Pleistocene Glacial Deposits Research Articles

Uranium-series isotopes as tracers of physical and chemical weathering in glacial sediments from Taylor Valley, Antarctica

The McMurdo Dry Valleys of Antarctica formed by extensive glacial erosion, yet currently exhibit hyperarid polar conditions canonically associated with limited chemical and physical weathering. Efficient chemical weathering occurs when moisture is available, and polythermal subglacial conditions may accommodate ongoing mechanical weathering and valley incision. Taylor Valley, one of the MDV, hosts several Pleistocene glacial drift deposits that record prior expansions of Taylor Glacier and sediment redistribution, if not sediment production. We present U-series isotopics of fine-grained sediments from these drifts to assess the timescales of physical weathering and subsequent chemical alteration. The isotopes 238U, 234U, and 230Th are sensitive to both chemical and physical fractionation processes in sedimentary systems, including the physical fractionation of daughter isotopes by energetic recoil following radioactive decay. By comparing U-series isotopic measurements with models of U-series response to chemical weathering and physical fractionation processes, we show that Pleistocene drift sediments record histories of significant chemical alteration. However, fine-grained sediments entrained in the basal ice of Taylor Glacier record only minor chemical alteration and U-series fractionation, indicating comparatively recent sediment comminution and active incision of upper Taylor Valley by Taylor Glacier over the Pleistocene. In addition, the results of this study emphasize the utility of U-series isotopes as tracers of chemical and physical weathering in sedimentary and pedogenic systems, with particular sensitivity to radionuclide implantation by α-recoil from high-U authigenic phases into lower-U detrital phases. This process has occurred extensively in >200 ka drifts but to a lesser degree in younger deposits. U-series α-recoil implantation is an important physicochemical process with chronometric implications in other hyperarid and saline sedimentary systems, including analogous Martian environments.

Influence of Pleistocene glacial deposits on the transport of agricultural nitrate in the river Wensum catchment, UK

Mitigating NO3− pollution requires an understanding of the hydrological processes controlling contaminant mobilisation and transport, particularly in agricultural catchments underlain by Pleistocene glacial deposits. Focusing on the Wensum catchment in East Anglia, UK, precipitation (n = 20), stream water (n = 50), field drainage (n = 22) and groundwater (n = 84) samples collected between February–March 2011 and April–September 2012 were variously analysed for water stable isotopes (δ2HH2O and δ18OH2O), the dual-isotopes of NO3− (δ15NNO3 and δ18ONO3), groundwater residence time indicators (CFCs and SF6) and hydrochemical parameters. The residence time indicators suggested a component of modern (post-1960) groundwater throughout the sequence of glacial deposits that corresponds with the penetration of agricultural NO3−. Denitrification and lower NO3− concentrations (<8 mg L−1) are observed in the glacial tills, compared with higher NO3− concentrations (<90 mg L−1) observed under more oxidising conditions in the glacial sands and gravels. Storm hydrograph separation for two storms in April and September 2012 using two- and three-component mixing models showed a faster response with field drainage (36–38 %) and baseflow (5–37 %) contributing to the total stream discharge in areas of clay loam soils over glacial tills. In these areas, the dual stable isotopes of NO3− (δ15NNO3 = +11.8 ‰ and δ18ONO3 = +7.1 ‰) indicated a denitrified source of nitrogen from field drainage and groundwater. In comparison, a dampened response and a higher percentage of baseflow (29–80 %) was observed in areas of sandy clay loam soils over glacial sands and gravels. In these areas, mean NO3− isotopic signatures (δ15NNO3 = +7.8 ‰ and δ18ONO3 = +5.0 ‰) indicated a source of nitrified NH4+. In conclusion, understanding hydrological processes in catchments underlain by variable glacial deposits can inform nutrient management plans and cultivation practices to reduce the risk of agricultural NO3− contamination.

