MELTWATER AND DEGLACIATION, SE BAFFIN SHELF (NE MARGIN LAURENTIDE ICE SHEET) BETWEEN 13.5 AND 7 KA: FROM O AND C STABLE ISOTOPIC DATA

Stable isotopic values on planktonic foraminifera in a suite of cores from basins across the SE Baffin Shelf are used to extract a record of meltwater events during Termination I deglaciation. Resolution and Hatton basins lie on the SE Baffin Shelf at water depths > 500 m, seaward of major conduits for ice drainage from the eastern sector of the Laurentide Ice Sheet ( LIS). Accelerator mass spectrometry C-14 dates are used to constrain our chronology of events in ten cores. In Resolution Basin, three cores have C-14 AMS dates on foraminifera of > 20 ka at their bases; whereas Hatton Basin cores terminate in sediment < s 13 kyr. Sedimentation rates varied between 0.1 to 4.5 m /ka. Stableo xygen and carbon isotopic ratios were obtained on 146 samples of the planktonic foraminifera Neogloboquadrina pachyderma (Ehrenberg) sinistral, from seven of the ten cores. No evidence was found to indicate that test morphology or size affected partial derivative O-18. Between 7 and 13.5 ka the surface water on the shelf was on average 1 o/oo lower than the open ocean signal. Significant temporal variations were found in both partial derivative O-18 and partial derivative C-13. Evidence for significant low partial derivative O-18 events occurred between 13 and 8 ka. The partial derivative C-13 record from the planktonic foraminifera suggestas threefold division of events between 13 and 7 ka, with positive values between 10.8 and 13.0 ka, negative values between 9 and 10.8 ka, and positive values from 7 to 9 ka. The partial derivative O-18 data suggest the presence of meltwater on the shelf some 3,000 years prior to the first late glacial dates on terrestrial deglaciation( a t circa 10.4 ka).