Hydrocarbon Resource Studies in the Southwest Pacific, 1982 By H. Gary Greene, Florence L. Wong, and the scientific staff of the 1982 CCOP/SOPAC cruise GEOLOGICAL SURVEY OPEN-FILE REPORT 83-293 Prepared in cooperation with the governments of Australia and New Zealand, the United Nations Committee for the Coordination of Joint Prospecting for Mineral Resources in South Pacific Offshore Areas, and the Circum-Pacific Council for Energy and Mineral Resources Second printing 1983 PREFACE This report summarizes the investigation conducted aboard the U.S. Geological Survey's Re- search Vessel S.P. Lee in 1982 under the terms of an agreement between Australia, New Zealand, and the United States (ANZUS Tripartite Agreement) in association with the United Nations Corn- mittee for the Coordination of Joint Prospecting for Mine] 'al Resources in South Pacific Offshore Areas. Data collected on the cruise were first presented at he S.P. Lee postcruise meeting in Hon- olulu, Hawaii on August 19 and 20, 1982, and further discussed at a meeting cosponsored by theie U.S. Geological Survey and the Circum-Pacific Council for Energy and Mineral Resources, a section of the American Association of Petroleum Geologists, in Menlo Par i, California, on April 5, 1983. PARTICIPATING SCIENTISTS Leg 1 (L5-82-SP)*, April 2 to April 20, 1982 Leg 3 (L7-82-SP)*: May 19 to June 11, 1982 Jon Childs USGS Liiiry Beyer USGS Neville Exon Bureau of Mineral Resources Canberra, Donna Blackman USGS Australia, CCOP/SOPAC Terry Bruns USGS Chris Gutmacher USGS GvyCochrane USGS Richard Herzer New Zealand Geological Survey, Wellington, Jim Colwell Bureau of Mineral Resources, New Zealand Canberra, Australia Kay Kinoshita USGS Alan Cooper USGS Dennis Mann USGS Frank Coulson Solomon Islands Geological Survey, tTun U. Maung CCOP/SOPAC Honiara, Solomon Islands Graig McHendrie USGS Kay Kinoshita USGS Robert Rowland USGS Greg Lewis USGS Mark Sandstrom Australia National University, Canberra, Loren Kroenke CCOP/SOPAC Australia Michael Marlow USGS tDavid W. Scholl USGS tDonald Tiffin CCOP/SOPAC Barbara Seekins USGS tJuck Vedder USGS Sione Soakai Ministry of Lands, Surveys and Natural Raymond Wood New Zealand Geological Survey, Resources, Nuku'alofa, Tonga Lower Hutt, New Zealand Andrew J. Stevenson USGS Tracy L. Vallier USGS Leg 2 (L6-82-SP)*: April 28 to May 16, 1982 Donna Blackman USGS Guy Cochrane USGS Jacque Daniel Office de la Recherche Scientifique et Technique OutreMer, Noumea, New Caledonia tDavid Falvey CCOP/SOPAC, Sydney University, Sydney, Australia Michael Fisher USGS tH. Gary Greene USGS Carol Hirozawa USGS Mark Holmes USGS David Johnson James Cook University, Townsville, Australia H.R. Katz New Zealand Geological Survey, Lower Hutt,New Zealand Kay Kinoshita USGS Greg Lewis USGS Alexander Macfarlane Dept. of Geology, Mines and Rural Water Supplies, Port Vila, Vanuatu Greg Smith USGS * cruise locating code t cochief scientist CONTENTS Page Preface -__. -_- _-._._ _.__--__-___.___..___.._._______.___. _____._. -_.___._..._._... ..- _. II Acknowledgments __________________________________________ 1 Leg i _ Tonga Ridge ___________ _____________________________ 2 Leg 2 Central Basin of Vanuatu ____________________________- ____ 2 Leg 3 Central Solomons Trough 11 I. Tonga Platform-Lau Ridge -- - - _. _. ._._.._.... 20 II. Vanuatu and Eastern Solomons Basins 20 III. Solomon Islands and Bougainville, Papua New Guinea 22 IV. New Ireland Basin, Papua New Guinea 22 V. North Fiji Basin _____________________________________ 23 ______________________________________________________________________________________ 23 ILLUSTRATIONS Page J.TPlPTTPT? IVxUXlI:* J.*1 xllUCA^rii"i«iY mar*lllaLP 2. Physiographic diagram of southwest Pacific with tracklines 3 3. Leg 1: Detailed tracklines and bathymetry of Tonga platform 4 4. Leg 1: Multichannel seismic line 8 across Tonga platform 5 5. Leg 1: Multichannel seismic line 11 across Tonga platform 6 T ,onr 1 TanriQ/*Vk man f\f i*ViA T^AYIGTJI nlat"frti*m ........ _ .... _ ... _ .... _ ... _ ............... _ . _ . _ . _ ... _ . _ . _ ..................._ ... _ .. 7 6 XJCg J.. J.Ov'^Jclv'll IIM*^ VX lill^ A Vllgc* ^FlAvl-Vl 111 7. Leg 2: Detailed tracklines and bathymetry of the Central Basin of Vanuatu 8 8. Leg 2: Structure and shelf sedimentary basins of the Central Basin of Vanuatu 10 9. Leg 2: Multichannel seismic line 10 across the New Hebrides Trench H 10. Leg 2: Isopach map of the Central Basin of Vanuatu 12 11. Leg 2: Single-channel seismic line 25 offshore of Espiritu Santo, Vanuatu 13 12. Leg 2: Single-channel seismic line 20A offshore of Espiritu Santo, Vanuatu 14 13. Leg 3: Detailed tracklines and bathymetry of the central Solomons Trough 16 14. Leg 3: Isopach map of the central Solomons Trough 18 15. Leg 3: Multichannel seismic line 30 between Santa Isabel and the Russell Islands 19 16. Leg 3: Rabaul harbor bathymetry and tracklines 19 17. Recommended