SEDIMENTARY FACIES AND DEPOSITIONAL ENVIRONMENTS OF CENOZOIC SEDIMENTARY FORMATIONS CROPPING OUT AT THE CENTRAL PART OF THE DOUALA BASIN

摘要

The Douala Basin is one of three units of the Cameroonian coastal basin in the Gulf of Guinea, formed from the east-west extension between African and South American plates generated during the opening of South Atlantic in the Early Cretaceous. This basin contains sediments from Lower Cretaceous to present. The Cretaceous depositional environments are well understood whereas there is very little information concerning Cenozoic depositional environments. Facies and their stratigraphical distribution analyses were conducted on Cenozoic formations exposed at the E-W central part of the Douala Basin in the Missole II, Piti, Missole I and Dibamba localities, with an objective to provide details on the depositional environments and to reconstruct the depositional model and their evolution over time. Seventeen (17) lithofacies were identified on the basis of lithology, grain size and sedimentary structures. The facies constitute three (3) main facies associations; the gravelly dominated, the sandy dominated and the fine grained dominated. These facies and facies associations were interpreted and five depositional environments successions were recognized; the fluvial-braided and meandered channel, the delta plain, the continental shelf and the marginal-littoral. The facies distribution shows a progradational succession from a fluvial to delta plain at the axial part of the basin and a storm dominated continental shelf to marginal-littoral at the central part of the basin. The facies stacking patterns depict sedimentation mainly controlled by sag subsidence and probably by climate.