Shelf erosion and glacial ice proximity in the Labrador Sea during and after Heinrich events (H-3 or 4 to H-0) as shown by foraminifera

Collapses of the marine-based Laurentide Ice Sheet during the last glaciation are documented by large, abrupt influxes of detrital carbonate into the northwest Labrador Sea, known as detrital carbonate or Heinrich events. The extent of grounded ice on the continental shelf is poorly constrained for these events, but has been assumed to be at the shelf edge. Possible grounding line positions of ice streams in Hudson Strait and Cumberland Sound over the last c. 34 ka are delimited using the abundance of shelf-dwelling benthic foraminifera, sediment colour and calcite to dolomite ratios in two Labrador Sea cores (87033-009 LCF and 75-009-IV-55 PC). Heinrich events 1 and 2 contain no evidence of glacial erosion of the continental shelf, suggesting that the Hudson Strait ice stream may have grounded on the Hudson Strait sill or on the inner shelf rather than at the shelf edge during these events. Dark grey, dolomite-rich sediments with abundant shelf-dwelling foraminifera document an advance of Cumberland Sound ice onto the shelf after H-3 or H-4 (c. 34 ka), but before H-2 (c. 21ka). Cumberland Sound ice readvanced to a position at or near the shelf edge at c. 11.1 ka, during the Younger Dryas chron. This advance is nearly synchronous with an advance of Labradorean ice on the southeastern Baffin Shelf and with a detrital carbonate event in Sunneshine Fjord, to the north, suggesting climatic forcing of separate ice dispersal centres during the Younger Dryas.