Transformation of kettle holes in paleoglaciated areas of Central European Russia according to geological and electrical resistivity tomography dataстатья
Аннотация:Late Pleistocene transformation of European glacial landscapes is often attributed to the impact of linear erosion. Yet in the marginal zone of MIS6 glaciation, extensive watersheds were protractedly affected by the postglacial flattening in periglacial and interglacial settings. Local sediment sinks such as kettle holes and dry valleys infilled throughout the postglacial stage serve not only as records of paleoenvironmental changes but also for assessing the scales of watershed denudation and landscape transformation since the last glacial cover degradation. We attempted to use electrical resistivity tomography (ERT) for a paleogeomorphological survey of local flat-bottomed depressions studied by conventional lithological and stratigraphic approaches in a series of cores at the Borisoglebsk Upland in the center of the East European Plain. ERT profiles showed a contrasting picture of the relatively higher-resistive glacial base embedded with low-resistive lenses up to 20–60 m thick. The latters were correlated with the postglacial loamy deposits of lacustrine and colluvial origin that infilled the lows of initial glacial topography. Complex inner structure of paleodepressions was revealed, embodying several buried kettle holes that functioned as separate basins during much of the Late Pleistocene and probably merged only at its final stages due to considerable sedimentary infill. ERT cross-sections showed an amplitude bottom relief of each kettle with slopes much steeper than its modern sides. 8 geological and 4 electrotomography facies were distinguished, with their correspondence to each other discussed and compared to the geophysical findings of similar geomorphic objects in analogue regions of Central and Eastern Europe. Thus, ERT prospecting proved to be useful for detecting the postglacial loamy infills of initial lows of the glacial topography and can be further employed to better understand the actual scales of the postglacial redeposition and landscape modeling during the last 130 ka. The study was supported by RSF (project 23-77-10063).
