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Superposed deformation straddling the continental-oceanic transition in deep-water Angola
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Resumo(s)
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; relative 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 of 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. q 2001
Elsevier Science Ltd. All rights reserved.
Descrição
Palavras-chave
Angola Basin evolution Congo Canyon Fold-and-thrust belt Gravity tectonics Kwanza Basin Lower Congo Basin Raft tectonics Salt tectonics
Contexto Educativo
Citação
Marine and Petroleum Geology, Vol. 17, nº10, pp. 1095-1109