SEDIMENTOLOGICAL STUDIES OF THE PALEOCLIMATE RECORD FROM CORE PG1351, EL’GYGYTGYN CRATER LAKE, NE RUSSIA

El’gygytgyn Lake is located in central Chukotka, NE Russia (67° 30’ N; 172° 05’ E). The ~18 km diameter lake was created by a meteorite impact, dated to ~3.6 Ma. In 1998, a multinational team collected a series of overlapping cores to a total depth of 13 m that extends to ~300 ka. Our preliminary chronology is based on magnetic susceptibility correlated to the GISP2 d¹⁸O curve and infrared-stimulated luminescence dates. Magnetic susceptibility varies by an order of magnitude and reflects the climatic and environmental history of northeastern Siberia over several glacial/interglacial cycles. High susceptibility correlates to warm conditions with more oxygenated bottom waters. Low susceptibility correlates to cold (glacial) periods when perennial ice-cover causes anoxia and the dissolution of magnetic carrier materials. The principle clay mineral assemblage identified is illite, highly inter-stratified illite-smectite (I-S) and chlorite. I-S is the most dominant. The mean grain-size is in the silt fraction, with few grains larger then 60 mm. The homogeneity of the grain-size downcore indicates that changes in magnetic susceptibility are not a function of grain size. Terrigenous input to the lake comes from over 50 streams that are filtered through storm berms, limiting clastic deposition into the lake system. Clay mineralogy is susceptible to changes in climate and can be used as a proxy for climate reconstruction. Under warm hydrolyzing conditions chlorite weathers more easily and I-S abundance increases, producing an inverse relationship in relative abundance of these clays. Trends in relative abundance show distinct downcore changes that correlate with susceptibility. These trends can be divided into eight climate related zones beginning with isotopic stage 3. Fluctuations in zones 6 - 4 show a change in climate that may represent the transition from the Bølling-Allerød (13-11 ka) into the Younger Dryas (11-10 ka). The study of this short record shows that El’gygytgyn Crater Lake is sensitive to climate variability. With over 350 m of sediment, El’gygytgyn Lake potentially offers the longest and most complete Late Cenozoic lacustrine paleoclimate records available from the Arctic.