CGRG Bibliography of Canadian Geomorphology
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Author : Barber, D.; Farmer, L.; and Andrews, J.T.
Date : 1997
Title : Ice-flow paths in the Hudson Strait region during Heinrich Events: provenance data from Nd & Pb isotopes.
Publication : Abstract, American Geophysical Union meeting, December 1997.
Issue :
Page(s) :
Abstract
Ice margins draining the NE Laurentide Ice Sheet dominated the iceberg flux to the North Atlantic during Heinrich (H-) events. The source of much of this ice is hypothesized to be an ice stream flowing southeastward down the axis of Hudson Strait. Although such an ice stream is a robust feature of numerical models, evidence supporting it has been scarce. The abundant glacial geologic evidence in the eastern Hudson Strait region instead records ice advances that flowed northward across the strait, not along it. However, the striae that record the N-ward ice advances at the eastern end of the strait most probably post-date H-events. In order to differentiate which flow path dominated during H-events, we have attempted to characterize sediment signatures indicative of both the SE-ward and the N-ward ice flow paths. The method we employ is analysis of Nd and Pb isotopes in silt- and clay-sized siliciclastic sediments from ice-proximal glacial-marine deposits at key Hudson Strait coresites. Sediments from the Western Basin of Hudson Strait characterize material derived from northern Hudson Bay and Foxe Basin. Thus the core -101 deposits should be a tracer of SE flow along the strait. In contrast, core -045 from the strait's Eastern Basin contain sediment derived from Labrador and transported by northward ice flow. The Pb and Nd isotopic signature of the Western Basin is nearly identical to that for fine-grained siliciclastics from H-layers in NW Labrador Sea core -009. Values within the cluster of Western Basin and H-layer sediment data are as follows:mean Pb-207/Pb-204 = 15.5 +/-0.1, mean Pb-206/Pb-204 = 18.3 +/-0.4; and mean epsilon Nd = -28.27 +/-.26. The deposits in core -045 that originated from the Labrador Dome (i.e., from northward ice flow) are isotopically distinct from the Western Hudson Strait source; Pb values are less radiogenic with mean Pb-207/Pb-204 = 15.2 +/-0.1, Pb-206/Pb-204= 17.5 +/-0.2. Nd data are slightly more radiogenic: mean epsilon Nd = -26.1 +/-0.3. Ambient sediments deposited during non-Heinrich intervals in the Labrador Sea are also isotopically distinct from H-layers but show no systematic affinity to either of the sources we characterized Our observations, of agreement between H-layers and Western Basin sediment, and the notably different character of Labrador-derived material, support the hypothesis that an ice stream draining the central Laurentide Ice Sheet via Hudson Strait was the dominant iceberg source during H-events.
Bibliography of Canadian Geomorphology