ИСТИНА

Information about structures of the upper crustal and sedimentary basins is still sparse in Antarctica because the continent is almost entirely covered by thick ice shields impeding in-situ measurements. Therefore, the analysis of potential fields such as gravity data can offer new insights. Traditionally, isostatic gravity anomalies are used to investigate upper crust structures. However, the density anomalies related to sedimentary and upper crustal structures are also compensated in an isostatic sense which i significantly reduces their gravity effect. To separate the effect of the upper crust and deep compensation, we apply so-called decompensative corrections to the isostatic anomalies for the Antarctic continent, which reach values of up to ±70mGal. Negative decompensative anomalies are assumed to be caused predominantly by low density sediments and correspond well with known sedimentary basins, such as in the areas of the Filchner-Ronne Ice Shelf and Lambert Graben. Additionally, they suggest the existence of other large sedimentary deposits both in West and East Antarctica, which are not or only sparsely mapped by existing seismic surveys (e.g. in coastal Dronning Maud Land and Enderby Land). The Transantarctic Mountains and the Wilkes Subglacial Basin are characterized by a dipole-like structure, suggesting the presence of isostatic disturbances linked to the dynamic uplift of the Transantarctic Mountains and thick sedimentary accumulations in the east. Extended positive anomalies in East Antarctica are likely related to old and dense cratonic crust as well as to isostatic disturbances caused by the transition from local to regional compensation around the Lambert Graben.