Paper No. 1
Presentation Time: 8:15 AM
THE LAST INTERGLACIAL IN BERINGIA: FROM THE PELUKIAN SHORELINE TO LAKE EL'GYGYTGYN
The history of interglacial high sea levels in the Bering Strait region is a fundamental part of the Hopkins legacy in Beringia. Mapped around the western and northern coast of Alaska from Nome to the Canadian border, the last interglacial MIS 5e Pelukian shoreline is recorded by storm beaches, terraces and ancient barrier islands up to 10 meters asl. By our best estimates summer sea surface temperatures were warmer, marine faunas were displaced northward toward Barrow and winter sea ice limits were nearly 800 km north of where they are today (Brigham-Grette and Hopkins, 1995). Warmer conditions with a longer open water season offshore lead to deeper snows on adjacent landscapes than at any time during glacial conditions, as suggested by the migration of trees and shrubs esp. in western Beringia (Anderson and Lozhkin, 1995). The terrestrial expression of the last interglacial is well recorded in Lake El'gygytgyn, a large meteorite impact lake in NE Siberia. Deeper snow and increased spring runoff in the catchment during 5e led to higher sedimentation rates and an increase in silt relative to clay. Clay minerals deposited during this time were coarser in size recording long periods of open water during interglacial summers and oxygenation of bottom waters. Cooler intervals during 5d and 5b prevented the ice-free summers stratifying the water column, creating anoxic bottom water conditions. The event stratigraphy within all of MIS stage 5 records changes in sediment character suggesting that the lake was sensitive to inferred changes in thermohaline circulation in the North Atlantic.