Flexural Rigidity Around Ross Island, Antarctica Based On Geodynamic Modeling And Seismic Stratigraphy

Quantifying the flexural subsidence history around Mt. Erebus, located on Ross Island 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. Toward this end, we analyze both broken and continuous plate models of flexural subsidence due to volcanic loading around Mt. Erebus. Seismic reflection data from the IT90AR71, NBP0401-118m and NBP0401-126m seismic surveys are used to identify stratigraphic horizons associated with loading during different eruptive events. Based on results obtained by ANTOSTRAT, we have identified 5 seismic horizons RSb1 (early Oligocene), RSb2 (late Oligocene to early Miocene), RSb3 (early Miocene), RSb4(early to middle Miocene) and RSb5 (middle Miocene), which are correlated with the CIROS-1 drill hole, in the Eastern Ross Sea to identify 5 episodes of flexural subsidence related to Ross Island volcanic loading. The seismic data indicate that the flexural bulge associated with all 5 volcanic loading events is located at an average distance of 250 km from Mt. Erebus. We use the position of the flexural bulge and the dip of strata within the basin to constrain geodynamic models of flexural subsidence due to volcanic loading. We assume a mantle density of 3200 kg/m^3 and density of sedimentary basin infill of 2700 kg/m^3. Our preliminary results suggest that a broken plate, point load model is the most ideal case for Ross Island. The flexural rigidity is approximately 10^22.5 N-m, and the cumulative load of all volcanic episodes of Mt. Erebus is 9x10^11 N.