ABSTRACT
The Lokoja Formation exposed on a road cut at Uluoke-Uzairue, along Auchi-Okene Road, Estako west, Edo state was examined, with the aim of characterizing sediments based on their nature and transport mechanisms and to ascertain depositional environments. The methodology employed involved, outcrop studies, visual textural analysis, sieve and hydrometer analyses as well as pebble morphometry. Five distinct lithofacies (L1, L2, L3, L4, and L5) were identified in this study. Five (05) representative samples from each lithofacies was collected throughout the exposed section of the Lokoja Basange Formation, which has a total thickness of 5.42 meters. The framework descriptions all refer to sediments with a significant amount of fine-grained matrix (over 15%) and loosely packed framework grains (around 30%). Despite mature minerals (quartz), poor sorting and angular grains in L1, L2, and L5 suggest minimal transport, indicating immaturity. L3 shows moderate maturity (mixed minerals, some sorting), while L4 is a complex case with both signs. Overall, these features suggest a single cycle of transport and deposition. Fining upwards grain size suggests a single depositional cycle with decreasing energy. However, trough and planar cross-bedding indicate high energy events during deposition. This combination points to a braided river system (alluvial to fluvial) influenced by marine processes, likely due to the absence of thick mud layers. Immature sediments suggest a single transport cycle near a source in the northwest. Basement rocks in that area support this, with likely sources like granite and mica schists.
