The Lake El’ gygytgyn drilling project - Objectives and current stage of preparation

Category Other
Group GSI.IR
Location International Geological Congress,oslo 2008
Author Juschus, Olaf
Holding Date 29 September 2008

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 decade the sedimentary record of the lake has become a major focus of multi-disciplinary multi-national paleoclimatic research. Recently, the International Continental Scientific Drilling Program (ICDP) has provided funding for a drilling operation on the lake and in its permafrost catchment in spring 2008. Additionally the project became involved into the IPY under the umbrella of APEX and BIPOMAC.
A full-length sediment core from Lake El’ gygytgyn would yield a complete record of Arctic climate evolution, 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. Two, 12.9 m and 16.5 m long sediment cores retrieved from the deepest part of the lake in 1998 and 2003 revealed a basal age of approx. 300 ka, confirmed the lack of glacial erosion, and underlined the sensitivity of this lacustrine environment to reflect high-resolution climatic change on Milankovitch and sub-Milankovitch time scales.
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 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 entire Quaternary and possibly parts of the late Tertiary record are reflected by the 170 m thick unit one, whilst the earliest history of the lake is presumably represented with a considerable higher sedimentation rate by unit two. There is no evidence for glacial erosion or complete lake drying in the entire sedimentary record.
Coring objectives include replicate cores of 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 offers the planetary community with the opportunity to study a well preserved crater uniquely found in igneous rocks like those on Mars. One additional core to ca. 200 m into permafrost from the adjacent catchment will allow us to test ideas about arctic permafrost history and sediment supply to the lake since the time of impact.
The permafrost coring will likely be conducted in 2008 and the lake based coring in spring 2009. The lake coring will use the ice cover as a platform and a modified GLAD-800 rig. The equipment will be carried by ship to Pevek, app. 180 km to the North of the lake. Main transportation from Pevek to the lake will happened during late winter/early spring 2009 using snow-trucks of local mining companies.