Paleoarchive of Late Pleistocene Sedimentary Environments on the Borisoglebskaya Upland

Abstract

Landscapes of Сentral European Russia were sculpted by the last Middle Pleistocene glaciation that constrained most of the following sedimentation in successive interglacial and periglacial settings to various depressions of the glacial paleolandscape. However, corresponding continuous postglacial sequences are extremely rare in the region due to the dramatic fluctuations of the regional base level and significant fluvial activity in most large depressions. Therefore, the fullest available core covering the entire last glacial-interglacial cycle from a kettle hole infill on the northeastern macroslope of the Borisoglebskaya Upland was chosen to reconstruct the local sedimentary environments and to correlate the recorded paleoenvironmental response with the major Late Pleistocene climatic changes. A thorough macro- and mesomorphological investigation of the mechanized press-auger core was complemented by the selective radiocarbon dating of organic-rich sediments. A 20 m thickness of clastic and organic-clastic deposits reflects a pronounced shift from a subaqueous rhythmic lacustrine and eutrophic palustrine accumulation of the Last Interglacial and Early–Middle Pleniglacial to sub- and superaqueous colluvial deposition during the Late Pleniglacial, followed by the final turn to the predominance of subaerial slopewash input during the Late Glacial. Based on the 14C age determinations, immanent hiatuses and sand lenses found in the sequence were correlated with the Early and Middle Pleniglacial fluvial activity, although the lacustrine sedimentation during those stages still prevailed, providing the major part of the entire sedimentary thickness.