ELECTRICAL RESISTIVITY INVESTIGATION OF SUBSURFACE STRUCTURES AT THE N.Y.S.C. PROPOSED PERMANENT ORIENTATION CAMP, PAIKO, NIGER STATE

Abstract

Youth Service Corp (N.Y.S.C.) proposed permanent orientation camp, Paiko of Paikoro Local Government Area (L.G.A.), with a view to determine the depth to the bedrock and thickness of the weathered basement. Vertical Electrical Sounding (VES) using Schlumberger electrode array was carried out along five (5) profiles having a total of fifty (50) VES stations. On each profile, were ten (10) VES stations. The inter profiles and inter VES stations were at uniform separation of 80m. The data were acquired using ABEM Terrameter, System Adjusted Signal (SAS) 1000. The field data obtained were analysed and interpreted using computer software (IPI2win and surfer 10) which gave an automatic interpretation of the apparent resistivity data. The IPI2win was used to obtain the sounding curves by plotting graphs of apparent resistivity against half the current electrode spacing log-log scale and to compute the true layered resistivity model from the soundings. Surfer 10 was used to plot the contour maps. Results from the interpretation suggest three (3) layers in most parts of the study area. However, there is a case of two (2) layers at a station (VES A6). The resistivity value for the topsoil varies from 10 to 751Ωm with thickness range from 0.98 to 4.23m (except for VES A6 where the top soil has been probably washed by erosion). The weathered basement has resistivity values ranging from 9 to 968Ωm and thickness of between 0.67 and 24.50m. The fresh basement (bedrock) has resistivity values as high as 2718Ωm.