These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

Occurrence of volcanic ash in the Quaternary alluvial deposits, lower Narmada basin, western India  

Microsoft Academic Search

This communication reports the occurrence of an ash layer intercalated within the late Quaternary alluvial succession of the\\u000a Madhumati River, a tributary of the lower Narmada River. Petrographic, morphological and chemical details of glass shards\\u000a and pumice fragments have formed the basis of this study. The ash has been correlated with the Youngest Toba Tuff. The finding\\u000a of ash layer

Rachna Raj

2008-01-01

2

Modern and ancient alluvial fan deposits  

SciTech Connect

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

Nilsen, T.H.

1985-01-01

3

Late Quaternary alluvial fans at the eastern end of the San Bernardino Mountains, Southern California  

NASA Astrophysics Data System (ADS)

Alluvial fans at the eastern end of the San Bernardino Mountains in Southern California provide a record of climate modulated sediment transfer and erosion, and are deformed and displaced in places by active faults. Alluvial fans within two study areas, the Mission Creek and the Whitewater River drainages, were examined using geomorphic, sedimentological, and 10Be terrestrial cosmogenic nuclide (TCN) surface exposure methods to define the timing of alluvial fan formation and erosion, and to examine the role of climatic, tectonic and autocyclic processes. These alluvial fan complexes were studied because they are amongst the best-preserved successions of alluvial fans in southern California and they are located at the mouths of two of the largest drainages, Whitewater River and Mission Creek, in the San Bernardino Mountains and traverse major faults, the Mission Creek and Banning. The alluvial fans comprise bouldery debris deposits that represent deposition dominated by flash flood and debris flow events. TCN surface exposure dating indicates that abandonment/incision of alluvial fan surfaces date to early in the Last Glacial or more likely the penultimate glacial cycle, to marine isotope stage (MIS) 4, and to the Holocene. The lack of alluvial fan ages during the latter part of the Last Glacial (MIS 2 and 3) suggests that there has been little alluvial fan lobe deposition/incision during that time. This is similar to findings for many other alluvial fans throughout the American Southwest, and supports the view that there is a strong climatic control on alluvial fan formation throughout this region. Furthermore, the oldest alluvial fan surfaces in the Mission Creek region are beheaded by the Whitewater River drainage, showing that the oldest alluvial fans in the Mission Creek region underwent significant capture by the Whitewater River drainage. This shows the autocyclic controls are also important on alluvial fan evolution in this region; but the importance of these processes to alluvial fan development in other regions of the American Southwest needs to be more fully assessed. The alluvial fans in the Mission Creek area traverse the Mission Creek fault, but are not deformed by it, which suggests that there may have been little if any movement along this fault since at least MIS 4. In contrast, alluvial fans in the Whitewater River study are displaced by active faults highlighting the influence of tectonism on alluvial fan development in this region. In addition to illustrating the importance of climatic controls on the development of alluvial fans in the American Southwest, a classic region for alluvial fan studies, this study illustrates the complex mixture of autocyclic and allocyclic factors that force alluvial fan development in tectonically active settings.

Owen, Lewis A.; Clemmens, Samuel J.; Finkel, Robert C.; Gray, Harrison

2014-03-01

4

Eustatic and tectonic control on Late Quaternary alluvial fans along the Tyrrhenian Sea coast of Calabria (South Italy)  

NASA Astrophysics Data System (ADS)

The Late Quaternary evolution of the western Coastal Range (northern Calabria) has been reconstructed by means of a multidisciplinary approach. We have focused on the role of allocyclic mechanisms, tectonics and base-level change considered as factors influencing alluvial fan development. In particular we identify no clear evidence for a major influence of climate. Age constraints were provided by a tephra layer and a paleosol, coupled with geomorphological correlations. Middle Pleistocene perched terraces and fan relicts hanging above fault scarps, indicate that tectonics caused switches in fan dynamics between aggradational and erosional phases. As tectonic activity declined during late Middle Pleistocene, eustatically driven changes in base-level, possibly plus low rates of tectonic subsidence, represent the main factor which controlled Late Pleistocene fan development. The two major fan aggradation phases occurred during periods of climate amelioration prior to highstands, whereas high sea levels (OIS 5 and 1) promoted channel incision into the fan surfaces; this continued during periods of climate deterioration with a seaward progradation of alluvial deposition. Sea-level rise is seen as creating accommodation space, producing very open fans, locally within mountain embayments. The fans are characterised by a mushroom shape in plan-view and by a retrograde stacking pattern of alluvial fan facies.

Robustelli, Gaetano; Muto, Francesco; Scarciglia, Fabio; Spina, Vincenzo; Critelli, Salvatore

2005-10-01

5

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

SciTech Connect

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

Donald S. Sweetkind; Ronald M. Drake II

2007-01-22

6

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

7

A model of the Quaternary geological deposits of Bucharest City  

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

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)

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

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

2012-12-01

9

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

10

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

11

Relict sheetflood bed forms on late Quaternary alluvial-fan surfaces in the southwestern United States  

NASA Astrophysics Data System (ADS)

Late Pleistocene and early Holocene alluvial-fan surfaces in southeastern California are locally mantled by narrow, widely spaced, transverse-to-slope bands of fine gravel and coarse sand. These features are interpreted to be relict bed forms of high-magnitude sheetfloods that inundated abandoned alluvial-fan surfaces. The majority of these sheetflood events apparently occurred in the latest Pleistocene to middle Holocene and produced meso bed forms with wavelengths of 2 6 m. These flood events mobilized sediment with mean grain sizes of 2 8 mm on inactive fan surfaces under calculated velocities of 30 60 cm/s and may be responsible for increased dissection of upper piedmonts and widespread alluvial-fan deposition in the lower piedmont regions. An older sheetflood event produced macro-bed forms with wavelengths of 20 80 m on a pedogenic CaCO3-cemented piedmont in southwestern Arizona. Both scales of bed forms display characteristics of confined-flow fluvial bed forms which form under diverse flow regimes that cause either megaripples or transverse ribs.

Wells, Stephen G.; Dohrenwend, John C.

1985-07-01

12

Faulting and folding in quaternary deposits of Tehran’s piedmont (Iran)  

NASA Astrophysics Data System (ADS)

Tehran lies on the southern flank of the Central Alborz, an active mountain belt characterized by many historical earthquakes, some of which have affected Tehran itself. The border between the Alborz Mountain and the Tehran's piedmont (northern part of Tehran City) is marked by the North Tehran Fault (NTF), dividing the Eocene rock formation from the alluvial units of different ages (Early Pleistocene to the recent alluvium). A detail mapping of the piedmont, combined with structural study reveal that two active thrust faults (situated south of the NTF) are of importance for hazard assessment of the City. The geomorphological evidences along the NTF are not in agreement with an active fault, indicating that the fault activity may have been shifted southward. Furthermore differentiation of newly recognized alluvial units and their inferred ages, together with the mapped fault pattern permit us to characterize the Quaternary deformation. The Late Pleistocene alluvial deposits consist of three alluvial fans among them the youngest one together with the modern alluvial fan defines the Holocene deposit. The present deformation in the piedmont is accommodated along vertically left-lateral strike-slip faults and low-angle thrust faults trending in range from N070 to N110E.

Abbassi, M. R.; Farbod, Y.

2009-04-01

13

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

14

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

15

Sedimentary and tectonic evolution of Plio Pleistocene alluvial and lacustrine deposits of Fucino Basin (central Italy)  

NASA Astrophysics Data System (ADS)

The Fucino Basin was the greatest lake of the central Italy, which was completely drained at the end of 19th century. The basin is an intramontane half-graben filled by Plio-Quaternary alluvial and lacustrine deposits located in the central part of the Apennines chain, which was formed in Upper Pliocene and in Quaternary time by the extensional tectonic activity. The analysis of the geological surface data allows the definition of several stratigraphic units grouped in Lower Units and Upper Units. The Lower Units (Upper Pliocene) are exposed along the northern and north-eastern basin margins. They consist of open to marginal lacustrine deposits, breccia deposits and fluvial deposits. The Upper Units (Lower Pliocene-Holocene) consist of interbedded marginal lacustrine deposits and fluvial deposits; thick coarse-grained fan-delta deposits are interfingered at the foot of the main relief with fluvial-lacustrine deposits. Most of the thickness of the lacustrine sequences (more than 1000-m thick) is buried below the central part of the Fucino Plain. The basin is bounded by E-W, WSW-ENE and NW-SE fault systems: Velino-Magnola Fault (E-W) and Tremonti-Celano-Aielli Fault (WSW-ENE) and S. Potito-Celano Fault (NW-SE) in the north; the Trasacco Fault, the Pescina-Celano Fault and the Serrone Fault (NW-SE) in the south-east. The geometry and kinematic indicators of these faults indicate normal or oblique movements. The study of industrial seismic profiles across the Fucino Basin gives a clear picture of the subsurface basin geometry; the basin shows triangular-shaped basin-fill geometry, with the maximum deposits thickness toward the main east boundary fault zones that dip south-westward (Serrone Fault, Trasacco Fault, Pescina-Celano Fault). On the basis of geological surface data, borehole stratigraphy and seismic data analysis, it is possible to recognize and to correlate sedimentary and seismic facies. The bottom of the basin is well recognized in the seismic lines available from the good and continuous signals of the top of Meso-Cenozoic carbonate rocks. The shape of sedimentary bodies indicates that the filling of the basin was mainly controlled by normal slip along the NW-SE boundary faults. In fact, the continental deposits are frequently in on-lap contact over the carbonate substratum; several disconformable contacts occurred during the sedimentary evolution of the basin. The main faults (with antithetic and synthetic fault planes) displace the whole sedimentary sequence up to the surface indicating a recent faults' activity (1915 Avezzano earthquake, Ms=7.0). The stratigraphic and tectonic setting of the Fucino Basin and neighboring areas indicates that the extensional tectonic events have had an important role in driving the structural-sedimentary evolution of the Plio-Quaternary deposits. The geometry of the depositional bodies, of the fault planes and their relationships indicate that the Fucino Basin was formed as a half-graben type structure during Plio-Quaternary extensional events. Some internal complexities are probably related to the fold-and-thrust structures of the Apenninic orogeny formed in Messinian time, in this area, and to a different activity timing of the E-W and WSW-ENE fault systems and the NW-SE fault systems. We believe, based on the similarity of the surface characteristics, that the structural setting of the Fucino Basin can be extrapolated to the other great intramontane basins in Central Italy (e.g. Rieti, L'Aquila, Sulmona, Sora, Isernia basins).

Cavinato, Gian Paolo; Carusi, Claudio; Dall'Asta, Massimo; Miccadei, Enrico; Piacentini, Tommaso

2002-04-01

16

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

NASA Astrophysics Data System (ADS)

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.

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

2015-01-01

17

Quaternary alluvial-fan development, climate and morphologic dating of fault scarps in Laguna Salada, Baja California, Mexico  

NASA Astrophysics Data System (ADS)

Late Quaternary slip across the Cañada David detachment has produced an extensive array of Quaternary scarps cutting alluvial-fans along nearly the entire length (~ 60 km) of the range-bounding detachment. Eight regional alluvial-fan surfaces (Q 1 [youngest] to Q 8 [oldest]) are defined and mapped along the entire Sierra el Mayor range-front. Terrestrial cosmogenic nuclide 10Be concentrations from individual boulders on alluvial-fan surfaces Q 4 and Q 7 yield surface exposure ages of 15.5 ± 2.2 ka and 204 ± 11 ka, respectively. Formation of the fans is probably tectonic, but their evolution is strongly moderated by climate, with surfaces developing as the hydrological conditions have changed in response to climate change on Milankovitch timescales. Systematic mapping reveals that the fault scarp array along active range-bounding faults in Sierras Cucapa and El Mayor can be divided into individual rupture zones, based on cross-cutting relationships with alluvial-fans. Quantitative morphological ages of the Laguna Salada fault-scarps, derived from linear diffusive degradation modeling, are consistent with the age of the scarps based on cross-cutting relationships. The weighted means of the maximum mass diffusivity constant for all scarps with offsets < 4 m is 0.051 and 0.066 m 2/ka for the infinite and finite-slope solutions of the diffusion equation, respectively. This estimate is approximately an order of magnitude smaller than the lowest diffusivity constants documented in other regions and it probably reflects the extreme aridity and other microclimatic conditions that characterize the eastern margin of Laguna Salada.

Spelz, Ronald M.; Fletcher, John M.; Owen, Lewis A.; Caffee, Marc W.

2008-12-01

18

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

NASA Astrophysics Data System (ADS)

As a low-gradient arid region spanning the tropics to the temperate zone, the Lake Eyre basin has undergone gentle late Cenozoic crustal warping leading to substantial alluvial deposition, thereby forming repositories of evidence for palaeoclimatic and palaeohydrological changes from the Late Tertiary to the Holocene. Auger holes and bank exposures at five locations along the lower 500 km of Cooper Creek, a major contributor to Lake Eyre in the eastern part of the basin, yielded 85 luminescence dates (TL and OSL) that, combined wit a further 142 luminescence dates from northeastern Australia, have established a chronology of multiple episodes of enhanced flow regime from about 750 ka to the Holocene. Mean bankfull discharges on Cooper Creek upstream of the Innamincka Dome at 250-230 ka or oxygen isotope stages (OIS) 7-6 are estimated to have been 5 to 7 times larger than those of today, however, substantially less reworking has occurred during and after OIS 5 than before. Lower Cooper Creek appears to have similarly declined. In the Tirari Desert adjacent to Lake Eyre there is evidence of widespread alluvial activity, perhaps during but certainly before the Middle Pleistocene, yet the river became laterally restricted in OIS 7 to 5. While the Quaternary has been characterised by a dramatically oscillating wet-dry climate, since oxygen isotope stage OIS 7 or 6 there has been a general decline in the magnitude of the episodes of wetness to which the eastern part of central Australia has periodically returned. During the last full glacial cycle, Cooper Creek's periods of greatest runoff and sand transport were not during the last interglacial maximum of OIS 5e (132-122 ka) but later in OIS 5 when sea levels and global temperatures were substantially below those of 5e or today. Fluvial activity returned in OIS 4 and 3, but not to the extent of mid and late OIS 5; strongly seasonal but still powerful flows transported sand and fed source-bordering dunes in OIS 5 and 3. This chronology of fluvial activity in the late Quaternary broadly coincides with that for rivers of southeastern Australia and suggests that the wet phases in eastern central Australia have not been governed as much by the northern monsoon as by conditions in the western Pacific close to the east coast both north and south. Flow confinement within the Innamincka Dome has locally amplified Cooper Creek's energy, and here evidence exists for short but high-magnitude episodes of flow during the Last Glacial Maximum and in the early to middle Holocene, conditions that were capable of forming large palaeochannels but that were not long-lived enough to rework the river's extensive floodplains elsewhere along its length.

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

2008-10-01

19

River response to Quaternary subsidence due to evaporite solution (Gállego River, Ebro Basin, Spain)  

Microsoft Academic Search

The stream terrace evolution of the Gállego river during the Quaternary was controlled by both climatic change and subsidence. Quaternary terrace deposits, overlying Tertiary clay and limestone, are between 2 and 5 m thick, whereas above evaporite formations the alluvial deposits may be as much as 110 m thick. Chronologically, the first period of alluvial thickening involved the stream terraces

Gerardo Benito; Alfredo Pérez-González; F. Gutiérrez; M. J. Machado

1998-01-01

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

ARC/INFO export and nonproprietary format files This diskette contains digitized aquifer boundaries, maps of hydraulic conductivity, recharge, and ground-water level elevation contours for the alluvial and terrace deposits along the Cimarron River from Freedom to Guthrie in northwestern Oklahoma. Ground water in 1,305 square miles of Quaternary-age alluvial and terrace deposits along the the Cimarron River from Freedom to Guthrie is an important source of water for irrigation, industrial, municipal, stock, and domestic supplies. Alluvial and terrace deposits are composed of interfingering lenses of clay, sandy clay, and cross-bedded poorly sorted sand and gravel. The aquifer is composed of hydraulically connected alluvial and terrace deposits that unconformably overlie the Permian-age Formations. The aquifer boundaries are from a ground-water modeling report on the alluvial and terrace aquifer along the Cimarron River from Freedom to Guthrie in northwestern Oklahoma and published digital surficial geology data sets. The aquifer boundary data set was created from digital geologic data sets from maps published at a scale of 1:250,000. The hydraulic conductivity values, recharge rates, and ground-water level elevation contours are from the ground-water modeling report. Water-level elevation contours were digitized from a map at a scale of 1:250,000. The maps were published at a scale of 1:900,000. Ground-water flow models are numerical representations that simplify and aggregate natural systems. Models are not unique; different combinations of aquifer characteristics may produce similar results. Therefore, values of hydraulic conductivity and recharge used in the model and presented in this data set are not precise, but are within a reasonable range when compared to independently collected data.

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

1997-01-01

21

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

E-print Network

SEQUENCE STRATIGRAPHIC INTERPRETATION METHODS FOR LOW- ACCOMMODATION, ALLUVIAL DEPOSITIONAL SEQUENCES: APPLICATIONS TO RESERVOIR CHARACTERIZATION OF CUT BANK FIELD, MONTANA A Dissertation by RAHILA RAMAZANOVA Submitted...- ACCOMMODATION, ALLUVIAL DEPOSITIONAL SEQUENCES: APPLICATIONS TO RESERVOIR CHARACTERIZATION OF CUT BANK FIELD, MONTANA A Dissertation by RAHILA RAMAZANOVA Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment...

Ramazanova, Rahila

2009-05-15

22

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

SciTech Connect

The degree to which local climatic variations, eustatic sea level fluctuations, and tectonic uplift have influenced the development of Quaternary marine and fluvial landforms and deposits along the Red Sea coast, Eastern Desert, Egypt was investigated using a combination of remote sensing and field data, age determinations of corals, and numerical simulations. False color composites generated from Landsat Thematic Mapper and SPOT image data, digital elevation models derived from stereophotogrammetric analysis of SPOT data, and field observations document that a {approximately}10-km-wide swath inland from the coast is covered in many places with coalescing alluvial fans of Quaternary age. Wadis cutting through the fans exhibit several pairs of fluvial terraces, and wadi walls expose alluvium interbedded with coralline limestone deposits. Further, three distinct coral terraces are evident along the coastline. Climatic, eustatic, and tectonic uplift controls on the overall system were simulated using a cellular automata algorithm with the following characteristics: (1) uplift as a function of position and time, as defined by the elevations and ages of corals; (2) climatic variations driven by insolation changes associated with Milankovitch cycles; (3) sea level fluctuations based on U/Th ages of coral terraces and eustatic data; and (4) parameterized fluvial erosion and deposition. Results imply that the fans and coralline limestones were generated in a setting in which the tectonic uplift rate decreased over the Quaternary to negligible values at present. During lowstands, wadis cut into sedimentary deposits; coupled with continuing uplift, fans were dissected, leaving remnant surfaces, and wadi-related terraces were generated by down cutting. Only landforms from the past three to four eustatic sea level cycles (i.e., {approximately} 300 to 400 kyr) are likely to have survived erosion and deposition associated with fluvial processes. 33 refs., 18 figs., 2 tabs.

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

1994-06-10

23

A Quaternary volcanic ash deposit in western Missouri  

Microsoft Academic Search

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

1993-01-01

24

Correlation and dating of Quaternary alluvial-fan surfaces using scarp diffusion  

NASA Astrophysics Data System (ADS)

Great interest has recently been focused on dating and interpreting alluvial-fan surfaces. As a complement to the radiometric methods often used for surface-exposure dating, this paper illustrates a rapid method for correlating and dating fan surfaces using the cross-sectional shape of gullies incised into fan surfaces. The method applies a linear hillslope-diffusion model to invert for the diffusivity age, ?t (m 2), using an elevation profile or gradient (slope) profile. Gullies near the distal end of fan surfaces are assumed to form quickly following fan entrenchment. Scarps adjacent to these gullies provide a measure of age. The method is illustrated on fan surfaces with ages of approximately 10 ka to 1.2 Ma in the arid southwestern United States. Two areas of focus are Death Valley, California, and the Ajo Mountains piedmont, Arizona. Gully-profile morphology is measured in two ways: by photometrically derived gradient (slope) profiles and by ground-surveyed elevation profiles. The ?t values determined using ground-surveyed profiles are more consistent than those determined using photo-derived ?t values. However, the mean ?t values of both methods are comparable. The photometric method provides an efficient way to quantitatively and objectively correlate and relatively-date alluvial-fan surfaces. The ?t values for each surface are determined to approximately 30-50% accuracy.

