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Sample records for pleistocene eolian features

  1. Late Pleistocene eolian features in southeastern Maryland and Chesapeake Bay region indicate strong WNW-NW winds accompanied growth of the Laurentide Ice Sheet

    USGS Publications Warehouse

    Markewich, H.W.; Litwin, R.J.; Pavich, M.J.; Brook, G.A.

    2009-01-01

    Inactive parabolic dunes are present in southeastern Maryland, USA, along the east bank of the Potomac River. More elongate and finer-grained eolian deposits and paha-like ridges characterize the Potomac River-Patuxent River upland and the west side of Chesapeake Bay. These ridges are streamlined erosional features, veneered with eolian sediment and interspersed with dunes in the low-relief headwaters of Potomac- and Patuxent-river tributaries. Axis data for the dunes and ridges indicate formation by WNW-NW winds. Optically stimulated luminescence and radiocarbon age data suggest dune formation from ??? 33-15??ka, agreeing with the 30-13??ka ages Denny, C.S., Owens, J.P., Sirkin, L., Rubin, M., 1979. The Parsonburg Sand in the central Delmarva Peninsula, Maryland and Delaware. U.S. Geol. Surv. Prof. Pap. 1067-B, 16??pp. suggested for eolian deposits east of Chesapeake Bay. Age range and paleowind direction(s) for eolian features in the Bay region approximate those for late Wisconsin loess in the North American midcontinent. Formation of midcontinent loess and Bay-region eolian features was coeval with rapid growth of the Laurentide Ice Sheet and strong cooling episodes (??18O minima) evident in Greenland ice cores. Age and paleowind-direction coincidence, for eolian features in the midcontinent and Bay region, indicates strong mid-latitude WNW-NW winds for several hundred kilometers south of the Laurentide glacial terminus that were oblique to previously simulated anticyclonic winds for the last glacial maximum.

  2. Late Pleistocene eolian features in southeastern Maryland and Chesapeake Bay region indicate strong WNW-NW winds accompanied growth of the Laurentide Ice Sheet

    NASA Astrophysics Data System (ADS)

    Markewich, Helaine W.; Litwin, Ronald J.; Pavich, Milan J.; Brook, George A.

    2009-05-01

    Inactive parabolic dunes are present in southeastern Maryland, USA, along the east bank of the Potomac River. More elongate and finer-grained eolian deposits and paha-like ridges characterize the Potomac River-Patuxent River upland and the west side of Chesapeake Bay. These ridges are streamlined erosional features, veneered with eolian sediment and interspersed with dunes in the low-relief headwaters of Potomac- and Patuxent-river tributaries. Axis data for the dunes and ridges indicate formation by WNW-NW winds. Optically stimulated luminescence and radiocarbon age data suggest dune formation from ˜ 33-15 ka, agreeing with the 30-13 ka ages Denny, C.S., Owens, J.P., Sirkin, L., Rubin, M., 1979. The Parsonburg Sand in the central Delmarva Peninsula, Maryland and Delaware. U.S. Geol. Surv. Prof. Pap. 1067-B, 16 pp. suggested for eolian deposits east of Chesapeake Bay. Age range and paleowind direction(s) for eolian features in the Bay region approximate those for late Wisconsin loess in the North American midcontinent. Formation of midcontinent loess and Bay-region eolian features was coeval with rapid growth of the Laurentide Ice Sheet and strong cooling episodes (δ 18O minima) evident in Greenland ice cores. Age and paleowind-direction coincidence, for eolian features in the midcontinent and Bay region, indicates strong mid-latitude WNW-NW winds for several hundred kilometers south of the Laurentide glacial terminus that were oblique to previously simulated anticyclonic winds for the last glacial maximum.

  3. Eolian evidence for climatic fluctuations during the Late Pleistocene and Holocene in Wyoming

    SciTech Connect

    Gaylord, D.R.

    1985-01-01

    Evaluation of eolian features, particularly sand dunes, in the Ferris-Lost Solider area of south-central Wyoming demonstrates the dynamic character of late Pleistocene and Holocene climatic fluctuations in a high altitude, intermontane basin. Directly- and indirectly-dated stratigraphic, sedimentary, and geomorphic evidence documents recurrent late Quaternary eolian activity as well as the timing and severity of episodic aridity during the Altithermal. Eolian activity in the Ferris-Lost Solider area began under cool and arid conditions by the late Pleistocene. Radiocarbon-dated dune and interdune strata reveal that Holocene sand dune building at Ferris-Lost Solider peaked between ca. 7660 and 4540 years b.p. The first phase of dune building was the most extensive and lasted until ca. 6460 years b.p. Warm, persistently arid conditions during this time favored active dunes with slipfaces, even in historically well-vegetated locales subject to high water tables. Increased effective moisture from ca. 6460 to 5940 years b.p. promoted dune stabilizing vegetation; but renewed dune building, lasting until ca. 4540 years b.p., followed this climatic moderation. Subsequent dune and interdune deposits reveal a return to climatic conditions where only sporadic and localized dune reactivations have interrupted overall dune stability. The most significant recent reactivation, probably associated with a regional decrease in effective moisture, occurred ca. 290 years b.p.

  4. Global map of eolian features on Mars

    NASA Technical Reports Server (NTRS)

    Ward, A. W.; Doyle, K. B.; Helm, P. J.; Weisman, M. K.; Witbeck, N. E.

    1985-01-01

    A variety of common eolian features on Mars have been identified from a survey of Mariner 9 and Viking orbiter images, and their regional and global distributions and orientations are discussed. Ten features have been mapped including: light and dark streaks, splotches, barchan and transverse dunes, crescentric and anomalous dunes, yardangs, wind grooves, and deflation pits. The north polar region shows a complex wind regime. Dunes and other ephemeral features reveal winds from the northwest and northeast. In the middle and low northern latitudes, northeasterly winds are the most effective winds. Southeast winds are the effective winds in most southern latitudes. Erosional features in bedrock indicate long-term and perhaps ancient wind trends, whereas depositional features may record relatively more recent winds. Deflation pits in the mantled terrain may contain the best record of both ancient and present-day winds.

  5. Global map of eolian features on Mars

    NASA Astrophysics Data System (ADS)

    Ward, A. W.; Doyle, K. B.; Helm, P. J.; Weisman, M. K.; Witbeck, N. E.

    1985-02-01

    A variety of common eolian features on Mars have been identified from a survey of Mariner 9 and Viking orbiter images, and their regional and global distributions and orientations are discussed. Ten features have been mapped including: light and dark streaks, splotches, barchan and transverse dunes, crescentric and anomalous dunes, yardangs, wind grooves, and deflation pits. The north polar region shows a complex wind regime. Dunes and other ephemeral features reveal winds from the northwest and northeast. In the middle and low northern latitudes, northeasterly winds are the most effective winds. Southeast winds are the effective winds in most southern latitudes. Erosional features in bedrock indicate long-term and perhaps ancient wind trends, whereas depositional features may record relatively more recent winds. Deflation pits in the mantled terrain may contain the best record of both ancient and present-day winds.

  6. Late Pleistocene eolian-alluvial interference in the Balearic Islands (Western Mediterranean)

    NASA Astrophysics Data System (ADS)

    Pomar, Francisco; Del Valle, Laura; Fornós, Joan J.; Gómez-Pujol, Lluís; Anechitei-Deacu, Valentina; Timar-Gabor, Alida

    2016-04-01

    This study deals with alluvial fan and aeolian sediments interference. Although initially they are two different environments, with different processes and resulting forms, very often their interaction produces deposits that share characteristics and features from both environments, as well as, maintain inherited elements from one to each other. In this sense, the aeolian-alluvial interference is the geomorphological expression of the coincidence, disruption and/or overlapping of aeolian and alluvial environments. Climate appears to be one of the most important controls on the role and magnitude of each environment in terms of sediment supply, precipitation, runoff or aeolian transport. In this study, eight major sedimentary facies have been described involving the succession of coastal, aeolian, colluvial and alluvial environments. Carbonate sandstones, breccias, conglomerates and fine-grained deposits are the main component of these sequences. OSL dating of aeolian levels indicate that their deposition took place during the Late Pleistocene, establishing a paleoclimatic evolution of Balearic coastal areas during the last 125 ka. The sedimentological and chronological analysis of these deposits allows reconstructing the coastal environmental changes during the Late Pleistocene at the Balearic archipelago. Keywords: Alluvial sedimentation, eolian sedimentation, alluvial-eolian interference, sea level, Late Pleistocene, Balearic Islands.

  7. Analogs of Martian eolian features in southwestern Egypt

    NASA Technical Reports Server (NTRS)

    El-Baz, F.

    1981-01-01

    Emphasis was placed on the morphology and patterns of streaks in the Uweinat region, the relationship of topography to streak patterns, and correlation of field and laboratory studies of the desert surface sediments with color and tonal variations seen from orbit. The research objectives were to provide the necessary groundtruth information on terrestrial eolian features in order to properly interpret the orbital data and to use the interpretations as a basis for investigation of Martian eolian features.

  8. Anisotropy of magnetic susceptibility of Eolian sediments in Altun Shan: implications for Altyn Tagh Fault tectonics since Pleistocene

    NASA Astrophysics Data System (ADS)

    Zhang, R.

    2015-12-01

    Ancient windblown (eolian) dust, such as in Chinese Loess Plateau (CLP), are treasured for understanding the evolution of aridity and influence by Plateau(mountain)uplift on climate change. Anisotropy of magnetic susceptibility (AMS) is an effective tool in tracking atmospheric direction under weak to moderate speed currents to reconstruct the paleomonsoon model was studied in recent years. Whilst it is sometimes directly or indirectly associated with the effects of tectonic process and developed as a results of burial diagenesis process for these eolian sediments. Here we firstly investigated AMS in a Red clay sequence (eolian deposits during Miocene to Pliocene) accumulated in the margin of Altun Mountains, which has the similar mineral content as that in CLP. The average north-west orientations of minimum magnetic susceptibility (Kmin) axes is tilting towards the active Althy Tagh Fault direction and the average direction of intermediate magnetic susceptibility (Kint) axes is close to be vertical and compacted by the gravity as a second force. The average maximum magnetic susceptibility (Kmax) is perpendicular to either tectonic or gravity directions. Considering there is no obvious metamorphic effects and plastic deformation of particles, we attribute these two stresses determined the transition of petrofabrics from the deposition to tectonics, by the intensified Pleistocene activity of Altyn Tagh Fault.

  9. Eolian Features Provide a Glimpse of Candor Chasma Mineralology

    NASA Technical Reports Server (NTRS)

    2008-01-01

    This image of Candor Chasma's eastern end was taken by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) at 0655 UTC (2:55 a.m. EDT) on March 24, 2007. CRISM's image captured 544 colors covering 0.36-3.92 micrometers, and shows features as small as 100 meters (330 feet) across. The region covered is roughly 10 kilometers (6.2 miles) at its narrowest point. Designed to look for a variety of materials on the walls and floor of Candor Chasma, this CRISM observation is somewhat unique in that it is extended along an extended path across the chasma floor to capture extra territory at the expense of spatial resolution.

    Candor Chasma is a deep, elongated, steep-sided depression some 813 kilometers (505 miles) in length. It is one of two large chasmata that make up the northern end of the Valles Marineris system. The top image, which illustrates the long path CRISM's cameras scanned to extend the observation in the along-track direction, shows the CRISM image on top of a mosaic of images from the Thermal Emission Imaging System (THEMIS) on Mars Odyssey. The lower two false-color images offer a glimpse of the topography and mineralogy contained within this large chasma. These views were constructed by draping the CRISM images over topography, and viewing the surface in perspective from the northeast. The southern part of CRISM's swath (to the left) covers interior layered deposits along with low ridges (far left) that are an erosional remnant of the chasma wall. The northern end (to the right) reveals the older, eroded chasma wall material, as well as the chasma floor. White lines in the images represent gaps in the data due to the stretching of the image.

    The erosive Martian wind appears to have removed dust and debris covering monohydrated sulfate-rich mineral deposits (bright green). Wind-abraded ridges of layered sediments (image center) reveal these deposits more readily, while ridges to the north and south also appear to retain more of a

  10. Late Pleistocene Climatic Changes in the Western Mediterranean Inferred from Temperature, Productivity and Eolian Input Records: Implications for Human Dispersal

    NASA Astrophysics Data System (ADS)

    Hambach, B.; Rosell Mele, A.; Martinez-Garcia, A.

    2009-12-01

    The relation between climate and hominid dispersal has yet a number of unsettled issues, largely due to the lack of regional climate records in areas with significant hominid remains. Scientific evidence from the Mediterranean region indicates that humans evolved into their present form during key climatic intervals as indicated by the records of the earliest Europeans from Atapuerca (Spain) and Dmanisi (Georgia). However, it remains unclear which route was used by the early hominids to populate Europe (via the strait of Gibraltar or the Levantine Corridor). In this sense, it is still not clear if the climatic conditions during this period were favorable for hominid crossing via the strait of Gibraltar or not. To gain a better insight into the Iberian peninsular climate during the late Pleistocene, a marine sediment core from the Alboran Sea, Western Mediterranean, is used to reconstruct climate relevant variables related to surface ocean and atmospheric circulation by applying a set of organic geochemical proxies (biomarkers). In a first approach we present high resolution data (2 ky) for the interval from 0 to 500 ky. The results of this multi-biomarker analysis give new insights into past ocean climate conditions as well as into the processes that occurred onshore during this period. The reconstruction of sea surface temperatures is done by the analysis of alkenones (UK37-index). Total chlorins concentration is used as proxy for paleoproductivity. Terrestrial eolian inputs and vegetation changes are determined by the analysis of n-alkyl compounds (long chain n-alkanes, n-alkenols and n-alkanoic acids) which are major components of leaf waxes from terrestrial higher plants. Like mineral aerosols, these compounds are wind-transported from local vegetation sources to adjacent oceans where the particles settle and are preserved in ocean sediments with very little diagenetic alteration. These biomarkers offer a promising tool for reconstructing terrestrial vegetation

  11. High resolution shallow geologic characterization of a late Pleistocene eolian environment using ground penetrating radar and optically stimulated luminescence techniques: North Carolina, USA

    USGS Publications Warehouse

    Mallinson, D.; Mahan, S.; Moore, Christine

    2008-01-01

    Geophysical surveys, sedimentology, and optically-stimulated luminescence age analyses were used to assess the geologic development of a coastal system near Swansboro, NC. This area is a significant Woodland Period Native American habitation and is designated the "Broad Reach" archaeological site. 2-d and 3-d subsurface geophysical surveys were performed using a ground penetrating radar system to define the stratigraphic framework and depositional facies. Sediment samples were collected and analyzed for grain-size to determine depositional environments. Samples were acquired and analyzed using optically stimulated luminescence techniques to derive the depositional age of the various features. The data support a low eolian to shallow subtidal coastal depositional setting for this area. Li-DAR data reveal ridge and swale topography, most likely related to beach ridges, and eolian features including low-relief, low-angle transverse and parabolic dunes, blowouts, and a low-relief eolian sand sheet. Geophysical data reveal dominantly seaward dipping units, and low-angle mounded features. Sedimentological data reveal mostly moderately-well to well-sorted fine-grained symmetrical to coarse skewed sands, suggesting initial aqueous transport and deposition, followed by eolian reworking and bioturbation. OSL data indicate initial coastal deposition prior to ca. 45,000 yBP, followed by eolian reworking and low dune stabilization at ca. 13,000 to 11,500 yBP, and again at ca. 10,000 yBP (during, and slightly after the Younger Dryas chronozone).

  12. Distinctive sedimentary features of cold-climate eolian deposits, North Park, Colorado

    USGS Publications Warehouse

    Ahlbrandt, T.S.; Andrews, S.

    1978-01-01

    Cold-climate eolianites contain diagnostic sedimentary features that contrast with the sedimentary features of warm-climate eolianites. Distinctive tensional, compressional, and dissipation sedimentary structures related to freezing, thawing and snow melting characterize eolian dune-sand deposits in North Park, Colorado. The North Park dunes have few of the characteristics considered to be diagnostic eolian indicators. A significant difference is the heterogeneous texture and composition of the sand. The migration rate of these active dunes is slow (???1.7 m/year) due to freezing of moisture in the sand or to burial of the sand by snow during half of the year, even though the dunes occur in a unimodal, high-energy wind environment. Bioturbation is common in both active and inactive dunes, although the dunes occur at a high elevation ({reversed tilde} 2500m) in a cold climate (3.0??C mean annual temperature). The distinctive sedimentary features observed in this cold-climate (snow-related) dune field should aid in the interpretation of eolianites and the paleoclimates in which they formed. ?? 1978.

  13. Cross-bedded limestone facies on San Salvador Island, Bahamas: New perspective on eolian calcarenites

    SciTech Connect

    Caputo, M.V. )

    1989-08-01

    Limestones of eolian origin have been known from worldwide tropical regins since the early 1900s. On San Salvador Island, most of the exposed bed rock is Holocene and Pleistocene eolian calcarenite made of skeletal, peloidal, and oolitic fine to medium sand. The Pleistocene Grotto Beach Formation is composed of 50-90% ooids. An eolian interpretation for this interval is supported by paleosols, subaerial crusts, vadose cement, terrestrial fossils, karst features, associated reef and beach deposits, grainfall, sandflow, and climbing ripple strata, and shore-parallel sand bodies. Whole dune-forms are locally preserved; they were stabilized or frozen in place by early cementation and/or vegetation.

  14. North-south asymmetry of eolian features in Martian polar regions - Analysis based on crater-related wind markers

    NASA Technical Reports Server (NTRS)

    Thomas, P.

    1981-01-01

    Crater-related wind markers in the north and south polar regions of Mars are analyzed in a study of possible north-south asymmetries in wind activity. Features including crater splotches and associated streaks, and depositional, erosional, frost and frost-sediment streaks were identified and analyzed as wind direction indicators on Viking Orbiter and Mariner 9 images of areas poleward of + or - 40 deg latitude. The wind streaks reveal eolian activity at present to be strongest in the north in winter and in the south in spring, due to the hemispherical asymmetry in climate. The alignment of the more massive intercrater dune fields with the presently strongest wind may reflect a longer-term asymmetry in spring flows, as the reorientation times of the dunes exceeded the period of climate asymmetry cycles. Finally, a wider distribution of dune latitudes in the southern polar region is noted to be suggestive of the greater effectiveness of windflow from the south pole.

  15. Eolian features in the Western Desert of Egypt and some applications to Mars.

    USGS Publications Warehouse

    El-Baz, F.; Breed, C.S.; Grolier, M.J.; McCauley, J.F.

    1979-01-01

    Relations of landform types to wind regimes, bedrock composition, sediment supply, and topography are shown by field studies and satellite photographs of the Western Desert. This desert provides analogs of Martian wind-formed features and sand dunes, alternating light and dark streaks, knob 'shadows' and yardangs. Surface particles have been segregated by wind into dunes, sand sheets, and light streaks, that can be differentiated by their grain size distributions, surface shapes, and colors. Throughgoing sand of mostly fine to medium grain size is migrating S in longitudinal dune belts and barchan chains whose long axes lie parallel to the prevailing W winds, but topographic variations such as scarps and depressions strongly influence the zones of deposition and dune morphology. -from Authors

  16. Late Pleistocene-early Holocene karst features, Laguna Madre, south Texas: A record of climate change

    SciTech Connect

    Prouty, J.S.

    1996-09-01

    A Pleistocene coquina bordering Laguna Madre, south Texas, contains well-developed late Pleistocene-early Holocene karst features (solution pipes and caliche crusts) unknown elsewhere from coastal Texas. The coquina accumulated in a localized zone of converging longshore Gulf currents along a Gulf beach. The crusts yield {sup 14}C dates of 16,660 to 7630 B.P., with dates of individual crust horizons becoming younger upwards. The karst features provide evidence of regional late Pleistocene-early Holocene climate changes. Following the latest Wisconsinan lowstand 18,000 B.P. the regional climate was more humid and promoted karst weathering. Partial dissolution and reprecipitation of the coquina formed initial caliche crust horizons; the crust later thickened through accretion of additional carbonate laminae. With the commencement of the Holocene approximately 11,000 B.P. the regional climate became more arid. This inhibited karstification of the coquina, and caliche crust formation finally ceased about 7000 B.P.

  17. Regional sedimentological variations among dark crater floor features: Toward a model for modern eolian sand distribution on Mars

    NASA Technical Reports Server (NTRS)

    Edgett, K. S.; Christensen, P. R.

    1993-01-01

    It has been known since 1972 that many Martian craters have dark features on their floors, and that when seen at higher image resolution, some of the dark units are dune fields. Interpretations of thermal inertia derived from Viking Infrared Thermal Mapper (IRTM) data have been used to suggest that many dark intracrater features, including those where dunes are not observed in images, contain some amount of sand or particles in the range 0.1-10 mm. However, it has never been known if all these dark features consist of dunes. We assembled a set of 108 carefully constrained Viking IRTM observations for dark crater-floor units. The data and selection criteria are described in detail elsewhere. Studied in conjunction with Mariner 9 and Viking orbiter images of each crater, these data indicate that the dark crater-floor units in some regions have different thermal properties than those in other regions. Thermal inertias were computed using the Viking thermal model of H. H. Kieffer and corrected for atmospheric CO2 effects using the relationship for a dust-free atmosphere shown by Haberle and Jakosky.

  18. Pleistocene permafrost features in soils in the South-western Italian Alps

    NASA Astrophysics Data System (ADS)

    D'Amico, Michele; Catoni, Marcella; Bonifacio, Eleonora; Zanini, Ermanno

    2015-04-01

    Because of extensive Pleistocenic glaciations which erased most of the previously existing soils, slope steepness and climatic conditions favoring soil erosion, most soils observed on the Alps (and in other mid-latitude mountain ranges) developed only during the Holocene. However, in few sites, particularly in the outermost sections of the Alpine range, Pleistocene glaciers covered only small and scattered surfaces because of the low altitude reached in the basins, and ancient soils could be preserved for long periods of time on particularly stable surfaces. In some cases, these soils retain good memories of past periglacial activity. We described and sampled soils on stable surfaces in the Upper Tanaro valley, Ligurian Alps (Southwestern Piemonte, Italy). The sampling sites were between 600 to 1600 m of altitude, under present day lower montane Castanea sativa/Ostrya carpinifolia forests, montane Fagus sylvatica and Pinus uncinata forests or montane heath/grazed grassland, on different quartzitic substrata. The surface morphology often showed strongly developed, fossil periglacial patterned ground forms, such as coarse stone circles on flat surfaces, or stone stripes on steeper slopes. The stone circles could be up to 5 m wide, while the sorted stripes could be as wide as 12-15 m. A strong lateral cryogenic textural sorting characterized the fine fraction too, with sand dominating close to the stone rims of the patterned ground features and silt and clay the central parts. The surface 60-120 cm of the soils were podzolized during the Holocene; as a result of the textural lateral sorting, the thickness of the podzolic E and Bs horizons varied widely across the patterns. The lower boundary of the Holocene Podzols was abrupt, and corresponded with dense layers with thick coarse laminar structure and illuvial silt accumulation (Cjj horizons). Dense Cjj diapiric inclusions were sometimes preserved in the central parts of the patterns. Where cover beds were developed

  19. Late Holocene eolian fossilization of Podzols in Northeastern Germany

    NASA Astrophysics Data System (ADS)

    Hirsch, Florian; Raab, Thomas; Schneider, Anna; Wechler, Klaus-Peter

    2016-04-01

    The North European lowland has been formed by glacial and periglacial processes in the Late Pleistocene. Multiple reshaping since the Late Glacial considerably changed the landscape up to and including especially historic times. Sediment sequences and (fossilized) soils can improve our understanding of Late Quaternary landscape development, but mapping of buried soils and surfaces is often limited to single outcrops. Ongoing archaeological rescue excavations in the pre-field of the open-cast mine Cottbus-Nord (northeastern Germany) with dense excavation trenches in an about 10 ha dune and drift sand area reveal multilayered sediment sequences with fossilized soils and sediments from the Late Pleistocene to the Late Holocene. Archaeological findings ranging from Mesolithic flint stones to an about 200 year old ceramics in eolian sediments covering plow horizons and wheel tracks suggest that eolian relocation of sandy material was intensive about 200 years ago. Still unpublished OSL dating underline the intense eolian activity. Recent studies showed that between the 15Th to the 19Th century an iron smelter 5 km to the west of our study site was supplied with charcoal, which was produced in a forest 5 km east to our study site. Our current findings about Late Holocene eolian activity raise the question if this eolian reshaping of the landscape is connected with the operation of the iron smelter either directly by transport or bog iron ore winning or indirectly by population pressure caused by the prospering iron smelter. Our ongoing research indicates, that already for historic land-use off-site effects causing further landscape changes have to be considered.

  20. Summary of 1990 eolian characterization studies, Hanford Site, Washington

    SciTech Connect

    Gaylord, D.R.; Stetler, L.D.; Smith, G.D.; Mars, R.W.

    1993-12-01

    A study of eolian activity was initiated to improve understanding of past climate change and the likely effect of wind on engineered protective barriers at the Hanford Site. Eolian features from a Holocene sand dune field located in the southeastern portion of the Hanford Site were investigated using a variety of field and laboratory techniques including stratigraphic examinations of hand-dug pits, textural and compositional analyses of dune sand and potential source detritus, and air photo interpretations. These investigations were undertaken to evaluate the provenance and eolian dynamics of the sand dunes. Interpretations of sand dune migration using archival air photo stereopairs document a 20% reduction in the volume of active sand dunes (measured from an approximate 15-km{sup 2} test area) between 1948 and 1987. Changes in annual precipitation appear to have influenced active dune migration strongly.

  1. Bahamian Pleistocene model for some Mississippian oolites

    SciTech Connect

    Bain, R.J. )

    1989-08-01

    San Salvador Island, unlike most Bahamian islands, is a narrow isolated platform surrounded by deep ocean. Therefore, sedimentary deposits on San Salvador must be explained in terms of processes and settings on this narrow, isolated shelf. Pleistocene oolite occurs between Illinoian and Wisconsinan paleosols. Dune ridges of up to 120 ft are composed of Pleistocene cross-bedded oolitic grainstone, whereas interdunal deposits are bioclastic packstone and wackestone containing abundant Chione cancellata. In lower dunal deposits, bioclastic content increases and the degree of sorting decreases. A fenestral porosity zone occurs approximately 5 ft above present-day sea level. In several ridges, oolite drapes over older paleosol-capped bioclastic ridges. During the Sangamonian, sea water flooded the platform, however some remnant Aftonian ridges remained above sea level. As cold water from the surrounding deep ocean warmed on the shelf, ooids were generated and were washed onto beaches and blown into dunes. Remnant ridges restricted water movement and acted as nucleii for eolian ooid dunes. As sea level continued to rise, ooids were replaced by lagoonal bioclastic deposits. Ooid production was restricted to the swash zone along beaches resulting in the mixture of ooids and bioclastic sand in later Sangamonian deposits. Numerous Mississippian oolites display features similar to the Pleistocene oolite of San Salvador Island. Possible comparisons include thick lenses of Ste. Genevieve and Bangor limestones, paleosols in the Ste. Genevieve halo-shaped bodies of Greenbrier oolite, and the relationship of nearly all olites with bioclastic facies.

  2. Age and sedimentary record of inland eolian sediments in Lithuania, NE European Sand Belt

    NASA Astrophysics Data System (ADS)

    Kalińska-Nartiša, Edyta; Thiel, Christine; Nartišs, Māris; Buylaert, Jan-Pieter; Murray, Andrew S.

    2015-07-01

    We present a study based on four inland eolian locations in Eastern, Central and Southeastern Lithuania belonging to the northeastern part of the 'European Sand Belt' (ESB). Although there have been several previous studies of the ESB, this north-eastern extension has not been investigated before in any detail. The sedimentary structural-textural features are investigated and a chronology was derived using optically stimulated luminescence on both quartz and feldspar. The sedimentary structures and the rounding and surface characteristics of the quartz grains argue for a predominance of eolian transport. Additionally, some structural alternations and a significant contribution of non-eolian grains are interpreted as inherited local glacial/glaciofluvial-bearing lithologies. Three main (glaciolacustrine-) eolian phases are distinguished based on the position in the landscape and the luminescence ages: (1) An older eolian series around 15 to 16 ka, possibly correlated with the cold GS-2a event according to the GRIP stratigraphy, and (2) a younger eolian series around 14.0 ka, possibly representing the GI-1d and 1c events. The older eolian series is underlain by (3) a glaciolacustrine-eolian series for which the period of deposition remains uncertain due to the significant discrepancy between the ages based on quartz and feldspar.

  3. Morphometric analysis of molars in a Middle Pleistocene population shows a mosaic of 'modern' and Neanderthal features.

    PubMed

    Martinón-Torres, María; Spěváčková, Petra; Gracia-Téllez, Ana; Martínez, Ignacio; Bruner, Emiliano; Arsuaga, Juan Luis; Bermúdez de Castro, José María

    2013-10-01

    Previous studies of upper first molar (M1) crown shape have shown significant differences between Homo sapiens and Homo neanderthalensis that were already present in the European Middle Pleistocene populations, including the large dental sample from Atapuerca-Sima de los Huesos (SH). Analysis of other M1 features such as the total crown base area, cusp proportions, cusp angles and occlusal polygon have confirmed the differences between both lineages, becoming a useful tool for the taxonomic assignment of isolated teeth from Late Pleistocene sites. However, until now the pattern of expression of these variables has not been known for the SH sample. This fossil sample, the largest collection from the European Middle Pleistocene, is generally interpreted as being from the direct ancestors of Neanderthals, and thus is a reference sample for assessing the origin of the Neanderthal morphologies. Surprisingly, our study reveals that SH M(1) s present a unique mosaic of H. neanderthalensis and H. sapiens features. Regarding the cusp angles and the relative occlusal polygon area, SH matches the H. neanderthalensis pattern. However, regarding the total crown base area and relative cusps size, SH M(1) s are similar to H. sapiens, with a small crown area, a strong hypocone reduction and a protocone enlargement, although the protocone expansion in SH is significantly larger than in any other group studied. The SH dental sample calls into question the uniqueness of some so-called modern traits. Our study also sounds a note of caution on the use of M(1) occlusal morphology for the alpha taxonomy of isolated M(1) s. PMID:23914934

  4. Morphometric analysis of molars in a Middle Pleistocene population shows a mosaic of ‘modern’ and Neanderthal features

    PubMed Central

    Martinón-Torres, María; Spěváčková, Petra; Gracia-Téllez, Ana; Martínez, Ignacio; Bruner, Emiliano; Arsuaga, Juan Luis; Bermúdez de Castro, José María

    2013-01-01

    Previous studies of upper first molar (M1) crown shape have shown significant differences between Homo sapiens and Homo neanderthalensis that were already present in the European Middle Pleistocene populations, including the large dental sample from Atapuerca-Sima de los Huesos (SH). Analysis of other M1 features such as the total crown base area, cusp proportions, cusp angles and occlusal polygon have confirmed the differences between both lineages, becoming a useful tool for the taxonomic assignment of isolated teeth from Late Pleistocene sites. However, until now the pattern of expression of these variables has not been known for the SH sample. This fossil sample, the largest collection from the European Middle Pleistocene, is generally interpreted as being from the direct ancestors of Neanderthals, and thus is a reference sample for assessing the origin of the Neanderthal morphologies. Surprisingly, our study reveals that SH M1s present a unique mosaic of H. neanderthalensis and H. sapiens features. Regarding the cusp angles and the relative occlusal polygon area, SH matches the H. neanderthalensis pattern. However, regarding the total crown base area and relative cusps size, SH M1s are similar to H. sapiens, with a small crown area, a strong hypocone reduction and a protocone enlargement, although the protocone expansion in SH is significantly larger than in any other group studied. The SH dental sample calls into question the uniqueness of some so-called modern traits. Our study also sounds a note of caution on the use of M1 occlusal morphology for the alpha taxonomy of isolated M1s. PMID:23914934

  5. Lethal Sandslides from Eolian Dunes.

    PubMed

    Loope; Mason; Dingus

    1999-11-01

    Fossil vertebrates entombed within the Upper Cretaceous Djadokhta Formation of southern Mongolia bear testimony to a heretofore unknown geologic phenomenon: mass wasting of eolian dunes during heavy rainstorms. Evaporation of shallow-penetrating rainwater led to progressive calcite accumulation in a thin layer of sand about 0.5 m below the surface of dune lee slopes. During rare heavy rainstorms, a perched water table developed at the top of calcitic zones. Positive pore water pressure led to translational slides and fast-moving sediment gravity flows that overwhelmed animals on the lee slopes of large dunes and in interdune areas. PMID:10517885

  6. Eolian cover sands: a sedimentologic model and paleoenvironmental implications

    SciTech Connect

    Lea, P.D.

    1985-01-01

    In periglacial areas, accumulations of eolian sand commonly form low-relief blankets without well-developed dunes. Internally, these sandsheet deposits exhibit subhorizontal lamination rather than high-angle cross-bedding. Such cover sands of late-Pleistocene age mantle extensive areas in northern Europe, but have been reported more rarely from North America. The processes by which cover sands, as opposed to dunes, accumulate have not yet been determined conclusively. Wind ripples and sand dunes do not form a continuum; flow separation and avalanching and negligible in the former and vital in the latter. Accretion of a sand patch into a mound sufficient to cause flow separation and dune growth requires a consistently available supply of loose sand. In cover-sand areas, sand may be immobilized prior to dune development by several factors: (1) a sparse vegetation cover, (2) moist ground conditions, (3) snow cover, and (4) a shallow permafrost table and/or an ice-cemented active layer. Detailed sedimentologic studies may allow discrimination among these various controls. The importance of the individual controlling factors can vary seasonally in a given deposit, as well as between deposits in different paleogeographic settings. However, all factors imply more mesic conditions than those associated with many dune deposits. The association of cover sands with paraboloid dunes is also consistent with somewhat moist conditions. The relatively mesic nature of cover sands controls their Pleistocene distribution; they become decreasingly important relative to dunes in maritime-to-continental transects across Alaska and northern Europe.

  7. Millennial-scale varnish microlamination dating of late Pleistocene geomorphic features in the drylands of western USA

    NASA Astrophysics Data System (ADS)

    Liu, Tanzhuo; Broecker, Wallace S.

    2013-04-01

    Varnish microlamination (VML) dating is a climate-based correlative age determination technique used to correlate and date various geomorphic features in deserts. In this study, we establish a generalized late Pleistocene (18-74 ka) millennial-scale microlamination sequence in fine-grained, fast-accumulating rock varnish for the drylands of western USA, radiometrically calibrate the sequence and correlate it with the δ18O record in the GISP2 Greenland ice core. We then use this climate-correlated varnish microstratigraphy to estimate surface exposure ages for radiometrically dated late Pleistocene geomorphic features in the study region. The VML dating of debris flow deposits on the Sehoo recessional shorelines of Lake Lahontan at the Jessup embayment of central Nevada yields a minimum-limiting age of 14.95-15.95 ka, in good agreement with a calibrated 14C age of 15.22 ± 0.12 ka for the timing of the lake recession. The VML dating of a giant ejecta block on the rim of Meteor Crater in northern Arizona yields a minimum-limiting age of 49.15 ka, closely matching a thermoluminescence (TL) age of 49 ± 3 ka and slightly younger than a recently updated cosmogenic 36Cl age of 56.0 ± 2.4 ka for the meteor impact event. The VML dating of distal Q2c fan surfaces on Hanaupah Canyon alluvial fan in Death Valley, California, yields a minimum-limiting age of 73.55 ka, in accord with cosmogenic 36Cl depth-profile ages of 66 + 22/-14 ka and 72 + 24/- 20 ka for the same fan deposits. The close agreement between the VML age estimates and the independently derived radiometric ages for these geomorphic features attests to the validity and reliability of millennial-scale VML dating. To further assess its potential in desert geomorphological research, we use the VML method to study alluvial-fan responses to millennial-scale climatic changes. The VML dating of a small tributary fan in Death Valley reveals two episodes of fan aggradation, one ceasing at 73.55-86.75 ka during the dry

  8. Patterns of permeability in eolian deposits

    SciTech Connect

    Goggin, D.J.; Chandler, M.A.; Kocurek, G.; Lake, L.W.

    1988-06-01

    The eolian, Jurassic Page sandstone of northeastern Arizona is marked by a highly ordered heterogeneity. The heterogeneity is expressed by the intricate association of stratification types, which are a direct result of the depositional processes. The dominant stratification types in eolian reservoirs are grainflow, grainfall, and wind-ripple deposits, which form on the lee faces of migrating dunes; interdune deposits, which form between migrating dunes; and extra-erg deposits, which occur sporadically when other depositional environments encroach upon an eolian system. These stratification types each have a unique permeability range, which implies that the fluid migration routes in eolian reservoirs will be dictated by the geometry and types of stratification present. One of the most important aspects of this study is the correlation of qualitative geologic descriptions with quantitative variables such as permeability. About 2,000 measurements were made with a field minipermeameter on an outcrop of the Page sandstone. These data show that three distinct permeability modes directly relate to the different stratification types.

  9. Eolian event stratigraphy - A conceptual framework

    SciTech Connect

    Kocurek, G.; Havholm, K.G. )

    1991-03-01

    A basis for eolian event stratigraphy is to distill the impact of events into fundamental processes and products. For accumulation (net deposit through time) to occur, the sediment budget must be positive. If the sediment budget becomes neutral or negative, accumulation ceases and a bypass or erosional super bounding surface, respectively, forms capping the genetic unit. Within the three types of eolian systems (dry, wet, stabilized), the mechanisms of accumulation and super-surface formation differ. In the dry system, accumulation occurs because of areal deceleration of sand-carrying winds. Because of dune-interdune flow conditions, accumulation begins when interdune flats are closed, requiring sand supply, time, and conditions for dune growth at the expense of interdune flats. In the wet system, accumulation of dune and interdune deposits occurs by trapping with a rising water table. Accumulations vary with the nature of the water table rise, proportion of dunes and interdune flats, and interdune topography. In the stabilized system, accumulation occurs with rapid stabilization of elements of active eolian systems; super surfaces form when the causes of stabilization cease. The eolian rock record consists of preserved accumulations and super surfaces. Accumulation space is distinct from preservation space. Preservation space is made by subsidence and water table rise. Without preservation space, an unconformity results. The dominance of subsidence versus water table rise is reflected in dry and wet accumulations respectively, such as the Jurassic Navajo and Entrada sandstones.

  10. Correlation of Plio Pleistocene Tephra in Ethiopian and Kenyan rift basins: Temporal calibration of geological features and hominid fossil records

    NASA Astrophysics Data System (ADS)

    WoldeGabriel, Giday; Hart, William K.; Katoh, Shigehiro; Beyene, Yonas; Suwa, Gen

    2005-10-01

    The 200-m-thick fossiliferous Konso Formation and overlying terrace deposits, which crop out at the end of the southern sector of the Main Ethiopian Rift (MER), contain more than 30 distal tephra layers. Local and regional tephra correlations of more than 20 tephra units were established using major and trace element data of discrete and purified bulk glass samples within the Konso study area. Eleven correlative marker tuffs were recognized in stratigraphic sections of both the Konso Formation and the Omo-Turkana Basin sediments in southern Ethiopia and northern Kenya. The Turoha, Hope, Ivory, Bright White, and Boleshe Tuffs in the Konso Formation, and the Upper White Tuff in the overlying terrace deposits are securely correlated with the KBS, Akait, Lokapetamoi, Chari, Lower Nariokotome, and Silbo Tuffs of the Omo-Turkana Basin, using least mobile major elements (CaO, Fe 2O 3*, and TiO 2) and geochronology. Preliminary correlations are also suggested between the Konso Formation distal tephra and proximal units of the Quaternary caldera-forming silicic centers in the central sector of the MER. The strongly peralkaline tuffs of the Konso Formation are compositionally similar to proximal eruptions mostly located along the Quaternary axial rift zone of the southern, central, and northern sectors of the MER. The tephra correlation provides information about the temporal and spatial features of the volcanic and tectonic processes recorded in the evolving basins. Thickness and sedimentation rate were determined for both the Konso Formation and the Omo-Turkana Basin sections, measured between the Turoha (=KBS; 1.91 ± 0.03 Ma) and the Bright White (=Chari; 1.40 ± 0.02 Ma) Tuffs. Although the lithostratigraphic sequence at the Konso study area is younger, sedimentation rate within the Konso Formation was comparable to that of the Koobi Fora Formation, higher in the Nachukui Formation, and lower in the Shungura Formation. Local and regional differences in thickness and

  11. Comparison of knobs on Mars to isolated hills in eolian, fluvial and glacial environments

    NASA Technical Reports Server (NTRS)

    Manent, L. S.; El-Baz, F.

    1986-01-01

    The isolated knobs of Mars, characterized in terms of length, width, geographic location, proximity to streaks, and geologic surroundings through Viking Orbiters' photomosaics, are compared to isolated hills on earth eroded by eolian, fluvia, and glacial processes. Comparison of length-to-width ratios indicates similarity of the knobs to the hills formed in a hyperarid environment. The hills formed on earth by fluvial and glacial processes have length-to-width ratios significantly higher than those of the Martian knobs and have other diagnostic features not associated with the knobs. Moreover, streaks, splotches, dunes, and pitted and fluted rocks, all indicative of an eolian regime, are associated with the Martian knobs.

  12. Riverine Eolian Dunes in Uruguay: OSL Ages and Paleoenvironmental Significance

    NASA Astrophysics Data System (ADS)

    Leigh, D. S.; Suarez, R.; Brook, G. A.

    2012-12-01

    Relict parabolic dunes occur along Rio Negro and Rio Tacuarembó in Uruguay under the current humid temperate climate. These dunes offer important terrestrial evidence of drier conditions in the past and may provide foresight about landscape consequences of future climate change. The ages of these dunes previously had not been measured by any absolute dating technique. Two dune fields were selected for optically stimulated luminescence (OSL) dating using the single aliquot regeneration method, including four samples along Rio Negro near Pueblo de la Arena and three samples along Rio Tacuarembó near Ansina. Results indicate that the dunes were active during the late Pleistocene, with five of the OSL ages in the 22 ka to 12 ka range. One OSL age at the Ansina dune field returned an age of 6 ka, indicating the possibility of limited dune reactivation during the Holocene. There is clear evidence of historical dune activation (e.g. buried fences) at both the Rio Negro and Rio Tacuarembó sites; one OSL sample from Rio Negro dunes confirms an historical age of 107 years BP. However, human land disturbance rather than climatic factors may explain the historical reactivation. Late Pleistocene dune activity in central Uruguay indicates much drier and windier paleoclimate (at least seasonally) than present, and correlates well with eolian activity in more arid parts of South America in western Argentina. Age and paleoenvironment of the riverine dunes in Uruguay are remarkably similar to those of the southeastern United States (USA), indicating similar patterns of paleoclimate in both hemispheres. Such similarities help to resolve the spatial patterns of global scale climate change.

  13. Observations Regarding Small Eolian Dunes and Large Ripples on Mars

    NASA Technical Reports Server (NTRS)

    Edgett, Kenneth S.

