(super 40) Ar/ (super 39) Ar and Pb-Pb study of individual hornblende and feldspar grains from southeastern Baffin Island glacial sediments; implications for the provenance of the Heinrich layers

Lead isotope analysis of individual feldspar grains and (super 40) Ar/ (super 39) Ar analysis of individual hornblende grains from three samples taken from Baffin Island ice-proximal till deposits are consistent with a provenance recording a two-stage geologic history including formation of continental crust in the Late Archean and partial isotopic resetting and (or) reequilibration during major Paleoproterozoic regional metamorphism and magmatism. Significantly, although the populations are small, and the two-stage Archean-Paleoproterozoic history of their sources are similar, the Pb isotope compositions of samples from Baffin Island do not match the results from Heinrich layer H (sub 2) in core HU87-033-009 from northeast of the Hudson Strait in the Labrador Sea. Specifically, in H (sub 2) samples from HU87-033-009, the (super 207) Pb/ (super 204) Pb is high for a given value of (super 206) Pb/ (super 204) Pb. Additionally, the range in (super 206) Pb/ (super 204) Pb is greater in HU87-033-009 samples, and there are two distinct trajectories of (super 208) Pb/ (super 204) Pb. The steeper of the (super 208) Pb/ (super 204) Pb versus (super 206) Pb/ (super 204) Pb trends is not seen in the studied Baffin Island glacial sediment samples. Samples of feldspar grains from Heinrich layers H1, H (sub 2) , H (sub 4) , and H (sub 5) from core V28-82 in the eastern North Atlantic have a (super 207) Pb/ (super 204) Pb versus (super 206) Pb/ (super 204) Pb relation similar to that of Baffin Island till samples, but there is also a high (super 208) Pb/ (super 204) Pb that we have not captured in this suite of glacial sediment samples. Our results highlight the strength of a combined radiogenic isotope approach to characterizing the geological history of sediment sources and provide a first step in assessing the variability in isotope character in this region of dynamic glacial events during the late Quaternary Period.