Long-term glacial and fluvial system coupling in southern Greece and evidence for glaciation during Marine Isotope Stage 16

Pleistocene glacial activity was a major influence on runoff and sediment supply in many river systems across the Mediterranean. The geomorphological impacts of changes in sediment supply between glaciated headwater terrains and downstream depocentres spanning several glacial cycles are, however, poorly understood. By applying uranium-series and optically stimulated luminescence dating to fluvial and glacial sediments preserved on Mount Chelmos (2355 m a.s.l.) in southern Greece, we show how changes in the long-term coupling between glacial and fluvial systems are preserved within a major glaciofluvial outwash fan system that functioned during multiple cold stages. We also present evidence in the form of a cemented till unit, stratigraphically below younger Middle Pleistocene glacial deposits, yielding a U-series age close to the limit of the technique, indicating glaciation during Marine Isotope Stage (MIS) 16 - one of the most severe cold stages recorded in the Mediterranean. This is the first time such early glaciation has been directly recorded in Greece and the wider Balkans and is defined here as the Valvousian Stage based on glacial deposits on Mount Chelmos. Geomorphological and geochronological data point to the formation of a more extensive plateau ice field over Chelmos during MIS 12, another severe glacial period in the Balkans that corresponds with the Skamnellian Stage glaciation of Northern Greece. During this phase, very strong coupling of glacial and fluvial systems led to meltwater flood events transferring large volumes of sediment to lower valley zones culminating in the formation of an extensive glaciofluvial outwash fan complex and glaciofluvial terraces. A smaller plateau ice field during MIS 6 and localised valley glaciers between MIS 5d to 5c correlate with the Vlasian and early Tymphian Stage glaciations in Greece, respectively. The delivery of much less meltwater and sediment through a single valley during MIS 6 and MIS 5b to MIS 4 signalled the transition to progressively weaker glacial and fluvial system coupling. After MIS 4 the uncoupling of depositional zones from sediment sources in glaciated catchments led to fluvial incision of glaciofluvial outwash deposits in several valleys. Despite this incision, the glaciofluvial outwash fans preserve a record of glacial and fluvial system interactions during the Middle Pleistocene and early stages of the Late Pleistocene.

THE STRUCTURE AND GLACIAL RELIEF OF THE GORODOK UPLAND (NORTH-EASTERN BELARUS)&lt;a href="#FN1"&gt;&lt;sup&gt;1&lt;/sup&gt;&lt;/a&gt;

The article presents the results of the first comprehensive study of the structure and morphology of the glacial relief of the Gorodok Upland in the north-eastern Belarus. New data were obtained using lithological-stratigraphic, petrographic and morphometric methods. It has been established that the formation of the upland is predetermined by the uplift in the top of the Upper Devonian rocks. This uplift of the pre-Quaternary surface is overbuilt by Middle Pleistocene glacial deposits with glacial tectonics and erratic masses. The presence of an uplift led to the formation of the upland in the ice divide zone between the Chud and Ladoga Ice Streams during the last glaciation. As a result, during the maximum advance of the last ice sheet, a moraine plateau with kames began to form in the center of the upland. During the Lepel Stage (18–20 cal. ka BP, Edrovo in Russia, Gruda in Lithuania, and Poznan in Poland) the ice lobes of the Chud and Ladoga Ice Streams moved from the periphery to the moraine plateau. In total, there were six distinct oscillations of the glacial edge. As a result, chains of hummocky and ridge end-moraine landforms were formed. Later, during the Braslav Stage (16–18 cal. ka BP, Vepsa in Russia, Baltija in Lithuania and Pomeranian in Poland), hummocky end-moraine landforms were formed on the north-western and north-eastern slopes of the upland. At the same time, large runoff troughs crossing the upland from the north to the south were formed as a result of ice melting. The results of the study are important for the rational conduct of geological surveys and prospecting for mineral building materials within the ice-divide zones of the last glaciation.

