HR: 15:15h
AN: C13C-07    [Abstracts]
TI: Sediments from the North Siberian Margin as Archive of Paleoenvironmental Change
AU: * Kassens, H
EM: hkassens@ifm-geomar.de
AF: IFM-GEOMAR, Wischhofstrasse 1-3, Kiel, 24148 Germany
AU: Bauch, H A
EM: hbauch@ifm-geomar.de
AF: Mainz Academy of Sciences, Humanities and Literature c/o IFM-GEOMAR, Wischhofstrasse 1-3, Kiel, 24148 Germany
AB: Empirical data as well as modelling experiments show that the stability of the Arctic cryosphere is today under threat due to global warming. Along the circum-arctic ocean periphery this cryosphere is comprised of terrestrial permafrost. However, during Quaternary times this frozen landscape was repeatedly changed due to global sea-level fluctuations which particularly affected the wide and shallow Siberian shelves. As western part of the Beringian landmass the entire Laptev Sea shelf was subaerially exposed in last glacial times. During postglacial sea-level rise the landscape gradually changed from a terrestrial permafrost landscape into a marine environment. Various geochemical, micropaleontological, palynological, and sedimentological data obtained from sediment cores reveal the strong influence of this tranformation process on the shelf environment. So far, sediment material older than early Holocene could not be obtained from the shelf by conventional means. A scientific drilling campaign was therefore conducted to the outer Laptev Sea shelf with the goal to recover sediments that would allow an environmental study of this area on time scales beyond the Holocene. Previous site investigations by acoustic profiling and a gravity core suggested a Holocene sediment package of about 10 m thickness. The cores recovered during the drilling campaign from below this depth level reveal various types of ice-bearing, frozen sediments which contain a rich terrestrial plant flora as well as beetle fauna, both suggesting a late glacial age in accordance with the other obtained dates. Further micropaleontological and isotopic analyses corroborate a strong influence of a terrestrial-fuvial environment during this time of permafrost formation, and that at present frozen sediments are being preserved on these shelves below a soft sediment cover of Holocene age.
DE: 3030 Micropaleontology
DE: 1823 Frozen ground
DE: 1833 Hydroclimatology
DE: 1615 Biogeochemical processes (4805)
SC: Cryosphere [C]
MN: 2004 AGU Fall Meeting