Upper Mantle Structure Beneath the Gamburtsev Subglacial Mountains & East Antarctica from Body-Wave Tomography

The geology and tectonic structure of East Antarctica is unknown due to the 2-3 km thick East Antarctic ice sheet that obscures all but a handful of outcrops along the coastal regions and in the Transantarctic Mountains. Geophysical methods (i.e., seismic, gravity, magnetic) and geochemical inferences suggest East Antarctica represents a Precambrian shield devoid of any major tectonic events since ~480 Ma, making the origin of the high and rugged topography of the East Antarctic highlands enigmatic. The highest feature within the East Antarctic highlands is the Gamburtsev Subglacial Mountains (GSM), located near the center of East Antarctica, beneath Dome Argus. This mountain range reaches elevations of ~3,000 m and exhibits rugged relief on the order of 1-2 km. The geophysical mechanism responsible for the uplift of the GSM is poorly understood and many uplift models for the region have been invoked, such as the existence of a hotspot or a series of Proterozoic/early Paleozoic orogenic events. Using seismic data from the GAMSEIS and TAMSEIS deployments, we investigate the upper mantle structure beneath the GSM and East Antarctica at unprecedented lateral resolutions via body wave tomography using P and S travel time residuals from teleseismic events that have been corrected for ice and crustal thickness. P and S wave velocity models exhibit strong spatial correlation of very small anomalies on the order of a few tenths of a percent relative to the mean of the model that are hundreds of kilometers wide. Resolution tests indicate that these anomalies are well resolved and can be interpreted as distinct lithospheric blocks within the East Antarctic shield. In particular, a slow to fast velocity pattern is observed orthogonal to the strike of the GSM indicating two distinct lithospheric blocks that correlate well with changes in shear wave splitting directions and may represent a suture zone. Such findings suggest an ancient origin for the GSM and reveal a portion of the tectonic framework within the interior of the East Antarctic shield.