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Sample records for quaternary alluvial deposits

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

    E-print Network

    Klinger, Yann

    Alluvial deposition and lake-level fluctuations forced by Late Quaternary climate change: the Dead-level fluctuations, alluvial deposition and river entrenchment in the Dead Sea­Wadi Araba area. The bulk of alluvium fan deltas along the margin of the Dead Sea. Wetter conditions settled at the end of this period

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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.

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

    E-print Network

    Dyer, Bill

    SEDIMENTOLOGY AND GEOMORPHOLOGY OF QUATERNARY ALLUVIAL FANS WITH IMPLICATIONS TO GROWTH STRATA......................................................................................14 5. UPPER CEDAR CREEK ALLUVIAL FAN.............................................. 19 Surface 6. JONES CREEK ALLUVIAL FAN......................................................... 67 Surface

  4. Modern and ancient alluvial fan deposits

    SciTech Connect

    Nilsen, T.H.

    1985-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2010-05-01

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

  6. A Quaternary volcanic ash deposit in western Missouri

    SciTech Connect

    Emerson, J.W. )

    1993-03-01

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

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

    SciTech Connect

    Donald S. Sweetkind; Ronald M. Drake II

    2007-01-22

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    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.

  11. Quaternary allostratigraphy of surficial deposit map units at Yucca Mountain, Nevada: A progress report

    SciTech Connect

    Lundstrom, S.C. ); Wesling, J.R.; Swan, F.H. ); Taylor, E.M.; Whitney, J.W. )

    1993-04-01

    Surficial geologic mapping at Yucca Mountain, Nevada, is relevant to site characterization studies of paleoclimate, tectonics, erosion, flood hazards, and water infiltration. Alluvial, colluvial, and eolian allostratigraphic map units are defined on the basis of age-related surface characteristics and soil development, as well as lithology and sedimentology indicative of provenance and depositional mode. In gravelly alluvial units, which include interbedded debris flows, the authors observe a useful qualitative correlation between surface and soil properties. Map units of estimated middle Pleistocene age typically have a well-developed, varnished desert pavement, and minimal erosional and preserved depositional microrelief, associated with a soil with a reddened Bt horizon and stage 3 carbonate and silica morphology. Older units have greater erosional relief, an eroded argillic horizon and stage 4 carbonate morphology, whereas younger units have greater preservation of depositional morphology, but lack well-developed pavements, rock varnish, and Bt and Kqm soil horizons. Trench and gully-wall exposures show that alluvial, colluvial and eolian dominated surface units are underlain by multiple buried soils separating sedimentologically similar deposits; this stratigraphy increases the potential for understanding the long-term Quaternary paleoenvironmental history of Yucca Mountain. Age estimates for allostratigraphic units, presently based on uranium-trend dating and regional correlation using soil development, will be further constrained by ongoing dating studies that include tephra identification, uranium-series disequilibrium, and thermoluminescence methods.

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

    USGS Publications Warehouse

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

    1979-01-01

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

  13. Late Quaternary alluvial fans of Emli Valley in the Ecemi? Fault Zone, south central Turkey: Insights from cosmogenic nuclides

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

    Alluvial fans within the paraglacial Ecemi? River drainages on the Alada?lar Mountains in south central Turkey were studied using geomorphological, sedimentological, and chlorine-36 terrestrial cosmogenic nuclide (TCN) surface exposure dating methods to examine the timing of alluvial fan abandonment/incision, and to understand the role of climatic and tectonic processes in the region. These alluvial fan complexes are among the best-preserved succession of alluvial fans in Turkey and they were offset by the major strike-slip Ecemi? Fault of the Central Anatolian Fault Zone. The alluvial fans are mostly composed of well-lithified limestone cobbles (5 to 25 cm in size), and comprise crudely stratified thick beds with a total thickness reaching up to about 80 m. TCN surface exposure dating indicates that the oldest alluvial fan surface (Yalak Fan) was likely formed and subsequently abandoned latest by 136.0 ± 23.4 ka ago, largely on the transition of the Penultimate Glaciation (Marine Isotope Stage 6, MIS 6) to the Last Interglacial (MIS 5) (i.e. Termination II). The second set of alluvial fan (Emli Fan) was possibly developed during the Last Interglacial (MIS 5), and incised twice by between roughly 97.0 ± 13.8 and 81.2 ± 13.2 ka ago. A younger alluvial fan deposit placed on relatively older erosional terraces of the Emli Fan suggests that it may have been produced during the Last Glacial Cycle (MIS 2). These events are similar to findings from other fluvial and lacustrine deposits throughout central Anatolia. The incision times of the Ecemi? alluvial fan surfaces largely coincide with major climatic shifts from the cooler glacial periods to warmer interglacial/interstadial conditions. This indicates that alluvial fans were produced by outwash sediments of paleoglaciers during cooler conditions, and, later, when glaciers started to retreat due to a major warming event, the excess water released from the glaciers incised the pre-existing fan surfaces. An alluvial fan in the study area was also cut by the Ecemi? Fault, highlighting the influence of tectonics on fan development. It was offset vertically 35 ± 3 m since at least 97.0 ± 13.8 ka, which suggests a 0.36 ± 0.06 mm a- 1 vertical slip-rate of the fault.

  14. Texture and depositional history of near-surface alluvial deposits in the central part of the western San Joaquin Valley, California

    USGS Publications Warehouse

    Laudon, Julie; Belitz, Kenneth

    1989-01-01

    Saline conditions and associated high levels of selenium and other soluble trace elements in soil, shallow ground water, and agricultural drain water of the western San Joaquin Valley, California, have prompted a study of the texture of near-surface alluvial deposits in the central part of the western valley. Texture is characterized by the percentage of coarse-grained sediment present within a specified subsurface depth interval and is used as a basis for mapping the upper 50 feet of deposits. Resulting quantitative descriptions of the deposits are used to interpret the late Quaternary history of the area. Three hydrogeologic units--Coast Range alluvium, flood-basin deposits, and Sierran sand--can be recognized in the upper 50 feet of deposits in the central part of the western San Joaquin Valley. The upper 30 feet of Coast Range alluvium and the adjacent 5 to 35 feet of flood-basin deposits are predominantly fine grained. These fine-grained Coast Range deposits are underlain by coarse-grained channel deposits. The fine-grained flood basin deposits are underlain by coarse-grained Sierran sand. The extent and orientation of channel deposits below 20 feet in the Coast Range alluvium indicate that streams draining the Coast Range may have been tributary to the axial stream that deposited the Sierran sand and that streamflow may have been to the southeast. The fining-upward stratigraphic sequence in the upper 50 feet of deposits and the headward retreat of tributary stream channels from the valley trough with time support a recent hypothesis of climatic control of alluviation in the western San Joaquin Valley.

  15. 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

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

    2006-01-01

    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.

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

    SciTech Connect

    Galloway, W.E.

    1980-01-01

    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.

  17. Depositional facies and Hohokam settlement patterns of Holocene alluvial fans, N. Tucson Basin, Arizona

    SciTech Connect

    Field, J.J.

    1985-01-01

    The distribution of depositional facies on eight Holocene alluvial fans of varying dimensions is used to evaluate prehistoric Hohokam agricultural settlement patterns. Two facies are recognized: channel gravelly sand facies and overbank silty sand facies. No debris flow deposits occur. The channel facies is characterized by relatively well sorted stratified sands and gravels with common heavy mineral laminations. Overbank facies deposits are massive and very poorly sorted due to heavy bioturbation. Lithostratigraphic profiles from backhoe trenches and sediment size analysis document headward migration of depositional facies which results in fining upward sequences. Each sequence is a channel fan lobe with an underlying coarse grained channel sand which fines to overbank silty sands. Lateral and vertical variations in facies distributions show that depositional processes are affected by drainage basin area (fan size) and distance from fan head. Gravelly channel sands dominate at the headward portions of the fan and are more pervasive on large fans; overbank silty sands are ubiquitous at fan toes and approach closer to the fan head of smaller alluvial fans. When depositional facies are considered as records of water flow over an alluvial surface, the farming potential of each fan can be analyzed. Depositional models of alluvial fan sedimentation provide the basis for understanding Hohokam settlement patterns on active alluvial surfaces.

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

    SciTech Connect

    Arvidson, R.; Becker, R.; Shanabrook, A.; Luo, W.; Sultan, M.; Sturchio, N.; Lotfy, Z.; Mahmood, A.M.; El Alfy, Z.

    1994-06-10

    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.

  19. Alluvial deposits and plant distribution in an Amazonian lowland megafan

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    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.

  20. 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

    Adams, G.P.; Runkle, Donna; Rea, Alan; Cederstrand, J.R.

    1997-01-01

    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.

  1. Dating intramontane alluvial deposits from NW Argentina using luminescence techniques: Problems and potential

    NASA Astrophysics Data System (ADS)

    Spencer, Joel Q. G.; Robinson, Ruth A. J.

    2008-01-01

    Intramontane basin sediments are an archive of the interaction between basin bounding faults, and alluvial fan and fluvial systems. The chronologies of intramontane basin sedimentation enable an understanding of the cycling of sediments within a basin through time, can be interrogated to identify periods of alluvial storage and erosion, provide rates of sediment accumulation and storage and date fault movement. If suitable dating methods (in terms of resolution and timescale) are applied to develop the chronologies of alluvial archives, it is then possible to discriminate between climate and tectonic forcing mechanisms on long-term basin behaviour. Optically stimulated luminescence (OSL) dating of quartz grains from alluvial sediments is an ideal technique for establishing a chronological framework of basin sedimentation as the method directly dates sedimentation events. However, our experience of OSL dating of quartz minerals extracted from Late Quaternary alluvial sequences in the quebradas of the Eastern Cordillera of NW Argentina has presented a number of challenges concerning selection of appropriate facies to analyse, mineral contamination, failure of fundamental protocol tests, proximity to saturation, and broad and multi-modal age distributions. Through careful analysis of the alluvial sedimentology and choice of sampling environments we have been able to locate suitable samples in most vertical sequences studied. A post-infrared-OSL approach demonstrated that contaminant signals were resulting in protocol test failure and, conversely, circumvention of this problem has increased confidence and reliability in the dating results. Assessment of dose-response characteristics suggests that the luminescence for the oldest samples is not likely to be saturated and in turn ages are not considered to be underestimated. Finally, different statistical tests have enabled objective identification of single low-dose populations in complex distributions and confirmed that broad distributions in some samples may be treated as single populations. These statistical approaches have considerably lowered uncertainty on OSL ages and confirmed concordance with other dating evidence.

  2. Atomic layer deposition of quaternary chalcogenides

    SciTech Connect

    Thimsen, Elijah J; Riha, Shannon C; Martinson, Alex B.F.; Elam, Jeffrey W; Pellin, Michael J

    2014-06-03

    Methods and systems are provided for synthesis and deposition of chalcogenides (including Cu.sub.2ZnSnS.sub.4). Binary compounds, such as metal sulfides, can be deposited by alternating exposures of the substrate to a metal cation precursor and a chalcogen anion precursor with purge steps between.

  3. West Cameroon Quaternary lacustrine deposits: preliminary results

    NASA Astrophysics Data System (ADS)

    Maley, J.; Livingstone, D. A.; Giresse, P.; Brenac, P.; Kling, G.; Stager, C.; Thouveny, N.; Kelts, K.; Haag, M.; Fournier, M.; Bandet, Y.; Williamson, D.; Zogning, A.

    We present preliminary results from the study of a 23.50 m core (BM-6) representing the last 25 000 years. The core was collected in Barombi Mbo, an explosion crater lake formed probably during the Quaternary. The finely laminated sediment are composed mostly of dark brown to green clay rich organic matter (5-10% organic carbon). Each couplet is commonly composed of a lower unit rich in quartz, plant debris, muscovite and sponge spicules, and of a more clayey upper unit often with siderite (FeCO 3) crystals. The average periodicity for one couplet is between 6 and 20 radiocarbon years. The pollen results, which are compared with those of another forested site in Ghana, demonstrate the presence of a forest refuge in West Cameroon during the last major arid period, about 18 000 years BP. At the same time that equatorial forest was broken up, elements of montain vegetation descended to the lowlands. To provide an explanation for these phenomena marked by a drying and cooling of the climate, modern examples of extensions of montain biotopes to low altitude are described. These localized extensions are due to the persistence of cloud cover, often of stratiform type, generated over the relatively cold water of ocean upwellings. Such lowering of sea-surface temperature might be the primary regional cause of the changes of climate and vegetation that occurred in humid tropical Africa. The upwelling, presently synchronous throughout the Guinea Gulf, amplify the trade winds, which could account for the observed changes inland.

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

    NASA Astrophysics Data System (ADS)

    Yarbasi, Necmi; Kalkan, Ekrem

    2009-08-01

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

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

    USGS Publications Warehouse

    Anderholm, S.K.

    1985-01-01

    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)

  6. 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

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

    1997-01-01

    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.

  7. Sedimentary facies of alluvial fan deposits, Death Valley, California

    SciTech Connect

    Middleton, G.V. )

    1992-01-01

    Fans in Death Valley include both diamicts and bedded gravels. Seven facies may be recognized. The diamicts include: (1) matrix-rich, coarse wackestones; (2) thin, matrix-rich, fine wackestones, that may show grading; (3) matrix-poor, coarse packstones, transitional to wackestones. The bedded facies include: (4) weakly bedded, poorly sorted packstones or grainstones, that show patchy imbrication, and cut-and-fill structures; (5) packed, imbricated cobble lenses, generally interbedded in facies 4; (6) distinctly bedded gravels, that are better bedded, finer and better sorted, and show better imbrication than facies 4, but still do not show clear separation of sand and gravel beds; (7) backfill cross-bedded gravels. Sand beds are not seen in fan deposits. Sand is present in eolian deposits, as plane-laminated, back-eddy deposits in Death Valley Wash, and as laminated or rippled sand in the Amargosa River. The most remarkable features of the fan deposits are the very weak segregation of sand and gravel, and the complete absence of any lower flow-regime structures produced by ripples or dunes. During floods, the slope of fan and even large wash surfaces is steep enough to produce upper flow regimes. There are also very few trends in facies abundance down fans: most fans in Death Valley itself are not strongly dominated by debris flow deposits (diamicts). The facies characteristics of a given fan vary little from proximal to distal regions, but may differ strongly from the facies seen in adjacent fans. Ancient deposits that show clear segregation of gravel from cross-bedded sand beds, or strong proximal to distal facies transitions, must have been deposited in environments quite different from Death Valley.

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

    SciTech Connect

    West, R.B.; Wilson, D.S. . Dept. of Geology)

    1993-04-01

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

  9. Sedimentology of a muddy alluvial deposit: Triassic Denwa Formation, India

    NASA Astrophysics Data System (ADS)

    Ghosh, Parthasarathi; Sarkar, Soumen; Maulik, Pradip

    2006-09-01

    Triassic Upper Denwa Formation (˜ 380 m) in the Satpura Gondwana basin, central India is a mudstone-dominated fluvial succession that comprises isolated ribbon-shaped (2-5-m-thick) channel-fill bodies encased within fine-grained extra-channel deposits. Eight architectural elements are recognized, of which five belong to channel-fill deposits and the remaining three to extra-channel deposits. Majority of channel-fill deposits are characterized by sandy or muddy inclined heterolithic strata (IHS) that record limited lateral accretion of point bars or benches (constrained by cohesive banks) in mixed- to suspended-load sinuous channels. A few ribbon bodies are mud rich and attest to nearly stagnant conditions in partly abandoned channels. A few single- or multistorey ribbon bodies that are dominantly sandy and lack inclined strata represent deposits of straight, laterally stable channel. The smallest ribbon bodies (˜ 1 m thick) of calcirudite/calcarenite possibly represent deposits of secondary channels in the interfluves. Coexistence of channel-fill bodies of different dimension, lithology and internal organization in restricted stratigraphic intervals suggests an anabranching system having channels with different fill histories. The extra-channel deposits mainly comprise red mudstone (1-5 m thick) that indicates pervasive oxidation of overbank sediments in well-aerated and well-drained setting. Sporadically developed calcic vertisols suggest a hot, semi-arid climate during the Upper Denwa period. Sandy to heterolithic sheets (70 cm to 2 m thick) with sharp, planar basal surfaces are replete with features suggestive of unconfined sheet flow. Also at places there are indications of subaqueous emplacement of sands. These bodies with paleocurrent oblique to that of the channel-fills are interpreted as crevasse splay deposits. Tabular heterolithic bodies (3-5 m thick) are characterized by undulating basal surface, complex organization of sandstone lenses interwoven with heteroliths and red mudstone (in decimeter-scale) with desiccation cracks. Such tabular bodies are attributed to repetitive, sheet-like and poorly channelized splaying. Very thick (10 to 20 m) mudstones intervals are inexplicable in terms of overbank flooding only. Poorly developed pedogenic features in sandy to muddy heterolithic sheets and certain mudstone intervals and well-developed cumulative paleosols in surrounding mudstone highlights the contrast between rapidly emplaced splay deposits and slowly accumulated floodplain deposits. The Denwa channels are comparable with modern, low-gradient and low-energy anabranching river system in which the sediment load is dominantly fine-grained. The semi-arid climate possibly facilitated enhanced supply of fines to the Upper Denwa system. However, sediment partitioning and distribution in a particular channel was controlled by flow diversion to and from other channels in that anabranching system. Low flow strength with periodic flood events, high bank strength and a rate of sediment supply that slightly exceeded that of onward transport probably were important factors for the development of the Upper Denwa anabranching system.

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

    NASA Astrophysics Data System (ADS)

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

    2008-07-01

    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.

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

    USGS Publications Warehouse

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

    2014-01-01

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

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

    PubMed

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

    2008-07-29

    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

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

    E-print Network

    Maps of Quaternary Deposits and Liquefaction Susceptibility in the Central San Francisco Bay Region.K., and Gans, K.D., 2006, Maps of Quaternary deposits and liquefaction susceptibility in the central San and Liquefaction Interpretation Additional products of this research include postscript and PDF files

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

    SciTech Connect

    Demko, T.M.; Gastaldo, R.A. )

    1990-05-01

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

  15. Local recharge processes in glacial and alluvial deposits of a temperate catchment

    NASA Astrophysics Data System (ADS)

    Fragalà, Federico A.; Parkin, Geoff

    2010-07-01

    SummaryThis study demonstrates that the composition and structure of Quaternary deposits and topography significantly influence rates of recharge and distribution of diffuse agricultural pollution at the hillslope scale. Analyses were made of vertical profiles of naturally-occurring chloride and nitrate, and artificially introduced bromide, in unsaturated and saturated sections of borehole cores of glacial till and alluvium under different land uses in the Upper Eden valley (UK). Estimates of local potential recharge were made based on chloride mass balance and nitrate peak methods. Persistent chloride bulges below the root zone were observed, and are interpreted to result from filtration processes at lithological boundaries. Changes in the shape of chloride profiles downslope, corroborated by nitrate profiles, indicate the roles of surface or near-surface runoff and runon, and the existence of lateral subsurface flows at depth. These findings have implications for estimation of recharge rates through unsaturated zones in Quaternary deposits, and the interpretation of potential 'hot-spots' of diffuse agrochemicals, particularly nitrates, moving through Quaternary deposits into groundwater.

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

    USGS Publications Warehouse

    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

    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.

  17. Late Quaternary depositional history of the Albemarle Embayment, NC

    SciTech Connect

    Riggs, S.R.; Klingman, C.R.; Wyrick, R.A. . Dept. of Geology)

    1993-03-01

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

  18. Soil erosion history in central Tanzania based on OSL dating of colluvial and alluvial hillslope deposits

    NASA Astrophysics Data System (ADS)

    Eriksson, M. G.; Olley, J. M.; Payton, R. W.

    2000-12-01

    The Irangi Hills in Kondoa District, central Tanzania, are severely degraded by sheet, rill and gully erosion. Using recently developed optically stimulated luminescence (OSL) dating techniques, and a detailed study of the hillslope stratigraphy and soils, we have determined the sequence of events that gave rise to this highly degraded landscape. Two major colluvial deposits have been identified on the slopes. The oldest colluvium gave OSL deposition dates of 14,700±1600, 14,200±1500 and 11,400±1300 years ago. These dates coincide with the climatic change from dry to wet conditions, which took place during the Late Pleistocene. It is possible that the erosion and deposition of the old colluvium occurred as a response to this change. This phase of erosion and deposition was followed by a long phase of stability and pedogenetic alteration of the old colluvium. A phase of accelerated soil erosion began not later than 900 years ago, as indicated by a dated alluvial fan, the presence of which indicates that some deeper gullies already existed on upper pediment slopes at that time. The second, more recent colluvial deposit gave OSL dates of 460±40, 590±70 and 660±50 years. A major period of gully formation and incision, with subsequent fan development, occurred sometime between 600 and 300 years ago. The recent phase of erosion (<1000 years), which is still continuing, is probably a result of the introduction and/or intensification of agriculture, livestock husbandry and iron smelting practices in the Irangi Hills.

  19. 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

    Adams, G.P.; Runkle, Donna; Rea, Alan; Becker, C.J.

    1997-01-01

    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.

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

    E-print Network

    Utrecht, Universiteit

    Palaeoenvironmental reconstruction of a middle Miocene alluvial fan to cyclic shallow lacustrine sedimentary fill of the Calatayud Basin in north-eastern Spain consists of proximal to distal alluvial fan are recognized: (1) proximal and medial alluvial fan facies that comprise clast-supported gravel and subordinate

  1. A discontinuity in the late Pleistocene alluvial deposits, Hwacheon-ri, Gyeongju, Korea: Occurrences and paleoenvironmental implications

    NASA Astrophysics Data System (ADS)

    Paik, In Sung; Kyeong Seol, Weon; Kim, Hyun Joo; Lee, Ho Il; Kang, Hee Cheol

    2015-04-01

    Sedimentary discontinuity surface occurs in the late Pleistocene alluvial deposits exposed along the cliff (about 10 m thick and over 140 m in length) in stream side, Gyeongju, Korea. The discontinuity surface is laterally extensive and marked by distinct carbonaceous dark horizon in the middle part of the deposits. The deposits are divided into lower and upper units by the discontinuity surface. The lower unit overlies unconformably the Cretaceous andesitic rock (basement), and consists of braided-river deposits. Lower part of the lower unit is mainly composed of lenticular-bedded and clast-supported conglomeratic deposits, whereas gray to dark gray sandy to muddy channel-plug deposits occur in the uppermost part of the lower unit. It is characteristic that iron-oxide crusts occur in the lower unit. They are cutting across the lower unit and truncated by the overlying upper unit. Rootlets mineralized by vivianite are present in the channel-plug deposits below the discontinuity surface. The upper unit overlying the lower unit with erosive contact (discontinuity surface) is mostly composed of matrix-supported conglomeratic alluvial fan deposits. Hornfelsic gravels are common in the lower unit, whereas andesitic gravels are predominant in the upper unit, suggesting the provenance change from the lower unit to the upper unit. OSL ages for the lower and the upper units are 125±9 ka and 94±9 ka, respectively, suggesting that the lower unit was deposited in MIS5e and the upper unit was formed in MIS5c to 5b. It is thus interpreted that the shift of depositional environment from a fluvial plain (lower unit) to an alluvial fan (upper unit) was an alluvial response to sea level change inducing fall of base level in an alluvial basin from the interglacial to the glacial stages. The development of iron-oxide crusts and diagenetic vivianite in the discontinuity surface suggest that humid condition persisted during the paleoclimatic shift from the last interglacial to the last glacial stages. Key words: Late Pleistocene, Alluvial deposits, Discontinuity, Iron-oxides, Vivianite

  2. Aggradation and degradation of alluvial sand deposits, 1965 to 1986, Colorado River, Grand Canyon National Park, Arizona

    USGS Publications Warehouse

    Schmidt, J.C.; Graf, J.B.

    1988-01-01

    High discharges occurring between 1983-1985 resulted in redistribution of sand stored in zones of recirculating current in the Colorado River in Grand Canyon National Park. Redistribution resulted in net loss in the number of reattachment deposits in narrow reaches and aggradation of some separation deposits. Separation deposits were more stable than other types of deposits. Alluvial sand deposits that are large enough and of sufficient size for use as campsites were more stable than smaller lower-elevation deposits. Fluctuating flows between October 1985 and January 1986 caused erosion throughout the Grand Canyon, and caused erosion of some deposits created by the high flows of 1983-1985. Data collected for this study included measurements of flow velocity, scour-and-fill of sand deposits, topographic and bathymetric surveys, mapping of surface-flow patterns, water-surface slope surveys, sedimentological analysis, and replication of photographs. A classification system of alluvial sand deposits was developed on the basis of morphometric characteristics and the location of these deposits in relation to parts of recirculation zones. (Author 's abstract)

  3. Aggradation and degradation of alluvial sand deposits, 1965 to 1986, Colorado River, Grand Canyon National Park, Arizona

    USGS Publications Warehouse

    Schmidt, John C.; Graf, Julia B.

    1990-01-01

    Alluvial sand deposits along the Colorado River in Grand Canyon National Park are used as campsites and are substrate for vegetation. The largest and most numerous of these deposits are formed in zones of recirculating current that are created downstream from where the channel is constricted by debris fans at tributary mouths. Alluvial sand deposits are classified by location and form. Separation and reattachment deposits are downstream from constrictions within recirculation zones. Separation deposits are near the point of flow separation and typically mantle large debris fans. Reattachment deposits are near the point of flow reattachment and project upstream beneath much of the zone of recirculating current. Upper-pool deposits are upstream from a constriction and are associated with backwaters. Channel-margin deposits line the channel and have the form of terraces. Some are created in small recirculation zones. Reattachment and channel-margin deposits are largest and most numerous in wide reaches, although small channel-margin deposits are used as campsites in the narrow Muav Gorge. Separation deposits are more uniformly distributed throughout Grand Canyon National Park than are other types of deposits. In some narrow reaches where the number of alluvial sand deposits used as campsites is small, separation deposits are a high percentage of the total. During high flows, both separation and reattachment deposits are initially scoured but are subsequently redeposited during flow recession. Sand is also exchanged between the main channel and recirculation zones. The rate of recession of high flows can affect the elevation of alluvial deposits that are left exposed after a flood has passed. Fluctuating flows that follow a period of steady discharge cause initial erosion of separation and reattachment deposits. A part of this eroded sand is transported to the main channel. Therefore, sand is exchanged between the main channel and recirculation zones and redistributed within recirculation zones over a broad range of discharges. Comparison of aerial photographs and reinterpretation of published data concerning changes of alluvial sand deposits following recession of high flows in 1983 and 1984 indicate that sand was eroded from recirculation zones in narrow reaches. In wide reaches, however, aggradation in recirculation zones may have occurred. In narrow reaches, the decrease of reattachment deposits was greater than that of separation deposits. In all reaches, the percentage of separation deposits that maintained a constant area was greater than for other deposits. Separation deposits, therefore, appear to be the most stable of the deposit types. Fluctuating flows between October 1985 and January 1986, which followed the higher and steadier flows of 1983 to 1985, caused erosion throughout the park. For separation deposits, erosion was greatest at those sites where deposition from the 1983 high flows had been greatest. The existing pattern of low campsite availability in narrow reaches and high campsite availability in wide reaches was thus accentuated by the sequence of flows between 1983 and 1985.

  4. Use of spectral data and Landsat TM for mapping alluvial fan deposits of the Rosillos Mountains in Brewster County, Texas

    SciTech Connect

    Bittick, S.M.; Morgan, K.M.; Busbey, A.B. . Dept. of Geology)

    1993-02-01

    The Rosillos Mountains consist of a large, highly faulted and fracture, exposed Tertiary igneous intrusion (laccolith) located adjacent to Big Bend National Park. This study examines the alluvial deposits that fan out over the 25,000 acre privately owned Rosillos Ranch located on the east side of the laccolith. Using a field spectrometer, spectral curves were generated for the various materials present. These surface reflectance patterns were used for spectral recognition and, along with Landsat digital data, for computer classification mapping of the alluvial fans. Several computer classification techniques will be presented along with mapping accuracies. Initial results indicate the resulting Landsat generated fan deposit maps are, in fact, related to the source areas and the age of deposition.

  5. 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

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

    1997-01-01

    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.

  6. Aggradation and degradation of alluvial sand deposits, 1965 to 1986, Colorado River, Grand Canyon National Park, Arizona; executive summary

    USGS Publications Warehouse

    Schmidt, J.C.; Graf, J.B.

    1988-01-01

    High discharges that occurred in 1983-85 resulted in redistribution of sand stored in zones of recirculating current in the Colorado River in Grand Canyon National Park. Redistribution resulted in net loss in the number of reattachment deposits in narrow reaches and aggradation of some separation deposits. Separation deposits were more stable than other types of deposits. Alluvial sand deposits that are large enough and of sufficient areal extent for use as campsites were more stable than smaller lower-elevation deposits. Fluctuating flows between October 1985 and January 1986 caused erosion throughout the Grand Canyon and caused erosion of some deposits created by the high flows of 1983-85. (Author 's abstract)

  7. Potential controls of alluvial bench deposition and erosion in southern Piedmont streams, Alabama (USA)

    NASA Astrophysics Data System (ADS)

    Haney, Nicholas R.; Davis, Lisa

    2015-07-01

    Benches are bank-attached channel deposits occurring at an elevation between the channel bed and top of banks. Their occurrence in a variety of geologic and hydrologic settings has led to confusion about the mechanisms driving their formation, which in turn contributes to difficulty identifying the active floodplain, bankfull stage, and the determination of environmental flows in some rivers. Hydrodynamic modeling software (River 2D), in combination with sediment particle size analysis and total station topographic surveys, was used to simulate flow conditions needed to erode and deposit the D84, D50, and D15 particle sizes of concave and lateral benches in two rivers (Talladega and Hillabee creeks) in Alabama. Results suggest that bench erosion requires flows at least 150% larger than benchfull stage at the Talladega site, while the Hillabee site experienced erosion at all discharges meeting and exceeding benchfull flow stage, likely owing to its overall smaller sediment particle sizes. At both sites, the presence of vegetation increased the bench area subjected to deposition but, somewhat counterintuitively, also helped influence the location of erosion by limiting flow vectors. In contrast with previous research findings, the occurrence of reverse flow was neither sustained nor widespread at either site. These findings provide new insight into alluvial benches, suggest that the study benches are relatively stable features under the prevailing hydrologic regime, and that in some temperate climate settings, such as the southern Piedmont, localized hydraulic controls on bench formation can be superseded in importance by hydrologic flow regime, even in the case of concave benches and where flow regulation is not a factor.

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

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

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

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

    USGS Publications Warehouse

    Stacy, B.L.

    1960-01-01

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

  10. Glaciers and Late Quaternary glacial deposits of Turkey

    NASA Astrophysics Data System (ADS)

    Çiner, A.

    2003-04-01

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

  11. Late Quaternary mass-wasting records and formation of alluvial terraces in the actively uplifting Lao-nong catchment, southwestern Taiwan

    NASA Astrophysics Data System (ADS)

    Tsui, H. K.; Hsieh, M. L.; Li, W. L.; Hsiao, Y. T.

    2014-12-01

    Although dominated by erosion over long term, the tectonically active mountains of Taiwan commonly contain thick landslide and debris-flow gravels capping hillslopes or forming alluvial terraces. These deposits and their associated landforms serve to study ancient mass-wasting histories and their controls on fluvial processes. This study focuses on the Lao-nong River draining the 1000-3000 m high mountain areas in southwestern Taiwan (current tectonic uplift: 10-20 mm/yr). The Lao-nong River exhibits numerous terraces, many of which are of tributary-fan origins and consist of fluvial/debris-flow gravels 20-200 m thick. The development of such alluvial terraces can be observed during 2009 Typhoon Morakot, which brought record-setting 2000 mm of rain. Triggered by this heavy rain, almost all the tributaries of the Lao-nong generated alluvial fans at their mouths and consequently caused up-to-30 m aggradation along the trunk river. The Lao-nong has yielded >100 radiocarbon dates (all <20 ka).These data reveal that the formation of the observed alluvial terraces (from deposition of thick gravels to subsequent incision) could proceed very rapidly (<1 ky), and that the trunk river has been characterized by repeated aggradation and incision. This fact highlights the significance of event-driven sediment supply in governing the river behavior, which has strongly obscured the effect of the concurrent tectonic uplift. Among the terraces consisting of thick gravels, the six with 100-200 m-thick gravels are dated~18ka, ~12ka (for two terraces), ~5.5ka, ~3.4ka, and ~1.4 ka. The seven terraces with 50-100 m-thick gravels are dated ~12ka, ~8.3ka, ~5.7ka, ~1.3ka and 0.2-1.6ka (two undated). These dates (and others) suggest the clusters of mass-wasting events around ~12ka, 5.5-5.7 ka, and <1.6 ka. However, note that most of the recorded mass-wasting events vary in time and magnitude among tributary catchments, which implies the controls of internal factors on the timing, magnitude, and frequency of the events. Our field observation suggests that at least some of the large Holocene tributary-fan terraces were sourced from pre-Holocene colluviums.

  12. Mineralogical characteristics of the superlarge Quaternary bauxite deposits in Jingxi and Debao counties, western Guangxi, China

    NASA Astrophysics Data System (ADS)

    Liu, Xuefei; Wang, Qingfei; Zhang, Qizuan; Feng, Yuewen; Cai, Shuhui

    2012-06-01

    In recent decades, more than 0.5 billion tons of ores scattered in the Quaternary laterite in western Guangxi, China have been explored. The ores were derived from a bauxite horizon in Permian via physical break-up and re-sediment process. Utilizing various test methods, i.e., XRD, DTA, TG/DTG, SEM/EDS and EPMA, the mineralogical characteristics of the Quaternary bauxite ores in Jingxi and Debao counties were investigated. XRD was used together with TG/DTG to obtain relatively accurate ore mineral abundance. Diaspore is the major phase, whereas hematite, kaolinite, anatase, chamosite, gibbsite, goethite, illite and rutile are minor. Diaspore is characterized by a small particle size, low degrees of crystallinity and complex chemical composition. Both gibbsite and goethite have a varied particle size, and goethite crystals contain high Al substitution and Si. It is clarified that diaspore, chamosite and anatase were formed in a mildly reduced and alkaline depositional environment in Permian, while gibbsite, hematite, goethite and part kaolinite were precipitated from Al3+-, Si4+- and Fe3+-enriched solutions within an Quaternary oxidized environment. The ions Al3+, Si4+ and Fe3+ are mostly released from chamosite in its dissolution process. The different physicochemical conditions between the Permian depositional and the Quaternary weathering periods resulted in a complex mineral assemblage in the Quaternary bauxite.

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

    SciTech Connect

    Harrington, C.D.

    1987-01-01

    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.

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

    USGS Publications Warehouse

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

    2013-01-01

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

  15. Jesse Ewing Canyon Formation, an interpreted alluvial fan deposit in the basal Uinta Mountain Group (Middle Proterozoic), Utah

    SciTech Connect

    Sanderson, I.D.; Wiley, M.T.

    1986-07-01

    The Jesse Ewing Canyon Formation, a member of the Middle Proterozic Uinta Mountain Group, is here proposed as a formal lithostratigraphic unit. It consists of interbedded dark reddish-brown to dark gray conglomerate with predominant white, pale green, gray, or pink metaquartzite clasts, light to dark brown or reddish-brown quartz arenite, and reddish-brown, red, or maroon shale. This represents the first proposal of a formation in the Uinta Mountain Group in the eastern part of the range and follows by only a few years beginning efforts to establish formations in the group in the western part. The Jesse Ewing Canyon Formation locally constitutes the basal member of the Uinta Mountain Group and is here reaffirmed as an alluvial fan deposit, based on a detailed comparison of observed features to those of modern alluvial fans. This interpretation supports the hypothesis that the Uinta Trough is an aulacogen.

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

    USGS Publications Warehouse

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

    2004-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2007-12-01

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

  18. Alluvial Fans on Mars

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

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

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

    E-print Network

    Neff, Jason

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

  20. Subsurface geology of upper Tertiary and Quaternary deposits, coastal Louisiana and adjacent Continental Shelf

    SciTech Connect

    McFarlan, E. Jr.; Leroy, D.O.

    1988-09-01

    Upper Tertiary and Quaternary deposits thicken seaward from a feather edge on the outcrop in the uplands of southern Louisiana to more than 7000 ft (2134 m) beneath the middle continental shelf. Through a study of cores and cuttings from 100 control wells and electric-log pattern correlations from 350 water and petroleum industry wells with seismic corroboration in the offshore area, these deposits have been divided into six major time-stratigraphic units, four of which correlate to outcropping terraces. This investigation presents a regional stratigraphic framework of the major upper Tertiary and Quaternary units from their updip pinch-outs in and beneath the terraced uplands, into the subsurface, across the coastal plain to the Louisiana offshore area.

