Reconstructing maastrichtian paleoenvironments and paleoclimate in the southern Bida Basin: A stratigraphic and foraminifera approach

This study examines the stratigraphy and paleoenvironment of Ahoko section within the southern Bida Basin, Nigeria. The investigation comprises combination of fieldwork-based sedimentology and lab-based foraminiferal study. The lithological sequence in two outcrops records alternating beds of shales, sandstones, claystones, coal seams and concretional ironstones, showing a transition between formation settings influenced by floodplains and swamps, and fluvio-deltaic to marginal marine deposits. The non-planktic nature indicated by the abundance of arenaceous benthic foraminiferids including predominant species Haplophragmoides, Ammobaculites, Miliammina and Trochammina, supported by micropaleontological data, and low salinity, shallow marine or estuarine environments with minimal planktic influence, also supports a Maastrichtian age in a varying climatic condition. Such findings suggest a distal delta plain to coastal swamp depositional system dominated by climatic seasonality, relative sea-level fluctuations and fluvial supply. The study fills gaps in regional correlation of the Bida Basin and offers micro-paleoenvironmental information that is useful in biostratigraphic correlation and in oil exploration.