New insights into the structural development and shortening of the southern Jasmund Glacitectonic Complex (Rügen, Germany) based on balanced cross sections

Late Pleistocene glacitectonism at the southern Scandinavian Ice Sheet margin caused folding and thrusting of Upper Cretaceous chalk layers and Pleistocene glacial deposits in parts of the southwestern Baltic Sea area in Europe. Beside Møns Klint (SE Denmark), the Jasmund Glacitectonic Complex (JGC) on Rügen Island (NE Germany) is a similar striking example of glacitectonic deformation creating large composite ridges. In spite of a long research history and new results from modern datasets, the structural development of the JGC is still poorly understood, especially the detailed evolution of the southern JGC and its relationship to the northern JGC remain enigmatic. In this contribution, we demonstrate how the understanding of the JGC benefits from the application of established structural geological methods comprehending the formation of fold-and-thrust belts. The methods include cross-section balancing of the eastern coast (southern JGC) and quantification of the amount of folding and faulting. The proposed geometric model shows the current fold-and-thrust stack of glacially deformed sedimentary strata ca. 5720 m in length evolved by shortening from the original length (11,230 m) by 5510 m (49.1%). We present a spatial and temporal development of fault-related folding with a transition from detachment folds through fault-propagation folds to fault-bend folds. Together with morphological information from a digital elevation model, the thrust faults mapped in the cliff section are mainly inclined towards the S to SW and imply that a local glacier push occurred from the south. These results highlight the complexity and individual architecture of the JGC when compared to other Pleistocene and modern glacitectonic complexes. Resolving its structural development provides new insight into the deformation history and shortening of this spectacular glacitectonic complex lying in the southwestern Baltic Sea region.

Mapping of spatial variations in Sr isotope signatures (87Sr/86Sr) in Poland — Implications of anthropogenic Sr contamination for archaeological provenance and migration research

This study presents first isoscape maps of strontium isotope signatures and their spatial variation in Poland, based on ~900 samples of rocks, sediments, surface water, and flora. This dataset is supplemented by 87Sr/86Sr ratios predicted for several carbonate rock units. High, radiogenic Sr isotope ratios (>0.72), related to the Pleistocene glacial deposits, are omnipresent throughout the country and are also found in the Sudetes and the Holy Cross Mountains, where igneous and clastic Palaeozoic rocks are widely exposed. The lowest Sr signatures (<0.71) occur predominantly in the Silesian-Małopolska and Lublin uplands and are related to exposures of Palaeozoic, Mesozoic, and Neogene carbonate rocks. The large variation of 87Sr/86Sr ratios in the environment across the country is chiefly driven by the diversity in the geological substrate, and locally, it is also influenced by anthropogenic contamination. Strontium isoscapes for the geological substrate and surface waters differ from each other, in terms of the range of 87Sr/86Sr values and their distributional pattern. The differences result primarily from mixing processes in the geosphere (weathering), hydrosphere, and biosphere that control Sr inputs from various natural sources present in the environment. On the other side, they are also created by anthropogenic contamination of surface water and presumably of soils. This situation has important implications for future archaeological provenance and migration studies, as isoscapes for surface water and vegetation cannot be directly used to estimate the local 87Sr/86Sr baselines for past human populations. Therefore, caution is required when modern Sr data of surface water and plants are used in archaeological research. 87Sr/86Sr values of the geological substrate, which may be affected by anthropogenic contamination to a lesser extent than water, soil, and vegetation, are favoured for the baseline estimation for historical times.

The multistage structural development of the Upper Weichselian Jasmund Glacitectonic Complex (Rügen, NE Germany)

Glacitectonic deformation in the Quaternary caused the tectonic framework of large-scale folds and displaced thrust sheets of Maastrichtian (Upper Cretaceous) chalk and Pleistocene glacial deposits in the southwestern Baltic Sea area. A wide spectrum of methods has been compiled to unravel the structural evolution of the Jasmund Glacitectonic Complex. The analyses of digital elevation models (DEM) suggest a division into two structural sub-complexes – a northern part with morphological ridges striking NW–SE and a southern part with SW–NE trending ridges. Geological cross sections from the eastern coast (southern sub-complex) were constructed and restored using the software Move™ and the complementary module 2D Kinematic Modelling™. The final geometric model of the southern sub-complex shows a small-scale fold-and-thrust belt. It includes three different orders of architectural surfaces (see PEDERSEN, 2014): erosional surfaces and the decollement (1st order), thrust faults (2nd order), and beds outlining hanging-wall anticlines as well as footwall synclines (3rd order). Thrust faults of the southern structural sub-complex are mainly inclined towards south, which indicates a local glacier push from the S/SE. The glacitectonic structures have a surface expression in form of sub-parallel ridges and elongated valleys in between. Geomorphological mapping and detailed landform analyses together with the structural investigations provide an insight into the chronology of sub-complexes formation. The northern part of the glacitectonic complex is suggested to have been formed before the southern one, considering the partly truncated northerly ridges and their superimposition by the southern sub-complex. Although there is a high number of scientific publications on the glacitectonic evolution of Jasmund, these presented models often lack a consistent theory for the development integrating all parts of the 100 km2 large complex. Therefore, the combination of all results leads to a more self-consistent genetic model for the entire Jasmund Glacitectonic Complex.

