A reconnaissance geophysical survey in the Andaman Sea and across the Andaman-Nicobar Island Arc

A marine geophysical study of the Andaman Sea has been conducted as part of the International Indian Ocean Expedition. A combination of magnetic, gravity, bathymetric, and sea-floor heat-flux measurements, seismic sparker reflection profiles, and bottom sediment samples has been used in a study of the seaward continuity of major subaerial tectonic trends. The data indicate positive continuity of the structural trend of the Barisan Range of northern Sumatra and the Burma Range. It was found that the central graben of the Barisan Range of northern Sumatra extends into the Andaman Sea north to latitude 10°N. A previously unreported interdeep has been observed between the outer sedimentary island arc and the inner igneous trend of the major primary arc which forms the western boundary of the Andaman Sea. Continental thickness of the crust is indicated under the sedimentary island platform. In the area of the backdeep, the north-northeast trends of the Malaysian peninsula are prominent.