AAPG Bulletin, V. 83 (1999), No. 5 (May 1999), P. 778-797.

Frontier Exploration in the South Atlantic: Structural Prospectivity in the North Falkland Basin¹

Ken Thomson² and John R. Underhill³
 

©Copyright 1999.  The American Association of Petroleum Geologists.  All Rights Reserved

¹Manuscript received June 24, 1997; revised manuscript received September 10, 1998; final acceptance October 3, 1998.
²Department of Geological Sciences, University of Durham, South Road, Durham, DH1 3LE, England, United Kingdom; e-mail: kenneth.thomson@ durham.ac.uk
³Department of Geology and Geophysics, The University of Edinburgh, Grant Institute, Kings Buildings,
West Mains Road, Edinburgh, EH9 3JW, Scotland, United Kingdom; e-mail: [email protected]

We would like to acknowledge the Falkland Islands government and Spectrum Energy and Information Technology Ltd. for access to the data on which this study was based. Michael Johnson (Spectrum) is especially thanked for his encouragement and constructive comments and for facilitating the release of data. K. Atkinson, Y. Cooper, L. Kerr, and G. White are thanked for assistance in producing figures. The paper has also benefited from discussions with Quentin Rigby, Kevin Fielding, and David Sturt (Amerada Hess); Tim Bushell and Martin Durham (Lasmo); and Phil Richards (British Geological Survey). We would also like to thank AAPG reviewers David Macdonald and Ian Daziel for their thorough and thoughtful comments. 

ABSTRACT

Seismic stratigraphic analysis of the continental shelf north of the Falkland Islands confirms that it is dissected by a significant extensional fault system that broadly defines the North Falkland Basin. The basin comprises a series of extensional subbasins that developed during two distinct rift episodes. Analysis of structural styles shows that while extension occurred predominantly on a series of planar normal faults with changes in rift polarity in northern areas, the southern portion of the basin has listric faults that sole out along preexisting thrusts. After rifting, the basin largely underwent postrift thermal subsidence with the passive infill of remnant topography; however, evidence exists for at least two uplift events affecting the postrift sediments. The earlier period of uplift tilted the basin to the south, resulting in the formation of a southerly prograding forced regressive wedge; the later episode of uplift tilted the basin northward, resulting in truncation of earlier strata and minor compressional reactivation and inversion in southernmost parts of the basin. The later tilting allows for the possibility that the original rift system once extended across the Falkland Islands. Although the lack of well control does not permit a comprehensive assessment of hydrocarbon plays, the seismic data do at least demonstrate the trapping potential of the basin. Interpreted structural and depositional styles found within the prerift, synrift, and postrift sequences are similar to those found in proven hydrocarbon provinces such as the North Sea and the Gulf of Suez. The success or failure of the frontier hydrocarbon province thus is likely to depend upon factors other than structural ones.