Late Pleistocene Age Research Articles

First record of coralline demosponges in the Pleistocene: implications for reef ecology

We report the first discovery of coralline sponges from Pleistocene reef limestones of Vanuatu. Sponges of the genus Acanthochaetetes were identified from two reef terraces of Middle and Late Pleistocene age. As these sponges document cryptic habitats in modern coral reefs, they may be index fossils of cryptic habitats in the Pleistocene as well, thereby providing clues on growth conditions in fossil reefs. The small size of the discovered specimens may be attributed to the transient nature of their cryptic habitats, either due to reef growth or the occurrence of an unusual event.

The Rockall Bank Mass Flow: Collapse of a moated contourite drift onlapping the eastern flank of Rockall Bank, west of Ireland

The Rockall Bank Mass Flow (RBMF) is a large, multi-phase submarine slope failure and mass flow complex. It is located in an area where the Feni Drift impinges upon the eastern flank of the Rockall Bank in the NE Atlantic. A 6100 km 2 region of slope failure scarps, extending over a wide water depth range and with individual scarps reaching up to 22 km long and 150 m high, lies upslope of a series of mass flow lobes that cover at least 18,000 km 2 of the base of slope and floor of the Rockall Trough. The downslope lobe complex has a negative topographic relief along much of its northern boundary, being inset below the level of the undisplaced contourite drift at the base of slope. The southern margin is topographically more subtle but is marked by the sharp termination of sediment waves outside the lobe. Within the lobe complex the southern margin of the largest lobe shows a positive relief along its southern margin. The initial failure is suggested to have occurred along coherent layer-parallel detachment surfaces at depths of up to 100 m and this promoted initial downslope block sliding which in turn transformed into debris flows which moved out into the basin. The remains of a deep erosional moat linked to the onlapping contourite complex bisects the region of failed slope, and post-failure thermohaline currents have continued to modify the mass flow in this area. Differential sedimentation and erosion associated with the moat may have promoted slope instability. Following the major failure phase, continuous readjustments of the slope occurred and resulted in small-volume turbidites found in shallow gravity cores collected on the lobes. The short term trigger for the failure remains uncertain but earthquake events associated with a deep-seated tectonic lineament to the north of the mass flow may have been important. A Late Pleistocene age for the slope failure is likely. The RBMF is unusual in that it records large-scale collapse of a contourite body that impinged on a sediment-undersupplied slope system. Unlike many other large slope failure complexes along the NE Atlantic margin, the RBMF occurs in a region where there was little overloading by glacial sediment.

A novel radiocarbon dating technique applied to an ice core from the Alps indicating late Pleistocene ages

Ice cores retrieved from high‐altitude glaciers are important archives of past climatic and atmospheric conditions in midlatitude and tropical regions. Because of the specific flow behavior of ice, their age‐depth relationship is nonlinear, preventing the application of common dating methods such as annual layer counting in the deepest and oldest part. Here we present a new approach and technique, allowing dating of any such ice core at arbitrary depth for the age range between ∼500 years B.P. and the late Pleistocene. This new, complementary dating tool has great potential for numerous ice core related paleoclimate studies since it allows improvement and extension of existing and future chronologies. Using small to ultrasmall sample size (100 μg > carbon content > 5 μg) accelerator mass spectrometry, we take advantage of the ice‐included, water‐insoluble organic carbon fraction of carbonaceous aerosols for radiocarbon (14C) dating. Analysis and dating of the bottom ice of the Colle Gnifetti glacier (Swiss‐Italian Alps, 45°55′50″N, 7°52′33″E, 4455 m asl) has been successful in a first application, and the results revealed the core to cover most of the Holocene at the least with indication for late Pleistocene ice present at the very bottom.

New stratigraphic markers in the late Pleistocene Palouse loess: novel fossil gastropods, absolute age constraints and non-aeolian facies

