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Climatic and associated hydrological changes controlled the transport processes and composition of the sediments in the central Red Sea during the last ca. 200 kyr. Three different source areas for mineral dust are identified. The dominant source is located in the eastern Sahara (Sudan and southernmost Egypt). We identify its imprint on Red Sea sediments by high smectite and Ti contents, low 87 Sr / 86 Sr, and high εNd. The availability of deflatable sediments was controlled by the intensity of tropical rainfall and vegetation cover over North Africa linked to the African monsoon. Intense dust input to the Red Sea occurred during arid phases, and low input occurred during humid phases. A second, less significant source indicated by palygorskite input is probably located on the eastern Arabian Peninsula and/or Mesopotamia, while the presence of kaolinite suggests an additional minor dust source in northern Egypt. Our grain size data reflect episodes of fluvial sediment discharge to the central Red Sea and document the variable strength in response to all of the precession-paced insolation maxima during our study interval including both those that were strong enough to trigger sapropel formation in the eastern Mediterranean Sea and those that were not. The African humid period most strongly expressed in our Red Sea record was the one during the Eemian last interglacial at ca. 125 ka (when the Baraka River was far more active than today), followed by those at 198, 108, 84, and 6 ka. [ABSTRACT FROM AUTHOR]

New information is presented on the configuration of the northern Barents Sea Ice Sheet ( BSIS) during the last glacial and deglaciation (21-11.5 ka). The glacial dynamics of the BSIS that we discuss are based on clay-mineral compositions of subglacial tills and a distinct kaolinite source in the central Barents Sea where previous workers have placed a large, single ice dome for the last glacial BSIS. Our results, which appear to show that subglacial sediments were sourced locally, suggest that the BSIS consisted at least temporarily of multiple domes and may have been more dynamic than previously thought. New radiocarbon dates are presented along with new ice-extent reconstructions for 16.5-15, 14, 13.5 and 11.5 ka. Our reconstructions add information to previous regional and continental-scale efforts in areas east of Svalbard. Ice retreat in the northern Barents Sea progressed as follows. (i) 19-16.5 ka. Major calving led to dynamic thinning in shelf troughs and was accompanied by significant ice-sheet thinning inland as a result of ice drawdown. (ii) 16.5-15 ka. Rapid ice-margin retreat of between 75-100 km occurred, via lift-off and iceberg calving, in Hinlopen and Kvitøya troughs, as well as major retreat (>300 km) in Franz Victoria Trough ( FVT) further east. (iii) 15-13.5 ka. Retreat progressed westwards from the FVT towards Svalbard with troughs east of Svalbard (Kvitøya, Olga, and Erik Eriksen) mostly ice-free by 13.5 ka. (iv) 13.5-11.5 ka. Ice retreated gradually towards residual ice masses on Svalbard, Kong Karls Land and possibly Storbanken. Our data require a modification of earlier views of the BSIS because they point toward a more dynamic ice sheet and decay that, once initiated at the shelf break, was dominated by the withdrawal of ice from the FVT that progressed westwards towards the Svalbard archipelago. [ABSTRACT FROM AUTHOR]

Clay mineral assemblages in a sediment core from the distal Nile discharge plume off Israel have been used to reconstruct the late Quaternary Nile sediment discharge into the eastern Mediterranean Sea (EMS). The record spans the last ca. 140 kyr. Smectite abundances indicate the influence of the Blue Nile and the Atbara River that have their headwaters in the volcanic rocks of the Ethiopian Highlands. Kaoli-nite abundances indicate the influence of wadis, which contribute periodically to the suspension load of the Nile. Due to the geographical position, the climate and the sedimentary framework of the EMS is controlled by two climate systems. The long-term climate regime was governed by the African monsoon that caused major African humid periods (AHPs) with enhanced sediment discharge at 132 to < 126 (AHP 5), 116 to 99 (AHP4), and 89 to 77 ka (AHP3). They lasted much longer than the formation of the related sapro-pel layers S5 (>2kyr), S4 (3.5kyr), and S3 (5kyr). During the last glacial period (Marine Isotope Stages (MISs) 4-2), the long-term changes in the monsoonal system were superimposed by millennial-scale changes in an intensified mid-latitude glacial system. This climate regime caused short but pronounced drought periods in the Nile catchment, which are linked to Heinrich events and alternate with more humid in-terstadials. The clay mineral record further implies that feedback mechanisms between vegetation cover and sediment discharge of the Nile are detectable but of minor importance for the sedimentary record in the southeastern Mediterranean Sea during the investigated African humid periods. [ABSTRACT FROM AUTHOR]

