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Geochemistry of Sedimentary Rocks from the Nkapa Formation, North Western Part of the Douala Basin, Cameroon: Implications for Provenance, Tectonic Setting and Paleoenvironmental Conditions

The Douala sedimentary basin in Cameroon is the main gas prospective 
basin in the country and has witnessed a number of investigations in this 
regard. The Nkapa Formation is one of the basin’s principal rock units and here 
we analyzed samples from sediments comprising this formation in order to 
constrain their provenance, tectonic setting and depositional environment using 
geochemical traits. Major and trace elements were analyzed by inductively 
coupled plasma mass spectrometry. Elemental ratios provide information on 
geochemical signatures of Eu/Eu ratios of the sandstones and shales, suggesting 
the provenance of the sediments was felsic from continental rock protoliths. 
Calculated K2O/Na2O ratios > 1 is reminiscent of 
quartz-rich sediments deposited in passive margin (PM) environments with 
significant terrigenous input. The elemental ratios La/Sc, La/Ca, Th/Sc, and 
Th/Co suggest that the sediment sources are felsic and mafic in nature. The clastic sediments were normalized using North 
American Shale Composite (NASC). The Ni/Co and V/(V + Ni) ratios reveal that the sediments were deposited under variable 
conditions including euxinic, dysoxic and anoxic. Overall, the evidence from discrimination diagrams using major and trace 
elements suggest that the sediments were derived from mostly Passive margins (PM) and 
continental island arc (CIA) with minor Oceanic island arch (OIA) sources. 
Limestones from the studied area at Kompina, rich in calcium carbonate above 
98.5% make them suitable for use in the chemical industries. In addition the felsic and 
mafic source rocks can lead to formation of light and dark colored minerals 
which can be of economic value.