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Under glacial climates, continental ice sheets such as, e.g., the Greenland Ice Sheet, extended onto the continental shelves and often carved out deep cross‐shelf troughs. The sedimentary infill of such troughs commonly is a product of the complex interactions between the ice sheets, largely driving sediment input into the ocean, and the surrounding water masses. Off West Greenland, research has focused on the Disko and Uummannaq troughs, leaving the northerly adjacent Upernavik trough relatively understudied. Hence, neither the chronology of deglaciation nor the details of its postglacial infill are sufficiently well understood. Here, we combine computed tomography image‐derived information with geochemical and granulometric data from four sediment cores recovered from the Upernavik trough that point to (i) deglaciation of the mid‐shelf probably around 13.4 cal. ka BP that was most likely driven by a northward advection of warmer Atlantic waters during the Bølling–Allerød, (ii) the presence of widespread mass wasting around 8 cal. ka BP on the inner shelf and (iii) the complex interplay between various modes of sediment input, transport and deposition under hemipelagic sedimentation afterwards. While this interplay complicates provenance studies, we identify two major sediment delivery mechanisms that control transport and deposition from four sediment source areas. Through the Early Holocene the relative contributions of sediments from the various sources changed from a predominantly local origin to more southerly sources, mainly driven by decreasing input from the local sources. The integration of relative sediment source contributions with varying sedimentation rates challenges previous studies postulating intensified sediment delivery from the south through a greater influence of the West Greenland Current and highlights the need for the integration of sediment input and transport mechanisms into provenance studies in the area. [ABSTRACT FROM AUTHOR]

Abstract Millennial scale events marked by the contribution of detrital sand are recorded in North Atlantic sediments during the Last Glacial Maximum (LGM), between Heinrich events (HE) 1 and 2, and left their imprint on Laurentian Fan (LF – 43°N) sediments off eastern Canada. The LF counterpart of the well-known detrital events consist of glacial red-brick sediments resulting from subglacial flows separated by olive-grey sediments appears at ∼21.4–19.9 and ∼19.5–18.65 cal kyr BP. High-resolution analyses of diatom assemblages and lithic grains coupled with planktonic oxygen isotopic records reveal that while the red sediment is almost barren of diatoms, foraminifera and lithics (>150 μm), they are abundant in the olive-grey sediment. Diatom assemblages reveal three phases during these events: (1) initial relatively warm/temperate conditions followed by (2) very cold surface water and drifting ice, and (3) a final phase characterized by relatively warmer waters and the appearance of detrital carbonate. Although these events possibly reflect the variability specific to the slope water region, they are likely the response to Atlantic Meridional Overturning Circulation perturbations and ice-sheet instability. Through a chain of mechanisms, meltwater inputs into the North Atlantic led ultimately to an increased volume of tropical waters and part of the heat stored in the subsurface was flushed by a brief convective episode that was not sustained, accounting for the return of cold conditions after the events. The sequence of mechanisms deduced from the paleo data here and elsewhere is consistent with previous modeling results. These data suggest that the detrital events between Heinrich event 1 and 2 may be synchronous across the North Atlantic, and that the LGM was probably not a time of prolonged steady state in the climate system. Highlights • Detailed description oceanographic changes of some LGM detrital events. • Diatom records evidence the presence of relatively warmer waters at the beginning and by the end of the events. • Possible links between detrital events, ice-sheets instability and AMOC perturbations. [ABSTRACT FROM AUTHOR]

Abstract The modern southern Mariana Trench is characterized by oligotrophic surface waters, resulting in low primary productivity and well-oxygenated bottom waters. This study investigates changes in the redox conditions of bottom waters in the southern Mariana Trench during the Last Glacial Maximum (LGM) and their potential causes. We measured major, trace, and rare earth elements (REE) in three gravity cores (GC03, GC04, and GC05) and one box core (BC11) retrieved from the southern Challenger Deep at water depths from 5289 to 7118 m. The upper sediment layers of both GC05 and BC11 are dominated by valve fragments of the giant diatom Ethmodiscus rex , forming laminated diatom mats (LDMs). 14C-AMS dates of bulk organic matter show that the LDMs accumulated between 18.4 and 21.8 kyr B.P., corresponding to the LGM. Modest enrichments of U and Mo along with weak or absent Ce anomalies in the LDM point to suboxic conditions during the LGM. In contrast, non-LDM samples exhibit little to no enrichment of redox-sensitive elements as well as negative Ce anomalies, indicating deposition under oxic bottom-water conditions. The Ce anomalies are considered valid proxies for bottom-water redox conditions because REE signatures were acquired in the early diagenetic environment, as indicated by strong P-REE correlations and middle-REE enrichment associated with early diagenetic cycling of Fe-Mn oxyhydroxides in the sediment column followed by capture of the REE signal by biogenic and/or authigenic apatite. We postulate that the more reducing bottom-water conditions during the LGM were linked to increased primary productivity induced by enhanced Asian dust input. As shown in earlier studies, the increased primary productivity associated with Ethmodiscus rex blooms in the eastern Philippine Sea played a significant role in capturing atmospheric CO 2 during the LGM. Consequently, the magnitude of atmospheric CO 2 sequestration by giant diatom blooms during the LGM may have been greater than previously envisaged. Highlights • Elemental and radiocarbon analysis of southern Mariana Trench (SMT) sediments since 30 ka. • Shift to more reducing (suboxic) deep waters during the Last Glacial Maximum (LGM). • Blooms of giant diatom Ethmodiscus rex formed laminated diatom mats (LDMs) during LGM. • Redox changes were due to increased primary productivity induced by enhanced Asian dust inputs. • Biogenic and authigenic apatite are the main carriers of rare earth elements (REEs) in SMT sediments. [ABSTRACT FROM AUTHOR]

Sea-surface conditions in northeastern Fram Strait since the last glacial maximum (LGM) were reconstructed from cores MSM5/5-712-2 and PS2863/1–2 based on palynological assemblages, ecological preferences of dinocysts and application of the modern analog technique. Dinocyst in LGM sediments are sparse, but their assemblages reflect mild summer conditions. Given the regional context and evidence from other tracers, the dinocyst assemblages of the LGM could relate to regional fluxes of dinocysts during exceptional mild summers. From 19 to 14.7 ka, dinocyst data suggest very cold conditions with extensive sea-ice cover, while abundant reworked palynomorphs indicate intense glacial erosion. An abrupt transition at 14.7–14.5 ka was marked by a peak in summer temperatures coinciding with a rapidly deposited sediment layer related to a regional meltwater plume event in western Svalbard. From 14.7 to 12.6 ka, large seasonal temperature contrasts with mild summers and cold winters together with low salinity indicate continuous melting of the Svalbard Barents Sea ice sheet fostered by warm climate. At 12.6 ka, the regional onset of the Younger Dryas was marked by cooling and increased salinity. On a regional scale, the 12.6–12 ka interval corresponds to an important transition involving enhanced circulation of Arctic waters around Svalbard and establishment of coastal fronts along its northern and western margins. Modern-like oceanic conditions with relatively high salinity and low seasonal temperature contrast developed at about 7.6 ka. Since then, a slight cooling is observed, especially in winter. This study offers a comprehensive picture of the deglacial phases in eastern Fram Strait with unique data on the sea-surface salinity, which controls surface water stratification and plays an important role in ocean circulation. [ABSTRACT FROM AUTHOR]

Little work has been completed on paleo-ice-sheet flow indicators of the Laurentide Ice Sheet, west of the Keewatin Ice Divide. Field mapping, sampling and analysis of glaciogenic sediment (∼500 sample sites) in a ∼33,000 km 2 region near the East Arm of Great Slave Lake in northwestern Canada, provided a rare opportunity to improve understanding of sediment erosion and transport patterns. Glacially-eroded bedrock and sedimentary landforms record east to west flow with NW and SW divergence, mapped within a portion of the Great Slave Lake flow tract. Transported till reflects a similar divergent flow pattern based on dispersal geometries for multiple indicators (e.g., heavy minerals and lithic fragments), which are aligned with the dominant and latest ice flow direction. Glaciofluvial erosion (e.g., s-forms and till removal), transport, and deposition (mainly as esker sediment) are set within 0.3–3 km wide meltwater erosional corridors, spaced regularly at 10–15 km intervals. Transport paths and distances are comparable in till and esker sediment, however, distances appear to be greater (∼5–25 km) in some esker constituents and indicator minerals are typically more concentrated in esker sediment than in till. Corridors form a divergent array identical to the pattern of ice-flow features. The congruence of ice and meltwater flow features is interpreted to be a response to a similar ice sheet gradient, and close timing of events (late dominant glacial ice flow and meltwater flow). The similarity in glacial and glaciofluvial flow patterns has important ramifications for event reconstruction and for exploration geologists utilizing mineral and geochemical tracing methods in this region, and possibly other parts of northern Canada. The correspondence between East Arm dispersal patterns, landforms and flow indicators supports interpretation of a simple and predictable single flow divergence model. This is in contrast to previous, multi-flow models, in which fan-shaped geometries are often reported to result from multiple transport events, compared to single-flow divergence. The observed widespread effects of glaciofluvial processes (e.g., erosional corridors) indicate a need to update existing terrain process models. [ABSTRACT FROM AUTHOR]