Abstract: The ratio between the clay minerals kaolinite and chlorite has been investigated in high resolution in a late Quaternary sediment core from the central Aegean Sea. The record spans the last ca. 105ka. The kaolinite/chlorite ratio was used to reconstruct the fine-grained aeolian dust influx from the North African deserts, mainly derived from desiccated lake depressions. It therewith can be used as a proxy for wind activity, aridity and vegetation cover in the source area. The data document three major humid phases in North Africa bracketing the formation of sapropel layers S4, S3 and S1. They occur at >105–95ka, 83.5–72ka and 14–2ka. The first two phases are characterised by relatively abrupt lower and upper boundaries suggesting a non-linear response of vegetation to precipitation, with critical hydrological thresholds. In contrast, the onset and termination of the last humid period were more gradual. Highest kaolinite/chlorite ratios indicating strongest aeolian transport and aridity occur during Marine Isotope Stage (MIS) 5b, at ca. 95–84ka. The long-term decrease in kaolinite/chlorite ratios during the last glacial period indicates a gradual decline of deflatable lake sediments in the source areas. [Copyright &y& Elsevier]

The Amundsen Sea embayment is a probable site for the initiation of a future collapse of the West Antarctic Ice Sheet. This paper contributes to a better understanding of the transport pathways of subglacial sediments into this embayment at present and during the last glacial period. It discusses the clay mineral composition of sediment samples taken from the seafloor surface and marine cores in order to decipher spatial and temporal changes in the sediment provenance. The most striking feature in the present-day clay mineral distribution is the high concentration of kaolinite, which is mainly supplied by the Thwaites Glacier system and indicates the presence of hitherto unknown kaolinite-bearing sedimentary strata in the hinterland, probably in the Byrd Subglacial Basin. The main illite input is via the Pine Island Glacier. Smectite originates from the erosion of volcanic rocks in Ellsworth Land and western Marie Byrd Land. The clay mineral assemblages in diamictons deposited during the last glacial period are distinctly different from those in corresponding surface sediments. This relationship indicates that glacial sediment sources were different from modern ones, which could reflect changes in the catchment areas of the glaciers and ice streams. [ABSTRACT FROM PUBLISHER]

Abstract: Clay mineral assemblages in sediments from ANDRILL drill core AND-2A were used to reconstruct the Neogene palaeoenvironment. For the first time a clay mineral data set can be presented for southern McMurdo Sound, Ross Sea, Antarctica, that covers an expanded and fairly continuous Lower and Middle Miocene section. Although the occurrence of some authigenic smectites, zeolites and opal-CT documents diagenetic processes, the clay mineral assemblages allow a subdivision of the core into three intervals that reflect changes in provenance and volcanic activity. Interval I (1000–440mbsf, 20.0–16.5Ma) is characterised by a dominant sediment source in the Transantarctic Mountains. Frequent and short-term changes in the illite and smectite concentrations were caused by the influx of volcanic sediment components from southern McMurdo Sound and by diagenesis. Interval II (440–225mbsf, 16.5–15.0Ma) has much more uniform illite and smectite contents. The assemblage is derived from the Transantarctic Mountains. Interval III (225–0mbsf, 15.0–0Ma, containing major hiatuses) shows a distinctly enhanced volcanic influence and sediment components that come from the south of McMurdo Sound. The AND-2A clay mineral assemblages indicate persistent physical weathering conditions and do not mirror the Mid-Miocene Climatic Optimum. They indicate that the climatic changes were probably not strong enough to cause a modification in the weathering regime on the Antarctic continent. [Copyright &y& Elsevier]

