Isotopic composition of groundwater of a semi-arid carbonate terrain, Sokoto basin, Nigeria. – S. A .Alagbe, K. Schoeneich and E. C. Ike
A study of the origin and recharge of groundwater in the semi-arid carbonate terrain, Sokoto Basin, northwestern Nigeria was performed with the aid of analyses of the environmental isotopes 18O, 2H, and 3H at the Isotope Hydrology Laboratory, Cairo, Egypt. This carbonate aquifer belongs to the Sokoto Group of sedimentary rocks and is composed of internally karstified Paleocene limestone. Results of the environmental isotopic composition of groundwater from this aquifer have proved infiltration of surface water of meteoric origin which is recharged under the present climatic conditions. The values of D and 18O are characteristics of modern waters from precipitation. The tritium enrichment in this groundwater shows that it is formed mainly after the thermonuclear explosions (the post-bomb) period. Deuterium and oxygen-18 results also indicate that the groundwater was recharged under cool conditions arising from intense evaporation arising from intense evaporation of the infiltrated water.