Geochemical and Grain-size Analysis of Salt-bearing Sediments from Nasarawa Area of North-central Nigeria

Abstract

Sediments belonging to the Keana Formation outcropping at Keana, Ribi and Azara areas of Nasarawa State, North-central Nigeria were mapped and sampled for granulometric and petrographic studies. This is necessary considering the domestic and industrial application of halide. The particle size distribution curves of the locations show that the area is dominated by fine to medium grained sand and this implies deposition in low to medium energy environment. Sediments range from poorly sorted to moderately sorted. This histogram plot of the percentage mass of sediments retained showed unimodal distribution pattern indicating deposition in fluvial environment. Petrographic studies on the sandstone show that the dominant mineral in the salt-rich sediment are sodium and chlorine thereby indicating marine flooding of the environment. Chemical analysis of the sediments also revealed an appreciable mean concentration of 235.0 mg/l and 226.0 mg/l for chlorine and sodium respectively. The total organic carbon (TOC) ranges from 0.64 to 1.02 corresponding to fair to good, which suggests that the Keana, Ribi and Azara shales are good source rocks and have good potential for hydrocarbon generation upon thermal maturity. The pH values vary from 4.5 to 4.8 signifying an acidic environment while the temperature ranged between 26.0oC and 28.0oC. The Na/Cl ratio indicates no negative effect for agricultural purposes.