Permafrost history in Arctic Siberia - insights from the cryogenic weathering record at Elgygytgyn crater, NE Siberia

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This proposal focusses on determining climate variations as expressed in variations of permafrost conditions in Arctic Siberia. Of particular interest is the establishment of a sedimentological method that allows estimating the degree of cryogenic weathering and palaeo soil temperatures through geologic time. The study explores a lake sediment record from Elgygytgyn crater lake, NE Siberia, spanning the last 300,000 years and currently representing the longest terrestrial palaeoclimate and -environment archive for the Arctic. Samples from short permafrost cores extracted in the catchment and spanning the last 14,000 years and a set of surface samples that represent modern conditions will be used as a reference. The following sediment-mineralogical properties, which are considered to mirror long term periglacial dynamics in NE Siberia, will be studied: (1) the ratio of quartz to feldspar in selected grain size fractions provides an indicator reflecting the degree of frost weathering; (2) image analysis of scanning electron micrographs of particles will be performed to yield a quantification of quartz grain morphology and surface features stemming from frost weathering; (3) heavy minerals will be used as provenance indicators to define changes in source rock composition and cryogenic detritus. The results prepare a fundamental tool that allows determining the intensity of permafrost conditions through Quaternary glacial cycles in the North Siberian Arctic. This is a conceptual outcome of future core studies from ICDP funded deep drillings.