HR: 17:30h
AN: PP24A-07    [Abstracts]
TI: Sedimentation in Lake El'gygytgyn, Northeastern Siberia, During the Past Three Climate Cycles
AU: * Melles, M
EM: melles@rz.uni-leipzig.de
AF: University Leipzig, Institute for Geophysics and Geology, Talstrasse 35, Leipzig, D-04103 Germany
AU: Anderson, P M
AF: University, of Washington, Seattle, 98195 United States
AU: Apfelbaum, M
AF: University, of Massachusetts, Amherst, 01003 United States
AU: Asikainen, C
AF: University, of Massachusetts, Amherst, 01003 United States
AU: Brigham-Grette, J
AF: University, of Massachusetts, Amherst, 01003 United States
AU: Cherepanova, M
AF: Institute for Biology, and Soil Science, Vladivostok, 690022 Russian Federation
AU: Kopsch, C
AF: Alfred Wegener, Institute, Potsdam, D-14473 Germany
AU: Forman, S
AF: University, of Illinois, Chicago, 60607 United States
AU: Juschus, O
AF: University Leipzig, Institute for Geophysics and Geology, Talstrasse 35, Leipzig, D-04103 Germany
AU: Lozhkin, A V
AF: North-East Interdiscipl., Sci. Res. Inst., Magadan, 685010 Russian Federation
AU: Minyuk, P
AF: North-East Interdiscipl., Sci. Res. Inst., Magadan, 685010 Russian Federation
AU: Niessen, F
AF: Alfred Wegener, Institute, Bremerhaven, D-27515 Germany
AU: Nowaczyk, N R
AF: GeoForschungs, Zentrum, Potsdam, D-14473 Germany
AU: Snyder, J
AF: Bowling Green, State University, Bowling Green, 43403 United States
AB: Lake El'gygytgyn, located in central Chukotka, NE Siberia, is a 3.6 million year old impact crater lake with a diameter of 12 km and a water depth of 170 m. Sediment cores of 13 and 16 m length from the deepest part of the lake were investigated for chronology, physical properties, sedimentology, biogeochemistry, inorganic geochemistry, mineralogy, palynology and diatom assemblages. The cores are undisturbed and complete. With basal ages of approx. 250 and 300 ka, respectively, they represent the longest continuous climate records as yet available from the Arctic continent. Besides two ash layers and a number of distal, fine-grained turbidites, four "pelagic" sediment units of different composition can be distinguished. During warm periods (units 1 and 2), summer melt of the ice cover leads to high aquatic primary production, ventilation of the entire water column by annual turnover, decomposition of most of the settling particulate organic matter, and bioturbation of the sediments. Among these periods, MIS 5.5 (Eemian) and to a smaller degree late MIS 1 (Holocene) exhibited significantly higher organic matter accumulation (unit 1) than MIS 3, 5.1, 5.3, 6.1, 6.3, 6.5, 7.1, 7.3, and 7.5 (unit 2). This was probably due to enhanced nutrient and organic matter supply from a more dense vegetation cover in the catchment. The density and composition of the regional vegetation, in turn, was not only controlled by insolation, but also by precipitation and/or temperature changes due to alterations in the atmospheric circulation pattern. During cold periods (units 3 and 4), a persistent ice cover hampers primary production and leads to a stratified water column with anoxic bottom waters, good preservation of the settling organic matter, and the formation of laminated sediments due to the absence of bioturbating organisms. Among these periods, cold and particularly dry climates lead to the widespread absence of blanketing snow on the lake ice cover, enabling the formation of sediment clasts and sufficient light penetration for significant primary production beneath the ice (unit 3). This mode prevailed during MIS 2, 5.2, 5.4, 6.2 and 6.4. The high aridity can best be explained by a predominance of westerly winds. A cold but more moist climate, in contrast, generates a blanketing snow cover on the ice, which hampers clast formation and significantly reduces the aquatic primary production (unit 4). Cold and moist climates prevailed at Lake El'gygytgyn during MIS 4, 6.6, 7.2, 7.4 and the top of MIS 8. The higher moisture supply could be due to northerly or easterly winds more frequently reaching the area in consequence of a westward migration or weakening of the Siberian High.
DE: 9604 Cenozoic
DE: 1035 Geochronology
DE: 1055 Organic geochemistry
DE: 1620 Climate dynamics (3309)
DE: 1650 Solar variability
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting