HR: 1340h
AN: PP23B-1404    [Abstracts]
TI: Last Glacial Maximum Sedimentation, and Bottom-Current Variability on the Western Svalbard Slope and Yermak Plateau, Fram Strait.
AU: * Howe, J A
EM: jaho@sams.ac.uk
AF: Scottish Association for Marine Science, Dunstaffnage Marine Laboratory Dunbeg, Oban, PA37 1QA United Kingdom
AB: Two sites in Fram Strait, between 74˚-80˚N, have been surveyed and sampled using multibeam bathymetry, sub-bottom profiling and gravity and multi-cores. This data provides a record of bottom-current variability (the West Spitsbergen Current) and sedimentation during the last 46ky. The most southerly site, on the western Svalbard margin sampled a small sediment mound in 1226m of water. The mound, interpreted as a sediment drift, is 80m high and 5km in lateral extent developed parallel to the margin and contain at least 100m of acoustically well laminated sediments. A 3.8m gravity core and associated multicore recovered from the crest of the drift contained fine-grained silty grayish-brown and dark greenish gray muds. Visible in x-radiograph, the upper section (above 1.50m) of the core contained centimeter-scale silty lamination, with little ice rafted debris (IRD), whilst the lower sections (below 1.50m) contained abundant IRD and no lamination. These sediments are interpreted as fine-grained laminated silty turbidites and muddy-silty contourites. 14C AMS dating indicates an age range of early Holocene (8,380 yrs BP) to late Pleistocene, including Last Glacial Maximum (LGM) (26,993 yrs BP). The more northerly site, sampled acoustically well-laminated sediments draped on the flank of the Yermak Plateau in water depths of 961m. A 3.5m gravity core and associated multicore recovered fine-grained, faintly laminated, greenish gray muds, with minor amounts of IRD common throughout. These sediments are interpreted as silty glaciogenic contourites. 14C dating reveal an age range of between 8,708 - 46,530yrs BP. Dinoflagellate cyst analyses of both cores, provides both biostratigraphic data and information on the surface water conditions. Three biostratigraphic units sub-divide both the cores: 1. Early Holocene-post LGM interval, dominated by a temperate, North Atlantic flora with high productivity and open water ameliorative conditions. 2. Last Glacial Maximum displaying poor cyst recovery and severe, high polar conditions, although with some short-lived open water conditions, indicative of some climatic amelioration. 3. Pre-LGM indicating severe polar conditions with poor cyst recovery, although again with some short-lived phases of open water and limited productivity. The record of bottom-current variability, indicating the activity of the West Spitsbergen Current during the last 46 ky, has been extracted from both cores by examining the mean sortable silt, deconvolved from the IRD signal. Bottom-current activity was weak throughout the LGM, but becomes highly variable and increases during the post-LGM and into the Holocene, corresponding to the onset of increased thermohaline circulation and deep-water production in Fram Strait during deglaciation.
DE: 9315 Arctic region
DE: 5462 Polar regions
DE: 3344 Paleoclimatology
DE: 4267 Paleoceanography
DE: 3022 Marine sediments--processes and transport
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting