Variations in the influence of riverine discharge on the Kara Sea during the last deglaciation and the Holocene

Several sediment cores from the Kara Sea have been analyzed with a special emphasis on heavy-mineral, foraminiferal, and stable-isotopic composition of sediments. The temporal variations of these characteristics, controlled by 14C ages in some cores, allow us to reconstruct the history of latest Weichselian and Holocene sedimentation in the Kara Sea in relation to the discharge of the large Siberian Obʹ and Yenisey rivers. We conclude that during the Last Glacial Maximum (LGM) these rivers were blocked by the Barents–Kara ice sheet that occupied the northern part of the Kara Sea. This blockage likely created a proglacial basin on the Kara Sea shelf; its effect on the Siberian drainage needs further investigation. With deglaciation and sea-level rise, river mouths migrated across the Kara Sea shelf to their modern estuaries. This retreat, combined with high early-Holocene insolation levels, had a profound influence on biota and sedimentation throughout the Kara Sea. Subsequent changes in riverine discharge did not affect the Kara Sea as strongly as during deglaciation and the early Holocene. A significant increase in discharge is inferred to have started after ca. 1.5 ka.