Frontispiece. Three-dimensional shaded-relief image of the Atlantis II Transform Valley from 32°25´S to 33°05´S and from 56°46´E to 57°20´E looking northeast (data from Dick et al., 1991¹). The view shows Atlantis Bank and the location of Ocean Drilling Program Holes 735B and 1105A from across the transform. The image covers an area of ~3850 km² (28 nmi × 40 nmi) with a maximum relief of 5.7 km from the valley floor to the crest of Atlantis Bank.

¹Dick, H.J.B., Schouten, H., Meyer, P.S., Gallo, D.G., Berg, H., Tyce, R., Patriat, P., Johnson, K., Snow, J., and Fisher, A., 1991. Bathymetric map of the Atlantis II Fracture Zone, Southwest Indian Ridge. In Von Herzen, R.P., Robinson, P.T., et al., Proc. ODP, Sci. Results, 118: College Station, TX (Ocean Drilling Program), foldout map.

Proceedings of the
Ocean Drilling Program

Volume 176
Initial Reports
Return to Hole 735B

Covering Leg 176 of the cruises of the Drilling Vessel JOIDES Resolution
Cape Town, South Africa, to Cape Town, South Africa
Site 735
8 October - 9 December 1997

SHIPBOARD SCIENTISTS
Henry J.B. Dick, James H. Natland, D. Jay Miller,
Jeffrey C. Alt, Wolfgang Bach, Daniel Bideau, Jeffrey S. Gee, Sarah Haggas, Jan G.H. Hertogen, Greg Hirth, Paul Martin Holm, Benoit Ildefonse, Gerardo J. Iturrino, Barbara E. John, Deborah S. Kelley, Eiichi Kikawa, Andrew Kingdon, Petrus J. Le Roux, Jinichiro Maeda, Peter S. Meyer, H. Richard Naslund, Yaoling Niu, Paul T. Robinson, Jonathan E. Snow, Ralph A. Stephen, Patrick W. Trimby, Horst-Ulrich Worm, Aaron Yoshinobu

SHIPBOARD STAFF SCIENTIST
D. Jay Miller

VOLUME EDITORS
Jennifer A. Marin and John M. Scroggs

Citation

Reference to the whole or to part of this volume should be made as follows:

WWW volume citation:
Dick, H.J.B., Natland, J.H., Miller, D.J., et al., 1999. Proc. ODP, Init. Repts., 176 [Online]. Available from World Wide Web: <http://www-odp.tamu.edu/publications/176_IR/176TOC.HTM>. [Cited YYYY-MM-DD]

WWW chapter citation (PDF):
Shipboard Scientific Party, 1999. Site 735. In Dick, H.J.B., Natland, J.H., Miller, D.J., et al., Proc. ODP, Init. Repts., 176, 1-314 [Online]. Available from World Wide Web: <http://www-odp.tamu.edu/publications/176_IR/VOLUME/CHAPTERS/CHAP_03.PDF>. [Cited YYYY-MM-DD]

WWW chapter citation (HTML):
Shipboard Scientific Party, 1999. Site 735. In Dick, H.J.B., Natland, J.H., Miller, D.J., et al., Proc. ODP, Init. Repts., 176 [Online]. Available from World Wide Web:
<http://www-odp.tamu.edu/publications/176_IR/CHAP_03/Output/chap_03.htm>. [Cited YYYY-MM-DD]

Printed booklet citation for Chapter 1:
Shipboard Scientific Party, 1999. Leg 176 Summary. In Dick, H.J.B., Natland, J.H., Miller, D.J., et al., Proc. ODP, Init. Repts., 176: College Station, TX (Ocean Drilling Program), 1–70.

CD-ROM volume citation:
Dick, H.J.B., Natland, J.H., Miller, D.J., et al., 1999. Proc. ODP, Init. Repts., 176 [CD-ROM]. Available from: Ocean Drilling Program, Texas A&M University, College Station, TX 77845-9547, U.S.A.