    2001-01-01

    Eolian bedforms occur at the interface between a planetary surface and its atmosphere; they present a proxy record of the influence of climate, expressed in sediment transport, over that surface. High resolution images (1.5 - 12 m/pixel) from the Mars Global Surveyor (MGS) Mars Orbiter Camera provide glimpses of the most recent events shaping the martian landscape. Thousands of images exhibit small transverse dunes or large eolian ripples that have crest-to-crest spacings of 10 to 60 m, heights of a few to 10 m. Bedforms of the size and patterns seen in the Mars photographs are rarely described among Earth's eolian landforms; in terms of size and morphology, most of these fall between traditional definitions of "ripples" and "dunes". Dunes are composed chiefly of materials transported by saltation, ripples are smaller forms moved along by the impact of saltating grains (traction). The largest reported eolian ripples on Earth (granule ripples, megaripples) are typically smaller than the bedforms observed on Mars; likewise, most dunes are typically larger. The small dunes and large ripples on Mars come in a variety of relative albedos, despite an early MGS impression that they are all of high albedo. Some ripples occur on the surfaces of sand dunes; these are most likely true granule ripples. However, most of these bedforms occur in troughs, pits, craters, and on deflated plains. Despite impressions early in the MGS mission, they do not occur everywhere (e.g., they are rare on the northern plains) but they do occur at a range of elevations from the highest volcanoes to the deepest basins. Where they occur on a hard substrate among larger sand dunes, the big dunes have over-ridden the smaller bedforms, indicating that the smaller features are older and perhaps indurated or very coarse-grained. At other locales, the small bedforms have been mantled by material settled from suspension, in other cases they are being exhumed and may be lithified. Still other examples are

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

    USGS Publications Warehouse

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

    2003-01-01

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

  15. In situ weathering vs eolian additions to soils: A proposed solution from lava tubes and cumulic soils, Owens Valley, Calif

    SciTech Connect

    Lafarge, D.W.; Burke, R.M. . Dept. of Geology)

    1993-04-01

    Natural dust traps in the form of open conduits to lava tubes, collapsed lava tubes, cinder cone depressions, and range-front half grabens create favorable environments for the accumulation of eolian materials through extended periods of geologic time. The radiometrically dated basalt flows in the Big Pine Lava Field, CA provide minimum and maximum constraining dates for accumulation rates of such eolian materials, which are also added, at least partially, to regional soils developed on moraines and alluvial fans. 1.2 meters of well sorted silts to fine sands are located within a lava tube formed in a flow emanating from the northern cone of the Stooges Range along the range front of the Inyo Mountains. This non-basaltic material records a minimum eolian accumulation rate of 4.8 mm/ka, whereas a somewhat thicker section in the subaerially exposed collapsed portion of the tube system suggests an accumulation rate of 8.0 mm/ka. Across Owens Valley along the Sierra Nevada range front, a cumulic soil described to a depth of 363+ cm is formed in a geomorphically youthful half graben near Crater Mountain (CM). This site records a bimodal particle size distribution of eolian silts and coarse sands, with locally derived very coarse sands and fine pebble gravels from juxtaposed granitic bedrock. Two plausible explanations for the cumulic, bimodal nature of the soil, with accompanying clay bulges are: (1) episodic sources for eolian dust induced by desiccation of pluvial Owens Lake, which would be in phase with Pleistocene climatic changes; or (2) continual input of the eolian component with episodic additions of the coarse-grained granitic materials brought about by periods of tectonism along the Sierra Nevada range front fault, thus not related to paleoclimate. Prevailing southerly winds suggested for times of peak dust availability, and the model of soil forming intervals proposed by Chadwick and Davis (1990) favor the first of these two explanations for the CM.

  16. Ground-water solutes and eolian processes: An example from the High Plains of Texas

    SciTech Connect

    Wood, W.W.; Sanford, W.E. )

    1992-01-01

    Eolian dunes associated with saline-lake basins are important geologic features in arid and semiarid areas. The authors propose that eolian processes may also be important in controlling solute concentration and composition of ground water in these environments. A study of Double Lakes on the Southern High Plains of Texas suggests that approximately 200 megagrams of chloride enters this topographically closed basin from the surrounding water table aquifer, direct precipitation and surface runoff. Solute-transport simulation suggest that approximately 70 of the 200 megagrams of the chloride annually leaves the basin by diffusion and ground-water advection through a 30 meter-thick shale underlying the lake. The remaining 130 megagrams is hypothesized to be removed by eolian processes. Closed water-table contours around the lake and a hydrologic analysis suggest that it is improbable that solutes will reach the surrounding water-table aquifer by ground-water transport from this lake system. The conceptual eolian-transport model is further supported by observed chloride profiles in the unsaturated zone. When analyzed with estimates of recharge fluxes, these profiles suggest that approximately 150 megagrams of chloride enter the unsaturated zone downwind of the lake annually. Thus two independent methods suggest that 130 to 150 megagrams of chloride enter the unsaturated zone downwind of the lake annually. Thus two independent methods suggest that 130 to 150 megagrams of chloride are removed from the basin annually by eolian process and redeposited downwind of the lake. Eolian input to the ground water is consistent with the observed plume shape as well as with the solute and isotopic composition of ground water in the water-table aquifer downwind of the lake basin.

  17. New optically stimulated luminescence ages provide evidence of MIS3 and MIS2 eolian activity on Black Mesa, northeastern Arizona, USA

    USGS Publications Warehouse

    Ellwein, A.L.; Mahan, S.A.; McFadden, L.D.

    2011-01-01

    Eolian deposition on the semiarid southern Colorado Plateau has been attributed to episodic aridity during the Quaternary Period. However, OSL ages from three topographically controlled (e.g. falling) dunes on Black Mesa in northeastern Arizona indicate that eolian sediments there were deposited in deep tributary valleys as early as 35-30. ka, with most sand deposited before 20. ka. In contrast, the oldest OSL ages for sand sheets fall within the Pleistocene-Holocene climatic transition (~. 12-8. ka). Thus most eolian sediment accumulated on Black Mesa under climatic conditions that were in general cooler, moister, and more variable than today, not more arid, pointing to a considerable increase in sediment supply. ?? 2010 University of Washington.

  18. Eolian sabkha sandstones in the Nugget Sandstone (Jurassic), Vernal area, Utah

    SciTech Connect

    Schenk, C.J.; Peterson, F. )

    1991-06-01

    The Jurassic Nugget Sandstone in the Vernal, Utah, area is characterized by thick (up to 25 m) sets of cross-stratified eolian dune sandstone separated by either erosional planar bounding surfaces or thin (mostly < 3 m) sandstones interpreted as sabkha sandstones. Structures in Nugget sabkha sandstones are predominantly wavy or irregular bedding and thin, remnant sets of dune cross-strata consisting of eolian ripple and avalanche strata. The types of sedimentary structures and erosional features in Nugget sabkha sandstones indicate a close relationship between sand deposition and erosion and fluctuations in the local water table. Thin, remnant eolian dune sets are common in Nugget sabkha sandstones. The remnant sets form when dunes migrating across a sabkha are partially wetted as the water table rises slightly (on a scale of tens of centimeters); the lower part of the dune with wetted sand remains on the sabkha as the rest of the dune continues to migrate. Typically, ripple strata of the dune apron and the toes of avalanche strata are preserved in dune remnants. The avalanche strata, being slightly coarser grained, are preferentially deflated, leaving microtopography. This topography is commonly filled in with ripple strata that form as dry sand again blows across the sabkha. Stacked sets of remnant dunes separated by erosional surfaces illustrate the control of sand deposition on eolian sabkhas by the local water table.

  19. Non-dune eolian sand in Indian mounds

    NASA Astrophysics Data System (ADS)

    Tanner, William F.

    1980-02-01

    Indian mounds, near Careyville, Florida, about 2.0 m high, are located on hillsides and hilltops 10 to 20 m above the floodplain of the nearest river (Choctawhatchee). Each mound is composed largely of quartz sand, with a scattering of artefacts and stream pebbles (not in layers), but with no visible bedding. Probability plots showed 25 Gaussian distributions, 18 having the 'dune hump', three having the 'surf break' and nine being doubly-truncated or having other patterns of unknown or uncertain origin. The surf breaks probably were inherited from pre-Pleistocene marine terraces in the area. The pebbles and the sand were not introduced by the same agency. The sand probability plots, taken as a set, indicate an eolian origin. The rough symmetry of the mounds, and the lack of cross-bedding, argue against a migrating dune origin. On a variability plot (showing the variability of the means versus the variability of the standard deviations), one suite of samples fell clearly within the 'dune' number field, a second suite in the overlap area between 'dune' and 'beach', and a third suite, taken immediately adjacent to a creek bed, plotted in the overlap area between 'beach' and 'coastal plain stream'. The pebbles, of common Southern Appalachian types, are attributed to the activities of the inhabitants, perhaps children. The sand is thought to have been carried by the wind, perhaps from nearby river sand bars, or from areas burned either by lightning-set wildfires or as part of "slash-and-burn" agriculture. The mounds are thought to represent clearings (for huts), and hence good trapping devices for wind-borne sand.

  20. Eolian paleotopographic highs as stratigraphic traps: origin and distinction

    SciTech Connect

    Eschner, T.B.; Kocurek, G.A.

    1985-02-01

    Significant hydrocarbon accumulations occur where eolian paleotopographic highs are preserved beneath transgressive marine deposits. Paleotopographic highs can represent erosional remnants of an unconformity, or partly preserved eolian dunes, or combinations of both. Paleotopography reflects the extent of modification undergone by eolian units prior to or during transgression. Modification varies between extremes of (1) destruction - where eolian deposits are deeply eroded and the former dunal profile is lost, and (2) preservation - where dunes and interdune areas are preserved nearly intact. The extent of modification that occurs during transgression is controlled primarily by (1) the energy of the transgressing sea, (2) the speed of transgression, and (3) the abundance of sand-stabilizing early cements or plants. High-energy seas destroy dunes through persistent erosion by tides and waves and by initiating dune collapse and mass flowage of dune sands. Preservation occurs where quiescent seas flood interdune areas and create shallow to periodically emergent marine environments, such as interdune sabkhas or tidal flats. Gradual filling of interdune areas with shallow marine sediments can fortify and preserve adjacent dunes. These varied processes that interact between marine and eolian environments to create different types of topography are exemplified in ancient eolian-marine sequences of the Western Interior of North America, and preserved Holocene dunes of coastal Australia. Different types of eolian highs can be recognized by analysis of bounding surfaces in outcrop or core. An understanding of eolian-marine processes and environments that create topography allows for prediction of areas of potential stratigraphic traps.

  1. Late Pleistocene dune activity in the central Great Plains, USA

    USGS Publications Warehouse

    Mason, J.A.; Swinehart, J.B.; Hanson, P.R.; Loope, D.B.; Goble, R.J.; Miao, X.; Schmeisser, R.L.

    2011-01-01

    Stabilized dunes of the central Great Plains, especially the megabarchans and large barchanoid ridges of the Nebraska Sand Hills, provide dramatic evidence of late Quaternary environmental change. Episodic Holocene dune activity in this region is now well-documented, but Late Pleistocene dune mobility has remained poorly documented, despite early interpretations of the Sand Hills dunes as Pleistocene relicts. New optically stimulated luminescence (OSL) ages from drill cores and outcrops provide evidence of Late Pleistocene dune activity at sites distributed across the central Great Plains. In addition, Late Pleistocene eolian sands deposited at 20-25 ka are interbedded with loess south of the Sand Hills. Several of the large dunes sampled in the Sand Hills clearly contain a substantial core of Late Pleistocene sand; thus, they had developed by the Late Pleistocene and were fully mobile at that time, although substantial sand deposition and extensive longitudinal dune construction occurred during the Holocene. Many of the Late Pleistocene OSL ages fall between 17 and 14 ka, but it is likely that these ages represent only the later part of a longer period of dune construction and migration. At several sites, significant Late Pleistocene or Holocene large-dune migration also probably occurred after the time represented by the Pleistocene OSL ages. Sedimentary structures in Late Pleistocene eolian sand and the forms of large dunes potentially constructed in the Late Pleistocene both indicate sand transport dominated by northerly to westerly winds, consistent with Late Pleistocene loess transport directions. Numerical modeling of the climate of the Last Glacial Maximum has often yielded mean monthly surface winds southwest of the Laurentide Ice Sheet that are consistent with this geologic evidence, despite strengthened anticyclonic circulation over the ice sheet. Mobility of large dunes during the Late Pleistocene on the central Great Plains may have been the result of

  2. Mineralogy of Eolian Sands at Gale Crater

    NASA Technical Reports Server (NTRS)

    Achilles, C. N.; Vaniman, D. T.; Blake, D. F.; Bristow, T. F.; Rampe, E. B.; Ming, D. W.; Chipera, S. J.; Morris, R. V.; Morrison, S. M.; Downs, R. T.; Fendrich, K. V.; Ehlmann, B. L.; Yen, A. S.; Sarrazin, P. C.; Treiman, A. H.; Craig, P. I.; Lapotre, M. G. A.; Edgett, K. S.; Gellert, R.; Crisp, J. A.; Morookian, J. M.; Grotzinger, J. P.; Des Marais, D. J.; Farmer, J. D.

    2016-01-01

    The Mars Science Laboratory rover Curiosity has been exploring outcrop and regolith in Gale crater since August 6, 2012. During this exploration, the mission has collected 10 samples for mineralogical analysis by X-ray diffraction (XRD), using the CheMin instrument. The CheMin (Chemistry and Mineralogy) instrument on the Mars Science Laboratory rover Curiosity uses a CCD detector and a Co-anode tube source to acquire both mineralogy (from the pat-tern of Co diffraction) and chemical information (from energies of fluoresced X-rays). A detailed description of CheMin is provided in [1]. As part of the rover checkout after landing, the first sample selected for analysis was an eolian sand deposit (the Rocknest "sand shadow"). This sample was selected in part to characterize unconsolidated eolian regolith, but primarily to prove performance of the scoop collection system on the rover. The focus of the mission after Rocknest was on the consolidated sediments of Gale crater, so all of the nine subsequent samples were collected by drilling into bedrock com-posed of lithified sedimentary materials, including mudstone and sandstone. No scoop samples have been collected since Rocknest, but at the time this abstract was written the mission stands poised to use the scoop again, to collect active dune sands from the Bagnold dune field. Several abstracts at this conference outline the Bagnold dune campaign and summarize preliminary results from analyses on approach to the Namib dune sampling site. In this abstract we review the mineralogy of Rocknest, contrast that with the mineralogy of local sediments, and anticipate what will be learned by XRD analysis of Bagnold dune sands.

  3. Origin of Martian outflow channels - The eolian hypothesis

    NASA Technical Reports Server (NTRS)

    Cutts, J. A.; Blasius, K. R.

    1981-01-01

    It has been recognized for many years that wind injects dust into the atmosphere on Mars and moves around thin layers of surface material. An investigation is conducted regarding the rates of eolian transport on Mars in the context of eolian channel formation. A model is developed for the formation of an erosional channel by sandblasting with materials transported by wind out of chaotic terrains. This model is applied to the interpretation of topographic measurements made in the chaotic terrain source area and channel of Aromatum Vallis, a small well-preserved channel system southwest of the Chryse basin, and constraints are developed on the eolian mechanism.

  4. Pennsylvanian to Jurassic eolian transportation systems in the western United States

    USGS Publications Warehouse

    Peterson, F.

    1988-01-01

    The direction of sediment transport in eolian sandstones of Pennsylvanian to Jurassic age was interpreted from crossbedding resultants (vector means) obtained from studies of eolian rocks in the western U.S., supplemented by data from the few eolian units of eastern North America. These were compiled from the published or unpublished (theses) literature, from unpublished field data contributed by colleagues, or from measurements made for this study. In addition, new paleogeographic maps were compiled to evaluate the influence of geographic features on the atmospheric circulation patterns that are inferred from the crossbedding studies. Regionally, the crossbedding indicates northeasterly, northerly, or northwesterly winds (present coordinates) from Pennsylvanian through most of Middle Jurassic time. A rather abrupt change in wind directions occurred in late Middle Jurassic time (late part of the Callovian Age) when westerly wind patterns developed. By the Late Jurassic the winds shifted to southwesterly. Calculations of the consistency factor (vector mean strength) made from region-wide analyses of the resultants indicate fairly unidirectional winds from the Pennsylvanian through the Early Jurassic. Middle Jurassic circulation was more varied, judging from crossbedding studies in the lower part of the Entrada Sandstone. Crossbedding in Upper Jurassic eolian rocks of Wyoming and South Dakota yielded a random pattern but Upper Jurassic rocks farther south on the Colorado Plateau and adjoining areas show a return to a fairly unidirectional pattern. Comparing the resultants with their reconstructed paleogeographic setting shows surprisingly little influence of major geographic features on overall circulation patterns. However, the greatest amount of local variation occurred at or near highly indented shorelines where the temperature contrast between land and water produces local wind currents that may vary appreciably from regional circulation patterns. Although they

  5. Observations on Ventifacts and Wind-Polished Boulders in Pleistocene Coversands, Ice-Marginal New Jersey

    NASA Astrophysics Data System (ADS)

    Demitroff, M. N.

    2014-12-01

    The nature of New Jersey Pine Barrens' paleoenvironment biome has been problematic. The region's Pleistocene environment has been interpreted as cool and moist, with boreal forest. A competing interpretation envisioned cold, dry, semidesert conditions. Pebble- to boulder-sized ventifacts with a wide suite of erosional forms provide evidence for strong Pleistocene wind action, which occurred when the land was sparsely vegetated allowing an abundance of abradants to be easily entrained and transported. Although commonplace, ventifact presence and utility in paleoenvironmental reconstruction is ignored. Most ventifacts occur on upland surfaces and attest to stability in this part of the region's otherwise low-relief landscape, and their subsequent disarrangement provides clues to geomorphic processes and landscape evolution. Ventifacts progressed downslope along upper valley-side slopes largely by gravitational mass movement, particularly under periglacial conditions. Development of eolian features such as pavement einkante, scallops, and weathering pit modification can evolve only where sustained wind velocities are very high and sand sources are abundant. Pine Barrens ventifacts provide evidence that desert-like conditions prevailed. Some ventifact surfaces are covered with a silica glaze or an iron-enriched metal film, or both, indicating multiple episodes of wind abrasion. Coating study holds much promise for future dating and climate reconstruction investigations.

  6. Holocene eolian activity in the Minot dune field, North Dakota

    USGS Publications Warehouse

    Muhs, D.R.; Stafford, Thomas W., Jr.; Been, J.; Mahan, S.A.; Burdett, J.; Skipp, G.; Rowland, Z.M.

    1997-01-01

    Stabilized eolian sand is common over much of the Great Plains region of the United States and Canada, including a subhumid area of ??? 1500 km2 near Minot, North Dakota. Eolian landforms consist of sand sheets and northwest-trending parabolic dunes. Dunes and sand sheets in the Minot field are presently stabilized by a cover of prairie grasses or oak woodland. Stratigraphic studies and accelerator mass spectrometry radiocarbon dating of paleosols indicate at least two periods of eolian sand movement in the late Holocene. Pedologic data suggest that all of the dune field has experienced late Holocene dune activity, though not all parts of the dune field may have been active simultaneously. Similar immobile element (Ti, Zr, La, Ce) concentrations support the interpretation that eolian sands are derived from local glaciofluvial and glaciolacustrine sediments. However, glaciolacustrine and glaciofluvial source sediments have high Ca concentrations from carbonate minerals, whereas dune sands are depleted in Ca. Because noneolian-derived soils in the area are calcareous, these data indicate that the Minot dune field may have had extended periods of activity in the Holocene, such that eolian abrasion removed soft carbonate minerals. The southwest-facing parts of some presently stabilized dunes were active during the 1930s drought, but were revegetated during the wetter years of the 1940s. These observations indicate that severe droughts accompanied by high temperatures are the most likely cause of Holocene eolian activity.

  7. Eolian reservoir characteristics predicted from dune type

    SciTech Connect

    Kocurek, G.; Nielson, J.

    1985-02-01

    The nature of eolian-dune reservoirs is strongly influenced by stratification types (in decreasing order of quality: grain-flow, grain-fall, wind-ripple deposits) and their packaging by internal bounding surfaces. These are, in turn, a function of dune surface processes and migration behavior, allowing for predictive models of reservoir behavior. Migrating, simple crescentic dunes produce tabular bodies consisting mainly of grain-flow cross-strata, and form the best, most predictable reservoirs. Reservoir character improves as both original dune height and preserved set thickness increase, because fewer grain-fall deposits and a lower percentage of dune-apron deposits occur in the cross-strata, respectively. It is probable that many linear and star dunes migrate laterally, leaving a blanket of packages of wind ripple laminae reflecting deposition of broad, shifting aprons. This is distinct from models generated by freezing large portions of these dunes in place. Trailing margins of linear and star dunes are prone to reworking by sand-sheet processes that decrease potential reservoir quality. The occurrence of parabolic dunes isolated on vegetated sand sheets results in a core of grain-flow and grain-fall deposits surrounded by less permeable and porous deposits. Compound crescentic dunes, perhaps the most preservable dune type, may yield laterally (1) single sets of cross-strate, (2) compound sets derived from superimposed simple dunes, or (3) a complex of diverse sets derived from superimposed transverse and linear elements.

  8. Geomorphic evidence for an eolian contribution to the formation of the Martian northern plains

    NASA Technical Reports Server (NTRS)

    Zimbelman, J. R.

    1993-01-01

    The northern plains of Mars have many morphologic characteristics that are uncommon or absent on the rest of the planet. Mariner 9 and Viking images obtained north of latitude 30 deg N revealed 'smooth' and 'mottled' plains of an uncertain origin. Some or all of the northern plains were interpreted to consist of lava plains intermixed with eolian and volcanic materials thick eolian mantles that buried portions of the mid latitudes periglacial deposits resulting from the presence of ground ice and as water-transported sediments derived from fluvial runoff, lacustrine deposition in standing bodies of water, or glacial runoff. The highest-resolution Viking images show many intriguing details that may provide clues to the origin of this complex and distinctive terrain. Some of the informative features present in the best Viking images, comparing the observations to what may be expected from various hypotheses of formation, are reviewed. While the results are not conclusive for any single hypothesis, eolian processes have played a major role in the erosion (and possibly deposition) of the materials that make up the surface exposures in the Martian northern plains.

  9. Middle to Late Pleistocene coastal deposits of Eivissa (Western Mediterranean): Chronology and evolution.

    NASA Astrophysics Data System (ADS)

    Del Valle, Laura; Pomar, Francisco; Fornós, Joan J.; Gómez-Pujol, Lluís; Anechitei-Deacu, Valentina; Timar-Gabor, Alida

    2016-04-01

    This study deals with the sedimentary and stratigraphical description of Pleistocene deposits from seven coastal areas of Eivissa (Balearic Islands). Twenty two sedimentary facies have been described involving the succession of eolian, colluvial and edaphic environments. Carbonate sandstones, breccias and silty deposits are the main component of these sequences. Despite the extensive eolian systems outcropping along the coast of Eivissa, there are very few studies performed to chronological framework of these deposits. Luminescence measurements were carried out using an automated RisØ TL/OSL-DA-20 reader in the Luminescence Dating Laboratory of Babes-Bolyai University (Cluj-Napoca, Romania) under low intensity red light. OSL dating of nineteen eolian levels indicate that their deposition took place between the Middle and Late Pleistocene, establishing a paleoclimatic evolution of Eivissa Island since 755 ka to 70 Ka. Eolian activity in the Eivissa Island can be correlated with regression episodes which took place during cold periods associated with different isotopic stages, concretely the MIS 18, 16, 12, 10, 8, 6 and 4. Similar results have been obtained from many sites along the western Mediterranean Sea such as Mallorca (Pomar i Cuerda, 1979; Nielsen et al, 2004; Fornós et al, 2009), Sardinia (Andreucci et al, 2009; Pascucci et al, 2014), Liguria (Pappalardo et al., 2013). Keywords: Eolian dunes, Pleistocene, Climatic evolution, Eivissa. References - Andreucci, S.; Pascucci, V.; Murray, A. S.; Clemmensen, L. B. 2009. Late Pleistocene coastal evolution of San Giovanni di Sinis, west Sardinia (Western Mediterranean). Sedimentary Geology, 216: 104- 116 - Fornós, J.J.; Clemmensen, L.B.; Gómez-Pujol, L.; Murray, A. 2009. Late Pleistocene carbonate aeolianites on Mallorca, Western Mediterranean: a luminescence chronology. Quaternary Science reviews 28: 2697-2709. -Nielsen, K.A.; Clemmensen, L.B.; Fornós, J.J. 2004. Middle Pleistocene magnetostratigraphy and

  10. Eolian Dust and the Origin of Sedimentary Chert

    USGS Publications Warehouse

    Cecil, C. Blaine

    2004-01-01

    This paper proposes an alternative model for the primary source of silica contained in bedded sedimentary chert. The proposed model is derived from three principal observations as follows: (1) eolian processes in warm-arid climates produce copious amounts of highly reactive fine-grained quartz particles (dust), (2) eolian processes in warm-arid climates export enormous quantities of quartzose dust to marine environments, and (3) bedded sedimentary cherts generally occur in marine strata that were deposited in warm-arid paleoclimates where dust was a potential source of silica. An empirical integration of these observations suggests that eolian dust best explains both the primary and predominant source of silica for most bedded sedimentary cherts.

  11. Late Pleistocene Environments of the Central Ukraine

    NASA Astrophysics Data System (ADS)

    Rousseau, Denis-Didier; Gerasimenko, Natalia; Matviischina, Zhanna; Kukla, George

    2001-11-01

    The Vyazivok loess sequence from the Dnieper Plain, Ukraine, documents regional environmental changes during the late Pleistocene and Holocene. Pedological and palynological analyses and low-field magnetic susceptibility document changes from dense temperate forest during the last interglacial maximum to open, harsh, loess-steppe during the latest Pleistocene. The Vyazivok section overlies hillwash derived from a lower Pleistocene terrace and consists of two stratified soil complexes (Kaydaky and Pryluky; marine isotope stage [MIS] 5 equivalent) separated by a layer of eolian dust (Tyasmyn silt). The lower soils in both complexes formed within forest. These soils are overlain by the Uday (MIS4) and Bug (MIS2) loess units, which are separated by boreal soils of the Vytachiv (MIS3) complex. The coldest conditions within the record occurred in the youngest loess. Holocene soils cap the Bug loess. The Vyazivok section shows remarkable similarities with other classical loess sequences in western Europe, the Czech Republic, and Austria. The Kaydaky, Pryluky, and Vytachiv deposits, correlate with the PKIII, PKII, and PKI soil complexes, respectively, of the Czech Republic. The Tyasmyn and Prylyky silt layers correspond to marker horizons from central Europe.

  12. Optical Dating of Martian Eolian Sediments by Robotic Spacecraft

    NASA Astrophysics Data System (ADS)

    Sears, Derek W. G.; Lepper, Kenneth; McKeever, W. S.

    2000-07-01

    The Martian polar ice caps record a wealth of information about the past history and climate of Mars, but as pointed out by Clifford et al. in the summary of the First International Conference on Mars Polar Science and Exploration, 'The single greatest obstacle to unlocking and interpreting the geologic and climatic record preserved at the [martian] poles is the need for absolute dating.' Stratification in the polar caps arises, at least in part, from the incorporation of eolian material into the ice, and dune fields near the poles indicate eolian transport is an important surfical process in this region of Mars. Eolian materials are ideally suited for sediment dating using luminescence methods. Luminescence dating techniques have been used successfully to make absolute age determinations for numerous terrestrial Quaternary eolian deposits. Clifford et al. also concluded that cost, simplicity, and potential for minaturization make luminescence dating more feasible than isotopic methods for in situ dating by robotic landers. In fact, the water detection equipment of the Deep Space 2 microprobes and the MECA on the Mars Polar Lander contain components similar to those required for luminescence dating.

  13. A pleistocene sand sea on the Alaskan arctic coastal plain

    USGS Publications Warehouse

    Carter, L.D.

    1981-01-01

    A ridge and thermokarst-basin landscape that is strikingly portrayed in Landsat winter imagery consists of large Pleistocene dunes that have been modified by younger eolian activity and thermokarst processes. This is the most extensive area of large stabilized dunes yet reported in the North American Arctic; the landscape is of particular interest because it has been proposed as a first-order analogfor martian fretted terrain. Recognition ofthe large dunes permits a new interpretation for linear and curvilinear trends visible in Landsat summer imagery.

  14. Eolian dust input to the Subarctic North Pacific

    NASA Astrophysics Data System (ADS)

    Serno, Sascha; Winckler, Gisela; Anderson, Robert F.; Hayes, Christopher T.; McGee, David; Machalett, Björn; Ren, Haojia; Straub, Susanne M.; Gersonde, Rainer; Haug, Gerald H.

    2014-02-01

    Eolian dust is a significant source of iron and other nutrients that are essential for the health of marine ecosystems and potentially a controlling factor of the high nutrient-low chlorophyll status of the Subarctic North Pacific. We map the spatial distribution of dust input using three different geochemical tracers of eolian dust, 4He, 232Th and rare earth elements, in combination with grain size distribution data, from a set of core-top sediments covering the entire Subarctic North Pacific. Using the suite of geochemical proxies to fingerprint different lithogenic components, we deconvolve eolian dust input from other lithogenic inputs such as volcanic ash, ice-rafted debris, riverine and hemipelagic input. While the open ocean sites far away from the volcanic arcs are dominantly composed of pure eolian dust, lithogenic components other than eolian dust play a more crucial role along the arcs. In sites dominated by dust, eolian dust input appears to be characterized by a nearly uniform grain size mode at ∼4 μm. Applying the 230Th-normalization technique, our proxies yield a consistent pattern of uniform dust fluxes of 1-2 g/m2/yr across the Subarctic North Pacific. Elevated eolian dust fluxes of 2-4 g/m2/yr characterize the westernmost region off Japan and the southern Kurile Islands south of 45° N and west of 165° E along the main pathway of the westerly winds. The core-top based dust flux reconstruction is consistent with recent estimates based on dissolved thorium isotope concentrations in seawater from the Subarctic North Pacific. The dust flux pattern compares well with state-of-the-art dust model predictions in the western and central Subarctic North Pacific, but we find that dust fluxes are higher than modeled fluxes by 0.5-1 g/m2/yr in the northwest, northeast and eastern Subarctic North Pacific. Our results provide an important benchmark for biogeochemical models and a robust approach for downcore studies testing dust-induced iron fertilization of

  15. Eolian inputs of lead to the North Pacific

    SciTech Connect

    Jones, C.E.; Halliday, A.N.; Rea, D.K.; Owen, R.M.

    2000-04-01

    The authors evaluate the importance of natural eolian Pb to the dissolved oceanic Pb budget by measuring the isotopic composition of Pb in 35 Holocene and late Quaternary sediment samples from the North Pacific and in 10 samples of Chinese loess. When the Pacific is divided into sediments provinces based on published {var_epsilon}{sub Nd} and sedimentological data, Pb from the central North Pacific tends to be the most radiogenic and homogeneous due to the dominance of eolian Chinese loess. Lead from the marginal North Pacific and the sparsely sampled regions south of 5{degree}N are less radiogenic and more variable owing to hemipelagic inputs from various volcanic arcs and older continental crust located around the Pacific Rim. {sup 208}Pb/{sup 204}Pb ratios provide the most distinctive provenance information due to the relatively high ratios in Chinese loess. The Chinese loess samples come from 3 localities and span up to 2 Myr of time. Acetic-acid leachate, bulk loess, and loess silicate fractions were analyzed separately. Leachate Pb is considerably less radiogenic than silicate Pb. The isotopic composition of the silicate component closely matches the sediment data from the central North Pacific, confirming the dominance of eolian loess in this region. The authors divided up a suite of published hydrogenous Pb-isotope data from the Pacific Ocean according to their locations within the three independently defined sediment provinces. These data define three distinct fields differentiated primarily by their {sup 206}Pb/{sup 204}Pb ratios, which increase going form the Central to Southern to Marginal provinces. This relationship with sediment province strongly suggests that natural eolian and probably hemipelagic inputs significantly impact the seawater Pb budget. Direct support for the dominance of eolian Chinese loess in the central North Pacific dissolved Pb budget comes from the close match between loess leachate Pb and the Central Province hydrogenous Pb data

  16. Environmental history recorded in eolian deposits under stone pavements, eastern Mojave Desert, USA

    NASA Astrophysics Data System (ADS)

    Wells, Stephen; Fuchs, Markus; Dietze, Elisabeth; Lomax, Johanna; Kleber, Arno; Dietze, Michael

    2016-04-01

    Reconstructing the evolution of arid landscapes is challenged by the limited availability of appropriate environmental archives. A widespread surface feature of arid landscapes - stone pavement - traps eolian fines and can form an accretionary archive, growing with time and thereby recording essential information about the conditions under which it evolves. Based on a regional example in the eastern Mojave Desert, USA, seven stone pavement-covered soil-sediment sections on 560 and 270 ka old basalt flows are condensed to a correlation framework, comprising five distinct, successive sedimentological units. An OSL-based chronology enables correlation of this new sediment archive with other environmental archives from the region. Three of the stratigraphic units are of accretionary nature and the top of each unit is mantled by a new generation of stone pavement. These stratigraphic units were deposited between >32.3-20.4 ka, 20.4-16.5 ka and younger than 16.5 ka, appearing to be strongly coupled with the history of the nearby ancient Lake Mojave and enhancing our knowledge of the eolian activity in this area. End-member modelling analysis of sampled grain-size distributions allows identification of a local detritus component, four separate eolian components and two distinct clay enrichment components, contributing different quantities of sediment sources to the five stratigraphic units. These findings improve current concepts about the evolution of stone pavements and their role as conveyers of information about environmental conditions in arid landscapes. Stone pavement-covered accretionary sediment deposits are a new key archive that allows quantifying the relative importance of dust accretion, slope processes, soil formation and vegetation cover.

  17. Evidence of an eolian ice-rich and stratified permafrost in Utopia Planitia, Mars

    NASA Astrophysics Data System (ADS)

    Séjourné, A.; Costard, F.; Gargani, J.; Soare, R. J.; Marmo, C.

    2012-01-01

    Western Utopia Planitia (UP) is dotted with scalloped depressions, small-sized polygons and pingo-like mounds. Within the planetary science community, there seems to be a general agreement that these relatively recent landscape features are indicative of an ice-rich permafrost. However, questions about the concentration of ice-content and the origin of the permafrost remain unanswered. The scalloped depressions (∼100 m to few km in diam.) are thought to be the product of degradation of ground-ice by thawing or sublimation. Indeed, most of the scalloped depressions display bright bands on their floors. These have been described as possible exposed sedimentary layers, markers of recessional ponded water or slumped material by previous works. As the depressions could represent probes of the permafrost, therefore the study of the inner bands could help to investigate the permafrost. Here, we evaluate the disparate hypotheses of band origin using several HiRISE images and a HiRISE DEM. We show that the depressions have an inner stepped-profile. This profile is reminiscent of exhumed and tilted sedimentary layers of different cohesion. Using ArcGIS, we estimate the dip of several layers (n=52). The stratification is complex comprising layers of ∼2-4 m thick having different shallow dips with generally a north or south plunge sense. This geometry of tilted layers is typical on Earth of fluviatile or eolian sedimentation. In the last few years, several evidences on Mars, among them the subkilometer-scale smoothing of the topography and climatic simulations, suggested that the northern mid-latitudes have been influenced by eolian processes. The inferred complex stratification inside scalloped depressions may support an eolian origin of the permafrost in UP. In periglacial regions on Earth where thermokarst lakes are formed by extensive thawing of ground-ice, ice-rich permafrost are composed of fluvial or eolian sediments containing ∼15-80% of ice by volume. By analogy

  18. Airflow-terrain interactions through a mountain gap, with an example of eolian activity beneath an atmospheric hydraulic jump

    SciTech Connect

    Gaylord, D.R.; Dawson, P.J.

    1987-09-01

    The integration of atmospheric soundings from a fully instrumented aircraft with detailed sedimentary and geomorphic analyses of eolian features in the Ferris dune field of south-central Wyoming lends insight into the manner in which topography interacts with airflow to modify eolian activity. Topographically modified airflow results in zones of airflow deceleration, acceleration, and enhanced atmospheric turbulence, all of which influence the surface morphology and sedimentology. Extreme lateral confluence of prevailing airflow produces accelerated, unidirectional winds. These winds correlate with unusually continuous and elongate parabolic dunes that extend into a mountain gap (Windy Gap). Persistently heightened winds produced at the entrance to Windy Gap have resulted in a concentration of active sand dunes that lack slipfaces. Common development of a strongly amplified atmospheric wave analogous to a hydraulic jump in the gap contributes to the formation of a variety of eolian features that mantle the surface of Windy Gap and the Ferris dune field tail. Heightened, unidirectional winds in this zone promote grain-size segregation, the formation of elongated and aligned sand drifts, climbing and falling dunes, elongate scour streaks, and parabolic dunes that have low-angle (< 20/sup 0/) cross-stratification. Deflation of bedrock and loose sediment has been enhanced in the zone of maximum turbulence beneath the hydraulic jump.

  19. Reconstruction of eolian sequences - a function of scale, Jurassic Page sandstone, Arizona

    SciTech Connect

    Kocurek, G.; Knight, J.; Havholm, K.

    1989-03-01

    Interpretation of sequences of ergs and bed forms that comprise an eolian unit is strongly dependent on the scale of mapping. A pentagon-shaped, three-dimensional outcrop of eolian Middle Jurassic Page sandstone near Page, Arizona, measuring 36 m high and nearly 1 km in perimeter, was mapped with the aid of an electronic tacheometer. The extent and orientation of bounding surfaces and sets of cross-strata were mapped in detail, foreset orientation were measured, and a general depiction was made of the lateral and vertical distribution of stratification types within sets and of features associated with the surfaces. The level of mapping is at a middle scale with respect to architectural elements and proved adequate for an interpretation of most bed forms in terms of shape (two or three dimensions, sinuosity, symmetry, and crestline-phase relationships), size (height and width), aerodynamics (overall primary and secondary airflow patterns), and migration behavior (degree of climb and recognition of cyclicity). These interpretations allow the determination of bed-form hierarchy (simple dunes or draas) and of the bed-form type according to the descriptive (crescentic, linear) and dynamic (transverse, oblique, longitudinal) classifications. In conjunction with this level of mapping, large-scale or regional mapping was used in order to identify distinct, stacked, dune-field, and erg deposits that comprise the Page sandstone. Local mapping of the out-crop at a fine scale was necessary for refined interpretation of cyclicity, bed-form size, migration rate, and airflow pattern.

  20. Eolian sediment responses to late Quaternary climate changes: Temporal and spatial patterns in the Sahara

    USGS Publications Warehouse

    Swezey, C.

    2001-01-01

    This paper presents a compilation of eolian-based records of late Quaternary climate changes in the Sahara. Although the data are relatively sparse, when viewed as a whole, they reveal a general pattern of widespread eolian sediment mobilization prior to 11,000 cal. years BP, eolian sediment stabilization from 11,000 to 5000 cal. years BP, and a return to widespread eolian sediment mobilization after 5000 cal. years BP. Furthermore, an eolian-based record from southern Tunisia reveals the existence of millennial-scale changes in eolian sediment behavior. These millennial-scale variations provide examples of eolian sediment responses to climate changes at a scale intermediate between seasonal and orbital ('Milankovitch') changes, and they are also coincident with abrupt atmospheric and oceanic changes. The general synchroneity of the eolian stratigraphic records and their coincidence with various oceanic and atmospheric changes suggest that global forcing mechanisms have influenced late Quaternary eolian sediment behavior in the Sahara. ?? 2001 Elsevier Science B.V.

  1. Eolian Soft-Sediment Deformation Records on Earth and Mars

    NASA Astrophysics Data System (ADS)

    Chan, M. A.; Okubo, C. H.; Bruhn, R. L.

    2014-12-01

    Eolian (wind-blown) dune deposits are widespread on Earth and Mars, with soft-sediment deformation preserved in cross-bedded sandstone deposits comprising important records of past environmental conditions. Exceptional 3-D exposures of the Jurassic Navajo Sandstone, in the Vermilion Cliffs National Monument of northern Arizona, contain distinctive intervals of decameter- scale soft-sediment contortions, up-turned dune sets, brittle strain, massive layers with breccia blocks, and associated geomorphic mounds. Both field studies and remote-controlled unmanned aerial vehicles (airplane or kite) images respectively provide "ground truth" and "bird's-eye" perspectives of the deformation. The nature of the continuous folds within stratigraphically constrained beds indicates confining layers breached by rapid fluid expulsion, strain softening, and cataclastic flow of partially lithified sandstone under water-saturated conditions (i.e., a relatively high-water table), consistent with theoretical and laboratory studies of deformation in saturated sand. Loose grain packing and high porosity and permeability in eolian sands allow for water-filled pores, which are conducive for soft-sediment deformation. The likely driver for this observed deformation was liquefaction-induced ground failure from strong ground motion, such as long-duration surface waves of a large earthquake. These eolian examples preserve complex geologic stories and serve as paleoenvironmental records. Mars Reconnaissance Orbiter (MRO) HiRISE images of exposed layer contortions and soft-sediment deformation in Candor Chasma are remarkably similar to the Jurassic examples. The Jurassic analog examples provide baseline criteria to help interpret high-water table conditions and subsequent strong ground motion in the late Hesperian to early Amazonian sediments on the floor of Candor Chasma and other chasmata of Valles Marineris.

  2. Late Pleistocene braided rivers of the Atlantic Coastal Plain, USA

    NASA Astrophysics Data System (ADS)

    Leigh, David S.; Srivastava, Pradeep; Brook, George A.

    2004-01-01

    Infrared Landsat imagery (band 4) clearly reveals braided river patterns on late Pleistocene terraces of unglaciated rivers in the Atlantic Coastal Plain of the southeastern United States, a region that presently exhibits meandering patterns that have existed throughout the Holocene. These Pleistocene braided patterns provide a unique global example of river responses to late Quaternary climate changes in an unglaciated humid subtropical region at 30-35° north latitude. Detailed morphological and chronological results are given for the Oconee-Altamaha River valley in Georgia and for the Pee Dee River valley in South Carolina, including 15 optically stimulated luminescence (OSL) dates and four radiocarbon dates. Correlative examples are drawn from additional small to large rivers in South- and North Carolina. OSL and radiocarbon ( 14C) dates indicate distinct braiding at 17-30 ka, within oxygen isotope stage 2 (OIS 2), and braiding probably existed at least during parts of OIS 3 and possibly OIS 4 back to ca 70 ka. The chronology suggests that braiding is the more common pattern for the late Quaternary in the southeastern United States. Braided terraces appear to have been graded to lower sea-levels and are onlapped by Holocene floodplain deposits up to 10-60 km from the coast. The braiding probably reflects the response of discharge and sediment yield to generally cooler and drier paleoclimates, which may have had a pronounced runoff season. Sedimentation of eolian dunes on the braid plains is coeval with braiding and supports the conclusion of dry soils and thin vegetation cover during the late Pleistocene. Our chronological data contribute to a body of literature indicating that reliable OSL age estimates can be obtained from quartz-rich bed load sand from braided rivers, based on good correlations with both radiocarbon dates from braided fluvial sediment and OSL dates from stratigraphically correlative eolian sand.

  3. Surface and subsurface features of the upper Pleistocene Beaumont Formation as studied in a proposed super collider site in Liberty and Hardin counties, southeastern Texas

    SciTech Connect

    Aronow, S.

    1994-12-31

    In 1987 an area in Hardin and Libery Counties in southeastern Texas was a much-studied candidate site for the ill-fated Superconducting Super Collider. The site is on the outcrop of the upper Pleistocene Beaumont Formation, which locally was deposited by a sequence of meandering, avulsing, suspended-load, paleo-Trinity River courses, now preserved as a well-defined to poorly defined depositional topography. Test holes in meanderbelt ridges showed that channel and point-bar silty fine to very fine sands are almost everywhere covered by approximately 10 to 40 ft ({approximately}3 to 12 m) of CH and CL overbank clays. Where completely penetrated, sand bodies are approximately 20 to 50 ft ({approximately}6 to 15 m) thick. Pedogenic calcareous deposits and slickensides at depths well below any influence from present-day surface processes are probably parts of lower horizons of truncated now-buried soils generated during the accumulation of the Beaumont, or on the surface of the underlying Lissie Formation. The relationship of one of the paleo-meanderbelts to the uplifted topographic surface of the Hull salt dome suggests that the rise of the surface postdated deposition of the Beaumont.

  4. On the Origin of the Crestone Crater: Low-Latitude Periglacial Features in San Luis Valley, Colorado

    NASA Astrophysics Data System (ADS)

    Schwans, E.; Meng, T. M.; Prudhomme, K.; Morgan, M. L.