Atmospheric CO 2 and global climate are closely coupled. Since 800 ka CO 2 concentrations have been up to 50% higher during interglacial compared to glacial periods. Because of its dependence on temperature, humidity, and erosion rates, chemical weathering of exposed silicate minerals was suggested to have dampened these cyclic variations of atmospheric composition. Cooler and drier conditions and lower non-glacial erosion rates suppressed in situ chemical weathering rates during glacial periods. However, using systematic variations in major element geochemistry, Sr–Nd isotopes and clay mineral records from Ocean Drilling Program Sites 1143 and 1144 in the South China Sea spanning the last 1.1 Ma, we show that sediment deposited during glacial periods was more weathered than sediment delivered during interglacials. We attribute this to subaerial exposure and weathering of unconsolidated shelf sediments during glacial sealevel lowstands. Our estimates suggest that enhanced silicate weathering of tropical shelf sediments exposed during glacial lowstands can account for ∼9% of the carbon dioxide removed from the atmosphere during the glacial and thus represent a significant part of the observed glacial–interglacial variation of ∼80 ppmv. As a result, if similar magnitudes can be identified in other tropical shelf-slope systems, the effects of increased sediment exposure and subsequent silicate weathering during lowstands could have potentially enhanced the drawdown of atmospheric CO 2 during cold stages of the Quaternary. This in turn would have caused an intensification of glacial cycles. [ABSTRACT FROM AUTHOR]

High-resolution lithic and sea surface climate records are used to portray the progression of North Atlantic climate, hydrography, and Greenland Ice Sheet (GIS) activity through the peak of Marine Isotope Stage (MIS) 5e into the last glacial inception. We use Eirik Drift sediment core MD03-2664 (57°26.34′N, 48°36.35′W), recovered south of Greenland, strategically located to monitor fluctuations in GIS extent and iceberg calving events. Our results show that a significant amount of ice-rafted debris (IRD) was present during the early MIS 5e, until gradually tapering off by 122 kyr BP due to a diminishing GIS. Sea surface temperatures (SSTs) in the northern subpolar gyre reached peak values early in MIS 5e coinciding with peak insolation. Regional cooling leading to the demise of the last interglacial started prior to the end of the MIS 5e benthic δ 18 O plateau, at approximately 119 kyr BP, as summer insolation waned. This gradual cooling trend is interrupted by an abrupt and brief cooling episode at ∼117 kyr BP. Increased IRD abundance during the 117 kyr BP cooling event suggests that regional ice sheet growth occurred prior to the end of the MIS 5e benthic δ 18 O plateau, and the major glacial inception. SSTs south of Greenland followed a two-step cooling during the glacial inception similar to the pattern observed across much of the North Atlantic and Europe. Benthic δ 18 O increases in parallel, suggesting that this two-step cooling is linked to a two-phased intensification of Northern Hemisphere glaciation. [ABSTRACT FROM AUTHOR]

In this study, we report standard quartz SAR OSL and post-IR infrared (IR) stimulated luminescence (post-IR IRSL; pIRIR290) measurements made on sand-sized quartz and K-feldspar extracts from the loess-palaeosol sequence at Niuyangzigou in northeastern China. The quartz OSL characteristics are satisfactory. Extensive pIRIR50,290 dose recovery tests were performed by adding doses on top of the natural dose. We found that dose recovery ratios improve significantly when the test dose ranges between ∼15 and ∼80% of the total dose, and good dose recovery (within ±5% of unity) can be obtained up to ~800 Gy. Otherwise, the dose recovery ratio deviates from unity. The De values also depend on the test dose size and so we conclude that the effect of test dose size should be routinely considered in pIRIR dating. First IR stimulation plateau pIRIR290 results are compared with multiple elevated temperature-pIRIR (MET-pIRIR) data. It appears that the low temperature MET-pIRIR data are strongly affected by poor dose recovery, but this is not the case for the pIRIR290 results. Natural signal measurements at the highest (first IR) stimulation temperature on a sample expected to be in field saturation suggest that ∼10% signal loss occurs in pIRIR signals. Long-term laboratory bleaching experiments (>80 days) show that a constant (or very difficult to bleach) residual pIRIR290 signal is reached after ∼300 h, corresponding to a dose of 6.2±0.7 Gy. Quartz OSL and feldspar pIRIR50,290 ages are in good agreement at least back to c. 70 ka. Beyond this the quartz ages begin to underestimate but the feldspar ages are in agreement with the expected Last Interglacial age palaeosol. [ABSTRACT FROM AUTHOR]

The shear wave velocity of surficial sediments ( V S ) and the fundamental site period ( T O ) are important parameters for analysis of the free-field seismic response. Their spatial distribution in the Ottawa and St. Lawrence Valleys, Canada, was determined applying a standardized method consisting of (i) updating the Quaternary geology; (ii) classifying the surficial units with similar physical properties into three broad categories: upper sandy sediments, intermediate clayey sediments and basal glacial and non-glacial deposits; (iii) delineating the spatial thickness of each category by way of 3D geologic modelling; (iv) sorting of available geophysical data with respect to each individual category and assigning representative V S relationships: a power velocity-depth function for sand and clay units combined, V S =119+8.1 Depth 0.5 (m/s), and a constant interval V S equal to the observed geometric mean velocity for glacial and non-glacial deposits, V S =385 (m/s). The respective T O values were computed as the ratio between the soil thickness and the average V S from ground surface to the bedrock. Validation of model results was conducted with V S and T O field data and available T O estimates from detailed urban-scale seismic zonation studies. The analyses of the uncertainty originating from the variation of the V S measurements showed that the standard deviations were roughly one-third of the modelled V S and T O values. [ABSTRACT FROM AUTHOR]

We present a high resolution sedimentary record of dinoflagellate cysts spanning the last ~ 900 years recovered from Effingham Inlet, a glacial fjord on the west coast of Vancouver Island, Canada. The combination of seasonal coastal upwelling supporting high levels of marine primary productivity in surface waters, together with restricted bottom water circulation in the silled fjord, fosters the preservation of laminated sediments in the inner basin of Effingham Inlet. Geochemical data are used to assess the sedimentary facies of the core, which is composed primarily of laminated units (50.2%) occasionally interrupted by “seismites” (39.5%) and homogenous units (10.2%). The chronology of the ~ 2 m-long core is based on varve counting and fifteen 14 C dates, and is anchored by a seismite previously dated at AD 1946. The dinoflagellate cyst assemblages are diverse (total of 47 taxa), abundant (average concentrations of 102,900 cyst g − 1 of dry sediment), and characterized by a proportionally equal contribution of autotrophic and heterotrophic cyst taxa in most samples. Overall, cyst assemblages are characterized by Operculodinium centrocarpum (36.2%) accompanied by Brigantedinium spp. (18.0%) and Dubridinium spp. (6.6%). Multivariate analyses are used to extract the dominant patterns of variability in autotrophic and heterotrophic dinoflagellate cyst assemblages separately, and help in identifying the temperature and primary productivity gradients encoded in the cyst sedimentary record in this particular estuary. Specific intervals identified in the dinoflagellate cyst record are interpreted to represent the local expression of the “Medieval Climate Anomaly” (from the base of the record, ~ AD 1090 to 1230), the “Little Ice Age” (~ AD 1230 to late 19th century) and warming in the second half of the 20th century. The timing of these intervals are consistent with the regional paleoclimate and help constrain past climatic and oceanographic variability on the west coast of Vancouver Island. The origin of homogenous units in the sedimentary record of Effingham Inlet and paleoseismicity in the region are also discussed. [ABSTRACT FROM AUTHOR]

Sea-surface temperatures (SSTs) based on radiolarian assemblage changes are estimated for the last 160 kyr, from a sediment core (Y9) recovered from Pukaki Saddle, northeast of Campbell Plateau. Site Y9 lies beneath Subantarctic Surface Water (SAW) immediately to the north of the Subantarctic Front (SAF), which in this region is bathymetrically constrained by the edges of Campbell Plateau and defines the northern boundary of the Antarctic Circumpolar Current (ACC). Radiolarian assemblages are characterised by an exceptionally high abundance of the Antarctic to subantarctic species Antarctissa spp. (up to 68%), especially during glacial intervals. SST estimates are derived using Factor Analysis and the Modern Analog Technique. Both methods capture the glacial-interglacial (G-I) pattern. The SST reconstructions show the changing relative influence of distinct water masses during the past G-I cycle, with major temperature variations of the order of 7–9 °C at glacial Terminations. Glacials (marine isotope stages (MIS) 6 and 2) are associated with particularly cool SSTs that are indicative of a more vigorous SAF/ACC and an enhancement of the inflow through Pukaki Saddle and/or frequent development of cold-core eddies at the SAF. By contrast, the influence of warmer waters and relaxation of the ACC during interglacials can be inferred from temperatures slightly warmer (e.g., mid-Holocene) and/or comparable to present day (e.g., MIS 5e). During these intervals, relatively warmer temperatures most likely indicate a higher warm-core eddy activity due to a strengthened Subtropical Front and/or a weakened inflow of cool water through Pukaki Saddle and/or an increased stratification in the Campbell Plateau region. Furthermore, the SST record is characterised by an abrupt warming at ca. 10 kyr (i.e., Termination I), the occurrence of a reversal at Termination I, and a warming event at the end of MIS 4, coinciding with the A4 event in the Byrd ice core. These characteristics, together with the pronounced G-I cycle shown by the SST estimates, suggest that Site Y9 is influenced by major oceanographic changes in the SW Pacific and responds to thermal changes at high southern latitudes. [ABSTRACT FROM AUTHOR]

