The aim of this research work was to report a facies analysis of the N'Kapa formation, identified the clay minerals present in those facies and evaluate their oil potential. For that to be done, Lithostratigraphic descriptions were performed on three natural outcrops chosen in three different localities of the northern border of Douala sedimentary basin. Ten shaly samples were then collected on those outcrops and submitted to X ray diffraction and Rock-Eval pyrolysis. Lithologically, the N'Kapa formation is made up of dark to grey shales and fine to coarse sandtones. The mineralogic content of the shales is made up of Kaolinite, dickite, low quartz and vaterite. Those shaly facies present high amount of immature organic matter (average TOC content around 2%). The petroleum potential is fair to poor (average S2 for all the samples around 3.33 mg HC/g of rock) though some samples (M1 and M2) presenting a good petroleum potential up to 6.62 kg HC/t of rock and 6.44 kg HC/t of rock respectively. They have undergone a low degree of diagenesis (early to burying diagenesis). This is evidenced by the predominance of kaolinite and dickite, low quartz and vaterite which are minerals stable at low temperature.

The Douala basin in Cameroon is one of the West African basins created during the opening of the South Atlantic Ocean after the break-up of the Gondwana superstructure. Until now, no detailed studies of age and paleo-environmental evolution of this basin during the Cenozoic have been carried out, especially on outcrops sections. Palynological and sequence analyses have been performed on the outcrops in the Missole I and Dibamba localities in the central part of this basin. This integrated approach allow us propose a new age and paleo-environmental evolution of the Douala Basin. Three palynomorph assemblages have been identified: (i) the Paleocene-Eocene palynomorph assemblage ( A) from the Missole I deposits; (ii) the Oligocene palynomorph assemblage ( B) from the lower part of the Dibamba deposits; and (iii) the Lower to Middle Miocene palynomorph assemblages ( C) from the upper part of the Dibamba deposits. Sequence analysis indicates four depositional sequences with a vertical succession, characterized by major transgressive depositional sequences (depositional sequence “a”, “b”, and “c”), and a minor regressive depositional sequence (“d”). The trangressive sequences were deposited in lagoon or marginal marine environments during Paleocene-Eocene, while the regressive sequence was deposited in prograding continental shelf during the Oligocene-Middle Miocene. The recognized depositional sequence and associated depositional environments were controlled by spasmodic subsidence, margin uplift and climatic variations. Climate evolved from a wet-dry subtropical to tropical during the Paleocene-Eocene and a warm humid subtropical during the Oligocene up to Lower Middle Miocene with overall shift of the Douala basin from the Southern to the Northern hemisphere. This study reveals the existence of Oligocene deposits (Souellaba Formation) in the outcrops and could be useful for future correlation with the offshore part of the Douala Basin.

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.

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An integration of geochemistry, mineralogical and palynological data is used to depict the sediment provenance and distribution, the sedimentary environment and the paleogeographic evolution of the Cretaceous Atlantic Basin of Cameroon. The basin is located along the African western coast, in the heart of the Guinea Gulf, and includes the Campo, Douala, and Rio-del-Rey sub-basins from South to North. The sediments of the Campo sub-basin are derived from rocks of intermediate composition, those of the Douala sub-basin from intermediate to ma c rocks in the southern and felsic rocks in the northern parts, and those of the Rio-del-Rey sub-basin from felsic rocks with a contribution of rocks of intermediate composition. The paleoweathering index and Index of Chemical Variability values, ranging respectively from 71.26 to 76.88 and 0.98 to 2.12, 67.15 to 99.39 and 0.37 to 0.90 and 73.17 to 92.90 and 0.44 to 10.03 respectively for Campo, Douala and Rio-del-Rey sub-basins, indicate sub-maturity, high maturity and sub-to high maturity, respectively, of the Campo, Douala and Rio-del-Rey deposits. Al 2 O 3 vs. V and Al 2 O 3 vs. P 2 O 5 plots, and palynologic data such as marine (e.g. dino agellates and microforaminifera and continental species (e.g. Classopollis sp., Ephedripites sp., Botryococcus sp.) suggest a deposition in more or less deep lacustrine (Campo sub-basin), uvio-deltaic to shallow marine (Douala sub-basin), and marginal to shallow marine (Rio-del-Rey sub-basin) environments. Chemical Index of Alteration, X-Ray diffraction and palynologic data point to arid to semi-arid, semi-arid and arid to semi-arid conditions, respectively in the Campo, Douala and Rio-del-Rey sub-basins. The tectonic setting diagram suggests collision tectonic events that are inconsistent with the classic geological history of the Atlantic Basin. The situation is in fact related to Precambrian events that affected the basement rocks from which the studied sediments were derived, and probably to the compressional tectonics during the evolution of the South Atlantic Ocean. Although these sub-basins share the same geological history, there are some differences, such as the degree of sediment maturity, the diagenetic effects, the lithology of rock sources, the paleoenvironments of deposition and their uctuation, depending on the moment the tectonic of Atlantic opening reached them (northward progression of the W-E extension) and the northern shearing along the southern area of the Benue through axis (Rio-del-Rey). The geological history of the Cameroon Atlantic Basin is similar to those of Gabonese and Nigerian basins, along the African western coast, and of those of the Brazilian basins along the eastern coast (Santos Basin to Pernambuco-Paraiba Basin)