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Worldwide Research
Superposed Deformation Straddling the Continental-Oceanic
Transition in Deep-Water Angola
Carlos Cramez and Martin P. A. Jackson

The Angolan margin is the type area for raft tectonics. New seismic data reveal the contractional buffer for this thin-skinned extension. A 200-km-long composite section from the Lower Congo Basin and Kwanza Basin illustrates a complex history of superposed deformation caused by (1) progradation of the margin and (2) episodic Tertiary epeirogenic uplift. Late Cretaceous tectonics was driven by a gentle slope created by thermal subsidence; extensional rafting took place updip, contractional thrusting and buckling downdip; some distal folds were possibly unroofed to form massive salt walls. Oligocene deformation was triggered by gentle kinking of the Atlantic Hinge Zone as the shelf and coastal plain rose by 2 or 3 km; uplift stripped Paleogene cover off the shelf, provided space for Miocene progradation, and steepened the continental slope, triggering more extension and buckling. In the Neogene, a subsalt half graben was inverted or reactivated, creating keystone faults that may have controlled the Congo Canyon; a thrust duplex of seaward-displaced salt jacked up the former abyssal plain, creating a plateau of salt 3-4 km thick on the present lower slope. The Angola Escarpment may be the toe the Angola thrust nappe, in which a largely Cretaceous roof of gently buckled strata, was transported seawards above the thickened salt by up to ~20 km.

Carlos Cramez, TotalFina Elf Exploration and Production, 2 Place de la Coupole, 92078 Paris La Defense Cedex, France.

For more information, please contact Martin Jackson. Telephone 512-471-9548; e-mail martin.jackson@beg.utexas.edu
March 2003
 
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