New Data on the Stratigraphic Significance of the Cheremoshnik Section (Yaroslavl Oblast)

For decades the northeastern slope of the Borisoglebsk Upland has been a focal point for natural scientists interested in geochronology and Quaternary environmental reconstructions. A key reference section of the Upper Volga River region is a set of geological cores, exposures and excavations on the sides of the Puzhbol Gully system. The ORV section (Eastern Cheremoshnik Gully) was studied in detail applying a comprehensive analytical approach. We revealed an intermittent geological record of local transformations in the exposed sequence as follows: unstable infilling of a lake depression by mineral and mineral-biogenic sediment during the Mikulino thermpxerotic stage; biogenic and mineral-biogenic accumulation in waterlogged settings during the transition to subaerial deposition in periglacial environment at an initial phase of the Early Glacial; discrete erosion and accumulation with associated slope processes during the Pleniglacial, Late Glacial; and an episode of colluvial deposition attributed to the cold Holocene stage. Hiatuses in the paleogeographic record were identified for several periods of different durations, at least for the Mikulino thermohygrotic interglacial stage and for significant intervals of the Late Glacial and the Holocene, mainly because of the occasional activation of erosion. Stratigraphic discordances exposed in the ORV section have shown its deficiency as a reference one for the reconstruction of the Late Pleistocene and Holocene environmental history of the region. Nevertheless, we can use the fractional particle size distribution in the infillings of lacustrine depressions and erosion cuts as a sensitive indicator of the local Late Pleistocene lithodynamics.