Initial Reports of the Deep Sea Drilling Project - Volume 37

This volume covers Leg 37 of the cruises of the Drilling Vessel Glomar Challenger. Leg 37 of the Deep Sea Drilling Project began in May, 1975 in Rio de Janeiro, Brazil and ended in Dublin, Ireland in July, 1975. The second planned attempt at deep penetration of the igneous section of the oceanic crust took place during Leg 37 of the DSDP. A previous unsuccessful attempt occurred on Leg 34. Leg 37 penetrated successfully the upper part of the oceanic crust on the western flank of the FAMOUS (Franco-American Mid-Ocean Undersea Study) area of the Mid-Atlantic Ridge at 36°N. The main purpose of Leg 37 was to investigate the petrological and geophysical nature of oceanic layer 2. This 1.5-km thick layer, which underlies the floor of most of the world's oceans, is thought to be generated at crustal spreading centers, and to hold evidence for the origin of oceanic magnetic anomalies, for crustal and mantle evolution, and perhaps, for the origin of some types of ore deposits. The prime objective for Leg 37 was the deep penetration of at least the upper part of the igneous section of the oceanic crust. With such penetration and its associated core recovery, we hoped to answer many of the problems associated with mid-oceanic ridges which are still outstanding, including the following: 1) The problem of the separation of the material now constituting layer 2, from layer 3 and, indirectly, the nature of the upper mantle beneath oceanic rises and other spreading centers. 2) The construction of layer 2. 3) Changes during the evolutionary history of layer 2. 4) The existence, nature, and thickness of the postulated highly magnetized layer 2A. 5) Constitution of submarine basalt lava flows. 6) Heat flow and heat production in layer 2. 7) The possibility that processes occur in layer 2 that result in the concentration of economic minerals such as sulfides. 8) The nature, provenance, and state of alteration of any sediment intercalated in the igneous rocks of layer 2.