BATHYMETRY, DEPTH TO MAGNETIC BASEMENT, AND SEDIMENT THICKNESS ESTIMATES FROM AEROGEOPHYSICAL DATA OVER THE WESTERN WEDDELL BASIN

We estimated the bathymetry and sediment thickness of a remote and dif ficult to access portion of the Antarctic continental margin using aer ogeophysical surveying techniques. The U.S., Argentina, Chile aerogeop hysical survey collected magnetic and gravity data over the basins sur rounding the Antarctic Peninsula. Thirty-seven of these flight lines w ere used to estimate bathymetry and depth to magnetic basement for the western Weddell Basin. A wavenumber technique was applied to individu al magnetic anomaly profiles in an automated fashion to obtain estimat es of the depth to magnetic basement. The bathymetric estimates were o btained by admittance inversions of the gravity field. The results wer e then gridded at a 40-km interval for the region 64 degrees W, 44 deg rees W, 73 degrees S, and 62 degrees S. Bathymetric estimates and dept h to magnetic basement estimates were differenced at each grid point t o obtain a regional estimate of the thickness of nonmagnetic overburde n (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 degrees W. We also postulate the existence of two moderately large basins flanki ng the eastward continuation of the Jason Peninsula. Farther east, the basement steps upward, with a correspondent thinning of the sedimenta ry layer. Along the east coast of the peninsula, results agree well wi th seismic studies on James Ross Island and magnetotelluric studies on Marambio Island and the Larsen nunatak, as well as the British Antarc tic Survey basement estimates from aeromagnetic data. This study furth er demonstrates the utility of combined application of airborne and sa tellite geophysical techniques in the study of structure and tectonic evolution of continental margins and marine basins.