--> Abstract: Seismic Record of Drift Deposits, Offshore Western Madagascar: Implications for Regional Tectonics and Sedimentation; #90063 (2007)

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Seismic Record of Drift Deposits, Offshore Western Madagascar: Implications for Regional Tectonics and Sedimentation

 

Burke, Benjamin C.1, Jeffrey U. Kraus1 (1) ExxonMobil Exploration Company, Houston, TX

 

Offshore western Madagascar, a 5500 km2 sedimentary sequence with clear internal structure visible on seismic data has been interpreted as a sedimentary drift deposit. These deposits sit at the base of the continental slope in an average of 3000 m of water in the Mozambique Channel. Seismic interpretation of the deposits indicates five major seismic–stratigraphic units and provides strong evidence that this unit not a slump feature. Mapping of depositional packages in the deposits reveals several unconformities, as well as inferred changes in sedimentation rate and paleocurrent direction. Unconformities within the sequence may record changes in ocean circulation and submarine erosion associated with an increase in regional tectonism.

 

The drift deposits are ponded against a prominent oceanic transform fault that appears to have been reactivated during the Late Cretaceous. This relationship suggests a South-North deep ocean current system existed at that time, well before the establishment of the modern Antarctic Bottom Water system. The drift deposits, which are up to 2 km thick, were shed in to the basin from western Madagascar during Late Cretaceous-Paleogene uplift. Understanding the complex interplay between tectonics, sedimentation, and paleocurrent patterns is fundamental to developing a model for reservoir deposition in the deepwater offshore basins.

 

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