Depositional Environment and Paleo - redox Indicator of the Maastrichian - Campanian Clay in Central Bida Basin, NW Nigeria: Insight from Geochemistry and S edimentology

Abstract

Bida basin is one of the younger sedimentary basins of Africa (Campanian – Maastrichitian) in Nigeria regarded as the northwestern extension of Anambra basin bounded by monotonous Precambrian basement rocks . Marine incursion in to the basin was suspected to have taken place during the early part of the uppermost Maastrichtian phase from the south via the Anambra basin, during which very extensive Sandstones an d thick Kaolinite beds of the Patti Formation in the southern Bida basin were deposited. Stratigraphically , Bida basin is divided into the southern and northern parts. A topographic base map on a scale of 1:200,000 was generated for the study. Geochemical characterizations of thirty clay samples were analyzed for major, minor and trace elements. Field mapping revealed seven clay occurrences on isolated hills, floodplain and plain. C lay s in the basin have h igh light REE/heavy REE ratio, negative Eu anomaly a nd P lot of Cr versus V suggest felsic source rocks. U/Th, V/Cr ratios and authigenic uranium values of the clays suggest an oxic environment of deposition in flood plain, alluvial fan and braided channel at the upper Maastrichian age that represent Upper c retaceous period