Note: This page contains sample records for the topic quaternary alluvial deposits from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: August 15, 2014.
1

In situ crystal chemical study of solid diamond inclusions from Quaternary alluvial deposit in the Siberian craton  

NASA Astrophysics Data System (ADS)

Kimberlites belong to rare rock type available only within the Earth's cratonic areas and have been a subject of detailed studies because of the great depth of their origin in the mantle. Kimberlitic diamonds often contain pristine inclusions derived from significant depths with different histories of their origins. Many of kimberlitic diamonds were formed in ultramafic (peridotitic) and mafic (eclogitic) environments of the upper mantle. Thus far only a handful of comprehensive in situ studies including single-crystal X-ray diffraction characterization of pristine diamond solid inclusions have been reported (e.g. Kunz et al. 2001, Nestola et al. 2011). In this study five single-crystal solid inclusions from diamonds found in the Quaternary alluvial deposit in NW of the Siberian craton have been investigated using a combination of in situ single-crystal X-ray diffraction, Raman spectroscopy, synchrotron X-ray microfluorescence and X-ray Absorption Near Edge Spectroscopy (XANES). The grains were identified to be a suite of major upper mantle minerals including olivine, enstatite orthopyroxene (opx), C2/c omphacite clinopyroxene (cpx) and majoritic garnet (two grains), indicating eclogitic origin. All five inclusions are chemically homogeneous, do not show compositional zoning, and exhibit very similar major element chemistry, with significant amounts of Mn2+, Ni2+ and Cr3+ incorporated into the crystal structures, suggesting common geologic origin. All samples were studied in situ, while still embedded in the diamond crystals. High quality single-crystal X-ray diffraction data was collected at the Advanced Photon Source, Argonne National Laboratory to reveal details of the crystal structures and provide crystal chemical information. Some of the structural characteristics of the solid inclusions were found to be fairly uncommon, e.g. the orthoenstatite exhibits an unusually high Ca2+ content (Carlson et al. 1988), and omphacite occurs as the less common C2/c polymorph (Banno, 1970), both of which are considered signatures of eclogitic high-temperature facies. Fe Ka-edge XANES was used to investigate the oxidation state of iron in the solid inclusions. All of the inclusions show predominantly Fe2+, indicating reducing conditions of formation. The combined results of our spectroscopic and diffraction experiments will be interpreted in the context of the conditions and mechanism of formation (syngenesis vs. protogenesis) and possible retrograde transformation the inclusions may have experienced when transported to the surface. References Carlson, W.D. J.S. Swinnea, D.E. Miser (1988) 'Stability of orthoenstatite at high temperature and low pressure' Amer. Mineral. 73: 1255-1263. Banno, S. (1970) 'Classification of eclogites in terms of physical condition of their origin' Phys. Earth. Planet. Interiors 3: 405-421. Kunz, M., P. Gillet, et al. (2002). "Combined in situ X-ray diffraction and Raman spectroscopy on majoritic garnet inclusions in diamonds." Earth and Planet. Sci. Lett. 198: 485-493. Nestola, F., P. Nimis, et al. (2011). "First crystal-structure determination of olivine in diamond: Composition and implications for provenance in the Earth's mantle." Earth and Planet. Sci. Lett. 305: 249-255.

Dera, P. K.; Manghnani, M. H.; Hushur, A.; Sobolev, N. V.; Logvinova, A. M.; Newville, M.; Lanzirotti, A.

2013-12-01

2

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

3

Reconstruction of the sediment transport conditions in the Quaternary Ürümqi alluvial system (northeast Tian Shan, China)  

NASA Astrophysics Data System (ADS)

Over the last twenty years, sediment transport by rivers and erosion dynamics have been the focus of a huge research effort. However, the morphological makers of erosion are often scarce, fragmented and they correspond to a very discontinuous record. At the outlet of drainage basins submitted to erosion, sedimentary series often constitute more frequent, perennial and continuous archives in space and through time for the evolution of reliefs upstream. Thus, some studies have used volumes of these deposits to roughly reconstruct this evolution. Yet, beyond their volume, the alluvial sediments also contain information about physical parameters of palaeorivers that have deposited them. That is why we decided to couple a physical analysis of water flow, erosion and transport in an active river with a faciological analysis of its present and past deposits to reconstruct some of its palaeohydraulic characteristics. As an example, we chose the northeastern foothills of the Tian Shan range where the Ürümqi braided and gravel-bed river is inset in its own Quaternary deposits. Hence, in this area, it is possible to observe and compare the present and ancient sediments of a single alluvial system. First, we gathered an extensive dataset on hydraulics and transport dynamics of the present river, as well as on grain size and structure of its deposits. These depositional features were characterized at the river-bed surface, but also in depth by the means of a trench. From the measurements performed, we built a facies model fully quantified, in term of grain and structure sizes of the present sediments, and calibrated regarding the relationships between deposition, transport and water flow. Additionally, we documented also the grain size and structure of the ancient Ürümqi deposits by describing the sediments of the Quaternary alluvial fan and terraces of the river. Eventually, the facies model calibrated in term of transport law and the data collected for the old deposits would be associated to reconstruct evolution curves of variables such as flow velocity or bed load during the study period (from - 250 to 0 kyr approximately). In this way, we hope to set the basis of palaeohydraulic reconstructions of the ancient Ürümqi river, which will bring precious information about the long-term sediment transport and erosion dynamics in the study area.

Guérit, Laure; Barrier, Laurie; Métivier, François; Narteau, Clément; Lajeunesse, Éric; Liu, Youcun; Ye, Beicheng

2010-05-01

4

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

Microsoft Academic Search

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

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

2007-01-01

5

Geochemical proxies for weathering and provenance of Late Quaternary alluvial core-sediments from NW India  

NASA Astrophysics Data System (ADS)

The Indo-Gangetic alluvial plains are formed by sediment deposition in the foreland basin as a result of upliftment and subsequent erosion of the Himalaya. Earlier study (Sinha et al., 2013) has shown the subsurface existence of buried channel bodies beneath the Ghaggar plains in NW Indo-Gangetic plains. The mapped sand bodies follow trace of a paleochannel that begins at the mountain front near the exit of river Sutlej and extends to the northern margin of the Thar desert, suggesting existence of a large Himalayan-sourced river (Singh et al., 2011) in the past. The buried sand bodies hold potential records of erosion history over the Himalaya that could be used to assess climate-controlled erosion over the Himalaya. Geochemical variations in the sediments from two (~45m long) cores drilled below the trace of the paleochannel (upstream) near Sirhind, Punjab and two cores (GS-10 & 11) from downstream near Kalibangan, Rajasthan, are used in this study to understand the erosional pattern over the Himalaya during Late Quaternary. Down-core variations in chemical index of alteration (CIA=51-79) along with K2O/Na2O and Al2O3/(CaO+Na2O) ratios are consistent with the trends of SW summer monsoonal fluctuations during the Glacial-Interglacial periods indicating climate controlled weathering at the source; higher values during Interglacial and lower during Glacial periods with maximum value during the Holocene. Sr-Nd isotopic compositions of drill-cores sediments, 87Sr/86Sr (0.7314-0.7946), ?Nd (-23.2 to -14) are within the range of silicate rocks from the Higher and Lesser Himalaya. Significant down-core variations in 87Sr/86Sr and ?Nd are observed that reflect the mixing of varying proportions of the Higher and Lesser Himalayan sediments, the two dominant sources to the core sites. Sediments deposited during MIS-2 and MIS-4, cold and dry Glacial periods, show high 87Sr/86Sr and low ?Nd suggesting an enhanced contribution from the Lesser Himalayan rocks that are characterized by more radiogenic Sr and less radiogenic Nd. Whereas those deposited during MIS-1 and MIS-3, warm and humid Interglacial periods, are distinctly less radiogenic in Sr and more radiogenic in Nd (Higher Himalayan signature) suggesting increased contribution from the Higher Himalayan rocks. These variations can be attributed to decreased contribution from the Higher Himalaya during Glacial periods due to increased glacial cover over the Higher Himalaya which in turn are caused by lower solar insolation and vice versa. The findings of this study, consistent with those from the Ganga-Yamuna interfluve sediments (Rahaman et al., 2009), indicate a dominant control of climate on sediment provenance and source weathering. References: Sinha et al. (2013), Quaternary International, 308-309, 66-75. Singh et al. (2011), AGU Fall Meeting 5-9 December 2011. Rahaman et al. (2009), Geology, 37, 559-526.

Singh, Ajit; Amir, Mohd; Paul, Debajyoti; Sinha, Rajiv

2014-05-01

6

Characterizing avulsion stratigraphy in ancient alluvial deposits  

NASA Astrophysics Data System (ADS)

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, J.P., Clough, S.R., 1989. Anatomy of an avulsion. Sedimentology 36, 1-23] of the modern Saskatchewan River system (Cumberland Marshes, central Canada), and serve to characterize avulsion depositional sequences in the ancient Willwood and Fort Union Formations (Paleogene, Bighorn Basin, NW Wyoming, USA). We recognize, however, that the model is not universally applicable to avulsion-dominated successions, specifically systems which lack defining "heterolithic avulsion deposits", 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]. Observations in several fluvial intervals suggest that the avulsion stratigraphy outlined 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] represents one category of avulsion stratigraphy found in the rock record, but does not capture the nature of avulsion deposits everywhere. Based on observations (using measured sections, outcrop photo-panels, and aerial photographs) in the Willwood Formation (Eocene, Wyoming) and Ferris Formation (Cretaceous/Paleogene, Wyoming), we present two end-member categories of avulsion stratigraphy in ancient deposits; stratigraphically abrupt, when a main paleochannel is stratigraphically juxtaposed directly atop floodplain/overbank deposits, and stratigraphically transitional, where crevasse splays and other non-floodplain/-overbank deposits stratigraphically precede a main paleochannel. This characterization provides a broader, more inclusive way to recognize and describe avulsion stratigraphy in ancient deposits and may be an important factor to consider when modeling connectivity in fluvial reservoirs. Furthermore, our observations show that one type of avulsion channel stratigraphy may prevail over another within an ancient basin, suggesting that system-wide factors such as splay-proneness or avulsion style (i.e. aggradational, incisional, etc.; [Slingerland, R., Smith, N.D., 2004. River avulsions and their deposits. Annual Review of Earth and Planetary Sciences 32, 257-285]) may be primary controls on the type of avulsion stratigraphy deposited and preserved in ancient basin-fills.

Jones, H. L.; Hajek, E. A.

2007-11-01

7

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

USGS Publications Warehouse

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

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

2007-01-01

8

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

USGS Publications Warehouse

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

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

2007-01-01

9

Late Quaternary activity of the Ecemi? Fault Zone, Turkey; implications from cosmogenic 36Cl dating of offset alluvial fans  

NASA Astrophysics Data System (ADS)

The Ecemi? Fault Zone is the southernmost segment of the Central Anatolian Fault Zone. The tectonic trough of the fault zone defines the boundary between the Central and Eastern Taurides Ranges. The presence of faulted alluvial fans and colluvium within this trough provide favorable conditions to unravel the Late Quaternary slip-rate of the fault zone by cosmogenic surface exposure dating. In this context, we focused on the main strand of the fault zone and also on the Cevizlik Fault that delimits the mountain front of the Alada?lar, Eastern Taurides. Geomorphic mapping and topographic surveying indicate four different alluvial fan levels deposited along the main strand. Our topographic survey reveals 60±5 m horizontal and 18±2 m vertical displacement of the oldest fan surface (AF1) associated with the main strand of the fault zone. We dated the surface of the AF1 with 13 cosmogenic 36Cl samples. Our results indicate that the AF1 surface was abandoned maximum 105.3±1.5 ka ago. Accordingly, we propose 0.57±0.05 mm/yr horizontal and 0.17±0.02 mm/yr vertical mean slip-rates since 100 ka for the main strand. On the other hand, we measured 20±2 m vertical displacement on the colluvium along the Cevizlik Fault. The surface exposure age of the colluvium yielded 21.9±0.3 ka that translates to 0.91±0.09 mm/yr vertical slip-rate for the Cevizlik Fault. Our results reveal significant Quaternary deformation, and low strain rates might indicate very long earthquake recurrence intervals along the fault zone.

Akif Sar?kaya, Mehmet; Y?ld?r?m, Cengiz; Çiner, Attila

2014-05-01

10

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

11

A model of the Quaternary geological deposits of Bucharest City  

NASA Astrophysics Data System (ADS)

Bucharest city is located in the central part of the Moesic Platform, in the Romanian Plain with micro-relief resulting from erosion and sedimentary processes which extended along the valleys of the Dambovita River to the south and the Colentina River to the north. The city is located in the axial area of a syncline where the thickness of the sedimentary deposits is up to 1000 m. The area lies on a rigid base is made of metamorphites, and various igneous intrusions (granodiorite, granite). The sedimentary deposits covering this rigid base are made by different phases of erosion and sedimentary processes of marine, lacustrian or continental sediments ending with Quaternary sediments. As a result, different alluvial deposits (such as piedmont, deltaic, alluvial cones, terrace, waterside and lacustrine deposits) can be met. Furthermore one also can find loess deposits which in turn cover totally the older deposits where rivers dug the present relief. To highlight the spatial extent of these geological structures, a geological model of Bucharest city is developed. A set of information coming from different sources as geological and geotechnical boreholes showing a detailed geological and lithological description, geological and topographical maps, geological and hydrogeological reports have been used to develop the 3D geological model of this region. 33 geological cross sections were defined and interpreted by using lithological and sedimentological criteria. Using these geological cross sections and prior geological knowledge, the Quaternary deposits have been described and classified into 6 structural units given from top to down as follows: (1) Superficial deposits represented by loess and anthropogenic materials. The geological model indicates that these deposits show a sporadic development becoming more concentrated in the central west part of the city. (2) Colentina Formations composed by of poorly sorted, cross-stratified sand and gravel with clayey lens indicating a high energy deposition environment. The geological model indicates more accentuate vertical lithological heterogeneity than a horizontal one as well as a decrease of the Colentina Formation thickness. (3) Intermediary deposits represented by silty-clay with fine sand intercalation indicating a mixed regime with limited lakes and dry lands. (4) Mostistea Formation made of sediments with a variety of grain size, from fine sand to coarse sand with small intercalations of gravels and scrap of woods. It was found that areas where the Intermediary deposits are less developed making the Colentina Formation in direct connection to Mostistea Formation. (5) Marly Complex composed by a succession of marls and clays with lenticular sandy intercalations indicating a fluvial-lacustrine environment. (6) Fratesti Strata made of sand and gravel which includes A, B and C Fratesti levels.

Serpescu, Irina; Radu, Emil; Radu Gogu, Constantin; Amine Boukhemacha, Mohamed; Gaitanaru, Dragos; Bica, Ioan

2013-04-01

12

Late Neogene and Quaternary alluvial fans give evidence for tectonic events at the eastern margin of the Eastern Alps  

NASA Astrophysics Data System (ADS)

The deposition of Neogene and Quaternary alluvial sediments along the southwestern margin of the Vienna Basin record significant tectonic events for the eastern margin of the Alps. After the early to middle Miocene marine sedimentation phase fresh-water environments prevailed in the Vienna Basin during the Pannonian (Lake Pannon). Unconformably above early to middle Pannonian sediments, a late Pannonian to Pliocene conglomerate succession, the Rohrbach Formation, was deposited, followed by Pleistocene gravels of the Mitterndorf basin. The Rohrbach Formation builds a fan-like sedimentary body from the southwestern margin of the Vienna Basin near Neunkirchen up to the city of Wiener Neustadt, where these conglomerates occur within a depth of about 40 m below Pleistocene gravels. Outcrops of these probably Pliocene (Dacian) conglomerates have been investigated at the quarry Rohrbach. Conglomerates are mainly coarse to fine-grained, crudely bedded, and display maximum particle sizes up to 10 cm. Erosive fluvial channels with dimensions from 1 to several meters are present. Sandstone intercalations are common and sometimes graded. Laterally extensive silt- and claystones layers are present in minor amounts. Clasts include mainly limestones, dolomites and sandstones, and minor amounts of mica schists, gneisses and quartzites. Heavy minerals are dominated by garnet, epidote and stable minerals like tourmaline. Minor amounts of chrome spinel and higher metamorphic minerals like kyanite and sillimanite are present in most of the samples. The Rohrbach Formation is interpreted as an alluvial fan-braided river system fed by source areas mainly in the Northern Calcareous Alps and subsidiary source areas in the Greywacke Zone and the Austro-Alpine basement units. Synsedimentary deformations may point to the activity of basin margin faults during the Pliocene/Dacian. After a stable and tectonically quiet period, subsidence in the Pleistocene Mitterndorf basin started around ~ 250.000 yrs BP. Subsidence created accommodation for alluvial fans (Piesting Fan, Schwarza Fan), which filled the basin and unconformably overly the Rohrbach Formation. Calculated maximum subsidence rates show values of ~ 0.7 mm/yr, largely corresponding to recent precise leveling values of around -1 mm/yr for that area. Although the stratigraphic architecture of the fans is largely controlled by climate cycles (Salcher et al., in press), the development of these mountain front alluvial fans calls for a renewed phase of tectonism which is still active today. As evidenced by pebble composition and heavy mineral assemblages the source areas for the fans are largely similar to that of the Rohrbach Formation. Our investigations thus point to two significant phases of Late Neogene to Quaternary tectonism at the eastern margin of the Eastern Alps: A first tectonic phase in the Dacian (early Pliocene, ca. 5.3 - 4.6 Ma, but starting in late Pannonian) resulted in sedimentation of the Rohrbach Formation, a second phase in the Middle to Late Pleistocene resulted in subsidence of the Mitterndorf subbasin and formation of mountain front alluvial fans.

Wagreich, M.; Salcher, B.; Koukal, V.

2009-04-01

13

Mapping Quaternary Alluvial Fans in the Southwestern United States based on Multi-Parameter Surface Roughness of LiDAR Topographic Data  

NASA Astrophysics Data System (ADS)

Quaternary alluvial fans, common landforms in hyper- to semi-arid regions, have diverse surface morphology, desert varnish accumulation, clasts rubification, desert pavement formation, soil development, and soil stratigraphy. Their age and surface topographic expression vary greatly within a single fan between adjacent fans. Numerous studies have demonstrated that the surface expression and morphometry of alluvial fans can be used as an indicator of their relative age of deposition, but only recently has there been an effort to utilize high resolution topographic data to differentiate alluvial fans with automated and quantifiable routines We developed a quantitative model for mapping the relative age of alluvial fan surfaces based on a multi-parameter surface roughness computed from 1-meter resolution LiDAR topographic data. Roughness is defined as a function of scale of observation and the integration of slope, curvature (tangential), and aspect topographic parameters. Alluvial fan roughness values were computed across multiple observation scales (3m×3m to 150m×150m moving observation windows) based on the standard deviation (STD) of slope, curvature, and aspect. Plots of roughness value versus size of observation scale suggest that the STD of each of the three topographic parameters at 7m×7m observation window best identified the signature of surface roughness elements. Roughness maps derived from the slope, curvature, and aspect at this scale were integrated using fuzzy logic operators (fuzzy OR and fuzzy gamma). The integrated roughness map was then classified into five relative morpho-stratigraphic surface age categories (active wash to ~400 ka) and statistically compared with a similar five-fold surface age map of alluvial fans developed using traditional field surveys and aerial photo interpretation. The model correctly predicted the distribution and relative surface age of ~61% of the observed alluvial fan map. The results of the multi-parameter model imply that the first order roughness elements of alluvial fan surfaces have the average wavelength of 7m, and the roughness contributed by these elements decreases with the age of alluvial fans.

Regmi, N. R.; McDonald, E.; Bacon, S. N.

2012-12-01

14

Mapping Quaternary alluvial fans in the southwestern United States based on multiparameter surface roughness of lidar topographic data  

NASA Astrophysics Data System (ADS)

alluvial fans have diverse surface morphologies related to both depositional and weathering processes. Numerous studies have demonstrated that the surface expression and morphometry of alluvial fans can be used as an indicator of their relative age of deposition, but only recently has there been an effort to utilize high-resolution topographic data to differentiate alluvial fans by surface age with automated and quantifiable routines. We developed a quantitative model for mapping the relative age of alluvial fan surfaces based on multiparameter surface roughness values computed from 1 m resolution lidar topographic data. Roughness is defined as a function of observational scale and integration of slope, curvature, and aspect topographic parameters. Alluvial fan roughness values were computed across multiple observation scales (3 × 3 m to 150 × 150 m) based on the standard deviation (SD) of slope, curvature (tangential), and aspect topographic parameters. Plots of roughness value versus size of observation scale suggest that the SD of each parameter over a 7 × 7 m observation window best identified the signature of surface roughness elements. Roughness maps derived from slope, curvature, and aspect at this scale were integrated using fuzzy logic. The integrated roughness map was then classified into five relative morphostratigraphic surface age categories (active wash to ~400 ka) and statistically compared with a similar fivefold surface age map of alluvial fans developed using traditional field surveys and aerial photographic interpretation. The model correctly predicted the distribution and relative surface age of ~61% of alluvial fan landforms based on traditional mapping techniques.

Regmi, Netra R.; McDonald, Eric V.; Bacon, Steven N.

2014-01-01

15

Late Quaternary alluvial sequence and uplift-driven incision of the Urumqi River in the north front of the Tian Shan, northwestern China  

NASA Astrophysics Data System (ADS)

This work focuses on the driving force behind the late Quaternary river incision and terrace formation of the Urumqi River in the north piedmont of the Tian Shan, northwestern China. Field investigations on geomorphic surfaces, terrace deposits, and its underlying bedrock identify four most significant features, which creates a local applicable framework for subdivision of the late Quaternary terrace sequence in the study area. Nine stepped river terraces are defined and designated as T1 to T9 increasing systematically in elevation. Morphologically, the highest T9 correlates with the oldest alluvial fan F1 of the Urumqi River. River incision and the resultant abandonment of fan F1 are chronologically constrained at ca. 550 ka. The stratigraphic geometry of the Saerqiaoke anticline, a structure developing at the fan end of F1, reveals the existence of growth strata, implying continuous growth of this fold when the F1 alluvial sediments were deposited. In the range front of the Urumqi River, growth of the Saerqiaoke anticline has derived tectonically from uplift and basinward thrusting of the Tian Shan range. Such thrusting and basinward extension of the range are expected to force rock uplift of the headwater of the Urumqi River with respect to the Chaiwopu basin to the north and thus river incision occurring at ca. 550 ka. During the subsequent period, several younger terraces have been formed in response to the further uplift of the Saerqiaoke anticline as well as climate changes during glacial-interglacial transitions. In the present study area, the total incision during Quaternary comes close to 400 m, with about 85% contribution likely attributed to rock uplift of the Saerqiaoke anticline.

Lu, Honghua; Zhang, Tianqi; Zhao, Junxiang; Si, Supei; Wang, Hao; Chen, Shiji; Zheng, Xiangmin; Li, Youli

2014-08-01

16

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

NASA Astrophysics Data System (ADS)

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

AlShuaibi, Arafat A.; Khalaf, Fikry I.

2011-08-01

17

Sinkhole Evolution in Alluvial Deposits within the Central Ebro Basin, Northeast Spain  

Microsoft Academic Search

We have used aerial photo analysis and geophysical data to study the evolution of sinkholes developed on alluvial deposits covering Tertiary gypsum. This data can be interpreted as indicating different mechanisms by which sinkholes form. Negative gravity anomalies reflect the movement of alluvial particles into deeper subsurface caves. Ground penetrating radar (GPR) anomalies may indicate formation of caves in the

G. BENITO

18

Physicochemical characteristics of the soils developed from alluvial deposits on Chongming Island in Shanghai, China  

Microsoft Academic Search

Characterization of the physico-chemical properties of the soils collected from Chongming Island in Shanghai, China, which is the largest alluvial island with a total area of about 1,070 km in the world, has been conducted in order to investigate the current status of agricultural soils, with special reference to the effect of alluvial deposits on the development and utilization of

Ming He; Katsutoshi Sakurai; Guoqing Wang; Zonghui Chen; Yi Shu; Jinjin Xu

2003-01-01

19

Alluvial evidence for major climate and flow regime changes during the middle and late Quaternary in eastern central Australia  

Microsoft Academic Search

As a low-gradient arid region spanning the tropics to the temperate zone, the Lake Eyre basin has undergone gentle late Cenozoic crustal warping leading to substantial alluvial deposition, thereby forming repositories of evidence for palaeoclimatic and palaeohydrological changes from the Late Tertiary to the Holocene. Auger holes and bank exposures at five locations along the lower 500 km of Cooper Creek,

Gerald C. Nanson; David M. Price; Brian G. Jones; Jerry C. Maroulis; Maria Coleman; Hugo Bowman; Timothy J. Cohen; Timothy J. Pietsch; Joshua R. Larsen

2008-01-01

20

Depositional processes of the gravelly debris flow deposits, South Dolomite alluvial fan, Owens Valley, California  

Microsoft Academic Search

Coarse-grained debris flow was instigated in the South Dolomite alluvial fan of the Inyo Mountains piedmont, Owens Valley,\\u000a California, by a concentration of flashy thunderstorm precipitation in 1984. The debris flow extends about 650 m from the\\u000a fan apex to the Owens Lake, and forms levee deposits along the sides of the passing tract in the steep (6–26°) upper-fan (proximal)

Bok Chul Kim; Donald R. Lowe

2004-01-01

21

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

USGS Publications Warehouse

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

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

2006-01-01

22

Late Quaternary alluvial fan response to climatic and tectonic base-level changes: Jakes Valley, Central Great Basin, USA  

NASA Astrophysics Data System (ADS)

Late Quaternary alluvial fans within the Jakes Valley region (White Pine County, Central Great Basin) are typically composed of up to 4 inset morphostratigraphic units. These units, Qf0 (oldest) through to Qf3 (youngest), are based upon field relationships (mapping & fan topographic profiles) and soil properties. Distal fan areas contain pluvial lake shoreline features (erosional benches and beach ridges) that record lake-level lowering since the last glacial maximum. Integration of the fan morphostratigraphy and pluvial lake shoreline features allows for the alluvial fan response to climate induced base-level lowering to be investigated. Geochronology is established by AMS C14 dating of gastropod shells sampled from a range of highstand (dates pending) through to lowstand (12,080 +/- 50 rcybp) beach ridges. Detailed analysis of two alluvial fans from the western (Cottonwood Fan) and eastern (Yamaha Fan) basin margins reveals some interesting differences in fan morphostratigraphy. The Cottonwood fan is characterised by a complete suite of morphostratigraphic units (Qf0-Qf3), whilst the Yamaha fan comprises only Qf0 and Qf3. The presence of a pronounced 17 m high scarp feature, some several hundreds of metres in length, within close proximity to the mountain front on the Cottonwood fan, suggests the occurrence of neotectonic activity. This extensional (?) faulting appears to be post QF0 and may have been responsible for influencing the observed stratigraphic differences between the Cottonwood and Yamaha fans via a tectonic lowering of base-level. Within this poster we explore the relative roles of climate and tectonic base-level lowering for alluvial fan development.

Stokes, M.; Garcia, A. F.

2003-12-01

23

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

SciTech Connect

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

Galloway, W.E.

1980-01-01

24

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

25

Seismic stratigraphy of Late Quaternary deposits in the eastern Skagerrak  

Microsoft Academic Search

High-resolution seismic profiles from the Swedish west coast divide Quaternary deposits into six seismic sequences, containing 13 different seismic facies. Documentation of these sequences and facies and their stratigraphic and geographic variability is the first step in a basin-fill analysis to interpret depositional environments and major controlling processes. The deposits are attributed to one deglaciation cycle. The seismic sequences are:

Olof Larsson; Rodney L. Stevens

2008-01-01

26

Geohydrology of the alluvial and terrace deposits of the North Canadian River from Oklahoma City to Eufaula Lake, central Oklahoma  

USGS Publications Warehouse

This investigation was undertaken to describe the geohydrology of the alluvial and terrace deposits along the North Canadian River between Lake Overholser and Eufaula Lake, an area of about 1,835 square miles, and to determine the maximum annual yield of ground water. A 1982 water-level map of the alluvial and terrace aquifer was prepared using field data and published records. Data from test holes and other data from the files of the U.S. Geological Survey and the Oklahoma Water Resources Board were used to establish the approximate thickness of the alluvial and terrace deposits. The North Canadian River from Lake Overholser, near Oklahoma City, to Eufaula Lake is paralleled by a 2- to 3-mile wide band of alluvium. Scattered terrace deposits on either side of the alluvium reach an extreme width of 8 miles. Rocks of Permian age bound the alluvial and terrace deposits from the west to the midpoint of the study area; Pennsylvanian rocks bound the alluvial and terrace deposits from that point eastward. Three major aquifers are present in the study area: the alluvial and terrace aquifer, consisting of alluvium and terrace deposits of Quaternary age in a narrow band on either side of the North Canadian River; the Garber-Wellington aquifer of Permian age, consisting of an upper unconfined zone and a lower confined zone separated by relatively impermeable shales; and the Ada-Vamoosa aquifer of Pennsylvanian age. At locations were the alluvial and terrace aquifer overlies either of the other aquifers, there is hydraulic continuity between the alluvial and terrace aquifer and the other aquifers, and water levels are the same. Most large-scale municipal and industrial pumping from the Garber-Wellington aquifer is from the lower zone and has little discernible effect upon the alluvial and terrace aquifer. The total estimated base flow of the North Canadian River for the studied reach is 264 cubic feet per second. Evapotranspiration from the basin in August is about 60 cubic feet per second for the North Canadian River from Lake Overholser to a measuring station above Eufaula Lake. Estimated recharge rates to the alluvial and terrace aquifer in the basin range from 1.7 inches at the west edge of the study area to 7.0 inches at the east edge. Total permitted withdrawal from the aquifer, according to records of the Oklahoma Water Resources Board, ranged from 2,107 acre-feet per year in 1942 to about 21,415 acre-feet per year in 1982. Simulations of the alluvial and terrace aquifer from Lake Overholser to Eufaula Lake were made using a finite-difference model developed by McDonald and Harbaugh (1984). The area of the aquifers was subdivided into a finite-difference grid having 30 rows and 57 columns with cells measuring 1 mile in the north-south direction and 2 miles in the east-west direction. The model was calibrated in two steps: A steady-state calibration simulated head distribution prior to extensive pumping of the aquifer in 1942, and a transient calibration simulated head distribution after extensive pumpage. The final horizontal hydraulic conductivity used for the alluvial and terrace aquifer was 0.0036 feet per second (310 feet per day) at all locations. The recharge rate for the alluvial and terrace aquifer ranged from 1.7 inch per year in the west to 7.0 inches per year in the east, and averaged about 3.3 inches per year. A specific yield of 15 percent was used for the transient simulation. Permitted pumpage for 1942 through 1982 was used in the digital model to estimate the annual volume of water in storage in the alluvial and terrace aquifer for the years for this time period. The 1982 permitted pumpage rates were used for projections for 1983 to 2020. The estimated volume of water in storage was 1,940,000 acre-feet in 1982. Because the estimated recharge rate is equal to the allowed pumpage rate in 1982, the projected volume of water in storage in both 1993 and 2020 was 1,890,000 acre-feet.

Havens, J. S.

1989-01-01

27

Alluvial deposits and plant distribution in an Amazonian lowland megafan  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

28

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

29

Climatic, eustatic, and tectonic controls on Quaternary deposits and landforms, Red Sea coast, Egypt  

SciTech Connect

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, Egypt 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 stereophotogrammetric 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 coralline limestone deposits. Further, three distinct coral terraces are evident along the coastline. 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) parameterized 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 Quaternary to negligible values at present. 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. 33 refs., 18 figs., 2 tabs.