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

    PubMed

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

    2009-05-30

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

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

    NASA Astrophysics Data System (ADS)

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

    2009-04-01

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

  3. Quaternary silicic pyroclastic deposits of Atitlán Caldera, Guatemala

    USGS Publications Warehouse

    Rose, William I., Jr.; Newhall, Christopher G.; Bornhorst, Theodore J.; Self, Stephen

    1987-01-01

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

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

    USGS Publications Warehouse

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

    2011-01-01

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

  5. 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)

    Masana, Eulalia; Stepancikova, Petra; Rockwell, Thomas

    2013-04-01

    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.

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

    USGS Publications Warehouse

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

    2007-01-01

    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.

  7. Late Quaternary loess landscape evolution on an active tectonic margin, Charwell Basin, South Island, New Zealand

    E-print Network

    Roering, Joshua J.

    Late Quaternary loess landscape evolution on an active tectonic margin, Charwell Basin, South in revised form 9 September 2009 Accepted 18 September 2009 Available online 4 October 2009 Keywords: Loess Landscape evolution Active tectonics Alluvial terraces Loess deposits constitute an important archive

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

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

    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.

  9. Quaternary mud deposits on the Korean shelf—processes, facies, stratigraphy: an introduction and future challenges

    NASA Astrophysics Data System (ADS)

    Chang, Tae Soo; Yoo, Dong-Geun

    2015-09-01

    On the Korean and adjacent Chinese epicontinental shelves of the Yellow Sea, a variety of mud deposits occur that all formed during the late Quaternary. The available evidence suggests that they were generated by different processes in different water depths and at different times. Over the last three decades, numerous studies have revealed the large-scale features and stratigraphic evolution histories of some of these mud deposits, but the nature of the deposits as such and, in particular, the factors controlling their deposition are still poorly understood. This has led to long-standing debates especially on the origin or provenance of the fine-grained sediments, but also on discrepancies concerning stratigraphic interpretations. To provide potential solutions to some of these issues, the international workshop "Quaternary Shelf Mud: Processes, Facies, and Stratigraphy" was held from 1-4 September 2014 at the Korea Institute of Geoscience & Mineral Resources (KIGAM), Daejeon, Republic of Korea. At the workshop, recent progress in various research fields using newly acquired datasets was presented. Although dealing with an essentially regional issue, the results of the Korean studies have undoubtedly yielded new insights into shelf mud deposition, many aspects of which should also be of interest to the international scientific community. This special issue of Geo-Marine Letters comprises selected contributions to the workshop, the focus lying on extensive, newly acquired datasets from the continental shelf bordering the west (southeastern Yellow Sea) and east (southern East Sea) coasts of the Korean Peninsula, and involving the Heuksan mud belt and mud deposits off the Nakdong delta, respectively. These contributions are complemented by a state-of-the-art overview of key mud depocenters worldwide. In spite of some progress and new interpretations elaborated in this special issue, some aspects still remain to be solved as future challenges.

  10. Quaternary mud deposits on the Korean shelf—processes, facies, stratigraphy: an introduction and future challenges

    NASA Astrophysics Data System (ADS)

    Chang, Tae Soo; Yoo, Dong-Geun

    2015-12-01

    On the Korean and adjacent Chinese epicontinental shelves of the Yellow Sea, a variety of mud deposits occur that all formed during the late Quaternary. The available evidence suggests that they were generated by different processes in different water depths and at different times. Over the last three decades, numerous studies have revealed the large-scale features and stratigraphic evolution histories of some of these mud deposits, but the nature of the deposits as such and, in particular, the factors controlling their deposition are still poorly understood. This has led to long-standing debates especially on the origin or provenance of the fine-grained sediments, but also on discrepancies concerning stratigraphic interpretations. To provide potential solutions to some of these issues, the international workshop "Quaternary Shelf Mud: Processes, Facies, and Stratigraphy" was held from 1-4 September 2014 at the Korea Institute of Geoscience & Mineral Resources (KIGAM), Daejeon, Republic of Korea. At the workshop, recent progress in various research fields using newly acquired datasets was presented. Although dealing with an essentially regional issue, the results of the Korean studies have undoubtedly yielded new insights into shelf mud deposition, many aspects of which should also be of interest to the international scientific community. This special issue of Geo-Marine Letters comprises selected contributions to the workshop, the focus lying on extensive, newly acquired datasets from the continental shelf bordering the west (southeastern Yellow Sea) and east (southern East Sea) coasts of the Korean Peninsula, and involving the Heuksan mud belt and mud deposits off the Nakdong delta, respectively. These contributions are complemented by a state-of-the-art overview of key mud depocenters worldwide. In spite of some progress and new interpretations elaborated in this special issue, some aspects still remain to be solved as future challenges.

  11. Quaternary geology and sapphire deposits from the BO PHLOI gem field, Kanchanaburi Province, Western Thailand

    NASA Astrophysics Data System (ADS)

    Choowong, Montri

    2002-01-01

    One of the most famous blue sapphire deposits in Thailand and SE Asia is from the Bo Phloi District, Kanchanaburi Province, Western Thailand. This paper presents the results of our gemstone investigation as well as establishing the Bo Phloi depositional sequence as one of the Quaternary Type Sections in the region. Relationships among the sedimentology, depositional sequences and geomorphology were investigated in order to understand the gemstone depositional features. Sedimentary structures and textures of the sequences show that the deposition of gemstones is related genetically to fluvial processes. Gemstones are recognized in floodplain and low terrace deposits where gemstone paystreaks concentrate mostly inside layers of gravel beds and foreset-bedded gravels lithofacies. C-14 dating of wood and peat within gemstone-bearing layers indicated that the deposit formed during the middle to late Pleistocene. The gemstone-bearing gravel bed defines a north-south trend along the incised palaeo-channel of an ancient braided river system in the middle part of the basin.

  12. Remote sensing analysis of depositional landforms in alluvial settings: Method development and application to the Taquari megafan, Pantanal (Brazil)

    NASA Astrophysics Data System (ADS)

    Zani, Hiran; Assine, Mario Luis; McGlue, Michael Matthew

    2012-08-01

    Traditional Shuttle Radar Topography Mission (SRTM) topographic datasets hold limited value in the geomorphic analysis of low-relief terrains. To address this shortcoming, this paper presents a series of techniques designed to enhance digital elevation models (DEMs) of environments dominated by low-amplitude landforms, such as a fluvial megafan system. These techniques were validated through the study of a wide depositional tract composed of several megafans located within the Brazilian Pantanal. The Taquari megafan is the most remarkable of these features, covering an area of approximately 49,000 km2. To enhance the SRTM-DEM, the megafan global topography was calculated and found to be accurately represented by a second order polynomial. Simple subtraction of the global topography from altitude produced a new DEM product, which greatly enhanced low amplitude landforms within the Taquari megafan. A field campaign and optical satellite images were used to ground-truth features on the enhanced DEM, which consisted of both depositional (constructional) and erosional features. The results demonstrate that depositional lobes are the dominant landforms on the megafan. A model linking baselevel change, avulsion, clastic sedimentation, and erosion is proposed to explain the microtopographic features on the Taquari megafan surface. The study confirms the potential promise of enhanced DEMs for geomorphological research in alluvial settings.

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

    SciTech Connect

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

    1987-05-01

    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 shoreface erosion during ensuing transgression, serve as markers to identify the boundaries of depositional sequences. Unconformities are recognizable on seismic profiles by high-amplitude reflectors as well as discordant relationships between reflectors. Within the upper Quaternary section, six depositional sequences have been recognized. Five of these are related to glacio-eustatic sea level fluctuations, involving sea level fall close to, or beyond, the margin of the continental shelf. Three of these fluctuations culminated in the deposition of shelf margin delta sequences. Extensive fluvial channeling characterizes the regressive phase of these sequences. Transgressive phases are marked by infilling of fluvial channels, flood-plain aggradation, truncation, or deposition of sand sheets, depending upon sediment supply and rate of sea level rise. Sequences 4 and 5 are correlated with the late Wisconsinan glacial stage and Holocene transgression. The upper portion of sequence 5 consists of an early Holocene Mississippi delta complex. Abandonment and transgression of this delta are responsible for the formation of sequence 6. Although these deposits cover a smaller area, this demonstrates that deltaic processes can produce sequences similar to those driven by glacially controlled sea level changes.

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

    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.

  15. Late quaternary history and uranium isotopic compositions of ground water discharge deposits, Crater Flat, Nevada

    USGS Publications Warehouse

    Paces, James B.; Taylor, Emily M.; Bush, Charles

    1993-01-01

    Three carbonate-rich spring deposits are present near the southern end of Crater Flat, NV, approximately 18 km southwest of the potential high-level waste repository at Yucca Mountain. We have analyzed five samples of carbonate-rich material from two of the deposits for U and Th isotopic compositions. Resulting U-series disequilibrium ages indicate that springs were active at 18 ?? 1, 30 ?? 3, 45 ?? 4 and >70 ka. These ages are consistent with a crude internal stratigraphy at one site. Identical ages for two samples at two separate sites suggest that springs were contemporaneous, at least in part, and were most likely part of the same hydrodynamic system. In addition, initial U isotopic compositions range from 2.8 to 3.8 and strongly suggest that ground water from the regional Tertiary-volcanic aquifer provided the source for these hydrogenic deposits. This interpretation, along with water level data from near-by wells suggest that the water table rose approximately 80 to 115 m above present levels during the late Quaternary and may have fluctuated repeatedly. Current data are insufficient to allow reconstruction of a detailed depositional history, however geochronological data are in good agreement with other paleoclimatic proxy records preserved throughout the region. Since these deposits are down gradient from the potential repository site, the possibility of higher ground water levels in the future dramatically shortens both vertical and lateral ground water pathways and reduces travel times of transported radionuclides to potential discharge sites.

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

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

    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.

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

    USGS Publications Warehouse

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

    1977-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

    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.

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

    USGS Publications Warehouse

    Hupp, C.R.; Simon, A.

    1991-01-01

    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.

  20. Depositional morphotypes and implications of the Quaternary travertine and tufa deposits from along Gafsa Fault: Jebel El Mida, southwestern Tunisia

    NASA Astrophysics Data System (ADS)

    Henchiri, Mohsen

    2014-02-01

    The diversity of depositional morphologies of tufa and travertine in the field, which are controlled by a complex set of bio-physio-chemical parameters, can make them difficult to distinguish. In Jebel El Mida, the Late Villafranchian faulted alluvial deposits are overlain by complex lithofacies and growth patterns of spring-fed tufa and travertine. Travertine facies include travertine pinnacles, microterraces, thermal ponds, pisoids and conical structures, oncoids, microbial crusts, bacterial shrubs, microstromatolites, lithified bubbles (foam rocks) and microfans and cones. Their formation is controlled by (i) the volume of spring water and gas supplies and their respective daily, monthly or annual fluctuations, and (ii) topography and location with respect to the spring vent. The travertines highlight the predominance of physico-chemical processes over biochemical processes in their formation. In this context, water turbulence, temperature, and/or pressure changes are the dominant agents in releasing CO2. Tufa facies include rhizocretions and cushions, plant moulds and imprints, lithified terrestrial land snails, gyttja and paleosols. Their formation is linked to the dominance of biochemical processes over physio-chemical processes. In this context the amount of CO2 in calmer waters is regulated by photosynthesis, which indirectly regulates the rate of calcium carbonate precipitation. Gafsa strike-slip Fault, in addition to its tectonic role in creating fluid paths to the surface through flowing springs, acts as a major regional sill that controlled paleoflow directions, discharge locations, volume, rate and fluctuations of the water supply.

  1. Survey of Martian Alluvial Fans

    NASA Astrophysics Data System (ADS)

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

    2004-12-01

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

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

    USGS Publications Warehouse

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

    2006-01-01

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

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

    SciTech Connect

    Hoover, D.L.

    1989-11-01

    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.

  4. Late Quaternary aeolianites, palaeosols and depositional environments on the Nepean Peninsula, Victoria, Australia

    NASA Astrophysics Data System (ADS)

    Zhou, Liping; Williams, Martin A. J.; Peterson, James A.

    The Nepean Peninsula is a bay-mouth bar near Melbourne. It is comprised of Late Quaternary aeolianites, palaeosols and calcretes. TL dates show that most of the sands from which the aeolianites developed as mobile sand dunes were deposited during times of low sea-level towards 47 and 23 ka BP, and others during times of relatively high sea-level towards 118 ka BP. Aeolian dust mantles were laid down during brief intervals when aeolianite formation had ceased. Incipient soil formation and minor organic staining of the upper 0.3-0.5 m of the dust mantles points to a lull in dune formation and the temporary development of a widespread plant cover. The dust mantles have TL ages of 118, 57, 54, 51 and 47 ka BP, indicating that apart from the 118 ka mantle, most of the deposition was when sea-level was low and the regional climate was drier, windier, colder and under a more continental climatic regime. During times of glacially lower sea-level, the coastal climate in this region was not invariably cold, dry and windy but was punctuated by brief intervals of milder, moister and less windy conditions during which dunes and dust mantles became vegetated and soils began to form. Rapid climatic fluctuations were coeval with aeolianite deposition during times of very low sea-level.

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

    SciTech Connect

    Winn, R.D. Jr. )

    1991-03-01

    A consortium of oil companies is undertaking a multiyear shallow coring and high-resolution seismic investigation of the outer shelf-slope deposits of the northern Gulf of Mexico. The program's objective is to reconstruct the depositional, seismic stratigraphic, biostratigraphic, isotopic, and organic geochemical record of the latest Quaternary of a portion of the Gulf margin. Results will serve as an analog to deeper hydrocarbon reservoirs and to help in understanding sedimentation with glacial-interglacial sea-level changes. Nearly continuous cores up to 850 ft long from Main Pass Blocks 303, 242, 288 and Viosca Knoll Block 774 are being described and analyzed. Main Pass 303 core samples Holocene to Oxygen Isotope Stage 6 deposits and as old or older strata are expected to have been penetrated in the other boreholes. Three or four sea level cycles are represented. Seismic acquisition is planned for late 1990. The outer shelf and slope of the northern Gulf is an area of active growth faulting, high sedimentation rate, diapirism, and slumping. Recent work, including this study, shows that near-surface stratigraphy consists of coarse clastics alternating with carbonate-rich mud. Sands and gravels are inferred to have been deposited mostly during lowstands and rising sea level in deltas and valley-fill systems. Delta clinoforms on high-resolution seismic may represent shelf-margin wedges, prograding wedges, or highstand systems tracts. Highstand deposits are characterized largely by thin, continuous intervals of bioturbated muds containing abundant diagenetic carbonate and pyrite. Precise dating and correlation of outer shelf-upper slope facies to magnitude and direction of sea level change is intended during the project.

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

    USGS Publications Warehouse

    Chirico, Peter G.; Malpeli, Katherine C.

    2014-01-01

    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.

  7. Radiocarbon dating late Quaternary loess deposits using small terrestrial gastropod shells

    USGS Publications Warehouse

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

    2013-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

    Chakraborty, Partha Pratim; Paul, Pritam

    2014-09-01

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

  9. 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)

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

    2012-12-01

    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.

  10. Optical dating of late Quaternary deposits preserved beneath the eastern English Channel

    NASA Astrophysics Data System (ADS)

    Mellett, C. L.; Mauz, B.; Hodgson, D. M.; Plater, A. J.; Lang, A.

    2012-04-01

    A stratigraphic model detailing the sequence and nature of processes responsible for sculpting the shallow continental shelf in the eastern English Channel has been developed through the interpretation of high resolution sub-bottom seismic records. The seafloor is an erosional unconformity and large sediment bodies are limited to palaeovalley infills and offshore extensions of present day coastal environments. In simplistic terms the stratigraphic model proposes fluvial incision and deposition during sea-level lowstand with periglacial processes operating on the sub-aerially exposed shelf under cold climate conditions. Subsequent sea-level rise triggers reworking of existing deposits and infilling of the palaeovalleys with shallow marine and coastal deposits that migrate in step with sea-level rise. The frequency and magnitude of sea-level changes during the late Quaternary lends to significant reworking of sediments during each glacial/interglacial cycle and remnants of previous cycles are rarely preserved. This study uses OSL dating to test the validity of the proposed stratigraphic model. Samples for OSL dating were taken from vibrocores tied to known seismic stratigraphic units representing fluvial, coastal and colluvial depositional environments. The single-aliquot-regenerative dose protocol was applied to 1 mm aliquots of fine quartz sand and individual aliquots were rejected following the criteria proposed by Wintle and Murray (2006). All samples exhibited low sensitivity and poor recycling ratios necessitating the rejection of up to 75% of all aliquots measured. A total of 40 to 60 aliquots were accepted per sample. For all samples regardless of depositional environment, normal equivalent dose (De) distributions were observed with overdispersion values typically <25% and weighted skewness values of ~0.2 advocating the application of the Central Age Model (CAM) to estimate Des. The OSL chronology places periglacial reworking of existing estuarine deposits at ~18 ka, deposition of fluvial sediments preserved in palaeovalleys at ~15ka and progradation of a shoreface at ~8 ka. The ages are remarkably consistent with the stratigraphic model and provide the first chronological control on the timing of processes responsible for the morphological evolution of the continental shelf. We demonstrate the successful application of OSL dating to fluvial, coastal and colluvial deposits preserved in the eastern English Channel.

  11. 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

    Harrelson, Larry G.; Addison, Adrian D.

    2006-01-01

    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.

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

    PubMed

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

    2010-01-01

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

  13. Quaternary investigation

    SciTech Connect

    Stieve, A.

    1991-05-15

    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.

  14. Quaternary tephrochronology and deposition in the subsurface Sacramento-San Joaquin Delta, California, U.S.A.

    USGS Publications Warehouse

    Maier, Katherine L.; Gatti, Emma; Wan, Elmira; Ponti, Daniel J.; Pagenkopp, Mark; Starratt, Scott W.; Olson, Holly A.; Tinsley, John

    2015-01-01

    We document characteristics of tephra, including facies and geochemistry, from 27 subsurface sites in the Sacramento-San Joaquin Delta, California, to obtain stratigraphic constraints in a complex setting. Analyzed discrete tephra deposits are correlative with: 1) an unnamed tephra from the Carlotta Formation near Ferndale, California, herein informally named the ash of Wildcat Grade (<~1.450 - >~0.780 Ma), 2) the Rockland ash bed (~0.575 Ma), 3) the Loleta ash bed (~0.390 Ma), and 4) a middle Pleistocene tephra resembling volcanic ash deposits at Tulelake, California, and Pringle Falls, Bend, and Summer Lake, Oregon, herein informally named the dacitic ash of Hood (<~0.211 to >~0.180 Ma, correlated age). All four tephra are derived from Cascades volcanic sources. The Rockland ash bed erupted from the southern Cascades near Lassen Peak, California, and occurs in deposits up to >7 m thick as observed in core samples taken from ~40 m depth below land surface. Tephra facies and tephra age constraints suggest rapid tephra deposition within fluvial channel and overbank settings, likely related to flood events shortly following the volcanic eruption. Such rapidly deposited tephra are important chronostratigraphic markers that suggest varying sediment accumulation rates (~0.07-0.29 m/1000 yr) in Quaternary deposits below the modern Sacramento-San Joaquin Delta. This study provides the first steps in developing a subsurface Quaternary stratigraphic framework necessary for future hazard assessment.

  15. Quaternary tephrochronology and deposition in the subsurface Sacramento-San Joaquin Delta, California, U.S.A.

    NASA Astrophysics Data System (ADS)

    Maier, Katherine L.; Gatti, Emma; Wan, Elmira; Ponti, Daniel J.; Pagenkopp, Mark; Starratt, Scott W.; Olson, Holly A.; Tinsley, John C.

    2015-03-01

    We document characteristics of tephra, including facies and geochemistry, from 27 subsurface sites in the Sacramento-San Joaquin Delta, California, to obtain stratigraphic constraints in a complex setting. Analyzed tephra deposits correlate with: 1) an unnamed tephra from the Carlotta Formation near Ferndale, California, herein informally named the ash of Wildcat Grade (<~1.450 to >~ 0.780 Ma), 2) the Rockland ash bed (~ 0.575 Ma), 3) the Loleta ash bed (~ 0.390 Ma), and 4) middle Pleistocene volcanic ash deposits at Tulelake, California, and Pringle Falls, Bend, and Summer Lake, Oregon, herein informally named the dacitic ash of Hood (<~0.211 to >~ 0.180 Ma). All four tephra are derived from Cascades volcanic sources. The Rockland ash bed erupted from the southern Cascades and occurs in up to > 7-m-thick deposits in cores from ~ 40 m subsurface in the Sacramento-San Joaquin Delta. Tephra facies and tephra age constraints suggest rapid tephra deposition within fluvial channel and overbank settings, likely related to flood events shortly following volcanic eruption. Such rapidly deposited tephra are important chronostratigraphic markers that suggest varying sediment accumulation rates in Quaternary deposits below the modern Sacramento-San Joaquin Delta. This study provides the first steps in a subsurface Quaternary stratigraphic framework necessary for future hazard assessment.

  16. Seismic Velocities and Thicknesses of Alluvial Deposits along Baker Creek in the Great Basin National Park, East-Central Nevada

    USGS Publications Warehouse

    Allander, Kip K.; Berger, David L.

    2009-01-01

    To better understand how proposed large-scale water withdrawals in Snake Valley may affect the water resources and hydrologic processes in the Great Basin National Park, the National Park Service needs to have a better understanding of the relations between streamflow and groundwater flow through alluvium and karst topography of the Pole Canyon Limestone. Information that is critical to understanding these relations is the thickness of alluvial deposits that overlay the Pole Canyon Limestone. In mid-April 2009, the U.S. Geological Survey and National Park Service used seismic refraction along three profiles adjacent to Baker Creek to further refine understanding of the local geology. Two refractors and three distinct velocity layers were detected along two of the profiles and a single refractor and two distinct velocity layers were detected along a third profile. In the unsaturated alluvium, average velocity was 2,000 feet per second, thickness ranged from about 7 to 20 feet along two profiles downstream of the Narrows, and thickness was at least 100 feet along a single profile upstream of the Narrows. Saturated alluvium was only present downstream of the Narrows - average velocity was 4,400 feet per second, and thickness ranged from about 40 to 110 feet. The third layer probably represented Pole Canyon Limestone or Tertiary granitic rock units with an average velocity of 12,500 feet per second. Along the upstream and middle profiles (profiles 3 and 1, respectively), the depth to top of the third layer ranged from at least 60 to 110 feet below land surface and is most likely the Pole Canyon Limestone. The third layer at the farthest downstream profile (profile 2) may be a Tertiary granitic rock unit. Baker Creek is disconnected from the groundwater system along the upstream profile (profile 3) and streamflow losses infiltrate vertically downward to the Pole Canyon Limestone. Along the downstream and middle profiles (profiles 2 and 1, respectively), the presence of a shallow water table indicates that low permeability Tertiary granitic rock may extend across the Baker Creek Drainage intersecting the Pole Canyon Limestone. The Tertiary granitic rock may be acting as a barrier to groundwater flow within the Pole Canyon Limestone.

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

    USGS Publications Warehouse

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

    2000-01-01

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

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

    USGS Publications Warehouse

    Gaggiani, N.G.

    1984-01-01

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

  19. Late quaternary depositional systems and sea level change-Santa Monica and San Pedro Basins, California continental borderland

    SciTech Connect

    Nardin, T.R.

    1983-07-01

    A suite of seismic reflection data that provides different degrees of resolution and penetration was used to map the depositional systems that have developed in Santa Monica and San Pedro basins during the late Quaternary. Submarine fan growth, particularly at the mouths of Hueneme and Redondo Canyons, has been the dominant mode of basin filling. Mass movement processes, ranging from creep to large-scale catastrophic slumping, have been important locally. In general, large-scale fan growth fits Normark's model in which the suprafan is the primary locus of coarse sediment deposition. Smaller scale morphologic and depositional patterns on the Hueneme and Redondo fans (e.g., distributary channels and coarse sediment concentrations basinward of the inner suprafan) suggest that a significant amount of coarse sediment presently bypasses the suprafans, however. Long-distance coarse sediment transport was particularly pronounced during late Wisconsinan lowstand of sea level and resulted in progradation of lower mid-fan and lower fan deposits.

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

    USGS Publications Warehouse

    Reheis, M.C.

    1992-01-01

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

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

    SciTech Connect

    Brouwers, E.M.; Bown, T.M. ); Hadley, D.G. )

    1993-04-01

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

  2. Quaternary geology of Avery Island, Louisiana

    SciTech Connect

    Autin, W.J.; McCulloh, R.P.; Davison, A.T.

    1986-09-01

    Avery Island, one of the Five Islands salt domes of south-central Louisiana, is a piercement-type dome that has been uplifted from several kilometers' depth. It is nearly circular in plan with a maximum elevation approximately 50 m above the surrounding coastal marsh. Dissection has produced a terrain of gullies and steep slopes. The features identified indicate a complex geologic history for Avery Island. Deposition of late Pleistocene sediments in a low-relief alluvial plain and subsequent soil development predate domal uplift. The stratigraphy of loess and colluvial silts indicates the island was emergent during loess depositions. The degree of dissection, distribution of colluvium, and shearing of Quaternary sediments reflects continual uplift after loess deposition.

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

    SciTech Connect

    Berry, M.E. . Dept. of Geology)

    1992-01-01

    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.

  4. Epiguruk: a late Quaternary environmental record from northwestern Alaska

    USGS Publications Warehouse

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

    1993-01-01

    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

  5. Evaluation of ERTS-1 imagery for mapping Quaternary deposits and landforms in the Great Plains and Midwest

    NASA Technical Reports Server (NTRS)

    Morrison, R. B. (principal investigator); Hallberg, G. R.

    1973-01-01

    The author has identified the following significant results. The main landform associations and larger landforms are readily identifiable on the better images and commonly the gross associations of surficial Quaternary deposits also can be differentiated, primarily by information on landforms and soils. Maps showing the Quaternary geologic-terrain units that can be differentiated from the ERTS-1 images are being prepared for 20-odd potential study areas in Illinois, Iowa, Missouri, Kansas, Nebraska, and South Dakota. Among the more distinct features are the major moraines and outwash channels of the last (Wisconsin) glaciation. Analysis of dissection/drainage patterns from the synoptic imagery is proving useful for detecting anomalies that may be caused by stream diversions and moraines of pre-Wisconsin glaciations, by variable loess deposition, by tectonism, and other factors. Numerous abandoned river valleys have been mapped. Trend-lines of several known pre-Wisconsin moraine systems have been identified in Iowa, Nebraska, and Kansas, and also several similar trend-lines, that may indicate previously unknown moraine systems of middle and possibly early Pleistocene age, have been found in Iowa and Missouri. The area inundated by a major flood in southwestern Iowa also has been delineated from ERTS-1 imagery.

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

    SciTech Connect

    Reneau, S.L.; McDonald, E.V.; Gardner, J.N.; Longmire, P.A.; Kolbe, T.R.; Carney, J.S.; Watt, P.M.

    1996-04-01

    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.

  7. Active Tectonics and Alluvial Rivers

    NASA Astrophysics Data System (ADS)

    Talwani, Pradeep

    Flying into San Francisco, California, for the AGU Fall Meeting from the east coast of the United States, one sees an ever-changing pattern of rivers below. From straight channels, the rivers take on a meandering pattern, become braided, and form oxbow lakes. Their drainage patterns change from regional directions in response to local structures and tectonic activity This carving of the landscape is the response of alluvial rivers to active tectonics manifested locally by ongoing tectonic uplift, river erosion, and alluvial deposition.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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.

  9. Quaternary glacial and post-glacial depositional history associated with the Green Bay lobe, east-central Wisconsin

    SciTech Connect

    Thieme, L.D.; Smith, G.L. . Dept. of Geology)

    1993-03-01

    Multiple layers of peat and wood fragments indicate that Quaternary glaciation of the east-central region of Wisconsin was punctuated by at least two interglacial periods. Till, outwash, and glaciolacustrine deposits suggest that deposition took place in alternating glacial and non-glacial environments due to oscillations in the position of the Green Bay Lobe terminus. The data for this study consists of 36 auger borings, 70 geologic logs and 100 well-construction reports from water wells. Nine vibracores were taken at the northern margin of Lake Winnebago in order to document in detail the post-glacial history of Glacial Lake Oshkosh/Lake Winnebago. Local bedrock consists of limestones and dolomites of the Middle Ordovician Sinnipee Group. Bedrock elevations range from 211--237 m; bedding dips regionally to the southeast at 1--2 degrees. Bedrock is overlain by a 3--13 m-thick layer of alternating red clay and gray silty-clay (basal Kewaunee Formation ) perhaps deposited in a proglacial lake. These sediments are overlain by apeat/wood layer indicating marsh deposition. This peat/wood layer is overlain by more proglacial lake sediment, 3--10 m of gray brown clay to silty-clay. A second peat/wood layer overlies the gray/brown sediment and may correlate with the Two Creeks buried forest bed. The uppermost unit consists of 2--3 m red silty-clay till (Middle Inlet Member of the Kewaunee Formation). Along the northern margin of present-day Lake Winnebago, red silty-clay is overlain by silty-sand deposited by Glacial Lake Oshkosh. Future work includes obtaining radiocarbon dates from buried peat/wood layers to verify these tentative correlations between east-central Wisconsin and the Lake Michigan Basin.

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

    PubMed

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

    2014-10-01

    Geostatistical variogram and inversion techniques combined with modern visualization tools have made it possible to re-model one-dimensional electrical resistivity data into two-dimensional (2D) models of the near subsurface. The resultant models are capable of extending the original interpretation of the data to depict alluvium layers as individual lithological units within the 2D space. By tuning the variogram parameters used in this approach, it is then possible to visualize individual lithofacies and geomorphological features for these lithologic units. The study re-examines an electrical resistivity dataset collected as part of a groundwater study in an area of the Bannu basin in Pakistan. Additional lithological logs from boreholes throughout the area have been combined with the existing resistivity data for calibration. Tectonic activity during the Himalayan orogeny uplifted and generated significant faulting in the rocks resulting in the formation of a depression which subsequently has been filled with clay-silt and dirty sand facies typical of lacustrine and flood plain environments. Streams arising from adjacent mountains have reworked these facies which have been eroded and replaced by gravel-sand facies along channels. It is concluded that the sediments have been deposited as prograding fan shaped bodies, flood plain, and lacustrine deposits. Clay-silt facies mark the locations of paleo depressions or lake environments, which have changed position over time due to local tectonic activity and sedimentation. The Lakki plain alluvial system has thus formed as a result of local tectonic activity with fluvial erosion and deposition characterized by coarse sediments with high electrical resistivities near the mountain ranges and fine sediments with medium to low electrical resistivities towards the basin center. PMID:25004850

  11. ELEVATED FOSSIL CORAL DEPOSITS IN THE HAWAIIAN ISLANDS: A MEASURE OF ISLAND UPLIFT IN THE QUATERNARY

    E-print Network

    Qiu, Bo

    ELEVATED FOSSIL CORAL DEPOSITS IN THE HAWAIIAN ISLANDS: A MEASURE OF ISLAND UPLIFT Gary McMurtry Johanna Resig #12;ABSTRACT The origin of emerged marine fossils in the Hawaiian Islands waves swept up to 326 m on Lanai and neighboring islands depositing marine fossils 105 ka; (3

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

    SciTech Connect

    Piper, D. ); Savoye, B. )

    1993-09-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

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

    USGS Publications Warehouse

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

    1992-01-01

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

  15. Author's personal copy Beryllium-10 terrestrial cosmogenic nuclide surface exposure dating of Quaternary

    E-print Network

    Frankel, Kurt L.

    Terrestrial cosmogenic nuclides Optically stimulated luminescence Alluvial fans Shore lines Lake Manly Quaternary alluvial fans, and shorelines, spits and beach bars were dated using 10 Be terrestrial cosmogenic. Comparisons of 10 Be TCN ages on alluvial fan surfaces with chronostratigraphies based on soil development

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

    USGS Publications Warehouse

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

    2007-01-01

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

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

    USGS Publications Warehouse

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

    2007-01-01

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

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

    USGS Publications Warehouse

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

    1979-01-01

    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.

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

    USGS Publications Warehouse

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

    1987-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Moore, Christopher R.

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

  1. Hyperactive neotectonic near the South Rifian front. Lifted Late Quaternary lagunal deposits (Atlantic Morocco)

    NASA Astrophysics Data System (ADS)

    Benmohammadi, Aïcha; Griboulard, Roger; Zourarah, Bendahhou; Carruesco, Christian; Mehdi, Khalid; Mridekh, Aziz; Moussaoui, Abderahmane El; Alaoui, Asmae Mhamdi; Carbonel, Pierre; Londeix, Laurent

    2007-10-01

    The recent discovery of emerged and lifted lagunal deposits near the Moulay Bouselham lagoon (North Moroccan Atlantic coast), up to 32 m above sea level, requires a new model to explain the evolution of this ecosystem. All the studies on these deposits seem to indicate that we are dealing with very recent lagoonal levels. The main problem is to explain the altitude of these deposits. Likely explanations are a historical tsunami, tempest, and/or a very strong neotectonics in this area. We choose the later hypothesis because it matches the occurrence of an argilokinetic tectonic in front of the North Atlantic Moroccan margin. In this tectonic context, results of 14C analysis data, i.e. 2400 ± 250 BP for one outcrop and 2170 ± 215 BP for a value in a core taken in the lagoon, we obtain a rate of uplift of about 14 mm/yr. Therefore, this region corresponds to an important tectonic junction between the stable Meseta to the south, the Rifian domain to the north and the accretionary prism, in relation with the subduction of the Atlantic crust under the African and European plates to the west. Moreover, in front of the studied site, many mud volcanoes have been observed in the Gulf of Cadiz, near the Moroccan margin.

  2. Late Pliocene to Late Quaternary Apparent Exposure Ages from Glacial Deposits in Ak-Shyrak, Central Kyrgyz Tian Shan

    NASA Astrophysics Data System (ADS)

    Blomdin, R.; Harbor, J.; Stroeven, A. P.; Petrakov, D. A.; Gribenski, N.; Heyman, J.; Ivanov, M.; Caffee, M. W.; Hättestrand, C.; Lifton, N. A.; Rogozhina, I.; Usubaliev, R.

    2014-12-01

    The Tian Shan in central Asia is one of the world's highest mountain ranges. The 2500 km-long WSW-ENE-trending arc of mountains extends from the western Kyrgyz Republic across northwestern China and almost to the border with Mongolia. Understanding the glacial history of this vast region is important because there is a general lack of paleoclimatic data from this highly continental location, at the confluence of major climate systems, and because glaciers are sensitive monitors of climate change. We examine the glacial history of the Ak-Shyrak massif and surrounding plateaus with average altitudes of ~3500 m a.s.l. To reconstruct the glacial history of this area we use a combined approach including geomorphological mapping, and cosmogenic nuclide surface exposure dating of erratic boulders on glacial landforms. We observe large site-specific scatter in our 10Be and 26Al exposure ages. Apparent minimum surface exposure ages range from ~2 ka to ~2.5 Ma, with early Quaternary- late Pliocene apparent exposure ages relating to some of the highest 10Be concentrations ever recorded for glacial deposits. Most dated boulders, however, fall in the apparent exposure age range of 100 ka to 300 ka. Consistent with previous results from the western and central Tian Shan, none of our boulders record a global last glacial maxima expansion of glaciers, and this contrasts to data from the eastern Kyrgyz Tian Shan. This spatial variation in glacier extent might be due to differences in paleoclimate. However, local physiographic conditions (e.g. altitude, slope, aspect) or external forcing factors other than climate (e.g., landslides) may cause local or regional differences in glacier response. We refrain from assigning mapped glacial advances to marine oxygen isotope stages because of the considerable age scatter. Finally we assess and discuss possible reasons for the observed age scatter and early Quaternary-late Pliocene apparent exposure ages in terms of prior and/or incomplete exposure histories of individual samples and compare our data to other regional datasets.

  3. 75 FR 62137 - Notice of Public Meeting; Proposed Alluvial Valley Floor Coal Exchange Public Interest Factors...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-07

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

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

    USGS Publications Warehouse

    Fournier, R.B.

