Sonograph Patterns of the Central Western Continental Shelf of India

Abstract

Side scan sonar and bathymetric surveys were conducted on the central western continental shelf of India. The sonographs portray a smooth, relatively featureless inner shelf, up to a depth less than 40-50 m, which is covered with fine grained sediments. The sonographs of the outer shelf, from beyond 60 m depth, to the shelf edge, exhibit bedforms such as reef outcrops (algal and oolitic ridges) and minor topographic undulations. Towards the shelf edge these give way to isolated colonies of algal knolls. A transition zone with tonal variations is present between 40 and 60 m water depth. Ground-truth data from sediment and rock distribution maps indicate depositional (inner shelf), nondepositional or erosional (outer shelf) environments and a combination of both in the transition zone. These match well with the sonographs.