tracklines for future work in southwest Pacific 21 in Hydrocarbon Resource Studies in the Southwest Pacific, 1982 By H. Gary Greene, Florence L. Wong, and the scientific staff of the 1982 CCOP/SOPAC cruise INTRODUCTION tion and operation of the investigation. Funds were also provided by the government of Au­ From April 2 to June 11, 1982, the USGS (U.S. stralia. CCOP/SOPAC in Fiji served as the basic Geological Survey) conducted a hydrocarbon re­ coordinator and provided, along with Australia, source investigation in the offshore areas of New Zealand, and CCOP/SOPAC member na­ Tonga, Vanuatu, and the Solomon Islands (fig. 1). tions, some of the scientific staff. The work was arranged under the ANZUS (Au­ The data collection phase of the joint program stralia, New Zealand, and United States) Tripar­ was a three-leg, 60-day resources survey by the tite Agreement in association with CCOP/SOPAC Research Vessel S.P. Lee. This report sum­ (United Nations Committee for the Coordination marizes that investigation, gives tentative re­ of Joint Prospecting for Mineral Resources in sults, outlines the future work schedule, and pro­ South Pacific Offshore Areas), as part of a pro­ poses significant work to be continued. gram of marine geoscientific research and min­ eral resource studies in the South Pacific region. ACKNOWLEDGMENTS The U.S. Department of State was instrumen­ tal in negotiating the agreement and establishing This report required the devotion and labor of the framework for the cooperative research. The many to meet the publication deadline. We are USGS provided instruments and scientific and grateful to Tom Chase for his efforts in supplying technical personnel. The Office of Energy of the us with bathymetric and navigation charts, and to United States Agency for International Develop­ Phyllis Swenson who spent many hours drafting ment (AID) provided funding for the implementa­ the illustrations for this report. David Scholl and SOUTH SOLOMON ISLANDS PACIFIC OCEAN SANTA CRUZ ISLANDS BANKS SAMOA ISLANDS ISLANDS VANUATU ISLANDS "" ISLANDS TONGA ISLANDS AUSTRALIA FIGURE 1. Location map of the South Pacific study area. Jack Vedder reviewed the manuscript and contrib­ dence that the forearc area, most of which is uted significantly to the improvement of the text. deeply submerged, may have been a source ter- We also appreciate the encouragement and sup­ rane for some of the volcaniclastic deposits of the port from the ANZUS Tripartite and CCOP/ platfioim section; (5) southwestward tracing (at SOP AC scientific participants. The studies were least 5550 km) of an axis of early Tertiary vol- funded by the U.S. Agency for International De­ camsmi that is situated along the Pacific side of velopment, the government of Australia, and the the platform and passes beneath or close to Eua U.S. Geological Survey and were conducted in Island (6) acoustical tracking of the subducted cooperation with the governments of Australia, surfac 3 of the Pacific plate 25-30 km landward of New Zealand, and the United States. the inner trench wall (fig. 5); this slope is not un- derlain by offscraped, low-velocity oceanic LEG I.TONGA RIDGE pelagi deposits; and (7) the probable detection of Departed Pago Pago, American Samoa, March 28 Arrived Nuku'alofa, Tonga, March 31; departed, April 2 a magina chamber 3-4 km below a spreading axis Arrived Suva, Fiji, April 20; departed, April 23 in Lau Basin (fig. 5). Arrived Port Vila, Efate, Vanuatu, April 26 A comprehensive evaluation of the petroleum METHODS potential of the Tonga platform area must await the ssults of laboratory analysis of rocks Leg 1, conducted mainly on the southern Tonga dredg d from the sea floor and sampled on land, platform up to 250 km south of Tongatapu, Tonga, and the interpretation of the fully processed mul- included over 5,700 km (3,078 n. mi.) of 12 kHz, 3.5 tifold reflection profiles. kHz, gravity, and magnetic profiles (fig. 2). In the area, 2,421 km (1,307 n. mi.) of 24-fold, CDP seis­ mic-reflection profiles, and 54 sonobuoy wide-angle LEG 2, CENTRAL BASIN OF VANUATU Departed Port Vila, Efate, Vanuatu, April 28 reflection-refraction profiles were obtained (fig. 3). Arrived Honiara, Guadalcanal, Solomon Islands, May 16 Also, at 13 sampling stations 9 dredge hauls and 4 gravity cores were taken. A brief (12-hr) sampling METHODS visit was included at Ata Island during data collec­ Leg 2, conducted in the Central Basin of Van- tion in the platform area (Scholl and others, 1982). uatu, ncluded 2,520 km (1,361 n. mi.) of 24-fold, Geophysical data were also gathered offshore CDP multi-channel seismic-reflection profiles (fig. of the western margin of the island of Viti Levu, 7). In addition, 622 km (336 n. mi.) of high-resolu- Fiji and over Baravi Basin at the request of the tion Uniboom seismic-reflection profiles and nearly Fiji Mineral Resources Department, and along 4,5001m (2,430 n.