Ice advance-retreat sediment successions along the Logata River, Taymyr Peninsula, Arctic Siberia

Abstract: A number of sites were investigated in river sections along the Logata River on the Taymyr Peninsula, Russia, and its adjacent areas to shed more light on the glaciation history over the last glacial cycles. The sediments exposed at the investigated sites are correlated and put into a local stratigraphic scheme divided into five main units. Unit 1 is positioned lowest in the stratigraphy and consists of greyish yellow sand with gravel horizons made up of shale. The poor exposure of the unit obstructs any attempt to interpret the depositional environment of the unit. Unit 2 is a matrix-supported silty clayey diamicton with glaciotectonic lamination and sand boudins; it is interpreted as a subglacial traction till deposited from NE. Unit 3 consists of intercalated massive and laminated beds of silt and clay with a varying abundance of marine molluscs and drop clasts (IRD). The unit is interpreted as deposited in an off-shore glaciomarine depositional environment. Unit 4 is made up of sorted sediments, primarily sand, but also coarser and finer sediments. Organic detritus is common in the unit. Unit 4 is interpreted as a fluvial depositional environment of a meandering river. Unit 5 is the uppermost unit in the local stratigraphic scheme and contains properties typical of so called ice complex deposits; it consists of sorted sediments of silt and sand with peat inclusions and an abundance of ground ice. Organic detritus and mega fauna fossils are common in the unit. The sites examined in detail were sampled for radiocarbon, OSL and ESR dating. All radiocarbon datings (13) on mollusc shells and organic macro remains yield infinite ages, while the results from the ESR and OSL datings are still pending. All units together suggest a full glacial-deglaciation cycle with a Kara Sea ice sheet advancing and retreating within a marine basin, and with an isostatically driven regression thereafter, ending with a terrestrial environment. The most probable timing is the Early Weichselian (100-80 kyr BP).