Presented by Barber, Donald C..
Andrews, John T.,
Farmer, G. Lang,
Jennings, Anne E.,
Kaplan, Michael R..
Key words: Laurentide, glacial-marine, radiogenic-isotopes, ice-stream, Heinrich
In Session 18 S23. North American Ice Sheets during Marine Isotope Stages 3 to 1: Extent, Chronology, Data and Modelling - GSA Quaternary Geology and Geomorphology Division Monday, 26-Oct-98 AM in Room: 802AB at 8:30 AM for 20 minutes.
Abstract: Hudson Strait and Cumberland Sound are two large, fault-bounded bedrock embayments along the northeastern Canadian margin that were occupied by ice streams draining the Laurentide Ice Sheet during the Late Foxe (=Wisconsin) Glaciation. These two ice streams advanced into the NW Labrador Sea several times during the Late Foxe, producing rapidly deposited, lithologically distinct layers on the adjacent continental slope. The distal facies of deposits originating in Hudson Strait are well known as the detrital carbonate (DC) component of ice-rafted detritus (IRD) that comprises the North Atlantic Heinrich (H-) layers. By analyzing sediment provenance, lithostratigraphy, and radiocarbon chronologies for cores from Hudson Strait and the SE Baffin Island shelf and slope, we constrained glacial sediment transport paths and the timing of deposition for material carried by the Hudson Strait and Cumberland Sound ice streams. Our radiogenic isotope analyses (Sr, Nd, Pb) of the silt and clay siliciclastic fraction of tills, proximal glacial-marine muds, and IRD-rich hemipelagic sediments in marine cores support ice-sheet reconstructions depicting a southeastward-flowing ice stream in Hudson Strait during H-1, -2 and -4. The Sr, Nd, and Pb data indicate that glacial processes transported isotopically distinct sediment a distance of 600 km, from western Hudson Strait to the slope, with no significant change in the isotopic composition of this basal sediment along the transport path. During H-events, slope sediment accumulation rates typically increased 8X, indicating the proximity of the advanced ice margin. Sedimentary structures in the DC-rich (i.e., Hudson Strait-derived) facies on the NW Labrador Sea slope imply that sediment-laden meltwater plumes coincided with the increased iceberg flux. A new core (HU97048-007) from the SE Baffin Island slope contains multiple layers of both Hudson Strait-derived DC and a black IRD-rich facies interpreted to originate in Cumberland Sound. Facies relationships and preliminary radiocarbon dates in this core suggest that ice advances in Cumberland Sound were more frequent, produced less meltwater, and were not coeval with the Hudson Strait advances (i.e., H-events). The differing responses of these two adjacent ice streams may imply non-climatic or complex climatically forced behavior of the NE Laurentide ice sheet.
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