Geochemistry and organic petrography of Cretaceous sediments of the Calabar Flank, southeastern, Nigeria

► Organo-petrography and geochemistry of Cretaceous Calabar Flank, Nigeria. ► The OM is immature to early-mature of marine and terrigenous types III and IV. ► Sulphate reduction (SRI > 2.5) of initial OM indicate degradation up to 70%. ► Paleoenvironment of deposition is interpreted based on the integration of all data. ► Amount and quality of OM are specifically controlled by local environmental factors.