Bathymetry, depth to magnetic basement, and sediment thickness estimates from aerogeophysical data over the western Weddell Basin

Abstract

We estimated the bathymetry and sediment thickness of a remote and difficult to access portion of the Antarctic continental margin using aerogeophysical surveying techniques. The U.S., Argentina, Chile aerogeophysical survey collected magnetic and gravity data over the basins surrounding the Antarctic Peninsula. Thirty‐seven of these flight lines were used to estimate bathymetry and depth to magnetic basement for the western Weddell Basin. A wavenumber technique was applied to individual magnetic anomaly profiles in an automated fashion to obtain estimates of the depth to magnetic basement. The bathymetric estimates were obtained by admittance inversions of the gravity field. The results were then gridded at a 40‐km interval for the region 64°W, 44°W, 73°S, and 62°S. Bathymetric estimates and depth to magnetic basement estimates were differenced at each grid point to obtain a regional estimate of the thickness of nonmagnetic overburden (assumed to be sediment). Subsequent spot measurements of topography in the estimated region of the continental margin generally agree to about 52 m. The estimated magnetic basement deepens from the Antarctic Peninsula margin eastward to a maximum of 10–12 km near 54°W. We also postulate the existence of two moderately large basins flanking the eastward continuation of the Jason Peninsula. Farther east, the basement steps upward, with a correspondent thinning of the sedimentary layer. Along the east coast of the peninsula, results agree well with seismic studies on James Ross Island and magnetotelluric studies on Marambio Island and the Larsen nunatak, as well as the British Antarctic Survey basement estimates from aeromagnetic data. This study further demonstrates the utility of combined application of airborne and satellite geophysical techniques in the study of structure and tectonic evolution of continental margins and marine basins.