EARLIEST SEA-FLOOR SPREADING MAGNETIC-ANOMALIES IN THE NORTH ARABIAN SEA AND THE OCEAN-CONTINENT TRANSITION

Magnetic and gravity data collected during a GLORIA survey of the Indus Fan provide new information on the earliest sea-floor spreading history of the Arabian Sea. A negative gravity anomaly correlates with the buried Laxmi Ridge. This ridge is interpreted here to be a sliver of continental crust adjacent to the ocean-continent transition which bounds thinned, probably intruded, transitional crust to the NE. The oldest sea-floor spreading anomaly is anomaly 28 (65-66 Ma), breakup occurring at the time of the Deccan Traps volcanic event. The earliest oceanic crust formed from two phases of rift propagation which accommodates the angular disparity between the E-W trending anomalies in the western Arabian Sea and the NE-SW trending western part of the Laxmi Ridge. Flow-line projection shows that the Laxmi ridge forms the conjugate structure to the northern Mascarene Plateau margin.