Four stratigraphic sections in the southern part of the Columbia Basin preserve a sequence of aeolian and non-aeolian sediments ranging in age from 9AE43 to >47AE0 14 C ka based on accelerator mass spectrometry radiocarbon dating of fossil molluscs, geochemistry of Cascade Mountain-sourced tephra and association with formally recognized pedostratigraphic units (the Washtucna and Old Maid Coulee soils). Study sections are interpreted as representing concurrent deposition of loess and distal Missoula Flood rhythmites in valleys tributary to main drainages backflooded during the Missoula Floods, and formation of carbonate and iron-rich soils. Sediments belong to the formally recognized L-1 and L-2 loess units established for the Palouse loess, which were deposited in the Columbia Basin subsequent to events of glacial outburst flooding. Sediments associated with the Mount Saint Helens set S and set C tephras in the study sections preserve a fauna of five species of gastropod mollusc which have not been reported previously from sediments of late Pleistocene age in the Palouse region. The fossils comprise two distinct faunules stratigraphically separated by the Mount Saint Helens So tephra. Accelerator mass spectrometry radiocarbon dating of the fossils collected above the tephra in two of the sections yielded ages of 12AE48 ± 0AE06 and 9AE43 ± 0AE05 14 C kyr. These ages suggest that independent determinations of the 13AE35 14 C kyr age of the So tephra in other areas where Missoula Flood sediments are preserved are probably accurate, and help to refine the age of the latest events in the most recent sequence of catastrophic glacial outburst flooding.

Differentiation of MIS 9 and MIS 11 in the continental record: vegetational, faunal, aminostratigraphic and sea-level evidence from coastal sites in Essex, UK

Multidisciplinary investigations of the vegetational, faunal and sea-level history inferred from the infills of buried channels on the coast of eastern Essex have a direct bearing on the differentiation of MIS 11 and MIS 9 in continental records. New data are presented from Cudmore Grove, an important site on Mersea Island that can be linked to the terrace sequence of the River Thames. The vegetational history has been reconstructed from a pollen sequence covering much of the interglacial represented. The temperate nature of the climate is apparent from a range of fossil groups, including plant remains, vertebrates (especially the rich herpetofauna), molluscs and beetles, which all have strong thermophilous components. The beetle data have been used to derive a Mutual Climatic Range reconstruction, suggesting that mean July temperatures were about 2°C warmer than modern values for southeast England, whereas mean January temperatures may have been slightly colder. The sea-level history has been reconstructed from the molluscs, ostracods and especially the diatoms, which indicate that the marine transgression occurred considerably earlier in the interglacial cycle than at the neighbouring Hoxnian site at Clacton. There are a number of palynological similarities between the sequence at Cudmore Grove and Clacton, especially the presence of Abies and the occurrence of Azolla filiculoides megaspores. Moreover, both sites have yielded Palaeolithic archaeology, indeed the latter is the type site of the Clactonian (flake-and-core) industry. However, the sites can be differentiated on the basis of mammalian biostratigraphy, new aminostratigraphic data, as well as the differences in the sea-level history. The combined evidence suggests that the infill of the channel at Cudmore Grove accumulated during MIS 9, whereas the deposits at Clacton formed during MIS 11. The infill of a much later channel, yielding non-marine molluscs and vertebrates including Hippopotamus, appears to have formed during the Ipswichian (MIS 5e). This evidence is compared with other important sites of late Middle Pleistocene age in Britain and elsewhere on the continent and the importance of a multidisciplinary approach is stressed.

Pleistocene raised marine deposits of the Cap Bon peninsula (N–E Tunisia): Records of sea-level highstands, climatic changes and coastal uplift

Morphostratigraphic and sedimentological studies were undertaken in the Cap Bon peninsula, north-eastern Tunisia. These studies have identified a series of middle to late Pleistocene–age marine deposits discontinuously cropping out on three raised platforms (Pf I, Pf II and Pf III). These stepped marine platforms (terraces) were related to the interplay between Pleistocene sea-level changes and progressive uplift movement during Quaternary period. We present here a description of facies organization and stratigraphic characteristics of the platform deposits, and their relation with eustatic and climatic variations. All the marine platforms unconformably overlie a Mio-Pliocene and Quaternary slope succession. The sedimentary sequences represented by mixed carbonate and siliciclastic bodies are related to the succession of highstand shorelines and contrasting climate conditions. The intercalated soils and calcretization occurred during episodes of relative sea-level fall. The oldest platforms (Pf I and Pf II), found at an elevation of about + 100 m and + 60 m respectively, have so far no equivalent in the northern, in the eastern or in the southern coasts of Tunisia. They are correspondingly attributed to MIS 11/13 and MIS 9/11. The youngest and lowest platform (Pf III) attains an altitude of + 40 m and shows three high-frequency cycles of sea-level rise and fall, probably associated with Marine Isotope Stage (MIS) 5e and MIS 7.