CD-ROM chapter citation:
Shipboard Scientific Party, 1999. Site 735. In Dick, H.J.B., Natland, J.H., Miller, D.J., et al., Proc. ODP, Init. Repts., 176, 1–314 [CD-ROM]. Available from: Ocean Drilling Program, Texas A&M University, College Station, TX 77845-9547, U.S.A.

This volume also appears on the World Wide Web. See www-odp.tamu.edu/publications for available volumes and Web citation formats.

ISSN
Printed booklet: 0884-5883; CD-ROM volume: 1096-2522; WWW volume: 1096-2158
Library of Congress 87-642-462

Effective publication dates of ODP Proceedings

According to the International Code of Zoological Nomenclature, the date of publication of a work and of a contained name or statement affecting nomenclature is the date on which the publication was mailed to subscribers, placed on sale, or when the whole edition is distributed free of charge, mailed to institutions and individuals to whom free copies are distributed. The mailing date, not the printing date, is the correct one.

The printing date of this volume: June 1999

The mailing dates of recent Proceedings of the Ocean Drilling Program:
Volumes 174A/174AX/174B (Initial Reports): November 1998
Volume 175 (Initial Reports): November 1998
Volume 177 (Initial Reports): May 1999
Volumes 159/159T (Scientific Results): October 1998
Volume 160 (Scientific Results): September 1998
Volume 161 (Scientific Results): February 1999

Copies of this publication may be obtained from Publications Distribution Center, Ocean Drilling Program, Texas A&M University, 1000 Discovery Drive, College Station, TX 77845-9547, U.S.A. See the ODP publication list at www-odp.tamu.edu/publications or contact ODP for prices and ordering information. Orders for copies require advance payment.

Publisher’s Notes

This publication was prepared by the Ocean Drilling Program, Texas A&M University, as an account of work performed under the international Ocean Drilling Program, which is managed by Joint Oceanographic Institutions, Inc., under contract with the National Science Foundation. Funding for the program was provided by the following agencies at the time of this cruise:

Australia/Canada/Chinese Taipei/Korea Consortium for Ocean Drilling: Department of Primary Industries and Energy (Australia), Natural Resources Canada (Canada), National Taiwan University in Taipei, and Korean Institute for Geology, Mining and Minerals

Deutsche Forschungsgemeinschaft (Federal Republic of Germany)

European Science Foundation Consortium for Ocean Drilling (Belgium, Denmark, Finland, Iceland, Italy, The Netherlands, Norway, Portugal, Spain, Sweden, Switzerland, and Turkey)

Institut Français de Recherche pour l’Exploitation de la Mer (France)

National Science Foundation (United States)

Natural Environment Research Council (United Kingdom)

University of Tokyo, Ocean Research Institute (Japan)

Any opinions, findings, and conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the National Science Foundation, the participating agencies, Joint Oceanographic Institutions, Inc., Texas A&M University, or Texas A&M Research Foundation.

Abbreviations for names of organizations and publications in ODP reference lists follow the style given in Chemical Abstracts Service Source Index (published by American Chemical Society).

The bulk of the shipboard-collected data from this leg is available on the World Wide Web and is accessible at www-odp.tamu.edu/database. If you cannot access this site or need additional data, please contact the ODP Data Librarian, Ocean Drilling Program, Texas A&M University, College Station, TX 77845-9547, U.S.A. (e-mail: database@odpemail.tamu.edu).

Supplemental data on the volume CD-ROM were provided by the authors and may not conform to ODP publication formats.

A site map showing the drilling locations for this leg and maps showing the drilling locations of all Ocean Drilling Program (ODP) and Deep Sea Drilling Project (DSDP) drilling sites are available on the volume CD in PDF format.

Beginning with Initial Reports Volume 176 and Scientific Results Volume 169, all Proceedings volumes will be published on CD-ROM and the World Wide Web at www-odp.tamu.edu/publications.