Latest Pleistocene glacial and climate history of the Wasatch Range, Utah

The geologic record of mountain glaciation is one of the most sensitive archives of terrestrial climate change during the late Quaternary Period. Pleistocene glacial deposits are exceptionally well preserved in the Great Basin of North America where they are found in close proximity to shoreline deposits of coeval paleo-lakes, representing a unique opportunity to investigate paleoclimate change using both hydrologic systems. Mountain glaciers advanced across much of the Wasatch Range, Utah during the same general time interval when Lake Bonneville expanded in the adjacent Bonneville Basin. Here we present a range-wide Latest Pleistocene glacial history for the Wasatch Range based on 22 new and 41 recalculated cosmogenic 10Be surface exposure ages, and reconstruct glaciers and climate for the Last Glacial Maximum (LGM) and Lateglacial periods. Our results indicate three distinct, range-wide phases of glaciation in the Wasatch including the Pinedale 1 (ca. 21–20 ka), Pinedale 2 (ca. 17.5 ka) and Pinedale 3 (ca. 15 ka). Our modeling results indicate that the Pinedale 1 advance, near the end of the global LGM, was primarily driven by decreased annual temperatures with little to no change in precipitation as compared to modern. Wasatch glaciers appear to have reoccupied near maximum positions after the end of the LGM during the Pinedale 2, responding to increased precipitation in concert with rising lake levels across Western North America, and then retreated from ice-distal positions near ca. 17.5 ka. Wasatch glaciers occupied recessional positions at approximately half their maximum lengths during Pinedale 3 until ca. 15 ka, followed by rapid (i.e. several millennia) deglaciation. Our glacial chronologies establish that Wasatch glaciers responded synchronously across the range to global and regional climate forcings during the Latest Pleistocene. The new Wasatch glacial chronology, combined with global glacial chronologies and paleoclimate proxies from Western North America, suggest glacier change was driven by a combination of long-term global temperature forcing as well as regional to local modifications in precipitation.

MINERAL COMPOSITION OF SOME LATGALE LAKE SEDIMENTS

Our research is focused on sedimentological conditions and postdepositional changes of recent fine grained lake sediments. We used bulk sediment mineralogical composition and grain size distribution as indicators to identify sediment source areas and possible changes during Holocene. We analysed fine grained (clayey) sediments from three Latgale lakes - Zeili, Pauguļi and Plusons, situated in Latgale upland. Lake sediments cover Late Pleistocene glacial deposits – loam and sandy loam. Bulk mineral composition of 6 sediment samples was determined by X-ray diffraction (XRD). Sediments contained typical minerals found in surrounding glacial sediments: rock-forming minerals as quartz, plagioclase, albite, enstatite, dolomite, calcite, and clay minerals - illite, kaolinite. To identify postdepositional changes in lake sediments of Holocene age clay minerals in clay fraction (&lt;2 mkm) should be analysed. Particularly illite, smectite mixed layered minerals - illite/smectite (I/Sm) and chlorite. Additionally, grain size distribution of studied lake sediments was analysed. Accordingly, our studied sediments are clays, silty clays and clayey silts with bimodal particle distribution, except two samples from Zeiļi and Plusons with unimodal distribution.

