SEISMIC REFLECTION AND MAGNETIC STUDY OFF BOMBAY, INDIA

Abstract

As part of the 1967 Global Expedition of the USC&GS Ship OCEANOGRAPHER, approximately 1700 km (920 nm) of reconnaissance seismic reflection and total magnetic field intensity traverses were made between 17° and 21° N latitude, over the shelf and slope off Bombay, India. This investigation was designed to determine why the shelf area off Bombay is as much as three times wider than the rest of the western Indian shelf. Near the landward edge of the continental shelf, the seismic reflection profiles show strata dipping west from Bombay. To the west, these profiles indicate that the configuration of the continental slope is influenced by anticlinal structures, suggesting that the western Indian shelf in the study area is a sediment‐filled structural basin. The greater shelf width off Bombay is due to the location of the anticlinal trends. Within the basin, a buried north‐south trending anticlinal high is present approximately 75 km (40 nm) west of Bombay in water depths of about 50 m (165 ft). The structural basin and subsurface anticlinal trend off Bombay may continue northward into the Cambay Basin, where similar features are present. This continuation may be locally interrupted by the westward extension of a fault zone from the Narbada Valley into the southern Cambay Basin. The magnetic field is relatively flat, except for a zone of high frequency anomalies, which may be caused by dikes extending from the Bombay coast westward for approximately 40 km (20 nm).