Duncan Young1, Enrica Quartini1, Donald Blankenship1
1University of Texas Institute for Geophysics, Austin, United States
West Antarctica hosts the large West Antarctic Rift System (WARS), a region of continental extension which has formed during several stages of rift reactivation from the Cretaceous through the Cenozoic.
Subglacial volcanic activity has been documented along the Executive Committee Range in Marie Byrd Land, where a swarm of deep long-period earthquakes was registered in 2010 and 2011 by the POLENET seismic network. Recent modeling has also evaluated the sensitivity of the West Antarctic Ice Sheet to hotspots; however, these results have not been evaluated in the context of basal conditions and crustal geology.
Here we analyze magnetic anomalies collected during recent aerogeophysical expeditions over Thwaites Glacier (THW), Pine Island Glacier (PI), and eastern Marie Byrd Land (MBL), in order to evaluate the distribution of potential hotspots in the region. We identify three different regions with distinct magnetic character and correlate each one of them to specific stages of tectonic and magmatic activity in WARS. Our interpretation supports both the hypothesis that MBL was tectonically and magmatically reactivated multiple times during the Cretaceous and that a hotspot was emplaced there later in the Cenozoic, therefore pointing to a hotter MBL compared to THW and PI.
We also evaluate the basal conditions in the interior flank of Marie Byrd Land, in the context of basal reflectivity, specularity, and subglacial water routing. We find a region of high specularity (indicative of elevated subglacial water) along the flank of Marie Byrd Land. We evaluate whether this water formed in place, or routed out of the Marie Byrd Land dome.
We place these observations in the context of the now well surveyed larger scale structure of the West Antarctic Rift System, and the crustal gradients observed by POLENET.