Sedimentological Evolution and Depositional Environments of the Afikpo Basin and Southern Benue Trough: A Comprehensive Review

Abstract

The Afikpo Basin and Southern Benue Trough preserve a critical Cretaceous sedimentary record, yet existing interpretations remain dispersed across tectonic, stratigraphic, sedimentological, ichnological, provenance, and geophysical studies. This fragmentation limits a unified explanation of how Santonian inversion, sea-level fluctuation, sediment supply, and depositional energy-controlled basin evolution, facies distribution, paleogeography, and sediment-routing systems. This review synthesizes published evidence on the tectonic framework, lithostratigraphic succession, depositional facies, sedimentary structures, trace fossils, transgression-regression cycles, paleocurrent indicators, provenance signatures, and emerging digital reconstruction methods in the Afikpo Basin and Southern Benue Trough. The analysis integrates field-based facies descriptions, ichnofacies interpretation, petrographic and QFL data, grain-size indicators, aeromagnetic and radar-derived structural information, reservoir-property evidence, and basin-modelling implications to develop a coherent tectono-sedimentary interpretation. The synthesis shows that Early Cretaceous rifting-initiated accommodation, while Santonian compression uplifted the Abakaliki Anticlinorium and shifted depocenters into the Afikpo and Anambra basins. Sediment thickness ranges from 513.9 m to more than 3469.6 m, with post-Santonian clastics sourced largely from uplifted hinterlands. Cross-bedding, ripple lamination, mud cracks, flaser bedding, herringbone structures, basal lag deposits, and bioturbated heteroliths indicate fluvial, deltaic, estuarine, tidal-flat, shoreface, and shelf systems. Skolithos, Ophiomorpha, Cruziana, Planolites, Chondrites, and Thalassinoides confirm variable energy, salinity, oxygenation, substrate consistency, and marine influence. Provenance evidence includes Akpoha quartz of 55-64%, feldspar of 22-30%, rock fragments of 1-9%, Eze-Aku Q90F10L0 composition, and mature to supermature Ajali Sandstone. The review supports integrated facies-ichnology-sequence stratigraphy, GIS paleogeographic mapping, digital outcrop analysis, and basin modelling for future studies