    1989-01-01

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

  5. Chronostratigraphic and paleoclimatic data for Quaternary loessial and fluvial deposits in the Mississippi River Valley of Arkansas and Tennessee

    SciTech Connect

    Markewich, H.W. ); Millard, H.T. Jr. ); Pavich, M.J. ); Rodbell, D.T. ); Rich, F.J. ); Rutledge, E.M. ); Ward, L. . Soil Conservation Service); Van Valkenberg, S. ); Wysocki, D. . Soil Conservation Service)

    1992-01-01

    Ongoing investigations into Quaternary paleoclimates of the Mississippi River Valley in eastern Arkansas and western Tennessee include age estimations using [sup 14]C, [sup 10]Be, thermoluminescent (TL), and optically stimulated luminescent (OSL) analyses; compositional studies using petrographic and diffractometer analyses; pedological analyses with complete characterization studies; and magnetic susceptibility measurements with laboratory analyses to investigate the source of the magnetism. Preliminary data on composition of the < 63-micron fraction, thickness, and age of the loesses and associated paleosols are available from selected stratigraphic sections that are being described and sampled in detail. These data suggest the following: (1) overall thickness of loess, as well as thickness of each loess sheet, decreases by one-half to two-thirds within the 96-km distance from the south end of Crowleys Ridge near Helena, AR northward to Forest City, AR and Memphis, TN; (2) near Helena, loess thicknesses are 25 to 30 m, 7 m, 6 m, and 6 m for the Peoria, Roxana, Loveland, and Crowleys Ridge respectively; (3) the depth of weathering in the Peoria ranges from 4.5 to 8.5 m near Helena, depending on slope position; (4) at the south end of Crowleys Ridge, near Helena, the Roxana has two associated paleosols and an intervening layer of weathered parent material; (5) isotopic data suggest that (a) loess deposition took place between 4,500 ka and 10 ka and that (b) each younger disconformity represents less time than the one before; (6) the predominantly illite and illite/smectite mineralogy of the paleosols, even that of the Sangamon soil, suggests minimal weathering of labile loessial minerals prior to pedogenic development; (7) pollen data indicate that by 10 ka this part of the valley had vegetation indicative of a cool temperate climate, with minimal cypress and no boreal components.

  6. Late Quaternary distal tephra-fall deposits in lacustrine sediments, Kenai Peninsula, Alaska

    USGS Publications Warehouse

    de Fontaine, C.S.; Kaufman, D.S.; Scott, Anderson R.; Werner, A.; Waythomas, C.F.; Brown, T.A.

    2007-01-01

    Tephra-fall deposits from Cook Inlet volcanoes were detected in sediment cores from Tustumena and Paradox Lakes, Kenai Peninsula, Alaska, using magnetic susceptibility and petrography. The ages of tephra layers were estimated using 21 14C ages on macrofossils. Tephras layers are typically fine, gray ash, 1-5??mm thick, and composed of varying proportions of glass shards, pumice, and glass-coated phenocrysts. Of the two lakes, Paradox Lake contained a higher frequency of tephra (0.8 tephra/100 yr; 109 over the 13,200-yr record). The unusually large number of tephra in this lake relative to others previously studied in the area is attributed to the lake's physiography, sedimentology, and limnology. The frequency of ash fall was not constant through the Holocene. In Paradox Lake, tephra layers are absent between ca. 800-2200, 3800-4800, and 9000-10,300??cal yr BP, despite continuously layered lacustrine sediment. In contrast, between 5000 and 9000??cal yr BP, an average of 1.7 tephra layers are present per 100 yr. The peak period of tephra fall (7000-9000??cal yr BP; 2.6 tephra/100 yr) in Paradox Lake is consistent with the increase in volcanism between 7000 and 9000 yr ago recorded in the Greenland ice cores. ?? 2007 Elsevier Inc. All rights reserved.

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

    USGS Publications Warehouse

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

    2009-01-01

    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.

  8. Terrestrial Cosmogenic-Nuclide Dating of Alluvial Fans in Death Valley, California

    USGS Publications Warehouse

    Machette, Michael N.; Slate, Janet L.; Phillips, Fred M.

    2008-01-01

    We have used terrestrial cosmogenic nuclides (TCN) to establish the age of some of the most extensive Quaternary alluvial fans in Death Valley, California. These intermediate-age alluvial fans are most extensive on the western side of the valley, where tectonic deformation is considerably less pronounced than on the eastern side of the valley. These fans are characterized by a relatively smooth, densely packed desert pavement formed by well-varnished (blackened) clasts. These surfaces have been mapped as the Q2 gravel by previous workers and as unit Qai (intermediate age) by us. However, the intermediate-age gravels probably contain multiple subunits, as evidenced by slight differences in morphologic expression, soil formation, and inset geomorphic relations. The TCN technique used herein sums the cosmogenic 36Cl in approximately 2.5-meter-deep profiles through soil and host alluvium, thus avoiding some of the problems associated with the more typical surface-exposure dating of boulders or smaller clasts. Our TCN 36Cl dating of 12 depth profiles indicates that these intermediate-age (Qai) alluvial fans range from about 100 to 40 kilo-annum (ka), with a mean age of about 70 ka. An alternative interpretation is that alluvial unit Qai was deposited in two discrete episodes from 90 to 80 ka and from 60 to 50 ka, before and after MIS (marine oxygen-isotope stage) 4 (respectively). Without an intermediate-age unit, such as MIS 4 lake deposits, we can neither disprove nor prove that Qai was deposited in two discrete intervals or over a longer range of time. Thus, in Death Valley, alluvial unit Qai largely brackets MIS 4, which is not associated with a deep phase of Lake Manly. These Qai fans extend to elevations of about -46 meters (150 feet below sea level) and have not been transgressed by Lake Manly, suggesting that MIS 4 or MIS 2 lakes were rather shallow in Death Valley, perhaps because they lacked inflow from surface runoff of the Sierra Nevada drainages through Panamint Valley and over Wingate Wash. A remnant of ancient lake shoreline deposits that once extended across the Hanaupah Canyon fan constrains the timing and extent of the last deep cycle of Pleistocene Lake Manly. The lacustrine delta complex yields a 36Cl depth-profile date of 130 ka, which is consistent with deposition during a highstand of Lake Manly at the end of MIS 6. These deposits are presently at an altitude of about 30 meters above sea level (asl), which relates to a lake with a maximum depth of about 115 meters. Remnants of shoreline deposits at higher elevations on the southern margin of the Hanaupah Canyon fan complex are cut across older alluvium (unit Qao) and may be related to an MIS 6 highstand of at least 67 meters asl or, more likely, an older (MIS 8 or earlier) highstand that is poorly preserved and still undated in the valley. As part of our work on the west-side fans, we also dated an older phase of alluvial-fan deposits from the Trail Canyon fan complex, which is north of Hanaupah Canyon. A 36Cl depth-profile age of 170 ka suggests alluvial deposition of unit Qaio (older phase of Qao) took place prior to the MIS 6 highstand of Lake Manly. Knowing the absolute ages (or range in ages) of the intermediate-age (Qai) surfaces in Death Valley allows us to estimate the following rates of geologic processes: (1) a lateral slip rate of 5 millimeters per year for the northern Death Valley fault zone; (2) uplift of 50 meters in roughly the past 80,000 years for parts of the Mustard Canyon hills in east-central Death Valley; and (3) an estimated 10-40 m of dip-slip thrust movement on the Echo Canyon fault in Furnace Creek Canyon.

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

    SciTech Connect

    Hillhouse, J.W.

    1987-12-31

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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.

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

    E-print Network

    Frankel, Kurt L.

    Characterizing arid region alluvial fan surface roughness with airborne laser swath mapping digital; accepted 5 January 2007; published 26 May 2007. [1] Range-front alluvial fan deposition in arid differences between alluvial fan units has proven to be difficult in the past, high-resolution airborne laser

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

    NASA Astrophysics Data System (ADS)

    Williams, Martin

    2014-05-01

    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.

  13. 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)

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

    2014-05-01

    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.

  14. Rock varnish microlamination dating of late Quaternary geomorphic features in the drylands of western USA

    NASA Astrophysics Data System (ADS)

    Liu, Tanzhuo; Broecker, Wallace S.

    2008-01-01

    Varnish microlamination (VML) dating is a correlative age determination technique that can be used to date and correlate various geomorphic features in deserts. In this study, we establish a generalized late Quaternary (i.e., 0-300 ka) varnish layering sequence for the drylands of western USA and tentatively correlate it with the SPECMAP oxygen isotope record. We then use this climatically correlated varnish layering sequence as a correlative dating tool to determine surface exposure ages for late Quaternary geomorphic features in the study region. VML dating of alluvial fan deposits in Death Valley of eastern California indicates that, during the mid to late Pleistocene, 5-15 ky long aggradation events occurred during either wet or dry climatic periods and that major climate shifts between glacial and interglacial conditions may be the pacemaker for alteration of major episodes of fan aggradation. During the Holocene interglacial time, however, 0.5-1 ky long brief episodes of fan deposition may be linked to short periods of relatively wet climate. VML dating of alluvial desert pavements in Death Valley and the Mojave Desert reveals that pavements can be developed rapidly (< 10 ky) during the Holocene (and probably late Pleistocene) in the arid lowlands (< 800 m msl) of these regions; but once formed, they may survive for 74-85 ky or even longer without being significantly disturbed by geomorphic processes operative at the pavement surface. Data from this study also support the currently accepted, "being born at the surface" model of desert pavement formation. VML dating of colluvial boulder deposits on the west slope of Yucca Mountain, southern Nevada, yields a minimum age of 46 ka for the emplacement of these deposits on the slope, suggesting that they were probably formed during the early phase of the last glaciation or before. These results, combined with those from our previous studies, demonstrate that VML dating has great potential to yield numerical age estimates for various late Quaternary geomorphic features in the western USA drylands.

  15. Late Quaternary aeolian sand deposition sustained by fluvial reworking and sediment supply in the Hexi Corridor - An example from northern Chinese drylands

    NASA Astrophysics Data System (ADS)

    Nottebaum, Veit; Lehmkuhl, Frank; Stauch, Georg; Lu, Huayu; Yi, Shuangwen

    2015-12-01

    Aeolian deposits are frequently used for palaeoenvironmental change studies. Their formation depends on an array of requirements: the supply of material suitable for aeolian transport and favorable conditions of sediment availability and wind strength. In order to infer palaeoenvironmental information from aeolian sand deposits these factors need to be carefully evaluated. We present a study from northern Chinese Hexi Corridor, based on 11 optically stimulated luminescence (OSL) dated sediment sections. These represent interchanging aeolian and alluvial deposits under gravel surfaces and aeolian sand in dune fields interrupted by interdunal flood deposits. Investigations in two subareas reveal contrasting geomorphologic and sedimentary histories: (1) sediment deposition during the Pleistocene-Holocene transition (~ 12 ka) followed by deflation during the Holocene and (2) frequent sediment recycling revealed by a wide spectrum of ages throughout the Holocene. The late glacial sediment pulse recorded in the western Hexi Corridor is attributed to high sediment supply, generated by efficient (peri-)glacial sediment production during glacial times in the adjacent Qilian Shan (< 5700 m asl) and a moisture increase inducing the reworking of those (glacio-)fluvial deposits during the Pleistocene-Holocene transition. The absence of a powerful reworking agent preserved these late glacial deposits in the western Hexi Corridor in contrast to moister eastern parts where Holocene sediment reworking prevailed. Geomorphological and hydrological preconditions of the subareas are discussed and reveal the controlling influence of fluvial processes on sand supply for the aeolian system. While a perennial drainage is missing in the drier western part, the Hei River drainage is fed by higher monsoonal precipitation in the central Hexi Corridor. It maintains a sediment recycling system and has ensured a sufficient sediment supply throughout the Holocene. The study promotes closer consideration of the fluvial influence on aeolian archives in palaeoenvironmental studies from central Asian and other drylands.

  16. Alluvial Fan in Icaria Planum, Mars

    NASA Astrophysics Data System (ADS)

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

    2005-12-01

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

  17. Surface roughness as a calibrated proxy for dating alluvial surfaces

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    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.

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

    SciTech Connect

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

    1993-04-01

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

  19. Giant landslide deposits in northwest Argentina

    SciTech Connect

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

    1985-01-01

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

  20. 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

    Robinson, Bret A.; Risch, Martin R.

    2006-01-01

    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.

  1. 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

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

    2005-08-26

    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.

  2. Laboratory alluvial fans in one dimension.

    PubMed

    Guerit, L; Métivier, F; Devauchelle, O; Lajeunesse, E; Barrier, L

    2014-08-01

    When they reach a flat plain, rivers often deposit their sediment load into a cone-shaped structure called alluvial fan. We present a simplified experimental setup that reproduces, in one dimension, basic features of alluvial fans. A mixture of water and glycerol transports and deposits glass beads between two transparent panels separated by a narrow gap. As the beads, which mimic natural sediments, get deposited in this gap, they form an almost one-dimensional fan. At a moderate sediment discharge, the fan grows quasistatically and maintains its slope just above the threshold for sediment transport. The water discharge determines this critical slope. At leading order, the sediment discharge only controls the velocity at which the fan grows. A more detailed analysis reveals a slight curvature of the fan profile, which relates directly to the rate at which sediments are transported. PMID:25215729

  3. Pollen preservation and Quaternary environmental history in the southeastern United States

    SciTech Connect

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

    1980-01-01

    Reconstructions of Quaternary environmental history based upon modern pollen/vegetation/climate calibrations are more tenable if the factors responsible for variation in pollen assemblages are evaluated. Examination of the state of preservation of Quaternary palynomorphs provides quantitative data concerning the degree of information loss due to alteration of pollen assemblages by syndepositional and post-depositional deterioration. The percentage, concentration, and influx values for total indeterminable pollen are useful criteria in providing an objective and quantitative basis for evaluating the comparability of pollen spectra within and between sites. Supporting data concerning sediment particle-size distribution, organic matter content, and concentration, influx, and taxonomic composition of both determinable pollen and plant macrofossils aid in reconstructing past depositional environments. The potential is high for deterioration of pollen in sediments from the southeastern United States, although considerable variation is found in both kind and degree of deterioration between lacustrine and alluvial sites of different ages and in different latitudes. Modern analogs are a basis for late Quaternary environmental reconstructions when pollen deterioration has not significantly biased the information content of fossil pollen assemblages.

  4. Provenance of the Heavy Mineral-enriched Alluvial Deposits at the West Coast of Red Sea. Implications to the Evolution of Arabian-Nubian Crust

    NASA Astrophysics Data System (ADS)

    Mahar, M. A.; Ibrahim, T.; Goodell, P.

    2014-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

  7. 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

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

    1983-03-01

    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.

  8. Sedimentology and depositional history of Neogene gravel deposits in lower Tornillo Creek area of Big Bend National Park, Texas

    SciTech Connect

    Thurwachter, J.E.

    1984-04-01

    Neogene gravel deposits in the lower Tornillo Creek area of Big Bend National Park, Texas, record the filling of a small structural basin formed during Basin and Range tectonism. Four lithofacies are recognized in the Late Miocene La Noria member (informal name): (1) a medial braided-stream lithofacies consisting of upward-fining packages of cross-bedded gravel, sandstone, and siltstone; (2) a distal braided-stream lithofacies consisting of poorly-defined upward-fining packages of fine gravel, sandstone, and mudstone; (3) a calcrete-rich gravel and sandstone lithofacies representing strike-valley and alluvial-fan deposition, and (4) and ephemeral lake-plain lithofacies consisting of massive and burrowed mudstones with sheet-like sandstone interbeds. Upward-fining packages in the braided-stream lithofacies represent the lateral migration and avulsion of the stream tract across the basin; together with the strike-valley and alluvial-fan deposits, these record the initial stages of basin filling. Provenance studies show that much of this sediment was derived from northern Mexico. Overlying ephemeral-lake deposits record the structural tilting and closing of the downstream (north) end of the basin. Gravels and minor sandstones of the Pleistocene Estufa member (informal name) represent basinward progradation of alluvial fans. Deposition of the Estufa member resulted from: (1) Quaternary tectonic activity in the Chisos Mountains area; (2) lowering of local base level by post-Miocene development of the Rio Grande drainage through the area; and (3) Pleistocene pluvial-period climatic changes. Subsequent Quaternary faulting has caused minor deformation of the deposits.

  9. Neogene-Quaternary depositional history of the eastern US continental rise seaward of the Washington-Norfolk Canyon systems

    SciTech Connect

    Locker, S.D.; Laine, E.P.

    1985-01-01

    High quality, digitally recorded and processed, water gun and air gun seismic reflection data collected seaward of the present position of the Washington-Norfolk canyon systems reveals new information on the development of the continental rise. This includes insight into the depositional history of the Washington-Norfolk fan system and the relative importance of gravity flow depositional processes versus abyssal bottom current reworking during rise development. Three major post-Horizon A/sup u/ accretionary sequences describe major changes in depositional processes and history within the region. Accretionary sequence I (early to middle Miocene) is characterized by the initial development of a depositional bulge seaward of the Washington-Norfolk canyon systems which is modified by bottom currents on the lower-most rise to form a proto-Hatteras Outer Ridge. The predominance of chaotic and hummocky seismic facies suggests widespread reworking by abyssal bottom currents. Accretionary sequence II (middle Miocene to late Pliocene) in this area is characterized by sediment waves (lower rise) and smooth, southward dipping, parallel reflectors associated with a thick central rise drift(.) deposit off the Hudson system to the North. Washington-Norfolk fan development appears less important during this time. Bottom currents are active, but more depositional in nature than during accretionary sequence I. Accretionary sequence III (late Pliocene to Present) is marked by gravity flow processes and distinct development of the Washington-Norfolk fan on the central rise.

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

    USGS Publications Warehouse

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

    2012-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    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.

  12. Preliminary U-series disequilibrium and thermoluminescence ages of surficial deposits and paleosols associated with Quaternary faults, eastern Yucca Mountain

    SciTech Connect

    Paces, J.B.; Menges, C.M.; Bush, C.A.; Futa, K.; Millard, H.T.; Maat, P.B.; Whitney, J.W.; Widmann, B.; Wesling, J.R.

    1994-12-31

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

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

    NASA Astrophysics Data System (ADS)

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

    2006-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2009-04-01

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

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

    USGS Publications Warehouse

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

    1994-01-01

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

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

    USGS Publications Warehouse

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

    2003-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

    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.

  19. Late quaternary activity of the Laguna Salada fault in northern Baja California, Mexico

    E-print Network

    Mueller, Karl

    Thomas K. Rockwell ABSTRACT Faulted alluvial fans and bajadas along the central Laguna Salada fault zone in northern Baja California record a recurrent history of oblique-slip Holocene earth- quakes. Alluvial. The recurrence interval determined from displaced alluvial deposits that are dated by soil profile development

  20. Delineation of groundwater development potential zones in parts of marginal Ganga Alluvial Plain in South Bihar, Eastern India.

    PubMed

    Saha, Dipankar; Dhar, Y R; Vittala, S S

    2010-06-01

    A part of the Gangetic Alluvial Plain covering 2,228 km(2), in the state of Bihar, is studied for demarcating groundwater development potential zones. The area is mainly agrarian and experiencing intensive groundwater draft to the tune of 0.12 million cubic metre per square kilometres per year from the Quaternary marginal alluvial deposits, unconformably overlain northerly sloping Precambrian bedrock. Multiparametric data on groundwater comprising water level, hydraulic gradient (pre- and post-monsoon), aquifer thickness, permeability, suitability of groundwater for drinking and irrigation and groundwater resources vs. draft are spatially analysed and integrated on a Geographical Information System platform to generate thematic layers. By integrating these layers, three zones have been delineated based on groundwater development potential. It is inferred that about 48% of the area covering northern part has high development potential, while medium and low development potential category covers 41% of the area. Further increase in groundwater extraction is not recommended for an area of 173 km(2), affected by over-exploitation. The replenishable groundwater resource available for further extraction has been estimated. The development potential enhances towards north with increase in thickness of sediments. Local deviations are due to variation of-(1) cumulative thickness of aquifers, (2) deeper water level resulting from localised heavy groundwater extraction and (3) aquifer permeability. PMID:19415511

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

    SciTech Connect

    Peterson, F.F.; Bell, J.W.; Ramelli, A.R.; Dorn, R.I.; Ku, T.L.

    1995-04-01

    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.

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

    SciTech Connect

    Birdseye, R.U.

    1985-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

    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

    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.

  4. Controls on alluvial fan long-profiles

    USGS Publications Warehouse

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

    2008-01-01

    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.

  5. The “Alluvial Mesovoid Shallow Substratum”, a New Subterranean Habitat

    PubMed Central

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

    2013-01-01

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

  6. Occurrence, Distribution, Sources, and Trends of Elevated Chloride Concentrations in the Mississippi River Valley Alluvial Aquifer in Southeastern Arkansas

    USGS Publications Warehouse

    Kresse, Timothy M.; Clark, Brian R.

    2008-01-01

    Water-quality data from approximately 2,500 sites were used to investigate the distribution of chloride concentrations in the Mississippi River Valley alluvial aquifer in southeastern Arkansas. The large volume and areal distribution of the data used for the investigation proved useful in delineating areas of elevated (greater than 100 milligrams per liter) chloride concentrations, assessing potential sources of saline water, and evaluating trends in chloride distribution and concentration over time. Irrigation water containing elevated chloride concentrations is associated with negative effects to rice and soybeans, two of the major crops in Arkansas, and a groundwater chloride concentration of 100 milligrams per liter is recommended as the upper limit for use on rice. As such, accurately delineating areas with high salinity ground water, defining potential sources of chloride, and documenting trends over time is important in assisting the agricultural community in water management. The distribution and range of chloride concentrations in the study area revealed distinct areas of elevated chloride concentrations. Area I includes an elongated, generally northwest-southeast trending band of moderately elevated chloride concentrations in the northern part of the study area. This band of elevated chloride concentrations is approximately 40 miles in length and varies from approximately 2 to 9 miles in width, with a maximum chloride concentration of 360 milligrams per liter. Area II is a narrow, north-south trending band of elevated chloride concentrations in the southern part of the study area, with a maximum chloride concentration of 1,639 milligrams per liter. A zone of chloride concentrations exceeding 200 milligrams per liter is approximately 25 miles in length and 5 to 6 miles in width. In Area I, low chloride concentrations in samples from wells completed in the alluvial aquifer next to the Arkansas River and in samples from the upper Claiborne aquifer, which underlies the alluvial aquifer, indicate that leakage from the river and upward flow of saline water in underlying aquifers are not likely sources for the saline water in the alluvial aquifer in Area I. A good comparison was noted for chloride concentrations in Area I and surface geomorphology. In the majority of cases, elevated chloride concentrations occurred in backswamp deposits, with low concentrations (less than 50 milligrams per liter) in areas of active or abandoned channel deposits. The fine-grained, clay-rich deposits associated with backswamp areas likely restrict recharge, induce increased ratios between evapotranspiration and recharge, and experience minimal flushing of salts concentrated during evapotranspiration. In Area II, chloride isoconcentration maps of the underlying upper Claiborne aquifer, in addition to samples from wells completed in the middle and lower Claiborne aquifers, showed a similar chloride distribution to that of the alluvial aquifer with decreasing chloride concentrations to the east of the zone of elevated chloride concentrations, which suggests a deeper source of saline water that affects Tertiary and Quaternary aquifer systems. Mixing curves developed from bromide/chloride ratios in water samples from the alluvial aquifer, Tertiary aquifers, and samples of brine water from the Jurrasic Smackover Formation additionally discounted upward flow of saline water from underlying Tertiary formations as a potential mechanism for salinity in the alluvial aquifer in Area II. A review of information on oil exploration wells in Chicot County revealed that most of these wells were drilled from 1960 to 1980, after the elevated chloride concentrations were detected in the early 1950s. The elongated nature of the zone of elevated chloride concentrations in Area II suggests a line source or linear conduit connection with the source. Maps of a fractured limestone in the Smackover Formation in Arkansas, Mississippi, and Louisiana for purpose

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

    USGS Publications Warehouse

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

    1980-01-01

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

  8. Quaternary geology and geologic hazards of the West Desert Hazardous Industry Area, Tooele County, Utah

    USGS Publications Warehouse

    Solomon, Barry J.; Black, Bill D.

    1990-01-01

    The study of Quaternary geology provides information to evaluate geologic conditions and identify geologic constraints on construction in the West Desert Hazardous Industry Area (WDHIA). The WDHIA includes portions of the Great Salt Lake Desert to the west, underlain by several thousand feet of sediments capped by saline mudflats, and Ripple Valley to the east, separated from the Desert by the Grayback Hills and underlain by several hundred feet of sediments in the Cedar Mountains piedmont zone. Quaternary surficial units include marginal, shore-zone, and deep-water lacustrine sediments deposited in Pleistocene Lake Bonneville; eolian deposits; and alluvial sediments. The level of Lake Bonneville underwent major oscillations resulting in the creation of four basin-wide shorelines, three of which are recognized in the WDHIA. Geologic hazards in the WDHIA include the possible contamination of ground water in basin-fill aquifers, debris flows and flash floods in the piedmont zone, and earthquakes and related hazards. Numerous factors contribute to unsafe foundation conditions. Silty and sandy sediments may be subject to liquefaction or hydrocompaction, clayey sediments and mud flats of the Great Salt Lake Desert may be subject to shrinking or swelling, and gypsiferous dunes and salt flats are subject to subsidence due to dissolution.

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

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

    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.

  10. Quaternary Geologic Map of Connecticut and Long Island Sound Basin

    USGS Publications Warehouse

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

    2005-01-01

    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.

  11. Influences of quaternary climatic changes on processes of soil development on desert loess deposits of the Cima volcanic field, California

    USGS Publications Warehouse

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

    1986-01-01

    Soils formed in loess are evidence of both relict and buried landscapes developed on Pliocene-to-latest Pleistocene basalt flows of the Cima volcanic field in the eastern Mojave Desert, California. The characteristics of these soils change systematically and as functions of the age and surface morphology of the lava flow. Four distinct phases of soil development are recognized: phase 1 - weakly developed soils on flows less than 0.18 M.y. old; phase 2 - strongly developed soils with thick argillic horizons on 0.18 - 0.7 M.y. old flows; phase 3 - strongly developed soils with truncated argillic horizons massively impregnated by carbonate on 0.7 to 1.1 M.y. old flows; and phase 4 - degraded soils with petrocalcic rubble on Pliocene flows. A critical aspect of the development of stage 1 soils is the evolution of a vesicular A horizon which profoundly affects the infiltration characteristics of the loess parent materials. Laboratory studies show that secondary gypsum and possibly other salt accumulation probably occurred during the period of phase 1 soil development. Slight reddening of the interiors of peds from vesicular-A horizons of phase 1 soils and presence of weakly developed B horizons indicates a slight degree of in situ chemical alteration. However, clay and Fe oxide contents of these soils show that these constituents, as well as carbonates and soluble salts, are incorporated as eolian dust. In contrast to phase 1 soils, chemical and mineralogical analysis of argillic horizons of phase 2 soils indicate proportionally greater degrees of in-situ chemical alteration. These data, the abundant clay films, and the strong reddening in the thick argillic horizons suggest that phase 2 and phase 3 soils formed during long periods of time and periodically were subjected to leaching regimes more intense than those that now exist. Flow-age data and soil-stratigraphic evidence also indicate that several major loess-deposition events occurred during the past ??? 1.0 M.y. Loess events are attributed to past changes in climate, such as the Pleistocene-to-Holocene climatic change, that periodically caused regional desiccation of pluvial lakes, reduction of vegetational density, and exposure of loose, unconsolidated fine materials. During times of warmer interglacial climates, precipitation infiltrates to shallower depths than during glacial periods. Extensive, saline playas which developed in the Mojave Desert during the Holocene are a likely source of much of the carbonates and soluble salts that are accumulating at shallow depths both in phase 1 soils and in the formerly noncalcareous, nongypsiferous argillic horizons of phase 2 and 3 soils. ?? 1986.

  12. Geology and mineral deposits of Churchill County, Nevada

    USGS Publications Warehouse

    Willden, Ronald; Speed, Robert C.

    1974-01-01

    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.

  13. Hydraulic processes on alluvial fans

    SciTech Connect

    French, R.H.

    1987-01-01

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

  14. Quaternary Tectonic and Climatic Processes shaping the Central Andean hyperarid forearc (southern Peru)

    NASA Astrophysics Data System (ADS)

    Audin, Laurence; Benavente, Carlos; Zerathe, Swann; Saillard, Marianne; Hall, Sarah R.; Farber, Daniel L.

    2015-04-01

    Understanding the forearc structure and processes related to Quaternary evolution and uplift of the Western Andean Cordillera remains an outstanding scientific issue. Models of Andean Plateau evolution based on Tertiary volcanic stratigraphy since 5Ma suggest that the deformation was focused along the eastern margin of the plateau and that minimal uplift occurred along the Pacific margin. On the contrary, new tectonic data and Quaternary surface 10Be dating highlight the presence of recently active deformation, incision and alluvial processes within the upper Andean forearc together with a regional uplift of the coastal zone. Additionally, the high obliquity observed in the northern Arica Bend region makes it an ideal target to discuss whether partitioning of the oblique convergence is accommodated by the neotectonic features that dissect the Quaternary forearc. Our goals are both to decipher the Quaternary tectonic and climatic processes shaping the hyperarid forearc along strike and across strike. Finally, we aim to quantify the respective influence of these factors in the overall uplift of the Western Andes. Indeed, sequences of pediment surfaces, landslide products, paleolake deposits and marine terraces found along the oblique Peruvian margin are a unique set of datable markers that can be used to quantify the rates of Quaternary processes. In this study, we focus on the southern Peru hyperarid Atacama area where regional surfaces and tectonic markers (scarps, folds, temporary streams and paleolake levels offsets…) are well preserved for the Quaternary timescale. Numerous landsliding events align on the major fault segments and reflect Plio-Pleistocene climatic and tectonic activity together with filled and strath terraces. As the present day sea-level is one of the highest levels recorded for Quaternary time span, any emerged marine terrace is preserved by tectonic coastal uplift. In particular, the geomorphic and chronologic correlation between marine and continental planation surfaces or terraces permit to deduce net vertical rates and suggests that the along strike uplift affected not only the coast but also the overall ~50 km-wide forearc of the Western Andes. We produced a chronology of remnant low-relief surfaces and a new neotectonic map of the Central Andean forearc between ~14° and 18°S based on detailed field mapping and 10Be cosmogenic dating. We address 1) the spatial and temporal correlations of various markers, and 2) the correlation of the surface abandonment ages to various regional climatic events and 3) the description of neotectonic activity accommodating both uplift and partitioning. Multiple markers yield 10Be surface abandonment ages that spanning 35 ka to >2 Ma. Erosion surfaces >2 Ma yield low erosion rates of <0.1mm/yr. However uplift rates of ~0.1-1mm/yr and multiple surfaces dated at ~35 ka suggest that the hyperarid forearc landscape has been recently modified through Quaternary surface uplift and climatic events, contradicting the Miocene fossil forearc hypothesis. Generally, surface abandonment ages and activated landslides periods tend to correlate with cold wet periods preceding Plio Pleistocene deglaciation on the Altiplano. Finally, neotectonic oblique faults connecting at depth participate to topography building in the Arica Bend region and suggest that Quaternary surface abandonment is the result of both surface uplift in the forearc and specific high-discharge climate periods in the high Andes. Obtained Quaternary regional uplift rates and individual slip-rates suggest that the Andean forearc may accommodate as much as 0.5 to 1 mm/yr of regional uplift for the Quaternary time period.

  15. Large Alluvial Fans on Mars

    NASA Technical Reports Server (NTRS)

    Moore, Jeffrey M.; Howard, Alan D.

    2004-01-01

    Several dozen distinct alluvial fans, 10 to greater than 40 km long downslope are observed exclusively in highlands craters. Within a search region between 0 deg. and 30 deg. S, alluvial fan-containing craters were only found between 18 and 29 S, and they all occur at around plus or minus 1 km of the MOLA-defined Martian datum. Within the study area they are not randomly distributed but instead form three distinct clusters. Fans typically descend greater than 1 km from where they disgorge from their alcoves. Longitudinal profiles show that their surfaces are very slightly concave with a mean slope of 2 degrees. Many fans exhibit very long, narrow low-relief ridges radially oriented down-slope, often branching at their distal ends, suggestive of distributaries. Morphometric data for 31 fans was derived from MOLA data and compared with terrestrial fans with high-relief source areas, terrestrial low gradient alluvial ramps in inactive tectonic settings, and older Martian alluvial ramps along crater floors. The Martian alluvial fans generally fall on the same trends as the terrestrial alluvial fans, whereas the gentler Martian crater floor ramps are similar in gradient to the low relief terrestrial alluvial surfaces. For a given fan gradient, Martian alluvial fans generally have greater source basin relief than terrestrial fans in active tectonic settings. This suggests that the terrestrial source basins either yield coarser debris or have higher sediment concentrations than their Martian counterpoints. Martian fans and Basin and Range fans have steeper gradients than the older Martian alluvial ramps and terrestrial low relief alluvial surfaces, which is consistent with a supply of coarse sediment. Martian fans are relatively large and of low gradient, similar to terrestrial fluvial fans rather than debris flow fans. However, gravity scaling uncertainties make the flow regime forming Martian fans uncertain. Martian fans, at least those in Holden crater, apparently formed around the time of the Noachian-Hesperian boundary. We infer that these fans formed during an episode of enhanced precipitation (probably snow) and runoff, which exhibited both sudden onset and termination.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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.

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

    SciTech Connect

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

    2010-04-30

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

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

    NASA Astrophysics Data System (ADS)

    Gaines, E. P.

    2013-12-01

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

  19. FUTURE STUDIES AT PENA BLANCA: RADIONUCLIDE MIGRATION IN THE VADOSE ZONE OF AN ALLUVIAL FAN

    SciTech Connect

    P. Goodell; J. Walton; P.J. Rodriguez

    2005-07-11

    The pathway to the accessible environment at Yucca Mountain contains volcanic rocks and alluvial fill. Transport properties in alluvial fill, specifically retardation and dispersivity, may be significant in determining the overall performance of the repository. Prior relevant studies, with the exception of the Nye County Tracer Test, are almost entirely in bedrock material. The proposed study will provide field data on radionuclide migration in alluvial material. High grade uranium ore was mined at the Nopal I deposit. This mined ore (60,000 tons) was moved in 1994 to its present site as open piles on an alluvial fan in the Boquilla Colorada Microbasin. Precipitation is approximately 20 cm/year, and has caused migration of radionuclides into the subsurface. We propose partial removal of an ore pile, excavation into the alluvial fan, sampling, and determination of radionuclide mobilities from the uranium decay chain. The proposed research would be taking advantage of a unique opportunity with a known time frame for migration.

  20. 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)

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

    2014-05-01

    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.

  1. Estimation of the tectonic slip-rate from Quaternary lacustrine facies within the intraplate Albacete province (SE of Spain)

    USGS Publications Warehouse

    Rodriguez-Pascua, M. A.; Bischoff, J.; Garduno-Monroy, Victor H.; Pérez-López, R.; Giner-Robles, J.L.; Israde-Alcántara, I.; Calvo, J.P.; Williams, Ross W.

    2009-01-01

    The Quaternary lacustrine basin of Cordovilla (CB) represents one of the most active tectonic areas of the Prebetic Zone (Albacete, SE of Spain). The Quaternary sedimentary deposits of this basin are mainly endoreic lacustrine carbonate and alluvial deposits, developed in a semi-arid climate (Pleistocene-present). The basin is a NW-SE-elongated graben bounded by a major right-lateral oblique-fault, the Pozohondo Fault. This fault trends NW-SE, with an approximate trace of 55 km, and is composed of various segments which are identified by fault scarps. In order to establish the slip-rate of the most active segment of the Pozohondo Fault, called the Cordovilla segment, we carried out a detailed study of the affected Quaternary lacustrine deposits. We found that the lacustrine facies could be related to episodic moderate paleoearthquakes. The slip-rate is calculated to be 0.05 and 0.09 mm/yr, using radiometric dating for the vertical offsets of the lacustrine facies. A trenching study at the northern part of the Cordovilla segment revealed two events caused by paleoearthquakes, with the most recent expressed as an oblique-fault off-setting a poorly-developed soil. The magnitude of the last event was greater than 6, using various empirical relationships for the fault displacement and the surface-length rupture. We estimate episodic activity across the Cordovilla segment, to be characterized by moderate-sized paleoearthquakes (M6), which is in agreement with the tectonic context of an intraplate zone of the Iberian plate. ?? 2009 Elsevier B.V.

  2. LATERAL MIGRATIONLATERAL MIGRATION ALLUVIAL CHANNELSALLUVIAL CHANNELS

    E-print Network

    Julien, Pierre Y.

    (IAHR-JHR, 1996) #12;15 Roaring River Alluvial Fan: Dramatic change in sediment supply Qs since flood1 1 LATERAL MIGRATIONLATERAL MIGRATION ofof ALLUVIAL CHANNELSALLUVIAL CHANNELS Pierre Y.Pierre YArgentina November 2011 #12;2 Objectives Discuss the lateral migration of alluvial channels and provide numerous

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

    USGS Publications Warehouse

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

    2007-01-01

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

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

    SciTech Connect

    Patterson, P.E.; Larson, E.E. )

    1991-03-01

    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.

  5. Quaternary and Geomorphology.

    ERIC Educational Resources Information Center

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

    1983-01-01

    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"…

  6. Integration of channel and floodplain suites. I. Developmental sequence and lateral relations of alluvial paleosols.

    USGS Publications Warehouse

    Bown, T.M.; Kraus, M.J.

    1987-01-01

    The lower Eocene Willwood Formation of the Bighorn Basin, northwest Wyoming, consists of about 770 m of alluvial rocks that exhibit extensive mechanical and geochemical modifications resulting from Eocene pedogenesis. Five arbitrary stages are proposed to distinguish these soils of different maturities in the Willwood Formation. An inverse relationship exists between soil maturity and short-term sediment accumulation rate. Illustrates several important principles of soil-sediment interrelationships in aggrading alluvial systems that have broad application to other deposits.-from Authors

  7. Morphodynamic equilibrium of alluvial estuaries

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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

  8. A model of late quaternary landscape development in the Delaware Valley, New Jersey and Pennsylvania

    USGS Publications Warehouse

    Ridge, J.C.; Evenson, E.B.; Sevon, W.D.

    1992-01-01

    In the Delaware Valley of New Jersey and eastern Pennsylvania the late Quaternary history of colluviation, fluvial adjustment, and soil formation is based on the ages of pre-Wisconsinan soils and glacial deposits which are indicated by feld relationships and inferred from mid-latitude climate changes indicated by marine oxygen-isotope records. The area is divided into four terranes characterized by sandstone, gneiss, slate and carbonate rocks. Since the last pre-Wisconsinan glaciation (> 130 ka, inferred to be late Illinoian), each terrane responded differently to chemical and mechanical weathering. During the Sangamon interglacial stage (??? 130-75 ka) in situ weathering is inferred to have occurred at rates greater than transportation of material which resulted in the formation of deep, highly weathered soil and saprolite, and dissolution of carbonate rocks. Cold climatic conditions during the Wisconsinan, on the other hand, induced erosion of the landscape at rates faster than soil development. Upland erosion during the Wisconsinan removed pre-Wisconsinan soil and glacial sediment and bedrock to produce muddy to blocky colluvium, gre??zes lite??es, and alluvial fans on footslopes. Fluvial gravel and overlying colluvium in the Delaware Valley, both buried by late Wisconsinan outwash, are inferred to represent episodes of early and middle Wisconsinan (??? 75-25 ka) upland erosion and river aggradiation followed by river degradation and colluvium deposition. Early-middle Wisconsinan colluvium is more voluminous than later colluvium despite colder, possibly permafrost conditions during the late Wisconsinan ??? 25-10 ka). Extensive colluviation during the early and middle Wisconsinan resulted from a longer (50 kyr), generally cold interval of erosion with a greater availability of easily eroded pre-Wisconsinan surficial materials on uplands than during the late Wisconsinan. After recession of late Wisconsinan ice from its terminal position, soil formation and landscape stability were delayed until the Holocene by a lingering cold climate, slope erosion, colluvium and alluvial fan deposition, and eolian sedimentation. Late Quaternary erosion in the Delaware Valley was dominated by glacial and periglacial processes during glacial stages. During the warm interglacial stages, soils developed on a more stable landscape. These souls were easily colluviated by periglacial erosion during periods of intermittent cold climate. ?? 1992.

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

    NASA Astrophysics Data System (ADS)

    Chaoli, Lan; Junfeng, Zhang; Weixiang, Tao

    2010-05-01

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

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

    SciTech Connect

    Cechovic, M.T.; Schmitt, J.G. . Dept. of Earth Sciences)

    1993-04-01

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

  11. Lateral groundwater inflows into alluvial aquifers of main alpine valleys

    NASA Astrophysics Data System (ADS)

    Burger, Ulrich

    2015-04-01

    In alpine regions the topography is mainly characterised by deep incised valleys, mountain slopes and ridges. Usually the main valleys contain aquifers in alluvial soft rock. Lateral these aquifers are confined by mountainous hard rock slopes covered by heterogeneous sediments with different thickness. The slopes can be incised by lateral valleys. Numerical models for the main alluvial aquifers ask for lateral hydrogeological boundaries. Usually no flow boundaries or Constant head Boundaries are used, even if the lateral inflows to the main aquifers are rarely known. In this example a data set for a detailed investigated and monitored area is studied to give an answer on the location and the quantification of these lateral subsurface inflows. The study area is a typical main alpine valley with a thick alluvial aquifer (appr. 120m thick), lateral confined by granite, covered at the base of the steep slopes by quaternary sediments (Burger at al. 2012). The study consists of several steps 1.) Analytical calculation of the inflows on the base of investigated and monitored 2d profiles along fault zones (Perello et al 2013) which pinch out in the main valley 2.) Analytical models along typical W-dipping slopes with monitored slope springs 3.) Evaluating temperature and electrical conductivity profiles measured in approx. 30 groundwater wells in the alluvial aquifers and along the slopes to locate main lateral subsurface inflows 4.) Output of a regional model used for the hydrogeological back analyses of the excavation of a tunnel (Baietto et al. 2014) 5.) Output of a local numerical model calibrated with a monitoring dataset and results of a pumping test of big scale (450l/s for 10days) Results of these analyses are shown to locate and quantify the lateral groundwater inflows in the main alluvial aquifer. References Baietto A., Burger U., Perello P. (2014): Hydrogeological modelling applications in tunnel excavations: examples from tunnel excavations in granitic rocks; congress of IAEG, Engineering Geology for Society and Territory, Torino Burger U., San Nicoló L. Bösel D. und Perello P. (2012): Hydrogeologische Modelle - Hilfsmittel für die Planung am Beispiel des Brenner Basistunnel, Beiträge zur Beiträge zur COGeo 2011, Salzburg COGEO Perello P., Baietto A., Burger U., Skuk S. (2013): Excavation of the Aica-Mules pilot tunnel for the Brenner base tunnel: information gained on water inflows in tunnels in granitic massifs, Rock Mechanics and Rock Engineering, DOI 10.1007/s00603-013-0480-x

  12. Quaternary geology of Alameda County, and parts of Contra Costa, Santa Clara, San Mateo, San Francisco, Stanislaus, and San Joaquin counties, California: a digital database

    USGS Publications Warehouse

    Helley, E.J.; Graymer, R.W.

    1997-01-01

    Alameda County is located at the northern end of the Diablo Range of Central California. It is bounded on the north by the south flank of Mount Diablo, one of the highest peaks in the Bay Area, reaching an elevation of 1173 meters (3,849 ft). San Francisco Bay forms the western boundary, the San Joaquin Valley borders it on the east and an arbitrary line from the Bay into the Diablo Range forms the southern boundary. Alameda is one of the nine Bay Area counties tributary to San Francisco Bay. Most of the country is mountainous with steep rugged topography. Alameda County is covered by twenty-eight 7.5' topographic Quadrangles which are shown on the index map. The Quaternary deposits in Alameda County comprise three distinct depositional environments. One, forming a transgressive sequence of alluvial fan and fan-delta facies, is mapped in the western one-third of the county. The second, forming only alluvial fan facies, is mapped in the Livermore Valley and San Joaquin Valley in the eastern part of the county. The third, forming a combination of Eolian dune and estuarine facies, is restricted to the Alameda Island area in the northwestern corner of the county.

  13. 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

    Dorr, J.A. Jr.

    1983-08-01

    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.

  14. First record of Eremotherium laurillardi (Lund, 1842) (Mammalia, Xenarthra, Megatheriidae) in the Quaternary of Uberaba, Triângulo Mineiro (Minas Gerais State), Brazil

    NASA Astrophysics Data System (ADS)

    Martinelli, Agustín G.; Ferraz, Patrícia Fonseca; Cunha, Gabriel Cardoso; Cunha, Isabella Cardoso; de Souza Carvalho, Ismar; Borges Ribeiro, Luiz Carlos; Neto, Francisco Macedo; Cavellani, Camila Lourencini; de Paula Antunes Teixeira, Vicente; da Fonseca Ferraz, Mara Lúcia

    2012-08-01

    Although the occurrence of Pleistocene mammals is abundant in many localities of Minas Gerais State (e.g., Lagoa Santa, Janaúba, Bambuí, Cordisburgo, Patos de Minas, Araxá), there are no references at present of Quaternary megafauna in Uberaba, Triângulo Mineiro, southeastern Brazil. This region is traditionally recognized for its taxonomically diverse fauna of the Late Cretaceous Bauru Group. In 2006, fossil material attributed to giant ground sloth Eremotherium laurillardi (Xenarthra, Megatheriidae), a typical taxon of the Brazilian Pleistocene, was discovered in the Uberaba City (Minas Gerais State). The specimen (CPP 1122) which is here described consists of several cranial and postcranial bones of a single individual. The material was confined to a small alluvial deposit, yielding in the Córrego da Saudade stream, which due its restricted area distribution it is not represented in geological maps.

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

    USGS Publications Warehouse

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

    1977-01-01

    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.

  16. Alluvial Fan Delineation from SAR and LIDAR-Derived Digital Elevation Models in the Philippines

    NASA Astrophysics Data System (ADS)

    Aquino, D. T.; Ortiz, I.; Timbas, N.; Gacusan, R.; Montalbo, K.; Eco, R. C.; Lagmay, A.

    2013-12-01

    Occurrence of floods and debris flows leading to the formation of alluvial fans at the base of mountains naturally improve fertility of alluvial plains. However, these formations also have detrimental effects to communities within these zones like the case of Barangay (village) Andap, New Bataan, Compostela Valley where the whole village was wiped out by debris flow when it was hit by Supertyphoon Bopha in 2012. Hence, demarcating the boundaries of alluvial fans is crucial in disaster preparedness and mitigation. This study describes a method to delineate alluvial fans through contour maps from SAR and LiDAR-derived digital elevation models. Based on this data, we used hydrographic apex point polygons to plot the outflow points of upstream watersheds. The watershed and alluvial fan polygons were used to simulate debris flows in the study sites. The fans generated from the flood simulation were consistent with the polygons delineated from the digital elevation model. Satellite imagery and evidences of alluvial deposits found on site revealed 392 alluvial fans in the country. Widest among these is the sprawling 760 sq km fan identified in Cagayan Valley threatening about 434,329 persons at risk of debris flow. Other fans include those identified in Calapan, Mindoro (531 sq km), Kaliwanagan, Pangasinan (436 sq km), Pampanga Alluvial Fan (325 sq km), Mina, Iloilo (315 sq km), Lamsugod, S. Cotabato (286 sq km), in Tignaman, Oton and Alimodian in Iloilo (272 sq km), and the bajada, a series of alluvial fan coalescing to form a larger fan, identified in Ilocos Norte (218 sq km).

  17. Directional scales of heterogeneity in alluvial fan aquifers

    SciTech Connect

    Neton, M.J.; Dorsch, J.; Young, S.C.; Olson, C.D. . Dept. of Geological Sciences Tennessee Valley Authority Engineering Lab., Norris, TN )

    1992-01-01

    Abrupt lateral and vertical permeability changes of up to 12 orders of magnitude are common in alluvial fan aquifers due to depositional heterogeneity. This abrupt heterogeneity is problematic, particularly in construction of a continuous hydraulic conductivity field from point measurements. Site characterization is improved through use of a scale-and-directionally-related model of fan heterogeneities. A directional classification of alluvial fan aquifer heterogeneities is proposed. The three directional scales of heterogeneity in alluvial fan aquifers are: (1) within-fan, (2) between-fan (strike-parallel), and (3) cross-fan (strike-perpendicular). Within-fan heterogeneity ranges from very small-scale intergrain relationships which control the nature of pores, to larger scale permeability trends between fan apex and toe, and includes abrupt lateral and vertical facies relationships. Between-fan heterogeneities are of a larger-scale and include differences between adjacent (non)coalescent fans along a basin-margin fault due primarily to changes in lithology between adjacent upland source basins. These differences produce different (a) grain and pore fluid compositions, (b) lithologic facies and proportions, and (c) down-fan fining trends, between adjacent fans. Cross-fan heterogeneities extend from source to basin. Fan deposits are in abrupt contact upgradient with low permeability, basin-margin source rock. Downgradient, fan deposits are in gradational to abrupt contact with time-equivalent, generally lower permeability deposits of lake, desert, longitudinal braided and meandering river, volcanic, and shallow marine environments. Throughout basin history these environments may abruptly cover the fan with low permeability horizons.

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

    NASA Astrophysics Data System (ADS)

    Davies, Neil S.; Gibling, Martin R.

    2010-02-01

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

  19. Report from working group on alluvial pedogenesis

    USGS Publications Warehouse

    Autin, W.J.; Aslan, A.; Bettis, E.A.; Walthall, P.M.

    1998-01-01

    These uses illustrate the complexity of alluvial pedogenesis as it relates to the analysis and interpretation of paleosols. Difficulties with interpretations of alluvial paleosols are probably greatest when applied to the preserved sedimentary record, where direct evidence of paleolandscape variability is scanty or lacking.

  20. The paradox of large alluvial rivers (Invited)

    NASA Astrophysics Data System (ADS)

    Latrubesse, E. M.

    2010-12-01

    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.

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

    USGS Publications Warehouse

    Knepper, Daniel H.

    2003-01-01

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

  2. Are North Slope surface alluvial fans pre-Holocene relicts?

    USGS Publications Warehouse

    Reimnitz, Erk; Wolf, Stephen C.

    1998-01-01

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

  3. Alluvial fans and fan deltas: a guide to exploration for oil and gas

    SciTech Connect

    Fraser, G.S.; Suttner, L.

    1986-01-01

    This volume is a result of a series of lectures presented to an oil company in 1985 and is intended for an audience of explorationists. Material is presented in the order in which an exploration program might proceed in a frontier area. The volume is divided into six chapters that cover definitions and tectonic setting, alluvial-fan morphology, processes and facies on alluvial fans, geomorphic controls, effects of extrinsic controls (chiefly tectonism and climate) on alluvial-fan sequences, and diagenesis. Previously published black-and-white line drawings from studies of modern and ancient fans and fan deltas provide almost all the illustrative material; only one photograph is included, an aerial view of fans in part of Death Valley. The authors emphasize the complexity and variability of fan deposits and their resultant architecture. Although the volume contains a useful review of previous literature, it contains little new material, and it is remarkably lacking subsurface examples and data for a volume intended for the exploration community. In addition, fan deltas receive only brief attention; the overwhelming part of the book is devoted to alluvial fans. The volume will be of interest to those involved in studies of modern and ancient alluvial-fan deposits. 165 references.

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

    NASA Astrophysics Data System (ADS)

    Frankel, Kurt L.; Dolan, James F.

    2007-06-01

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

  5. Quaternary vertebrates from Greenland: A review

    NASA Astrophysics Data System (ADS)

    Bennike, Ole

    Remains of fishes, birds and mammals are rarely reported from Quaternary deposits in Greenland. The oldest remains come from Late Pliocene and Early Pleistocene deposits and comprise Atlantic cod, hare, rabbit and ringed seal. Interglacial and interstadial deposits have yielded remains of cod, little auk, collared lemming, ringed seal, reindeer and bowhead whale. Early and Mid-Holocene finds include capelin, polar cod, red fish, sculpin, three-spined stickleback, Lapland longspur, Arctic hare, collared lemming, wolf, walrus, ringed seal, reindeer and bowhead whale. It is considered unlikely that vertebrates could survive in Greenland during the peak of the last glaciation, but many species had probably already immigrated in the Early Holocene.

  6. Bedload transport in alluvial channels

    USGS Publications Warehouse

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

    2003-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

    Farr, Tom G.; Chadwick, Oliver A.

    1996-01-01

    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.

  8. Quaternary Glacial Mapping in Western Wisconsin Using Soil Survey Information

    ERIC Educational Resources Information Center

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

    2011-01-01

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

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

    SciTech Connect

    Quade, J.; Mifflin, M.D.; Pratt, W.L.; McCoy, W.; Burckle, L.

    1995-02-01

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

  10. Morphometric Characterization and Classification of Alluvial Fans in Eastern Oman

    NASA Astrophysics Data System (ADS)

    Leuschner, Annette; Mattern, Frank; van Gasselt, Stephan

    2015-04-01

    Morphologic characteristics of alluvial fans are a product of fluvial erosion, transportation and deposition. Consequently, fans have been described and defined on the basis of their shape, their composition, conditions and processes under which they from, their so-called "controlling factors", and their geomorphic and tectonic settings. The aim of our study is to reconstruct the morphologic evolution and to relate it to past and present climate conditions. In order to achieve this, we first characterize alluvial fans based on their climatic settings and conditions and classify them accordingly using satellite image data and digital elevation models. For mapping of different alluvial fan bodies multispectral images of the Landsat Enhanced Thematic Mapper (ETM+) with a scale of 15-30 m/px were utilized. For the detection of morphometric parameters as input data for subsequent hydrological studies digital terrain model data of the Shuttle Radar Topography Mission (SRTM) and the ASTER GDEM with a scale of 90 m/px and 30m, respectively, were used. Using these datasets morphological characteristics, such as sizes of drainage basins, transport areas and areas of deposition derived from spatial semi-automatic analysis, have been computed. The area of Muscat at the Oman Mountains has been selected as a study area because of its size, accessibility and climate conditions and it is considered well-suited for studying the development of alluvial fans and their controlling factors. The Oman Mountains are well-known for the world's largest intact and best exposed obducted ophiolite complex, the Semail Ophiolite. They are today subjected to a mild desert climate (Bwh), influenced by the Indian Ocean but they have experienced extensive pluvial periods in the geologic past. Formation of alluvial fans was, therefore, likely triggered by the interplay of increased sediment production caused by high rainfalls with enhanced erosion of hillslopes and transport rates during pluvial periods. Typical morphometric parameters controlled by hydrological conditions are sizes of catchment areas, the morphometry of associated rivers and slope angles as well as sizes of alluvial fans. In order to distinguish the catchment areas, semi-automatized spatial analyses based on DEM data were carried out within a commercial GIS environment. Our analyses generally verify that there is a positive correlation between, e.g., fan areas and sizes of catchment areas as well as between fan areas and lengths of valley lines of associated rivers. Furthermore, our analyses show a negative correlation between average fan slopes and sizes of catchment areas. The observations are in good agreement with previous analyses from other areas we conducted. The applied methodology has shown to be adequate to be compared to and combined with future field investigations. Flow events are dominant in fan evolution, but the way in which alluvial fan systems responded to fluvial environmental conditions differs between systems under different climate conditions. We compared our results with data from other places located in different climate zones around the world. This allows us to constrain boundary conditions and their potential influence on shapes in a more efficient way.

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

    SciTech Connect

    Eliet, P.P.; Gawthorpe, R.L.

    1996-12-31

    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.

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

    SciTech Connect

    Eliet, P.P. ); Gawthorpe, R.L. )

    1996-01-01

    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.

  13. Alluvial plain dynamics in the southern Amazonian foreland basin

    NASA Astrophysics Data System (ADS)

    Lombardo, U.

    2015-10-01

    Alluvial plains are formed with sediments that rivers deposit on the adjacent flood-basin, mainly through crevasse splays and avulsions. These result from a combination of processes, some of which push the river towards the crevasse threshold, while others act as triggers. Based on the floodplain sedimentation patterns of large rivers in the southern Amazonian foreland basin, it has been suggested that alluvial plain sediment accumulation is primarily the result of river crevasse splays triggered by above normal precipitation events due to La Niña. However, more than 90 % of the Amazonian river network is made of small rivers and it is unknown whether small river floodplain sedimentation is influenced by the ENSO cycle as well. Using Landsat images from 1984 to 2014, here I analyse the behaviour of all the twelve tributaries of the Río Mamoré with a catchment in the Andes. I show that these are very active rivers and that the frequency of crevasses is not linked to ENSO activity. I found that most of the sediments eroded from the Andes by the tributaries of the Mamoré are deposited in the alluvial plains, before reaching the parent river. The mid- to late Holocene paleo-channels of these rivers are located tens of kilometres further away from the Andes than the modern crevasses. I conclude that the frequency of crevasses is controlled by intrabasinal processes that act on a year to decade time scale, while the average location of the crevasses is controlled by climatic or neo-tectonic events that act on a millennial scale. Finally, I discuss the implications of river dynamics on rural livelihoods and biodiversity in the Llanos de Moxos, a seasonally flooded savannah covering most of the southern Amazonian foreland basin and the world's largest RAMSAR site.

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

    USGS Publications Warehouse

    Stamm, John F.; Hoogestraat, Galen K.

    2012-01-01

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

  15. Geometry and evolution of a syntectonic alluvial fan, Southern Pyrenees

    SciTech Connect

    Arminio, J.F. ); Nichols, G.J. )

    1993-02-01

    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.

  16. Particle Dynamics: Bedrock versus Alluvial River Segments

    NASA Astrophysics Data System (ADS)

    Wohl, E.

    2014-12-01

    Many channels alternate longitudinally between bedrock and alluvial substrate. These alternations occur over a range of spatial scales and associated temporal scales. Transient bedrock and alluvial patches alternate over downstream distances of a few meters to hundreds of meters, whereas persistent bedrock and alluvial reaches alternate downstream over distances of kilometers to hundreds of kilometers. These longitudinal alternations are significant because of the differences in process and form between bedrock and alluvial reaches. Bedrock reaches limit the response of the channel and the greater drainage basin to relative base level fall. Alluvial reaches limit the rate and distance of particle movement downstream, as well as limiting the habitat available for riverine organisms, biogeochemical reactions and nutrient storage, and water quality. In both types of substrate, particle movement is a limiting factor. (Here, particles include mineral sediment and particulate organic matter.) In bedrock channels, particle movement largely governs the rate and manner of erosion. In alluvial channels, particle movement governs channel form and the stability of habitat. Fundamental research questions for both channel types center on particle dynamics: How do interactions among bedrock substrate, sediment supply, sediment transport, and hydraulics influence rates of bedrock erosion? How do interactions among sediment supply, sediment transport, and biota influence particle transport and residence time? Although bedrock channel segments likely exert a more fundamental influence on river response to relative base level change and landscape evolution, alluvial channel segments likely exert a stronger limiting effect on downstream fluxes of water, solutes, and particles, as well as more critical influences on riverine habitat.

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

    SciTech Connect

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

    1999-04-28

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

  18. Alluvial Diamond Resource Potential and Production Capacity Assessment of Ghana

    USGS Publications Warehouse

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

    2010-01-01

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

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

    E-print Network

    Fitch, Michael Anthony

    1996-01-01

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

  20. 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

    Watts, K.R.

    1995-01-01

    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.

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

    SciTech Connect

    Hemphill-Haley, M.A.; Sawyer, T.L.; Wong, I.G. ); Knuepfer, P.L.K. ); Forman, S.L. . Byrd Polar Research Center); Smith, R.P. . Idaho National Engineering Lab.)

    1993-04-01

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

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

    NASA Astrophysics Data System (ADS)

    Mange, Maria A.; Otvos, Ervin G.

    2005-12-01

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

  3. Alluvial diamond resource potential and production capacity assessment of Guinea

    USGS Publications Warehouse

    Chirico, Peter G.; Malpeli, Katherine C.; Van Bockstael, Mark; Diaby, Mamadou; Cissé, Kabinet; Diallo, Thierno Amadou; Sano, Mahmoud

    2012-01-01

    In May of 2000, a meeting was convened in Kimberley, South Africa, by representatives of the diamond industry and leaders of African governments to develop a certification process intended to assure that export shipments of rough diamonds were free of conflict concerns. Outcomes of the meeting were formally supported later in December of 2000 by the United Nations in a resolution adopted by the General Assembly. By 2002, the Kimberley Process Certification Scheme (KPCS) was ratified and signed by diamond-producing and diamond-importing countries. The goal of this study was to estimate the alluvial diamond resource endowment and the current production capacity of the alluvial diamond mining sector of Guinea. A modified volume and grade methodology was used to estimate the remaining diamond reserves within Guinea's diamondiferous regions, while the diamond-production capacity of these zones was estimated by inputting the number of artisanal miners, the number of days artisans work per year, and the average grade of the deposits into a formulaic expression. Guinea's resource potential was estimated to be approximately 40 million carats, while the production capacity was estimated to lie within a range of 480,000 to 720,000 carats per year. While preliminary results have been produced by integrating historical documents, five fieldwork campaigns, and remote sensing and GIS analysis, significant data gaps remain. The artisanal mining sector is dynamic and is affected by a variety of internal and external factors. Estimates of the number of artisans and deposit variables, such as grade, vary from site to site and from zone to zone. This report has been developed on the basis of the most detailed information available at this time. However, continued fieldwork and evaluation of artisanally mined deposits would increase the accuracy of the results.

  4. Quaternary shorelines of the broader area of Cape Maleas - Neapolis - Elafonissos Isl. (SE Peloponnese)

    NASA Astrophysics Data System (ADS)

    Karymbalis, Efthimios; Gaki-Papanastassiou, Kalliopi; Papanastassiou, Dimitris; Tsodoulos, Ioannis; Tsivgoulis, Nikolaos; Tsanakas, Konstantinos; Valkanou, Kanella

    2015-04-01

    The aim of this study is to provide information about the landscape evolution of the broader area of Cape Maleas - Neapolis - Elafonissos Isl. during the Quaternary. In order to investigate the geomorphic evolution of the study area the uplifted coastal landforms, such as shore platforms, notches and remnants of marine terraces, were studied in detail through extensive field-work using topographic diagrams at a scale of 1:5,000, obtained from the Hellenic Military Geographical Service. Additionally, a spatial database was constructed derived from analogue topographic maps at various scales (1:50,000 and 1:5,000), geological maps (1:50,000 maps of IGME), aerial photographs and Google earth images using GIS techniques. The study area is located in SE Peloponnese in a particularly tectonically active area. Geodynamic processes in the region, which is part of the Hellenic island arc, are related to the active subduction of the African lithosphere beneath the Eurasian plate. The Paleozoic basement of the study area consists of geological formations of the geotectonic units of Arna, Tripolis, and Pindus. The Alpine basement is overlain by extensive outcrops of Pliocene and Pleistocene deposits. Upper Pliocene to Lower Pleistocene formations are composed of marine - lacustrine deposits which are mainly pelites, sandstones, conglomerates, calcarenites and carbonate rocks with red algae whereas Pleistocene formations consist of fluvioterrential deposits (clay, sands, loams and angular rock fragments). The Holocene deposits consist of talus cones, scree, and unconsolidated alluvial deposit, eluvial mantle materials and coastal sand dunes along the N, NE and S shoreline of Elafonissos Isl. as well as at Cape Punta. The general trend of the faults in the study area is mainly NW-SE with some secondary ones having NE-SW direction. Along the coast between Cape Koulendi and Cape Maleas, uplifted geomorphological features were mapped, including marine terraces, shore platforms and marine notches. Remnants of Quaternary marine terraces have also been identified at several locations on the Elafonissos Isl. The marine terraces are imprinted into pre-existing Pleistocene marine - lacustrine formations and only a few of them have a thin sandstone caprock. The uplifted Quaternary marine terraces are excellent morphological markers and have been used worldwide to recognize past sea-level changes. Their correlation with the main interglacial high-stands can be done only in areas where a continuous uplift at a regional scale exists combined by dating their exposure. Selected samples were collected for OSL dating in order to correlate the terraces in space and time. The detailed field geomorphological mapping of the study area revealed a sequence of seven to eight marine terraces, according their location, ranging in elevations from 2 to 180m. Based on the raised coastal features of the study area it becomes evident that the prevailing tectonic movement is positive (emergence) during the Pleistocene and Holocene periods. The occurrence of the terraces at different elevations supports the suggestion that the study area is composed by different tectonic blocks moving disparately.

  5. Silicate weathering in the Ganges alluvial plain

    NASA Astrophysics Data System (ADS)

    Frings, Patrick J.; Clymans, Wim; Fontorbe, Guillaume; Gray, William; Chakrapani, Govind J.; Conley, Daniel J.; De La Rocha, Christina

    2015-10-01

    The Ganges is one of the world's largest rivers and lies at the heart of a body of literature that investigates the interaction between mountain orogeny, weathering and global climate change. Three regions can be recognised in the Ganges basin, with the Himalayan orogeny to the north and the plateaus of peninsular India to the south together delimiting the Ganges alluvial plain. Despite constituting approximately 80% of the basin, weathering processes in the peninsula and alluvial plain have received little attention. Here we present an analysis of 51 water samples along a transect of the alluvial plain, including all major tributaries. We focus on the geochemistry of silicon and its isotopes. Area normalised dissolved Si yields are approximately twice as high in rivers of Himalaya origin than the plain and peninsular tributaries (82, 51 and 32 kmol SiO2 km-2 yr-1, respectively). Such dissolved Si fluxes are not widely used as weathering rate indicators because a large but variable fraction of the DSi mobilised during the initial weathering process is retained in secondary clay minerals. However, the silicon isotopic composition of dissolved Si (expressed as ?30Si) varies from + 0.8 ‰ in the Ganges mainstem at the Himalaya front to + 3.0 ‰ in alluvial plain streams and appears to be controlled by weathering congruency, i.e. by the degree of incorporation of Si into secondary phases. The higher ?30Si values therefore reflect decreasing weathering congruency in the lowland river catchments. This is exploited to quantify the degree of removal using a Rayleigh isotope mass balance model, and consequently derive initial silica mobilisation rates of 200, 150 and 107 kmol SiO2 km-2 yr-1, for the Himalaya, peninsular India and the alluvial plain, respectively. Because the non-Himalayan regions dominate the catchment area, the majority of initial silica mobilisation from primary minerals occurs in the alluvial plain and peninsular catchment (41% and 34%, respectively).

  6. Observations on Alluvial Fans with Relevance to Recent Sediment Transport

    NASA Astrophysics Data System (ADS)

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

    2004-12-01

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

  7. Synthesis of Late Cretaceous-Quaternary tectonic, sedimentary and magmatic processes and basin formation related to episodic subduction-collision in the easternmost Mediterranean region

    NASA Astrophysics Data System (ADS)

    Robertson, Alastair; Kinnaird, Timothy; McCay, Gillian; Palamakumbura, Romesh; Tasl?, Kemal

    2015-04-01

    Mesozoic oceanic crust of the easternmost Mediterranean has experienced northwards subduction during Late Cretaceous-Cenozoic, either continuously or discontinuously based on kinematic evidence. Much of the existing information on sedimentation within the easternmost Mediterranean oceanic basin comes from the non-emplaced continental margins of the Levant and North Africa. In addition, sedimentary basins related to plate convergence are recorded along the northern margin of the Southern Neotethyan ocean, mainly in the Kyrenia Range of northern Cyprus and its extension into the Misis Mountains of southern Turkey, coupled with the adjacent submerged areas. In a setting of only incipient continental collision such as the easternmost Mediterranean the sedimentary basins would be expected to remain entirely submarine. In contrast, the Kyrenia Range has been strongly uplifted and subaerially exposed during Late Pliocene-Quaternary time. This allows the recognition of a number of discrete phases of sedimentary basin formation: 1. Late Cretaceous (Campanian-Maastrichtian): silicic volcanism to create a subaqueous volcaniclastic apron; 2. Maastrichtian-Paleocene: pelagic carbonate deposition interspersed with proximal gravity flows and within-plate type alkaline volcanics; 3. Early Eocene: large-scale sedimentary melange (olistostrome) emplacement; 4. Late Eocene-Late Miocene: terrigenous gravity-flow deposition in a deep-water fault dissected 'fore arc' setting. Initial, Late Eocene non-marine coarse clastic alluvial fan deposition was succeeded by Oligocene-Miocene deep-marine siliciclastic gravity flow deposits, fining and shallowing upwards during the Late Miocene; 5. Messinian: localised precipitation of evaporites in small fault-controlled basins; 6. Pliocene: shallow-marine siliciclastic-carbonate deposition in a shelf-depth, overall regressive setting; 7. Latest Pliocene to mid-Pleistocene: gravitational accumulation of coarse talus along a strongly uplifting subaerial lineament; 8. Mid-Late Quaternary: gradual tectonic uplift giving rise to a flight of shallow marine to non-marine terrace deposits, that were also influenced by eustatic sea-level fluctuations and climatic change. The stages of basin development were punctuated by four main episodes of compression/uplift. A. Late Miocene underthrusting/metamorphism/exhumation; B. Mid-Eocene southwards thrusting; C. Late Miocene southward thrusting/left-lateral transpression; D. Late Pliocene-Mid Quaternary tectonic uplift. In a setting of continuing plate convergence why did the nature of sedimentation change so dramatically through time? The deformation front between the Kyrenia Range and the Troodos Massif is delineated by the Ovgos Fault which shows an episodic development including Late Miocene compression (transpression) and Quaternary left-lateral strike slip. The Late Cretaceous volcanogenic rocks relate to a phase of regional arc magmatism also documented in SE Turkey. Subduction appears to have slowed or ceased during the Maastrichtian-Palaeocene while the active margin experienced extension or transtension. Following final closure of a Tethyan oceanic basin further north ('northern Neotethys') subduction appears to have relocated southwards and re-activated/accelerated during the Early Eocene triggering large-scale collapse of the over-riding plate and olistostrome formation. Diachronous continental collision was in progress during Early Miocene causing strong uplift of the over-riding plate, intense erosion and voluminous siliciclastic sediment supply to a fore-arc type basin in the N Cyprus-Misis area (becoming foreland basin further east, in SE Turkey). The Pliocene was characterised by eastward 'tectonic escape' of the Anatolian plate towards the Aegean and this allowed relatively fine-grained deposition to accumulate along the former convergent continental margin in northern Cyprus and adjacent areas (e.g. Mesaoria basin). The dramatic late Pliocene to mid-Quaternary uplift of the Kyrenia-Misis lineament, plus the Troodos massif to the south, can be explaine

  8. Profiling of late Trias-early Quaternary surface in the Eskisehir basin using microtremors

    NASA Astrophysics Data System (ADS)

    Tün, Muammer; Pekkan, Emrah; Özel, O?uz

    2015-04-01

    Earthquakes in our country and in the world cause damage and collapse of engineering structures due to several reasons. Settlement areas are under the effect of strong and long-duration seismic vibrations due to resonance and focusing effects. In this study, we propose the first approximation for thickness of Quaternary sediment and late Trias topography for the Eskisehir basin in microtremor methods. The 3-D basin structures and site resonance frequencies in the Eski?ehir Basin were investigated by geophysical measurements based on the 318 single station and 9 array sites microtremor methods situated on soft soil sediments and rock units within the study area. The microtremor data collection, processing, and interpretation of the H/V curves were carried out following the recommendations and guidelines of the SESAME consortium (Site EffectS assesment using AMbient Excitation) The signals recorded were analysed for horizontal to the vertical (H/V) spectral ratio using GEOPSY software. The H/V ratios were calculated for the frequency range 0.2 to 20 Hz, using 60 s as a time window length and removing time windows contaminated by transients. Almost of the HVSR curves on the alluvium deposits have a low-frequency peak at 0.6-0.8 Hz and a second peak at 4-10 Hz. We used the Spatial Autocorrelation (SPAC) method in Eskisehir Basin using broadband seismometers distributed in triangular arrays. We derive a power-law relationship that correlates the fundamental site resonance frequencies with the sedimentary cover thickness obtained from the seismic reflection data, borehole data and shear wave velocity data in the study area. We use this relationship to estimate bedrock depth and thickness of alluvial deposits in the Eskisehir basin. Our estimation of maximum basin depths is 650 m for the Muttalip. The thickness of quaternary sediment is 25 m for Eskisehir alluvium. The estimated thickness is used to plot digital elevation model and cross profiles correlating with geomorphology and geology of the study area. The inferred sediment-bedrock interface along a cross-section shows an half graben shaped basin with a sedimentary cover thickness reaching about 500 m at the deepest part of the Eskisehir basin.

  9. Nucleation of Waterfalls at Fault Scarps Temporarily Shielded By Alluvial Fan Aggradation.

    NASA Astrophysics Data System (ADS)

    Malatesta, L. C.; Lamb, M. P.

