Christian C. Agbo, Samuel O. Onyekuru, Diugo Ikoro

The Anambra Basin, situated in southeastern Nigeria, stands out as a significant sedimentary basin characterized by its intricate and multifaceted geological history. This complexity arises from a combination of marine, fluvial, and deltaic processes that have shaped the basin over geological time. Our study is dedicated to examining the sedimentary rock formations within this basin, with a particular focus on key units: the Nkporo, Mamu, Ajali, and Nsukka Formations. The primary aim is to reconstruct past hydrodynamic conditions and sediment transport mechanisms that influenced sediment deposition and distribution in the basin. Through a detailed analysis that incorporates both field observations and quantitative methods, we have estimated crucial paleohydrodynamic parameters. These include channel depth, bedform height, sediment transport modes, and flow velocities. By evaluating these parameters, we gain insights into the ancient environmental conditions and sedimentary processes that prevailed during the deposition of these formations. Our findings reveal a wide array of depositional environments within the Anambra Basin. The Nsukka Formation is associated with transitional flow conditions characterized by moderate sediment suspension. This indicates that the depositional environment experienced a balance between sediment being carried by the flow and sediment settling out of suspension. In contrast, the Ajali Formation is marked by a stable environment where sediment transport was predominantly in the form of bed load, suggesting a more consistent and less turbulent flow regime. The Mamu Formation is indicative of highly dynamic and turbulent flow conditions. This environment facilitated both bed load and suspended sediment transport, reflecting a setting with strong currents and significant sediment mobilization. Additionally, the Owelli Sandstone Formation displays transitional flow characteristics that point towards a coastal or shallow marine environment, where sediment transport and deposition were influenced by interactions between marine and continental processes. Overall, this study significantly contributes to our understanding of sedimentary processes within the Anambra Basin. By reconstructing past hydrodynamic conditions and sediment transport mechanisms, the research not only enhances our knowledge of the basin’s geological history but also provides valuable insights into the broader sedimentary dynamics at play. This comprehensive analysis offers a foundation for future research and exploration, highlighting the intricate interplay between geological processes and sedimentary environments in the Anambra Basin