Hsu, Leslie; Pelletier, Jon D.

2004-06-01

25

Digital data sets that describe aquifer characteristics of the alluvial and terrace deposits along the North Canadian River from Canton Lake to Lake Overholser in Central Oklahoma  

USGS Publications Warehouse

ARC/INFO export and nonproprietary format files This diskette contains digitized aquifer boundaries and maps of of hydraulic conductivity, recharge, and ground-water level elevation contours for the alluvial and terrace deposits along the alluvial and terrace deposits along the North Canadian River from Canton Lake to Lake Overholser in central Oklahoma. Ground water in approximately 400 square miles of Quaternary-age alluvial and terrace aquifer is an important source of water for irrigation, industrial, municipal, stock, and domestic supplies. The aquifer consists of clay, silt, sand, and gravel. Sand-sized sediments dominate the poorly sorted, fine to coarse, unconsolidated quartz grains in the aquifer. The hydraulically connected alluvial and terrace deposits unconformably overlie Permian-age formations. The aquifer is overlain by a layer of wind-blown sand in parts of the area. Most of the lines in the aquifer boundary, hydraulic conductivity, and recharge data sets were extracted from published digital surficial geology data sets based on a scale of 1:250,000. The ground-water elevation contours and some of the lines for the aquifer boundary, hydraulic conductivity, and recharge data sets were digitized from a ground-water modeling report about the aquifer published at a scale of 1:250,000. The hydraulic conductivity values and recharge rates also are from the ground-water modeling report. Ground-water flow models are numerical representations that simplify and aggregate natural systems. Models are not unique; different combinations of aquifer characteristics may produce similar results. Therefore, values of hydraulic conductivity and recharge used in the model and presented in this data set are not precise, but are within a reasonable range when compared to independently collected data.

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

1997-01-01

26

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

NASA Astrophysics Data System (ADS)

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.

Ghosh, Parthasarathi; Sarkar, Soumen; Maulik, Pradip

2006-09-01

27

Reconstruction of the Palaeo-environment of the Alluvial Deposits in the Eastern Free State, South Africa  

NASA Astrophysics Data System (ADS)

Small alluvial fan systems have formed off the hillslopes of the remnant Karoo koppies at Heelbo in the Eastern Free State, South Africa. The landform geometry is a result of complex relationships between climate, lithology, structure and vegetation. This research area, which includes a large mammal mass death site, potentially contains a wealth of palaeo-environmental and specifically palaeoclimatic information. Palaeo-environmental information and proxy records on past climates in southern Africa has traditionally been obtained from a variety of techniques including stable isotope analysis of speleothems, pollen , faunal analyses at archeological sites, animal remains and crater-lake sediments (see references below). However, little information exists in the scientific literature on the use of palaeosols for defining the depositional palaeoenvironments in southern Africa. The aim of this research is to attempt to address the lack of palaeo-environmental information by extracting palaeoclimatic information from the sedimentary processes and the palaeosols at the Heelbo farm that have been extensively exposed through gullying. The sedimentary fans in the area have experienced climatically controlled histories of erosion, sedimentation and pedogenesis. Extreme sedimentation is assumed to have occurred during relatively arid climatic intervals, when decreased vegetation cover provided little surface protection. In contrast pedogenesis occurs during humid intervals when vegetation cover is restored, the land stabilizes and the uppermost gravely sands weather to form soils. A combined approach of both radiocarbon- and luminescence -dating may provide a detailed chronology of these successive hillslope events in order to relate hillslope instability to climatic forcing factors. Preliminary results indicate that at least 3 depositional events are recorded within the large mammal mass death site, which have been confirmed by the radiocarbon dates of 3,610 ±110 in the top section and 4,610 ±30 at the bottom section. References: Klein, R.G., Cruz-Uribe, K., Beaumont, P.B., 1991. Environmental, ecological, and paleoanthropological implications of the Late Pleistocene mammalian fauna from Equus Cave, northern Cape Province, South Africa. Quaternary Research. 36, 94 119. Lee-Thorp, J.A., Beaumont. PB., 1995. Vegetation and seasonality shift during the late Quaternary deduced from 13C/12C ratios of grazers at Equus Cave, South Africa. Quaternary Research. 43, 426 432. Partridge, T.C., Demenocal, P.B., Lorentz, S.A., Paiker, M.J., Vogel, J.C., 1997: Orbital forcing of climate over South Africa: A 200,000-year rainfall record from Pretoria Saltpan, Quaternary Science Reviews, 16, 1125-1133. Partridge, T.C., Kerr, S.J., Metcalfe, S.E., Scott, L., Vogel, J.C., 1993: The Pretoria Saltpan: A 200,000 year South African lacustrine sequence. Palaeogeography, Palaeoclimatology, Palaeoecology, 101, 317-337. Scott, L. and Thackeray, J.F., 1987: Multivariate analysis of late Pleistocene and Holocene pollen spectra from Wonderkrater, Transvaal, South Africa. South African Journal of Science, 83, 93- 98. Talma, A.S. and Vogel, J.C., 1992: Late Quaternary palaeotemperatures derived from a speleotherm from Cango Caves, Cape Province, South Africa, Quaternary Research, 37, 203-213. Vogel, J.C., 1983. Isotopic evidence for past climates and vegetation of southern Africa. Bothalia 14, 391-394.

Evans, M. Y.

2009-04-01

28

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

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

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

2014-01-01

29

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

30

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

31

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

USGS Publications Warehouse

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

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

2007-01-01

32

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

NASA Astrophysics Data System (ADS)

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.

Fragalà, Federico A.; Parkin, Geoff

2010-07-01

33

Late Quaternary carbonate deposition at the bottom of the world  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

34

Alluvial fan response to climatic change: Insights from numerical modeling (Invited)  

Microsoft Academic Search

Alluvial fans in the western U.S. exhibit a regionally correlative sequence of Plio-Quaternary deposits. Cosmogenic and U-series dating has greatly improved the age control on these deposits and their associated terraces and generally strengthened the case for aggradation during humid-to-arid transitions. Still, the linkages between climate change, upland basin response, and alluvial fan response are not well constrained. Fans may

J. D. Pelletier

2009-01-01

35

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

Microsoft Academic Search

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

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

2008-01-01

36

Fracture Detection in Alluvial Fan Deposits Using Near-Surface Seismic Reflection Techniques  

NASA Astrophysics Data System (ADS)

In this study we document the observation of probable extensive shallow vertical fracture systems in unprocessed 2-D source gathers from near-surface seismic reflection surveys conducted over unconsolidated materials in alluvial fans environments. Mapping of fracture and fault systems within the sedimentary sections at hydrocarbon exploration scales has become common practice. This is due to the advent of post-stack attribute analysis of 3-D seismic images worldwide. However, examples of fracture detection and imaging in the near-surface are currently lacking in the literature. In addition, examples of fracture detection and mapping in the pre-stack domain are also lacking. In this study, unprocessed seismic source gathers from very high-resolution reflection surveys over alluvial fan deposits in tectonically active areas appear to display distinct patterns of amplitude drop off, geometrically similar to patterns expected for vertical fracture systems. The patterns can also be extracted by attribute analysis using techniques such as envelope and coherency analyses. Simple standard processing steps such as trace editing, muting, and bandpass filtering enhance interpretability. The patterns appear to be consistent and spatially fixed in the subsurface from source location to source location. These are observed in areas of obvious recent local large-scale fault movement. Examples are given from two areas, eastern Queen Valley in California and eastern Fish Lake Valley in Nevada. The stratigraphic and sedimentation patterns are quite complicated in both areas, and sediment characteristics vary considerably between sites. The surface sediments in the Queen Valley case are, in general, much coarser with many more boulder-sized clasts in the shallow subsurface. The seismic source consisted of a 30-06 rifle fired downhole at a depth of 0.5m. While the boulders interfered with seismic source operations, the record quality was excellent. The alluvial materials, especially those in Fish Lake Valley, are also probably unsaturated due to the desert environment and long-term, historic, upper watershed management by miners and ranchers. The unsaturated nature of the sediments probably contributes to the seismic detectability of the features. Other non-geological explanations for the observed amplitude features are possible, including aliasing effects, display artifacts, etc. However, the data are highly oversampled in both time and space, and the features appear in different types of displays. They are not observable in standard variable area/wiggle trace seismic displays traditionally used for displaying field records. Wider-scale mapping of these features would be an important contribution in studies of off-fault tectonic deformation, alluvial fan development, unsaturated flow, and near-surface hydrological systems in tectonically active areas.

Black, R. A.; Miller, B.

2012-12-01

37

Nearshore and alluvial facies in the Sant Llorenç del Munt depositional system: recognition and development  

NASA Astrophysics Data System (ADS)

The Eocene Sant Llorenç del Munt fan-delta complex forms a part of the coarse-grained foreland basin fill of the southeastern margin of the Ebro Basin. It was sourced from the rising Catalan Coastal Range in the SE and shows an overall northwesterly progradation during a time period of approximately six million years. Coarse clastic deposits (coarse sands and gravels) dominated this fan delta, whereas finer-grained sands, silts, and muds were deposited laterally off active sedimentation sites or in the more marine area. Depositional processes were clearly influenced by the high sediment input, giving a dominance of sediment gravity flow deposits. The sediments studied have been grouped into four distinct facies belts including coastal plain, proximal fan-delta front, distal fan-delta front and fan-delta slope sediments, respectively. The facies belts combine to form the nearshore and coastal alluvial reaches of the fan-delta system, developed during a transgressive phase lasting some 50,000 years.

Rasmussen, H.

2000-12-01

38

Digital data sets that describe aquifer characteristics of the alluvial and terrace deposits along the North Canadian River from Oklahoma City to Eufaula Lake in east-central Oklahoma  

USGS Publications Warehouse

ARC/INFO export and nonproprietary format files This diskette contains digitized aquifer boundaries and maps of of hydraulic conductivity, recharge, and ground-water level elevation contours for the alluvial and terrace deposits along the North Canadian River from Oklahoma City to Eufaula Lake in east-central Oklahoma. Ground water in 710 square miles of Quaternary-age alluvial and terrace deposits along the North Canadian River is an important source of water for irrigation, industrial, municipal, stock, and domestic supplies. The aquifer, composed of alluvial and terrace deposits, consists of sand, silt, clay, and gravel. The aquifer is underlain and in hydraulic connection with the upper zone of the Permian-age Garber-Wellington aquifer and the Pennsylvanian-age Ada-Vamoosa aquifer. Most of the lines in the four digital data sets were digitized from a published ground-water modeling report but portions of the aquifer boundary data set was extracted from published digital geologic data sets. Ground-water flow models are numerical representations that simplify and aggregate natural systems. Models are not unique; different combinations of aquifer characteristics may produce similar results. Therefore, values of hydraulic conductivity and recharge used in the model and presented in this data set are not precise, but are within a reasonable range when compared to independently collected data.

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

1997-01-01

39

The tectonic deformation of Quaternary deposits within the Kleszczów Graben, central Poland  

NASA Astrophysics Data System (ADS)

Three, well recognizable structural stages can be observed within the Kleszczów Graben (Central Poland). They are divided by angular discordances. The Valachian stage consists of strongly folded and faulted deposits of Miocene age. The Belchatów stage consists both of Pliocene and Quaternary deposits. The last stage dates back to the beginning of the Drenthe-Warthe interglacial. The tectonic origin or Quaternary deformation (folding) of the Belchatovian age seems rather unquestionable. In the uppermost structural stage only some glaciotectonic deformations can be observed.

Krzyszkowski, Dariusz

1989-07-01

40

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

USGS Publications Warehouse

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

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

1997-01-01

41

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

USGS Publications Warehouse

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

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

2013-01-01

42

Fourier grain shape analysis: a means for correlating alluvial deposits at the Nevada Test Site  

Microsoft Academic Search

Quartz sand derived from alluvial fans that drain different lithologies at the Nevada Test Site can be distinguished on the basis of grain shape as described by the Fourier series in closed form. Specifically, we examined tuff units from the Piapi Canyon and Indian Trail Formations as well as carbonate-bearing clastic units from the Eleana Formation. Discrimiation between rock types

B. T. Grothaus; G. L. Hage

1978-01-01

43

Stratigraphy and chronology of late Quaternary andesitic tephra deposits, Tongariro Volcanic Centre, New Zealand  

Microsoft Academic Search

A stratigraphy and chronology of andesitic tephras erupted from Mt Ruapehu, and other volcanoes of Tongariro Volcanic Centre, is constructed from the tephra record preserved on the southeastern Mt Ruapehu ring plain. Here, tephras of late Quaternary age (c. 22,500 years B.P. to present) are found interbedded with local laharic and fluvial deposits, and with distal rhyolitic tephras from Taupo

S. L. Donoghue; V. E. Neall; A. S. Palmer

1995-01-01

44

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

E-print Network

Quaternary deposits and landscape evolution of the central Blue Ridge of Virginia L. Scott Eatona,*, Benjamin A. Morganb , R. Craig Kochelc , Alan D. Howardd a Department of Geology and Environmental Science. Scott Eaton), bmorgan@usgs.gov (B.A. Morgan), kochel@bucknell.edu (R. Craig Kochel). www

Eaton, L. Scott

45

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

E-print Network

Late Quaternary deposition and facies model for karstic Lake Estanya (North-eastern Spain) MARIO sedimentary infill comprising: (i) a `basal unit', seismically transparent and restricted to the depocentres techniques. The chronological model for the sediment sequence is based on 17 accelerator mass spectrometry 14

Gilli, Adrian

46

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

NASA Astrophysics Data System (ADS)

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.

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

2012-06-01

47

Plio-Quaternary seismic stratigraphy and depositional history in the Ulleung Basin, East Sea  

NASA Astrophysics Data System (ADS)

Analysis of multi-channel seismic data from the Ulleung basin reveals that Plio-Quaternary sequence in the area consists of nine stacked sedimentary units bounded by erosional unconformities. On the southern slope, these units are acoustically characterized by chaotic seismic facies without distinct internal reflections, interpreted as mass-transport deposits. Toward the basin floor, the sedimentary units are defined by well-stratified facies with good continuity and strong amplitude, interpreted as turbidite/hemipelagic sediments. The seismic facies distribution suggests that deposition of Plio-Quaternary sediments in the area was controlled mainly by tectonic effects associated with sea-level fluctuations. During Pliocene, sedimentation was mainly controlled by tectonic movements related to the back-arc closure of the East Sea. The back-arc closure that began in the Miocene caused compressional deformation along the southern margin of the Ulleung Basin, resulting in regional uplift which continued until the Pliocene. Large amounts of sediments, eroded from the uplifted crustal blocks, were supplied to the basin, forming Unit 1 which mainly consists of mass-transport deposits. During the Quaternary, sea-level fluctuations resulted in stacked sedimentary units (2 to 9) consisting of mass-transport deposits, formed during sea-level fall and lowstands, and thin hemipelagic/turbidite sediments, deposited during sea-level rise and highstands.

Yoo, Dong-Geun; Kang, Nyeon-Keon; Yi, Bo-Yeon; Kim, Seong-Pil

2014-05-01

48

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

Microsoft Academic Search

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

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

1998-01-01

49

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

E-print Network

Late Quaternary eolian dust in surficial deposits of a Colorado Plateau grassland: Controls sandy deposits that support grass and shrub communities. These deposits also contain eolian dust, especially in paleosols. Eolian dust in these deposits is indicated by several mineralogic and chemical

Ahmad, Sajjad

50

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

USGS Publications Warehouse

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

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

2011-01-01

51

Sedimentary environment and sequence stratigraphy of the late Quaternary deposits in the central Yellow Sea  

NASA Astrophysics Data System (ADS)

In the central Yellow Sea, approximately 52,600 line-km of Chirp seismic profiles and 5,060 line-km of Sparker seismic profiles were used to define the sedimentary environments and to investigate the sequence stratigraphy of the late Quaternary deposits. On the basis of topography, depth, formation of deposition, and seismic facies, the central Yellow Sea are classified into three sedimentary environments: (1) a various scale sand ridges/waves and mud belt (the western inner-shelf of the Korean Peninsula), (2) recent- and paleo-channels, erosional and broad surface (the center of the Yellow Sea), and (3) prodelta mud patch (the eastern offshore of China). According to correlation of high-resolution seismic data and sediment cores in the central Yellow Sea, the late Quaternary deposits in the central Yellow Sea are divided into five distinctive sedimentary units (units CY1~5), consisting of two depositional sequences that can be defined as erosional and disconformable strata. The major depositional processes and sediment dispersal systems during the late Quaternary in the central Yellow Sea are: (1) regressive estuarine/deltaic deposits (unit CY1), (2) transgressive incised channel fill (unit CY2), (3) transgressive sand sheet (unit CY3), (4) transgressive sand ridges (unit CY4), and (5) prodelta/recent mud (unit CY5). The depositional sequences follow the general concepts of sequence stratigraphy very well. Lower sequence (DI) correspond to the falling stage systems tract regarded as regressive estuarine or deltaic deposits (unit CY1), whereas upper sequence (DII) consists of a set of the transgressive (units CY2, CY3, and CY4) and highstand systems tract (unit CY5) formed since the last-glacial period.

Lee, G.; Yoo, D.; Kim, D. C.; Kim, S.; Choi, H.; Yi, H.

2013-12-01

52

LATE QUATERNARY GLACIERS AND GLACIAL DEPOSITS INER, Attila1, ZREDA, Marek2, BAYARI, Serdar1, and SARIKAYA, M. Akif1, (1) Dept. of Geological Engineer-  

E-print Network

LATE QUATERNARY GLACIERS AND GLACIAL DEPOSITS OF TURKEY Ã?INER, Attila1, ZREDA, Marek2, BAYARI glaciations. Citation: Ã?iner, Attila, Marek Zreda, Serdar Bayari and Akif M. Sarikaya, 2003, Late Quaternary

Zreda, Marek

53

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

NASA Astrophysics Data System (ADS)

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

Coetzee, Louise; Brink, James S.

2003-03-01

54

Depositional environments of quaternary peats, Yukon Delta, Alaska  

SciTech Connect

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

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

1980-01-01

55

A silicified bird from Quaternary hot spring deposits  

Microsoft Academic Search

The first avian fossil recovered from high-temperature hot spring deposits is a three-dimensional external body mould of an American coot (Fulica americana) from Holocene sinters of Yellowstone National Park, Wyoming, USA. Silica encrustation of the carcass, feathers and colonizing microbial communities occurred within days of death and before substantial soft tissue degradation, allowing preservation of gross body morphology, which is

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

2005-01-01

56

Late Quaternary depositional history of Alaskan Beaufort Shelf  

Microsoft Academic Search

Diverse nonmarine and shallow marine deposits blanketing the coastal plain and continental shelf of northern Alaska are known collectively as the Gubik Formation. In the Beaufort coastal region between Barrow and Prudhoe Bay and along the Chukchi coastline southwest of Barrow, five distinct marine subunits have been recognized with the Gubik, ranging in age from middle Pliocene to late Pleistocene.

Dinter

1985-01-01

57

A silicified bird from Quaternary hot spring deposits.  

PubMed

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

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

2005-05-01

58

A silicified bird from Quaternary hot spring deposits  

PubMed Central

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

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

2005-01-01

59

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

60

Quaternary geology, tectonics and distribution of palaeo- and present fluvio\\/glacio lacustrine deposits in Ladakh, NW Indian Himalaya—a study based on field observations  

Microsoft Academic Search

The Ladakh region of the northwestern Indian Himalaya is rich in Quaternary deposits but it has not received much attention. Previous Quaternary research in the region has focused on the glacial sequences and only some scattered data of the lacustrine deposits are available. This article addresses the reconstruction of the palaeo-lacustrine deposits and the present-day lakes and their distribution in

Binita Phartiyal; Anupam Sharma; Rajeev Upadhyay; Ram-Awatar; Anshu K. Sinha

2005-01-01

61

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

SciTech Connect

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

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

1999-09-01

62

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

NASA Astrophysics Data System (ADS)

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

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

2005-12-01

63

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

USGS Publications Warehouse

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

Hupp, C.R.; Simon, A.