    2014-12-01

    Waterfalls are important components of mountain river systems and they can serve as an agent to transfer tectonic, climatic, or authigenic signals upstream through a catchment. Retreating waterfalls lower the local base level of the adjacent hillslopes, and temporarily increase sediment delivery to the fluvial system. Their creation is often attributed to seismic ruptures, lithological boundaries, or the coalescence of multiple smaller steps. We explore here a mechanism for the nucleation of waterfalls that does not rely on sudden seismic slip but on the build-up of accumulated slip during periods of fault burial by fluvial aggradation. Alluvial fans are common features at the front of mountain ranges bound by normal or thrust faults. Climate change or internal forcing in the mountain catchment modifies the equilibrium slope of alluvial fans. When alluvial fans aggrade, they shield the active fault scarp from fluvial erosion allowing the scarp to grow undisturbed. The scarp may then be exposed when the channel incises into the fan exposing a new bedrock waterfall. We explore this mechanism analytically and using a numerical model for bedrock river incision and sediment deposition. We find that the creation of waterfalls by scarp burial is limited by three distinct timescales: 1) the critical timescale for the scarp to grow to the burial height, 2) the timescale of alluvial re-grading of the fan, and 3) the timescale of the external or internal forcing, such as climate change. The height of the waterfall is controlled by i) the difference in equilibrium alluvial-fan slopes, ii) the ratio of the respective fan and catchment sizes, iii) the catchment wide denudation rate, and iv) the fault slip rate. We test whether an individual waterfall could be produced by alluvial shielding of a scarp, and identify the tectonic, climatic, or authigenic nature of waterfalls using example field sites in the southwest United States.

  10. Rapid delineation of alluvial fans using IfSAR-derived DEM for selected provinces in the Philippines

    NASA Astrophysics Data System (ADS)

    Ortiz, Iris Jill; Aquino, Dakila; Norini, Gianluca; Narod Eco, Rodrigo; Mahar Lagmay, Alfredo

    2015-04-01

    Alluvial fans are fan-shaped geomorphic features formed when sediments from a watershed are transported and deposited downstream via tributaries flowing out from the sudden break of a slope. Hazards usually associated with alluvial fans are flooding and debris flows. In this study, we used an Interferometric Synthetic Aperture Radar-derived digital elevation model of Pangasinan and Nueva Ecija Provinces in the Philippines to identify and delineate alluvial fans. Primary parameters considered include the geomorphic characteristics of the catchment area, stream network and slopes ranging from 0.11 to 8 degrees. Using this method, 12 alluvial fans were identified in Pangasinan and 16 in Nueva Ecija with areas ranging from 0.35 to 80 sq. km. The largest fan identified is the Mangatarem-Aguilar fan in Pangaisnan with a total area of 80.87 sq km while the Gabaldon fan in Nueva Ecija with total area of 48.11 sq km. We observed from the results that some alluvial fans have multiple feeder streams, and others have overlapping lateral extents with adjacent fans. These overlapping fans are called bajadas. In addition, the general location of fans and their apices in the two provinces appear to coincide with segments of the Philippines Fault System. There are about people 1.4 million living within these alluvial fans. Mapping and characterizing and identifying their associated hazards is crucial in the disaster preparedness efforts of the exposed population.

  11. Cosmogenic 10 Cl geochronology of offset alluvial fans

    E-print Network

    Frankel, Kurt L.

    Cosmogenic 10 Be and 36 Cl geochronology of offset alluvial fans along the northern Death Valley alluvial fan, which exposes clean dextral offsets of seven channels. Analysis of airborne laser swath Be and 36 Cl geochronology of offset alluvial fans along the northern Death Valley fault zone: Implications

  12. Arsenate adsorption by unsaturated alluvial sediments

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Arsenate adsorption as a function of solution arsenic concentration and solution pH was investigated on five alluvial sediments from the Antelope Valley, Western Mojave Desert, California. Arsenate adsorption increased with increasing solution pH, exhibited a maximum around pH 4 to 5, and then decr...

  13. INTRODUCTION River courses, alluvial fans, shorelines, and

    E-print Network

    Lacassin, Robin

    INTRODUCTION River courses, alluvial fans, shorelines, and glacial valleys are geomorphological markers that can record offset along active strike-slip faults. Of these markers, rivers are the most- cult. This is because the magnitude of offset of any particular river course depends on the age

  14. Alluvial Fan, Rocky Mountain National Park

    USGS Multimedia Gallery

    The Alluvial Fan is a fan-shaped area of disturbance in Rocky Mountain National Park. It was created on July 15, 1982, when the earthen Lawn Lake Dam above the area gave way, flooding the Park and nearby town of Estes Park with more than 200 million gallons of water. Enormous boulders were displaced...

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

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

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

  16. 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)

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

    2012-12-01

    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.

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

    NASA Astrophysics Data System (ADS)

    Latrubesse, E. M.

    2012-12-01

    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

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

    E-print Network

    Jiménez-Moreno, Gonzalo

    evolution. Sedimentation commenced in the late Miocene with the deposition of proximal­medial alluvial fan and fluvial fa- cies (Damdere Formation; FA1). At this stage, alluvial fans developed in elevated areas and local alluvial fans. The basin was progressively incised by modern rivers that have largely smoothed out

  19. The Irish quaternary fauna project

    NASA Astrophysics Data System (ADS)

    Woodman, Peter; Mccarthy, Margaret; Monaghan, Nigel

    Much of Ireland's Pleistocene and Early Holocene mammalian faunas are derived from a series of late 19th/early 20th century cave excavations. In many instances it would appear that the deposits containing these faunal remains were disturbed. This project assessed the chronological range of the mammalian species present in the caves using 14C dating, in particular accelerator mass spectrometry (AMS). The research has shown that (1) a wide range of mammals colonised Ireland in the period between at least 45 ka and 20 ka, with some elements surviving until close to the Last Glacial Maximum; (2) a more restricted range of species re-colonised Ireland during the Lateglacial period, with evidence for a slightly more temperature fauna being replaced by an Arctic fauna at about 11 ka; (3) certain elements of Ireland's Holocene fauna may have survived through from the Lateglacial into the Holocene; (4) there is a lack of evidence for red deer, Cervus elaphus, being present in the Early Holocene in Ireland; and (5) horse is only documented in the Irish Holocene from 4 ka. The paper also discusses the implications of the Quaternary Fauna Project for the Late Pleistocene of Ireland, the mechanism and period of colonisation of Ireland as well as the introduction of domesticates in the Mid Holocene.

  20. Interaction of fine sediment with alluvial streambeds

    USGS Publications Warehouse

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

    1989-01-01

    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

  1. Exploring the use of weathering indexes in an alluvial fan chronology

    NASA Astrophysics Data System (ADS)

    Hardenbicker, Ulrike; Watanabe, Makiko; Kotowich, Roberta

    2015-04-01

    Alluvial fan sediments can act as an archive of local environmental history. Two borehole cores (FN 350 cm and AG 850cm) from Holocene alluvial fans located in the Qu'Appelle Valley in southern Saskatchewan were analyzed in order to identify how changes in land use of upland catchment plateaus modified the pattern and rate of sediment delivery to the fan. Due to the lack of material for radiometric dating a chronology of depositional events within the alluvial fans was established by using lithostratigraphy data of soils and sediments. In order to establish a more detailed relative chronology we evaluated if weathering indexes (the Parker Index, the CaO/ZrO2 molar ratio, the Product Index) originally developed for studies of in situ weathering of bedrock, are suitable to assess sediment weathering within alluvial fan sediments. To quantify the degree of weathering within the sediment samples the three indexes of weathering were calculated using the proportions of elements measure by Energy Dispersive X-ray Spectroscopy and there is an inverse relationship between weathering index and sample age. For further statistical analyses the fan sediments were classified into three groups: a sheet flow facies of well sorted silt loam and sandy loam textures, bed load facies characterized by high sand and gravel content and layers with high organic matter in combination with higher clay content indicative of in situ weathering and soil development. First results show that the Product Index may be the most suitable weathering index to indicate weathering or input of less weathered sediment within the sheet flow and bed load facies. In general, the weathering indexes do not take into account complexities of the weathering processes nor the overall environmental conditions in an alluvial fan. But chemical weathering indexes accompanied by geophysical and geo-chemical information have value, especially when the amount of sample material is limited.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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.

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

    PubMed

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

    2014-11-15

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

  4. Changes of chromium concentration in alluvial sediments of the Obra river valley

    NASA Astrophysics Data System (ADS)

    M?ynarczyk, Z.; Sobczy?ski, T.; S?owik, M.

    2006-06-01

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

  5. Are the topsoil structures relevant indicators of alluvial soil evolution ?

    NASA Astrophysics Data System (ADS)

    Salomé, Clémence; Le Bayon, Renée.-Claire; Guenat, Claire; Hallaire, Vincent; Bullinger Weber, Géraldine; Verrecchia, Eric

    2010-05-01

    Floodplains contain a wide range of all steps of soil evolution, which are relevant in order to study the initial steps of soil structuring. Alluvial soils exhibit characteristics of both sediment and / or inherited soil deposition, and in situ soil formation resulting in different types of soil structure, especially in the topsoil layers. In calcareous alluvium deposits, the structuration processes of the topsoil are fast resulting in different structures. In this context, our aim is to verify if these topsoil structures, at macroscopic and microscopic scales, are relevant indicators of in situ soil evolution in a carbonate-rich and calcium saturated environment. We hypothesise that along a soil-vegetation stabilisation gradient both macroscopic and microscopic structures of topsoil reflect this in situ soil evolution. Along this evolutionary gradient the type of structure changes and becomes more stable and widespread within the topsoil. We characterize the topsoil structure in three different vegetation types from the pioneer stage (willow vegetation) on new sediment deposits (carbonate-rich FLUVIOSOLS BRUTS according to the Sound Reference base for soils, 1998) to mature forests (beech, ash, spruce) on stable soils (carbonate-rich FLUVIOSOLS TYPIQUES) at three different altitudes (subalpine to hill levels). In order to evaluate the heterogeneity within each site and between them three replicates are made resulting in a total of 27 soil samples. At the macroscopic scale, topsoil structure is described based on morphological and macroscopic descriptions (humus form, type and size of structure) as well as structure stability (Mean Weight Diameter, MWD) and water stable macro aggregates (WSA%) according to Kemper and Rossenau (1986). At the microscopic scale, polished slabs (dimension of 7cm X 10 cm and 0.5 cm in thickness) are used to quantify pore space using a morphological approach and 2D image analysis. After binarization of the image, leading to the detection and quantification of the soil porosity, a multi fractal algorithm is applied in order to characterize the pores by the slope value of the regression line between the frequencies and their associated amplitudes. In addition, the pore size distribution is described using moments of the third and the fourth orders applied on the pore cumulative curve (pore size vs frequency). These holistic parameters of the structure can be compared with other evolution indicators (e.g. vegetation stage, soil type, structural stability) and are pertinent to evaluate the stage of the humiferous topsoil evolution. They can be considered as relevant indicators of in situ alluvial soil evolution.

  6. Southern Dobrogea coastal potable water sources and Upper Quaternary Black Sea level changes

    NASA Astrophysics Data System (ADS)

    Caraivan, Glicherie; Stefanescu, Diana

    2013-04-01

    Southern Dobrogea is a typical geologic platform unit, placed in the south-eastern part of Romania, with a Pre-Cambrian crystalline basement and a Paleozoic - Quaternary sedimentary cover. It is bordered to the north by the Capidava - Ovidiu fault and by the Black Sea to the east. A regional WNW - ESE and NNE - SSW fault system divides the Southern Dobrogea structure in several tectonic blocks. Four drinking water sources have been identified: surface water, phreatic water, medium depth Sarmatian aquifer, and deep Upper Jurassic - Lower Cretaceous aquifer. Surface water sources are represented by several springs emerged from the base of the loess cliff, and a few small rivers, barred by coastal beaches. The phreatic aquifer develops at the base of the loess deposits, on the impervious red clay, overlapping the Sarmatian limestones. The medium depth aquifer is located in the altered and karstified Sarmatian limestones, and discharges into the Black Sea. The Sarmatian aquifer is unconfined where covered by silty loess deposits, and locally confined, where capped by clayey loess deposits. The aquifer is supplied from the Pre-Balkan Plateau. The Deep Upper Jurassic - Lower Cretaceous aquifer, located in the limestone and dolomite deposits, is generally confined and affected by the regional WNW - ESE and NNE - SSW fault system. In the south-eastern Dobrogea, the deep aquifer complex is separated from the Sarmatian aquifer by a Senonian aquitard (chalk and marls). The natural boundary of the Upper Jurassic - Lower Cretaceous aquifer is the Capidava - Ovidiu Fault. The piezometric heads show that the Upper Jurassic - Lower Cretaceous aquifer is supplied from the Bulgarian territory, where the Upper Jurassic deposits crop out. The aquifer discharges into the Black Sea to the east and into Lake Siutghiol to the northeast. The cyclic Upper Quaternary climate changes induced drastic remodeling of the Black Sea level and the corresponding shorelines. During the Last Glacial Maximum (MIS 2), the shoreline retreats eastwards, reaching the 100-120 m isobaths. In these conditions, the surface drainage base level was very low. Phreatic nape closely followed the river valleys dynamics. Mean depth aquifer discharged on the inner shelf , where Sarmatian limestones outcrop. The deep aquifer discharge was restricted by the Capidava- Ovidiu Fault to the north-east and by a presumed seawards longitudinal Fault. This process enabled the migration of the prehistoric human communities, from Asia to Europe, who established settlements on the newly created alluvial plain on the western Black Sea shelf. The Holocene Transgression (MIS 1) determined a sea level rise up to the modern one, and probably higher. Under the pressure of these environmental changes, the Neolithic settlements slowly retreated upstream. During the Greek colonization, the rising sea level caused the salinisation of the previous drinking water phreatic sources. In these conditions, in the Roman Age, a new hydraulic infrastructure had to be developed, using aqueducts for available inland water delivery.

  7. Turkana Grits - a Cretaceous braided alluvial system in northern Kenya

    SciTech Connect

    Handford, C.R.

    1987-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  9. Alluvial and bedrock aquifers of the Denver Basin; eastern Colorado's dual ground-water resource

    USGS Publications Warehouse

    Robson, Stanley G.

    1989-01-01

    Large volumes of ground water are contained in alluvial and bedrock aquifers in the semiarid Denver basin of eastern Colorado. The bedrock aquifer, for example, contains 1.2 times as much water as Lake Erie of the Great Lakes, yet it supplies only about 9 percent of the ground water used in the basin. Although this seems to indicate underutilization of this valuable water supply, this is not necessarily the case, for many factors other than the volume of water in the aquifer affect the use of the aquifer. Such factors as climatic conditions, precipitation runoff, geology and water-yielding character of the aquifers, water-level conditions, volume of recharge and discharge, legal and economic constraints, and water-quality conditions can ultimately affect the decision to use ground water. Knowledge of the function and interaction of the various parts of this hydrologic system is important to the proper management and use of the ground-water resources of the region. The semiarid climatic conditions on the Colorado plains produce flash floods of short duration and large peak-flow rates. However, snowmelt runoff from the Rocky Mountains produces the largest volumes of water and is typically of longer duration with smaller peak-flow rates. The alluvial aquifer is recharged easily from both types of runoff and readily stores and transmits the water because it consists of relatively thin deposits of gravel, sand, and clay located in the valleys of principal streams. The bedrock aquifer is recharged less easily because of its greater thickness (as much as 3,000 feet) and prevalent layers of shale which retard the downward movement of water in the formations. Although the bedrock aquifer contains more than 50 times as much water in storage as the alluvial aquifer, it does not store and transmit water as readily as the alluvial aquifer. For example, about 91 percent of the water pumped from wells is obtained from the alluvial aquifer, yet water-level declines generally have not exceeded 40 feet. By contrast, only 9 percent of the water pumped from wells is obtained from the bedrock aquifer, yet water-level declines in this aquifer have exceeded 500 feet in some areas. Depth to water in the alluvial aquifer generally is less than 40 feet, while depth to water in the bedrock aquifer may exceed 1,000 feet in some areas. Cost of pumping water to the surface and cost of maintaining existing supplies in areas of rapidly declining water levels in the bedrock aquifer affect water use. Water use is also affected by the generally poorer quality water found in the alluvial aquifer and, to a lesser extent, by the greater susceptibility of the alluvial aquifer to pollution from surface sources. Because of these factors, the alluvial aquifer is used primarily as a source of irrigation supply, which is the largest water use in the area. The bedrock aquifer is used primarily as a source of domestic or municipal supply, which is the smaller of the two principal uses, even though the bedrock aquifer contains 50 times more stored ground water than the alluvial aquifer.

  10. CHANNEL EVOLUTION IN MODIFIED ALLUVIAL STREAMS.

    USGS Publications Warehouse

    Simon, Andrew; Hupp, Cliff R.

    1987-01-01

    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).

  11. Macro-roughness model of bedrock-alluvial river morphodynamics

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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.

  12. Macro-roughness model of bedrock-alluvial river morphodynamics

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

    The 1-D saltation-abrasion model of channel bedrock incision of Sklar and Dietrich (2004), 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 to unphysical consequences. Here we present a unified morphodynamic formulation of both channel incision and alluviation that specifically tracks the spatiotemporal variation in both bedload transport and alluvial thickness. It does so by relating the bedrock cover fraction to the ratio of alluvium thickness to bedrock macro-roughness, rather than to the ratio of bedload supply rate to capacity bedload transport. The new formulation (MRSAA) 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, thus 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 tectonically more complex case of rock uplift subject to a localized zone of subsidence (graben) yields a steady-state solution that is not attainable 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 progressively buried not far below the alluvium. Because the model tracks the spatiotemporal variation in 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.

  13. 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)

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

    2006-12-01

    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.

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

    E-print Network

    Nicolas, Chamot-Rooke

    for Petroleum Geoscience and CO2 Sequestration, School of Earth and Environment, University of Western Australia" lobe deposits in a tectonically-active confined basin. Age determination from radiocarbon dating to 358 ka BP old (MIS 10). The origin of these Late Quaternary deposits are inves- tigated in the context

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

    NASA Astrophysics Data System (ADS)

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

    2004-12-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-01-01

    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.

  17. ERODIBILITY OF URBAN BEDROCK AND ALLUVIAL CHANNELS, NORTH TEXAS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Major erosion of urban stream channels is found in smaller basins in the North Texas study area with contributing drainage areas of less than ten square miles. Within these basins, four basic channel types are identified based on bed and bank lithologies: alluvial banks and bottoms, alluvial banks ...

  18. Fertilizers mobilization in alluvial aquifer: laboratory experiments

    NASA Astrophysics Data System (ADS)

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

    2009-02-01

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

  19. Capturing and modelling high-complex alluvial topography with UAS-borne laser scanning

    NASA Astrophysics Data System (ADS)

    Mandlburger, Gottfried; Wieser, Martin; Pfennigbauer, Martin

    2015-04-01

    Due to fluvial activity alluvial forests are zones of highest complexity and relief energy. Alluvial forests are dominated by new and pristine channels in consequence of current and historic flood events. Apart from topographic features, the vegetation structure is typically very complex featuring, both, dense under story as well as high trees. Furthermore, deadwood and debris carried from upstream during periods of high discharge within the river channel are deposited in these areas. Therefore, precise modelling of the micro relief of alluvial forests using standard tools like Airborne Laser Scanning (ALS) is hardly feasible. Terrestrial Laser Scanning (TLS), in turn, is very time consuming for capturing larger areas as many scan positions are necessary for obtaining complete coverage due to view occlusions in the forest. In the recent past, the technological development of Unmanned Arial Systems (UAS) has reached a level that light-weight survey-grade laser scanners can be operated from these platforms. For capturing alluvial topography this could bridge the gap between ALS and TLS in terms of providing a very detailed description of the topography and the vegetation structure due to the achievable very high point density of >100 points per m2. In our contribution we demonstrate the feasibility to apply UAS-borne laser scanning for capturing and modelling the complex topography of the study area Neubacher Au, an alluvial forest at the pre-alpine River Pielach (Lower Austria). The area was captured with Riegl's VUX-1 compact time-of-flight laser scanner mounted on a RiCopter (X-8 array octocopter). The scanner features an effective scan rate of 500 kHz and was flown in 50-100 m above ground. At this flying height the laser footprint is 25-50 mm allowing mapping of very small surface details. Furthermore, online waveform processing of the backscattered laser energy enables the retrieval of multiple targets for single laser shots resulting in a dense point cloud of, both, the ground surface and the alluvial vegetation. From the acquired point cloud the following products could be derived: (i) a very high resolution Digital Terrain Model (10 cm raster), (ii) a high resolution model of the water surface of the River Pielach (especially useful for validation of topo-bathymetry LiDAR data) and (iii) a detailed description of the complex vegetation structure.

  20. Historical Ground-Water Development in the Salinas Alluvial Fan Area, Salinas, Puerto Rico, 1900-2005

    USGS Publications Warehouse

    Rodriguez, Jose M.; Gómez-Gómez, Fernando

    2008-01-01

    The Salinas alluvial fan area has historically been one of the most intensively used agricultural areas in the South Coastal Plain of Puerto Rico. Changes in agricultural practices and land use in the Salinas alluvial fan have also caused changes in the geographic distribution of ground-water withdrawals from the alluvial aquifer. As a result, the ground-water balance and ground-water flow pattern have changed throughout the years and may explain the presence of saline ground water along parts of the coast at present. By providing a reconstruction of historical ground-water development in the Salinas alluvial fan area, from the initial years of aquifer development at about 1900 to the most recent conditions existing in 2005, water resources managers and planners can use the results of the analysis for a more complete understanding of aquifer conditions especially pertaining to water quality. This study effort was conducted by the U.S. Geological Survey in cooperation with the Puerto Rico Department of Natural and Environmental Resources as a contribution in the management of the Jobos Bay National Estuarine Research Reserve. The study area encompasses about 20 mi2 (square miles) of the extensive South Coastal Plain alluvial aquifer system (fig. 1). The study area is bounded to the north by foothills of the Cordillera Central mountain chain, to the south by the Caribbean Sea, and to the east and west by the Rio Nigua de Salinas and the Quebrada Aguas Verdes, respectively. Fan-delta and alluvial deposits contain the principal aquifers in the study area.

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

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

    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.

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

    SciTech Connect

    Speer, S.W.

    1986-03-01

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

  3. Differentiating tectonic from climatic factors in the evolution of alluvial fans

    SciTech Connect

    Wilson, D.S.; West, R.B. . Dept. of Geology)

    1993-04-01

    Alluvial fans are integral parts of landscapes of arid and semi-arid regions and are most commonly found along the flanks of tectonically active mountain ranges. Alluvial fans are sensitive indicators of tectonic and climatic activity through time. Three dimensional fan modelling has the potential to discriminate between these two forces and provide quantitative estimates of deformation of fan surfaces due to tilting, faulting, or folding. The model has tremendous potential for seismic hazard evaluation at both the reconnaissance and detailed level of investigation. The ability to recognize deformation of alluvial fans alleviates the need for postulation of complex interactions between climate and internal variables in the depositional system leading to present fan morphology. The greatest problems associated with fan modelling come from failure to identify individual segments. Inclusion of more than one segment can lead to poor model performance or, more likely, inaccurate results. The long term tectonic influence on a fan's evolution can be assessed from the differences in deformation of different segments. Reliable correlations of segments from different fans along the same mountain front can provide a means to asses regional deformation. Once tectonic effects are taken into account, then climatic effects can be evaluated. Previous fan models have failed to recognize areal limitations, failed to account for deformation, or assumed deformation geometry.

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

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

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

  5. Estimation of hydraulic conductivity in an alluvial system using temperatures

    USGS Publications Warehouse

    Su, G.W.; Jasperse, J.; Seymour, D.; Constantz, J.

    2004-01-01

    Well water temperatures are often collected simultaneously with water levels; however, temperature data are generally considered only as a water quality parameter and are not utilized as an environmental tracer. In this paper, water levels and seasonal temperatures are used to estimate hydraulic conductivities in a stream-aquifer system. To demonstrate this method, temperatures and water levels are analyzed from six observation wells along an example study site, the Russian River in Sonoma County, California. The range in seasonal ground water temperatures in these wells varied from < 0.2??C in two wells to ???8??C in the other four wells from June to October 2000. The temperature probes in the six wells are located at depths between 3.5 and 7.1 m relative to the river channel. Hydraulic conductivities are estimated by matching simulated ground water temperatures to the observed ground water temperatures. An anisotropy of 5 (horizontal to vertical hydraulic conductivity) generally gives the best fit to the observed temperatures. Estimated conductivities vary over an order of magnitude in the six locations analyzed. In some locations, a change in the observed temperature profile occurred during the study, most likely due to deposition of fine-grained sediment and organic matter plugging the streambed. A reasonable fit to this change in the temperature profile is obtained by decreasing the hydraulic conductivity in the simulations. This study demonstrates that seasonal ground water temperatures monitored in observation wells provide an effective means of estimating hydraulic conductivities in alluvial aquifers.

  6. Characterization of dust emission from alluvial sediments using aircraft observations and modeling

    NASA Astrophysics Data System (ADS)

    Schepanski, K.; Flamant, C.; Chaboureau, J.; Kocha, C.; Banks, J.; Brindley, H. E.; Lavaysse, C.; Marnas, F.; Pelon, J.; Tulet, P.

    2013-12-01

    Recent studies using satellite observations show that numerous dust sources are located in the foothills of arid and semi-arid mountain regions such as over North Africa. Alluvial sediments deposited on the valley bottoms and flood plains are very prone to wind erosion and frequently serve as dust source. High surface wind speeds related to the break-down of the nocturnal low-level jet (LLJ) during the morning hours are identified as a frequent driving mechanism for dust uplift. We investigate dust emission from alluvial dust sources located within the upland region in northern Mauritania and discuss the impact of valleys with regard to their role as dust source. Measures for local atmospheric dust burden were retrieved from airborne observations, MSG SEVIR dust AOD fields and MesoNH model simulations, and analyzed in order to provide complementary information on dust source activation and local dust transport at different horizontal scales. Vertical distribution of atmospheric mineral dust was obtained from the LNG backscatter lidar system flying aboard the French Falcon-20 aircraft. Lidar extinction coefficients were compared to topography, aerial photographs, and dust AOD fields to confirm the relevance of alluvial sediments at the valley bottoms as dust source. The observed dust emission event was further evaluated using the regional model MesoNH. A sensitivity study on the impact of the horizontal grid spacing highlights the importance of the spatial resolution on simulated dust loadings. The results further illustrate the importance of an explicit representation of alluvial dust sources in such models to better capture the spatial-temporal distribution of airborne dust concentrations.

  7. Regional water quality patterns in an alluvial aquifer: direct and indirect influences of rivers.

    PubMed

    Baillieux, A; Campisi, D; Jammet, N; Bucher, S; Hunkeler, D

    2014-11-15

    The influence of rivers on the groundwater quality in alluvial aquifers can be twofold: direct and indirect. Rivers can have a direct influence via recharge and an indirect one by controlling the distribution of fine-grained, organic-carbon rich flood deposits that induce reducing conditions. These direct and indirect influences were quantified for a large alluvial aquifer on the Swiss Plateau (50km(2)) in interaction with an Alpine river using nitrate as an example. The hydrochemistry and stable isotope composition of water were characterized using a network of 115 piezometers and pumping stations covering the entire aquifer. Aquifer properties, land use and recharge zones were evaluated as well. This information provided detailed insight into the factors that control the spatial variability of groundwater quality. Three main factors were identified: (1) diffuse agricultural pollution sources; (2) dilution processes resulting from river water infiltrations, revealed by the ?(18)OH2O and ?(2)HH2O contents of groundwater; and (3) denitrification processes, controlled by the spatial variability of flood deposits governed by fluvial depositional processes. It was possible to quantify the dependence of the nitrate concentration on these three factors at any sampling point of the aquifer using an end-member mixing model, where the average nitrate concentration in recharge from the agricultural area was evaluated at 52mg/L, and the nitrate concentration of infiltrating river at approximately 6mg/L. The study shows the importance of considering the indirect and direct impacts of rivers on alluvial aquifers and provides a methodological framework to evaluate aquifer scale water quality patterns. PMID:25249478

  8. Downstream hydraulic geometry of alluvial rivers

    NASA Astrophysics Data System (ADS)

    Julien, P. Y.

    2015-03-01

    This article presents a three-level approach to the analysis of downstream hydraulic geometry. First, empirical concepts based on field observations of "poised" conditions in irrigation canals are examined. Second, theoretical developments have been made possible by combining basic relationships for the description of flow and sediment transport in alluvial rivers. Third, a relatively new concept of equivalent channel widths is presented. The assumption of equilibrium may describe a perpetual state of change and adjustments. The new concepts define the trade-offs between some hydraulic geometry parameters such as width and slope. The adjustment of river widths and slope typically follows a decreasing exponential function and recent developments indicate how the adjustment time scale can be quantified. Some examples are also presented to illustrate the new concepts presented and the realm of complex river systems.

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

    NASA Astrophysics Data System (ADS)

    Pelletier, J. D.

    2014-03-01

    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.

  10. Late Quaternary evolution of the La Cantera Fault System (Central Precordillera, Argentina): A morphotectonic and paleoseismic analysis

    NASA Astrophysics Data System (ADS)

    Perucca, Laura; Rothis, Martín; Bezerra, Francisco Hilario; Vargas, Nicolás; Lima, Jean

    2015-10-01

    The La Cantera Fault System (LCFS) is the most active Quaternary structure in the Central Precordillera of San Juan, in central-western Argentina; the system extends for 47 km along the intermountain valley that separates the Sierra de La Cantera and La Invernada, north of the San Juan River. The average fault trend is 20°; it dips at angles varying between 15° and 30° W in the northern section, to approximately 40° W in the central section, and up to 60° W in the southern section. The fault affects Holocene to recent alluvium deposits in the western piedmont of the Sierra de La Cantera and is defined by a series of landforms found in compressive tectonic environments, including simple and compound counterslope fault scarps, staircased alluvial terraces, sag ponds, flexural scarps, aligned springs, broom-shaped drainage patterns, river diversions, beheaded channels, changes in incision depths, sinuosity and a river gradient along channels. Trench investigations indicated that at least three events occurred in the past 1.1-10.1 ky. The topographic profiles of the selected channels and interfluves cutting across the northern and central trace of the fault were analyzed using a Stonex Vector GPS differential system to establish the relationship between the topography and slope of the rivers. This morphometric analysis of scarps indicates that active tectonics have played an essential role in controlling the drainage pattern in the piedmont, leading the rivers to adjust to these slope variations. Based on the analyzed geomorphologic, stratigraphic and structural characteristics, the LCFS is considered to be a relevant seismogenic source in the intraplate portion of southern South America, with a recurrence interval of at least 2000 ± 500 years for moderate magnitude earthquakes during the last 11,000 years.

  11. Estimating alluvial fan surface ages using Landsat 8 multispectral imagery

    NASA Astrophysics Data System (ADS)

    D'Arcy, Mitch; Mason, Philippa J.; Whittaker, Alexander C.; Roda Boluda, Duna C.

    2015-04-01

    Accurate exposure age models are now essential for geomorphological and stratigraphic field research, and generally depend on laboratory analyses such as radiocarbon, cosmogenic nuclide or luminescence approaches. However, these techniques cannot be deployed in situ in the field, meaning other methods are needed to produce a preliminary age model, map depositional surfaces of different ages, and select sampling sites for the types of laboratory analyses outlined above. With the widespread availability of high-resolution multispectral imagery, a promising approach is to use remotely sensed data to discriminate depositional surfaces with different ages. Here, we use new Landsat 8 Operational Land Imager (OLI) multispectral imagery to characterise the reflectance of 35 alluvial fan surfaces in the semi-arid Owens Valley, California. These surfaces have been mapped in detail in the field, have similar granitic compositions, and have well-constrained exposure ages ranging from modern to ~ 125 ka, measured using a high density of 10-Be cosmogenic nuclide samples. We identify a clear age signal recorded in the spectral properties of these surfaces. With increasing exposure age, there is a predictable redshift effect in the reflectance of the surfaces across the visible and short-wave infrared spectrum. Simple calculations, such as the brightness ratio of red/blue wavelengths, produce sensitive power law relationships with exposure age for at least 125 ka, meaning Landsat 8 imagery can be used to estimate surface exposure age remotely, at least in this calibrated dryland location. The ability to remotely sense exposure age has useful implications for field mapping, selecting suitable sampling sites for laboratory-based exposure age techniques, and correlating existing age constraints to previously un-sampled surfaces. We present the uncertainties associated with this spectral approach to exposure dating, evaluate its likely physical origins, and discuss its applicability in other locations and with other remotely sensed datasets.

  12. Late Quaternary faulted landforms characteristics on the Tumen-Jiazhu village segment of Luoyunshan piedmont fault

    NASA Astrophysics Data System (ADS)

    Sun, C.; Xie, X.; Xu, J.

    2013-12-01

    Luoyunshan piedmont fault is located west of Linfen basin, controlling the western border of the basin. Based on the fault 1:50000 geological mapping, river and gully terraces and piedmont faulted landforms survey, this paper mainly introduces late Quaternary faulted landforms characteristics on the Tumen-Jiazhu village segment of Luoyunshan piedmont fault. Luoyunshan piedmont alluvial-pluvial fans are divided into three stages, named alluvial-pluvial fans D1, D2 and D3. The gullies on the upthrown plate of Luoyunshan piedmont fault has five terraces: T1~T5. Alluvial-pluvial fans D1 and terraces T1 and T2 formed in the early and middle Holocene. Alluvial-pluvial fans D2 and terraces T3 formed in the middle-late stage of late Pleistocene. Alluvial-pluvial fans D3 and terraces T4 and T5 formed in the middle-late stage of middle Pleistocene. Faulted landforms characteristics on different parts of the middle segment of the Luo Yunshan piedmont fault are different. The dislocation of alluvial-pluvial fans D1 is about 2.9m and 3m respectively in the Xifanggou area and the piedmont of southwest of Yukou village, Jindian town. The dislocation of alluvial-pluvial fans D2 is about 2.5m, 4m, 6m and 7.7m respectively in the southwest of Puzi village, Tumen town, piedmont of west of Yangjiazhuang village, west of Jingcun village and piedmont of southwest of Langquangou, Xiangling town. The faulted landforms on the Tumen-Jiazhu village segment of Luoyunshan piedmont fault are obvious. The latest activity times of the fault is Holocene. The latest activity times of Tumen segment and Longci segment of the fault are early Holocene and middle-late Holocene respectively. Since the Middle-Late Pleistocene an activity rate of the middle segment of Luoyunshan piedmont fault is 0.18~0.54mm/yr, and activity showed an increasing trend from north to south. Since Early-Middle Holocene it is 0.4~0.9mm/yr, and fault activities mainly concentrated on the segment from Xifanggou to Yukou village. An increasing trend of the activity rate of the middle segment of Luoyunshan piedmont fault from the Middle-Late Pleistocene to Holocene, it is in good agreement with an increasing trend of the uplift rate of the terraces on the upthrown plate of the fault from the Middle-Late Pleistocene to Holocene and the sedimentation rate of Linfen basin which also has an increasing trend from the Late Pleistocene to Holocene.

  13. Alluvial Bars of the Obed Wild and Scenic River, Tennessee

    USGS Publications Warehouse

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

    2007-01-01

    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.

  14. Particle dynamics: The continuum of bedrock to alluvial river segments

    NASA Astrophysics Data System (ADS)

    Wohl, Ellen

    2015-07-01

    Particle dynamics refers to production, erosion, transport, and storage of particulate material including mineral sediment and organic matter. Particle dynamics differ significantly between the end members of bedrock and alluvial river segments and between alluvial river segments with different grain-size distributions. Bedrock segments are supply limited and resistant to change, with relatively slow, linear adjustments and predominantly erosion and transport. Particle dynamics in alluvial segments, in contrast, are transport limited and dominated by storage of mineral sediment and production of organic matter. Alluvial segments are resilient to change, with relatively rapid, multidirectional adjustments and stronger internal influences because of feedbacks between particles and biota. Bedrock segments are the governors of erosion within a river network, whereas alluvial segments are the biogeochemical reactors. Fundamental research questions for both types of river segments center on particle dynamics, which limit network-scale incision in response to base level fall (bedrock segments) and habitat, biogeochemical reactions, and biomass production (alluvial segments). These characterizations illuminate how the spatial arrangement of bedrock and alluvial segments within a river network influence network-scale resistance and resilience to external changes in relative base level, climate, and human activities.

  15. Quaternary Science Reviews ] (

    E-print Network

    Knight, Peter G.

    -marginal moraines, Russell Glacier, West Greenland William G. Adam*, Peter G. Knight School of Earth Sciences be recognised in moraines deposited where the dispersed facies is present. This permits reconstruction of the distribution of basal ice characteristics and subglacial conditions from moraine sediments. Here, we study

  16. Tributary debris fans and the late Holocene alluvial chronology of the Colorado River, eastern Grand Canyon, Arizona

    USGS Publications Warehouse

    Hereford, R.; Thompson, K.S.; Burke, K.J.; Fairley, H.C.