Blown sand movement at Kiskunhalas on the Danube-Tisza interfluve, Hungary

The largest blown-sand area of Hungary is located on the Danube-Tisza Interfluve. Here the most significant aeolian activity took place during the Pleistocene, however the aeolian transformation of the landscape occurred also in the Holocene and even in historical times. The aims of the study were (1) to reconstruct the relief at different historical periods; (2) to determine the periods of sand remobilisation during historical times; (3) to identify the changing of climatic conditions and possible types of human activities enabling aeolian activity and (4) to specify the spatial extension of sand movements. To reconstruct the spatial characteristic of sand and palaeosoil layers a 3Dmodel of the deposits at the archaeological site was created using total station measurements and Surfer 8.0 software. In order to determine the exact time of blown-sand movement optically stimulated luminescence (OSL) measurements (6) were applied. Based on the results, the lowermost sandy-loess layer had a late Pleistocene age, on which sequences of palaeosoils and blown-sand layers were formed during the Holocene. The spatial extension of the palaeosoils and sandy layers suggest that the relief has changed significantly over historical times. The former Pleistocene blowout depression has altered because of both the climatic conditions and the human impact on the environment. Blown-sand movements in historical times filled up the blowout depression. The sand sheets reshaped the original morphology and soil properties. Today the surface is more elevated and even, the site is covered by dry and slightly humic sandy soils.

IR-OSL studies of till and inter-till deposits from the Lithuanian Maritime Region

Glacial till and inter-till deposits exposed in the Lithuanian coastal region are evidence for multiple glacial advances during the Pleistocene. Stratigraphically, tills are the most important, prominent and well preserved deposits. However, despite the importance of these deposits, there is limited chronological control and it is widely debated whether they belong to one or another Pleistocene glaciation. The aim of the present study was to find features of the glacigenic tills, which allow us to temporally constrain these deposits, which are usually deemed to be undateable by luminescence methods. To achieve the goal, 15 samples from five different till beds and 12 samples from underlying sandy inter-till deposits from the same area were taken for analysis by feldspar-based IR-OSL technique. This paper presents the results, which suggest that the studied deposits, including glacial tills, are mostly of late Pleistocene age (MIS 5 and 4). We discuss analytical data obtained for these materials and implications for stratigraphic subdivision of the till-bearing deposits in the Lithuanian Maritime Region.

Taxonomy and palaeoecology of Ostracoda from the Middle to Late Pleistocene upper Karewa formation of Kashmir Valley, Northern India

Abstract. Ostracoda from a 25 m thick exposure in sediments of the upper Karewa formation indicate lacustrine conditions in the Kashmir intermontane basin during the Middle to Late Pleistocene. The Middle to Late Pleistocene age is established on the basis of lithostratigraphy and confirmed by two thermoluminescence age determinations at the top of the section. The ostracod assemblages show that the lake water remained fresh or, at most, was very slightly saline, throughout the period represented by the section. Nearly all ostracod taxa identified from the sediments are cold stenothermal forms and they include inhabitants of the littoral and profundal domain as well as running waters and springs. The Ostracoda present within the section indicate that during deposition of the upper Karewa sediments a large, but fairly shallow, well-oxygenated open-basin freshwater lake existed in that central part of the Kashmir Basin. Although the sequences suggest changes in water depth may have occurred, lacustrine conditions were otherwise largely unchanged over the period represented by the section, up until the demise of the lake during the early part of the Late Pleistocene.

Hydrologic Characterization of Desert Soils with Varying Degrees of Pedogenesis: 1. Field Experiments Evaluating Plant‐Relevant Soil Water Behavior

To assess the effect of pedogenesis on the soil moisture dynamics influencing the character and quality of ecological habitat, we conducted infiltration and redistribution experiments on three alluvial deposits in the Mojave National Preserve: (i) recently deposited active wash sediments, (ii) a soil of early Holocene age, and (iii) a highly developed soil of late Pleistocene age. At each, we ponded water in a 1‐m‐diameter infiltration ring for 2.3 h and monitored soil water content and matric pressure during and after infiltration, using probes and electrical resistivity imaging (ERI). Infiltration and downward flow rates were greater in younger material, favoring deep‐rooted species. Deep‐rooted species tend to colonize the margins of washes, where they are unaffected by sediment transport that inhibits colonization. The ERI results support important generalizations, for example that shallower than 0.5 m, infiltrated water persists longer in highly developed soil, favoring shallow‐rooted species. Soil moisture data for the two youngest soils suggested that saturation overshoot, which may have significant but unexplored hydroecologic and pedogenic effects, occurred at the horizontally advancing wetting front. Spatial heterogeneity of soil properties generally increased with pedogenic development. Evidence suggested that some early‐stage developmental processes may promote uniformity; the intermediate‐age soil appeared to have the least heterogeneity in terms of textural variation with depth, and also the least anisotropy. Lateral heterogeneity was pronounced in older soil, having a multitude of effects on the distribution and retention of soil water, and may facilitate certain water‐conserving strategies of plants over what would be possible in a laterally homogeneous soil.

