A PRELIMINARY 10BE CHRONOLOGY OF THE FJORD STADE MORAINES IN THE SØNDRE ISORTOQ REGION, WESTERN GREENLAND

Reconstructions of Greenland Ice Sheet (GrIS) margin fluctuations during the Holocene place empirical constraints on the extent of the GrIS that can be used as benchmark data for ice-sheet climate models. Here, we reconstruct the early Holocene ice margin history of the Søndre Isortoq region of western Greenland to evaluate the response of the GrIS to Holocene climate change. The moraines in this region are part of an extensive moraine system known as the Fjord Stade moraines. These moraines have been directly dated to 8.2 ka in the Disko Bugt region, suggesting that they represent a readvance or stillstand of the GrIS in response to the 8.2 ka abrupt cooling event. However, because the Fjord Stade moraines have not been directly and precisely dated elsewhere, it is unclear whether the entire western GrIS margin responded to the 8.2 ka event or not. To address this issue, we selected boulders from two sites in the Søndre Isortoq region for cosmogenic ¹⁰Be exposure dating. In Nunatarssuaq, the northern of the two study sites, we sampled eight erratic boulders perched on bedrock beyond (west) and inside (east) of the Fjord Stade moraines. Samples from the southern field site at Qátqatsiaq include nine Fjord Stade moraine boulders and seven erratic boulders that bracket the moraines. Beryllium-10 ages of these boulders are pending but we hope to have them available for presentation. They will be the first direct ages of the Fjord Stade moraines in the Søndre Isortoq region. These data will shed light on the glacial history of a largely unstudied sector of the GrIS and contribute to a more complete understanding of Holocene GrIS margin changes.