Explained and Unexplained Spatial and Temporal Variability in Rates of Marine Sediment Accumulation Along the Northeast Margin of the Laurentide Ice Sheet <= 14 Ka

Abstract

ABSTRACT Changes in sediment accumulation rate (SAR, cm/ky) for fifteen AMS 14C dated late Quaternary sites from along the NE margin of Canada (between 66° and 54° N) are examined. These 15 cores cover the last deglacial cycle of sediment input from the decaying Laurentide Ice Sheet, and subsequent postglacial marine sedimentation on these arctic and subarctic shelves and basins. It is shown that the spatial and temporal variability of the 15 SAR time series do not simply parallel the known glacial chronology. Deglaciation of the shelves initially occurred after Heinrich event 1 (H-1, 14.5 ka; all dates are in 14C yr). Subsequently, there were major ice advances during the Younger Dryas (YD/H-0, 10-11 ka) and the Noble Inlet glacial events (8.6 ka), with final collapse of the ice sheet ca. 8.0 ka. A total of 73 radiocarbon dates were used, which led to 58 SAR estimates. The median SAR is 69 cm/ky; however, the distribution is strongly positively skewed because of short-lived intervals of very high SAR ( 5000 cm/ky, ca. 5000 kg m-2 ky-1). On the Labrador Shelf, high SAR are associated with ice retreat from the Noble Inlet maximum (< 8.6 ka), whereas on the SE Baffin Shelf there is little response in the sediment system to this event. Conversely, during the Younger Dryas/Heinrich-0 (YD/H-0) event, high SARs occur on the SE Baffin Shelf, but along the Labrador Shelf the interval 10-11 ka is marked by modest SARS. Both the 11-10 and 8.6-8 ka rapid sediment accumulation events are marked by considerable increases in the detrital carbonate content, hence bear similarities to the major Heinrich events in the NW Labrador Sea. These unexpected spatial and temporal differences in sediment deposition probably reflect changes in sediment transport trajectories associated with differences in ice (glacial or sea-ice) extent, and atmospheric/oceanic circulations.