Subglacial geology and tectonics of the Dome F Region, Dronning Maud Land, East Antarctica

Abstract:

The region around Dome Fuji is considered as one of the most suitable areas in East Antarctica to find a continuous glacial stratigraphy reaching the oldest ice on Earth. Besides this importance, a basic understanding of the subglacial geology and its interpretation in terms of the tectonic histories of Rodinia and Gondwana is lacking. To address this, the Alfred Wegener Institute acquired new airborne magnetic data covering ca. 170 000 km² at 10-15 km line spacing during the austral summer 2016/17. The magnetic data analysis, combined with the survey’s radar-derived bed topography and gravity data from the ANTGG compilation, allow mapping of geological domains and their assumed bounding structures. Combined with existing studies of the adjacent areas, this approach provides a regional tectonic interpretation. Magnetic data reveal three magnetic domains delineated by mostly N-S oriented boundaries that are enhanced by the upward continuation data filtering technique. These magnetic domains partly correlate with gravity domains characterized by imaging and filtering of isostatic residual gravity anomalies. In addition, three major sets of magnetic lineaments can be distinguished: (1) NW–SE-oriented lineaments that correlate with mountain ranges and valleys; (2) E-W and ENE–WSW-oriented lineaments that correlate with steep slopes and often the locations of marked magnetic anomaly offsets, and thus can be interpreted as strike-slip faults; (3) less numerous N–S trending lineaments. A set of curvilinear magnetic highs correlate well with gravity highs. These may represent granitoids embedded in a continuation of the Tonian Oceanic Arc Super Terrane (TOAST), allowing us to determine its continuation further south than previously known. In addition, this central zone related to the TOAST present sigmoid-shaped magnetic highs correlating with the subglacial topography trends, which can be interpreted as a broad scale shear zone. The new magnetic data combined with previously acquired magnetic, gravity and bedrock maps allow the revision of the tectonic map of a part of East Antarctica by revealing the possible eastern extent of the recently-proposed subglacial Valkyrie Craton; the western extent of the Ruker Craton and the southern extent of the TOAST. Finally, a geodynamic scenario related to the collision between the African- and Indo-Antarctic domains is proposed involving a broad scale shear zone between the two cratons.