Postglacial shelf erosion, riverine input and lake drainage in the eastern Kara Sea, Russia

Abstract

Marine sediment core PS2719-1 represents a key sedimentary record for the reconstruction of the postglacial shelf evolution of the eastern Kara Sea west of the entrance to the Vilkitsky Strait. Sedimentological, chronological, geochemical, mineral magnetic and micropaleontological data were used to investigate the sedimentary evolution of the area in unprecedented detail. Four phases of sedimentation were identified, which are closely related to sea-level rise and input from the Yenisei and Taymyr Rivers. Sedimentation likely commenced directly after regional deglaciation prior to 13.6 cal ka BP. Basal sediments are coarse grained and rich in terrestrial organic matter, which points to shelf erosion as the dominating sedimentation process. Around 13.6 cal ka BP Yenisei River water masses reached the area, causing a shift in heavy mineral assemblages and a distinct peak in magnetic susceptibility. This phase was followed by increased sedimentation rates during the early Holocene, which were related to high sediment supply from Lake Taymyr, possibly due to the opening of an ice dam in the Lower Taymyra River area. These sediments are characterized by high terrestrial organic matter accumulation, a fine-grained composition, and a heavy mineral assemblage reflecting the sediment source on the Taymyr Peninsula. High burial rates are reflected by high Mn contents. The transition to modern conditions commenced already around 8.5 cal ka BP and were fully established at ca. 5 cal ka BP, being documented in mineral magnetic evidence and foraminiferal assemblages and are characterized by more marine conditions and a strong influence of the Yenisei River.