New insights into the structural and tectonic settings of the Bay of Bengal using high-resolution earth gravity model data

The residual anomaly of GECO model-derived gravity data has been enhanced using first vertical derivative, tilt derivative and balanced horizontal derivative for delineation of structural and tectonic features over the Bay of Bengal (BOB). Entire BOB basin is classified in eastern, central and western basins for analysis of the delineated lineaments to understand the tectonic setting. It is observed that major lineament trends in the western and central basins are N-S, NE-SW, and in the eastern basin N-S, NNE-SSW, while prominent lineament trend for the entire BOB basin is in N-S direction. The statistical analysis of the lineament attributes, viz. lineament density, circular standard deviation, circular variance for the lineaments, reveals that the crust under the central basin has experienced the maximum tectonic disturbances followed by the western and the eastern basins. Euler depth solutions for structural index (SI) zero estimate the possible source depths of the lineaments as (i) 3.0-9.0 km (possibly top sedimentary layer), (ii) 9.0-18.0 km (possibly intermediate sedimentary layer), (iii) 18.0-24.0 km (possibly upper crustal layer), (iv) 24.0-33.0 km (possibly lower crustal layer) and (v) 33.0-64.0 km (possibly associated with Lithosphere). Power spectral analysis and 2D forward modelling indicate that sediment thickness varies from 2.0 to 17.0 km; crustal thickness varies from 4.0 to 16.0 km, and Moho varies from 10 to 34 km depth over the BOB. The present study confirms that the origin of the 85 degrees E ridge is due to the sagging of ridge crust into the mantle lithosphere, whereas the NER has a hotspot origin.