Geochemistry of onshore deposits from Rio del Rey sub-basin of the western Atlantic margin of Cameroon (Coastal basin, Southwest Cameroon): provenance and environments of sedimentation

The Rio del Rey sub-basin belonging to the Cretaceous–Cenozoic coastal basins of Cameroon is studied with geochemistry (major and trace elements) associated mineralogy, palynology petrography. One dominant facies (calcareous shales/siltstones/claystones) occurs in Cretaceous series two others fine- coarse-grained sandstones calcareous claystones/shales Paleocene series. Ratios LREE/HREE (9.27–24.23), Cr/Th (2.24–12.60), Th/Sc (0.54–6.10), Eu/Eu* (> 1 on PAAS normalized ? Chondrite normalized), Al2O3/TiO2 (10.42–112.93) plotted Ce vs. La/Yb, Zr vs.TiO2 La/Sc vs.Th/Co diagrams indicate that sediments derivate from felsic rocks subordinate intermediate composition mafic igneous rocks. CIA (Chemical Index Alteration, 61.69–92.76), PIA (Plagioclase Alteration; 62.16–99.47) K2O/Na2O ratios (0.08–22.13) suggest source have experienced low high weathering (during Paleocene), chemical (at Campanian–Maastrichtian transition) moderate Cenomanian). Zr/Sc diagram sample groups reveals higher zircon content. Al/Si ratios, (0.04–0.06) fine-grained (0.2–0.58) sediments, behavior some elemental concentrations, such as Zr, Hf, Ca, K, Na, geochemical controlled by grain sizes. petrographic X-ray diffraction results point early mesodiagenesis effects an important role sea level change environments sedimentation. These latter vary marginal shallow marine during fluctuated between marine/lagoonal brackish/littoral settings according analysis palynology, species Dinopterygium cladoides continental Classopollis sp. SiO2 Al2O3 + K2O Na2O plot suggests a predominant semi-arid arid climate periodically semi-humid periods was rule Paleocene, Arc-Rift-Collision, sets low-silica diagrams, indicates Collisional or Active Continental Margin tectonic also recorded deposits Douala Campo Cameroon. events could reflect Precambrian basement history linked Neoproterozoic orogeny. geological similar those Nigerian Brazilian East costal basins, local variations changes both sides Atlantic Ocean distribution which related rock lithology.