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The AAPG/Datapages Combined Publications Database

AAPG Special Volumes

Abstract

Pub. Id: A110 (1982)

First Page: 49

Last Page: 74

Book Title: M 34: Studies in Continental Margin Geology

Article/Chapter: Post-Paleozoic Succession and Structure of the Southwestern African Continental Margin: Rifted Margins: Field Investigations of Margin Structure and Stratigraphy

Subject Group: Geologic History and Areal Geology

Spec. Pub. Type: Memoir

Pub. Year: 1982

Author(s): I. Gerrard (*), G. C. Smith (*)

Abstract:

Four seismic horizons -- T, R, P and L from bottom to top -- form major seismic sequence boundaries that range in age from Mesozoic to Cenozoic. Horizon T is regarded as the rift-onset unconformity and horizon R as the drift-onset unconformity, with the post-R succession being drift-stage deposits. Three periods of Mesozoic to Cenozoic igneous activity are represented, but, owing to extensive alteration, the few age determinations are suspect. The drift-onset unconformity R, with dipping reflections beneath it, can be traced westward to where it is juxtaposed with the top of typical reflection-free oceanic crust. We believe that this marks the position of the continent-ocean boundary and that the distinctive magnetic and gravity anomaly G, much nearer the coast, i produced by the pinchout of the T-to-R wedge with its substantial basaltic component.

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