Initial Reports Scientific Results
Booklet format: ISSN 0884-5883 Book: ISSN 0884-5891
CD-ROM format: ISSN 1096-2522 CD-ROM format: ISSN 1096-2514
WWW format: ISSN 1096-2158 WWW format: ISSN 1096-7451

Cover photograph of the JOIDES Resolution by ODP Photographer John Beck.

Foreword

By Joint Oceanographic Institutions, Inc.

This volume presents scientific and engineering results from the Ocean Drilling Program (ODP). These results address the scientific and technical goals of the program, which are focused on the study of the dynamics of Earth’s interior and environment.

ODP, an international partnership of scientists and research institutions from 22 countries, operates the drillship JOIDES Resolution. This state-of-the-art research vessel contains seven levels of laboratories and other scientific facilities required for carrying out the program’s objectives.

The management of ODP involves a partnership of scientists and governments. International oversight and coordination are provided by the ODP Council, which is made up of representatives from the member countries. Overall scientific and management guidance is provided by representatives from the Joint Oceanographic Institutions for Deep Earth Sampling (JOIDES).

Joint Oceanographic Institutions, Inc. (JOI), a nonprofit consortium of eleven U.S. oceanographic institutions, serves as the National Science Foundation’s prime contractor for ODP. JOI implements scientific objectives, plans, and recommendations of the JOIDES committees through major subcontracts to Texas A&M University (TAMU) for science operations and to Lamont-Doherty Earth Observatory (LDEO) of Columbia University for logging services.

JOI, TAMU, and LDEO have worked together successfully for many years to manage the Ocean Drilling Program. We look forward to many exciting discoveries and continued international collaboration as we further our scientific mission, especially the planning for the future of ocean drilling beyond 2003.

James D. Watkins
Admiral, U.S. Navy (Retired)
President, Joint Oceanographic Institutions, Inc., Washington, D.C.

Ocean Drilling Program*

*At time of publication. See Publisher’s Notes, for list of funding agencies at time of cruise. For an up-to-date list of current member organizations and office contact information, see the ODP Web site: www.oceandrilling.org.

National Science Foundation
4201 Wilson Boulevard
Arlington, VA 22230, U.S.A.
Tel: (703) 306-1581; Fax: (703) 306-0390
Web site: www.nsf.gov

Member Organizations of the Joint Oceanographic Institutions for Deep Earth Sampling (JOIDES)

University of California at San Diego, Scripps Institution of Oceanography

Columbia University, Lamont-Doherty Earth Observatory

University of Hawaii, School of Ocean and Earth Science and Technology

University of Miami, Rosenstiel School of Marine and Atmospheric Science

Oregon State University, College of Oceanic and Atmospheric Sciences

University of Rhode Island, Graduate School of Oceanography

Rutgers, The State University of New Jersey, Institute of Marine and Coastal Sciences

Texas A&M University, College of Geosciences

University of Texas at Austin, Institute for Geophysics

University of Washington, College of Ocean and Fishery Sciences

Woods Hole Oceanographic Institution

Australia/Canada/Chinese Taipei/Korea Consortium for Ocean Drilling: Department of Primary Industries and Energy (Australia), Department of Energy, Mines and Resources (Canada), National Taiwan University in Taipei, and Korean Institute for Geology, Mining and Minerals

European Science Foundation Consortium for Ocean Drilling (Belgium, Denmark, Finland, Iceland, Italy, The Netherlands, Norway, Portugal, Spain, Sweden, Switzerland, and Turkey)

Federal Republic of Germany, Bundesanstalt für Geowissenschaften und Rohstoffe

France, Institut Français de Recherche pour l’Exploitation de la Mer

Japan, University of Tokyo, Ocean Research Institute

People’s Republic of China, Marine High-Technology Bureau of the State Science and Technology Commission of the People’s Republic of China

United Kingdom, Natural Environment Research Council

Ocean Drilling Program (ODP)
Web site: www.oceandrilling.org

Leg 176 Participants*

*Mailing addresses at time of cruise. Addresses may be updated. Send requests to
pub_production@odp.tamu.edu.

