Abstract Ice-rafted tephra deposits, of Marine Isotope Stage 6 (MIS 6) age, from Site U 1304 on the Gardar Drift, North Atlantic were examined for their shard size distribution and major element composition. The heterogeneous composition, large shard sizes and association with ice-rafted debris (IRD) indicate that these late MIS 6 deposits were transported by iceberg-rafting from Iceland to Site U 1304. Comparison of individual shard geochemistry with the geochemistry of Holocene volcanic systems from Iceland allows the identification of different potential volcanic source regions. This detailed geochemical analysis, when combined with Icelandic Ice Sheet (IIS) flow models for the Last Glacial Maximum (LGM), suggests that the IIS had calving margins to both the north and south during the late MIS 6 and that icebergs could have been transported to the Site U 1304 by following surface ocean circulation patterns similar to those that prevailed during the LGM. We demonstrate that the descriptive concept of Icelandic glass in the characterization of tephra components within North Atlantic IRD can be significantly improved through quantitative characterization and that such data hold the potential to help constrain surface ocean circulation models, while also potentially yielding new information about the IIS during earlier glacial periods. Supplementary material: Statistical tests, major element concentrations of analysed shards, primary and secondary standards are available at http://www.geolsoc.org.uk/SUP18716

Abstract We present results of a multi-proxy study on marine sediment core JR179-PC466 recovered from the crest of a sediment drift off the West Antarctic Peninsula at approximately 2300 m water depth. The 10.45 m-long core consists dominantly of glaciomarine terrigenous sediments, with only traces of calcium carbonate (<1 wt%). Despite the very low abundance of calcareous foraminifera, planktonic shell numbers are sufficient for stable isotope analyses in two-thirds of the samples studied. The core chronology is based on oxygen isotope stratigraphy and correlation of its relative palaeomagnetic intensity (RPI) with a stacked reference curve. According to the age model, core PC466 spans the last 75 ka, with average sedimentation rates of between about 4 and 25 cm ka −1 . Planktonic foraminifera abundances fluctuate between 0 and 30 individuals per gram throughout the core, with minima observed during Marine Isotope Stage (MIS) 2 (14–29 ka before present, BP) and MIS4 (57–71 ka BP). Planktonic foraminifera are present in the Holocene but more abundant in sediments deposited during MIS3 (29–57 ka BP), owing to less dilution by terrigenous detritus and/or better carbonate preservation. During MIS3, foraminifera maxima correlate with Antarctic warming events as recorded in the δ 18 O signal of the EPICA Dronning Maud Land (EDML) ice core. They indicate higher planktonic foraminifera production and better carbonate preservation west of the Antarctic Peninsula during that time. The abundance of ice-rafted detritus (IRD) in core PC466 increased during the last deglaciation between about 19 and 11 ka BP, when numerous icebergs drifted across the core site, thereby releasing IRD. During this time, sea-level rise destabilized the Antarctic Peninsula (APIS) and West Antarctic (WAIS) ice sheets that had advanced onto the shelf during the sea-level low-stand of the Last Glacial Maximum (LGM; c . 19–23 ka BP). Overall, our results demonstrate that it is possible to establish an age model and reconstruct palaeoceanographical and climatic changes at high temporal resolution from sedimentary sequences recovered at 2300 m water depth from a West Antarctic drift.

Abstract Qilu Hu (area =37 km-, zmax = 7 m) and XingyunHu (area =39 km-, zmax =12 m) lie at 1797m and 1723mabove mean sea level (Whitmore et al. 1997), respectively,on the Yunnan Plateau, southwest China (Figure1). Analyses of water-column nutrients and Secchidisk measurements show that Qilu Hu is currentlyeutrophic and Xingyun Hu is meso-eutrophic (Mooreet al., 1988; Whitmore et al., 1994a, 1997). Upper Tertiarydeposits in Yunnan Province are rich in browncoalbut karsted limestone dominates the surface rock(Li and Walker, 1986). Valleys in the region often possessfluvial and lacustrine deposits of Quaternary age.An 11.0-m sediment core was collected from Qilu Huin 1987and an 8.4-m section was obtained from XingyunHu in 1989. Chronologies for the sediment cores were established by standard 14C dates on bulk organic matter and an AMS 14C date on wood (Figure 2). Sediment profilescontain records of lacustrine deposition from the latePleistocene to present (Brenner et al., 1991;Whitmore etal., 1994a, 1994b).The 14C date on wood at 7.39m in QiluHu is younger than the date on bulk organic matter from5.99-5.81 m, suggesting that hard-water-Iake error makesdates on lacustrine organic matter about 1800 yr olderthan true 14C ages (Brenner et al., 1991).Paleoecological studies in Yunnan Province have employed ostracod remains (Jiang, 1990) or magneticmeasurements in lake sediments to infer paleoenvironmentalconditions (Yu et al., 1990). Fang (1991) presentedreconstructions of past lake levels.Paleoenvironmental inferences for the 1987 Qilu Hucore and the 1989 Xingyun Hu core were based on geochemical,palynological, and diatom analyses (Brenneret al., 1991; Deevey et al., 1988; Long et al., 1991;