Hydrologic Characterization of Desert Soils with Varying Degrees of Pedogenesis: 2. Inverse Modeling for Effective Properties

To understand their relation to pedogenic development, soil hydraulic properties in the Mojave Desert were investigated for three deposit types: (i) recently deposited sediments in an active wash, (ii) a soil of early Holocene age, and (iii) a highly developed soil of late Pleistocene age. Effective parameter values were estimated for a simplified model based on Richards' equation using a flow simulator (VS2D), an inverse algorithm (UCODE_2005), and matric pressure and water content data from three ponded infiltration experiments. The inverse problem framework was designed to account for the effects of subsurface lateral spreading of infiltrated water. Although none of the inverse problems converged on a unique, best‐fit parameter set, a minimum standard error of regression was reached for each deposit type. Parameter sets from the numerous inversions that reached the minimum error were used to develop probability distributions for each parameter and deposit type. Electrical resistance imaging obtained for two of the three infiltration experiments was used to independently test flow model performance. Simulations for the active wash and Holocene soil successfully depicted the lateral and vertical fluxes. Simulations of the more pedogenically developed Pleistocene soil did not adequately replicate the observed flow processes, which would require a more complex conceptual model to include smaller scale heterogeneities. The inverse‐modeling results, however, indicate that with increasing age, the steep slope of the soil water retention curve shifts toward more negative matric pressures. Assigning effective soil hydraulic properties based on soil age provides a promising framework for future development of regional‐scale models of soil moisture dynamics in arid environments for land‐management applications.

The Padul mammoth finds — On the southernmost record of Mammuthus primigenius in Europe and its southern spread during the Late Pleistocene

Fossil remains of at least four mature to old mature male individuals of Mammuthus primigenius have been discovered in a peat-bog of Late Pleistocene age, situated near to the town of Padul in the Granada Basin (Southern Spain). Radiocarbon dates indicate the presence of woolly mammoth in Southern Spain between 35.8 and 25.7 ka BP (40.4–30.6 cal ka BP), a time span corresponding with the later part of MIS 3. The Padul mammoths did not differ morphometrically from individuals of contemporaneous populations of other European regions, but represent the westernmost portion of an extended and continuous Holarctic belt of mammoth distribution. The area immediately northwest of the Pyrenees including a slender belt of dry land along the coast of the Bay of Biscay is considered the immigration route of M. primigenius into the Iberian Peninsula. The southernmost extent of Iberian woolly mammoths correlates with periods of particularly dry and cold climatic conditions, where they are documented in terrestrial and marine sediment sequences of the region. The southern expansion of M. primigenius during the Late Pleistocene extended to similar latitudes in Europe, Asia and North America, paralleling the distribution of suitable steppe- or tundra-steppe like environments. The woolly mammoth's southernmost advances were limited by the vegetational character of corresponding landscapes, by the configuration of marine shore lines and high mountain chains and by the extension of semideserts and deserts. Phases of mammoth dispersal into the Iberian and Italian Peninsulas during the later part of MIS 3 and early MIS 2 can be roughly correlated with the southern distribution of the species in the eastern Palaearctic. Along the eastern coast of the Pacific Ocean, the topography and glaciation of the Rocky Mountains range prevented a similar dispersal of woolly mammoths into western North America. The expansion of Late Pleistocene M. primigenius within the inner-continental areas of Eurasia and North America differs chronologically from those at the continental margins.

Thermodynamic indices of active invertase from the buried soil horizons of Late Pleistocene age in northern Yakutia

New data on the enzymatic activity of the tundra peaty gleyey soil and permafrost sediments of Late Pleistocene age (11–25 thousand years) are analyzed. It is shown that invertase, protease, phosphatase, catalase, and peroxidase are well conserved in yedoma and in buried soil horizons; urease is conserved to a smaller extent. On the basis of the investigation of thermodynamic characteristics of active invertase, such as temperature coefficient and activation energy, it was established that this enzyme is present in soil in the free and bound forms (immobilized on the surface of organomineral colloids). The degree of immobilization of active invertase in the buried soil horizons is high, which plays an important part in the long-term conservation of its molecules at subzero temperatures.

