Biostratigraphy of Cretaceous-Neogene sedimentary infill of the Mamfe basin, southwest Cameroon: Paleoclimate implication

Abstract 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., Polypodiisporites 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.