Constraining the depositional history of the Neoproterozoic Shaler Supergroup, Amundsen Basin, NW Canada: Rhenium-osmium dating of black shales from the Wynniatt and Boot Inlet Formations

New Re-Os ages from black shales of the Neoproterozoic Shaler Supergroup from the Minto Inlier, Victoria Island, Arctic Canada, constrain the late Tonian to early Cryogenian depositional history of the Amundsen Basin. The Re-Os ages of 761 +/- 41 Ma and 848 +/- 49 Ma for the Wynniatt Fm., and 892 +/- 13 Ma for the Boot Inlet Fm., along with recently reported U-Pb ages, provide anchor points for correlation of stable isotope stratigraphy, most notably the Bitter Springs isotopic anomaly within the Wynniatt Fm. across the Tonian-Cryogenian transition in NW Canada. These data suggest that deposition of lower units of the Shaler Supergroup began earlier than previously estimated. Initial 1870s/1880s for all three sample suites is around 0.6, lower than modern seawater, but significantly higher than unradiogenic Archean/Paleoproterozoic seawater composition, supporting a Proterozoic transition from mantle-dominated Os input into the global ocean towards a crust-dominated flux. (C) 2013 Elsevier B.V. All rights reserved.