Finite Markov chain model in lithofacies analysis: an example from the bida sandstone, Bida Basin, Nigeria

Abstract

The Markov Chain Stochastic Process has been used both to analyze the vertical lithofacies of the Bida Sandstone (Campanian – Maastrichtian) in Bida area and interprete the corresponding depositional systems. Six lithofacies, comprising of F1: conglomerates (breccias); F2 : medium – very coarse, pebbly sandstone with dominant trough beddings ; F3: coarse-grained pebbly sandstone with small scale trough or planar cross-beds; F4: mediumgrained planar cross- bedded or massive sandstone lithofacies with abundant scattered pebbles ; F5: very fine to fine -grained, planar cross-bedded or parallel laminated sandstones; and F6: siltstone and claystone, variegated and mottled in places - ripple/parallel laminations and rootlets were recognised. A high frequency fining-upward (FU) transition pattern (or cycles) with a “memory function” was distilled from the sequence using the Markov Chain Stochastic Process. The fining- upward (FU) motif is interpreted as a product of braided river depositional system with well- developed flood plains and lakes behind non-cohesive river banks. The cycles indicate channel migration within a broad topographically variable alluvial plain, fed by basin-margin fans.