    2015-12-01

    Located within the northern boundary of the Great Sand Dunes National Park is the Crestone Crater, a elliptical bowl-shaped feature consisting of a raised rim surrounding a central depression. The elongate crater has an approximate diameter of 100 m and reaches a depth of 10 m at its center relative to its rim, which rises 10 m above the elevation of the surrounding surface. Its precise origin is largely unknown and has perplexed regional geologists and residents of Crestone, Colorado for more than 80 years. This project used on-site and remote geophysical methods to characterize the processes that led to the geomorphologic surface expression observed today. Formation hypotheses examined encompass extraterrestrial, eolian, and periglacial processes. Field methods included a new gravity survey and reanalysis of gravity data collected in a previous student investigation of the feature. Additionally, a recent LiDAR dataset spanning San Luis Valley was examined to analyze the main structure, similar features in the area, and surrounding eolian and alluvial surfaces. An extraterrestrial origin, as suggested by numerous previous investigators, was deemed unlikely due to the non-unique gravity signature of the crater, its topographic similarity to many other like features identified in San Luis Valley, as well as its failure to excavate below the elevation of the surrounding surface. Furthermore, the expression of confirmed eolian landforms in San Luis Valley indicates that eolian processes alone would not produce such a prominent form in the level of vegetation observed. Proximal glacial deposits in the Sangre de Cristo Mountains show that the windblown sand in which all these features are clustered is adjacent to areas of past glaciations, and thus would have been affected by freeze-thaw cycles and thin, localized permafrost. Ice extent maps provided by the Colorado Geological Survey, as well as research on the timing of the formation of the Great Sand Dunes reinforce

  5. Organic matter in eolian dusts over the Atlantic Ocean

    NASA Technical Reports Server (NTRS)

    Simoneit, B. R. T.

    1977-01-01

    The elemental and mineralogical composition and the microfossil and detritus content of particulate fallout from the lower troposphere over the Atlantic Ocean have been extensively documented in earlier work, and it was possible to ascribe terrigenous source areas to such fallout. A brief review of the organic geochemistry of eolian dusts is also presented here. The lipids of eolian dusts sampled from the air mass over the eastern Atlantic from about 35 deg N to 30 deg S were analyzed here. These lipids consisted mainly of normal alkanes, carboxylic acids and alcohols. The n-alkanes were found to range from n-C23 to n-C35 with high CPI values and maximizing at n-C27 in the North Atlantic, at n-C29 in the equatorial Atlantic and at n-C31 in the South Atlantic. The n-fatty acids had mostly bimodal distributions, ranging from n-C12 to n-C30 (high CPI), with maxima at n-C16 and in the northern samples at n-C24 and in the southern samples at n-C26. The n-alcohols ranged from n-C12 to n-C32, with high CPI values and maxima mainly at n-C28. The compositions of these lipids indicated that their terrigenous sources were comprised mainly of higher plant vegetation and desiccated lacustrine mud flats on the African continent.

  6. Diagenesis Along Fractures in an Eolian Sandstone, Gale Crater, Mars

    NASA Technical Reports Server (NTRS)

    Ming, D. W.; Yen, A. S.; Rampe, E. B.; Grotzinger, J. P.; Blake, D. F.; Bristow, T. F.; Chipera, S. J.; Downs, R.; Morris, R. V.; Morrison, S. M.; Vaniman, D. T.; Gellert, R.; Sutter, B.; Treiman, A. H.

    2016-01-01

    The Mars Science Laboratory rover Curiosity has been exploring sedimentary deposits in Gale crater since August 2012. The rover has traversed up section through approx.100 m of sedimentary rocks deposited in fluvial, deltaic, lacustrine, and eolian environments (Bradbury group and overlying Mount Sharp group). The Stimson formation lies unconformable over a lacustrine mudstone at the base of the Mount Sharp group and has been interpreted to be a cross-bedded sandstone of lithified eolian dunes. Mineralogy of the unaltered Stimson sandstone consists of plagioclase feldspar, pyroxenes, and magnetite with minor abundances of hematite, and Ca-sulfates (anhydrite, bassanite). Unaltered sandstone has a composition similar to the average Mars crustal composition. Alteration "halos" occur adjacent to fractures in the Stimson. Fluids passing through these fractures have altered the chemistry and mineralogy of the sandstone. Silicon and S enrichments and depletions in Al, Fe, Mg, Na, K, Ni and Mn suggest aqueous alteration in an open hydrologic system. Mineralogy of the altered Stimson is dominated by Ca-sulfates, Si-rich X-ray amorphous materials along with plagioclase feldspar, magnetite, and pyroxenes, but less abundant in the altered compared to the unaltered Stimson sandstone and lower pyroxene/plagioclase feldspar. The mineralogy and geochemistry of the altered sandstone suggest a complicated history with several (many?) episodes of aqueous alteration under a variety of environmental conditions (e.g., acidic, alkaline).

  7. Erosion and transport of eolian materials on Mars

    NASA Technical Reports Server (NTRS)

    Krinsley, D.

    1983-01-01

    An abrasion chamber was constructed to produce grain to grain impacts and to eliminate, as far as possible, grain to wall impact. Quartz, basalt, olivine, and volcanic ash were used as abrasives to determine particle longevity on Mars during eolian abrasion. The various abrasion velocities, measured velocity or particles, calculated velocity of collision, time during which abrasion took place, the charge (material) in grams, and the percent remaining after completion are tabulated. The tests show that if coarse sand-sized particles of the composition presumably present on Mars are moved at the wind velocities given, almost complete destruction can occur in geologically insignificant time periods. Grain to rock collisions are not necessary for almost complete destruction; grain to grain collisions are sufficient.

  8. BISON ANTIQUUS OCCURRENCE AND PLEISTOCENE-HOLOCENE STRATIGRAPHY, CANADA DEL BUEY, PAJARITO PLATEAU, NEW MEXICO

    SciTech Connect

    RENEAU, STEVEN L.; DRAKOS, PAUL G.; MORGAN, GARY S.

    2007-02-12

    A Bison. (probable Bison antiguus) distal humerus fragment was found within a Pleistocene colluvial deposit on a hillslope above Canada del Buey near White Rock, New Mexico. The Bison fossil is preserved within a buried soil with an inferred age of ca. 50-100 ka, based on soil properties and on stratigraphic position below a deposit of ca. 50-60 ka EI Cajete pumice. This represents the second oldest dated Bison in New Mexico, and one of the few occurrences of this genus in the northern mountains of the state. It is also only the second record of a Pleistocene vertebrate from Los Alamos County, and is a rare occurrence of a pre-25 ka Bison fossil in good stratigraphic context. Hillslopes in the study area are underlain by a sequence of truncated Pleistocene and Holocene soils that are inferred to represent colluvial deposition and soil formation followed by erosion in the mid Pleistocene (buried soil 'b3'), the late Pleistocene (buried soil 'b2'), and the mid-to-late Holocene (buried soil 'b1'). The surface soil is developed in depOSits that overlie 600-800 year-old Ancestral Puebloan sites. Colluvium is dominated by relatively fine-grained (fine to very fine sand) slopewash colluvium deposited by overland flow, but also includes rocky colluvium on hillslopes below mesas. The fine-grained colluvium is likely derived mainly from reworking of eolian deposits. Episodic colluvial deposition appears to, at least in part, accompany and follow episodic eolian events, with intervening periods dominated by erosion and the development of truncated soils.

  9. The deep structure of the Eolian arc (Filicudi-Panarea-Vulcano sector) in light of gravity, magnetic and volcanological data

    NASA Astrophysics Data System (ADS)

    Barberi, F.; Gandino, A.; Gioncada, A.; La Torre, P.; Sbrana, A.; Zenucchini, C.

    1994-07-01

    The magnetic and gravimetric methods of investigation have been applied to the central sector of the Eolian arc, combined with geovolcanological data, for the purpose of defining the structural framework in which the volcanism developed. The processing of the magnetic and gravimetric data involved 3D modeling of the volcanic bodies and the application of a "depth separation filter", in order to subtract from the measured field the effect caused by the subaerial and submarine volcanic edifices and by all surface inhomogeneities. Magnetic and gravimetric 2.5D modeling on selected profiles has also been done, in a joint interpretation of the magnetic and gravimetric data, constrained by volcanological knowledge. The interpretation of the final maps and profiles has demonstrated the existence of extensional tectonics, resulting in the development of horst and graben. Volcanism occurs in the graben areas. In particular, the Salina-Lipari-Vulcano magmatic axis has developed in a very deep articulated graben of lithospheric importance and completely filled by volcanic deposits and intrusive bodies. The origin of this structure and of the associated igneous activity is suggested to be related to trans-tensional tectonics along a Plio-Pleistocene regional strike-slip fault system.

  10. Temporal labyrinths of eastern Eurasian Pleistocene humans

    PubMed Central

    Wu, Xiu-Jie; Crevecoeur, Isabelle; Liu, Wu; Xing, Song; Trinkaus, Erik

    2014-01-01

    One of the morphological features that has been identified as uniquely derived for the western Eurasian Neandertals concerns the relative sizes and positions of their semicircular canals. In particular, they exhibit a relatively small anterior canal, a relatively larger lateral one, and a more inferior position of the posterior one relative to the lateral one. These discussions have not included full paleontological data on eastern Eurasian Pleistocene human temporal labyrinths, which have the potential to provide a broader context for assessing Pleistocene Homo trait polarities. We present the temporal labyrinths of four eastern Eurasian Pleistocene Homo, one each of Early (Lantian 1), Middle (Hexian 1), and Late (Xujiayao 15) Pleistocene archaic humans and one early modern human (Liujiang 1). The labyrinths of the two earlier specimens and the most recent one conform to the proportions seen among western early and recent modern humans, reinforcing the modern human pattern as generally ancestral for the genus Homo. The labyrinth of Xujiayao 15 is in the middle of the Neandertal variation and separate from the other samples. This eastern Eurasian labyrinthine dichotomy occurs in the context of none of the distinctive Neandertal external temporal or other cranial features. As such, it raises questions regarding possible cranial and postcranial morphological correlates of Homo labyrinthine variation, the use of individual “Neandertal” features for documenting population affinities, and the nature of late archaic human variation across Eurasia. PMID:25002467

  11. Vertebrate-bearing eolian unit from the Ogallala Group (Miocene) in northwestern Texas

    SciTech Connect

    Winkler, D.A.

    1987-08-01

    The upper Couch Formation is part of the lower of two formations composing the Ogallala Group in Blanco and Yellowhouse canyons in northwestern Texas. An eolian origin for the upper Couch Formation is indicated by its mean grain size, pedogenic carbonate nodules, massive bedding, and blanketlike morphology. The unit conforms poorly to the usual eolian depositional models; it resulted from a combination of the processes involved in loess and sand-sheet formation. Grassland or savanna vegetation probably existed over the area and aided in sediment trapping. Vertebrates are unusual in eolian units, but the adaptations and mode of preservation of those in the upper Couch Formation also support an eolian interpretation. This and other widespread silty sand sheets in the Ogallala indicate major fluctuations in depositional style, possibly climatically controlled. Lateral continuity and preservation of vertebrates give silty sand sheets great potential as correlation tools.

  12. Three-dimensional analysis of eolian systems in Jurassic Wingate sandstone

    SciTech Connect

    Nation, M.J.; Blakey, R.C.

    1989-03-01

    Regional bounding surfaces in ancient eolian sequences aid in establishing lateral profiles not previously obtainable using standard stratigraphic methods. Correlation of detailed measured sections permits three-dimensional analysis of erg dynamics in the Jurassic Wingate Sandstone on the Colorado Plateau. Four periods of erg development marked by contrasting styles of eolian architecture are documented in the Salt Anticline region (in ascending stratigraphic order): (1) discontinuous sand sheets, isolated dunes, and aqueous environments; (2) large compound dunes with decreasing amounts of dune margin material; (3) compound dunes and draas alternating with locally thick sandsheet deposits; and (4) widespread dunes and draas prior to erosion by Kayenta fluvial systems. Regional bounding surface characteristics reflect different mechanisms for erg stabilization, including deflation to the water table, climate change, and negative net sand budget. Lateral reconstruction and correlation of erg sequences indicate significant intrabasinal paleogeographic and tectonic controls on eolian systems. Localities removed from the Salt Anticline region contain much larger compound draa deposits and lack extensive accumulations of sand-sheet material. Regional comparison of these characteristics suggests that the salt uplifts modified eolian processes within the Wingate depositional basin. Existence of additional geographic variations not associated with salt tectonism is indicated by local accumulations of noneolian deposits in northeastern Arizona. The use of regional bounding surfaces to construct lateral profiles is a powerful method to establish three-dimensional models of eolian systems. Analysis of erg dynamics in other ancient eolian formations is possible utilizing the criteria documented in the Wingate Sandstone.

  13. Sources of Fe in eolian and soil detritus at Yucca Mountain, Nevada, USA

    SciTech Connect

    Vaniman, D.; Chipera, S.; Bish, D.

    1997-12-31

    Eolian deposits and adjacent soil horizons at Exile Hill near Yucca Mountain, Nevada, provide a desert environment where the origins of exotic eolian materials can be discerned. Petrographic, chemical, X-ray diffraction, and electron microprobe data allow an assessment of Fe mineral sources. Fe-rich minerals in local rhyolitic tuff bedrock consist of distinctive biotite and amphibole phenocrysts and groundmass Mn-hematites. Although the local tuffs contain only 1% FeO, detrital components of eolian and soil deposits have {approximately}3% FeO. Exotic minerals from distant sources provide most of the excess Fe in the surficial deposits. The exotic Fe sources are principally smectite, low-Mn hematite, low-F biotite, and high-Fe amphibole not found in local tuffs. Iron contents and the exotic Fe fraction increase with decreasing grain size, such that the clay fractions have {approximately}5--6% FeO, almost all of which is in exotic smectites. The distant origin of these smectites is evident in their high Fe content and distinct Sc/FeO enrichment trends, which differ from the strong local Sc/FeO control defined by coarser soil detritus. Approximate crustal average lanthanide composition in soil and eolian smectites rule out any significant contribution of local smectite derived from tuff alteration. The eolian and soil smectites instead inherit their high Fe content from eolian biotite.

  14. Eolian transport of geogenic hexavalent chromium to ground water

    USGS Publications Warehouse

    Wood, W.W.; Clark, D.; Imes, J.L.; Councell, T.B.

    2010-01-01

    A conceptual model of eolian transport is proposed to address the widely distributed, high concentrations of hexavalent chromium (Cr+6) observed in ground water in the Emirate of Abu Dhabi, United Arab Emirates. Concentrations (30 to more than 1000 μg/L Cr+6) extend over thousands of square kilometers of ground water systems. It is hypothesized that the Cr is derived from weathering of chromium-rich pyroxenes and olivines present in ophiolite sequence of the adjacent Oman (Hajar) Mountains. Cr+3 in the minerals is oxidized to Cr+6 by reduction of manganese and is subsequently sorbed on iron and manganese oxide coatings of particles. When the surfaces of these particles are abraded in this arid environment, they release fine, micrometer-sized, coated particles that are easily transported over large distances by wind and subsequently deposited on the surface. During ground water recharge events, the readily soluble Cr+6 is mobilized by rain water and transported by advective flow into the underlying aquifer. Chromium analyses of ground water, rain, dust, and surface (soil) deposits are consistent with this model, as are electron probe analyses of clasts derived from the eroding Oman ophiolite sequence. Ground water recharge flux is proposed to exercise some control over Cr+6 concentration in the aquifer.

  15. Synthesis of late Paleozoic and Mesozoic eolian deposits of the Western Interior of the United States

    NASA Astrophysics Data System (ADS)

    Blakey, Ronald C.; Peterson, Fred; Kocurek, Gary

    1988-04-01

    Late Paleozoic and Mesozoic eolian deposits include rock units that were deposited in ergs (eolian sand seas), erg margins and dune fields. They form an important part of Middle Pennsylvanian through Upper Jurassic sedimentary rocks across the Western Interior of the United States. These sedimentary rock units comprise approximately three dozen major eolian-bearing sequences and several smaller ones. Isopach and facies maps and accompanying cross sections indicate that most eolian units display varied geometry and complex facies relations to adjacent non-eolian rocks. Paleozoic erg deposits are widespread from Montana to Arizona and include Pennsylvanian formations (Weber, Tensleep, Casper and Quadrant Sandstones) chiefly in the Northern and Central Rocky Mountains with some deposits (Hermosa and Supai Groups) on the Colorado Plateau. Lower Permian (Wolfcampian) erg deposits (Weber, Tensleep, Casper, Minnelusa, Ingleside, Cedar Mesa, Elephant Canyon, Queantoweap and Esplanade Formations) are more widespread and thicken into the central Colorado Plateau. Middle Permian (Leonardian I) erg deposits (De Chelly and Schnebly Hill Formations) are distributed across the southern Colorado Plateau on the north edge of the Holbrook basin. Leonardian II erg deposits (Coconino and Glorieta Sandstones) are slightly more widespread on the southern Colorado Plateau. Leonardian III erg deposits formed adjacent to the Toroweap-Kaibab sea in Utah and Arizona (Coconino and White Rim Sandstones) and in north-central Colorado (Lyons Sandstone). Recognized Triassic eolian deposits include major erg deposits in the Jelm Formation of central Colorado-Wyoming and smaller eolian deposits in the Rock Point Member of the Wingate Sandstone and upper Dolores Formation, both of the Four Corners region. None of these have as yet received a modern or thorough study. Jurassic deposits of eolian origin extend from the Black Hills to the southern Cordilleran arc terrain. Lower Jurassic intervals

  16. Red/violet contrast reversal on Mars - significance for eolian sediments

    SciTech Connect

    Thomas, P.; Veverka, J.

    1986-04-01

    Viking Orbiter images of Mars are analyzed to define relationships between the observed contrast reversals (CR) and specific surface features. The link between CR phenomena and surface composition was first detected in contrast comparisons between UV and visible wavelength Mariner 9 data. Viking data, taken through red and violet filters, showed that the CRs occurred only with crater splotches and splotch-related streaks and in bright depositional and dark erosional streaks, both being low-albedo markings presumably caused by eolian forces. The splotch phenomena is confined mainly to the Oxia Palus region, although there are other regions where splotches and streaks commingle. Laboratory tests to mimic the CR characteristics showed that CRs are a common phenomena of different size fractions of iron oxides, e.g., goethite, where particles under 5 microns have been removed. The splotches, including dune formations, are therefore believed to indicate the presence of particles in the 100-800 microns diam range. Finer particles ride on the tops of the dust storms, and are continually removed from the surface by saltation. 51 references.

  17. Red/violet contrast reversal on Mars - Significance for eolian sediments

    NASA Technical Reports Server (NTRS)

    Thomas, P.; Veverka, J.

    1986-01-01

    Viking Orbiter images of Mars are analyzed to define relationships between the observed contrast reversals (CR) and specific surface features. The link between CR phenomena and surface composition was first detected in contrast comparisons between UV and visible wavelength Mariner 9 data. Viking data, taken through red and violet filters, showed that the CRs occurred only with crater splotches and splotch-related streaks and in bright depositional and dark erosional streaks, both being low-albedo markings presumably caused by eolian forces. The splotch phenomena is confined mainly to the Oxia Palus region, although there are other regions where splotches and streaks commingle. Laboratory tests to mimic the CR characteristics showed that CRs are a common phenomena of different size fractions of iron oxides, e.g., goethite, where particles under 5 microns have been removed. The splotches, including dune formations, are therefore believed to indicate the presence of particles in the 100-800 microns diam range. Finer particles ride on the tops of the dust storms, and are continually removed from the surface by saltation.

  18. Geochemical and Isotopic Estimates of Eolian Dust in Soils of the San Juan Mountains, USA.

    NASA Astrophysics Data System (ADS)

    Lawrence, C. R.; Neff, J. C.; Farmer, L.; Painter, T. H.; Landry, C.

    2007-12-01

    Eolian dust deposition in the San Juan Mountain Range in southern Colorado has increased 5-7 fold in the past two centuries. This dust deposition contributes an exogenous supply of biologically relevant elements such as Ca, K, Mg, and P to these alpine ecosystems in the form of fine textured mineral particulates. The deposition of eolian dust may be an underestimated factor of soil formation and soil chemistry in these alpine settings. The importance of eolian dust relative to the weathering of local bedrock likely varies across bedrock types. The San Juan Range is geologically diverse with distinct regions of Meso-proterozic crystalline granites in the Weminuche Wilderness, Mesozoic sedimentary layers near Molas Pass in the San Juan National Forest, and Tertiary volcanic geology found on Red Mountain Pass in the Uncompahgre National Forest. Principle component analysis of element chemistry shows that bedrock and soils from these sites cluster by geology. In addition, these groups are chemically distinct from eolian dust collected from snow in the San Juan Range. Several elements seem to drive the difference of dust from soils and bedrock including Ca, Sr, Cu and Cd. The purpose of this research was to estimate the relative contribution of eolian dust to alpine soil element pools in the San Juan Mountains across a range of local geologic parent material. A calculation of element mass- balance shows that Cu and Cd are enriched in the surface soils of both volcanic and sedimentary soils relative to concentrations in local bedrock. However, Ca is enriched only in volcanic soils. These observations support the notion that eolian dust contributes to soil formation and that the relative contribution of dust across the landscape varies with geology. In addition to element mass-balance estimates we utilize Sr and Nd isotope measurements of soil, bedrock, and dust to further constrain the importance of eolian dust to these alpine soils.

  19. An Upper Pleistocene to Holocene limnic record from the Carpathian Basin near Vrsac (Vojvodina, Serbia)

    NASA Astrophysics Data System (ADS)

    Zeeden, Christian; Hambach, Ulrich; Fisher, Peter; Obreht, Igor; Schulte, Philipp; Bösken, Janina; Wennrich, Voelker; Schäbitz, Frank; Klasen, Nicole; Gavrilov, Milivoj; Veres, Daniel; Markovic, Slobodan; Vött, Andreas; Lehmkuhl, Frank

    2016-04-01

    Upper Pleistocene geoarchives in the Pannonian Basin are predominantly composed of loess-paleosol sequences accompanied by only few fluvial archives dating to this time frame. In 2015 a 10 m sediment core was recovered within an extensive loess area by means of vibracoring, with the recovered sedimentary succession mainly composed of limnic sediments. Coring was conducted within a depression northwest of Vrsac and east of the Banat Sands in the eastern Carpathian Basin (North-Eastern Serbia) in a region still lacking in paleoenvironmental records but which must have played a crucial role in the spread of modern human into Europe along the main rivers valley tributary to the Danube. Radiocarbon dating places the upper half of the core within the last ca. 20 ka, whereas luminescence dating is on going. Sedimentological analyses give evidence of phases of eolian sediment input within a predominantly limnic depositional environment. Aeolian sediment input has been altered, and early diagenesis is expected to have superimposed the eolian sediment. In addition, levels of carbonate precipitation can be observed in the core, some intervals being very rich in clay and decalcified; both show strong alteration of original sediment. No indications for fluvial input are apparent, suggesting a continuous sedimentation during the Upper Pleistocene and into the Holocene. Here preliminary results are presented including core images and description, XRF scans, grain-size data and an age model in progress. Based on these findings a detailed interpretation on the sedimentary system and (paleo)environmental processes involved are given.

  20. Chronology and geochemistry of late Holocene eolian deposits in the Brandon Sand Hills, Manitoba, Canada

    USGS Publications Warehouse

    Wolfe, S.A.; Muhs, D.R.; David, P.P.; McGeehin, J.P.

    2000-01-01

    Accelerator mass spectrometry and conventional radiocarbon age determinations of organic matter from paleosols indicate that the Brandon Sand Hills area of southern Manitoba has been subjected to recurrent intervals of eolian activity in the past 5000 years. Although precise regional correlations are precluded by dating uncertainties, periods of most notable paleosol development occurred around 2300 to 2000, 1400 to 1000, and 600 to 500 cal yr BP with eolian activity occurring before and after each of these periods. Episodes of eolian activity may correspond to periods of regional drought, whereas paleosols mark periods of increased moisture availability and stabilization by vegetation. The geochemistry of the eolian sands, paleosols and source sediments indicates that partial leaching of carbonates occurs from pedogenesis during humid climatic phases, and that this is probably the primary mechanism of carbonate depletion of eolian sands in this area. Recent trends in sand dune activity from historic aerial photography and early explorers' accounts indicate that the few active dunes that presently exist have stabilized at a rate of 10-20% per decade, despite several severe droughts in the 20th century. This may be attributed to pre-settlement droughts that were more severe than those in historic times although regional dune stabilization may also be related, in part, to the spread of forest cover in the past few hundred years. Crown copyright (C) 2000 Published by Elsevier Science Ltd. All rights reserved.

  1. Organic constituents in eolian dust and surface sediments from northwest Africa

    NASA Technical Reports Server (NTRS)

    Lepple, F. K.; Brine, C. J.

    1976-01-01

    Samples of eolian dust and comparably sized desert surface sediment samples collected over widely scattered regions of northwest Africa were analyzed for carbon, nitrogen, and hydrogen content and total carbohydrate. Infrared analysis and gas chromatographic analysis were also performed on organic components extracted from several of these samples. Although the total carbon content of the eolian dust samples varies from 2.8 to 7.0% by weight, the organic carbon component is relatively uniform at 2.9 + or - 0.5%. By comparison, the average organic carbon content of the African surface sediments is 0.7 + or - 0.5%. Total carbohydrate content averages 0.128% for the dust and 0.022% for the desert sediments. It is shown that these desert regions are not presently the principal sources of eolian material transported over the North Atlantic Ocean.

  2. Lunette dunes and yardangs of the Carson desert, Nevada: Implications for Holocene eolian activity in the northern Great Basin

    SciTech Connect

    Lancaster, N. . Quaternary Sciences Center)

    1993-04-01

    A large complex of lunette dunes consisting of two and locally three ridges up to 40 m high occurs on the northeast margin of the Carson Sink playa. The outer, or north-easterly, ridge consists of a core of fine and coarse and partially cemented by saline clay and silt (Unit 1) with avalanche face cross-beds dipping to the north-east at 25--30[degree], as well as planar sets of wind ripple laminae with dips to both the northeast and west at 2--5[degree]. Overlying this unit on the crest and lee side of the ridge is 2--5 m of mobile poorly sorted, very fine and coarse sand that forms an active avalanche face up to 25 m high on the east side of the ridge (Unit 3). At a number of localities, the indurated core of the larger dune ridge is carved into yardanges, or streamlined small hills with a lemniscate shape that result from wind erosion of homogeneous sediments. The dunes overlie, with an erosional contact, Late Pleistocene saline lacustrine clays of paleolake Lahontan. They represent at least two episodes of mid- to late-Holocene deflation of sediments from the Carson Sink playa. Erosion of the dunes and yardang formation suggests: (1) termination of sediment supply from the playa as a result of reduced sediment supply and runoff from the Carson River, (2) cementation of the dunes by clay and silt accumulation, and (3) modern eolian erosion through flow acceleration on dune windward slopes.

  3. Pleistocene succession of the central interior United States

    USGS Publications Warehouse

    Frye, J.C.

    1973-01-01

    The Quaternary of the continental interior of the United States is characterized by deposits from glacial ice, with associated outwash and eolian deposits, and by alluvial deposits produced by the same climatic pulses. Erosional incision of valleys occurred early in the glacial pulse, outwash deposition during the waning phase of the pulse, and soil formation during times of relative stability between the glacial pulses. These features of deposition, erosion, and soil formation are presented in a series of curves. One way the marine record could be correlated with that of the continental interior is to compare and match the physical records of both environments. ?? 1973.

  4. Equatorial Cross-Cutting Ripples on Titan - Regularly Warped Subsiding Methane Plains, not Eolian Dunes.

    NASA Astrophysics Data System (ADS)

    Kochemasov, G. G.

    2008-09-01

    Widely circulating opinion that titanian methane lowlands in a broad equatorial region are covered with eolian formations needs to be carefully checked. Of coarse, all three solid bodies with atmospheres in the inner solar system have dunes. Why do not have them on Titan? Most probably they do exist but discovered by radar up to now cross-cutting rippling features cannot be taken for them. For this there are several reasons. How it can be that prevailing "dune" strike coincides with prevailing wind direction? Normally (with some African exceptions) one sees real terrestrial dunes stretching across winds. And this is understandable from a point of view eolian dunes formation. This formation gives particular cross profile to dunes. Asymmetric profile - one slope is long and gentle and another one short and abrupt. But titanian "dunes" are mostly uniform and symmetric. And this characteristic is preserved for many hundreds of kilometers of very straight features. Then, the finest solid particles precipitation from the thick atmosphere of Titan should be distributed on the satellite surface more uniformly and cover dark lowlands and light icy highlands of the wide equatorial belt more or less evenly. But "dunes" are strictly associated with dark lowlands and tend to turn round light icy obstacles. Cindering smoggy particles to produce sands for making dunes is a pure imagination. Then, radar preferably sees one direction but nevertheless one or more crossing directions of rippling are distinguished (Fig.3, 4) They mean two wind directions at the same time or another wind direction at another time? If so, the earlier "dunes" should be more or less obliterated by the later ones. Nothing of the kind! Both crossing ripples directions are fresh. Then, eolian action is not seen at the higher latitudes (Fig. 5). There are no winds there? Probably it is not so. Only a liquid state of methane can help (but liquid should be disturbed by winds). Solid methane there is also

  5. Equatorial Cross-Cutting Ripples on Titan - Regularly Warped Subsiding Methane Plains, not Eolian Dunes.

    NASA Astrophysics Data System (ADS)

    Kochemasov, G. G.

    2008-09-01

    Widely circulating opinion that titanian methane lowlands in a broad equatorial region are covered with eolian formations needs to be carefully checked. Of coarse, all three solid bodies with atmospheres in the inner solar system have dunes. Why do not have them on Titan? Most probably they do exist but discovered by radar up to now cross-cutting rippling features cannot be taken for them. For this there are several reasons. How it can be that prevailing "dune" strike coincides with prevailing wind direction? Normally (with some African exceptions) one sees real terrestrial dunes stretching across winds. And this is understandable from a point of view eolian dunes formation. This formation gives particular cross profile to dunes. Asymmetric profile - one slope is long and gentle and another one short and abrupt. But titanian "dunes" are mostly uniform and symmetric. And this characteristic is preserved for many hundreds of kilometers of very straight features. Then, the finest solid particles precipitation from the thick atmosphere of Titan should be distributed on the satellite surface more uniformly and cover dark lowlands and light icy highlands of the wide equatorial belt more or less evenly. But "dunes" are strictly associated with dark lowlands and tend to turn round light icy obstacles. Cindering smoggy particles to produce sands for making dunes is a pure imagination. Then, radar preferably sees one direction but nevertheless one or more crossing directions of rippling are distinguished (Fig.3, 4) They mean two wind directions at the same time or another wind direction at another time? If so, the earlier "dunes" should be more or less obliterated by the later ones. Nothing of the kind! Both crossing ripples directions are fresh. Then, eolian action is not seen at the higher latitudes (Fig. 5). There are no winds there? Probably it is not so. Only a liquid state of methane can help (but liquid should be disturbed by winds). Solid methane there is also

  6. Mars Eolian Geology at Airphoto Scales: The Large Wind Streaks of Western Arabia Terra

    NASA Technical Reports Server (NTRS)

    Edgett, Kenneth S.

    2001-01-01

    More than 27,000 pictures at aerial photograph scales (1.5-12 m/pixel) have been acquired by the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) since September 1997. The pictures are valuable for testing hypotheses about geologic history and processes of Mars. Of particular interest are eolian features connected to surface albedo patterns. This work is focused on low-albedo wind streaks, some over 100 km long, in western Arabia Terra. Each streak is widest where it originates at an impact crater (typically 25-150 km diameter). The streaks taper downwind. Within the associated craters there is a lower-albedo surface that, in nearly all observed cases, includes barchan dunes indicative of transport in the same direction as the wind streaks. Upwind of the dunes there is usually an outcrop of layered material that might have served as a source for dune sand. MOC images show that the west Arabia streaks consist of a smooth-surfaced, multiple-meters-thick, mantle (smooth at 1.5 m/pixel) that appears to be superposed on local surfaces. No dunes are present, indicating that down-streak transport of sediment via saltation and traction have not occurred. Two models might explain the observed properties: (1) the streaks consist of dark silt- and clay-sized grains deflated from the adjacent crater interiors and deposited from suspension or (2) they are remnants (protected in the lee of impact crater rims) of a formerly much larger, regional covering of low albedo, smooth-surfaced mantle. The latter hypothesis is based on observation of low albedo mantled surfaces occurring south of west Arabia in Terra Meridiani. For reasons yet unknown, a large fraction of the martian equatorial regions are covered by low albedo, mesa-forming material that lies unconformably atop eroded layered and cratered terrain. Both hypotheses are being explored via continued selective targeting of new MOC images as well as analyses of the new data.

  7. Late Holocene eolian activity in the mineralogically mature Nebraska Sand Hills

    USGS Publications Warehouse

    Muhs, D.R.; Stafford, Thomas W., Jr.; Swinehart, J.B.; Cowherd, S.D.; Mahan, S.A.; Bush, C.A.; Madole, R.F.; Maat, P.B.

    1997-01-01

    The age of sand dunes in the Nebraska Sand Hills has been controversial, with some investigators suggesting a full-glacial age and others suggesting that they were last active in the late Holocene. New accelerator mass spectrometry radiocarbon ages of unaltered bison bones and organic-rich sediments suggest that eolian sand deposition occurred at least twice in the past 3000 14C yr B.P. in three widely separated localities and as many as three times in the past 800 14C yr at three other localities. These late Holocene episodes of eolian activity are probably the result of droughts more intense than the 1930s "Dust Bowl" period, based on independent Great Plains climate records from lake sediments and tree rings. However, new geochemical data indicate that the Nebraska Sand Hills are mineralogically mature. Eolian sands in Nebraska have lower K-feldspar (and K2O, Rb, and Ba) contents than most possible source sediments and lower K-feldspar contents than dunes of similar age in Colorado. The most likely explanation for mineralogical maturity is reduction of sand-sized K-feldspar to silt-sized particles via ballistic impacts due to strong winds over many cycles of eolian activity. Therefore, dunes of the Nebraska Sand Hills must have had a long history, probably extending over more than one glacial-interglacial cycle, and the potential for reactivation is high, with or without a future greenhouse warming. ?? 1997 University of Washington.

  8. Quaternary eolian dunes in the Savannah River valley, Jasper County, South Carolina, USA

    NASA Astrophysics Data System (ADS)

    Swezey, Christopher S.; Schultz, Arthur P.; González, Wilma Alemán; Bernhardt, Christopher E.; Doar, William R.; Garrity, Christopher P.; Mahan, Shannon A.; McGeehin, John P.

    2013-09-01

    Sand hills in the Savannah River valley in Jasper County (South Carolina, USA) are interpreted as the remnants of parabolic eolian dunes composed of sand derived from the Savannah River and stabilized by vegetation under prevailing climate conditions. Optically stimulated luminescence ages reveal that most of the dunes were active ca. 40 to 19 ka ago, coincident with the last glacial maximum (LGM) through early deglaciation. Modern surface winds are not sufficient for sustained eolian sand transport. When the dunes were active, winds blew at velocities of at least 4 m/s from west to east, and some vegetation was present. The ratio of annual precipitation to potential evapotranspiration (P:PE) was less than the modern ratio of 1.23 and may have been < 0.30, caused by stronger winds (which would have resulted in greater evaporation) and/or reduced precipitation. The Savannah River dunes are part of a larger assemblage of eolian dunes that were active in the eastern United States during and immediately after the LGM, suggesting that eolian sediment behavior in this region has been controlled by regional forcing mechanisms during the Quaternary.

  9. Loess record of the Pleistocene-Holocene transition on the northern and central Great Plains, USA

    USGS Publications Warehouse

    Mason, J.A.; Miao, X.; Hanson, P.R.; Johnson, W.C.; Jacobs, P.M.; Goble, R.J.

    2008-01-01

    Various lines of evidence support conflicting interpretations of the timing, abruptness, and nature of climate change in the Great Plains during the Pleistocene-Holocene transition. Loess deposits and paleosols on both the central and northern Great Plains provide a valuable record that can help address these issues. A synthesis of new and previously reported optical and radiocarbon ages indicates that the Brady Soil, which marks the boundary between late Pleistocene Peoria Loess and Holocene Bignell Loess, began forming after a reduction in the rate of Peoria Loess accumulation that most likely occurred between 13.5 and 15 cal ka. Brady Soil formation spanned all or part of the B??lling-Aller??d episode (approximately 14.7-12.9 cal ka) and all of the Younger Dryas episode (12.9-11.5 cal ka) and extended at least 1000 years beyond the end of the Younger Dryas. The Brady Soil was buried by Bignell Loess sedimentation beginning around 10.5-9 cal ka, and continuing episodically through the Holocene. Evidence for a brief increase in loess influx during the Younger Dryas is noteworthy but very limited. Most late Quaternary loess accumulation in the central Great Plains was nonglacigenic and was under relatively direct climatic control. Thus, Brady Soil formation records climatic conditions that minimized eolian activity and allowed effective pedogenesis, probably through relatively high effective moisture. Optical dating of loess in North Dakota supports correlation of the Leonard Paleosol on the northern Great Plains with the Brady Soil. Thick loess in North Dakota was primarily derived from the Missouri River floodplain; thus, its stratigraphy may in part reflect glacial influence on the Missouri River. Nonetheless, the persistence of minimal loess accumulation and soil formation until 10 cal ka at our North Dakota study site is best explained by a prolonged interval of high effective moisture correlative with the conditions that favored Brady Soil formation. Burial

  10. Provenance of Palouse Loess and Relation to Late Pleistocene Glacial Outburst Flooding, Washington State

    NASA Astrophysics Data System (ADS)

    Sweeney, M. R.; Busacca, A. J.; Gaylord, D. R.; Zender, C. S.

    2002-12-01

    The eolian system of the Pacific Northwest is a product of long-term deflation of expansive sedimentary units by prevailing winds throughout the Quaternary. The Palouse loess is a deposit of wind-blown silt that covers approximately 10,000 sqare km up to 75 m thick. Late Quaternary units of the loess become finer texturally and thinner to the northeast, suggesting that they were derived from sedimentary basins south and west. The source of the loess has been inferred and hypothesized but never directly determined. A geochemical study of the late-Pleistocene to Holocene L1 unit of the Palouse loess and its possible sources was conducted to determine its provenance. There are two sedimentary units that lie upwind of the loess that may have contributed sediment via eolian deflation: 1) sand- and silt-rich slackwater sediment derived from late-Pleistocene outburst flooding of glacial Lake Missoula, and 2) sand- and silt-rich sediment from the Miocene-Pliocene Ringold Formation. Both are very similar in mineral composition, being derived from plutonic, metamorphic, and volcanic rocks of the western United States and southern British Columbia. Major and trace element data determined by x-ray fluorescence (XRF) of silt to very fine sand from loess and potential source sediments was used to pinpoint the exact source of the loess. A one-to-one relationship of major and trace elements exists between eolian and flood sediments, whereas Ringold Formation sediments have elevated Ti, P, Mg, and Ca oxides and lower K oxide values as well as scattered trace element values relative to Palouse loess. These trends may be due to the presence of basalt lithic grains in flood sediment that have been broken down and distributed throughout the loess. The Ringold Formation lacks appreciable amounts of basalt. The geochemical data from this study demonstrates that flood sediment is the dominant source of eolian material for the Palouse loess. The spatial distribution of the possible source

  11. Pleistocene sediments of Lake Baikal: Lithology and stratigraphic correlation

    NASA Astrophysics Data System (ADS)

    Akulov, N. I.; Mashchuk, I. M.; Akulova, V. V.

    2015-01-01

    The Cenozoic sediments of Lake Baikal penetrated by boreholes and investigated by the manned submersible Pisces, as well as coeval deposits cropping out in beach scarps, recovered by mine workings, and drilled in the coastal zone were the object of this investigation. The main attention was paid to Pleistocene bottom sediments penetrated by Borehole BDP-99-2. The investigations included the detailed analysis of the lithology (grain-size composition, immersion mineralogy of light and heavy fractions, X-ray structural analysis of clayey fraction) and palynological assemblages to specify facies features of Cenozoic sediments, correlate all their known stratigraphic units constituting the sedimentary section of the lake with their analogs in the onshore part of the Baikal rift zone, and compile the composite Cenozoic section. The following features of these sediments are noted: (1) as a whole, Pleistocene sediments are characterized by the hydromica-smectite composition of their clayey fraction with an insignificant share of kaoline; (2) the heavy fraction is dominated by the terrigenous epidote-amphibole association poorly resistant to weathering; (3) Pleistocene sediments of the lake contain siderite, vivianite, pyrite, and goethite concretions and micrometeorites, in addition to well-known ferromanganese nodules; (4) the presence of relict palynomorphs in Pleistocene sediments of Baikal is determined by their erosion from Miocene and Pliocene cavernous clays cropping out on underwater slopes of the Posol'skaya Bank and subsequent reburial along with Pleistocene palynological assemblages.

  12. The paleoclimatic record provided by eolian deposition in the deep sea: The geologic history of wind

    NASA Astrophysics Data System (ADS)

    Rea, David K.

    1994-05-01

    The mineral component of pelagic sediment is brought to the deep sea by transport in the wind. Extraction and analysis of this dust allows estimation of the past aridity of the eolian source region, via flux determinations, and of the intensity of the transporting winds, from grain size data. These two parameters, the grain size and mass flux of dust, vary independently. There are three significant sources of modern dust, eastern and central Asia, northwest Africa, and Arabia, all in the northern hemisphere. As the rainfall associated with the Intertropical Convergence Zone is an effective barrier to southerly transport of dust, the northern hemisphere is an order of magnitude more "dusty" than is the southern, an asymmetry that has characterized most of the Cenozoic. Eolian flux data show that most of the northern hemisphere was more arid during glacial maxima, with 3 to 5 times as much dust transported during glacial stages than during interglacials; only northwestern South America varied in the opposite sense. The periodicity of Quaternary variation in both eolian flux and eolian grain size data is strongly influenced by the Milankovitch cycles of orbital variability. Wind intensities vary on a shorter time scale than the general 100-kyr cycles of glaciation and general aridity. Eolian grain sizes display forcing at precessional (19 and 23 kyr), tilt (41 kyr), and at approximately 30 kyr periodicities. As a result the generalization that winds are uniformly stronger during glacial times is not valid. Whole-Cenozoic records show that the largest change in dust flux, an order of magnitude increase, occurred in the northern hemisphere and reflects continental drying associated with the late Pliocene onset of northern hemisphere glaciation. Southern hemisphere eolian records show no sign of paleoclimatic changes in the late Pliocene. The most important change in Cenozoic atmospheric circulation was a severalfold reduction in wind intensity that occurred at the time

  13. Origins of relief along contacts between eolian sandstones and overlying marine strata

    SciTech Connect

    Eschner, T.B.; Kocurek, G.

    1988-08-01

    Origins of large-scale relief along eolian-marine unit contacts, which form significant stratigraphic traps for hydrocarbons, can be recognized as inherited, reworked, and/or erosional. The Permian Rotliegende-Weissliegende Sandstone and Yellow Sands of Europe may best exemplify inherited relief in that dunes are preserved largely intact. Reworked relief, which shows significant destruction of original dune topography but with remnants of the bedforms preserved, is shown by relict Holocene dunes of coastal Australia, the Jurassic Entrada Sandstone of the San Juan basin, and the Pennsylvanian-Permian Minnelusa Formation of Wyoming. Erosional relief results from post-eolian processes and is exemplified by the Jurassic Entrada Sandstone of northeastern Utah. 11 figs., 1 tab.

  14. Eolian additions to late Quaternary alpine soils, Indian Peaks Wilderness Area, Colorado Front Range

    USGS Publications Warehouse

    Muhs, D.R.; Benedict, J.B.

    2006-01-01

    Surface horizons of many alpine soils on Quaternary deposits in high-mountain settings are enriched in silt. The origin of these particles has been debated, particularly in the Rocky Mountain region of North America. The most common explanations are frost shattering of coarser particles and eolian additions from distant sources. We studied soil A horizons on alpine moraines of late-glacial (Satanta Peak) age in the Colorado Front Range. Surface horizons of soils on these moraines are enriched in silt and have a particle size distribution that resembles loess and dust deposits found elsewhere. The compositions of sand and silt fractions of the soils were compared to possible local source rocks, using immobile trace elements Ti, Nb, Zr, Ce, and Y. The sand fractions of soils have a wide range of trace element ratios, similar to the range of values in the local biotite gneiss bedrock. In contrast, silt fractions have narrower ranges of trace element ratios that do not overlap the range of these ratios in biotite gneiss. The particle size and geochemical results support an interpretation that silts in these soils are derived from airborne dust. Eolian silts were most likely derived from distant sources, such as the semiarid North Park and Middle Park basins to the west. We hypothesize that much of the eolian influx to soils of the Front Range occurred during an early to mid-Holocene warm period, when sediment availability in semiarid source basins was at a maximum.

  15. Geochemical evidence for an Eolian sand dam across the North and South Platte rivers in Nebraska

    USGS Publications Warehouse

    Muhs, Daniel R.; Swinehart, James B.; Loope, David B.; Been, Josh; Mahan, Shannon; Bush, Charles A.

