Bathymetry and acoustic facies beneath the former Larsen-a and Prince Gustav ice shelves, NW Weddell Sea

We present preliminary results of the first detailed surveys of the former Larsen-A Ice Shelf, Larsen Inlet aiid southern Prince Gustav Channel. where disintegration of small ice shelvcs in the past ten years has exposed the seafloor. Glacial troughs in the Larsen-A area, Larsen Inlet and Prince Gustav Channel reach 900-1 100 m in depth and have hunitnocky floors. Farther south-cast, the continental shelf is shallower (400-500 m in) and its surface is fluted to smooth, with the density of iceberg furrowing increasing towards the shelf edge. Acoustic profiles show a drape of transparent sediment 4-8 m thick in Princc Gustav Channel, thinning southwards. In cores, this drape corresponds to diatom-bearing marine and glacial-marine mud. In the Larsen-A area aiid Larsen Inlet, acoustically opaque sediment includes proximal ice shelfglaciomarine gravelly aiid sandy muds. aiid firm to stiff diamicts probably deposited subglacially. These arc overlain by thin (up to 1.3 in) glacioniariiie muds, locally with distinctivc diatom ooze laminae.

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