ALBERT

Description: Seismic profiles of Far East Russian Lake El’gygytgyn which was formed by a meteorite impact some 3.6 million years ago show a stratified sediment succession that can be separated into Subunits Ia and Ib at approximately 167 m below lake floor (= ∼3.17 Ma). The former is well-stratified, while the latter is acoustically more massive. The sediments are intercalated with frequent mass movement deposits mainly in the proximal parts, while the distal part is almost free of such deposits at least in the upper part. In spring 2009, a long core drilled in the lake center within the framework of the International Continental Scientific Drilling Program (ICDP) penetrated the entire lacustrine sediment succession down to ~320 m below lake floor and about 200 m further into the meteorite-impact related bedrock. Downhole logging data down to 390 m below lake floor show that the bedrock and the lacustrine part of the core differ largely in their petrophysical characteristics. The contact between the bedrock and the lacustrine sediments is not abrupt, but rather transitional with a mixture of impact-altered bedrock clasts in a lacustrine matrix with varying percentages. Physical and chemical proxies measured on the cores can be used to divide the lacustrine part into five different clusters. These can be plotted in a redox-condition vs. input type diagram with total organic carbon content and magnetic susceptibility values indicating anoxic or oxic conditions and with the Si/Ti ratio representing more clastic or more biogenic input. Plotting the clusters in this diagram allows identifying clusters that represent glacial phases (Cluster I), super interglacials (Cluster II), and interglacial phases (Clusters III and IV).