Marine sedimentation at a calving glacier margin

A 2-month study at a subpolar, tidewater glacier was conducted at Anvers Is land, Antarctic Peninsula (lat 64 degrees S), to improve understanding of s edimentary processes and associated deposits in glacial marine settings. Da ta collected in the ice-proximal environment were (1) brash ice-size distri bution and melt rates to assess sediment source and transport mechanisms; ( 2) conductivity-temperature-turbidity-depth (CTTD) profiles, water samples, and sediment-trap catches to study processes and patterns of sediment disp ersal; (3) bottom cores and grabs to document recent glacial marine sedimen tation; and (4) remotely operated vehicle video surveys of the ice terminus and sea bottom to obtain images of physical and biological processes. The water column is stratified and a halocline occurs at similar to 20-30 m, Wa ter temperature ranged from -1 to 1.6 degrees C, salinity was 32 parts per thousand-34 parts per thousand, and suspended solids were 3-5 mg/l well abo ve the bottom. Ephemeral turbid horizons contain 8-15 mg/l suspended solids ; rare surface plumes and a quasipermanent turbid layer produced by resuspe nsion during during events reach 25-35 mg/l, Meltwater drains from the glac ier surface, but no subglacial meltwater was detected directly entering the sea. The most important sources of sediment appear to be the direct meltin g of the submerged ice front and melting of calved glacial ice. Most fragme nts of floating ice melt within 1 km of the ice front. Some sediment may be contributed as low-density (1.1 g/cm(3)) algae-bound sediment pellets by m eltwater streams draining the ablating ice surface. Sediment enters the str atified water column and is moved by tidal and wind-driven circulation. Mar ine sedimentation rates are low (similar to 3 mm/yr) relative to depth of b ioturbation, resulting in unstratified sandy mud with dispersed clasts.