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Foraminiferal zones, radiocarbon ages on shells, and corrected ages on pretreated organic sediment from four cores from the eastern Baffin Island continental shelf suggest a three-stage deglacial to postglacial history (Late Wisconsin to Holocene). The earliest sediments in the cores contain foraminiferal species (Elphidium excavatum, Cassidulina reniforme, Islandiella helenae) indicative of distal glaciomarine environments that lasted at least several thousand years. An oceanographic change about 8500 years ago is indicated by a Melonis zaandamae zone in northern and central shelf cores collected from 200–800 m water depth. The presence of M. zaandamae in the north and its absence in the south suggest warmer and more saline postglacial water in northern Baffin Bay, whose influence became diluted with cooler coastal meltwater as the current flowed south along the Baffin Island Shelf. Sediments after 6000 years ago on the northern and central shelf are dominated by agglutinated foraminifera, suggesting dissolution of calcareous species. This dissolution event, which affected deeper water cores sooner than cores from the shelf, may be related to the influx of cold, CO2-rich water from the Arctic Ocean during the mid-Holocene. Thus, postglacial oceanographic changes in Baffin Bay appear first in deep northern waters; the lag time in the response to these changes in the shallower water on the shelf and to the south may have been as long as several thousand years.

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Figure 1. Locations of four cores discussed herein. Locations of hypoxia zone frequency taken from Committee on Environment and Natural Resources (2000), based on measurements done by N. Rabalais since 1985.

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