Lithostratigraphy of Bida Formation, Bida Basin, Nigeria

Abstract

Outcrop and subsurface analysis of the sediments of Bida Formation based on inferred environment of deposition allowed the definition of five facies (1) alluvial fan facies which dominate in the northern part of the basin and consists of conglomerates and sandstones of debris flow and flood plains (2) lacustrine facies characterised by siltstones, sandy mudstones, silty mudstones and mudstones (3) fluvial facies recognised by there basal conglomerates, coarse-grained channel sandstones and fine to medium grained bar top sandstones organised in to series of fining upward successions (4) floodplain facies with horizontally laminated fine-grained sandstones, siltstones and mudstones and (5) mire facies characterized by peat/lignite beds. Some of these lithofacies are being recognized in the Formation for the first time. It is also demonstrated that the alluvial fan facies represent the proximal element while the medial element is characterised by braided and meandering river deposits and the lacustrine deposits form the bulk of the distal fan element of the fluvial Bida Formation. Palynoflora studies suggest that sedimentation ensued in the basin probably before the Campanian due to the presence of Classopollis-Circulina