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Abstract:
Despite a big progress in the study of the Antarctic ice shield, still little is known about the structure of the uppercrust including sedimentary basins, which are hidden under the ice. In this work, we infer density heterogeneityof the upper crust of Antarctica by computing decompensative anomalies of the gravity field. These anomaliesare based on the isostatic anomalies, which are initially computed using the observed gravity field (satellite andterrestrial models), basement topography, ice thickness provided by the Bedmap2 project (Fretwell et al., 2013)and bathymetry of the surrounding ocean. In the isostatic model, we have also taken into account variations ofthe effective elastic thickness of the lithosphere and Moho depth from previous studies. Although the isostaticanomalies chiefly reflect the upper crust density heterogeneities, their impact is substantially reduced by isostaticcompensation. To refine this effect from the deep sources, we applied a so-called decompensative correction(Kaban et al., 2017). Therefore, the computed decompensative gravity anomalies are most appropriate to study theupper crust density structure. The obtained decompensative anomalies well correspond to the known sedimentarybasins, such as in the areas of the Filchner-Ronne Ice Shelf and Lambert Graben, however they suggest theexistence of other large sedimentary deposits both in West and East Antarctica, which are not yet revealed due toa lack of seismic surveys. The extended positive anomaly in East Antarctica is likely related to the old and densecratonic crust.
