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Publication
Cramez, C.,
and Jackson, M. P. A., 2000, Superposed deformation straddling the
continental-oceanic transition in deep-water Angola: Marine and
Petroleum Geology, v. 17, p. 1095-1109
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Superposed
Deformation Straddling the Continental-Oceanic
Transition in Deep-Water Angola
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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
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more information, please contact Martin Jackson. Telephone 512-471-9548;
e-mail martin.jackson@beg.utexas.edu |
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March
2003
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