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. During the last 8 years the sedimentary record of the lake has become a major focus of multidisciplinary multinational paleoclimatic research. Recently, the International Continental Scientific Drilling Program (ICDP) and national agencies have provided funding for a drilling operation on the lake and in its permafrost catchment in winter 2007/08.

A full-length sediment core from Lake El'gygytgyn would yield a complete record of climate evolution of the Arctic, back one million years prior to the first major glaciation of the Northern Hemisphere. Geomorphological evidence from the catchment suggests that the crater was never glaciated during the entire Late Cenozoic. A 12.9 m long sediment core retrieved from the deepest part of the lake in 1998 revealed a basal age of approx. 250 kyr, confirmed the lack of glacial erosion, and underlined the sensitivity of this lacustrine environment to high-resolution climatic change on Milankovitch and sub-Milankovitch time scales. Four sediment units were distinguished, reflecting relatively warm, peak warm, cold and dry, and cold but more moist climates. A 16.7 m long sediment core taken in 2003 dates to nearly 300 kyr and confirms the reproducibility of the record. Additional cores from the western lake have shown that the formation of debris flows at the slope is associated with partial erosion of the underlying sediments. This leads to the development of suspension clouds, whose deposition generally takes place all over the lake as «pelagic rain» without erosion. Hence, the sediment records in the central lake during at least the past 300 ka are continuous, and the existing cores represent the longest continuous climate records as yet available from the arctic continent.

Seismic investigation carried out during expedtions in 2000 and 2003 revealed a depth-velocity model of brecciated bedrock overlain by a suevite layer, in turn overlain by two lacustrine sedimentary units up to 350 m in thickness. The upper well-stratified sediment unit appears undisturbed apart from intercalation with the debris flows near the slopes. Based on extrapolation of sedimentation rates the 170 m thick unit one reflects the entire Quaternary and possibly parts of the late Tertiary, whilst the earliest history of the lake is presumably represented by unit two with a higher sedimentation rate. In the entire sedimentary record there is no evidence of glacial erosion or complete drying out.

Coring objectives include replicate cores of up to 630 m length to retrieve a continuous paleoclimate record from the deepest part of the lake and into the underlying impact breccias and bedrock. Studies of the impact rocks offer the planetary community an opportunity to study a well preserved crater uniquely found in igneous rocks like those on Mars. One additional core to с 200 m deep in permafrost of the adjacent catchment will allow us to test ideas about arctic permafrost history and sediment supply to the lake since the time of impact.

Reference:

Melles M., Minyuk P.S., Brigham-Grette J., Koeberl Ch. and El'gygytgyn Scientific Party Lake El'gygytgyn, NE Siberia: deep drilling in 2007/08 for the first continuous 3.6 mio year paleoclimate record in the terrestrial Arctic. Correlation of Pleistocene Events in the Russian North. International Workshop Abstracts. 4-6 December 2006. Saint-Petersburg, 2006, p. 62.