    2000-01-01

    Geochemical and geomorphic data from dune fields in southwestern Nebraska provide new evidence that the Nebraska Sand Hills once migrated across the North and South Platte rivers and dammed the largest tributary system to the Missouri River. The Lincoln County and Imperial dune fields, which lie downwind of the South Platte River, have compositions intermediate between the Nebraska Sand Hills (quartz-rich) and northeastern Colorado dunes (K-feldspar-rich). The most likely explanation for the intermediate composition is that the Lincoln County and Imperial dunes are derived in part from the Nebraska Sand Hills and in part from the South Platte River. The only mechanism by which the Nebraska Sand Hills could have migrated this far south is by complete infilling of what were probably perennially dry North Platte and South Platte river valleys. Such a series of events would have required an extended drought, both for activation of eolian sand and decreased discharges in the Platte River system. A nearby major tributary of the North Platte River is postulated to have been blocked by eolian sand about 12,000 14C yr B.P. We propose that an eolian sand dam across the Plattes was constructed at about this same time.

  16. Quantifying the seasonal variations in fluvial and eolian sources of terrigenous material to Cariaco Basin, Venezuela

    NASA Astrophysics Data System (ADS)

    Elmore, Aurora C.; Thunell, Robert C.; Styles, Richard; Black, David; Murray, Richard W.; Martinez, Nahysa; Astor, Yrene

    2009-02-01

    The varved sediments that accumulate in the Cariaco Basin provide a detailed archive of the region's climatic history, including a record of the quantity of fluvial and wind-transported material. In this study, we examine the sedimentological characteristics (clay mineralogy and grain size) of both surface sediments and sinking lithogenic material collected from sediment trap samples over a three-year period from 1997 to 2000. Data from biweekly sediment trap samples show a tri-modal particle size distribution, with prominent peaks at 2, 22 and 80 μm, indicating sediment contributions from both eolian and fluvial sources. The clay mineralogy of the water column samples collected from 1997 to 1999 also shows distinctive characteristics of eolian and fluvial material. An examination of surface sediment samples from the Cariaco Basin indicates that the Unare River is the main source of riverine sediments to the eastern sub-basin. By combining these sedimentological proxies, we estimate that ˜10% of the terrigenous material delivered to the Cariaco Basin is eolian, while ˜90% is fluvial. This represents an annual dust accumulation rate of ˜0.59 mg/cm 2/yr. Since aerosols are closely linked to climate variability, the ability to quantify paleo-dust fluxes using sedimentological characteristics will be a useful tool for future paleoclimate studies looking at sub-Saharan aridity and latitudinal migration of the Intertropical Convergence Zone.

  17. Martian crater degradation by eolian processes: Analogy with the Rio Cuarto Crater Field, Argentina

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    Numerous degraded and rimless craters occur across broad areas of the Martian surface that are mantled by thick, unconformable deposits. These regions include Arabia, Mesogaea, Electris, Tempe, the interior and surface to the northwest of Isidis Basin, southern Ismenius Lacus, and the polar layered terrains. Occurrence of the deposits and low regional thermal inertias indicate that at least some accumulated fine-grained sediment (effective particle diameters of 0.1-0.5 mm or coarse silt to medium sand) to a thickness of 100's to 1000's of meters. Most unconformable deposits experienced some eolian modification that may be recent in some locales. Despite the presence of these deposits, simple eolian deposition appears incapable of creating the numerous degraded and rimless craters occurring within their limits. Nevertheless, terrestrial analyses of the Rio Cuario craters formed into loessoid deposits demonstrates that eolian redistribution of fine-grained sediment in and around craters produces degraded morphologies that are analogous to some found in mantled regions on Mars.

  18. Vegetation, substrate, and eolian sediment transport at Teesto Wash, Navajo Nation, 2009-2012

    USGS Publications Warehouse

    Draut, Amy E.; Redsteer, Margaret Hiza; Amoroso, Lee

    2012-01-01

    On the Navajo Nation, southwestern United States, warming temperatures and recent drought have increased eolian (windblown) sediment mobility such that large, migrating sand dunes affect grazing lands, housing, and road access. We present an assessment of seasonal variations in sand transport, mobility, and ground cover (vegetation and substrate) within a 0.2-km2 study area near Teesto Wash, southern Navajo Nation, as part of a multiyear study measuring the effects of drought on landscape stability. Sand mobility in the study area decreased substantially as one year (2010) with near-normal monsoon rainfall somewhat abated a decade-long drought, temporarily doubling vegetation cover. The invasive annual plant Russian thistle (Salsola sp.), in particular, thrived after the monsoon rains of 2010. Vegetation that grew during that year with adequate rain died off rapidly during drier conditions in 2011 and 2012, and the proportion of bare, open sand area increased steadily after summer 2010. We infer that isolated seasonal increases in rainfall will not improve landscape stability in the long term because sustained increase in perennial plants, which are more effective than annual plants at stabilizing sand against wind erosion, requires multiple consecutive seasons of adequate rain. On the basis of climate projections, a warmer, drier climate and potentially enhanced sediment supply from ephemeral washes may further increase eolian sediment transport and dune activity, worsening the present challenges to people living in this region. Connections between climate, vegetation cover, and eolian sediment erodibility in this region also are highly relevant for studies in other regions worldwide with similar environmental characteristics.

  19. Pleistocene extinctions: haunting the survivors.

    PubMed

    Hofreiter, Michael

    2007-08-01

    For many years, the megafaunal extinctions at the end of the Pleistocene have been assumed to have affected only those species that became extinct. However, recent analyses show that the surviving species may also have experienced losses in terms of genetic and ecological diversity. PMID:17686436

  20. Polymorphism in pleistocene land snails.

    PubMed

    Owen, D F

    1966-04-01

    Under suitable conditions the colors and patterns of the shells of land snails may be preserved for thousands of years. In a late Pleistocene population of Limicolaria martensiana all the major color forms that occur in modern living snails may be distinguished, and the basic polymorphism is at least 8,000 to 10,000 year old. PMID:17830234

  1. Reconstruction of Eolian Bedforms from Cross-Bedded Strata at Victoria Crater, Meridiani Planum, Mars

    NASA Astrophysics Data System (ADS)

    Hayes, A. G.; Grotzinger, J. P.; Squyres, S. W.; Lewis, K.; Metz, J.; Bell, J. F.; Athena Science Team

    2007-12-01

    Outcrop exposures imaged by the Opportunity rover at Meridiani Planum have depicted cross-bedded strata with geometries and scales similar to eolian and subaqeous deposits on Earth. On Earth preserved cross-strata are rich in geologic information, providing insight into the depositional environment and sediment transport directions. The high-resolution stratigraphy of these cross-bedded strata can be used to reconstruct sedimentary bedforms on Mars to infer formation process and describe the depositional environment. Meter-scale cross bedding at Victoria Crater is similar to terrestrial eolian deposits and is interpreted as a dry dune field. Sets of cross-strata in the Cape St. Vincent and Cape St. Mary sections of Victoria Crater are comparable to Jurassic-age eolian deposits of the western US. The Opportunity Rover has spent ~300 sols traversing 90 degrees of the rim of Victoria crater, obtaining images of rock outcrops exposed by several promontories along the way. The outcrops at the Cape St. Mary and Cape St. Vincent promontories, which are located at opposite ends of the traverse, have proven to be the best examples of meter scale cross-bedding observed on Mars to date. Super-resolution imaging techniques and long baseline stereo observations were utilized during an extended imaging campaign of both outcrop faces. Cape St. Mary is characterized by meter-scale trough-style cross bedding, suggesting sinuous crested dunes with scour pits migrating perpendicular to the outcrop face. Cape St. Vincent, which is striking 110° away from Cape St. Mary, has layering indicative of a single climbing bedform with dune heights of several meters. The findings at Cape St. Mary and Cape St. Vincent are combined with other bedding faces to produce an eolian deposition model for layering exposed at Victoria Crater. Any depositional model used to explain the bedding must conform to an observed N-S paleo-flow direction. In addition to bedded layering, a bright band is observed

  2. Late-Pleistocene (MIS 3-2) palaeoenvironments as recorded by sediments, palaeosols, and ground-squirrel nests at Duvanny Yar, Kolyma lowland, northeast Siberia

    NASA Astrophysics Data System (ADS)

    Zanina, O. G.; Gubin, S. V.; Kuzmina, S. A.; Maximovich, S. V.; Lopatina, D. A.

    2011-08-01

    A detailed study of the Duvanny Yar section in the Kolyma Lowland (Yakutia) provides the most extensive knowledge to date about late-Pleistocene soil formation processes and environments in the North-East Siberian Arctic. Late-Quaternary palaeoenvironmental changes were reconstructed using paleopedological data and a range of palaeoecological bio-indicators (palynomorphs, plant macrofossils and insects). The frozen sediments representing marine isotope stage 3 (MIS-3), which encompasses the Karginsky interstadial, include profiles of four palaeosols of different ages. The oldest palaeosol is early Karginskian, and three overlying soil horizons represent a late-Karginskian pedocomplex. Palaeopedological data indicate a change of from synlithogenic soil formation processes to epigenic ones during these intervals. The intervening periods of synlithogenic pedogenesis were accompanied by active accumulation of eolian deposits. The Earlier Karginskian period of pedogenesis occurred in the absence of eolian sedimentation and when summer conditions were warm. The wide spectrum of peaty and peaty-gley soils observed in the late-Karginskian deposits developed under conditions of progressive cooling. The structure and content of fossil rodent burrows dated to approximately 30 000 yr BP from frozen late-Pleistocene deposits at Duvanny Yar indicate an arid and severe climate, a depth of active layer of 60-80 cm, and a wide distribution of disturbed habitats with pioneer and steppe vegetation.

  3. Eolian depositional phases during the past 50 ka and inferred climate variability for the Pampean Sand Sea, western Pampas, Argentina

    NASA Astrophysics Data System (ADS)

    Tripaldi, Alfonsina; Forman, Steven L.

    2016-05-01

    The Pampean Sand Sea, which occurs from the Argentinian Pampas to the eastern Andean piedmont, hosts presently stabilized dune fields spanning the late Quaternary. This study integrates previous results and presents new geomorphic, stratigraphic, sedimentological, and chronologic data for nineteen >2 m-thick eolian successions for the San Luis paleo-dune field, western Pampas, to better constrain the depositional history. Six eolian depositional phases are identified spanning the past 50 ka, interposed with paleosols and/or bounded by erosive surfaces. Age control was from 61 OSL ages of small aliquots of quartz grains from eolian stratigraphic units. The inferred timing of eolian phases are at ca. 70 ± 10 yr, 190 ± 20 yr, 12 to 1 ka, 22 to 17 ka, 29 to 24 ka, and 40 to 32 ka. A maximum span for periods of pedogenesis at ca. 12 to 17 ka, 22 to 24 ka, and 29 to 32 ka was provided by bounding OSL ages, which broadly overlap with high stands of pluvial lakes and glacier advances in the central Andes. We infer that the added precipitation may reflect expansion of the Southern Hemisphere monsoon, associated with Northern Hemisphere Heinrich events, leading to episodes of significantly wetter conditions (>350 mm MAP) to at least 35° S. Most of the Holocene (12 ka to 0.8 ka) was characterized by sand sheet deposit under drier than present conditions (100-450 mm MAP), associated with Monte-type vegetation (shrub steppe). The latest two eolian depositional phases, occurred at ca. 190 and 70 yr ago, during the historic period with European settlement and are related to anthropogenic landscape disturbance, though the youngest phase was concomitant with 1930s drought. Wet conditions dominated since ca. AD 1970 with new lakes and rivers forming across this eolian terrain; an incongruous environmental response in reference to drier conditions for most of the Holocene.

  4. Continental sequence stratigraphy of a wet eolian system -- A key to relative sea level change

    SciTech Connect

    Crabaugh, M.; Kocurek, G. . Dept. of Geological Sciences)

    1993-04-01

    The Jurassic Entrada Sandstone, as studied in detail along a 2.7 km traverse in NE Utah, is interpreted as having formed as a wet eolian system, with depositional sequences defined by accumulations and bounding super surfaces. In a wet system, accumulation occurs during a relative rise of the water table, whereas super surfaces mark periods of a static or falling water table when sediment bypass or erosion occur, respectively. The ratio of dune to interdune accumulations within a depositional sequence is an estimate of the available sand supply, which in turn is a function of rates of sediment supply and water-table fluctuations. For the Entrada, variables of sand supply and water table should be regional in nature; moreover, the coastal position of the Entrada suggests relative sea level as the control. Verifying this hypothesis, an 80 km transect of the Entrada from north of Monticello southward to Bluff, Utah, shows a similar sequence architecture as in NE Utah. The geometry and composition of sequences along the transect identify components of a relative water table rise that occurred because of differential subsidence rates and an overall relative rise in sea level. The coupling of eolian sequences with their controls allows not only an understanding of the resultant facies architecture, but also shows the response of continental systems on basin margins to basin interior events.

  5. Giant desiccation fissures filled with calcareous eolian sand, Hermosa Formation (Pennsylvanian), southeastern Utah

    NASA Astrophysics Data System (ADS)

    Loope, David B.; Haverland, Zsolt E.

    1988-04-01

    At two stratigraphic intervals within the upper member of the Upper Pennsylvanian Hermosa Formation, calcareous eolian sand fills downward-tapering fissures that are as much as 18 cm wide and 5.7 m deep. Fissure fillings define orthogonal polygons 10 m or more in diameter. One of the host beds is primarily composed of subtidally deposited limestone, the other is a thinly laminated, nonmarine red siltstone. Both systems of fissure fillings are directly overlain and underlain by large-scale cross-stratified, calcareous eolianites. The limestone host bed contains chert pseudomorphs after gypsum. Compaction of host rocks contorted fissure fillings and caused doming of eolian strata over each fissure. Platy mineral grains in fissure fillings are aligned subparallel to bedding in the host rocks, supporting the view that the fissures were passively filled rather than forcefully injected. These ancient fissure systems are similar in scale and pattern to those that define giant desiccation polygons in numerous Great Basin playas. The Pennsylvanian fissures, like their Holocene counterparts, probably formed when groundwater tables dropped from shallow levels within fine-grained, impermeable deposits into underlying aquifers, greatly decreasing the extent of the capillary fringe. Our study of the fissures and host rocks supports the hypothesis that carbonate grains within the eolianites were deflated from uncemented marine sediments that were broadly exposed during regressive intervals.

  6. Wind profiles on the stoss slope of sand dunes: Implications for eolian sand transport

    SciTech Connect

    Frank, A.; Kocurek, G. . Dept. of Geological Sciences)

    1993-04-01

    Starting with the work of R.A. Bagnold it has been recognized that the shear stress exerted by the wind on sand grains is the driving force for eolian sand transport. Calculation of accurate rates of sand transport is essential for prediction of migration rates of sand dunes in modern environments as well as reconstructing paleoclimates (wind speed and direction) from eolian deposits. Because a sand dune is a streamlined obstacle in the path of the wind, continuity necessitates that the flow field is compressed over the windward side of a dune and shear stress should progressively increase up the slope as the flow accelerates. However, airflow measurements over 14 dunes (at White Sands, New Mexico; Algodones, CA; and Padre Island, TX) show that compression of the flow field occurs very close to the surface and as a consequence, the overlying flow actually shows an overall decrease in shear stress up the slope. Measurements commonly collected in the overlying zone are not representative of the near-surface, sand-driving wind. Furthermore, near-surface compression of the flow field implies that a pressure gradient exists that would render the current transport models inappropriate for sloping surfaces that dominate natural sandy desert terrains.

  7. Sulfate-rich eolian and wet interdune deposits, erebus crater, meridiani Planum, Mars

    USGS Publications Warehouse

    Metz, J.M.; Grotzinger, J.P.; Rubin, D.M.; Lewis, K.W.; Squyres, S. W.; Bell, J.F.

    2009-01-01

    This study investigates three bedrock exposures at Erebus crater, an ?? 300 m diameter crater approximately 4 km south of Endurance crater on Mars. These outcrops, called Olympia, Payson, and Yavapai, provide additional evidence in support of the dune-interdune model proposed for the formation of the deposits at the Opportunity landing site in Meridiani Planum. There is evidence for greater involvement of liquid water in the Olympia outcrop exposures than was observed in Eagle or Endurance craters. The Olympia outcrop likely formed in a wet interdune and sand sheet environment. The facies observed within the Payson outcrop, which is likely stratigraphically above the Olympia outcrop, indicate that it was deposited in a damp-wet interdune, sand sheet, and eolian dune environment. The Yavapai outcrop, which likely stratigraphically overlies the Payson outcrop, indicates that it was deposited in primarily a sand sheet environment and also potentially in an eolian dune environment. These three outcrop exposures may indicate an overall drying-upward trend spanning the stratigraphic section from its base at the Olympia outcrop to its top at the Yavapai outcrop. This contrasts with the wetting-upward trend seen in Endurance and Eagle craters. Thus, the series of outcrops seen at Meridiani by Opportunity may constitute a full climatic cycle, evolving from dry to wet to dry conditions. ?? 2009, SEPM (Society for Sedimentary Geology).

  8. Middle Holocene aridity, eolian-dune accretion, and the formation of Lake Mattamuskeet, eastern North Carolina

    NASA Astrophysics Data System (ADS)

    Rodriguez, A. B.; Waters, M. N.; Piehler, M. F.

    2009-12-01

    The stratigraphic record of Lake Mattamuskeet, eastern North Carolina, shows an interval of eolian activity in the middle Holocene. There are about 500,000 elliptical lakes, wetlands, and depressions with elevated rims located on the Atlantic Coastal Plain named Carolina Bays. Lake Mattamuskeet is the largest (162 km2; mean depth 1.0 m), and formed when a blowout depression of a parabolic dune flooded 1540-1635 cal yr. BP. The parabolic dune is up to 2.0-m thick, contains sedimentary structures that indicate rapid deposition, and is composed of a coarsening-upward sequence of silt at the base to sandy silt at the top. Below the dune is an 8420-8605 cal yr. BP paleosol, which corresponds to a wet period in the area. The bottom half of the dune deposit contains abundant charcoal beds and laminae dated at ~6600 cal yr. BP, indicating fire was associated with initial formation of the parabolic dune. Middle Holocene climate of the southeast Atlantic coastal plain is not well constrained. Deposition of the eolian dune could be a local response to fire; or indicate a time of reduced effective moisture in the area. Given that pedogenesis on the dune did not initiate until ~2780-2965 cal yr. BP and flooding of the Lake basin did not occur for ~1000 years after that, effective moisture may have been low for approximately 3600 years after initial dune accretion.

  9. Variations in productivity and eolian fluxes in the northeastern Arabian Sea during the past 110 ka

    NASA Astrophysics Data System (ADS)

    Pourmand, Ali; Marcantonio, Franco; Schulz, Hartmut

    2004-04-01

    High-resolution (one to two samples/ka) radionuclide proxy records from core 93KL in the northeastern Arabian Sea provide evidence for millennial climate variability over the past 110 ka. We interpret 230Th-normalized 232Th fluxes as a proxy for eolian input, and authigenic uranium concentrations as a proxy for past productivity. We attribute orbital and suborbital variations in both proxies to changes in the intensity of the southwest Indian Ocean monsoon. The highest 230Th-normalized 232Th fluxes occur at times that are consistent with the timing of the Younger Dryas, Heinrich events 1-7 and cold Dansgaard-Oeschger stadial events recorded in the GISP2 ice core. Such high dust fluxes may be due to a weakened southwest monsoon in conjunction with strengthened northwesterlies from the Arabian Peninsula and Mesopotamia. Authigenic uranium concentrations, on the other hand, are highest during warm Dansgaard-Oeschger interstadials when the southwest monsoon is intensified relative to the northwesterly winds. Our results also indicate that on orbital timescales maximum average eolian fluxes coincide with the timing of marine isotopic stage (MIS) 2 and 4, while minimum fluxes occur during MIS 1, 3 and 5. Although the forcing mechanism(s) controlling suborbital variabilities in monsoonal intensity is still debated, our findings suggest an atmospheric teleconnection between the low-latitude southwest monsoon and North Atlantic climate.

  10. Canyon Creek: A late Pleistocene vertebrate locality in interior Alaska

    USGS Publications Warehouse

    Weber, F.R.; Hamilton, T.D.; Hopkins, D.M.; Repenning, C.A.; Haas, H.

    1981-01-01

    The Canyon Creek vertebrate-fossil locality is an extensive road cut near Fairbanks that exposes sediments that range in age from early Wisconsin to late Holocene. Tanana River gravel at the base of the section evidently formed during the Delta Glaciation of the north-central Alaska Range. Younger layers and lenses of fluvial sand are interbedded with arkosic gravel from Canyon Creek that contains tephra as well as fossil bones of an interstadial fauna about 40,000 years old. Solifluction deposits containing ventifacts, wedge casts, and rodent burrows formed during a subsequent period of periglacial activity that took place during the maximum phase of Donnelly Glaciation about 25,000-17,000 years ago. Overlying sheets of eolian sand are separated by a 9500-year-old paleosol that may correlate with a phase of early Holocene spruce expansion through central Alaska. The Pleistocene fauna from Canyon Creek consists of rodents (indicated by burrows), Mammuthus primigenius (woolly mammoth), Equus lambei (Yukon wild ass), Camelops hesternus (western camel), Bison sp. cf. B. crassicornis (large-horned bison), Ovis sp. cf. O. dalli (mountain sheep), Canis sp. cf. C. lupus (wolf), Lepus sp. cf. L. othus or L. arcticus (tundra hare), and Rangifer sp. (caribou). This assemblage suggests an open landscape in which trees and tall shrubs were either absent or confined to sheltered and moist sites. Camelops evidently was present in eastern Beringia during the middle Wisconsin interstadial interval but may have disappeared during the following glacial episode. The stratigraphic section at Canyon Creek appears to demonstrate that the Delta Glaciation of the north-central Alaska Range is at least in part of early Wisconsin age and was separated from the succeeding Donnelly Glaciation by an interstadial rather than interglacial episode. ?? 1981.

  11. Canyon Creek: A late Pleistocene vertebrate locality in interior Alaska

    NASA Astrophysics Data System (ADS)

    Weber, Florence R.; Hamilton, Thomas D.; Hopkins, David M.; Repenning, Charles A.; Haas, Herbert

    1981-09-01

    The Canyon Creek vertebrate-fossil locality is an extensive road cut near Fairbanks that exposes sediments that range in age from early Wisconsin to late Holocene. Tanana River gravel at the base of the section evidently formed during the Delta Glaciation of the north-central Alaska Range. Younger layers and lenses of fluvial sand are interbedded with arkosic gravel from Canyon Creek that contains tephra as well as fossil bones of an interstadial fauna about 40,000 years old. Solifluction deposits containing ventifacts, wedge casts, and rodent burrows formed during a subsequent period of periglacial activity that took place during the maximum phase of Donnelly Glaciation about 25,000-17,000 years ago. Overlying sheets of eolian sand are separated by a 9500-year-old paleosol that may correlate with a phase of early Holocene spruce expansion through central Alaska. The Pleistocene fauna from Canyon Creek consists of rodents (indicated by burrows), Mammuthus primigenius (woolly mammoth), Equus lambei (Yukon wild ass), Camelops hesternus (western camel), Bison sp. cf. B. crassicornis (large-horned bison), Ovis sp. cf. O. dalli (mountain sheep), Canis sp. cf. C. lupus (wolf), Lepus sp. cf. L. othus or L. arcticus (tundra hare), and Rangifer sp. (caribou). This assemblage suggests an open landscape in which trees and tall shrubs were either absent or confined to sheltered and moist sites. Camelops evidently was present in eastern Beringia during the middle Wisconsin interstadial interval but may have disappeared during the following glacial episode. The stratigraphic section at Canyon Creek appears to demonstrate that the Delta Glaciation of the north-central Alaska Range is at least in part of early Wisconsin age and was separated from the succeeding Donnelly Glaciation by an interstadial rather than interglacial episode.

  12. Vertebrate trackways in Pleistocene eolianites on Antiparos (Cyclades, Greece)

    NASA Astrophysics Data System (ADS)

    Bickel, L.; Draganits, E.; Gier, S.; Zuschin, M.

    2010-05-01

    Yellowish calcarenites have been mapped at many localities along the NW coast of Antiparos. These sandstones, which form dm to 5 m thick layers unconformably resting on greenschist to amphibolite facies metamorphic rocks of the Attic-Cycladic Crystalline of the Central Hellenides, have been traced from below sea-level up to an elevation of approximately 80 m. Generally, the bedding and internal laminae are oriented parallel to the slope of the underlying crystalline rocks without forming any morphological terraces. Cross-bedding, with dip-angles >35°, has only rarely been recorded. Petrographically, the rocks are dominated by marine bioclasts including mainly corallinacean red algae, benthic foraminifers and fragments of gastropods and bivalves with siliciclastic components forming less than 20% of the rock, cemented by calcite. Grains are well-rounded and well-sorted, with grain sizes ranging from medium sand to granule sizes. Based on the areal distribution of the sedimentary structures (e.g. pin-stripe lamination, high-angle cross-bedding), the occurrence of terrestrial gastropod shells and the correlation with almost identical sandstones elsewhere in the Mediterranean, they most likely have both an eolian origin and a Pleistocene age. At several localities, vertebrate tracks and trackways have been found in the sandstones; this is the first report of vertebrate trackways in Pleistocene sandstones of the Aegean. However, comparable trackways, both in age and size, have been reported on Mallorca and Sardinia. Tracks have been found on both exposed bedding surfaces and in cross-section, where tracks are concentrated along certain horizons; the tracks are about 11 cm wide and 4 cm deep. On bedding surfaces, at least two distinguishable trackways have been observed but, due to their overlapping and weathering, the differentiation between manus and pes impressions is challenging. This, and the relatively short length of individual trackways - the longest traceable

  13. Eolian Dune, interdune, sand sheet, and Siliciclastic Sabkha sediments of an offshore prograding Sand Sea, Dhahran Area, Saudi Arabia

    SciTech Connect

    Fryberger, S.G.; Al-Sari, A.M.; Clisham, T.J.

    1983-02-01

    An offshore prograding sand sea exists along portions of the Arabian Gulf coastline near Dhahran, Saudi Arabia. In this region, sediments of eolian dune, interdune, sand sheet, and siliciclastic sabkha intercalate with marine deposits. This depositional setting is characterized by strong offshore winds which supply abundant sand to the coastline, and cause at present time the outbuilding of the dune system. This quartz-detrital dominant setting contrasts markedly with the carbonate dominant setting resulting from onshore winds in the Trucial Coast area to the south. The broad intercalation of eolian and marine deposits which results creates ideal potential for subregional stratigraphic petroleum traps, due to pinch-out of porous and permeable dune sands into impermeable marine mudstones. Within the eolian system itself are potential reservoir rocks, sources, (organic-rich sabkha and interdune deposits), and seals (zones of early cementation in all deposits). Early cementation is very common in all facies of the eolian sand sea. The early cementation occurs owing to (1) soil formation, (2) deposition of pore-filling gypsiferous cements from saturated solutions near water table, and (3) addition of sand-size windblown evaporitic material to sands downwind of sabkhas.

  14. Paleoclimate cycles and tectonic controls on fluvial, lacustrine, and eolian strata in upper Triassic Chinle Formation, San Juan basin

    SciTech Connect

    Dubiel, R.F. )

    1989-09-01

    Sedimentologic study of the Upper Triassic Chinle Formation in the San Juan basin (SJB) indicates that Late Triassic paleoclimate and tectonic movements influenced the distribution of continental lithofacies. The Shinarump, Monitor Butte, and Petrified Forest Members in the lower part of the Chinle consist of complexly interfingered fluvial, floodplain, marsh, and lacustrine rocks; the Owl Rock and Rock Point Members in the upper part consists of lacustrine-basin and eolian sandsheet strata. Facies analysis, vertebrate and invertebrate paleontology, and paleoclimate models demonstrate that the Late Triassic was dominated by tropical monsoonal circulation, which provided abundant precipitation interspersed with seasonally dry periods. Owl Rock lacustrine strata comprise laminated limestones that reflect seasonal monsoonal precipitation and larger scale, interbedded carbonates and fine-grained clastics that represent longer term, alternating wet and dry climatic cycles. Overlying Rock Point eolian sand-sheet and dune deposits indicate persistent alternating but drier climatic cyclicity. Within the Chinle, upward succession of lacustrine, alternating lacustrine/eolian sand-sheet, and eolian sand-sheet/dune deposits reflects an overall decrease in precipitation due to the northward migration of Pangaea out of low latitudes dominated by monsoonal circulation.

  15. Mapping the Potential for Eolian Surface Activity in Grasslands of the High Plains using Landsat Images

    NASA Technical Reports Server (NTRS)

    Gutmann, Ethan Dain

    2002-01-01

    There are over 100,000 square kilometers of eolian sand dunes and sand sheets in the High Plains of the central United States. These land-forms may be unstable and may reactivate again as a result of land-use, climate change, or natural climatic variability. The main goal of this thesis was to develop a model that could be used to map an estimate of future dune activity. Multi-temporal calibrated Landsats 5 Thematic Mapper (TM) and 7 Enhanced Thematic Map per Plus (ETM+) NDVI imagery were used in conjunction with the CENTURY vegetation model to correlate vegetation cover to climatic variability. This allows the creation of a predicted vegetation map which, combined with current wind and soil data, was used to create a potential sand transport map for range land in the High Plains under drought conditions.

  16. Controls on the height and spacing of eolian ripples and transverse dunes: A numerical modeling investigation

    NASA Astrophysics Data System (ADS)

    Pelletier, Jon D.

    2009-04-01

    Ripples and transverse dunes in areas of abundant sand supply increase in height and spacing as a function of time, grain size, and excess shear velocity. How and why each of these factors influence ripple and transverse dune size, however, is not precisely known. In this paper, the controls on the height and spacing of ripples and transverse dunes in areas of abundant sand supply are investigated using a numerical model for the formation of eolian bedforms from an initially flat surface. This bedform evolution model combines the basic elements of Werner's [Werner, B.T., 1995. Eolian dunes: Computer simulations and attractor interpretation. Geology 23, 1107-1110.] cellular automaton model of dune formation with a model for boundary layer flow over complex topography. Particular attention is paid to the relationship between bed shear stress and slope on the windward (stoss) side of evolving bedforms. Nonlinear boundary layer model results indicate that bed shear stresses on stoss slopes increase with increasing slope angle up to approximately 20°, then decrease with increasing slope angle as backpressure effects become limiting. In the bedform evolution model, the linear boundary layer flow model of Jackson and Hunt [Jackson, P.S., Hunt, J.C.R., 1975. Turbulent wind flow over a low hill. Quarterly Journal of the Royal Meteorological Society 101, 929-955.], generalized to 3D, is modified to include the nonlinear relationship between bed shear stress and slope. Bed shear stresses predicted by the modified Jackson and Hunt flow model are then used to predict rates of erosion and deposition iteratively through time within a mass-conservative framework similar to Werner [Werner, B.T., 1995. Eolian dunes: Computer simulations and attractor interpretation. Geology 23, 1107-1110.]. Beginning with a flat bed, the model forms ripples that grow in height and spacing until a dynamic steady-state condition is achieved in which bedforms migrate downwind without further growth

  17. Middle Jurassic incised valley fill (eolian/estuarine) and nearshore marine petroleum reservoirs, Powder River basin

    SciTech Connect

    Ahlbrandt, T.S.; Fox, J.E.

    1997-07-01

    Paleovalleys incised into the Triassic Spearfish Formation (Chugwater equivalent) are filled with a vertical sequence of eolian, estuarine, and marine sandstones of the Middle Jurassic (Bathonian age) Canyon Springs Sandstone Member of the Sundance Formation. An outcrop exemplifying this is located at Red Canyon in the southern Black Hills, Fall River County, South Dakota. These paleovalleys locally have more than 300 ft of relief and are as much as several miles wide. Because they slope in a westerly direction, and Jurassic seas transgressed into the area from the west there was greater marine-influence and more stratigraphic complexity in the subsurface, to the west, as compared to the Black Hills outcrops. In the subsurface two distinctive reservoir sandstone beds within the Canyon Springs Sandstone Member fill the paleovalleys. These are the eolian lower Canyon Springs unit (LCS) and the estuarine upper Canyon Springs unit (UCS), separated by the marine {open_quotes}Limestone Marker{close_quotes} and estuarine {open_quotes}Brown Shale{close_quotes}. The LCS and UCS contain significant proven hydrocarbon reservoirs in Wyoming (about 500 MMBO in-place in 9 fields, 188 MMBO produced through 1993) and are prospective in western South Dakota, western Nebraska and northern Colorado. Also prospective is the Callovian-age Hulett Sandstone Member which consists of multiple prograding shoreface to foreshore parasequences, as interpreted from the Red Canyon locality. Petrographic, outcrop and subsurface studies demonstrate the viability of both the Canyon Springs Sandstone and Hulett Sandstone members as superior hydrocarbon reservoirs in both stratigraphic and structural traps. Examples of fields with hydrocarbon production from the Canyon Springs in paleovalleys include Lance Creek field (56 MMBO produced) and the more recently discovered Red Bird field (300 MBO produced), both in Niobrara County, Wyoming.

  18. Sandstone geometry, porosity and permeability distribution, and fluid migration in eolian system reservoirs

    USGS Publications Warehouse

    Lupe, Robert; Ahlbrandt, Thomas S.

    1975-01-01

    Upper Paleozoic to Mesozoic eolian blanket sandstones of the Colorado Plateau and the Rocky Mountains of Colorado and southern Wyoming are texturally complex. As petroleum reservoirs they commonly have poor performance histories. They contain the sediments of a depositional system comprised of three closely associated depositional subenvironments: dune, interdune, and extradune. Sediments of each subenvironment have different textural properties which resulted from different depositional processes. Dune sediments are usually more porous and permeable than interdune or extradune sediments and may be better quality reservoirs than interdune or extradune sediments. Interdune sediments are here restricted to those nondune sediments deposited in the relatively flat areas between dunes. Extradune sediments (a new term) include all deposits adjacent to a dune field and are mainly subaqueous deposits. Dune sediments may be enveloped by extradune sediments as the depositional system evolves resulting in a texturally inhomogeneous reservoir having poor fluid migration properties. This model of textural inhomogeneity in eolian blanket sandstones. was applied to the Weber (Tensleep) Sandstone in Brady, Wertz, and Lost Soldier fields, Sweetwater County, Wyoming. Data were obtained from both outcrop and subsurface and included environmental interpretation, textural analysis, and plotting of the distribution of depositional subenvironments. As predicted from the model, the texture of dune sediments in Brady field differed markedly from interdune and extradune sediments. The predicted geometric distribution of subenvironments was confirmed in Lost Soldier and Wertz fields. However, secondary cementation and fracturing there has obscured the original porosity and permeability contrasts. The porosity and permeability distribution, a characteristic depending partly on depositional processes, could impede fluid migration in the reservoir and significantly reduce recovery of

  19. Reconstruction of pliocene-pleistocene ecological conditions of Western Transbaicalia

    NASA Astrophysics Data System (ADS)

    Vashukevich, N. V.

    2009-04-01

    The aim of this study is to examine paleoenvironmental conditions and soil evolution during the Late Pliocene and the Early -Middle Pleistocene in the Western Transbaikalia (Eastern Siberia, Russia). The basic objects of study are the palaeontologycal sites Udunga and Tologoy. Our researches based on pedohumic method (Dergacheva, 1997), when the pedogenic humus properties of site sediments analysed and used as the basis for reconstructing soil-forming processes. On the basis study of pliocene sediments of the Udunga site has revealed three different pedogenetic cycles, depending on water regime and duration of pedogenesis in subtropical environment. The stratigraphic section of the early -middle pleistocene part of the Tologoy site has 4 zones of pedogenesis that are distinguishable by pedogenic humus and other features, and consequently by the character of ancient soil forming processes. Climatic change trends both to humidity and to aridity, the landscape was similar to today, an environmental сombination of dry steppes, wetlands and alkaline areas.

  20. Megafauna and ecosystem function from the Pleistocene to the Anthropocene

    PubMed Central

    Malhi, Yadvinder; Doughty, Christopher E.; Galetti, Mauro; Smith, Felisa A.; Svenning, Jens-Christian; Terborgh, John W.

    2016-01-01

    Large herbivores and carnivores (the megafauna) have been in a state of decline and extinction since the Late Pleistocene, both on land and more recently in the oceans. Much has been written on the timing and causes of these declines, but only recently has scientific attention focused on the consequences of these declines for ecosystem function. Here, we review progress in our understanding of how megafauna affect ecosystem physical and trophic structure, species composition, biogeochemistry, and climate, drawing on special features of PNAS and Ecography that have been published as a result of an international workshop on this topic held in Oxford in 2014. Insights emerging from this work have consequences for our understanding of changes in biosphere function since the Late Pleistocene and of the functioning of contemporary ecosystems, as well as offering a rationale and framework for scientifically informed restoration of megafaunal function where possible and appropriate. PMID:26811442

  1. Megafauna and ecosystem function from the Pleistocene to the Anthropocene.

    PubMed

    Malhi, Yadvinder; Doughty, Christopher E; Galetti, Mauro; Smith, Felisa A; Svenning, Jens-Christian; Terborgh, John W

    2016-01-26

    Large herbivores and carnivores (the megafauna) have been in a state of decline and extinction since the Late Pleistocene, both on land and more recently in the oceans. Much has been written on the timing and causes of these declines, but only recently has scientific attention focused on the consequences of these declines for ecosystem function. Here, we review progress in our understanding of how megafauna affect ecosystem physical and trophic structure, species composition, biogeochemistry, and climate, drawing on special features of PNAS and Ecography that have been published as a result of an international workshop on this topic held in Oxford in 2014. Insights emerging from this work have consequences for our understanding of changes in biosphere function since the Late Pleistocene and of the functioning of contemporary ecosystems, as well as offering a rationale and framework for scientifically informed restoration of megafaunal function where possible and appropriate. PMID:26811442

  2. Size variation in Middle Pleistocene humans.

    PubMed

    Arsuaga, J L; Carretero, J M; Lorenzo, C; Gracia, A; Martínez, I; Bermúdez de Castro, J M; Carbonell, E

    1997-08-22

    It has been suggested that European Middle Pleistocene humans, Neandertals, and prehistoric modern humans had a greater sexual dimorphism than modern humans. Analysis of body size variation and cranial capacity variation in the large sample from the Sima de los Huesos site in Spain showed instead that the sexual dimorphism is comparable in Middle Pleistocene and modern populations. PMID:9262474

  3. Pleistocene drainage incision in the upper Mississippi Valley Driftless Area

    SciTech Connect

    Knox, J.C.

    1985-01-01

    The deep dissection of the Wisconsin Driftless Area and topographically similar, but glaciated areas in adjacent states is generally acknowledged to have occurred during the Pleistocene, but the precise chronology has been poorly understood. The distribution of pre-Illinoian glacial outwash gravels on uplands and valley side benches near the Mississippi River, on the western margin of the Wisconsin Driftless Area, indicates that the major incision (50-60 m) of drainage had occurred during the very early Pleistocene. Deposits in cut-off valley meanders, a common feature in the lower reaches of Driftless Area rivers, provide a basis for relative dating of the valley incision. The cut-offs appear to have evolved episodically when, at various times during the Pleistocene, glacial debris blocked the drainages of the Mississippi and Wisconsin Rivers causing massive alluviation of side valley tributaries. A radiocarbon date of 21,910 +/- 350 year B.P., representing a buried soil horizon at 22 m depth and about 9 m above the bedrock floor of a cut-off valley meander and 18 m above the bedrock floor of the adjacent present-day valley, supports stratigraphic interpretations that suggest modest valley incision into bedrock probably occurred during the Illinoian and may have also occurred during the early Wisconsinan.

  4. Late Pleistocene wind-action and periglacial phenomena in sandy terrain, New Jersey Pine Barrens

    NASA Astrophysics Data System (ADS)

    Demitroff, M. N.; Cicali, M.

    2013-12-01

    Examination of the Pinelands past permafrost environment will add insight to the relatively scant record of the Mid-Atlantic region's periglacial realm, a place where cold, dry, and windy conditions predominated during the recent glacials. This area is especially important to the understanding of mid-latitudinal climate change dynamics in ice-marginal locations - areas greatly affected by diurnal, seasonal, and long-term climate perturbations. We provide examples from a well-preserved pine-forest reserve on coastal plain (39-40° N) that experienced multiple episodes of permafrost aggradation and degradation during the last 200,000 years. While a large number of publications describe an array of relict periglacial phenomena from low-relief areas in Europe's sand belt (UK-Russia), much less is known about the ice-marginal continental mass of North America. High-resolution geodetically corrected airborne LiDAR data enhanced with alternate views through the use of early aerial photo imagery is provided and analyzed to produce bare earth landforms revealing perspective eolian structures. Fieldwork at sand mine operations adjacent to relict dune fields offered sectional views of what lies beneath wind-affected land surfaces. This region was found to have been sparsely vegetated land akin to polar barrens during cold epochs. Coversand is the dominant eolian depositional form, with parabolic dune fields scattered along downwind banks of larger watercourses. Eolian systems interact with the local paleohydrology. Wind-erosional features include ventifacts, blowouts, and, on occasion, yardangs. Sand-filled frost cracks attest to aridity during permafrost aggradation and deep-seasonal frost. These periglacial macrostructures often deform into furrows and sediment-filled pots upon permafrost degradation. The sites are easily accessible providing ample opportunities for frozen ground and climate change studies.

  5. Stratigraphic and lithologic characteristics of Pleistocene fluvial deposits in the Danube and Sava riparian area near Belgrade (Serbia)

    NASA Astrophysics Data System (ADS)

    Nenadić, D.; Gaudenyi, T.; Bogićević, K.; Tošović, R.

    2016-07-01

    The Quaternary sediments in the Danube and Sava riparian area near Belgrade have a considerable thickness. Several categories of deposits (fluvial-lacustrine, fluvial and aeolian) of Pliocene and Quaternary age have been identified. Their thickness, granulometric composition and paleontological features change depending on the distance from the recent Danube and Sava riverbeds. The Pleistocene fluvial deposits are underlain by sediments of the Late Miocene (Sarmatian and Pannonian) or the Plio-Pleistocene age, and are overlain by fluvial-palustrine deposits of the Pleistocene age and recent alluvial deposits. Pleistocene fluvial deposits that form a major part of the Quaternary sediments, have a great significance, since they are proved to be excellent collectors of ground water. Although these deposits are at lower altitudes in the area of Srem, they could be correlated with the high Danube and Morava terraces in Serbia and Drava in Croatia on the basis of their lithologic and paleontological features.

  6. Radiocarbon studies of latest Pleistocene and Holocene lava flows of the Snake River Plain, Idaho: Data, lessons, interpretations

    USGS Publications Warehouse

    Kuntz, M.A.; Spiker, E. C.; Rubin, M.; Champion, D.E.; Lefebvre, R.H.

    1986-01-01

    Latest Pleistocene-Holocene basaltic lava fields of the Snake River Plain, Idaho, have been dated by the radiocarbon method. Backhoe excavations beneath lava flows typically yielded carbon-bearing, charred eolian sediment. This material provided most of the samples for this study; the sediment typically contains less than 0.2% carbon. Charcoal fragments were obtained from tree molds but only from a few backhoe excavations. Contamination of the charred sediments and charcoal by younger carbon components is extensive; the effects of contamination were mitigated but appropriate pretreatment of samples using acid and alkali leaches. Twenty of the more than 60 lava flows of the Craters of the Moon lava field have been dated; their ages range from about 15,000 to about 2000 yr B.P. The ages permit assignment of the flows to eight distinct eruptive periods with an average recurrence interval of about 2000 yr. The seven other latest Pleistocene-Holocene lava fields were all emplaced in short eruptive bursts. Their 14C ages (yr B.P.) are: Kings Bowl (2222?? 100), Wapi (2270 ?? 50), Hells Half Acre (5200 ?? 150), Shoshone (10,130 ?? 350), North Robbers and South Robbers (11.980 ?? 300), and Cerro Grande (13,380 ?? 350). ?? 1986.

  7. Radiocarbon studies of latest Pleistocene and Holocene lava flows of the Snake River Plain, Idaho: Data, lessons, interpretations

    NASA Astrophysics Data System (ADS)

    Kuntz, Mel A.; Spiker, Elliott C.; Rubin, Meyer; Champion, Duane E.; Lefebvre, Richard H.

