 m of the sequence, which were drilled with almost 100 % recovery and, using the chronological information we have available, likely reflect the initial lake stage during the Pliocene and the last ca. 2.8 Ma, respectively. In between, the quality of the record is restricted due to lower recovery as a consequence of technical problems and/or sequences of coarse sand and gravel interbedded with lacustrine mud. Second, a ca. 200 m thick, almost complete section of impact breccias was recovered underneath the lake sediments, consisting of a ca. 100 m thick suevite layer above broken and fractured volcanic basement rocks. Investigation of this core sequence promises new information concerning the Elgygytgyn impact event, including the composition and nature of the meteorite, the energy released, and the shock behavior of the volcanic basement rocks. Third, a 142 m long sequence was recovered from the permafrost deposits in the western lake catchment, only a few hundred meters from the lake shore. The core consists of gravelly and sandy alluvial fan deposits, which are continuously frozen and rich with ground ice. The sediment and ice composition promises to provide complementary information on the regional climatic history and lake-level fluctuations. Besides, a thermistor chain installed in the drill hole as part of the “Thermal State of Permafrost Network” of the International Permafrost Association will contribute to the understanding of the permafrost behavior in light of contemporary rapid change. Processing and subsampling of the drill cores commenced in autumn 2009 and will be completed by the end of 2010. The presentation will summarize the operational success of the drilling campaign and highlight the scientific results obtained so far based on the limited onsite and ongoing offsite core processing. Special attention will be put on the lake sediment record and its significance for climatic and environmental changes in the area during Pliocene and Quaternary times.

Melles, M.; Brigham-Grette, J.; Minyuk, P.; Koeberl, C.; El'Gygytgyn Scientific Party

2010-12-01

353

Quaternary geology of the Rhode Island inner shelf  

USGS Publications Warehouse

Five sedimentary units and three erosional unconformities identified in high-resolution seismic-reflection profiles reveal the stratigraphic framework and Quaternary history of the inner continental shelf south of Narragansett Bay, Rhode Island. Late Tertiary to early Pleistocene rivers eroded the pre-Mesozoic bedrock and the Upper Cretaceous to lower Tertiary coastal plain and continental shelf strata to form a lowland and cuesta having a north-facing escarpment. The lowland and landward flanks of the cuesta were modified by glaciers during Pleistocene time and subsequently were overlain by drift and end moraine deposits of the late Wisconsinan ice advance. During deglaciation, freshwater lakes formed between the retreating ice and end moraines. Prior to sea-level rise, the drift and older deposits were cut by streams flowing south and southwestward toward Block Island Sound. As sea level rose, postglacial valleys were partly filled by fluvial, freshwater-peat, estuarine and salt-marsh deposits. Transgressing seas eroded the sea floor, exposing bedrock and coastal plain outcrops, and deposited marine sediments. ?? 1983.

Needell, S. W.; O'Hara, C. J.; Knebel, H. J.

1983-01-01

354

Uplift of quaternary shorelines in eastern Patagonia: Darwin revisited  

NASA Astrophysics Data System (ADS)

During his journey on the Beagle, Darwin observed the uniformity in the elevation of coastal Eastern Patagonia along more than 2000 km. More than one century later, the sequences of Quaternary shorelines of eastern Patagonia have been described and their deposits dated but not yet interpreted in terms of geodynamics. Consequently, we i) mapped the repartition of the Quaternary coastal sequences in Argentinean Patagonia, ii) secured accurate altitudes of shoreline angles associated with erosional morphologies (i.e. marine terraces and notches), iii) took into account previous chrono-stratigraphical interpretations in order to calculate mean uplift rates since ~ 440 ka (MIS 11) and proposed age ranges for the higher and older features (up to ~ 180 m), and iv) focused on the Last Interglacial Maximum terrace (MIS 5e) as the best constrained marine terrace (in terms of age and altitude) in order to use it as a tectonic benchmark to quantify uplift rates along the entire passive margin of Eastern South America. Our results show that the eastern Patagonia uplift is constant through time and twice the uplift of the rest of the South American margin. We suggest that the enhanced uplift along the eastern Patagonian coast that interested Darwin during his journey around South America on the Beagle could originate from the subduction of the Chile ridge and the associated dynamic uplift.

