Offshore Stratigraphic Architecture of the Miocene to Actual Deposits in the Southern Margin of Rio-Del-Rey (South Cameroon)

Abstract

The study of the geometric deposits in a basin allows the reconstitution of its tectonic and eustatic history. The Rio-del Rey basin, upon which this study is being carried out, constitutes one of the two Cameroon margin basins located North of the Cameroon volcanic line. To study the stratigraphic architecture of the Miocene deposits consists in characterizing the deposits geometry by discriminating the controlling factors. This study is based on data, made up of 13 seismic lines and 07 wells and then on various methods related on seismostratigraphy and diagraphies. The obtained lithologies in the study area constituted essentially of sandy and clayey deposits from Paleocene to Recent. They are grouped differently in to Akata, Agbada and Benin Formations, and the Isongo Member. These deposits are set up in marines (bathyal and neritic), deltaics, turbiditic cones slope and fluvial channels environments. Three second-orders sequences were identified (S1, S2 and S3), they are made up of deposits presenting variable geometries along the basin. They are prograding, aggrading, in domes and synclinal. The disposition of the deposits was influenced by tectonic structures such as folds and faults. The isochronal map allows understand the sedimentary flow impact on topographic evolution of the basin in the upper- Miocene. It turns out that, deposits of this basin present various geometric tectonics control (subsidence and uplift) that constitute a major influential factor, being marked by the presence of synclines (gravity tectonics), domes (argilocinesis) and syn-sedimentary faults. The fall in marine level eustatism gives rise to progradations, whereas, a rise in marine level is responsible for retrogradations and aggradations. Thus, the sedimentary flow exerts a secondary control. It is related to the above two major factors