Previous reconstructions of the British–Irish Ice Sheet (BIIS) envisage ice streaming from the Irish Sea to the Celtic Sea at the Last Glacial Maximum, to a limit on the mid-shelf of the Irish-UK sectors. We present evidence from sediment cores and geophysical profiles that the BIIS extended 150 km farther seaward to reach the continental shelf edge. Three cores recently acquired from the flank of outer Cockburn Bank, a shelf-crossing sediment ridge, terminated in an eroded glacigenic layer including two facies: overconsolidated stratified diamicts; and finely-bedded muddy sand containing micro- and macrofossil species of cold water affinities. We interpret these facies to result from subglacial deformation and glacimarine deposition from turbid meltwater plumes. A date of 24,265 ± 195 cal BP on a chipped but unabraded mollusc valve in the glacimarine sediments indicates withdrawal of a tidewater ice sheet margin from the shelf edge by this time, consistent with evidence from deep-sea cores for ice-rafted debris peaks of Celtic Sea provenance between 25.5 and 23.4 ka BP. Together with terrestrial evidence, this supports rapid (ca 2 ka) purging of the BIIS by an ice stream that advanced from the Irish Sea to the shelf edge and collapsed back during Heinrich event 2. [ABSTRACT FROM AUTHOR]

The Levant, a transition zone between the temperate Mediterranean domain and subtropical deserts, is a key area to study the latitudinal migrations of zonal climatic belts in response to glacial-interglacial conditions. The region underwent large climatic shifts during the Late Quaternary, with dramatic impacts on water resources and human populations. This paper presents the unique long-term hydroclimatic record (ca. 400 ka) from Northern Levant, derived from a sediment core taken from a small tectonic basin of northern Lebanon, the currently wettest area of the Levant. Combined biotic (pollen, biologic aquatic remains) and abiotic proxies (sediment properties, carbonate oxygen isotopes) reveal relatively high water availability during interglacials and generally drier glacials periods during the past four climate cycles. These general trends are in line with pollen records from southeastern and near east Mediterranean areas, but differ from some paleohydrological records from the southern Levant. Southward migrations of the rain-bearing mid-latitude westerlies during glacial periods and regional land topography are likely to explain the observed regional climate signatures. In addition, distinctive climate signatures of the successive wetter/drier intervals reflect interactions between global forcing (insolation, atmospheric greenhouse gas concentration), eastern Mediterranean Sea surface conditions intimately linked to North Atlantic climate and to ice-sheet and sea-ice extent at high northern latitudes, land topography, and local hydrogeological processes. Our record brings new benchmarks for understanding the spatial heterogeneity of eastern Mediterranean responses to global climate changes. [ABSTRACT FROM AUTHOR]

In this study we investigate how climate fluctuation in the Late Glacial period influenced the development of a lake and its catchment located in the East European Plain. We analyzed the sediments of the lake for pollen, subfossil Cladocera, macrofossils and chemical composition. We aimed at disentangling: (1) the climate changes and their limno-ecological responses, (2) temperature dynamics with the use of Cladocera-based transfer function (MJT) and macrofossil-based reconstruction of mean minimum July temperature (MMJT), (3) timing of the response of different proxies to environmental changes. The results of multiproxy analyses explicitly suggest that the main driver for changes in aquatic and terrestrial ecosystems as well as geomorphological processes in the catchment was climate. Reconstructed temperatures generally follow the known trends showing the increase at the beginning of the Allerød and decrease at the beginning of the Younger Dryas. However, there are some discrepancies between the two reconstructions as well as between the generally accepted temperature trends in Late Glacial. The timing of the proxy response to climate change differs, the aquatic proxies responding first. [ABSTRACT FROM AUTHOR]

Two sediment cores, KCES1 and ODP797, which were recovered from the Sea of Japan (JS), were measured for alkenone-derived sea surface temperatures ( $$U^{{\text{K}}^{\prime}}_{37} {\text{-SSTs}}$$ ). Our results revealed that the SSTs closely follow the glacial-interglacial cycles during the last 170 ka, except in the last glacial maximum (LGM), during which the SST was higher than in the Holocene. The anomalous high temperature in the LGM is considered as an effect of the intrusion of a low salinity water mass into the JS when the sea level was almost below 130 m. On the glacial-interglacial to orbital timescale, the $$ U^{{\text{K}}^{\prime }}_{37} {\text{-SSTs}} $$ record in the JS correlated well with the benthic foraminiferal δO record and solar insolation, which suggests the dominant control of solar insolation and its related sea ice development on the SST in the JS. On the sub-orbital/millennial timescale, reduced SST corresponds to an enhanced east asian winter monsoon (EAWM) during the last glacial period (MIS3 and MIS4), indicating the dominant control of sea ice expansion due to the enhanced EAWM on the SST in the JS. In contrast, during the last interglacial period (MIS5), the SST in the JS was controlled by variations in the east Asian summer monsoon. These results highlight the key role of solar insolation and associated glacial-interglacial conditions in the variations of the SST in the JS since the last 170 ka. [ABSTRACT FROM AUTHOR]

We discuss in this paper the first detailed environmental magnetic record of glacial–interglacial climatic variations in the Schirmacher Oasis, East Antarctica. We determined environmental magnetic properties and inter-parametric ratios (χ lf , χ fd %, χ ARM , SIRM, χ ARM /SIRM, χ ARM /χ lf , χ ARM /χ fd , SIRM/χ lf , S-ratio and HIRM) for sediment samples of a core from the Sandy Lake. Accelerator mass spectrometer (AMS) 14 C dates were obtained on the organic matter from bulk sediment samples. The sediment core spans the past ~ 42.5 cal. ka B.P. The magnetic minerals are mainly detrital and catchment-derived, as there is no evidence for the presence of authigenic greigite, bacterial magnetite or diagenetic dissolution. The last glacial period is characterized by a high concentration of ferrimagnetic minerals such as titanomagnetite (high values of χ lf, SIRM etc.) and coarse magnetic grain size (low χ ARM /SIRM and χ ARM /χ lf values and high S-ratio values). Deglaciation in the Schirmacher Oasis began around 21 cal. ka B.P. as suggested by the low magnetic mineral concentration. The Holocene period is characterized by relatively warm climatic events as seen in the low values of magnetic susceptibility which is primarily contributed by fine-grained titanomagnetite resulting from pedogenesis (high χ fd % values). Several of the relatively warm and cold events that we deciphered from the environmental magnetic data are correlatable with lake sediments from the Schirmacher Oasis and other ice-free areas in East Antarctica and from ice-core records on the Antarctic Plateau. [ABSTRACT FROM AUTHOR]

Analysis of a high-resolution suite of modern glacial sediments from Jostedalen, southern Norway, using a portable optically stimulated luminescence ( OSL) reader, provides insights into the processes of sediment bleaching in glacial environments at the catchment scale. High-magnitude, low-frequency processes result in the least effective sediment bleaching, whereas low-magnitude, high-frequency events provide greater bleaching opportunities. Changes in sediment bleaching can also be identified at the scale of individual bar features: tails of braid-bars and side-attached bar deposits have the lowest portable reader signal intensities, as well as the smallest conventional OSL residual doses. In addition to improving our understanding of the processes of sediment bleaching, portable reader investigations can also facilitate more rapid and comprehensive modern analogue investigations, which are commonly used to confirm that the OSL signals of modern glacial sediments are well bleached. [ABSTRACT FROM AUTHOR]

The transport of sediment from the mouth of the Indus River on to the deep-water submarine fan is complicated by temporary storage within large clinoforms on the shelf on either side of the submarine canyon, where most of the sedimentation since the start of the Holocene has occurred. In contrast, shelf edge clinoform deltas represent the products of forced regression and not the progradation of highstand clinoforms as far as the shelf edge. Clinoform sediments have a mixed provenance that involves significant reworking of older sediment deposited during or before the last glacial maximum. Recent sedimentation in the canyon head has been very rapid in the last few centuries ( ca. 10 cm year−1), but has been starved of sand probably because of 20th century damming. Sandy layers appear to represent annual monsoonal floods with a particularly large flood every 50-70 years. This canyon head sediment is also reworked by currents flowing along the canyon axis before being deposited deeper into the canyon. The last sandy sediment to reach the mid-canyon ( ca. 1300 m depth) was transported around 7000 year BP at a time of rising sea-levels, and might reflect reworking by the transgression, or local slumping from the walls of the canyon. Dating of the uppermost in a series of terraces in the mid-canyon area suggests that the canyon may have been partly filled and emptied of sediment at least three times since ca. 50 ka. We conclude from the Holocene record that sediment flux to the deep-water fan experiences major buffering, reworking and recycling both on the shelf and within the submarine canyon prior to its deposition, so that turbidite sands in the deep Arabian Sea cannot be used to correlate with climatic or tectonic events onshore over timescales of 103-105 years. [ABSTRACT FROM AUTHOR]