1991-01-01

64

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

NASA Astrophysics Data System (ADS)

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

Chakraborty, Partha Pratim; Paul, Pritam

2014-09-01

65

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

66

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

USGS Publications Warehouse

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

Harrelson, Larry G.; Addison, Adrian D.

2006-01-01

67

Isopach map showing Quaternary deposits in the Gulf of Santa Catalina area, California  

USGS Publications Warehouse

The Gulf of Santa Catalina is part of the California Continental Borderand, an active transform margin characterized by narrow shelves, steep slopes, and deep closed basin separated by shallow banks and islands. The Gulf of Santa Catalina extend from Point Fermin south to San Diego. It is bounded on the west by prominent bedrock ridges, 30 to 45 km offshore, compromising Santa Catalina Island and Thirtymile Bank. The predominant structural grain within the Gulf of Santa Catalina trends northwesterly. Two major fault zones bound a relatively undeformed structural block, the Catalina block (Clarke and others, 1983). The Newport-Inglewood-Rose Canyon Fault Zone forms the northeast boundary of the Catalina block, and the Palos Verdes Hills-Coronafo Bank Fault Zone forms the southwest boundary (Figure 1). Both of these fault zones are characterized by discontinuous, right-stepping en echelon faults and associated folds. Major structural and physiographic features within and bounding the Catalina block are compatible with wrench-style tectonism (Harding, 1973; Wilcox and others, 1973; Nardin and Henyey, 1978). The distribution of seismicity, along with geophysical evidence showing local displacement of sea floor and Holocene deposits, indicate that Newport-Inglewood, Palos Verdes Hills, and subsidiary faults are active (Clarke and others, 1983). The distribution of Quaternary sediments (Pleistocene and Holocene) off the coast of southern California provides insight into recent sedimentation patterns and recency of faulting and tectonic deformation. This report focuses on the distribution of Quaternary sediments, particularly in the shelf and upper slop areas, the sources of detrial sediment, and depositional environments of Holocene as well as relict deposits.

McCrory, Patricia A.

1993-01-01

68

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)

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.

Henchiri, Mohsen

2014-02-01

69

Tidal signatures in Neogene to Quaternary mixed deposits of southern Italy straits and bays  

NASA Astrophysics Data System (ADS)

Some of the Neogene to Quaternary sedimentary successions cropping out in the southern Italy orogenic belt exhibit distinct stratigraphic intervals of mixed, silici-bioclastic arenites. These deposits represent bay- and strait-fill successions that accumulated during tectonically-driven, rapid transgressions in peripheral marine basins of the central Mediterranean, experiencing microtidal conditions similar to those presently existing in the Mediterranean Sea. The Upper Miocene to Middle Pleistocene successions of Basilicata, Calabria and NE Sicily, show laterally-accreted, cross-strata of mixed composition, with the siliciclastic fraction derived from either sedimentary or metamorphic rocks and the bioclastic fraction produced by an in situ or near situ heterozoan factory. Tidal cyclicity of semi-diurnal and diurnal to monthly and yearly periodicities has been detected in the studied deposits, where tidal bundling is revealed by the rhythmic alternation of siliciclastic and bioclastic set of laminae, repeated according to different cycles. This rhythmic signature appears to be more evident where randomly-occurring processes, such as waves, storms and currents, were mitigated by engulfed or strait palaeo-settings. Palaeo-bays preserved short-term tidal cycles in shoreface to offshore-transition mixed deposits because hydrodynamically isolated from open marine conditions and therefore subjected to tidal influence only during fair-weather periods. On the contrary, palaeo-straits recorded tidal cyclicities of longer duration in deeper mixed deposits subjected to steady tidal currents.

Longhitano, Sergio G.; Chiarella, Domenico; Di Stefano, Agata; Messina, Carlo; Sabato, Luisa; Tropeano, Marcello

2012-11-01

70

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

71

Age of Tunica Hills (Louisiana-Mississippi) Quaternary fossiliferous creek deposits; Problems of radiocarbon dates and intermediate valley terraces in coastal plains  

NASA Astrophysics Data System (ADS)

Among numerous stream-valley terrace deposits of the Gulf and Atlantic coastal plains that occupy chronologically and spatially intermediate positions between the youngest coastwise (coast-parallel) Pleistocene surface and the present, active floodplain, those of the Tunica Hills seem to provide by far the best opportunity for radiometric dating. Earlier views on the age of the Little Bayou Sara creek alluvium, represented by a single, 8 to 10-m-thick unit, ranged between the last interglaciation and middle Holocene. Reexamination of these deposits in the Little Bayou Sara and adjacent valleys clearly suggests their Late Pleistocene (apparently Farmdalian Interstade) age. The majority of the 14 available dates from the Little Bayou Sara and Tunica Bayou valleys proved to be too young, due to postdepositinal contamination. Dates ranging between 33,720 and 25,965 yr B.P. came from samples thought to be uncontaminated. Plant and faunal elements with boreal affinities in the unique fossil assemblage appear to be relicts of a preceding, full-glacial period, as regarded by Brown (1938). The absence of colder climate taxa from the Wilcox Bluff flora on Bayou Sara is insufficient evidence for a suggested Sangamon Interglacial age of the flora, and the terrace stratigraphy holds no proof for that view either. Only a single, loess-mantled, constructional, Quaternary, valley-terrace surface is present in the area. A narrow, low, actively developing floodplain terrace along Little Bayou Sara, cut into the Pleistocene alluvial unit, is primarily erosional in origin and has no bearing on the age of that unit. The age of the Tunica Hills terrace unit may provide comparison for dating intermediate valley-terrace deposits in favorable coastal settings elsewhere.

Otvos, Ervin G.

1980-01-01

72

Forms and deposits of the continental quaternary of the Saharan margin of Eastern Maghreb (tentative synthesis)  

NASA Astrophysics Data System (ADS)

The Saharan margin of Eastern Maghreb extends from Aurès in the West to the Gulf of Gabès in the East. The Plio-Quaternary boundary is very complex in the West where it is characterized by the persistence of Tertiary sedimentation with the development of ablation forms, presence of crusts and the formation of a lacustrine system. This is followed by the development of accumulation forms during the Middle Pleistocene and mostly during the Upper Pleistocene to Holocene with contemporaneous diminution in the granulometry of the deposits. The evolution of gypcretes at the expense of calcretes crust suffered a partial reverse during the Middle Pleistocene. At this time a lacustrine phase settled down in the Algero-Tunisian Chotts (sebkhas). The end of the Middle-Pleistocene corresponded with a major climatic break with the disappearance of the calcretes. By the end of the Upper Pleistocene, the gypcretes attained their maximum development and latter disappeared during the Holocene.

Ballais, J. L.; Ouezdou, H. Ben

73

Some aspects on the variations in depositional flux of excess Thorium230 in the Central Indian basin during Late Quaternary  

Microsoft Academic Search

Examined in this paper is the tentative history of the depositional flux of230Thxs (the unsupported fraction of230Th scavenged from the overlying water column), for the Late Quaternary period from a sediment core of the Central Indian Basin\\u000a (CIB). The measured depositional flux of230Thxs is found substantially higher than that of the possible theoretical flux from the overlying water column. Historical

N. P. Sukumaran

1994-01-01

74

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

E-print Network

response of the water drainage system to climate change. D 2003 Elsevier B.V. All rights reserved. Keywords sediment supply during most of the Lisan period. During this period, a reduced sediment flux fed subaquatic, the water level rose to about 280 m b.s.l. around 15 kyears B.P. and prevailed in the early Holocene (10

Klinger, Yann

75

Sputtered tungsten-based ternary and quaternary layers for nanocrystalline diamond deposition.  

PubMed

Many of today's demanding applications require thin-film coatings with high hardness, toughness, and thermal stability. In many cases, coating thickness in the range 2-20 microm and low surface roughness are required. Diamond films meet many of the stated requirements, but their crystalline nature leads to a high surface roughness. Nanocrystalline diamond offers a smoother surface, but significant surface modification of the substrate is necessary for successful nanocrystalline diamond deposition and adhesion. A hybrid hard and tough material may be required for either the desired applications, or as a basis for nanocrystalline diamond film growth. One possibility is a composite system based on carbides or nitrides. Many binary carbides and nitrides offer one or more mentioned properties. By combining these binary compounds in a ternary or quaternary nanocrystalline system, we can tailor the material for a desired combination of properties. Here, we describe the results on the structural and mechanical properties of the coating systems composed of tungsten-chromium-carbide and/or nitride. These WC-Cr-(N) coatings are deposited using magnetron sputtering. The growth of adherent nanocrystalline diamond films by microwave plasma chemical vapor deposition has been demonstrated on these coatings. The WC-Cr-(N) and WC-Cr-(N)-NCD coatings are characterized with atomic force microscopy and SEM, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and nanoindentation. PMID:22905536

Walock, Michael J; Rahil, Issam; Zou, Yujiao; Imhoff, Luc; Catledge, Shane A; Nouveau, Corinne; Stanishevsky, Andrei V

2012-06-01

76

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

USGS Publications Warehouse

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

Gaggiani, N.G.

1984-01-01

77

Radiocarbon dating late Quaternary loess deposits using small terrestrial gastropod shells  

USGS Publications Warehouse

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

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

2013-01-01

78

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

USGS Publications Warehouse

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

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

2000-01-01

79

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

PubMed

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

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

2010-01-01

80

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

NASA Astrophysics Data System (ADS)

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

Mehl, A.; Blasi, A.; Zárate, M.

2012-12-01

81

Palaeoenvironmental dynamics inferred from late Quaternary permafrost deposits on Kurungnakh Island, Lena Delta, Northeast Siberia, Russia  

NASA Astrophysics Data System (ADS)

Late Quaternary palaeoenvironments of the Siberian Arctic were reconstructed by combining data from several fossil bioindicators (pollen, plant macro-fossils, ostracods, insects, and mammal bones) with sedimentological and cryolithological data from permafrost deposits. The record mirrors the environmental history of Beringia and covers glacial/interglacial and stadial/interstadial climate variations with a focus on the Middle Weichselian interstadial (50-32 kyr BP). The late Pleistocene to Holocene sequence on Kurungnakh Island reflects the development of periglacial landscapes under changing sedimentation regimes which were meandering fluvial during the Early Weichselian, colluvial or proluvial on gently inclined plaines during the Middle and Late Weichselian, and thermokarst-affected during the Holocene. Palaeoecological records indicate the existence of tundra-steppe vegetation under cold continental climate conditions during the Middle Weichselian interstadial. Due to sedimentation gaps in the sequence between 32 and 17 kyr BP and 17 and 8 kyr BP, the Late Weichselian stadial is incompletely represented in the studied outcrops. Nevertheless, by several palaeoecological indications arctic tundra-steppe vegetation under extremely cold-arid conditions prevailed during the late Pleistocene. The tundra-steppe disappeared completely due to lasting paludification during the Holocene. Initially subarctic shrub tundra formed, which later retreated in course of the late Holocene cooling.

Wetterich, Sebastian; Kuzmina, Svetlana; Andreev, Andrei A.; Kienast, Frank; Meyer, Hanno; Schirrmeister, Lutz; Kuznetsova, Tatyana; Sierralta, Melanie

2008-08-01

82

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

USGS Publications Warehouse

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

Reheis, M.C.

1992-01-01

83

Magnetic fabrics of slumped and normally deposited Quaternary sediments: Ursa Basin, northern Gulf of Mexico  

NASA Astrophysics Data System (ADS)

Late Quaternary sediment successions originating from the northern Gulf of Mexico continental slope show one of the highest sedimentation rates in the world. Poorly consolidated muds and mudstones younger than about 56 kyr were cored during IODP Expedition 308 at two sites (U1322 and U1324) in the Ursa Basin. High pore fluid overpressures define potential slope instability, with alternating formation of mass transport deposits (MTD) and intervening intervals of normal fallout sedimentation. In order to characterize differences in magnetic fabrics resulting from fallout and compaction, in particular the MTD-related deformation overprints, we have determined AMS ellipsoids for 250 specimens from Site U1322, for which a complete sampling record exists. The samples originate from eleven MTD's and from the interleaved normally sedimented layers. Reorientation of AMS principal axes was undertaken using the available tensor tool orientation data for the drill cores. AMS ellipsoid shapes in the MTD samples are mostly triaxial, showing with a tendency towards prolate shapes, except for the uppermost MTD 1. AMS ellipsoids derrived from the normally sedimented layers subjacent to the individual MTD's depict distinct oblate shapes. In the normally deposited sediments short axes of AMS ellipsoids are vertical, whereas in the MTD they are generally inclined in the direction of downslope transport. Our preliminary interpretation is that all these differences reflect a purely compactive history in the normally sedimented sections, and a combination of compaction and transport-related shearing in the MTD. Below 174 mbsf, in the deeper part of the cored section (MTD 6 - MTD 11), this distinction is present as well, but the database is generally smaller. A common feature of almost all MTD is the larger P-factor of AMS ellipsoids when compared with the subjacent normally deposited sediments. We relate this to intense sediment deformation: a feature that was probably imprinted onto the Ursa Basin muds and clays during downslope movement. The long AMS ellipsoid axes in both types of deposits seem to be linked to the initial eastward suspension transport off the axial zones of the Ursa and Southwest Pass Canyons located in the West. In summary, we show that magnetic fabrics of fine grained sediments in the Ursa Basins were capable to record the complete history of sediment transport, compaction and downslope movement and shearing.

Meissl, S.; Behrmann, J. H.; Franke, Ch.

2009-04-01

84

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

SciTech Connect

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

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

1993-04-01

85

Recurring deposition of eolian sand during the Late Quaternary in northeastern Colorado  

SciTech Connect

Three superposed units of late Quaternary eolian sand separated by buried soils and (or) clayey pond sediment are present along the southeast side of the South Platte River valley in northeastern Colorado. The oldest unit consists of at least 1.5 m of pale-brown sheet sand in which an A/Bw/C soil profile is developed; the solum is typically 45-55 cm thick. At Sterling, the oldest unit is overlain by organic-rich pond sediment that yielded a radiocarbon age of 9,010[+-]100 B.P. The middle unit consists of at least 0.4-2 m of pale-brown, massive to horizontally stratified sand. An A/C soil profile, with a light brownish-gray A horizon 13-25 cm thick, marks the upper limit of the unit. Radiocarbon ages from the Sterling site indicate that the middle unit was deposited between 9,010[+-]100 B.P., the age of underlying pond sediment, and 2,860[+-]60 B.P., the age of organic matter from the horizon at the top of the unit. The youngest unit consists of 0.5-8 m of pale-brown dune sand in which a faint A horizon (Valent series), typically 3-10 cm thick, has developed. Data from the cutbanks near Brush indicate that this unit was deposited about 1 ka or later. Organic matter from a buried A horizon beneath the youngest unit yielded a radiocarbon age of 1,380[+-]90 B.P. More importantly, however, the dated paleosol contained Plains Woodland ceramics, and Upper Republican ceramics were present just above the paleosol. The Plains Woodland culture was present in eastern Colorado between about 1.9 and 1 ka, and the Upper Republican culture between about 1 and 0.7 ka. The dune topography and soil development in the youngest unit near Brush are characteristic of large tracts of dune sand in northeastern Colorado, which suggests that the most recent episode of eolian activity may be younger than 1 ka.

Madole, R.F. (U.S. Geological Survey, Denver, CO (United States))

1992-01-01

86

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

Microsoft Academic Search

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

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

1995-01-01

87

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

Microsoft Academic Search

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

Storrs L. Olson

2008-01-01

88

Late Quaternary sea-level position: Evidence from Bahamian carbonate deposition and dissolution cycles  

Microsoft Academic Search

The Bahama Islands offer a unique opportunity to examine Late Quaternary sea-level position, as the island group places significant constraints on the time and space boundary conditions for climatic events recorded there. The Bahamian Archipelago extends as a series of large and small islands on shallow carbonate banks of various sizes for 1400km, across a climatic gradient wet in the

John E. Mylroie

2008-01-01

89

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

NASA Technical Reports Server (NTRS)

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.

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

1973-01-01

90

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

USGS Publications Warehouse

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

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

1992-01-01

91

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

92

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

SciTech Connect

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

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

1996-04-01

93

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

94

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

PubMed

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

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

2014-10-01

95

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

96

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

Federal Register 2010, 2011, 2012, 2013

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

2010-10-07

97

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

E-print Network

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

Luther, Douglas S.

98

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

SciTech Connect

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

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

1993-09-01

99

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

100

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

101

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

102

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

USGS Publications Warehouse

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

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

1987-01-01

103

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

USGS Publications Warehouse

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

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

2006-01-01

104

Unraveling fan-climate relationships: Milankovitch cyclicity in a Miocene alluvial fan (Teruel Basin, Spain)  

NASA Astrophysics Data System (ADS)

The role of climate change in alluvial fan sedimentation is often evident in geomorphological studies dealing with Quaternary successions, but remains hard to assess in the pre-Quaternary stratigraphic record, for which an additional obstacle is represented by detailed chronologies difficult to established within coarse clastic systems. The Teruel Basin (eastern Spain) is an extensional trough whose main tectonic activity spanned from late Oligocene to Pliocene times. Permanent internal drainage and a Mediterranean semi-arid climate made the basin and its sedimentary signatures highly sensitive to climate fluctuations, especially in terms of hydrological balance. Recent studies have proved orbital control on the development of facies sequences from low-energy, basinal settings in Teruel. In particular, high-resolution chronological and paleoclimatic information has been derived by orbital tuning of mudflat to ephemeral lake deposits in the Prado area (Villastar), linking basic facies rhythms to alternating, relatively humid/arid phases paced mainly by climatic precession. Clastic lobes from a coeval alluvial fan distally interfinger with this reference section. Stratigraphic relationships show how fan sedimentation patterns were also influenced by climate cyclicity. Highest volumes of debris transfer towards the distal mudflat repeatedly coincide with relatively humid periods. Furthermore, distal to medial fan outcrops feature prominent rhythms of distinct, alternating coarse and fine clastic packages. Such a highly organized architecture, unusual in alluvial fan successions, points to the influence of a rhythmic forcing mechanism which might have been climate variability, as evidenced by the adjacent reference section. Rather than on processes of sediment transport basinwards, climate change would have acted on sediment production and availability at the source, within the fan catchment.

Ventra, D.; Abels, H. A.; Hilgen, F. J.; de Boer, P. L.

2009-04-01

105

Ramiform aggregates in ash-fall deposits of Late Quaternary rhyolitic eruptions from Acigol Complex, central Anatolia, Turkey  

NASA Astrophysics Data System (ADS)

Direct observations have shown that most fine-grained particles fall from volcanic plumes as aggregates (Gilbert and Lane, 1994). For instance, fine-ash particles up to 50 µm fell mainly as aggregates from Vulcanian explosions and co-pyroclastic flow plumes from dome collapses in the eruption of Soufriére Hills Volcano, Montserrat, during the 1995-1999 period (Bonadonna et al., 2002a). Aggregation is a major influence on tephra fallout and on the characteristics of the associated deposits causing premature fallout of fine particles as responsible for polymodal grain-size distributions (Carey and Sigurdsson, 1982; Brazier et al., 1983; Bonadonna et al., 2002a) and anomalous thicknesses of deposits (Carey and Sigurdsson, 1982; Hildreth and Drake, 1992; Bonadonna et al., 2002b). Careful investigation of different types of ash aggregates is important for interpretation of the origin of pyroclastic deposits which can be critically important in hazard assessments (Brown et al., 2010). Therefore, incorporation of ash aggregates into simulations and numerical modelling for hazard assessments are crucial. However, too little is known about the dynamics of aggregation (Gilbert and Lane, 1994; Bonadonna et al., 2002b) therefore detailed studies on ash aggregates may improve the results of modelling and enable interpretations to be made of atmospheric conditions within past eruption plumes (Gilbert and Lane, 1994). We found a new type aggregate in ash-fall deposits of Late Quaternary rhyolitic explosions from Acigol Complex, Central Anatolia, Turkey. This type of aggregate has not been described previously. They resemble to the cylindrical aggregates which were reported by Scolamacchia et al. (2005) for the first time in the volcanological literature. However, our new type aggregates are in ramiform with branches interconnecting to a main tubular void on the long axis of the aggregates. The main voids have maximum diameter of 1 mm. The branches are tubular voids having diameters smaller than the main void on the long axis of the aggregate. These aggregates are found within 1-4 mm grain size intervals of deposits. The inner structures of aggregates were observed after X-ray tomography imaging. Probably the particles which were the initial nucleus for aggregation are twigs or plant stems. The existence of any carbonaceous material in the main void and grains-size distribution in aggregates will be presented after SEM and X-ray spectroscopy analysis.

