The summits and slopes of some islands along the northeastern and northern coasts of the White Sea are covered with dried out peatlands. The thickness of the peat deposit is 30-80 cm and it is separated by troughs into gently sloping polygonal peat blocks up to 20 m 2 in size. On some northern islands the peat blocks have permafrost cores. The main components of the dried out peatlands vegetation are dwarf shrubs and lichens. The peat stratigraphy reveals two stages of peatland development. On

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... he first stage, the islands were covered with wet cottongrass carpets, which repeated the convex relief shape. On the second stage, they were occupied by the xeromorphic vegetation. We suggest that these polygonal patterned peatlands are the remnants of blanket bogs, the formation of which assumes the conditions of a much more humid climate in the historical past. The time of their active development was calculated according to the White Sea level changes and radiocarbon dates from 1000-4000 BP.