An extensive, high-resolution, sedimentological–geochemical survey was done using geo-acoustics, XRF-core scans, ICP-AES, AMS 14C-dating and grain size analyses of sediments in 11 cores from the Gulf of Taranto, the southern Adriatic Sea, and the central Ionian Sea spanning the last 16cal.kaBP. Comparable results were obtained for cores from the Gallipoli Shelf (eastern Gulf of Taranto), and the southern Adriatic Sea suggesting that the dominant provenance of Gallipoli Shelf sediments is from the western Adriatic mud belt. The 210Pb and 14C-dated high-accumulation-rate sediments permit a detailed reconstruction of climate variability over the last 16cal.kaBP. Although, the Glacial–Interglacial transition is generally dry and stable these conditions are interrupted by two phases of increased detrital input during the Bølling–Allerød and the late Younger Dryas. The event during the Younger Dryas period is characterized by increased sediment inputs from southern Italian sources. This suggests that run-off was higher in southern- compared to northern Italy. At approximately ~7cal.kaBP, increased detrital input from the Adriatic mud belt, related to sea level rise and the onset of deep water formation in the Adriatic Sea, is observed and is coincident with the end of sapropel S1 formation in the southern Adriatic Sea. During the mid-to-late Holocene we observed millennial-scale events of increased detrital input, e.g. during the Roman Humid Period, and of decreased detrital input, e.g., Medieval Warm Period. These dry/wet spells are consistent with variability in the North Atlantic Oscillation (NAO). A negative state of the NAO and thus a more advanced penetration of the westerlies into the central Mediterranean, that result in wet conditions in the research area concord with events of high detrital input e.g., during the Roman Humid Period. In contrast, a positive state of the NAO, resulting in dry conditions in the Mediterranean, dominated during events of rapid climate change such as the Medieval Warm Period and the Bronze Age. [ABSTRACT FROM AUTHOR]

Abstract: Sediments from the continental shelf/coastal region bear significant signals of sea-level, climate change as well as local tectonic information. This study presents a high-resolution magnetostratigraphic and rock magnetic study of a 212.4m core (BH08, with a basal age of 1.06Ma) recovered from the shallow (<30m below sea level) Bohai Sea, China. Astronomical tuning based on the sediment redness (a*) of core BH08 allows the construction of a high-resolution chronology that is assisted by magnetostratigraphic data. Sedimentology and associated proxies (grain size and redness) indicate that the cyclic alternation of neritic/littoral sandy deposits and terrestrial silts/clayey silts was mainly controlled by changes in sea-level and associated base-level at glacial–interglacial timescales. The a* record of the core can be correlated with marine δ18O records at 40- and 100-kyr cycles, indicating that the sediments in the study area are continuous at least at orbital timescales regardless of significant base-level variations. This is likely due to continued subsidence in the basin and creation of accommodation space. The significant lower sedimentary accumulation rates since 750ka might be due to the deviation of the depositional locus from core site because of extreme low sea-level stands during the glacials since the Mid-Pleistocene transition (MPT). Especially the glacial sea-level lowstands might have resulted in bypassing or erosion of sediments on the BH08 core site during peak glacials (MIS 6, MIS 10 and MIS 16), limiting the sediment preservation potential. This study documents the longest Quaternary sedimentary succession in the Bohai Sea and provides, for the first time, a clear link between sedimentation in the area and glacial–interglacial climate-driven sea-level changes. This study also highlights the feasibility of astronomical tuning to obtain high-resolution chronology for shallow shelf deposits, which is otherwise very difficult to be achieved on the basis of magnetostratigraphic data alone. [Copyright &y& Elsevier]

Abstract: Dust over the Himalayas and southern Tibetan Plateau may influence high-elevation temperature and hydrology across Asia, but little is known about long-term dust variability and its relationship with regional climate over the last millennium. Here we have reconstructed a proxy record of past dust and temperature impacts on glacial streamflow and sediment deposition in Kiang Co, a small lake on the southwestern Tibetan Plateau. Terrigenous elemental variability in the Kiang Co sediment record, a proxy for glaciofluvial sediment deposition in the lake, covaries with the Dasuopu ice core dust record from the central Himalayas on centennial timescales. The relationship between the Kiang Co sediment record and Dasuopu indicates coherent dust forcing across the central Himalayas over much of the last millennium, and suggests that regional dustiness influences glacial streamflow and sediment transport on centennial timescales. In addition, the Kiang Co terrigenous elemental abundance record is positively correlated with May–September temperatures from the Tibetan Plateau to central India from 1870 to 2007AD, highlighting the important influence of temperature on melting and streamflow in this region, as well as a relationship between dust and temperature on centennial timescales. These findings strengthen the likelihood of future dustiness with continued warming, along with further increases in melting and high-elevation streamflow in coming decades. [Copyright &y& Elsevier]

Abstract: The freshwater budget of the Arctic Ocean is a key component governing the deep water formation in the North Atlantic and the global climate system. We analyzed the isotopic composition of neodymium (ε Nd) in authigenic phases of marine sediments on the Mendeleev Ridge in the western Arctic Ocean spanning an estimated time interval from present to about 75ka BP. This continuous record was used to reconstruct the ε Nd of the polar deep water (PDW) and changes in freshwater sources to the PDW through time. Three deviations in ε Nd from a long term average of −10.2 were identified at estimated 46–51, 35–39 and 13–21ka BP. The estimated 46–51ka BP event can be traced to bursting of ice-dammed lakes accompanying the collapse of the Barents–Kara Ice Sheet, which would have released radiogenic Nd to the eastern Arctic Ocean. The cyclonic surface circulation in the eastern Arctic Ocean must have been stronger than at present for the event to be recorded on the Mendeleev Ridge. For the 35–39 and 13–21ka BP events, it is likely that the Laurentide Ice Sheet (LIS) supplied the unradiogenic freshwater. The configuration of the anticyclonic circulation in the western Arctic was probably similar to today or expanded eastward. Our simple mass balance calculations suggest that large amounts of freshwater were released but due to significant deep water formation within the Arctic Ocean, the effect on the formation of NADW was probably minor. [Copyright &y& Elsevier]

Abstract: The record of well preserved palynomorphs from sediment samples of Lake Suigetsu mirrors temporal changes in the flora around the lake and spatial changes in the vegetation cover of central Japan during the late Quaternary. This study presents photographic images of 169 identifiable types of moss, lycophyte and fern spores and pollen of gymnospermous and angiospermous plants from the SG06 core sediment obtained at a standard magnification of ca. 750×. Additionally non-pollen palynomorphs (NPPs), which appeared in the pollen slides, are documented, including remains of fungi, rhizopods, arthropods, rotifers, flatworms as well as green algae and plant tissue fragments. All documented taxa are presented in taxonomical order on 66 plates, including 55 plates for pollen and spores of higher plants and 11 plates for NPPs. This study renders an overview on quality of preservation and on the range of palynomorphs found in the last glacial-interglacial sediments of Lake Suigetsu, and furthermore, may serve as a handy and thorough guide for palynological investigations, aiming at the reconstruction of past vegetation, environmental and climate dynamics. [Copyright &y& Elsevier]

Abstract: Floodplain and aeolian sediments near Burdukovo reveal a detailed record of Holocene environmental change in the lower Selenga River Valley (Lake Baikal region, Siberia). During the late Pleistocene and early Holocene fine-grained alluvium accumulated on the floodplain followed by a period of increased landform stability and subsequent pedogenic formation. This part of the stratigraphical sequence yielded rich assemblages of terrestrial molluscs, which increase in species diversity from early pioneer communities with about ten taxa to levels containing over twice that number. The land snail assemblages also record an episode of relatively drier local habitats prior to ∼9.2 ka BP with subsequent wetter conditions lasting until ∼8.0 ka BP. This was followed by an abrupt and sustained change in floodplain deposition, shifting from overbank alluvium to aeolian sedimentation, within which a series of weakly developed soil horizons formed during the middle and late Holocene periods. The onset of aeolian processes and relatively drier conditions in the middle Holocene at Burdukovo coincides with major changes observed both in other regional palaeoenvironmental proxy records and in local archaeological sequences, although it is still not clear how the two are linked. [Copyright &y& Elsevier]

