When coupled with the previous map of source areas documented by Bond et al (1992), this slide strongly suggests that the major cause of Heinrich events was fluctuations in the Hudson Strait ice
stream, which drained a large fraction of the former Laurentide Ice Sheet.
Heinrich events have several distinctive properties that allow them to be distinguished over large distances. The thickness of H-1 and H-2 events (radiocarbon dated at
14.5 kyr and 20.5 kyr, respectively) in each core were measured. Next, these thicknesses were plotted on a map. Finally, lines of equal thickness were drawn through the map, much as the isotherms (lines of equal temperature) and isobars (lines of
equal pressure) on a meteorological map. The thickest sediments were found to lie off the southern coast of Baffin Island, right where the Hudson ice stream flowed into the ocean. To the south and northeast of this area as documented by Bond et al
(1992), the detrital carbonate sediments became thin or even absent, suggesting that the carbonate rich layers were restricted to areas of high IRD counts that amassed during the last glaciation.
John T. Andrews, Thomas G. Andrews
NOAA Paleoclimatology Program and
INSTAAR, University of Colorado, Boulder
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