Human occupation of northern Europe in MIS 13: Happisburgh Site 1 (Norfolk, UK) and its European context

The timing, environmental setting and archaeological signatures of an early human presence in northern Europe have been longstanding themes of Palaeolithic research. In the space of 20 years, the earliest record of human occupation in Britain has been pushed back from 500 ka (Boxgrove) to 700 ka (Pakefield) and then to >800 ka (Happisburgh Site 3). Other sites also contribute to this record of human occupation; a second locality at Happisburgh, referred to as Site 1, attests to human presence at around 500 ka (MIS 13). This paper provides the first comprehensive account of research undertaken at Happisburgh Site 1 since 2000. The early human landscape and depositional environment was that of a river floodplain, where an active river channel, in which a grey sand was deposited, was abandoned, forming a floodplain lake, with marginal marsh/swamp environments, which was infilled with organic mud. This succession is sealed by Middle Pleistocene glacial deposits. An assemblage of 199 flint flakes, flake tools and cores was recovered from the grey sand and organic mud. The evidence from Happisburgh Site 1 is placed in the context of the wider British and European MIS 13 record. The growing evidence for a significant dispersal of humans into northern Europe around 500 ka raises critical questions concerning the environmental conditions under which this took place. We also consider the evolutionary and behavioural changes in human populations that might have enabled the more widespread and persistent period of human presence in northern Europe at this time.

Glacial history reflected by geochemically constrained stratigraphic sections in the Chaudière River drainage basin of the Canadian Appalachians

AbstractThe Chaudière River region in the Appalachian Mountains of eastern Canada is approximately 700 km north of the southernmost Pleistocene glacial deposits in New York and New Jersey. Detailed compositional analyses of glacial and non-glacial sediments from stratigraphic exposures and more than 40 boreholes drilled to bedrock provide a compositionally constrained record of glacial events, which include deposits of one Marine Oxygen Isotope Stage (MIS) 6 and two post-MIS 5 glaciations. The glacial and associated proglacial deposits rest on compositionally distinctive, preglacial saprolite that is preserved in deeper valleys. These observations constrain interpretations of the glacial/Pleistocene history of the eastern United States and Canada. The fact that there is no unequivocal evidence of pre-MIS 6 till in the Chaudière River region, while there are well-documented pre-MIS 6 glacial deposits south of there and in the American Midwest, also has major climatic implications. The Laurentide Ice Sheet and its ancestors must have been more robust in the west in the early Pleistocene and in the east most recently.

Holocene eolian modification of Pleistocene glacial outburst flood deposits on the Hanford Site, Washington

Petrographic and geostatistical analysis of linear dune forms on the Hanford Site, south-central Washington, have resulted in data supporting reinterpretation of depositional environments from eolian to primary glaciofluvial with post-depositional eolian modification. Miocene basalt flows of the Columbia River Basalt Group form the bedrock across the region overlain by Pliocene fluvial deposits from the preglacial Columbia River. Between ~21,000 and 12,000 YBP, glacial outburst floods scoured eastern Washington forming the Channeled Scablands. In the Pasco Basin, floodwaters were ponded behind flow restrictions resulting in deposition of coarse-grained gravel and sand sheets capped by fine-grained cyclic Touchet beds in higher elevation peripheral canyons. Outflow of ponded water mobilized the upper few meters of sediment forming a series of giant current ripples or megaripples. Modification of the surfaces of the megaripples under the influence of the Holocene wind regime has produced an eolian surficial signature. Subsurface excavations in these dune forms revealed the primary glaciofluvial provenance. Sedimentologic and petrographic evidence supports a general winnowing of fine-grained sediments from west to east under the current wind regime and includes both quartz and heavy minerals. These processes have resulted in the formation of an active dune field along the western bank of the Columbia River that overlies flood deposits locally.

