Geophysical Investigation of Nsukka Area, Using Gravity Method

Abstract

Gravity method was used in this work to map the survey area and to obtain the causes of the observed anomalies in the area. Digitized airborne gravity data were obtained over Nsukka area from Nigeria Geological Survey Agency (NGSA). The data were processed and reduced to a format suitable for interpretation by the following methods: vertical derivative, downward continuation and analytic signal. Some portions of the survey area were modelled. From the model, the densities of the anomalous bodies were 1.498, 3.523, 2.508, 4.127, and 3.707g/cm3 located at depth of about 923, 604, 268, 815, and 1893m respectively. The densities indicate clay, sandstone and ironstone located at those various depths. Density of 1498kg/m3 corresponds to clay material located at depth of about 923m from the surface. The densities of 3523, 4127 and 3707kg/m3 correspond to that of ironstone located at depths of about 604, 815 and 1893m respectively from the surface. The density of 2508kg/m3 corresponds to sandstone located at the depth of about 268m below the surface; this represents the most prolific aquifer in the study area. The depth estimated using Euler method ranged between 89.13m and 2296.92m. This shows that some parts of the study area may have possible potential for hydrocarbon accumulation (depth of about 2.2km).