Shipboard Scientific Party

ODP Publications Staff^*

*At time of publication.
†Lead staff members for this volume.

Dedication

Among the many people who contribute to the day-to-day and leg-to-leg success of the Ocean Drilling Program, some carry out their tasks with particular skill and distinction. With this publication of the Initial Reports Volume 176, we would like to recognize one individual who stands out, in our estimation, as a friend, a gentleman, a seaman, a leader, and a crucial contributor, not just to our drilling leg, but to the Ocean Drilling Program as a whole.

A wall plaque on the Bridge Deck of JOIDES Resolution lists Captain Ed Oonk as master of the vessel during virtually every alternate leg of drilling beginning with Leg 101. Captain Oonk was master during both Legs 118 and 176; thus, he served during all of the drilling at Site 735, which is the only deep hole in the lower ocean crust. Captain Oonk, his officers, and crew were with us from the start and at the end of a scientific venture that spanned 10 years.

Leg 176 was Captain Oonk’s final leg as master of JOIDES Resolution. We all enjoyed a special retirement celebration for him as we sailed from Site 735 to Cape Town. We were privileged to acknowledge his skilled seamanship, his judgment during those days of high wind and rough seas when it was difficult to continue drilling, the thorough safety program he supervised (including the boat drills when all of us, scientists included, actually learned something about how to stay alive at sea), and the high morale of his crew, which he promoted by word and deed. We knew we were on a well-managed ship, and this made all our work that much easier to accomplish.

It is fair to say, as even Captain Oonk himself might admit, that JOIDES Resolution is still afloat and that the Ocean Drilling Program itself persists because he and his crew knew what to do, and how to do it, through some desperate hours in a severe storm that suddenly trapped the vessel near the dangerous coast of Greenland during Leg 163. At that time the day-to-day activities and skills of a working captain and crew were challenged to the utmost, to the extent that survival itself hung in the balance.

However, simply from the perspective of Leg 176, we would like to acknowledge the special contribution that Captain Oonk made over two legs of drilling at our location in the Indian Ocean. A great deal of our success and certainly the quality of our time at sea can be attributed to him. He is the best of friends and the finest of shipmates. We shall miss his judgment, good humor, and wise counsel when we sail again. We are pleased and proud to be able to dedicate this Initial Reports Volume 176 to Captain Ed Oonk.

Acknowledgments

The Leg 176 Shipboard Scientific Party thanks Captain Ed Oonk and the officers and crew of JOIDES Resolution, as well as the staff of the Ocean Drilling Program, for helping to make our deep-drilling venture into the lower ocean crust on the Southwest Indian Ridge a success. We especially thank Operations Manager Mike Storms, Drilling Superintendent Wayne Malone, and the rig-floor drilling crew for their efforts to make Hole 735B so deep and for recovering so much spectacular core. Both Wayne and Rig Superintendent Pepe Estevez made their second venture to Hole 735B during Leg 176, 10 years after Leg 118.

We also thank the marine technical staff, headed by Laboratory Specialist Dennis Graham, who made it possible for nearly two dozen scientists to describe and analyze the record 866 m of rock recovered without tripping over themselves or anyone else. The gabbros are an unprecedented contribution to the scientific study of Earth’s crust, and they provide the first clear picture of the structure and composition of the lower ocean crust. Shipboard Curator Lorraine Southey worked unstintingly to properly acquire and record thousands of shipboard and shore-based samples. Three of the marine technical staff participated in the drilling at Hole 735B during both Legs 118 and 176. Marine Lab Specialist Ted "Gus" Gustafson ably made more than 200 polished thin sections for us. Yeoperson Michiko Hitchcox displayed her usual exemplary efficiency and good humor. Don Sims was instrumental in the XRF laboratory.

The preparation of this volume was facilitated by the efforts of Editor John Scroggs, Production Editor Amy Brundeen, and Illustrator Coleena Burt. They were ably assisted in various capacities by Marianne Gorecki, Katerina Petronotis, Angeline Miller, Susan Freeman, and others. We thank them, one and all.