The study focuses on the structure of thick peatlands with syngenetic ice wedges in the Yamal and Gydan Peninsulas (northern West Siberia). Thick polygonal peatlands formed in floodplains and laidas or in lacustrine-palustrine inliers within hypsometrically higher terraces. Peat accumulated at rates of several mm per year so the peatland reached thicknesses of 4-5 m in 700-1000 years. The presence of Boreal (Holocene) tree macrofossils at the base of many peat sections confirms the tree line advance as far as the contemporary tundra during the Holocene optimum.

Data was submitted and proofread by Yurij K Vasil'chuk and Lyubov Bludushkina at the faculty of Geography, department of Geochemistry of Landscapes and Geography of Soils, Lomonosov Moscow State University.