GEOMAGNETIC DEEP SOUNDING INVESTIGATIONS AT THE TRANSITION BETWEEN THE TRANSANTARCTIC MOUNTAINS AND THE WILKES SUBGLACIAL BASIN, NORTHERN VICTORIA LAND

North Victoria Land (NVL) features two major tectonic elements: the Transantarctic Mountains (TAM), forming the uplifted flank of the Mesozoic and Cenozoic West Antarctic Rift System, and the Wilkes Subglacial Basin (WSB). Structure of the TAM rift flank has been partially investigated with different geophysical approaches. To the West, the Wilkes Subglacial Basin is present, a broad depression over 400 km wide at the George V Coast and 1200 km long. Geology, lithospheric structure and tectonics of the Basin are only partially known because the Basin is buried beneath the East Antarctic Ice Sheet and is located in a remote region which makes geophysical exploration logistically challenging. Different authors have proposed contrasting hypothesis regarding the origin of the WSB: it could represent a region of rifted continental crust or it may have a flexural origin or might represent an "extended terrane". Here we present inferences on the electrical conductivity structures at the transition between the TAM and the eastern margin of the WSB, based on Geomagnetic Depth Soundings (GDS) carried out during three different international Antarctic campaigns supported by the Italian Antarctic Projet: the BACKTAM, WIBEM and WISE expeditions. All the data have been processed in the frame of the ISEE project, aimed at evaluate the bias effect of the Polar Electrojet on geomagnetic transfer functions at different high geomagnetic latitudes and to study processing algorithms for magnetotelluric impedance tensor and magnetovariational transfer function estimate with high geomagnetic latitudes data. The qualitative analysis of the induction arrows, in the period range 20-170 s, reveals an approximately 2D regional electrical conductivity pattern with a clear differentiation between the three Terrains crossed by the GDS transect: the Robertson Bay, the Bowers and the Wilson Terrain. Bi-dimensional models suggest a differentiation of the investigated area in three crustal sectors separated by the Daniels Range and the Bowers Mts., in close relation with main known structural lineaments; to the West, a deep conductivity anomaly is associated with the transition to the Wilkes Subglagial Basin.