Magnetic stratigraphy and sedimentology of Holocene glacial marine deposits in the Palmer Deep, Bellingshausen Sea, Antarctica: implications for climate change? Marine Geology 152
Abstract The Palmer Deep is a closed bathymetric depression on the Antarctic Peninsula continental shelf. It contains three separate sub-basins. These basins lie along a northeast-southwest axis with water depths ranging from >1400 m to the southwest (Basins II and III) to just over 1000 m to the northeast (Basin I). Six sediment piston cores were collected from the study region; these cores clearly demonstrate the varied sediment character for each basin. Sediments in Basin I are laminated and thinly bedded consisting of diatomaceous, pelagic=hemipelagic sediments, siliciclastic, terrigenous sediments, and ice rafted, hemipelagic sediments. In concurrence with other investigators, we propose that these laminations and thin beds represent climatically forced productivity cycles. Basin II and Basin III sediments alternate between pelagic=hemipelagic units and bio-siliceous mud turbidites. Correlations between cores are based on their remarkable magnetic susceptibility (MS) records which indicate alternating biogenic (low MS) and siliciclastic (high MS) dominated sedimentation; the bio-siliceous mud turbidites are characterized by intermediate to low MS values. Cores taken from within the main axis of the basins are expanded ultra-high resolution sections. A core collected on the sill between Basins II and III represents a condensed sediment section and may contain a complete Holocene record of changing paleoenvironments, one that records the transition from a glacial, ice shelf environment to an open marine, Holocene environment. A sharp drop in magnetic susceptibility at mid-core is a common sedimentological feature of each basin. Presently, we favor a climate change hypothesis for this magnetic lithostratigraphic transition which may reflect the termination of the Holocene Hypsithermal and a marked change in productivity dated ca. 2500 years BP
