--> Abstract: Sequence Stratigraphy of the Latest Cretaceous and Cenozoic Shelf to Basin Transition NW Madagascar: Significance for Future E; #90063 (2007)

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Sequence Stratigraphy of the Latest Cretaceous and Cenozoic Shelf to Basin Transition NW Madagascar: Significance for Future Exploration

 

Watkinson, Matthew P.1, Mark A. Enfield2, Edward P. Blunt3 (1) PDF Fellowship, University of Plymouth, Plymouth, United Kingdom (2) PDF Ltd, Streatley, United Kingdom (3) Sterling Energy plc, Harpenden, United Kingdom

 

Significant exploration potential is recognised in deep water basinal settings offshore NW Madagascar. We present here the results of detailed structural and seismic sequence stratigraphic analysis of the shelf to basin transition of the Ambilobe Basin, and show its significance for future deep-water exploration potential.

 

Sequences of inferred Late Cretaceous age show evidence of growth across normal fault systems and can be related to rifting between Madagascar and India/Seychelles. Above a major base Paleogene hiatus, a prolonged phase of shelf-basin deposition commenced dominated by siliciclastic sedimentation fed from onshore Madagascar, but with phases of carbonate deposition, notably in the Eocene and Neogene.

 

Probable Eocene and Oligocene shelf-edge sedimentation shows dramatic variations along depositional strike caused by rapid subsidence apparently associated with salt mobilisation. Base-of-slope mass flow complexes and turbidite systems were ponded and redirected within small salt withdrawal and structural depocentres.

 

A series of major regressive events, thought to be coincident with Oligocene global sea-level falls, led to by-passing of clastic sediments into basinal areas. Subsequent Neogene sedimentation was dominated by progradation of deltas to the present day shelf margin. This regressive phase coincided with uplift of Paleogene sequences and onshore volcanism. The Neogene inversion of Paleogene depocentres resulted in alongshore offlap of clastic depositional systems, and to the establishment of reefal carbonates localised on uplifted highs.

 

This analysis has improved our understanding of the distribution, nature and timing of key play elements (including basin floor reservoirs), and is being applied to help constrain exploration risk in deep water areas.

 

AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California