Reactivation of precambrian faults on the southwestern continental margin of India: Evidence from gravity anomalies

Abstract

Gravimetric and bathymetric studies on the southwestern continental margin of India confirm the extension of onshore NW-SE-, NNW-SSE-, N-S-, NE-SW-, ENE-WSW- and E-W-trending lineaments of Precambrian age over a considerable distance into the offshore region. The bight in the bathymetry off Coondapoor the offsets of Bessas de Pedro bank and the Cora Divh Island of the Laccadive group, the Prathap Ridge, and the inferred mid-shelf basement ridge suggest block movements on the southwestern continental margin. The physiographic expression on the Prathap Ridge (around 14 degrees 20'N and 72 degrees 50'E) is unaffectEd. by some of the ENE-WSW lineaments, which probably indicates that these lineaments predate, the evolution of the topographic expression. As seafloor spreading advanced with respect to the Carlsberg Ridge, some of the ENE-WSW and NE-SW lineaments on the western continental margin appear to have been reactivated, and block movements took place. The presence of a basement ridge in the mid-shelf and the shelf margin basement high (Prathap Ridge) west of the slope resembles the structural style of a passive continental margin