Specific features of sedimentology in the outer part of the East Siberian Arctic Shelf

Lithological investigations performed in the outer part of the East Siberian Arctic Shelf (ESAS) revealed specific features in the structure and distribution of bottom sediments in the studied area. Predominant type of sediments found in the uppermost layers of sediments was mud (that is silt and clay) with particle size <0.01 mm. This is typical for the outer shelves and reflects lowering energy of the depositional environment and sediment maturity towards the shelf break. However, in some areas within the ESAS outer shelf, we found poorly sorted sediments comprised of multiple grain sizes - from <0.01 mm (mud) to >1 mm (coarse sand). Some authors described existence of such areas in the outer part of the Laptev Sea shelf earlier without attributing such variability in sediment grain size to any processes. We hypothesize three possible mechanisms to explain intrusion of high energy processes into the low energy environment: 1) effect of geo-fluid and/or gas (methane) escape through open/deep taliks forming within subsea permafrost due to long-lasting warming by seawater and underlying fault zones (southern end of the Gakkel Ridge); 2) release of underground water through intra-permafrost hydraulic system; and 3) bottom erosion caused by ice-scouring.