    1986-03-01

    Latest Pleistocene-Holocene basaltic lava fields of the Snake River Plain, Idaho, have been dated by the radiocarbon method. Backhoe excavations beneath lava flows typically yielded carbon-bearing, charred eolian sediment. This material provided most of the samples for this study; the sediment typically contains less than 0.2% carbon. Charcoal fragments were obtained from tree molds but only from a few backhoe excavations. Contamination of the charred sediments and charcoal by younger carbon components is extensive; the effects of contamination were mitigated but appropriate pretreatment of samples using acid and alkali leaches. Twenty of the more than 60 lava flows of the Craters of the Moon lava field have been dated; their ages range from about 15,000 to about 2000 yr B.P. The ages permit assignment of the flows to eight distinct eruptive periods with an average recurrence interval of about 2000 yr. The seven other latest Pleistocene-Holocene lava fields were all emplaced in short eruptive bursts. Their 14C ages (yr B.P.) are: Kings Bowl (2222± 100), Wapi (2270 ± 50), Hells Half Acre (5200 ± 150), Shoshone (10,130 ± 350), North Robbers and South Robbers (11.980 ± 300), and Cerro Grande (13,380 ± 350).

  8. Plio-pleistocene African climate

    SciTech Connect

    deMenocal, P.B.

    1995-10-06

    Marine records of African climate variability document a shift toward more arid conditions after 2.8 million years ago (Ma), evidently resulting from remote forcing by cold North Atlantic sea-surface temperatures associated with the onset of Northern Hemisphere glacial cycles. African climate before 2.8 Ma was regulated by low-latitude insolation forcing of monsoonal climate due to Earth orbital precession. Major steps in the evolution of African hominids and other vertebrates are coincident with shifts to more arid, open conditions near 2.8 Ma, 1.7 Ma, and 1.0 Ma, suggesting that some Pliocene (Plio)-Pleistocene speciation events may have been climatically mediated. 65 refs., 6 figs.

  9. Plio-Pleistocene African Climate

    NASA Astrophysics Data System (ADS)

    Demenocal, Peter B.

    1995-10-01

    Marine records of African climate variability document a shift toward more arid conditions after 2.8 million years ago (Ma), evidently resulting from remote forcing by cold North Atlantic sea-surface temperatures associated with the onset of Northern Hemisphere glacial cycles. African climate before 2.8 Ma was regulated by low-latitude insolation forcing of monsoonal climate due to Earth orbital precession. Major steps in the evolution of African hominids and other vertebrates are coincident with shifts to more arid, open conditions near 2.8 Ma, 1.7 Ma, and 1.0 Ma, suggesting that some Pliocene (Plio)-Pleistocene speciation events may have been climatically mediated.

  10. Short-term soil loss by eolian erosion in response to different rain-fed agricultural practices

    NASA Astrophysics Data System (ADS)

    Tanner, Smadar; Katra, Itzhak; Zaady, Eli

    2016-04-01

    Eolian (wind) erosion is a widespread process and a major form of soil degradation in arid and semi-arid regions. The present study examined changes in soil properties and eolian soil loss at a field scale in response to different soil treatments in two rain-fed agricultural practices. Field experiments with a boundary-layer wind tunnel and soil analysis were used to obtain the data. Two practices with different soil treatments (after harvest), mechanical tillage and stubble grazing intensities, were applied in the fallow phase of the rotation (dry season). The mechanical tillage and the stubble grazing had an immediate and direct effects on soil aggregation but not on the soil texture, and the contents of soil water, organic matter, and CaCO3. Higher erosion rates, that was measured as fluxes of total eolian sediment and particulate matter <10 μm (PM10), were recorded under mechanical tillage and grazing intensities compared with the undisturbed topsoil of the control plots. The erosion rates were higher in grazing plots than in tillage plots. The calculated soil fluxes in this study indicate potentially rapid soil degradation due to loss of fine particles by wind. The finding may have implications for long-term management of agricultural soils in semi-arid areas.

  11. 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)

    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

    We present Plio-Pleistocene records of sediment color, %CaCO3, foraminifer fragmentation, benthic carbon isotopes (δ13C) 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

  12. Hybrid eolian dunes of William River Dune field, northern Saskatchewan, Canada

    SciTech Connect

    Carson, M.A.; MacLean, P.A.

    1985-02-01

    A series of northwest-southeast aligned, large-scale (up to 30 m high) eolian dunes, occurring in a confined (600 km/sup 2/) desert area in northern Saskatchewan, Canada, was examined in the field. Observations were made of dune morphology and internal structure, and patterns of sand movement on the dunes were analyzed in relation to wind events during the summer of 1981. Present cross-sectional profiles exhibit steeper northeast slopes, the lower segment of which are intermittently covered by psammophilous grasses. Dune structure is dominated by northeast-dipping accretion laminae. Three /sup 14/C dates from organic material cropping out on the lower southwest slopes reveal that the dunes have migrated as transverse bed forms at rates of roughly 0.5 m/yr during the last few hundred years. However, a progressive increase in height, bulk, and symmetry along the dune axis from northwest to southeast, suggests an along-dune component of sand transport. This view is supported by (1) field measurements of airflow and along-dune sand transport patterns on 2 dunes, and (2) the present-day wind regime (1963-78). Dominated by north-northeast to northeast winds from January to June and by west-southwest winds from July to December, the resultant potential sand transport vector is toward the southeast, virtually identical to the dune axis.

  13. Early diagenesis of eolian dune and interdune sands at White Sands, New Mexico

    USGS Publications Warehouse

    Schenk, C.J.; Fryberger, S.G.

    1988-01-01

    The degree of early diagenesis in eolian dune and interdune sands at White Sands, New Mexico, is largely a function of the relationship between sand location and the water table. Most active and vegetation-stabilized dune sands are in the vadose zone, whereas interdune sands are in the capillary fringe and phreatic zones. Crystallographically controlled dissolution of the framework gypsum grains results in elongate, prismatic etch pits on sand grains from the capillary fringe and phreatic zones, whereas dissolution of sand grains in the vadose zone is slight, causing minute irregularities on grain surfaces. Vadose water percolating through the sand is manifest as meniscus layers. Consequently, dune sands in the vadose zone are cemented mainly by meniscus-shaped gypsum at grain contacts. Pendant cements formed on the lower margins of some sand grains. Cementation in the capillary fringe and the phreatic zone is more extensive than the vadose regardless of strata type. Typically, well-developed gypsum overgrowths form along the entire edge of a grain, or may encompass the entire grain. Complex diagenetic histories are suggested by multiple overgrowths and several episodes of dissolution on single grains, attesting to changing saturation levels with respect to gypsum in the shallow ground water. These changes in saturation are possibly due to periods of dilution by meteoric recharge, alternating with periods of concentration of ions and the formation of cement due to evaporation through the capillary fringe. ?? 1988.

  14. Impact of early diagenesis of Eolian reservoirs, Great Sand Dunes National Monument, Colorado

    SciTech Connect

    Krystinik, L.F.; Andrews, S.; Fryberger, S.G.

    1985-02-01

    Dune and associated alluvial and playa deposits at Great Sand Dunes National Monument, Colorado, provide an excellent opportunity to study early diagenetic development of vertical and horizontal permeability barriers in recent eolian deposits (> 10 ka). Cements observed include calcite, aragonite, protodolomite(.), amorphous silica, iron hydroxide, smectite, trona, and halite. Cementation is controlled by the availability of water, with several hydrologic subenvironments producing different cements. Evaporative cementation in dunes adjacent to playas is commonly dominated by trona and halite, but calcite, aragonite, and amorphous silica also bind the sediment. These cements are generally most concentrated in fine laminations where capillary action has pulled water into dunes. Iron hydroxides, calcite, and amorphous silica precipitate at the interface between ground water and streams or lakes, where the pH gradient may exceed 5 pH units (pH 5.7-11.5). Subsequent movement of the ground-water table can result in cross-cutting cement zones. Early cementation in dunes prevents deflation and provides a mechanism for preservation of the reservoir unit. Intense cementation may permanently occlude porosity, or leaching may reestablish well-interconnected porosity. An understanding of the extent and composition of early cement zones can be used to improve hydrodynamic models for production and enhanced recovery.

  15. Two-Phase Abrasion in Eolian Transport of Gypsum Sand, White Sands NM

    NASA Astrophysics Data System (ADS)

    Shaw, S.; Jerolmack, D. J.; Miller, K. L.

    2014-12-01

    Downstream rounding of grains is consistently observed in natural sediment transport settings. A recent theory put forth by Domokos et al. (2014) attributes particle rounding and size reduction to a geometric curvature-driven abrasion process. This process occurs in two phases, in which irregularly shaped or angular particles round to convex shapes with negligible change in axis dimension, then slowly reduce in particle diameter. Miller et al (in review) establish the existence of two-phase abrasion in the natural setting of a fluvial gravel stream. This study examines field samples from White Sands, NM to investigate the presence of two-phase abrasion in a different, non-idealized natural environment - a high-energy, eolian gypsum dunefield. Analysis of grain shapes from White Sands confirms the two-phase abrasion process, dependent upon mode of sediment transport. We find that large sand grains carried in saltation bed load transport exhibit shape change indicative of two-phase abrasion, while smaller particles carried in suspension do not. We observe rapid shape change in bed load particles approaching a convex shape, followed by slower reduction in grain axis dimensions. Confirmation of this process in a natural, non-idealized setting establishes two-phase abrasion as a general application for bed load transport.

  16. Middle Pleistocene hominin teeth from Longtan Cave, Hexian, China.

    PubMed

    Xing, Song; Martinón-Torres, María; Bermúdez de Castro, José María; Zhang, Yingqi; Fan, Xiaoxiao; Zheng, Longting; Huang, Wanbo; Liu, Wu

    2014-01-01

    Excavations at the Longtan Cave, Hexian, Anhui Province of Eastern China, have yielded several hominin fossils including crania, mandibular fragments, and teeth currently dated to 412 ± 25 ka. While previous studies have focused on the cranial remains, there are no detailed analyses of the dental evidence. In this study, we provide metric and morphological descriptions and comparisons of ten teeth recovered from Hexian, including microcomputed tomography analyses. Our results indicate that the Hexian teeth are metrically and morphologically primitive and overlap with H. ergaster and East Asian Early and mid-Middle Pleistocene hominins in their large dimensions and occlusal complexities. However, the Hexian teeth differ from H. ergaster in features such as conspicuous vertical grooves on the labial/buccal surfaces of the central incisor and the upper premolar, the crown outline shapes of upper and lower molars and the numbers, shapes, and divergences of the roots. Despite their close geological ages, the Hexian teeth are also more primitive than Zhoukoudian specimens, and resemble Sangiran Early Pleistocene teeth. In addition, no typical Neanderthal features have been identified in the Hexian sample. Our study highlights the metrical and morphological primitive status of the Hexian sample in comparison to contemporaneous or even earlier populations of Asia. Based on this finding, we suggest that the primitive-derived gradients of the Asian hominins cannot be satisfactorily fitted along a chronological sequence, suggesting complex evolutionary scenarios with the coexistence and/or survival of different lineages in Eurasia. Hexian could represent the persistence in time of a H. erectus group that would have retained primitive features that were lost in other Asian populations such as Zhoukoudian or Panxian Dadong. Our study expands the metrical and morphological variations known for the East Asian hominins before the mid-Middle Pleistocene and warns about the

  17. Middle Pleistocene Hominin Teeth from Longtan Cave, Hexian, China

    PubMed Central

    Xing, Song; Martinón-Torres, María; Bermúdez de Castro, José María; Zhang, Yingqi; Fan, Xiaoxiao; Zheng, Longting; Huang, Wanbo; Liu, Wu

    2014-01-01

    Excavations at the Longtan Cave, Hexian, Anhui Province of Eastern China, have yielded several hominin fossils including crania, mandibular fragments, and teeth currently dated to 412±25 ka. While previous studies have focused on the cranial remains, there are no detailed analyses of the dental evidence. In this study, we provide metric and morphological descriptions and comparisons of ten teeth recovered from Hexian, including microcomputed tomography analyses. Our results indicate that the Hexian teeth are metrically and morphologically primitive and overlap with H. ergaster and East Asian Early and mid-Middle Pleistocene hominins in their large dimensions and occlusal complexities. However, the Hexian teeth differ from H. ergaster in features such as conspicuous vertical grooves on the labial/buccal surfaces of the central incisor and the upper premolar, the crown outline shapes of upper and lower molars and the numbers, shapes, and divergences of the roots. Despite their close geological ages, the Hexian teeth are also more primitive than Zhoukoudian specimens, and resemble Sangiran Early Pleistocene teeth. In addition, no typical Neanderthal features have been identified in the Hexian sample. Our study highlights the metrical and morphological primitive status of the Hexian sample in comparison to contemporaneous or even earlier populations of Asia. Based on this finding, we suggest that the primitive-derived gradients of the Asian hominins cannot be satisfactorily fitted along a chronological sequence, suggesting complex evolutionary scenarios with the coexistence and/or survival of different lineages in Eurasia. Hexian could represent the persistence in time of a H. erectus group that would have retained primitive features that were lost in other Asian populations such as Zhoukoudian or Panxian Dadong. Our study expands the metrical and morphological variations known for the East Asian hominins before the mid-Middle Pleistocene and warns about the

  18. Environmental Influences on Pleistocene Hominid Dental Evolution

    ERIC Educational Resources Information Center

    Greene, David L.

    1970-01-01

    Considers natural and cultural environmental factors likely to have been responsible for reduction in size of hominid teeth and simplification of their morphology during the Pleistocene. Cites fossil evidence and postulates selective mechanisms. (EB)

  19. Late Pleistocene human skull from Hofmeyr, South Africa, and modern human origins.

    PubMed

    Grine, F E; Bailey, R M; Harvati, K; Nathan, R P; Morris, A G; Henderson, G M; Ribot, I; Pike, A W G

    2007-01-12

    The lack of Late Pleistocene human fossils from sub-Saharan Africa has limited paleontological testing of competing models of recent human evolution. We have dated a skull from Hofmeyr, South Africa, to 36.2 +/- 3.3 thousand years ago through a combination of optically stimulated luminescence and uranium-series dating methods. The skull is morphologically modern overall but displays some archaic features. Its strongest morphometric affinities are with Upper Paleolithic (UP) Eurasians rather than recent, geographically proximate people. The Hofmeyr cranium is consistent with the hypothesis that UP Eurasians descended from a population that emigrated from sub-Saharan Africa in the Late Pleistocene. PMID:17218524

  20. Deep-sea pleistocene biostratigraphy.

    PubMed

    Lidz, L

    1966-12-16

    The first detailed paleontological analysis of a deep-sea pistoncore from the Caribbean Sea has been completed. The core, P6304-8, was raised from 3927 meters, east of Beata Ridge at 14 degrees 59'N, 69 degrees 20'W. Formerly, stratigraphic works in this area were based on studies of paleotemperature, measured by the oxygen isotope mass spectrometry method, or on micropaleontological analysis by means of rapid or cursory examinations. For core P6304-8, samples for foraminiferal analysis were taken at 10-centimeter intervals and split into smaller samples containing an average of 710 individuals (smallest sample, 517 individuals); all individuals were then identified and counted. By use of data derived from populations of this size, a statistical reliability was insured within a 5 percent limnit. Temperature oscillations, the best method of portraying Pleistocene stratigraphy, were shown by using ratios of the relative abundances of tropical and subtropical planktonic foraminifera to those found in temperate and cooler waters. These ratios correlate well with existing paleotemperature measurements for the same core, obtained by the oxygen isotope mass spectrometry method. PMID:17821563

  1. Evaluating the Contribution of Eolian Dust to the Weathering Flux From Mountain Soils

    NASA Astrophysics Data System (ADS)

    Lawrence, C. R.; Neff, J. C.; Farmer, G. L.

    2008-12-01

    The weathering of silicate minerals is an important control on the global carbon cycle over geologic timescales. In order to accurately characterize the influence of silicate weathering on the carbon cycle, it is important to quantify the mechanisms that may influence weathering. Tectonics, erosion, climate, and rock chemistry are all important factors in the weathering process. There is also evidence that eolian dust deposition may influence weathering fluxes in some settings. The transport of fine sediments from arid regions, with relatively slow rates of chemical weathering, to regions more favorable to weathering may act to accelerate global weathering rates. Detailed studies of dust deposition and soil evolution are required to better quantify the role that dust plays in the weathering process. The San Juan Mountains of southern Colorado are situated downwind from large dust producing regions of the Colorado Plateau and the Mojave Dessert. A recent study suggests the transport of dust from these semi-arid environments to the downwind mountain ecosystems has increased by 500% over the past century, likely as a result of human land-use changes. At present, the San Juan Mountains receive between 5-15 g/m2 of fine textured dust deposition each year. Over many years, dust accretion may have altered the geochemical characteristics of soils and could be an important factor for the chemical weathering flux from these soils. We combine soil geochemical mass balance calculations with quantitative mineralogy and strontium isotope measurements of sequential soil leaches to better constrain the input of dust to soils and to estimate the contribution of dust to the long- term chemical weathering flux.

  2. A low-order dynamical model of global climatic variability over the full Pleistocene

    SciTech Connect

    Maasch, K.A.; Saltzman, B. )

    1990-02-20

    A previously formulated dynamical model of the late Pleistocene ice ages (based on the hypothesis that the global CO{sub 2} system can provide the instability to drive a natural oscillation involving feedbacks between the cryosphere, atmosphere, and ocean) is extended to include (1) additive earth orbital forcing (summer insolation changes at 65{degree}N) and (2) tectonic forcing in the form of a postulated variation in the multiplicative parameters (rate constants) of the model system. The structural (e.g., bifurcation) properties of the model are examined in detail to reveal the regions of parameter space wherein the geologically inferred features of the full Pleistocene can be simulated, including the observed chronology, the phase relationships between ice, CO{sub 2}, and North Atlantic Deep Water formation, and the mid-Pleistocene transition.

  3. Empirical Validation of Conceptual Climate Models for the Mid-Pleistocene Transition

    NASA Astrophysics Data System (ADS)

    Gallatin, A.; Camp, C. D.

    2015-12-01

    Conceptual climate models are useful for testing hypotheses regarding the processes underlying observations; but they generally can only qualitatively match the empirical records. Models based on substantially different underlying physics can have comparable correlations with any given observation, thus robust model validation procedures are needed. The Mid-Pleistocene Transition (MPT) is an ideal test case for the development of such procedures because the character and cause of the transition from a dominant 41 kyr cycle in the early Pleistocene to a dominant 100 kyr cycle in the late Pleistocene is poorly understood. Using Ensemble Empirical Mode Decomposition, we analyze multiple conceptual models for the MPT which are based on differing physical hypotheses and show how modern time-series-analysis techniques can improve climate-model validation by extracting and comparing subtler features of both the observations and models.

  4. The medial pterygoid tubercle in the Atapuerca Early and Middle Pleistocene mandibles: evolutionary implications.

    PubMed

    Bermúdez de Castro, José-María; Quam, Rolf; Martinón-Torres, María; Martínez, Ignacio; Gracia-Téllez, Ana; Arsuaga, Juan Luís; Carbonell, Eudald

    2015-01-01

    Numerous studies have attempted to identify the presence of uniquely derived (autoapomorphic) Neandertal features. Here, we deal with the medial pterygoid tubercle (MTP), which is usually present on the internal face of the ascending ramus of Neandertal specimens. Our study stems from the identification of a hypertrophied tubercle in ATD6-96, an Early Pleistocene mandible recovered from the TD6 level of the Atapuerca-Gran Dolina site and attributed to Homo antecessor. Our review of the literature and study of numerous original fossil specimens and high quality replicas confirm that the MTP occurs at a high frequency in Neandertals (ca. 89%) and is also present in over half (ca. 55%) of the Middle Pleistocene Sima de los Huesos (SH) hominins. In contrast, it is generally absent or minimally developed in other extinct hominins, but can be found in variable frequencies (Pleistocene and recent H. sapiens samples. The presence of this feature in ATD6-96 joins other traits shared by H. antecessor, the SH hominins and Neandertals. Since the TD6 hominins have been attributed either to MIS 21 or to MIS 25, it seems that a suite of assumed derived Neandertal features appeared in the Early Pleistocene, and they should be interpreted as synapomorphies shared among different taxa. We suggest that H. antecessor, the SH hominins and Neandertals shared a common ancestor in which these features appeared during the Early Pleistocene. The presence of the MTP in taxa other than H. neanderthalensis precludes this feature from being a Neandertal autapomorphy. PMID:25279839

  5. Cougars’ key to survival through the Late Pleistocene extinction: insights from dental microwear texture analysis

    PubMed Central

    DeSantis, Larisa R. G.; Haupt, Ryan J.

    2014-01-01

    Cougars (Puma concolor) are one of only two large cats in North America to have survived the Late Pleistocene extinction (LPE), yet the specific key(s) to their relative success remains unknown. Here, we compare the dental microwear textures of Pleistocene cougars with sympatric felids from the La Brea Tar Pits in southern California that went extinct at the LPE (Panthera atrox and Smilodon fatalis), to clarify potential dietary factors that led to the cougar's persistence through the LPE. We further assess whether the physical properties of food consumed have changed over time when compared with modern cougars in southern California. Using dental microwear texture analysis (DMTA), which quantifies surface features in three dimensions, we find that modern and Pleistocene cougars are not significantly different from modern African lions in any DMTA attributes, suggesting moderate durophagy (i.e. bone processing). Pleistocene cougars from La Brea have significantly greater complexity and textural fill volume than Panthera atrox (inferred to have primarily consumed flesh from fresh kills) and significantly greater variance in complexity values than S. fatalis. Ultimately, these results suggest that cougars already used or adopted a more generalized dietary strategy during the Pleistocene that may have been key to their subsequent success. PMID:24759373

  6. Cougars' key to survival through the Late Pleistocene extinction: insights from dental microwear texture analysis.

    PubMed

    Desantis, Larisa R G; Haupt, Ryan J

    2014-01-01

    Cougars (Puma concolor) are one of only two large cats in North America to have survived the Late Pleistocene extinction (LPE), yet the specific key(s) to their relative success remains unknown. Here, we compare the dental microwear textures of Pleistocene cougars with sympatric felids from the La Brea Tar Pits in southern California that went extinct at the LPE (Panthera atrox and Smilodon fatalis), to clarify potential dietary factors that led to the cougar's persistence through the LPE. We further assess whether the physical properties of food consumed have changed over time when compared with modern cougars in southern California. Using dental microwear texture analysis (DMTA), which quantifies surface features in three dimensions, we find that modern and Pleistocene cougars are not significantly different from modern African lions in any DMTA attributes, suggesting moderate durophagy (i.e. bone processing). Pleistocene cougars from La Brea have significantly greater complexity and textural fill volume than Panthera atrox (inferred to have primarily consumed flesh from fresh kills) and significantly greater variance in complexity values than S. fatalis. Ultimately, these results suggest that cougars already used or adopted a more generalized dietary strategy during the Pleistocene that may have been key to their subsequent success. PMID:24759373

  7. Pattern of dental development in Hominid XVIII from the Middle Pleistocene Atapuerca-Sima de los Huesos site (Spain).

    PubMed

    Bermudez De Castro, J M; Rosas, A

    2001-04-01

    . We describe the pattern of dental development of Hominid XVIII from the Middle Pleistocene Sima de los Huesos (SH) site of the Sierra de Atapuerca (Burgos, Spain). As expected, this pattern is similar to that of modern humans. A delay of development of the lower and upper canines was observed. In contrast, the relative advanced development of the lower second molars and, especially, the upper and lower third molars is noteworthy. This latter feature seems to be common in Pleistocene hominids, and suggests that the pattern of dental development evolved in the genus Homo during the Pleistocene. In European Middle Pleistocene hominids, this pattern probably was facilitated by the extra space available in the mandible and maxilla for developing teeth. PMID:11275961

  8. Comparative morphology and paleobiology of Middle Pleistocene human remains from the Bau de l'Aubesier, Vaucluse, France

    PubMed Central

    Lebel, Serge; Trinkaus, Erik; Faure, Martine; Fernandez, Philippe; Guérin, Claude; Richter, Daniel; Mercier, Norbert; Valladas, Helène; Wagner, Günther A.

    2001-01-01

    The discovery of later Middle Pleistocene human remains from the Bau de l'Aubesier, France reinforces an evolutionary model of the gradual accumulation of Neandertal-derived facial and dental features during the Middle Pleistocene of the northwestern Old World. The pronounced maxillary incisor beveling of Aubesier 4 helps to extend the antiquity of nondietary use of the anterior dentition. The interproximal “toothpick” groove on the Aubesier 10 molar increases the sample for these lesions. The pathological loss of the mandibular dentition of Aubesier 11 indicates advanced antemortem masticatory impairment, at a level previously undocumented before the Late Pleistocene. These remains support a view of later Middle Pleistocene humans able to support debilitated individuals despite the considerable use of their bodies to accomplish routine activities. PMID:11553766

  9. Early Pleistocene human humeri from the Gran Dolina-TD6 site (Sierra de Atapuerca, Spain).

    PubMed

    Bermúdez de Castro, José María; Carretero, José Miguel; García-González, Rebeca; Rodríguez-García, Laura; Martinón-Torres, María; Rosell, Jordi; Blasco, Ruth; Martín-Francés, Laura; Modesto, Mario; Carbonell, Eudald

    2012-04-01

    In this report, we present a morphometric comparative study of two Early Pleistocene humeri recovered from the TD6 level of the Gran Dolina cave site in Sierra de Atapuerca, northern Spain. ATD6-121 belongs to a child between 4 and 6 years old, whereas ATD6-148 corresponds to an adult. ATD6-148 exhibits the typical pattern of the genus Homo, but it also shows a large olecranon fossa and very thin medial and lateral pillars (also present in ATD6-121), sharing these features with European Middle Pleistocene hominins, Neandertals, and the Bodo Middle Pleistocene humerus. The morphology of the distal epiphysis, together with a few dental traits, suggests a phylogenetic relationship between the TD6 hominins and the Neandertal lineage. Given the older geochronological age of these hominins (ca. 900 ka), which is far from the age estimated by palaeogenetic studies for the population divergence of modern humans and Neandertals (ca. 400 ka), we suggest that this suite of derived "Neandertal" features appeared early in the evolution of the genus Homo. Thus, these features are not "Neandertal" apomorphies but traits which appeared in an ancestral and polymorphic population during the Early Pleistocene. PMID:22328492

  10. Erosional remnants and adjacent unconformities along an eolian-marine boundary of the Page Sandstone and Carmel Formation, Middle Jurassic, south-central Utah

    SciTech Connect

    Jones, L.S.; Blakey, R.C. . Dept. of Geology)

    1993-09-01

    Sandstone ridges along the marine-eolian boundary of the Middle Jurassic Page Sandstone (eolian) with the lower Carmel Formation (restricted marine) in south-central Utah have been identified as erosional remnants consisting of strata of siliciclastic sabkha and eolian origin. The ridges lie within two distinct units of the Thousand Pockets Tongue of the Page. Two equally plausible models explain the genesis of these ridges. One model involves (1) early cementation of eolian and sabkha strata, (2) wind erosion leading to development of yardangs and unconformities, (3) yardang tilting due to evaporite dissolution, and (4) renewed deposition and burial. The alternative model explains ridge development through (1) subsidence, with tilting, of eolian and sabkha strata into evaporites due to loading from linear dunes, (2) evaporite dissolution and unconformity development, and (3) renewed deposition and burial. These models provide important clues about the nature of a missing part of the rock record. Reconstruction of units that were deposited but later eroded improves paleogeographic interpretation and here indicates that the Carmel paleo-shoreline was considerably farther to the northwest than previously believed.

  11. 200,000 years of climate change recorded in eolian sediments of the High Plains of eastern Colorado and western Nebraska

    USGS Publications Warehouse

    Muhs, Daniel R.; Swinehart, James B.; Loope, David B.; Aleinikoff, John N.; Been, Josh

    1999-01-01

    Loess and eolian sand cover vast areas of the western Great Plains of Nebraska, Kansas and Colorado (Fig. 1). In recent studies of Quaternary climate change, there has been a renewed interest in loess and eolian sand. Much of the attention now given to loess stems from new studies of long loess sequences that contain detailed records of Quaternary glacial-interglacial cycles, thought to be a terrestrial equivalent to the foraminiferal oxygen isotope record in deep-sea sediments (Fig. 2). Loess is also a direct record of atmospheric circulation, and identification of loess paleowinds in the geologic record can test atmospheric general circulation models. Until recently, eolian sand on the Great Plains had received little attention from Quaternary geologists. The past decade has seen a proliferation of studies of Great Plains dune sands, and many studies, summarized below, indicate that landscapes characterized by eolian sand have had dynamic histories. On this field trip, we will visit some key eolian sand and loess localities in eastern Colorado and southwestern Nebraska (Fig. 1). Stratigraphic studies at some of these localities have been conducted for more than 50 years, but others have been systematically studied only in the past few years. Many of the data which appear in this guidebook have been derived from previous studies (Swinehart and Diffendal, 1990; Madole, 1994; Loope and others, 1995; Maat and Johnson, 1996; Muhs and others, 1996, 1997a, 1999; Mason and others, 1997; Aleinikoff and others, 1999), but some are presented here for the first time.

  12. Pleistocene Indian Monsoon Rainfall Variability

    NASA Astrophysics Data System (ADS)

    Yirgaw, D. G.; Hathorne, E. C.; Giosan, L.; Collett, T. S.; Sijingeo, A. V.; Nath, B. N.; Frank, M.

    2014-12-01

    The past variability of the Indian Monsoon is mostly known from records of wind strength over the Arabian Sea. Here we investigate proxies for fresh water input and runoff in a region of strong monsoon precipitation that is a major moisture source for the east Asian Monsoon. A sediment core obtained by the IODP vessel JOIDES Resolution and a gravity core from the Alcock Seamount complex in the Andaman Sea are used to examine the past monsoon variability on the Indian sub-continent and directly over the ocean. The current dataset covers the last glacial and deglacial but will eventually provide a Pleistocene record. We utilise the ecological habitats of G. sacculifer and N. dutertrei to investigate the freshwater-induced stratification with paired Mg/Ca and δ18O analyses to estimate seawater δ18O (δ18Osw). During the last 60 kyrs, Ba/Ca ratios and δ18Osw values generally agree well between the two cores and suggest the weakest surface runoff and monsoon during the LGM and strongest monsoon during the Holocene. The difference in δ18O between the species, interpreted as a proxy for upper ocean stratification, implies stratification developed around 37 ka and remained relatively constant during the LGM, deglacial and Holocene. To investigate monsoon variability for intervals in the past, single shell Mg/Ca and δ18O analyses have been conducted. Mg/Ca ratios from individual shells of N. dutertrei suggest relatively small changes in temperature. However, individual N. dutertrei δ18O differ greatly between the mid-Holocene and samples from the LGM and a nearby core top. The mid-Holocene individuals have a greater range and large skew towards negative values indicating greater fresh water influence.

  13. Late Pleistocene oscillations of the Drau Glacier (southern Austria)

    NASA Astrophysics Data System (ADS)

    Karnitschar, Christina; Reitner, Jürgen; Draganits, Erich

    2016-04-01

    The Drau Glacier was the largest Pleistocene glacier in the southeastern part of the Alps and significantly shaped the landscape in this region. The study area is located at the termination of the Drau Glacier in the southern part of Austria (Carinthia). The investigation aims to decipher glacial dynamics during the Late Pleistocene glacial advance, stabilisation and final recession of this glacier based on geological/geomorphological mapping, interpretation of airborne laser scan (ALS) topographic data and lithostratigraphic investigations of glacial and periglacial sediments. Special emphasis is laid on the reconstruction of the maximum extent of the glaciation (LGM). Based on previous mapping by Bobek (1959) and Ucik (1996-1998) more details have been gained for the paleogeographic reconstruction based on glacial and non-glacial erosion and accumulation features. These include traces of pre-Upper Pleistocene glaciation, drumlins, terminal moraines and kettle holes. Paleogeographic reconstruction was done with correlation of different outcrops based on lithostratigraphy and ALS topography. Sequences of gravel related to glacial advance covered by till, followed by periglacial sediments allowed detailed reconstruction of the glacial sequence in this area and the complex succession of various extents of the Drau Glacier. References Bobek, Hans. 1959: Der Eisrückgang im östlichen Klagenfurter Becken. In: Mitteilungen der österreichischen geographischen Gesellschaft, Wien. Ucik, Friedrich Hans. 1996: Bericht über geologische Aufnahmen im Quartär auf Blatt 204 Völkermarkt, Jb. Geol. B.-A., 141, S. 340, Wien. Ucik, Friedrich Hans. 1997: Bericht über geologische Aufnahmen im Quartär auf Blatt 204 Völkermarkt, Jb. Geol. B.-A., 141, S. 325-326, Wien. Ucik, Friedrich Hans. 1998: Bericht über geologische Aufnahmen im Quartär auf Blatt 204 Völkermarkt, Jb. Geol. B.-A., 142, S. 333-334, Wien.

  14. Glaciers and rivers: Pleistocene uncoupling in a Mediterranean mountain karst

    NASA Astrophysics Data System (ADS)

    Adamson, K. R.; Woodward, J. C.; Hughes, P. D.

    2014-06-01

    Large-scale coupling between headwater catchments and downstream depocentres is a critical influence on long-term fluvial system behaviour and on the creation of the fluvial sedimentary record. However, it is often difficult to examine this control over multiple Quaternary glacial cycles and it has not been fully explored in karst basins. By investigating the Pleistocene glacial and fluvial records on and around Mount Orjen (1894 m) in Montenegro, we show how the changing connectivity between glaciated mountain headwater source zones and downstream alluvial basins is a key feature of long-term karst system behaviour - especially in relation to the creation and preservation of the surface sedimentary record. Middle and Late Pleistocene glacial deposits are well preserved on Mount Orjen. Uranium-series dating of 27 carbonate cements in fluvial sediments shows that many alluvial depocentres were completely filled with coarse glacial outwash before 350 ka during the largest recorded glaciation. This major glaciation is correlated with the Skamnellian Stage in Greece and Marine Isotope Stage 12 (MIS 12, c 480-420 ka). This was a period of profound landscape change in many glaciated catchments on the Balkan Peninsula. Later glaciations were much less extensive and sediment supply to fluvial systems was much diminished. The extreme base level falls of the Late Miocene produced the world's deepest karst networks around the Mediterranean. After MIS 12, the subterranean karst of Mount Orjen formed the dominant pathway for meltwater and sediment transfer so that the depositional basins below 1000 m became disconnected (uncoupled) from the glaciated headwaters. There is little evidence of post-MIS 12 aggradation or incision in these basins. This absence of later Pleistocene and Holocene fluvial activity means these basins contain some of the thickest and best-preserved outwash deposits in the Mediterranean.

  15. Mineral-magnetic Record of Pleistocene Climatic Changes In The Mediterranean

    NASA Astrophysics Data System (ADS)

    Dinarès-Turell, J.; Hoogakker, B. A. A.; Roberts, A. P.; Rohling, E. J.; Sagnotti, L.

    High resolution magnetic measurements on u-channels from Mediterranean piston cores LC07 (3808.72N/1004.73E, length 23.66 m, water depth 488 m) and LC10 (3512.77 N/1634.88E, 19.86 m, 1322 m) are evaluated. The age model for these cores is derived by a two-step approach: firstly, the magnetostratigraphic results which document the upper Jaramillo (990 ka) and the Matuyama/Brunhes (778 ka) transi- tions in both cores and possibly the Punaruu (~1122 ka) and Cobb Mountain (~1.19 ka) in core LC10 permit to derive a preliminary age model by assuming constant sedimentation rates between the astronomically calibrated reversal boundaries (mean sedimentation rates are 1.9 and 2.3 cm/kyr in cores LC10 and LC07, respectively). In a second step, rock magnetic parameters which appear to be climatically controlled are used to derive a precise astronomically tuned age model for the studied interval by cor- relation to a global ice volume model derived from summer insolation at 65N. The final age model is further corroborated by oxygen isotope data from the Tyrrhenian core LC07, which is apparently homogeneous in lithology, and the presence of some sapropel/sapropelitic layers in the Ionian core LC10 that correlate with pronounced insolation maxima peaks. Warm interglacial periods are characterized by relatively small ferrimagnetic grain sizes and cold glacial intervals are dominated by a relatively coarser fraction as indicated by the kARM/k values and by the hysteresis parameters. Also, the relatively lower values of the S-ratio within the glacial periods are indica- tive of an increased high coercivity contribution, that may reflect an enhanced eolian input. High kARM/k values for core LC07 are compatible with stable single-domain (SD) particles of probable bacterial origin. On the other hand, the Pleistocene climatic variability in core LC10 seems to be better expressed by the HIRM parameter which is a measure of the concentration of the high-coercivity magnetic fraction. The

  16. Surficial geology and stratigraphy of Pleistocene Lake Manix, San Bernardino County, California

    USGS Publications Warehouse

    Reheis, Marith C.; Redwine, Joanna R.; Wan, Elmira; McGeehin, John P.; VanSistine, D. Paco

    2014-01-01

    Pluvial Lake Manix and its surrounding drainage basin, in the central Mojave Desert of California, has been a focus of paleoclimate, surficial processes, and neotectonic studies by the U.S. Geological Survey (USGS) since about 2004. The USGS initiated studies of Lake Manix deposits to improve understanding of the paleoclimatic record and the shifts in atmospheric circulation that controlled precipitation in the Mojave Desert. Until approximately 25,000 years ago, Lake Manix was the terminus of the Mojave River, which drains northeasterly from the San Bernardino Mountains; the river currently terminates in the Soda Lake and Silver Lake playas. Pleistocene Lake Manix occupied several subbasins at its maximum extent. This map focuses on the extensive exposures created by incision of the Mojave River and its tributaries into the interbedded lacustrine and alluvial deposits within the central (Cady) and northeastern (Afton) subbasins of Lake Manix, and extends from the head of Afton Canyon to Manix Wash. The map illuminates the geomorphic development and depositional history of the lake and alluvial fans within the active tectonic setting of the eastern California shear zone, especially interactions with the left-lateral Manix fault. Lake Manix left an extraordinarily detailed but complex record of numerous transgressive-regressive sequences separated by desiccation and deposition of fan, eolian, and fluvial deposits, and punctuated by tectonic movements and a catastrophic flood that reconfigured the lake basin. Through careful observation of the intercalated lacustrine and fan sequences and by determining the precise elevations of unit contacts, this record was decoded to understand the response of the lake and river system to the interplay of climatic, geomorphic, and tectonic forces. These deposits are exposed in steep badland topography. Mapping was carried out mostly at scales of 1:12,000, although the map is presented at 1:24,000 scale, and employs custom unit

  17. Guatemalan forest synthesis after Pleistocene aridity

    PubMed Central

    Leyden, Barbara W.

    1984-01-01

    Sediments from two lakes in the Peten Department, Guatemala, provide palynological evidence from Central America of late Pleistocene aridity and subsequent synthesis of mesic forests. Late Glacial vegetation consisted of marsh, savanna, and juniper scrub. An early Holocene temperate forest preceded a mesic tropical forest with Brosimum (ramon). Thus “primeval” rain forests of Guatemala are no older than 10,000 to 11,000 years and are considerably younger in the Peten due to Mayan disturbances. Among dated Neotropical sites, the Peten has the most mesic vegetation yet shown to have supplanted xeric vegetation present during the Pleistocene. The arid late Glacial-humid early Holocene transition appears to have been pantropical in the lowlands. The Peten was not a Pleistocene refugium for mesophytic taxa, as has been suggested. Thus genesis of extant rain forests in northern Central America and southern Mexico remains unexplained. Images PMID:16593498

  18. Eolian delivery of highly reactive iron to the glacial ocean of the late Paleozoic

    NASA Astrophysics Data System (ADS)

    Sur, S.; Soreghan, G. S.; Owens, J. D.; Lyons, T. W.; Soreghan, M. J.

    2010-12-01

    The potential biogeochemical impact of iron-rich dust delivery to the oceans is well recognized for Earth’s recent record but virtually unexplored in deeper time, despite recognition of large ancient dust fluxes. Abundant eolian dust (loess) deposits have been documented in western equatorial Pangaea (western U.S.), dating from the late Paleozoic (300 Ma), a time of known continental-scale glaciation. The role of iron in ancient ecosystems is elucidated by analytical techniques that enable identification of three iron pools within the total iron (FeT) pool: highly reactive (FeHR), poorly reactive, and unreactive. FeHR consists of amorphous and crystalline iron oxides and (oxyhydr)oxides that are readily reactive to H2S on an early diagenetic time scale. FeHR in our ancient sediments is dominated by crystalline oxide forms soluble in a citrate-bicarbonate, Na dithionite (CBD) solution, iron transformed to pyrite (Fepy), and magnetite. If the crystalline oxide phases that we measure in the record at least partially reflect less crystalline, more soluble oxyhydroxide precursors, then ancient FeHR roughly tracks its initial bioavailability and thus can be used as a proxy for potential primary productivity. Here, we report the uniqueness of Fe relationships (enriched FeHR/FeT values and relatively depleted FeT/Al) from a Pennsylvanian (Upper Carboniferous), loess-derived mudrock that accumulated at lowstand (glacial) time within a carbonate buildup of the so-called “Horseshoe Atoll” of the Midland basin (west Texas). This relationship is atypical compared to modern fluvial sediment and soil-derived dust and suggests an enhancement of the reactivity of an internal Fe pool and possible loss of Fe phases through unknown, but extreme biogeochemical processing. Comparisons of our data with other Permo-Carboniferous dusts, pedogenically altered loess, and emerging data on modern dusts suggest that the high values of FeHR/FeT in the mudrock may reflect glacial weathering

  19. Opal burial in the Eastern Equatorial Pacific controlled by Si leakage and eolian dust inputs.

    NASA Astrophysics Data System (ADS)

    Dubois, Nathalie; Kienast, Markus; Kienast, Stephanie; François, Roger

    2010-05-01

    The Silicic Acid Leakage Hypothesis (SALH) attempts to explain part of the large and regular atmospheric CO2 changes over the last glacial-interglacial cycles by a floral shift in the equatorial ecosystem from coccolithophorids to diatoms. The SALH predicts that increased eolian iron input or extended sea ice cover during glacial stages created a pool of excess Si in the Southern Ocean that escaped to the low-latitudes. Numerous downcore opal records from the Equatorial Pacific have recently been investigated in an effort to test the SALH. In contrast to SALH predictions, sedimentary records from the Eastern Equatorial Pacific (EEP) do not show enhanced opal burial during the Last Glacial Maximum (LGM), but during the deglaciation and during Marine Isotopic Stage 3 (MIS3) [e.g. Bradtmiller et al., Paleoceanography, 2006; Kienast et al., GRL, 2006]. The peak in opal productivity during the deglaciation has been attributed to increased supply of nutrient-rich waters driven by stronger upwelling of deep water in the Southern Ocean [Anderson et al., Science, 2009]. The larger peak in opal burial during MIS3 was interpreted as evidence of Si leakage when Southern Ocean diatom productivity is limited by both low dust flux and extended sea ice [Kienast et al., GRL, 2006]. On the other hand, the paradoxical LGM decline in opal accumulation in the EEP was explained by enhanced dust input lowering the diatom Si:C uptake ratio [Pichevin et al., Nature, 2009]. Here we use a combination of molecular fingerprints of algal productivity and radioisotope tracers of sedimentation to revisit opal burial in the EEP, in particular during the MIS3 "opal peak". An increase in algal productivity is not supported by the sedimentary concentration of brassicasterol, a biomarker for diatoms, nor by the ratio of (231Pa/230Th)xs,0, a proxy for opal export production. We therefore conclude that the large peak in opal burial during MIS3 more likely reflects enhanced preservation of diatoms

  20. Practical characterization of eolian reservoirs for development: Nugget Sandstone, Utah—Wyoming thrust belt

    NASA Astrophysics Data System (ADS)

    Lindquist, Sandra J.