Abstract: The drivers of the Indo-Asian monsoon dynamics during terminations have recently emerged as a controversial issue. Cheng et al. (2009. Ice Age Terminations. Science 326, 248–252), using East-Asian speleothem records, proposed a strict northern hemisphere insolation control at the orbital timescale with weak monsoon intervals occurring at terminations. On the contrary, An et al. (2011. Glacial–Interglacial Indian Summer Monsoon Dynamics. Science 333, 719–723), using a record from the Hequing paleolake basin, highlight the importance of the southern hemisphere climate forcings on Indian summer monsoon dynamics at glacial–interglacial timescale. The purpose of this note is to propose an explanation of the weak monsoon intervals at terminations, using a deep sea sediment stack monsoon record. The mechanism involved is linked to interhemispheric interactions, as proposed by An et al. (2011), superimposed to the role of orbital forcing (precession and obliquity parameters). This explanation clarifies the combination of complex drivers acting on the Indo-Asian monsoon dynamic at terminations. [Copyright &y& Elsevier]

Abstract: Clay mineralogy combined with high-resolution element geochemistry of core MD90-9064, located in the distal part of the Nile deep-sea fan (Levantine Basin), have been investigated to reconstruct rainfall changes in northeastern Africa during the Quaternary and to determine possible climatic controls. Clay minerals of core MD90-964 are derived mainly from three sedimentary sources (the Sahara, Nile River and Egyptian wadis) and are characterized by contrasted mineralogical composition. Variations in illite content and logarithm ratios of Si/Al and K/Al permit the tracking of eolian input from Sahara to the Mediterranean Sea. It is suggested that precipitation changes in the Sahara are mainly dominated by glacial–interglacial cycles. Such variations are owing to a shift of climatic conditions in the North Atlantic from a NAO-positive-like condition in glacial times to a NAO-negative-like condition in interglacial times. Fe content in the Levantine sediments is mostly derived from Fe-bearing heavy minerals brought by the Nile River. Therefore, variations of Fe/Al ratios can be used to establish precipitation changes in the Nile River basin. Long-term variation in precipitation in the Nile River basin is governed by precessional and eccentricity signals, implying that the African monsoon is the most significant controlling factor for precipitation changes in this region. Precipitation changes in the northeastern coasts of Africa are reconstructed using kaolinite contents provided by the Egyptian wadis. It is reported that precipitation in coastal northeastern Africa is mainly of the Mediterranean-climate type. Long-term variations in rainfall in this region are also affected by the NAO-like climatic variability and thus dominated by the glacial–interglacial cycles. [Copyright &y& Elsevier]

Abstract: The Okinawa Trough in the East China Sea continuously receives terrigenous sediments from the surrounding East Asian continent during the late Quaternary, which makes it an ideal site for the studies of land–sea interaction and sediment source-to-sink transport. Geochemical and Sr–Nd isotopic compositions of the detrital sediments in the middle Okinawa Trough allow the provenance discrimination and the reconstruction of paleoenvironmental changes over the last 30ka. Large variations in 87Sr/86Sr ratios and εNd values occur between 14.0 and 7.1ka, suggesting a significant change in sediment provenances from the dominance of the Changjiang (Yangtze River) and/or continental shelf to that of Taiwan Island. During the last glacial maximum, the continental shelf was largely exposed and the fine-grained sediments from the Changjiang and the shelf with higher 87Sr/86Sr ratios and lower εNd values might be transported directly into the middle Okinawa Trough. With the sea level rise during the deglacial period, the strengthening Kuroshio Current increasingly delivered Taiwan-derived fine sediments (lower 87Sr/86Sr ratios and higher εNd values) to the middle trough, while the sediment contribution from the East Asian continent became subordinate. This study suggests that the changes in sea level and the Kuroshio Current pathway during the late Quaternary predominantly determined the dispersal and deposition of the terrigenous sediments in the Okinawa Trough, and the Kuroshio Current might have obviously influenced the Okinawa Trough since 14ka. This study illustrates that the radiogenic isotopic compositions of the fined-grained sediments are sensitive proxies to trace the sediment provenance and to reconstruct oceanic circulations in the west Pacific marginal seas. [Copyright &y& Elsevier]

Abstract: A long-standing debate concerning Neogene Antarctic climate in the McMurdo Dry Valleys relies largely on evidence from landscape evolution, glacial modeling and stratigraphy. We provide new evidence from meteoric 10Be for the onset of frozen, hyper-arid conditions on a high elevation (1840m) interfluve at Table Mountain. A simple decay model for the co-occurrence of meteoric 10Be and illuviated clay in cores of ice-cemented glacial sediments indicates that the clays were actively migrating down from the surface in a warm climate until the system froze between 6 and 9Ma. Although this age range may be sensitive to possible interference by in situ produced 10Be, the implied minimum age of 6Ma for the Sirius Group indicates that the Dry Valleys were permanently frozen down to this elevation at this time. The model also suggests denudation rates of 1–6cmMyr−1 since freezing. These data provide an independent test of glacial-stratigraphic evidence used to determine Antarctic paleoclimate. [Copyright &y& Elsevier]

Sediments from the last interglacial ( Eemian) in Jameson Land, East Greenland, and the Thule area, NW Greenland, have revealed a number of insect fragments of both arctic and more or less warmth-demanding species. Altogether, the interglacial fauna of Coleoptera (beetles) indicates boreal conditions. Undoubtedly, a large fraction of the insect fauna succumbed when the mild Eemian climate cooled drastically during the last glacial stage. However, a group of hardy species now found far north into the High Arctic might be glacial survivors. It is, however, still puzzling why well-adapted arctic beetle species such as Amara alpina and Isochnus arcticus did not survive the last glacial stage in Greenland. Two factors that have not been sufficiently considered when discussing survival contra extinction are the importance of microclimate and the number of sun-hours during the Arctic summer. Even among the Coleoptera, which as a group fares quite badly in the Arctic, there might be survivors, at least among those found both during the interglacial and as fossils during the early Holocene. First of all, glacial survival applies to the seed bug Nysius groenlandicus, which was widespread during the Eemian, was found soon after the last deglaciation, and is now almost omnipresent in Greenland. [ABSTRACT FROM AUTHOR]

New glacial varve records from long cores combined with records from key surface exposures and new radiocarbon ages have allowed the correction, consolidation, expansion, and calibration of Ernst Antevs' original New England Varve Chronology (NEVC) in the Connecticut Valley of New England, U.S.A. The varve records have been reformulated, with corrections and a new numbering system, as the new North American Varve Chronology (NAVC), which is a continuous 5659-yr varve sequence that spans most of the last deglaciation (18,200-12,500 yr BP) in the northeastern United States. Rates of ice recession for separate intervals terminated by abrupt glacial stillstands and readvances have been determined for western New England. Ice recession history is coupled to varve thickness changes that depict changes in meltwater production in the Connecticut Valley and show the relationship of changes in ablation rate (summer climate variation) to glacial readvances and periods of halted and rapid ice recession (up to 300 m/yr). Comparison of varve thickness records to Greenland ice-core climate records show that after 15,000 yr BP, climate changes of sub-century and longer scales recorded in both records appear identical and synchronous. After 15,000 yr BP, therefore, there was a link between North Atlantic climate and marginal processes of the southeastern sector of the Laurentide Ice Sheet (LIS). Prior to 15,000 yr BP, when the LIS was closer to an equilibrium condition, retreat rates were generally lower and changes in varve thickness and ablation were more subtle, but can still be linked to ice sheet activity. Only weak relationships between varve thickness changes and Greenland climate are evident suggesting that changes in the southeastern LIS during this time may have been significantly influenced by climate patterns unique to the North American continent or ice dynamics. [ABSTRACT FROM AUTHOR]

Abstract: Rapid climatic switches during marine isotope stage 3 (29–59 ka BP) are often attributed to ocean circulation changes caused by freshwater input into the North Atlantic through the melting of large amounts of icebergs and sea ice. However, recent studies have questioned this direct coupling between factors influencing the ocean-climate system. By combining multiple proxies from two mid depth northern North Atlantic sediment cores we assess temporal offsets and links between freshwater input and response of the near bottom flow as well as between near bottom flow and sea surface temperatures changes. Grain size, mineralogical and magnetic proxies for ice rafting and near-bottom flow speed, interpreted as indicators of freshwater input and deep circulation strength, consistently indicate a delay in the recovery of the deep circulation after freshwater perturbations. Sea surface temperature variability is inferred from foraminiferal assemblages and Mg/Ca and δ18O of Neogloboquadrina pachyderma s. The records show rapid switches towards higher temperatures following the ice-rafting events. Interestingly, near sea surface temperatures increased and decreased again during periods of accelerating bottom flow speed, likely reflecting the sudden release of heat from deeper in the water column, rather than circulation changes. Our data thus confirm the impact of freshwater forcing on the Atlantic deep circulation, but suggest that temperature variability at the surface was not directly linked to these circulation changes. [Copyright &y& Elsevier]