Ersoy, Orkun; ?en, Erdal; At?c?, Gökhan; Aydar, Erkan; Tatar, Ä.°Lkan; Hamdi ?elik, H.

2010-05-01

106

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

USGS Publications Warehouse

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

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

2007-01-01

107

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

USGS Publications Warehouse

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

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

2007-01-01

108

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

USGS Publications Warehouse

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

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

1979-01-01

109

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

Microsoft Academic Search

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

Frederick Grady

1996-01-01

110

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

Microsoft Academic Search

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

G. Uenzelmann-Neben; H. Miller

2003-01-01

111

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

USGS Publications Warehouse

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

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

2009-01-01

112

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

USGS Publications Warehouse

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

Fournier, R.B.

1989-01-01

113

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

USGS Publications Warehouse

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

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

1996-01-01

114

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

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

115

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

NASA Astrophysics Data System (ADS)

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

Williams, Martin

2014-05-01

116

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

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

117

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

USGS Publications Warehouse

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

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

1995-01-01

118

Glacio-eustatic Control of Continental-Shallow Marine Cyclicity from Late Quaternary Deposits of the Southeastern Po Plain, Northern Italy  

NASA Astrophysics Data System (ADS)

Integrated sedimentological and micropaleontological (foraminifera, ostracods, pollens) investigations of a 173-m-long continuous core in the subsurface of the SE Po Plain reveal a cyclic facies distribution of continental to shallow-marine deposits. Radiometric and pollen data enable an age attribution of the study units to the late Middle Pleistocene-Holocene. Glacioeustasy appears to have exerted a major control on facies development, as documented by the close relationships between cyclic lithofacies patterns and the curves of eustatic fluctuation. Particularly, relative sea-level falls and lowstand phases were characterized by the development of alluvial sedimentation, whereas major transgressive pulses and subsequent highstands are reflected by abrupt shifts to paralic and shallow-marine deposits. This facies architecture is paralleled by a distinctive pollen distribution, reflecting the alternation of a glacial type of vegetation, dominated by Pinus and nonarboreal pollen types, with interglacial mixed deciduous broad-leaved forests.

Amorosi, Alessandro; Colalongo, Maria Luisa; Fusco, Fabio; Pasini, Giancarlo; Fiorini, Flavia

1999-07-01

119

Late Quaternary Depositional History and Anthropogenic Impacts of Western Long Island Sound, New York  

NASA Astrophysics Data System (ADS)

In June 2006, we surveyed the seafloor of western Long Island Sound with the R/V HUGH SHARP and collected multibeam bathymetry, chirp subbottom profiling, side-scan sonar imagery, and sediment samples (25 gravity cores, 11 multicores, and 10 grabs). In addition, 36 CTD hydrocast stations measured O, pH, alkalinity, trace metals, nutrients, Polonium-210, Lead-210, Thorium-234, organic carbon, and pigments. Continuous weather measurements, and water column properties using both CTD casts and a towed Scanfish were also carried out. Biological sampling included benthic grabs and plankton nets. The National Science Foundation under the "Opportunities to Enhance Diversity in the Geosciences" Program funded this one-week survey. Nine students from underrepresented groups in the geosciences and five P.I.'s participated in the field program. The major scientific objectives were to study the deglaciation of the Laurentide Ice Sheet and Holocene transgression of sea level to document age, sedimentation processes, and climate, and the impact of anthropogenic activities in the sediments, biota, and waters of the estuary. A deep (35 m) and narrow (< 1km) channel incised into bedrock characterizes the East River section of western Long Island Sound. In contrast, thick sedimentary deposits characterize the eastern part of the study area, 20 to 45 km east of New York City. Subbottom penetration reached in some instances 40 m, but is limited to less than 5 m where sediments are gas-charged. Four seismic sequences are imaged in the chirp records that we interpret to span the Last Glacial Maximum to Present: strong irregular erosional surfaces beneath parallel seismic reflectors are interpreted as glacial erosional surface and/or moraines, and as Glacial lake Connecticut sediments ~25 m thick, respectively. A thin veneer (<1 m) of acoustically transparent sediment is interpreted as recent deposits. It overlays a roughly 15 m thick unit interpreted as Holocene transgressive marine. Pipelines, cables, and shipwrecks were clearly imaged with the sonar data (multibeam bathymetry, sidescan imagery, and chirp profiles) and will be systematically inventoried.

McHugh, C. M.; Cormier, M.; Marchese, P.; Zheng, Y.; Stewart, G.; Acosta, V.; Bowman, A.; Cortes, A.; Leon, L.; Rosa, M.; Semple, D.; Thaker, N.; Vargas, W.; Williams, L.

2006-12-01

120

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

NASA Astrophysics Data System (ADS)

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

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

1995-06-01

121

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

NASA Astrophysics Data System (ADS)

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

Mead, Jim I.; Grady, Frederick

1996-01-01

122

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

USGS Publications Warehouse

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.

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

2007-01-01

123

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

USGS Publications Warehouse

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

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

1990-01-01

124

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

125

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

126

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

SciTech Connect

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

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

2005-08-26

127

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

128

Alluvial fan response to climatic change: Insights from numerical modeling (Invited)  

NASA Astrophysics Data System (ADS)

Alluvial fans in the western U.S. exhibit a regionally correlative sequence of Plio-Quaternary deposits. Cosmogenic and U-series dating has greatly improved the age control on these deposits and their associated terraces and generally strengthened the case for aggradation during humid-to-arid transitions. Still, the linkages between climate change, upland basin response, and alluvial fan response are not well constrained. Fans may fill and cut as a result of autogenetic processes/internal adjustments, changes in regional temperature (which controls snowmelt-induced flooding), changes in the frequency-size distribution of rainfall events, and/or changes in upslope vegetation. Here I describe the results of a numerical modeling study designed to better constrain the relationships between different end-member forcing mechanisms and the geologic record of alluvial fan deposits and terraces. The model solves the evolution of the fan topography using Exner's equation (conservation of mass) coupled with a nonlinear, threshold-controlled transport relation for sand and gravel. Bank retreat is modeled using an advection equation with a rate proportional to bank shear stress. I begin by considering the building of a fan under conditions of constant water and sediment supply. This simple system exhibits all of the complexity of fans developed under experimental conditions, and it provides insights into the mechanisms that control avulsions and it provides a baseline estimate for the within-fan relief that can result from autogenetic processes. Relationships between the magnitude and period of variations in the sediment-to-water ratio and the geomorphic response of fans are then discussed. I also consider the response of a coupled drainage basin-fan system to changes in climate, including the hydrologic and vegetation response of upland hillslopes. Fans can aggrade or incise in response to the same climatic event depending on the relief of the upstream drainage basin, which exerts a first-order control on sediment supply. The modeled fan response to changes in upstream vegetation, temperature, and precipitation are discussed can compared to available constraints on the timing and spatial distribution of fill and cut events on alluvial fans in the western U.S.

Pelletier, J. D.

2009-12-01

129

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

130

Fluvial response to late Quaternary climatic fluctuations, central Kobuk Valley, northwestern Alaska  

SciTech Connect

Much of northwestern Alaska remained unglaciated during the Pleistocene and thus offers a favorable setting for examining long-term records of high-latitude geological and biological change. Epiguruk, a large cut bank 3.5 km long and up to 36 m high on the Kobuk River south of the Brooks Range in eastern Beringia, exposes complex sedimentary successions representing cycles of upper quaternary alluviation and eolian sedimentation, downcutting, and soil formation. A rich record of plants and mammals is also preserved in the section. Deposits of fluvial channels and flood plains, eolian dunes, sand sheets, loess, and ponds, as well as organic soils (Histosols) are represented. Parallel-bedded fine sand and coarse silt couplets that commonly contain root structures, ripple cross-lamination, silt drapes are flood-plain sediments apparently deposited at the interface of fluvial and eolian environments. Multiple fluvial-to-eolian depositional sequences were caused by influx of eolian sediment to the river from intermittently active dune fields south of the Kobuk River. Alluviation in the Kobuk Valley was coeval with glaciation in the Brooks Range, whereas downcutting occurred during interstadials when dune stabilization limited sediment supply. The depositional model developed at Epiguruk may be useful in interpreting some of the widespread subhorizontally stratified late-glacial deposits of Europe and North America.

Ashley, G.M. (Rutgers Univ., New Brunswick, NJ (United States). Dept. of Geological Sciences); Hamilton, T.D. (U.S. Geological Survey, Anchorage, AK (United States))

1993-09-01

131

Giant landslide deposits in northwest Argentina  

SciTech Connect

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

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

1985-01-01

132

New identification and interpreted correlation, deposition, and significance of widespread Quaternary volcanic ash in the Sacramento-San Joaquin Delta, California  

NASA Astrophysics Data System (ADS)

We recently identified and correlated volcanic ash deposits buried in the Sacramento-San Joaquin Delta, California, with widespread ash in the Pacific Northwest. The Sacramento-San Joaquin Delta (herein, the Delta) contains stratigraphic records of climate change, sea level variability, and tectonic processes. It drains the interior of central and northern California, covers ~1400 km2, and is underlain by Quaternary deposits that are difficult to correlate and date. Tephrochronology provides maximal depositional ages and regional sequence stratigraphic correlations. Using Electron Microprobe analysis, we identified the Loleta (0.390 Ma), the Rockland (~0.575 Ma), and an unnamed volcanic ash (>0.78-<1.45 Ma) in ten samples from eight boreholes in the Delta drilled by the California Department of Water Resources. These tephra correlate chemostratigraphically with widespread volcanic ash found in California, Nevada, and the Pacific Northwest. Major and minor element compositions of glass shards from each tephra sample also indicate that these deposits derive from Cascade Range volcanic sources. The Rockland ash erupted from the southern Cascades near Lassen Peak, California. The Loleta ash is the distal equivalent of the Bend pumice tuff that probably originated from the Three Sisters volcanoes, Oregon. The unnamed, but chemically distinctive, ash bed also resembles Cascade -type tephra. The ash layers are identified in 27 boreholes in the northern to central Delta that we correlate using facies. Grain-size distributions and sedimentary structures are inconsistent within the tephra units and indicate variations in concentrations, deposition rates, and depositional environments. Much of the Delta tephra was transported and deposited in fluvial settings. The tephra deposits occur as three facies: 1) volcanic ash, in thick deposits containing silt- to sand-size glass shards; 2) pumice, in thick deposits of bedded and variably current-structured coarse-sand to pebble-size grains; and 3) volcanic ash, in thin deposits or mixed with non-volcanic sediments. The Rockland ash occurs as facies 1 and 2 in the Delta and indicates changing conditions during a large flood following eruption. The Loleta ash in the Delta occurs as facies 3 and represents lower energy depositional environments than facies 1 and 2. Ash is distinguished from non-volcanic silt with diatoms that can provide paleoenvironmental indicators. Both the Rockland and Loleta ash layers were deposited during sea-level lowstands. The Loleta ash is found at deeper depths in the central Delta than depths in the northern Delta where the older Rockland ash occurs owing to thickening of deposits in the central Delta, where organic-rich units may record sea level highstands. Rockland and Loleta ash layers in the subsurface Delta provide extensive new examples of these tephra and help to constrain depositional responses to Quaternary climate, sea level, and tectonic activity.

Maier, K. L.; Gatti, E.; Wan, E.; Ponti, D. J.; Tinsley, J. C.; Starratt, S. W.; Hillhouse, J.; Pagenkopp, M.; Olson, H. A.; Burtt, D.; Rosa, C. M.; Holzer, T. L.

2013-12-01

133

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

USGS Publications Warehouse

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

Robinson, Bret A.; Risch, Martin R.

2006-01-01

134

Pollen preservation and Quaternary environmental history in the southeastern United States  

SciTech Connect

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.

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

1980-01-01

135

Maps showing altitude of the potentiometric surface and changes in water levels of the alluvial aquifer in eastern Arkansas, Spring 1983  

USGS Publications Warehouse

The Mississippi River Alluvial Aquifer is a major source of water supply for irrigation in much of eastern Arkansas. Hydrologic maps of the potentiometric surface, water-level changes and depths to water in the aquifer, based on Spring 1983 measurements, are presented. The Mississippi River Alluvial Aquifer is comprised of Quaternary alluvial flood-plain and terrace deposits. The aquifer generally is partially-confined. Recharge to the aquifer is principally through precipitation and surface-water bodies. The potentiometric surface map indicates two cones of depression occurring in the aquifer beneath Arkansas, Poinsett, and Cross Counties as a result of heavy pumpage within these areas. A comparison of water-level data from 1982 and 1983 shows water levels in the aquifer generally decreasing in the area within the cones of depression. Water levels generally increased in the remainder of the area south and west of the White River, and along the Mississippi River. A map showing the depth to water below land surface indicates that water levels are generally shallowest near the Mississippi River and the Fall Line and deepest within the cone of depression. (USGS)

Edds, Joe; Fitzpatrick, Daniel J.

1984-01-01

136

Quaternary Studies  

NSDL National Science Digital Library

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

137

Generalized sorting profile of alluvial fans  

NASA Astrophysics Data System (ADS)

Alluvial rivers often exhibit self-similar gravel size distributions and abrupt gravel-sand transitions. Experiments suggest that these sorting patterns are established rapidly, but how—and how fast—this convergence occurs in the field is unknown. We examine the establishment of downstream sorting patterns in a kilometer-scale alluvial fan. The sharp transition from canyon to unconfined, channelized fan provides a well-defined boundary condition. The channel changes from deep and entrenched at the fan apex to shallow and depositional over a short distance, exhibiting nonequilibrium behavior. The resulting gravel-fining profile is not self-similar; the particle size distribution narrows until approximate equal mobility is achieved. Downfan, the gravel-sand transition appears to exhibit a self-similar form; field and laboratory data collapse when downstream distance is normalized by the location of the transition. Results suggest a generalized sorting profile for alluvial fans as a consequence of the threshold of motion and nonequilibrium channels.

Miller, Kimberly Litwin; Reitz, Meredith D.; Jerolmack, Douglas J.

2014-10-01

138

Neogene to Quaternary ash deposits in the Coastal Cordillera in northern Chile: Distal ashes from supereruptions in the Central Andes  

NASA Astrophysics Data System (ADS)

Silicic volcanic ash deposits investigated at 14 localities between 22° and 25°S in the Chilean Coastal Cordillera are found to be the distal ash fall from supereruptions in the Central Andean cordillera several hundreds of kilometers to the east. Depositional textures, modal composition and granulometry of the ashes and tuffs (the latter lithified by halite and gypsum under ultra-arid conditions) allow for a distinction between primary fallout/aeolian deposits (mean 4-5 ?, sorting 1.5-2 ?) and secondary deposits that formed by down wash from hill slopes during local rain fall. Primary volcanic components comprise two types of glass shards (with small stretched vesicles and coarse-walled with rounded to elliptic vesicles), and biotite.

Breitkreuz, Christoph; de Silva, Shanaka L.; Wilke, Hans G.; Pfänder, Jörg A.; Renno, Axel D.

2014-01-01

139

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

SciTech Connect

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.

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

1985-01-01

140

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

Microsoft Academic Search

The topic of this study is the effect of anthropogenic metals on the geochemical quality of urban soils. This is accomplished by comparing the metal contents and associations between two alluvial soils of the lower Mississippi River Delta, freshly deposited alluvial parent materials and alluvial soils collected from a nearby urban environment. Fresh alluvium samples (n=97) were collected from the

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

2000-01-01

141

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

NASA Astrophysics Data System (ADS)

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

Zembo, Irene

2010-01-01

142

Geometry of Quaternary Fault Scarps in the East Potrillo Mountains, Dona Ana County, New Mexico  

NASA Astrophysics Data System (ADS)

The East Potrillo Mountains are located just north of the Mexico-United States border in southwestern Dona Ana County, New Mexico, west of El Paso, Texas and southwest of Las Cruces, New Mexico. The structural features exposed in the East Potrillo Mountains formed in response to Laramide and Rio Grande Rift deformation and include middle Tertiary low-angle normal faults and late Tertiary high-angle normal faults. Along the range bounding faults are piedmont scarps that indicate continuous movement on the high-angle faults into the late Quaternary. The most dramatic of these is a north-striking fault scarp in the eastern foothills of the East Potrillo Mountains, a structure that may pose a major seismic hazard to El Paso and Las Cruces. Thus, the purpose of this study is to better understand the Quaternary deformation history of this structure using field and remote sensing observations. I will present measurements of the geometry of Quaternary deformation as constrained by displacements of geomorphic surfaces, including alluvial fans and fluvial deposits. To reproduce the fault scarp geometry, a number of profiles perpendicular to the scarp will be surveyed. From these profiles, estimations of fault scarp age will be made by using scarp-height-slope-angle relationships. The final outcome of this study will be an estimate of the average deformation rate on the fault and of when the last major earthquake occurred. These measurements are vital for constraining seismic hazards in the region.

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

2005-12-01

143

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

144

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

SciTech Connect

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

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

1994-12-31

145

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

SciTech Connect

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

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

1994-12-31

146

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

147

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

SciTech Connect

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

Birdseye, R.U.

1985-01-01

148

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

NASA Astrophysics Data System (ADS)

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

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

2009-04-01

149

Late Quaternary Evolution of the Northwest Florida Coast and Margin: Development of a Conceptual Model for Identifying and Characterizing Shelf Sediment Deposits  

Microsoft Academic Search

The objective of this investigation was the interpretation of the late Quaternary history of the northwest Florida margin and the development of a conceptual model for understanding the late Quaternary evolution of the regional coast and margin. The study area extends from the coastal Alabama-Florida border eastward to the mouth of the Ochlockonee River. Sea-level history, paleogeographic and coastal evolution

Jennifer Lynn Koch

2006-01-01

150

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

USGS Publications Warehouse

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

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

2003-01-01

151

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

152

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

153

Geochronology, geochemistry, and tectonic characterization of Quaternary large-volume travertine deposits in the southwestern United States and their implications for CO2 sequestration  

NASA Astrophysics Data System (ADS)

Travertines are freshwater carbonates that precipitate from carbonic groundwater due to the degassing of CO2. Travertine deposits are often situated along faults that serve as conduits for CO2-charged groundwater and their geochemistry often records mixing of deeply-derived fluids and volatiles with shallow meteoric water. Travertines are surface expressions of dynamic mantle processes related to the tectonic setting. This dissertation includes four chapters that focus on different aspects of travertine formation and their scientific value. They are excellent, although underestimated, diagnostic tools for climatology, hydrology, tectonics, geochemistry, geomicrobiology, and they can inform carbon sequestration models. Quaternary large-volume travertine deposits in New Mexico and Arizona occur in an extensional tectonic stress regime on the southeastern Colorado Plateau and along the Rio Grande rift. They accumulated above fault systems during episodes of high hydraulic head in confined aquifers, increased regional volcanic activity, and high input of mantle-derived volatiles such as CO 2 and He. Stable isotope and trace element geochemistry of travertines is controlled by groundwater geochemistry as well as the degassing of CO 2. The geochemical composition allows for distinguishing different travertine facies and evaluating past groundwater flow. The travertine deposits in New Mexico are interpreted to be extinct CO2 fields due to the large volumes that accumulated and in analogy to the travertine deposits in Arizona that are associated with an active CO2-gas field. Travertines are natural analogues for CO2 leakage along fault systems that bypassed regional cap rocks and they provide important insight into the migration of CO2 from a reservoir to the surface. The volume of travertine can be used to infer the integrated CO2 leakage along a fault system over geologic time. This leakage is estimated as: (1) CO2 that becomes fixed in CaCO3/travertine (tons of carbon converted into tons of carbonate), (2) the amount of CO2 that degassed into the atmosphere (twice the amount of (1), based on reaction stoichiometry), (3) dissolved CO 2 that is carried away with the water discharging from a spring (based on modern spring discharge and dissolved carbon content), and (4) CO 2 that escapes through the soil (based on modern soil flux measurements). Better understanding of integrated CO2 leakage and fault-related seal bypass is needed to design CO2 sequestration sites to effectively store anthropogenic CO2 in the subsurface.

