Landform assemblage produced by the Biscoe Trough ice stream, northern Antarctic Peninsula

Abstract

The continental shelf off the Biscoe Archipelago has one of the largest cross-shelf troughs on the Pacific margin of the North Antarctic Peninsula (NAP), the Biscoe Trough (Fig. 1a, b). Grooved and streamlined bedrock, drumlins, mega-scale glacial lineations (MSGLs) and grounding-zone wedges (GZWs) define a continuum of landforms over 130 km that provide evidence that ice streams sourced in three different interior drainage basins converged and flowed along the trough during the Last Glacial Maximum (LGM). The Biscoe Trough is important in understanding the configuration of the Antarctic Peninsula Ice Sheet during the LGM (Lavoie et al. 2015) and the onset of the modern Antarctic ice sheet in the Late Pliocene (Rebesco et al. 2006). Fig. 1. ( a ) Location of study area (red box; map from IBCSO v. 1.0). ( b ) Multibeam-bathymetric image of Biscoe Trough collected during RV Hesperides COHIMAR/SEDANO cruise in 2002. Background bathymetry (in grey) from GEBCO\_08. Acquisition system Simrad EM12-S. Frequency 12.5 kHz. Grid-cell size 50 m. Land area from Landsat Image Mosaic of Antarctica, US Geological Survey. PD, Palmer Deep; HIT, Hugo Island Trough. ( c ) Enlarged multibeam image of Biscoe Trough. 100 m contours from GEBCO\_08. ( d ) Schematic diagram of the main geomorphic features of Biscoe Trough. The main trunk of the Biscoe Trough follows an ESE–WNW orientation. Two NE–SW- and SSE–NNW-orientated tributary troughs enter Biscoe Trough from the north and south, respectively (Fig. 1c). The elongate bedforms revealed in multibeam data are initially aligned parallel to these orientations, and show overall convergence towards the shelf edge. The north and south tributary troughs are deepest, with water depths >800 m and 1000 m, respectively (Fig. 1c). The trough boundaries are steep and straight, with a relief of 600 m with respect to the <200 m deep steep-sided banks. A third area of overdeepening, with …