Hydrogeochemical Signatures of Different Aquifer Layers in the Crystalline Basement of Oban Area (SE Nigeria)

The shallow and deep aquifer horizons of the crystalline basement of Oban massif of (SE Nigeria) were studied during the dry and wet seasons. The criteria were ascertaining hydrogeochemistry relative to seasonal and spatial variations across the study region. The results obtained show that major elements such as Ca, Mg, Na and K were higher in the shallow aquifers than in the deep aquifers, during the study period. The major anions Cl, SO4, HCO3 and NO3 were higher in the deep aquifers compared to the shallow ones. Two water types were identified for both (shallow and deep) aquifers: Ca/Mg-HCO3 and Ca/Na-Cl/SO4. Most of the water parameters considered was within the international limits for drinking and domestic purposes. Assessment by use of Sodium Absorption Ratio (SAR), percent Sodium (% Na) and the Wilcox diagram reveal that the waters are suitable for irrigation purposes.