Provenance and paleoenvironment of the Albian-Lower Turonian detrital deposits in the northern part of the Coastal Douala sub-basin (Cameroon)

Abstract

The Douala sub-basin is a coastal basin located in the heart of the Guinea Gulf. The study area is located in the North part of this basin, and the study deposits are detrital of Albian-Cenomanian to Lower Turonian age. The geochemical data reveal that the studied sediments from both sides of the Mungo River consist mainly of Shales associated with Wacke, rare arkoses and sub-arkoses originated mainly from intermediate rocks composition according to the SiO₂ vs. Al₂O₃/TiO₂ plot, high LREE/HREE ratios (11.25 to 38.48) and slight positive or no to positive Eu anomalies (0.99 to 1.36). The CIA (Chemical Index of Alteration) and ICV (Index of Compositional Variability) values ranging respectively from 67.00 to 83.42 and from 0.37 to 1.12 suggest that these sediments are globally mature and were mainly deposited in a fluvio-deltaic to shallow marine or marginal environments as indicate the sequential analysis, associated with palynological content, with continental (e.g., Ephedripites sp. and Integritetradites sp,) and marine (e.g., microforaminiferal test lining) species. The tectonic setting diagram suggests collision tectonic events that are inconsistent with the classic geological history of the Atlantic Basin margin, but consistent with the geological history of the basement. The deposits from the both sides of the Mungo River are separated each other’s during the evolution of the South Atlantic at the Cenozoic period by the Precambrian fault reactivations. The geological history of the Douala sub-basin is similar to those of Nigerian and Brazilian East costal basins, with marine transgression on both sides of the South Atlantic Ocean and the sediment lithology is related to the source rock lithology varying along the coastal areas.