Arvidson, R.; Becker, R.; Shanabrook, A.; Luo, W.; Sultan, M. [Washington Univ., St. Louis, MO (United States)] [Washington Univ., St. Louis, MO (United States); Sturchio, N. [Argonne National Lab., IL (United States)] [Argonne National Lab., IL (United States); Lotfy, Z.; Mahmood, A.M. [Ain Shams Univ., Cairo (Egypt)] [Ain Shams Univ., Cairo (Egypt); El Alfy, Z. [Egyptian Geological Survey and Mining Authority, Cairo (Egypt)] [Egyptian Geological Survey and Mining Authority, Cairo (Egypt)

1994-06-10

30

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

Microsoft Academic Search

The Westwater Canyon Member is one of several large, low-gradient alluvial fans that compose the Morrison Formation in the Four Corners area. Morrison fans were deposited by major laterally migrating streams entering a broad basin bounded by highlands to the west and south. The Westwater Canyon sand framework consists of a downfan succession of 1) proximal braided channel, 2) straight

1980-01-01

31

Clay sized fraction and powdered whole-rock X-ray analyses from alluvial basin deposits in central and southern New Mexico  

USGS Publications Warehouse

As part of the study of the water quality and geochemistry of Southwest Alluvial Basins (SWAB) in parts of Colorado, New Mexico, and Texas, which is a Regional Aquifer-System Analysis (RASA) program, whole rock x-ray analysis and clay-size fraction mineralogy (x-ray) analysis of selected samples from alluvial basin deposits were done to investigate the types of minerals and clay types present in the aquifers. This was done to determine the plausible minerals and clay types in the aquifers that may be reacting with groundwater and affecting the water quality. The purpose of this report is only to present the whole rock x-ray and clay-fraction mineralogy data. Nineteen surface samples or samples from outcrop of Tertiary and Quaternary alluvial basin deposits in the central and southern Rio Grande rift were collected and analyzed. The analysis of the samples consisted of grain size analysis, and clay-size fraction mineralogy and semiquantitative analysis of the relative abundance of different clay mineral groups present. (USGS)

Anderholm, S. K.

1985-01-01

32

Depth dependence and exponential models of permeability in alluvial-fan gravel deposits  

NASA Astrophysics Data System (ADS)

To determine depth dependence of permeability in various geologic deposits, exponential models have often been proposed. However, spatial variability in hydraulic conductivity, K, rarely fits this trend in coarse alluvial aquifers, where complex stratigraphic sequences follow unique trends due to depositional and post-depositional processes. This paper analyzes K of alluvial-fan gravel deposits in several boreholes, and finds exponential decay in K with depth. Relatively undisturbed gravel cores obtained in the Toyohira River alluvial fan, Sapporo, Japan, are categorized by four levels of fine-sediment packing between gravel grains. Grain size is also analyzed in cores from two boreholes in the mid-fan and one in the fan-toe. Profiles of estimated conductivity, overline{K} , are constructed from profiles of core properties through a well-defined relation between slug-test results and core properties. Errors in overline{K} are eliminated by a moving-average method, and regression analysis provides the decay exponents of overline{K} with depth. Moving-average results show a similar decreasing trend in only the mid-fan above ˜30-m depth, and the decay exponent is estimated as ?0.11 m-1, which is 10- to 1,000-fold that in consolidated rocks. A longitudinal cross section is also generated by using the profiles to establish hydrogeologic boundaries in the fan.

Sakata, Yoshitaka; Ikeda, Ryuji

2013-06-01

33

Alluvial deposits liquefied by the Flims rock slide  

Microsoft Academic Search

The origin of the Bonaduz gravel (Switzerland) in the vicinity of the large Holocene Flims rock slide deposits has been discussed for a century. The internal structure shows many features that imply transport as an over-sized mud\\/debris stream. This flow of gravel, sand and fines must have been triggered by the mobilisation of the valley alluvium by the impact of

A. von Poschinger; Th. Kippel

2009-01-01

34

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

35

Alluvial deposits liquefied by the Flims rock slide  

NASA Astrophysics Data System (ADS)

The origin of the Bonaduz gravel (Switzerland) in the vicinity of the large Holocene Flims rock slide deposits has been discussed for a century. The internal structure shows many features that imply transport as an over-sized mud/debris stream. This flow of gravel, sand and fines must have been triggered by the mobilisation of the valley alluvium by the impact of the rock slide. The mobilised mud with a volume of several 100 million m 3 must have had enormous transport capacities as large units of loose material were transported over kilometres without breaking apart. Accordingly, the shear forces in the flow must have been negligible. Similar features have been found at several other sites in the Alps, all in the vicinity of large rock slides. Our interpretation of these sediments as catastrophic mass movement deposits suggests that such events could happen again, also in other parts of the world.

von Poschinger, A.; Kippel, Th.

2009-01-01

36

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

37

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

PubMed

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

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

2008-07-29

38

Luminescence chronology of river adjustment and incision of Quaternary sediments in the alluvial plain of the Sabarmati River, north Gujarat, India  

Microsoft Academic Search

River adjustment and incision in the Sabarmati basin, Gujarat, India have been examined at a site near Mahudi. Towards this, the morphostratigraphy and depositional chronometry of the middle alluvial plains were investigated. The upper fluvial sequence, along with the overlying aeolian sand and riverbed scroll plains, provide clues to the evolution of the present Sabarmati River. Sedimentological analyses of the

Pradeep Srivastava; Navin Juyal; Ashok K Singhvi; Robert J Wasson; Mark D Bateman

2001-01-01

39

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

NASA Astrophysics Data System (ADS)

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

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

2009-04-01

40

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

41

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

NASA Astrophysics Data System (ADS)

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). The deposits are considered Tertiary in age and chronocorrelated with those identified in the Atibaia region and at other sites up to 100 km east and northeast of Jundiaí. The depositional model adopted to explain the filling of the basin proposes that the alluvial fans, which directly derive from the source area, terminated in a braided channel longitudinal to the basin axis that flowed to northwest, in a similar configuration to that of the present day. This basin may have extended to the Atibaia region or formed a set of small basins laterally contiguous to the faults associated with the rift. Such occurrences show that the formation of rift basins was broader than the area presently occupied by the main deposits.

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

2005-09-01

42

Late Quaternary carbonate deposition at the bottom of the world  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

43

A geophysical survey of faulted alluvial ''terrace'' deposits near Pembroke, Virginia  

SciTech Connect

Shallow excavation of alluvial ''terrace'' deposits near Pembroke, Virginia has exposed an antiform cut by high angle faults. Seismic refraction measurements reveal the ''terrace'' deposits are more than 40 m thick. P-wave velocities ranging between 719 m/s and 1,578 m/s indicate lateral inhomogeneity in these deposits which consists of clay and sand units interbedded with cobble and boulder units. P-wave velocity is 3,200 m/s in the underlying bedrock indicating the same broken limestone terrane which is exposed beyond the borders of the alluvial ''terrace'' deposits. Anomalies on electrical resistivity pseudo-sections prepared from roll-along offset soundings suggest that faulted structure may extend more than 100 m WSW from the excavation where it is exposed. A gravity survey over the area south and west of the excavation reveals a linear anomaly extending more than 200 m in a SW direction parallel to, but offset from faults exposed by the excavation. The 0.3 mgal change across the 30 m width of this anomaly is too large to attribute only to a linear bedrock escarpment or only by a linear density contrast within the unconsolidated sediment. Other local gravity anomalies of less than 0.2 mgal also appear to be related to density variations within the ''terrace'' deposits. Analysis of Bouguer gravity differences at seismic control-points indicate average density values of approximately 1.8 g/cm[sup 3] for the unconsolidated ''terrace'' deposits, and 2.4 g/cm[sup 3] for the broken limestone directly beneath. Magnetic field intensity values measured at the gravity observation sites indicate several local anomalies of between 10 nT and 20 nT.

Robinson, E.S.; Sayer, S.; Phinney, E.J.; Law, R.D. (Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States). Dept. of Geological Sciences)

1994-03-01

44

Mineral Occurrence, Translocation, and Weathering in Soils Developed on Four Types of Carbonate and Non-carbonate Alluvial Fan Deposits in Mojave Desert, Southeastern California  

NASA Astrophysics Data System (ADS)

Soil geomorphology and mineralogy can reveal important clues about Quaternary climate change and geochemical process occurring in desert soils. We investigated (1) the mineral transformation in desert soils developed on four types of alluvial fans (carbonate and non-carbonate) under the same conditions of climate and landscape evolution; and (2) the effects of age, parent materials, and eolian processes on the transformation and translocation of the minerals. Four types of alluvial-fan deposits along the Providence Mountains piedmonts, Mojave Desert, southeastern California, USA were studied: (1) carbonate rocks, primarily limestone and marble (LS), (2) fine-grained rhyodacite and rhyolitic tuff mixed with plutonic and carbonate rocks (VX), (3) fine- to coarse- grained mixed plutonic (PM) rocks, and (4) coarse-grained quartz monzonite (QM). These juxtaposed fan deposits are physically correlated in a small area (about 20 km by 15 km) and experienced the same climatic changes in the late Pleistocene and Holocene. The soils show characteristic mineral compositions of arid/semiarid soils: calcite is present in nearly all of the samples, and a few of the oldest soils contain gypsum and soluble salts. Parent material has profound influence on clay mineral composition of the soils: (1) talc were observed only in soils developed on the volcanic mixture fan deposits, and talc occurs in all horizons; (2) palygorskite occur mainly in the petrocalcic (Bkm) of old soils developed on the LS and VX fan deposits, indicating pedogenic origin; (3) chlorite was observed mainly in soils developed on VX fan deposits (all ages) and on some LS deposits, but it is absent in soils developed on PM and QM fan deposits; and (4) vermiculite was common throughout soils developed on plutonic rock fan deposits. These mineralogical differences suggest that minerals in the soils are primarily inherited from their parent materials and that mineral weathering in this area was weak. Except the abundance of palygorskite, soils developed on alluvial fans with different ages (4,000 to 200,000 yrs old) did not show other distinct mineralogy difference as a function of age or soil development, which supports the weak weathering of the soils. The results suggest that the clays in the argillic horizons are primarily derived from the accumulation of desert dust, and with time, are translocated into subsoil horizons. The pedogenic accumulation of dust is a soil-geomorphic process common to the Mojave Desert, as well as other deserts in the world.

Deng, Y.; McDonald, E. V.

2007-12-01

45

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

Microsoft Academic Search

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

Donald S. Sweetkind; Ronald M. Drake II

2007-01-01

46

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

47

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

48

The deep channel and alluvial deposits of the Ohio Valley in Kentucky  

USGS Publications Warehouse

The alluvial deposits of Pleistocene age in the Ohio Valley form a ground-water reservoir of large storage capacity and yield. In this region it is the only source of large supplies of water that are both cool and of good quality the year round. The reservoir is heavily drawn upon, yet has very large potentialities for future development because of the favorable conditions for both natural and artificially induced infiltration of water from the river into the alluvial deposits. The principal features of the Ohio Valley were formed during the Pleistocene, or glacial, epoch. The drainage area upriver from Cincinnati was added when ice first advanced south, blocked rivers draining northwestward off the Appalachians, and diverted their waters southwest into the headwaters of the early Ohio River. A deep channel, the bottom of which is at a lower altitude than the present river bed, was excavated before the third (Illinoian) glacial stage. The thick body of sand and gravel that now lies in the deep channel was deposited by floods of melt water as the ice sheet of the Wisconsin stage melted away from the Ohio basin. The vertical distance between river pool level and the base of the old channel increases from 25 feet at Ashland, Ky., to 110 feet at the mouth of the river, for the old channel has a steeper gradient than the present river. The width of the bedrock valley ranges from half a mile at one point near Cincinnati to almost 10 miles near Uniontown, Ky. Where the valley is narrow, the flat-floored deep channel extends from one side of the valley to. the other. Where the valley is wide, the deep channel occupies only part of the width of the valley, the rest being underlain by rock benches mantled with alluvium. The alluvium consists of a sheet of sand and gravel overlain by a thinner layer of silt and clay. The sheet of sand and gravel is continuous across and up and down the valley, and at most places along the valley it is exposed in part of the river channel. The gravel is coarse and cobbly near Cincinnati but finer downstream, and near Paducah most of it is no larger than pea size. The thickness of water-saturated sand and gravel increases downvalley in the same way as does the distance between river level and the base of the old channel, roughly from 2b to 110 feet. The storage coefficient is likely to about 0.2, or 1.5 gallons of water per cubic foot of sand and gravel.

Walker, Eugene H.

1957-01-01

49

Depositional environment mapping in alluvial plains based on wetness seasonal changes  

NASA Astrophysics Data System (ADS)

Depositional environment mapping in alluvial plains is a basic step in geomorphological, pedological and archaeological studies, where remotely sensed data give an indirect contribution in assessing soil moisture, which could be correlated to sediment texture. However, a textural discrimination based on soil wetness is strictly season- dependent, and any procedure used to map different deposits from remotely sensed data fails when the acquisition time is not appropriate, and the appropriate time is generally different for the various sediments in a study area; hence the need for a multitemporal approach. In the present study a multitemporal Wetness (Tasseled Cap Transformation, TCT) analysis has been performed on the Pisa plain (Central Italy), in order to reconstruct the environment hosting a Roman harbour which seems to be one of the most important Roman harbors ever discovered, as is emerging from the archaeological excavation in progress. Four geocoded and atmospheric corrected images, acquired in March, July, October and December 1991, were processed to obtain just as many Wetness maps. Wetness multitemporal images were produced, and the seasonal changes of this parameter were correlated with grain-size characteristics in selected points in which the soil was bare at each flying over. A Principal Component Analysis on Wetness images was also carried out and synthetic images were produced. Out of all the images, a reliable textural discrimination in the study area was obtained, together with palaeo-geographical information useful in order for a better understanding of the role of the ancient harbor.

Pranzini, Enzo; Santini, Carolina

1999-12-01

50

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

51

Alluvial sinkholes over gypsum in the Ebro basin (Spain): genesis and environmental impact  

Microsoft Academic Search

The Ebro Basin is located in the northeast of Spain. Its central part is filled with gypsum and carbonate deposits of Neogene age. Quaternary sediments overlie the Tertiary layers. Alluvial sinkholes have developed in this region, causing high economic losses. From the study of aerial photographs, from the compilation of historical cases of collapse and from data on the lithological

M. A. SORIANO; J. L. SIMON; J. GRACIA; T. SALVADOR

52

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

2007-06-01

53

Seismic stratigraphy of the Upper Pliocene and Quaternary deposits in the South Caspian Basin  

Microsoft Academic Search

More than 10,000 km of seismic data were used for seismic stratigraphic analysis and differentiation of major depositional environments of Upper Pliocene and Quaternary strata in the central deepwater and eastern parts of the South Caspian Basin (SCB). The study shows that the conventional sequence stratigraphy concept works well in the South Caspian Basin. Clinoform complexes within Paleo-Amudarya shelf margin

N. R Abdullayev

2000-01-01

54

Tectonic and climatic influences on the deposition and preservation of Quaternary units along the range-front of the Manastash Anticline, Yakima Fold Belt, Washington  

NASA Astrophysics Data System (ADS)

Based on multiple independent data sets, we infer episodic base-level lowering of the Kittitas Valley relative to tributaries flowing northward off the Manastash Ridge range-front and within the neighboring Lower Yakima River Canyon of central Washington. Manastash Ridge is a southeast-striking anticline within the Yakima fold and thrust belt, which deforms the extensive Miocene Columbia River Basalt flows that cover the region. Understanding the roles of climate aggradation and degradation cycles in concurrence with tectonic faulting along Manastash Ridge suggests both have contributed to the landscape evolution of the southern Kittitas Valley and Manastash range-front. Previously described proglacial outwash terraces within the northern Kittitas Valley and Upper Yakima River Canyon document periods of aggradation followed by fluvial degradation and entrenchment due to alteration in hillslope sediment production and transport capacity related to glacial and interglacial conditions. Luminescence age determinations and tephrochronology for Manastash range-front Quaternary units yield preliminary timing for aggradation of alluvial units, which we correlate to the late Pleistocene (MIS Stage V) glacial-interglacial climate transition. Seismic-reflection imagery, LiDAR, aeromagnetic surveys, and field mapping of Quaternary deposits reveal fault scarp lineaments within the Manastash range-front, west of the canyon entrance. We suggest these scarps are related to a series of north-verging thrust faults accommodating growth of the Manastash anticline. These faults isolate and uplift fan complexes, each complex generated during climate conditions favorable to fan aggradation. Entrenched alluvial fan deposits along the rangefront, strath terrace sequences, coincident knickpoints within tributary longitudinal profiles, and fault scarp lineaments suggest uplift rates of 0.02 to 0.2 m/1000yrs.

Ladinsky, T. C.; Kelsey, H. M.; Sherrod, B. L.; Mahan, S.; Pratt, T. L.; Blakely, R. J.

2012-12-01

55

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

56

Geochemical survey on faults overland with alluvial deposits, part 1. Application for the Neodani and the Atera faults survey  

NASA Astrophysics Data System (ADS)

The effectiveness of the geochemical survey was evaluated as a technique for investigating the fault which is overlaid with alluvial deposits. This was done, using underground gas as the indicator, at the Neodani Fault (NF) and Atera Fault (AF) where the location of faults has been known by the trenches. Five measuring lines were established normally crossing with the NF. Measuring points at AF were selected at crossing points of 15 to 30 m grids in an area of 90 m in the south to north direction and 150 m in east to west direction. Several zones with commonly high ratios of He/Ar and Ne/Ar and Rn concentration were found, and zones that coincide with the faults were observed in both areas. At zones with high concentrations and those corresponding to the faults, high values of He/Ar and Ne/Ar ratios distributed immediately above faults and high Rn concentations were found at the hanging wall side. Some zones other than those with confirmed faults have shown high values of concentrations, suggesting other faults overlaid under the alluvial deposits.

Kiho, Kenzo; Kanaori, Yuji

1988-08-01

57

Application of rock varnish dating of quaternary surficial deposits in determining times of fault movement  

SciTech Connect

Rock varnish, a coating commonly found on rock surfaces in arid and semiarid regions, has a significant potential in paleoseismic studies, as a wide variety of Quaternary surfaces and surficial deposits can be dated with the rock varnish technique. If the formation of geomorphic surfaces or surficial deposits can be related to times of faulting or if faulting has broken or deformed such features, then rock varnish dating can be used to constrain maximum and minimum times of motion on the related fault.

Harrington, C.D.

1987-01-01

58

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

USGS Publications Warehouse

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

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

2004-01-01

59

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

NASA Astrophysics Data System (ADS)

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

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

1995-07-01

60

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

Microsoft Academic Search

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

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

1998-01-01

61

Paleohydrological implications of late Quaternary fluvial deposits in and around archaeological sites in Syria  

NASA Astrophysics Data System (ADS)

The importance of fluvial processes to the development of late Quaternary landforms in arid regions is well established, particularly for the American Southwest. In contrast, much less information exists about past fluvial processes for other arid regions, such as Arabic countries in the Middle East. This paper reviews the characteristics of late Quaternary fluvial deposits and landforms in Syria, an arid country with little previous Quaternary geomorphic research. Relatively detailed information has been obtained from areas adjacent to archaeological sites because of collaborative activities with geomorphologists and other geoscientists. Such activities have resulted in intensive field surveys, and associated results of complementary archaeological studies of lithic artifacts are useful for establishing the chronology of fluvial deposits. Although the number of existing studies is limited, the available information points to marked changes in the mode of fluvial processes in response to late Quaternary climatic change. Fluvial sedimentation was enhanced during the wet periods of MIS 3-4, the Pleistocene-Holocene transition, and the mid-Holocene. In contrast, the LGM was characterized by limited fluvial sedimentation under a drier climate as well as enhanced carbonate precipitation near the land surface to form calcrete and oncoids.

Oguchi, Takashi; Hori, Kazuaki; Oguchi, Chiaki T.

2008-10-01

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

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

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

64

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

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

Comparison of high-resolution P- and SH-wave reflection seismic data in alluvial and pyroclastic deposits in Indonesia  

NASA Astrophysics Data System (ADS)

Seismic reflection is one of the stable methods to investigate subsurface conditions. However, there are still many unresolved issues, especially for areas with specific and complex geological environments. Here, each location has an own characteristic due to material compounds and the geological structure. We acquired high-resolution, P-and SH-wave seismic reflection profiles at two different locations in Indonesia. The first location was in Semarang (Central Java) and the second one was in Tiris (East Java). The first region is located on an alluvial plain with thick alluvial deposits of more than 100 m estimated thickness, and the second location was located on pyroclastic deposit material. The seismic measurements for both locations were carried out using a 48-channel recording system (14-Hz P-wave, 10-Hz SH-wave geophones) with geophone intervals of 5 m (P-waves) and 1 m (SH-waves), respectively. The seismic source for the P-wave was a ca. 4 kg sledge hammer which generated a seismic signal by by hitting on an aluminum plate of 30x30 cm, whereas the SH-wave source was a mini-vibrator ELVIS (Electrodynamic Vibrator System), version 3. Thirteen seismic profiles at Semarang and eighth profiles at Tiris were acquired. The results of seismic data in Semarang show fair to good seismic records for both P-and SH-waves. The raw data contain high signal-to-noise-ratio. Many clear reflectors can be detected. The P-wave data shows reflectors down to 250 ms two-way time while the SH-wave records show seismic events up to 600 ms two-way time. This result is in strong contrast to the seismic data result from the Tiris region. The P-wave data show very low signal to noise ratio, there is no reflection signal visible, only the surface waves and the ambient noise from the surrounding area are visible. The SH-waves give a fair to good result which enables reflector detection down to 300 ms two-way time. The results from the two seismic campaigns show that SH-wave reflection seismic seems to be the suitable method, which could be applied in Indonesia mainly in both alluvial and pyroclastic regions. In contrast, P-wave energy in the pyroclastic area is strongly attenuated and scattered within the uppermost layer. This prevented that the P-wave seismic signal reaches deeper reflectors, and therefore seismic P-wave records contain only noise from surface waves and ambient noise from the surrounding area, without any reflection signal.

Wiyono, Wiyono; Polom, Ulrich; Krawczyk, Charlotte M.

2013-04-01

67

Fossil oribatid mites (Acari, Oribatida) from the Florisbad Quaternary deposits, South Africa  

NASA Astrophysics Data System (ADS)

In a pioneer application of acarology to Quaternary fossil-bearing sediments in southern Africa, the oribatid composition in the Florisbad Quaternary sediments was determined and compared to the currently known distribution of those species. Nine species of oribatid mites were recorded in the Holocene aeolian deposits of the third test pit, three species from the Middle Stone Age (MSA) horizon sediments of the third test pit, and thirteen species from the Holocene spring sediments. The Florisbad results indicate a better agreement between the oribatid fauna of the last interglacial MSA horizon of the third test pit and the organic-rich mid-Holocene deposits near the spring than between either of these and early- and late-Holocene aeolian sediments of the third test pit, suggesting some similarity in microsedimentary environments. The majority of the species recorded in the sediments are parthenogenetic and can be regarded as pioneer species.

Coetzee, Louise; Brink, James S.

2003-03-01

68

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

69

Late Quaternary depositional history of Alaskan Beaufort Shelf  

SciTech Connect

Diverse nonmarine and shallow marine deposits blanketing the coastal plain and continental shelf of northern Alaska are known collectively as the Gubik Formation. In the Beaufort coastal region between Barrow and Prudhoe Bay and along the Chukchi coastline southwest of Barrow, five distinct marine subunits have been recognized with the Gubik, ranging in age from middle Pliocene to late Pleistocene. A sixth pre-Holocene transgressive marine subunit, about a meter thick and bearing abundant ice-striated dropstones that originated in the Canadian Arctic Islands, is present along much of the Alaskan Beaufort coast. The aggregate thickness of the Gubik Formation on the coastal plain is no more than a few tens of meters. Offshore beneath the Beaufort shelf, however, the Gugik Formation is locally thicker than 100 m and includes not only deposits that probably correlate with those mapped onshore but also subunits of intermediate and younger ages. These have been studied mainly through the interpretation of a network of high-resolution seismic reflection profiles that covers most the Alaskan Beaufort shelf at 18 to 35-km intervals seaward of the 25-m isobath.

Dinter, D.

1985-04-01

70

A deformed Pliocene-Quaternary alluvial and red paleosol succession in the Eastern Betics: Paleomagnetic, rock-magnetic and sedimentological pilot study  

Microsoft Academic Search

Summary  An integrated pilot paleomagnetic and sedimentological study has been conducted in the Neogene-Quaternary infilling materials of the Bajo Segura Basin (Eastern Betics, SE Spain). The studied sediments belong to the youngest (late Pliocene-Quaternary) lithostratigraphic unit of the basin (P-Q unit). The statistical analysis of tectonic striations and stylolitic dissolutions on the conglomerate limestone clasts indicates a NNW-SSE maximum compression direction.

Jaume Dinarès-Turell; Pedro Alfaro; Jesús Soria

1995-01-01

71

Bank accretion and the development of vegetated depositional surfaces along modified alluvial channels  

USGS Publications Warehouse

This paper describes the recovery of stable bank form and development of vegetated depositional surfaces along the banks of channelized West Tennessee streams. Most perennial streams in West Tennessee were straightened and dredged since the turn of the century. Patterns of fluvial ecological responses to channelization have previously been described by a six-stage model. Dendrogeomorphic (tree-ring) techniques allowed the determination of location, timing, amount, and rate of bank-sediment deposition. Channel cross sections and ecological analyses made at 101 locations along 12 streams, encompassing bends and straight reaches, show that channel and bank processes initially react vertically to channelization through downcutting. A depositional surface forms on banks once bed-degradation and heightened bank mass wasting processes have eased or slowed. The formation of this depositional surface marks the beginning of bank recovery from channelization. Dominating lateral processes, characteristic of stable or natural channels, return during the formation and expansion of the depositional surface, suggesting a relation with thalweg deflection, point-bar development, and meanderloop extension. Characteristic woody riparian vegetation begins to grow as this depositional surface develops and becomes part of the process and form of restabilizing banks. The depositional surface initially forms low on the bank and tends to maintain a slope of about 24??. Mean accretion rates ranges from 5.9 cm/yr on inside bends to 0 cm/yr on most outside bends; straight reaches have a mean-accretion rate of 4.2 cm/yr. The relatively stable, convex upward, depositional surface expands and ultimately attaches to the flood plain. The time required for the recovery process to reach equilibrium averaged about 50 years. Indicative pioneer speccies of woody riparian vegetation include black willow, river birch, silver maple, and boxelder. Stem densities generally decrease with time after and initial flush of about 160 stems per 100 m2. Together bank accretion and vegetative regrowth appear to be the most important environmental processes involved in channel bank recovery from channelization or rejuvenation. ?? 1991.

Hupp, C. R.; Simon, A.

1991-01-01

72

Triassic alluvial braidplain and braided river deposits of the La Ternera Formation, Atacama region, northern Chile  

NASA Astrophysics Data System (ADS)

The La Ternera Formation is a thick (>2,100 m) succession of terrigenous clastic sediments, with andesitic and basaltic intercalations, exposed in the Quebrada de Paipote area of the Atacama Region, northern Chile. The strata were deposited in an active rift basin during Late Triassic to (?) Early Jurassic times. The lower 1,000 m of the studied elastic succession comprises pebbly granule paraconglomerates, unconformably overlying Upper Paleozoic sedimentary successions, volcanics, and granitoids. These sediments were derived from the east and are interpreted as braid-plain deposits. The upper 800 m of the succession comprises interbedded orthoconglomerates, sandstones and mudstones. Abundant plant fossils include trees in growth position and carbonaceous horizons. Small scale depositional cycles were the product of migrating braided-river channel systems. Larger scale successions resulted from tectonic uplift. The sediments of the La Ternera Formation were derived predominantly from a tectonically uplifted area of Upper Paleozoic acidic volcanic and plutonic rocks (Pantanoso Formation, Choiyoi Group). Active uplift on the eastern margin of the sedimentary basin probably occurred along north-south trending faults. Continued subsidence of the basin resulted in a Sinemurian to Bajocian marine transgression. Occurrences of Triassic andesitic and basaltic volcanic rocks both to the west and the east of the La Ternera formation suggest deposition in an intea-volcanic graben or half-graben.

Bell, C. M.; Suárez, M.

1995-01-01

73

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

74

Triassic alluvial braidplain and braided river deposits of the La Ternera Formation, Atacama region, northern Chile  

Microsoft Academic Search

The La Ternera Formation is a thick (>2,100 m) succession of terrigenous clastic sediments, with andesitic and basaltic intercalations, exposed in the Quebrada de Paipote area of the Atacama Region, northern Chile. The strata were deposited in an active rift basin during Late Triassic to (?) Early Jurassic times.The lower 1,000 m of the studied elastic succession comprises pebbly granule

C. M Bell; M Suárez

1995-01-01

75

A methodological toolkit for field assessments of artisanally mined alluvial diamond deposits  

USGS Publications Warehouse

This toolkit provides a standardized checklist of critical issues relevant to artisanal mining-related field research. An integrated sociophysical geographic approach to collecting data at artisanal mine sites is outlined. The implementation and results of a multistakeholder approach to data collection, carried out in the assessment of Guinea’s artisanally mined diamond deposits, also are summarized. This toolkit, based on recent and successful field campaigns in West Africa, has been developed as a reference document to assist other government agencies or organizations in collecting the data necessary for artisanal diamond mining or similar natural resource assessments.

Chirico, Peter G.; Malpeli, Katherine C.

2014-01-01

76

Chronology of Quaternary loess deposits of Uzbekistan on the basis of paleomagnetic data  

NASA Astrophysics Data System (ADS)

Let us consider the basic concepts that define the physical phenomena underlying the magnetic stratigraphy: - Secular variations - the characteristic features of the main geomagnetic field, covering a wide range of cyclic changes of the magnitude and direction of the geomagnetic field from tens to thousands of years and having different specific characteristics and the different nature; - Excursions - short geomagnetic events in which the virtual geomagnetic pole deviates from its position in the 60-180°, and then returns to its original position without changing the sign of polarity with duration 102Quaternary loess deposits in Uzbekistan have established short-term deviations of the geomagnetic field of the Quaternary period. The main results: 1. It was found that the Quaternary loess deposits of Uzbekistan have measurable residual magnetization and are suitable for paleomagnetic studies. In regard to paleomagnetic they are quite informative; they recorded as a stable period, and the fine structure of the geomagnetic field of the Quaternary period. The history of the geomagnetic field is equally recorded in all studied genetic types of sediments for various parts of the region and can be used for detailed correlation of loess sections. Fine structure of the geomagnetic field can serve as a regional stratigraphic frame. 2. In the layers of loess deposits are set the direct and reverse of polarity of geomagnetic field that are used as paleomagnetic indicators of correlation of loess deposits. The loess deposits of the Quaternary period have following of geomagnetic zones: the sediments of Eopleistocene have six reverse zones and five straight magnetized episodes, sediments of Neopleistocene have four straight magnetized area and the same short-term deviations, the sediments of Holocene has straight magnetized zone that have three short-term deviations. 3. In the loess deposits are set short-term deviations of the geomagnetic field, which belong to the epoch of Matuyama and Brunhes.

Toychiev, H. A.; Stelmakh, A. G.

2011-12-01

77

Evolution of the late Holocene terraces in the hanging wall of the Chihshang Fault: interactions between alluvial fan deposition and fault uplift  

NASA Astrophysics Data System (ADS)

In this study, we aim at studying the interactions between alluvial fan deposition and reverse fault uplift through analyzing the genesis of the terraces and their evolution in Chihshang area. Located in eastern Taiwan, the NNE-SSW trending Longitudinal Valley is the plate suture between the Philippine Sea plate and Eurasia. The east-dipping Longitudinal Valley Fault (LVF), often on the eastern side of the valley, is the major fault of this suture zone. The Chihshang area is located in the central-southern Longitudinal Valley, where the Chihshang Fault cuts through the eastern edge of the Xinwulyu River alluvial fan, one of the major alluvial fans. The Chihshang Fault is one of the most active segments of the LVF with a continuous uplifting rate up to ~3 cm/yr. A series of fan terraces with different height distribute on the hanging wall, where the front of the alluvial fan was uplifted by the reverse fault. Because of the special geological settings of this area, by studying the evolution of the terraces we could get insights on both the deposition behavior of the alluvial fan and the long term uplift rate of Chihshang Fault, and furthermore, their interactions through the late Holocene. We used 5-m high-resolution DEM and aerial photographs to identify the terraces and characterize their geomorphic features. We also distinguished the Xinwulyu River alluvial fan terraces from other terraces formed by other tributary rivers based on the lithology of terrace deposit as well as the geomorphic characters. Several outcrops and six trenches of 3-6 m depth allow us to analyze the composition of the fan terraces and to collect dating materials. Fan terraces are distinguished into ten levels according to height difference relative to the present fan surface. Terraces belonging to same level were assumed to form at similar time period. The lower the terraces, the better the terraces preservation, and the larger the terraces surface area. Distribution of terrace is not geographically uniform: higher levels (T5-T9) and the lowest level (T1) are mainly found on northern part, while medium levels (T2-T4) can only be found on southern part. Assuming that the long-term fault uplifting is a nearly continuous creeping process, the genesis of terraces should have also been influenced by the periodic deposition process of alluvial fan. Each level of terraces represents a major deposition episode of the Xinwulyu River. These deposition episodes might indicate period with larger river sediment flux. However, each deposition episode might not have the same influenced area, which caused the different fan terraces character in different areas. Most of the terraces are found to have secondary deposits covering over the fluvial gravels. The thickest is found on one T5 terrace, which is composed of homogeneous fine-grain sediments and with thickness up to five meters. The source is hard to tell from the field observation, but the radiocarbon dating results of the datable materials (most are charcoals) found a reverse time-series in the ages of around 9,000-40,000 BP cal., which implies the steady erosion and redeposition process from an old pre-existing terrace. These results allow us to reconstruct the evolution of the terraces, and the mechanisms behind it.

