Lithospheric Flexure Modeling around Mt. Erebus, Ross Island in Western Antarctica

Sumant Jha
Department of Geosciences, Colorado State University

Separating tectonic, volcanic and climatic signals in stratigraphic records contained in regional seismic reflection and borehole data helps in quantifying the subsidence history around Mt. Erebus, located in southern Ross Sea of West Antarctica.

We use seismic reflection data collected by Italian and New Zealand Antarctic research agencies, to identify episodes of flexural subsidence surrounding Mt. Erebus. Our preliminary results are based on the L284AN-401, IT90AR71, NBP0401-118m and NBP0401-126m seismic surveys from the region. We identify 5 seismic horizons, which are considered as representative of flexural subsidence owing to volcanic episodes of Mt. Erebus. These horizons are correlated to the CIROS-1 drill hole in eastern Ross Sea, and range in age from Early Oligocene to Middle Miocene, which is consistent with the Miocene ages of volcanic episodes from drill holes from ANDRILL Cores.

Based on the seismic data, we infer that the flexural bulge associated with volcanic loading is located at an average distance of 250 km from Mt. Erebus. Using the location of flexural bulge and dips of seismic horizons as constraints, we compare broken plate and continuous plate flexure models and find that the broken plate model with point load fits the data better than a continuous plate model. Assuming a mantle density of 3200 kg/m³ and density of basin sedimentary infill of 2700 kg/m³, we estimate the flexural rigidity to be 10^22.5N-m, and the cumulative load owing to all episodes of volcanic eruptions of Mt. Erebus being 9x10¹¹N.

Future work will involve tying seismic loops, decompaction, revising flexure model and identifying tectonic signatures with higher confidence. These signatures can then be removed from present data to account for sea level fluctuations owing to climate changes.

Keywords: Seismic Reflection, ANDRILL, Ross Island, Mt. Erebus, Flexural Rigidity, Plate Flexure, Antarctica

AAPG Search and Discovery Article #90181©2013 AAPG/SEG Rocky Mountain Rendezvous, University of Wyoming, Laramie, Wyoming, September 27-30, 2013