Emplacement and subsidence of Indian Ocean plateaus and submarine ridges

Ocean Drilling Program, Deep Sea Drilling Project, and industrial borehole results from Indian Ocean plateaus and submarine ridges help to constrain their subsidence histories. I use a simple Airy isostatic model to calculate basement depths at ODP sites in the absence of sediment, and then backtrack these sites using previously determined age-depth relationships for oceanic lithosphere to determine the original depth or elevation of the sites. Resulting subsidence curves for each site were then checked by examining sedimentologic and biostratigraphic evidence for when each site subsided below shelf depths. The analysis suggests that thermal subsidence has been the dominant tectonic process affecting Indian Ocean plateaus and submarine ridges following emplacement. I conclude that large portions of these features were emplaced and began subsiding well above sea level, similar to large igneous provinces (LIPs) worldwide today. This resulted in significant subaerial erosion and redeposition of volcanic material mixed with biogenic sediment, and a gradual development of facies from terrestrial through terrigenous to shallow water and pelagic, resulting in a sedimentary record with both continental and oceanic characteristics.