Late Quaternary palaeo-environmental history of Muostakh Island, Northern Siberia based on sedimentological and geocryological studies


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Hanno.Meyer [ at ] awi.de

Abstract

Muostakh Island (N 71°36’; E 129°57’) is a spectacular site in the Siberian Arctic due to its very high coastal erosion rates of up to 20 m/year as well as substantial permafrost subsidence (Günther et al., 2015). The island extends about 7.5 km in the N-S direction and up to 500m in E-W direction and has been connected to the mainland until a few thousand years ago. Sediments and ground ice of the Yedoma type (the so called Ice Complex; Schirrmeister et al., 2011) form up to 20 m high coastal cliffs on Muostakh Island. The main aim of this multi-proxy study is to cover the complete sedimentological and geocryological sequence for a detailed palaeoenvironmental interpretation of the island. In general, the sedimentary sequence from Muostakh Island is divided into three stratigraphic units and consists of sediments of late Pleistocene to Holocene age. The lowermost unit A is approximately 8 m thick, rich in ground ice and comprises mostly sandy silt alternating with thin peat layers. At the top of this unit, a prominent 1 m thick peat layer is found in many sections on the island. In unit A, the ice wedges may reach widths of up to 5 m. At ca. 10m a.s.l., a hiatus from ca. 41.6 kyr BP to ca. 19.7 kyr BP is indicated by an erosional plane sharply intersecting ice wedges and sedimentary structures as well as by geocryological observations, i.e. distinctly narrower ice wedges above the discordance. Above this erosional plane, unit B, which is composed of 8-9 m of coarse-grained material, is indicative for fast and highly-energetic deposition, absent in many other sites of Ice Complex exposures in the Laptev Sea region (i.e. at nearby Mamontovy Khayata outcrop on Bykovsky Peninsula; Meyer et al., 2002). The upper (and youngest) sedimentary unit C reaches a maximum thickness of about 4-5 m and is laterally discontinuous. About 10 m wide peaty patches of Holocene organic-rich and ice-rich sandy silts cover the underlying deposits. Peat patches are intersected by ice wedges of generally less than 1 m wide, but in exceptions also reaching 3-5 m in width, penetrating downwards into the older layers. Here we present the complete sedimentological sequence of Muostakh Island including new AMS 14C radiocarbon ages both from sediment and ice wedges. Sedimentological, geochemical and geocryological data include the coarse-grained layer for the first time, which highlights an episode of erosion and rapid deposition in Siberian Ice Complex during the Last Glacial Maximum. Stable isotope data from ice wedges complement this study with winter season paleoclimate information. This multidisciplinary study will re-evaluate the Late Quaternary depositional and palaeo-environmental history of the region.



Item Type
Conference (Poster)
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Primary Division
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Not peer-reviewed
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Published
Event Details
XI. International Conference on Permafrost, 20 Jun 2016 - 23 Jun 2016, Potsdam, Germany.
Eprint ID
41438
Cite as
Meyer, H. , Opel, T. , Derevyagin, A. Y. , Fritz, M. , Manthey, C. , Siegert, C. , Schirrmeister, L. and Grigoriev, M. N. (2016): Late Quaternary palaeo-environmental history of Muostakh Island, Northern Siberia based on sedimentological and geocryological studies , XI. International Conference on Permafrost, Potsdam, Germany, 20 June 2016 - 23 June 2016 .


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