Late Pleistocene stratigraphy according to the sediment sequence from eastern Kola Peninsula, Ponoi River Valley (North-Western Russia)

The sedimentary sequence from the local stratotype section of the Mikulinian (MIS 5) marine deposits at the Ponoi River Valley, easternmost Kola Peninsula, North-Western Russia, has been investigated to define the geological and numerical ages, and chronostratigraphic position of a marine unit identified previously as a lithostratigraphic unit of the lower part of the Mikulinian and named the Ponoi Beds in the regional Kola stratigraphic scheme. The new data indicate that the Ponoi Beds has two-part sedimentary succession, which was formed during two successive interglacial Boreal and Belomorian marine transgressions in the Mikulinian (MIS 5) time. The lower clay part of this succession accumulated in the interglacial marine basin until c. 96 ka under favourable environmental and climatic conditions. The upper sandy part of this lithostratigraphic formation, also previously attributed to the Ponoi Beds, accumulated in the late Mikulinian marine basin about 70 ka ago under relatively cold and damp climate conditions. In accordance with our new data obtained in this study, it has to be attributed to another marine unit referred to as the Strelna Beds, formed during the second Belomorian interglacial marine transgression, also during the Mikulinian time. Formerly the Strelna Beds was correlated with the Podporozhian (MIS 4) Horizon in the current regional Kola stratigraphic scheme. Both the Ponoi and Strelna Beds marine sediments have to be related and linked with the marine basin during MIS 5. These marine units have to be correlated with the Mikulinian (MIS 5) Horizon.