Initial Reports of the Deep Sea Drilling Project - Volume 15

This volume covers Leg 15 of the cruises of the Drilling Vessel Glomar Challenger. The Glomar Challenger departed from San Juan, Puerto Rico on 5 December 1970 on the fifteenth cruise and arrived in Cristobal, Panama on 2 February 1971 after drilling 9 sites. Sites were drilled in the Colombian and Venezuelan Basins, the Cariaco Basin (Trench), on the Aves Swell, Beata Ridge, and Nicaragua Rise. The overall scientific objectives outlined by the JOIDES Atlantic Advisory Panel were to determine the age and history of the Caribbean Sea and to establish a standard biostratigraphic section for the region. Scientists of Leg 4 of the Glomar Challenger drilled three sites in the eastern Caribbean with similar objectives in mind. However, left untouched and unknown on Leg 4 were those sediments that lie beneath Horizon A" and overlie another smooth strong reflector below which reflectors were rarely recorded. This smooth reflector is called Horizon B" and, like Horizon A" it extended throughout the Venezuelan Basin and could even be recognized west of the Beata Ridge to the lower slopes of the Nicaragua Rise. With improved technology on Leg 15, it was hoped that the objectives lost to Leg 4 scientists could finally be met. The origin and history of the Caribbean Sea were clearly the prime objectives of Leg 15. To achieve them, Horizon B" had to be sampled and hopefully cores could be taken from well below this level.