Abstract: Marine Isotope Stage 31 (MIS-31) is one of the major interglacials of the early Pleistocene ~1.08 to 1.06Ma. Data from proximal sediment cores around several sectors of Antarctica indicate strong sea surface warming and ice shelf and sea ice retreat. Benthic deep-sea-core δ18O values at this time are some of the lowest of the Pleistocene, indicating both deep sea warming and reduced global ice volume. A coeval alignment of orbital parameters produces one of the strongest high-latitude summer insolation anomalies of the last several million years. Here we use a 3-D ice sheet-shelf model to simulate the evolution of Antarctic ice sheets through the event, and a global climate model to simulate temperatures and sea ice during peak Antarctic warmth. The ice model predicts nearly complete collapse and subsequent recovery of marine ice in West Antarctica, and the ice and climate model results agree well with proximal sediment core data in the Ross Embayment recovered by the ANDRILL and Cape Roberts drilling projects. The dominant forcing is found to be variations in sub-ice-shelf oceanic melting, with insignificant surface melting of terrestrial ice flanks even during peak warmth. Implications are noted in light of other observations and theories of Pliocene–Pleistocene Antarctic ice sheet variability that do involve surface melt. [Copyright &y& Elsevier]

Abstract: Multi-proxy records (geochemistry, clay mineralogy and paleontology) from three sediment cores from Lake Hovsgol, northwest Mongolia, provide paleoenvironmental changes in continental Asia from the last glacial to the present (during the last 29calka BP). This paper presents the first continuous δ13C and δ18O dataset for ostracod shells (Cytherissa lacustris) from Lake Hovsgol sediments. A positive shift in ostracod δ13C values (from +0.5‰ to +3.2‰) began at ca. 21calka BP, and was associated with a decrease in δ13C values of total organic carbon (from −24.7‰ to −27.3‰) and an increase in the mass accumulation rate of total organic carbon (MAR-TOC). These results suggest that increased lake productivity led to the 13C-enrichment of dissolved inorganic carbon in Lake Hovsgol. In addition, decreases in clay content and the illite crystallinity index (full width at half maximum of the 10Å peak) began at ca. 21calka BP, indicating an increase in surface runoff and a change in sources of clastic materials in the watershed. The highest δ18Oostracod values (up to −4.8‰) at 16–15calka BP indicate the increases in precipitation from the East Asian monsoon. The total pollen amount increased, and Betula, Alnus, and Salix were dominant (up to 53%, 30%, and 6%, respectively) after 16–15calka BP. These findings indicate that broad-leaved trees expanded around Lake Hovsgol. In addition, fossil diatom valves appeared after 16–15calka BP, suggesting climate amelioration, and increased input of soil-derived nutrients and dissolved silica. Between 10 and 5calka BP (Holocene climate optimum), productivity was high in and around the lake (MAR-TOC, up to 47.3mg/cm2 kyr; MAR-diatoms, up to 14.4×108 valves/cm2 kyr; total pollen concentration, up to 9.0×105 grains/cm3). Environmental changes during the last 29kyr in and around Lake Hovsgol are clearly associated with fluctuations in summer insolation and East Asian monsoon intensity. [Copyright &y& Elsevier]

Abstract: The calcium carbonate (CaCO3) content of deep-sea sediments in the Pacific Ocean increases during glacials of the late Pleistocene in comparison to interglacials, whereas records of sedimentary CaCO3 in the Atlantic Ocean show an anticorrelated pattern across glacial-interglacial cycles. Here we show that this anticorrelation in inter-ocean CaCO3 cycles arose comparatively recently, at ~1.10million years ago (Ma), during the mid-Pleistocene transition. Before this time, we show that the CaCO3 content of Pacific and Atlantic Ocean sediments experienced in-phase cyclicity, both having ‘Atlantic-style’ phasing with respect to glacial–interglacial cycles. The onset of anticorrelated cyclicity at 1.10Ma involved a twofold switch in the Pacific''s CaCO3 cycles: glacial CaCO3 preservation became consistently better while interglacial preservation became consistently worse. We demonstrate that the cause of this glacial–interglacial ‘mirror imaging’ of Pacific CaCO3 dissolution cyclicity at 1.10Ma was a switching over of the relative ventilation state of abyssal South Pacific waters between glacials and interglacials. Specifically, we suggest that a consistent strengthening of deep water ventilation within the Pacific sector of the Southern Ocean during glacials drove glacial Pacific CaCO3 dissolution to diminish, while a contemporaneous weakening of very well-ventilated ‘upstream’ North Atlantic Deep Water during interglacials drove interglacial Pacific CaCO3 dissolution ‘downstream’ to intensify. We propose that the increased mean alkalinity of the global deep ocean (driven by the geographically and bathymetrically vast Pacific Ocean) during glacials after 1.10Ma may explain part of the drawdown in glacial atmospheric CO2 levels hypothesised to have been linked to the increased severity of these late Pleistocene glacials. [Copyright &y& Elsevier]

Abstract: We measured terrestrial plant biomarker (long-chain n-alkanes) in the sediment cores taken from the Sea of Okhotsk to examine paleoclimatic utility of long-chain n-alkanes in marine sediments. This study demonstrates that sedimentary record of n-alkane in the sea has a high potential to provide important complementary paleo-climate/paleo-environmental information. Molecular distributions of long-chain n-alkanes in marine sediments show a typical signature of terrestrial plant wax derived n-alkanes with strong odd carbon number predominance from the last glacial to the present, suggesting a source of long-chain n-alkanes in the Okhotsk Sea sediments has been terrestrial higher plants throughout the time. The down core profiles of concentrations of C25–C35 n-alkanes in XP07-C9 collected from the northwestern site revealed three events of enhanced terrestrial organic matter input during the last deglaciation. The two pronounced events correspond to Melt Water Pulse (MWP) events 1A (14.5–12.5ka) and 1B (11–6.5ka). These events possibly linked to increases in river discharge and erosion of submerged continental shelf due to drastic rise in sea level. Down core profiles of molecular distributions of n-alkanes in the Okhotsk Sea sediments significantly vary over the last 25kyr, and are similar to that of a peat core sequence in the East Russia and essentially consistent with pollen data from marine and peat core sequences. [Copyright &y& Elsevier]

Abstract: High-resolution physical, chemical and biological-based climate proxies from the Ain el Beida (AEB) section in Atlantic Morocco reveal the imprint of the three main orbital parameters precession (19–23kyr), obliquity (41kyr) and eccentricity (95–125 and 400kyr) between 6.5 and 5.5 million years before present (Ma). The precession-related variations are most prominently reflected in the color reflectance and chemical composition of the sediment, showing that precession minimum configurations lead to more humid climate conditions in Northwest Africa probably related to the Atlantic system, while more arid climate conditions prevailed during precession maxima. In addition, precession-bound changes in planktonic foraminifera and calcareous nannofossil assemblages indicate that sea surface temperature (SST) increased during the humid phases, while productivity conditions increased during the dry periods. The clear imprint of the short and long-term eccentricity cycles is explained by a non-linear climatic response to the precession forcing with overall more humid climate conditions during eccentricity maxima. The obliquity-controlled variations in SST and aridity conditions concur with glacial–interglacial variability that is conspicuously recorded in both planktonic and benthic δ18O records of AEB. The observed warm and wet climates during interglacial periods most likely reflect the direct ice driven thermal response to the reduced ice sheets and more active Atlantic depressions. Similar as during the Pliocene and Pleistocene, obliquity-controlled variations in the planktonic and benthic carbon isotope (δ13C) records of AEB are inversely related to the oxygen isotope records with more depleted values during glacial stages, although with a small lag. The close correspondence between the δ13C records of AEB and other open ocean sites (i.e., Sites 982 and 926) may therefore point to large-scale glacial-controlled variations in the deep-sea carbon reservoir. Superimposed on the orbital variations, the imprint of the – onset of the – Messinian Salinity Crisis can be traced by a marked ~1.0‰ negative excursion in planktonic δ13C at 6.0Ma, followed by a prominent peak in Ti/Al at ~5.97Ma. [Copyright &y& Elsevier]

The majority of soils in the western Wisconsin have developed from glacial sediments deposited during the Quaternary Period (2.6 million years before present). In many regions, multiple advances and retreats have left a complex landscape of diverse glacial sediments and landforms. The soils that have developed on these deposits reflect the nature of the parent material and glacial sediments. Data from the Soil Survey Geographic (SSURGO) database were utilized to digitally map Quaternary deposits and in St. Croix County, Wisconsin. Maps of ice source region (northwest vs. northeast) and parent materials (till vs. outwash) were produced. Results were compared to a preliminary Quaternary surficial geology map. Overall agreement between the geologic map and the map created using soil survey information was generally greater than 60%. This research shows that soil surveys can provide reliable, accurate, and high-resolution data on Quaternary surficial geology. In addition, this research shows the linkage and value of soil science to other disciplines such as geology. [ABSTRACT FROM AUTHOR]

