SEDIMENTOLOGICAL AND GEOCHEMICAL ANALYSIS OF THE SEDIMENT IN THE NIGER DELTA BASIN

Abstract

The Niger Delta underlies an area of about 256,000km2 and was initially built over an older transgressive Paleocene prodelta. Sedimentological and geochemical studies have been carried out on the sediments of the Y-field in the Niger Delta Basin with a view to deducing the provenance, palaeodepositional characteristics and tectonic history of the sediments. Twenty-one core samples were collected, washed, dried, grinded, pulverized and subjected to inorganic analysis which includes major oxides, trace elements, and rare earth element. The provenance and prevalent conditions of deposition from various elemental ratios indicate that the Th/U ratio has an average of 4.1 which is very close to that of the upper continental crust of 3.8. The high ratios of Th/Sc and Zr/Sc indicate a slight input of felsic materials from recycled sedimentary provenance. Elevated values of thorium with respect to uranium may imply a felsic source. Th/Sc values for the analyzed samples were in the range of 0.83-2.83, implying a felsic igneous provenance. The same applies for the Th/Co ratio as most of the values are above 0.27 and less than 19.5 (Th/Sc and Th/Co values for felsic rocks are 0.84-20.05 and 0.27-19.5, resp.). From major oxides, it can be concluded that the tectonic setting of the Niger delta is an active continental margin. The trace elements confirmed the tectonic settings of the sediments as active continental margins. The trivariate plots of La-Th-Sc, Th-Sc-Zr/10, and Th-Co-Zr/10 all show the provenance of the sediments to be active continental margins.