Mapping tectonic provinces with airborne gravity and radar data in Dronning Maud Land, East Antarctica

Abstract

Antarctica represents a key component in the investigation of the geological history and reconstruction of the supercontinents Rodinia and Gondwana. Remnants of the formation and disintegration of these ancient land masses can be found, although great uncertainties remain in the location of tectonic boundaries beneath the ice sheet of Antarctica due to general lack of outcrops and the limited amount of geological data. Airborne and space measurements are the only possibility to obtain comprehensive spatial data coverage for geological studies in the remote polar areas. More than 100000 line kilometers of airborne geophysical data, including radio echo sounding, gravity and magnetic data, were acquired over an area of 1.2 million square kilometers in the center of Dronning Maud Land (DML) over four austral summer campaigns between 2001 and 2005. The data are presented here as compilations of homogeneous topographic and gravity data for the DML region, ranging from 14°W to 20°E and from 70°S to 78.5°S. With respect to older airborne geophysical investigations in DML, up to 85% of the gravity data cover unexplored regions. Analyses of the maps of topography and gravity anomalies, by filtering and isostatic analysis, reveal information about geologic and tectonic structures in DML. Different gravity maps provide hints for the general tectonic fabric of the area. For the first time the southern boundary of the continent-ocean boundary formed during the Jurassic dispersal of Gondwana is identified. Especially the mountain range in Dronning Maud Land is most likely not in isostatic balance. The area is still uplifting as a consequence of glacial rebound. Interpretations of the Jutul-Penck graben as failed Jurassic rift system can be confirmed by the gravity inversion. Thinned continental crust compared to the surrounding geological units strongly support this hypothesis. Besides on other interpreted anomalies, the data shows a gravity structure, which starts approximately at 73.25°S/006°E and strikes in southwestern direction. We speculate that this pattern represents the suture zone (eastern termination of EAAO) between southern Africa and the cratonic part of Antarctica.