Sediment Record of the Earliest Stage of the Evolution of Lake Kanozero (Sw Kola Peninsula): New Data for Regional Deglaciation Reconstructions and Relative Sea-Level Studies

Abstract

The multi-proxy study of the lowermost part of the sediment sequence of Lake Kanozero (south-western part of the Kola Peninsula, ca. 53 m a.s.l.) revealed the evidences for marine waters penetration into the basin during the earliest stage of its evolution. The diatom analysis inferred the conditions of a large brackish-water basin. Sediments composition and very low organic content also supported large-basin and low-productivity environments. Based on the pollen study, this stage covers a cooling period preceding the Allerød (tentatively assigned to the Older Dryas) and the onset of the Allerød. Periglacial vegetation typical of the cold and dry climate prevailed in the area for the most of the period. The subsequent transition to the freshwater conditions inferred from the diatom study took place in the Allerød, according to the pollen data. Except for a minor decrease in the fine sand fraction, no other corresponding changes were observed in the sediment record suggesting no major shifts in sedimentary environments. In the late Allerød and throughout the Younger Dryas, Lake Kanozero remained a large, low-productive freshwater basin. Our results indicate that ice-free conditions with aquatic sedimentation in the Kanozero depression had already existed in the Older Dryas. This assumes earlier deglaciation of the study area than it was previously thought. The study also suggests that brackish conditions in the White Sea basin established earlier than reported before. While the previous studies found no signals of marine transgression above ca. 41 m a.s.l., our results indicate that the local marine limit in the study area exceeds ca. 53 m a.s.l.