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@
3Department of Geology and Geophysics, The University of
Edinburgh, Grant Institute, Kings Buildings,
West Mains Road, Edinburgh, EH9 3JW, Scotland, United Kingdom; e-mail:
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.
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.