Integrated sedimentological, petrographic and mineralogical analysis of provenance and diagenesis in the Carnot-Berberati Basin, Central African Republic (CAR)

Abstract

The Carnot-Berberati Basin in the southwestern region of the Central African Republic (CAR) was investigated to determine the provenance, sedimentation conditions and diagenetic evolution of its detrital deposits. A total of nine (09) stratigraphic columns and eight distinct lithofacies were identified. Sedimentological, petrographic and mineralogical data revealed that the sediments are primarily composed of quartz (72.25%), feldspar (11.8%), mica (4.75%), rock fragment (5.4%), heavy minerals (1.95%) and other minerals (5.80%). The presence of polycrystalline quartz exhibiting undulatory extinction, along with monocrystalline quartz with non-undulatory extinction, indicates contributions from both stable cratonic and recycled orogenic sources. Heavy mineral analysis provided insights into sediment provenance, whereas x-ray diffraction facilitated precise mineral identification, aiding in the reconstruction of diagenetic processes such as cementation, mineral transformation and post-depositional alteration. Grain morphological analysis further elucidated the sediment transport dynamics and depositional conditions, offering evidence of past tectonic and environmental influences. The sandstones are mainly classified as sub-arkose, with some quartz arenite, and a minor amount of sublitharenite, arkose and lithic-arkose. This classification reflects their origin from the Precambrian basement rocks. Integrated analyses showed that the sediment was sourced from continental terrain and was deposited as a fluvial environment. Diagenetic evolution is influenced by both mineralogical composition and post-deposition processes. This study indicates that the sediments originated from a lithology of the provenance and were deposited in a basin. This study provides valuable insight into basin diagenetic processes and depositional history.