    1996-01-01

    Bouldery debris fans and sandy alluvial terraces of the Colorado River developed contemporaneously during the late Holocene at the mouths of nine major tributaries in eastern Grand Canyon. The age of the debris fans and alluvial terraces contributes to understanding river hydraulics and to the history of human activity along the river, which has been concentrated on these surfaces for at least two to three millennia. Poorly sorted, coarse-grained debris-flow deposits of several ages are interbedded with, overlie, or are overlapped by three terrace-forming alluviums. The alluvial deposits are of three age groups: the striped alluvium, deposited from before 770 B.C. to about A.D. 300; the alluvium of Pueblo II age deposited from about A.D. 700 to 1200; and the alluvium of the upper mesquite terrace, deposited from about A.D. 1400 to 1880. Two elements define the geomorphology of a typical debris fan: the large, inactive surface of the fan and a smaller, entrenched, active debris-flow channel and fan that is about one-sixth the area of the inactive fan. The inactive fan is segmented into at least three surfaces with distinctive weathering characteristics. These surfaces are conformable with underlying debris-flow deposits that date from before 770 B.C. to around A.D. 660, A.D. 660 to before A.D. 1200, and from A.D. 1200 to slightly before 1890, respectively, based on late-19th-century photographs, radiocarbon and archaeologic dating of the three stratigraphically related alluviums, and radiocarbon dating of fine-grained debris-flow deposits. These debris flows aggraded the fans in at least three stages beginning about 2.8 ka, if not earlier in the late Holocene. Several main-stem floods eroded the margin of the segmented fans, reducing fan symmetry. The entrenched, active debris-flow channels contain deposits <100 yr old, which form debris fans at the mouth of the channel adjacent to the river. Early and middle Holocene debris-flow and alluvial deposits have not been recognized, as they were evidently not preserved adjacent to the river or are buried by younger deposits.

  17. Design of flood protection for transportation alignments on alluvial fans

    SciTech Connect

    French, R.H.

    1991-01-01

    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.

  18. Distribution and Orientation of Alluvial Fans in Martian Craters

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

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

  19. Alluvial diamond resource potential and production capacity assessment of Mali

    USGS Publications Warehouse

    Chirico, Peter G.; Barthelemy, Francis; Kone, Fatiaga

    2010-01-01

    In May of 2000, a meeting was convened in Kimberley, South Africa, and attended by representatives of the diamond industry and leaders of African governments to develop a certification process intended to assure that rough, exported diamonds were free of conflictual concerns. This meeting was supported later in 2000 by the United Nations in a resolution adopted by the General Assembly. By 2002, the Kimberley Process Certification Scheme (KPCS) was ratified and signed by diamond-producing and diamond-importing countries. Over 70 countries were included as members of the KPCS at the end of 2007. To prevent trade in "conflict diamonds" while protecting legitimate trade, the KPCS requires that each country set up an internal system of controls to prevent conflict diamonds from entering any imported or exported shipments of rough diamonds. Every diamond or diamond shipment must be accompanied by a Kimberley Process (KP) certificate and be contained in tamper-proof packaging. The objective of this study was (1) to assess the naturally occurring endowment of diamonds in Mali (potential resources) based on geological evidence, previous studies, and recent field data and (2) to assess the diamond-production capacity and measure the intensity of mining activity. Several possible methods can be used to estimate the potential diamond resource. However, because there is generally a lack of sufficient and consistent data recording all diamond mining in Mali and because time to conduct fieldwork and accessibility to the diamond mining areas are limited, four different methodologies were used: the cylindrical calculation of the primary kimberlitic deposits, the surface area methodology, the volume and grade approach, and the content per kilometer approach. Approximately 700,000 carats are estimated to be in the alluvial deposits of the Kenieba region, with 540,000 carats calculated to lie within the concentration grade deposits. Additionally, 580,000 carats are estimated to have been released from the primary kimberlites in the region. Therefore, the total estimated diamond resources in the Kenieba region are thought to be nearly 1,300,000 carats. The Bougouni zones are estimated to have 1,000,000 carats with more than half, 630,000 carats, contained in concentrated deposits. When combined, the Kenieba and Bougouni regions of Mali are estimated to be host to 2,300,000 carats of diamonds.

  20. The Role of Climatic Change in Alluvial Fan Development Ronald I. Dorn

    E-print Network

    Dorn, Ron

    Chapter 24 The Role of Climatic Change in Alluvial Fan Development Ronald I. Dorn The Persistence of Climatic Change in Alluvial-Fan Studies Alluvial fans develop at the base of drainages where feeder, often blur the fan-shape resulting in a merged bajada. Alluvial fans can be found in almost all

  1. Sanders, J. E.; and Merguerian, Charles, 1995b, New York City region: Unique testing ground for flow models of Quaternary continental glaciers.

    E-print Network

    Merguerian, Charles

    for flow models of Quaternary continental glaciers. The Mesozoic red-bed fills of the Newark (NY for inferring the flow directions of the Quaternary continental glaciers. The most-recent glacier (Woodfordian that this glacier did not reach much of Long Island and thus did not deposit the Harbor Hill Moraine. The next

  2. B6) Quaternary Geology QUATERNARY GEOLOGY AND LANDFORMS BETWEEN

    E-print Network

    Briner, Jason P.

    The Quaternary geology and landforms in western New York State north of the southern Finger Lakes (Valley Heads recession across a scarp-dominated bedrock landscape from Batavia to the southern Lake Ontario shoreline. The complex sequence of proglacial lakes that accompanied glacial recession across the Great Lakes region

  3. Kinematic wave model of bed profiles in alluvial channels 

    E-print Network

    Tayfur, Gokmen; Singh, Vijay P.

    2006-06-21

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Williams, martin

    2014-05-01

    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.

  6. The role of tropical cyclones on landscape dynamics in southern Baja California, Mexico based on Late Pleistocene-Holocene alluvial stratigraphy

    NASA Astrophysics Data System (ADS)

    McDonald, Eric; Antinao, Jose Luis; Rhodes, Edward J.; Brown, Nathan; Gosse, John

    2015-04-01

    Region-wide alluvial records provide evidence that time-transgressive changes in climate can be a major driver of landscape evolution. Historically, landfall of eastern Pacific tropical cyclones in southwestern North America during the late summer and early fall provide the strongest storms that have demonstrated geomorphic impact on the landscape. The alluvial fan record of the southern portion of Baja California (Mexico) was investigated to determine if linkages exist between region-wide fluvial deposits and tropical cyclones. The regional distribution and Pleistocene to Holocene morphostratigraphy of alluvial fans has been established for the southern portion of Baja California with primary focus on the La Paz and San José del Cabo basins. Six discrete morphopedosedimentary alluvial units (Qt1 through Qt6) were differentiated across the region using a combination of geomorphologic mapping, sedimentological analysis, and soil development further reinforced with geochronology using radiocarbon, optically stimulated luminescence and cosmogenic depth-profiles. A first phase of regional aggradation began before ~ 100 ka (Qt1) and culminated ~10 ka (Qt4). After deposition of Qt4, increasing regional incision of older units and the progressive development of a channelized alluvial landscape coincide with deposition of Qt5 and Qt6 units in a second, incisional phase. All units are conformed of multiple 1-3 m thick alluvial packages deposited in upper-flow regime and representing individual storms. Aggradational units (Qt1-Qt4) covered broad (>2 km) channels in the form of sheetflood deposition while incisional stage deposits are mostly confined to channels of ~0.5-2 km width. Continuous deposition of the thicker sequences is demonstrated by closely spaced luminescence dates in vertical profiles. In a few places disconformities between major units are evident and indicated by partly eroded buried soils. Analysis of historical terraces as part of the younger units incised into older fans show that deposition was accomplished by large tropical cyclone events. Older units feature the same sedimentological traits as these historical deposits. We interpret the whole sequence as indicating discrete periods during the Late Pleistocene and Holocene when climatic conditions allowed large tropical cyclone events that today are not expressed. These discrete periods can be associated with specific periods when (a) insolation at the Equator was at peaks determined by precessional cycles and (b) the Tropical Pacific might have shown a state similar to that currently displayed during El Niño events.

  7. Hydraulic Modeling of Alluvial Fans along the Truckee Canal using the 2-Dimensional Model SRH2D

    NASA Astrophysics Data System (ADS)

    Wright, J.; Kallio, R.; Sankovich, V.

    2013-12-01

    Alluvial fans are gently sloping, fan-shaped landforms created by sediment deposition at the ends of mountain valleys. Their gentle slopes and scenic vistas are attractive to developers. Unfortunately, alluvial fans are highly flood-prone, and the flow paths of flood events are highly variable, thereby placing human developments at risk. Many studies have been performed on alluvial fans in the arid west because of the uncertainty of their flow paths and flood extents. Most of these studies have been focused on flood elevations and mitigation. This study is not focused on the flood elevations. Rather, it is focused on the attenuation effects of alluvial fans on floods entering and potentially failing a Reclamation canal. The Truckee Canal diverts water from the Truckee River to Lahontan Reservoir. The drainage areas along the canal are alluvial fans with complex distributary channel networks . Ideally, in nature, the sediment grain-size distribution along the alluvial fan flow paths would provide enough infiltration and subsurface storage to attenuate floods entering the canal and reduce risk to low levels. Human development, however, can prevent the natural losses from occurring due to concentrated flows within the alluvial fan. While the concentrated flows might mitigate flood risk inside the fan, they do not lower the flood risk of the canal. A 2-dimensional hydraulic model, SRH-2D, was coupled to a 1-dimensional rainfall-runoff model to estimate the flood attenuation effects of the alluvial fan network surrounding an 11 mile stretch of the Truckee Canal near Fernley, Nevada. Floods having annual exceedance probabilities ranging from 1/10 to 1/100 were computed and analyzed. SRH-2D uses a zonal approach for modeling river systems, allowing areas to be divided into separate zones based on physical parameters such as surface roughness and infiltration. One of the major features of SRH-2D is the adoption of an unstructured hybrid mixed element mesh, which is based on the arbitrarily shared element method for geometric representation. The flexibility of the mesh generation allowed the complex alluvial network of incised channels to be modeled in greater detail. The SRH-2D model was modified to allow for Green-Ampt infiltration losses, thus producing more accurate characterization of the alluvial fan process where such losses can be significant. The SRH-2D model was built using a LiDAR based terrain grid, and the assumed channel mesh was refined using a geologic map. Water conveyance was modeled to coincide with the young geologic unit . By developing lateral inflow hydrographs using the SRH-2D model, a more accurate risk assessment was achieved. Model results show basins without human development have the highest flood attenuation, and development tends to concentrate channel flows. The SRH-2D model improved Reclamation's understanding of flood flows entering the Truckee Canal from alluvial fans.

  8. Quaternary extensional and compressional tectonics revealed from Quaternary landforms along Kosi River valley, outer Kumaun Lesser Himalaya, Uttarakhand

    NASA Astrophysics Data System (ADS)

    Luirei, Khayingshing; Bhakuni, S. S.; Kothyari, Girish Ch.; Tripathi, Kavita; Pant, P. D.

    2015-06-01

    A portion of the Kosi River in the outer Kumaun Lesser Himalaya is characterized by wide river course situated south of the Ramgarh Thrust, where huge thickness (~200 m) of the landslide deposits and two to three levels of unpaired fan terraces are present. Brittle normal faults, suggesting extensional tectonics, are recognized in the Quaternary deposits and bedrocks as further supported by surface morphology. Trending E-W, these faults measure from 3 to 5 km in length and are traced as discontinuous linear mini-horst and fault scarps (sackungen) exposed due to cutting across by streams. Active normal faults have displaced the coarsely laminated debris fan deposits at two sites located 550 m apart. At one of the sites, the faults look like bookshelf faulting with the maximum displacement of ~2 m and rotation of the Quaternary boulders along the fault plane is observed. At another site, the maximum displacement measures about 0.60 cm. Thick mud units deposited due to blocking of the streams by landslides are observed within and above the fan deposit. Landslide debris fans and terrace landforms are widely developed; the highest level of fan is observed ~1240 m above mean sea level. At some places, the reworking of the debris fans by streams is characterized by thick laminated sand body. Along the South Almora Thrust and Ramgarh Thrust zones, the valleys are narrow and V-shaped where Quaternary deposits are sparse due to relatively rapid uplift across these thrusts. Along the South Almora Thrust zone, three to four levels of fluvial terraces are observed and have been incised by river exposing the bedrocks due to recent movement along the RT and SAT. Abandoned channel, tilted mud deposits, incised meandering, deep-cut V-shaped valleys and strath terraces indicate rapid uplift of the area. Thick mud sequences in the Quaternary columns indicate damming of streams. A ~10-km-long north-south trending transverse Garampani Fault has offset the Ramgarh Thrust producing tectonic landforms.

  9. Geomorphologic flood-hazard assessment of alluvial fans and piedmonts

    USGS Publications Warehouse

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

    1997-01-01

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

  10. Effects of weathering and lithology on the quality of aggregates in the alluvial fans of Northeast Rivand, Sabzevar, Iran

    NASA Astrophysics Data System (ADS)

    Bahrami, Shahram; Fatemi Aghda, Seyed Mahmoud; Bahrami, Kazem; Motamedi Rad, Mohammad; Poorhashemi, Sima

    2015-07-01

    Alluvial fans as depositional landforms can be considered as potential sources of aggregates. As the age of alluvial fans increases, their constituent sediments are exposed to longer periods of weathering and increased mineral alteration, resulting in a decrease in aggregate quality. In this study, physical properties and point load tests were used to assess the aggregate quality on three alluvial fan surfaces (relict, old and young) in the northeastern part of Rivand village in west of Sabzevar, Northeast Iran. Differentiating young from old and relict fans was carried out based on geomorphic criteria such as weathering features, fan surface morphology and drainage pattern. The young alluvial fan is characterized by sub-rounded and unvarnished clasts, distributary drainage patterns and a relatively flat surface, whereas old and relict fans are characterized by incised and rough surfaces, tributary drainage pattern and highly weathered and varnished clasts due to their long-term exposure to weathering. Due to a range of rock types occurring across each fan surface, lithological studies were performed to eliminate the effect of lithology on aggregate quality. A total of 18 rock types comprising comparable lithologies were sampled from each of the three alluvial fans. Results show that, in almost all 18 rock types, the point load test values increases from relict to young fans whereas porosity and percentage of water absorption decrease, implying that aggregate quality decreases with time as a function of duration of exposure to weathering. Also, the strength of aggregates in all three fans decreases from the fan apex to the fan toe. Data show that micaceous, intrusive igneous rocks, tuffs with high porosity and fine-grained extrusive igneous rocks with some porosity are more sensitive to physical weathering, and therefore have lower strength, particularly on the relict and old fans. Overall, variations in aggregate strength on these fans can be attributed to the relative ages of fans, with relict and old fans containing lower quality aggregates due to the longer-term exposure to weathering.

  11. Chronology of late Quaternary glaciation and landform evolution in the upper Dhauliganga valley, (Trans Himalaya), Uttarakhand, India

    NASA Astrophysics Data System (ADS)

    Bisht, Pinkey; Ali, S. Nawaz; Shukla, Anil D.; Negi, Sunil; Sundriyal, Y. P.; Yadava, M. G.; Juyal, Navin

    2015-12-01

    Detailed field mapping of glacial and paraglacial landforms supported by optical and radiocarbon dating is used to reconstruct the history of late Quaternary glaciation and landform evolution in the Trans Himalayan region of the upper Dhauliganga valley. The study identifies four events of glaciations with decreasing magnitude which are termed as Purvi Kamet Stage -Ia (PKS-Ia), PKS-Ib, PKS-II, PKS-III and PKS-IV respectively. The oldest PKS-Ia and Ib are assigned the Marine Isotopic Stgae-3 (MIS-3), the PKS-II to the Last Glacial Maximum (MIS-2), PKS-III dated to 7.9 ± 0.7 ka, and the PKS-IV is dated to 3.4 ± 0.3 ka and 1.9 ± 0.2 ka respectively. The largest valley glaciations viz. the (PKS-Ia) occurred during the strengthened summer monsoon corresponding to the MIS-3, following this, the recessional moraines (PKS-Ib) represent the gradual decline in summer monsoon towards the later part of MIS-3. The valley responded to the global Last Glacial Maximum (LGM), which is represented by the PKS-II moraine implying the influence of strengthened mid-latitude westerlies during the LGM. The post-LGM deglaciation was associated with the onset of summer monsoon and is represented by the deposition of four distinct outwash gravel terraces. The early Holocene PKS-III glaciation occurred around 7.9 ± 0.7 ka and broadly coincides with the early Holocene cooling event (8.2 ka). This was followed by the deposition of stratified scree deposits and the alluvial fan (between 5.5 ka and 3 ka) during the mid to late Holocene aridity. This was followed by marginal re-advancement of the valley glacier (viz. PKS-IV) during the late Holocene cool and moist climate. Although glaciers respond to a combination of temperature and precipitation changes, however during the Holocene it seems that temperature played a major role in driving the glaciation.

  12. Robustness of Quaternary glacial cycles

    NASA Astrophysics Data System (ADS)

    Ganopolski, Andrei; Brovkin, Victor; Calov, Reinhard

    2015-04-01

    In spite of significant progress in paleoclimate reconstructions and modeling some aspects of Quaternary climate cycles are still poorly understood. Among them is the question of whether glacial cycles are deterministic and solely externally forced or, at least partially, they are stochastic. The answer to this question can only be obtained using a comprehensive Earth system models which incorporates all major components of the Earth system - atmosphere, ocean, land surface, northern hemisphere ice sheets, terrestrial biota and soil carbon, aeolian dust and marine biogeochemistry. Here, we used the Earth system model of intermediate complexity CLIMBER-2. The model was optimally tuned to reproduce climate, ice volume and CO2 variability for the last 0.8 million years. Using the same model version, we performed a large set of simulations covering the entire Quaternary (3 million years). By starting the model at different times (with the time step of 100,000 years) and using identical initial conditions we run the model for 500,000 years using the Earth's orbital variations as the only prescribed radiative forcing. We show that within less than 100,000 years after the beginning of each experiment the modeling results converge to the same solution which depends only on the orbital forcing and boundary conditions, such as topography and terrestrial sediment thickness for the ice sheets or volcanic CO2 outgassing for the carbon cycle. By using only several sets of the Northern Hemisphere orography and sediment thickness which represent different stages of landscape evolution during Quaternary, we are able to reproduce all major regimes of Quaternary long-term climate variability. Our results thus strongly support the notion that Quaternary glacial cycles are deterministic and externally forced.

  13. Comparison of different investigation methods to characterise alluvial gravel aquifers

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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.

  14. Surfactant enhanced remediation of an alluvial aquifer contaminated with DNAPL

    SciTech Connect

    Londergan, J.T.; Meinardus, H.W.; Pope, G.A.; Brown, C.L.

    1997-12-31

    During 1996, a successful demonstration of surfactant-enhanced-aquifer-remediation (SEAR) and the use of partitioning interwell tracer tests (PITTs) was conducted beneath the former waste disposal trenches at Operable Unit 2 at Hill AFB, Utah. The trenches had received large volumes of chlorinated solvents from degreasing operations. The solvents drained downward, pooling in an alluvial sand aquifer confined in a buried paleochannel eroded into thick clay deposits. The hydraulic conductivity of the alluvium is in the range of 10{sup -3} to 10{sup -2} cm/sec. The well array installed for the demonstration consisted of a line of three injection wells, a line of three extraction wells, a central observation well, and a single hydraulic control well. The distance between injectors and extractors was 20 feet; the distance between individual injectors and extractors in line was 10 feet. The water table was 25 feet below ground surface with a saturated zone approximately 19 feet thick. There was a 4 foot thick zone of DNAPL 42-46 feet below ground surface. The injectors and extractors were completed in this DNAPL zone. The demonstration was conducted in two phases. The first of these consisted of an initial partitioning interwell tracer test (PITT) followed by a pilot scale surfactant flood. The PITT indicated that a total of approximately 346 gallons of DNAPL was present in, the demonstration area. The pilot scale surfactant flood demonstrated the efficacy of the surfactant, showed there was no degradation of hydraulic conductivity due to the introduction of a surfactant solution, and demonstrated that the effluent could be efficiently treated by the on-site steam stripper. Approximately 185 gallons of DNAPL were removed from the aquifer by the pilot scale surfactant flood. The second phase consisted of a pre-flood PITT, a line drive surfactant flood, and a post-flood PITT.

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

    NASA Astrophysics Data System (ADS)

    Köykkä, Juha

    2011-03-01

    An integrated approach of facies analysis, geochemistry and paleohydrology provides new insight into the sedimentology and paleogeography of alluvial sediments in the Precambrian. Here, alluvial fan and braidplain sedimentation patterns are documented in a Mesoproterozoic rift basin, called (known as) the Rjukan Rift Basin in southern Norway. The studied formation (Heddersvatnet Formation) consists of volcanoclastic breccias and conglomerates, cross-bedded sandstones with associated mudstones, and subaerial basaltic lava beds, deposited in a rift basin during the syn-rifting phase. Based on genetically related major lithofacies associations and individual minor lithofacies, the sedimentation is characterized by colluvial and screen apron deposits, subaerial debris flows, hyperconcentrated or sheet flood deposits in the proximal part, representing waning-flood cycles. The distal part contains shallow-water traction current deposits and associated subaerial continental flood basalts that flowed down the rift valleys. The synsedimentary intra-rift faulting formed seasonal or climatically controlled, intrafan ponded-lake with playa lake type cycles and shrinkage cracks. The geochemical composition of the of the studied sandstones and mudstones suggests a passive rifted continental margin with minor to moderate chemical weathering, possible in a semi-arid/arid paleoclimate. Clastic petrofacies of the sandstones indicate a locally uplifted and syn-rift paleotectonic setting during the main sedimentation stage, passing toward a post-rifting stage of the depositional basin. Small-scale structures within the sedimentary basin affected the depositional patterns of the Heddersvatnet Formation by creating local sites of uplift and erosion, controlling the sediment transport, and defining the accommodation space for deposition. The sedimentation of the Heddersvatnet Formation reflects a tectonic base level fall, which resulted in an accumulation of thick alluvial fan or braidplain sediments near uplifted flank(s) of the sedimentary basin. This was combined with intensive erosion of the basement in the pre-vegetation landscape, which resulted in changes in the hydraulic geometry of flow and sediment discharge of stream channels. The following criteria, observed from the Heddersvatnet Formation, are suggestive of an ancient alluvial fan and associated braidplain sedimentation: (1) deposition close to the source area; (2) slightly divergent paleoflows; (3) high-energy flows with waning flood-cycles; (4) abundance of poorly sorted and laterally extensive subaerial debris flows, and related streamflows, possible sheetfloods, hyperconcentrated flows, and their associations; (5) great distribution of grain size and lithofacies changes in proximal vs. distal parts; (6) limited suite of sedimentary structures (cross-stratification, ripple-marks, and desiccanation cracks); (7) fault bounded basin (graben) with hanging wall close to uplifted flank(s); (8) paleoslope estimation indicating at least moderate paleotopographic highs; (9) colluvial and scree apron breccias; (10) lack of any typical braided stream channel fill conglomerates and floodplains; and (11) channelized sediment bodies lacking extensive lateral continuity.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    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

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

    USGS Publications Warehouse

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

    2001-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2001-10-01

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

  20. Variations in alluvial style of Tertiary units in response to tectonism, Las Monas area, middle Magdalena valley, Colombia

    SciTech Connect

    Jordan, D.W.; Siemers, C.T.

    1989-03-01

    Detailed sedimentologic and petrographic analyses of Tertiary alluvial sandstone outcrops within and east of producing oil fields in the Las Monas area in Colombia, South America, indicate that depositional style changed from fluvial-deltaic to braided streams atop alluvial fans to high-sinuosity meandering streams in response to uplifts in the surrounding areas. Diverse paleocurrent trends in the Tertiary formations in the perimeter area demonstrate that streams flowed northeast and northwest. Streams in the oil field had easterly and southerly components. Source areas contributing sediment were different and reflected uplifts to the west and south of the Las Monas area. Petrographic composition of sandstones that have easterly and southerly paleocurrent trends in the field area contain more feldspar and less polycrystalline strained quartz than sandstones having a northerly trend in the perimeter area. Sandstones in the field area represent an unroofing of a western granitic terrain, possibly in the ancestral Central Cordillera.

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

    SciTech Connect

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

    1985-01-01

    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.

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

    Code of Federal Regulations, 2011 CFR

    2011-10-01

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

  3. 43 CFR 3436.2-2 - Federal coal deposits subject to disposal by exchange.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

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

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

    USGS Publications Warehouse

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

    2012-01-01

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

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

    SciTech Connect

    Bell, J.W. . Nevada Bureau of Mines and Geology)

    1993-04-01

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

  6. Andrei Sher and Quaternary science

    NASA Astrophysics Data System (ADS)

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

    2011-08-01

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

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

    NASA Astrophysics Data System (ADS)

    Dassargues, A.

    2013-12-01

    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.

  8. Denudation rates from mass balance on alluvial fans in the chinese Tian Shan

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    Denudation is a key process for mountain ranges evolution as it is an essential parameter to study the mass transfer over the Earth surface, the evolution of reliefs, or the complex relationships between climate, erosion and landscape changes. Several methods have been develop to quantify denudation such as the estimation of paleo-sediment fluxes from mass budget. In fact, markers of erosion within drainage areas are often scarce, temporary and difficult to reach. At the outlet of mountain belts, more continuous and perennial records of deposition can be found in sedimentary basins. Sediment budget is thus a powerful approach, generally used at the scale of sedimentary basins. However, this method can also be applied on smaller sedimentary systems, such as alluvial fans. Yet, it is seldom used on these systems, and consequently, its accuracy is barely questioned. We propose to implement such a method on several alluvial fan systems in the Chinese part of the Tian Shan Range, where estimations of denudation rates have already been proposed. Based on the reconstruction of two generations of alluvial fans, we estimate the volume of sediment exported out of the drainage system of the range for the Middle- Late Pleistocene (300 000 to ~11 000 y) and for the Holocene (~11 000 y to present). From these volumes, we derive denudation rates of ~135 m/My at maximum for these two periods, in good agreement with previous mass balance studies. Despite a strong change in the morphology of the piedmont at the onset of the Holocene, denudation rate seems quite stable within the hinterland mountains. This value is quite low for such a range. Based on a comparison of denudation rates observed in other areas over the world with comparable shortening or precipitation rates, we suggest that the low denudation rate observed in the chinese Tian Shan is related to the limited amount of precipitation.

  9. Quaternary ecology: A paleoecological perspective

    SciTech Connect

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

    1991-01-01

    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.

  10. Experimental investigation into Quaternary badland geomorphic development

    NASA Astrophysics Data System (ADS)

    Kasanin-Grubin, Milica; Kuhn, Nikolaus; Yair, Aaron; Bryan, Rorke; Schwanghart, Wolfgang

    2010-05-01

    Badland morphology is commonly linked to lithological properties of the bedrock. However, recent investigations indicate that the geomorphic development is sensitive to climate and in particular to precipitation characteristics. In this study, the precipitation characteristics that are critical for the Quaternary landscape development in the Dinosaur Badlands in Alberta, Canada, and Zin Valley Badlands, Negev Desert, Israel are investigated. Runoff, erosion and weathering were simulated in the field and the laboratory to determine rates for modeling different precipitation regimes. Currently, the geomorphic development in the Dinosaur badlands is characterized by weathering/supply limited conditions, leading to slope retreat independent of lithology. In the Negev, transport limited conditions cause frequent runoff discontinuity, creating a pattern of areas dominated by erosion or deposition. The results of the weathering and erosion experiments show that the balance between snowmelt induced weathering in the spring and summer rainfall and erosion determine the rate of slope retreat in the Dinosaur Badlands. In the Zin Valley, on the other hand, the magnitude of the individual rainstorms determines whether a slope section is eroded or acts as a sediment sink. The experiments illustrate that the badland slopes experienced an auto-stabilization during the Quaternary in the Zin Valley. In the Dinosaur Badlands Holocene climatic variations have not caused a permanent differentiation of patterns of erosion and deposition. Based on these results the reaction of badland slopes to changing precipitation characteristics was modeled. In their current state, both badland slope systems appear to be fairly stable against climate change in the range of those occurring during the Holocene. However, the stability is achieved in different ways. In the Dinosaur Badlands, weathering rates are low compared to erosion capacity, maintaining continuous evacuation of sediment from slopes to the flood planes of the Red Deer River system. Only a very pronounced contrast between winter weathering and drier summers would generate a colluvium and thus change slope hydrology. In the Zin Valley the development of a thick colluvium at the foot of the slopes has increased infiltration capacity, reducing runoff and sediment yield into the floodplain. Here, only an increase in rainfall magnitude would improve runoff continuity and induce the erosion of the colluvium. This would in turn reduce infiltration capacity and thus initiate a positive feedback on runoff and sediment yield into the Zin River. Overall, Holocene climate change appears to be insufficient to change the geomorphic development in both badlands. However, this stability is achieved not despite of climate, but because of the specific history of geomorphic development. In addition, the combination of erosion and weathering experiments with numerical modeling demonstrates the versatility of Experimental Geomorphology in landscape evolution studies.

  11. 40 CFR 721.10511 - Quaternary ammonium salts (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...2014-07-01 false Quaternary ammonium salts (generic). 721.10511 Section 721...Substances § 721.10511 Quaternary ammonium salts (generic). (a) Chemical substance...identified generically as quaternary ammonium salts (PMNs P-07-320,...

  12. 21 CFR 172.165 - Quaternary ammonium chloride combination.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...2013-04-01 false Quaternary ammonium chloride combination. 172.165 Section 172...Preservatives § 172.165 Quaternary ammonium chloride combination. The food additive, quaternary ammonium chloride combination, may be safely used...

  13. 21 CFR 172.165 - Quaternary ammonium chloride combination.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...2011-04-01 false Quaternary ammonium chloride combination. 172.165 Section 172...Preservatives § 172.165 Quaternary ammonium chloride combination. The food additive, quaternary ammonium chloride combination, may be safely used...

  14. 21 CFR 172.165 - Quaternary ammonium chloride combination.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...2009-04-01 true Quaternary ammonium chloride combination. 172.165 Section 172...Preservatives § 172.165 Quaternary ammonium chloride combination. The food additive, quaternary ammonium chloride combination, may be safely used...

  15. 21 CFR 172.165 - Quaternary ammonium chloride combination.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...2014-04-01 false Quaternary ammonium chloride combination. 172.165 Section 172...Preservatives § 172.165 Quaternary ammonium chloride combination. The food additive, quaternary ammonium chloride combination, may be safely used...

  16. 21 CFR 172.165 - Quaternary ammonium chloride combination.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...2012-04-01 false Quaternary ammonium chloride combination. 172.165 Section 172...Preservatives § 172.165 Quaternary ammonium chloride combination. The food additive, quaternary ammonium chloride combination, may be safely used...

  17. 40 CFR 721.655 - Ethoxylated alkyl quaternary ammonium compound.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...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...

  18. Multiple sources of alkanes in Quaternary oceanic sediment of Antarctica

    USGS Publications Warehouse

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

    1987-01-01

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

  19. Charophytes as lacustrine biomarkers during the quaternary in North Africa

    NASA Astrophysics Data System (ADS)

    Soulié-Märsche, I.

    The use of charophytes as biomarkers is discussed with emphasis on the differences in study methods for cosmopolitan and ecotype species. A first extensive inventory of Quaternary deposits of charophytes in Africa north of the equator comprising 18 sites from Senegal to the Sudan is drawn up with data on spatial and temporal distribution. The existence of relatively deep cold lakes in the Holocene is shown by the frequent presence of specimens of cold flora no longer present in Africa today. All the original data show the complementary nature of the study of fossil Charophyta for the multidisciplinary reconstitution of palaeoenvironments.

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

    NASA Astrophysics Data System (ADS)

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

    2012-09-01

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

  1. Reconnaissance mapping of likely alluvial valley floors in five western states

    SciTech Connect

    Schmidt, J.C.; Nimick, D.A.

    1984-12-01

    Regional mapping of areas which potentially qualify as alluvial valley floors has been conducted under contract to the Office of Surface Mining in important coal fields of west-central North Dakota, central Utah, western Colorado, and the entire Powder River basin. Reconnaissance-level data were collected on the hydrology, geomorphology, and agricultural practices in each study area. Identification of unconsolidated deposits found in valleys was based on interpretation of aerial photography, topographic and geologic maps, and field data. Surface-irrigated sites were mapped based on irrigation surveys and an extensive regional inventory conducted during this project. An analysis of patterns of agricultural practices, physiography, geomorphology, and climate resulted in the designation of broad regions with similar styles of irrigation development. Criteria for assigning irrigation capability were developed for each region based on the irrigation practices and key physical components of the developed drainages. Subirrigated areas were interpreted from Landsat imagery taken during the moisture-stress period of mid- to late summer in five different years. Site-specific data available for small areas were used to calibrate the Landsat interpretation. These maps can be useful for planning and decision-making to regulatory and land management agencies as well as industry and public interest groups; they provide a regional perspective of the different components of alluvial valley floors and guidance regarding environmental concerns specific to each valley.

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

    SciTech Connect

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

    1981-12-31

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

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

    NASA Astrophysics Data System (ADS)

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

    2010-05-01

    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.

  4. Impact of the alluvial style on the geoarcheology of stream valleys

    NASA Astrophysics Data System (ADS)

    Guccione, Margaret J.

    2008-10-01

    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.

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

    NASA Astrophysics Data System (ADS)

    Pelletier, J. D.

    2014-08-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2010-08-01

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

  7. Mid-Eocene alluvial-lacustrine succession at Gebel El-Goza El-Hamra (Shabrawet area, NE Eastern Desert, Egypt): Facies analysis, sequence stratigraphy and paleoclimatic implications

    NASA Astrophysics Data System (ADS)

    Wanas, H. A.; Sallam, E.; Zobaa, M. K.; Li, X.

    2015-11-01

    This study aims to provide the depositional facies, sequence stratigraphic and paleoclimatic characteristics of the Mid-Eocene (Bartonian) continental succession exposed at Gebel El-Goza El-Hamra (Shabrawet Area, NE Eastern Desert, Egypt). The studied succession consists of siliciclastic rocks followed upward by carbonate rocks. Detailed field observation and petrographic investigation indicate accumulation in floodplain-dominated alluvial and shallow lacustrine systems. The floodplain-dominated alluvial facies (45 m thick) is composed mainly of carbonate nodules-bearing, mottled mudrock with subordinate sandstone and conglomerate beds. The conglomerate and pebbly sandstone bodies interpreted as ephemeral braided channel deposits. The massive, laminated, planner cross-bedded, fine- to medium-grained sandstone bodies interlayered within mudstone reflect sheet flood deposits. The mudrocks associated with paleosols represent distal floodplain deposits. The shallow lacustrine facies (15 m thick) is made up of an alternation of marlstone, micritic limestone, dolostone and mudrock beds with charophytes and small gastropods. Both the alluvial and lacustrine facies show evidence of macro-and micro-pedogenic features. Pollen assemblages, stable ?18O and ?13C isotopes, and paleopedogenic features reflect prevalence of arid to semi-arid climatic conditions during the Bartonian. The sequence stratigraphic framework shows an overall fining-upward depositional sequence, consisting of Low- and High-accommodation Systems Tracts (LAST, HAST), and is bounded by two sequence boundaries (SB-1, SB-2). Conglomerate and pebbly sandstone deposits (braided channel and sheet flood deposits) of the lower part of the alluvial facies reflect a LAST. Mudrock and silty claystone facies (distal floodplain deposits) of the upper part of alluvial facies and its overlying lacustrine facies correspond to a HAST. The LAST, HAST and SB were formed during different accommodation-to-sediment supply (A/S) ratio phases. The variation in A/S ratios was mainly controlled by sea-level change as well as by local tectonic subsidence and uplift of the basin coincident with the reactivation of the Syrian Arc System during the Bartonian.

  8. 44 CFR 65.13 - Mapping and map revisions for areas subject to alluvial fan flooding.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... areas subject to alluvial fan flooding. 65.13 Section 65.13 Emergency Management and Assistance FEDERAL... areas subject to alluvial fan flooding. This section describes the procedures to be followed and the... provides protection from the base flood in an area subject to alluvial fan flooding. This information...

  9. 44 CFR 65.13 - Mapping and map revisions for areas subject to alluvial fan flooding.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... areas subject to alluvial fan flooding. 65.13 Section 65.13 Emergency Management and Assistance FEDERAL... areas subject to alluvial fan flooding. This section describes the procedures to be followed and the... provides protection from the base flood in an area subject to alluvial fan flooding. This information...

