Late Pleistocene-Holocene deglaciation history in the Baffin Bay from radiogenic isotope provenance studies

Ice sheets dynamics as well as corresponding meltwater pulses and iceberg calving events play a major role in the delivery and dispersion of continental detritus into the ocean in glaciated environments. To trace Greenland, and potentially, Innuitian and Laurentian ice sheet history and freshwater routing during late Pleistocene to Holocene climate transition, we generate strontium (Sr), neodymium (Nd) and lead (Pb) isotope records as proxies for the provenance of continental detritus on sediment cores from the Baffin Bay: GeoTÜ SL 170, from the Greenland side, covering the last 18.000 years of climate history and GeoTÜ SL 174, close to the western coast, covering 48.000 years. For SL 170, a pronounced shift can be observed in all three isotope systems at 12 ka, what coincides with the Younger Dryas cold event. 87Sr/86Sr is around 0.74 before the event and reaches up to 0.72 during it. Nd isotope composition (IC) changes from ɛNd -32 to -26, and the 206Pb/204Pb values range from 18 to 17. The shift suggests a change in the continental sources from the Archean Southern West Greenland to a slightly younger Proterozoic source of the Nagssugtoqidian Mobile Belt in the Central West Greenland. These results allow us to estimate patterns and timings of deglaciation for different regions of the western Greenland Ice Sheet. In core SL174 variations in ɛNd ( -24 to -30) and 206Pb/204Pb ( 17 to 19) provide no clear evidence for a change of the sediment source within the Younger Dryas, despite the similar range of the values as in core SL 170. 87Sr/86Sr is more radiogenic than in SL 170, reaching values of up to 0.75, but without a systematic relation to the deposition age. Since SL 174 core is located closer to the coast and to the LGM (last glacial maximum) ice sheet border, it was possibly exposed to the direct influence of the marine-terminating ice sheet, which supplied material from enhanced glacial and subglacial erosion. Therefore, radiogenic isotope results for this core could be affected by the variable supply of minerals (e.g., micas) delivering radiogenic Sr signature.