Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

S. C. Garde ¹, E. A. Ojelabi ²

Affiliations
1 Department of Physics, University of Ibadan, Ibadan, NG
2 Department of Physics, Ogun State University, Ago-Iwoye, NG

Abstract

Low-field hysteresis (LFH) loop and relative magnetic susceptibility (RMS) values in a field of 0.5 to 10 Oe has been used to evaluate the stability of magnetic directions of Tertiary basalts from Jos Plateau Nigeria. Graphs of magnetic moments (MM), susceptibility (S) and relative magnetic susceptibility (RMS) against applied field (AF) were plotted. The results showed that in a field of 0.5 to 1.5 Oe, the MM varied linearly with the AF while for Af > 1.5 Oe MM remained approximately constant. Rocks having stable tilted lines without any Rayleigh loop have relative susceptibility values in the range of 0.2 to 0.245 and ≥0.3 at 10 Oe, an indication of their being paiaeomagnetically stable. Rocks having thin Rayleigh loops had corresponding RMS values in the range 0.15 to 0.19. On the other hand wide loops were found to correspond to RMS value in the range ≤0.145.

Keywords

Geophysics, Palaeomagnetism, Tertiary Basalt, Low-Field Hysteresis, Nigeria.

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E. A. Ojelabi ¹, B. S. Badmus ², A. A. Salau ²

Affiliations
1 Geophysics Research Group, Department of Physics, University of Lagos, Lagos, NG
2 Department of Physical Sciences, University of Agriculture, Abeokuta, Ogun State, NG

Abstract

The accuracy of two common electrode arrays - the Wenner and Schlumberger - used in the geoelectric resistivity method for groundwater exploration has been investigated within a typical area of basement complex. The results of the comparative study show that Schlumberger electrode array has a high investigating depth per unit current electrode separation and is more suitable for subsurface delineation and groundwater exploration. The studies have indicated an average depth to basement of 9.75 m, and six geoelectric formations viz Lateritic top-soil, Clay, Clayey sand, Weathered basement, Fractured basement and Fresh basement.

Keywords

Geoelectric Sounding, Wenner and Sclumberger Methods, Groundwater Exploration, Southwestern Nigeria.

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