Integrated geophysical appraisal of crustal structure and tectonic evolution of the Angria Bank, western continental margin of India

Abstract

Angria Bank, a submerged plateau with coral reefs, is located off the central-west coast of India. Biologically, the bank attracts scientific community for its coral formations. But geologically, origin and tectonic setting of this feature are not established yet due to scarcity of geological and geophysical data. Newly acquired bathymetry and magnetic data along with existing geophysical data have allowed us to determine crustal structure and tectonic evolution of the Angria Bank. The entire geological setup of the bank consists of 34 km long water plateau (average water depth approx. 20 m), and two prominent spurs extending to its western side. The area of water plateau and entire geological setup are 365 square kilometer and 1460 square kilometer, respectively. The bank is characterized by two prominent magnetic low with a relative high in the middle. Integrated gravity and magnetic models revealed that flood basalt has carpeted the entire geological structure which later acted as a foundation for coral growth. The crust below the bank is continental in nature and underplated by high-density magmatic material. Moho is almost flat and lies at a depth of approx. 27 km. The results of 3D Euler deconvolution suggest that the study area is characterized by two types of linear trend viz. NE-SW to NNE-SSW and NW-SE. These trends are interpreted mostly as basement faults but at few places, they might be associated with sills/dykes. The geological setup of the bank is fault-bounded and comprised of two horst structure (interpreted as spurs) trending NE-SW to NNE-SSW. Integrated interpretation of the geophysical data revealed that the Angria Bank is an isolated feature, evolved during rifting between India and Seychelles-Laxmi Ridge in the Late Cretaceous.