Abstract

The concentration or ratio of redox-sensitive trace elements is one of the frequently applied redox conditions indicators in both contemporary and prehistoric sedimentary rocks. This work was carried out basically to establish paloe-redox condition of deposition and to classify the sandstones in the wells. Geochemical investigation was performed on sediments obtained from NS-1 and NS-2 wells in the Coastal Swamp Depobelt of the Niger Delta Basin. The samples were analyzed using XRF and ICP-MS techniques. The classification of the sandstone facies in NS-1 and NS-2 wells was done by plotting Log (SiO2/Al2O3) against Log (Fe2O3/K2O). Also, Log (SiO2/Al2O3) was plotted against Log (Na2O/K2O). The two wells yielded information on ten major and forty-three trace elements. The ratios of Ni to Co, V to Cr and U to Th were determined to ascertain the paleo-redox condition of deposition. In the wells, Ni to Co ratio spans from 2.38 to 5.26 (NS-1) and 2.48 to 4.62 (NS-2), the U to Th ratio runs from 0.19 to 0.28 (NS-1) and 0.17 to 0.27 (NS-2), while V to Cr ratio ranges from 0.55 to 2.68 (NS-1), and 0.37 to 3.83 (NS-2). The ratios in both wells suggest deposition in an oxic environment. The sandstones penetrated by NS-1 and NS-2 wells were primarily in the sublitharenite and quartz arenite domain.

Keywords: Facies, Sandstones, Arenites, Depobelt