Pedoja, Kevin; Regard, Vincent; Husson, Laurent; Martinod, Joseph; Guillaume, Benjamin; Fucks, Enrique; Iglesias, Maximiliano; Weill, Pierre

2011-04-01

355

Slope clay-with-flints (biefs à silex) as indicators of Quaternary periglacial dynamics in the western part of the Paris Basin, France  

NASA Astrophysics Data System (ADS)

The lithology and distribution of the clay-with-flints occurring on slopes, called biefs à silex in French, suggests a twofold classification of these deposits according to slope angle. Biefs à silex formed as a solifluction deposit under Quaternary periglacial conditions during valley development. Two biefs à silex facies suggest two phases of development between 800 000 and 20 000 yr BP.

Laignel, B.; Quesnel, F.; Spencer, C.; Meyer, R.; Lautridou, J. P.

2003-02-01

356

Mineralogical and chemical distribution patterns of placers and ferricretes in Quaternary sediments in SE Germany: The impact of nature and man on the unroofing of pegmatites  

Microsoft Academic Search

Placer deposits mark the ultimate stage of mineral separation in clastic sediments by physical processes in an aquatic regime, whereas duricrusts are an example of extreme element separation by chemical processes in continental environments of deposition. In Quaternary sediments in SE Germany such contrasting types of sediments formed on the NE Bavarian Basement which is underlain by metamorphic and pegmatitic

H. G. Dill; A. Techmer; B. Weber; M. Füßl

2008-01-01

357

Impacts of Urban Development on Channel Slope, Erosion, and Depositional Processes  

NASA Astrophysics Data System (ADS)

Watershed land uses, including urbanization, influence erosion and depositional processes in a tributary to the Navarro basin in north coastal California. The Robinson Creek subwatershed is deeply incised into easily erodible Quaternary alluvial river and terrace valley-fill deposits in the vicinity of the urbanizing town of Boonville. Remnant riparian forest vegetation exists at the top of the terrace. Detailed field surveys of a 1.3 km channel reach document spatial variation in slope and suggest that a series of knickzones accommodate elevation differences between areas upstream and downstream of the urbanizing area. Average reach slope is ~0.012 whereas average terrace slope is ~0.009. This difference accounts for lower bank heights (~4.6 m) at the upstream end of the reach than at the downstream end (~8.1 m). The apparent recent increase in channel slope, an indicator of channel adjustment, leads to an increase in shear stress available to erode and transport bed and bank sediment in the relatively narrow channel. Temporal variation in bed elevation is related to episodic floods in this actively adjusting channel; up to 0.2 m of incision occurred during floods in water year 2006. Bank erosion is considerable and erosion-control structures are a typical response to land loss, threats to residential structures and domestic water wells, and undercutting of bridge piers and individual streamside trees. Existing bank erosion control structures limit geomorphic processes and aquatic and riparian restoration options over the long term. Moreover, progressive urban development including building structures near the top-of-bank further limit alternatives for restoration of geomorphic processes and associated aquatic and riparian habitat that require increases in channel width as a response to continuing channel incision.

Florsheim, J. L.

2007-12-01

358

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

359

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

360

Deformation of Quaternary strata and its relationship to crustal folds and faults, south-central Puget Lowland, Washington State  

Microsoft Academic Search

Folded Quaternary deposits across the south-central Puget Lowland, an area just south of the Seattle fault that extends across the Seattle uplift and its boundary with the adjacent Tacoma basin, provide increased resolution of the character and rate of crustal deformation. They also constrain alternative, and partly incom- patible, views of crustal structure previously suggested by geo- physical investigations. Tectonic

Derek B. Booth; Kathy Goetz Troost; Jonathan T. Hagstrum

2004-01-01

361

7. PLIOCENE AND QUATERNARY MUD TURBIDITES IN THE GULF OF CALIFORNIA: SEDIMENTOLOGY, MASS PHYSICAL PROPERTIES AND SIGNIFICANCE1  

Microsoft Academic Search

A large proportion of the Pliocene and Quaternary basin fill in the Gulf of California is composed of relatively fine- grained mud turbidites which have sedimentary structures that are more subtle than those of sandy turbidites in flysch deposits. Basal contacts are sharp, sometimes accompanied by thin, laminated, muddy sands; the silty body commonly appears massive, and the tops consist

Gerhard Einsele; Kerry Kelts

362

Interpretation of alluvial beds through bed-elevation distribution moments  

NASA Astrophysics Data System (ADS)