Chang, Q.; Lee, J.; Wang, S.; Chen, R.; Chen, Y.

2012-12-01

78

Extensive Quaternary aeolian deposits in the Drakensberg foothills, Rooiberge, South Africa  

NASA Astrophysics Data System (ADS)

Deposits of aeolian sand are known to have accumulated in periglacial environments during the cold phases of the late Quaternary. In many instances, however, they form low-relief topographic units which may not be readily identified without detailed field survey. This study aims to use a multidisciplinary approach, combining remotely sensed data analysis and field survey, to investigate the extent and palaeoenvironmental significance of sand ramps in the Drakensberg/Rooiberge foothills of South Africa. Analysis of Google Earth™ imagery has demonstrated that gully systems are a common component of the landscape, and heterogeneously distributed across the landscape. Field investigation confirmed the hypothesis that the gullies are mainly eroding into sand ramps of fine sands and very coarse silts which mantle many of the lower hillslopes of the region. These sand units include palaeosols and occasional gravel lags, but are otherwise remarkable for their homogenous composition, cross-bedding and the complete absence of clasts. Much of the sediment is thus interpreted as aeolian in origin. The deposits are sufficiently similar in many respects to the Masotcheni Formation, a late Quaternary colluvium which outcrops abundantly in the Drakensberg, to propose an assignation to this unit. However, an aeolian component in the Masotcheni has not previously been described. The distribution of aeolian accumulation in the region is consistent with southward transport during late Quaternary cold phases from a source on the Highveld to the north of the study area. The low relief and complex fluvial network in this region would concentrate sediment eroded from the Drakensberg/Rooiberge, which would subsequently be available for deflation when the balance between fluvial flow regime, seasonally frozen ground and north-westerly trade winds were optimal for aeolian entrainment. Deposition is primarily topographically controlled, and is in places sufficiently extensive that it may be better described as a discontinuous coversand. This study suggests that aeolian deposits may be overlooked in other environments subject to past periglacial landscape development, and develops a potential methodology by which this problem may be overcome.

Telfer, M. W.; Mills, S. C.; Mather, A. E.

2014-08-01

79

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

USGS Publications Warehouse

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

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

1977-01-01

80

Hydraulic and field water-chemistry characteristics of piedmont alluvial deposits in the Middle Tyger River near Lyman, Spartanburg County, South Carolina, 2005  

USGS Publications Warehouse

This study explores the possibility of developing a bank-filtration process to improve water quality in which alluvial deposits serve as a natural sand filter to pretreat water to be used as a secondary drinking-water source in a small piedmont reservoir along the Middle Tyger River near Lyman in Spartanburg County, South Carolina. From January 2004 to September 2005, data from 10 auger borings, 2 sediment cores, 29 ground-penetrating radar transects, and 3 temporary observation wells, and field water-chemistry data were collected and analyzed. These data were collected and used to characterize the lithology, geometry, hydraulic properties, yield potential, and water-chemistry characteristics of the alluvial deposits in the channel and on the right bank of the reservoir. The assessment was undertaken to determine if an adequate amount of water could be withdrawn from the alluvial deposits to sustain a bank-filtration process and to characterize the water chemistry of the surface water and pore water. The heterogeneous alluvial and fill material at the study site--clay, silty clay, clayey sand, fine- to coarse-grained sand, and mica--on the right bank of the Middle Tyger River ranges in thickness from 0.6 to 7 meters, has a calculated horizontal hydraulic conductivity of 1 meter per day, and yields approximately 0.07 liter per second of water. The small calculated horizontal hydraulic conductivity and water yield for these deposits restrict the use of the right bank as a potential bank-filtration site. The coarse-grained alluvial sand deposit in the channel of the Middle Tyger River, however, may be used for a limited bank-filtration process. The discharge during pumping of the channel deposit yielded water at the rate of 1.9 liters per second. The coarse-grained channel deposit is approximately 49 meters wide and 3 meters thick near the dam. At approximately 183 meters upstream from the dam, the channel narrows to roughly 9 meters and the channel deposits thin to approximately 0.1 meter. Slug tests conducted in the channel deposits near the dam produced a calculated horizontal hydraulic conductivity of 60 meters per day. The limited thickness and aerial extent of the coarse-grained channel deposits coupled with large horizontal hydraulic conductivity likely would allow rapid transmission of water and may degrade the effectiveness of some water-chemistry improvements typical of a bank-filtration process. Field water-chemistry data were collected for approximately 1 hour and 45 minutes at 10 to 15 minute intervals to compare the surface-water and pore-water quality in and beneath the channel of the Middle Tyger River. The waterchemistry data indicate that (1) the mean water temperature was higher in surface water (22.5 degrees Celsius) than in pore water (18.5 degrees Celsius), (2) the mean specific conductance was less in surface water (56.9 microsiemens per centimeter at 25 degrees Celsius) than in pore water (125.7 microsiemens per centimeter at 25 degrees Celsius), (3) alkalinity was lower in surface water (22.5 milligrams per liter) than in pore water (44.6 milligrams per liter), and (4) recorded pH values ranged between 6.2 and 6.3 in the surface water and pore water during the sampling period. The flow velocity was orders of magnitude slower in the pore water than in the surface water; therefore, the pore water interacts with the alluvial sediment for a longer period of time producing the variation in water-chemistry data between the two waters.

Harrelson, Larry G.; Addison, Adrian D.

2006-01-01

81

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

82

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

Microsoft Academic Search

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

S. Flint; E. J. Jolley; P. Turner; G. D. Williams; T. Buddin

1990-01-01

83

Relating lithofacies to hydrofacies: outcrop-based hydrogeological characterisation of Quaternary gravel deposits  

NASA Astrophysics Data System (ADS)

A considerable part of today's drinking water supplies in Europe and North America rely on clean groundwater from gravelly valley aquifers of Quaternary age. The sedimentary architecture, the distribution of lithofacies and of architectural elements in such heterogeneous deposits are of fundamental importance for the analysis of groundwater flow and contaminant transport. As the aquifers are not directly accessible for observation, representative outcrop analogues were used to study the sedimentology on a local scale. Conventional sedimentological classification schemes were adapted for the purpose of hydrogeological evaluations. Measurements of hydraulic properties were then used to define a set of 5 hydrofacies from 23 possible sediment lithofacies. A digital-photographic mapping procedure was developed to allow fast data acquisition in the field. The sedimentologically interpreted outcrops were stored in a GIS style database and thus allow the output for further sedimentological or hydrogeological analysis.

Klingbeil, Ralf; Kleineidam, Sybille; Asprion, Ulrich; Aigner, Thomas; Teutsch, Georg

1999-12-01

84

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

NASA Astrophysics Data System (ADS)

The late Quaternary marginal marine deposits along eastern Argentina (Southwestern Atlantic) are reviewed according to our present knowledge. In the northeastern coastal area of Buenos Aires Province they have been assigned to a series of transgressions and regressions ranging from the late Pliocene to the late Quaternary. The most widely accepted model is Frenguelli's (1957) classical chronostratigraphical scheme of: 'Belgranense', late Pleistocene marine sediments at 3-6 m above m.s.l. and ca. 26,000->35,000 14C years BP, the 'Querandinense', Pleistocene-Holocene estuarine sediments below or at present m.s.l., and the most extensive 'Platense', mid-Holocene marine deposits at 4.5-2 m above m.s.l. dated at ca. 8000-1340 14C years BP. The restricted 'Belgranense' deposits, recorded in Samborombon Bay, in Magdalena at ca. 32,000 BP, near Mar Chiquita at ca. 24,900 and 30,500 BP and southwards in Bahía Blanca at ca. 26,000-35,500 BP, may belong to an interstadial (González et al., 1986). The molluscan composition suggests a marine invasion of the area but not a typical interglacial cycle characterized by euhaline and warm water elements. However, the oxygen isotope record argues against an interstadial during the interval 34-27 ka and the chronological control for these deposits is very poor, suggesting that they most probably have been elevated neotectonically. The Pleistocene-Holocene 'Querandinense' deposits, extensively distributed along the Bonaerensian coastal plain and continental shelf (ca. 11,000 14C years BP), with very low faunal diversity, abundance of freshwater ostracods and absence of the warm water molluscs characteristic of the Holocene ridges, indicate low salinity and cool water conditions. Further dating and isotope analysis of these deposits are required for a better understanding of the chronology of climatic events by the end of the Pleistocene in this area and to establish whether or not they could correspond to the Younger Dryas event of the northern hemisphere. 'Platense' littoral ridges formed between ca. 7600 and 2500 BP extend in several subparallel rows from ca. 34° S to ca. 39° S. They formed either as beaches or possibly as sublittoral bars in Samborombon Bay, where they reach 120 km long, 10-30 m wide and up to 5 m thick at 4.5-5 m above m.s.l., or in the supratidal and intertidal zones in Mar Chiquita at 2-4 m above m.s.l. Molluscs and ostracods suggest a brackish marine to marine brackish environment of lower salinity than the modern Atlantic littoral. During the mid-Holocene, the oceanic waters were mixing with large amounts of Antarctic ice melting in the South Atlantic (Isla, 1990) probably reducing salinity along the Bonaerensian littoral. The oldest littoral ridges accumulated during the Hypsithermal and in the Punta Indio area, their different geometry and alignment, greatest age, highest diversity and warmer affinity of the molluscan fauna suggest a short interval of reversal of the atmospheric circulation pattern. Further research is necessary for a better understanding of the chronology of the marine late Quaternary deposits, coastal evolution and climatic changes in this area.

Aguirre, M. L.; Whatley, R. C.

85

Radiocarbon dating late Quaternary loess deposits using small terrestrial gastropod shells  

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

86

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

87

Radiocarbon dating late Quaternary loess deposits using small terrestrial gastropod shells  

USGS Publications Warehouse

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

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

2013-01-01

88

Trace metal-rich Quaternary hydrothermal manganese oxide and barite deposit, Milos Island, Greece  

USGS Publications Warehouse

The Cape Vani Mn oxide and barite deposit on Milos Island offers an excellent opportunity to study the three-dimensional characteristics of a shallow-water hydrothermal system. Milos Island is part of the active Aegean volcanic arc. A 1 km long basin located between two dacitic domes in northwest Milos is filled with a 35-50 m thick section of Quaternary volcaniclastic and pyroclastic rocks capped by reef limestone that were hydrothermally mineralized by Mn oxides and barite. Manganese occurs as thin layers, as cement of sandstone and as metasomatic replacement of the limestone, including abundant fossil shells. Manganese minerals include chiefly ?-MnO2, pyrolusite and ramsdellite. The MnO contents for single beds range up to 60%. The Mn oxide deposits are rich in Pb (to 3.4%), BaO (to 3.1%), Zn (to 0.8%), As (to 0.3%), Sb (to 0.2%) and Ag (to 10 ppm). Strontium isotopic compositions of the Mn oxide deposits and sulphur isotopic compositions of the associated barite show that the mineralizing fluids were predominantly sea water. The Mn oxide deposit formed in close geographical proximity to sulphide-sulphate-Au-Ag deposits and the two deposit types probably formed from the same hydrothermal system. Precipitation of Mn oxide took place at shallow burial depths and was promoted by the mixing of modified sea water (hydrothermal fluid) from which the sulphides precipitated at depth and sea water that penetrated along faults and fractures in the Cape Vani volcaniclastic and tuff deposits. The hydrothermal fluid was formed from predominantly sea water that was enriched in metals leached from the basement and overlying volcanogenic rocks. The hydrothermal fluids were driven by convection sustained by heat from cooling magma chambers. Barite was deposited throughout the time of Mn oxide mineralization, which occurred in at least two episodes. Manganese mineralization occurred by both focused and diffuse flow, the fluids mineralizing the beds of greatest porosity and filling dilatational fractures along with barite.

Hein, J.R.; Stamatakis, G.; Dowling, J.S.

2000-01-01

89

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

90

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

USGS Publications Warehouse

A catastrophic storm that struck the central Virginia Blue Ridge Mountains in June 1995 delivered over 775 mm (30.5 in) of rain in 16 h. The deluge triggered more than 1000 slope failures; and stream channels and debris fans were deeply incised, exposing the stratigraphy of earlier mass movement and fluvial deposits. The synthesis of data obtained from detailed pollen studies and 39 radiometrically dated surficial deposits in the Rapidan basin gives new insights into Quaternary climatic change and landscape evolution of the central Blue Ridge Mountains. The oldest depositional landforms in the study area are fluvial terraces. Their deposits have weathering characteristics similar to both early Pleistocene and late Tertiary terrace surfaces located near the Fall Zone of Virginia. Terraces of similar ages are also present in nearby basins and suggest regional incision of streams in the area since early Pleistocene-late Tertiary time. The oldest debris-flow deposits in the study area are much older than Wisconsinan glaciation as indicated by 2.5YR colors, thick argillic horizons, and fully disintegrated granitic cobbles. Radiocarbon dating indicates that debris flow activity since 25,000 YBP has recurred, on average, at least every 2500 years. The presence of stratified slope deposits, emplaced from 27,410 through 15,800 YBP, indicates hillslope stripping and reduced vegetation cover on upland slopes during the Wisconsinan glacial maximum. Regolith generated from mechanical weathering during the Pleistocene collected in low-order stream channels and was episodically delivered to the valley floor by debris flows. Debris fans prograded onto flood plains during the late Pleistocene but have been incised by Holocene stream entrenchment. The fan incision allows Holocene debris flows to largely bypass many of the higher elevation debris fan surfaces and deposit onto the topographically lower surfaces. These episodic, high-magnitude storm events are responsible for transporting approximately half of the sediment from high gradient, low-order drainage basins to debris fans and flood plains. ?? 2003 Elsevier Science B.V. All rights reserved.

Scott, Eaton, L.; Morgan, B. A.; Craig, Kochel, R.; Howard, A. D.

2003-01-01

91

Chronology of Quaternary coastal aeolianite deposition and the drowned shorelines of southwestern Western Australia - a reappraisal  

NASA Astrophysics Data System (ADS)

Aeolianite successions of low-gradient continental margins commonly show complex records of coastal dune deposition linked to a wide range of sea-level positions and climatic periods of the middle and late Pleistocene, recording both regional and broader-scale drivers of sediment production, coastal dune development and landform preservation. To better characterise the general pattern of sedimentation that occurs over Quaternary glacial-interglacial cycles on low-gradient, temperate carbonate continental shelves we examine the morphology, stratigraphy and age of aeolianite deposits in the Perth region, Western Australia. This includes an analysis of well-defined drowned coastal landforms preserved on the adjacent shelf. New and previously published optical ages provide a preliminary timeframe for the deposition of aeolianite in the Perth region and on Rottnest Island, 17 km offshore. An extensive aeolianite ridge near Perth, representing a former barrier, has Optically Stimulated Luminesence (OSL) ages that range from 120 ± 12 to 103 ± 10 ka (MIS 5e-5a in the context of associated age uncertainties). OSL ages for an exposure in the same ridge 2.5 km inland, record the onlap of much older aeolianite, OSL age 415 ± 70 ka, by shell-rich estuarine beds, OSL age 290 ± 30 ka. A further 5.5 km inland from the coast, two thick aeolianite units, separated by a well-developed palaeosol, have stratigraphically consistent OSL ages of 310 ± 30 and 155 ± 20 ka. In contrast, aeolianite units that form the northern coast of Rottnest Island have OSL ages of 77 ± 12 ka and 27 ± 5 ka. The new OSL ages and previously reported TL and U/Th ages indicate that the bulk of the island comprises dunes deposited around the end of the Last Interglacial sensu lato (MIS 5a-4) and during the Last Glacial (MIS 4-2), accumulating over a Last Interglacial coral reef and basal calcarenite. Drowned barrier and dune landforms preserved on the adjacent continental shelf reveal that barriers were formed during periods of intermediate sea level (e.g. MIS 3) and significant dune mobility occurred when the shelf was subaerially exposed. The pattern of shelf sedimentation discernible in the Perth region - large-scale coastal carbonate dune deposition during periods of high and intermediate sea level and reactivation during glacial lowstands - is largely consistent with published stratigraphic and age data for large-scale aeolianite deposits on other low-gradient carbonate shelves. Based on these data, a general model is proposed for the cycle of Quaternary sedimentation and landform evolution that occurs on these shelves, which are dynamic sedimentary environments with coastal landforms and sedimentary successions that are very sensitive to erosion and sediment reworking.

Brooke, B. P.; Olley, J. M.; Pietsch, T.; Playford, P. E.; Haines, P. W.; Murray-Wallace, C. V.; Woodroffe, C. D.

2014-06-01

92

Stratigraphy, petrochemistry and Quaternary depositional record of the Songaksan tuff ring, Jeju Island, Korea  

NASA Astrophysics Data System (ADS)

The Songaksan tuff ring (STR) is one of several recent hydrovolcanic centers on Jeju Island, Korea, which provides an excellent example of proximal-to-distal facies changes in wet pyroclastic surge deposits. A multidisciplinary study has been carried out on the STR and adjacent lithostratigraphic units to constrain absolute age, geochemical characteristics, and Quaternary depositional history. A number of rock units were identified inside the crater of the STR, including Scoria deposit I, trachybasalt lava, Scoria deposit II, and a late-stage basaltic tuff, indicative of a rather complex sequence of magmatic and phreatomagmatic eruptions after the construction of the tuff ring. Petrochemical analysis shows that the STR was generated from different magma batches that fractionated from a homogenous magma chamber, and the early erupted magma was more evolved and volatile-rich. Reworking of the STR commenced shortly after the hydromagmatic eruption in a high-energy nearshore environment, resulting in deposition of the Hamori Formation. The formation is composed of planar-stratified and low- to high-angle cross-stratified tuffaceous (pebbly) sandstones and occurs up to an altitude of about 4 m above present sea level. 14C dating of molluscan shells beneath the formation indicates that it began to be deposited after about 4000 yr BP. Detailed sedimentary logging reveals that the formation consists of several stratal packages bounded by laterally persistent and distinct lithologic boundaries, probably formed by millennial-scale sea-level fluctuations. Occurrence of another hydrovolcanic sequence (the Sinyangri Formation) on the opposite side of Jeju Island, having similar sedimentary characteristics and ages, suggests that the sea-level fluctuations as seen in the Hamori Formation have affected a wide area of Jeju Island, probably related to the high-frequency sea-level oscillations during the post-6 ka BP regression period in the East Asian region. It can be concluded that the formation of the STR was possible because of the Holocene transgression, which made the present coastal areas water-saturated and adequate for hydrovolcanic eruptions. The STR in turn contributed to record high-frequency sea-level fluctuations during the Holocene via acting as a local and short-lived but affluent source of loose sediment.

Sohn, Y. K.; Park, J. B.; Khim, B. K.; Park, K. H.; Koh, G. W.

2003-01-01

93

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

94

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

95

Composition and provenance of Late Pleistocene-Holocene alluvial sediments of the eastern Andean piedmont between 33 and 34° S (Mendoza Province, Argentina)  

NASA Astrophysics Data System (ADS)

The Andean cordillera, and its piedmont in the central western Argentina, has been long considered as one of the main source areas of detritus for the Chaco-Pampean plain sand dune fields and loess/loess-like deposits of central Argentina. The main goal of this study is to evaluate the composition of the late Pleistocene-Holocene alluvial deposits of the Andes cordillera piedmont, from 33° to 34° S. The results are interpreted in the context of the regional geology, tectonic setting of the study area and its implications in the continent-wide perspective of modern alluvial sands proposed by Potter (1994). Sampling was conducted at the alluvial stratigraphic sequences of four study sites along three Andean piedmont arroyos; modal mineralogy in the very fine sand fraction (3 phi to 4 phi) was determined using standard petrographic microscope methods. Q:F:LF average compositions indicate that the Late Pleistocene-Holocene very fine-grained alluvial sands of the Cordillera Frontal piedmont reflects the modern lithic arenites of the Argentine Association reported by Potter (1994). The results show two geologically distinct sources in the catchment areas, volcaniclastic and metamorphic rocks. High concentrations of mica and volcanic glass are likely related to particle morphologies and to the deposition sedimentary environment recorded in the alluvial sequences—floodplains. The overabundance of micas over the volcanic glass in the mid-late Holocene alluvial sequence indicates the drainage of a metamorphic area at the expense of other lithological sources. Source areas are located mainly in the Frontal cordillera, and to a lesser extent, in the piedmont Tertiary deposits, another likely source for the analyzed Quaternary alluvial sediments. The mineralogical signature of the late Pleistocene and Holocene alluvial sequences is in agreement with the composition of the southern Pampean sand mantles, loess and loess-like deposits mainly formed by a volcanic mineral assemblage with source areas placed at the headwaters of the main Andean rivers.

Mehl, A.; Blasi, A.; Zárate, M.

2012-12-01

96

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

97

Sedimentology and Age Control of Late Quaternary New Jersey Shelf Deposits  

NASA Astrophysics Data System (ADS)

High-resolution Chirp geophysical profiles have delineated a complex network of shallowly buried stratigraphic features within the New Jersey shelf. These features have been interpreted as fluvial channel incisions ("channels" horizon) and associated infill and regional erosional unconformities (e.g., "R" horizon) related to sea-level fluctuations during the late Quaternary. Age control on these features has been difficult to obtain, hindering geologic interpretations and stratigraphic model development. In addition, the ONR Geoclutter Initiative, also carried out on the New Jersey margin, is seeking to understand and model the interaction of these and similar buried structures with incident acoustic energy from tactical sonars. To address both these needs, drill cores were collected at 3 sites with the DOSECC AHC-800 from the RV KNORR in Sept-Oct 2002. Sites were selected from Chirp profiles to target prominent geologic features and cores were analyzed for texture, AMS C-14 age control and physical properties. These results will be integrated with complementary geophysical studies to provide a better understanding of the Quaternary geologic history of the New Jersey margin. Site 1 (129 m water depth) penetrated the outer shelf wedge, which has been interpreted as predominantly a submarine deltaic deposit. Sediments are sandy from 0-1.0 mbsf, and exhibit ages of ~7-10 kyr BP, whereas deeper than ~1.0 mbsf, sediments are clays interlaminated with silts and are much older, ~32 Kyr BP. This transition from sand to silty clay and a hiatus of 20 kyrs suggests transgression-related nearshore storage of coarser terrigenous material and outer shelf sediment starvation and/or erosion. Site 2 (80 m water depth) penetrated the axis of a large, infilled channel beneath the mid-shelf. These dominantly sandy channel-fill sediments have been previously interpreted as the infill of a fluvial/estuarine(?) system. Below the surficial sand sheet, from ~0.8-3.3 mbsf, ages fall between 12.8 and 12.3 kyr BP, whereas from ~4.0-10.8 mbsf, ages fall between 13.5 and 13.4 kyr BP. The boundary between these two units with distinct age ranges corresponds to a downcore change in dominant sediment type from sand to mud, suggesting a transition from estuarine to nearshore/open marine shelf conditions ~13 kyr BP. Site 3 (76 m water depth) penetrated through both the surficial sand sheet and the "R" erosional unconformity. Although sediments are similarly sandy throughout, ages above "R" are younger than ~10 kyr BP, whereas ages below "R" vary between ~40 and 35 ky BP, confirming previous interpretations of "R" as a lowstand erosional unconformity and/or a transgression-related hiatus.

Alexander, C.; Sommerfield, C.; Austin, J.; Christensen, B.; Fulthorpe, C.; Goff, J.; Gulick, S.; Nordfjord, S.; Nielson, D.; Schock, S.

2003-12-01

98

Oki sekisoka ni fukuzai suru danso no chikagaku chosa (1). Neodani danso Atera danso eno tekiyo. (Geochemical survey on faults overland with alluvial deposits (Part 1). Application for the Neodani and the Atera faults survey).  

National Technical Information Service (NTIS)

The effectiveness of the geochemical survey was evaluated as a technique for investigating the fault get overlaid in alluvial deposits. This was done, using underground gas as the indicator, at the Neodani (NF) and Atera faults (AF) where the location of ...

K. Kiho Y. Kanaori

1988-01-01

99

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

100

An Alluvial Fan at Apollinaris Patera, Mars  

NASA Astrophysics Data System (ADS)

The large fan-like deposit at Apollinaris Patera, Mars, is demonstrated from Mola, Themis and Moc data to have an alluvial origin, indicating that active volcanism and a caldera lake coexisted for an extended period of time.

Ghail, R. C.; Hutchison, J. E.

2003-03-01

101

Epiguruk: a late Quaternary environmental record from northwestern Alaska  

USGS Publications Warehouse

Epiguruk, a prominent bluff along the Kobuk River in northwestern Alaska, exposes a rich depositional record of Quaternary eolian and fluvial sand, with associated loess, paleosols, and periglacial features. Three major complexes of alluvial and eolian deposits are separated by two conspicuous organic-rich paleosols which formed during cool-moist interstadial intervals. Sediments between the two paleosols include eolian, channel, and floodplain deposits that formed during alluviation of the Kobuk River to a height of about 12m above the present level. The youngest depositional complex, which overlies the upper paleosol, is divisible into late Wisconsinan and Holocene components and into fluvial-channel, flood-plain, eolian-dune, sand-sheet, loess, and pond facies. Eolian sand from the active Kobuk sand sea overloaded the river during late Wisconsinan time, causing it to alluviate to about 13m above its modern level. The Holocene record reflects erosion and deposition by a small southern Tributary to the Kobuk River, downcutting by the Kobuk River toward its modern level, and subsequent erosion across a meander belt nearly 8km wide. 66 radiocarbon ages, many from rooted shrubs, provide a firm chronology for the past 35 k.y. at Epiguruk. -from Authors

Hamilton, T. D.; Ashley, G. M.

1993-01-01

102

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

103

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

104

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

105

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

106

Neogene-Quaternary contourite and related deposition on the West Shetland Slope and Faeroe-Shetland Channel revealed by high-resolution seismic studies  

Microsoft Academic Search

The Neogene and Quaternary sediments of the Faeroe-Shetland Channel and West Shetland shelf and slope rest upon a major regional unconformity, the Latest Oligocene Unconformity (LOU), and have been deposited through the interaction of downslope and parallel-to-slope depositional processes. The upper to middle continental slope is dominated by mass-transport deposits (debris flows), which progressively diminish downslope, and were largely generated

John E. Damuth; Hilary Clement Olson

2001-01-01

107

Delineation of Late Quaternary depositional sequences by high-resolution seismic stratigraphy, Louisiana continental shelf  

Microsoft Academic Search

Interpretations of over 20,000 line km of single-channel, high-resolution seismic reflection profiles, coupled with nearshore vibracores and logs of industrial platform borings, provide the data base for determining the history and stratigraphy of late Quaternary sea level fluctuations on the Louisiana continental shelf. Regional unconformities, formed by subaerial exposure of the shelf during glacio-eustatic sea level withdrawals and modified by

J. R. Suter; H. L. Jr. Berryhill; S. Penland

1987-01-01

108

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

109

Redoximorphic paleosols in alluvial and lacustrine deposits, 1.8 GA Lochness Formation, Mount Isa, Australia: Pedogenic processes and implications for paleoclimate  

SciTech Connect

Paleosols in the Lochness Formation (1.8 Ga, Australia) include both rare, non-red and abundant, strongly reddened varieties that formed at subaerial exposure surfaces in both ephemeral-river and lacustrine settings. Physical processes dominated non-red paleosols, which were characterized by repeated episodes of desiccation, shrinking, and cracking alternating with wetting and introduction of sand, silt, clay, and iron oxyhydroxides into planar voids. Redoximorphic (oxidation-reduction) processes were especially intense for the red paleosols; redox depletions of Fe and Mn (hypoalbans) occur immediately adjacent to desiccation-related macropores and peds, whereas redox concentrations of Fe and Mn (quasi-coatings) occur within paleosol matrix adjacent to redox depletions. Redoximorphic features indicate periodic water infiltration and saturation, accompanied by development of reducing conditions along planar macropores and ped surfaces in Lochness Formation paleosols. Variations in soil saturation were caused by seasonal fluctuations of lake level in lacustrine deposits, and by formation of perched saturation zones within floodplain deposits, respectively. Occurrences of red, hematitic paleosols in the Lochness Formation are compatible with previous interpretations of a weakly oxygenated 1.8 Ga paleoatmosphere. Redoximorphic features in the paleosols suggest a warm to cool temperate paleoclimate characterized by seasonal saturation, by analogy with Quaternary redoximorphic soils. A minimal concentration of organic C, possibly of microbial or bacterial origin, must have been present in these Proterozoic soils to allow for Fe reduction.

Driese, S.G. [Univ. of Tennessee, Knoxville, TN (United States). Dept. of Geological Sciences; Simpson, E.L. [Kutztown Univ., PA (United States). Dept. of Physical Sciences; Eriksson, K.A. [Virginia Polytechnic Institute and State Univ., Blacksburg, VA (United States). Dept. of Geological Sciences

1995-10-02

110

Integration of High and Very High-resolution Seismic Reflection Profiles to Study Upper Quaternary Deposits of a Coastal Area in the Western Gulf of Lions, SW France  

Microsoft Academic Search

High resolution (HR – sparker) and very high resolution (VHR – boomer) seismic reflection data acquired in shallow water environments of the Roussillon coastal area are integrated to provide an accurate image of the stratigraphic architecture of the Quaternary deposits. The complementary use of the two systems is shown to be of benefit for studies of shallow water environments. The

Caroline Labaune; Michel Tesson; Bernard Gensous

2005-01-01

111

Using the Messinian and Plio-Quaternary deposits as markers of the vertical motions in the tectonically inverted Algerian margin  

NASA Astrophysics Data System (ADS)

The Algerian margin represents one of the rare examples of tectonically inverted margins worldwide. The inversion is characterized by blind reverse thrust faults dipping landwards the below the continental slope, and by uplift of the coastal domain. The inversion process is active as evidenced by the offshore seismicity of Algeria (2003 Boumerdes earthquake, Mw 6.9); however the onset of inversion is poorly constrained. The morphology of the Algerian margin results from the interplay between tectonic and sedimentation together with periodic sea level changes during Quaternary. A major sea level fall at the end of Miocene marks the onset of the Messinian Salinity Crisis (MSC). In this study, we focus on a part of the Algerian margin located west of Algiers: the Khair al Din Bank (KADB). The KADB is a major structure interpreted as a tilted block originated during the opening of the Algerian basin in early Miocene. Because of its weak (low) slope, the sedimentary record all along the continental slope is better preserved than in the rest of the Algerian margin. The aim of this study is to constrain deformation and vertical motion of several sedimentary units in order to quantify the amount of uplift and the timing of inversion. We selected for uplift calculations 6 sedimentary units as follows. Sedimentary units onshore are: the highest marine terrace, the marine-continental transition and the MIS 5.5 uplifted beach. Sedimentary units offshore are: the boundary of the upper Unit of the MSC, and the erosion surfaces of the MIS 6 and MIS 2 sea level lowstand. The age of these units ranges between 5.6 Ma and 20 ka BP and permits to estimate the uplift and uplift rates all along the Plio-Quaternary time. Our interpretation is based on geophysical data acquired in 2003 (Maradja 1 cruise). We describe the main characteristics of the MSC erosion surface, i.e. the initial stage, and the sedimentary evolution during the Plio-Quaternary time. During the MSC sea level lowstand, the KADB area formed a deeply incised subaerial area continued in the marine domain by detrital chaotic deposits and evaporitic series. The subaerial domain exhibits a peculiar shape related to the inherited morphology of the passive margin as the river valley flows to the ENE and turns abruptly to the WNW on the mid-slope. In the inner shelf, the sedimentary evolution during Plio-Quaternary time is mostly characterized by the deposition of foresets and the absence of sediment aggradation, suggesting that the sedimentary evolution is dominated by a long term tectonic uplift of the KADB. Plio-Quaternary anticlines are present both onshore and offshore. As these structures do not correspond with crests and valleys of the MCS drainage network, we suggest that folding occurred after the MSC. We estimate maximum uplift values of 400 m for the oldest sedimentary marker suggesting that the inversion of the margin started at least 3.5 Ma ago.