Abstract: The sediments in the upwelling area off central Vietnam are totally bioturbated and display a low-diverse assemblage of bioturbational structures. During interglacial times (Marine Isotope Stage MIS 1, 5a, 5c, 5e), summer monsoon leads to pronounced upwelling and seasonally pulsed arrival of organic matter on the seafloor. These deposits are characterized by a 4-tier bioturbated zone with Zoophycos. Zoophycos producers used this seasonal food source and show a cache behavioral strategy. During glacial periods upwelling was weak and oxygenation of bottom water decreased as evidenced by bioturbational structures that show a decrease in size, penetration depth and diversity. Enlarged freshwater influx during glacial times fuelled primary production and led to estuarine circulation. The resultant oxygen minimum layer favored an increased deposition of organic matter that in turn affected sediment properties. During MIS 2 and 5b oxygenation was probably a little lower than today. During MIS 3 and 5d Chondrites-like burrows point to a stronger oxygen deficiency. During MIS 4 bottom water oxygenation was even lower and only biodeformational structures occur in soft sediment rich in benthic food. Based on these findings an ichnofabric model for food-rich, fairly soft deposits experiencing oxygen deficiency is suggested having biodeformational structures as low-oxygen end member. [Copyright &y& Elsevier]

Abstract: New diatom-biostratigraphic age data derived from piston core were used to constrain the chronology for a seismic-based interpretation of West Antarctic Ice Sheet (WAIS) advance and retreat from the North Basin outer shelf in western Ross Sea. The data demonstrates that grounded ice occupied the outer shelf on at least ten occasions during the last 2.0Ma of the Pleistocene. Although the biostratigraphic resolution is low, the constraints permit correlations to coeval section recently drilled in South McMurdo Sound at the AND-1B drill site. Our interpretation of regional-scale correlations suggests that the Pleistocene dynamics of the WAIS involved grounding-line translations in excess of 600km. However, the data also suggests that only two major advances of grounded ice occurred since ~0.71Ma. In other words, several of the late Pleistocene sediment cycles at AND-1B must represent only minor advance and retreat of grounded ice to and from South McMurdo Sound. The results prove false the long-standing tacit assumption that the WAIS experienced major advances in association with peak glacials and eustatic lowstands during the last 700ka of the Pleistocene. These results show that piston cores can be used to constrain the timing of pre-Holocene grounding events. These data also highlight the need for regional-scale correlations to distinguish between major versus minor grounding-line translations of grounded ice in the marine setting. [Copyright &y& Elsevier]

Lüthgens, C., Böse, M. & Preusser, F. 2011: Age of the Pomeranian ice-marginal position in northeastern Germany determined by Optically Stimulated Luminescence (OSL) dating of glaciofluvial sediments. Boreas, 10.1111/j.1502-3885.2011.00211.x. ISSN 0300-9843 The Pomeranian ice margin is one of the most prominent ice-marginal features of the Weichselian glaciation in northern Europe. Previous results of surface-exposure dating (SED) of this ice margin disagree with established chronologies and ice retreat patterns, i.e. are much younger than previously expected. We crosscheck the age of the Pomeranian ice-marginal position in northeastern Germany using single-grain quartz Optically Stimulated Luminescence (OSL) dating of glaciofluvial sediments. OSL dating indicates an active ice margin between 20.1±1.6 ka and 19.4±2.4 ka forming outwash plains attributed to the Pomeranian ice-marginal position. On the basis of these results, we suggest a critical reassessment of previous SED data available for the Pomeranian ice-marginal position within their respective regional geomorphological contexts. From a process-based point of view, SED ages derived from glacigenic boulders document the stabilization of the landscape after melting of dead ice and landscape transformation under periglacial conditions rather than the presence of an ice margin. SED indicates a first phase of boulder stabilization at around 16.4±0.7 ka, followed by landscape stabilization within the area attributed to the recessional Gerswalder subphase around 15.2±0.5 ka. A final phase of accumulation of glaciolacustrine and glaciofluvial sediments at around 14.7±1.0 ka documents the melting of buried dead ice at that time. [ABSTRACT FROM AUTHOR]

Abstract: Fossil arctic ground squirrel (Spermophilus parryii) middens were recovered from ice-rich loess sediments in association with Sheep Creek-Klondike and Dominion Creek tephras (ca 80ka) exposed in west-central Yukon. These middens provide plant and insect macrofossil evidence for a steppe-tundra ecosystem during the Early Wisconsinan (MIS 4) glacial interval. Midden plant and insect macrofossil data are compared with those previously published for Late Wisconsinan middens dating to ∼25–2914CkaBP (MIS 3/2) from the region. Although multivariate statistical comparisons suggest differences between the relative abundances of plant macrofossils, the co-occurrence of steppe-tundra plants and insects (e.g., Elymus trachycaulus, Kobresia myosuroides, Artemisia frigida, Phlox hoodii, Connatichela artemisiae) provides evidence for successive reestablishment of the zonal steppe-tundra habitats during cold stages of the Late Pleistocene. Arctic ground squirrels were well adapted to the cold, arid climates, steppe-tundra vegetation and well-drained loessal soils that characterize cold stages of Late Pleistocene Beringia. These glacial conditions enabled arctic ground squirrel populations to expand their range to the interior regions of Alaska and Yukon, including the Klondike, where they are absent today. Arctic ground squirrels have endured numerous Quaternary climate oscillations by retracting populations to disjunct “interglacial refugia” during warm interglacial periods (e.g., south-facing steppe slopes, well-drained arctic and alpine tundra areas) and expanding their distribution across the mammoth-steppe biome during cold, arid glacial intervals. [Copyright &y& Elsevier]

Abstract: Chronologies of sediments that document the last glacial history of the Black Sea “Lake” are hampered by issues relating to reservoir age. Regulated by basin hydrology, reservoir ages represent a tool that could potentially be used to better understand the response of Black Sea “Lake” hydrology to climate change. Therefore, deciphering reservoir age evolution is crucial both for better constraining the basin chronological framework and for providing new insights into our understanding of Black Sea “Lake” hydrology. By tuning a meaningful new high-resolution geochemical dataset (obtained from core MD04-2790) to a climate reference record, here, we propose a reliable chronology spanning the last 32kyr BP. The chronology is compared to a large AMS radiocarbon dataset (n=51). Pairs of calendar and radiocarbon ages allowed us to compute reservoir ages, and to, then, reconstruct a high-resolution quantitative reservoir age record for the last glacial history of the Black Sea “Lake”. The main factor controlling reservoir ages in lakes is the Hard Water Effect (HWE), which is regulated by basin hydrology. Therefore, changes in the reconstructed reservoir age record have been qualitatively interpreted in terms of the hydrologic responses of the Black Sea “Lake” to climate change. Our results allowed us to determine periods of complete isolation or outflow for the Black Sea “Lake”. During Heinrich Event 2 (HE2) and during the Last Glacial Maximum (LGM) the basin was strictly isolated, whereas prior to HE2 and during HE1 it outflowed into the Marmara Sea. Following the onset of the Bølling–Allerød, factors other than the HWE are thought to have influenced the reservoir age, preventing conclusive interpretations. We also determined an undocumented, to date, phase of Black Sea “Lake” stratification during the full glacial (HE2 and LGM). Our results indicate that reservoir age is a powerful tool for investigating and better understanding past hydrologic changes in lakes and inland seas. [Copyright &y& Elsevier]

Finlayson, A., Golledge, N., Bradwell, T. & Fabel, D. 2011: Evolution of a Lateglacial mountain icecap in northern Scotland. Boreas, Vol. 40, pp. 536-554. 10.1111/j.1502-3885.2010.00202.x. ISSN 0300-9483. Detailed geomorphological mapping of the Beinn Dearg massif, northern Scotland, was conducted to examine the maximum (Younger Dryas) extent, and earlier interstadial evolution, of an icecap that existed during the Lateglacial period (14.7-11.7 cal. ka BP). Landform evidence indicates a plateau icecap configuration during the Younger Dryas. The interpreted age is supported by new cosmogenic exposure ages and previously reported interstadial sediments beyond the icecap margin. The reconstructed Younger Dryas Beinn Dearg icecap covered 176 km. Equilibrium line altitudes (ELAs) of ∼570-580 m were calculated for the icecap as a whole. The empirically reconstructed icecap is compared with recent numerical model simulations. The two methods produce an icecap with a similar configuration; however, differences are apparent in the extent of eastern and western outlets (±1-5 km), and in the spatial variation of ELAs. Results suggest that the numerical simulation overestimates the western and underestimates the eastern icecap extent. We attempt to quantify these differences in terms of icecap mass balance and assess their possible causes. Geomorphological evidence for the pre-Younger Dryas icecap configuration indicates that the Beinn Dearg massif remained an important source during earlier deglaciation. In contrast, the neighbouring Fannich mountains acted as an 'unzipping' zone, and were ice-free on their northern side by the Allerød (Greenland Interstadial 1c to 1a). Deglaciation continued over the western Beinn Dearg plateau, with the possibility that glaciers remained in some central and eastern catchments prior to (Younger Dryas) icecap (re)growth. [ABSTRACT FROM AUTHOR]

