Stop 2. Glacial Inheritance vs Postglacial Metamorphoses Of Borisoglebsk Upland Interfluves

Ch. 2. P. 37–63.

Ekaterina Garankina, Posazhennikova V., Lobkov V., Shorkunov I.

Editor of translation: Ekaterina Garankina

Detailed analysis of the E Borisoglebsk Upland suggests that most of the surface drift materials initially interpreted as polygenetic mantle loams were likely formed by continuous postglacial lacustrine deposition. Major arguments for such genetic interpretation are the dominance of fine-grained fractions; clear and texturally contrast multiscale lamination (up to five levels of laminae thickness); mottled colors typical for standing water environment. The Late Pleistocene age of that lacustrine sedimentation is stratigraphically evidenced by the Mikulino (Eemian) interglacial paleopedofeatures on the eroded surface of underlying Moscow glacial till and several organic-rich layers (paleosol humus horizons, peat, gyttja and plant debris lenses) in the lacustrine sequence dated to the Mikulino (MIS5) interglacial and Middle Valdai (Middle Weichselian) interstadial (MIS3). – Despite certain lithological variability observed between cores and sections, particularly those located at different elevations and in varying paleogeomorphic positions, general structural organization and textural composition of lacustrine stratum commonly exhibit evident alternation through time reflecting the same lithodynamic (and, possibly climatic) signals. Those can, therefore, be considered typical and most common sedimentary sequences of the Late Pleistocene at the Borisoglebsk Upland. This conclusion is certainly novel in contrast with most of the previously published models of the dominantly subaerial polygenetic origin of mantle loams. – The observed lacustrine sediments of the Late Pleistocene age systematically occur both on all studied interfluve surfaces below 190 m and in buried parts of the fluvial network. Its thickness is comparable or, at places, even exceeds local relative elevations. It means that the lacustrine sedimentation was the main and yet underestimated agent of the Late Pleistocene topography transformation in the study area.

Keywords: late Pleistocene, Middle Pleistocene, Glacial landscapes, postglacial sediments, lacustrine paleoarchives, glacial till

In book

Valdai Periglacial Field Symposium Guidebook, 27–30 August 2023 [Electronic edition]

Гаранкина Е. В., Константинов Е. А., Лобков В. А., Макеев А. О., Панин А. В., Шоркунов И. Г., Бричева С. С., Захаров А. Л., Карпухина Н. В., Куст П. Г., Лазукова Л. И., Лебедева М. П., Посаженникова В. С., Рудинская А. И., Русаков А. В., Самусь А. В., Сычев Н. В., Украинцев В. Ю., Шеремецкая Е. Д. M.: -, 2023.