Geomorphological Mapping and Spatial Analyses of an Upper Weichselian Glacitectonic Complex Based on LiDAR Data, Jasmund Peninsula (NE Rügen), Germany

Glacitectonic deformation in the Upper Weichselian led to the tectonic framework of large-scale folds and displaced thrust sheets of Maastrichtian (Upper Cretaceous) chalk and Pleistocene glacial deposits in the southwestern Baltic Sea region. They form surface expressions of sub-parallel ridges and elongated valleys in between and on the Jasmund Peninsula. Geomorphological mapping and detailed landform analyses give another insight into the arrangement and the formation history of these proglacial surface structures. Light detection and ranging (LiDAR) digital elevation models (DEM) analysis techniques were applied to a proglacial rather than a subglacial environment. Results suggest a division into a northern part with morphological ridges striking NW–SE and a southern part with SW–NE trending ridges. The observation of partly truncated northerly ridges and their superimposition by the southern sub-complex suggest that the northern part was generated earlier than the southern part. The applied spatial analyses tools were used to develop a new, self-consistent genetic model integrating all parts of the 100 km2 large Jasmund Glacitectonic Complex. Results suggest a more consistent terminology for the tectonic setting and a revised genetic model for Jasmund, including three evolutional stages that are characterized by different ice flow patterns.

Revised Quaternary glacial succession and post-LGM recession, southern Wind River Range, Wyoming, USA

We present here a more complete cosmogenic chronology of Pleistocene glacial deposits for the Wind River Range, Wyoming, USA. Fifty-one new and thirty-nine re-calculated 10Be and 26Al exposure ages from Sinks and North Fork canyons, Stough Basin, Cirque of the Towers and the Temple Lake valley allow us to more tightly constrain the timing and sequence of glacial alloformations in the southern portion of the range.Moraines, diamicts and bedrock exposures here have previously been correlated with as many as five Pleistocene and four Holocene glacial events. Exposure ages from Pleistocene alloformations associated with trunk glaciers in Sinks Canyon and North Fork Canyon generally confirm earlier age estimates. Cosmogenic radionuclide (CRN, 10Be and 26Al) ages from moraines and striated bedrock surfaces previously mapped as Pinedale correspond to MIS2, while boulder exposure ages from moraines mapped as Bull Lake correspond generally to MIS5-MIS6. Geomorphic data from a moraine previously mapped as Younger pre-Sacagawea Ridge appears to correspond most closely to the Sacagawea Ridge glacial episode (MIS-16), but the uncertainty of a single 10Be exposure age suggests the unit could be as young as MIS-10 or as old as MIS-18. Boulders from a diamict on Table Mountain previously reported as Older pre-Sacagawea Ridge yield two 10Be exposure ages that suggest the presence of Early Pleistocene glacial activity here possibly older than 1–2 Ma (>MIS-30).Bedrock exposure ages within Sinks Canyon suggest the Pinedale valley glacier had retreated from the floor of Sinks Canyon to above PopoAgie Falls by ca. 15.3 ka. Cirque glaciers in Stough Basin appear to have retreated behind their riegels by ca. 16 ka, which suggests the cirque glaciers were decoupling across their riegels from the valley glaciers below at this time, prior to their readvance to form Lateglacial moraines.New 10Be boulder exposure ages from moraines previously correlated to the Temple Lake and Alice Lake allostratigraphic units in the cirques of Stough Basin and Cirque of the Towers show general equivalence to the stadial event just prior to the onset of the Bølling interstadial (17.5–14.7 ka) and to the Intra-Allerød Cold Period-Younger Dryas stadial phase (13.9–11.7 ka), respectively. From this evidence, the Temple Lake Alloformation of the Wind River Mountains now should correspond to the INTIMATE GS-2.1a (Oldest Dryas) stadial event while the Alice Lake Alloformation should correspond to the INTIMATE GS-2 stadial (IACP-Younger Dryas). Thus, we consider that evidence no longer exists for early-to mid-Holocene glacial events in the southern Wind River Range.

Factors controlling the variability of organic matter in the top- and subsoil of a sandy Dystric Cambisol under beech forest

