Facies association and sequence stratigraphic analysis of the lower Cretaceous Bima Formation in Yola arm of the Upper Benue Trough, Northeastern Nigeria

Abstract

The Lower Cretaceous Bima Formation is the oldest sedimentary rock in the Upper Benue Trough. This research is aimed at understanding the facies, facies association, and sequence stratigraphic framework of the continental Bima Formation. Detail field mapping, lithostratigraphic studies, petrography, and paleocurrent analysis revealed that the formation is composed of three facies associations; gravel facies association FAI (gravelly dominated), sandstone facies association FAII (sand-sandstones dominated), and fine-grained facies association FAIII and four facies successions; proximal alluvial fan facies succession, braided river facies succession, fluvio-lacustrine facies succession, and flood plain facies association. The Bima Formation is punctuated by three major bounding surfaces, these provide the means of subdividing the Bima Formation into four depositional sequences namely; SQ1, SQ2, SQ3, and SQ4. Four system tracts were also identified within the Bima Formation; aggradational and high accommodation system tracts represent positive accommodation/sediments supply, and low accommodation system tract-A and B suggest negative accommodation/sediment supply. The overall sedimentation processes in the Bima Formation are controlled by climate, tectonic subsidence, and uplift. The paleocurrent data from the northern part of the study area suggest a unidirectional flow in NNW while the southern part of the study area shows SSW direction.