Priewisch, Alexandra

154

Large Alluvial Fans on Mars  

NASA Technical Reports Server (NTRS)

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.

Moore, Jeffrey M.; Howard, Alan D.

2004-01-01

155

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

156

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

NASA Astrophysics Data System (ADS)

In the Denizli Basin (Turkey), located in the western Anatolian extensional province, travertine and tufa deposition has been an ongoing process for at least 600,000 years. Travertine bodies, which are 30 to 75 m thick and each covers areas of 1 to 34 km2, are up to 1 km3 in volume. Today, spring waters in this area have temperatures of 19 to 57 °C, are of the Ca-Mg-HCO3-SO4 type in the Pamukkale, Kelkaya and P?narba?? areas and the Ca-Mg-SO4-HCO3 type at Çukurba?. Thermal waters along the northern margin of the basin are generally hotter than those in the east-southeast and south. The ?18O and ?D values of the spring waters indicate a meteoric origin. The average temperatures of the hydrothermal systems in the Denizli Basin appear to have decreased from Pleistocene to Holocene. Travertine, which formed from the hotter water, is more widespread than the tufa that formed in the cooler spring waters. Deposition of the travertine, which formed largely on slopes, in depressions, and along fissure ridges (mostly on northern basin margins), was controlled by the interplay between various intrinsic and extrinsic parameters. The travertines are formed largely of calcite with only minor amounts of aragonite in some of the vertically banded, crystalline crust, raft and pisoid travertines found in some of the northern sites. The aragonitic samples, rich in Sr, are typically found around the spring orifices and along the central axis of the fissure ridges. The stable isotope values of the travertine found in the northwest and southeast parts of the basin are different. The ?13C values of the northern travertine deposits are more positive (3.7 to 11.7‰ VPBD) than those found in the south-southeast areas (- 4 to 5.8‰ VPDB). In contrast, the travertine and tufa in the southeastern areas have higher ?18O values (- 15.2 to - 7.8‰ VPDB) than those of the northern areas (- 16.6 to - 4.8‰ VPDB). Available evidence indicates that spring activity and associated travertine precipitation in the Denizli Basin were controlled largely by tectonic activity rather than by climatic conditions.

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

2013-08-01

157

Quaternary faults of west Texas  

Microsoft Academic Search

North- and northwest-striking intermontane basins and associated normal faults in West Texas and adjacent Chihuahua, Mexico, formed in response to Basin and Range tectonism that began about 24 Ma ago. Data on the precise ages of faulted and unfaulted Quaternary deposits are sparse. However, age estimates made on the basis of field stratigraphic relationships and the degree of calcic soil

E. W. Collins; J. A. Raney

1993-01-01

158

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

USGS Publications Warehouse

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

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

1980-01-01

159

Quaternary Geologic Map of Connecticut and Long Island Sound Basin  

USGS Publications Warehouse

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

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

2005-01-01

160

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

NASA Astrophysics Data System (ADS)

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

Alçiçek, Hülya; Varol, Baki; Özkul, Mehmet

2007-12-01

161

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

NASA Astrophysics Data System (ADS)

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 ?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 9% 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 f? and weathering effects. We discuss several independent methods for obtaining f? on individual samples that may be useful for future studies.

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

2010-08-01

162

Desert pavement characteristics on wadi terrace and alluvial fan surfaces: Wadi Al-Bih, U.A.E. and Oman  

Microsoft Academic Search

In arid mountain areas, the dating and correlation of alluvial depositional surfaces is often uncertain. Especially in regions where the geomorphology is not well known, surface modification by the development of soil and desert pavement may allow the correlation of geomorphic surfaces and estimation of at least their relative ages. Pleistocene wadi terraces and associated alluvial fans occur in Wadi

Asma Al-Farraj; Adrian M Harvey

2000-01-01

163

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

USGS Publications Warehouse

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.

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

1986-01-01

164

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

165

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

SciTech Connect

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

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

1991-03-01

166

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

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

167

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

168

Irish Quaternary Association (IQUA)  

NSDL National Science Digital Library

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

1969-12-31

169

The Alaska Quaternary Center  

NSDL National Science Digital Library

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

1969-12-31

170

Alluvial Fans and Megafans Along the Southern Side of the Alps  

NASA Astrophysics Data System (ADS)

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

Fontana, A.; Mozzi, P.

2011-12-01

171

Paleovalley systems: Insights from Quaternary analogs and experiments  

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

172

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

NASA Astrophysics Data System (ADS)

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

Gaines, E. P.

2013-12-01

173

Alluvial terraces on the Ionian coast of northern Calabria, southern Italy: Implications for tectonic and sea level controls  

NASA Astrophysics Data System (ADS)

In this paper we present the results of an integrated geomorphological, pedological and stratigraphical study carried out along the Ionian coast of northern Calabria (southern Italy). This area is characterised by the occurrence of five orders of alluvial terraces that are striking features of the landscape, where large and steep catchments debouch from the mountain front to the hilly coastal belt. Field investigations indicate that the deposits of all five terraces are suggestive of shallow gravel-bed braided streams. On the basis of the age of the Pleistocene substratum and morphostratigraphic correlation with marine terraces cropping out in the nearby areas, each order has been associated to specific marine oxygen isotope stages. Consequently, we focused on the interplay of allocyclic factors influencing stream aggradation/degradation. Soil features and other climatic proxies suggest that climate didn't play an important role with respect to tectonic and base-level changes in controlling fluvial dynamics. In particular, we recognised that during the middle Pleistocene the study area experienced a period of subaerial landscape modelling, as suggested by the thick and complex alluvial sequence of the highest terrace (T1). The onset of regional uplift marks a change in the geomorphic scenario, with tectonic and eustatically driven changes in base-level working together in causing switches in fluvial aggradational/erosional phases (T2-T5 terraces). Because of the uplift, river dissection occurred during phases of sea level fall, whereas aggradation phases occurred during periods of climate amelioration (sea level rise) just before highstands were attained. As a consequence, the stepped terraces in the study area reflect the interplay between tectonics (uplift) and sea level changes, in which terraces define episodes of relative sea level fall during the late Quaternary.

Robustelli, Gaetano; Lucà, Federica; Corbi, Fabio; Pelle, Teresa; Dramis, Francesco; Fubelli, Giandomenico; Scarciglia, Fabio; Muto, Francesco; Cugliari, Domenico

2009-05-01

174

Assessing the impact of Quaternary climate change on landscape evolution using luminescence dating  

NASA Astrophysics Data System (ADS)

Luminescence dating has undergone dramatic developments in the past decade, with significant improvements in dating sediment deposition using the optically stimulated luminescence (OSL) signals of quartz. This method determines the time since grains were heated or exposed to daylight during transport through the environment, using the concentration of trapped charge, which increases as a function of environmental radiation dose. Many of the previously serious limitations imposed by incomplete signal zeroing can now be overcome using single grain quartz OSL determinations. We introduce the timescales and processes available for luminescence applications, and provide details for three examples including low temperature thermochronology in New Zealand, the dating of sediments from glacial and fluvial contexts in northern Spain, and alluvial deposition in the Australian arid zone. In the Southern Alps of New Zealand, we have used the relatively low blocking temperature of the OSL signal to assess exhumation rates on timescales of glacial cycles, to assess the relative efficiencies of glacial and fluvial erosion in relief generation. In the Pyrenees in northern Spain we have dated glacial sediments and related outwash deposits to produce a record of ice advances over the last glacial cycle, and have extended the fluvial record into the sedimentary basins to the south in order to understand the climatic driving forces on incision and aggradation. In arid western New South Wales, a high density of sampling of late Pleistocene and Holocene alluvial sediments using single grain OSL provides a record of episodic fluvial activity. These examples demonstrate how quartz OSL can be used to assess the impact of Quaternary climate change on landscape evolution, in particular the magnitude and rates of geomorphic processes, and illustrate current practice and limitations besides future potential for this approach.

Rhodes, E. J.; Herman, F.; Marcén, C. S.

2009-12-01

175

Interpretation of floodplain pollen in alluvial sediments from an Arid Region*1  

NASA Astrophysics Data System (ADS)

Pollen was collected from modern alluvium and from the atmosphere to document the nature and amount of paleoenvironmental information reflected by alluvial pollen chronologies. Results indicate that pollen in alluvium is a homogeneous mixture derived almost entirely from the floodplain itself. The few pollen grains derived from nonfloodplain plant communities and preserved in alluvial sediments are so well mixed that their frequencies no longer reflect the geographic distribution of the specific plant communities in which they originated. In contrast, the abundance of alluvial pollen grains, derived from the major floodplain taxa (Chenopodiineae, Ambrosia type), varies with summer and winter climate. This annual variation is preserved in alluvial pollen assemblages through a combination of processes within sedimentation basins involving discontinuous deposition events and mechanical pollen degradation. The high-frequency, wide-amplitude pollen variance in alluvial pollen assemblages contrasts with the low-frequency, narrow-amplitude pollen variance in sediments of lakes and ponds. The slight geographic variance in alluvial pollen assemblages, in contrast to the large variance in soil pollen, allows use of alluvial pollen to infer climate throughout the watershed in which pollen is sampled.

Solomon, Allen M.; Blasing, T. J.; Solomon, J. A.

1982-07-01

176

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

USGS Publications Warehouse

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.

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

2009-01-01

177

Active erosion-deposition cycles in the hyperarid Atacama Desert of Northern Chile  

NASA Astrophysics Data System (ADS)

There is significant debate over the rates and types of fluvial activity at the Plio-Pleistocene boundary in the hyperarid Atacama Desert of Chile. To quantify fluvial processes and help resolve this debate, we measure terrestrial cosmogenic nuclide (TCN) (10Be and 21Ne) concentration depth profiles in three settings representing a chronosequence: (1) a late Pliocene alluvial fan representative of major regional deposits, (2) a modern, active channel and (3) an adjacent low terrace inset into the Pliocene alluvium. Late Pliocene deposits that are widely preserved in the region contain TCN profiles consistent with relatively rapid stripping of upland sediment at the Plio-Pleistocene boundary. Deposits inset into these Late Pliocene features record cut and fill cycles that rework sediment throughout the Quaternary. The TCN profile in the modern channel is best explained by sediment aggradation at 2.1 m Myr-1 during the last 250,000 yr. Similarly, the adjacent low terrace sediments contain TCN concentration profiles consistent with aggradation of 2.0 m Myr-1 over a period of 250,000-750,000 yr prior to the last 250,000 yr of stability. In summary, depth profiles of two TCNs provide constraints on the rates of sediment deposition, sources of sediment and transport history, as well as the subsequent exposure conditions of the sediment following deposition. Our results are consistent with early Quaternary initiation of hyperaridity for the region. During the Quaternary, winter precipitation events experienced at our sites' latitude (24°S) drive active erosion-deposition cycles. The northward migration of the subtropical front during Quaternary glacial cycles may have enhanced precipitation at 24°S, leading to more active fluvial processes during cooler periods.

Jungers, Matthew C.; Heimsath, Arjun M.; Amundson, Ronald; Balco, Greg; Shuster, David; Chong, Guillermo

2013-06-01

178

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

NASA Astrophysics Data System (ADS)

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).

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

2013-12-01

179

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

E-print Network

and the linked, northeast-striking Can~on Rojo normal fault. The length of ground rupture and amountLate quaternary activity of the Laguna Salada fault in northern Baja California, Mexico Karl J Thomas K. Rockwell ABSTRACT Faulted alluvial fans and bajadas along the central Laguna Salada fault zone

Mueller, Karl

180

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

Microsoft Academic Search

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

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

2004-01-01

181

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

USGS Publications Warehouse

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.

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

1992-01-01

182

The morphology of alluvial rivers  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

183

Quaternary and Geomorphology.  

ERIC Educational Resources Information Center

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

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

1983-01-01

184

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

SciTech Connect

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

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

1995-01-02

185

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

SciTech Connect

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

Dorr, J.A. Jr.

1983-08-01

186

Uplift of quaternary shorelines in eastern Patagonia: Darwin revisited  

Microsoft Academic Search

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

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

2011-01-01

187

Quaternary Stratigraphy and Paleogeography of the Galilee Coastal Plain, Israel  

Microsoft Academic Search

The Quaternary deposits in the Galilee coastal plain comprise alternating calcareous sandstone, red loam, dark clay, and uncemented sand. The calcareous sandstone in the lower part of the sequence represents a Pliocene to early Pleistocene marine transgression, and is covered unconformably by the late Quaternary sequence. The base of this sequence has an estimated age of ?500,000 yr. It is

Dorit Sivan; Gedaliahu Gvirtzman; Eytan Sass

1999-01-01

188

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

NASA Astrophysics Data System (ADS)

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

Davies, Neil S.; Gibling, Martin R.

2010-02-01

189

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)

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.

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

190

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

NASA Astrophysics Data System (ADS)

Late Pleistocene fluvial sediments that were deposited in a slowly sinking basin are now exposed as 30-50 m high incised vertical cliffs all along the Lower Narmada Valley in western India. The exposed fluvial deposits have been classified into two sediment packages, alluvial fan sediments overlain by alluvial plain sediments. The alluvial plain sequence has not been studied previously. It consists mainly of sands and silts and is dominated by overbank deposits. Occurrence of large scale bedforms in the alluvial plain sequence points to the existence of a large sand bed river in an alluvial plain setting. The major sedimentary facies in stratigraphic order include large channel fills, giant epsilon cross bedded strata, overbank fines occurring in horizontal, massive and undulatory stratified forms associated with crevasse splay and backswamp deposits, and a reddish brown palaeosol overlain by thinly stratified sands and silts at the top of the exposed sediment succession. Large sized channel fills occur at two stratigraphic levels, which are morphologically similar and are indicative of high rates of deposition and avulsion. The large channel fill structures and the giant epsilon cross bedded strata indicate a large single channel river that was consistently 10-15 m deep and about 70-80 m wide even during the dry seasons. These dimensions are larger than those of the present day Narmada River at low discharge levels. The overbank sediments indicate rapid deposition through frequent overbank floods and floodplain aggradation by a laterally shifting river. Available chronologic data suggests that the reddish brown palaeosol correlates with a regional phase of pedogenesis in the alluvial plain of Gujarat prior to the Last Glacial Maximum (LGM). The thinly stratified sands and silts overlying the palaeosol were deposited by a considerably depleted but perennial river during the arid phase of the Last Glacial Maximum. Overall, the alluvial plain sediments of the Lower Narmada valley, particularly those below the palaeosol, have been attributed to a hyper-avulsive large river with low sinuosity whose high discharge levels were determined primarily by a large catchment area further to the east and not by the semiarid climate prevailing in the Gujarat alluvial plain during the upper part of the Late Pleistocene. The study concludes that the Narmada River has maintained a large catchment at least since the last 100 ka, however, the river was characterised by a much bigger channel during much of the Late Pleistocene with discharge levels higher than the present day.

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

2005-01-01

191

Quaternary evolution of the Agri Valley, Southern Italy  

NASA Astrophysics Data System (ADS)

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

Caputo, R.; Bianca, M.

2003-04-01

192

Bedload transport in alluvial channels  

USGS Publications Warehouse

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

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

2003-01-01

193

Are North Slope surface alluvial fans pre-Holocene relicts?  

USGS Publications Warehouse

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

Reimnitz, Erk; Wolf, Stephen C.

1998-01-01

194

The geology and chronology of the Acheulean deposits in the Mieso area (East-Central Ethiopia).  

PubMed

This paper presents the Quaternary sequence of the Mieso area of Central-East Ethiopia, located in the piedmont between the SE Ethiopian Escarpment and the Main Ethiopian Rift-Afar Rift transition sector. In this region, a piedmont alluvial plain is terraced at +25 m above the two main fluvial courses, the Mieso and Yabdo Rivers. The piedmont sedimentary sequence is divided into three stratigraphic units separated by unconformities. Mieso Units I and II contain late Acheulean assemblages and a weakly consolidated alluvial sequence, consisting mainly of fine sediments with buried soils and, to a lesser degree, conglomerates. Palaeo-wetland areas were common in the alluvial plain, represented by patches of tufas, stromatolites and clays. At present, the piedmont alluvial surface is preserved mainly on a dark brown soil formed at the top of Unit II. Unit III corresponds to a fluvial deposit overlying Unit II, and is defined by sands, silty clays and gravels, including several Later Stone Age (LSA) occurrences. Three fine-grained tephra levels are interbedded in Unit I (tuffs TBI and TA) and II (tuff CB), and are usually spatially-constrained and reworked. Argon/argon ((40)Ar/(39)Ar) dating from tuff TA, an ash deposit preserved in a palustrine environment, yielded an age of 0.212 ± 0.016 Ma (millions of years ago). This date places the top of Unit I in the late Middle Pleistocene, with Acheulean sites below and above tuff TA. Regional correlations tentatively place the base of Unit I around the Early-Middle Pleistocene boundary, Unit II in the late Middle Pleistocene and within the Late Pleistocene, and the LSA occurrences of Unit III in the Late Pleistocene-Holocene. PMID:25440135

Benito-Calvo, Alfonso; Barfod, Dan N; McHenry, Lindsay J; de la Torre, Ignacio

2014-10-17

195

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

NASA Technical Reports Server (NTRS)

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

Farr, Tom G.; Chadwick, Oliver A.

1996-01-01

196

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

NASA Astrophysics Data System (ADS)

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

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

2009-04-01

197

Geometry and evolution of a syntectonic alluvial fan, Southern Pyrenees  

SciTech Connect

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

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

1993-02-01

198

Estimating the surface age of arid-zone alluvial fans using spaceborne radar data  

NASA Astrophysics Data System (ADS)

Alluvial fans constitute important recorders of tectonic and climatic signals. Thus, determining the age of alluvial deposits is a common and pivotal component in many quantitative studies of recent tectonic activity, past climatic variations and landscape evolution processes. In this study we build on the established relation between surface age and surface roughness and examine the use of radar backscatter data as a calibrated proxy for constraining the age of alluvial surfaces in such environments. This study was conducted in the hyper-arid environment of the southern Arava rift valley north of the Gulf of Aqaba. ALOS-PALSAR L-Band dual-polarized (i.e., HH, HV) data with different incidence angles (24°, 38°) and resolutions (6.25m, 12.5m) were examined for 11 alluvial surfaces, for which surface ages ranging from 5-160 ka were previously determined. As expected, radar backscatter in such low-relief hyper-arid desert environments responded primarily to SR at pixel-scales and below. Nonetheless, measured backscatter values for single pixels were found to be unsuitable proxies for surface age because of the natural variability in SR across alluvial units of a given age. Instead, we found the statistical properties of radar pixel populations within a given unit to be the most effective proxies for surface age. Our results show that the mean backscatter value within representativeROI's (region of interest) provided the best predictor for surface age: Lower mean backscatter values correlated well with older and smoother alluvial surfaces. The HHpolarized image with ~38° incidence angle and 6.25 m/pixel resolution allowed the best separation of surface ages. This radar-based approach allows us to quantitatively constrain the age of alluvial surfaces in the studied region at comparable uncertainty to that of "conventional" surface dating techniques commonly used.

