FLEXURAL SUBSIDENCE AROUND MT. EREBUS, ROSS ISLAND, ANTARCTICA

Quantifying the flexural subsidence history around Mt. Erebus, located in the southern Ross Sea of West Antarctica, is essential to separating the tectonic, volcanic, and climatic signals in the stratigraphic record contained in regional seismic reflection and borehole data. We have used seismic reflection data from previously conducted seismic surveys by the Italian Antarctic Program and National Science Foundation to identify episodes of flexural subsidence in the area surrounding Mt. Erebus. Our Preliminary result uses the IT90AR71, NBP0401-118m and NBP0401-126m seismic surveys. We have identified 5 seismic horizons, which we consider as representative of flexural subsidence owing to volcanic episodes of Mt. Erebus. These horizons (RSb1, RSb2, RSb3, RSb4, and RSb5) are correlated with the CIROS-1 drill hole in the eastern Ross Sea, and range in age from Early Oligocene to Middle Miocene, which is consistent with Miocene ages of volcanic episodes from drill holes from ANDRILL Cores. The seismic data show that the flexural bulge associated with volcanic loading is located at an average distance of 250 km from Mt. Erebus. Using the location of the flexural bulge and the dips of the seismic horizons as constraints, we compare broken plate and continuous plate flexural models and find that the broken plate model with a point load fits the data better than a continuous plate model. Assuming a mantle density of 3200 kg/m³ and a 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 9x10¹¹ N.