Strzerzynski, P.; Lofi, J.; Sage-Khadir, F.; Gaullier, V.; Cattaneo, A.; Déverchère, J.

2009-12-01

112

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

113

Stratigraphy of late Quaternary estuarine deposits and amino acid stereochemistry of oyster shells beneath San Francisco Bay, California  

NASA Astrophysics Data System (ADS)

The sequence of Quaternary deposits beneath the floor of San Francisco Bay includes four to seven noncontemporaneous estuarine units intercalated with alluvium and dune sand. Units L (0-10,000 B.P.), M (>40,000 B.P., probably ca. 80,000-140,000 B.P.), and N (older than unit M) are distinctly superposed. The dominant molluscan fossil in each of these three units is Ostrea lurida Carpenter, the native oyster along much of the pacific Coast of North America. Despite a lamellar structure that suggests vulnerability to contamination, O. lurida shells generally yield amino acid enantiomeric ratios that are analytically reproducible and stratigraphically consistent. The kinetics of racemization in O. lurida conceivably resembles that of Protothaca and Saxidomus, other bivalves whose kinetics of racemization are relatively well understood. Assuming such a resemblance, enantiomeric ratios in O. lurida imply that (1) unit M is the same approximate age as estuarine terrace deposits bordering San Pablo Bay and Carquinez Strait, providing that the terrace deposits have been at diagenetic temperatures 1°-2°C warmer than unit M; and (2) the age of unit N is about four times greater than that of unit M, providing that both units have been at the same approximate diagenetic temperature.

Atwater, Brian F.; Ross, Bruce E.; Wehmiller, John F.

1981-09-01

114

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

115

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

NASA Astrophysics Data System (ADS)

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

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

2007-05-01

116

Late Quaternary history of the Vakinankaratra volcanic field (central Madagascar): insights from luminescence dating of phreatomagmatic eruption deposits  

NASA Astrophysics Data System (ADS)

The Quaternary Vakinankaratra volcanic field in the central Madagascar highlands consists of scoria cones, lava flows, tuff rings, and maars. These volcanic landforms are the result of processes triggered by intracontinental rifting and overlie Precambrian basement or Neogene volcanic rocks. Infrared-stimulated luminescence (IRSL) dating was applied to 13 samples taken from phreatomagmatic eruption deposits in the Antsirabe-Betafo region with the aim of constraining the chronology of the volcanic activity. Establishing such a chronology is important for evaluating volcanic hazards in this densely populated area. Stratigraphic correlations of eruption deposits and IRSL ages suggest at least five phreatomagmatic eruption events in Late Pleistocene times. In the Lake Andraikiba region, two such eruption layers can be clearly distinguished. The older one yields ages between 109 ± 15 and 90 ± 11 ka and is possibly related to an eruption at the Amboniloha volcanic complex to the north. The younger one gives ages between 58 ± 4 and 47 ± 7 ka and is clearly related to the phreatomagmatic eruption that formed Lake Andraikiba. IRSL ages of a similar eruption deposit directly overlying basement laterite in the vicinity of the Fizinana and Ampasamihaiky volcanic complexes yield coherent ages of 68 ± 7 and 65 ± 8 ka. These ages provide the upper age limit for the subsequently developed Iavoko, Antsifotra, and Fizinana scoria cones and their associated lava flows. Two phreatomagmatic deposits, identified near Lake Tritrivakely, yield the youngest IRSL ages in the region, with respective ages of 32 ± 3 and 19 ± 2 ka. The reported K-feldspar IRSL ages are the first recorded numerical ages of phreatomagmatic eruption deposits in Madagascar, and our results confirm the huge potential of this dating approach for reconstructing the volcanic activity of Late Pleistocene to Holocene volcanic provinces.

Rufer, Daniel; Preusser, Frank; Schreurs, Guido; Gnos, Edwin; Berger, Alfons

2014-05-01

117

Late Pleistocene alluvial plain sedimentation in Lower Narmada Valley, Western India: Palaeoenvironmental implications  

Microsoft Academic Search

Late Pleistocene fluvial sediments that were deposited in a slowly sinking basin are now exposed as 30–50 m high incised vertical cliffs all along the Lower Narmada Valley in western India. The exposed fluvial deposits have been classified into two sediment packages, alluvial fan sediments overlain by alluvial plain sediments. The alluvial plain sequence has not been studied previously. It

S. Bhandari; D. M. Maurya; L. S. Chamyal

2005-01-01

118

Geochemistry of Late Quaternary Terrestrial Tephra Deposits From the Eastern Mediterranean  

Microsoft Academic Search

Tephra layers provide geologists and archaeologists with isochronous marker deposits, which, if interpreted correctly, can provide valuable chronostratigraphic information. Explosive volcanic activity in the Hellenic arc over the last 150 000 years has left a record of terrestrial, lacustrine and marine tephra deposits across the Aegean and western Anatolia which are of great value in stratigraphic correlation. Some of these

J. S. Hart; N. J. Pearce; W. J. Eastwood

2004-01-01

119

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

120

Deposition of binary, ternary and quaternary metal selenide thin films from diisopropyldiselenophosphinato-metal precursors  

NASA Astrophysics Data System (ADS)

The tetragonal chalcopyrite phases CuInSe2, CuGaSe2 and CuIn0.7Ga0.3Se2 have been deposited onto the glass substates by Aerosol Assisted Chemical Vapour Deposition (AACVD) from a mixture of [Mx(iPr2PSe2)y] complexes (M=In, Ga, Cu) at temperatures between 300 °C and 500 °C. The thin films were characterized by powder X-ray diffraction (p-XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The bulk compositional properties have been studied by energy dispersive X-ray (EDX) analysis. SEM and AFM studies demonstrate a significant variation in morphology of the deposited materials at different deposition temperatures.

Mahboob, Sumera; Malik, Sajid N.; Haider, Nazre; Nguyen, C. Q.; Malik, Mohammad A.; O'Brien, Paul

2014-05-01

121

Alluvial Pollen on the North China Plain  

NASA Astrophysics Data System (ADS)

Mordern alluvial pollen varies with geomorphic setting and depositional facies in sediments of the Yellow, Hutuo, and Luan rivers and in Baiyangdian and Hengshuihu lakes. Most of the arboreal pollen is derived from the mountains, whereas most of the nonarboreal pollen is derived from the plain itself. Alluvium dominated by Pinuspollen and Selaginellaspores was deposited during a flood. Hydrodynamic sorting of alluvial pollen exists in the sediments of floodplain, central bar, natural levees, and point bar. In reconstructing the ancient vegetation and past climate based on pollen in alluvium, it is important to consider sedimentary facies and geomorphologic setting.

Qinghai, Xu; Xiaolan, Yang; Chen, Wu; Lingyao, Meng; Zihui, Wang

1996-11-01

122

Source area, depositional environment, and composition of Quaternary sands, Monterey Bay, California  

SciTech Connect

A suite of 173 sand samples from the Monterey Bay region was studied, using a stepwise discriminant function analysis, to determine the role of source area and depositional environment in controlling the modal framework constituents of the sands. These medium to fine-grained sands were derived from the Salines, Pajaro, and Carmel drainage basins, and were deposited in fluvial, nearshore marine, and eolian environments. They range in age from recent to early Pleistocene. Provenance exerts the most significant control on composition, providing an 87% assignment efficiency (independent of depositional environment); volcanic and sedimentary rock fragments were the most important variables. There was a 100% efficiency when discriminating between fluvial sands from the three drainage basins; however, the efficiencies were less strong in marine and eolian sands (90.5 and 86%, respectively). This difference is, in part, the result of modification in transit and mixing of sources.

O'Brien, W.D. Jr.; Dupre, W.R.

1988-01-01

123

Timing and nature of alluvial fan and strath terrace formation in the Eastern Precordillera of Argentina  

NASA Astrophysics Data System (ADS)

Sixty-eight 10Be terrestrial cosmogenic nuclide (TCN) surface exposure ages are presented to define the timing of alluvial fan and strath terrace formation in the hyper-arid San Juan region of the Argentine Precordillera. This region is tectonically active, and numerous fault scarps traverse Quaternary landforms. The three study sites, Marquesado strath complex, Loma Negra alluvial fan and Carpintería strath complex reveal a history of alluvial fan and strath terrace development over the past ˜225 ka. The Marquesado complex Q3m surface dates to ˜17 ± 3 ka, whereas the Loma Negra Q1ln, Q2ln, Q3ln, Q4ln, and Q5ln surfaces date to ˜24 ± 3 ka, ˜48 ± 2 ka, ˜65 ± 13 ka, ˜105 ± 21 ka, and ˜181 ± 29 ka, respectively. The Carpintería complex comprises eight surfaces that have been dated and include the Q1c (˜23 ± 3 ka), Q2c (˜5 ± 5 ka), Q3ac (˜25 ± 12 ka), Q3bc (˜29 ± 15 ka), Q4c (˜61 ± 12 ka), Q5c (˜98 ± 18 ka), Q6c (˜93 ± 18 ka), and Q7c (˜212 ± 37 ka). 10Be TCN depth profile data for the Loma Negra alluvial fan complex and Carpintería strath terrace complex, as well as OSL ages on some Carpintería deposits, aid in refining surface ages for comparison with local and global climate proxies, and additionally offer insights into inheritance and erosion rate values for TCNs (˜10 × 10410Be atoms/g of SiO2 and ˜5 m Ma-1, respectively). Comparison with other alluvial fan studies in the region show that less dynamic and older preserved surfaces occur in the Carpintería and Loma Negra areas with only younger alluvial fan surfaces preserved both to the north and south. These data in combination with that of other studies illustrate broad regional agreement between alluvial fan and strath terrace ages, which suggests that climate is the dominant forcing agent in the timing of terrace formation in this region.

Hedrick, Kathryn; Owen, Lewis A.; Rockwell, Thomas K.; Meigs, Andrew; Costa, Carlos; Caffee, Marc W.; Masana, Eulalia; Ahumada, Emilio

2013-11-01

124

A Geophysical Survey of the Quaternary Beatty Junction Paleolake Shoreline Deposit, Death Valley National Park, California  

NASA Astrophysics Data System (ADS)

We conducted a ground-penetrating radar (GPR) and seismic refraction survey of the Beatty Junction Shoreline Deposit in Death Valley National Park in March 2005. The deposit is a beach barrier bar approximately 500 m long, 50 m wide, and 5 m high, at an elevation of about 30 m above sea level and corresponds to a relict shoreline of the former Lake Manly (Orme and Orme, Phys. Geog., 12, pp. 334-346, 1980). The bar is oriented WSW-ENE, slopes to the east and is cut by the Beatty Junction Road. The longitudinal profile of the bar slopes to the east and is slightly concave upward. A total of 730 m of GPR data were recorded, including a longitudinal line 360 m in length, oriented along the crest of the bar, and four transverse lines, each approximately 100 m long. A hammer seismic refraction line was also recorded along the crest of the bar, and yielded a 3-layer model consisting of a surface layer about 1 m thick with a velocity of 200 m/s, a second layer 4-9 m thick with a velocity of 700 m/s, and a basal unit with a velocity of 1500 m/s. The uppermost layer apparently corresponds to an unconsolidated surface veneer of coarse gravel that has been winnowed to form desert pavement. The second layer is presumably sand and gravel that forms the main portion of the bar, and which thins in the longitudinal direction, from 9 m in the west to 4 m in the east. The third, basal layer represents older, more consolidated fan sediments. Shallow reflectors on the lakeward side of two of the transverse GPR lines have a distinct step-like appearance that may represent berms. All GPR lines show a thin surface layer, about 1 m thick, that unconformably covers all reflectors in the interior of the deposit, similar to the Hanaupah Shoreline Deposit at Tule Spring, described by Ibbeken and Warnke ( J. Paleolimnology, 23, pp. 439-447, 2002). The age of the deposit is given as 153 ± 12 Ka, late in Marine Isotope Stage 6 (Orme and Orme, 1991). Since this age range overlaps with that given by Machette et al. for the Tule Spring deposit ( GSA Abstracts with Programs, 34, pp. 257-258, 2003), we consider both deposits nearly time equivalent, deposited near or during Termination II.

Craig, M.; Warnke, D.; Teitler, L.; Narvaez, R.

2005-12-01

125

Contribution of geophysics to the study of alluvial deposits: a case study in the Val d'Avaray area of the River Loire, France  

Microsoft Academic Search

The purpose of the geophysical campaign carried out in the Val d'Avaray was to contribute to a reconstruction of fluvial dynamics in the middle reaches of the River Loire. The campaign used of three classical geophysical methods (electromagnetic profiling supplemented by electrical soundings, electrical resistivity tomography and ground penetrating radar [GPR]) to define alluvial bodies. In addition, it aimed to

Jean-Christophe Gourry; Francoise Vermeersch; Manuel Garcin; Denis Giot

2003-01-01

126

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

Microsoft Academic Search

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

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

2009-01-01

127

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

Microsoft Academic Search

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

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

2003-01-01

128

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

Microsoft Academic Search

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

WILLIAM SUAREZ; STEPHEN DIAZ-FRANCO

129

Amino-acid racemizarion in Quaternary shell deposits at Willapa Bay, Washington  

USGS Publications Warehouse

Extents of racemization ( d l ratios) of amino acids in fossil Saxidomus giganteus (Deshayes) and Ostrea lurida Carpenter were measured on shell deposits exposed at 21 sites on the east side of Willapa Bay, Washington. Amino acids from Saxidomus show less variability in d Spl ratios and, therefore, are of greater use in correlation and age estimation than are amino acids from Ostrea. Shells of two different ages, about 120,000 ?? 40,000 yr old and about 190,000 ?? 40,000 yr old, are present. These ages correspond to Stages 5 and 7 of the marine isotope record defined by Shackleton and Opdyke in 1973 and hence the shell deposits likely formed during two different high stands of sea level. The stratigraphic record at Willapa Bay is consistent with this interpretation. ?? 1979.

Kvenvolden, K. A.; Blunt, D. J.; Clifton, H. E.

1979-01-01

130

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

Microsoft Academic Search

Pikas (Ochtona)—small gnawing mammals, related to rabbits—range today throughout parts of the Northern Hemisphere, but had a wider distribution during the Pleistocene. Nine caves from northeastern North America (a region not occupied by pikas today) have Pleistocene deposits containing remains ofOchotona.We examine 526 fossil specimens (ranging in age from approximately 850,000 to 8670 yr B.P.) from five of these caves.

Frederick Grady

1996-01-01

131

Congo Fan Neogene and Quaternary sedimentation: Interplay of riverine and current induced deposition  

Microsoft Academic Search

The incorporation of information regarding sedimentation rates and lithology from ODP Leg 175 Sites 1075, 1076 and 1077 into the analysis and interpretation of high-resolution seismic reflection data led to the revision and refinement of a depositional model for the upper Congo Fan area presented earlier by Uenzelmann-Neben (1998). For four time slices since the Eocene (Late Oligocene - Miocene\\/Pliocene,

G. Uenzelmann-Neben; H. Miller

2003-01-01

132

Geochemistry of Late Quaternary Terrestrial Tephra Deposits From the Eastern Mediterranean  

NASA Astrophysics Data System (ADS)

Tephra layers provide geologists and archaeologists with isochronous marker deposits, which, if interpreted correctly, can provide valuable chronostratigraphic information. Explosive volcanic activity in the Hellenic arc over the last 150 000 years has left a record of terrestrial, lacustrine and marine tephra deposits across the Aegean and western Anatolia which are of great value in stratigraphic correlation. Some of these eruptions have produced substantial volumes of ash (e.g. Kos, 150 ka, Santorini 3600 years BP) and for stratigraphic correlation accurate recognition of these individual tephra deposits is imperative. This project investigates the tephrochronology of the Eastern Mediterranean which is believed to be important in two contexts, (i) in placing time constraints on the evolution of civilisations in that area and (ii) in understanding the evolution of the Hellenic arc. Results from analysis of single glass shards from tephra deposits on Kos, Yiali, Rhodes and Santorini as well as other minor islands and selected sites in Turkey are presented. Major and trace elements were analysed by electron probe, ion probe and LA-ICP-MS techniques. A trace element database has been generated for both distal and proximal samples and has aided in the understanding of the magma chamber evolution of the volcanoes in question. These analyses also provide a detailed, single grain, chemical stratigraphy of many islands which will enable temporal and spatial correlations and ultimately, will aid in the discussions of the impact volcanic eruptions exerted upon Aegean civilisations. Arguments related to the timing of Santormi's eruptions are considered and data are also-presented for tephra from the Alaskan volcano, Aniakchak. Thus, adding further weight to disproving a 1645 BC date for the Minoan eruption, but confirming the time of the eruption of Aniakchak. Finally the study provides a comparison between two trace element analytical techniques, ion probe and the LA-ICP-MS. This serves to increase confidence in comparisons between previous studies which employed these techniques.

Hart, J. S.; Pearce, N. J.; Eastwood, W. J.

2004-12-01

133

The chemistry and origin of groundwater in Triassic sandstone and Quaternary deposits, northwest England and some UK comparisons  

NASA Astrophysics Data System (ADS)

The Triassic Sherwood Sandstone Group is a major UK aquifer. In this study the groundwater geochemistry of a 60 km 2 area has been investigated to improve the understanding of the hydrogeology of the area and to determine the origin of groundwater. Archived analyses of groundwater samples were interpreted to determine the dominant geochemical processes and subsequently samples were taken from selected sites for stable and radio-isotope measurements. Near areas of direct recharge of the Sherwood Sandstone, groundwaters are unsaturated with respect to carbonate minerals. Sulphate and chloride are contributed to the groundwater in the Sherwood Sandstone from the overlying Quaternary glacial drift deposits and Mercia Mudstone. The groundwater chemistry and isotopes of sulphate indicate that the source of sulphate is gypsum in the Triassic sequence and the Triassic-derived glacial deposits. A significant proportion of the calcium in groundwater is shown to be exchanged for sodium in the aquifer matrix. However, in the more mineralised waters, carbonate minerals are precipitated because of contributions to the groundwater of calcium from dissolution of gypsum. Up piezometric gradient, groundwaters are modem and have relatively high 14C and tritium contents. The oldest water which was sampled for 14C is estimated to be about 4000 years older than the modern waters which were sampled from near recharge zones. The groundwater regime in the study area may be compared and contrasted with Triassic sandstone aquifers elsewhere in the UK. Incongruent carbonate dissolution occurs, as described in the Triassic of the East Midlands, the Lower Mersey Basin and southwest England. Exchange reactions are important in determining the groundwater chemistry as found elsewhere in the Triassic of northwest England, and in contrast to the East Midlands and southwest England.

Kimblin, R. T.

1995-11-01

134

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

135

Lithological and palynological evidence of late Quaternary depositional environments in the subaqueous Yangtze delta, China  

NASA Astrophysics Data System (ADS)

AMS 14C ages of post-glacial core sediments from the subaqueous Yangtze delta, along with sedimentary structures and distributions of grain size, pollen spores, and dinoflagellate cysts, show an estuarine depositional system from 13 to 8.4 cal ka BP and a deltaic system from 5.9 cal ka BP to the present. The estuarine system consists of intertidal to subtidal flat, estuarine, and estuarine-front facies, characterized by sand-mud couplets and a high sedimentation rate. The deltaic system includes nearshore shelf and prodelta mud featured by lower sedimentation rate, markedly fewer coastal wetland herbaceous pollens, and more dinoflagellate cysts. We explain the extremely high sedimentation rate during 9.2-8.4 cal ka BP at the study site as a result of rapid sea-level rise, high sediment load due to the unstable monsoonal climate, and subaqueous decrease of elevation from inner to outer estuary. A depositional hiatus occurred during 8.2-5.9 cal ka BP, the transition from estuarine to deltaic system, caused possibly by a shortage of sediment supply resulting from delta initiation in paleo-incised Yangtze valley and strong tidal or storm-related reworking in offshore areas. The subsequent development of deltaic system at the study site indicates accelerated progradation of Yangtze delta post-5.9 cal ka BP.

Wang, Zhanghua; Xu, Hao; Zhan, Qing; Saito, Yoshiki; He, Zhongfa; Xie, Jianlei; Li, Xiao; Dong, Yonghong

2010-05-01

136

Surface roughness as a calibrated proxy for dating alluvial surfaces  

NASA Astrophysics Data System (ADS)

Determining the age of alluvial deposits, which often constitute effective recorders of tectonic and climatic signals, is a pivotal component in many quantitative studies of recent tectonic activity, past climatic variations and landscape evolution processes. In arid to semi-arid desert environments the scarcity in suitable materials for dating commonly implies that numerical dating of alluvial surfaces remains a challenging and fairly expensive task, carried out on an opportunistic basis and typically requiring substantial commitment of resources. With the goal of addressing this problem, we present a new and widely applicable surface dating technique that builds on surface roughness as a quantitative calibrated proxy for the age of alluvial surfaces in desert environments. The well-studied development of reg soils provides the physical basis for the approach, and recent technological advances in the form of portable ground-based laser scanners (LiDAR), facilitate its application by allowing quantitative high resolution (~several millimeters) 3D characterization of the roughness of alluvial chronosequences as they mature into smooth and stable desert pavements. We construct regional age-roughness calibration curves using 'conventional' numerical dating techniques and LiDAR to quantitatively characterize the evolution trends and time-scales associated with roughness changes of reg soils through time. Here, we present results from two previously dated late Quaternary alluvial chronosequences along the Dead Sea Transform in the hyper-arid Negev desert of southern Israel. LiDAR scanning was applied on representative areas (~30-50 m2) of 10 separate terraces ranging from rough (active surfaces) to fairly smooth surfaces with well-developed pavements displaying an OSL age of 87 kyr. Power spectral density (PSD) analysis was used to characterize the roughness evolution trend of these terraces: We find typical and recurring time-dependent changes in the offset as well as shape of the PSD curves in both chronosequences: PSD offset is continuously reduced over time reflecting the overall reduction in the amplitude of roughness at all wavelengths. All PSD curves display moderation of slopes at the longer wavelengths, which consistently increases with increasing surface age. The kink point itself in the PSD curves is systematically shifted to shorter wavelengths. This characteristic evolution of PSD offset and slope moderation at longer wavelengths reflects the typical break up of boulder-sized clasts through time as such reg soil surfaces mature into well-developed desert pavements. Deviation of the PSD curve from the characteristic evolution pattern also serves as an indication in cases where the natural surface evolution was interrupted. Accordingly, we thus suggest that with suitable regional calibration curves, PSD analysis of desert alluvial surfaces can serve as a practical and quantitative proxy for constraining surface age in places where 'conventional' dating cannot be applied.

Mushkin, A.; Sagy, A.; Trabelci, E.

2012-12-01

137

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

NASA Astrophysics Data System (ADS)

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

williams, martin

2014-05-01

138

Congo Fan Neogene and Quaternary sedimentation: Interplay of riverine and current induced deposition  

NASA Astrophysics Data System (ADS)

The incorporation of information regarding sedimentation rates and lithology from ODP Leg 175 Sites 1075, 1076 and 1077 into the analysis and interpretation of high-resolution seismic reflection data led to the revision and refinement of a depositional model for the upper Congo Fan area presented earlier by Uenzelmann-Neben (1998). For four time slices since the Eocene (Late Oligocene - Miocene/Pliocene, Pliocene - 600 ky, 600 ky - ~160 ky, ~160 ky - Recent) the main sediment contributor to the upper fan was determined. Thus we can say that in the Late Paleogene input of sediments from the north dominated the area by either a south setting current or the Kouilou/Niari River. This situation continued to the period Pliocene - 600 ky when southern sediment sources (the Congo River and upwelling) became dominant with the material being deflected to the north by the Benguela Current. Upwelling as a sediment source on the upper fan became even more important after 600 ky while the main sediment load of the Congo River is guided to the middle and lower fan via the Congo Canyon.

Uenzelmann-Neben, G.; Miller, H.

2003-04-01

139

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

USGS Publications Warehouse

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

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

2009-01-01

140

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

141

Variations in fluvial deposition on an alluvial plain: an example from the Tongue River Member of the Fort Union Formation (Paleocene), southeastern Powder River Basin, Wyoming, U.S.A.  

USGS Publications Warehouse

The Tongue River Member of the Paleocene Fort Union Formation is an important coal-bearing sedimentary unit in the Powder River Basin of Wyoming and Montana. We studied the depositional environments of a portion of this member at three sites 20 km apart in the southeastern part of the basin. Six lithofacies are recognized that we assign to five depositional facies categorized as either channel or interchannel-wetlands environments. (1) Type A sandstone is cross stratified and occurs as lenticular bodies with concave-upward basal surfaces; these bodies are assigned to the channel facies interpreted to be the product of low-sinuosity streams. (2) Type B sandstone occurs in parallel-bedded units containing mudrock partings and fossil plant debris; these units constitute the levee facies. (3) Type C sandstone typically lacks internal structure and occurs as tabular bodies separating finer grained deposits; these bodies represent the crevasse-splay facies. (4) Gray mudrock is generally nonlaminated and contains ironstone concretions; these deposits constitute the floodplain facies. (5) Carbonaceous shale and coal are assigned to the swamp facies. We recognize two styles of stream deposition in our study area. Laterally continuous complexes of single and multistoried channel bodies occur at our middle study site and we interpret these to be the deposits of sandy braided stream systems. In the two adjacent study sites, single and multistoried channel bodies are isolated in a matrix of finer-grained interchannel sediment suggesting deposition by anastomosed streams. A depositional model for our study area contains northwest-trending braided stream systems. Avulsions of these systems created anastomosed streams that flowed into adjacent interchannel areas. We propose that during late Paleocene a broad alluvial plain existed on the southeastern flank of the Powder River Basin. The braided streams that crossed this surface were tributaries to a northward-flowing, basin-axis trunk stream that existed to the west. ?? 1990.

Johnson, E. A.; Pierce, F. W.

1990-01-01

142

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

143

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

144

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

SciTech Connect

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

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

2005-08-26

145

Mississippi Alluvial Valley  

USGS Publications Warehouse

Available data are summarized according to the following major topics: (1) characteristics of the Mississippi Alluvial Valley (MAV); (2) waterfowl populations associated with the MAV; (3) habitat requirements of migrating and wintering waterfowl in the MAV; (4) current habitat management practices in the MAV, including croplands, moist-soil impoundments, and forested wetlands; (5) status and classification of winter habitat in the MAV; and (6) research and management information needs.

Reinecke, K.J.; Kaminski, R.M.; Moorhead, D.J.; Hodges, J.D.; Nasser, J. R.

1989-01-01

146

Late Quaternary landscape evolution, climate, and neotectonism along the eastern margin of the Puna Plateau: Pucará Valley, NW Argentina  

NASA Astrophysics Data System (ADS)

The eastern margin of the Puna Plateau has been the focus of many studies seeking to link climatically-moderated surface processes and tectonism through dynamic feedbacks. However, evaluating any theories regarding climatic-tectonic feedbacks requires the determination of tectonic, climatic, and geomorphic chronologies across a wide region, from plateau to wedge-top to foreland. In this study, we contribute to that effort by examining Quaternary landscape evolution of a single intermontane basin of spatially uniform climate, adjacent to the plateau margin. The semi-arid Pucará Valley contains eight abandoned and incised geomorphic surfaces, most of which are deformed by active structures. These geomorphic surfaces - thin alluvial fans and strath terraces - dominate the landscape and record multiple pulses of incision in the late Quaternary. We find no evidence for significant depositional intervals and valley incision continues currently. Substantial accumulations of pedogenic carbonate and pedogenic gypsum within abandoned surfaces indicate that arid or semi-arid conditions are long lived in this valley. Conversely, relict periglacial morphology in adjacent ranges supports cooler temperatures in the past. River incision is enhanced across active structures, but preliminary observations suggest that the magnitude of deformation cannot fully explain the magnitude of incision. As a result, we argue that extrabasinal base-level lowering is the primary driver of incision in the Pucará Valley, but Quaternary deformation is significant enough to spatially influence erosion. Cooler climatic intervals may influence the sedimentology of alluvial and fluvial deposits, but we find no evidence for significant climatic changes that could change rates or styles of landscape evolution over this time frame. Pending cosmogenic nuclide analysis of fan deposits and river sediments will permit the derivation of fault slip rates, surface ages, modern and paleo-erosion rates, and sediment transport histories. These results will further refine our understanding of tectonic and climatic forcing of surface processes in the Quaternary.

McCarthy, J. A.; Schoenbohm, L. M.; Bierman, P. R.; Rood, D. H.

2013-12-01

147

Depositional environments in an alluvial-lacustrine system: molluscan paleoecology and lithofacies relations in upper part of Tongue River Member of Fort Union Formation, Powder River Basin, Wyoming  

SciTech Connect

The upper part of the Tongue River Member of the Fort Union Formation (Paleocene) in the northern Powder River basin, Wyoming, contains assemblages of excellently preserved nonmarine mollusks which occur in laterally continuous outcrops of diverse lithologic sequences and sedimentary structures. Three facies are recognized vertically within an alluvial-lacustrine system. The interfluvial lake and lake splay facies is characterized by sequences of coarsening-upward detritus, abundant continuous limestone beds, and few beds of discontinuous coal and continuous carbonaceous shale. Limestones contain two lacustrine mollusk assemblages: a locally reworked assemblage dominated by the bivalve Plesielliptio (two species), and the gastropods Viviparus, Lioplacodes (three species), and Clenchiella; and a quite-water assemblage dominated by sphaeriid bivalves. The interfluvial crevasse splay-crevasse channel facies is characterized by sequences of coarsening-upward detritus and few discontinuous limestone beds, separated vertically by thick, continuous coal and carbonaceous shale beds. This facies includes small crevasse channel sandstones which scour into splay sandstones. Biofabric of lacustrine mollusk assemblages, which are identical in composition (but with dwarfed species of Plesielliptio) to locally reworked lacustrine assemblages of the interfluvial lake and lake splay facies, reflects deterioration of lakes through active infilling by crevasses. The fluvial channel and interchannel facies is typified by thick channel sandstones laterally separated by sequences of coarsening-upward detritus, overbank sediments, and rare limestones. This facies includes thick, continuous coal and carbonaceous shale beds.

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

1983-03-01

148

Quaternary Studies  

NSDL National Science Digital Library

First, 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" (1). Visitors can learn about the importance of quaternary studies as well as find out the latest news and upcoming meetings. At the second website, the University of Wisconsin-Madison describes the current and recent studies dealing with "basic and applied problems in glacial geology, surficial geology, palynology, sedimentology, geologic mapping, hydrogeology, soils, and environmental geology "(2). The website offers abstracts of publications of members of the Department of Geology and Geophysics and the Wisconsin Geological and Natural History Survey along with descriptions of the lab, a shaded relief map of the Wisconsin area, and amusing glacial songs. Next, the Godwin Institute of Quaternary Research (GIQR) presents the University of Cambridge's history in quaternary research and the seven current research groups and four recent research projects (3 ). The website furnishes news from the research groups, a gallery of historical images of the East Anglia excursion, and summaries of the Institute's reference collections. Fourth, the International Union for Quaternary Research (INQUA) discusses quaternary scientists' investigations "to interpret the changing world of the glacial ages and their impact on our planet's surface environments" (4). Researchers can find out about INQUA-funded projects, meetings, and scientific commissions. Next, the Quaternary Research Association explains that it "exists to promote understanding of the Quaternary Period by publishing field guides, technical guides, and an international journal as well as holding field meetings and speaker meetings" (5). Students and researchers can discover employment, research, grant, meetings, and educational opportunities. Sixth, the University of Wales presents its investigations in the Remote Sensing Laboratory, Palaeoecology Laboratory, and the Luminescence Laboratory (6 ). Users can find concise descriptions of individual researchers' successes, abstracts of published papers, and links to conference information. The seventh website illustrates the Alaska Quaternary Center's commitment "to the promotion of interdisciplinary research and the enhancement of interdisciplinary instruction in Quaternary sciences" (7). Users can view images of the field work and learn how to obtain quaternary data from the Geographic Information Network of Alaska (GINA). Lastly, 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 (8). Students and educators can find information on the researchers involved with the program and the necessary course work.

