Laurentide Ice Sheet dynamics across multiple glacial-interglacial cycles from Quaternary stratigraphic records in central Canada

Quaternary terrestrial stratigraphic records are key to understanding the long-term behaviour of past ice sheets beyond the most recent glaciation. Glacial sediments provide important information on ice-flow direction and dispersal patterns, while intertill organic-bearing sediments provide insight into climatic conditions during past ice-free periods. The Hudson Bay Lowland (HBL) is situated near the geographic centre of glaciated North America and contains amongst the best preserved and laterally extensive Quaternary stratigraphic successions that were deposited over at least three glacial-interglacial cycles. The extensive stratigraphic record in the HBL is ideal for understanding the temporal evolution of the Laurentide Ice Sheet (LIS). Here, we investigate a remote region of the western HBL and construct the first stratigraphic framework of the region using a hybrid lithostratigraphic-allostratigraphic approach. The stratigraphic framework consists of Holocene-aged sediments that are underlain by nine glacial (till) units, three proglacial units and three interglacial units. Stratigraphic and geochronologic constraints indicate that the study area was likely inundated by marine waters following terminations II (~130 ka; MIS 6–5 transition) and III (~243 ka; MIS 8–7 transition) and both marine incursions reached a greater elevation compared to the Holocene (Termination I) marine limit in the region. These marine inundations were then followed by fluvial and/or lacustrine deposition during interglacials. The glacial record indicates a predominance of ice flowing from the Quebec-Labrador dome or a dome situated in Hudson Bay during glaciations. This field-based record is important for constraining the long-term behaviour of the LIS and provides important limits for ice-sheet modelling.