With equipment advances now enabling the measurement and processing of alluvial-bed elevation data at high spatial and temporal resolutions, the moments of measured bed-elevation distributions can be used to characterize riverbed structure. From analyses of a wide range of high-quality data sets for a range of flows, sediments, and types of bed surface (e.g., armoured gravels, uniform sands, ripples, and dunes), at laboratory and field scales, the standard deviation of bed elevations ? is found to provide a robust integral measure of bed-roughness height. This approach has the statistical advantage of utilizing all relevant bed-elevation information, and also removes any potential need to subjectively identify valid individual roughness elements within the measured bed data. In addition to ? defining the vertical roughness scale for a bed surface, the general shape of the bed surface forms or elements can be characterized by the bed-elevation distribution skewness Sk, with the distribution kurtosis Ku providing a measure of the evenness or intermittency of these elements. Based on the present analyses, a schematic Sk-Ku plane is presented to aid interpretation of the structure of steady state and developing alluvial bed surfaces from measured bed-elevation distributions, where various bed surface types (e.g., artificially smoothed beds, armoured gravel beds, planar beds of mobile uniform sediments, ripples, and dunes) can be differentiated based on this diagram. Relatively large values of Ku that can occur for a measured riverbed surface are associated with intermittent bed-roughness elements, as can arise for supply-limited dunes or widely distributed pebble clusters or bed forms on an otherwise plane bed.

Coleman, Stephen E.; Nikora, Vladimir I.; Aberle, Jochen

2011-11-01

363

Rapid subsidence in the Nile delta and the effects of a mobile depositional surface on stratigraphic facies development  

SciTech Connect

Radiocarbon-dated late Quaternary sedimentary sections serve as a base to quantify high rates of subsidence in the northern Nile delta of Egypt. Measurements of recent vertical shifts of land relative to the sea, coupled with eustatic changes, are used to interpret temporal and spatial facies distribution patterns and delta lobe migration in the major recent depocenter in the eastern Mediterranean. The study is based largely on cores, collected during two drilling expeditions, which recovered material deposited during the past 30,000 years. These borings, plus an additional 50 core logs, allow good correlation for the region around Lake Manzala. There, variable thicknesses of Holocene marine and fluvio-marine units lie above transgressive coastal sands (upper Pleistocene to lower Holocene) and older alluvial delta-plain deposits. Mapping of these facies shows that the top of the transgressive sand becomes younger (to -- 7,000 years ago) and shallower toward the south of the present coastline. Progradation of delta lobes began about 8,000 years ago, and the coastline has advanced northward at a rate of approximately 1 km/100 years. Lake Manzala lies almost directly above, and is clearly related to, a 60-km long, narrow, linear northwest-southeast region of rapid subsidence; its axis trends parallel to, but is 10-15 km inland of, the present coastline. Holocene coastal and marine sediments lie at depths of 50 m, suggesting a lowering of land relative to the sea of about 40 cm per century. This linear zone, probably the surface expression of a growth fault, has been highly active during deposition. Similar neotectonic dislocation of sedimentary sections underlying the other lakes and lagoons in the northern delta is postulated. Facies patterns have been more extensively affected by rapid subsidence in the Nile delta than previously indicated.

Stanley, D.J.

1988-01-01

364

3-D sedimentary architecture of a Quaternary gravel delta (SW-Germany): Implications for hydrostratigraphy  

Microsoft Academic Search

This paper investigates a Quaternary Gilbert-type gravel delta that was formed in an ice-marginal environment at the end of the last glacial period.Outcrop, sediment core and ground-penetrating radar (GPR) studies reveal the sedimentary facies and depositional architecture of the delta that comprises three major units: (1) a 2–5 m thick, gravelly topset with an erosional base, formed by accretion of

Boris Kostic; Andreas Becht; Thomas Aigner

2005-01-01

365

Multiple landslide clusters record Quaternary climate changes in the northwestern Argentine Andes  

Microsoft Academic Search

The chronology of multiple landslide deposits and related lake sediments in the semi-arid eastern Argentine Cordillera suggests that major mass movements cluster in two time periods during the Quaternary, i.e. between 40 and 25 and after 5 14C kyr BP. These clusters may correspond to the Minchin (maximum at around 28–27 14C kyr BP) and Titicaca wet periods (after 3.9

Martin H. Trauth; Bodo Bookhagen; Norbert Marwan; Manfred R. Strecker

2003-01-01

366

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