Organic carbon in subsoils amounts to 40–60% of the global soil carbon pool and is generally characterized by apparent turnover times of hundreds to thousands of years and an increasing spatial variability with depth. The objective of this study was to analyze the amounts and distribution of SOC and to elucidate the turnover and storage mechanisms throughout deep soil profiles of a sandy Dystric Cambisol on Pleistocene glacial deposits under beech forest in northern Germany. The soil was sampled within a grid design at three replicated profiles, each at 8 sampling depths (10, 35, 60, 85, 110, 135, 160, 185cm) and 8 horizontal sampling points. 192 samples were analyzed for bulk density, texture, pH, SOC, total N, 13C-SOC, oxalate- and dithionite-extractable Fe and Al, root bio- and necromass, and microbial biomass C. For each sampling depth, a multi-effect model analysis was performed to identify the parameters explaining SOC variability. While SOC in the topsoil is only related to pH and dithionite-extractable Al, SOC in the subsoil is always related to root bio- and necromass and to Fe oxides and/or silt content. The comparison of SOC within rooted and root-free subsoil samples showed an up to 10 times higher SOC content in the rooted soil samples in comparison to the root-free samples. While the SOC content in the root-free soil declined with increasing depth the rooted soil samples showed no stratification with depth but were characterized by a higher spatial variability of SOC. At the same time, SOC in rooted soil samples has the same δ13C values as in root-free samples, indicating a similar degree of microbial processing. Microbial biomass C (Cmic) was not different between rooted and root-free samples, resulting in much higher Cmic:SOC ratios in the root-free soil. Since rooted soil samples are characterized by significantly higher silt and oxalate-extractable Fe (Feo) contents, it appears that roots preferentially grow into these chemically and physically slightly more favorable zones. At the same time, these higher inputs were apparently better stabilized through sorption to silt and metal oxyhydroxides, thus leading to the longer-term SOC sequestration in these hot-spots enhancing the spatial variability of SOC in subsoils.

Reference section of Neogene-Quarternary deposits in the Uimon Basin (Gorny Altai)

An extraordinary-thick (400 m) section of the Neogene-Quaternary deposits is for the first time exposed by well No. 1 in the central Uimon Basin. The Miocene-Pliocene lacustrine Tueryk Formation is recognized at the base of the continuous section, verified by new paleontological data (ostracods, spores, and pollen). As assumed, overlaying deposits are represented by the Lower Pleistocene lacustrine-alluvial Beken Formation, Middle Pleistocene alluvial-proluvial Bashkaus Formation, undifferentiated Middle Pleistocene glacial, fluvioglacial, and alluvial deposits, and Upper Pleistocene lacustrine-glacial deposits. The data obtained from the core of well No. 1 undisputably demonstrate that the Uimon Basin had been developed prior the beginning of the Miocene Epoch, when it was characterized by accumulation of the lacustrine Tueryk Formation, incompletely exposed within the studied section. The presence of thick unexposed lower-Ohm interval of sedimentary filling of the basin suggests that the Uimon Basin was developed as early as the Paleogene. Therefore, the tectonic evolution and sedimentation history of the basin are assumed to have features similar to those of the Chuya and Kurai Basins of Gorny Altai.

Chronological investigations of Pleistocene interglacial, glacial and aeolian deposits from Schöningen (Germany) using post-IR IRSL dating and pollen analysis

Chronological investigations of Pleistocene interglacial, glacial and aeolian deposits from Schöningen (Germany) using post-IR IRSL dating and pollen analysis

Trace fossils from the Baltoscandian erratic boulders in SW Poland

Many well preserved trace fossils were found in erratic boulders and the fossils preserved in them, occurring in the Pleistocene glacial deposits of the Fore-Sudetic Block (Mokrzeszow Quarry, Świebodzice outcrop). They include burrows ( Arachnostega gastrochaenae , Balanoglossites isp., ? Balanoglossites isp., ? Chondrites isp., Diplocraterion isp., Phycodes isp., Planolites isp., ? Rosselia isp., Skolithos linearis , Thalassinoides isp., root traces) and borings ? Gastrochaenolites isp., Maeandropolydora isp., Oichnus isp., Osprioneides kampto , ? Palaeosabella isp., Talpina isp., Teredolites isp., Trypanites weisei , Trypanites isp., ? Trypanites isp., and an unidentified polychaete boring in corals. The boulders, Cambrian to Neogene (Miocene) in age, mainly came from Scandinavia and the Baltic region. The majority of the trace fossils come from the Ordovician Orthoceratite Limestone, which is exposed mainly in southern and central Sweden, western Russia and Estonia, and also in Norway (Oslo Region). The most interesting discovery in these deposits is the occurrence of Arachnostega gastrochaenae in the Ordovician trilobites (? Megistaspis sp. and Asaphus sp.), cephalopods and hyolithids. This is the first report of Arachnostega on a trilobite (? Megistaspis ) from Sweden. So far, this ichnotaxon was described on trilobites from Baltoscandia only from the St. Petersburg region (Russia). Arachnostega on a trilobite ( Asaphus ), a cephalopod and hyolithids is from Russia or Estonia. Another interesting ichnotaxon is Balanoglossites , which also was encountered in the erratic boulders from the Ordovician Orthoceratite Limestone of Sweden. So far, this ichnotaxon was known only from Russia (St. Petersburg region). Some rare borings (e.g., Osprioneides kampto , ? Palaeosabella isp.) also were found in glacial erratics of Silurian stromatoporoids, excellent outcrops of which are located in Gotland (Sweden) and Saaremaa (Estonia). In addition, stromatoporoid/coral, coral/coral and some new fossil associations are reported. The material studied probably was transported from the N, the NE, and less commonly from the NW.