149

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

150

Deglacial Flood Origin of the Charleston Alluvial Fan, Lower Mississippi Alluvial Valley  

NASA Astrophysics Data System (ADS)

Large-magnitude flooding of the Mississippi River from proglacial lakes Agassiz and Superior most likely occurred between 11,300 and 10,900 and 9900 and 9500 yr B.P. The Charleston alluvial fan, a depositional remnant of one of these floods, is located at the head of a wide alluvial plain near Charleston, Missouri. The fan is an elongate, convex-up sand body (16 × 24 km) composed of medium- and fine-grained sand at least 8 m thick. This sand contrasts with the older coarse-grained sand of the braided stream surface to the west and south and younger silty clay of the meandering stream level to the north and east. A weakly developed soil separates the underlying braided steam deposits from the alluvial fan. A bulk-soil radiocarbon date of 10,590 ± 200 yr B.P. from the contact between the fan and clays of the meandering stream system indicates that the Charleston fan was deposited near the end of the early interval of flooding from Lake Agassiz about 10,900 yr B.P. If the Charleston fan is the last remnant of deglacial flooding in the lower Mississippi Valley, then deposition of significant quantities of sediment from largemagnitude floods between 10,000 and 9500 yr B.P. did not extend into the lower Mississippi Valley through Thebes Gap.

Porter, Donna A.; Guccione, Margaret J.

1994-05-01

151

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

152

Geomorphology and late Quaternary of the Chaco (South America)  

NASA Astrophysics Data System (ADS)

The Chaco is a large tropical plain located in the interior of South America, consisting of parts of Argentina, Paraguay and Bolivia. It is 840,000 km 2 in area and is characterized by forests, savannas and extensive swamps, which give it a marked climatic and biogeographic identity. It encompasses five huge alluvial fans built by the major rivers which cross the region: Salado, Bermejo, Pilcomayo, Parapetí and Grande. The fans are composed of several sedimentary units, deposited during different times of the late Quaternary under diverse climates. Two fluvial terraces appear at the apex of each fan; the older one is probably late Pleistocene in age, the second was formed in postglacial times. Humid climates, such as the present one, favoured the generation of soils and stable fluvial belts; drier climates led to widespread sedimentation along small ephemeral channels and large spill-outs. During two intervals, on in the late Quaternary glacial maximum and the late Holocene dry climates occurred in the region, leading to the formation of dune fields and loess mantles.

Iriondo, Martin

1993-08-01

153

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

154

Late Quaternary Deposition of Ice-Rafted Sand in the Subpolar North Atlantic (lat 40 deg to 65 deg N).  

National Technical Information Service (NTIS)

A major change in the North Atlantic pattern of ice-rafting deposition, during the last interglacial-glacial cycle, occurred approximately 75,000 B. P. Prior to this time, deposition for a period of almost 50,000 yr during isotopic stage 5 was greatest in...

W. F. Ruddiman

1976-01-01

155

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

156

Bedrock versus alluvial channel geometry  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

157

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

158

The Quaternary Deformational History of the East Potrillo Fault, Dona Ana County, New Mexico  

NASA Astrophysics Data System (ADS)

The East Potrillo Mountains are located immediately north of the U.S.-Mexico border in southwestern Dona Ana County, New Mexico. Along the east flank of the East Potrillo Mountains are north-striking piedmont scarps that indicate continuous, late Quaternary movement on the high-angle normal faults of the East Potrillo Fault system. This East Potrillo fault may pose a major seismic hazard to the 2.2 million people that live in the El Paso, Texas border region. We investigate the Quaternary deformational history in this area using GPS, field and remote sensing observations, traditional survey techniques, and new advances in desert varnish geochronology. We focus on estimating the average slip rate on the East Potrillo fault and the earthquake recurrence interval. The amount of Quaternary deformation is constrained by measuring displacements of geomorphic surfaces, including alluvial fans and fluvial deposits. A total of thirteen profiles perpendicular to the scarp have been surveyed to reproduce the fault scarp geometry. From these profiles, we estimate fault scarp age by using three types of slope degradation modeling: calibrated scarp-height-slope-angle relationships, a diffusion model, and a general morphologic dating method for transport-limited hillslopes. A total of 18 varnished rock samples were also collected from displaced alluvial fan surfaces and from cut terraces associated with slip events on the East Potrillo fault. These samples were analyzed using x-ray fluorescence (XRF) to obtain concentrations of Mn and Fe present in the varnish. The accumulation of Fe and Mn reflects the amount of time that varnish has accumulated on a clast, and, thus, provides a constraint on the age of the surface from which the clast was obtained. The morphologic dating results will be compared with the desert varnish results to better understand landform evolution, fault mechanics, and determine the slip history in the study area. These measurements are vital for constraining paleoseismic and tectonic activity as well as seismic hazards in the region.

Cervera, S. N.; Hurtado, J. M.; Clague, J. W.; Andronicos, C. L.

2006-12-01

159

Quaternary geologic map of the Glasgow 1° x 2° quadrangle, Montana  

USGS Publications Warehouse

The Glasgow quadrangle encompasses approximately 16,084 km2 (6,210 mi2). The northern boundary is the Montana/Saskatchewan (U.S./Canada) boundary. The quadrangle is in the Northern Plains physiographic province and it includes the Boundary Plateau, Peerless Plateau, and Larb Hills. The primary river is the Milk River. The map units are surficial deposits and materials, not landforms. Deposits that comprise some constructional landforms (for example, ground-moraine deposits, end-moraine deposits, and stagnation-moraine deposits, all composed of till) are distinguished for purposes of reconstruction of glacial history. Surficial deposits and materials are assigned to 23 map units on the basis of genesis, age, lithology or composition, texture or particle size, and other physical, chemical, and engineering characteristics. It is not a map of soils that are recognized in pedology or agronomy. Rather, it is a generalized map of soils recognized in engineering geology, or of substrata or parent materials in which pedologic or agronomic soils are formed. Glaciotectonic (ice-thrust) structures and deposits are mapped separately, represented by a symbol. The surficial deposits are glacial, ice-contact, glaciofluvial, alluvial, lacustrine, eolian, colluvial, and mass-movement deposits. Residuum, a surficial material, also is mapped. Till of late Wisconsin age is represented by three map units. Till of Illinoian age is also represented locally but is widespread in the subsurface. This map was prepared to serve as a database for compilation of a Quaternary geologic map of the United States and Canada (scale 1:1,000,000). Letter symbols for the map units are those used for the same units in the Quaternary Geologic Atlas of the United States map series.

Fullerton, David S.; Colton, Roger B.; Bush, Charles A.

2012-01-01

160

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

161

Stratigraphic architecture and quaternary evolution of the Val d'Agri intermontane basin (Southern Apennines, Italy)  

NASA Astrophysics Data System (ADS)

The sedimentary record of the Val d'Agri basin is of great importance for understanding the Quaternary tectonic activity and climatic variability in the Southern Apennines. Changes in tectonic controls, sediment supply and climatic input have been identified. The interval from ˜ 56 to ˜ 43 ka was associated with asymmetric subsidence restricted to the north-eastern actively faulted margin of the basin and development of axial braided river and transverse alluvial fan systems. Short-lasting Mediterranean-type pedogenesis between ˜ 43 and ˜ 32 ka (MIS Stage 3) coexisted with progradation-aggradation of the southern alluvial fan deposits and southwards tilting of the basin floor. Aggradation ended with consumption of accommodation space after 32 ka. During a subsequent stage of decline of vegetation cover, possibly as a consequence of climatic cooling (probably MIS Stage 2), active progradation of alluvial fans occurred. Breakthrough of the basin threshold and entrenchment of the drainage network must therefore be attributed to a latest Pleistocene to Holocene age. The first stages of basin opening and fill, predating ˜ 56 ka have only been inferred by stratigraphic considerations: the earliest lacustrine sedimentation should be middle Pleistocene or older in age. The following south-eastward basin widening allowed progradation of alluvial fan systems, which completely filled the lacustrine area (tentatively late middle Pleistocene). Pedogenesis in "Mediterranean-like" climate conditions caused the final development of a highly mature fersiallitic paleosol at the top of the fan surfaces, in areas of morpho-tectonic stability, plausibly during MIS Stage 5. The study results demonstrate the potential of applying a multidisciplinary approach in an intermontane continental settings marked by a relative rapid and constant tectonic subsidence and a high rate of sediment supply during the Pleistocene glacial-interglacial cycles.

Zembo, Irene

2010-01-01

162

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

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

163

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

164

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

165

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

166

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

167

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

168

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)] [Univ. of Nevada, Reno, NV (United States); Dorn, R.I. [Arizona State Univ., Tempe, AZ (United States)] [Arizona State Univ., Tempe, AZ (United States); Ku, T.L. [Univ. of Southern California, Los Angeles, CA (United States)] [Univ. of Southern California, Los Angeles, CA (United States)

1995-04-01

169

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

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

170

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

NASA Astrophysics Data System (ADS)

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

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

2002-02-01

171

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. Today, spring waters in this area have temperatures of 19 to 57 °C, are of the Ca-Mg-HCO3-SO4 type in the Pamukkale, Kelkaya and P?narba?? areas and the Ca-Mg-SO4-HCO3 type at Çukurba?. Thermal waters along the northern margin of the basin are generally hotter than those in the east-southeast and south. The ?18O and ?D values of the spring waters indicate a meteoric origin. The average temperatures of the hydrothermal systems in the Denizli Basin appear to have decreased from Pleistocene to Holocene. Travertine, which formed from the hotter water, is more widespread than the tufa that formed in the cooler spring waters. Deposition of the travertine, which formed largely on slopes, in depressions, and along fissure ridges (mostly on northern basin margins), was controlled by the interplay between various intrinsic and extrinsic parameters. The travertines are formed largely of calcite with only minor amounts of aragonite in some of the vertically banded, crystalline crust, raft and pisoid travertines found in some of the northern sites. The aragonitic samples, rich in Sr, are typically found around the spring orifices and along the central axis of the fissure ridges. The stable isotope values of the travertine found in the northwest and southeast parts of the basin are different. The ?13C values of the northern travertine deposits are more positive (3.7 to 11.7‰ VPBD) than those found in the south-southeast areas (- 4 to 5.8‰ VPDB). In contrast, the travertine and tufa in the southeastern areas have higher ?18O values (- 15.2 to - 7.8‰ VPDB) than those of the northern areas (- 16.6 to - 4.8‰ VPDB). Available evidence indicates that spring activity and associated travertine precipitation in the Denizli Basin were controlled largely by tectonic activity rather than by climatic conditions.

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

172

Late Quaternary valley infill and dissection in the Indus River, western Tibetan Plateau margin  

NASA Astrophysics Data System (ADS)

The Indus, one of Earth's major rivers, drains large parts of the NW Himalaya and the Transhimalayan ranges that form part of the western Tibetan Plateau margin. In the western Himalayan syntaxis, where local topographic relief exceeds 7 km, the Indus has incised a steep bedrock gorge at rates of several mm yr-1. Upstream, however, the upper Indus and its tributaries alternate between bedrock gorges and broad alluvial flats flanked by the Ladakh and Zanskar ranges. We review the late Quaternary valley history in this region with a focus on the confluence of the Indus and Zanskar Rivers, where vast alluvial terrace staircases and lake sediments record major episodes of aggradation and incision. New absolute dating of high-level fluvial terrace remnants using cosmogenic 10Be, optically and infrared stimulated luminescence (OSL, IRSL) indicates at least two phases of late Quaternary valley infilling. These phases commenced before ?200 ka and ?50-20 ka, judging from terrace treads stranded >150 m and ?30-40 m above modern river levels, respectively. Numerous stacks of lacustrine sediments that straddle the Indus River >200 km between the city of Leh and the confluence with the Shyok River share a distinct horizontal alignment. Constraints from IRSL samples of lacustrine sequences from the Leh-Spituk area reveal a protracted lake phase from >177 ka to 72 ka, locally accumulating >50-m thick deposits. In the absence of tectonic faulting, major lithological differences, and stream capture, we attribute the formation of this and other large lakes in the region to natural damming by large landslides, glaciers, and alluvial fans. The overall patchy landform age constraints from earlier studies can be reconciled by postulating a major deglacial control on sediment flux, valley infilling, and subsequent incision that has been modulated locally by backwater effects of natural damming. While comparison with Pleistocene monsoon proxies reveals no obvious correlation, a late- or post-glacial sediment pulse seems a more likely source of this widespread sedimentation that has partly buried the dissected bedrock topography. Overall, the long residence times of fluvial, alluvial and lacustrine deposits in the region (>500 ka) support previous studies, but remain striking given the dominantly steep slopes and deeply carved valleys that characterise this high-altitude mountain desert. Recalculated late Quaternary rates of fluvial bedrock incision in the Indus and Zanskar of 1.5 ± 0.2 mm yr-1 are at odds with the longevity of juxtaposed valley-fill deposits, unless a lack of decisive lateral fluvial erosion helps to preserve these late Pleistocene sedimentary archives. We conclude that alternating, ?104-yr long, phases of massive infilling and incision have dominated the late Quaternary history of the Indus valley below the western Tibetan Plateau margin.

Blöthe, Jan H.; Munack, Henry; Korup, Oliver; Fülling, Alexander; Garzanti, Eduardo; Resentini, Alberto; Kubik, Peter W.

2014-06-01

173

The timing of alluvial activity in Gale crater, Mars  

NASA Astrophysics Data System (ADS)

Curiosity rover's discovery of rocks preserving evidence of past habitable conditions in Gale crater highlights the importance of constraining the timing of responsible depositional settings to understand the astrobiological implications for Mars. Crater statistics and mapping reveal the bulk of the alluvial deposits in Gale, including those interrogated by Curiosity, were likely emplaced during the Hesperian, thereby implying that habitable conditions persisted after the Noachian. Crater counting data sets and upper Peace Vallis fan morphology also suggest a possible younger period of fluvial activation that deposited ~10-20 m of sediments on the upper fan after emplacement of the main body of the fan. If validated, water associated with later alluvial activity may have contributed to secondary diagenetic features in Yellowknife Bay.

Grant, John A.; Wilson, Sharon A.; Mangold, Nicolas; Calef, Fred; Grotzinger, John P.

2014-02-01

174

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

175

Quaternary Geologic Map of Connecticut and Long Island Sound Basin  

USGS Publications Warehouse

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

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

2005-01-01

176

Quaternary geologic map of the Shelby 1° x 2° quadrangle, Montana  

USGS Publications Warehouse

The Shelby quadrangle encompasses approximately 16,084 km2 (6,210 mi2). The northern boundary is the Montana/Saskatchewan (U.S./Canada) boundary. The quadrangle is in the Northern Plains physiographic province and it includes the Sweet Grass Hills. The primary river is the Marias River. The ancestral Missouri River was diverted south of the Bearpaw Mountains by a Laurentide ice sheet. The fill in the buried ancestral valleys of the Missouri River and Marias River in the southeast quarter of the quadrangle contains a complex stratigraphy of fluvial, glaciofluvial, ice-contact, glacial, lacustrine, and eolian deposits. The map units are surficial deposits and materials, not landforms. Deposits that comprise some constructional landforms (for example, ground-moraine deposits, end-moraine deposits, stagnation-moraine deposits, all composed of till) are distinguished for purposes of reconstruction of glacial history. Surficial deposits and materials are assigned to 21 map units on the basis of genesis, age, lithology or composition, texture or particle size, and other physical, chemical, and engineering characteristics. It is not a map of soils that are recognized in pedology or agronomy. Rather, it is a generalized map of soils recognized in engineering geology, or of substrata or parent materials in which pedologic or agronomic soils are formed. Glaciotectonic (ice-thrust) structures and deposits are mapped separately, represented by a symbol. On the glaciated plains, the surficial deposits are glacial, ice-contact, glaciofluvial, alluvial, lacustrine, eolian, colluvial, and mass-movement deposits. In the Sweet Grass Hills, beyond the limit of Quaternary glaciation they are fluvial, colluvial, and mass-movement deposits. Till of late Wisconsin age is represented by three map units. Tills of Illinoian and pre-Illinoian glaciations are not mapped, but are widespread in the subsurface. Linear ice-molded landforms (primarily drumlins) indicate directions of ice flow during late Wisconsin glaciation.

Fullerton, David S.; Colton, Roger B.; Bush, Charles A.

2013-01-01

177

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

178

Morphodynamic equilibrium of alluvial estuaries  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

179

Late Quaternary faulting in the Vallo di Diano basin (southern Apennines, Italy)  

NASA Astrophysics Data System (ADS)

The Vallo di Diano is the largest Quaternary extensional basin in the southern Apennines thrust-belt axis (Italy). This portion of the chain is highly seismic and is currently subject to NE-extension, which triggers large (M> 6) normal-faulting earthquakes along NW-trending faults. The eastern edge of the Vallo di Diano basin is bounded by an extensional fault system featuring three main NW-trending, SW-dipping, right-stepping, ~15-17 km long segments (from north to south: Polla, Atena Lucana-Sala Consilina and Padula faults). Holocene activity has been documented so far only for the Polla segment. We have therefore focused our geomorphological and paleoseismological study on the southern portion of the system, particularly along the ~ 4 km long Atena Lucana-Sala Consilina and Padula faults overlap zone. The latter is characterized by a complex system of coalescent alluvial fans, Middle Pleistocene to Holocene in age. Here we recognized a > 4 km long and 0.5-1.4 km wide set of scarps (ranging in height between 1 m and 2.5 m) affecting Late Pleistocene - Holocene alluvial fans. In the same area, two Late Pleistocene volcanoclastic layers at the top of an alluvial fan exposed in a quarry are affected by ~ 1 m normal displacements. Moreover, a trench excavated across a 2 m high scarp affecting a Holocene fan revealed warping of Late Holocene debris flow deposits, with a total vertical throw of about 0.3 m. We therefore infer the overlap zone of the Atena Lucana-Sala Consilina and Padula faults is a breached relay ramp, generated by hard-linkage of the two fault segments since Late Pleistocene. This ~ 32 km long fault system is active and is capable of generating Mw ?6.5 earthquakes.

Villani, F.; Pierdominici, S.; Cinti, F. R.

2009-12-01

180

Geology and mineral deposits of Churchill County, Nevada  

USGS Publications Warehouse

Churchill County, in west-central Nevada, is an area of varied topography and geology that has had a rather small total mineral production. The western part of the county is dominated by the broad low valley of the Carson Sink, which is underlain by deposits of Lake Lahontan. The bordering mountain ranges to the west and south are of low relief and underlain largely by Tertiary volcanic and sedimentary units. Pre-Tertiary rocks are extensively exposed east of the Carson Sink in the Stillwater Range, Clan Alpine Mountains, Augusta Mountains, and New Pass Mountains. The eastern valleys are underlain by Quaternary alluvial and lacustrine deposits contemporaneous with the western deposits of Lake Lahontan. The eastern mountain ranges are more rugged than the western ranges and have higher relief; the eastern valleys are generally narrower.

Willden, Ronald; Speed, Robert C.

1974-01-01

181

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

182

Sedimentary facies, depositional environments and palaeogeographic evolution of the Neogene Denizli Basin, SW Anatolia, Turkey  

NASA Astrophysics Data System (ADS)

The Denizli Basin (southwestern Anatolia, Turkey) contains a record of environmental changes dating since the Early Miocene. Detailed facies analysis of the Neogene formations in this half-graben enables us to document successive depositional regimes and palaeogeographic settings. Sedimentation commenced in the Early Miocene with the deposition of alluvial-fan and fluvial facies (K?z?lburun Formation). At this stage, alluvial fans sourced from elevated areas to the south prograded towards the basin centre. The Middle Miocene time saw the establishment of marginal lacustrine and wetland environments followed by the development of a shallow lake (Sazak Formation). The uppermost part of this unit consists of evaporitic saline lake and saline mudflat facies that grade upward into brackish lacustrine deposits of Late Miocene-Pliocene age (Kolankaya Formation). The lake became shallower at the end of the Pliocene time, as is indicated by expansion shoreface/foreshore facies. In the Early Quaternary, the Denizli Basin was transformed into a graben by the activation of ESE-trending normal faults. Alluvial fans were active at the basin margins, whereas a meandering river system occupied the basin central part. Oxygen isotope data from carbonates in the successive formations show an alternation of wetter climatic periods, when fresh water settings predominated, and very arid periods, when the basin hosted brackish to hypersaline lakes. The Neogene sedimentation was controlled by an active, ESE-trending major normal fault along the basin's southern margin and by climatically induced lake-level changes. The deposition was more or less continuous from the Early Miocene to Late Pliocene time, with local unconformities developed only in the uppermost part of the basin-fill succession. The unconformable base of the overlying Quaternary deposits reflects the basin's transformation from a half-graben into a graben system.

Alçiçek, Hülya; Varol, Baki; Özkul, Mehmet

2007-12-01

183

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

184

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

185

Paleovalley systems: Insights from Quaternary analogs and experiments  

NASA Astrophysics Data System (ADS)

Ancient fluvial valley systems are long recognized as important features in the stratigraphic record, but emerged as a specific focus of attention with publication of first-generation sequence-stratigraphic concepts. This paper reviews current understanding of paleovalley systems from the perspective of Quaternary analogs and experimental studies. Paleovalley systems can include distinct mixed bedrock-alluvial, coastal-plain, and cross-shelf segments. Mixed bedrock-alluvial segments are long-lived, cut across bedrock of significantly older age, and have an overall degradational architecture. By contrast, coastal-plain and cross-shelf segments are non-equilibrium responses to high-frequency cycles of relative sea-level change: most coastal-plain and cross-shelf segments form as a geometric response to relative sea-level fall, as river systems cut through coastal-plain and inner shelf clinothems, and extend basinward to track the shoreline. After incision and cross-shelf extension, lateral channel migration and contemporaneous channel-belt deposition creates a valley-scale feature. Coastal-plain and cross-shelf paleovalley widths are set by the number of channel-belt sandbodies deposited during this time. Paleovalley systems play a key role in source-to-sink sediment routing. Early views included the model of incision and complete sediment bypass in response to relative sea-level fall. However, this model does not stand up to empirical, theoretical, or experimental scrutiny. Instead, there is a complex dynamic between incision, deposition, and sediment export from an evolving valley: periods of incision correspond with sediment export minima, whereas periods of lateral migration and channel-belt construction result in increased flux to the river mouth. Sediment export from evolving valleys, and merging of drainages during cross-shelf transit, play key roles in sediment transfer to the shelf-margin and genetically-linked slope to basin-floor systems. Connection between the river mouth and the shelf margin likely occurs for different periods of time depending on gradient of the river and shelf, as well as amplitude of high-frequency sea-level changes. Late Quaternary analogs and experimental studies provide an alternative sequence-stratigraphic interpretation for paleovalley systems. In coastal-plain paleovalleys, basal valley-fill surfaces meet criteria for an unconformity and a classically-defined sequence boundary: however, this surface is mostly everywhere of the same age as overlying fluvial deposits, and does not correspond to a long period of incision and sediment bypass. In cross-shelf paleovalleys, the basal contact between fluvial and deltaic or shoreface deposits is commonly interpreted as a sequence boundary, but is not an unconformity characterized by incision and sediment bypass. Instead, this surface is a facies contact that separates genetically-related fluvial and deltaic strata: the surface that correlates to the basal valley-fill surface within the coastal-plain paleovalley dips below cross-shelf prograding deltaic and/or shoreface strata, which are fed by deposition within the evolving valley itself, and should be the downlap surface. Many issues deserve attention in the future. We have stressed understanding the inherent scales and physical processes that operate during the formation and evolution of paleovalley systems. We also suggest the relative roles of allogenic forcing vs. autogenic dynamics, and the potential significance of high-frequency isostatic adjustments should be topics for future discussion.

Blum, M.; Martin, J.; Milliken, K.; Garvin, M.

2013-01-01

186

Alluvial Fans and Megafans Along the Southern Side of the Alps  

NASA Astrophysics Data System (ADS)

The Po Plain extents for about 40.000 km2 and fills an area representing the foreland of the Alps and the foredeep of the Apennines. Towards East, the Po plain continues in the Venetian-Friulian Plain, which has an area of 10.000 km2. Along the Alpine piedmont sector the alluvial deposition has been related to the major Alpine rivers, that drain a total mountain catchement of about 50.000 km2, with a maximum elevation between 2800-4810 m. A major depositional phase occurred in the area during LGM (24-17 ka BP), when the fronts of the glaciers hosted in the main Alpine valleys reached the plain and fed the related fluvioglacial and fluvial systems. These experienced a large and widespread aggradation and led to the formation of several megafans (i.e. Isonzo, Tagliamento, Piave, Brenta, Chiese, Oglio, Adda, Ticino) and fans (e.g. Cellina, Astico, Serio, Lambro). The LGM megafans have an extent between 1000-3000 km2 and are characterized by a piedmont sector (10-25 km from the apex) of amalgamated gravels related to unconfined braided channels; the distal sector is fine-dominated and channels are sandy braided, whereas the meandering typology started from the terminal portion (40-60 km from apex). The thickness of LGM alluvial sedimentation spans between 30-20 m in the plain and thins to 10 m in the Adriatic seabed. Soon after the ice decay (since 17 ka BP), the sedimentary delivery from Alpine catchments to the plain stopped, mainly due to the formation of intramontane lakes trapping the bedload. Thus, an erosive phase affected the whole pede-Alpine sector, leading the Alpine rivers to entrench for tens of meters in the apical gravelly portions of their fans or megafans. In the Venetian-Friulian Plain a single incision characterize the apical portion, whereas 2-5 fluvial incisions developed in the distal sector, up to the present coastal area, where they have a depth of 15-30 m and a width of 600-2000 m. The incised-valley fills (IVF) have been recognized in the Isonzo, Tagliamento, Piave and Brenta systems and they display a similar internal architecture, characterized by coarse gravel deposits at bottom and a general fining-upward trend. Radiocarbon datings demonstrate that fluvial entrenchment and coarse-gravel transport mainly occurred during Lateglacial and early Holocene and almost stopped around 8.0-7.0 ka cal. BP. In the Venetian-Friulian Plain, directly connected with Adriatic Sea, some abandoned incisions were drowned by marine transgression since 7.0 ka cal. BP, allowing the formation of 15-km long tidal inlets and to the deposition of lagoonal and estuarine sediments inside the incisions. Late Holocene fluvial activity has been characterized by the formation of fluvial ridges along the last 30 km of Alpine rivers, which largely contributed to silt-up completely the Lateglacial incisions. In the central and western Po Plain, due to its more internal position from the coast, the incisions are still present along the Alpine tributaries of Po River, up to their junction with this course. A very different late Quaternary evolution characterize the southern sector of Po Plain, where the alluvial systems are fed by the Apennines and LGM glacial activity was very limited.

Fontana, A.; Mozzi, P.

2011-12-01

187

A giant flightless pigeon gen. et sp. nov. and a new species of Ducula (Aves: Columbidae), from Quaternary deposits in Fiji  

Microsoft Academic Search

A new genus and species are erected for a giant flightless pigeon described from post?cranial fossil bones from four Quaternary sites on Viti Levu, Fiji, in the South Pacific Lack of cranial material and transformations associated with large size and loss of flight obscure its relationships, but some characters of the tarsometatarsus, tibiotarsus, and humerus are closer to Goura than

T. H. Worthy

2001-01-01

188

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

Microsoft Academic Search

Investigations and mapping of surficial deposits in Ohio have focused largely on the glacial deposits which cover nearly two-thirds of the state. Research on Quaternary deposits beyond the glacial border has been done by Foster, Hildreth, Andrews, Leverett, Tight, Stout, Goldthwait, Forsyth, Lessig, White, Totten, Hoyer, and Noltimier. However, growing human interaction with surficial materials of southeast Ohio now requires

1992-01-01

189

Quaternary and Geomorphology.  

ERIC Educational Resources Information Center

Highlights conferences and meetings of organizations involved with quaternary geology and geomorphology, including International Union of Quaternary Research Conference held in Moscow. The impetus of a revision of "The Quaternary of the United States" resulted from this conference. Includes activities/aims of "Friends of the Pleistocene"…

Andrews, J. T.; Graf, W. L.

1983-01-01

190

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

191

Resistivity imaging of Pleistocene alluvial aquifers in a contractional tectonic setting: A case history from the Po plain (Northern Italy)  

NASA Astrophysics Data System (ADS)

In this work we present the hydrogeophysical imaging of a key sector of the Quaternary Po foreland basin (northern Italy), focussing on the reconstruction of clastic aquifers and aquitards in a complex tectono-sedimentary subsurface architecture. The study area includes the relic reliefs of Casalpusterlengo and Zorlesco, two smooth morphological features involving uplifted and gently folded Pleistocene marine to alluvial sediments, plausibly linked to the buried Northern Apennines thrust and fold belt. The geophysical data include 35 Direct Current Vertical Electrical Soundings collected over a 37 km2 wide area, acquired with Schlumberger array and maximum half-spacing of 500 m. 1-D resistivity-depth profiles were computed for each VES. An integrated hydrostratigraphic approach was applied, to constrain the interpretation of the geophysical data along several cross-sections, including the comparison of resistivity soundings to stratigraphic logs, borehole electric logs and the pore-water properties. The resistivity interfaces, traceable with the same laterally continuous vertical polarity, were used to develop an electrostratigraphic model in order to portray the stacking of electrostratigraphic units down to 200 m below ground surface. Their vertical associations show a general upward increase of electrical resistivity. This assemblage mimics the regional coarsening upwards depositional trend, from the conductive units of the Plio-Pleistocene marine-to-transitional depositional systems to the resistive units of the Middle-Late Pleistocene fluvial and alluvial plain depositional systems. Middle Pleistocene depositional systems host an alternation of North-dipping, high-to-intermediate permeability aquifer systems (70-180 ?m, thickness of 5-70 m) separated by low permeability aquitards (20-50 ?m, thickness up to 40 m). These units pinch out against the Casalpusterlengo and Zorlesco relic reliefs, where they cover the uplifted and folded regional aquitard (20-50 ?m) formed by Pliocene-Lower Pleistocene clays to sandy silts with gravel lenses in agreement with borehole data. In the deepest part of the local stratigraphy, a broad low-resistivity anomaly (< 10 ?m) was clearly mapped through the study area. By comparison with electrical borehole logs in deep oil-wells, it could be interpreted as the fresh-saltwater interface due to the presence of connate waters and brines hosted by the marine-to-transitional shales.

Mele, M.; Bersezio, R.; Giudici, M.; Inzoli, S.; Cavalli, E.; Zaja, A.

2013-06-01

192

The morphology of alluvial rivers  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

193

Guidelines for Determining Flood Hazards on Alluvial Fans.  

National Technical Information Service (NTIS)

Alluvial fans, and flooding on alluvial fans, show great diversity. This document provides an approach that considers site-specific conditions in the identification and mapping of flood hazards on alluvial fans.