Hetz, Guy; Mushkin, Amit; Blumberg, Dan G.; Baer, Gidi

2013-10-01

199

Quaternary Research Association  

NSDL National Science Digital Library

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

200

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

201

The interplay of eustasy, climate and human activity in the late Quaternary depositional evolution and sedimentary architecture of the Po Delta system  

Microsoft Academic Search

The late Pleistocene and Holocene environmental evolution and sequence stratigraphic architecture of the Po Delta region, Northern Italy, are examined. The study units record the depositional evolution from lowstand continental accumulation to marine transgression and highstand progradation. Interpretation of the high-resolution, three-dimension geological mapping of the central Po Delta area was framed within the evolution of the whole of the

Marco Stefani; Stefano Vincenzi

2005-01-01

202

Alluvial Diamond Resource Potential and Production Capacity Assessment of Ghana  

USGS Publications Warehouse

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

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

2010-01-01

203

International Union for Quaternary Research  

NSDL National Science Digital Library

The International Union for Quaternary Research (INQUA) discusses quaternary scientists' investigations "to interpret the changing world of the glacial ages and their impact on our planet's surface environments.". Researchers can find out about INQUA-funded projects, meetings, scientific commissions, and INQUA's two publicaions, Quaternary International, and Quaternary Perspectives.

1969-12-31

204

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

SciTech Connect

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

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

1999-04-28

205

Changes in the frequency, scale, and failing areas of latest Quaternary (<29.4 cal. ka B.P.) slope failures along the SW Ulleung Basin, East Sea (Japan Sea), inferred from depositional characters of densely dated turbidite successions  

NASA Astrophysics Data System (ADS)

The depositional characters of densely dated turbidite successions originating from the southwestern margin of the Ulleung Basin reveal changes in high-resolution frequency, failing areas, and relative volumes of slope failures over the past 29.4 cal. ka. Between 29.4 and 19.1 cal. ka B.P., various thin- to very thick-bedded turbidites accumulated at an average recurrence interval of ca. 605 years. After 19.1 cal. ka B.P., turbidites were deposited with an average recurrence interval of 3,183 years, and their thickness abruptly decreased upward. These features suggest that various-scale slope failures occurred frequently during the eustatic lowering of sea level, and the frequency and relative volumes of slope failures suddenly decreased after sea level began to rise. When sea level was lowest (20.0-19.1 cal. ka B.P.), successive stacks of very thick turbidites can most likely be ascribed to larger-volume mass failures. An upward change from muddy to sandy turbidites around 21.4 cal. ka B.P. suggests that the failing areas retrograded from the muddy upper-middle slope to the sandy uppermost slope when sea level was nearly at its lowest. Based on these findings together with published evidence, frequent mass failures between 29.4 and 19.1 cal. ka B.P. were plausibly triggered by earthquakes, in combination with reduced hydrostatic pressure that promoted gas-hydrate dissolution during the eustatic lowering of sea level. These data on the frequency, scale, failing areas, and triggering causes of slope failures along the southwestern margin over the past 29.4 cal. ka, not documented in earlier studies, provide invaluable information to better understand the basin-scale characters and occurrences of latest Quaternary slope failures in the Ulleung Basin.

Lee, Sang Hoon; Bahk, Jang J.; Kim, Han J.; Lee, Kyung E.; Jou, Hyeong T.; Suk, Bong C.

2010-04-01

206

Quaternary vertebrates from Greenland: A review  

NASA Astrophysics Data System (ADS)

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.

Bennike, Ole

207

Clarifying stages of alluvial fan evolution along the Sfakian piedmont, southern Crete: New evidence from analysis of post-incisive soils and OSL dating  

NASA Astrophysics Data System (ADS)

Analysis of fan sediments and post-incisive soils was combined with luminescence dating to re-assess Nemec and Postma's [Nemec, W., Postma, G., 1993. Quaternary alluvial fans in southwestern Crete: sedimentation processes and geomorphic evolution. In: Marzo, M., Puigdefábregas, C. (Eds.), Alluvial Sedimentation. Special Publication of the International Association of Sedimentologists, vol. 17, pp. 235-276] model of fan evolution on the Sfakian piedmont, southern Crete. Field mapping supports the assertion that sedimentation occurred in three developmental stages. Stage 1 sediments comprise angular debris flows forming small cone-like deposits; stage 2 fluvial gravels form large, relatively steep streamflow-dominated telescopic fans; and stage 3 sediments consist of coarse sieve-type alluvium, localised mudflows and hyperconcentrated flow deposits. Irrespective of gradient, fan surfaces are capped by post-incisive soils that form a chronosequence comprising remnant chromic luvisols. The most developed profiles, highest redness rating, and greatest concentrations of Fe d and magnetic minerals are associated with soils formed on stage 1 surfaces. The stage 2 and 3 soils record progressively lower redness rating, Fe d, and magnetic values, indicating that the stage 1 soils and fan surfaces formed first, followed by stage 2 and 3 soils and fan surfaces. Nanofossil data strongly suggest that stage 1 sedimentation commenced no earlier than the Early Pleistocene. Optically stimulated luminescence (OSL) results suggest that sedimentation responsible for stage 2 surfaces occurred between Marine Isotope Stage (MIS) 6 and MIS 2, while archaeological data indicate that stage 3 sedimentation is of Holocene age. The re-investigation of fan sediments and morphology corroborates the sedimentary and morphological elements of Nemec and Postma's model. The soil data support the model's assumptions that sedimentation was broadly synchronous across the piedmont and the locus of deposition progressively shifted away from the range-front zone. OSL dating suggests that previous age estimates assigned to fan stages 1 and 2 are too old. Climate appears to exert a fundamental control over fan development, with sedimentation occurring during cold stages and cold stage-interglacial transitions. Tectonic activity provides the relief required for fan development and controls fan incision. Local uplift resulted in variable rates of incision that culminated in differential fan segmentation across the piedmont.

Pope, Richard; Wilkinson, Keith; Skourtsos, Emmanuel; Triantaphyllou, Maria; Ferrier, Graham

2008-02-01

208

Sedimentology of high-stage flood deposits of the Tagus River, Central Spain  

NASA Astrophysics Data System (ADS)

This paper details the sedimentology of high-stage flood deposits, with the definition of sedimentary environments and their characteristic sequences, along two bedrock reaches of the Tagus River (Central Spain). High-stage flood deposits accumulated in bedrock canyons include slackwater flood deposits (SWD) and other types of deposits located at flow separation zones and associated with slow-moving flow (<1 m s -1). These flood deposits are common indirect indicators of flood stages used in palaeoflood studies for estimating the discharges associated with Quaternary floods. Depositional environments of flood deposits include (1) channel widening, (2) canyon expansion, (3) bedrock obstacles, and (4) backflooded areas along tributary streams. These flood deposits can be found associated with other non-fluvial environments, namely aeolian reworked and slope washflow facies. Channel widening, due to flood stage variations, comprises internal and external zones of the channel margins, and their characteristic sequences contain similar facies to those of alluvial floodplains. Canyon expansion environments favour vertical accretion of slackwater units and the development of flood deposit benches, which contain four sequences related to bench elevation and distance from the channel's main thread of flow. At the lee side of bedrock obstacles, characteristic sedimentary sequences are dominated by reverse flow structures (e.g. climbing ripples migrating upstream) due to eddies with a high sand concentration. Flood deposits located within tributary mouths contain typical sequences of reworked floodplain deposits. Backflooding of tributaries during flood stages produces deposition from suspension of sand, silt and clay within three sequences characterised by non-structure or parallel lamination and intense bioturbation. A better understanding of the flood deposit sequences may contribute to the characterisation of flood magnitudes and flood hydraulics and can also be applied to some ancient depositional environments.

Benito, Gerardo; Sánchez-Moya, Yolanda; Sopeña, Alfonso

2003-03-01

209

Spatio-temporal dynamics of nitrogen in river-alluvial aquifer systems affected by diffuse pollution from agricultural sources: Implications for the implementation of the Nitrates Directive  

NASA Astrophysics Data System (ADS)

SummaryReducing nitrate pollution from diffuse agricultural sources is the major environmental challenge in the two adjacent catchments of the Oja-Tirón and Zamaca rivers (La Rioja and Castilla y León, northern Spain). For this reason, part of their territory was designated a Nitrate Vulnerable Zone (NVZ) according to the Nitrates Directive. The Oja Alluvial Aquifer, the Tirón Alluvial Aquifer and their associated rivers are particularly vulnerable to nitrogen pollution due to the shallow water table, the high permeability of alluvial deposits, interconnections between the alluvial aquifers and surface waters and pressures from agriculture. To this end, nine sampling campaigns, organised on a semi-annual basis and focused on the rivers and alluvial aquifers of the two catchments, were carried out from April 2005 to April 2009. The main objectives of the study were: (1) to investigate the chemical forms of nitrogen in river-alluvial aquifer systems of the Oja-Tirón and Zamaca catchments, (2) to improve our understanding of the spatio-temporal patterns of nitrogen distribution in the alluvial aquifers and associated rivers by integrating hydrochemical data and hydrogeological and environmental parameters, (3) to estimate the amount of nitrogen exported from the rivers and alluvial aquifers to the River Ebro, and (4) to evaluate the suitability of the current method of designating NVZs in the area. High groundwater flow velocities in the upper alluvial zones favoured the advective transport of nitrate and generated a dilution effect. In these areas, inter-annual variations in nitrate concentrations were observed related to precipitation and N-input from agriculture. However, low flow velocities favoured processes of accumulation in the lower alluvial zones. Our results demonstrated that the entire alluvial surface was highly vulnerable, according to dynamics of the nitrogen in the river-alluvial aquifer systems being studied. The amount of nitrogen exported from these river-alluvial aquifer systems to the River Ebro was estimated at 2.4 ± 0.2 kt year -1. Findings from this investigation highlight the need to include the alluvial area corresponding to the Tirón aquifer as a NVZ, particularly as the Tirón sub-catchment provides more than half of the nitrogen exported from the River Tirón to the River Ebro. Based in these results, at least the entire alluvial surface in the study area should be considered a NVZ in order to address the recovery of water quality.

Arauzo, M.; Valladolid, M.; Martínez-Bastida, J. J.

2011-12-01

210

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

NASA Astrophysics Data System (ADS)

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

Mange, Maria A.; Otvos, Ervin G.

2005-12-01

211

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...

212

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...

213

Simulating Fine grained Alluvial Fan Sedimentation on Mars  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

214

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

NASA Astrophysics Data System (ADS)

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

Alçiçek, Hülya; Jiménez-Moreno, Gonzalo

2013-06-01

215

Quaternary evolution of the Gulf of ?zmit (NW Turkey): a sedimentary basin under control of the North Anatolian Fault Zone  

Microsoft Academic Search

The Quaternary evolution of the Gulf of Izmit, situated on the tectonically active North Anatolian Fault Zone (NAFZ), was investigated using seismic reflection, paleontologic, and sediment textural data. On the basis of seismic stratigraphic and sedimentologic-paleontologic interpretations, four depositional units were distinguished within the Plio-Quaternary sequence of the Gulf of Izmit. According to these data, Plio-Quaternary deposits supplied from the

Erdal Dolu; Erkan Gökasan; Engin Meriç; Mustafa Ergin; Tolga Görüm; Hüseyin Tur; Berkan Ecevitoglu; Niyazi Avsar; Muhittin Görmüs; Fatmagül Batuk; Bugser Tok; Oktay Çetin

2007-01-01

216

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

NASA Astrophysics Data System (ADS)

The complexity of alluvial fan depositional systems makes detailed characterization of their heterogeneity difficult, yet such detailed characterizations are commonly needed for construction of reliable groundwater models. The transition probability geostatistical approach provides a means to quantify the distribution of hydrofacies in the subsurface. However, a key assumption used in this and other geostatistical approaches is that of stationarity. Stratigraphic character often varies within a deposit, making this assumption tenuous. Sequence stratigraphic concepts help us overcome this problem by dividing the strata into units that have similar properties, called sequences, based on recognition of unconformities and timelines within the sedimentary record. By using transition probability geostatistics in a sequence stratigraphic framework, realizations of the alluvial fan facies distributions are produced that account for multi-scale heterogeneity represented by spatially variable hydrofacies within sequences, laterally extensive aquitard units at sequence boundaries, and spatial variability attributes that are unique to each sequence. Incorporation of conceptual geologic information into the Markov chain model of transition probability also allows development of improved coregionalization models in the typically undersampled, lateral directions. The Kings River Alluvial Fan, located southeast of Fresno, California, provides an excellent test case for the approach. Several sequences within the alluvial fan were produced by outwash from Pleistocene glaciations in the Sierra Nevada Mountains. Five sequences, separated by large-scale (>3 km laterally), mature, red paleosols, were recognized in the alluvial fan strata. Markov chain models were developed to characterize the intermediate-scale (0.3-1.5 km laterally) distribution of hydrofacies in each individual sequence and to characterize the spatial distribution of paleosols. Separate conditional simulation of each sequence provides realizations of hydrofacies distributions. Combining these five sequence realizations into a single realization, then overprinting the paleosol distributions onto this realization, produced a geologically plausible image of the subsurface facies distribution that accounts for non-stationarity between stratigraphic units. Importantly, the resulting realization preserves the lateral continuity of the large-scale sequence boundary paleosols, which are potentially important confining beds within the fan deposits. Additionally, facies juxtaposition tendencies (e.g. upward fining tendencies of the fluvial deposits) and known directional anisotropy and dip of units within the fan are preserved in the realization. These physical attributes, accurately reproduced by the geostatistical method, are essential components of the overall hydrogeologic character of the alluvial fan.

Weissmann, G. S.; Fogg, G. E.

1999-12-01

217

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

218

Downstream effects of dams on alluvial rivers  

Microsoft Academic Search

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

G. P. Williams; M. G. Wolman

1985-01-01

219

Interaction of fine sediment with alluvial streambeds  

USGS Publications Warehouse

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

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

1989-01-01

220

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

NASA Astrophysics Data System (ADS)

Alluvial fan stratigraphic sequences record fire history in charcoal-rich deposits and buried burned soil surfaces. Deposit characteristics provide information about the magnitude of fire-related sedimentation events and severity of associated fires, and radiocarbon-dating of charcoal establishes the timing of fires. Unlike lakes, alluvial fans are ubiquitous in mountain environments. Although alluvial-fan fire records lack the annual resolution of tree-ring records, compilation of data from many alluvial fan sites provides a statistical sample of fire timing and approximate severity that can be related to climate variations over centennial to millennial timescales. We examine alluvial fan records from xeric Pinus ponderosa-dominated forests of central Idaho, and compare them with similar records from cooler, high-elevation Pinus contorta-dominated forests of Yellowstone National Park. Identification of charcoal macrofossils from Idaho fan deposits limits inbuilt age errors in radiocarbon dating, and shows that similar forest compositions have existed over the last ca. 4000 years in the fan drainage basins. Limited data from ca. 4000-7000 yr ago suggest that Pinus ponderosa was either sparse or absent in the 4 basins represented. Large fire-related debris flows in both Idaho and Yellowstone indicate severe fires during the ca. 1050-750 cal yr BP Medieval Climatic Anomaly (MCA), which included widespread and severe western US droughts. Another such episode 2700-1600 cal yr BP is less prominent in the Idaho record. Numerous small, fire-induced sedimentation events in Idaho ca. 350-500 (Little Ice Age), 1200-1400, and 2800-3000 cal yr BP likely indicate frequent low- to mixed-severity fires, and coincide with indicators of generally cool, moist conditions in the western USA and North Atlantic, and with minimal fire activity in Yellowstone. We infer that these effectively wetter periods allow greater grass growth, fueling frequent surface fires in ponderosa forests, but limiting fires in general in the effectively wetter forests of Yellowstone. Maxima in dated small events may relate to significant droughts within these intervals, e.g. in the late AD 1500s, but widespread severe fires are not indicated. Alluvial-fan records add to data from other charcoal-based proxy records of fire that indicate the importance of centennial- to millennial-scale climate change in modulating fire activity and geomorphic response in conifer forests over the Holocene.

Pierce, J. L.; Meyer, G. A.

2004-12-01

221

Permafrost sequences on Kurungnakh Island, Lena Delta (NE Siberia, Russia) as key site of the late Quaternary environmental history of West Beringia  

Microsoft Academic Search

Late Quaternary permafrost sequences are widely distributed in the arctic lowlands of Siberia. Because the existence of permafrost has been sensitive to climate changes during the Quaternary past, such frozen deposits are regarded as an archive of palaeoenvironmental dynamics. Late Quaternary palaeoenvironments of the Siberian Arctic were reconstructed by combining data from several fossil bioindicators (pollen, plant macro-fossils, ostracods, insects,

S. Wetterich; S. Kuzmina; A. A. Andreev; F. Kienast; H. Meyer; L. Schirrmeister; T. Kuznetsova; M. Sierralta

2009-01-01

222

Quaternary Faunal Environments  

NSDL National Science Digital Library

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

Christopher Hill

223

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

224

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

PubMed

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

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

2014-11-15

225

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

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

226

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

227

Turkana Grits - a Cretaceous braided alluvial system in northern Kenya  

SciTech Connect

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

Handford, C.R.

1987-05-01

228

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

229

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

230

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

NASA Astrophysics Data System (ADS)

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

Latrubesse, E. M.

2012-12-01

231

CHANNEL EVOLUTION IN MODIFIED ALLUVIAL STREAMS.  

USGS Publications Warehouse

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

Simon, Andrew; Hupp, Cliff R.

1987-01-01

232

Macro-roughness model of bedrock-alluvial river morphodynamics  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

233

Effects of Quaternary Sea Level Cycles on Strontium in Seawater  

Microsoft Academic Search

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

Heather M Stoll; Daniel P Schrag

1998-01-01

234

Geomorphology, internal structure and evolution of alluvial fans at Motozintla, Chiapas, Mexico  

NASA Astrophysics Data System (ADS)

Alluvial fans and terraces develop in diverse regions responding to different tectonic and climatic conditions. The Motozintla basin is located in the State of Chiapas, southern Mexico and has an E-W orientation following the trace of the left-lateral Polochic Fault. The evolution of the Motozintla basin and the alluvial plain is related to several factors, such as fault movement, intense erosion by hydrometeorological events, and anthropogenic activity. This study presents the geomorphology of the alluvial plain that between the villages of Motozintla and Mazapa de Juárez exposes 31 alluvial fans, 5 hanging terraces and 13 ramps. Fourteen of these alluvial fans have been truncated by the Polochic fault, exposing maximum uplifts of ~ 12 m. The internal structure of truncated fans consists of single massive beds (monolithologic fans) or stacked beds (polygenetic fans). The fans' stratigraphy is made of debris flow deposits separated by paleosols and minor hyperconcentrated flows, fluviatile beds, and pyroclastic fall deposits. The reconstruction of the stratigraphy assisted by radiocarbon geochronology suggests that these fans have been active since late Pleistocene (25 ka) to the present. This record suggests that at least 10 events have been recorded at the fan interior during the past ~ 1840 years. One of these events at 355 ± 65 14C yrs. BP (cal yrs. AD 1438 to 1652) can be correlated across the fans and is likely associated with an extreme hydrometeorologic event. The presence of a 165 ± 60 14C yrs. BP (cal yrs. AD 1652-1949) debris flow deposit within the fans suggests that movement along the Polochic fault formed the fans' scarp afterwards. In fact, a historic earthquake along the fault occurred east of Motozintla on July 22, 1816 with a Mw of 7.5-7.75. Recent catastrophic floods have affected Motozintla in 1998 and 2005 induced by extreme hydrometeorological events and anthropogenic factors. Therefore, scenarios for Motozintla involved several types of mass movement processes that pose a serious hazard and threat to the inhabitants of the region.

Sánchez-Núñez, J. M.; Macías, J. L.; Saucedo, Ricardo; Zamorano, J. J.; Novelo, David; Mendoza, M. E.; Torres-Hernández, J. R.

2015-02-01

235

Late Quaternary history of southern Chesapeake Bay  

SciTech Connect

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

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

1985-01-01

236

Vertical flow in heavily exploited hard rock and alluvial aquifers  

Microsoft Academic Search

This paper examines the flow in heavily exploited alluvial and hard rock aquifers and demonstrates that vertical components of flow are of great importance. In a typical example of an alluvial aquifer it is shown that most of the discharge from tube wells originates from the phreatic surface flowing vertically through clay layers to the well screens. A second study

K. R. Rushton

1986-01-01

237

Large alluvial fans on Mars Jeffrey M. Moore  

E-print Network

Large alluvial fans on Mars Jeffrey M. Moore Space Sciences Division, NASA Ames Research Center-relief source areas, terrestrial low-gradient alluvial ramps in inactive tectonic settings, and older Martian basin relief than terrestrial fans in active tectonic settings. This suggests that the terrestrial

Howard, Alan D.

