Major and Trace Element Evaluation of the Campano-Maastrichtian Sediments of Anambra Basin Exposed around Enugu, Nigeria

Abstract

An integrated geochemical and sedimentological study of the Campano- Maastrichtian sediment of Ajali and Owelli Formation exposed within the southern portion of the Anambra basin was undertaken to determine the
sandstone provenance, tectonic setting, and paleo-weathering conditions. All sandstone samples are enriched in quartz (Q) but poor in feldspar (F) andlithic-fragments (L). The major-element concentrations of these sandstones reveal the relative homogeneity of their source. Geochemically, the sandstones are classified as quartzarenite, sub-litharenite, and subarkose. Tectonic setting discrimination diagrams suggest a passive continental margin. The sediments are enriched in SiO₂ and depleted in Na₂O, CaO and TiO₂.Chemical index of weathering (CIW) of the sample suggests intense recycling and high degree of weathering in a humid climatic condition. Results of the elemental ratios critical of provenance compared to those of felsic and basic derived sediment of UCC and PAAS values suggests a felsic source rock. Cu/Zn, U/Th, Ni/Co and (Cu+Mo)/Zn paleo-oxygenation ratios used as redox parameters depicts an oxic environment. Finally, presence of minerals, like Anatase, Rutile and  Microcline depicts an igneous and metamorphic source terrain.

Keywords: Provenance, Sub-litharenite, Sandstone, Minerals.