Recent progress in magnetic anomaly mapping over Victoria Land (Antarctica) and the GITARA 5 survey

Magnetic anomaly mapping is used to interpret crustal structure and tectoni c evolution of Victoria Land and of the adjacent Ross Sea. Previous interpr etation of magnetic anomalies verified seismic and gravimetric findings in the Ross Sea by placing additional constraints both on crustal structure an d magmatism of the West Antarctic rift system. An aeromagnetic map of the c entral-southern part of Victoria Land produced in the framework of the GITA RA project, provides new crustal images of part of the Trans antarctic Moun tains rift shoulder. The map was interpreted to study the transition betwee n the Wilson Terrane and the Precambrian East Antarctic Craton, the extent and distribution of Jurassic tholeiitic magmatism, and the occurrence of po st-Jurassic faulting oblique to the rift basins. A compilation with adjacen t aeromagnetic data was recently used to study the structures inherited fro m the Palaeozoic terranes and their reactivation as major fault zones separ ating different crustal blocks along the TAM rift shoulder. Additional aero magnetic coverage over a 35 500 km(2) sector of northern Victoria Land was acquired during the GITARA 5 (1996/97) survey. The flight altitude was 9000 ft and profile line spacing was 4.4 km for the regional grid and 2.2 km fo r the detailed one, with a tie line interval of 22 km. Standard processing techniques, optimized with microlevelling procedures were applied to the da ta to produce a 1:250 000 magnetic anomaly map. The processed GITARA 5 magn etic dataset is a new tool to study the structure of the Rennick Graben, an d its relationship to the Palaeozoic Wilson Terrane-Bowers Terrane and Robe rtson Bay Terrane suture zone. The new map also represents important progre ss towards a magnetic anomaly compilation over the whole of VictoriaLand, s ince it links previous efforts near the Pacific Coast with those near the R oss Sea.