Age of theLavaCreek supereruption and magma chamber assembly at Yellowstone based on40Ar/39Ar andU‐Pb dating of sanidine and zircon crystals

AbstractThe last supereruption from the Yellowstone Plateau formed Yellowstone caldera and ejected the &gt;1000 km3of rhyolite that composes the Lava Creek Tuff. Tephra from the Lava Creek eruption is a key Quaternary chronostratigraphic marker, in particular for dating the deposition of mid Pleistocene glacial and pluvial deposits in western North America. To resolve the timing of eruption and crystallization history for the Lava Creek magma, we performed (1)40Ar/39Ar dating of single sanidine crystals to delimit eruption age and (2) ion microprobe U‐Pb and trace‐element analyses of the crystal faces and interiors of single zircons to date the interval of zircon crystallization and characterize magmatic evolution. Sanidines from the two informal members composing Lava Creek Tuff yield a preferred40Ar/39Ar isochron date of 631.3 ± 4.3 ka. Crystal faces on zircons from both members yield a weighted mean206Pb/238U date of 626.5 ± 5.8 ka, and have trace element concentrations that vary with the eruptive stratigraphy. Zircon interiors yield a mean206Pb/238U date of 659.8 ± 5.5 ka, and reveal reverse and/or oscillatory zoning of trace element concentrations, with many crystals containing high U concentration cores that likely grew from highly evolved melt. The occurrence of distal Lava Creek tephra in stratigraphic sequences marking the Marine Isotope Stage 16–15 transition supports the apparent eruption age of ∼631 ka. The combined results reveal that Lava Creek zircons record episodic heating, renewed crystallization, and an overall up‐temperature evolution for Yellowstone's subvolcanic reservoir in the 103−104year interval before eruption.

Palaeoenvironmental Interpretation of Yedoma Silt (Ice Complex) Deposition as Cold‐Climate Loess, Duvanny Yar, Northeast Siberia

Uncertainty about the geological processes that deposited syngenetically frozen ice-rich silt (yedoma) across hundreds of thousands of square kilometres in central and northern Siberia fundamentally limits our understanding of the Pleistocene geology and palaeoecology of western Beringia, the sedimentary processes that led to sequestration of hundreds of Pg of carbon within permafrost and whether yedoma provides a globally significant record of ice-age atmospheric conditions or just regional floodplain activity. Here, we test the hypotheses of aeolian versus waterlain deposition of yedoma silt, elucidate the palaeoenvironmental conditions during deposition and develop a conceptual model of silt deposition to clarify understanding of yedoma formation in northern circumpolar regions during the Late Pleistocene. This is based on a field study in 2009 of the Russian stratotype of the ‘Yedoma Suite’, at Duvanny Yar, in the lower Kolyma River, northern Yakutia, supplemented by observations that we have collected there and at other sites in the Kolyma Lowland since the 1970s. We reconstruct a cold-climate loess region in northern Siberia that forms part of a vast Late Pleistocene permafrost zone extending from northwest Europe across northern Asia to northwest North America, and that was characterised by intense aeolian activity.