The discrepancy of tectonic setting inferred from whole-rock geochemical data of sedimentary deposits of the Atlantic Basin margin of Cameroon: an evaluation of the effect of reworked and sorted sediments

This work integrates field investigations and geochemical-based tectonic discrimination diagrams (DF1 vs. DF2) from the Atlantic Basin margin of Cameroon of Cretaceous to Recent age. Discrimination diagrams were based on geochemical data from new results of 13 samples compared with 245 samples of whole-rock geochemical data from the literature. The work aims to discuss the probable reasons for any discrepancies observed between the geological history and tectonic setting based on geochemical data. New field studies revealed that the source rocks of sediments have experienced polyphase deformation during Archean, Eburnean/Trans-Amazonian and Pan-African collisional orogenic cycles. The available geochemical data on sediments from the Lower Cretaceous to Recent were plotted in the DF1 vs DF2 tectonic discrimination diagrams. These plots revealed collisional setting for Cretaceous-Cenozoic deposits, consistent with the geological history of the basement rocks, passive or rift setting of some samples indicates likely the contribution of the Precambrian dikes and post-orogenic rocks according to the geological history of Cameroon. The discrepancy of passive margin setting interpretations recorded from beach sediments and surface to subsurface stream sediments can be explained by the fact that they correspond to reworked and sorted deposits which are unreliable and for provenance and tectonic interpretations due to modification of their chemical composition. The results of this work clearly indicate that the tectonic setting inferred from whole-rock geochemical data of sediment cannot be interpreted as the depositional setting but matches well with the emplacement setting in relation to their source rocks.