EFFECT OF TOPOGRAPHIC AND GEOLOGIC HETEROGENEITIES ON THE DISTRIBUTION PATTERN OF AQUIFERS IN AKWA IBOM STATE, SOUTHEASTERN NIGERIA

Abstract

Geologic heterogeneities and topographic variations in relation to aquifer distribution ad occurrence in Akwa Ibom State have been assessed based on geologic and geophysical studies sixty-six sounding points together with electric log responses of representative wells together with surface geologic data have been integrated and used in deciphering subsurface variations in hydrologic unit in the state. The results show that three aquiferous units, made up of medium to coarse grained whitish sands exist within a depth range of 72 to 98 meters and having resistivities less than 1500 ohm metres. These aquifers are clearly defined in those locations close to the coast and in the hinterlands whereas towards the northern parts of the state they appear to pinch-out or dip downward to much greater depths. Measurements of elevation across the study area show a drastic decrease in altitude tending toward the mean sea level within the hinterland and coastal regions, whereas towards the northern part, relatively higher elevations-exist. The increase in altitude in addition to the occurrence of thick columns of compacted shales greatly account for the scarcity of aquiferous zones in this northern part of the study area contrary to the localities within and surrounding the coastal and central regions.


KEY WORDS: Heterogeneities, aquifer, topography, pinch-out, hydrologic.


Global Jnl Geological Sciences. Vol.2(1) 2004: 125-138