CGRG Bibliography of Canadian Geomorphology
Search Results
Author : Barber, D.C.; Funk, J.T.; and Jennings, A.E.
Date : 1997
Title : Isotopic and mineralogic provenance of glacial-marine sediments from Hudson Strait, northeast Canada
Publication : Geological Society of America, Abstracts with Programs
Issue : 29(6):
Page(s) : A-35.
Abstract
Hudson Strait was an important ice and meltwater conduit during Heinrich (H) events (e.g., H-2 = 21 ka) and during the deglaciation of NE Canada (ca. 11 - 8 ka). We have investigated the provenance of glacial-marine sediments from Hudson Strait to shed light on dyn-amics of the NE Laurentide Ice Sheet (LIS) during these periods of rapid climate change. The Pb isotopic signature of fine-grained (< 63 micron) siliciclastics in Hudson Strait¹s Western Basin is nearly identical to that of the same sediment fraction from H-layers in the NW Labrador Sea (mean Pb-207/Pb-204 = 15.5, Pb-206/Pb-204 = 18.3). A similar agreement is found among the Nd isotopic values (mean epsilon Nd = -28.2; Sm-147/Nd-144 = 0.115), and both deposits contain ca. 40% detrital CaCO3. The provenance of ambient sediment deposited during non-Heinrich intervals in the Labrador Sea is distinct from H-layers. The observed agreement between Western Basin sediment and Labrador Sea H-layers provides support for glaciologic models of an ice stream draining the LIS via Hudson Strait during H-events. We used X-ray diffractometry to investigate the mineralogy of clay-size particles in glacial-marine deposits in cores from Eastern Basin, Hudson Strait. Most sediment retrieved in these cores was deposited during the last northward ice advance from Labrador across eastern Hudson Strait. This Labrador-derived sediment is characterized by about 40% detrital CaCO3, with mean calcite/dolomite ratios of 3.5. Pb isotopic values are less radiogenic than in the Western Basin (mean Pb-207/Pb-204 = 15.1, Pb-206/Pb-204Pb = 17.3). In the upper sediment column, two additional units are identified: both contain less detrital CaCO3 with lower calcite/dolomite ratios than the underlying Labrador-derived deposit, and are isotopically and mineralogically distinct from each other. Our data indicate that glacial-marine deposition from the Labrador-dome ice margin ceased immediately prior to a short-lived depositional event that occurred throughout the strait (aka: the ³redbed², Kerwin, 1996, Quat. Res. 46: 89-98). After this event, Labrador-derived sediment was not deposited in Eastern Basin; instead, material with a provenance more typical of the Western Basin was deposited. A vestigial Keewatin ice margin probably supplied this uppermost deposit, suggesting that by this time (ca. 7.5 C-14 kyr BP) there was no impediment to water flow between Hudson Bay and the Labrador Sea.
Bibliography of Canadian Geomorphology