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Geophagia, the deliberate ingestion of clayey materials, is a complex eating behaviour with obscure etiology and numerous health/medical problems. Geological, mineralogical and geochemical studies were carried out on Sabga geophagic clayey materials located within a trachyte Bamenda mountain, about 16 km east of Bamenda town (North West Cameroon), in order to define the genesis, and its medical interest. Four (04) samples were characterized by different techniques: description of outcrops and pits, particle size distribution by laser dispersion, X-ray diffraction, Fourier transform infrared spectrometry, Scanning electron microscopy and bulk chemical analyses. The main clay minerals were smectite (49-60%) and kaolinite (4-6%). The other major minerals are quartz (19-34%), feldspar (6-12%), goethite (3-6%), and hematite (1-3%). The average particle diameter varied from 2 to 9 µm. Results from the different analytical techniques point out a meteoric weathering of feldspar as petrogenetic origin of geophagic clayey materials. Smectite and kaolinite, which are the main desirable minerals components of the geophagic clayey materials, were geochemically derived from surrounding trachytes. However the presence of crystalline silica (quartz) up to 2% limits the application of some Sabga geophagic clayey materials for pharmaceutical clays. The high radioactive (Th, U), carcinogenic (Cr, Cu, Pb, Ni) and teratogenic (or birth defects) (Cu, Zn, Pb) elements contents in some Sabga geophagic clayey materials implied some pretreatment.

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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 mafic 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. Al2O3 vs. V and Al2O3 vs. P2O5 plots, and palynologic data such as marine (e.g. dinoflagellates 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), fluvio-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 fluctuation, 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)