Initial Reports of the Deep Sea Drilling Project - Volume 25

This volume covers Leg 25 of the cruises of the Drilling Vessel Glomar Challenger. Leg 25 provided the first opportunity to study the relatively unknown basins and ridges of the western Indian Ocean. The drilling program was set up to drill as many of the physiographic provinces as possible and, therefore, no two successful holes were drilled in any one province. Among the physiographic provinces drilled were the Mascarene Basin (Site 239), Somali Basin (Site 240), East African continental rise (Site 241), Davie Ridge in the Mozambique Channel (Site 242), Mozambique Channel (Sites 243 and 244), Madagascar Basin (Site 245), Madagascar Ridge (Sites 246 and 247), Mozambique Basin (Site 248), and Mozambique Ridge (Site 249). Leg 25 results were designed to provide a broad understanding of the western Indian Ocean rather than to concentrate on any one problem or group of related problems as some legs in the Indian Ocean have been able to do (e.g., Legs 22 and 23). The original objectives of Leg 25 were (a) to determine the age and mode of formation of the western Somali Basin and its western margin on the East African continental rise near Kenya, (b)to establish as deeply as possible the stratigraphic column in the Mozambique Channel, (c) to determine the significance of the Davie Ridge in relation to possible movements of Madagascar, (d) to determine if the basement of the Madagascar and Mozambique ridges are of continental or oceanic type and to establish on these ridges a midlatitude biostratigraphic succession above the carbonate compensation depth (CCD), (e) to check the proposed magnetic anomaly pattern in the Madagascar and Crozet basins, which lie on both sides of the Southwest Indian Ridge, and which are related to spreading from the Central Indian Ridge and the Southeast Indian Ridge, respectively, and (f) to provide lithologic and paleontologic data relating to the initiation of uplift and activity of the Southwest Indian Ridge. Glomar Challenger left Mauritius on June 28, 1972, and terminated its cruise in Durban, South Africa on August 22, 1972, having steamed 5408 miles and drilled 13 holes at 11 sites.