Post-Depositional Processes Affecting Archaeological Deposits Along the Niger River Banks, Kebbi State

Understanding post-depositional processes is fundamental to the accurate interpretation of archaeological stratigraphy, yet these processes are rarely studied systematically in Nigerian river floodplain contexts. This study investigates the physical, chemical, and biological agents that affect archaeological deposit formation and alteration along a section of the Niger River bank in Kebbi State, focusing on a series of eroding archaeological exposures that contain ceramic sherds, iron slag, and faunal remains. The research employs sedimentological description, soil micromorphology through field observation, and documentation of visible bioturbation and erosion features across the study exposures. Results indicate that annual flood cycles produce significant lateral displacement of surface artefacts, with tracking experiments using marked sherds demonstrating displacement of up to twelve metres over a single flood season. Root bioturbation and termite activity are identified as additional significant agents disturbing the vertical integrity of deposits, particularly in the upper fifty centimetres. The study applies a site formation theory framework drawing on recent geomorphological archaeology publications from tropical African contexts, and argues that standard stratigraphic interpretations at comparable riparian sites must account for these processes before cultural phases are inferred. Practical recommendations include deeper test excavation below the bioturbated zone and the use of optically stimulated luminescence dating to establish sediment deposition chronologies independent of cultural materials. Keywords: post-depositional processes, Niger River, Kebbi State, site formation, floodplain archaeology.