SEDIMENT DISTRIBUTION IN INDIAN OCEAN

Seismic data in the Indian Ocean are used to construct an isopach map of unconsolidated sediments. The major thickness of sediments is found in the following places: (a) the Indus and Ganges cones, which comprise about 40% of the sediment of the Indian Ocean; (b) basins adjacent to the continents on the east and west containing largely terrigenous sediments; (c) a zone south of the Polar Front, which is high in biologic productivity and where extensive non-stratified accumulations of sediment occur. Sediment cores indicate that the sediments in this last category are largely siliceous oozes. The crestal area of the mid-oceanic ridge is consistently bare of sediment to a distance of at least 100 km from the axis, except on the southwestern branch where thick sediment pockets have been found within 100 km of the crest. This relative abundance of sediment close to the ridge axis in places on the southestern branch may be related to a much slower spreading rate here than elsewhere, or to the complications introduced by the numerous fracture zones offsetting the ridge crest. © 1969.