Late Glacial and Early Holocene lacustrine sedimentation history of the northern Mologa-Sheksna Lowland derived from Lake Beloye sediments (NW Russia)

Abstract

Few detailed case studies have been devoted so far to the Late Pleistocene palaeogeography of the northern Mologa-Sheksna Lowland (MSL), compared to adjacent regions covering the Valdai glaciation marginal zone. Lake Beloye (Russia, Vologda region, Babaevo district) bottom sediments were studied using ground penetrating radar (GPR) and subsequently were cored in order to build a palaeoclimatic reconstruction for the northern MSL, because lacustrine deposits are considered to be valuable and representative palaeoarchive of the area. Chronology of regional palaeoclimatic and palaeohydrological changes from the Bølling — Allerød warming to the Early Holocene was traced on the basis of inorganic and organic geochemistry, mineralogical proxies, grain-size, magnetic susceptibility, accelerator mass spectrometry radiocarbon dating and optical microanalysis. During the Late Glacial and the Pleistocene/Holocene transition in the northern MSL interstadial climatic conditions were determined at ~ 14.0 cal. ka BP (Bølling, stage GI-1e of the GICC05 timescale) and ~ 13.0 cal. ka BP (Allerød, stages GI-1c3 — GI-1a). A pronounced cold period associated with Younger Dryas (stage GS- 1) was registered in the multiproxy record at 12.8–11.7 cal. ka BP. High-resolution x-ray fluorescence (XRF) core scanning helped to reveal short-term “cold” events at ~ 13.7, ~ 13.1 and ~11.5 cal. ka BP, which were associated with Older Dryas (stage GI-1d), Gerzensee-Killarney oscillation (stage GI-1b) and Preboreal oscillation respectively, and “warm” episodes at ~ 13.2 and ~ 11.8 cal. ka BP, which presumably correspond to the end of the stage GI-1c1 and Greenlandian Stage/Age respectively. Ultimate interglacial (Holocene) climate onset within the MSL was attributed to ~ 11,7 cal. ka BP, which is marked by the sharp rise of total organic carbon content in the sediments and lithological changes to muddy fraction. Numerous water level oscillations occurred in the large proglacial lakeduring the last glacial termination, ending with Its final drainage in the northern MSL by ~ 10.9 cal. ka BP. The reconstructed palaeoclimatic dynamics is in overall agreements with the global reconstructions for the North Atlantic and Fennoscandia regions.