ABSTRACT
A 2-D resistivity survey was carried out in Abudu, Edo State, a sedimentary terrain of South-South Nigeria. The wenner alpha electrode configuration was engaged through out in this study. Three lines were taken at Girl’s Model Secondary School, Orhionmwon area of Abudu, Edo state. To obtain a good 2-D picture of the subsurface, the coverage of the measurements must be 2-D as well. The equipment used to take the resistivity values was the Pasi Earth Resistivity meter. The data from each 2-D survey line was inverted independently with RES2DINV to give 2-D cross-sections with RMS error of 8.15%.
A contoured pseudosection conveys a qualitative two- dimensional resistivity variation with depth within the subsurface. The inversed model resistivity sections created models for the subsurface resistivity using an iterative smoothness constrained least square inversion and are interpreted to generate the subsurface geologic characteristics.
Results from 2-D inversed resistivity section showed that the first line with resistivity of laterites ranges from 800-1500Ω, while that of lateritic soils ranges from 120-750Ωm from depth 2-10m. It can seen that the resistivity of the sub-surface soils corresponds with the resistivity of laterites, thereby confirming the existence of laterites deposits in the survey area. From the resistivity block section obtained from line 2, it can be seen that the survey area is rich in laterite deposits and lateritic soils, the top of the soil is composed of laterites and as we go deeper, it becomes lateritic soil because of the increase in the composition of non-lateritic materials with depth. From the resistivity block section obtained from line 3, it can be inferred that the surface of the survey area has slight deposits of laterites and a minimal deposits of lateritic soils. The resistivity value of laterites falls between 800-1500Ωm, which can clearly be seen from the block section of line 3. Thus the survey area has scanty and sparse distribution of laterites and lateritic soils deposits at depth 0-5m.
