REPEATED GLACIAL ADVANCES FROM THE QUEBEC-LABRADOR SECTOR INTO WESTERN HUDSON BAY LOWLAND

The western region of the Hudson Bay Lowland (HBL) contains a long and unique geological record that can be used to investigate the complex spatio-temporal behaviour of the Keewatin and Quebec-Labrador ice dispersal centres within the Laurentide Ice Sheet (LIS). Previous till stratigraphy studies have identified multiple SE- (Keewatin) and/or NW-trending (Quebec-Labrador) ice-flow phases that crossed the area, which creates challenges when determining the ice-flow direction that deposited a specific till unit. In this study, we use till clast-lithology, till-matrix geochemistry and detrital hornblende ⁴⁰Ar/³⁹Ar ages to confidently determine till provenance. We then incorporate this robust till provenance data within detailed stratigraphic observations to show that two major NW-trending ice-flow events over-rode sorted intertill sediments at different stratigraphic positions. Both of the NW-trending ice-flow phases are interpreted to record glacial advances following non-glacial periods. The repeated advance of ice sheets emanating from the Quebec-Labrador Sector into western HBL has important implications for modelling the growth of the LIS and suggests that growth of the Keewatin Sector was slower in comparison to the Quebec-Labrador Sector, which indicates asymmetric build-up of the LIS. This study highlights several issues with the current stratigraphic framework of the western HBL and emphasizes a need to acknowledge the fragmented nature of the Quaternary stratigraphic record in order to improve the correlations within glacial sediments.