LAKE SEDIMENT RECORDS FROM ISOLATION BASINS CONSTRAIN RELATIVE SEA LEVEL CHANGES DURING THE HOLOCENE NEAR NORDENSKIÖLD GLETSCHER, WESTERN GREENLAND

We analyzed lake sediments from three isolation basin lakes in western Greenland to create a record of relative sea level (RSL) during the Holocene. Our record assesses the glacial isostatic adjustment and associated RSL change from retreat of the Greenland Ice Sheet (GrIS) during the early-middle Holocene. Previous RSL research in western Greenland has focused on the shorelines of Disko Bugt, far from the current ice margin. In comparison, the RSL data we present are from lakes near a fjord system approximately 100 km to the east of Baffin Bay that is situated only 5-10 km to the west of the present ice margin. The main objective of this study is to inform current RSL models of western Greenland about Holocene GrIS history. We obtained sediment sequences from four lakes located near the margin of Nordenskiӧld Gletscher, approximately 100 km to the south of Ilulissat. Lake S3 (informal name; 65 m asl) was above the local marine limit and was used to constrain deglaciation of the area. Lakes S1, S2 and S4 (informal names) are isolation basins with elevations of 8.67 m, 34 m and 35 m asl, respectively, and are used to constrain the age and elevation of the marine to lacustrine transition. Sediment cores have been analyzed using magnetic susceptibility and loss-on-ignition to determine organic-rich versus minerogenic-rich material and identify changes in stratigraphy. A chronology is created from six radiocarbon ages on macrofossils (n=5) and bulk sediment (n=1) sampled at key contacts from within the four cores. We compare our results to the previously published RSL curves from the region and discuss the implications within a regional context, focusing on the relationship between timing of isolation at our inland site to those along the shores of Disko Bugt and elsewhere in Greenland.