Abstract: High-resolution diatom, sediment and pollen analyses of two sections from the annually laminated SG06 core from Lake Suigetsu were used to study the onset and termination of the late-glacial climate reversal in central Japan. Its broadly recognised counterpart is the Younger Dryas or Greenland Stadial-1 (ca. 12.85–11.65cal. kyr BP based on the NGRIP ice core records). Our study suggests that accumulation of the analysed late-glacial sediments occurred in a deep and relatively cold water meso-eutrophic lake with a strong mixing regime and relatively high silica content. Combining these results together with available pollen-based environmental reconstructions we suggest that climate cooling, together with an intensified winter monsoon and thicker snow cover could influence changes in regional vegetation, sedimentation processes and trophic status of the lake during the transition from the last interstadial to stadial around Lake Suigetsu. A decrease in total pollen concentration and increase in Fagus pollen percentage indicate local vegetation stress/disturbances and suggest that cooling started at least 2–3 decades prior to the major shift in the inorganic sediment (accumulation of detrital layers) and in diatom assemblages (change from Aulacoseira ambigua to Aulacoseira subarctica dominance), which took about 10years. The transition from the last stadial to the Holocene again shows that vegetation in the lake catchment area reacted first to the regional climate change, i.e. to the weakening of the winter monsoon and decrease in winter snow accumulation. The increase in the vegetation cover density and reduced volume of surface runoff associated with the decrease in melt water supply is likely responsible for the reduced soil erosion activity which caused the cessation in detrital layer accumulation and consequent decrease in the amount of nutrients brought to the lake and lowering of the water nutrient status. The latter process finally influenced changes in the diatom assemblages, including the return to dominance of A. subarctica ca. 30years after the virtual disappearance of detrital layers from the sediment. Our results demonstrate the rapid response of the Lake Suigetsu system to the global cooling and subsequent warming, and allow clear definition of the onset and termination of the late-glacial climate reversal. Despite the fact that the lake system shows a more abrupt shift from the warm to cold (and cold to warm) environments than terrestrial records of vegetation demonstrate, we do not see any delayed response of local vegetation to the climate change. This last conclusion is of particular importance for application of the SG06 pollen record for quantitative climate reconstruction. [Copyright &y& Elsevier]

Abstract: Core and seismic data from the Venice lagoon area, located in the foreland region between the northern Apennines and the southern Alps (northern Italy), allow a detailed investigation of the Late Pleistocene fully continental succession accumulated during the last glacial phase. These deposits consist of an aggrading alluvial plain, some tens of meters thick, which is locally incised by river channels, while both patchy and continuous peat layers complete the succession. In particular, a very continuous peat layer up to 1m thick (P1), sandwiched within alluvial plain sediments, is well recognizable in the whole lagoon area in both cores and seismic lines. 14 C datings of P1 reveal an age ranging between 22 and 24cal ka B.P., confirming its lateral continuity. All these elements suggest that P1 developed after an episode of marked moisture and large scale cut-off of terrigenous sediment, leading to the establishment of generalized paludal conditions probably during the Laugerie interstadial. As at these latitudes interstadial phases were commonly typified by enhanced arboreal vegetation cover preventing significant terrigenous supply, swamp areas characterized by peat accumulation developed. The present evidence is helpful to recognize stadial–interstadial cycles during the last glacial phase, and may integrate the current knowledge to establish a correlation between cycles recorded in fully continental deposits and those recognizable in ice cores and marine successions. [Copyright &y& Elsevier]

Abstract: The early Oligocene interval in several boreholes from the eastern North Sea and Denmark has been studied for dinoflagellate cysts. The cold water dinoflagellate cyst Svalbardella cooksoniae was recorded in a narrow lowermost Oligocene interval in all offshore sections. A critical evaluation of previous records of Svalbardella cooksoniae reveals that it is present in the same narrow interval of Chron 12r, close to the NP21/NP22 boundary in many high and mid latitude Northern Hemisphere sections, ranging from the Greenland Sea in the north to Italy in the south. The Svalbardella cooksoniae interval is closely associated with the LO of the dinoflagellate cyst Areosphaeridium diktyoplokum. The age of the Svalbardella cooksoniae event indicates that it is synchronous with the Oi1a oxygen isotope maximum of Pekar and Miller (1996) and Pekar et al. (2002). In the Danish land area the Svalbardella cooksoniae interval and hence the Oi1a event is shown to coincide with an unconformity. A regional comparison shows that synchronous unconformities are present also in Belgium and New Jersey. A slightly older regional unconformity occurring on both sides of the North Atlantic coincides with the Oi1 oxygen isotope maximum of Pekar and Miller (1996). The finding of a sedimentary package separated by two successive regional unconformities is interpreted to reflect a significant, temporary eustatic sea level rise, and hence a melting phase on the East Antarctic ice sheet between the Oi1 and Oi1a glacioeustatic sea level falls. The paleogeographic distribution and lower frequency of Svalbardella during the earliest Oligocene Oi1a event, as compared with the mid Oligocene Oi2b Svalbardella spp. event, suggest that the Oi1a glacial episode was less severe than the Oi2b glaciation. This is in agreement with recent ice volume estimates for the two events. [Copyright &y& Elsevier]

Abstract: Fossil pollen and charcoal analyses of sediments from Lake Titicaca, Peru/Bolivia, provide a record of palaeoclimatic variation spanning four full glacial cycles. Pollen, aquatic microfossils, and charcoal, as well as previously published data including diatom assemblages, carbonate content, and stable carbon isotopic ratios of organic carbon, indicate that interglacials were warm and dry whereas the peaks of glacials were cold and wet. Each of the interglacials documented in the record are somewhat different, with those of MIS 5e and MIS 9 inducing lower lake levels and a drier vegetation signature than those of MIS 7 and 1. The presence of charcoal particles in sediments deposited during previous interglacials provides evidence of the long-term role of fire in shaping Andean ecosystems. [Copyright &y& Elsevier]

The late glacial to Holocene sedimentary record of the northern shelf of the Sea of Marmara (SoM) has been documented by detailed seismo-, chrono-, and biostratigraphic analyses using sub-bottom (Chirp) profiles and sediment cores. During MIS 3 and the main part of MIS 2 (60-15 C ka b.p.), disconnection from the Mediterranean and Black seas together with a dry climate resulted in a regression in the SoM, when the Sea was transformed into a brackish lake. The river incisions below 105 m water depth along the northern shelf took place during the last glacial maximum, when the lake level was modulated by stillstands at −98 and −93 m. The post-glacial freshwater transgressive stage of the Marmara 'Lake' occurred between 15 and 13.5 C ka b.p., leading to a rise in water level to −85 m by 13.0 C ka b.p., as evidenced by broad wave-cut terraces along the northern shelf. Since 12 C ka b.p., high-frequency sea-level fluctuations have been identified at the SoM entrance to the Strait of İstanbul (SoI). Thus, wave-cut terraces have been recorded at water depths of −76 and −71 m that, according to an age model for core MD04-2750, have ages of 11.5 and 10.5 C ka b.p., respectively. Ancient shoreline at −65 m along the northern shelf presumably formed soon after the Younger Dryas (YD) at ca. 10.1 C ka b.p. Moreover, there is compelling evidence of Holocene outflow from the Sea of Marmara to the Black Sea. At the SoM entrance to the SoI, the existence of bioherms on the reflector surface together with abundant Brizalina spathulata and Protoglobulimina pupoides in a core suggests a return to higher salinities due to strong Mediterranean water incursion into the SoM at ∼8.8 C ka b.p. This finding is consistent with earlier suggestions that, after the YD, the Black Sea was flooded by outflow from the SoM as a result of global sea-level rise. [ABSTRACT FROM AUTHOR]

Abstract: We have combined tensor radio magnetotelluric- (RMT, 15–250kHz) and controlled source tensor magnetotelluric (CSTMT, 1–12kHz) data for the mapping of aquifers in gravel formations lying in between crystalline bedrock and clay rich sediments in the Heby area some 40km west of Uppsala in Sweden. The estimated transfer functions, the impedance tensor and the tipper vector generally satisfy 1D or 2D necessary conditions except for the lowest CSTMT frequencies where near field effects become more dominant. The data measured from 8 profiles were inverted with the Rebocc code of Siripunvaraporn and Egbert (2000) assuming plane wave conditions. This meant that only 12 frequencies in the range of 4–180kHz could be used. The four lowest frequencies of CSTMT in the range of 1–2.8kHz were excluded because of source effects. Data from all profiles were inverted with a starting model of 100Ω-m and a relative error floor of 0.02 on apparent resistivity, corresponding to less than 1° on phase. Tipper vectors are generally small except when source effects become dominant in the lowest frequencies of CSTMT and were therefore not used for inversion. Comparing with models derived from vertical electrical soundings, refraction and reflection seismic data as well as ground truth from exploration wells assessed the reliability of the deep part of the models. Furthermore we carried out a non-linear resolution analysis to better quantify the depth extent of the aquifers. The inverted models from the Heby area show well the thickness variations of glacial deposits overlying crystalline bedrock. Generally, the upper 20m of the models have resistivities below 40Ω-m, taken to represent clay rich formations. Below the clay layer resistivities increase to about 40–400Ω-m, interpreted to represent sand/gravel formations with a maximum thickness of about 40m and a width of several hundred metres. This is a potential aquifer that extends in approximately N–S direction for some kilometres. [Copyright &y& Elsevier]