Late Quaternary sedimentation history of a coastal permafrost landscape, Western Laptev Sea, NE Siberia

• Main Authors: Winterfeld, Maria, Schirrmeister, Lutz, Overduin, Pier Paul, Grigoriev, M., Kunitsky, V.
• Format: Conference Object
• Language: unknown
• Published: 2010
• Subjects: Ice; laptev; Laptev Sea; permafrost; Taymyr; Taymyr Peninsula; Siberia
• Online Access: https://epic.awi.de/id/eprint/22771/; https://hdl.handle.net/10013/epic.35500

Palaeoenvironmental reconstructions of the land-scape history of the western Laptev Sea are primar-ily based on studies of exposed cliffs and surface sediment cores. During the COAST drilling cam-paign in April 2005 a transect of deeper cores was drilled at Cape Mamontov Klyk in the western Lap-tev Sea. Here, we present the reconstruction of a coastal permafrost landscape including periods of permafrost aggradation and degradation and reach-ing back to at least the Eemian interglacial based on cryolithological, sedimentological, geochronological (14C-AMS, OSL on quartz, IR-OSL on feldspars), and palaeoecological (pollen, diatoms) analyses.The study area is located in the western Laptev Sea at the coastal cliff of Cape Mamontov Klyk (73.61°N, 117.18°E). The investigated borehole transect reached up to ~12 km offshore including 5 cores, one terrestrial (C1) and four marine cores (C2 to C5) at different distances from the coast. The most distant core (C2) reached the maximum depth of 77 m below sea level (b.s.l.). The lowermost unit I (figure 1) was only observed in core C2 (77 to 64.7m b.s.l.) and mainly consisted of silty sands with several clayey layers. The largely plastic-cryotic state (i.e. ice-bearing but not ice-bonded) was a result of pore water salinities of 11.7 to 30.8 depressing the freezing point, combined with temperatures of -1.0 to -1.4°C at these depths. Along with pollen data, pore water isotope values and one IR-OSL age of 111±7.5 ka ( at 77 m b.s.l.) a marine interglacial (Eemian) origin seems to be pos-sible although the depth b.s.l. was unexpected, par-ticularly when compared to marine Eemian deposits on the Taymyr Peninsula identified up to 100 m above sea level (a.s.l.). The subsequent landscape development was primarily governed by sea level changes. Aggradation of terrestrial permafrost (unit II + III) on the shelf occurred during the Weichselian glaciation and the Holocene (unit IVa). The unfro-zen, cryotic (<0°C) sediment unit IVb was a result of modern coastal erosion of unit III ...