Super-thick sedimentary, basin, bay of Bengal

A super-thick (−20km) sedimentary basin under the northern Bay of Bengal is proposed, based on data from surface wave dispersion, seismic refractior, S n attenuation, and geology. Surface wave data of Brune and Singh (1986) suggested an oceanic Moho depressed to 30 km. Traditional interpretation of refraction data by Curray and others, suggested sedimentary thickness up to 15 km. This led Brune and Singh (1986) and Brune and Priestley (1989) to suggest an anomalously thick oceanic crust (layers 2 and 3), possibly a result of underplating related to early margin and ridge formation, or to reactivation of magmatic activity by thermal blanketing. We present new high frequency S n propagation data which indicate a cold upper mantle beneath the B3ay of Bengal and is strong evidence against any mechanism requiring high temperatures at present.