Glacial and interglacial sediment history on Bol’shoy Lyakhovsky, New Siberian Archipelago, from multiple permafrost cores

• Main Authors: Schwamborn, Georg, Schirrmeister, Lutz, Wetterich, Sebastian, Fuchs, Margret, Meyer, Hanno, Siegert, Christine
• Format: Conference Object
• Language: unknown
• Published: Bibliothek Wissenschaftspark Albert Einstein Telegrafenberg 14473 Potsdam 2016
• Subjects: East Siberian Sea; Ice; Ice Sheet; permafrost; Thermokarst; wedge*; Siberia
• Online Access: https://epic.awi.de/id/eprint/41967/; https://hdl.handle.net/10013/epic.48772

Bol’shoy Lyakhovsky, the southernmost island of the New Siberian Archipelago, holds the longest record of palaeoenvironmental history in the non-glaciated Siberian Arctic preserved in permafrost. It stretches back to ~200 kyr before present and includes prominent last interglacial thermokarst and Yedoma (Ice Complex) sections. Yet, it is unknown, whether or not the depositional history of the site is affected by the deglaciation of the northern part of the New Siberian Archipelago. Potentially, it could give insight into the break-up of the proposed MIS 6 ice sheet located on the East Siberian Sea shelf (Jakobsson et al., 2014). The lithostratigraphy of southern part of the island consists of palaeosols, floodplain and lake deposits, subaerial Yedoma and lacustrine to palustrine alas formations. Large ice wedges (partially up to several meters high and thick), segregation and pore ice record a syngenetic freezing of the Yedoma silts. Polymodal particle size distributions suggest that more than one transport mechanism drove sediment accumulation from more than one source. Recent papers conclude that the palaeoclimate record matches the general Late Quaternary climate history in northern Siberia (Andreev et al., 2011; Wetterich et al., 2011). From a multi proxy data set we focus on (i) the mineral composition (63-125 μm fraction) to determine the provenance of the deposits and to identify possible changes of transport pathways. Complementary, we use (ii) pore ice hydrochemistry as a means to track changes of the soil solution that principally reflects the site’s chemical weathering history preserved in permafrost. Presumably the two approaches complement each other, since the weathering solution should largely reflect the mineral matter composition. The heavy mineral association suggests that most of the minerals derive from the underlying bedrock (Upper Jurassic-Lower Cretaceous sandstones and Upper Cretacous granites and diorites); among others it has high amounts of ilmenite and leucoxene, epidote, pyroxenes ...