VARIATIONS IN LATE HOLOCENE DEPOSITION CONDITIONS FROM TWO ARCTIC ISOLATION BASINS, NUNAVUT, CANADA

Cape Hurd Lake and Danielle Point Lake are marine inlets in the Canadian High Arctic that have been isolated from marine waters by postglacial isostatic rebound in the late Holocene. Both basins represent an intermediate stage in the evolution of "isolation basin lakes" between open marine inlets and isolated coastal lakes. In both lakes, prominent sills separate the basins from the adjacent sea. Circulation with the open marine environment, through narrow tidal channels, is restricted to the late summer after breakup of sea ice. The basins are density stratified with anoxic bottom waters. These conditions, coupled with the distinct seasonality of the arctic climate favor laminated sediment deposition and preservation providing long-term and high-resolution records of environmental change. Sediment cores and water column data were recovered in June 2001 from the basins, and approach 6 meters in length. The cores contain finely laminated biogenic and terrigenous mud up to 3.5 meters thick (isolation phase) overlying massive, fossiliferous mud with dropstones (open marine phase). Analyses in progress (loss-on-ignition, grain size, C/N, magnetic susceptibility, and thin sections) indicate major shifts in depositional conditions through the late Holocene including changes in runoff, ice thickness and basin productivity.