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The volcano-sedimentary infill of the Dschang basin in the Western part of Cameroon is poorly known. The present study provides the first biostratigraphical data of the volcano-sedimentary sequence and allows constraining the age and the position of this basin within the regional context of Central Africa. The studied sequence is composed of three depositional units. The first unit is a fining-upwards sequence of coarse-grained sandstone that gets finer towards the top, passing to thick layers of fossiliferous claystone. The second unit is strongly affected by volcanic activity and consists of a volcano-sedimentary sequence. The third unit is marked by basaltic volcanism and covers the series. Diverse and well-preserved palynomorphs were recovered and are used to provide valuable information for age determination of the Dschang volcano-sedimentary sequence, namely to be of late Eocene- Early Miocene age. The recovered spores, pollen, green algae and fungal remains from the bottom of the sequence include Bombacidites spp., Clavainaperturites cf. clavatus , Crototricolpites sp., Perfotricolpites digitatus , Proteacidites spp., Psilastephanocolporites minor , Psilastephanocolporites spp., Retitrescolpites spp., Retitricolporites irregularis , Retitricolporites spp., Retitriporites sp., Spirosyncolpites bruni (probably synonymous to Spirosyncolpites spiralis ), Striatopollis bellus , (considered synonymous to Striatopollis catatumbus ), Striatopollis sp., Tetracolporites quadratus , Tetratricolporites sp., ?Verrutricolporites rotundiporis , Cyathidites sp., Laevigatosporites spp., Polypodiaceoisporites spp., Verrucatosporites usmensis , Verrucatosporites spp., Botryococcus sp., Tasmanites sp., and fungal remains. The samples are assigned to the Verrucatosporites usmensis Zone of Salard-Cheboldaeff (1979). The palynological assemblages are similar to those of other Late Eocene to Early Miocene palynological records from the West, Central and Northern African basins. Study of the organic matter by pyrolysis Rock-Eval 6 (Types I, II and III), the sedimentological setting, the palynofacies and the palynomorph assemblages show evidences of tidal influence (presence of the prasinophyte Tasmanites ) in an active continental margin (semi-arid to humid lacustrine depositional environment). The Ngoua sedimentary sequence is fluvio-lacustrine, and believed to have witnessed some occasional marine incursions possibly during the opening of the Central Atlantic Ocean (CAO) and strongly disturbed later by intense volcanic activity. [ABSTRACT FROM AUTHOR]

A palynological investigation of sixteen (16) outcrops from Mamfe Basin, southwest Cameroon, has been carried out using spores, pollen and organic matter components to establish the biostratigraphic framework of the basin and reconstruct the depositional and paleoclimatic conditions. The inferred climatic trend is based on the distribution pattern of the recovered species, mainly the vertical occurrence and disappearance, for the time window investigated. Particulate organic matter are represented mainly by gymnosperm pollen grain Classopollis spp. and opaque phytoclasts. Some fern spores such as Cicatricosisporites venustus , Verrucatosporites spp. , P olypodiisporites aff. specious , Deltoidospora spp., Laevigatosporites spp., Polypodiaceoisporites spp., and Foveotriletes ornatus occur in significant amounts. Angiosperm pollen, including Echitricolporites spinosus, Monoporopollenites annulatus, Pachydermites diederixi and Sabicea-type, are locally present. Araucariacites spp. and Afropollis jardinus are less abundant, depending on the stratigraphic level. The palynological assemblage suggests an age ranging from early Barremian to Cenomanian. Additionally, we identified a level dated as Miocene to Pleistocene in one of the sections. Hygrophilous flora such as pteridophyte (Cyathidites spp.) and angiosperm (Afropollis jardinus) is less present compared to xerophytic flora (Classopollis) along the studied sections, indicating significant climatic variation. Variation in palynomorph assemblages led to define three significant settings of the paleoclimate: 1) humid conditions prior to Barremian coinciding with the opening of the Atlantic Ocean; 2) arid to semi-arid conditions intermittent with short-lived humid phases from the Barremian to the Cenomanian; 3) humid conditions from the Miocene onwards. Thus, the palynological assemblage allows constraining the age of the basin infill and accessing the paleoclimatic states in the hinterland in Mamfe Basin, where powerful climate proxies are currently very limited. The basin appears to record regional rather than local climate fluctuations. • Mesozoic and Cenozoic paleoclimate conditions reconstructed using palynomorphs. • Conditions humid and dry during Mesozoic and humid during Cenozoic. • Opaque and translucent phytoclasts suggest the proximity to a terrestrial source. • Intermittent freshwater influx recorded in the Nfaitok Formation. • Terrestrial derived palynomorphs are the main components in the intervals studied. [ABSTRACT FROM AUTHOR]

The Hama-Koussou Basin is one of the offset structures of the eastern end of the Benue Trough in Northern Cameroon. This sedimentary basin is an asymmetrical syncline whose axis is strongly shifted towards the East, filled predominantly with Cretaceous deposits, The basin has experienced at least three (3) phases of sedimentation during its geological history: two (2) fluvial phases with one at the top and the second at the bottom consisting of conglomerate, micro-conglomerate, and sandstone, sandwiching one fluvio-lacustrine phase consisting of fossiliferous claystones and marlstones with intercalations of siltstones and carbonate cemented fine sandstone. Numerous sedimentary structures including planar, oblique, and cross stratifications, convolute bedding, desiccation cracks, ripple marks and loadcast have been recorded. The mineral assemblage is dominated by quartz, plagioclase, mica and microcline, accompagnied by diagenetic phases (iron oxide, silica and carbonate). Clay minerals consist of kaolinite, illite and chlorite/smectite. Palynofloral analysis reveals various taxa indicative of a fluvio-lacustrine environment: These include Classopollis sp., Eucommiidites sp., Concavisporites sp., Cicatricosisporites sp, Araucariacites australis , Callialasporites dampieri , Callialasporites microvelatus. The occurrence of Callialasporites microvelatus confirms the Cretaceous age whereas age determination for all other samples was uncertain due to scarcity in palynomorphs. Low numbers of bisaccate, grass, and other angiosperm pollen grains may be indicative of a Cenozoic or younger age, although contamination by modern pollens cannot be excluded.The region experienced volcanism represented by explosive and effusive phases, recorded as sills and dykes. Plutonism is characterized by the establishment of intrusive granite. The East-West elongation observed in the HSB is the same in the Mayo-Oulo-Lere and Babouri Figuil basins and can be interpreted as the result of the same tectonic event linked to the opening of the Atlantic Ocean resulting in the formation of the Benue Trough and adjoins basins. • The Hama-koussou Sedimentary Basin is a fluvio-lacustrine deposit environment. • This basin experienced two magmatic phenomena. • The mineral assemblage is dominated by quartz; plagioclase, microcline, mica, cemented by clay and diagenetic fluids rich in iron oxide, silica and carbonates. • Diagenetic minerals are made by kaolinite, illite and interbedded chlorite/smectite. • Various taxa confirms the presence of the Cretaceous and may be indicative of a Cenozoic or younger age. [ABSTRACT FROM AUTHOR]