Upper Mantle Structure of Central and West Antarctica from Array Analysis of Rayleigh Wave Phase Velocities

• Main Authors: Heeszel, David S., Wiens, Douglas A., Anandakrishnan, Sridhar, Aster, Richard C., Dalziel, Ian W.D., Huerta, Audrey D., Nyblade, Andrew A., Wilson, Terry J., Winberry, J. Paul
• Format: Text
• Language: unknown
• Published: ScholarWorks@CWU 2016
• Subjects: Marie Byrd LandRoss Sea; mantle plume; heat flow; lithosphere; rift zone; seismic velocity structure; tectonics; Geophysics and Seismology; Tectonics and Structure; Antarctic; Byrd; Marie Byrd Land; Ross Island; Transantarctic Mountains; West Antarctica; Antarc*; Antarctica; Ice Sheet
• Online Access: https://digitalcommons.cwu.edu/geological_sciences/15; https://digitalcommons.cwu.edu/cgi/viewcontent.cgi?article=1020&context=geological_sciences

The seismic velocity structure of Antarctica is important, both as a constraint on the tectonic history of the continent and for understanding solid Earth interactions with the ice sheet. We use Rayleigh wave array analysis methods applied to teleseismic data from recent temporary broadband seismograph deployments to image the upper mantle structure of central and West Antarctica. Phase velocity maps are determined using a two–plane wave tomography method and are inverted for shear velocity using a Monte Carlo approach to estimate three-dimensional velocity structure. Results illuminate the structural dichotomy between the East Antarctic Craton and West Antarctica, with West Antarctica showing thinner crust and slower upper mantle velocity. West Antarctica is characterized by a 70–100 km thick lithosphere, underlain by a low-velocity zone to depths of at least 200 km. The slowest anomalies are beneath Ross Island and the Marie Byrd Land dome and are interpreted as upper mantle thermal anomalies possibly due to mantle plumes. The central Transantarctic Mountains are marked by an uppermost mantle slow-velocity anomaly, suggesting that the topography is thermally supported. The presence of thin, higher-velocity lithosphere to depths of about 70 km beneath the West Antarctic Rift System limits estimates of the regionally averaged heat flow to less than 90 mW/m2. The Ellsworth-Whitmore block is underlain by mantle with velocities that are intermediate between those of the West Antarctic Rift System and the East Antarctic Craton. We interpret this province as Precambrian continental lithosphere that has been altered by Phanerozoic tectonic and magmatic activity.