FOLLOWING THE LATE WEICHSELIAN RETREAT OF THE NW ICELAND ICE CAP FROM SHELF TO LAND

The retreat of the Last Glacial Maximum (LGM) ice sheet from its maximum position is recorded in marine and lacustrine sedimentary archives in a transect from the shelf, along a major fjord, and onto land in the Northwest Peninsula (NWP). Lithofacies, carbon content, magnetic susceptibility (MS), and ice-rafted debris (IRD) record the change from ice-covered, through ice-proximal and eventually to ice-distal environments.

NW Iceland is the region where the Polar Water in the East Greenland Current meets the warmer Irminger current of Atlantic origin. The position of the boundary between the two currents is known to vary depending on fresh water flow from the Arctic Ocean, and advection of warm water as a branch of the North Atlantic Drift. Sediment from this area should thus give the first indication of changes in the strength of the two opposing currents.

Marker tephra layers serve as a correlation tool between terrestrial and marine archives in addition to numerous AMS dates on bulk sediment and mollusks. Our data indicates a more restricted extent of ice on the NWP shelf during the LGM than previously thought, and shows a near continuous accumulation of IRD from 35 to 11 cal ka on the shelf. However, the inferred LGM margin between 19 and 22 cal ka is characterized by no IRD, which we interpret to be an interval of extensive landfast sea-ice. This interpretation is supported by the existence of laminated sediment, sulfide streaks and the foraminifera species S. feylingi in the shelf sediments. A rapid but stepwise retreat of the ice into the fjord system is detected after 15 cal ka, with IRD pulses around 12 cal ka and 11 cal ka.

MS and organic carbon content from lake sediment on the NWP reveal the disappearance of local ice in the basins before or around 11 cal ka. Rapid changes in both parameters between 11 cal ka and 10 cal ka indicate readvances occurred following initial deglaciation of the lake basins. A comparison of the lake cores with the fjord and shelf cores shows similarities in total carbon % over the last 10,000 yrs. A minimum in total carbon correlative with the 8.2 ka event in the GISP/GRIP cores is seen in both the marine record off NW Iceland and the lake record. These similarities suggest we may be able to correlate land and sea records for both the deglacial period and more subtle environmental changes during the Holocene.