Twenty years of groundwater evolution in the Triassic sandstone aquifer of Lorraine: Impacts on baseline water quality

Abstract The Lorraine Triassic Sandstone Aquifer (LTSA), which has already been the subject of a chemical and radioisotopic study (1979), is used to investigate the impacts of 20 a of large scale pumping on baseline water quality. In parallel, new sampling of the aquifer (2001) provides new inorganic geochemical data (including trace elements) that allow improving the knowledge of baseline conditions and hydrochemical functioning of a major sandstone aquifer. The good correlation between 14 C activities, temperature and depth along the main flow line indicate regular downgradient trends and possible water stratification. Unreactive tracers, mainly stable isotope ratios 18 O and 2 H, as well as C isotopes are used to define a timescale for the aquifer, showing two groups of groundwater, namely of modern and Holocene age, and late Pleistocene age, with a mixing zone. Baseline quality is then represented by a wide range of concentrations, mainly the result of time-dependent water–rock interaction, as already observed elsewhere in Triassic sandstone aquifers. Some trace elements such as Li, Rb, Cs, which are not limited by solubility constraints, show linear trends. During saturated flow downgradient, the chemistry is also specifically characterised by a regular increase in Na and Cl (and locally SO 4 ) as a result of evaporite dissolution related to overlying or basement limits. The aquifer is mostly oxidising with a redox boundary marked by U decrease, some 40 km from outcrop. Groundwater abstraction since the 1970s has created a strong lowering (10–150 m) of the water table, especially from 1970 to 1980. Based on nine boreholes, previously sampled in 1979, a decreasing evolution in radiocarbon content of the TDIC, together with significant evolution of 18 O content, indicate that old groundwater has moved upgradient. The major difference in terms of baseline evolution is observed using Cl and Na concentration and, locally, SO 4 , indicating an increasing influence of water circulation involving overlying or basement formations, or of mixing with Permian waters. From the point of view of aquifer management, the perceptible NO 3 increase could provide information on the progress of any contamination under the aerobic conditions. In addition, the few key elements, indicators of disequilibrium, related to overlying or deep waters, should be included in regular monitoring programmes.

Durations of soil formation and soil development indices in a Holocene Mediterranean floodplain

Holocene and late Pleistocene alluvial sequences of the mid-Medjerda floodplain (Northern Tunisia) reveal three types of soils with gradual transitions: Fluvisols (Calcaric), Cambisols (Calcaric) and Calcic Luvisols (Chromic). Stratigraphic cross-correlations, palaeomagnetic secular variation, and 14C and IRSL dating enable detailed information about ages and durations of soil formation in the floodplain. Weakly developed Fluvisols (Calcaric) commonly reveal late Holocene ages with soil formation durations lasting between 100 and 300 years. Hence, Holocene soil formation is detectable in the exposures from durations of around 100 years onwards. Cambisols show predominantly mid-Holocene ages. The durations of soil formation are between 800 and 5000 years. Calcic Luvisols (Chromic) feature late Pleistocene ages, with durations of soil formation between 10,000 and 40,000 years. Profile Development Indices were computed from simple field parameters like soil structure, soil colour, horizon thickness and leaching features. The derived development indices show good correlation ( R 2 = 0.804) with the calculated durations of soil formation. Field parameters are well suited for a quantitative development index of Holocene soil formation, even if very weak developed soils are predominant. The study shows that maturity stages of Holocene alluvial soils in a homogeneous Mediterranean environment are predominantly driven by soil formation duration.

Direct dating indicates a Mid‐Holocene Age for archaic rock engravings in arid Central Australia

AbstractArchaic rock engravings are found widely across the arid interior of Australia and are thought to represent an early pan‐continental tradition. A late Pleistocene age is assumed because of extensive weathering, but attempts to test this by direct dating have been unsuccessful. We use AMS 14C dating of calcium oxalate skins covering archaic engravings at two rock shelter sites in Central Australia (Wanga East and Puritjarra), constrained by 14C dates of charcoal in sedimentary layers beneath the same engraved slabs, to show this rock art is mid‐Holocene in age. Despite a limited range of simple geometric designs and uniformity across the arid interior, this corpus of rock art is not associated with the initial peopling of the Australian desert, but is a later development reflecting the dynamics of established desert societies. © 2009 Wiley Periodicals, Inc.

