23. DRILLING DIFFICULTIES IN BASEMENT DURING DEEP SEA DRILLING PROJECT LEG 54

• Main Author: La Jolla California
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Galapagos; Pacific; North Atlantic
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.546.8437; http://www.deepseadrilling.org/54/volume/dsdp54_23.pdf

The principal objective of Leg 54, to drill a deep multiple, re-en-try hole in young, fast-spreading East Pacific Rise crust, was not achieved. Instead, eight shallow-penetration holes were drilled into basement on the East Pacific Rise, and five on the Galapagos Rift. The deepest penetration was 52.2 meters in Hole 428A. Most holes were abandoned at an early stage because of extreme torquing on the drill string and caving of rocks into the holes. The drilling difficulties were much more severe than experienced with crust of similar age in the North Atlantic. They were caused by a combination of factors, \ of which the most important are: 1) The basalts are highly fractured, possibly a result of dropping of fault blocks from the East Pacific Rise axial plateau; 2) the lavas consist of a large proportion of sheet flows rather than pillows, and therefore do not have the interlocking joint struc-