    1988-04-01

    The Jurassic eolian Nugget Sandstone of the Utah-Wyoming thrust belt is a texturally heterogeneous formation with anisotropic reservoir inherited primarily from the depositional environment. Original reservoir quality has been reduced somewhat by cementation and slightly enhanced by dissolution. Low-permeability, gouge-filled micro-faults compartmentalize the formation, whereas intermittently open fractures provide effective permeability paths locally. Where productive, the Nugget Sandstone ranges from approximately 800 to 1050 ft (244-320 m) thick at subsurface depths of 7500 to 15,000 ft (2286-4572 m). Porosity ranges from several percent to 25%, and permeability covers five orders of magnitude from hundredths of milliDarcies to Darcies. Some Nugget reservoirs are fully charged with hydrocarbons. Different stratification types have unique depositional textures, primary and diagenetic mineralogies, and deformational fabrics resulting in characteristic porosity, permeability, permeability directionality, and pore geometry attributes. Such characteristics can be determined from core analysis, mercury injection, nuclear magnetic resonance, conventional log, dipmeter and production data. Nugget dune deposits (good reservoir facies) primarily consist of grainflow and wind-ripple cross-strata, the former of which have the better reservoir quality and the lesser heterogeneity in bedding texture. High-permeability facies are commonly affected by local quartz and nodular carbonate cementation, chlorite (and lesser illite) precipitation, and minor framework and cement dissolution. Gouge-filled micro-faults are the predominant deformational overprint. Interdune, sand-sheet, and other water-associated deposits (poor reservoir facies) are characterized by low-angle wind-ripple laminae and more irregular bedding, some of which is associated with damp or wet conditions. Water-associated Nugget stratification generally contains the finest grained depositional textures and has the

  1. Episodic Eolian Sand Deposition in the Past 4000 Years in Cape COD National Seashore, Massachusetts, USA in Response to Possible Hurricane/storm and Anthropogenic Disturbances

    NASA Astrophysics Data System (ADS)

    Forman, Steven

    2015-02-01

    The eolian sand depositional record for a dune field within Cape Cod National Seashore, Massachusetts is posit as a sensitive indicator of environmental disturbances in the late Holocene from a combination of factors such as hurricane/storm and forest fire occurrence, and anthropogenic activity. Stratigraphic and sedimentologic observations, particularly the burial of spodosol-like soils, and associated 14C and OSL ages that are concordant indicate at least six eolian depositional events at ca. 3750, 2500, 1800, 960, 430 and <250 years ago. The two oldest events are documented at just one locality and thus, the pervasiveness of this eolian activity is unknown. However, the four younger events are identified in three or more sites and show evidence for dune migration and sand sheet accretion. The timing of eolian deposition, particularly the initiation age, corresponds to documented periods of increased storminess/hurricane activity in the North Atlantic Ocean at ca. 2.0 to 1.6, and 1.0 ka and also a wetter coastal climate, which suppressed the occurrence of forest fire. Thus, local droughts are not associated with periods of dune movement in this mesic environment. Latest eolian activity on outer Cape Cod commenced in the past 300 to 500 years and may reflect multiple factors including broad-scale landscape disturbance with European colonization, an increased incidence of forest fires and heightened storminess. Eolian systems of Cape Cod appear to be sensitive to landscape disturbance and prior to European settlement may reflect predominantly hurricane/storm disturbance, despite generally mesic conditions in past 4 ka.

  2. Low Albedo Surfaces and Eolian Sediment: Mars Orbiter Camera Views of Western Arabia Terra Craters and Wind Streaks

    NASA Technical Reports Server (NTRS)

    Edgett, Kenneth S.

    2001-01-01

    High spatial resolution (1.5 to 12 m/pixel) Mars Global Surveyor Mars Orbiter Camera images obtained September 1997 through June 2001 indicate that the large, dark wind streaks of western Arabia Terra each originate at a barchan dune field on a crater floor. The streaks consist of a relatively thin coating of sediment deflated from the dune fields and their vicinity. This sediment drapes a previous mantle that more thickly covers nearly all of western Arabia Terra. No dunes or eolian bedforms are found within the dark wind streaks, nor do any of the intracrater dunes climb up crater walls to provide sand to the wind streaks. The relations between dunes, wind streak, and subjacent terrain imply that dark-toned grains finer than those which comprise the dunes are lifted into suspension and carried out of the craters to be deposited on the adjacent terrain. Such grains are most likely in the silt size range (3.9-62.5 micrometers). The streaks change in terms of extent, relative albedo, and surface pattern over periods measured in years, but very little evidence for recent eolian activity (dust plumes, storms, dune movement) has been observed.

  3. Spatial grain size sorting in eolian ripples and estimation of wind conditions on planetary surfaces: Application to Meridiani Planum, Mars

    NASA Astrophysics Data System (ADS)

    Jerolmack, Douglas J.; Mohrig, David; Grotzinger, John P.; Fike, David A.; Watters, Wesley A.

    2006-05-01

    The landscape seen by the Mars Exploration Rover (MER) Opportunity at Meridiani Planum is dominated by eolian (wind-blown) ripples with concentrated surface lags of hematitic spherules and fragments. These ripples exhibit profound spatial grain size sorting, with well-sorted coarse-grained crests and poorly sorted, generally finer-grained troughs. These ripples were the most common bed form encountered by Opportunity in its traverse from Eagle Crater to Endurance Crater. Field measurements from White Sands National Monument, New Mexico, show that such coarse-grained ripples form by the different transport modes of coarse- and fine-grain fractions. On the basis of our field study, and simple theoretical and experimental considerations, we show how surface deposits of coarse-grained ripples can be used to place tight constraints on formative wind conditions on planetary surfaces. Activation of Meridiani Planum coarse-grained ripples requires a wind velocity of 70 m/s (at a reference elevation of 1 m above the bed). From images by the Mars Orbiter Camera (MOC) of reversing dust streaks, we estimate that modern surface winds reach a velocity of at least 40 m/s and hence may occasionally activate these ripples. The presence of hematite at Meridiani Planum is ultimately related to formation of concretions during aqueous diagenesis in groundwater environments; however, the eolian concentration of these durable particles may have led to the recognition from orbit of this environmentally significant landing site.

  4. Pleistocene Speciation in the Genus Populus (Salicaceae)

    PubMed Central

    Levsen, Nicholas D.; Tiffin, Peter; Olson, Matthew S.

    2012-01-01

    The macroevolutionary consequences of recent climate change remain controversial, and there is little paleobotanical or morphological evidence that Pleistocene (1.8–0.12 Ma) glacial cycles acted as drivers of speciation, especially among lineages with long generation times, such as trees. We combined genetic and ecogeographic data from 2 closely related North American tree species, Populus balsamifera and P. trichocarpa (Salicacaeae), to determine if their divergence coincided with and was possibly caused by Pleistocene climatic events. We analyzed 32 nuclear loci from individuals of P. balsamifera and P. trichocarpa to produce coalescent-based estimates of the divergence time between the 2 species. We coupled the coalescent analyses with paleodistribution models to assess the influence of climate change on species' range. Furthermore, measures of niche overlap were used to investigate patterns of ecological differentiation between species. We estimated the divergence date of P. balsamifera and P. trichocarpa at approximately 75 Ka, which corresponds closely with the onset of Marine Isotope Stage 4 (∼76 Ka) and a rapid increase in global ice volume. Significance tests of niche overlap, in conjunction with genetic estimates of migration, suggested that speciation occurred in allopatry, possibly resulting from the environmental effects of Pleistocene glacial cycles. Our results indicate that the divergence of keystone tree species, which have shaped community diversity in northern North American ecosystems, was recent and may have been a consequence of Pleistocene-era glaciation and climate change. PMID:22213709

  5. The Plio-Pleistocene scimitar-toothed felid genus Homotherium Fabrini, 1890 (Machairodontinae, Homotherini): diversity, palaeogeography and taxonomic implications

    NASA Astrophysics Data System (ADS)

    Antón, M.; Salesa, M. J.; Galobart, A.; Tseng, Z. J.

    2014-07-01

    The systematics of the Plio-Pleistocene scimitar toothed felid Homotherium have remained problematic after more than a century of fossil findings in Eurasia, Africa and the Americas. Ranging in age between around 4 million and 10,000 years, fossils of this genus display considerable variation, but the distribution of that variation has largely failed to fit a consistent pattern that would allow a clear distinction between species, especially in the Eurasiatic record. The study of undescribed mandibular and cranial fossils of Homotherium from Pleistocene sites in Spain and Alaska provides new insights into the morphological variability within this widespread genus. The results of our study and comparison of the new material with the published fossils of Homotherium confirm the difficulty in dividing the sample into clear-cut species. The new mandible from Incarcal (Spain) shows in a more dramatic way than before how the sample from that Spanish site encompasses the range of variability observed in the Villafranchian and Pleistocene Eurasiatic record, while older, possibly Ruscinian fossils of Homotherium from East Europe display less reduced lower premolars and probably correspond to a different species. The Alaskan fossils, on the other hand, add to the variability in mandibular and cranial morphology of the late Pleistocene North American record. We find no evidence to allow a species-level division within the Villafranchian-Pleistocene Homotherium sample from Eurasia, which for now is best classified as a single variable species, Homotherium latidens, but there are indications of evolution within the lineage, such as the presence of a pocketed anterior margin of the mandibular masseteric fossa, a feature found in the younger fossils of middle or late Pleistocene age but consistently absent in older specimens. A comparable pattern is found in the American record, where the same mandibular feature is observed in late Pleistocene fossils, although in that continent

  6. A morphometric analysis of the Late Pleistocene Human Skeleton from the Moh Khiew Cave in Thailand.

    PubMed

    Matsumura, Hirofumi; Pookajorn, Surin

    2005-01-01

    Few Late Pleistocene human remains have been found in Southeast Asia and the morphological features of the people of that age are still largely unknown due to the virtual lack of human remains in the area. Recent excavations at the Moh Khiew Cave in Thailand resulted in the discovery of a Late Pleistocene human skeleton in a relatively good state of preservation. An AMS radiocarbon date on the charcoal sample gathered from the burial gave a result of 25,800 +/- 600 BP, implying that the inhabitants of Moh Khiew Cave resided in a part of Sundaland during the last glacial age. In debates on the population history of Southeast Asia, it has been repeatedly advocated that Southeast Asia was occupied by indigenous people akin to present-day Australo-Melanesians prior to an expansion of migrants from Northeast Asia into this area. Morphometric analyses were undertaken to test the validity of this hypothesis. In the present study, cranial and dental measurements recorded from the Moh Khiew remains are compared with those of early and modern samples from Southeast Asia and Australia. These comparisons demonstrate that the Moh Khiew specimen resembles the Late Pleistocene series from Coobool Creek, Australia in both cranial and dental measurements. These results suggest that the Moh Khiew skeleton, as well as other fossil remains from the Tabon, Niah and Gua Gunung sites, represents a member of the Sundaland population during the Late Pleistocene, who may share common ancestry with the present-day Australian Aborigines and Melanesians. PMID:16130834

  7. Eolian sedimentation and soil development on a semiarid to subhumid grassland, Tertiary Ogallala and Quaternary Blackwater Draw Formations, Texas and New Mexico High Plains

    SciTech Connect

    Gustavson, T.C.; Holliday, V.T.

    1999-05-01

    Eolian sediments have accumulated as non-glacigenic loess and thin sand sheets on the Central and Southern High Plains grasslands of Texas and new mexico since the late Miocene. Locally as much as 110 m of eolian sediments with numerous paleosols are preserved in the Quaternary Blackwater Draw formation and the upper part of the Miocene-Pleiocene Ogallala formation. These sediments and paleosols, which cover more than 130,000 km{sup 2}, are similar to recent surface sediments and soils and record a long period of episodic eolian transport and sedimentation, and pedogenesis on a stable low-relief grass-covered landscape. Eolian sections, which comprise the fine sand to coarse silt lithofacies of the Ogallala formation, and the very fine to fine sand and sandy mud lithofacies of the Blackwater Draw formation, generally lack primary sedimentary structures. Grain size of Ogallala sediments decreases from west to east and grain size of Blackwater Draw sediments decreases from southwest to northeast. Soil horizonation is well developed in most sections, and buried calcic and argillic horizons are common. Calcic horizons are characterized by sharply increased CaCO{sub 3} content in the form of filaments, nodules, and petrocalcic horizons (calcretes). Argillic horizons are characterized by increased illuvial clay, pedogenic structure, and darker reddish hues. Rhizocretions are common locally. Open root tubules, which are typically less than 1 mm in diameter and characteristic of small plants like grasses, are present in all Ogallala and Blackwater Draw eolian sediments. Paleosols preserved in eolian sediments of the High Plains reflect periods of sedimentation followed by episodes of landscape stability and pedogenesis, and negligible sedimentation. Episodes of sedimentation and soil development likely resulted from cyclic decreases and increases in available moisture and vegetative cover. Eolian sediments were eroded and transported eastward during dry periods when

  8. Palaeomagnetism of the Laowogou and Hongya Pliocene/Pleistocene sections, Nihewan Basin, China

    NASA Astrophysics Data System (ADS)

    Liddicoat, Joseph; Baoquan, Cai; Shaohua, Zheng; Deng, Chenglong; Zhu, Rixiang; Zhang, Rui; Ao, Hong; Pan, Yongxin

    2010-05-01

    The Nihewan Formation is exposed fluvio-lacustrine sediment in the Nihewan Basin about 150 km northwest of Beijing, China. The formation is of interest because it contains vertebrate mammal fossils that have been studied by geologists, palaeontologists, geochronologists, and palaeoanthropologists since the 1920s (Barbour, 1925; Teilhard de Chardin and Piveteau, 1930; many others). Laowogou (40˚08'59"N, 114˚39'31"E) and Hongya (40˚08'07"N, 114˚39'57.1"E), which are less than a km apart on the west side of the Huliu River, are two localities that are used in those investigations. Palaeomagnetic polarity has been measured in the sections and shows that they record similar polarity episodes. Near the base of each section above eolian red clay is normal polarity that Deng et al. (2008) interpret to be the in the Gauss Normal Chron (>2.581 Ma, Gradstein et al., 2004), and the underlying reverse polarity to be the Kaena Reverse Subchron (3.116-3.032 Ma, Gradstein et al., 2004)) in that Chron. About 30 m higher in the sections are 30 m of normal polarity that Deng et al. (2008) assign to the Olduvai Normal Subchron (1.945-1.778 Ma, Gradstein et al., 2004)). However, because Pliocene vertebrate mammal fossils (Huaxiamys downsi-Chardinomys yusheensis and Mimomys-Ungaromys assemblage zones) are in that interval at Laowogou (Cai et al., 2008), an alternate interpretation for the age of those sediments is that they were deposited during the upper Gauss Normal Chron. Regardless of the age presently assigned to the 30 m of normal polarity in the Laowogou and Hongya sections, magnetostratigraphy is a desired chronologic method for dating localities that contain important Pliocene and Pleistocene mammalian fauna in North China, and specifically in the Nihewan Basin.

  9. Centennial eolian cyclicity in the Great Plains, USA: A dominant pattern of wind transport over the past 4000 years?

    USGS Publications Warehouse

    Schwalb, Antje; Dean, Walter E.; Fritz, C. Sherilyn; Geiss, Christoph E.; Kromer, Bernd

    2010-01-01

    Proxy evidence at decadal resolution from Late Holocene sediments from Pickerel Lake, northeastern South Dakota, shows distinct centennial cycles (400-700 years) in magnetic susceptibility; contents of carbonate, organic carbon, and major elements; abundance in ostracodes; and delta18O and delta13C values in calcite. Proxies indicate cyclic changes in eolian input, productivity, and temperature. Maxima in magnetic susceptibility are accompanied by maxima in aluminum and iron mass accumulation rates (MARs), and in abundances of the ostracode Fabaeformiscandona rawsoni. This indicates variable windy, and dry conditions with westerly wind dominance, including during the Medieval Climate Anomaly. Maxima in carbonates, organic carbon, phosphorous, and high delta13C values of endogenic calcite indicate moister and less windy periods with increased lake productivity, including during the Little Ice Age, and alternate with maxima of eolian transport. Times of the Maunder, Sporer and Wolf sunspot minima are characterized by maxima in delta18O values and aluminum MARs, and minima in delta13C values and organic carbon content. We interpret these lake conditions during sunspot minima to indicate decreases in lake surface water temperatures of up to 4-5 degrees C associated with decreases in epilimnetic productivity during summer. We propose that the centennial cycles are triggered by solar activity, originate in the tropical Pacific, and their onset during the Late Holocene is associated with insolation conditions driven by precession. The cyclic pattern is transmitted from the tropical Pacific into the atmosphere and transported by westerly winds into the North Atlantic realm where they strengthen the Atlantic Meridional Overturning Circulation during periods of northern Great Plains wind maxima. This consequently leads to moister climates in Central and Northern Europe. Thus, Pickerel Lake provides evidence for mechanisms of teleconnections including an atmospheric link

  10. Pleistocene vertebrates of the Yukon Territory

    NASA Astrophysics Data System (ADS)

    Harington, C. R.

    2011-08-01

    Unglaciated parts of the Yukon constitute one of the most important areas in North America for yielding Pleistocene vertebrate fossils. Nearly 30 vertebrate faunal localities are reviewed spanning a period of about 1.6 Ma (million years ago) to the close of the Pleistocene some 10 000 BP (radiocarbon years before present, taken as 1950). The vertebrate fossils represent at least 8 species of fishes, 1 amphibian, 41 species of birds and 83 species of mammals. Dominant among the large mammals are: steppe bison ( Bison priscus), horse ( Equus sp.), woolly mammoth ( Mammuthus primigenius), and caribou ( Rangifer tarandus) - signature species of the Mammoth Steppe fauna ( Fig. 1), which was widespread from the British Isles, through northern Europe, and Siberia to Alaska, Yukon and adjacent Northwest Territories. The Yukon faunas extend from Herschel Island in the north to Revenue Creek in the south and from the Alaskan border in the west to Ketza River in the east. The Yukon holds evidence of the earliest-known people in North America. Artifacts made from bison, mammoth and caribou bones from Bluefish Caves, Old Crow Basin and Dawson City areas show that people had a substantial knowledge of making and using bone tools at least by 25 000 BP, and possibly as early as 40 000 BP. A suggested chronological sequence of Yukon Pleistocene vertebrates ( Table 1) facilitates comparison of selected faunas and indicates the known duration of various taxa.

  11. Carbon cycle instability as a cause of the late Pleistocene ice age oscillations - Modeling the asymmetric response

    NASA Technical Reports Server (NTRS)

    Saltzman, Barry; Maasch, Kirk A.

    1988-01-01

    A dynamical model of the Pleistocene ice ages is presented, which incorporates many of the qualitative ideas advanced recently regarding the possible role of ocean circulation, chemistry, temperature, and productivity in regulating long-term atmospheric carbon dioxide variations. This model involves one additional term (and free parameter) beyond that included in a previous model (Saltzman and Sutera, 1987), providing the capacity for an asymmetric response. It is shown that many of the main features exhibited by the delta(O-18)-derived ice record and the Vostok core/delta(C-13)-derived carbon dioxide record in the late Pleistocene can be deduced as a free oscillatory solution of the model.

  12. A comparative study of frontal bone morphology among Pleistocene hominin fossil groups.

    PubMed

    Athreya, Sheela

    2009-12-01

    Features of the frontal bone that are conventionally used to distinguish among fossil hominin groups were quantitatively examined. Fifty-five fossil crania dating from the early to the late Pleistocene were analyzed. Using a modified pantograph, outlines of the frontal bone were collected along the midsagittal and two parasagittal planes. The profile from nasion to bregma, as well as two profiles above the medial and lateral sections of the orbit, respectively, extending from the orbital margin to the coronal suture were traced. The outlines were measured using Elliptical Fourier Function Analysis (EFFA), which enabled a quantification of aspects of the frontal bone that have historically been described primarily in nonmetric or linear terms. Four measurements were obtained: 1) overall morphology as expressed in the Fourier harmonic amplitudes; 2) maximum projection of the supraorbital torus at three points along the browridge (glabella and the medial and lateral aspects of the torus above the orbit); 3) maximum distance of the frontal squama from the frontal chord, capturing forehead curvature; and 4) nasion-bregma chord length. The results indicate that the midsagittal profile is significantly different among all Pleistocene groups in analyses that include both size and shape, as well as size-adjusted data. Homo erectus is significantly different from the late Pleistocene groups (Neandertals and early modern H. sapiens) in glabellar projection. Anatomically modern humans are significantly different from all other groups in both raw and size-standardized analyses of all three outlines that captured overall morphology, as well as forehead curvature and lateral supraorbital torus prominence, and middle Pleistocene Homo are significantly different in both medial and lateral overall parasagittal form. However, for the majority of analyses there were no significant differences among the Pleistocene archaic groups in supraorbital torus projection, frontal squama

  13. Mid-Late Pleistocene OSL chronology in western Amazonia and implications for the transcontinental Amazon pathway

    NASA Astrophysics Data System (ADS)

    Rossetti, Dilce F.; Cohen, Marcelo C. L.; Tatumi, Sonia H.; Sawakuchi, André O.; Cremon, Édipo H.; Mittani, Juan C. R.; Bertani, Thiago C.; Munita, Casimiro J. A. S.; Tudela, Diego R. G.; Yee, Márcio; Moya, Gabriela

    2015-12-01

    underlying the Mid-Late Pleistocene strata characterized herein. The combination of data from this work with previously published provenance studies supports main Andean sediment sources only in the Mid-Late Pleistocene. It is proposed that before this time, the Amazon River was restricted to eastern Amazonia, being separated from western Amazonian drainage basins due to the presence of the Purus Arch. Erosion and/or subsidence of this geological feature would have promoted the connection of these drainage systems, ultimately with the expressive record of the transcontinental Amazon pathway into the Atlantic Ocean in the Mid-Late Pleistocene.

  14. Middle Pleistocene infill of Tibetan Plateau margin rivers, Zanskar, India

    NASA Astrophysics Data System (ADS)

    Munack, Henry; Blöthe, Jan; Korup, Oliver; Fülöp, Réka-Hajnalka; Codilean, Alexandru T.; Fink, David

    2015-04-01

    The Indus, one of Asia's premier rivers, drains the NW Himalaya and the Transhimalayan ranges that fringe the western Tibetan Plateau margin. There, upstream of the western Himalayan syntaxis, river valleys alternate between deeply incised bedrock gorges and broad alluviated reaches, while average denudation rates decrease by an order of magnitude towards the Tibetan Plateau margin to rates of ~10 mm ka-1. Vast fill terrace staircases, the highest of them located up to 400 m above current river level, and intercalated lake sediments indicate alternating phases of incision and aggradation within the region, underlining the high landform preservation potential in the rain shadow of the High Himalaya. However, despite a broad interest in a better understanding of mechanisms that modulate plateau erosion, age constraints on the generation of these impressive features are sparse, though indicate mainly Pleistocene formation ages. We present new age constraints from the More Plains section in the headwaters of the Zanskar River, a major tributary to the upper Indus. The vast sedimentary successions of the More Plains originally belonged to a former endorheic basin that has been tapped by the Zanskar River, today revealing exposures of >250 m of sedimentary fill that continues to smother a previously dissected alpine headwater landscape. We combine 10Be surface exposure dating and catchment-averaged denudation rates, morphometric analysis and field observation to constrain the late Quaternary history of this section. Analysis of a 10Be depth profile on top of the More Plains, together with the dating of nearby amalgamated surface samples, indicate a surface exposure of ~170 +/- 20 ka such that deposition of this valley fill ceased during a Middle Pleistocene cold stage (MIS 6). Using GIS-based algorithms we estimate that ~3.6 km3 was removed from this section by fluvial erosion, requiring a specific sediment yield of >130 t km-2 yr-1 averaged over the past 170 ka. This

  15. Palaeogeography of the Caspian Sea marine Pleistocene

    NASA Astrophysics Data System (ADS)

    Yanina, Tamara; Svitoch, Aleksander; Makshaev, Radik; Khomchenko, Denis

    2016-04-01

    Vertical succession of the fossil molluscs of Didacna genus along the Pleistocene sequence of the Caspian Sea area allows for detailed subdivision of the sediments. Zone, i.e. the Caspian Sea Pleistocene, is the highest stratigraphical unit of the regional Quaternary stratigraphic scale. It corresponds to the biozone of Didacna Eichwald subgenus. Based on the fossil groups of Didacna molluscs, the deposits are subdivided into the Baku, Urundzhik-Singil', lower and upper Khazarian, Khvalinian, and post-Khvalinian horizons. Further subdision is based on the changes in Didacna assemblages. Three big transgressive epochs are distinguished in the Pleistocene history of the Caspian Sea that were separated by deep and long regressions. These are the Baku, early Khazarian and Khvalinian transgressions. In transgressive sea basins, the sea level reached the height of 40-50 m and was regulated by the outflow of the Caspian waters into the Black Sea via the Manych depression. The areas of transgressive basins were similar. At the Caucasian coast, the extent of the Baku and early Khazarian transgressions exceeded that of the Khvalinian transgression, while in the Northern Caspian Sea Region the latter was slightly more extensive than the preceding ones. The Urundzhik, late Khazarian and New Caspian transgressions represented sea-level rise of lower rank. All of them were recorded within big regressive epochs being usually related to warm (interglacial) climatic conditions: Singil' (Likhvin), Mikulino and Holocene, respectively. Like at present, the Pleistocene Caspian Sea represented a self-regulating system. Maximal extent of ancient sea basins was dependent upon the height of the Manych sill (that was the main regulating factor), the amount of precipitation, river runoff, and decrease in evaporation. Minimal extent of the sea basin was dependent upon the area and capacity of its southern and middle depressions. At the same time, the rest states (extents) of the Caspian Sea

  16. An Early Pleistocene Till, Okanagan Valley, British Columbia, Canada

    NASA Astrophysics Data System (ADS)

    Barendregt, R. W.; Roed, M.; Smith, S.; Sanborn, P.; Greenough, J.; Layer, P. W.; Huscroft, C.; Mathewes, R.; Benowitz, J.; Tessler, D.

    2011-12-01

    During construction of a road cut related to the Westside Road Interchange Project in West Kelowna, British Columbia, a till was encountered below one of the Lambly Creek valley basalts. The basalts are composed of a number of flows, ranging in age from 0.97 +- 0.05 Ma to 1.62 +-0.25 Ma based on new and available 40Ar/39Ar dating of basalt ground mass. Paleomagnetic data from all major units at the study site fall within one of the normal subchrons of the late Matuyama Reversed Chron and are in general agreement with the radiometric dates. Chemical signatures of the basalt are nearly identical to similar flows belonging to the Chilcotin Group of plateau lavas. This newly identified Chilcotin flow, combined with coeval flows at other locations imply that Chilcotin volcanism was more active during the Quaternary than previously thought. The underlying till is up to four metres thick and is mantled by a minimal Ah horizon in a paleosol. The till overlies laminated and cross bedded fluvial silty sand up to five metres thick that displays injection features and minor faulting. A layer of stratified gravel underlain by gray banded clay of unknown thickness underlies the sand. The till represents the earliest evidence of glaciation in the Okanagan Valley. Till fabric analysis indicates a southeasterly flow of this glacier. The present study site has yielded radiometric ages and polarities similar to those described by Mathews and Rouse for the Dog Creek locality, 320 km to the northwest in south-central British Columbia, where basalts occur below and above glacial deposits. The newly identified glacial till, here referred to as the Westbank First Nations till, is discussed in relation to other Early Pleistocene glaciations in the Cordillera and to the global paleoclimate record. Key Words: Early Pleistocene glaciations, Cordilleran glaciations in western Canada, magnetostratigraphy of glacial sediments, Lambly Creek basalt, Chilcotin Group, Ar/Ar ages of basalts

  17. Latest Early Pleistocene remains of Lynx pardinus (Carnivora, Felidae) from the Iberian Peninsula: Taxonomy and evolutionary implications

    NASA Astrophysics Data System (ADS)

    Boscaini, Alberto; Alba, David M.; Beltrán, Juan F.; Moyà-Solà, Salvador; Madurell-Malapeira, Joan

    2016-07-01

    The Iberian lynx (Lynx pardinus) is a critically endangered felid that, during the last fifty years, has been subject to an intensive conservation program in an attempt to save it from extinction. This species is first recorded at ca. 1.7-1.6 Ma (late Villafranchian, late Early Pleistocene) in NE Iberian Peninsula, roughly coinciding with the large faunal turnover that occurred around the middle to late Villafranchian boundary. Here we describe the largest collection of L. pardinus remains available to date from the Iberian late Early Pleistocene (Epivillafranchian), including localities from the Vallparadís Section (Vallès-Penedès Basin, NE Iberian Peninsula) and Cueva Victoria (Cartagena, SE Iberian Peninsula). The morphology and biometry of the studied material attests to the widespread occurrence of L. pardinus in the Mediterranean coast of the Iberian Peninsula since the latest Early Pleistocene, i.e., about 0.5 million years earlier than it was generally accepted (i.e., at the beginning of the Middle Pleistocene). Based on the features observed in the large sample studied in this paper, we conclude that Lynx spelaeus is a junior synonym of L. pardinus and further propose to assign all the Epivillafranchian and younger fossil lynxes from SW Europe to the extant species L. pardinus. Due to the arrival of the Eurasian lynx (Lynx lynx) into Europe at the beginning of the Late Pleistocene, the attribution of specimens younger than MIS 5e to either this species or L. pardinus solely on morphological grounds has proven equivocal. Here we discuss the main diagnostic features of both species of European lynxes and further review their evolutionary history and paleobiogeography throughout the Pleistocene.

  18. A new small-bodied hominin from the Late Pleistocene of Flores, Indonesia.

    PubMed

    Brown, P; Sutikna, T; Morwood, M J; Soejono, R P; Jatmiko; Saptomo, E Wayhu; Due, Rokus Awe

    2004-10-28

    Currently, it is widely accepted that only one hominin genus, Homo, was present in Pleistocene Asia, represented by two species, Homo erectus and Homo sapiens. Both species are characterized by greater brain size, increased body height and smaller teeth relative to Pliocene Australopithecus in Africa. Here we report the discovery, from the Late Pleistocene of Flores, Indonesia, of an adult hominin with stature and endocranial volume approximating 1 m and 380 cm3, respectively--equal to the smallest-known australopithecines. The combination of primitive and derived features assigns this hominin to a new species, Homo floresiensis. The most likely explanation for its existence on Flores is long-term isolation, with subsequent endemic dwarfing, of an ancestral H. erectus population. Importantly, H. floresiensis shows that the genus Homo is morphologically more varied and flexible in its adaptive responses than previously thought. PMID:15514638

  19. Structural cross sections, Plio-Pleistocene Series, southeastern Texas Continental Shelf

    SciTech Connect

    Not Available

    1989-01-01

    The Plio-Pleistocene Series in the western Gulf Coast basin comprises a thick wedge of terrigenous clastic sediment that produces modest volumes of hydrocarbons from offshore leases along the outer shelf and upper slope. Sandstone reservoirs within this wedge have yielded more than 40 million bbl of oil and 2.5 Tcf of gas. They initially contained about 1.6 billion bbl of oil equivalent, or nearly two-thirds of the estimated total recoverable reserves beneath the Texas Outer Continental Shelf. To interpret the structural and stratigraphic framework of the area, the authors used publicly available electric logs, paleontological reports, and published information, in addition to proprietary data released by operators and approximately 2,000 miles of multichannel seismic profiles. In this book biostratigraphic zones of the Plio-Pleistocene Series, locations of major oil and gas fields and trends, and areas of tectonic features and salt structures are included.

  20. A new early Pleistocene hominin mandible from Atapuerca-TD6, Spain.

    PubMed

    Bermúdez de Castro, José María; Pérez-González, Alfredo; Martinón-Torres, María; Gómez-Robles, Aida; Rosell, Jordi; Prado, Leyre; Sarmiento, Susana; Carbonell, Eudald

    2008-10-01

    We present the description of a new mandibular specimen, ATD6-113, recovered in 2006 from the TD6 level of the Gran Dolina cave site in Sierra de Atapuerca, northern Spain. A detailed study of the lithostratigraphy of the top sequence of this level, the section from where all human remains have been recovered so far, is also presented. We have observed that the hominin stratum, previously defined as Aurora Stratum, represents a condensed deposit of at least six layers, which could not be distinguished in the test pit made in 1994-95. Therefore, the human fossil remains were probably deposited during a discrete and undetermined time period. The new mandibular fragment exhibits a very similar morphology to that of the most complete specimen, ATD6-96, which was recovered in 2003 from a different layer. This suggests that both specimens represent the same biological population. The two mandibles, as well as the small mandibular fragment ATD6-5 (which constitutes part of the holotype of Homo antecessor), present a morphological pattern clearly derived with regard to that of the African early Homo specimens usually included in H. habilis and H. rudolfensis, the mandibles D211 and D2735 from Dmanisi, and most of the early Pleistocene mandibles from Sangiran. The TD6 mandibles also exhibit some derived features with regard to the African early Pleistocene specimens included in H. ergaster (or African H. erectus). Thus, the TD6 hominins seem to represent a lineage different from other African and Asian lineages, although some (metric in particular) similarities with Chinese middle Pleistocene mandibles are noted. Interestingly, none of the apomorphic mandibular features of the European middle and early late Pleistocene hominins are present in the TD6 mandibles. PMID:18657300

  1. Eolian sediments generated by anthropogenic disturbance of playas: human impacts on the geomorphic system and geomorphic impacts on the human system

    NASA Astrophysics Data System (ADS)

    Gill, Thomas E.

    1996-09-01

    In many of the Earth's arid and semiarid lands, saline lakes, playas, and similar landforms are disturbed as a result of human activity. Diversion and/or consumptive use of surface or groundwaters has created the effect of a climate change in numerous drainage basins, resulting in the desiccation of lakes and reactivation of eolian processes at many locations. Playas are natural sites for extensive eolian activity because of the deposition of clastic and chemical sediments in basins by surface water (via fluvial transport) and groundwater (via efflorescence). Wind erosion and deposition of playa sediments has had a major role in the development of landforms and sedimentary units in the present (lunette fields worldwide; Simpson Desert, Australia) and geological past, from the Triassic (Mercia Mudstone, England) to the Quaternary (Lahontan Basin and Cima Volcanic Field, USA). Anthropogenic disturbance or desiccation of playa systems has resulted in the eolian transport of sand (e.g. Lop Nor, China; Konya Basin, Turkey; Rajasthan, India; Kappakoola, Australia; several sites in West Africa) and/or dust (e.g. Aral Sea, Kazakhstan/Uzbekistan; Old Wives Lake, Canada; Kara Bogaz Gol, (ex-)USSR; Lake Texcoco, Mexico; Owens (dry) Lake, Mono Lake and other playas, USA). Typically, this is accomplished by abstraction of water and/or removal of vegetation from terminal lake basins. An extensive review of the literature documents many examples and/or potential examples of such phenomena in numerous nations. The reactivation of eolian processes from closed basins produces air pollution in the form of fugitive dust (naturally occurring compounds released into the atmosphere by human actions), and has significant environmental and economic impacts on human activities in the surrounding areas. Restoration or mitigation of degraded land on or surrounding playas has been accomplished at Lake Texcoco, Kara Bogaz Gol and the Konya Basin, and is being actively implemented at Mono Lake

  2. Correlation of the Late Pleistocene Usselo Horizon (Europe) and the Clovis Layer (North America)

    NASA Astrophysics Data System (ADS)

    Kloosterman, J. B.

    2007-05-01

    In 1940, a dark charcoal-rich layer, 10 to 15cm thick, was found within the Late Pleistocene Coversands of the Netherlands, and named the Usselo Layer (de Laag van Usselo) by its discoverer, archaeologist CCJW Hijszeler (1902-1982). Usselo is a village near Enschedé, a few kilometres from the Dutch-German border. Research started after the war, and publications, both scientific and popular, came forth in the 1950s. By pollen content, the layer was dated to the Alleröd, the last interstadial of the Würm (Wisconsin) glaciation; radiocarbon dating indicated (pre-AMS) dates of about 11,200 14C BP. Identification of the layer at other localities was visual, and it was found in Belgium, France, Germany, Poland, and Belarus; it was also found in the UK and in Denmark, in which countries, however, no correlation was made with the other occurrences. Hijszeler had found the layer all over the Netherlands and abroad from Ostende to Hamburg, and he hypothesized the cause as a general wildfire provoked by the eruption of an Eiffel volcano. The European geologists and archaeologists, however, did not adopt his views and interpreted the layer as a paleosol, vitiating the chronology by representing the layer as the result of a long development, instead of as an eolian sediment laid down perhaps in a day or even less that provides us with a sharp marker horizon. The prehistoric Clovis culture of North America was found in the 1930s and dated to the Twocreekan, the last interstadial of the Wisconsin glaciation. The Clovis layer was especially investigated by archaeologist C.Vance Haynes Jr. Visually, the layer is easily identifiable with the Usselo Horizon of Europe. Its stratigraphic position is coincident with the end of the Clovis culture and with the disappearance of the Pleistocene megafauna. In Europe, there is a clear correlation with the sudden demise of the Magdalenian culture, best known for the Franco-Cantabrian cave paintings, and with megafaunal extinctions such as

  3. First Asian record of Panthera (Leo) fossilis (Mammalia, Carnivora, Felidae) in the Early Pleistocene of Western Siberia, Russia.

    PubMed

    Sotnikova, Marina V; Foronova, Irina V

    2014-08-01

    A lion-like pantherine felid is described as Panthera (Leo) fossilis from the late Early Pleistocene sediments of the Kuznetsk Basin (Western Siberia, Russia). The find of P. fossilis first recorded in Asia considerably extends the current notion of the eastward expansion of the most ancient lions. The Siberian lion is geologically the oldest form and is dimensionally among the largest members of the group of fossil lions on the Eurasian continent. Although known by mandibular remains only, it is readily distinguished from Panthera (Leo) spelaea by a heavy built mandibular corpus with rectangular profile in the cheek teeth area, a deep, well-outlined and narrow anterior section of the masseteric fossa, and a large p4 supported by a big unreduced anterior root. The Siberian lion shares these features with the European Middle Pleistocene P. fossilis and the American Late Pleistocene P. (Leo) atrox, which suggests their close relationship. P. atrox originated from P. fossilis and was isolated in North America south of the Late Pleistocene ice sheets. This explains why the American lion has retained more primitive features than the coeval Eurasian cave lion P. (L.) spelaea. PMID:24382145

  4. Mars Hand Lens Imager (MAHLI) Efforts and Observations at the Rocknest Eolian Sand Shadow in Curiosity's Gale Crater Field Site

    NASA Technical Reports Server (NTRS)

    Edgett, K. S.; Yingst, R. A.; Minitti, M. E.; Goetz, W.; Kah, L. C.; Kennedy, M. R.; Lipkaman, L. J.; Jensen, E. H.; Anderson, R. C.; Beegle, L. W.; Carsten, J. L.; Cooper, B.; Deen, R. G.; Dromart, G.; Eigenbrode, J. L.; Grotzinger, J. P.; Gupta, S.; Hamilton, V. E.; Hardgrove, C. J.; Harker, D. E.; Herkenhoff, K. E.; Herrera, P. N.; Hurowitz, J. A.; Jandura, L.; Ming, D. W.

    2013-01-01

    The Mars Science Laboratory (MSL) mission is focused on assessing the past or present habitability of Mars, through interrogation of environment and environmental records at the Curiosity rover field site in Gale crater. The MSL team has two methods available to collect, process and deliver samples to onboard analytical laboratories, the Chemistry and Mineralogy instrument (CheMin) and the Sample Analysis at Mars (SAM) instrument suite. One approach obtains samples by drilling into a rock, the other uses a scoop to collect loose regolith fines. Scooping was planned to be first method performed on Mars because materials could be readily scooped multiple times and used to remove any remaining, minute terrestrial contaminants from the sample processing system, the Collection and Handling for In-Situ Martian Rock Analysis (CHIMRA). Because of this cleaning effort, the ideal first material to be scooped would consist of fine to very fine sand, like the interior of the Serpent Dune studied by the Mars Exploration Rover (MER) Spirit team in 2004 [1]. The MSL team selected a linear eolian deposit in the lee of a group of cobbles they named Rocknest (Fig. 1) as likely to be similar to Serpent Dune. Following the definitions in Chapter 13 of Bagnold [2], the deposit is termed a sand shadow. The scooping campaign occurred over approximately 6 weeks in October and November 2012. To support these activities, the Mars Hand Lens Imager (MAHLI) acquired images for engineering support/assessment and scientific inquiry.

  5. Lethal Interpersonal Violence in the Middle Pleistocene

    PubMed Central

    Sala, Nohemi; Arsuaga, Juan Luis; Pantoja-Pérez, Ana; Pablos, Adrián; Martínez, Ignacio; Quam, Rolf M.; Gómez-Olivencia, Asier; Bermúdez de Castro, José María; Carbonell, Eudald

    2015-01-01

    Evidence of interpersonal violence has been documented previously in Pleistocene members of the genus Homo, but only very rarely has this been posited as the possible manner of death. Here we report the earliest evidence of lethal interpersonal violence in the hominin fossil record. Cranium 17 recovered from the Sima de los Huesos Middle Pleistocene site shows two clear perimortem depression fractures on the frontal bone, interpreted as being produced by two episodes of localized blunt force trauma. The type of injuries, their location, the strong similarity of the fractures in shape and size, and the different orientations and implied trajectories of the two fractures suggest they were produced with the same object in face-to-face interpersonal conflict. Given that either of the two traumatic events was likely lethal, the presence of multiple blows implies an intention to kill. This finding shows that the lethal interpersonal violence is an ancient human behavior and has important implications for the accumulation of bodies at the site, supporting an anthropic origin. PMID:26018668

  6. Lethal interpersonal violence in the Middle Pleistocene.

    PubMed

    Sala, Nohemi; Arsuaga, Juan Luis; Pantoja-Pérez, Ana; Pablos, Adrián; Martínez, Ignacio; Quam, Rolf M; Gómez-Olivencia, Asier; Bermúdez de Castro, José María; Carbonell, Eudald

    2015-01-01

    Evidence of interpersonal violence has been documented previously in Pleistocene members of the genus Homo, but only very rarely has this been posited as the possible manner of death. Here we report the earliest evidence of lethal interpersonal violence in the hominin fossil record. Cranium 17 recovered from the Sima de los Huesos Middle Pleistocene site shows two clear perimortem depression fractures on the frontal bone, interpreted as being produced by two episodes of localized blunt force trauma. The type of injuries, their location, the strong similarity of the fractures in shape and size, and the different orientations and implied trajectories of the two fractures suggest they were produced with the same object in face-to-face interpersonal conflict. Given that either of the two traumatic events was likely lethal, the presence of multiple blows implies an intention to kill. This finding shows that the lethal interpersonal violence is an ancient human behavior and has important implications for the accumulation of bodies at the site, supporting an anthropic origin. PMID:26018668

  7. Denali fault slip rates and Holocene-late Pleistocene kinematics of central Alaska

    USGS Publications Warehouse

    Matmon, A.; Schwartz, D.P.; Haeussler, P.J.; Finkel, R.; Lienkaemper, J.J.; Stenner, H.D.; Dawson, T.E.

    2006-01-01

    The Denali fault is the principal intracontinental strike-slip fault accommodating deformation of interior Alaska associated with the Yakutat plate convergence. We obtained the first quantitative late Pleistocene-Holocene slip rates on the Denali fault system from dating offset geomorphic features. Analysis of cosmogenic 10Be concentrations in boulders (n = 27) and sediment (n = 13) collected at seven sites, offset 25-170 m by the Denali and Totschunda faults, gives average ages that range from 2.4 ± 0.3 ka to 17.0 ± 1.8 ka. These offsets and ages yield late Pleistocene-Holocene average slip rates of 9.4 ± 1.6, 12.1 ± 1.7, and 8.4 ± 2.2 mm/yr-1 along the western, central, and eastern Denali fault, respectively, and 6.0 ± 1.2 mm/yr-1 along the Totschunda fault. Our results suggest a westward decrease in the mean Pleistocene-Holocene slip rate. This westward decrease likely results from partitioning of slip from the Denali fault system to thrust faults to the north and west. 2006 Geological Society of America.

