ИСТИНА

For the Upper Volga region located within the last Middle Pleistocene (Moscow – Saalian) glaciation marginal zone, phase of uninterrupted fluvial network evolution is limited to the later glacial-interglacial climatic cycle. In attempt to reconstruct past extent, density and distribution of fluvial systems and to correlate incision-widening-infill cycles between their presently dynamic and inactive parts, an interdisciplinary research of the present and buried topography, lithology and pedogenic properties of surface deposits was carried out. We engaged DGPS profiling, remote sensing data interpretation, detailed description of geological sections and cores followed by comprehensive analysis of grainsize, chemical and organic contents, pedogenic features on macro, meso- and micromorphological levels, and correlating of organic-rich layers. Integrating the available results, we propose a scenario of landscape evolution of the Eastern Borisoglebsk Upland over the last 150 ka. At least, four successive stages of erosional incision are emphasized in the fluvial network: Late Moscow, Early-Middle Valdai, Late Valdai with several substages and Late Holocene, those were preceded by successive Late Moscow meltwater incisions and accumulations due to uneven ice cover degradation. Main stage of the Late Moscow incision was followed by general landscape stabilization and pedogenesis during the Mikulino interglacial. Meltwater channel network is inherited by planiform structure of modern fluvial systems. However, Late Moscow glaciofluvial and Valdai fluvial systems were much denser and had greater extents than the present-day fluvial network. Although periods of depressions infilling were uneven in different parts of the area and caused by local lacustrine, biogenic and colluvial accumulations.