40 Ar/ 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

• Published in: Canadian Journal of Earth Sciences
• Main Authors: Hemming, S R, Gwiazda, R H, Andrews, J T, Broecker, W S, Jennings, A E, Onstott, T C
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 2000
• Subjects: Baffin Island; Baffin; Hudson Strait; Labrador Sea; North Atlantic
• Online Access: http://dx.doi.org/10.1139/e00-009; http://www.nrcresearchpress.com/doi/pdf/10.1139/e00-009

Lead isotope analysis of individual feldspar grains and 40 Ar/ 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 2 in core HU87-033-009 from northeast of the Hudson Strait in the Labrador Sea. Specifically, in H 2 samples from HU87-033-009, the 207 Pb/ 204 Pb is high for a given value of 206 Pb/ 204 Pb. Additionally, the range in 206 Pb/ 204 Pb is greater in HU87-033-009 samples, and there are two distinct trajectories of 208 Pb/ 204 Pb. The steeper of the 208 Pb/ 204 Pb versus 206 Pb/ 204 Pb trends is not seen in the studied Baffin Island glacial sediment samples. Samples of feldspar grains from Heinrich layers H 1 , H 2 , H 4 , and H 5 from core V28-82 in the eastern North Atlantic have a 207 Pb/ 204 Pb versus 206 Pb/ 204 Pb relation similar to that of Baffin Island till samples, but there is also a high 208 Pb/ 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.