  10. Hiatal shell concentrations,sequence analysis, and sealevel history of a Pleistocene coastal alluvial fan,

    E-print Network

    alluvial fan, Punta Chueca, Sonora NANCY BECKVAR AND SUSAN M. KIDWELL LnHAIA Beckvar, Nancy & Kidwell of a Pleistocene coastal alluvial fan, Punta Chueca, Sonora. Lethaia, Vol. 21. pp. 257- 270. Oslo. ISSN 0024 surfaces is possible in the complex, alluvial fan-to-shallow marine transition at Punta Chueca despite

  11. 44 CFR 65.13 - Mapping and map revisions for areas subject to alluvial fan flooding.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... areas subject to alluvial fan flooding. 65.13 Section 65.13 Emergency Management and Assistance FEDERAL... areas subject to alluvial fan flooding. This section describes the procedures to be followed and the... provides protection from the base flood in an area subject to alluvial fan flooding. This information...

  12. The diachroneity of alluvial-fan lithostratigraphy? A test case from southeastern Ebro basin magnetostratigraphy

    E-print Network

    Swanson-Hysell, Nicholas

    The diachroneity of alluvial-fan lithostratigraphy? A test case from southeastern Ebro basin: R.W. Carlson Available online 12 July 2007 Abstract Alluvial-fan strata contain valuable proxy data composite alluvial-fan sections assumes the chronostratigraphic significance of lithostratigraphy. We

  13. 44 CFR 65.13 - Mapping and map revisions for areas subject to alluvial fan flooding.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... areas subject to alluvial fan flooding. 65.13 Section 65.13 Emergency Management and Assistance FEDERAL... areas subject to alluvial fan flooding. This section describes the procedures to be followed and the... provides protection from the base flood in an area subject to alluvial fan flooding. This information...

  14. Spatial patterns of ecohydrologic properties on a hillslope-alluvial fan transect, central New Mexico

    E-print Network

    Small, Eric

    Spatial patterns of ecohydrologic properties on a hillslope-alluvial fan transect, central New, as well as landform type. On gently sloping alluvial fans, both microtopography and Ksat are high under. Keywords: Spatial patterns; Ecohydrology; Alluvial fans; Bajada; Hillslope; Vegetation; Soil properties 1

  15. Late Quaternary history of the Atacama Desert

    E-print Network

    #12;#12;#12;#12;#12;73 Late Quaternary history of the Atacama Desert Claudio Latorre, Julio L and Kate Rylander Of the major subtropical deserts found in the Southern Hemisphere, the Atacama Desert is the driest. Throughout the Quaternary, the most pervasive climatic influence on the desert has been

  16. Sediments and processes on a small stream-flow dominated, devonian alluvial fan, Shetland Islands

    NASA Astrophysics Data System (ADS)

    Allen, Philip A.

    1981-05-01

    The main conglomerate type of a small Devonian alluvial fan in Shetland, northern Britain, is an inverse to normally graded framework-supported gravel. The sedimentological details of these beds and fundamental considerations of the mechanics of movement of highly concentrated flows suggests that neither debris-flow nor grain-flow were responsible for the deposition of these conglomerates. On the contrary, these inverse to normally graded conglomerates were deposited by water as thick gravel sheets with little topographic relief, but broadly analogous to longitudinal bars. They were deposited under high aggradation conditions first on the rising and then on the falling flood. The high concentration of material in transport on the rising and peak flood was responsible for the polymodal and unstratified nature of the conglomerates. As the flood waned, normal grading was developed and a preferred horizontal fabric was produced under low concentrations of sediment. Other conglomerate types, comparatively of lesser importance, were deposited from highly concentrated clast dispersions and are notably richer in matrix and locally possess inverse grading. The hydrological environment was one of flashy discharges of short duration but of high velocity. Flow was dissipated rapidly, perhaps due to extreme water loss. This example from the Devonian of Shetland provides an interesting alternative to the mass-transport dominated fan models currently in vogue.

  17. Ancient biomolecules in Quaternary palaeoecology

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

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

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

    NASA Technical Reports Server (NTRS)

    Peltzer, Gilles; Tapponnier, Paul; Armijo, Rolando

    1989-01-01

    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.

  19. Magnitude of late quaternary left-lateral displacements along the north edge of tibet.

    PubMed

    Peltzer, G; Tapponnier, P; Armijo, R

    1989-12-01

    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. PMID:17832223

  20. MAP OF ECOREGIONS OF THE MISSISSIPPI ALLUVIAL PLAIN

    EPA Science Inventory

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

  1. HYDRAULIC ANALYSIS OF BASEFLOW AND BANK STORAGE IN ALLUVIAL STREAMS

    EPA Science Inventory

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

  2. An aminostratigraphy for the British Quaternary based on Bithynia opercula

    PubMed Central

    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

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

  3. 43 CFR 3436.2-2 - Federal coal deposits subject to disposal by exchange.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 43 Public Lands: Interior 2 2012-10-01 2012-10-01 false Federal coal deposits subject to disposal... LEASES Coal Lease and Coal Land Exchanges: Alluvial Valley Floors § 3436.2-2 Federal coal deposits subject to disposal by exchange. The coal deposits offered in exchange by the Secretary shall...

  4. 43 CFR 3436.2-2 - Federal coal deposits subject to disposal by exchange.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 43 Public Lands: Interior 2 2011-10-01 2011-10-01 false Federal coal deposits subject to disposal... LEASES Coal Lease and Coal Land Exchanges: Alluvial Valley Floors § 3436.2-2 Federal coal deposits subject to disposal by exchange. The coal deposits offered in exchange by the Secretary shall...

  5. No surface breaking on the Ecemi? Fault, central Turkey, since Late Pleistocene (~ 64.5 ka); new geomorphic and geochronologic data from cosmogenic dating of offset alluvial fans

    NASA Astrophysics Data System (ADS)

    Sar?kaya, M. A.; Y?ld?r?m, C.; Çiner, A.

    2015-05-01

    The Ecemi? Fault Zone (EF) has been recognized as a major left lateral strike-slip fault in the Central Anatolian Fault Zone (CAFZ) of Turkey. However, its Quaternary slip-rate has been challenging to determine due to the difficulty of dating offset markers. Using high-precision offset measurements and 36Cl cosmogenic nuclide dating, we present the first geochronologically determined Late Quaternary slip-rate for the EF. Our study focuses on the excellent exposures of offset alluvial fan surfaces, originating from the Alada?lar, a Late Quaternary glaciated mountain. Analysis of airborne orthophotogrametry and GNSS (Global Navigation Satellite System) surveys indicates 168 ± 2 m left lateral and 31 ± 1 m vertical displacements. In-situ terrestrial cosmogenic 36Cl geochronology obtained from eleven surface boulders provides a minimum abandonment/incision age of 104.2 ± 16.5 ka for the oldest offset alluvial fan surface. Our geomorphic observations together with Self-potential geophysical surveys revealed the presence of an unfaulted alluvial fan terrace, which allows us to constrain the timing of deformation. The abandonment/incision age of this fan is 64.5 ± 5.6 ka based on thirteen 36Cl depth profile samples. Accordingly, we obtained a geologic fault slip-rate of 4.2 ± 1.9 mm a- 1 horizontally and 0.8 ± 0.3 mm a- 1 vertically for the time frame between 104.2 ± 16.5 ka and 64.5 ± 5.6 ka. Our analysis indicates that the EF has not been producing a major surface breaking earthquake on the main strand at least since 64.5 ± 5.6 ka (mid-Late Pleistocene). This could be the result of abandonment of the main strand and accommodation of deformation by other faults within the EF. Nevertheless, a recently occurred (30 September 2011) low magnitude (ML: 4.3) left lateral strike-slip earthquake indicates recent seismic activity of the EF. Comparison of the recent GPS velocity field with the longer slip history along the CAFZ indicates a constant but low strain release without surface breaking and very long large earthquake recurrence intervals.

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

    USGS Publications Warehouse

    Justus, B.G.

    2003-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Huber, E.; Huggenberger, P.

    2012-12-01

    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.

  8. Quaternary geochronology and distribution of Mammuthus on the Colorado Plateau

    SciTech Connect

    Agenbroad, L.D.; Mead, J.I. )

    1989-09-01

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

  9. Changes in alluvial architecture associated with Eocene hyperthermals: Preliminary results from the Bighorn Basin Coring Project

    NASA Astrophysics Data System (ADS)

    Acks, R.; Kraus, M. J.

    2012-12-01

    The Paleocene-Eocene Thermal Maximum (PETM) was followed by two lesser hyperthermal events: ETM2 and H2 both at ~53.7 Ma. The carbon isotope excursion for ETM2 was approximately half that of the PETM and the H2 excursion even smaller, indicating lower increases in temperature than during the PETM. The paleohydrologic responses to these events are less well understood than the response to PETM warming. Although the ETM2 and H2 events are better known from marine than continental strata, both events have been identified from outcrops of the alluvial Willwood Formation from the Deer Creek and Gilmore Hill areas of the Bighorn Basin, Wyoming (Abels et al., 2012). Here, we analyze two cores drilled from stratigraphically equivalent Willwood strata from Gilmore Hill. The cores provide an opportunity to examine the impact of these events on the architecture of fluvial strata. Willwood strata are composed largely of channel sandstones, heterolithic deposits generated by channel avulsion, and paleosols that formed on overbank deposits. The paleosols provide qualitative and quantitative information on changes in soil moisture and precipitation through this interval. The cores also show a distinct change in the stacking of paleosols The core is subdivided into three parts: (1) the lowest ~third has thinner, more densely spaced paleosols, (2) the middle has thicker paleosols that are more widely spaced, and (3) the upper third has thicker and more common channel sandstones interspersed with avulsion deposits and fewer red paleosols; this corresponds to the hyperthermal interval. In particular, a ~20 m thick sandstone complex caps the section and appears to truncate part of the hyperthermal interval. Although vertical variations in alluvial architecture can reflect tectonic or climatic change, the correspondence of the sandstone-rich part of the cores with the hyperthermals suggests climate was the major control on their formation. Thick purple paleosols associated with the hyperthermals at Deer Creek suggest wetter conditions, and our preliminary interpretation is that a change to wetter conditions caused increased discharge and deposition of coarser (sandy) sediment. The thick sandstone complex at Gilmore Hill is underlain by paleosols with abundant calcrete nodules, which indicate drier soil conditions prior to deposition of the sandstone, and the change from drier to wetter conditions probably also caused increased sediment yield.

  10. Late Quaternary paleosols and climate change in southern New Mexico

    SciTech Connect

    Monger, H.C. . Agronomy Dept.); Cole, D.R. ); Gish, J.W. )

    1992-01-01

    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.

  11. Estimating hydraulic conductivity using grain-size analyses, aquifer tests, and numerical modeling in a riverside alluvial system in South Korea

    NASA Astrophysics Data System (ADS)

    Cheong, Jae-Yeol; Hamm, Se-Yeong; Kim, Hyoung-Soo; Ko, Eun-Joung; Yang, Kyounghee; Lee, Jeong-Hwan

    2008-09-01

    Hydraulic conductivity ( K) for an alluvial system in a riverbank filtration area in Changwon City, South Korea, has been studied using grain-size distribution, pumping and slug tests, and numerical modeling. The alluvial system is composed of layers: upper fine sand, medium sand, lower fine sand, and a highly conductive sand/gravel layer at the base. The geometric mean of K for the sand/gravel layer (9.89 × 10-4 m s-1), as determined by grain-size analyses, was 3.33 times greater than the geometric mean obtained from pumping tests (2.97 × 10-4 m s-1). The geometric mean of K estimates obtained from slug tests (3.08 × 10-6 m s-1) was one to two orders of magnitude lower than that from pumping tests and grain-size analyses. K estimates derived from a numerical model were compared to those derived from the grain-size methods, slug tests and pumping tests in order to determine the degree of deviation from the numerical model. It is considered that the K estimates determined by the slug tests resemble the uppermost part of the alluvial deposit, whereas the K estimates obtained by grain-size analyses and pumping tests are similar to those from the numerical model for the sand/gravel layer of the riverside alluvial system.

  12. Minturn and Sangre de Cristo Formations of southern Colorado: a prograding fan-delta to alluvial-fan sequence shed from ancestral Rocky Mountains

    SciTech Connect

    Lindsey, D.A.; Clark, R.F.; Ashe, S.J.; Flores, R.J.

    1983-08-01

    The Pennsylvanian Minturn and Pennsylvanian-Permian Sangre de Cristo Formations of the northern Sangre de Cristo Mountains comprise a 3,800-m (12,500-ft) thick progradational sequence of coarse clastic sediments shed into a basin on the northeastern side of the late Paleozoic San Luis-Uncompahgre highland. From bottom to top, the mostly marine Minturn Formation contains probable deltaic (700 m, 2,300 ft), mixed fan-delta and prodelta (800 m, 2,600 ft), and fan-delta (600 m, 2,000 ft) deposits; the mostly continental Sangre de Cristo Formation contains distal alluvial fan (600 m, 2,000 ft) and proximal alluvial fan (1,100m 3,600 ft) deposits. At least three episodes of uplift are indicated by the distribution of unconformities, geometry of intertonguing facies, and abrupt vertical changes in facies. The deltaic and mixed fan-delta and prodelta deposits of the lower and middle parts of the Minturn Formation consist of coarsening-upward cycles 30 to 300 m (100 to 1,000 ft) thick of shale, siltstone, sandstone, and conglomeratic sandstone. The mixed deposits in the middle part of the Minturn contain cycles of shale, proximalturbidite sandstones, and conglomeratic sandstone; such cycles are interpreted as deposits of submarine fans overridden by fan deltas. Continental deposits of the lower member of the Sangre de Cristo Formation consist of fining-upward cycles 2 to 37 m (6.5 to 121 ft) thick of cross-bedded conglomerate, sandstone, and siltstone deposited by braided streams on the distal parts of alluvial fans.

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

    USGS Publications Warehouse

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

    1966-01-01

    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

  14. Quaternary and Neogene Sediments in the Northern Vienna Basin and adjacent areas: Geology in construction sites of the highways A5-Nordautobahn and S1-Wiener Außenring-Schnellstraße (Lower Austria, Austria)

    NASA Astrophysics Data System (ADS)

    Posch-Troezmueller, G.; ?ori?, St.; Peresson, M.; Draxler, I.; Harzhauser, M.

    2009-04-01

    The section Eibesbrunn - Schrick of the A5 motorway (Nordautobahn) and the section Eibesbrunn - Korneuburg of the S1 motorway (Wiener Außenring-Schnellstraße) were documented geologically. A variety of samples was taken and analysed sedimentologically, paleontologically and mineralogically. For the most part the construction sites are situated in the Northern Vienna Basin (A5 and S1). Within the tunnel "Tradenberg" (S1) the Flysch Zone is passed through, west of the tunnel the route crosses the Korneuburg Basin and leads to the highway A22 within the alluvial sediments of the Danube. Construction started in spring 2007, the opening of both highway-sections ist scheduled for the beginning of 2010. Along the construction sites in the Vienna Basin (A5 and eastern part of the S1) a great variety of geological features can be found within small areas. The Quaternary consists mostly of loess, which differs greatly in appearance and thickness. Besides massive developed loess with pseudomycelia and sometimes molluscs, stratified loess can be observed. The loess is often weathered to loess clay and interstratified with paleosols. Up to three consecutive paleosol-horizons can be observed, which are distinguished mainly by color. In the area of Schrick a thin red, clayey layer is situated between an underlying sequence of sand and gravel and overlying loess. Most likely this red layer is a Pliocene to early Pleistocene fluvial deposit with paleosol. Quaternary gravels can be found only locally and occasionally, sometimes they show signs of permafrost. Often Neogene sediments, which were resedimented in channels during the Quaternary, are observed, for example east of the Tradenberg tunnel, north and west of Gaweinstal, as well as north of Wolkersdorf. Neogene sediments are represented by the Sarmatian and Pannonian, consisting of clay, marl, silt-sand, and gravel. Sometimes these sediments are rich with fossils and therefore could be classified stratigraphically. The Tradenberg tunnel passes through the Rhenodanubian Flysch Zone. Both at the portals and in the excavation itself, an alternate bedding of clay, marl and calcareous sandstone could be seen. During tunnelling only few bigger sandstone layers were intercepted, so nearly the whole tunnel could be advanced by loader. Analysis of calcareous nannoplankton of samples from all 4 excavations documented Paleocene age (Danian NP 2/3). West of the Tradenberg tunnel the Korneuburg Basin is passed through. Sediments of the Karpatian (Lower Miocene) Korneuburg-Formation can be observed, consisting of clay, marl and sand. A thin layer of gravel, containing large fragments of Ostrea, also can be found. North of Korneuburg the route passes through thick layers of Quaternary gravels of the Danube. The problem of slope stability is often revealed along construction sites in Neogene and Quaternary sediments. Small, but impressive slope failures occur frequently in the fine-grained sediments. Faults in these young sediments bear witness to the young tectonics within the Basins.

  15. Loess and its geomorphic, stratigraphic and paleoclimatic significance in the Quaternary

    USGS Publications Warehouse

    Muhs, Daniel R.

    2013-01-01

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

  16. Chemical and Physical Weathering in a Hot-arid, Tectonically Active Alluvial System (Anza-Borrego Desert, CA)

    NASA Astrophysics Data System (ADS)

    Joo, Y. J.; Elwood Madden, M.; Soreghan, G. S.

    2014-12-01

    Climate and tectonics are primary controls on bedrock erosion, and sediment production, transport, and deposition. Additionally, silicate weathering in tectonically active regions is known to play a significant role in global climate owing to the high rates of physical erosion and exposure of unweathered bedrock to chemical weathering, which removes CO2 from the atmosphere. Therefore, the feedback between weathering and climate is key to understanding climate change through Earth history. This study investigates chemical and physical weathering of alluvial sediments in the Anza-Borrego Desert, California, located in the southern part of the San Andreas Fault System. This setting provides an ideal opportunity to study weathering in a hot and arid climate with mean annual temperatures of ~23 °C and mean annual precipitation of ~160 mm in the basin. Samples were collected along a proximal-to-distal transect of an alluvial-fan system sourced exclusively from Cretaceous tonalite of the Peninsular Range. The single bedrock lithology enables exploration of the effects of other variables — climate, transport distance, drainage area, and tectonics— on the physical and chemical properties of the sediments. Although minimal overall (CIA = 56-61), the degree of chemical weathering increases down transect, dominated by plagioclase dissolution. BET surface area of the mud (<63µm) fraction decreases distally, which is consistent with coarsening grain-size. Chemical alteration and BET surface area both increase in a distal region, within the active Elsinore Fault zone. Extensive fracturing here, together with a more-humid Pleistocene climate likely facilitated in-situ bedrock weathering; specifically, dissolution of primary minerals (e.g. plagioclase), preceding the arid alluvial erosion, transport, and deposition in the Holocene. This study further seeks to disentangle the complex record of the climate and tectonic signals imprinted in these sediments.

  17. Alluvial fans and their natural distinction from rivers based on morphology, hydraulic processes, sedimentary processes, and facies assemblages

    SciTech Connect

    Blair, T.C. ); McPherson, J.G. )

    1994-07-01

    Contrary to common contemporary usage, alluvial fans are a naturally unique phenomenon readily distinguishable from other sedimentary environments, including gravel-bed rivers, on the basis of morphology, hydraulic processes, sedimentologic processes, and facies assemblages. The piedmont setting of alluvial fans where the feeder channel of an upland drainage basin intersects the mountain front assures that catastrophic fluid gravity flows and sediment gravity flows, including sheetfloods, rock falls, rock slides, rock avalanches, and debris flows, are major constructional processes, regardless of climate. The unconfinement of these flows at the mountain front gives rise to the high-sloping, semiconical form that typifies fans. The plano-convex cross-profile geometry inherent in this form is the inverse of the toughlike cross-sectional form of river systems, and precludes the development of floodplains that characterize rivers. The relatively high slope of alluvial fans creates unique hydraulic conditions where passing fluid gravity flows attain high capacity, high competency, and upper flow regime, resulting in sheetfloods that deposit low-angle antidune or surface-parallel planar-stratified sequences. These waterlaid facies contrast with the typically lower-flow-regime thick-bedded, cross-bedded, and lenticular channel facies, and associated floodplain sequences, of rivers. The unconfinement of flows on fans causes a swift decrease in velocity, competency, and capacity as they attenuate, inducing rapid deposition that leads to the angular, poorly sorted textures and short radii typical of fans. This condition is markedly different than for rivers, where sediment gravity flows are rare and water flows remain confined by channel walls or spill into floodplains, and increase in depth downstream.

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

    SciTech Connect

    Lisitsyn, A.P.

    1986-07-01

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

  19. A model of channel response in disturbed alluvial channels

    USGS Publications Warehouse

    Simon, A.

    1989-01-01

    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

  20. ALLUVIAL CHANNEL GEOMETRY: THEORY AND ApPLICATIONS

    E-print Network

    Julien, Pierre Y.

    ALLUVIAL CHANNEL GEOMETRY: THEORY AND ApPLICATIONS 8 TABLE 2. Variation of q with hid. according to (32) and (36) hId. q (1) (2) Discussion by Willi H. Hager,3 Fellow, ASCE 10° 1.23 x J(i 10' 6.5 x 10 this function and one may note that q increases very rapidly with hid" The function under consideration may

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

    USGS Publications Warehouse

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

    1971-01-01

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

  2. Uranium in framboidal pyrite from a naturally bioreduced alluvial sediment.

    PubMed

    Qafoku, Nikolla P; Kukkadapu, Ravi K; McKinley, James P; Arey, Bruce W; Kelly, Shelly D; Wang, Chongmin; Resch, Charles T; Long, Philip E

    2009-11-15

    Samples of a naturally bioreduced, U-contaminated alluvial sediment were characterized with various microscopic and spectroscopic techniques and wet chemical extraction methods. The objective was to investigate U association and interaction with minerals of the sediment. Bioreduced sediment comprises approximately 10% of an alluvial aquifer adjacent to the Colorado River, in Rifle, CO, that was the site of a former U milling operation. Past and ongoing research has demonstrated that bioreduced sediment is elevated in solid-associated U, total organic carbon, and acid-volatile sulfide, and depleted in bioavailable Fe(III) confirming that sulfate and Fe(III) reduction have occurred naturally in the sediment. SEM/EDS analyses demonstrated that framboidal pyrites (FeS(2)) of different sizes ( approximately 10-20 microm in diameter), and of various microcrystal morphology, degree of surface weathering, and internal porosity were abundant in the <53 microm fraction (silt + clay) of the sediment and absent in adjacent sediments that were not bioreduced. SEM-EMPA, XRF, EXAFS, and XANES measurements showed elevated U was present in framboidal pyrite as both U(VI) and U(IV). This result indicates that U may be sequestered in situ under conditions of microbially driven sulfate reduction and pyrite formation. Conversely, such pyrites in alluvial sediments provide a long-term source of U under conditions of slow oxidation, contributing to the persistence of U of some U plumes. These results may also help in developing remedial measures for U-contaminated aquifers. PMID:20028047

  3. Geomorphic and hydraulic controls on large-scale riverbank failure on a mixed bedrock-alluvial river system, the River Murray, South Australia: a bathymetric analysis.

    NASA Astrophysics Data System (ADS)

    De Carli, E.; Hubble, T.

    2014-12-01

    During the peak of the Millennium Drought (1997-2010) pool-levels in the lower River Murray in South Australia dropped 1.5 metres below sea level, resulting in large-scale mass failure of the alluvial banks. The largest of these failures occurred without signs of prior instability at Long Island Marina whereby a 270 metre length of populated and vegetated riverbank collapsed in a series of rotational failures. Analysis of long-reach bathymetric surveys of the river channel revealed a strong relationship between geomorphic and hydraulic controls on channel width and downstream alluvial failure. As the entrenched channel planform meanders within and encroaches upon its bedrock valley confines the channel width is 'pinched' and decreases by up to half, resulting in a deepening thalweg and channel bed incision. The authors posit that flow and shear velocities increase at these geomorphically controlled 'pinch-points' resulting in complex and variable hydraulic patterns such as erosional scour eddies, which act to scour the toe of the slope over-steepening and destabilising the alluvial margins. Analysis of bathymetric datasets between 2009 and 2014 revealed signs of active incision and erosional scour of the channel bed. This is counter to conceptual models which deem the backwater zone of a river to be one of decelerating flow and thus sediment deposition. Complex and variable flow patterns have been observed in other mixed alluvial-bedrock river systems, and signs of active incision observed in the backwater zone of the Mississippi River, United States. The incision and widening of the lower Murray River suggests the channel is in an erosional phase of channel readjustment which has implications for riverbank collapse on the alluvial margins. The prevention of seawater ingress due to barrage construction at the Murray mouth and Southern Ocean confluence, allowed pool-levels to drop significantly during the Millennium Drought reducing lateral confining support to the over-steepened channel margins triggering large-scale riverbank failure.

  4. From source to sink in the sediment cascade of the Hei-River Basin: Implications for late Quaternary landscape dynamics in the Gobi Desert, NW China

    NASA Astrophysics Data System (ADS)

    Schimpf, Stefan; Nottebaum, Veit; Diekmann, Bernhard; Hartmann, Kai; Lehmkuhl, Frank; Wünnemann, Bernd; Zhang, Chi

    2014-05-01

    The Hei River Basin with a catchment size of ~130,000 km² is host to one of the largest continental alluvial fans in the world. The basin comprises: (1) its high-elevated river sources in the glacier and the permafrost zone of the Qilian Mountains, (2) the semi-arid foreland of the Hexi Corridor in the middle reaches and (3) the endorheic Ejina Basin (Gaxun Nur Basin) as its recent sink. The river basin is characterized by small subcatchments of hyper-arid mountain ranges of the Gobi-Tienshan and Beishan as well as of smooth and fuzzy water divides of the Hexi-Corridor and the Badain Jaran Sand Sea. Up to 300 m of Quaternary sediments establish the large Ejina Basin, with a size of 28,000 km², as an excellent archive for environmental reconstructions located at the recent intersection of westerly and monsoonal air masses. Three sediment cores (up to 230 m long) provide evidence of sedimentation dynamics over the last 250,000 years, and cover at least two terminations since OIS 6. The sediments have to be regarded as a result of the interplay between tectonic activity and climate dynamics, accompanied by a related eolian and hydrological response of the catchment. Thus, it is crucial to understand and reconstruct the sedimentary processes along the huge sediment cascades, and to identify the most important sediment sources. Here we present a provenance analysis from mineralogical fingerprints of modern sediments that have been deposited along recent pathways from the sources to the Ejina Basin. The methodical approach combines the analysis of clay minerals, bulk mineralogy, and bulk geochemistry. Furthermore, we use heavy mineral data obtained from automated particle-analysis via a computer-controlled scanning electron microscope (CCSEM) and XRD measurements. We analyzed ~200 surface samples from the whole catchment as reference material, as well as the upper 19 m of cored sediments, to gain insight into temporal changes of depositional processes and provenance. Geostatistical analyses of the compositional data reveal a clear discrimination between sediments from the Qilian Shan in the south and from local basin sediments in the north. Moreover the mineralogical fingerprints allow the differentiation of sources from intrusive rocks that are dominant in the Bei Shan mountain sub-catchment, and from greenschist-bearing metamorphic rocks, that are widespread in the Qilian Mountain catchment. Finally, we draw conclusions about the main transport processes and pathways from assumed source regions to the sink (Ejina Basin). The provenance analysis of the sediment core reveals strong changes from local (Bei Shan) to long-distant (Qilian Shan) sources. The Late Pleistocene record reveals frequently changing sediment supply between periodic high mountain runoff and local episodic runoff. We assume that these variations are related to basin internal processes (e.g. fan dynamics, tectonics) and changing environmental conditions that are linked with variations in meltwater runoff and precipitation in the upper reaches of the southern catchment. These conclusions are supported by grain size characteristics that indicate phases of predominant alluvial activity and limnic deposition around the Late Glacial to Holocene transition and enhanced pre-Holocene eolian activity.

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

    USGS Publications Warehouse

    Knepper, D.H., Jr.

    2005-01-01

    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.

  6. Patterns of late Quaternary shelf-margin sedimentation, southwest Louisiana

    SciTech Connect

    Suter, J.R.; Berryhill, H.L.

    1986-09-01

    Late Quaternary extension of the continental shelf in the northern Gulf of Mexico has been largely accomplished by deposition at the shelf margin during sea level lowstands. The distribution and geometry of facies suggest that delta progradation during sea level fall and lowstand is a principal process for shelf accretion. Along the shelf margin of southwest Louisiana, sets of deltaic deposits corresponding to the last two lowstands of sea level have been mapped from high-resolution seismic profiles. Individual deltas extend farther than 5000 m/sup 2/ and are more than 160 m thick. Diapirism has had a controlling effect on sedimentation patterns of the shelf-margin deltas throughout their depositional histories. Shelf-margin deltas have also been the loci for the transfer of large volumes of sediment from the shelf to the upper slope by mass transport, with buried submarine troughs formed by retrogressive shelf-edge failure in association with major streams acting as conduits for sediment movement. In southwest Louisiana, mass transport deposits follow depressions formed by salt diapirism rather than creating broad aprons on the slope.

  7. Quaternary geology of the Rhode Island inner shelf

    USGS Publications Warehouse

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

    1983-01-01

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

  8. Quaternary Science Reviews 24 (2005) 19631968 Quaternary coastal morphology and sea-level

    E-print Network

    Laughlin, Robert B.

    2005-01-01

    Quaternary Science Reviews 24 (2005) 1963­1968 Editorial Quaternary coastal morphology and sea-level timescales. The position of sea level (ultimate base level) and changes of sea level over geological geomorphological and environmental change in adjacent landscapes. Sea level determines the lower limit

  9. Late Quaternary terrestrial vertebrate coprolites from New Zealand

    NASA Astrophysics Data System (ADS)

    Wood, Jamie R.; Wilmshurst, Janet M.

    2014-08-01

    Over the past decade, concerted efforts to find and study Late Quaternary terrestrial vertebrate coprolites in New Zealand have revealed new insights into the diets and ecologies of New Zealand's prehistoric birds. Here, we provide a broader review of the coprolites found in natural (non-archaeological) Late Quaternary deposits from New Zealand. We summarise the morphological diversity of the coprolites, and discuss the taphonomy of the sites in which they are found. Since the 1870s more than 2000 coprolites have been discovered from 30 localities, all restricted to the South Island. The distribution of coprolite localities appears to reflect the presence of geological and climatic factors that enhance the potential for coprolite preservation; coprolites require dry conditions for preservation, and have been found on the ground surface within drafting cave entrances and at shallow (<300 mm) depths beneath rock overhangs with a northerly aspect. We classify the coprolites into eleven morphotypes, each of which may represent a range of different bird and/or reptile species. A review of genetically identified specimens shows that coprolites of different bird species overlap in size and morphology, reinforcing the need for identifications to be based on ancient DNA analysis.

  10. First Quaternary Fossil Record of Caecilians from a Mexican Archaeological Site

    NASA Astrophysics Data System (ADS)

    Wake, Thomas A.; Wake, Marvalee H.; Lesure, Richard G.

    1999-07-01

    A single vertebra from an Early Formative period archaeological site in coastal Chiapas, México, is identified as belonging to the amphibian Dermophis mexicanus (Duméril and Bibron) 1841 (Amphibia: Gymnophiona: Caeciliidae). The vertebra was recovered from deposits dated to approximately 1200-1350 B.C. The specimen represents the first Quaternary fossil record for gymnophiones. Its presence suggests the possible role of the species as a bioturbator. Its recovery is further evidence of the utility of fine-grained archaeological recovery techniques.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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.

  12. The Chilean nitrate deposits.

    USGS Publications Warehouse

    Ericksen, G.E.

    1983-01-01

    The nitrate deposits in the arid Atacama desert of northern Chile consist of saline-cemented surficial material, apparently formed in and near a playa lake that formerly covered the area. Many features of their distribution and chemical composition are unique. The author believes the principal sources of the saline constituents were the volcanic rocks of late Tertiary and Quaternary age in the Andes and that the nitrate is of organic origin. Possible sources of the nitrate, iodate, perchlorate and chromate are discussed. -J.J.Robertson

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

    NASA Astrophysics Data System (ADS)

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

    2009-04-01

    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

  14. Architectural analysis and chronology of an Alpine alluvial fan using 3D ground penetrating radar investigation and quantitative outcrop analysis

    NASA Astrophysics Data System (ADS)

    Franke, D.; Hornung, J.; Hinderer, M.

    2012-04-01

    Alluvial fans represent sediment sinks directly at the outlet of the source area in mountain landscapes. They contain multiple information on short-term as well as on long-term changes of sediment supply and of environmental parameters like climate and vegetation. However, most studies on alluvial fans are restricted to selective surface analysis and almost no studies exist which aim to clear the subsurface geometry of an alluvial fan in total. Our study is embedded in the SedyMONT research program within the TOPO-EUROPE framework and aims to clarify the subsurface structure of an alluvial fan by a time-controlled 3D architectural model. The Illgraben fan is located in the Central Alps of Switzerland within the Rhone valley and covers an area of about 6.5 km2. Currently construction works for a highway cuts through the fan exposing its deposits (mainly gravel and diamicton) up to 15 m depth and therefore offers the unique opportunity to link ground penetrating radar (GPR) investigations with quantitative outcrop analysis. GPR measurements on the Illgraben fan have been carried out at two different scales: (i) a fan-wide scale with about 80 km radar sections forming a half spiderweb pattern to identify the fundamental architecture of the fan (using 100 MHz and 40 MHz antenna), and (ii) four orthogonal grids of about 50 m x 100 m for detailed architectural analysis (using a 200 MHz antenna). Penetration depth was up to 15 m for high and low frequency antennas. The radargrams were processed, georeferenced and transferred into a 3D-modeling software (GOCAD®) to map radar facies units. By means of quantitative sedimentological analyses and precisely scaled photo panels we could translate radar facies pattern into sedimentary facies, and interpret reflectors and their properties in terms of sedimentary units. These geobodies can be characterized in terms of volume, shape, geometrical key parameters, their spatial distribution, as well as internal sedimentary structures in order to identify depositional processes. Preliminary results show distinct horizons ('palaeosurfaces') indicating fan-wide depositional starvation and minimized sediment supply. Furthermore, between these horizons the Illgraben fan is built up by multi-storey and multilateral architectural elements of different type and at characteristic scales which can be attributed to specific depositional processes (e.g. debris flows, channel fills, levees). At small-scale a heterogeneous and complex stacking pattern of geobody interfaces was observed, showing a distinct multi-fold hierarchy of mainly concave, convex and horizontal structures. First 14C AMS ages from the central part of the alluvial fan (ca. 10 m depth) indicate high sedimentation rates during the past 2000 years. We found no control of natural spectral gamma-ray radiation by lithofacies units. Hence variations must indicate changes in the source areas and/or climate-controlled weathering conditions in the drainage basin (ca. 9.5 km2).

  15. Quaternary eustatic sedimentary accretion of southern Bahamas Archipelago

    SciTech Connect

    Mitchell, S.W.

    1985-02-01

    Surficial geologic mapping indicates that the southern half of the Bahamas Archipelago is forming by the accretion of discrete depositional sequences resulting from successive eustatic sea level changes: (1) multiple beach and dune ridges, (2) estuarine, (3) lacustrine, (4) shallow subtidal, (5) reef and reef rubble, and (6) megadune complexes. The lithologies are accreted along unconformable erosional-solutional contacts - marine terraces and subaerial caliche crusts. During periods of significant transgression, sequences 1-5 are accreted. Sediments are predominantly skeletal and peloid. During periods of significant regression, megadune complexes are accreted. Ooids are the dominant sediment. Erosional-solutional features reflect areas of subaerial exposure and/or coastline erosion. Terraces at 10, 20, and 40 ft elevations are preserved along arid eastern Great Inagua Island. The calichification of Bahamian Quaternary carbonates has concentrated insoluble residues (quartz, feldspar, heavy minerals, crandallite, micrometeorites). Insoluble residue analysis provides a basis for the correlation of accreted eustatic sedimentary sequences.

  16. Variations in rock types on alluvial fan surfaces as an indicator of source reach and geomorphic process, Fish Lake Valley, Nevada-California

    SciTech Connect

    Slate, J.L. )

    1993-04-01

    Lithologic composition of fan-surface clasts can reflect the source of alluvial fan deposits within those drainages where rock types vary with location in the basin, provided that clasts at the surface resemble the makeup of rocks within the deposit. Interpreting the reach from which deposits were derived may, in turn, be used to infer the relation of fan deposition to causal events and source-area conditions. A multiparameter study of alluvial fans in four drainage basins of Fish Lake Valley, Nevada-California, included assessing modal lithology and the lithologic ratio among three main rock types. The author tallied rock types of 100 surface pebbles described on geomorphic surfaces along 50-m-long transects oriented perpendicular to streamflow direction near the mountain fronts. Source areas for the fan deposits shifted from the Pleistocene to the late Holocene, and may be a result of changes in weathering and transport conditions. The middle and lower reach sources of the two youngest (late Holocene) units (based on 7 transects) suggest that they were deposited in response to events that were only sufficient to transport material from these areas and not the headwaters, or that insufficient material was available for transport from the headwaters. The presence of these units of apparently similar age in the four mapped areas rules out localized storms or isolated faulting events as causes of deposition. The headwater and drainage-basin wide sources of two Pleistocene fan units (based on 13 transects) indicate deposition of these units may have occurred in response to significant climatic events that weathered material in the headwaters areas and transported that material to the fans. Thus, climatic conditions or elapsed time or a combination of the two may control sources of fan deposits.

