Structure of the Earth’s Crust and Tectonic Evolution of the Central Bengal Basin

A comprehensive analysis of geological and geophysical data characterizing the structure of the Central Bengal Basin (CBB) and its framing structures was carried out. For the first time, a submeridional section of the deep seismic sounding crossing the CBB was presented. It is found that the consolidated crust in the CBB has a complex block structure. The velocity characteristics of the basement and the gradient two-layer structure of the upper mantle unambiguously indicate that the basin was formed on continental rather than oceanic crust. The mechanism of the CBB basement sinking, the amplitude of which reaches 11 km, may be the compaction of the basic rocks of the lower part of the continental crust at its contact with the heated upper mantle and the transition of gabbroid rocks into eclogites with density of (3.6 g/cm) which is higher than that of mantle peridotites (3.3 g/cm). We conclude that the CBB, the 85° E Ridge, and the Bengal sector of the East Indian Ridge are relict fragments of the differentially submerged eastern part of the Indian paleocontinent.