A multi-proxy centennial-resolution paleoecological record of Holocene lake sediments in the marginal zone of Last Scandinavian Glaciation (Tver Region, Russia)

Abstract

This paper presents a new centennial-resolution multi-proxy record of the Holocene environmental changes obtained from the small Petrovskoe Lake in the former marginal zone of the Last Scandinavian (Valdai) Glaciation. The series of analyses of the lacustrine deposits includes grain size, loss on ignition, magnetic susceptibility, pollen, macrofossils, cladoceran, chironomids and macrocharcoals, were conducted on a 16.35 m-long sediment core. Based on the data obtained, mass accumulation rate was calculated and the stages of vegetation change were determined using biomisation method. The stages of the reservoir development were identified. It was revealed that during the initial stage of development (11000–10200 cal yr BP), a Sphagnum mire formed on a buried block of dead ice, which was subsequently flooded, resulting in the formation of a kettle hole lake. In the period from 11000 to 10000 cal yr BP, "cold" biomes with dominance of Betula and Pinus prevailed. The periods of most active erosion during the early Holocene correspond to 10200–9400 cal yr BP. The further development of the lake followed а path of steadily increasing trophicity and sedimentation rate. A rapid increase in broadleaved taxa led to the emergence of warm mixed forests biome already 9500 cal yr BP. A long warm period, characterized by the dominance of broadleaved species (Tilia, Quercus, Fraxinus, Ulmus), lasted until 4200 cal yr BP when taiga and cold deciduous forests biomes began to replace the warm mixed forests. Key moments of anthropogenic impact that influenced the progressive degradation of primary forests and their replacement by secondary stands began at the time of 4200, 2900, 2200, 1500, 1200 and 800 cal yr BP that coincide with archaeological cultural shifts, short-term episodes of erosion and correlates well with fire activity.