Abstract
Abstract. Seismic profiles of Far East Russian Lake El'gygytgyn, 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 upper (Ia) is well-stratified, while the lower is acoustically more massive and discontinuous. The sediments are intercalated with frequent mass movement deposits mainly in the proximal areas, while the distal region 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 farther into the meteorite-impact-related bedrock. Downhole logging data down to 390 m below lake floor show that the bedrock and the lacustrine part differ significantly in their petrophysical characteristics. The contact between the bedrock and the lacustrine sediments is not abrupt, but rather transitional with a variable mixture of impact-altered bedrock clasts in a lacustrine matrix. Physical and chemical proxies measured on the cores can be used to divide the lacustrine part into five different statistical 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).
Highlights
Earth System SciencesThe Arctic region is highly susceptible to global change and, at the same time, plays a major role in the global climate system through feedback processes in the oceans, the atmosphere, and the cryOospcheerae.nAScccorideinngclyeit is important to understand past climate changes under different climateforcing conditions in order to make accurate predictions about future climate development
When plotting facies and clusters together vs. depth (Fig. 7) it becomes obvious that only some parts of facies C were captured by cluster II: between ∼ 62 and ∼ 62.7 m b.l.f., facies C sediments were visually described, but have rather low Si / Ti content and only slightly enhanced total organic carbon (TOC) values, so they were statistically gathered into clusters I and IV; these samples are part of the 5.82 % of facies C samples that were found in cluster I and 6.11 % in cluster IV
Seismic reflection profiles of Lake El’gygytgyn exhibit mostly well-stratified sediments with frequent mass movement deposits intercalated in the more proximal areas
Summary
The Arctic region is highly susceptible to global change and, at the same time, plays a major role in the global climate system through feedback processes in the oceans, the atmosphere, and the cryOospcheerae.nAScccorideinngclyeit is important to understand past climate changes under different climateforcing conditions in order to make accurate predictions about future climate development. Lakes of the higher latitudes are sparsely investigated even though they are highly sensitive to shifts in climatological and environmental conditions (e.g. temperature, preciSpitoatliiodn, Einsaorlatthion, vegetation, ice coverage), and as such they are valuable tracers of climate change. This paper aims to characterize the lacustrine part of core 5011-1 as well as the transitional zone between the lacustrine sediments and the impact-related bedrock by means of petrophysical parameters such as physical properties and downhole logging measurements. These findings are compared to the facies description by Melles et al (2007, 2012) and Brigham-Grette et al (2013) and their interpretation contained therein. The El’gygytgyn area has never been subjected to glacial overprint since its formation (Glushkova and Smirnov, 2007), and, the lake contains an undisturbed climate record
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