SPECIES OF THE ACRITARCH GENUS PALAEOSTOMOCYSTIS: POTENTIAL INDICATORS OF NERITIC SUBPOLAR TO POLAR ENVIRONMENTS IN ANTARCTICA DURING THE CENOZOIC

A palynological analysis was undertaken on 16 samples from seven piston cores collected along two offshore transects near Seymour and James Ross Islands. Diverse assemblages of reworked marine microplankton (including organic-walled dinoflagellate cysts, cymatiosphaerids, leiospheres, and other acritarchs) and terrestrial palynomorphs (including pollen and spores) were recovered from glacio-marine sediments of late Pleistocene age. Among the reworked taxa, four species belonging to the acritarch genus Palaeostomocystis Deflandre 1937 comprise up to 17% of all palynomorphs. Highest abundances were recorded from sites close to the coast. The potential use of Palaeostomocystis as a proxy for early ice-sheet development on the Antarctic margins is evaluated in light of earlier studies. This evaluation suggests that the high abundances of Palaeostomocystis on the Antarctic Peninsula reflect neritic-type environments (shallow waters, bay-like areas, or marginal seas) and sub-polar to polar conditions as exist in the Bering Sea, Greenland margins, and other subarctic to arctic areas today.

Geoarchaeological Investigations in the Upper North Fork River Valley in Southern Missouri

The first geoarchaeological investigations in the upper North Fork River valley in 1993 and 1994 revealed the presence of multiple terraces and associated sediment assemblages that contain archaeological deposits. Most of the field work, however, focused on the two lowest and youngest sediment assemblages. These include an aggrading flood plain (F-1) and a low terrace (T-1). The flood plain sediment assemblage is late Holocene in age, probably less than 2,000 years old. Although not common, Late Woodland and Mississippian artifacts are deeply buried in this unit. The T-1 appears to be late Pleistocene in age. Artifacts dating from Late Paleoindian to Mississippian times are very common on T-1 landforms, but they appear to be restricted to the upper 1 m of the sediment assemblage. Alluvial deposits similar to the F-1 sediment assemblage appear to be widespread in the Ozarks, whereas chronological and sedimentological discrepancies exist between the T-1 sediment assemblage in the North Fork River valley and those located elsewhere in the Ozarks, especially north of the Ozarks Divide.

Early Diagenesis of Carbonates on a Cool-Water Carbonate Shelf, Southern Australia

Abstract The southern Australian continental margin is an immense cool-water carbonate factory. The high-energy open shelf is blanketed by heterozoan carbonates of both Holocene and late Pleistocene age. Three distinct grain types have been identified and radiocarbon dated. These include (1) relict grains, highly abraded iron-stained intraclasts formed during the intermediate sea-level stands of Marine Isotope Stages 3 and 4, (2) stranded grains, gray and buff-colored abraded biofragments and intraclasts marooned during the sea-level rise associated with Marine Isotope Stage 2, and (3) Holocene grains, unaltered biofragments formed during Marine Isotope Stage 1. Optical, mineralogical, and chemical characterization of grains of each age has revealed pathways of early diagenesis in this realm. Both calcitic and aragonite biogenic grains undergo dissolution. While dissolution of calcitic components is minor and incomplete (relict sediments are predominantly Mg calcite), aragonitic skeletons undergo significant dissolution within ~ 30,000 years. In contrast to early dissolution of aragonite, micritic calcite cement, with ~ 12 mol% MgCO3, is a significant diagenetic phase in these sediments, infilling many stranded and most relict skeletons. Similar cement precipitates between grains, forming small numbers of cemented grain aggregates in most samples. Microprobe and ICP-MS analysis demonstrates Fe oxides, Mn oxides, and associated clay minerals discolor stranded and relict grains, by coating grain surfaces and infesting micropores. Such coatings begin to form on Holocene grains during or soon after formation. The oxides scavenge trace elements including V, Ti, Cr, and REE, altering the elemental compositions of biogenic carbonate.

Climatic implications of latest Pleistocene and earliest Holocene mammalian sympatries in eastern Washington state, USA

For more than fifty years it has been known that mammalian faunas of late-Pleistocene age are taxonomically unique and lack modern analogs. It has long been thought that nonanalog mammalian faunas are limited in North America to areas east of the Rocky Mountains and that late-Pleistocene mammalian faunas in the west were modern in taxonomic composition. A late-Pleistocene fauna from Marmes Rockshelter in southeastern Washington State has no modern analog and defines an area of maximum sympatry that indicates significantly cooler summers than are found in the area today. An earliest Holocene fauna from Marmes Rockshelter defines an area of maximum sympatry, including the site area, but contains a single tentatively identified taxon that may indicate slightly cooler than modern summers.