Initial Reports of the Deep Sea Drilling Project - Volume 50

This volume covers Leg 50 of the cruises of the Drilling Vessel Glomar Challenger. Our knowledge of the earliest stages in the evolution of the Atlantic Ocean remains very limited. Although much progress has been made by studying the geological record of sedimentary basins from various Atlantic margins and by drilling in the deep ocean, the oldest part of the record is still unknown. Recent Glomar Challenger cruises in the Central and North Atlantic, including DSDP Leg 50, have added substantial information bearing on our still-schematic views on the evolution of rifted margins. Although drilling into the deep oceanic basins at sites as close as possible to the foot of a margin is a direct and powerful method to study the early history of margins, this approach is difficult because the most interesting targets are generally beneath the thick sediments of continental rises. In the search for target areas where the Glomar Challenger drill could reach very old strata, the eastern Atlantic margins have long been considered particularly attractive, because unlike their western counterparts that are buried by a thick wedge of Tertiary hemipelagic rise sediments they are characterized by poorly developed continental rises. The margin off Morocco is one of these "starved" margins and has many features that make it especially suitable for study by deep drilling. Since it is among the oldest "starved" passive margins of the Atlantic — and hence of the world — we can here address both the Jurassic history of the ocean and the fundamental questions of the evolution of passive margins. Drilling into the Moroccan Basin on Leg 50 aimed at filling a specific gap in our understanding of the pre-Oxfordian history of both the Atlantic and the world ocean. The Glomar Challenger left Funchal, on the island of Madeira on 11 September 1976 and returned to Funchal, Madeira Islands in November, 1976.