Structure of the Wilkes Basin Lithosphere along the ITASE01 Geotraverse

Abstract

During the 2000/2001 scientific expedition a new gravity, magnetic and airborne radar dataset has been acquired along the regional geotraverse ITASE01A/B to improve the knowledge about the tectonic setting and geodynamic origin of East Antarctica. This new traverse crosses the Northern Wilkes Basin, the Webb Sub-glacial Trench, the Southern Cross Subglacial Highlands and the Astrolabe Trench. The gravity data have been converted to free air anomaly. First, the Free Air gravity anomalies has been modelled assuming two isostatic models, Airy and flexural, and later using a raw 2D forward model along the ITASE01A/B traverse. The isostatic approach fails to predict the observed gravity anomaly due to the oversimplification of the assumed model, the lack of extensive information such as heat flow, age, mantle viscosity, rheology and Moho depth, etc. The raw 2D forward gravity model points to a thick crust, of about 40 km, and the presence of a sedimentary body along the traverse and yields a good fit between the observed and predicted gravity anomaly. The thickness of this sedimentary body is variable and ranges from 6 to 7 km in the Astrolabe Trench to 5 km in the Wilkes Basin and decreases further in the Southern Cross Subglacial Highlands. There is no evidence of recent rifting along the traverse considering the time decay of thermal anomalies following a rift-ing episode and the state of relative compression of the whole Antarctic continent. The shape and origin of the East Antarctic basins should be traced back before the Gondwana disruption in Early Cretaceous. At present, the studied area behaves as a stable area even if this conclusion can be affected by the limited spatial extension of known data, mainly recorded along traverse, the lack of any geological hints about