Late Quaternary stratigraphy and soils of Gydan, Yamal and Taz Peninsulas, northwestern Siberia

Ground ice preserved in Pleistocene deposits of northwestern Siberia has been considered to have originated from either glacial ice, sea ice or by segregation processes. The sediments have been considered by other researchers to have various origins including glacial, estuarine and alluvial. Thus, considerable differences of opinion exist regarding the extent of glaciation in the region. Detailed analysis of six sections on Yamal, Gydan and Taz Peninsulas, provide a corpus of stratigraphic evidence confirming an estuarine-alluvial origin for the sediments enclosing massive ice bodies. Radiocarbon and optically-stimulated luminescence dates on parts of two sections permit an evaluation of the two dating methods.18O analysis confirms that contemporary ground ice averages −18‰ and can be significantly less negative, while older ice generally has a composition between −19‰ and −24‰. Soils in the area are all arctic brown (Inceptisols) to tundra (Entisols) types and show horizon deformation patterns associated with permafrost. On comparing Cox or Cg horizon mineralogy with Bw and Ah horizons weathering sequences in these soils show weak transformations of illite and illite-smectite to smectite, vermiculite and chlorite.