  8. Evidence for latest Pleistocene to Holocene movement on the Santa Cruz Island fault, California

    SciTech Connect

    Pinter, N.; Sorlien, C. )

    1991-09-01

    Timing of the latest movement on the Santa Cruz Island fault, a dramatic physiographic feature of the southern boundary of the California Transverse Ranges, is demonstrated to be latest Pleistocene to Holocene in age. Faulting of dated terrace gravels confirms that the most recent rupture on the fault is no older than 11.78 {plus minus}0.1 ka. This represents an order of magnitude increase over the recency suggested by previous work and requires proportional increases in estimates of the minimum slip rate and seismic hazard posed by the fault. Uplifted latest Pleistocene to Holocene fill terraces are consistent with models of high rates of uplift and high sediment supply. Numerical solution of the interaction of sea-level rise with uplift at the west end of Santa Cruz Island predicts that the youngest strata in the faulted terrace sequence are about 6.1 ka. Reevaluation of high-resolution seismic sections just west of the island supports the latest Pleistocene to Holocene timing of the most recent rupture on the fault. The Santa Cruz Island fault apparently represents an active seismogenic element of southern California, the recent and high rate of activity of which have not been previously recognized.

  9. The role of stochastic noise in the abrupt climatic transitions of the pleistocene

    SciTech Connect

    Matteucci, G.

    1991-01-01

    Analyses of marine [delta][sup 18]O records suggest that the variations of the Earth's orbital parameters have induced and provided the timing of the Pleistocene climatic oscillations. This dissertation analyses some statistical properties of the Pleistocene climate by estimating the Probability Density Function (PDF) of the [delta][sup 18]O record. The results allow to define statistically what were the [open quotes]typical conditions[close quotes] (in a probabilistic sense) of the Quaternary, to identify the modes of the PDF as the mean glacial and interglacial climatic states, and to clarify the meaning and the abruptness of the climatic transitions. A zero-dimensional Energy Balance Model is developed. The nonlinearity of the ice albedo-temperature feedback leads to multiple steady-state equilibria. The role of stochastic perturbations and their interaction with the orbital forcing in producing the periodic and abrupt climatic transitions of the late Pleistocene are illustrated. A stochastic sensitivity analysis is used to clarify the results, especially the selective amplification of the orbitally-induced 100 kyr cycle, and the predictability of the system on the time scales of the orbital cycles. From the analysis of GCM simulations and observational zonally- averaged data a one-dimensional EBM is then developed. The strong nonlinearity of this model and the occurrence of multiple equilibria is caused by the presence of the Thin Ice Cap Instability. A discussion of the features that stochastic perturbations would introduce, follows. Finally a GCM sensitivity study to atmospheric CO[sub 2] shows how the effects of varying CO[sub 2] concentrations can be included in simple EBMs. The role that stochastic perturbations, orbital forcing, and the known past concentrations of atmospheric CO[sub 2] have played in producing the abrupt climatic transitions of the late Pleistocene is discussed.

  10. Drainage reversals in Mono Basin during the late pliocene and Pleistocene

    USGS Publications Warehouse

    Reheis, M.C.; Stine, S.; Sarna-Wojcicki, A. M.

    2002-01-01

    Mono Basin, on the eastern flank of the central Sierra Nevada, is the highest of the large hydrographically closed basins in the Basin and Range province. We use geomorphic features, shoreline deposits, and basalt-filled paleochannels to reconstruct an early to middle Pleistocene record of shorelines and changing spillways of Lake Russell in Mono Basin. During this period of time, Lake Russell repeatedly attained altitudes between 2205 and 2280 m-levels far above the present surface of Mono Lake (~1950 m) and above its last overflow level (2188 m). The spill point of Lake Russell shifted through time owing to late Tertiary and Quaternary faulting and volcanism. During the early Pleistocene, the lake periodically discharged through the Mount Hicks spillway on the northeastern rim of Mono Basin and flowed northward into the Walker Lake drainage basin via the East Walker River. Paleochannels recording such discharge were incised prior to 1.6 Ma, possibly between 1.6 and 1.3 Ma, and again after 1.3 Ma (ages of basaltic flows that plugged the paleochannels). Faulting in the Adobe Hills on the southeastern margin of the basin eventually lowered the rim in this area to below the altitude of the Mount Hicks spillway. Twice after 0.76 Ma, and possibly as late as after 0.1 Ma, Lake Russell discharged southward through the Adobe Hills spillway into the Owens-Death Valley system of lakes. This study supports a pre-Pleistocene aquatic connection through Mono Basin between the hydrologically distinct Lahontan and Owens-Death Valley systems, as long postulated by biologists, and also confirms a probable link during the Pleistocene for species adapted to travel upstream in fast-flowing water.

  11. Ecospaces occupied by Homo erectus and Homo sapiens in insular Southeast Asia in the Pleistocene

    NASA Astrophysics Data System (ADS)

    Hertler, Christine; Haupt, Susanne; Volmer, Rebekka; Bruch, Angela

    2014-05-01

    Hominins migrated to the islands of the Sunda Shelf multiple times. At least two immigration events are evident, an early immigration of Homo erectus in the late Early Pleistocene and a second immigration of Homo sapiens during the Late Pleistocene. Regional environments changed considerably in the Pleistocene. Expansion patterns among hominins are at least co-determined by their ecologies and environmental change. We examine these expansion patterns on the basis of habitat reconstructions. Mammalian communities provide a geographically extensive record and permit to assess hominin ecospaces. Although chronological resolution is low, they represent the most complete record of habitat changes associated with hominin expansion patterns. In order to reconstruct and compare hominin ecospaces on a quantitative scale, we set up a reference sample consisting of mammalian communities of 117 national parks in South Asia and Sub-Saharan Africa. The diversity of such communities is assessed by ecological profiling of specialized herbivore taxa. Moreover, datasets on climate and vegetation correlate with the diversity structure of such specialized herbivore communities. Reconstructing the diversity structure of communities at key sites in Pleistocene Southeast Asia permits to infer features of the climatic and vegetation framework associated with different hominin taxa. Our results show that Homo erectus and Homo sapiens did not occupy similar ecospaces. The ecospace of Homo erectus is characterized by comparatively low diversity among frugivorous and folivorous taxa, while obligate grazers are part of the assemblages. Specialized herbivore communities with such a diversity structure occur at present in East Africa, while they are absent in Southeast Asia. In the reference sample, this type of ecospace corresponds to seasonal wetlands. Although Homo sapiens still inhabits this type of environment in Southeast Asia, his ecospace is wider. Homo sapiens is associated with

  12. Increased late Pleistocene erosion rates during fluvial aggradation in the Garhwal Himalaya, northern India

    NASA Astrophysics Data System (ADS)

    Scherler, Dirk; Bookhagen, Bodo; Wulf, Hendrik; Preusser, Frank; Strecker, Manfred R.

    2015-10-01

    The response of surface processes to climatic forcing is fundamental for understanding the impacts of climate change on landscape evolution. In the Himalaya, most large rivers feature prominent fill terraces that record an imbalance between sediment supply and transport capacity, presumably due to past fluctuations in monsoon precipitation and/or effects of glaciation at high elevation. Here, we present volume estimates, chronological constraints, and 10Be-derived paleo-erosion rates from a prominent valley fill in the Yamuna catchment, Garhwal Himalaya, to elucidate the coupled response of rivers and hillslopes to Pleistocene climate change. Although precise age control is complicated due to methodological problems, the new data support formation of the valley fill during the late Pleistocene and its incision during the Holocene. We interpret this timing to indicate that changes in discharge and river-transport capacity were major controls. Compared to the present day, late Pleistocene hillslope erosion rates were higher by a factor of ∼2-4, but appear to have decreased during valley aggradation. The higher late Pleistocene erosion rates are largely unrelated to glacial erosion and could be explained by enhanced sediment production on steep hillslopes due to increased periglacial activity that declined as temperatures increased. Alternatively, erosion rates that decrease during valley aggradation are also consistent with reduced landsliding from threshold hillslopes as a result of rising base levels. In that case, the similarity of paleo-erosion rates near the end of the aggradation period with modern erosion rates might imply that channels and hillslopes are not yet fully coupled everywhere and that present-day hillslope erosion rates may underrepresent long-term incision rates.

  13. The Thermal Evolution of the Western Equatorial Pacific During the Midde and Early Pleistocene

    NASA Astrophysics Data System (ADS)

    Medina, M. A.; Lea, D. W.; Spero, H. J.

    2004-12-01

    Magnesium/calcium data from planktonic foraminifera in the equatorial Pacific sediment cores suggested that tropical Pacific sea surface temperatures (SST's) were about 3 deg.C colder than modern conditions during glacial episodes of the last 500 thousand years (ky). We have extended the Western Equatorial Pacific (WEP) Globigerinoides ruber Mg/Ca and d18O records, from the Ontong Java Plateau, Ocean Drilling Program Hole 806B (0 19.11'N, 159 21.69'E, 2520m), back to 1.3 ma. For temperature conversion we used a G. ruber calibration based on core-tops from the tropical Pacific (Lea and Martin, 1996), which yields the following relationship: Mg/Ca(mmol/mol)= 0.30exp[0.089 X SST deg. C)]. Our SST record shows that the previously observed 3 deg C-colder SST's than modern conditions during glacial episodes are generally the rule for the entire 1.3 ma period. Glacial-interglacial temperature differences as great as 4 deg. C are observed, even in the Early Pleistocene (1-1.8 ma). Preliminary observations suggest the presence of ~40 Ky SST cycles during the Early Pleistocene, of similar amplitude to the dominant SST cycles seen in Late Pleistocene Tropical records. Early Pleistocene WEP SST's, as suggested by our record, oscillated between 26 and 30 deg. C. MIS 11 stands out as the most prominent feature of the WEP SST record. The potential bias on temperature estimates due to the influence of changes in lysocline depth (Farrell and Prell, 1989) and decrease preservation with depth (Lea et al., 2000) is ± 0.8 deg.C. Preliminary point to point comparison between the SST and the d18O records shows that Mg/Ca-based temperatures lead over d18O by about 3 ky as previously determined by Lea et al. (2000).

  14. Male strategies and Plio-Pleistocene archaeology.

    PubMed

    O'Connell, J F; Hawkes, K; Lupo, K D; Blurton Jones, N G

    2002-12-01

    Archaeological data are frequently cited in support of the idea that big game hunting drove the evolution of early Homo, mainly through its role in offspring provisioning. This argument has been disputed on two grounds: (1) ethnographic observations on modern foragers show that although hunting may contribute a large fraction of the overall diet, it is an unreliable day-to-day food source, pursued more for status than subsistence; (2) archaeological evidence from the Plio-Pleistocene, coincident with the emergence of Homo can be read to reflect low-yield scavenging, not hunting. Our review of the archaeology yields results consistent with these critiques: (1) early humans acquired large-bodied ungulates primarily by aggressive scavenging, not hunting; (2) meat was consumed at or near the point of acquisition, not at home bases, as the hunting hypothesis requires; (3) carcasses were taken at highly variable rates and in varying degrees of completeness, making meat from big game an even less reliable food source than it is among modern foragers. Collectively, Plio-Pleistocene site location and assemblage composition are consistent with the hypothesis that large carcasses were taken not for purposes of provisioning, but in the context of competitive male displays. Even if meat were acquired more reliably than the archaeology indicates, its consumption cannot account for the significant changes in life history now seen to distinguish early humans from ancestral australopiths. The coincidence between the earliest dates for Homo ergaster and an increase in the archaeological visibility of meat eating that many find so provocative instead reflects: (1) changes in the structure of the environment that concentrated scavenging opportunities in space, making evidence of their pursuit more obvious to archaeologists; (2) H. ergaster's larger body size (itself a consequence of other factors), which improved its ability at interference competition. PMID:12473486

  15. GroundwaterGeochemistry,SeasonalChangesandControlsonEolianMorphology.WhiteSandsNationalMonument,NewMexi co,TX

    NASA Astrophysics Data System (ADS)

    Rose, J. M.; Langford, R. P.; Cueto, M. J.

    2005-12-01

    column in the parabolic dune area. These may correlate with very fine grained layers (mean 5 microns) in the soil. In the Transition sites, salinity decreases from December to May but hovers around 10,000 mg/L. The Barchan sites have relatively low salinity readings above the groundwater, whereas the groundwater is very saline. The values at the barchans sites remained relatively the same throughout the six months at around 20,000 mg/L. TDS (total dissolved solids) decreases from 7 g/L in the barchan to 2g/L in the parabolic dunes. In the barchan area, the amount of DO (dissolved oxygen) is also greater. It is presumed the vegetation and the associated ecology withdraw soil water, creating higher salinities in the soil column. These layers may have formed through precipitation from groundwater or through soil alteration of the eolian sand. The dramatic changes in groundwater salinity suggest dune fields can be shaped by dynamic feedback between eolian dynamics, vegetation and groundwater chemistry.

  16. Assessing the Pleistocene hemispheric climate links through correlating loess, marine and ice-core records

    NASA Astrophysics Data System (ADS)

    Guo, Z.

    2015-12-01

    Near continuous loess-soil records in China cover the past 22 million years. Here, we compare various independent climate proxies from the terrestrial, marine and ice-core domains to re-evaluate the regional and global significance of the China loess with special emphases to the Quaternary portion. The results confirm that the intensity of loess deposition in China is closely coupled with the northern high latitude climate from the over-orbital to millennial scales, and that loess accumulation rates (LAR) and loess particle-size reflect many features of the northern high latitude ice conditions. Consequently, correlating the loess and marine records could offer the possibility for addressing the hemispheric climate links. Our loess-marine correlations show that both records are broadly coupled during the Pleistocene. However, numerous decoupled features exist between the two records. Marine oxygen isotope record shows a general trend of increased ice-volume during the Pleistocene. This trend has no clear reflection in the loess LAR and grain-size data. A prominent change at ~ 430 ka, referred to as the Mid-Brunhes Event (MBE), is clearly documented in both marine and EPICA ice records while its reflections in loess are rather ambiguous. Both marine and EPICA data show a cooler-than-average interglacial for the marine-oxygen isotope stage 13 (MIS-13) while a series of terrestrial records show a warm-extreme interglacial for the northern hemisphere. During a number of glacial intervals, such as MIS-16, MIS 14, MIS-12 and MIS-3, interglacial-level of loess grain-size are observed while they have no obvious reflections in the marine and EPICA ice records. Based on a multi-proxy approach, we argue that these decoupled features between the loess and marine records are attributable to the asymmetrical behaviors of the Pleistocene climates between the southern and northern hemispheres.

  17. Significance of Late Pliocene-Early Pleistocene stratigraphy to development of Buena Vista field, San Joaquin Valley, California

    SciTech Connect

    Kuespert, J.G.

    1987-05-01

    Late Pliocene to early Pleistocene depositional patterns of upper Etchegoin and lower San Joaquin Formation sand and shale units in the Buena vista field area were controlled by changes in clastic input, eustatic sea level, structural growth, and circulation patterns in the south end of the San Joaquin Valley. Wireline and drill-strip logs, core depositions, paleontology, and petrographic data from these units suggest the interpretation of a series of shallow to marginal marine deposits with distinctive morphologic features and production characteristics. Late Pliocene marginal marine drainage systems transported clastics from southerly sources as structural and/or eustatic changes shoaled the southern area. An erosional hiatus and shallow marine transgression marked the extent of Plio-Pleistocene shoaling and rapid early Pleistocene foundering. Later Pleistocene changes in sediment supply and structural growth isolated the area from marine conditions as the basin filled with nonmarine sediments. Early field development was influenced by the areal distribution and reservoir characteristics of these sands as well as by the timing of such development activity. Depositional models derived from these data are useful in constructing paleogeographic models with regional hydrocarbon significance.

  18. A new find of a Middle Pleistocene mandible from Bilzingsleben, Germany

    NASA Astrophysics Data System (ADS)

    Vlcek, E.; Mania, D.; Mania, U.

    The Middle Pleistocene site at Bilzingsleben is being excavated by the Forschungsstelle Bilzingsleben, FSU Jena. It is a living floor with structures of settlement and a great number of Lower Palaeolithic cultural remains. So far, 28 human skull fragments have been discovered, which can be reconstructed into two individual skulls. Recently, the right mandible has also been discovered (Bilzingsleben E7). Morphological comparisons indicate that there is a great similarity to the mandibles of HI and BI of Sinanthropus. A strong likeness to Arago II and XIII was also discovered. There are various different archaic features which assign the Bilzingsleben mandible and the two skulls to the advanced Homo erectus.

  19. A hominid from the lower Pleistocene of Atapuerca, Spain: possible ancestor to Neandertals and modern humans.

    PubMed

    Bermúdez de Castro, J M; Arsuaga, J L; Carbonell, E; Rosas, A; Martínez, I; Mosquera, M

    1997-05-30

    Human fossil remains recovered from the TD6 level (Aurora stratum) of the lower Pleistocene cave site of Gran Dolina, Sierra de Atapuerca, Spain, exhibit a unique combination of cranial, mandibular, and dental traits and are suggested as a new species of Homo-H. antecessor sp. nov. The fully modern midfacial morphology of the fossils antedates other evidence of this feature by about 650, 000 years. The midfacial and subnasal morphology of modern humans may be a retention of a juvenile pattern that was not yet present in H. ergaster. Homo antecessor may represent the last common ancestor for Neandertals and modern humans. PMID:9162001

  20. A terminal Pleistocene child cremation and residential structure from eastern Beringia.

    PubMed

    Potter, Ben A; Irish, Joel D; Reuther, Joshua D; Gelvin-Reymiller, Carol; Holliday, Vance T

    2011-02-25

    The dearth of human remains and residential sites has constrained inquiry into Beringian lifeways at the transition of the late Pleistocene-early Holocene. We report on human skeletal remains and a residential structure from central Alaska dated to ~11,500 calendar years ago. The remains are from a ~3-year-old child who was cremated in a pit within a semisubterranean house. The burial-cremation and house have exceptional integrity and preservation and exhibit similarities and differences to both Siberian Upper Paleolithic and North American Paleoindian features. PMID:21350175

  1. Late Pleistocene human remains from Wezmeh Cave, western Iran.

    PubMed

    Trinkaus, Erik; Biglari, Fereidoun; Mashkour, Marjan; Monchot, Hervé; Reyss, Jean-Louis; Rougier, Hélène; Heydari, Saman; Abdi, Kamyar

    2008-04-01

    Paleontological analysis of remains from Wezmeh Cave in western Iran have yielded a Holocene Chalcolithic archeological assemblage, a rich Late Pleistocene carnivore faunal assemblage, and an isolated unerupted human maxillary premolar (P(3) or possibly P(4)). Species representation and U-series dating of faunal teeth place the carnivore assemblage during oxygen isotope stages (OIS) 3 and 2, and noninvasive gamma spectrometry dating of the human premolar places it at least as old as early OIS 2. The human premolar crown morphology is not diagnostic of late archaic versus early modern human affinities, but its buccolingual diameter places it at the upper limits of Late Pleistocene human P(3) and P(4) dimensions and separate from a terminal Pleistocene regional sample. Wezmeh Cave therefore provides additional Paleolithic human remains from the Zagros Mountains and further documents Late Pleistocene human association with otherwise carnivore-dominated cave assemblages. PMID:18000894

  2. Early Pleistocene third metacarpal from Kenya and the evolution of modern human-like hand morphology.

    PubMed

    Ward, Carol V; Tocheri, Matthew W; Plavcan, J Michael; Brown, Francis H; Manthi, Fredrick Kyalo

    2014-01-01

    Despite discoveries of relatively complete hands from two early hominin species (Ardipithecus ramidus and Australopithecus sediba) and partial hands from another (Australopithecus afarensis), fundamental questions remain about the evolution of human-like hand anatomy and function. These questions are driven by the paucity of hand fossils in the hominin fossil record between 800,000 and 1.8 My old, a time interval well documented for the emergence and subsequent proliferation of Acheulian technology (shaped bifacial stone tools). Modern and Middle to Late Pleistocene humans share a suite of derived features in the thumb, wrist, and radial carpometacarpal joints that is noticeably absent in early hominins. Here we show that one of the most distinctive features of this suite in the Middle Pleistocene to recent human hand, the third metacarpal styloid process, was present ∼1.42 Mya in an East African hominin from Kaitio, West Turkana, Kenya. This fossil thus provides the earliest unambiguous evidence for the evolution of a key shared derived characteristic of modern human and Neandertal hand morphology and suggests that the distinctive complex of radial carpometacarpal joint features in the human hand arose early in the evolution of the genus Homo and probably in Homo erectus sensu lato. PMID:24344276

  3. Postcranial morphology of the middle Pleistocene humans from Sima de los Huesos, Spain.

    PubMed

    Arsuaga, Juan Luis; Carretero, José-Miguel; Lorenzo, Carlos; Gómez-Olivencia, Asier; Pablos, Adrián; Rodríguez, Laura; García-González, Rebeca; Bonmatí, Alejandro; Quam, Rolf M; Pantoja-Pérez, Ana; Martínez, Ignacio; Aranburu, Arantza; Gracia-Téllez, Ana; Poza-Rey, Eva; Sala, Nohemi; García, Nuria; Alcázar de Velasco, Almudena; Cuenca-Bescós, Gloria; Bermúdez de Castro, José María; Carbonell, Eudald

    2015-09-15

    Current knowledge of the evolution of the postcranial skeleton in the genus Homo is hampered by a geographically and chronologically scattered fossil record. Here we present a complete characterization of the postcranium of the middle Pleistocene paleodeme from the Sima de los Huesos (SH) and its paleobiological implications. The SH hominins show the following: (i) wide bodies, a plesiomorphic character in the genus Homo inherited from their early hominin ancestors; (ii) statures that can be found in modern human middle-latitude populations that first appeared 1.6-1.5 Mya; and (iii) large femoral heads in some individuals, a trait that first appeared during the middle Pleistocene in Africa and Europe. The intrapopulational size variation in SH shows that the level of dimorphism was similar to modern humans (MH), but the SH hominins were less encephalized than Neandertals. SH shares many postcranial anatomical features with Neandertals. Although most of these features appear to be either plesiomorphic retentions or are of uncertain phylogenetic polarity, a few represent Neandertal apomorphies. Nevertheless, the full suite of Neandertal-derived features is not yet present in the SH population. The postcranial evidence is consistent with the hypothesis based on the cranial morphology that the SH hominins are a sister group to the later Neandertals. Comparison of the SH postcranial skeleton to other hominins suggests that the evolution of the postcranium occurred in a mosaic mode, both at a general and at a detailed level. PMID:26324920

  4. Postcranial morphology of the middle Pleistocene humans from Sima de los Huesos, Spain

    PubMed Central

    Arsuaga, Juan Luis; Carretero, José-Miguel; Lorenzo, Carlos; Gómez-Olivencia, Asier; Pablos, Adrián; Rodríguez, Laura; García-González, Rebeca; Bonmatí, Alejandro; Quam, Rolf M.; Pantoja-Pérez, Ana; Martínez, Ignacio; Aranburu, Arantza; Gracia-Téllez, Ana; Poza-Rey, Eva; Sala, Nohemi; García, Nuria; Alcázar de Velasco, Almudena; Cuenca-Bescós, Gloria; Bermúdez de Castro, José María; Carbonell, Eudald

    2015-01-01

    Current knowledge of the evolution of the postcranial skeleton in the genus Homo is hampered by a geographically and chronologically scattered fossil record. Here we present a complete characterization of the postcranium of the middle Pleistocene paleodeme from the Sima de los Huesos (SH) and its paleobiological implications. The SH hominins show the following: (i) wide bodies, a plesiomorphic character in the genus Homo inherited from their early hominin ancestors; (ii) statures that can be found in modern human middle-latitude populations that first appeared 1.6–1.5 Mya; and (iii) large femoral heads in some individuals, a trait that first appeared during the middle Pleistocene in Africa and Europe. The intrapopulational size variation in SH shows that the level of dimorphism was similar to modern humans (MH), but the SH hominins were less encephalized than Neandertals. SH shares many postcranial anatomical features with Neandertals. Although most of these features appear to be either plesiomorphic retentions or are of uncertain phylogenetic polarity, a few represent Neandertal apomorphies. Nevertheless, the full suite of Neandertal-derived features is not yet present in the SH population. The postcranial evidence is consistent with the hypothesis based on the cranial morphology that the SH hominins are a sister group to the later Neandertals. Comparison of the SH postcranial skeleton to other hominins suggests that the evolution of the postcranium occurred in a mosaic mode, both at a general and at a detailed level. PMID:26324920

  5. Early Pleistocene third metacarpal from Kenya and the evolution of modern human-like hand morphology

    PubMed Central

    Ward, Carol V.; Tocheri, Matthew W.; Plavcan, J. Michael; Brown, Francis H.; Manthi, Fredrick Kyalo

    2014-01-01

    Despite discoveries of relatively complete hands from two early hominin species (Ardipithecus ramidus and Australopithecus sediba) and partial hands from another (Australopithecus afarensis), fundamental questions remain about the evolution of human-like hand anatomy and function. These questions are driven by the paucity of hand fossils in the hominin fossil record between 800,000 and 1.8 My old, a time interval well documented for the emergence and subsequent proliferation of Acheulian technology (shaped bifacial stone tools). Modern and Middle to Late Pleistocene humans share a suite of derived features in the thumb, wrist, and radial carpometacarpal joints that is noticeably absent in early hominins. Here we show that one of the most distinctive features of this suite in the Middle Pleistocene to recent human hand, the third metacarpal styloid process, was present ∼1.42 Mya in an East African hominin from Kaitio, West Turkana, Kenya. This fossil thus provides the earliest unambiguous evidence for the evolution of a key shared derived characteristic of modern human and Neandertal hand morphology and suggests that the distinctive complex of radial carpometacarpal joint features in the human hand arose early in the evolution of the genus Homo and probably in Homo erectus sensu lato. PMID:24344276

  6. A regional geochronological study of late pleistocene permafrost

    SciTech Connect

    Kostyukevich, V.V. . Geochemistry Lab.)

    1993-01-01

    The use of radiocarbon dating in geocryological investigations makes it possible to establish a chronology for permafrost-geological development during the Late Pleistocene. Both global and regional time scales for the formation of Late Pleistocene permafrost have been worked out over the past 15--20 years at the Permafrost Institute of the Siberian Branch of Russian Academy of Sciences. He presents here results from study areas of northwestern Siberia and of North, Central and West Yakutia.

  7. Arctic ocean sediment texture and the Pleistocene climate cycle

    SciTech Connect

    Clark, D.L.; Morris, T.H.

    1985-01-01

    Arctic Ocean sediment texture accurately reflects the Plio-Pleistocene climate cycle. The precision of paleoclimate interpretation is improved when deglaciation is recognized as a distinct climate stage, overlapping both glacial and interglacial stages, and for the later Pleistocene, perhaps never completed. Oxygen isotope stratigraphy and foraminifera productivity are out of phase but can be understood in the context of the transitional nature of the glacial, deglacial and interglacial climate stages of the Arctic Ocean.

  8. Principles of pleistocene stratigraphy, applied to the Gulf of Mexico

    SciTech Connect

    Fillon, R.H.; Healy-Williams, N.; Ledbetter, M.T.; Thunell, R.C.; Williams, D.F.

    1984-01-01

    This study of one of the world's major oil provinces is an examination of advances made in the past decade in high resolution stratigraphy of Pleistocene marine sediments. Topics covered include magnetostratigraphy, planktonic foraminiferal biostratigraphy, oxygen isotope stratigraphy, tephrochronology and a review and updating of terrestrial-marine correlations during the Pleistocene. The emphasis is on the Gulf of Mexico, but the techniques described can be applied to other marine sedimentary basins.

  9. Extent of Pleistocene lakes in the western Great Basin

    USGS Publications Warehouse

    Reheis, Marith C.

    1999-01-01

    During the Pliocene to middle Pleistocene, pluvial lakes in the western Great Basin repeatedly rose to levels much higher than those of the well-documented late Pleistocene pluvial lakes, and some presently isolated basins were connected. Sedimentologic, geomorphic, and chronologic evidence at sites shown on the map indicates that Lakes Lahontan and Columbus-Rennie were as much as 70 m higher in the early-middle Pleistocene than during their late Pleistocene high stands. Lake Lahontan at its 1400-m shoreline level would submerge present-day Reno, Carson City, and Battle Mountain, and would flood other now-dry basins. To the east, Lakes Jonathan (new name), Diamond, Newark, and Hubbs also reached high stands during the early-middle(?) Pleistocene that were 25-40 m above their late Pleistocene shorelines; at these very high levels, the lakes became temporarily or permanently tributary to the Humboldt River and hence to Lake Lahontan. Such a temporary connection could have permitted fish to migrate from the Humboldt River southward into the presently isolated Newark Valley and from Lake Lahontan into Fairview Valley. The timing of drainage integration also provides suggested maximum ages for fish to populate the basins of Lake Diamond and Lake Jonathan. Reconstructing and dating these lake levels also has important implications for paleoclimate, tectonics, and drainage evolution in the western Great Basin. For example, shorelines in several basins form a stair-step sequence downward with time from the highest levels, thought to have formed at about 650 ka, to the lowest, formed during the late Pleistocene. This descending sequence indicates progressive drying of pluvial periods, possibly caused by uplift of the Sierra Nevada and other western ranges relative to the western Great Basin. However, these effects cannot account for the extremely high lake levels during the early middle Pleistocene; rather, these high levels were probably due to a combination of increased

  10. Pleistocene megafaunal interaction networks became more vulnerable after human arrival.

    PubMed

    Pires, Mathias M; Koch, Paul L; Fariña, Richard A; de Aguiar, Marcus A M; dos Reis, Sérgio F; Guimarães, Paulo R

    2015-09-01

    The end of the Pleistocene was marked by the extinction of almost all large land mammals worldwide except in Africa. Although the debate on Pleistocene extinctions has focused on the roles of climate change and humans, the impact of perturbations depends on properties of ecological communities, such as species composition and the organization of ecological interactions. Here, we combined palaeoecological and ecological data, food-web models and community stability analysis to investigate if differences between Pleistocene and modern mammalian assemblages help us understand why the megafauna died out in the Americas while persisting in Africa. We show Pleistocene and modern assemblages share similar network topology, but differences in richness and body size distributions made Pleistocene communities significantly more vulnerable to the effects of human arrival. The structural changes promoted by humans in Pleistocene networks would have increased the likelihood of unstable dynamics, which may favour extinction cascades in communities facing extrinsic perturbations. Our findings suggest that the basic aspects of the organization of ecological communities may have played an important role in major extinction events in the past. Knowledge of community-level properties and their consequences to dynamics may be critical to understand past and future extinctions. PMID:26336175

  11. The impact of large terrestrial carnivores on Pleistocene ecosystems

    PubMed Central

    Van Valkenburgh, Blaire; Ripple, William J.; Meloro, Carlo; Roth, V. Louise

    2016-01-01

    Large mammalian terrestrial herbivores, such as elephants, have dramatic effects on the ecosystems they inhabit and at high population densities their environmental impacts can be devastating. Pleistocene terrestrial ecosystems included a much greater diversity of megaherbivores (e.g., mammoths, mastodons, giant ground sloths) and thus a greater potential for widespread habitat degradation if population sizes were not limited. Nevertheless, based on modern observations, it is generally believed that populations of megaherbivores (>800 kg) are largely immune to the effects of predation and this perception has been extended into the Pleistocene. However, as shown here, the species richness of big carnivores was greater in the Pleistocene and many of them were significantly larger than their modern counterparts. Fossil evidence suggests that interspecific competition among carnivores was relatively intense and reveals that some individuals specialized in consuming megaherbivores. To estimate the potential impact of Pleistocene large carnivores, we use both historic and modern data on predator–prey body mass relationships to predict size ranges of their typical and maximum prey when hunting as individuals and in groups. These prey size ranges are then compared with estimates of juvenile and subadult proboscidean body sizes derived from extant elephant growth data. Young proboscideans at their most vulnerable age fall within the predicted prey size ranges of many of the Pleistocene carnivores. Predation on juveniles can have a greater impact on megaherbivores because of their long interbirth intervals, and consequently, we argue that Pleistocene carnivores had the capacity to, and likely did, limit megaherbivore population sizes. PMID:26504224

  12. The impact of large terrestrial carnivores on Pleistocene ecosystems.

    PubMed

    Van Valkenburgh, Blaire; Hayward, Matthew W; Ripple, William J; Meloro, Carlo; Roth, V Louise

    2016-01-26

    Large mammalian terrestrial herbivores, such as elephants, have dramatic effects on the ecosystems they inhabit and at high population densities their environmental impacts can be devastating. Pleistocene terrestrial ecosystems included a much greater diversity of megaherbivores (e.g., mammoths, mastodons, giant ground sloths) and thus a greater potential for widespread habitat degradation if population sizes were not limited. Nevertheless, based on modern observations, it is generally believed that populations of megaherbivores (>800 kg) are largely immune to the effects of predation and this perception has been extended into the Pleistocene. However, as shown here, the species richness of big carnivores was greater in the Pleistocene and many of them were significantly larger than their modern counterparts. Fossil evidence suggests that interspecific competition among carnivores was relatively intense and reveals that some individuals specialized in consuming megaherbivores. To estimate the potential impact of Pleistocene large carnivores, we use both historic and modern data on predator-prey body mass relationships to predict size ranges of their typical and maximum prey when hunting as individuals and in groups. These prey size ranges are then compared with estimates of juvenile and subadult proboscidean body sizes derived from extant elephant growth data. Young proboscideans at their most vulnerable age fall within the predicted prey size ranges of many of the Pleistocene carnivores. Predation on juveniles can have a greater impact on megaherbivores because of their long interbirth intervals, and consequently, we argue that Pleistocene carnivores had the capacity to, and likely did, limit megaherbivore population sizes. PMID:26504224

  13. Pleistocene megafaunal interaction networks became more vulnerable after human arrival

    PubMed Central

    Pires, Mathias M.; Koch, Paul L.; Fariña, Richard A.; de Aguiar, Marcus A. M.; dos Reis, Sérgio F.; Guimarães, Paulo R.

    2015-01-01

    The end of the Pleistocene was marked by the extinction of almost all large land mammals worldwide except in Africa. Although the debate on Pleistocene extinctions has focused on the roles of climate change and humans, the impact of perturbations depends on properties of ecological communities, such as species composition and the organization of ecological interactions. Here, we combined palaeoecological and ecological data, food-web models and community stability analysis to investigate if differences between Pleistocene and modern mammalian assemblages help us understand why the megafauna died out in the Americas while persisting in Africa. We show Pleistocene and modern assemblages share similar network topology, but differences in richness and body size distributions made Pleistocene communities significantly more vulnerable to the effects of human arrival. The structural changes promoted by humans in Pleistocene networks would have increased the likelihood of unstable dynamics, which may favour extinction cascades in communities facing extrinsic perturbations. Our findings suggest that the basic aspects of the organization of ecological communities may have played an important role in major extinction events in the past. Knowledge of community-level properties and their consequences to dynamics may be critical to understand past and future extinctions. PMID:26336175

  14. New insights into Eastern Beringian mortuary behavior: A terminal Pleistocene double infant burial at Upward Sun River

    PubMed Central

    Potter, Ben A.; Irish, Joel D.; Reuther, Joshua D.; McKinney, Holly J.

    2014-01-01

    Here we report on the discovery of two infant burials dating to ∼11,500 calibrated years (cal) B.P. at the Upward Sun River site in central Alaska. The infants were interred in a pit feature with associated organic and lithic grave goods, including the earliest known North American hafted bifaces with decorated antler foreshafts. Skeletal and dental analyses indicate that Individual 1 died shortly after birth and Individual 2 was a late-term fetus, making these the youngest-aged late Pleistocene individuals known for the Americas and the only known prenate, offering, to our knowledge, the first opportunity to explore mortuary treatment of the youngest members of a terminal Pleistocene North American population. This burial was situated ∼40 cm directly below a cremated 3-y-old child previously discovered in association with a central hearth of a residential feature. The burial and cremation are contemporaneous, and differences in body orientation, treatment, and associated grave goods within a single feature and evidence for residential occupation between burial episodes indicate novel mortuary behaviors. The human remains, grave goods, and associated fauna provide rare direct data on organic technology, economy, seasonality of residential occupations, and infant/child mortality of terminal Pleistocene Beringians. PMID:25385599

  15. New insights into Eastern Beringian mortuary behavior: a terminal Pleistocene double infant burial at Upward Sun River.

    PubMed

    Potter, Ben A; Irish, Joel D; Reuther, Joshua D; McKinney, Holly J

    2014-12-01

    Here we report on the discovery of two infant burials dating to ∼11,500 calibrated years (cal) B.P. at the Upward Sun River site in central Alaska. The infants were interred in a pit feature with associated organic and lithic grave goods, including the earliest known North American hafted bifaces with decorated antler foreshafts. Skeletal and dental analyses indicate that Individual 1 died shortly after birth and Individual 2 was a late-term fetus, making these the youngest-aged late Pleistocene individuals known for the Americas and the only known prenate, offering, to our knowledge, the first opportunity to explore mortuary treatment of the youngest members of a terminal Pleistocene North American population. This burial was situated ∼40 cm directly below a cremated 3-y-old child previously discovered in association with a central hearth of a residential feature. The burial and cremation are contemporaneous, and differences in body orientation, treatment, and associated grave goods within a single feature and evidence for residential occupation between burial episodes indicate novel mortuary behaviors. The human remains, grave goods, and associated fauna provide rare direct data on organic technology, economy, seasonality of residential occupations, and infant/child mortality of terminal Pleistocene Beringians. PMID:25385599

  16. Quantifying the astronomical contribution to Pleistocene climate change: A non-linear, statistical approach

    NASA Astrophysics Data System (ADS)

    Crucifix, Michel; Wilkinson, Richard; Carson, Jake; Preston, Simon; Alemeida, Carlos; Rougier, Jonathan

    2013-04-01

    The existence of an action of astronomical forcing on the Pleistocene climate is almost undisputed. However, quantifying this action is not straightforward. In particular, the phenomenon of deglaciation is generally interpreted as a manifestation of instability, which is typical of non-linear systems. As a consequence, explaining the Pleistocene climate record as the addition of an astronomical contribution and noise-as often done using harmonic analysis tools-is potentially deceptive. Rather, we advocate a methodology in which non-linear stochastic dynamical systems are calibrated on the Pleistocene climate record. The exercise, though, requires careful statistical reasoning and state-of-the-art techniques. In fact, the problem has been judged to be mathematically 'intractable and unsolved' and some pragmatism is justified. In order to illustrate the methodology we consider one dynamical system that potentially captures four dynamical features of the Pleistocene climate : the existence of a saddle-node bifurcation in at least one of its slow components, a time-scale separation between a slow and a fast component, the action of astronomical forcing, and the existence a stochastic contribution to the system dynamics. This model is obviously not the only possible representation of Pleistocene dynamics, but it encapsulates well enough both our theoretical and empirical knowledge into a very simple form to constitute a valid starting point. The purpose of this poster is to outline the practical challenges in calibrating such a model on paleoclimate observations. Just as in time series analysis, there is no one single and universal test or criteria that would demonstrate the validity of an approach. Several methods exist to calibrate the model and judgement develops by the confrontation of the results of the different methods. In particular, we consider here the Kalman filter variants, the Particle Monte-Carlo Markov Chain, and two other variants of Sequential Monte

  17. Pleistocene cave art from Sulawesi, Indonesia.

    PubMed

    Aubert, M; Brumm, A; Ramli, M; Sutikna, T; Saptomo, E W; Hakim, B; Morwood, M J; van den Bergh, G D; Kinsley, L; Dosseto, A

    2014-10-01

    Archaeologists have long been puzzled by the appearance in Europe ∼40-35 thousand years (kyr) ago of a rich corpus of sophisticated artworks, including parietal art (that is, paintings, drawings and engravings on immobile rock surfaces) and portable art (for example, carved figurines), and the absence or scarcity of equivalent, well-dated evidence elsewhere, especially along early human migration routes in South Asia and the Far East, including Wallacea and Australia, where modern humans (Homo sapiens) were established by 50 kyr ago. Here, using uranium-series dating of coralloid speleothems directly associated with 12 human hand stencils and two figurative animal depictions from seven cave sites in the Maros karsts of Sulawesi, we show that rock art traditions on this Indonesian island are at least compatible in age with the oldest European art. The earliest dated image from Maros, with a minimum age of 39.9 kyr, is now the oldest known hand stencil in the world. In addition, a painting of a babirusa ('pig-deer') made at least 35.4 kyr ago is among the earliest dated figurative depictions worldwide, if not the earliest one. Among the implications, it can now be demonstrated that humans were producing rock art by ∼40 kyr ago at opposite ends of the Pleistocene Eurasian world. PMID:25297435

  18. A Late Pleistocene sea level stack

    NASA Astrophysics Data System (ADS)

    Spratt, Rachel M.; Lisiecki, Lorraine E.

    2016-04-01

    Late Pleistocene sea level has been reconstructed from ocean sediment core data using a wide variety of proxies and models. However, the accuracy of individual reconstructions is limited by measurement error, local variations in salinity and temperature, and assumptions particular to each technique. Here we present a sea level stack (average) which increases the signal-to-noise ratio of individual reconstructions. Specifically, we perform principal component analysis (PCA) on seven records from 0 to 430 ka and five records from 0 to 798 ka. The first principal component, which we use as the stack, describes ˜ 80 % of the variance in the data and is similar using either five or seven records. After scaling the stack based on Holocene and Last Glacial Maximum (LGM) sea level estimates, the stack agrees to within 5 m with isostatically adjusted coral sea level estimates for Marine Isotope Stages 5e and 11 (125 and 400 ka, respectively). Bootstrapping and random sampling yield mean uncertainty estimates of 9-12 m (1σ) for the scaled stack. Sea level change accounts for about 45 % of the total orbital-band variance in benthic δ18O, compared to a 65 % contribution during the LGM-to-Holocene transition. Additionally, the second and third principal components of our analyses reflect differences between proxy records associated with spatial variations in the δ18O of seawater.

  19. Simulation of eolian saltation.

    PubMed

    Anderson, R S; Haff, P K

    1988-08-12

    Saltation is important in the transport of sand-sized granular material by wind and in the ejection of dust from the bed both on Earth and on Mars. The evolution of the saltating population and all its characteristic profiles is calculated from inception by pure aerodynamic entrainment through to steady state. Results of numerical simulations of single-grain impacts into granular beds are condensed into analytic expressions for the number and speeds of grains rebounding or rejected (splashed) from the bed. A model is combined with (i) this numerical representation, (ii) an expression for the aerodynamic entrainment rate, and (iii) the modification of the wind velocity profile by saltating grains. Calculated steady state mass fluxes are within the range of mass fluxes measured in wind tunnel experiments; mass flux is nonlinearly dependent on the shear velocity. Aerodynamically entrained grains in the system are primarily seeding agents; at steady state, aerodynamic entrainment is rare. The time for the entire system to reach steady state is roughly 1 second, or several long-trajectory hop times. PMID:17829176

  20. Onset of major Pleistocene glaciations in the Alps

    NASA Astrophysics Data System (ADS)

    Muttoni, G.; Carcano, C.; Garzanti, E.; Ghielmi, M.; Piccin, A.; Pini, R.; Rogledi, S.; Sciunnach, D.

    2003-04-01

    Since alligators patrolled Greenland swamps in the Eocene, the Earth's climate underwent significant cooling, which culminated in the Pleistocene Ice Age with recurring glaciations in vast regions of the Alps, Eurasia and North America, and overgrowth of polar icecaps in Antarctica and Greenland. During main Pleistocene glacial penetrations, the Alpine icecap invaded the low gradients of the Central Europe uplands and Italian Po plain. Peri-glacial sedimentary basins such as the Po Basin are natural collectors of past biological and climatic changes involving the waxing and waning of major icecaps. We have found in a 200m-thick core from the central Po plain near Milan stratigraphic evidence for a major glacial pulsation of the nearby Alpine icecap, which occurred in correspondence of a seismically traceable unconformity of regional relevance, termed the "Red Unconformity" (RU) in Eni/Agip terminology. The RU is associated with a major reorganization of vegetation cover and Alpine drainage pattern. The age of the RU was constrained magnetostratigraphically to the the first major Pleistocene glacio-eustatic low-stand at 0.87Ma (Oxygen Isotope Stage 22). This corresponds to the end of the "Mid Pleistocene Revolution" (MPR), a marked reorganization of northern hemisphere glaciation pattern which took place in the late Early Pleistocene. We suggest that the MPR/MIS 22 was associated with the onset of the first major Pleistocene glaciation in the Alps. Noticing the similarity in number of major Pleistocene glacieustatic low-stands starting with MIS 22, and the four-fold Alpine glacial subdivision of Penck and Brückner (1909), we conclude that "Penck and Brückner in 1909 may not have been, after all, that wrong" (Kukla and Cilek, 1996).