2000-01-01

194

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

195

Bedload transport in alluvial channels  

USGS Publications Warehouse

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

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

2003-01-01

196

Quaternary evolution of the Agri Valley, Southern Italy  

NASA Astrophysics Data System (ADS)

The Agri Valley (Southern Italy) is a key area for understanding the Quaternary evolution of a large sector of the external Southern Apennines, due to its E-W orientation across the mountain chain. It also represents one of the most tectonically active regions of Southern Italy and it therefore deserves a particular interest. Based on the great sensitivity of the rivers in recording even small changes of the topographic gradient, a detailed morphological analysis of the fluvial terraces has been carried out along the valley. We also carefully analysed the several orders of marine terraces occurring along the final sector of the valley. Available structural, stratigraphic, geophysical, seismotectonic and other morphological data have been taken into account in order to reconstruct the Quaternary evolution of the area. Accordingly, the Agri Valley can be subdivided into three reaches, diachronously developed during Pleistocene times and characterized by a differentiated geological evolution. Two major tectonic structures are mainly responsible for this segmentation and namely the Armento Thrust, to the West, and the Rotondella anticline-Scorciabuoi Fault, to the East. The high Agri Valley represents the first reach both morphologically and chronologically. It formed during (Late?) Pliocene, while erosional processes producing progressive deepening, widening and lengthening of the valley certainly persisted throughout the Early Pleistocene. The general uplift of this sector was probably induced by activity along the Armento Thrust. However, from Middle to Late Pleistocene this sector was characterised by depositional conditions associated to the accumulation of a 200-300 m thick sedimentary succession, the so-called Complesso Val d'Agri. Possible causes of this inversion will be discussed. Only from latest Quaternary onwards, this sector of the valley was newly affected by entrenching due to a progressive phenomenon of regressive erosion across the lithological threshold of the Armento anticline. The second reach of the Agri Valley entirely crosses the Sant'Arcangelo Basin from West to East. The sedimentary infilling mainly consists of a marine succession where only the youngest conglomeratic Serra Corneta Fm, of Early to early Middle Pleistocene age, represents a pure continental environment. Although this alluvial plain was certainly crossed by several water streams, the second reach of the Agri Valley began forming only when the regional uplift prevailed and diffused alluvial conditions were therefore abandoned. As a consequence, since Middle Pleistocene this sector of the valley was continuously deepening and widening though the occurrence of river terraces clearly document the stepping behaviour of the process. Because of the lithological contrast occurring where the river crosses the Armento anticline, to the West, and due to the probable recent activity along the Scorciabuoi Fault, to the East, this second reach of the Agri Valley can be still easily delimited by two knick-points occurring along the river bed. Also the third reach of the valley started forming during Middle Pleistocene due to the seaward river lengthening consequent of the progressive entrenching of the marine sediments that were continuously uplifted and inexorably brought into subaerial conditions. The occurrence of several orders of morphologically linked fluvial and marine terraces clearly documents this regional geodynamic process and the role played by eustasy. In particular, this latter phenomenon allowed to attempt some estimates on the amount of uplift rate affecting the region. Also the analysis of the fluvial pattern, the load-type and the sinuosity allows to segment the river in several sectors with different characteristics and behaviour ranging from purely meandering to transitional meandering-thalweg braided channels. Longitudinal variations are observed and are likely associated to major tectonic structures.

Caputo, R.; Bianca, M.

2003-04-01

197

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

198

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

199

Flow resistance in alluvial and mountain rivers  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

200

Late Quaternary climatic evolution of the Arno coastal plain (Western Tuscany, Italy) from subsurface data  

NASA Astrophysics Data System (ADS)

A multidisciplinary study of a 105-m-long core was carried out on the Tyrrhenian coast of Tuscany, Western Italy. Detailed description of sedimentary facies, foraminifer and ostracod assemblages, pollen, and 14C ages is presented in this paper. Identification in core of two transgressive surfaces (TSs) as the most prominent stratigraphic markers allows subdivision of the Late Quaternary stratigraphic succession into two transgressive-regressive (T-R) sequences, attributed to the last 150 kyr BP. Sequence boundaries have no unequivocal physical expression in the core. Detailed pollen analysis documents a direct relationship between vertical facies evolution and climate fluctuations. Coastal to shallow-marine sediments in the lower part of T-R sequences were deposited during the last two interglacial periods (OIS 1 and 5e), under rising sea-level conditions and during the following sea-level highstands. By contrast, alluvial sedimentation (upper part of T-R sequences) took place during periods of sea-level fall and subsequent sea-level lowstands, and was invariably linked to the onset of glacial periods (OIS 4-2 and 6, respectively). This paper presents the first detailed facies documentation of a Late Quaternary incised-valley fill sequence from Italy. About 51 m of Holocene sediments are recorded beneath the present Arno River valley. Early transgression is documented in the lower part of the incised-valley fill by wave-dominated estuarine facies overlying lowstand fluvial deposits. Late transgression records the rapid landward migration of a beach-barrier system, followed by the establishment of an open-marine environment. Highstand sedimentation is represented by a shallowing-upward succession, which reflects progradation of the modern delta/strandplain.

Aguzzi, Margherita; Amorosi, Alessandro; Colalongo, Maria Luisa; Lucchi, Marianna Ricci; Rossi, Veronica; Sarti, Giovanni; Vaiani, Stefano Claudio

2007-11-01

201

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

202

Input Data Formats for Alluvial Channel Experiments.  

National Technical Information Service (NTIS)

Various experiments covering hydraulic, morphologic and sediment characteristics of alluvial channels are being conducted on the Link Canals of Pakistan. Data from these experiments are to be punched on cards for use on digital computers. The formats have...

K. Mahmood T. Masood G. L. Eyster

1976-01-01

203

Quaternary deformation mapping with ground penetrating radar  

Microsoft Academic Search

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

J. P Busby; J. W Merritt

1999-01-01

204

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

NASA Technical Reports Server (NTRS)

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

Farr, Tom G.; Chadwick, Oliver A.

1996-01-01

205

Multi-scale alluvial fan heterogeneity modeled with transition probability geostatistics in a sequence stratigraphic framework  

Microsoft Academic Search

The complexity of alluvial fan depositional systems makes detailed characterization of their heterogeneity difficult, yet such detailed characterizations are commonly needed for construction of reliable groundwater models. The transition probability geostatistical approach provides a means to quantify the distribution of hydrofacies in the subsurface. However, a key assumption used in this and other geostatistical approaches is that of stationarity. Stratigraphic

G. S. Weissmann; G. E. Fogg

1999-01-01

206

Quaternary Research Association  

NSDL National Science Digital Library

The Quaternary Research Association explains that it "exists to promote understanding of the Quaternary Period by publishing field guides, technical guides, and an international journal as well as holding field meetings and speaker meetings." Students and researchers can discover employment, research, grant, meetings, and educational opportunities.

1969-12-31

207

The influence of bed roughness on partial alluviation in an experimental bedrock channel  

NASA Astrophysics Data System (ADS)

The extent of alluvial cover on a bedrock channel bed strongly influences the efficiency of river incision, and can affect the quality of habitat for aquatic ecosystems. The extent of partial cover is commonly modeled as a simple function of sediment supply relative to the transport capacity of the stream, although other factors are likely to be important, particularly the roughness of the underlying bedrock surface. Here we report results of a set of laboratory experiments investigating the influence of bedrock channel bed topography on the dynamics of partial bed alluviation. The experiments were conducted in a tilting flume 8 m long and 0.3 m wide with an erodible bedrock bed made of a sand-cement mixture. The flume has a calibrated sediment feed and a double-basket sediment trap that provides a continuous record of sediment flux out of the downstream end. We used a uniform grain size of 5 mm, and varied the sediment supply rate from zero to that sufficient to create a fully alluviated bed. We created a variety of bedrock roughness conditions, from smooth, nearly planar surfaces to an egg-carton texture made with a plaster-coated foam mold. Intermediate roughness was achieved by chiseling into smooth beds and by allowing the bed topography to evolve by sustained bedload abrasion. We used a laser microtopography scanning device to make topographic maps of the bed surface, with a vertical resolution of 0.2 mm and a horizontal spacing of 5 mm. From these data we quantify bedrock bed roughness as the standard deviation of the distribution of bed elevations relative to a plane inclined at the mean bed slope. To guide our selection of bed roughness values we made topographic surveys of a number of bedrock channel beds, including partially alluviated channels where we dug trenches through alluvial deposits to expose the underlying bedrock surface. For each bed roughness condition we systematically varied the sediment supply rate and repeatedly mapped the extent of partial alluvial cover. We also calculated the volume of sediment stored within the channel as a function of time, from the cumulative difference between the sediment feed rate and measured sediment output. We find that low-roughness beds require a relatively high sediment supply before any alluvial patch formation occurs, and as supply increases, can accommodate only low levels of partial alluvial cover before a runaway alluviation process rapidly converts the bed to an aggrading alluvial condition. In contrast, highly rough bedrock surfaces partially alluviate at very low sediment feed rates, and do not experience runaway alluviation at high supply rates, and allow stable high fractional bed coverage. The dynamics of partial bed alluviation can be described by plotting sediment output from the flume as a function of sediment storage within the flume. Stable partial coverage corresponds to curves of increasing sediment output with increasing sediment storage, while the instability that leads to runaway alluviation corresponds to curves with a negative relationship between output and storage. For stable partial bed cover, sediment deposits within the flume have the effect of increasing the sediment transport capacity, presumably by altering the lateral distribution of boundary shear stress.

Davis, J. R.; Sklar, L. S.; Demeter, G. I.; Johnson, J. P.; Whipple, K. X.

2005-12-01

208

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

209

Barium and High Explosives in a Semiarid Alluvial System, Cañon de Valle, New Mexico.  

NASA Astrophysics Data System (ADS)

Barium and RDX (a military high explosive compound) were evaluated from 1998 to 2002 within a semiarid alluvial system, Cañon de Valle (CdV), New Mexico. A high explosive (HE) machining facility discharged effluent containing these analytes to the canyon from 1951 to 1996. Surface water, alluvial groundwater, active channel sediments, and floodplain sediments were characterized along a 2 km long reach of canyon. Barium concentrations were higher in the alluvial groundwater than the surface water with the highest concentration centered approximately 500 m downgradient from the HE facility. Of the 21,000 kg of Ba estimated to be in CdV sediment in 1999, about 65% is estimated to have been contained in fine-grained floodplain deposits, 10% in the active channel, and 25% in coarse-grained deposits below the floodplains. The ratio of Ba concentration in fine grained deposits to the active channel increases downstream and increased over time. These data indicate that Ba from the effluent was first stored in the active channel where it could preferentially bind to fine sediment particles, and then was redistributed onto floodplains following scour and suspension during floods. The Ba residing within the floodplain sediments appears relatively stable, and remains isolated from surface water and alluvial groundwater. Approximately 5 kg of RDX was estimated to reside in CdV sediment, also preferentially in fine-grained sediment. RDX concentrations in groundwater were highest (up to 759 ug/L) during high flow snowmelt runoff. The highest average RDX concentration was from an alluvial well approximately 1000 m down gradient. There was a positive correlation between saturated thickness in CdV alluvial wells and RDX concentration. The strong correlation between RDX concentration and saturated thickness suggests that RDX resides in the vadose zone and mobilizes during wet periods when the effective saturated area increases. RDX and Ba show markedly different transport pathways through the alluvial system. Barium is readily sorbed and transported with the sediment fraction. In contrast, RDX is unbuffered and conservative. Thus as the alluvial system wets up, the RDX mobilizes. Knowledge of the distribution of Ba and RDX is critical to design and implementation of corrective measures for this system.

Reid, K. D.; Hickmott, D. D.; Reneau, S. L.; Newman, B. D.; Gram, P. E.; Heikoop, J. M.; Alcon, E. D.; Herrell, K. A.; Jercinovic, D. E.; Lawler, D. S.; Pietz, J. M.

2003-12-01

210

Tectonics and Quaternary sequence development of basins along the active Vienna Basin strike-slip fault  

NASA Astrophysics Data System (ADS)

The Vienna Basin strike-slip fault is a continent scale active fault extending over a distance of some 300 km from the Eastern Alps through the Vienna Basin into the Western Carpathians. Sinistral movement causes the formation of several tight Pleistocene strike-slip basins within the older Miocene Vienna Basin. These sub-basins not only have a high relevance for groundwater exploitation but their fault activities depict serious seismic hazards. Basins are filled with fluvial sediments from the Danube and, closer to the Alpine front, with thick alluvial fan deposits. However, knowledge on the stratigraphy and tectonics is sparse and rather limited to the Miocene part of the Vienna Basin as it hosts giant hydrocarbon fields. This study tackles two major questions: (i) What is the effect of Quaternary climatic oscillations and subsidence on the sequence development of the alluvial fans and (ii) what is the deformation style of these basins? To answer (i) we present a series of new OSL ages and biotic data from both, surface and cores, to better constrain the timing of fan activity, fan abandonment but also to constrain the onset of Pleistocene basin formation. For (ii) we utilize information from unparalleled geophysical and geological data. Specifically we utilize industrial Bouguer gravity's derivatives to highlight shallow structures and to compensate for the lag of fault trace information. The integration of geological and geophysical data highlights textbook-like models of strike-slip basins, with typical features like Riedel shears with intervening relay ramps, en-echelon sidewall faults and a cross-basin fault zone delimiting opposite depocenters. The infill reflects a distinct cyclicity with thick sequences of coarse sediments deposited during colder periods and thin sequences of paleosol and flood sediments deposited during warmer periods. Ages indicate main activity around the short peak glacial periods and basin formation starting c. 300 ka ago. The distinct sequence development and the strong contrast to the underlying marine deposits is a very suitable setting to apply geophysical methods constraining basins' deformation style.

Salcher, B.; Lomax, J.; Meurers, B.; Smit, J.; Preusser, F.; Decker, K.

2012-04-01

211

Combined velocity and depth mapping on developing laboratory alluvial fans  

NASA Astrophysics Data System (ADS)

Large-scale particle image velocimetry (LSPIV) is a nonintrusive method for measuring free-surface velocities using tracer patterns in a sequence of images. This method has been applied in both natural rivers and large-scale hydraulic models (Muste et al., 2008). Here the method is used to map channel and sheet flow velocity during the development of laboratory-scale alluvial fans. Measuring the time and space varying hydraulics on laboratory fans by traditional methods is not practical since flows are quite shallow (~1 cm). Additionally, the highly dynamic environment makes positioning of traditional probe-type instruments difficult and their physical presence could alter autogenic fan evolution. These difficulties can be overcome by using particle image velocimetry techniques. Furthermore, images collected in the LSPIV method can be used to extract flow depth using a calibrated dye-intensity method (Gran and Paola, 2001). This allows for simultaneous measurement of flow velocity and depth everywhere over the fan at any point in time. To validate the method, a set of controlled small-scale experiments were run for depths ranging from 0.2-1.5 cm and velocities from 10-100 cm/sec. Comparison of the LSPIV and dye-intensity method measurements to the known values indicated that the methodology was able to accurately capture simultaneous flow velocity and depth in this range of conditions, i.e., those encountered during the development of laboratory-scale alluvial fans and streams. The method is then used to map the hydraulics associated with various fan processes during development as demonstrated in figure 1. The ability to measure hydraulic properties during fan development is important since physical models provide an arena for observing the time evolution and morphodynamic feedback in depositional systems such as alluvial fans.

Hamilton, P.; Strom, K. B.; Hoyal, D. C.

2011-12-01

212

The depositional history of the Bavarian Allgäu area at the turn of the Tertiary\\/Quaternary, Northern Alpine Foreland, Germany — a set of paleogeological maps  

Microsoft Academic Search

The Northern Alpine Foreland in southwestern Bavaria is characterized by Miocene Molasse overlain by deposits of glacial and glacifluvial origin. One peculiarity of this region is the occurrence of extended fluvial terraces of the Upper Pliocene\\/Lower Pleistocene, which can be subdivided into several distinct levels. From these sediments good information on the stratigraphy, palaeogeography and palaeoenvironment of the Illerglacier Foreland

Raimo A Becker-Haumann

2001-01-01

213

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

214

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

215

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

216

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

NASA Astrophysics Data System (ADS)

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

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

2008-07-01

217

Quaternary Research Center  

NSDL National Science Digital Library

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

218

Combining sedimentological and geophysical data for high-resolution 3-D mapping of fluvial architectural elements in the Quaternary Po plain (Italy)  

Microsoft Academic Search

Current approaches to the reconstruction of the geometry of fluvial sediments of Quaternary alluvial plains and the characterization of their internal architecture are strongly dependent on core data (1-D). Accurate 2-D and 3-D reconstructions and maps of the subsurface are needed in hydrostratigraphy, hydrogeology and geotechnical studies. The present study aims to: 1) improve current methods for geophysical imaging of

R. Bersezio; M. Giudici; M. Mele

2007-01-01

219

Longitudinal profiles in simple alluvial systems  

NASA Astrophysics Data System (ADS)

Theoretical considerations suggest that exponential or quadratic functions are apt for describing the longitudinal profiles of aggrading, alluvial systems that are unaffected by significant lateral inputs of water or sediment. A new set of field data confirms this for individual sedimentary links along a wandering gravel-bed river in British Columbia, Canada. Each link is viewed as a simple alluvial system, without major water or sediment inputs, within which grain size typically fines downstream in a relatively systematic manner. Such homogeneous reaches are suitable for the investigation of simple profile form. It is found that quadratic approximations are the most flexible descriptor for link longitudinal profiles. Overall, the river forms an irregularly cuspate long profile structured by these fundamental length-scale units. Both link gradients and link fining rate reflect size-selective aggradation associated with the bounding lateral inputs.

Rice, Stephen P.; Church, Michael

2001-02-01

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

Case studies of groundwater - surface water interactions and scale relationships in small alluvial aquifers  

Microsoft Academic Search

An alluvial aquifer can be described as a groundwater system, generally unconfined, that is\\u000ahosted in laterally discontinuous layers of gravel, sand, silt and clay, deposited by a river in a\\u000ariver channel, banks or flood plain. In semi-arid regions, streams that are associated with\\u000aalluvial aquifers tend to vary from discharge water bodies in the dry season, to recharge

David Love; Hamer de Wouter; Richard J. S. Owen; Martijn Booij; Stefan Uhlenbrook; Arjen Y. Hoekstra; Zaag van der Pieter

2007-01-01

222

Interaction of fine sediment with alluvial streambeds  

USGS Publications Warehouse

An alluvial streambed can have a large capacity to store fine sediments that are extracted from the flow when instream concentrations are high and it can gradually release fine sediment to the flow when the instream concentrations are low. Several types of storage mechanisms are available depending on the relative size distribution of the suspended load and bed material, as well as the flow hydraulics. -from Authors

Jobson, H. E.; Carey, W. P.

1989-01-01

223

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

224

Quaternary Alloy Microwave MESFET.  

National Technical Information Service (NTIS)

Liquid phase epitaxial growth techniques have been used to grow quaternary alloys, Ga sub 1-x In sub x P sub 1-y As sub y, on InP substrates, using (100), (111) A and (111) B orientations. Liquidus and solidus data at 660 C have been used to determine dis...

J. W. Harrison S. B. Phatak M. A. Littlejohn G. Kelner H. H. Stadelmaier

1979-01-01

225

Quaternary Faunal Environments  

NSDL National Science Digital Library

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

Hill, Christopher

226

Tributary stream infiltration as a source of herbicides in an alluvial aquifer  

USGS Publications Warehouse

Where Walnut Creek flows across the South Skunk River alluvial aquifer, it provides a potential source of herbicides and herbicide metabolites. This straightened reach of the creek loses water and dissolved contaminants to the alluvial aquifer through a layer of fine-grained flood plain deposits. Estimates of potential flux of chemicals were based on measurements taken during baseflow in April 1994 before herbicides were applied to the watershed and in June 1994 after chemical application and when stream discharge included runoff and tile-drainage water. Hydraulic head measurements between the creek and flood plain deposits and between the creek and aquifer confirmed the potential for downward groundwater flow during both sampling periods. Hydraulic conductivity estimates from slug tests were used to calculate an average linear groundwater velocity of 0.5 m d-1 in the fine- grained flood plain deposits. At this velocity, contaminants could be advectively transported to the aquifer within 6 d. The potential for atrazine (2-chloro-4-ethylamino-6-isopropyl-amino-s-triazine) flux to the aquifer from the creek was estimated to be between 60 and 3000 ??g d-1 m-2. This rate is one to three orders of magnitude greater than the estimated flux via leaching beneath a typical field. If the process of vertical stream leakage occurs in many hydrologic settings, it may constitute a substantial source of herbicides to shallow alluvial aquifers in many areas of the Midwest.

Burkart, M. R.; Simpkins, W. W.; Squillace, P. J.; Helmke, M.

1999-01-01

227

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

Microsoft Academic Search

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

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

2010-01-01

228

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

Microsoft Academic Search

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

Victoria E. Lee; Donald J. Depaolo; John N. Christensen

2010-01-01

229

Late Quaternary sea-level highstands in the Tasman Sea: evidence from Lord Howe Island  

Microsoft Academic Search

Lord Howe Island, situated 600 km east of Australia, provides a unique opportunity to evaluate Late Quaternary highstands of sea level in the Tasman Sea. The mid-ocean island, which is the site of the southernmost coral reef, is composed of basalts of late Tertiary age, and calcarenites derived from bioclastic reefal carbonates. Both erosional and depositional evidence of Late Quaternary

C. D. Woodroffe; C. V. Murray-Wallace; E. A. Bryant; B. Brooke; H. Heijnis; D. M. Price

1995-01-01

230

A Preliminary Geomorphic Overview of Late Quaternary Glacier Fluctuations in the South Shetland Islands, West Antarctica  

Microsoft Academic Search

?The timing and extent of glaciations during the Late Quaternary in the South Shetland Islands, West Antarctica were defined using field mapping, geomorphic analysis and radiocarbon dating. Landforms of glacial erosion and deposition, in particular subglacial meltwater channel erosion, suggest that at least three glaciations occurred during the late Quaternary within the study region. During the global LGM, glacial troughs

Yeong Bae Seong; Hyoun Soo Lim; Ho Il Yoon; Yong Il Lee; Yeadong Kim; Lewis A. Owen

2006-01-01

231

Orbital forcing of glacioeustasy: Evaluation of the alluvial clastic source/sink term  

SciTech Connect

Orbital forcing of climate change at key latitudes has long been recognized as a probable cause of variation in continental ice budget and thereby sea level. The precession cycle, variation in tilt of the earth's axis relative to the sun, and variation in the eccentricity of the earth's orbit about the sun all affect seasonal solar insolation. The seasonal solar insolation signal at any particular latitude is complex, with periods ranging upward from 20,000 yr to hundreds of thousands of years, Further, nonlinear responses of the earth system (e.g., slow buildup and rapid destruction of continental ice sheets) can convert modulation of short-period signal into long-period sea level variation. The alluvial valley/floodplain can be an important factor in sand supply to the marine environment. The alluvial system is constantly linked to the marine depositional system by sea level. With rising sea level, the alluvial system may store sand, thus depriving the marine system. With falling sea level, incisement may release sand previously sequestered in the alluvial system. To investigate these relationships in the context of numerous, rapid, and complex glacioeustatic sea level fluctuations, the authors have incorporated into their two-dimensional forward model an interactive, model-driven alluvial source/sink sediment supply term which includes numerous user-specified parameters. Valley/floodplain geomorphic evolution includes incisement, terrace erosion, and floodplain sedimentation. Sensitivity tests suggest the system seldom reaches equilibrium for geologically reasonable parameterizations. Source/sink relations, which might be ignored if one assumed sea level to be moving slowly in one direction for long periods, can drastically modify availability of sand to the marine environment.

Matthews, R.K. (Brown Univ., Providence, RI (USA)); Frohlich, C. (Institute for Geophysics, Austin, TX (USA))

1990-05-01

232

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

233

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

Microsoft Academic Search

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

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

1985-01-01

234

Late Quaternary activity and dextral strike-slip movement on the Karakax Fault Zone, northwest Tibet  

NASA Astrophysics Data System (ADS)

Field observations and interpretations of satellite images reveal that the westernmost segment of the Altyn Tagh Fault (called Karakax Fault Zone) striking WNW located in the northwestern margin of the Tibetan Plateau has distinctive geomorphic and tectonic features indicative of right-lateral strike-slip fault in the Late Quaternary. South-flowing gullies and N-S-trending ridges are systematically deflected and offset by up to ~ 1250 m, and Late Pleistocene-Holocene alluvial fans and small gullies that incise south-sloping fans record dextral offset up to ~ 150 m along the fault zone. Fault scarps developed on alluvial fans vary in height from 1 to 24 m. Riedel composite fabrics of foliated cataclastic rocks including cataclasite and fault gouge developed in the shear zone indicate a principal right-lateral shear sense with a thrust component. Based on offset Late Quaternary alluvial fans, 14C ages and composite fabrics of cataclastic fault rocks, it is inferred that the average right-lateral strike-slip rate along the Karakax Fault Zone is ~ 9 mm/a in the Late Quaternary, with a vertical component of ~ 2 mm/a, and that a M 7.5 morphogenic earthquake occurred along this fault in 1902. We suggest that right-lateral slip in the Late Quaternary along the WNW-trending Karakax Fault Zone is caused by escape tectonics that accommodate north-south shortening of the western Tibetan Plateau due to ongoing northward penetration of the Indian plate into the Eurasian plate.

Lin, Aiming; Kano, Ken-ichi; Guo, Jianming; Maruyama, Tadashi

2008-06-01

235

Long-term interactions between man and the fluvial environment - case of the Diyala alluvial fan, Iraq  

NASA Astrophysics Data System (ADS)

The Mesopotamian alluvial plain is dominated by large aggradading river systems (the Euphrates, Tigris and their tributaries), which are prone to avulsions. An avulsion can be defined as the diversion of flow from an existing channel onto the floodplain, eventually resulting in a new channel belt. Early civilizations depended on the position of rivers for their economic survival and hence the impact of channel shifts could be devastating (Wilkinson 2003; Morozova 2005; Heyvaert & Baeteman 2008). Research in the Iranian deltaic part of the Mesopotamian plain has demonstrated that deliberate human action (such as the construction of irrigation canals and dams) triggered or obstructed the alluvial processes leading to an avulsion on fluvial megafans (during preconditioning, triggering and post-triggering stages) (Walstra et al. 2010; Heyvaert et al. 2012, Heyvaert et al.2013). Thus, there is ample evidence that the present-day alluvial landscapes in the region are the result of complex interactions between natural and anthropogenic processes. Here we present a reconstruction of the Late Holocene evolution of the Diyala alluvial fan (one of the main tributaries of the Tigris in Iraq), with particular attention to the relations between alluvial fan development, changes in channel pattern, the construction of irrigation networks and the rise and collapse of societies through historic times. The work largely draws on the use of remote sensing and GIS techniques for geomorphological mapping, and previously published archaeological field data (Adams 1965). By linking archaeological sites of known age with traces of ancient irrigation networks we were able to establish a chronological framework of alluvial activity of the Diyala alluvial fan. Our results demonstrate that centralized and technologically advanced societies were able to maintain a rapidly aggradading distibutary channel system, supplying water and sediment across the entire alluvial fan. As a consequence, during these periods (Parthian, Sasanian and again in modern times), significant human modification of the landscape took place. Periods of societal decline are associated with reduced human impact and the development of a single-threaded incising river system. Adams, R.M. (1965). Land behind Baghdad: A history of settlement on the Diyala plains. University of Chicago Press, Chicago, Illinois. Heyvaert, V.M.A. & Baeteman, C. (2008). A Middle to Late Holocene avulsion history of the Euphrates river: a case study from Tell ed-D-er, Iraq, Lower Mesopotamia. Quaternary Science Reviews, 27, 2401-2410. Heyvaert, V. M. A., Walstra, J., Verkinderen, P., Weerts, H. J. T. & Ooghe, B. (2012). The role of human interference on the channel shifting of the river Karkheh in the Lower Khuzestan plain (Mesopotamia, SW Iran). Quaternary International, 251, 52-63. Heyvaert, V.M.A., Walstra, J., Weerts, H.J.T. (2013). Human impact on avulsion and fan development in a semi-arid region: examples from SW Iran. Abstractbook of the 10th International Fluvial Sedimentology Conference, July 2013,Leeds, United Kingdom. Morozova, G.S. (2005). A review of Holocene avulsions of the Tigris and Euphrates rivers and possible effects on the evolution of civilizations in lower Mesopotamia. Geoarchaeology, 20, 401-423. Walstra, J., Heyvaert, V. M. A. & Verkinderen, P. (2010). Assessing human impact on alluvial fan development: a multidisciplinary case-study from Lower Khuzestan (SW Iran). Geodinamica Acta, 23, 267-285. Wilkinson, T.J. (2003). Archaeological Landscapes of the Near East. The University of Arizona Press, Tucson, Arizona.

Heyvaert, Vanessa M. A.; Walstra, Jan; Mortier, Clément

2014-05-01

236

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

237

Incision Rates in Mixed Bedrock-Alluvial Channels Dominated by Transience Over 103-107 Year Timescales (Invited)  

NASA Astrophysics Data System (ADS)

Measured rates of river incision into bedrock are commonly interpreted as proxies for rates of rock uplift and as indices of the strength of climate forcing of erosion. In mixed bedrock-alluvial rivers, incision of the bed can only occur when stripping of deposited alluvial material exposes bedrock to processes of abrasion, weathering and plucking. Bedrock incision therefore only occurs when the alluvial bed elevation returns to the elevation of the bedrock underlying it, for example following flood scour into alluvium. If the long time series of alluvial bed elevation can be considered a stochastic process (for which much supporting evidence exists) then the return time to bedrock will follow a power-law probability distribution in the long time limit, resulting in a power-law distribution of incision hiatus lengths. The effect of power-law hiatuses is well known in the sedimentary geology literature because it results in a negative power-law dependence of accumulation rate on measurement interval. This so-called 'Sadler Effect' potentially confounds efforts to infer climatic or tectonic forcing from rate data alone. In this contribution, we explore the extent to which stochastic variation in alluvial bed elevation also impacts rate scaling in bedrock rivers. We test the common assumption that rates of river incision convey simple information about external climatic and tectonic forcing by examining the relationship between bedrock river incision rate and observational timescale for 440 measured rates from 19 settings around the world. Our analysis reveals negative power-law scaling of incision rate with measurement interval for 17 of the 19 examined datasets. The simplest interpretation of the data is that hiatuses in bedrock incision triggered by alluvial deposition have lengths with a power-law distribution, implying that processes of alluvial cover erosion and deposition are stochastic across the full spectrum of timescales examined (103-107 years). We find no evidence for a transition to constant incision rate at any timescale. Thus, neither tectonic uplift nor periodic climate forcing is apparently recorded in a straightforward way by the process of river incision. This result suggests that an understanding of the geomorphic processes that generate long periods of non-incision in mixed bedrock-alluvial channels is arguably more important to understanding rates of landscape change than is an understanding of the incision process itself.

Finnegan, N. J.; Schumer, R.; Finnegan, S.

2013-12-01

238

Macro-roughness model of bedrock-alluvial river morphodynamics  

NASA Astrophysics Data System (ADS)

The 1-D saltation-abrasion model of channel bedrock incision of Sklar and Dietrich, in which the erosion rate is buffered by the surface area fraction of bedrock covered by alluvium, was a major advance over models that treat river erosion as a function of bed slope and drainage area. Their model is, however, limited because it calculates bed cover in terms of bedload sediment supply rather than local bedload transport. It implicitly assumes that as sediment supply from upstream changes, the transport rate adjusts instantaneously everywhere downstream to match. This assumption is not valid in general, and thus can give rise unphysical consequences. Here we present a unified morphodynamic formulation of both channel incision and alluviation which specifically tracks the spatiotemporal variation of both bedload transport and alluvial thickness. It does so by relating the cover fraction not to a ratio of bedload supply rate to capacity bedload transport, but rather to the ratio of alluvium thickness to a macro-roughness characterizing the bedrock surface. The new formulation predicts waves of alluviation and rarification, in addition to bedrock erosion. Embedded in it are three physical processes: alluvial diffusion, fast downstream advection of alluvial disturbances and slow upstream migration of incisional disturbances. Solutions of this formulation over a fixed bed are used to demonstrate the stripping of an initial alluvial cover, the emplacement of alluvial cover over an initially bare bed and the advection-diffusion of a sediment pulse over an alluvial bed. A solution for alluvial-incisional interaction in a channel with a basement undergoing net rock uplift shows how an impulsive increase in sediment supply can quickly and completely bury the bedrock under thick alluvium, so blocking bedrock erosion. As the river responds to rock uplift or base level fall, the transition point separating an alluvial reach upstream from an alluvial-bedrock reach downstream migrates upstream in the form of a "hidden knickpoint". A solution for the case of a zone of rock subsidence (graben) bounded upstream and downstream by zones of rock uplift (horsts) yields a steady-state solution that is unattainable with the original saltation-abrasion model. A solution for the case of bedrock-alluvial coevolution upstream of an alluviated river mouth illustrates how the bedrock surface can be progressive buried not far below the alluvium. Because the model tracks the spatiotemporal variation of both bedload transport and alluvial thickness, it is applicable to the study of the incisional response of a river subject to temporally varying sediment supply. It thus has the potential to capture the response of an alluvial-bedrock river to massive impulsive sediment inputs associated with landslides or debris flows.

Zhang, L.; Parker, G.; Stark, C. P.; Inoue, T.; Viparelli, E.; Fu, X.; Izumi, N.