  17. Development rates of Late Quaternary soils, Silver Lake Playa, California

    USGS Publications Warehouse

    Reheis, M.C.; Harden, J.W.; McFadden, L.D.; Shroba, R.R.

    1989-01-01

    Soils formed on alluvial fan deposits that range in age from about 35 000 to 200 yr BP near Silver Lake playa in the Mojave Desert permit study of the rates of soil development in an arid, hyperthermic climate. Field-described properties of soils were quantified and analyzed using a soil development index that combines properties and horizon thicknesses. Pedogenic CaCO3 (as indicated by color), pH increase, and dry consistence appear to change with age at linear rates, whereas rubification appears to change at a logarithmic rate. The linear rates are best attributed to the progressive accumulation of CaCO3- and salt-rich eolian dust derived from the playa and other mnore distant sources. The total-texture values of soils on fans older than 10 000 yr BP are similar, which suggests that playas in this area may have been wet enough to restrict the availability of fines from these sources for many thousands of years prior to 10 000 yr BP. Equations derived from regressions of soil age and properties can be used to estimate ages of undated, lithologically similar deposits in similar climates and geomorphic settings. -from Authors

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

    SciTech Connect

    Cline; De Long; Pelletier; Harrington

    2005-09-06

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

  19. Summary of Quaternary Stratigraphy and history, Eastern Canada

    NASA Astrophysics Data System (ADS)

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

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  1. Sublacustrine depositional fans in southwest Melas Chasma Joannah M. Metz,1

    E-print Network

    Grotzinger, John P.

    -bottom sediments, terraced alluvial fans inferred to have formed in response to lake-level rise, and deltasSublacustrine depositional fans in southwest Melas Chasma Joannah M. Metz,1 John P. Grotzinger,1. [1] Two depositional fan complexes have been identified on the floor of southwest Melas Chasma

  2. Stratigraphy of Aeolis Dorsa, Mars: Stratigraphic context of the great river deposits

    E-print Network

    erosion has exhumed a stratigraphic section of sedimentary rocks consisting of at least four unconformity of sedimentary rock. The river deposits are eroding out of at least two distinguishable units. There is evidence and alluvial-fan deposits in the Aeolis Dorsa sedimentary basin, 10°E of Gale crater. At Aeolis Dorsa, wind

  3. 43 CFR 3436.1-2 - Federal coal deposits subject to lease by exchange.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 43 Public Lands: Interior 2 2012-10-01 2012-10-01 false Federal coal deposits subject to lease by... Coal Lease and Coal Land Exchanges: Alluvial Valley Floors § 3436.1-2 Federal coal deposits subject to lease by exchange. The lease offered by the Secretary in exchange for existing coal leases shall be...

  4. 43 CFR 3436.1-2 - Federal coal deposits subject to lease by exchange.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 43 Public Lands: Interior 2 2011-10-01 2011-10-01 false Federal coal deposits subject to lease by... Coal Lease and Coal Land Exchanges: Alluvial Valley Floors § 3436.1-2 Federal coal deposits subject to lease by exchange. The lease offered by the Secretary in exchange for existing coal leases shall be...

  5. Characteristics of sedimentary structures in coarse-grained alluvial rivers

    NASA Astrophysics Data System (ADS)

    Ackerley, David; Powell, Mark

    2013-04-01

    The characteristics of coarse-grained alluvial surfaces have important implications for the estimation of flow resistance, entrainment thresholds and sediment transport rates in gravel-bed rivers. This area of research has, thus, demanded attention from geomorphologists, sedimentologists, and river engineers. The majority of research has focused towards understanding the characteristics and adjustments in surface grain size. Bed stability, however, is not ultimately defined by particle size but how grains are arranged within the bed surface. For example, by the organisation of particles into a variety of grain and form scale sedimentary structures and bedforms (e.g. imbrication; pebble clusters, stone nets, transverse ribs). While it is widely acknowledged sedimentary structuring must be considered within estimates of flow resistance and sediment transport, relatively little is known about the structural properties of water-worked river gravels. As a consequence, we remain woefully ignorant of this important aspect of gravel-bed river sedimentology. The aim of this poster is to present some preliminary results of a study designed to characterise the morphodynamics of sedimentary structures in coarse-grained alluvial rivers and their implications upon entrainment thresholds and sediment transport rates. The poster focuses on investigating the variability in grain and form scale sedimentary structuring across a number of field sites. Representative patches of three gravel bars on the Rivers Wharfe, Manifold and Afon Elan, UK, have been surveyed using a Leica HDS 3000 Terrestrial Laser Scanner. The resultant raw point-cloud data, recorded at a 4mm resolution, has been registered, filtered, and interpolated to produce highly detailed 2½D digital elevation models of gravel-bed surface topography. These surfaces have been analysed using a number of structural parameters including bed elevation probability distribution function statistics (standard deviation, skewness, kurtosis), semivariograms, and inclination indices. This research enhances our understanding of alluvial bed surface structures and lays the foundations for developing a more detailed understanding of their morphodynamics.

  6. Braided alluvial fan in the Terra Sirenum region, Mars

    NASA Astrophysics Data System (ADS)

    Adeli, S.; Hauber, E.; Le Deit, L.; Kleinhans, M. G.; Platz, T.; Fawdon, P.; Jaumann, R.

    2015-10-01

    Here we report the presence of an Amazonian-aged outflow channel located on the rim of the Ariadnes Colles basin (37°S/178°E) that has an alluvial fan on its downstream part. The study area is located in the Noachian highlands of Terra Sirenum, the site of a large hypothesized paleolake [3]. This so-called Eridania lake existed during the Late Noachian -Early Hesperian and drained into Ma'adim Vallis, one of the largest valleys on Mars. The Ariadnes Colles basin was part of the Eridania paleolake and hosted later a closed lake.

  7. Co-contamination of As and F in alluvial aquifer

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

  8. Tracing sources of water to an alluvial aquifer using strontium isotopes and radon

    NASA Astrophysics Data System (ADS)

    Pritchard, J. L.; Herczeg, A. L.

    2003-04-01

    87Sr/86Sr and 222Rn were measured in groundwaters of an alluvial aquifer adjacent to an ephemeral stream to quantify the extent of surface water infiltration versus upward groundwater leakage from the brackish regional aquifer system, and their degree of mixing. These tracers were used to differentiate between the potential sources of water to the alluvial aquifer because hydraulic gradients between the regional groundwater, alluvial groundwater and surface water reservoirs were low. The pumping of near-stream alluvial groundwater in the Wollombi Brook Catchment (SE Australia) has compromised the health of the stream ecosystem, potentially affecting water quality and flow rates. It is crucial to understand stream water and groundwater interactions in the alluvial aquifer to balance both consumptive and environmental water requirements. The distinct 87Sr/86Sr and 222Rn signatures of the surface water and groundwater reservoirs were used to differentiate between the potential sources of water to the alluvial aquifer system. These were compared to the alluvial groundwater signatures sampled from a piezometer network that was installed at various depths beneath the water table and at various distances from the stream channel. 222Rn emanation rates from the alluvial sands were also measured to discriminate between the production of 222Rn within the alluvial aquifer and influxes from other water flow paths. Regional groundwater had low 87Sr/86Sr (0.7051 to 0.7069) and relatively high Sr concentrations, whereas surface waters had higher 87Sr/86Sr (0.7095 to 0.7141) and relatively low Sr concentrations. Alluvial groundwater 87Sr/86Sr (0.7056 to 0.7118) and Sr concentrations were more variable. 222Rn emanation rates from the alluvial aquifer ranged from 2 to 7 Bq/L, whereas surface water 222Rn activities were < 1 Bq/L and regional groundwaters were generally an order of magnitude higher. 87Sr/86Sr and 222Rn activities showed there was some regional groundwater leakage into the alluvial aquifer system. However, 87Sr/86Sr also indicated that regional groundwater had little influence on the near-stream alluvial groundwater quality. Infiltration of stream water into the alluvial aquifer, following periodic flooding, appeared to buffer the transfer of water and solutes from the regional groundwater into the near-stream zone. This was, however, a very narrow buffer zone that could easily be eroded by further surface water diversions or excessive groundwater pumping from the alluvial aquifer.

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

    NASA Astrophysics Data System (ADS)

    Bavec, Miloš; Tulaczyk, Slawek M.; Mahan, Shannon A.; Stock, Gregory M.

    2004-03-01

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

  10. Late Quaternary glaciation of the Upper Soca River Region (Southern Julian Alps, NW Slovenia)

    USGS Publications Warehouse

    Bavec, Milos; Tulaczyk, Slawek M.; Mahan, Shannon; Stock, Gregory M.

    2004-01-01

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

  11. 40 CFR 721.10569 - Tricyclic quaternary amine salt (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...2013-07-01 false Tricyclic quaternary amine salt (generic). 721.10569 Section 721...721.10569 Tricyclic quaternary amine salt (generic). (a) Chemical substance...generically as tricyclic quaternary amine salt (PMN P-08-471) is subject to...

  12. 21 CFR 172.165 - Quaternary ammonium chloride combination.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Quaternary ammonium chloride combination. 172.165... HUMAN CONSUMPTION Food Preservatives § 172.165 Quaternary ammonium chloride combination. The food additive, quaternary ammonium chloride combination, may be safely used in food in accordance with...

  13. 21 CFR 172.165 - Quaternary ammonium chloride combination.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Quaternary ammonium chloride combination. 172.165... HUMAN CONSUMPTION Food Preservatives § 172.165 Quaternary ammonium chloride combination. The food additive, quaternary ammonium chloride combination, may be safely used in food in accordance with...

  14. 40 CFR 721.10569 - Tricyclic quaternary amine salt (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Tricyclic quaternary amine salt... Specific Chemical Substances § 721.10569 Tricyclic quaternary amine salt (generic). (a) Chemical substance... tricyclic quaternary amine salt (PMN P-08-471) is subject to reporting under this section for...

  15. 40 CFR 721.10569 - Tricyclic quaternary amine salt (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Tricyclic quaternary amine salt... Specific Chemical Substances § 721.10569 Tricyclic quaternary amine salt (generic). (a) Chemical substance... tricyclic quaternary amine salt (PMN P-08-471) is subject to reporting under this section for...

  16. 21 CFR 172.165 - Quaternary ammonium chloride combination.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Quaternary ammonium chloride combination. 172.165... § 172.165 Quaternary ammonium chloride combination. The food additive, quaternary ammonium chloride... the following compounds: n-dodecyl dimethyl benzyl ammonium chloride (CAS Reg. No. 139-07-1);...

  17. 21 CFR 172.165 - Quaternary ammonium chloride combination.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Quaternary ammonium chloride combination. 172.165... HUMAN CONSUMPTION Food Preservatives § 172.165 Quaternary ammonium chloride combination. The food additive, quaternary ammonium chloride combination, may be safely used in food in accordance with...

  18. Mapping the North Sea base-Quaternary: using 3D seismic to fill a gap in the geological record

    NASA Astrophysics Data System (ADS)

    Lamb, Rachel; Huuse, Mads; Stewart, Margaret; Brocklehurst, Simon H.

    2014-05-01

    The identification and mapping of the base-Quaternary boundary in the central parts of the North Sea is problematic due to the change from an unconformable transition between Pliocene and Pleistocene deltaic deposits in the southern North Sea to a conformable one further north (Sejrup et al 1991; Gatliff et al 1994). The best estimates of the transition use seismic reflection data to identify a 'crenulated reflector' (Buckley 2012), or rely on correlating sparse biostratigraphy (Cameron et al 1987). Recent integration of biostratigraphy, pollen analysis, paleomagnetism and amino acid analysis in the Dutch and Danish sectors (Rasmussen et al 2005; Kuhlmann et al 2006) allows greater confidence in the correlation to a regional 3D seismic dataset and show that the base-Quaternary can be mapped across the entire basin. The base-Quaternary has been mapped using the PGS MegaSurvey dataset from wells in the Danish Sector along the initially unconformable horizon and down the delta front into the more conformable basin giving a high degree of confidence in the horizon pick. The mapped horizon is presented here alongside the difference between this new interpretation and the previously interpreted base-Quaternary (Buckley 2012). The revised base-Quaternary surface reaches a depth of 1248 ms TWT or approximately 1120 m (assuming average velocity of 1800 m/s) showing an elongate basin shape that follows the underlying structure of the Central Graben. The difference between the revised base-Quaternary and the traditional base-Quaternary reaches a maximum of over 600 ms TWT or approximately 540 m in the south-west with over 300 ms TWT or approximately 270 m at the Josephine well (56° 36.11'N, 2° 27.09'E) in the centre of the basin. Mapping this new base-Quaternary allows for the interpretation of the paleo-envionrment during the earliest Quaternary. Seismic attribute analysis indicates a deep water basin with sediment deposition from multiple deltas and redistribution by deep water currents. This has strong implications for both the Quaternary climate archive and petroleum systems in the North Sea. Key Words: base-Quaternary; chronostratigraphy: seismic interpretation; paleoenvironments References Buckley, F.A., (2012) 'An Early Pleistocene grounded ice sheet in the Central North Sea' From: Huuse, M., Redfern, J., Le Heron, D.P., Dixon, R.J., Moscariello, A., Craig, J. (eds) 'Glaciogenic reservoirs and Hydrocarbon Systems' Geological Society, London, Special Publications, 368 Cameron, T.D.J., Stoker, M.S., Long, D., (1987) 'The history of Quaternary sedimentation in the UK sector of the North Sea Basin' Journal of the Geological Society, 144, 43-58 Gatliff, R.W, Richards, P.C, Smith, K, Graham, C.C, McCormac, M, Smith, N.J.P, Long, D, Cameron, T.D.J, Evans, D, Stevenson, A.G, Bulat, J, Ritchie, J.D, (1994) 'United Kingdom offshore regional report: the geology of the central North Sea.' London: HMSO for the British Geological Survey Kulhmann, G., Langereis C.G., Munsterman, D., van Leeuwen, R.-J., Verreussel, R., Meulenkamp, J.E., Wong, Th.E., 2006 'Intergrated chronostratigraphy of the Pliocene-Pliestocene interval and its relation to the regional stratigraphical stages in the Southern North Sea region' Netherlands Journal of Geosciences 85(1), 29-45 Rasmussen, E.A., Vejb?k O.V., Bidstrup, T., Piasecki, S., Dybkj?r, K., 2005 'Late Cenozoic depositional history of the Danish North Sea Basin: implications for the petroleum systems in the Kraka, Halfdan, Siri and Nini fields', Petroleum Geology Conference series 6, 1347-1358 Sejrup, H.P., Aareseth, I., Haflidason, H., 1991 'The Quaternary succession in the northern North Sea' Marine Geology 101 103-111

  19. Catalytic enantioselective synthesis of quaternary carbon stereocentres

    NASA Astrophysics Data System (ADS)

    Quasdorf, Kyle W.; Overman, Larry E.

    2014-12-01

    Quaternary carbon stereocentres--carbon atoms to which four distinct carbon substituents are attached--are common features of molecules found in nature. However, before recent advances in chemical catalysis, there were few methods of constructing single stereoisomers of this important structural motif. Here we discuss the many catalytic enantioselective reactions developed during the past decade for the synthesis of single stereoisomers of such organic molecules. This progress now makes it possible to incorporate quaternary stereocentres selectively in many organic molecules that are useful in medicine, agriculture and potentially other areas such as flavouring, fragrances and materials.

  20. Catalytic Enantioselective Synthesis of Quaternary Carbon Stereocenters

    PubMed Central

    Quasdorf, Kyle W.; Overman, Larry E.

    2015-01-01

    Preface Quaternary carbon stereocenters–carbon atoms to which four distinct carbon substituents are attached–are common features of molecules found in nature. However, prior to recent advances in chemical catalysis, there were few methods available for constructing single stereoisomers of this important structural motif. Here we discuss the many catalytic enantioselective reactions developed during the past decade for synthesizing organic molecules containing such carbon atoms. This progress now makes it possible to selectively incorporate quaternary stereocenters in many high-value organic molecules for use in medicine, agriculture, and other areas. PMID:25503231

  1. Effect of waves on delta foreset bedding in synchronism with generation of alluvial cyclic steps: 1D flume experiment

    NASA Astrophysics Data System (ADS)

    Sekiguchi, Tomohiro; Tanabe, Kazuho; Muto, Tetsuji

    2015-04-01

    Cyclic steps, a kind of upper regime bedforms associated with spatially-periodic hydraulic jumps, autogenically produce distinct cyclicity in delta-foreset bedding. This notion was obtained in our previous series of experiments where discrete packages of sediment accumulation on the foreset slope is synchronized with upstream migration of hydraulic jumps that depart from shoreline, i.e. the topset-foreset break of the delta. In the present series of experiments, conducted within a flume (50 cm × 50 cm × 20 m) with a piston-type wave generator at one end, waves were imposed on a prograding delta, the topset surface of which is characterized with the development of alluvial cyclic steps. A particular set of upstream water discharge, sediment feed rate, and water depth was adopted in all runs, and the experimental conditions including wave period and height were kept constant during each run. A mixture of two quartz sands with different colors and sizes was used in order to visualize sediment grain distribution. The experimental results suggest that waves do not affect behavior of hydraulic jumps (occurrence period at the river mouth, and rate of upstream migration), alluvial topset slope, rate of delta progradation, and the synchronism of cyclic foreset bedding with hydraulic-jump that is about to leave the river mouth. When waves were imposed, a foreshore/upper shoreface layer was intercalated between foreset and topset deposits. This layer became thicker and the foreset slopes tended to be gentler as wave height increased.

  2. Late Quaternary land-sea correlations, northern Labrador, Canada

    SciTech Connect

    Clark, P.; Josenhans, H.

    1985-01-01

    Late Quaternary glacial and postglacial units in the Torngat Mountains, northern Labrador, are correlated with units identified on the adjacent continental shelf. The late Wisconsinan Laurentide Ice Sheet drained through major valleys of the Torngat Mountains as outlet glaciers, depositing the Saglek Moraines. These are of regional extent and have been mapped from Saglek Fiord north to Noodleook Fiord. A C-14 date of 18,210 +/- 1900 BP on total organic matter (TOM) from lake sediment dammed by a segment of the Saglek Moraines is interpreted as a maximum date for deposition of the Saglek Moraine system because of possible contamination. Glacial sediments comprising the Saglek Moraines are correlated with upper till mapped in troughs and saddles on the continental shelf. Outlet glaciers depositing a late Wisconsinan unit flowed through Labrador fiords and onto the shelf at low basal shear stresses, particularly on the shelf where, although grounded, they were hydrostatically buoyed up and moved principally by sliding. A glaciomarine unit conformably overlies late Wisconsinan till on the shelf and on the land. This unit is a gravelly clayey silt, contains abundant foraminifera, and has up to 60% limestone in the pebble fraction. C-14 dates suggest deposition of this unit began ca. 10,000 BP on the shelf and 9000 BP on the land, an ended by 8000 BP. Limestone pebbles in this unit suggest a source in part from sediment-laden icebergs and pack-ice from the north. Marine deposition from ca. 8000-0 BP is characterize by basinal sedimentation.

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

    E-print Network

    Julien, Pierre Y.

    A. Reservoir Effects of Stream Channels DAM IMPACTS ON AND RESTORATION OF AN ALLUVIAL RIVER ­ RIO and reservoirs on alluvial rivers extends both upstream and downstream of the dam. Downstream of dams, both the water and sediment supplies can be altered leading to adjustments in the river channel geometry

  4. Herbicide interchange between a stream and the adjacent alluvial aquifer

    USGS Publications Warehouse

    Wang, W.; Squillace, P.

    1994-01-01

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

  5. Manganese Deposits in the Artillery Mountains Region, Mohave County, Arizona

    USGS Publications Warehouse

    Lasky, S.G.; Webber, B.N.

    1944-01-01

    The manganese deposits of the Artillery Mountains region lie within an area of about 25 square miles between the Artillery and Rawhide Mountains, on the west side of the Bill Williams River in west-central Arizona. The richest croppings are on the northeast side of this area, among the foothills of the Artillery Mountains. They are 6 to 10 miles from Alamo. The nearest shipping points are Congress, about 50 miles to the east, and Aguila, about 50 miles to the southeast. The principal manganese deposits are part of a sequence of alluvial fan and playa material, probably of early Pliocene age, which were laid down in a fault basin. They are overlain by later Pliocene (?) basalt flows and sediments and by Quaternary basalt and alluvium. The Pliocene (?) rocks are folded into a shallow composite S1ncline ttat occupies the valley between the Artillery and Rawhide Mountains, and the folded rocks along either side of the valley, together with the overlying Quaternary basalt, are broken by faults that have produced a group of horsts, grabens, and step-fault blocks. The manganiferous beds, lie at two zones, 750 to 1,000 feet apart stratigraphically, each of which is locally as much as 300 to 400 feet thick. The main, or upper, zone contains three kinds of ore - sandstone ore, clay ore, and 'hard' ore. The sandstone and clay ores differ from the associated barren sandstone and clay, with which they are interlayered and into which they grade, primarily in containing a variable proportion of amorphous manganese oxides, besides iron oxides and clayey material such as are present in the barren beds. The 'hard' ore is sandstone that has been impregnated with opal and calcite and in which the original amorphous manganese oxides have been largely converted to psilomelane and manganite. The average manganese content of the sandstone and clay ores is between 3 and 4 percent and that of the 'hard' ore is between 6 and 7 percent. The ore contains an average of 3 percent of iron, 0.08 percent of phosphorus, 1.1 percent of barium, and minute quantities of copper, lead, and zinc. Although the manganese content of the sandstone and clay ore may change abruptly from bed to bed, the content within any individual bed changes gradually, and for any large volume of ore both the nanganese and iron content are remarkably uniform. Explorations to June 1941 consisted chiefly of 49 holes diamond-drilled in the upper zone on the Artillery Mountains side of the area. The district is estimated to contain an assured minimum of 200,000,000 tons of material having an average manganese content of 3 to 4 percent. About 20,000,000 tons of this total contains 5 percent or more of manganese, and 2,000,000 to 3,000,000 tons contains 10 percent or more. To what extent these deposits can be utilized is a metallurgical and economic problem. Although the clay and sandstone ores, as well as the 'hard' ore, are present in large tonnages, the 'hard' ore is the only kind that combines minable tonnage with promising grade. About 15,000,000 tons of 'hard' ore is present; about 500,000 tons of this contains 15 percent or more of manganese and averages 17 percent, and somewhat over 2,000,000 tons contains 10 percent or more and averages nearly 13 percent. Except for closer drilling to determine such things as the tonnage, grade, spacing, and form of the richer shoots with greater accuracy before beginning to mine them, further explorations are not recommended, for any new ore found is likely to be similar, both in grade and kind, to that already discovered.

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

    USGS Publications Warehouse

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

    2002-01-01

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

  7. Thermoluminescence and new 14C age estimates for late quaternary loesses in southwestern Nebraska

    USGS Publications Warehouse

    Maat, P.B.; Johnson, W.C.

    1996-01-01

    Loess of late Quaternary age mantles most of Nebraska south of the Platte River Valley. At least five late Quaternary loesses are recognized: from oldest to youngest, one or more undifferentiated pre-lllinoian loesses, the Loveland Loess, the Gilman Canyon Loess, which exhibits a well developed soil and rests unconformably on the Sangamon soil, the Peoria Loess capped by the Brady soil, and the Bignell Loess, which is distributed discontinuously. Previous research shows that the Loveland Loess is Illinoian. the Gilman Canyon Loess and Peoria Loess are Wisconsin, and the Bignell Loess is Holocene. We present here the first thermoluminescence (TL) age estimates and new C ages for these late Quaternary loesses at two key sections in southwestern Nebraska, the Eustis ash pit and the Bignell Hill road cut. TL age estimates from all samples collected from Eustis ash pit and Bignell Hill were internally consistent. TL and C age estimates from these two sections generally agree and support previous age determinations. The TL age estimate on Loveland Loess indicates deposition at 163 ka. TL and radiocarbon age estimates indicate that Oilman Canyon Loess, believed to be deposited during the Farmdale interstade, first began to accumulate at about 40 ka: the lower part of the Gilman Canyon Loess is 36 ka at Eustis and the middle of the unit is 30 ka at Bignell Hill. The lower and upper parts of the Peoria Loess give age estimates of 24 ka and 17 ka, respectively. TL age estimates for deposition of the Bignell Loess are 9 ka near the base, in agreement with radiocarbon age estimates, and 6 ka immediately below the modern soil, substantiating its Holocene age. Comparisons of TL age estimates with ??18O and insolation curves which show loess deposition during interglacial and interstadial as well as glacial periods, indicate that loess deposition on the Great Plains can occur under a variety of climatic conditions.

  8. Arctic climates of the Quaternary

    NASA Astrophysics Data System (ADS)

    Spielhagen, R. F.; Bauch, H. A.; Frank, M.; Haley, B. A.

    2009-04-01

    The Atlantic Water (AW) inflow through the Fram Strait and across the Barents Sea and the freshwater runoff and brine rejection from sea ice formation on and close to the surrounding shelves are important processes for the formation of modern water masses in the interior Arctic Ocean. From microfossil and sedimentological data, isotopic data from planktic and benthic foraminifers, and 143Nd/144Nd ratios in leached sediment coatings from several well-dated Arctic sediment cores it is possible to reconstruct the variable influence of both processes on surface and intermediate waters in the Late Quaternary. Interglacials and interstadials were characterized by a broken sea ice cover with some open waters (leads) and a strong subsurface AW advection of Atlantic Water, feeding the deeper water masses. During the last ca. 250 ky such events usually were of a relatively short duration (10 ky or less), at times when the northern Eurasian shelves were ice-free. An exception is the last 50 ky interval, when a continuous inflow is recorded. Low Nd ratios indicate also a strong AW contribution to the intermediate waters since 50 ka and during MIS 5e. This conclusion is corroborated by high benthic carbon isotope values, indicative of well-ventilated waters at ca. 1500 m water depth. The good correlation between microfossil contents and insolation values suggests a dominant solar control of the AW inflow history. The time intervals of extended glaciations in northern Eurasia at ca. 190-130, 80-90, and 50-60 ka were characterized by a weak or lacking AW inflow and a strong input of terrestrial ice-rafted debris (IRD). Deglaciations were marked by strong influxes of freshwater from melting ice sheets and/or discharges from previously ice-dammed lakes. High Nd ratios indicate a significant contribution of brines from northern Siberian shelf/ice sheet margins to intermediate waters on the Lomonosov Ridge. The strongest freshwater events occurred at ca. 130 and 52 ka and resulted in an enhanced stratification of the upper water masses and poorly ventilated halocline and deep waters. While sediment records from the northernmost North Atlantic indicate a trend towards warmer peak interglacials and lesser IRD input during peak glacials in the last 500 ky, Arctic records do not reveal such a development. First strong IRD input occurred only during the Saalian glaciation, while earlier and even more extensive glaciations in northern Asia probably did not reach the Arctic paleo-coastline.

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  10. A new astronomical timescale for the loess deposits of Northern China

    E-print Network

    Utrecht, Universiteit

    A new astronomical timescale for the loess deposits of Northern China D. Heslop *, C.G. Langereis Here, we present a refined timescale for the entire sequence of Quaternary Chinese loess, which relies that is consistent with the current understanding of loess depositional and post-depositional processes. Analysis

  11. Statistic inversion of multi-zone transition probability models for aquifer characterization in alluvial fans

    E-print Network

    Zhu, Lin; Gong, Huili; Gable, Carl; Teatini, Pietro

    2015-01-01

    Understanding the heterogeneity arising from the complex architecture of sedimentary sequences in alluvial fans is challenging. This paper develops a statistical inverse framework in a multi-zone transition probability approach for characterizing the heterogeneity in alluvial fans. An analytical solution of the transition probability matrix is used to define the statistical relationships among different hydrofacies and their mean lengths, integral scales, and volumetric proportions. A statistical inversion is conducted to identify the multi-zone transition probability models and estimate the optimal statistical parameters using the modified Gauss-Newton-Levenberg-Marquardt method. The Jacobian matrix is computed by the sensitivity equation method, which results in an accurate inverse solution with quantification of parameter uncertainty. We use the Chaobai River alluvial fan in the Beijing Plain, China, as an example for elucidating the methodology of alluvial fan characterization. The alluvial fan is divided...

  12. New perspectives on quaternary faulting in the southern Walker Lane, Nevada and California

    SciTech Connect

    Reheis, M.C.; Noller, J.S.

    1987-12-31

    A preliminary survey of aerial photographs of the southern Walker Lane began in late 1986. The purpose of this survey is to determine the nature and scope of future studies required to ascertain whether the apparent concentration of Quaternary faults in and near the Nevada Test Site is real or is simply a result of the greater effort invested in mapping Quaternary deposits in that area, and determine whether faults in the southern Walker Lane are active and could produce significant earthquakes. The survey is focused on the area extending south from Lone Mountain to Pahrump Valley and east from the Furnace Creek fault zone to an irregular line passing through the Cactus Range and Pahute Mesa. Lineaments and scraps were identified on stereopairs of black-and-white aerial photographs at scales of 1:80,000 or 1:60,000. The lineaments and and scarps were plotted on 1:24,000- and 1:62,500-scale topographic maps using a PG-2 plotter, and were color-coded according to distinctness and occurrence in Quaternary or Tertiary deposits (age assignments based on appearance in aerial photographs and on existing geologic maps). Additional lineaments identified on the topographic maps were also plotted. Areas of particular interest were selected for more detailed study using larger-scale aerial photographs. Most of the lineaments and scraps identified in the survey, although referred to as faults in this paper, have not been checked in the field. 11 refs., 1 fig.

  13. Quaternary morphotectonic mapping of the Wadi Araba and implications for the tectonic activity of the southern Dead Sea fault

    NASA Astrophysics Data System (ADS)

    Le BéOn, Maryline; Klinger, Yann; MéRiaux, Anne-Sophie; Al-Qaryouti, Mahmoud; Finkel, Robert C.; Mayyas, Omar; Tapponnier, Paul

    2012-10-01

    The Dead Sea strike-slip fault accommodates the northward motion of Arabia relative to Sinai at a rate of ˜5 mm/yr. The southern segment of the fault, the Wadi Araba fault, runs along a valley blanketed in Quaternary sediments. We first focused on understanding the relative and absolute timing of emplacement of the alluvial surfaces. We then determined the probable source of the sediments before assessing their lateral offset to constrain the late Pleistocene fault slip rate. Seven successive morphostratigraphic levels were identified. At two sites, we recognized an alluvial sequence of five to seven successive levels with ages getting younger northward, a pattern consistent with the western block moving southward relative to two fixed feeding channels located to the east. Surface samples were collected for10Be cosmogenic radionuclide dating. Fans F3 and F5 were found to be synchronous from site to site, at 102 ± 26 ka and 324 ± 22 ka, respectively, while F4 could be dated at 163 ± 19 ka at one site only. These are minimum ages, assuming no erosion of the alluvial surfaces. At least two of these periods are correlated with wet periods that are regionally well documented. Further analyses of tectonic offsets are affected in most cases by large uncertainties due to the configuration of the sites. They indicate maximum offsets of ˜5.5 km for the oldest, possibly ˜1 Ma old, surfaces. They lead to bracketing of the fault slip rate between 5 and 12 mm/yr, with preferred values of 5-7 mm/yr, for the last 300 ka.

  14. Similarity analysis of soils formed on limestone/marl-alluvial parent material and different topography using some physical and chemical properties via cluster and multidimensional scaling methods.

    PubMed

    Sa?lam, Mustafa; Dengiz, Orhan

    2015-03-01

    The aim of this study is to analyze the similarity of soils formed on limestone/marl alluvial parent material and different topography using some physical and chemical properties via cluster analysis (CA) and multidimensional scaling analysis (MDSA). Physical and chemical soil properties included in this study are texture, CaCO3, organic matter, pH, electrical conductivity, cation exchange capacity, and available water content. The study was carried out in Çetinkaya region located on Bafra Deltaic Plain. The study area has two main physiographic units. The first one is the flat or gently slope alluvial lands (0-2 %), and the other one involves hills with slopes ranging from middle to steep (3-20 %). The soil in the study area is mainly classified as entisol, inceptisol and vertisol. According to the CA results, while C horizons of the soils formed on alluvial deposits (typic ustifluvent and typic ustipsamment) bear similarity, Ap horizons of the soils formed on lime/marl parent material (vertic ustorhent, vertic calciustept, and calci haplustert) appear in the same group. Additionally, in order to support CA, MDSA was performed. Significant correlations were observed between the results of both analyses. PMID:25663394

  15. Long-term slip rate of the southern San Andreas Fault Al surface exposure dating of an offset alluvial fan

    E-print Network

    Klinger, Yann

    of an offset alluvial fan Je´ro^me van der Woerd,1,2 Yann Klinger,3,4 Kerry Sieh,3 Paul Tapponnier,5 Frederick alluvial fan surface. Field mapping complemented with topographic data, air photos and satellite images Andreas Fault from 10 Be-26 Al surface exposure dating of an offset alluvial fan, J. Geophys. Res., 111, B

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

    E-print Network

    apart from alluvial fans and large rivers. Alluvial scrub is composed of an assortment of droughtALLUVIAL SCRUB VEGETATION IN COASTAL SOUTHERN CALIFORNIA1 Ted L. Hanes, Richard D. Friesen- parian woodlands due to a lack of perennial water. Allu- vial scrub occurs on outwash fans and riverine

  17. Hydrogeochemistry of groundwaters in an alluvial aquifer: removal of Fe and Mn in an alluvial aquifer by sulfate reduction

    NASA Astrophysics Data System (ADS)

    Kim, H.; Kim, K.; Choi, B.; Kim, S.; Jeong, H.; Koh, D.

    2006-12-01

    Alluvial aquifer is considered as an optimal site to produce riverbank filtration water in Korea. However, the application of riverbank filtration is greatly hindered in those aquifers due to high nitrate levels caused by agricultural activities occurring above it. Nitrate is readily attenuated by denitrification under a moderately reducing condition. In contrast, Fe and Mn generally become the additional problems as nitrate is removed by denitrification. This study shows that Fe/Mn can also be removed from groundwater under a more reducing condition with high sulfate concentration. This study was performed in an agricultural, alluvial aquifer located alongside of the Mankyeong River. For this study, we installed six multi-level samplers to collect minimally disturbed water samples. Our results show that the shallow groundwaters are highly contaminated with nitrate due to excessive fertilizer application. However, nitrate is soon removed from groundwater by denitrification at the depth 10-15 m. The study site also shows that Fe and Mn concentrations drastically increase up to 50 mg/l and 5 mg/l, respectively, after the removal of nitrate. Interestingly, the levels for Fe and Mn steeply decrease to the detection limit of the analysis at the deeper depths. A precise inspection of the chemical data suggests that the abrupt decreases in Fe and Mn levels are the results of sulfate reduction. It is likely that Fe and Mn are removed as sulfide minerals by reaction with sulfide ions produced from sulfate reduction.

  18. Quaternary Geochronology 1 (2006) 7485 Research paper

    E-print Network

    Briner, Jason P.

    2006-01-01

    of complete shielding by the LIS. The lack of glacial erosion for at least the past 400 kyr suggests Island; Glacial history; Interglaciation; Erosion 1. Introduction The large-scale physiography of BaffinQuaternary Geochronology 1 (2006) 74­85 Research paper Limited ice-sheet erosion and complex

  19. Enantioselective construction of remote quaternary stereocentres

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

    Small molecules that contain all-carbon quaternary stereocentres--carbon atoms bonded to four distinct carbon substituents--are found in many secondary metabolites and some pharmaceutical agents. The construction of such compounds in an enantioselective fashion remains a long-standing challenge to synthetic organic chemists. In particular, methods for synthesizing quaternary stereocentres that are remote from other functional groups are underdeveloped. Here we report a catalytic and enantioselective intermolecular Heck-type reaction of trisubstituted-alkenyl alcohols with aryl boronic acids. This method provides direct access to quaternary all-carbon-substituted ?-, ?-, ?-, ?- or ?-aryl carbonyl compounds, because the unsaturation of the alkene is relayed to the alcohol, resulting in the formation of a carbonyl group. The scope of the process also includes incorporation of pre-existing stereocentres along the alkyl chain, which links the alkene and the alcohol, in which the stereocentre is preserved. The method described allows access to diverse molecular building blocks containing an enantiomerically enriched quaternary centre.