Lithostratigraphic, geophysical and morpho-tectonic studies of the South Cameroon shelf

A geological and structural sketch of the southern Cameroon shelf was drawn on the basis of a high-resolution seismic survey, dredgings and Kullenberg core sampling of the outcropping rocks at sea bed. Palynological and mineralogical data (X-ray diffractometry), supported by occasional foraminiferal evidence, revealed four main lithostratigraphic sets resting on a Precambrian basement: Upper Cretaceous (Albian to Senonian), Paleocene–Lower Eocene, Miocene–Pliocene and Pleistocene. Three successive deformational types characterise the structure of this margin: (1) N–S trending fractures parallel to the onshore Precambrian structural directions formed during the rifting period and crosscut by N60°E trending cross-faults induced by the transform movement of the South Atlantic; (2) compressive structures governed by local stresses during the Eocene transcurrent reactivation along the N60°E transform faults excluding a salt-controlled deformation; (3) a set of approximately N–S faults affecting the unfolded sequence of the Miocene–Pliocene or the Quaternary and indicative of distensive conditions. The geodynamic evolution is placed in the general framework of the Central and South-Atlantic rifting and passive margin history. Interestingly, the age of the compressive deformation varies from Late Albian to Mid-Eocene depending on the regional plate motion events which are generated along the narrow fracture zones extending as far as or even into the continental domain.