2014-05-01

239

Morphostratigraphy, Chronostratigraphy, and Evolution of Alluvial Terraces Within the Kansas River Valley, Kansas, USA  

NASA Astrophysics Data System (ADS)

The Kansas River valley, located in the Central Great Plains, is an important locale for studying the relationships between climate and river evolution because, unlike other Great Plains rivers, i.e., the Missouri, Platte, and Arkansas, it and its tributaries lie entirely within the Great Plains. Four terraces are formally recognized within the Kansas River valley: the Menoken, Buck Creek, Newman, and Holliday; however, little is known of their stratigraphy and chronology of formation. To increase our understanding, these terraces were mapped and stratigraphic and chronologic evaluations were conducted, yielding new data on the evolution and history of the Kansas River. Oldest and highest of the terraces (T4) is the Menoken, with fill consisting of a thick, clay-rich diamicton hypothesized to have formed from fluvially reworked glacial sediments deposited during a Pre-Illinoian glacial stage. Independent, but limited, age control based on the presence of Lava Creek B ash found within the terrace provides a maximum limiting age of ~620 ka. Mantling the Menoken Terrace are isolated aeolian dunes constructed of sand winnowed from the Kansas River floodplain following Menoken deposition. Optical dating documents this deposition during MIS 3, between 36 and 31 ka. About 15 m below the Menoken is the Buck Creek (T3), a late-Pleistocene feature. This terrace is characterized by thick, fine-grain deposits, which were deposited prior to ~ 15 ka. Some data suggest that the Buck Creek may contain a sandy unit in the upper reaches of the river valley, and unpublished AMS 14C ages place this sand deposition after ~ 40 ka. Holocene river evolution has resulted in two terraces. The Newman (T2), older of the two, is the most extensive of all terraces in the river valley and is characterized by a thick basal soil formed at ~ 14-10 ka, and overlying Holocene alluvial sediments and soils. Most recent intrenchment produced the Holliday terrace (T1), which is the youngest of the alluvial terraces and is elevated only two meters above the modern floodplain (T0). The Holliday is predominantly comprised of sandy alluvial packages interspersed between weak floodplain (soil) deposits. In addition, the Holliday is morphologically distinct from the other terraces in that it is comprised primarily of meander scars. AMS 14C ages from the Holliday suggest alluviation occurred within the last 3.5 k years with limited entrenchment occurring ~ 1.2 ka.

Halfen, A. F.; Johnson, W. C.

2011-12-01

240

Quaternary megafans, large rivers and other avulsive systems: a potential "who is who" in the geological record  

NASA Astrophysics Data System (ADS)

A fascinating discussion has been recently calling the attention of sedimentologists and geomorphologists regarding to the dominant fluvial styles preserved in the geological record. While some authors postulate that distributary (or distributive) patterns are the most important systems likely to dominate the alluvial rock record (Weissmann et al.2010, among others) others suggest that a variety of fluvial styles are remarkably preserved in the geological record, rejecting the importance of the distributary systems (such as megafans and other like fans coastal systems) (Fielding et al, 2012 among others). However, the Quaternary record of the largest depositional tracks on Earth has been not assessed in a comparative and detailed way. Here I present results from some of the most important Quaternary areas of sedimentation of the world such as the alluvial belts of the largest rivers, the largest megafans and other impressive fluvial dominated wetlands in active tectonic basins. My study is based on field work I carried out in many of the analyzed areas, a literature review and remote sensing products. Specific examples are discussed from several rivers of the Amazon basin, the Parana River, the Mississippi River, among others. Large depositional tracks in forelands, platforms and intracratonic basins such as the Chaco, the Orinoco Llanos, the Bananal and Pantanal basin, the Ucamara depression, and the Indo-Gangetic plain, which contain a variety of complex avulsive systems and megafans, are discussed. A main conclusion is that megafans and similar distributary systems, avulsive systems with a variety of channel patterns and linear fluvial belts of major rivers, have the potential for preservation in the geological record. The scarcity of purely braided systems in large rivers is noticeable and they are mainly constrained to small-medium size channels, short length piedmont courses or related to relatively small alluvial fans. Meandering and anabranching systems are dominant in large rivers while anabranching systems are characteristic of megarivers. Despite the findings above, a remarkable challenge remains to identify characteristic facies assemblages for reconstructing large rivers, as they are not clearly identified in the geological record. The scale-size limitation of the architectural characteristics of fluvial landforms and the floodplain complexity of large systems are some of the challenges that need additional research when looking for analogs in the sedimentary record. References: Fielding, Christopher R., Ashworth, Philip J., Best, James L., Prokocki, EricW., Smith, Gregory H. Sambrook, (2012). Tributary, distributary and other fluvial patterns: What really represents the norm in the continental rock record?, Sedimentary Geology doi: 10.1016/j.sedgeo.2012.03.004 Weissmann, G.S., Hartley, A.J., Nichols, G.J., Scuderi, L.A., Olson, M., Buehler, H., Banteah, R., 2010. Fluvial form in modern continental sedimentary basins: distributive fluvial systems. Geology 38, 39-42

Latrubesse, E. M.

2012-12-01

241

Late Quaternary Blind Thrust Faults along the Southern Margin of the Cul-de-Sac Plain, Haiti: A Newly Recognized Seismic Source?  

NASA Astrophysics Data System (ADS)

Joint inversion of geologic, geodetic, and seismologic data showed that most of the moment release associated with the 2010 M 7.0 Haiti earthquake occurred on a blind thrust fault, the Léogâne fault, adjacent to the transpressional plate-bounding Enriquillo-Plantain Garden fault (EPGF). Preliminary geomorphic and stratigraphic analysis of folded alluvial-fan deposits north of the EPGF and beneath and directly east of Port-au-Prince suggests that they have a similar style and orientation to the structure or structures associated with the 2010 earthquake. A series of east-southeast-trending, unnamed, low hills extend across the southern Cul-de-Sac Plain adjacent to a right bend in the EPGF. The hills are the surface expression of doubly-plunging folds that trend approximately 285°, or 15-25° more northwesterly than the neighboring EPGF. We used optical imagery and LiDAR topographic data to identify two main fold belts: a western belt that spans at least 12 km of southern Port-au-Prince and Petionville and an eastern belt that extends more than 20 km from Fond Parisien to Croix-des-Bouquets. Our field reconnaissance along the eastern belt shows that these hills are cored by steeply folded to overturned alluvial-fan deposits of probable Quaternary age. Active folding has sequentially deflected north-flowing drainages, and wind gaps indicate that the folding was sufficiently active to defeat drainages and deform river channels. When folding defeated the drainages, lacustrine sediment locally ponded against the south flank of the folds. In an unnamed drainage about 2 km west of Ganthier, charcoal from a 10-m-thick section of interbedded fluvial and ponded lacustrine sediments yielded a calibrated radiocarbon age of 4978 ± 158 cal. yr B.P. We speculate that the base of each fine-grained lacustrine section may be an event horizon corresponding with an earthquake that rejuvenated the fold; however, more detailed mapping of these sediments is needed to test this hypothesis. In summary, the overall geomorphic expression of the folds in the broad, gently north-sloping Cul-de-Sac Plain is suggestive of late Quaternary activity. Because the folds are similar in orientation and style to the Léogâne fault and are located in similar positions north of the EPGF, they are likely underlain by blind thrust faults, and thus may represent additional earthquake sources that should be considered in seismic-hazard assessments for Port-au-Prince.

Briggs, R. W.; Prentice, C. S.; Crone, A. J.; Gold, R. D.; Hudnut, K. W.; Narcisse, R.

2012-12-01

242

Design of flood protection for transportation alignments on alluvial fans  

Microsoft Academic Search

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

1991-01-01

243

Pliocene and Quaternary geology of Mana Island (Note)  

Microsoft Academic Search

Mana Island, off the south-west coast of the North Island, is capped by the Mana Surface which dips south-east at about 2. This dip is considered to be tectonic in origin. The surface, considered to be a marine abrasion platform, has no overlying deposits except late Quaternary loesses. No continuity with mainland surfaces can be demonstrated, but correlation with the

D. N. Williams

1978-01-01

244

Quaternary geology of the Channeled Scabland and adjacent areas  

Microsoft Academic Search

The quaternary history of the channeled scabland is characterized by discrete episodes of catastrophic flooding and prolonged periods of loess accumulation and soil formation. The loess sequence was correlated with Richmond's Rocky Mountain glacial chronology. At least five major catastrophic flood events occurred in the general vicinity of the channeled scabland. The earliest episode occurred prior to the extensive deposition

V. R. Baker

1978-01-01

245

Landscape paleoecology and late Quaternary extinctions in the Hudson Valley  

Microsoft Academic Search

Stratigraphic palynological analyses of four late Quaternary deposits comprise a landscape-level study of the patterns and processes of megafaunal extinction in the southeastern New York region. Distinctive spores of the dung fungus Sporormiella are used as a proxy for megafaunal biomass and charcoal particle analysis as a proxy for fire history. A decline in spore values at all sites is

Guy Schuyler Robinson

2003-01-01

246

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

247

Quaternary turbidite systems on the northern margins of the Balearic Basin (Western Mediterranean): a synthesis  

Microsoft Academic Search

The Balearic Basin is a young basin composed of thick Plio–Quaternary sediments, including active gravity sedimentation. During the Quaternary, gravity processes deposited (1) turbidite systems, either as symmetrical fans (Petit-Rhne and Valencia fans) or asymmetrical ridges (Marseille–Planier, Grand-Rhne and Pyreneo-Languedocian ridges) and (2) several mass-transport deposits, indicating recurrent sedimentary failures of the margin. This paper synthesizes previous works and proposes

L. Droz; A. T. dos Reis; M. Rabineau; S. Berné; G. Bellaiche

2006-01-01

248

Agricultural contaminants in Quaternary aquitards: A review of occurrence and fate in North America  

Microsoft Academic Search

.   The intensity of agriculture has increased significantly during the past 30 years, resulting in increased detection of agricultural\\u000a contaminants (nutrients, pesticides, salts, trace elements, and pathogens) in groundwater. Till, glaciolacustrine, and loess\\u000a deposits of Quaternary age compose the most common surficial deposits underlying agricultural areas in North America. Quaternary\\u000a aquitards generally contain higher concentrations of solid organic carbon (SOC, as

S. J. Rodvang; W. W. Simpkins

2001-01-01

249

Pleistocene calcrete deposits from southern Spain as indicators of climatic conditions and tectonic activity  

NASA Astrophysics Data System (ADS)

Quaternary calcrete horizons are common weathering products in arid and semi-arid regions of southern Spain. We have analysed a calcrete profile developed within poorly sorted gravels of an alluvial fan. These deposits were sourced from the Carrascoy Range, a fault generated mountain front located in the Internal Zones of the Betic Cordillera (South Spain). During the Pleistocene the climate in southern Spain was dry, either in the form of semi-arid/arid conditions or as seasonal moisture deficits. Alluvial channel incision trends appeared to be disrupted by episodes of alluvial aggradation produced during cold and dry glacial periods. At the top of the aggradational phases, pedogenic processes operated profusely, and, as a result, several calcretes (stage V mature calcrete profiles) were formed. We have analysed one of these calcrete profiles that appears subvertical within the forelimb of a regional fold in relation to the Carrascoy Fault activity. The calcrete consist of a densely cemented hardpan horizon (20 to 40 cm thick) overlain by a thin, 2-cm thick laminar crust. Below the hardpan horizon, carbonate concentrations gradually decrease to clast-coating textures. Calcretes form progressively and a wide range of carbonate phases occur within a single horizon, being the laminar crust the final stage of evolution within a mature pedogenic calcrete deposit, and, therefore, the carbonate within it postdates all the cement phases within the profile. The location of the latest cement phase of the calcrete deposit has been estimated by microscopic observations (to establish their suitability for dating) together with a detailed sedimentological analysis of the calcrete profile in the field. The laminar crust consists of less than 1 mm thick laminae characterized by the alternation of layers of micrite and layers of micrite with ooids, detrital grains and clays indicating environmental conditions in which sedimentation rates were low and episodic. By using radiometric 232Th/238U dating methods we obtain an age of formation of the laminar crust of ~209 Ka (upper part of the Middle Pleistocene). This age corresponds to the warm stage 7c within the glacial Riss period. As pointed out before, the studied calcrete appears subvertical as a result of the activity of the Carrascoy Fault, and, therefore, the fault was active only after the calcrete was formed. Our study permits, as well, to reliably asses the timing of changes in alluvial processes, to characterized this part of the stratigraphic succession as corresponding to an arid to semi-arid environment, and to conclude that this particular calcrete was developed during a relative European warm period within a glacial stage.

Herrero, Maria J.; Insua-Arevalo, Juan M.; Garcia-Mayordomo, Julian; Martin-Banda, Raquel

2014-05-01

250

Topic in Depth - Quaternary Studies  

NSDL National Science Digital Library

Quaternary Studies examines the geologic period of the Quaternary, the last two million years up to the present day. Glaciers formed and receded; animals evolved and went extinct. Here, visitors can learn all about current research and education initiatives in this field of stratigraphic geology.

2010-09-14

251

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

PubMed

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

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

2013-08-01

252

Possible Late Quaternary faulting in the Benton Hills, southeastern Missouri  

SciTech Connect

Geologic mapping in the 1930's by Dan Stewart and Lyle McManamy identified numerous faults in the Thebes Gap area of the Benton Hills, including two post-late Quaternary faults (max. of 10 m displacement) along the southeastern escarpment. Recent geologic mapping (Richard Harrison, pers. comm.) suggests dextral strike-slip displacement on most of these faults; some deformation post-dates the Pliocene-Pleistocene Mounds gravel. Small historical earthquake epicenters have been recorded in the Benton Hills area. Review of these data and analysis of the geologic and structural relationships to small- and large-scale drainage and alluvial features suggest tectonic control of the southeastern escarpment of the Benton Hills. The authors propose the coincidence of geologic structures and landforms resembles tectonically active alluvial basin margins, with the Benton Hills southeastern margin representing a fault block uplift escarpment. Future seismic reflection, drilling and trenching studies are planned to determine if the escarpment is fault controlled and of recent origin.

Palmer, J.R.; Hoffman, D. (Missouri Geological Survey Program, Rolla, MO (United States). Dept. of Natural Resources)

1993-03-01

253

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

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

254

Kinematic wave model for transient bed profiles in alluvial channels under nonequilibrium conditions  

NASA Astrophysics Data System (ADS)

Transient bed profiles in alluvial channels are generally modeled using diffusion (or dynamic) waves and assuming equilibrium between detachment and deposition rates. Equilibrium sediment transport can be considerably affected by an excess (or deficiency) of sediment supply due to mostly flows during flash floods or floods resulting from dam break or dike failure. In such situations the sediment transport process occurs under nonequilibrium conditions, and extensive changes in alluvial river morphology can take place over a relatively short period of time. Therefore the study and prediction of these changes are important for sustainable development and use of river water. This study hence developed a mathematical model based on the kinematic wave theory to model transient bed profiles in alluvial channels under nonequilibrium conditions. The kinematic wave theory employs a functional relation between sediment transport rate and concentration, the shear-stress approach for flow transport capacity, and a relation between flow velocity and depth. The model satisfactorily simulated transient bed forms observed in laboratory experiments.

Tayfur, Gokmen; Singh, Vijay P.

2007-12-01

255

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

256

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

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

257

Interrelation between tectonism, climate, geomorphology and sedimentary deposits: a view from the eastern Himalayan foredeep  

NASA Astrophysics Data System (ADS)

In the continental basin-fill models, tectonically driven rejuvenation/quiescence of the hinterland, rate of basin subsidence and climate are considered as important controls of sedimentation. In applying this model-derived knowledge to the interpretation of ancient sedimentary successions, it has become common to relate the caliber of clastic sedimentary units (conglomerate, sandstone or mudstone) to the climatic or tectonic events. However, any of the modern continental basins will show coexistence of an array of different geomorphic elements in the same time plane defining a landscape (similar to the concept of systems tract. Sediments of different type and caliber are deposited in each of these geomorphic environments. A three dimensional view of the basin incorporating lateral coexistence of different geomorphic niches and their influence on the sedimentary facies has been neglected in many of these basin-fill models or interpretation of stratigraphic successions based on a single-line transect of basin-fill. Although tectonism will affect both sediment supply and discharge, their quantitative value will vary from point to point in the same basin. This variation will be controlled by the drainage basins morphology, or in other words the geomorphic setting. Major geomorphic elements recognized in the Ganga-Brahmaputra alluvial plain include proximal high-gradient alluvial fans (AF), megafans (MF), major channel belts (CB) and interfluve or intermegafan plains (IP). Each of these geomorphic settings has distinctive geomorphic forms and features, and comprises characteristic deposits. Study of the late Quaternary near-surface deposits of the eastern part of the alluvial plain reveals that the contrasting facies associated with different geomorphic units coexist laterally at the same stratigraphic level and locally intertongue with each other. A few OSL age obtained shows overlapping time of their deposition. These sediments have a high likelihood of being preserved as the foreland basin-fill. An orogen parallel transect of this succession, will show a mosaic of laterally coexistent alluvial-fan conglomerate, megafan or braided river sandstone and mudstone-dominated successions deposited in the interfluve or intermegafan areas. Different orogen-perpendicular sections drawn at different points of the foreland basin will show remarkable variation from the idealised succession generated by two dimensional basin models. In the modern Himalayan foredeep, spatial organization of the drainage networks probably controls the distribution of fans, megafans, major channel belts and muddy interchannel or intermegafan areas. Drainage basin configurations are known to respond to different tectonic and climatic perturbations over a period of ~104 - 106 years. In a foreland basin setting, tens of meters sediment may accumulate over this period in each of the geomorphic niches identified from the present landscape. In the central Ganga Plain thick intermegafan mud deposits flank sandy deposits of the megafans. In the eastern part of the alluvial plain, megafan sand and fan gravels laterally intertongue. All these lithofacies have accumulated under similar climatic and tectonic regime. In this scenario relating a particular bed lithology to tectonic or climatic forcing might be misleading. It is suggested that a three dimensional reconstruction of the landscape comprising a mosaic of geomorphic domains and depositional environments, together with age data from the sediments and hinterland tectonic events, should be considered together for confident analysis of basin tectonics.

Chakraborty, Tapan

2010-05-01

258

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

259

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

260

Quantum realization of some quaternary circuits  

Microsoft Academic Search

We present the design of quaternary quantum version of reversible circuits such as Toffoli gate, modified Fredkin gate, mux, demux, encoder-decoder using linear ion realizable quaternary Muthukrishnan-Stroud gates. Our realization of quaternary Toffoli gate is more efficient than the previous realization and other quaternary circuits are realized for the time in literature.

Mahmud Muntakim Khan; Ayan Kumar Biswas; Shuvro Chowdhury; M. Tanzid; K. M. Mohsin; M. Hasan; A. I. Khan

2008-01-01

261

Characterization of alluvial aquifers by multiscale hydrostratigraphic interpretation of DC resistivity data  

NASA Astrophysics Data System (ADS)

The characterization of aquifer heterogeneity plays a key role for the 3-D modelling of conductivity (K) distribution in the subsurface of alluvial plains. DC methods such as Vertical Electrical Soundings (VES) and Electrical Resistivity Ground Imaging (ERGI) yield respectively the 1-D and 2-D resistivity (?) distribution in the ground and are often applied in hydrogeology because ? is controlled by the prevailing process of current conduction ('shale' vs. electrolytic conduction) determined by the occurrence of fine-grained sediments and saline groundwater. Assuming that the sedimentary heterogeneity can be described with hierarchical elements at different scales (from hydrofacies to hydrostratigraphic systems) and recalling that the resolution of DC surveys decreases with depth, we propose an interpretation of the subsurface ? distribution as a function of the hierarchical properties of aquifers (i.e., the vertical trends of facies with prevailing 'shale' or electrolytic conduction) with hydrostratigraphic constrains. A correlation between ? and pore-fluid saturation and chemistry permits the use of resistivity as a 'proxy' of facies stacking. Our case-study is the Quaternary valley of palaeo-Sillaro extinct meandering river (Po plain, Italy). The local stratigraphy up to 80 m below ground surface consists of LGM sand-gravel point bar and channel bodies overlying: i) clay to fine sand aquitard of an Upper Pleistocene flood plain, ii) alternating gravel-sand aquifer bodies and fine sand to silty-clay drapes formed by Middle-Upper Pleistocene braiding to meandering depositional systems that developed above iii) a basal aquiclude of silty-clays. To interpret 1-D resistivity models obtained by 89 VES collected with Schlumberger array (maximum half-spacing 300 m) over an area of 30 km2, a Coarse-to-Fine (C/F) litho-textural ratio (particle size cut-off=0.30 mm) was used to classify hydrofacies. The variability of C/F was compared with the K and ? values of hydrofacies, both in the unsaturated and the saturated zone. A local relationship between K and ? was then established and used to identify i) a fine litho-textural association (C/F1), with a prevailing electrolytic conduction, high ? and high K. The electrical resistivity was then reclassified in terms of the prevailing hydraulic behaviour (low or high K units), taking into account the differences between the saturated and unsaturated zones. A representation of the sedimentary heterogeneity and connectivity was obtained through the correlation of VES models by vertical polarity of electrical contrasts and lateral persistence of ? values which led us to map geoelectrical bodies informally named electrostratigraphic units (EsUs). The EsUs are defined by horizontal variations of the vertical electrostratigraphic sequence and characterized by a thickness coherent with the principles of electrical equivalence and suppression. 3000 m of 2-D ERGI sections collected with Wenner-Schlumberger array (electrodes spacing 5 m) led us to a further characterization of the EsUs at metric scale up to 40 m b.g.s.. Shallow EsUs represent vertical variations of ? related to the litho-textural contrasts at the scale of the hydrofacies, as a function of the proportion between fine and coarse textures within each sedimentary facies (C/F ratio). Deeper EsUs represent vertical variations ? related to the litho-textural contrasts within an heterogeneous and hierarchically stratified medium at the hydrostratigraphic systems scale.

Mele, Mauro; Bersezio, Riccardo; Giudici, Mauro

2010-05-01

262

Quaternary GIS Laboratory  

NSDL National Science Digital Library

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

263

Quaternary GIS Laboratory  

NSDL National Science Digital Library

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

2007-02-27

264

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

265

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

266

The Shape of Trail Canyon Alluvial Fan, Death Valley  

NASA Technical Reports Server (NTRS)

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

Farr, Tom G.; Dohrenwend, John C.

1993-01-01

267

Late-Quaternary paleoenvironmental evolution of Lesina lagoon (southern Italy) from subsurface data  

NASA Astrophysics Data System (ADS)

Integrated sedimentological and micropaleontological (foraminifers and ostracods) analyses of two 55 m long borehole cores (S3 and S4) drilled in the subsurface of Lesina lagoon (Gargano promontory—Italy) has yielded a facies distribution characteristic of alluvial, coastal and shallow-marine sediments. Stratigraphic correlation between the two cores, based on strong similarity in facies distribution and AMS radiocarbon dates, indicates a Late Pleistocene to Holocene age of the sedimentary succession. Two main depositional sequences were deposited during the last 60-ky. These sequences display poor preservation of lowstand deposits and record two major transgressive pulses and subsequent sea-level highstands. The older sequence, unconformably overlying a pedogenized alluvial unit, consists of paralic and marine units (dated by AMS radiocarbon at about 45-50,000 years BP) that represent the landward migration of a barrier-lagoon system. These units are separated by a ravinement surface (RS1). Above these tansgressive deposits, highstand deposition is characterised by progradation of the coastal sediments. The younger sequence, overlying an unconformity of tectonic origin, is a 10 m-thick sedimentary body, consisting of fluvial channel sediments overlain by transgressive-regressive deposits of Holocene age. A ravinement surface (RS2), truncating the transgressive (lagoonal and back-barrier) deposits in core S4, indicates shoreface retreat and landward migration of the barrier/lagoon system. The overlying beach, lagoon and alluvial deposits are the result of mid-Holocene highstand sedimentation and coastal progradation.

Ricci Lucchi, Marianna; Fiorini, Flavia; Luisa Colalongo, Maria; Vittorio Curzi, Pietro

2006-01-01

268

Upland interfluve (Doab) deposition: Alternative model to muddy overbank deposits  

Microsoft Academic Search

Summary  Major alluvial plains contain large tracts of fine-grained muddy sediments, deposited away from the main river channels, which\\u000a are mostly classed as overbank or floodplain deposits. Systematic study of the Ganga plain shows that such large tracts of\\u000a deposition of muddy sediments are located several metres above the major channels, and are not flooded by overtopping of the\\u000a major river

Indra Bir Singh; Pradeep Srivastava; Shikha Sharma; Maneesh Sharma; Dhruv Sen Singh; Govindaraja Rajagopalan; Urea Kant Shukla

1999-01-01

269

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

270

Post-Paleozoic alluvial gravel transport as evidence of continental tilting in the U.S. Cordillera  

Microsoft Academic Search

The western United States contains three thin but remarkably widespread alluvial conglomeratic units that record episodes of large-scale tilting across the U.S. Cordille- ran orogen in post-Paleozoic time. These units are: (1) the Shinarump Conglomerate of Late Triassic age exposed in northern Arizona and adjacent parts of Utah, Neva- da, and New Mexico; (2) Lower Cretaceous gravel deposits that overlie

Paul L. Heller; Kenneth Dueker; Margaret E. McMillan

2003-01-01

271

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

Microsoft Academic Search

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 18,000years 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

Brian D. Collins; David R. Montgomery

2011-01-01

272

Synthesis of Quaternary Heterocyclic Salts  

PubMed Central

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

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

2014-01-01

273

The upper Quaternary sedimentary sequence at the Rieti Basin (central Italy): a record of sedimentation response to climatic changes  

Microsoft Academic Search

Lithostratigraphy, chronology and depositional environments of sixteen Holocene alluvial fill sediment cores from the southern part of the Conca of Rieti (central Italy) was established by sedimentological, palaeontological and 14C analyses. The study area experienced a lacustrine (or palustrine) conditions and the water level was effectively controlled by a natural damming of the valley due to intermitted travertine deposition at

Guerrino Calderini; Gilberto Calderoni; Gian Paolo Cavinato; Elsa Gliozzi; Paolo Paccara

1998-01-01

274

Optimal alluvial channel width under a bank stability constraint  

NASA Astrophysics Data System (ADS)

To properly predict alluvial channel width using rational regime models, an analysis of bank stability must be included in the model. When bank stability is not considered, optimizations assuming maximum sediment transport capacity (MTC) typically under-predict alluvial channel width for natural and laboratory streams. Such discrepancies between regime model predictions and observed channel widths have been used to argue that optimizations such as MTC do not describe the behaviour of alluvial systems. However, rational regime models that explicitly consider bank stability exhibit no such bias and can predict alluvial channel widths quite accurately. We present an analysis of both laboratory and natural alluvial channels, using both kinds of models, and demonstrate the importance of bank stability in constraining optimization solutions. We also identify a scale effect, whereby the effect of vegetation on bank strength declines as the absolute scale of the system increases. We argue that comparisons of alluvial channel widths against predictions from rational regime models unconstrained by bank stability are inappropriate, because they introduce a known and quantifiable bias (toward under-prediction by the model) due to the absence of a bank stability constraint.

Eaton, Brett C.; Millar, Robert G.

2004-09-01

275

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

276

Valley-fill alluviation during the Little Ice Age (ca. A.D. 1400–1880), Paria River basin and southern Colorado Plateau, United States  

Microsoft Academic Search

Valley-fill alluvium deposited from ca. A.D. 1400 to 1880 is widespread in tribu- taries of the Paria River and is largely co- incident with the Little Ice Age epoch of global climate variability. Previous work showed that alluvium of this age is a map- pable stratigraphic unit in many of the larger alluvial valleys of the southern Col- orado Plateau.

Richard Hereford

2002-01-01

277

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

278

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

279

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

NASA Astrophysics Data System (ADS)

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

Williams, martin

2014-05-01

280

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

281

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

282

Comparison of different investigation methods to characterise alluvial gravel aquifers  

NASA Astrophysics Data System (ADS)

For reliable groundwater transport modelling of unconsolidated porous aquifers, high resolution characterisation of spatially heterogeneous hydraulic and transport properties is of great importance. Predictions of first-arrival times and long term behaviour depend strongly on the quality of estimated hydraulic and transport parameters. By neglecting small-scale structures such as sand lenses and sediment intra-channel deposits, predictions are hardly accurate. This paper deals with the comparison of methods to characterize hydraulic parameters governing solute transport in unconsolidated porous aquifer materials. A large number of single-well slug tests, cross-well slug tests, a pumping test and a multi-level tracer test were conducted in a shallow alluvial gravel aquifer. This facilitated describing the spatial variation of hydraulic and transport parameters with high resolution. Multi-level slug tests results show distinct positive correlation with porosity-logs and drill cores and are thus an effective means to identify and characterize subsurface structures at high resolution. Values for hydraulic conductivity gained from pumping tests and cross-well slug tests revealed good accordance but were around one order of magnitude higher than the values derived from multi-level slug tests. This might be due to the fact that the three methods are involving different test-volumes. Hence, the determination of hydraulic conductivity underlies a scale dependency: larger test volumes tend to be characterized by larger K-values. Furthermore, our pumping test results show the importance of a high sampling rate, in our case 50 Hz, in order to determine reliably the hydraulic properties storage and anisotropy of hydraulic conductivity. Although pumping tests typically estimate hydraulic parameters on large-scale, small-scale heterogeneity could also be identified and characterized. This was again possible through the high resolution records of the early time drawdown. Finally, results of multi-level tracer testing supported observations from slug tests and porosity logs.

Reist, Fabian; Brauchler, Ralf; Jiménez, Santos; Bühler, Lukas; Hu, Linwei; Leuenberger-West, Fanny; Bayer, Peter

2014-05-01

283

Lower Mississippi River: A Mixed Bedrock-alluvial Channel  

NASA Astrophysics Data System (ADS)

High-resolution multibeam bathymetric and CHIRP sub-bottom seismic data from the lower most 110 km of the Mississippi River offer a detailed depiction of the bed surface, revealing portions of the channel covered by sediment and areas of exposed substrate. A single line data swath running from Head of Passes to the English Turn bend was collected during low water discharge conditions. The swath zigzags up the river channel, intersecting each bank at an oblique angle of roughly 45 degrees, thereby ensuring that the entire channel bottom is adequately represented by the survey. Local composition of the channel bed is determined based on distinctive bathymetric characteristics, and is corroborated by grab samples collected along the survey path. Dune fields, composed of active and inactive dunes, cover 77% of the channel bottom and are most abundant in straight reach segments. Stagnant dunes, mantled by high-porosity ephemeral mud, cover 7% of the channel bed and tend to be located in shallower water near the river banks (10-15 m depth). Active bedforms cover 70% of the bed and are centered on the channel thalweg at water depths of 15-25 m. The remainder of the river bed is devoid of dunes, and consists of highly-consolidated and stratified sedimentary deposits that are part of the Pleistocene and Holocene substrata that lies beneath the modern Mississippi River (23% coverage). Steeply dipping channel sidewalls (30-80 degrees) are composed of the relict sediments and make up 10% of the bed area. Erosion-resistant substrate covers 13% of the channel bottom, and is frequently exposed in the deepest portions of the thalweg (25-60 m depth). Grooves and flutes are cut into this exposed substrate implying active river incision. Based on the proportion of modern sediment cover versus exposed erosion-resistant substrate on the channel bed, we propose that the lower Mississippi River is best classified as a mixed bedrock-alluvial channel.

Nittrouer, J. A.; Mohrig, D.; Allison, M. A.