238

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

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

239

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

USGS Publications Warehouse

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.

Rodriguez, Jose M.; Gómez-Gómez, Fernando

2008-01-01

240

Quaternary Research Association Educational Resources  

NSDL National Science Digital Library

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

241

Topic in Depth - Quaternary Studies  

NSDL National Science Digital Library

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

2010-09-14

242

Assessing an Alluvial Channel Behavioral Problem  

NASA Astrophysics Data System (ADS)

Modern alluvial rivers appear to be highly organized physical systems. Although empirical relations provide much insight into the fundamental organizing principles of rivers across multiple scales, current theory does not fully explain these relations. In particular the bankfull Shields stress and particle Reynolds number characterize mutual adjustments of basal shear stress and median grain size of the sediment load within a channel, and it has been derived that the bankfull Shields stress should scale with the particle Reynolds number to the -2/3 power. However, empirical results do not support this. In order to explore this discrepancy we develop theory and add new data to existing datasets of alluvial bankfull properties. We compiled a dataset of 641 bankfull measurements from previous compilations and new, previously un-compiled studies. Using Bayesian linear regression, we find a relation between the logarithms of bankfull Shields stress and particle Reynolds number with a slope that has a 95% high posterior probability density interval probability of (-0.499, -0.463). Either a parameter is missing or one of the current parameters is incorrectly formulated. We propose that the particle Reynolds number is nondimensionalized in a way that, although is correctly unitless, is not the scaled internally in the most advantageously for this application. Unfortunately, without measured variability of kinematic viscosity, fluid density, or sediment density, the data is confounded and a new, more correct formulation of the particle Reynolds number cannot be proposed. A future work could resolve this issue with variation of any one of these parameters. Results from that dataset will have application to a wide range of modern and ancient planetary environments.

Trampush, S.; McElroy, B. J.; Huzurbazar, S. V.

2012-12-01

243

Regional water quality patterns in an alluvial aquifer: Direct and indirect influences of rivers  

NASA Astrophysics Data System (ADS)

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 (50 km2) 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 ?18OH2O and ?2HH2O 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 52 mg/L, and the nitrate concentration of infiltrating river at approximately 6 mg/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.

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

2014-11-01

244

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

PubMed

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

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

2014-11-15

245

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

NASA Astrophysics Data System (ADS)

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.

Caraivan, Glicherie; Stefanescu, Diana

2013-04-01

246

Alluvial Bars of the Obed Wild and Scenic River, Tennessee  

USGS Publications Warehouse

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

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

2007-01-01

247

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

248

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

NASA Astrophysics Data System (ADS)

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

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

2006-01-01

249

Laramide thrust-generated alluvial-fan sedimentation, Sphinx conglomerate, southwestern Montana  

SciTech Connect

The uppermost Cretaceous-lower Tertiary Sphinx Conglomerate crops out over an area of approximately 20 km{sup 2} (8 mi{sup 2}) in the Madison Range of southwestern Montana. The Sphinx consists of more than 1,000 m (3,300 ft) of synorogenic boulder and cobble conglomerate derived from a Late Cretaceous Laramide uplift that was located in the area presently occupied by the Madison River valley. Palynological and radiometric age data indicate that the Sphinx was deposited 75-58 Ma, and that thrusting and folding of the deposit had largely ceased by 56 Ma. Compositions of Sphinx clasts and paleocurrent data indicate that the Sphinx was produced by uplift and unroofing of Mesozoic and Paleozoic rocks located on two thrust sheets to the west and southwest. The lower Sphinx was deposited on the distal portions of an eastward prograding alluvial-fan system. Clast assemblages and lithofacies indicate that deposition of the middle Sphinx was controlled by a combination of progradation in response to ongoing thrusting and an influx of resistant clasts derived from middle Paleozoic carbonates in the source area. Deposition of the upper Sphinx was probably controlled by source lithology, as the influx of very coarse, resistant clasts from middle and lower Paleozoic carbonates overwhelmed the fan system's ability to organize its load of sediment by normal fan processes. A preliminary facies model for thrust-generated alluvial-fan deposits predicts intraformational deformation, cannibalization of proximal synorogenic fan facies, and abrupt compositional breaks in response to episodes of thrusting. 14 figs., 1 tab.

Decelles, P.G.; Tolson, R.B.; Graham, S.A.; Smith, G.A.; Ingersoll, R.V.; White, J.; Schmidt, C.J.; Rice, R.; Moxon, I.; Lemke, L.; handschy, J.W.; Follo, M.F.; Edwards, D.P.; Cavazza, W.; Caldwell, M.; Bargar, E. (Univ. of Rochester, NY (USA))

1987-02-01

250

Liquefaction potential of Quaternary alluvium in Bolu settlement area, Turkey  

NASA Astrophysics Data System (ADS)

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

Ulamis, Koray; Kilic, Recep

2008-09-01

251

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

NASA Astrophysics Data System (ADS)

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

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

2006-12-01

252

Empirical assessment of theory for bankfull characteristics of alluvial channels  

NASA Astrophysics Data System (ADS)

compiled a data set of 541 bankfull measurements of alluvial rivers (see supporting information) and used Bayesian linear regression to examine empirical and theoretical support for the hypothesis that alluvial channels adjust to a predictable condition of basal shear stress as a function of sediment transport mode. An empirical closure based on channel slope, bankfull channel depth, and median grain size is proposed and results in the scaling of bankfull Shields stress with the inverse square root of particle Reynolds number. The empirical relationship is sufficient for purposes of quantifying paleohydraulic conditions in ancient alluvial channels. However, it is not currently appropriate for application to alluvial channels on extraterrestrial bodies because it depends on constant-valued, Earth-based coefficients.

Trampush, S. M.; Huzurbazar, S.; McElroy, B.

2014-12-01

253

The Shape of Trail Canyon Alluvial Fan, Death Valley  

NASA Technical Reports Server (NTRS)

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

Farr, Tom G.; Dohrenwend, John C.

1993-01-01

254

Quaternary GIS Laboratory  

NSDL National Science Digital Library

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

255

Synthesis of Quaternary Heterocyclic Salts  

PubMed Central

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

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

2014-01-01

256

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

NASA Astrophysics Data System (ADS)

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

Fenton, C.; Pelletier, J.

2005-12-01

257

Comparison of different investigation methods to characterise alluvial gravel aquifers  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

258

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

NASA Astrophysics Data System (ADS)

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.

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

2013-12-01

259

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

NASA Astrophysics Data System (ADS)

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

Lukram, I. M.

2007-12-01

260

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

NASA Astrophysics Data System (ADS)

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

Baltzer, Frédéric; Purser, Bruce H.

1990-05-01

261

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

262

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

USGS Publications Warehouse

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

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

2001-01-01

263

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

NASA Astrophysics Data System (ADS)

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.

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

2001-10-01

264

10Be, OSL/IRSL Luminescence and 14C Cross-Dating of a Series of Abandoned Alluvial Surfaces Laterally Offset by the Dead Sea Fault, Jordan  

NASA Astrophysics Data System (ADS)

Active tectonics studies are often limited by the uncertainties in accurately and precisely dating Late Quaternary deposits, especially alluvial deposits that often lack organic matter datable by 14C method. This is the case along the Wadi Araba Fault (WAF), the southernmost segment of the Dead Sea Fault, which delineates the 1000-km long plate boundary between the Arabia plate and the Sinai sub-plate. Geodetic, geomorphic and geologic studies converge to a fault slip rate of 5 ± 2 mm/a. Yet, long-term Late Pleistocene slip rates cover a wide range due to large uncertainties, mostly related to the dispersion of 10Be cosmogenic radionuclide (CRN) ages. The maximum slip rate since ~100 ka is up to a value of 11 mm/a, possibly suggesting significant variations in fault activity with time. In order to reduce the uncertainty on the Late Pleistocene slip rate and draw further conclusions regarding the seismic behavior of the WAF, we targeted one of the sites previously investigated for detailed morphotectonic analysis and 10Be CRN dating and we apply other chronometers, such as Optically stimulated luminescence (OSL) dating on quartz and feldspar minerals, and 14C dating when possible. The site consists in an abandoned bajada composed of four alluvial surface levels, offset by the WAF. We extensively sampled the terraces F2 and F4, which are offset by 160 ± 8 m and 626 ± 37 m, respectively. Our samples are collected from ~50-cm deep pits on the top of the terraces. On F2, we collected one OSL sample downstream from the fault and two upstream, where land snail shells were also found. Preliminary OSL ages agree on ~8 ± 2 ka upstream, also consistent with a 14C date, whereas the OSL age downstream is much older, ~41 ± 4 ka. On F4, we collected three samples downstream from the fault and two upstream. Preliminary OSL ages cluster between ~32 ± 4 ka and ~46 ± 5 ka. Five of the OSL samples have been collected at a similar location to surficial cobbles for 10Be, both on F2 and F4. At every site, the OSL dates are much younger than the 10Be CRN model ages. For example, on F4, 19 samples out of 23 yielded 10Be ages from between 64 ka and 123 ka, 3 cobbles being ~50 ka and one 33 ka. Although OSL growth curves of quartz do not appear to be saturated, we started complementary analyses by infra-red luminescence (IRSL) on the feldspar minerals from the same samples. If the feldspar IRSL ages confirm F4 being as young as ~40 ka, the 10Be CRN model ages must then be affected by significant inheritance. Also, combining such age with the offset of F4 would lead to a very fast fault slip rate of ~15 mm/a since ~40 ka, which is three times faster than the GPS slip rate and long-term slip rates average during the Holocene and Miocene periods.

Le Beon, M.; Jaiswal, M.; Al-Qaryouti, M.; Moumani, K.; Burr, G. S.; Chen, Y.; Klinger, Y.; Abdelghafoor, M.; Suppe, J.

2010-12-01

265

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

266

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

USGS Publications Warehouse

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

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

2012-01-01

267

Summary of available hydrogeologic data for the northeast portion of the alluvial aquifer at Louisville, Kentucky  

USGS Publications Warehouse

The hydrogeologic characteristics of the unconsolidated glacial outwash sand and gravel deposits that compose the northeast portion of the alluvial aquifer at Louisville, Kentucky, indicate a prolific water-bearing formation with approximately 7 billion gallons of ground-water storage and an estimated sustainable yield of over 280 million gallons per day. This abundance of ground water and the need to properly develop and manage this resource has prompted many past investigations (since 1956), which have produced reports, maps, and data files covering a variety of topics relative to the movement, availability, and use of ground water in this area. These data have been compiled into a single report to assist in future development and use of the ground-water resources. Available ground-water data for the alluvial aquifer at Louisville, Kentucky, from Beargrass Creek to Harrods Creek, were compiled from the U.S. Geological Survey National Water Information System and the Kentucky Groundwater Data Repository. Data contained in these databases include ground-water well-construction details and historical ground-water levels, drillers' logs, and water-quality information. Additional data and information were gathered from project files at the U.S. Geological Survey--Kentucky Water Science Center and files at the Louisville Water Company. Information contained in these files included data from area pumping tests describing aquifer characteristics and ground-water flow. Data describing current conditions of the ground-water system in the northeast portion of the alluvial aquifer also are included. Ground-water levels from a network of observation wells show recent trends in the flow system, and information from the Kentucky Division of Water-Groundwater Branch lists current permitted ground-water withdrawals in the area.

Unthank, Michael D.; Nelson, Hugh L.

2006-01-01

268

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

NASA Astrophysics Data System (ADS)

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

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

2006-12-01

269

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

NASA Astrophysics Data System (ADS)

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

Warburton, Jeff; Evans, Martin

2011-07-01

270

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

Code of Federal Regulations, 2012 CFR

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

2012-10-01

271

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

Code of Federal Regulations, 2013 CFR

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

2013-10-01

272

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

Code of Federal Regulations, 2013 CFR

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

2013-10-01

273

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

Code of Federal Regulations, 2012 CFR

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

2012-10-01

274

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

... 2014-10-01 2014-10-01 false Federal coal deposits subject to disposal by exchange. 3436...MINERALS MANAGEMENT (3000) NONCOMPETITIVE LEASES Coal Lease and Coal Land Exchanges: Alluvial Valley Floors §...

2014-10-01

275

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

... 2014-10-01 2014-10-01 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 §...

2014-10-01

276

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

Code of Federal Regulations, 2011 CFR

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

2011-10-01

277

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

Code of Federal Regulations, 2011 CFR

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

2011-10-01

278

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

279

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

NASA Astrophysics Data System (ADS)

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

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

2009-06-01

280

Quaternary uplift of southern Italy  

Microsoft Academic Search

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

Rob Westaway

1993-01-01

281

Quaternary Studies: An Interdisciplinary Program  

NSDL National Science Digital Library

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

2014-09-02

282

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,...

283

On Earthquake Ground Motion and Structural Response in Alluvial Valleys  

E-print Network

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

Shewchuk, Jonathan

284

Intra-meander hyporheic flow in alluvial rivers  

Microsoft Academic Search

Several geomorphological fluvial features are able to induce hyporheic exchange between the rivers and the alluvial sediments. However, while the small-scale exchange induced by bed forms has been thoroughly investigated, the role of the larger features remains poorly understood. Here, we focus on the hyporheic flows driven by the channel sinuosity in the intrameander zone. A physically based model is

Roberto Revelli; Fulvio Boano; Carlo Camporeale; Luca Ridolfi

2008-01-01

285

Fluvial geomorphic features of the Lower Mississippi alluvial valley  

Microsoft Academic Search

The Lower Mississippi Valley (LMV) has been one of the most intensively studied alluvial valleys in the world in terms of it's geological and geomorphic framework and history. A brief outline of the history of the major geological and geomorphological investigations of the LMV is provided. The results of these investigations are discussed in terms of the fluvial geomorphic framework

Lawson M. Smith

1996-01-01

286

Quaternary fluvial archives: achievements of the Fluvial Archives Group  

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

287

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

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

288

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

PubMed

Recharge of waste water in an unconsolidated poorly sorted alluvial aquifer is a complex process, both physically and hydrochemically. The aim of this paper is to analyse and conceptualise vertical transport mechanisms taking place in an urban area of extensive wastewater infiltration by analysing and combining the water balance, the microbial (Escherichia coli) mass balance, and the mass balance for dissolved solutes. For this, data on sediment characteristics (grain size, organic carbon, reactive iron, and calcite), groundwater levels, and concentrations of E. coli in groundwater and waste water were collected. In the laboratory, data on E. coli decay rate coefficients, and on bacteria retention characteristics of the sediment were collected via column experiments. The results indicated that shallow groundwater, at depths of 50 m below the surface, was contaminated with E. coli concentrations as high as 10(6) CFU/100 mL. In general, E. coli concentrations decreased only 3 log units from the point of infiltration to shallow groundwater. Concentrations were lower at greater depths in the aquifer. In laboratory columns of disturbed sediments, bacteria removal was 2-5 log units/0.5 cm column sediment. Because of the relatively high E. coli concentrations in the shallow aquifer, transport had likely taken place via a connected network of pores with a diameter large enough to allow bacterial transport instead of via the sediment matrix, which was inaccessible for bacteria, as was clear from the column experiments. The decay rate coefficient was determined from laboratory microcosms to be 0.15 d(-1). Assuming that decay in the aquifer was similar to decay in the laboratory, then the pore water flow velocity between the point of infiltration and shallow groundwater, coinciding with a concentration decrease of 3 log units, was 0.38 m/d, and therefore, transport in this connected network of pores was fast. According to the water balance of the alluvial aquifer, determined from transient groundwater modelling, groundwater flow in the aquifer was mainly in vertical downward direction, and therefore, the mass balance for dissolved solutes was simulated using a 1D transport model of a 200 m column of the Quaternary Alluvium aquifer. The model, constructed with PHREEQC, included dual porosity, and was able to adequately simulate removal of E. coli, cation-exchange, and nitrification. The added value of the use of E. coli in this study was the recognition of relatively fast transport velocities occurring in the aquifer, and the necessity to use the dual porosity concept to investigate vertical transport mechanisms. Therefore, in general and if possible, microbial mass balances should be considered more systematically as an integral part of transport studies. PMID:17854950

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

2008-01-01

289

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

290

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

USGS Publications Warehouse

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

Justus, B.G.

2003-01-01

291

Changes in the frequency, scale, and failing areas of latest Quaternary (<29.4 cal. ka B.P.) slope failures along the SW Ulleung Basin, East Sea (Japan Sea), inferred from depositional characters of densely dated turbidite successions  

Microsoft Academic Search

The depositional characters of densely dated turbidite successions originating from the southwestern margin of the Ulleung\\u000a Basin reveal changes in high-resolution frequency, failing areas, and relative volumes of slope failures over the past 29.4\\u000a cal. ka. Between 29.4 and 19.1 cal. ka B.P., various thin- to very thick-bedded turbidites accumulated at an average recurrence\\u000a interval of ca. 605 years. After

Sang Hoon Lee; Jang J. Bahk; Han J. Kim; Kyung E. Lee; Hyeong T. Jou; Bong C. Suk

2010-01-01

292

Changes in the frequency, scale, and failing areas of latest Quaternary (<29.4 cal. ka B.P.) slope failures along the SW Ulleung Basin, East Sea (Japan Sea), inferred from depositional characters of densely dated turbidite successions  

Microsoft Academic Search

The depositional characters of densely dated turbidite successions originating from the southwestern margin of the Ulleung Basin reveal changes in high-resolution frequency, failing areas, and relative volumes of slope failures over the past 29.4 cal. ka. Between 29.4 and 19.1 cal. ka B.P., various thin- to very thick-bedded turbidites accumulated at an average recurrence interval of ca. 605 years. After

Sang Hoon Lee; Jang J. Bahk; Han J. Kim; Kyung E. Lee; Hyeong T. Jou; Bong C. Suk

2010-01-01

293

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

NASA Astrophysics Data System (ADS)

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.

Acks, R.; Kraus, M. J.

2012-12-01

294

Late Quaternary sedimentation and sea level changes on the inner Scotian Shelf  

Microsoft Academic Search

The inner Scotian Shelf off the Eastern Shore of Nova Scotia forms an irregular surface that extends some 25 30 km seaward of the present coastline to water depths of about 100 m where it drops off into Emerald Basin. The distribution of Late Quaternary deposits is highly variable both along and across the shelf. These sediments preserve a record

D. L. Forbes; R. Boyd; J. Shaw

1991-01-01

295

First Quaternary Fossil Record of Caecilians from a Mexican Archaeological Site  

Microsoft Academic Search

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

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

1999-01-01

296

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

Microsoft Academic Search

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

Daniel R. Muhs; James R. Budahn

2006-01-01

297

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

Microsoft Academic Search

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

Pinxian Wang; Luejiang Wang; Yunhua Bian; Zhimi Jian

1995-01-01

298

Time constraints from 230 Pa data in late Quaternary, low sedimentation  

E-print Network

deposition, as indicated by their high sand content. This study suggests a mean sedimentation rate of about 1 compared with parent uranium isotopes (Moore and Sackett, 1964). These particle-reactive radionuclidesTime constraints from 230 Th and 231 Pa data in late Quaternary, low sedimentation rate sequences

Long, Bernard

299

Quaternary volcanism in the Salton Sea geothermal field, Imperial Valley, California  

Microsoft Academic Search

The Salton Sea geothermal field lies in the Salton Trough, the landward extension of the Gulf of California, an area of active crustal spreading. Surface volcanic rocks of the field consist of five small rhyolite domes extruded onto Quaternary sediments of the Colorado River delta. Two domes are linked by subaqueous pyroclastic deposits; the others are single extrusions with or

PAUL T. ROBINSON; WILFRED A. ELDERS; L. J. P. Muffler

1976-01-01

300

Quaternary ecology: A paleoecological perspective  

SciTech Connect

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

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

1991-01-01

301

Detectability of minerals on desert alluvial fans using reflectance spectra  

NASA Technical Reports Server (NTRS)

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

Shipman, Hugh; Adams, John B.