  1. Periglacial process and Pleistocene environment in northern China

    SciTech Connect

    Guo Xudong; Liu Dongsheng ); Yan Fuhua )

    1991-03-01

    In the present time, five kinds of periglacial phenomena have been defined: ice wedges, periglacial involutions, congelifolds, congeliturbations, and loess dunes. From the stratigraphical and geochronological data, the periglacial process is divided into six stages. (1) Guanting periglacial stage, characterized by the congeliturbative deposits that have developed in early Pleistocene Guanting loess-like formation. Paleomagnetic dating gives 2.43 Ma B.P. (2) Yanchi periglacial stage, characterized by the congelifold that has developed in middle Pleistocene Yanchi Lishi loess formation. Paleomagnetic dating gives 0.50 Ma B.P. (3) Zhaitang periglacial stage (II), characterized by the periglacial involutions that have developed in lower middle Pleistocene Lishi loess formation. Paleomagnetic dating gives 0.30 Ma B.P. (4) Zhaitang periglacial state (I), characterized by the ice (soil) wedge that has developed in upper-middle Pleistocene Lishi loess formation. Paleomagnetic dating gives 0.20 Ma B.P. (5) Qiansangyu periglacial stage (II), characterized by the ice (sand) wedges that has developed in late Pleistocene Malan loess formation. Paleomagnetic dating gives 0.13 Ma B.P. (6) Qiansangyu periglacial stage (I), characterized by the ice (soil) wedge that has developed in late Pleistocene Malan loess-like formation. Thermoluminescent dating gives 0.018 Ma B.P. Spore-pollen composition analysis shows that the savannah steppe environment prevailed in northern China during Pleistocene periglacial periods. These fossilized periglacial phenomena indicate a rather arid and windy periglacial environment with a mean annual temperature estimated some 12-15C colder than that in the present.

  2. Eolian deposits of the southwestern margin of the Botucatú paleoerg: Reconstruction of the Gondwana landscape in Central Northern Argentina

    NASA Astrophysics Data System (ADS)

    Peri, V. Gisel; Naipauer, Maximiliano; Pimentel, Marcio; Barcelona, Hernan

    2016-06-01

    The Mesozoic Botucatú paleoerg at the southwestern margin of Gondwana includes a succession of eolian dunes cross-strata which are presently exposed in Otumpa Hills (Central Northern Argentina). Here, the architectural facies, petrology, and provenance of those rocks were studied in order to investigate depositional environments and paleoclimates. The stratigraphic sequence included basal eolian two-dimensional crescentic dunes (Slp) overlain by three-dimensional crescentic dunes of smaller scale (Smt). These were correlated with the Upper Member Rivera of the Tacuarembó Formation (Uruguay), or its equivalent in Brazil, the Botucatú Formation. These outcrops partially mark the southwestern margin of the Botucatú paleoerg along the Chaco-Paraná Basin boundary. The paleocurrents from the W, NW, and SW and the U-Pb ages of detrital zircons indicate a main Pampean cratonic and secondary Andean magmatic arc (180 Ma) source. A detrital zircon of 180 Ma by U-Pb limits a maximum depositional age at 180 Ma (Toarcian) for facies Slp. Upwards, the phreatic silcrete and calcrete indicate semiarid conditions during the Paleocene, which are correlated with the Queguay Formation of Uruguay. A saprolite paleoweathering profile, recording wet tropical-hyper-tropical climate at the Early Eocene and representing the Gondwana landscape and climate conditions, crowns the sequence. This study represents the first provenance and surface texture analysis of minerals from the Botucatú paleoerg and was instrumental to unravel past environmental and sedimentary conditions.

  3. Comparative stability calculations of the Pleistocene landslide in France

    NASA Astrophysics Data System (ADS)

    Fabre, R.; Martins Campina, B.; Riss, J.; Bertran, P.

    2003-04-01

    Remnants of the Petit-Bost landslide that occurred during the Pleistocene have been observed during field investigations in Quaternary alluvial formations, southwestern France. The work presented demonstrates how field observations can be used to calculate slope stability. A sliding surface and other related features due to soil deformation have been discovered within a clay layer that overlays the gravel. Abundant periglacial features such as ice-wedge casts have also been found in the colluvium and testify to a former permafrost, suggesting that sliding may be closely linked with Pleistocene periglacial conditions. The surface of rupture is located in a 0.5 m thick, very plastic mottled clay at the top of an alluvial gravel. The initial topography at the time of sliding is not known, but the gradient was thought to be close to that of the present soil surface. This ranges between 3 and 4°; a value of 3° has been used in the following stability calculations. The landslide corresponds to a 2-m-thick colluvium formations with 1.5-m thick permafrost that has been subjected to gravity-induced instability in saturated soil in a periglacial environment. The stability calculations for the Petit-Bost landslide have been performed using an infinite plane sliding and according to two complementary methods. The first one has been usually used for plane sliding, the Carter method. The second one used also for plane sliding with the FLAC computer method (Fast Lagrangian Analysis of Continua method). Following the first one Carter method, calculations were made for an impermeable upper layer, that leads to the development of high pore water pressure in the clay layer. These first results show that instability in the clay only occurs for very low angle of internal friction and cohesion values. Under such conditions, artesian water pressures may have triggered sliding. This could have occurred if the thawed clay layer was trapped between a permafrost table and an overlying

  4. N zooming into the Mediterranean outflow fossil moat during the 1.2-1.8 million years period (Early-Pleistocene) - An approach by radiogenic and stable isotopes

    NASA Astrophysics Data System (ADS)

    Lebreiro, Susana M.; Antón, Laura; Reguera, M. Isabel; Fernández, Marta; Conde, Estefanía; Barrado, Ana I.; Yllera, Abel

    2015-12-01

    The fossil Alvarez Cabral erosive Moat contains hemipelagite, contourite and turbidite facies where oceanography changes in the Mediterranean outflow are archived over the 1.2-1.8 Myr time period. Here we used Pb and Sr radiogenic isotopes to trace water masses and sediment source changes, for the first time in twenty glacial-interglacial (G-I) cycles of the Early-Pleistocene interval, and the last Glacial Maximum through Holocene cycle (including the Younger Dryas and Heinrich Stadial-1). A mixing line of Pb isotopes gives reliable low radiogenic 208Pb/204Pb, 206Pb/204Pb, and 206Pb/207Pb typical of Mediterranean Outflow Water (MOW) in one end-member and the signature of high radiogenic isotopes of Atlantic Waters (AW) towards the second end-member. The 87Sr/86Sr isotopes also display two end-members of the mixing line between eolian transport/dust source (0.71) and fluvial transport/weathering source (0.73) previously proposed in the Gulf of Cadiz. Combination of Pb and Sr radiogenic isotopes with O and C stable isotopes of planktonic and benthic foraminifera, and the response of foraminifera benthos over the Early-Pleistocene interval, reveals a direct link between water masses circulation and shifts in G-I. We found a persistent cyclic pattern of MOW circulation and fluvial deposition during glaciations and AW and aeolian influence during interglaciations. On site U1386B/C, the upper-MOW was less ventilated but productive and with high flux of organic flux matter during glacials, while Atlantic Waters were better ventilated, enriched in O, but less productive during interglacials. We infer that shifts in ocean and atmospheric processes in the Gulf of Cadiz were strongly controlled by Earth's obliquity (41 kyr-cycle) and 35°NH insolation during the Early-Pleistocene. We propose a correlation in changes in phase-relationship between precession and obliquity. In general terms, physical properties of fine sediments (glacials) show lower NGR, low reflectance and

  5. Newly recognized Pleistocene human teeth from Tabun Cave, Israel.

    PubMed

    Coppa, Alfredo; Grün, Rainer; Stringer, Chris; Eggins, Stephen; Vargiu, Rita

    2005-09-01

    Seven human teeth from Tabun Cave, Israel, curated at the Natural History Museum London since 1955, are of uncertain provenance and identity. They are all from the upper dentition, without duplications, and are characterized by a similar preservation. The Catalogue of Fossil Hominids (1975) suggested that they might have derived from Tabun Layer A (Bronze Age to Recent). However, one of us (AC) noted some distinctive features of these teeth that warranted further study. They are here assigned to a single individual, Tabun BC7. Their morphology and metrics were then compared with the frequency of Late Pleistocene and Early Holocene groups from Europe, North Africa and Middle East. A fragment of the right M3 crown of Tabun BC7 was removed for ESR and U-analysis, and it was determined that only samples from Layer B have similar dose values. Using the sediment dose values of layer B, preliminary age estimates of 82 +/- 14 ka (early U-uptake) and 92+/-18 ka (linear uptake) were obtained. U-series disequilibrium determined from other samples attributed to Layer B resulted in a U-uptake history close to linear uptake, giving a very comparable age estimate of 90(+30)(-16) ka. The dose value previously obtained on an enamel fragment from the Tabun C1 dentition is nearly double the value measured for BC7, and tentative age estimates for C1 were in the range of 143+/-37 ka. However, due to uncertainties in the exact provenance of the human fossils, we cannot confirm that C1 is older than the new tooth sampled here, and both C1 and BC7 can be attributed to Layer B on chronological grounds. On the basis of chronology, dental morphology and metrics, the specimen named Tabun BC7 was identified as a probable Neanderthal. PMID:15964608

  6. Extended Late Pleistocene Sea Level Record

    NASA Astrophysics Data System (ADS)

    Fairbanks, R. G.; Cao, L.; Mortlock, R. A.

    2006-12-01

    Several hundred new closed system 230Th/234U and radiocarbon dates and the addition of more cores and coral samples from the islands of Barbados, Kiritimati and Araki contribute to an enhanced sea level record for the late Pleistocene ranging from the present to 240,000 yrs BP. Application of more rigorous sample screening criteria, including redundant 231Pa/235U dates have resulted in more closed system ages and better sea level resolution. In addition, a multibeam survey has mapped an extensive glacial lowstand reef on a ridge south of Barbados that is capped by a set of pinnacle reefs that grew during the early deglaciation. Among our new observations, the more detailed Barbados sea level record now resolves a Younger Dryas still- stand and a sea level drop between 16,140 and 14,690, overlapping the timing of H1 by some age estimates. The coral ages bracketing melt water pulse 1A have been further refined to 14,082 +/- 28 yrs BP and 13,632 +/- 32 yrs BP (2-sigma). The Isotope Stage 3 interstadial ended with sea level near 87.5 meters below present at 29,500 years ago before dropping to full glacial levels. The last glacial sea level lowstand began as early as 26,000 yrs BP. Extensive dating of Marine Isotope Stage 3 interstadial reefs on the islands of Araki and Barbados have added considerable resolution to this time interval and reliably bracket lowstand intervals separating the interstadials. A new diagenesis model has improved our prospecting success for closed system ages from older reefs and added some critical dates to the sparse closed-system data set for MIS-5 and MIS-7 high stand reefs..

  7. Retardation of arsenic transport through a Pleistocene aquifer

    PubMed Central

    van Geen, Alexander; Bostick, Benjamín C.; Trang, Pham Thi Kim; Lan, Vi Mai; Mai, Nguyen-Ngoc; Manh, Phu Dao; Viet, Pham Hung; Radloff, Kathleen; Aziz, Zahid; Mey, Jacob L.; Stahl, Mason O.; Harvey, Charles F.; Oates, Peter; Weinman, Beth; Stengel, Caroline; Frei, Felix; Kipfer, Rolf; Berg, Michael

    2013-01-01

    Groundwater drawn daily from shallow alluvial sands by millions of wells over large areas of South and Southeast Asia exposes an estimated population of over 100 million to toxic levels of arsenic (1). Holocene aquifers are the source of widespread arsenic poisoning across the region (2, 3). In contrast, Pleistocene sands deposited in this region more than ~12,000 years ago mostly do not host groundwater with high levels of arsenic. Pleistocene aquifers are increasingly used as a safe source of drinking water (4) and it is therefore important to understand under what conditions low levels of arsenic can be maintained. Here we reconstruct the initial phase of contamination of a Pleistocene aquifer near Hanoi, Vietnam. We demonstrate that changes in groundwater flow conditions and the redox state of the aquifer sands induced by groundwater pumping caused the lateral intrusion of arsenic contamination over 120 m from Holocene aquifer into a previously uncontaminated Pleistocene aquifer. We also find that arsenic adsorbs onto the aquifer sands and that there is a 16–20 fold retardation in the extent of the contamination relative to the reconstructed lateral movement of groundwater over the same period. Our findings suggest that arsenic contamination of Pleistocene aquifers in South and Southeast Asia as a consequence of increasing levels of groundwater pumping have been delayed by the retardation of arsenic transport. PMID:24025840

  8. Carbon cycle instability as a cause of the late Pleistocene ice age oscillations - Modeling the asymmetric response

    SciTech Connect

    Saltzman, B.; Maasch, K.A. )

    1988-06-01

    A dynamical model of the Pleistocene ice ages is presented, which incorporates many of the qualitative ideas advanced recently regarding the possible role of ocean circulation, chemistry, temperature, and productivity in regulating long-term atmospheric carbon dioxide variations. This model involves one additional term (and free parameter) beyond that included in a previous model (Saltzman and Sutera, 1987), providing the capacity for an asymmetric response. It is shown that many of the main features exhibited by the delta(O-18)-derived ice record and the Vostok core/delta(C-13)-derived carbon dioxide record in the late Pleistocene can be deduced as a free oscillatory solution of the model. 35 refs.

  9. Pleistocene leopards in the Iberian Peninsula: New evidence from palaeontological and archaeological contexts in the Mediterranean region

    NASA Astrophysics Data System (ADS)

    Sanchis, Alfred; Tormo, Carmen; Sauqué, Víctor; Sanchis, Vicent; Díaz, Rebeca; Ribera, Agustí; Villaverde, Valentín

    2015-09-01

    This study analyses the fossil record of leopards in the Iberian Peninsula. According to the systematic and morphometric features of new remains, identified mainly in Late Pleistocene palaeontological and archaeological sites of the Mediterranean region, they can be attributed to Panthera pardus Linnaeus 1758. The findings include the most complete leopard skeleton from the Iberian Peninsula and one of the most complete in Europe, found in a chasm (Avenc de Joan Guitón) south of Valencia. The new citations and published data are used to establish the leopard's distribution in the Iberian Peninsula, showing its maximum development during the Late Pleistocene. Some references suggest that the species survived for longer here (Lateglacial-Early Holocene) than in other parts of Europe. Finally, the contexts of appearance and origin of leopard remains are described and the processes of interaction with prehistoric human groups are assessed.

  10. Milankovitch insulation forcing and cyclic formation of large-scale glacial, fluvial, and eolian landforms in central Alaska

    NASA Technical Reports Server (NTRS)

    Beget, J. E.

    1993-01-01

    Continuous marine and ice-core proxy climate records indicate that the Earth's orbital geometry modulates long-term changes. Until recently, little direct evidence has been available to demonstrate correlations between Milankovitch cycles and large-scale terrestrial landforms produced during worldwide glaciations. In central Alaska large areas of loess and sand fill valleys and basins near major outwash streams. The streams themselves are bordered by sets of outwash terraces, and the terraces grade up valley into sets of moraines. The discovery of the Stampede tephra (approximately 175,000 yr ago) reworked within push moraines of the Lignite Creek glaciation suggests that this event correlates with the glaciation of marine isotope stage 6. A new occurrence of the Old Crow tephra (approximately 140,000 yr ago) on the surface of the oldest outwash terrace of the Tanana River, correlated with Delta glaciation, suggests this event also occurred at this time. The penultimate Healy glaciation apparently correlates with marine isotope stage 4, while radiocarbon dates indicate the latest Pleistocene moraines correlate with marine isotope stage 2. Recognition of the importance of orbital forcing to the cyclical formation of glacial landforms and landscapes can help in interpretations of remotely sensed glacial and proglacial land forms.

  11. Milankovitch insulation forcing and cyclic formation of large-scale glacial, fluvial, and eolian landforms in central Alaska

    NASA Astrophysics Data System (ADS)

    Beget, J. E.

    Continuous marine and ice-core proxy climate records indicate that the Earth's orbital geometry modulates long-term changes. Until recently, little direct evidence has been available to demonstrate correlations between Milankovitch cycles and large-scale terrestrial landforms produced during worldwide glaciations. In central Alaska large areas of loess and sand fill valleys and basins near major outwash streams. The streams themselves are bordered by sets of outwash terraces, and the terraces grade up valley into sets of moraines. The discovery of the Stampede tephra (approximately 175,000 yr ago) reworked within push moraines of the Lignite Creek glaciation suggests that this event correlates with the glaciation of marine isotope stage 6. A new occurrence of the Old Crow tephra (approximately 140,000 yr ago) on the surface of the oldest outwash terrace of the Tanana River, correlated with Delta glaciation, suggests this event also occurred at this time. The penultimate Healy glaciation apparently correlates with marine isotope stage 4, while radiocarbon dates indicate the latest Pleistocene moraines correlate with marine isotope stage 2. Recognition of the importance of orbital forcing to the cyclical formation of glacial landforms and landscapes can help in interpretations of remotely sensed glacial and proglacial land forms.

  12. The Taxonomic and Phylogenetic Affinities of Bunopithecus sericus, a Fossil Hylobatid from the Pleistocene of China

    PubMed Central

    Ortiz, Alejandra; Pilbrow, Varsha; Villamil, Catalina I.; Korsgaard, Jessica G.; Bailey, Shara E.; Harrison, Terry

    2015-01-01

    Fossil hylobatids are rare, but are known from late Miocene and Pleistocene sites throughout East Asia. The best-known fossil hylobatid from the Pleistocene of China is a left mandibular fragment with M2-3 (AMNH 18534), recovered from a pit deposit near the village of Yanjinggou in Wanzhou District, Chongqing Province. Matthew and Granger described this specimen in 1923 as a new genus and species, Bunopithecus sericus. Establishing the age of Bunopithecus has proved difficult because the Yanjinggou collection represents a mixed fauna of different ages, but it likely comes from early or middle Pleistocene deposits. Although the Bunopithecus specimen has featured prominently in discussions of hylobatid evolution and nomenclature, its systematic status has never been satisfactorily resolved. The present study reexamines the taxonomic and phylogenetic relationships of Bunopithecus by carrying out a detailed comparative morphometric study of its lower molars in relation to a large sample of modern hylobatids. Our results show that differences in M2 and M3 discriminate extant hylobatids fairly well, at least at the generic level, and that AMNH 18534 is not attributable to Hylobates, Nomascus or Symphalangus. Support for a close relationship between Bunopithecus and Hoolock is more equivocal. In most multivariate analyses, Bunopithecus presents a unique morphological pattern that falls outside the range of variation of any hylobatid taxon, although its distance from the cluster represented by extant hoolocks is relatively small. Our results support the generic distinction of Bunopithecus, which most likely represents an extinct crown hylobatid, and one that may possibly represent the sister taxon to Hoolock. PMID:26154175

  13. One Species, Three Pleistocene Evolutionary Histories: Phylogeography of the Italian Crested Newt, Triturus carnifex

    PubMed Central

    Canestrelli, Daniele; Salvi, Daniele; Maura, Michela; Bologna, Marco A.; Nascetti, Giuseppe

    2012-01-01

    Phylogeographic patterns of temperate species from the Mediterranean peninsulas have been investigated intensively. Nevertheless, as more phylogeographies become available, either unique patterns or new lines of concordance continue to emerge, providing new insights on the evolution of regional biotas. Here, we investigated the phylogeography and evolutionary history of the Italian crested newt, Triturus carnifex, through phylogenetic, molecular dating and population structure analyses of two mitochondrial gene fragments (ND2 and ND4; overall 1273 bp). We found three main mtDNA lineages having parapatric distribution and estimated divergence times between Late Pliocene and Early Pleistocene. One lineage (S) was widespread south of the northern Apennine chain and was further geographically structured into five sublineages, likely of Middle Pleistocene origin. The second lineage (C) was widespread throughout the Padano–Venetian plain and did not show a clear phylogeographic structure. The third lineage (N) was observed in only two populations located on western Croatia/Slovenia. Results of analysis of molecular variance suggested that partitioning populations according to the geographic distribution of these lineages and sublineages explains 76% of the observed genetic variation. The phylogeographic structure observed within T. carnifex and divergence time estimates among its lineages, suggest that responses to Pleistocene environmental changes in this single species have been as diverse as those found previously among several codistributed temperate species combined. Consistent with the landscape heterogeneity, physiographic features, and palaeogeographical evolution of its distribution range, these responses encompass multiple refugia along the Apennine chain, lowland refugia in large peri-coastal plains, and a ‘cryptic’ northern refugium. PMID:22848590

  14. Pleistocene survival of an archaic dwarf baleen whale (Mysticeti: Cetotheriidae)

    NASA Astrophysics Data System (ADS)

    Boessenecker, Robert W.

    2013-04-01

    Pliocene baleen whale assemblages are characterized by a mix of early records of extant mysticetes, extinct genera within modern families, and late surviving members of the extinct family Cetotheriidae. Although Pleistocene baleen whales are poorly known, thus far they include only fossils of extant genera, indicating Late Pliocene extinctions of numerous mysticetes alongside other marine mammals. Here a new fossil of the Late Neogene cetotheriid mysticete Herpetocetus is reported from the Lower to Middle Pleistocene Falor Formation of Northern California. This find demonstrates that at least one archaic mysticete survived well into the Quaternary Period, indicating a recent loss of a unique niche and a more complex pattern of Plio-Pleistocene faunal overturn for marine mammals than has been previously acknowledged. This discovery also lends indirect support to the hypothesis that the pygmy right whale ( Caperea marginata) is an extant cetotheriid, as it documents another cetotheriid nearly surviving to modern times.

  15. Dental evidence on the hominin dispersals during the Pleistocene.

    PubMed

    Martinón-Torres, M; Bermúdez de Castro, J M; Gómez-Robles, A; Arsuaga, J L; Carbonell, E; Lordkipanidze, D; Manzi, G; Margvelashvili, A

    2007-08-14

    A common assumption in the evolutionary scenario of the first Eurasian hominin populations is that they all had an African origin. This assumption also seems to apply for the Early and Middle Pleistocene populations, whose presence in Europe has been largely explained by a discontinuous flow of African emigrant waves. Only recently, some voices have speculated about the possibility of Asia being a center of speciation. However, no hard evidence has been presented to support this hypothesis. We present evidence from the most complete and up-to-date analysis of the hominin permanent dentition from Africa and Eurasia. The results show important morphological differences between the hominins found in both continents during the Pleistocene, suggesting that their evolutionary courses were relatively independent. We propose that the genetic impact of Asia in the colonization of Europe during the Early and Middle Pleistocene was stronger than that of Africa. PMID:17684093

  16. Dental evidence on the hominin dispersals during the Pleistocene

    PubMed Central

    Martinón-Torres, M.; Bermúdez de Castro, J. M.; Gómez-Robles, A.; Arsuaga, J. L.; Carbonell, E.; Lordkipanidze, D.; Manzi, G.; Margvelashvili, A.

    2007-01-01

    A common assumption in the evolutionary scenario of the first Eurasian hominin populations is that they all had an African origin. This assumption also seems to apply for the Early and Middle Pleistocene populations, whose presence in Europe has been largely explained by a discontinuous flow of African emigrant waves. Only recently, some voices have speculated about the possibility of Asia being a center of speciation. However, no hard evidence has been presented to support this hypothesis. We present evidence from the most complete and up-to-date analysis of the hominin permanent dentition from Africa and Eurasia. The results show important morphological differences between the hominins found in both continents during the Pleistocene, suggesting that their evolutionary courses were relatively independent. We propose that the genetic impact of Asia in the colonization of Europe during the Early and Middle Pleistocene was stronger than that of Africa. PMID:17684093

  17. PALEOECOLOGY. Abrupt warming events drove Late Pleistocene Holarctic megafaunal turnover.

    PubMed

    Cooper, Alan; Turney, Chris; Hughen, Konrad A; Brook, Barry W; McDonald, H Gregory; Bradshaw, Corey J A

    2015-08-01

    The mechanisms of Late Pleistocene megafauna extinctions remain fiercely contested, with human impact or climate change cited as principal drivers. We compared ancient DNA and radiocarbon data from 31 detailed time series of regional megafaunal extinctions and replacements over the past 56,000 years with standard and new combined records of Northern Hemisphere climate in the Late Pleistocene. Unexpectedly, rapid climate changes associated with interstadial warming events are strongly associated with the regional replacement or extinction of major genetic clades or species of megafauna. The presence of many cryptic biotic transitions before the Pleistocene/Holocene boundary revealed by ancient DNA confirms the importance of climate change in megafaunal population extinctions and suggests that metapopulation structures necessary to survive such repeated and rapid climatic shifts were susceptible to human impacts. PMID:26250679

  18. Applying modern measurements of Pleistocene loads to model lithospheric rheology

    NASA Astrophysics Data System (ADS)

    Beard, E. P.; Hoggan, J. R.; Lowry, A. R.

    2011-12-01

    The remnant shorelines of Pleistocene Lake Bonneville provide a unique opportunity for building a dataset from which to infer rheological properties of the lower crust and upper mantle. Multiple lakeshores developed over a period of around 30 kyr which record the lithosphere's isostatic response to a well-constrained load history. Bills et al. (1994) utilized a shoreline elevation dataset compiled by Currey (1982) in an attempt to model linear (Maxwell) viscosity as a function of depth beneath the basin. They estimated an effective elastic thickness (Te) for the basin of 20-25 km which differs significantly from the 5-15 km estimates derived from models of loading on geologic timescales (e.g., Lowry and Pérez-Gussinyé, 2011). We propose that the discrepancy in Te modeled by these two approaches may be resolved with dynamical modeling of a common rheology, using a more complete shoreline elevation dataset applied to a spherical Earth model. Where Currey's (1982) dataset was compiled largely from observations of depositional shoreline features, we are developing an algorithm for estimating elevation variations in erosional shorelines based on cross-correlation and stacking techniques similar to those used to automate picking of seismic phase arrival times. Application of this method to digital elevation models (DEMs) will increase the size and accuracy of the shoreline elevation dataset, enabling more robust modeling of the rheological properties driving isostatic response to unloading of Lake Bonneville. Our plan is to model these data and invert for a relatively small number of parameters describing depth- and temperature-dependent power-law rheology of the lower crust and upper mantle. These same parameters also will be used to model topographic and Moho response to estimates of regional mass variation on the longer loading timescales to test for inconsistencies. Bills, B.G., D.R. Currey, and G.A. Marshall, 1994, Viscosity estimates for the crust and upper

  19. Multivariate analysis of a small pleistocene catchment: tracing hydrological change

    NASA Astrophysics Data System (ADS)

    Boettcher, Steven; Merz, Christoph; Dannowski, Ralf

    2013-04-01

    The water budget of catchments in north-east Germany has decreased considerably over the last decades. Especially small catchments are affected due to the small amount of water stored within. Climate projections for the next decades hint to even more negative impacts on the water budgets of these catchments. Therefore, a new concept of water resource management for this region must be developed, including counter measures to extreme events such as low and high flow conditions. In order to manage a hydrological system one needs to know the typical behavior and be able to effectively counteract if needed. Within the network activity INKA-BB (Inovationsnetzwerk Klimaanpassung Brandenburg Berlin) dealing with possible adaptation measures to climate change in the Brandenburg and Berlin region, this study aims at identifying the typical hydraulic behavior of the Fredersdorfer Mühlenfließ catchment located north-east of Berlin as a basis for a sustainable water resource management concept. Established schemes are followed, including the application of numerical geochemical and hydraulic models as well as chemical graphical interpretation approaches. A common problem is the sparse spatial as well as temporal resolution of the data at hand. Here, these schemes are too inflexible and vague with respect to analyzing and parameterization of complex features used for identifying operative hydraulic-geochemical processes including intensive non-linear interactions. Hence, methods must be applied that are able to effectively utilize the limited information available. Ordination methods such as the Principle Component Analysis (PCA) or the non-linear Isometric Feature Mapping (Isomap) can provide such a tool. Ordination methods are used in order to derive a meaningful low-dimensional representation of a high-dimensional input data set. The approach is based on the hypothesis, that the amount of processes which explain the variance of the data is relative low although the

  20. Provenance changes of eolian dust at Lingtai section in the Chinese Loess Plateau since 7 Ma and its implication for desert development in East Asia

    NASA Astrophysics Data System (ADS)

    Isozaki, Y.; Tada, R.; Sun, Y.; Nagashima, K.; Zheng, H.; Toyoda, S.; Tani, A.

    2008-03-01

    It is suggested that the uplift of Himalaya-Tibetan Plateau enhanced interior aridity in East Asia and resulted in development of middle latitude gobi and sandy deserts and accumulation of the eolian sediments in the Chinese Loess Plateau. Therefore, estimation of the provenance for eolian sediments in the Chinese Loess Plateau is critical to reconstruct the environmental changes in East Asia and their relation to the Himalaya-Tibetan Plateau uplift. We recently developed a new provenance tracing method by using a combination of Electron Spin Resonance (ESR) signal intensity and Crystallinity Index (CI) of quartz, and demonstrated that fine fraction of the surface sediments from nine major deserts in East Asia could be distinguished one another on the ESR signal intensity versus CI diagram. Here, we measured ESR signal intensity and CI of quartz in fine fractions of samples covering the last 7 Ma obtained from Lingtai section in the central Chinese Loess Plateau, and compared the results with those of the surface samples from nine major deserts in East Asia. The results suggest that the provenance of fine fraction of the eolian sediment in Lingtai section changed at 4.3, 2.1, 1.4, 1.1, 0.8 and 0.4 Ma. During 7 to 4.3 Ma, the dust might be have been supplied from Precambrian to Paleozoic metamorphic and granitic rocks and granite exposed in the present central to eastern part of the Tian Shan Mountains. The contribution from the Taklimakan desert appeared at 4.3 Ma, increased drastically at 1.1 Ma, and persisted till 0.8 Ma, whereas the main source of detrital material to the Taklimakan desert might have changed from eastern part of the Kunlun and the Altyn Mountains to western part of the Kunlun and the Tian Shan Mountains. During 0.8 to 0.4 Ma, contribution from the Badain Juran desert gradually increased. Finally, contribution from the Tengger desert appeared from 0.4 to 0 Ma. Together with tectonic evidences from literatures, the provenance changes from 4.3 to 0

  1. Pleistocene Glaciations on the Northwestern Tibet

    NASA Astrophysics Data System (ADS)

    Kong, P.; Na, C.; Huang, F.; Fink, D.

    2003-12-01

    As a result of its immense size and high elevation, the Tibetan plateau plays a major role in affecting global climatic changes, and in particular the Asian monsoon system. Consequently knowledge of its glacial evolution during the Quaternary is an essential parameter. However, the chronology and extent of Quaternary glaciations on the Tibetan plateau is still in debate. Based on ice cores and other geological settings from the Tibetan plateau, it is inferred that temperatures during LGM were depressed by 6-9 ° C. Kuhle (1998) proposed an extensive ice sheet on the Tibetan plateau during LGM, whereas others believe that, because of extreme aridity, the ELA depression in the western and interior sections is less than 300m. Thus, given that a large fraction of the Tibetan plateau surface would be below the ELA during LGM times, the extent of the proposed ice sheet would presumably be limited. We determined in situ cosmogenic nuclides Be-10 and Al-26 in young volcano samples located in Ashikule basin, western Kunlun Shan. The eruption ages of the samples are 130+/-40ka, 340+/-10ka and 780+/-140ka, dated by the K-Ar method. The exposure ages of the samples are, however, 70+/-7ka, 150+/-7ka, 160+/-8ka, respectively. All samples analyzed possess lava flowing textures, which suggests no erosion since eruption. Field observations indicate no sediment nor vegetation on the samples. Thus, the age differences most likely reflect ice and snow cover on the samples. The current ELA in western Kunlun Shan is about 6000m, whereas the samples are located at an elevation of 4800m. This implies that ELA depression in the western part of the Tibetan plateau was most likely larger than 1200m during LGM. If the interior of Tibetan plateau has a similar ELA depression, a large part of Tibetan plateau surface would be above the ELA during LGM. Therefore, Pleistocene ice coverage on the Tibetan plateau may be more extensive than previously recognized. Kuhle (1998) Quaternary International

  2. Diagenesis in coastal carbonates related to Pleistocene sea level, Bermuda Platform

    SciTech Connect

    Vollbrecht, R.; Meischner, D.

    1996-01-01

    Pleistocene glacioeustatic sea-level oscillation on the stable Bermuda Platform is expressed in a succession of shallow-water carbonates interrupted by lowstand unconformities. In Bermuda, the maximum highstands of the last 400,000 yr ranged within 10 m around the present level. Coastal carbonates of various highstands are exposed along the present shoreline. These carbonates were penetrated by meteoric and marine pore waters during lowstands and highstands following on deposition. Two representative Pleistocene shoreline sections were studied to see whether early diagenesis has recorded these pore-water changes. The sediments of both sections show multiple generations of cement. Optical and scanning electron microscopy, cathodoluminescence microscopy, X-ray diffraction, microprobe studies and stable-isotope analyses were used to determine the diagenetic environments involved. Regardless of the degree of substrate cementation, freshwater alteration was mainly vadose whereas marine cementation was either phreatic or vadose or both. Early diagenetic oscillation is easier recorded in coastal successions than in lagoonal sediments, mainly because marine cementation is more active nearshore.Because the coastal environment is prone to wave destruction, the potential for preserving these diagenetic features is usually low. Data published on tectonically unstable areas suggest that early diagenetic oscillation may characterize stable coastlines.

  3. An Early Pleistocene hominin mandible from Atapuerca-TD6, Spain

    PubMed Central

    Carbonell, E.; Bermúdez de Castro, J. M.; Arsuaga, J. L.; Allue, E.; Bastir, M.; Benito, A.; Cáceres, I.; Canals, T.; Díez, J. C.; van der Made, J.; Mosquera, M.; Ollé, A.; Pérez-González, A.; Rodríguez, J.; Rodríguez, X. P.; Rosas, A.; Rosell, J.; Sala, R.; Vallverdú, J.; Vergés, J. M.

    2005-01-01

    We present a mandible recovered in 2003 from the Aurora Stratum of the TD6 level of the Gran Dolina site (Sierra de Atapuerca, northern Spain). The specimen, catalogued as ATD6-96, adds to the hominin sample recovered from this site in 1994–1996, and assigned to Homo antecessor. ATD6-96 is the left half of a gracile mandible belonging to a probably female adult individual with premolars and molars in place. This mandible shows a primitive structural pattern shared with all African and Asian Homo species. However, it is small and exhibits a remarkable gracility, a trait shared only with the Early and Middle Pleistocene Chinese hominins. Furthermore, none of the mandibular features considered apomorphic in the European Middle and Early Upper Pleistocene hominin lineage are present in ATD6-96. This evidence reinforces the taxonomic identity of H. antecessor and is consistent with the hypothesis of a close relationship between this species and Homo sapiens. PMID:15824320

  4. Nuclear DNA sequences from the Middle Pleistocene Sima de los Huesos hominins.

    PubMed

    Meyer, Matthias; Arsuaga, Juan-Luis; de Filippo, Cesare; Nagel, Sarah; Aximu-Petri, Ayinuer; Nickel, Birgit; Martínez, Ignacio; Gracia, Ana; Bermúdez de Castro, José María; Carbonell, Eudald; Viola, Bence; Kelso, Janet; Prüfer, Kay; Pääbo, Svante

    2016-03-24

    A unique assemblage of 28 hominin individuals, found in Sima de los Huesos in the Sierra de Atapuerca in Spain, has recently been dated to approximately 430,000 years ago. An interesting question is how these Middle Pleistocene hominins were related to those who lived in the Late Pleistocene epoch, in particular to Neanderthals in western Eurasia and to Denisovans, a sister group of Neanderthals so far known only from southern Siberia. While the Sima de los Huesos hominins share some derived morphological features with Neanderthals, the mitochondrial genome retrieved from one individual from Sima de los Huesos is more closely related to the mitochondrial DNA of Denisovans than to that of Neanderthals. However, since the mitochondrial DNA does not reveal the full picture of relationships among populations, we have investigated DNA preservation in several individuals found at Sima de los Huesos. Here we recover nuclear DNA sequences from two specimens, which show that the Sima de los Huesos hominins were related to Neanderthals rather than to Denisovans, indicating that the population divergence between Neanderthals and Denisovans predates 430,000 years ago. A mitochondrial DNA recovered from one of the specimens shares the previously described relationship to Denisovan mitochondrial DNAs, suggesting, among other possibilities, that the mitochondrial DNA gene pool of Neanderthals turned over later in their history. PMID:26976447

  5. Pleistocene cryostructures and landslide at Petit-Bost (southwestern France, 45°N)

    NASA Astrophysics Data System (ADS)

    Bertran, Pascal; Fabre, Richard

    2005-11-01

    Remnants of a Pleistocene landslide have been observed during field investigations of Quaternary alluvial formations of the Isle River at Petit-Bost, southwestern France. The main features of the landslide-induced deformation give a good indication of its size and depth. The surface of rupture is located in a 0.5 m thick, very plastic mottled clay at the top of an alluvial gravel. The clay is overlain by 1.7 m thick loamy colluvial deposits with a polygonal net of bleached wedges that testify to past permafrost conditions. The mechanical parameters used in stability calculations for the case of an infinite planar sliding surface, that fits well the geomorphological data, are given by triaxial tests. Stability calculation indicates that the slope is very stable at present and that rupture can only have occurred in fully unconsolidated and undrained conditions. This likely happened during permafrost degradation and subsequent thawing of ice-rich soil layers. Oedometric tests indicate post-sliding over-consolidation of the clay. With regards to the debate on permafrost distribution in France during the Pleistocene, this study gives support to a wide extent of permafrost, at least to the latitude 45°N southward, during the coldest periods. It also points out that frost-induced slope instability may have played a major, but still underestimated, role in many French regions north to this latitude.

  6. Ice shelves in the Pleistocene Arctic Ocean inferred from glaciogenic deep-sea bedforms.

    PubMed

    Polyak, L; Edwards, M H; Coakley, B J; Jakobsson, M

    2001-03-22

    It has been proposed that during Pleistocene glaciations, an ice cap of 1 kilometre or greater thickness covered the Arctic Ocean. This notion contrasts with the prevailing view that the Arctic Ocean was covered only by perennial sea ice with scattered icebergs. Detailed mapping of the ocean floor is the best means to resolve this issue. Although sea-floor imagery has been used to reconstruct the glacial history of the Antarctic shelf, little data have been collected in the Arctic Ocean because of operational constraints. The use of a geophysical mapping system during the submarine SCICEX expedition in 1999 provided the opportunity to perform such an investigation over a large portion of the Arctic Ocean. Here we analyse backscatter images and sub-bottom profiler records obtained during this expedition from depths as great as 1 kilometre. These records show multiple bedforms indicative of glacial scouring and moulding of sea floor, combined with large-scale erosion of submarine ridge crests. These distinct glaciogenic features demonstrate that immense, Antarctic-type ice shelves up to 1 kilometre thick and hundreds of kilometres long existed in the Arctic Ocean during Pleistocene glaciations. PMID:11260709

  7. Characterization of Fundamental Luminescence Properties of the Mars Soil Simulant JSC Mars-1 and Their Relevance to Absolute Dating of Martian Eolian Sediments

    NASA Astrophysics Data System (ADS)

    Lepper, Kenneth; McKeever, Stephen W. S.

    2000-04-01

    This report explores the potential for luminescence dating techniques to provide absolute age determinations of eolian sediments on the surface of Mars, including those incorporated in the martian polar ice caps. Fundamental thermally and optically stimulated luminescence properties of bulk samples of JSC Mars-1 soil simulant are reported and their relevance to the development of dating procedures is discussed. The radiation-induced luminescence signals (both thermoluminescence, TL, and optically stimulated luminescence, OSL) from JSC Mars-1 are found to have a wide dynamic dose-response range, with the luminescence increasing linearly to the highest doses used (936 Gy), following irradiation with 90Sr/ 90Y beta particles. The signals are also susceptible to solar resetting, with the OSL signals decreasing to <10% of their original levels within the first 20 min of exposure to sunlight. The TL signal also decays rapidly, being reduced to ˜15% within the first 20 min, but reaches a stable, nonzero level at long bleaching times. Neither the TL nor the OSL signals exhibit fading (i.e., loss of signal after irradiation before TL or OSL readout), nor do they exhibit significant sensitivity changes upon repeated irradiation and readout. These three properties (wide dynamic range, solar bleaching, and signal stability) form a stable base for future investigation of the material for luminescence dating and form a preliminary step toward development of dating protocols for terrestrial analogs of Mars surface materials. We conclude that luminescence dating, properly developed, holds the potential to be a valuable tool for absolute dating of martian eolian sediments

  8. Late Pleistocene age and archaeological context for the hominin calvaria from GvJm-22 (Lukenya Hill, Kenya)

    PubMed Central

    Tryon, Christian A.; Crevecoeur, Isabelle; Faith, J. Tyler; Ekshtain, Ravid; Nivens, Joelle; Patterson, David; Mbua, Emma N.; Spoor, Fred

    2015-01-01

    Kenya National Museums Lukenya Hill Hominid 1 (KNM-LH 1) is a Homo sapiens partial calvaria from site GvJm-22 at Lukenya Hill, Kenya, associated with Later Stone Age (LSA) archaeological deposits. KNM-LH 1 is securely dated to the Late Pleistocene, and samples a time and region important for understanding the origins of modern human diversity. A revised chronology based on 26 accelerator mass spectrometry radiocarbon dates on ostrich eggshells indicates an age range of 23,576–22,887 y B.P. for KNM-LH 1, confirming prior attribution to the Last Glacial Maximum. Additional dates extend the maximum age for archaeological deposits at GvJm-22 to >46,000 y B.P. (>46 kya). These dates are consistent with new analyses identifying both Middle Stone Age and LSA lithic technologies at the site, making GvJm-22 a rare eastern African record of major human behavioral shifts during the Late Pleistocene. Comparative morphometric analyses of the KNM-LH 1 cranium document the temporal and spatial complexity of early modern human morphological variability. Features of cranial shape distinguish KNM-LH 1 and other Middle and Late Pleistocene African fossils from crania of recent Africans and samples from Holocene LSA and European Upper Paleolithic sites. PMID:25730861

  9. Giant trees from the Middle Pleistocene of Northern Thailand

    NASA Astrophysics Data System (ADS)

    Philippe, Marc; Boonchai, Nareerat; Ferguson, David K.; Jia, Hui; Songtham, Wickanet

    2013-04-01

    Giant fossil trees from the Middle Pleistocene of Thailand are described. The longest log is measured at 72.2 m. Morphological analysis suggests that the original trees towered to more than 100 m, in a wet tropical forest. As contemporaneous archaic pebble tools were reported in the same area, the subtropical rainforest was no impenetrable ecological barrier to a population of Homo erectus.

  10. Biostratigraphy of marine Pliocene-Pleistocene deposits, Simi Valley, California

    SciTech Connect

    Groves, L.T.; Squires, R.L.

    1988-03-01

    Richly fossiliferous, marine deltaic deposits exposed in the northern Simi Valley, southern California, are important biostratigraphically because they straddle the Pliocene-Pleistocene boundary. These deposits consist of fine to coarse-grained sandstone with interbedded conglomerate. The best exposure is in Gilibrand Quarry, where 250 m are exposed in a continuous section with four main fossiliferous zones rich in mollusks. Most of these mollusks are complete and display growth series that represent a life assemblage with minimal postmortem transport. An erosional surface is present between the second and third fossiliferous beds in the quarry. Beds below the erosional surface contain mollusks indicative of Pliocene age. These mollusks are the pectinid Patinopecten healeyi and the epitoniid gastropod Opalia varicostata. Beds above the erosional surface contain a calcareous nannofossil assemblage that suggests a Pleistocene age. These species are Coccolithus pelagicus, Helicosphaera carteri, and Dictyococcites productus. (An absence of discoaster species and Emiliana huxleyi would place this assemblage in the early or medial Pleistocene.) The name lower Saugus Formation is assigned to all of these marine Pliocene-Pleistocene deposits because W.S. W. Kew in 124 originally named and mapped these strata as Saugus Formation. Confusion will be avoided by discontinuing usage of the names Fernando Formation, Pico Formation, and Sunshine Ranch Member of the Saugus Formation in this area for these strata. The lower Saugus Formation in the Simi Valley is faunally similar and time-correlate with the San Diego Formation in San Diego County.