2007-12-01

284

Quaternary strain rates distribution and crust-mantle structure of the southern Northeast Japan  

NASA Astrophysics Data System (ADS)

Driving mechanisms of intracontinental deformation at subduction margins have been a interesting research target to understand dynamic interaction between subducting oceanic slabs, overriding continental crust and mantle structures. Driven by this motivation, we estimated spatial distributions of intraplate permanent strain rates accommodated by active faults and fault-related folds in southern Northeast Japan during the late Cenozoic time, based on combinations of recently obtained deep to shallow seismic re?ection data, and rates of fault slip determined by offsets of geomorphic features or stratigraphic horizons identified of drilled shallow boreholes across fault and/or fold scarps. Tectonic setting of the northeastern Japan in late Cenozoic times, underlain by westward subducting old and cold Pacific plate, is characterized by north to northeast trending active thrust sheets that deform Neogene deposits. Although previous studies indicated that active reverse faults are predominant in this region, revised active fault mapping after the 2011 Tohoku-oki earthquake (M9.0) and its normal-fault aftershock sequence indicate that active normal faults are widely distributed on the southeastern flank of the coastal mountains along the Pacific coast and continental shelf off the southern Northeast Japan. Estimated strain rates accommodated by active faults and folds are an order of 10-8/yr for each structures, that are in general 10 to 100 times higher than previous estimates only from surficial Quaternary active fault data and historical seismicity. Contrastingly, geodetic strain rates observed the 2011 Tohoku-oki earthquake shows 10 times higher than those estimates in this study. Most of these active thrusts are reactivated normal faults originally formed during Miocene in extensional stress regimes. Trench-normal, spatial distributions of the longer-term permanent strain rates is characterized by a distinctive trend that strain rates in back-arc are apparently 10 times higher than in fore-arc region, quite similar to those estimated based on late Cenozoic folded/faulted strata. Most of these active thrusts are reactivated normal faults originally formed during Miocene in extensional stress regimes. Longer-wavelength, late Quaternary uplift and subsidence overprinting these short wavelength strains, estimated by fluvial incision rates based on terhrostratigraphy, and borehole stratigraphy in alluvial plains, indicate relatively uniform, moderate uplift rates in fore-arc and west of the volcanic front, and very fast subsidence rates in back-arc. Late Cenozoic major tectonic records in southern Northeastern Japan after Miocene Japan Sea opening are, in summary, mainly characterized by Quaternary strong compression and coeval fast subsidence in back-arc region. Crust-mantle structures of the southern Northeast Japan based on seismic tomography, seismic reflection and refraction profiles indicates crustal thickening beneath the Ou backbone Range probably due to magmatic underplating. In addition, back-arc subsidence is underlain by low Vp in the upper mantle, suggesting that downwelling of the mantle lithosphere may be driving present-day surface fast subsidence.

Ishiyama, Tatsuya; Sato, Hiroshi; Kato, Naoko; Imaizumi, Toshifumi; Matsubara, Makoto; Takeda, Tetsuya

2013-04-01

285

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

NASA Astrophysics Data System (ADS)

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

Baltzer, Frédéric; Purser, Bruce H.

1990-05-01

286

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

287

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  

NASA Astrophysics Data System (ADS)

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 tributary streams, with small catchments namely Turung Khola and Bembung Khola are important in this context. Three major fan lobes (F2, F1, and F0) are preserved at Turung Khola. In contrast, two fan lobes (F1,F0) are preserved at the confluence of the Bembung Khola. Terraces, floodplains, channel bars, chute bars are associated geomorphic features in this part of the Teesta basin. Landslides cover an area of 7% and 15% in the catchment of Turung Khola and Bembung Khola, respectively. Dense forest covers 24% and 12%; open forest covers 30% and 29 %; and scrubby vegetation covers 39% and 49% of the Turung Khola and Bembung Khola, respectively. The landslides mainly occur along the margins of the dense forest where they are active in every rainy season. Tributary longitudinal profiles and Hack profiles indicate a relationship between the knick points and high SL-Index values, where fault /thrust intersections are present. Active landslides and scarps are close to the major fault/thrust planes. Sediment characteristics of these fan deposits suggest that four types of depositional flows viz. debris flows, hyperconcentrated flows, sheet flows and channel flows laid down these sequences. The channel flow deposits are dominant (32%-54 %) in the fan sequence of the Turung Khola followed by sheet flow deposits (28.5%), hyperconcentrated flow deposits (26%) and debris flow deposits (12%), respectively. Hyperconcentrated flow deposits are dominant (44%) in the F1 sequence, whereas the active channel fanlobe is dominant (80%) in the channel flow deposits. The rest of the active channel sequence is composed of sheet flow deposits (20%). On the other hand, the major part (52%) of the F1 fanlobe of Bembung Khola is built up of debris flow deposits and F0 fanlobe is composed of channel flow deposits and flood sediment. From the above analysis, an evolutionary model of the deposition and incision at the tributary stream fan confluence is proposed. The insetting of the younger fan lobes into older fan lobe surfaces is an evidence of tectonic uplift in the region. The landform and their depositional pattern are a responds to link tectonic- climatic process systems; some depositional lithofacies assemblages are responses to climatic events.

Lukram, I. M.

2007-12-01

288

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

USGS Publications Warehouse

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

Madole, Richard F.

2012-01-01

289

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

NASA Astrophysics Data System (ADS)

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

Pelletier, J. D.

2014-03-01

290

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

291

Heat Transfer Characterization Using Heat and Solute Tracer Tests in a Shallow Alluvial Aquifer  

NASA Astrophysics Data System (ADS)

Very low enthalpy geothermal systems are increasingly considered for heating or cooling using groundwater energy combined with heat pumps. The design and the impact of shallow geothermal systems are often assessed in a semi-empirical way. It is accepted by most of the private partners but not by environmental authorities deploring a lack of rigorous evaluation of the mid- to long-term impact on groundwater. In view of a more rigorous methodology, heat and dye tracers are used for estimating simultaneously heat transfer and solute transport parameters in an alluvial aquifer. The experimental field site, is equipped with 21 piezometers drilled in alluvial deposits composed of a loam layer overlying a sand and gravel layer constituting the alluvial aquifer. The tracing experiment consisted in injecting simultaneously heated water and a dye tracer in a piezometer and monitoring evolution of groundwater temperature and tracer concentration in 3 control panels set perpendicularly to the main groundwater flow. Results showed drastic differences between heat transfer and solute transport due to the main influence of thermal capacity of the saturated porous medium. The tracing experiment was then simulated using a numerical model and the best estimation of heat transfer and solute transport parameters is obtained by calibrating this numerical model using inversion tools. The developed concepts and tests may lead to real projects of various extents that can be now optimized by the use of a rigorous and efficient methodology at the field scale. On the field: view from the injection well in direction of the pumping well through the three monitoring panels Temperature monitoring in the pumping well and in the piezometers of the three panels: heat transfer is faster in the lower part of the aquifer (blue curves) than in the upper part (red curves). Breakthrough curves are also more dispersed in the upper part with longer tailings.

Dassargues, A.

2013-12-01

292

Reconstructing the evolution of the Chamoson alluvial fan (Swiss Rhône Valley) from outcrop observations and geo-radar survey.  

NASA Astrophysics Data System (ADS)

Following the withdrawal of the Wurmian glacier occupying the Rhône Valley (Swiss Alps), a complex of glacial sediments, alluvial fan deposits generated form tributary valleys, and lacustrine sediments were accumulated. Here, we focus on the Chamoson alluvial fan, the largest (ca. 8 km2) fan in the area , characterised by frequent floods (4 to 6 event per year) which are confined within its incised channel. The study aims to understand the spatial and temporal evolution of the fan in particular with respect to the larger trunk of the Rhône Valley. The methodology includes (1) the description of sedimentary logs and photo mosaics along both 400 metre-long walls in the incised channel, (2) a Ground Penetrating Radar (GPR) survey designed to obtain a 3D model for identifying the internal architecture and geometry of the alluvial fan complex, and (3) carbon-14 age-determinations on suitable material in order to constrain a chronological framework of the sedimentary events observed in outcrop. The Chamoson alluvial fan largely consists of a vertical stack of amalgamated waterline debris flow deposits alternated with graded gravels and coarse sandstones associated with bedload processes. Intercalated within the coarse debris flow succession, field observations revealed the presence of a ca. 2 m-thick lacustrine silty and clayey interval containing wood fragments and well-preserved fresh-water gastropod shells. The AMS 14C-dating on gastropods indicates a Late Bronze Age for the formation of these deposits. The GPR data also show the wide 3D spatial extension of a sharp horizontal reflector, which was interpreted to be the lacustrine deposit within the fan by correlation with the sedimentological logs. These lacustrine deposits are situated 40 m above the current altitude of the Rhône Valley, which may suggest a very different depositional and physiographic setting in this part of the Rhône Valley at the end of the Late Bronze Age. The finding of these extensive fine-grained deposits raises lots of questions on the origin and existence of a presumed upper Rhone Valley lake. Such a lake, if confirmed, will have to be explained within the context of the known Holocene climatic variations, the well-known history of habitation in the region at that time, and the geology of the Rhone Valley in order to explain the genesis of the inferred lake (e.g. valley damming by landslide, frontal moraine).

Boulicault, Lise; Moscariello, Andrea; Ventra, Dario; Moreau, Julien

2014-05-01

293

A New Quaternary Strand of the Karakoram Fault System, Ladakh Himalayas  

NASA Astrophysics Data System (ADS)

The NW-SE striking, dextral Karakoram fault system stretches for more than 1200 km from the Pamirs of Central Asia at least as far southeast as the Kailas area of Tibet. Estimates for the total lateral displacement along the fault system range from 150-1000 km, and estimated Quaternary rates of slip range from 1 to 30 mm/yr. In the Ladakh region of NW India (~ 33°28’N, 78°45’E), the fault system expresses as northern and southern strands bounding the Pangong Range. Studies of ductile deformation fabrics along these strands suggest that slip began in the Miocene, and Brown et al. (2002) documented Quaternary right-lateral slip along the northern strand at ~4 mm/yr on the basis of offset geomorphic features. The lack of documented Quaternary offset along the southern strand has led most researchers to assume that Quaternary slip on the Karakoram fault system in this region was partitioned exclusively to the northern strand. Our summer 2009 field work in the Pangong Range and adjacent Nubra Valley provides the first documentation of significant Quaternary activity along the southern strand. In the valley between the villages of Tangste (34°01’ N, 78°10’ E) and Durbuk (34°06’ N, 78°07’), the fault is visible high on the northeastern mountain side as a break in slope with offset Quaternary paleosurfaces and beheaded and offset stream channels, the largest of which have been displaced by as much as 250 m. Field mapping north of Durbuk, near the town of Tangyar (34°15’N, 77°52’E), shows that the southern strand continues northwest and cuts across the landscape as a sinuous, continuous trace with shutter ridges, offset alluvial fan surfaces, and sag ponds developed along its length. In this region, the northern and southern strands are linked by a Quaternary, E-directed thrust fault that places high-grade metamorphic rocks over poorly consolidated Quaternary alluvium. The partitioning of dextral slip between two strands of the Karakoram system, rather than one strand, suggests that previous estimates of total Karakoram fault system slip rates in this sector of the Himalaya may be too low. Efforts to determine the slip rate on the newly recognized active strand and to better quantify total slip rates are underway. Determining these rates is essential for answering first-order questions about the evolution and behavior of the Karakoram fault system in this region, the late-stage exhumation kinematics of the Pangong Range, and regional seismic hazard potential.

Bohon, W.; Hodges, K.; Arrowsmith, R.; Tripathy, A.

2009-12-01

294

Late Quaternary vegetation - climate feedbacks  

Microsoft Academic Search

Feedbacks between vegetation and other components of the climate system are discussed with respect to their influence on climate dynamics during the late Quaternary, i.e., the last glacial - interglacial cycles. When weighting current understanding based on interpretation of palaeobotanic and palaeoclimatic evidence by numerical climate system models, a number of arguments speak in favour of vegetation dynamics being an

M. Claussen

2009-01-01

295

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

296

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

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

297

Experimental alluvial fan evolution: Channel dynamics, slope controls, and shoreline growth  

NASA Astrophysics Data System (ADS)

River deltas and alluvial fans have channelization and deposition dynamics that are not entirely understood, but which dictate the evolution of landscapes of great social, economic, and ecologic value. Our lack of a process-based understanding of fan dynamics hampers our ability to construct accurate prediction and hazard models, leaving these regions vulnerable. Here we describe the growth of a series of experimental alluvial fans composed of a noncohesive grain mixture bimodal in size and density. We impose conditions that simulate a gravel/sand fan prograding into a static basin with constant water and sediment influx, and the resulting fans display realistic channelization and avulsion dynamics. We find that we can describe the dynamics of our fans in terms of a few processes: (1) an avulsion sequence with a timescale dictated by mass conservation between incoming flux and deposit volume; (2) a tendency for flow to reoccupy former channel paths; and (3) bistable slopes corresponding to separate entrainment and deposition conditions for grains. Several important observations related to these processes are: an avulsion timescale that increases with time and decreases with sediment feed rate; fan lobes that grow in a self-similar, quasi-radial pattern; and channel geometry that is adjusted to the threshold entrainment stress. We propose that the formation of well-defined channels in noncohesive fans is a transient phenomenon resulting from incision following avulsion, and can be directly described with dual transport thresholds. We present a fairly complete, process-based description of the mechanics of avulsion and its resulting timescale on our fans. Because the relevant dynamics depend only on threshold transport conditions and conservation of mass, we show how results may be directly applied to field-scale systems.

Reitz, Meredith D.; Jerolmack, Douglas J.

2012-06-01

298

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

299

Pliocene-Pleistocene continental deposits in western Kentucky: A new look at regional stratigraphy and depositional history  

Microsoft Academic Search

Pliocene and Pleistocene age sediments of the northernmost Mississippi Embayment consist of a thick sequence of continental deposits which rest unconformably on Cretaceous through Eocene strata. The continental deposits have been tentatively correlated to the Pliocene Mounds Gravel and Pleistocene Henry and Equality Formations of southern Illinois. These sediments have previously been interpreted as representing alluvial fan and fluvial deposits.

1992-01-01

300

A Sediment Transport Model for Straight Alluvial Channels  

Microsoft Academic Search

The paper presents a simple mathematical model for sediment transport in straight alluvial channels. The model, which is based on physical ideas related to those introduced by Bagnold (1954), was originally developed in two steps, the first describing the bed load transport (Engelund 1975) and the second account- ing for the suspended load (Fredsae and Engelund 1976). The model is

Frank Engelund; Jergen Fredsee

1976-01-01

301

Finite amplitude bars in mixed bedrock-alluvial channels  

NASA Astrophysics Data System (ADS)

We present a nonlinear asymptotic theory of fully developed flow and bed topography in a wide channel of constant curvature to describe finite amplitude perturbations of bottom topography, subject to an inerodible bedrock layer. The flow field is evaluated at the leading order of approximation as a slowly varying sequence of locally uniform flows, slightly perturbed by a weak curvature-induced secondary flow. Using the constraint of constant fluid discharge and sediment flux, we calculate an analytical solution for the cross-sectional profile of flow depth and bed topography, and we determine the average slope in the bend necessary to transport the sediment supplied from a straight, alluvial, upstream reach. Both fully alluvial bends and bends with partial bedrock exposure are shown to require a larger average slope than a straight upstream reach; the relative slope increase is much larger for mixed bedrock-alluvial bends. Curvature and sediment supply are shown to have a strong effect on the characteristics of the point bars in mixed bedrock-alluvial channels. Higher curvature bends produce bars of larger amplitude and more bedrock exposure through the cross section, and increasing the sediment supply leads to taller and wider point bars. Differences in the relative roughness of sediment and bedrock have a smaller, secondary effect on point bar characteristics. Our analytical approach can potentially be extended to the case of arbitrary, yet slowly varying, curvature, and should ultimately lead to an improved understanding of the formation of meanders in bedrock channels.

Nelson, Peter A.; Bolla Pittaluga, Michele; Seminara, Giovanni

2014-03-01

302

Alluvial charcoal in the Sigatoka Valley, Viti Levu Island, Fiji  

Microsoft Academic Search

Charcoal concentrations in alluvial sediments throughout the Sigatoka (and adjacent) catchments, western Viti Levu Island, Fiji were located, sampled and, where possible, dated. The earliest date (5579–5052 cal year BP) almost certainly predates human arrival and represents a natural fire, perhaps associated with drought conditions during an El Niño event. The next three dates are clustered around the time just

Patrick D. Nunn; Roselyn Kumar

2004-01-01

303

Effect of coal ash disposal upon an unconfined alluvial system  

Microsoft Academic Search

Fly and bottom ash from coal combustion has been disposed in four ash ponds in an alluvial valley. Three of the ash ponds are receiving ash and one was filled and closed. Twenty eight monitoring wells ranging in depth from 10 feet to 65 feet have been installed at the site to study groundwater flow and chemistry. Hydraulic heads are

B. S. Shergill; L. V. A. Sendlein; J. S. Dinger

1992-01-01

304

Late-Quaternary morphodynamics of Ejina Basin, Inner Mongolia, China: Quantification of neotectonic subsidence and palaeohydrological implications  

NASA Astrophysics Data System (ADS)

From space, the Ejina Basin (Gaxun Nur Basin) - enclosed by the Tibetan Plateau in the south and the Gobi -Tien Shan in the north - appears as the world's second largest inland delta of approx. 28,000 km2. Today, the crescent-shaped series of terminal lakes (Gaxun Nur, Sogo Nur and Juyanze) represent the endorheic erosion base for the Black River (Hei River) drainage system originating in the Qilian Mountains (>5,000 m asl.). The up to 300 m thick Quaternary basin fill of lacustrine and alluvial origin was deposited during the last approx. 250,000 yrs. Gobi gravel plains protecting Late Pleistocene fine sediments against deflation cover most parts of the basin. They are considered to be a unique sequence within the sediment stratigraphy of the entire basin. The slightly convex-shaped surface of the western basin resembles the prograding formation of an alluvial fan with clear evidence of local subsidence to the north and west, as indicated by the concave shaped surface there. However, the recent terminal lake basins at the northern margin of Ejina Basin are structurally related to tectonic pull-apart basins that were active since Late Pleistocene. The rhomb-shaped Gaxun Nur basin is the most distinct pull-apart feature indicating a left-lateral strike-slip movement parallel to the continental Gobi-Tien-Shan Fault in the north. New radiocarbon dates of lacustrine sediments within a fossil cliff at the southern shore support the estimated subsidence rate of >0.8m per kyr (Hartmann et al. 2011) after the Last Glacial Maximum (LGM). The more trapezoid fault system of the Juyanze pull-apart basin exhibits a more manifold set of tectonically induced geomorphological features. Whereas Hartmannn et al. (2011) assumed a W-E-striking fault by comparing dating inversions along yardangs of lacustrince chalks that host seismites. A nearby new railway construction pit revealed a normal fault that affected the lake sediments that are 35±1 kyr BP in age. The most impressive set of features related to young tectonic subsidence in Ejina basin resembles inverted channels south of western Juyanze. Radiocarbon dates of lacustrine sediments below the gravel cover suggest a reversal of surface gradient, conservation and dissection of gravel beds by subsidence that most likely occurred after 13.6 kyr BP. The continuation of the S-N-striking strike-slip-duplex of the Gurinai structure separates Juyanze in two basins by an impressive >20 m emerging cliff formed within remains of an isolated large alluvial fan. This fan should have been active after approx. 18 kyr BP. Hence, a synopsis of at least 65 radiocarbon dates of lacustrine sediments from the margins and centres of the sub-basins suggests four times higher subsidence rates from the north-western (0.8 m/kyr) to the north-eastern (2-3.6 m/kyr) margin of Ejina Basin. Considering the flat and spatially uncertain water divide to the depression of Wentugaole (and its continuation to the northwest), it seems likely that the basin has lost its endorheic character at least once. Hence, the morphology of basin margins of this large intermontane foreland basin shows up with tectonically active margins and sensitive water divides. Reference: Hartmann, K., Wünnemann, B., Hölz, S., Kraetschell, A., Zhang, H. (2011): Neotectonic constraints on the Gaxun Nur inland basin in north-central China, derived from remote sensing, geomorphology and geophysical analyses. - In: Gloaguen, R. & Ratschbacher, L. (eds.): Growth and Collapse of the Tibetan Plateau. - Geological Society of London Special Publications 353: 221-233.

Hartmann, Kai; Wünnemann, Bernd; Reicherter, Klaus; Rudersdorf, Andreas; Blaauw, Maarten; Diekmann, Bernhard; Bölscher, Judith; Lu, Huayu

2014-05-01

305

Quaternary corals from reefs in the Wakatobi Marine National Park, SE Sulawesi, Indonesia, show similar growth rates to modern corals from the same area  

Microsoft Academic Search

We have used digital photography, image analysis and measurements in the field to determine the growth rates of Quaternary corals in the Wakatobi Marine National Park, Indonesia, and compared them to growth rates of similar corals in the same area. In the Quaternary deposits it was possible to measure the growth rates of two massive coral genera Porites and Favites.

M. James C. Crabbe; Moyra E. J. Wilson; David J. Smith

2006-01-01

306

Quaternary sedimentation of the principal deltas of Vietnam  

NASA Astrophysics Data System (ADS)

Quaternary depressions in Vietnam (namely the Cuulong River, the Red River, and coastal depressions in the central part of the country) were filled mainly by continental deposits in five cycles as follows: (V) Upper Holocene (Thaibinh and Dongkhoi formations); (IV) Lower to Middle Holocene (Haihung and Tanthanh Binh-chanh formations); (III) Upper Pleistocene (Vinhphuc formation); (II) Middle to Upper Pleistocene (Hanoi and Thuduc formations); (I) Lower Pleistocene (Lechi, Trangbom, and Hoanghoa formations). Each cycle starts with a regression and ends with a transgression. Within the Quaternary the maximum regressive phase was in the Middle to Upper Pleistocene (beginning of cycle II) and the maximum transgressive phase in the Middle Holocene (end of cycle IV).

Nghi, Tran; Ngo Quang Toan; Do Thi Van Thanh; Nguyen Dinh Minh; Nguyen Van Vuong

307

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

NASA Astrophysics Data System (ADS)

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

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

2008-01-01

308

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

SciTech Connect

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

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

1985-01-01

309

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

310

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

311

Incorporating Sedimentological Observations, Hydrogeophysics and conceptual Knowledge to Constrain 3D Numerical Heterogeneity Models of Coarse Alluvial Systems  

NASA Astrophysics Data System (ADS)

Accurate predictions on groundwater flow and transport behavior within fluvial and glaciofluvial sediments, but also interaction with surface water bodies, rely on knowledge of distributed aquifer properties. The complexity of the depositional and erosional processes in fluvial systems leads to highly heterogeneous distributions of hydrogeological parameters. The system dynamics, such as aggradation rates and channel mobility of alluvial systems; its influence on the preservation potential of the key depositional elements in the geological record; and its influence on the heterogeneity scales and the relevance for groundwater hydraulics is topic of the presentation. The aims of our work are to find a relation between surface morphological structures and the sedimentary structures in vertical profiles (i.e. gravel pits or GPR sections) and to derive rules for the interpretation of horizontal time-slices from 3D GPR data. Based on these data we set-up conceptual models of the structures of coarse alluvial systems at different scales which can be tested by stochastic methods. Relevant depositional elements and a hierarchy or genetic relationship of such elements will be defined based on the knowledge of depositional processes in alluvial systems inferred from: field observations after major flood events; 2D and 3D GPR data; and from existing data derived from laboratory flumes. Extensive geophysical field experiments within the Tagliamento alluvial system gave new insights to the sedimentary structures developing at high flows. Owing to the fact that rivers often destroy at least part of their bed during or shortly after large floods and subsequently rebuild, it is not easy to establish a simple relationship between surface morphology and the sedimentary structures found in vertical sections of many alluvial outcrops. According to these findings we suppose that surface or near-surface structures will not catch the essence of heterogeneity of alluvial aquifers. Horizontal time-slices of 3D GPR provide images which allow correlations to be made between vertical and horizontal sections. We show, that true-scale map views of time slices reveal geometries in the horizontal direction more accurately. Horizontal geophysical sections (time-slices) offer an opportunity to relate vertical and horizontal information. Time-slices of 3D GPR surveys offer a possibility to derive training images and multiple point statistical analysis. Combining the data from 2D and 3D geophysical field surveys and observations from outcrops in gravel pits we develop a 3D object-based model of the main structural elements considering depositional and erosional capabilities of the structural elements depending on the dynamics of the system. The algorithm contains the definition of objects to reproduce the different sedimentary structures distinguished within the studied system in a realistic way, and generates different realizations of the defined object types. The quality of the different realisations is compared with the observation (geophysics, borehole and geological parameters). The input parameters set required for reproducing a sedimentary object is composed of qualitative data, such as global shape of the profile, and quantitative data, such as typical object dimensions and directions.

Huber, E.; Huggenberger, P.

2012-12-01

312

Detectability of minerals on desert alluvial fans using reflectance spectra  

NASA Technical Reports Server (NTRS)

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

Shipman, Hugh; Adams, John B.

1987-01-01

313

40 CFR 721.10582 - Quaternary ammonium compound (generic).  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Quaternary ammonium compound (generic). 721.10582 Section... § 721.10582 Quaternary ammonium compound (generic). (a) Chemical substance...identified generically as quaternary ammonium compound (PMN P-10-571) is subject...

2013-07-01

314

40 CFR 721.655 - Ethoxylated alkyl quaternary ammonium compound.  

Code of Federal Regulations, 2013 CFR

...Ethoxylated alkyl quaternary ammonium compound. 721.655 Section 721.655 ...Ethoxylated alkyl quaternary ammonium compound. (a) Chemical substance and significant...ethoxylated alkyl quaternary ammonium compound (PMN P-96-573) is subject...

2013-07-01

315

A model of channel response in disturbed alluvial channels  

USGS Publications Warehouse

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

Simon, A.

1989-01-01

316

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

317

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

318

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

319

A Possible Heptaxodontine and Other Caviidan Rodents from the Quaternary of Jamaica1  

Microsoft Academic Search

New World hystricognath rodents (parvorder Caviida) easily qualify as the most diversified members of the nonvolant Quaternary land mammal fauna of the West Indies. This paper describes three intriguing but problematic representatives of this group from Jamaican cave deposits. The first is the holotype (and still the only) specimen of Alterodon major from Wallingford Roadside Cave, a taxon that continues

R. D. E. MacPHEE; CLARE FLEMMING

2003-01-01

320

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

321

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

322

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

323

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

NASA Astrophysics Data System (ADS)

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

Lonsert, Reece

324

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

325

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

NASA Technical Reports Server (NTRS)

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

Peltzer, Gilles; Tapponnier, Paul; Armijo, Rolando

1989-01-01

326

Quaternary glaciations of the southern Andes  

NASA Astrophysics Data System (ADS)

The southern Andes comprise the southernmost portion of the Andean Cordillera, beginning at the edge of the Puna Altiplano (lat.27°S) and ending at Isla de los Estados (lat.55°S). The late Cainozoic glacial record of these mountains spans the interval from the Late Miocene to the present and is one of the most complete to be found anywhere in the world. This has arisen for several reasons: (i) the conterminous mountain ice cap extended to the piedmont zone on both flanks of the range, where the sedimentary and morphological record has been well preserved; (ii) periodic volcanism, mainly from monogenetic fissure eruptions of basalt east of the range and from central tephra-producing cones along the mountain crest, has provided opportunity for the preservation and radiometric dating of interbedded glacial deposits; (iii) a tectonically-induced interval of stream incision in the Mid Pleistocene and simultaneous uplift has preserved glacial sediments on interfluves; (iv) in the Chilean lakes region west of the mountains, Late Quaternary glaciers terminated in a well-vegetated landscape, thus creating scope for radiocarbon dating of interbedded and incorporated organic materials; consequently, the last glaciation in the Llanquihue area of Chile is one of the best dated sequences in South America; thus the 'Llanquihue' Glaciation is proposed as the South American equivalent of the 'Wisconsin' and 'Weichsel' glaciations of North America and north west Europe respectively.

Rabassa, Jorge; Clapperton, Chalmers M.

327

A model of early calcite cementation in alluvial fans: Evidence from the Burdigalian sandstones and limestones of the Vallès-Penedès half-graben (NE Spain)  

NASA Astrophysics Data System (ADS)

The Vallès-Penedès half-graben developed during a Neogene extensive period as part of the Catalan Coastal Ranges in the northwestern edge of the Valencia Trough. The Neogene deposits of the Vallès-Penedès half-graben consist of, from base to top, three lithostratigraphic complexes: i) a lower continental complex of Aquitanian?-early Langhian age; ii) a continental to marine complex with reefal carbonate platforms of Langhian age and; iii) an upper continental complex of middle Serravallian-Tortonian age. This study focuses on the calcite cements of the lower continental complex consisting of red beds (mudstones, sandstones and conglomerates) and lacustrine limestones deposited in alluvial fan environments. The studied materials are cemented by calcite precipitated from meteoric waters that circulated through the sediments during the early diagenesis at shallow burial depths. The calcite cement was studied by means of petrographic, cathodoluminescence, microprobe and ? 18O and ? 13C isotopic analysis. The petrographic and geochemical results show that these cements vary according to the sedimentary environment: (i) sandstones deposited in proximal alluvial fan environments cemented by calcite with low contents of Mg, Fe, Mn, Sr and Na, ? 13C values of - 7,4‰ PDB and ? 18O values from - 6.5 to - 6.2‰ PDB; (ii) sandstones sedimented in medium to distal alluvial fan environments cemented by Mn-rich and Mg, Fe, Sr and Na-poor calcite with ? 13C values from - 7.9 to - 6.9‰ PDB and ? 18O values from - 10.5 to - 8.6‰ PDB; and (iii) lacustrine limestones of distal alluvial fan environments cemented by Fe-rich calcite with variable contents of Mn and low contents of Mg, Sr and Na. The distribution of these calcite cements allows us to propose a model of fluid circulation and early calcite cementation within an alluvial fan indicating spatial and temporal variations in chemical composition of meteoric water during migration from proximal to distal alluvial fan environments. Residence time of waters, Eh-pH conditions, and the degree of sediment-water interactions, influenced by the mineral composition of the host sediments, are the most important parameters controlling variations in calcite cement composition.

Parcerisa, D.; Gómez-Gras, D.; Travé, A.

2005-07-01

328

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

329

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

USGS Publications Warehouse

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

Knepper, Jr. , D. H.

2005-01-01

330

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

331

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

332

An aminostratigraphy for the British Quaternary based on Bithynia opercula  

PubMed Central

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

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

2013-01-01

333

A combined hydrochemical - isotopic approach for assessing the regional pollution of an alluvial aquifer in a urbanized environment  

NASA Astrophysics Data System (ADS)

The alluvial aquifer of the Meuse River is contaminated at regional scale in the urbanized and industrialized area of Liège in Belgium with different types of contaminants, in particular inorganics such as sulfate, nitrate and ammonium. The sources of those contaminants are numerous: brownfields, urban waste water, subsurface acid mine drainage from former coal mines, atmospheric deposits related to pollutants emissions in the atmosphere... Sulfate, nitrate and ammonium are both typical pollutants of the aquifer and tracers of the possible pollution sources. According to the European legislation on water, groundwater resources should reach a good quality status before 2015. However, an exemption can be obtained if it may be unfeasible or unreasonably expensive to achieve good status. In this case, groundwater quality objectives and management plans can be adapted to these specific conditions. To obtain such an exemption for the Meuse alluvial aquifer, it is required to demonstrate that the poor qualitative status is caused by acid mine drainage, or by widespread historical atmospheric deposition from industries, and not by recent anthropogenic contamination from the urban and industrial context. In this context, a detailed hydrogeochemical characterization of groundwater has been performed, with the aim of determining the origin of the inorganic contaminations and the main processes contributing to poor groundwater quality. A large hydrochemical sampling campaign was performed, based on 71 selected representative sampling locations, to better characterize the different vectors (end-members) of contamination of the alluvial aquifer and their respective contribution to groundwater contamination in the area. Groundwater samples were collected and analyzed for major and minor compounds and metallic trace elements. The analyses also include stable isotopes in water, sulfate, nitrate, ammonium, boron and strontium. Different hydrogeochemical approaches are combined to obtain a global understanding of the hydrogeochemical processes at regional scale. Hydrochemical interpretations are based on classical diagrams (e.g. Piper), spatial distribution maps, geochemical equations, multivariate statistics and isotopic analyses. With this combined approach, the location of the contaminant sources and most contaminated sectors of the alluvial aquifer together with a better understanding of geochemical processes involved are obtained.

Gesels, Julie; Orban, Philippe; Popescu, Cristina; Knöller, Kay; Brouyère, Serge

2014-05-01

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

A Quaternary Geomagnetic Instability Time Scale  

NASA Astrophysics Data System (ADS)

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

Singer, B. S.

2013-12-01

336

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

NASA Astrophysics Data System (ADS)

The Stagner Creek fault, located along the southern margin of the Owl Creek Mountains in central Wyoming, is one of several east-west striking Quaternary faults that may correspond with scattered, present-day, intraplate seismicity in the region. These Quaternary faults are peculiar in that they strike nearly orthogonal to the Basin and Range faults observed in western Wyoming, and