Initial Reports of the Deep Sea Drilling Project - Volume 36

This volume covers Leg 36 of the cruises of the Drilling Vessel Glomar Challenger. Leg 36 started in Ushuaia, Argentina, on 4 April, 1974 and finished in Rio de Janeiro, Brazil on 22 May, 1974. It completed the second of three austral summer seasons of drilling planned for Antarctic waters during Phase III of the Deep Sea Drilling Project. The two main objectives of the leg as originally conceived by the Antarctic Advisory Panel were to investigate the geologic histories of the Scotia Arc and of the Argentine Basin. The Scotia Sea area is a distinctive part of the Antarctic margin, and as such has important bearings on the geologic history of the continent and its surroundings. However, the region has geologic significance far beyond its own boundaries. Problems that can be addressed through a drilling program in the Scotia Sea area, in addition to the tectonic evolution of the Scotia Arc itself, include: (a) The nature of the upper part of the arc-trench gap in a very young and relatively simple island arc; (b) Tectonics, sedimentation and lava geochemistry in a back-arc basin of known spreading rate and age; (c) Evolution of Drake Passage and the Scotia Sea with their implications for faunal migration and climatic change; (d) History of Antarctic Bottom Water production and circulation and their effect on climatic and sedimentologic processes in the South Atlantic. A total of six sites in the Drake Passage, the Scotia Sea, and the South Atlantic Ocean were planned with the above objectives in mind. In addition, three sites were selected in the southwest Atlantic Ocean basin and on the Falkland (Malvinas) Plateau with the following objectives: (a) To elucidate the geologic history of the southwestern part of the Atlantic Ocean basin which had been extensively studied geophysically but never drilled; (b) To test the age of magnetic anomaly number 34; (c) To date the major reflecting horizons of the Argentine Basin; and (d) To compare the biostratigraphy of the southwestern Atlantic with that of the southeastern Pacific and thereby to help date the opening of the Drake Passage and onset of the circum-Polar current.