ИСТИНА

Stratigraphic investigations of sections with organic deposits of the Mikulinian Interglacial (MIS 5e) or Early - Middle Weichselian ages (MIS 5b - MIS 3) are a reliable method for assessing the development of the Late Valdai (Weichselian) glaciation. The Kileshino section is one of the key sections for studying the Last Glacial Maximum (LGM) position in the central part of the Valday Upland. Investigations of the section were started in the late 50s XX century. Most researchers try to correlate peat observed in the section with the Mikulinian Interglacial (MIS 5e). Also, some researchers were able to detect the layer of till which covers organogenic deposits in the section; others did not find any till. The uncertainty in the section structure does not allow to reasonably show the LGM boundary in the central part of the Valday Upland. In 2017 detailed investigations of the section in village Kileshino were carried out for the purpose of revision. The section opened the valley side of the r. Sizhina. On the base of visual structure observations, grain size, loss on ignition at 550 and 900 C, magnetic susceptibility, pollen, paleocarpology and 14C analyzes were distinguished stratigraphic horizons: alluvial deposits of the Late Valdai Age (0–2,86 m); floodplain facies of alluvial deposits of the Early Valdai Age (2,86-5,3 m); lacustrine-peat deposits of the Mikulinian Interglacial (5,3-7,0 m); lacustrine and limnoglacial sediments of the Late Moscow age (7,0-13,40 m). The stratigraphy of section allows making a correlation between boreholes along the profile line through the key section. It needs for understanding the bed position of organogenic deposits. Analysis of the profile shows that till represented by loams with the inclusion of carbonate and crystalline rocks debris, were found at the upper parts of interfluves and some boreholes. It suggests that organo-mineral deposits which studied in the section were formed in the depression between hills of the Late Moscow age. In the Late Valdai (MIS 2) the ice cover could hardly spread to the south from the section. This research is supported by the Russian Science Foundation, project no. 17-17-01289.