Malaysian Journal of Geosciences (MJG)

This study examines Oligocene-Miocene pebbly sandstones within Asaba – Ibusa locality in southern Nigeria using the pebble morphometric analysis technique to determine the palaeoenvironmental and palaeodepositional environments. The transport history and the energy of deposition of the sediment have been inferred by examining shape, roundness, and sphericity of pebbles. Major morphometric parameters such as Zingg classification, flatness ratios, and indices of elongation were used on 237 pebble samples collected in 2 strategic sites including: Lander Brothers Quarry (Ibusa) and Dennis Osadebay University Spring (Asaba). Results indicate a fluvial dominated depositional environment, supported by high sphericity values (mean MPSI > 0.65), sub rounded pebbles (mean roundness 36-38%), and negative oblate-prolate indices (mean OPI: -1.10 to -0.61). A comparative analysis between Asaba and Ibusa pebbles indicate that there are spatial differences in palaeoflow energy and sediment transport processes with Ibusa pebbles exhibiting a little more sphericity implying a downstream rise in the energy of the fluvial. The research presents the quantitative uniqueness of the examined silt and is relevant to the idea of the processes of hinterland fluvial in the research at the time of the Oligocene-Miocene transition. These findings will enhance regional stratigraphic models and offer insights into sediment routing systems linked to Benue Trough tectonics and climatic shifts.