Characterization of fossils and typomorphic minerals and its implications for source rocks in the Lower Congo Basin

The development of source rocks is closely related to palaeoproductivity and preservation conditions. This study examined the developmental characteristics of fossils and typomorphic minerals in different strata in the Lower Congo Basin. This study utilized thin section examination, SEM (scanning electron microscope), cathodoluminescence and chemical element analysis. The results show that there are strata rich in fossils, phosphate and pyrite in the Madingo Formation. The palaeontological record reflects the level of palaeoproductivity. The appearance of phosphate minerals is closely related to upwelling, which can bring nutrients from the subsurface. Pyrite develops in anoxic water environment, so it can be used to identify palaeoredox conditions. The Madingo Formation is rich in organic matter, which results from its high palaeoproductivity and good preservation conditions. The microstructures of sedimentary rocks and typomorphic minerals are examined, and the sedimentary characteristics and preservation conditions of organic matter in shale are comprehensively discussed. This study provides suitable tools to determine the formation mechanism and the complex heterogeneous distribution of source rocks and has great significance for oil exploration in the Lower Congo Basin.