1987-01-01

302

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

NASA Astrophysics Data System (ADS)

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

Pelletier, J. D.

2014-08-01

303

40 CFR 721.4095 - Quaternary ammonium alkyltherpropyl trialkylamine halides.  

Code of Federal Regulations, 2010 CFR

... 2010-07-01 false Quaternary ammonium alkyltherpropyl trialkylamine halides...Substances § 721.4095 Quaternary ammonium alkyltherpropyl trialkylamine halides...substances identified generically as quaternary ammonium alkyltherpropyl trialkylamine...

2010-07-01

304

21 CFR 172.165 - Quaternary ammonium chloride combination.  

Code of Federal Regulations, 2010 CFR

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

2010-04-01

305

40 CFR 721.4467 - Quaternary ammonium hydroxide.  

Code of Federal Regulations, 2010 CFR

... 2010-07-01 false Quaternary ammonium hydroxide. 721.4467 Section 721...Substances § 721.4467 Quaternary ammonium hydroxide. (a) Chemical substance...identified generically as a quaternary ammonium hydroxide (PMN P-95-1806)...

2010-07-01

306

40 CFR 721.655 - Ethoxylated alkyl quaternary ammonium compound.  

Code of Federal Regulations, 2010 CFR

... false Ethoxylated alkyl quaternary ammonium compound. 721.655 Section 721...655 Ethoxylated alkyl quaternary ammonium compound. (a) Chemical substance...generically as an ethoxylated alkyl quaternary ammonium compound (PMN P-96-573) is...

2010-07-01

307

40 CFR 721.10511 - Quaternary ammonium salts (generic).  

...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,...

2014-07-01

308

40 CFR 721.655 - Ethoxylated alkyl quaternary ammonium compound.  

Code of Federal Regulations, 2011 CFR

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

2011-07-01

309

Multiple sources of alkanes in Quaternary oceanic sediment of Antarctica  

USGS Publications Warehouse

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

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

1987-01-01

310

A model of channel response in disturbed alluvial channels  

USGS Publications Warehouse

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

Simon, A.

1989-01-01

311

Uranium in framboidal pyrite from a naturally bioreduced alluvial sediment.  

PubMed

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

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

312

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

313

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

NASA Astrophysics Data System (ADS)

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

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

2005-07-01

314

Structural and Tectonic Constraints on the Origin of Gold Deposits in the Ballarat  

E-print Network

* Structural and Tectonic Constraints on the Origin of Gold Deposits in the Ballarat Slate Belt). The vast proportion of this gold, much of which was recovered from Tertiary alluvial deposits gold deposition,re- gional deformation and granite genesis within the slate belt remain the subject

Sandiford, Mike

315

Charophytes as lacustrine biomarkers during the quaternary in North Africa  

NASA Astrophysics Data System (ADS)

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.

Soulié-Märsche, I.

316

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

NASA Astrophysics Data System (ADS)

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

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

2005-12-01

317

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

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

318

Hydrogeology and simulation of ground-water flow in the alluvial aquifer at Louisville, Kentucky  

USGS Publications Warehouse

The alluvial aquifer at Louisville, Ky., lies in a valley eroded by glacial meltwater that was later partly filled with outwash sand and gravel deposits. The aquifer is primarily unconfined, and the direction of flow is from the adjacent limestone and shale valley wall toward the Ohio River and major pumping centers. Pumpage and water-level data indicate that the alluvial aquifer was in a steady-state condition in November 1962 and again in November 1983. Between these two dates, water-level data indicate a general rise in the water table. A two-dimensional finite-element ground-water-flow model of the alluvial aquifer was calibrated for both the steady-state and the transient-state period of 1962-83. The year 1962 represented a period in time when pumping was nearly three times that in 1983. The simulated steady-state water budget for 1962 indicated that of the total recharge to the aquifer of 5.19 million feet per day, 37.2 percent was flow from the river to pumped wells, 28.3 percent was recharge from rainfall, 19.7 percent was flow across the eastern valley wall, and 14.8 percent was upward flow from the bedrock. Discharge from the aquifer was to wells (68.9 percent) and to the Ohio River (31.1 percent). The simulated steady-state water budget for 1983 indicated that of the total recharge to the aquifer of 4.11 million feet per day, 42.6 percent was recharge from rainfall, 18.2 percent was flow across the eastern valley wall, 17.8 percent was flow from the river to pumped wells, 15.6 percent was upward flow from the bedrock, and 5.8 percent was flow from septic systems. The transient simulation resulted in an acceptable match between measured and simulated hydrographs. This gave additional confidence to the model calibration, choice of boundary conditions, and published values of specific yield. Both steady-state and transient-state models demonstrated that the main source of water needed to meet increased pumping requirements was induced flow from the Ohio River.

Lyverse, M.A.; Starn, J.J.; Unthank, M.D.

1996-01-01

319

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

USGS Publications Warehouse

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

Knepper, D.H., Jr.

2005-01-01

320

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

Vuille, Mathias

321

Determinants of quaternary association in legume lectins  

Microsoft Academic Search

It is well known that the sequence of amino acids in proteins code for its tertiary structure. It is also known that there exists a relationship between sequence and the quaternary structure of proteins. The question addressed here is whether the nature of quaternary association can be predicted from the sequence, similar to the three-dimensional structure prediction from the sequence.

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

2004-01-01

322

Stereoselective Synthesis of Quaternary Proline Analogues  

PubMed Central

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

Calaza, M. Isabel

2009-01-01

323

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

324

An aminostratigraphy for the British Quaternary based on Bithynia opercula.  

PubMed

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

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

2013-02-01

325

An aminostratigraphy for the British Quaternary based on Bithynia opercula  

PubMed Central

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

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

2013-01-01

326

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

NASA Astrophysics Data System (ADS)

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

Shukla, U. K.

2009-03-01

327

Magnetic properties of alluvial soils contaminated with lead, zinc and cadmium  

NASA Astrophysics Data System (ADS)

Several proxy methods have been used recently to outline increased levels of pollution. One of them is based on measurements of the concentration of (ferri)magnetic minerals of anthropogenic origin. This method has been used recently in the mapping of both polluted and unpolluted areas. In order to validate this method, a more detailed study of links between magnetic parameters characterising the physical shape of magnetic minerals and concentrations of heavy metals is needed. In this study, we analysed the magnetic characteristics of alluvial soils, formed as a result of several breakdowns of wet deposit sink of ashes from a lead ore smelter. The soils were previously analysed for concentration of lead, zinc and cadmium. Our results show that in this case of a shared source of heavy metals and magnetic minerals, simple measurements of magnetic susceptibility discriminate well between polluted and clean areas. In addition, the concentration pattern agrees with the concentrations of the heavy metals studied in deeper soil layers that were not affected by post-depositional changes due to climate and remediation efforts.

Petrovský, E.; Kapi?ka, A.; Jordanova, N.; Bor?vka, L.

2001-09-01

328

Late Quaternary paleosols and climate change in southern New Mexico  

SciTech Connect

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

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

1992-01-01

329

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

NASA Astrophysics Data System (ADS)

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).

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

2012-04-01

330

A Quaternary Geomagnetic Instability Time Scale  

NASA Astrophysics Data System (ADS)

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

Singer, B. S.

2013-12-01

331

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

NASA Astrophysics Data System (ADS)

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

Sahu, Sudarsan; Saha, Dipankar

2014-08-01

332

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

SciTech Connect

Pliocene and Pleistocene age sediments of the northernmost Mississippi Embayment consist of a thick sequence of continental deposits which rest unconformably on Cretaceous through Eocene strata. The continental deposits have been tentatively correlated to the Pliocene Mounds Gravel and Pleistocene Henry and Equality Formations of southern Illinois. These sediments have previously been interpreted as representing alluvial fan and fluvial deposits. The continental deposits are generally divided into three lithofacies: (1) silt/clay dominated; (2) sand dominated, and (3) gravel dominated. A subsurface study utilizing approximately 300 soil borings has shown that (1) the continental deposits, particularly the gravel facies, exhibit significant local changes in thickness, (2) the upper portion of the sequence consists predominantly of finer-grained silt/clay lithofacies, and (3) sand and gravel lithofacies within the upper sequence often occur at predictable horizons. These observations indicate a paleovalley fill with distinct depositional episodes. As a result of Pleistocene base level fluctuations, stream systems became deeply entrenched in the Pliocene alluvial fan and older sediments. Fan deposits were initially transported and redeposited in a braided fluvial system. As valley alluviation continued and gradients decreased, the braided fluvial system evolved into a meandering system. During Woodfordian time, slackwater lakes created by glacial outwash dams produced extensive lacustrine deposits. At least two major episodes of lacustrine sedimentation are apparent. Significant fluctuations of lake level are recognized in the subsurface by local erosional surfaces overlain by coarser-grained sediments deposited in basinward-migrating channel and shoreline facies.

Phillips, B.E. (Martin Marietta Energy Systems, Inc., Paducah, KY (United States))

1992-01-01

333

Dynamic classification of alluvial gold placers in the northeast of Russia  

NASA Astrophysics Data System (ADS)

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

Goldfarb, Yu. I.

2007-08-01

334

Herbicide interchange between a stream and the adjacent alluvial aquifer  

USGS Publications Warehouse

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

Wang, W.; Squillace, P.

1994-01-01

335

Tephrochronological study in the quaternary Val d'Agri intermontane basin (Southern Apennines, Italy)  

NASA Astrophysics Data System (ADS)

In the south-eastern depocentre of the Val d'Agri basin (Southern Apennines), a volcanic ash layer crops out interbedded within poorly structured alluvial fan deposits of Late Pleistocene age. Textural, depositional and pedological features of this weathered layer suggest a primary deposition from a pyroclastic fall-out of volcanic ash. Chemical analyses of feldspars show an alkali trachytic composition and accessory minerals association allow to correlate this tephra layer with the regionally dispersed Y-7 marine tephra layer (Tufo Verde Epomeo eruption, Ischia volcano), dated at 56 ± 4 ka. The Val d'Agri tephra here described for the first time was deposited during MIS Stage 3. Its recovery and characterization permit to contribute to regional correlation of the Mediterranean climatic and volcanic events from marine to continental successions and to describe landscape evolution of the Southern Apennines during glacial-interglacial cycles.

Zembo, Irene; Vignola, Pietro; Andò, Sergio; Bersezio, Riccardo; Vezzoli, Luigina

2011-01-01

336

Late quaternary tephra layers along the Cilento coastline (southern Italy)  

NASA Astrophysics Data System (ADS)

The results of stratigraphic and tephrostratigraphic analyses of several pyroclastic levels, collected along the coastal sector of the Cilento region (southern Italy), are presented. Some of these levels are here described for the fist time, others, already known in literature, were reconsidered in order to better understand their stratigraphic position and to point out the possible volcanic sources. The main outcrops are located along the southern coast of the Campania region (Cilento coast). All pyroclastic layers are interbedded within coastal or continental successions younger than the substage 5e of the Last Interglacial (< 130 ka) or cover erosional coastal morphologies belonging to the same period. Only in one site the sampled tephra can be considered older. As a consequence, the age range for their emplacement is constrained to the last 200 ka. The results of SEM-EDS analyses on well preserved glass fragments indicate a composition falling between the trachyte and phonolite fields of the TAS plot, as typical of Phlaegrean Fields products. By comparing their composition with those of the main tephra marker layers recorded in southern Italy, the correlation of the Cilento pyroclastic layers with well known eruptive episodes was hypothesised. In summary, four different eruptions were recognised. The first one is testified by a pyroclastic layer, not correlated with a terrestrial counterpart, covered by a Middle Pleistocene alluvial fan, the second one is the eruptive event emplacing the X-6 marker tephra layer, and dates around 107 ka, the third is the Campanian Ignimbrite eruption (39 ka), and the last one is testified by the layers correlated with the Y-3 tephra (about 30 ka). These pyroclastic layers can be useful tools for stratigraphic correlations of Late Quaternary successions in southern Italy.

Marciano, Roberta; Munno, Rosalba; Petrosino, Paola; Santangelo, Nicoletta; Santo, Antonio; Villa, Igor

2008-10-01

337

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

Microsoft Academic Search

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

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

338

Holocene environments of the central Great Plains: multi-proxy evidence from alluvial sequences, southeastern Nebraska  

Microsoft Academic Search

Pollen, plant macrofossils, phytoliths, carbon isotopes, and alluvial history from sediments exposed along the South Fork of the Big Nemaha River, southeastern Nebraska, USA, provide an integrated reconstruction of changes in Holocene vegetation, climate, and fluvial activity. From 9000 to 8500 uncalibrated 14C yr BP, climate became more arid and the floodplain and alluvial fans in the main valley aggraded

Richard G. Baker; Glen G. Fredlund; Rolfe D. Mandel; E. A. Bettis

2000-01-01

339

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

E-print Network

of 35 dams on large rivers in the Western U.S. that rivers with braided patterns tended to narrowA. 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

Julien, Pierre Y.

340

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)

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.

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

2014-05-01

341

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

342

Channel and landscape dynamics in the alluvial forest mosaic of the Carmanah River valley, British Columbia, Canada  

NASA Astrophysics Data System (ADS)

The highly diverse shifting-mosaic of forest patches of an alluvial forest within the Carmanah River valley on the west coast of Vancouver Island, British Columbia was studied to examine the hydrogeomorphic disturbance regime that structures it. We used a landscape-scale analysis to quantify historical channel migrations and changes in the extent of specific forest types. This GIS-based analysis using a 70-year aerial photographic record was complemented by field-based research. Thirty-eight plots containing 4509 trees were sampled for forest structure, age, and elevation above the contemporary channel. These data, including a vegetation chronosequence spanning over 500 years, were used to examine channel and landscape dynamics. Our findings support a general conceptual model that describes cycles of patch development and destruction in unconfined alluvial forests of the Pacific Coastal Ecoregion. Over the past century, Carmanah River has eroded nearly 30% of the alluvial forest in this study area, and approximately 65% over the past 500 years. At least 80% of the 2007 channel was forested area within the past 70 years. Younger landforms were disturbed more frequently than mature forest patches, which suggest that as biogeomorphic succession progresses the likelihood of future disturbance decreases. Estimated half lives of landforms ranged from 24 years for pioneer bars to over 1500 years for old growth terraces. Years of regional high magnitude floods resulted in a net loss of floodplain forest area indicating that disturbance was climate driven in this pluvial watershed, whereby rain events result in flood disturbance that converted forests to channel. These events initiate a subsequent course of vegetation succession and geomorphic development, and often result in the deposition of large wood that modifies the channel environment and contributes to channel avulsion and further hydrogeomorphic disturbance. The composition of the landscape is a reflection of the balance between the disturbance rate and successional development. We also observed a relationship between landscape composition and watershed size. Specifically, the ratio of mature to developing alluvial forests was higher in this smaller watershed compared to larger watersheds in the region. Results imply that larger flood events predicted to occur with climate change may change the disturbance regime of floodplain forests and alter landscape composition.

Little, Patrick J.; Richardson, John S.; Alila, Younes

2013-11-01

343

Statistic inversion of multi-zone transition probability models for aquifer characterization in alluvial fans  

E-print Network

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...

Zhu, Lin; Gong, Huili; Gable, Carl; Teatini, Pietro

2015-01-01

344

Neotectonics and Plio-Quaternary landscape development within the eastern Huércal-Overa Basin (Betic Cordilleras, southeast Spain)  

NASA Astrophysics Data System (ADS)

The Huércal-Overa Basin is one of a series of Neogene sedimentary basins located within the Betic Cordillera of southeast Spain. Its geological and geomorphological history has been controlled by tectonic activity culminating in basin inversion during the Plio-Quaternary. Deformation of the Huercal-Overa Basin is associated with left-lateral strike-slip faulting in relation to its position within the Trans-Alboran shear zone. In this paper, we focus upon the eastern portion of the Huercal-Overa Basin and make the first attempt to reconstruct the long-term landscape development during the Plio-Quaternary. This is done through integration of geological and geomorphological data obtained through field observations and GIS and remote sensing techniques. In particular, this paper provides a case study that contributes to the understanding of landscape development within tectonically active shear zones. Within the eastern part of the Huércal-Overa Basin, the main tectonic activity is associated with the left-lateral strike-slip Lorca-Alhama fault (oriented NE-SW). During the Late Pliocene and Early Pleistocene, the interaction of this fault with older Miocene ENE-WSW to E-W orientated structures formed a subsiding area with pull-apart basin characteristics termed the Cubeta del Saltador. Subsidence within the Cubeta del Saltador enabled sedimentary infilling by braided rivers with sediment being derived from the Sierra de Las Estancias to the north and the Sierra de Almagro to the south. Sedimentary deformation has resulted in the development of a series of progressive unconformities, angular unconformities and faulting within the alluvial sediments. Towards the end of this stage of landscape development, an increase in tectonic activity resulted in the creation of elevated tectonic highs in the north (Alto de la Garita del Diablo) and east (Loma de Garc?´a) of the Cubeta del Saltador. From the middle Pleistocene onwards, a progressive decrease in tectonic activity is recorded. Alluvial sediments infilled the Cubeta del Saltador. These were dominated by braided river sediments that formed part of a fan-shaped alluvial distributary system derived from the Sierra de las Estancias to the north. In contrast, smaller debris-flow-dominated alluvial fans were derived from the Sierra de Almagro along the southern margin. Currently, the study area presents an asymmetric configuration, reflecting the different topographic characteristics of the northern and southern limiting mountain fronts.

García-Meléndez, E.; Goy, J. L.; Zazo, C.

2003-02-01

345

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

PubMed

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

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

2000-02-10

346

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

NASA Astrophysics Data System (ADS)

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

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

2003-02-01

347

Quaternary evolution of ephemeral playa lakes on the Southern High Plains of Texas, USA: cyclic variation in lake level recorded in sediments  

Microsoft Academic Search

Ephemeral playa lakes on the Southern High Plains northeast of Amarillo, Texas, are underlain by more than 10 m of Quaternary lake deposits. Sediments beneath 12 lakes were examined in 76 hollow-stem auger cores and in excavations. Stacked depositional cycles recognized in lake sediments record repeated phases of (1) initial highstand, (2) ephemeral lake, and (3) lake shrinkage and prolonged

Susan D. Hovorka

1997-01-01

348

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

349

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

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

Sa?lam, Mustafa; Dengiz, Orhan

2015-03-01

350

Responses of Riparian Cottonwoods to Alluvial Water Table Declines.  

PubMed

/ Human demands for surface and shallow alluvial groundwater have contributed to the loss, fragmentation, and simplification of riparian ecosystems. Populus species typically dominate riparian ecosystems throughout arid and semiarid regions of North American and efforts to minimize loss of riparian Populus requires an integrated understanding of the role of surface and groundwater dynamics in the establishment of new, and maintenance of existing, stands. In a controlled, whole-stand field experiment, we quantified responses of Populus morphology, growth, and mortality to water stress resulting from sustained water table decline following in-channel sand mining along an ephemeral sandbed stream in eastern Colorado, USA. We measured live crown volume, radial stem growth, annual branch increment, and mortality of 689 live Populus deltoides subsp. monilifera stems over four years in conjunction with localized water table declines. Measurements began one year prior to mining and included trees in both affected and unaffected areas. Populus demonstrated a threshold response to water table declines in medium alluvial sands; sustained declines >/=1 m produced leaf desiccation and branch dieback within three weeks and significant declines in live crown volume, stem growth, and 88% mortality over a three-year period. Declines in live crown volume proved to be a significant leading indicator of mortality in the following year. A logistic regression of tree survival probability against the prior year's live crown volume was significant (-2 log likelihood = 270, chi2 with 1 df = 232, P < 0.0001) and trees with absolute declines in live crown volume of >/=30 during one year had survival probabilities <0.5 in the following year. In contrast, more gradual water table declines of thick similar0.5 m had no measurable effect on mortality, stem growth, or live crown volume and produced significant declines only in annual branch growth increments. Developing quantitative information on the timing and extent of morphological responses and mortality of Populus to the rate, depth, and duration of water table declines can assist in the design of management prescriptions to minimize impacts of alluvial groundwater depletion on existing riparian Populus forests. PMID:9950697

SCOTT; SHAFROTH; AUBLE