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The AAPG/Datapages Combined Publications Database
AAPG Bulletin
Abstract
AAPG Bulletin, V.
Reactivation of an obliquely rifted margin, Campos and Santos basins, southeastern Brazil
Peter R. Cobbold,1 Kristian E. Meisling,2 Van S. Mount3
1Geosciences-Rennes, 35042 RENNES Cedex, France; email: [email protected]
2ARCO Exploration Technology and Operations, 2300 W. Plano Parkway, Plano, Texas, 75075; current address: BP America, Inc., 200 Westlake Park Blvd., Houston, Texas, 77079; email: [email protected]
3ARCO Latin America, 2300 W. Plano Parkway, Plano, Texas, 75075; current address: Anadarko Petroleum Corporation, 17001 Northchase Drive, P.O. Box 1330, Houston, Texas, 77251; email: [email protected]
AUTHORS
Peter Cobbold received his B.Sc. degree and Ph.D. in geology from Imperial College, London. After short periods as a lecturer at London and Leeds, he moved to Rennes, France. He now works as a research director for the Centre National de la Recherche Scientifique, France, and consults for the oil and mining industries. His research interests include structural geology, tectonics, and basin development. He has been active in analog modeling, palinspastic restoration, and field work, especially in South America and central Asia.
Kristian Meisling earned his Ph.D. in geology from Caltech and his B.S. degree in engineering geology from UCLA. His 17-year career includes positions in research, applied technology, and exploration at ARCO, Mobil, and BP-Amoco. While at ARCO Kris was director of the Structural Geology Research Group. Kris has broad research interests, including strike- and oblique-slip structures, regional tectonics, syntectonic sedimentation, basin analysis, and paleogeographic reconstructions. He is currently in the Upstream Technology Group at BP America, Inc.
Van S. Mount received a Ph.D. in structural geology from Princeton University and a B.A. degree in geology from Hamilton College, New York. Van joined the Structural Geology Research Group at ARCO in 1989, where his work focused on quantitative analysis and interpretation of complexly deformed structures and regional structural syntheses. His exploration work at ARCO International concentrated on the Middle East and Latin America. Van is presently in the Basin Studies Group at Anadarko Petroleum Corporation.
ACKNOWLEDGMENTS
We thank the management of ARCO Latin America and New Exploration Ventures, including Steve Sinclair, Dusty Marshall, and Jamie Robertson, for supporting our work and its release for publication. We have benefited greatly from discussions with colleagues on the Brazil Bid Round team at ARCO, including Chandra Suria, Christopher Legg, Stephen Scott, Stuart Gordon, Mike Crawford, Wayne Suyenaga, Zhiyong He, Ed Elliot, Lih Quo, Randy Roe, Steve Bergman, Mark Ward, and Brad Huizinga. We also thank those who contributed insights in previous years, including Bob Krantz, Lillian Flakes, and Claudio Bartolini. Robert Sprague and Jan-Nel Nye kindly provided graphics support. Peter Cobbold is grateful to Manuel Figueiredo, Peter Szatmari, and Jose Aires of Petrobras for providing transport and guidance during visits to the onshore Tertiary basins of southeastern Brazil in 1990 and 1995. We are grateful to the reviewers, Ian Davison, Edison J. Milani, and Chris Morley, for their constructive comments. Finally, we thank the management of BP Trinidad Exploration and BP America, Inc. for supporting the publication of this article.
ABSTRACT
We interpret and document Late Cretaceous and Cenozoic reactivation of older structures on the obliquely rifted margin of southeastern Brazil, attributing them to the combined effects of far-field stresses and hot-spot activity. Our conclusions are based on current seismicity, digital topography, fission-track ages, gravity data, regional reflection seismic profiles, and well data. Our results have important implications for risk factors associated with deep-water exploration plays, especially the prolific Early Cretaceous lacustrine petroleum system of the Campos and Santos basins.
Onshore, widespread crustal seismicity indicates a current transpressional stress regime. The Moho is 37-42 km deep, and neotectonic fault-block tilting has resulted in mountain ranges up to 2700 m high and extensive river capture. Based on fission-track data, the mountains were exhumed in the Cretaceous and Eocene. A series of Tertiary continental pull-apart basins, developed during Paleogene right-lateral transtension, became inverted during Neogene right-lateral transpression. Late Cretaceous-Paleogene alkaline intrusions, attributable to the Trindade hot spot, were emplaced along reactivated Neocomian strike-slip faults and transfer zones.
Offshore, current seismicity is widespread across the continental margin. The locus of clastic fan deposition shifted during the Late Cretaceous and Tertiary because of onshore block faulting and drainage reorganization. Cretaceous sedimentary rocks were folded, tilted, eroded, and unconformably onlapped above an inferred Neocomian Moho uplift to produce an accentuated nearshore hinge line. Neocomian transfer zones were reactivated during ongoing sedimentation, accompanied by abundant volcanism and deep-seated folds attributed to lithospheric buckling. In the Campos area, a coastal salient was uplifted and turbidites were redeposited. In general, regional tilting resulted in thin-skinned deformation above Aptian salt.
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