Sedimentological Characterization of Clastic Sediments of Anambra Basin: Implications for Provenance and Palaeoenvironments.

Abstract

Grain size and heavy mineral studies carried out on eleven samples from sandstone, siltstone and shale beds that are exposed along road cuts and river channels were used to decipher palaeodepositional conditions, provenance and tectonic setting within the Anambra Basin, south-eastern Nigeria. The study revealed three lithofacies belonging to the Lokoja-Basange and Mamu Formations. The sandstones mostly exhibit fining upward sequences with poorly sorted angular to subangular grains that have poor compositional maturity. These are characteristic of short transportation history and fluvial depositional environments. The siltstones and shale display a coarsening upward progradational pattern that is suggestive of deltaic sedimentation. Heavy mineral assemblages observed in the sandstone samples include zircon, rutile, magnetite, topaz and tourmaline which suggest igneous and metamorphic provenance derived from neighbouring rocks of the Precambrian Basement Complex of Nigeria.