Radiocarbon-dated glacial-geologic evidence documents an abrupt advance of the northern margin of the Labrador sector of the Laurentide Ice Sheet during the last deglaciation. Ice-flow directional indicators, together with ice-marginal features found onshore and offshore, delimit an ice stream that advanced north-northeast >300 km, crossed the mouth of Hudson Strait and outer Frobisher Bay, and overran summits ∼400 m above sea level on outer Hall Peninsula, southeast Baffin Island. Fifty-eight 14C ages, including 27 accelerator mass spectrometry ages on single shells, indicate that the advance was extremely rapid. The entire advance-retreat cycle took place in an ∼300 yr (14C) interval, 9.9-9.6 ka. At its maximum extent, the ice stream supported a calving margin >200 km long terminating in open water ∼500 m deep, implying a massive iceberg release. Marine evidence for the outflow is preserved along the Labrador Sea shelf as thick carbonate-rich glacial-marine drift but has not been recognized farther east in the North Atlantic. Either the discharge of icebergs was insufficient to produce a trans-North Atlantic, carbonate-rich (Heinrich) layer, or the icebergs tracked southward where they encountered warming sea-surface temperatures. Although the advance seems to have been coincident with a brief interval of minor regional cooling, it failed to trigger a significant climate perturbation, suggesting that the ocean-atmosphere system had attained its stable interglacial condition by that time.

This content is PDF only. Please click on the PDF icon to access.

First Page Preview

First page PDF preview
You do not have access to this content, please speak to your institutional administrator if you feel you should have access.