The African monsoon system controlled the mobilisation and delivery of clay-sized sediment particles to the Eastern Mediterranean Sea in the late Quaternary. During African Humid Periods of the last 200 kyr, smectite-rich suspension load was provided by the Nile river and by palaeo-rivers discharging into the Gulf of Sirte. After the termination of the African Humid Periods, kaolinite- and palygorskite-rich clay was mobilised from desiccated soils, lake and river beds, and delivered in form of dust pulses to the Eastern Mediterranean Sea. Magnitude and abruptness of the dust pulses depend on the distance of the accumulation sites from the dust sources. Proximal sites experienced large amounts of dust from local sources, while more distal sites received dust from the wider Saharan region, documenting the time-transgressive termination of the humid periods. The strengths of individual dust pulses reflect the intensity of the preceding humid periods. Distinct droughts during the last glacial period can be associated with Heinrich events and are best documented at a semi-distal site, illustrating links between the African monsoon and the climate of the high-latitudes. • Review of the dynamics of North African humid and dry periods during the last ca. 200 kyr. • Marine clay mineral assemblages allow the reconstruction of aeolian and fluvial influx to the Eastern Mediterranean Sea. • Distinct kaolinite- and palygorskite-rich dust pulses occur after the terminations of the African Humid Periods. • The dust pulses reflect the intensities of the preceding humid periods. • Intense fluvial suspension influx by the Nile and Libyan palaeo-river systems during humid periods. [ABSTRACT FROM AUTHOR]

West Antarctica hosts one of the largest continental rift systems on earth. Due to the extensive ice cover and the lack of exposed sedimentary rocks, little is known about the detailed geological and climatic evolution of West Antarctica. Here we present initial geochronologic, petrographic, stratigraphic, palynologic and clay mineralogy data of the first drill cores from the Amundsen Sea, off West Antarctica. The drilled succession revealed fine-grained, plant-bearing sediments of late Cretaceous age (~93 to 85 Ma), deposited during continental stretching and breakup between West Antarctica and New Zealand. The Cretaceous deposits are separated by a peat layer from coarse-grained sandstones, which contain zircon and apatite yielding U-Pb ages of ca. 46-39 Ma. This implies a hiatus of at least 40 Myr between the fine-grained Cretaceous deposits and the overlying sandstones, which is in agreement with the absence of in-situ or reworked Paleocene to early/mid-Eocene palynomorphs. We tentatively interpret this hiatus as reflecting tectonic quiescence and slow downwearing, or non-deposition. This interpretation supports our previous thermochronological data from the onshore realm, which show that extension-related exhumation ceased at the end of the Cretaceous. We interpret renewed deposition during the upper Eocene to Oligocene to reflect renewed rapid exhumation along the West Antarctic Rift System and the rise of the Transantarctic Mountains. As well as the Eocene dates, the Eocene to Oligocene sandstones contain Cambro-Silurian, Permo-Triassic, Early Jurassic and Cretaceous apatite U-Pb age groups, which we interpret as derived from the Transantarctic Mountains (igneous and metamorphic rocks of the Cambro-Ordovician Ross Orogeny, and volcanic rocks related to the Early Jurassic Ferrar volcanic event) and Marie Byrd Land / West Antarctica (Permo-Triassic magmatic arc and widespread Cretaceous batholiths). Unusual for this kind of lithology, the sandstones' apatite yield is low, and lattice defects of apatite grains frequently show etching features. Cretaceous rhyolite clasts, abundant in the sandstones, are sometimes heavily kaolinized, and the clay fraction of the sandstones contains up to >70% kaolinite. All these features, along with the results of palynology, imply an acidic, swamp-like deposition environment characterised by moderate to strong chemical weathering, and a temperate climate with warm intervals, becoming cooler towards the Oligocene. [ABSTRACT FROM AUTHOR]