Ivory Coast-Ghana Margin: Model of a Transform Margin

J. Mascle, E. Blarez

We present a marine study of the eastern Ivory Coast-Ghana continental margins which we consider one of the most spectacular extinct transform margins. This margin has been created during Early-Lower Cretaceous time and has not been submitted to any major geodynamic reactivation since its fabric. Based on this example, we propose to consider during the evolution of the transform margin four main and successive stages. Shearing contact is first active between two probably thick continental crusts and then between progressively thinning continental crusts. This leads to the creation of specific geological structures such as pull-apart graben, elongated fault lineaments, major fault scarps, shear folds, and marginal ridges. After the final continental breakup, a "hot" center (the mid-oceanic ridge axis) is progressively drifting along the newly created margin. The contact between two lithospheres of different nature should necessarily induce, by thermal exchanges, vertical crustal readjustments. Finally, the transform margin remains directly adjacent to a hot but cooling oceanic lithosphere; its subsidence behavior should then progressively be comparable to the thermal subsidence of classic rifted margins.

AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.