Relict permafrost features identification in landscape and deposits of Borisoglebsk Upland, Central European Russia

Relict permafrost features (RPF) indicated by specific patterns of soil, sedimentary and landform structure are characteristic of Central Russian Plain watersheds. Paleocryogenic polygonal networks appear in a pattern of semi-regular spots, blocks and polygons on the surface usually associated with pseudomorphs of ice wedges or sand casts in correlated deposits. This research aimed at distinguishing RPF in sedimentary structure and its correlation with the modern and paleolandscape structure of 3 ha watershed area exposed in constantly expanding trenches. Interpretation of multi-temporal UAV-photography, lithological investigation of 21 sections and apparent magnetic susceptibility measurements allowed to reconstruct spatial organization of the postglacial sedimentary sequence of the key site. Eight sedimentary beds were distinguish starting with Late Saalian limnoglacial base followed by lacustrine (pond-like) facies of the Pleniglacial and solifluction-colluvial lenses of the Late Pleniglacial and Late Glacial up to Holocene colluvial and agrogenic slope facies. At least three generations of inherited wedge-like deformations have been revealed in these stratified thicknesses preliminary attributed to the onset of the last glaciation and its maximum and to one of the Late Glacial coolings. It is established that established are contrastingly displayed in the sedimentary structure, paleolandscapes and modern soil and vegetative cover, however, are rarely or almost not shown in the actual microtopography. Established relationship of ice wedge pseudomorphs and shallow dry gullies allowed interpreting the origin of the latter as initially cryogenic dells infilled by colluvial, incl. agrogenic, deposits and partially incised by agrogenically instigated slope erosion of the last century.