GEOPHYSICAL SITE INVESTIGATION OF THE FEDERAL COLLEGE OF EDUCATION, ZARIA, NIGERIA

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Date
1999-08
Authors
OLATUNJI, SAMINU
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Abstract
A comprehensive geophysical survey was carried out over the premises of the Federal College of Education, Zaria, with a view to investigating the depth to basement, depth to and thickness of aquifer, depth to and thickness of the weathered basement as well as the subsurface structural systems such as the fractures and faults. The D.C. Resistivity and VLF methods were employed to accomplish the study. The conventional vertical Electrical Sounding (VES) using Schlumberger array was carried out at 40 stations, 8 of which were Radial stations with 4 profiles per station. So a total of 64 profiles were sounded. VLF data were taken from all the VES stations as well. ABM Terrameter (SAS 300P) was used to collect resistivity data while EM/6 VLF equipment was used to collect the VLF data. Results from the interpretation of the data collected suggest 3 layers in most parts of the area studied. However, there are cases of 2 layers. The resistivity value for the first layer (topsoil) varies from 30 to 300 ohm-meters with thickness ranging between 3.5 and 14 m. The second layer (weathered basement) has resistivity values of 84 to 480 ohmmeters and thickness of between 9 and 36.5 meters. Its depth varies from 5 to 14 meters. The third layer appeared to be the bedrock with the resistivity value as much as 3000 ohmmeters in some locations. Towards the eastern part of the study area, the fresh bedrock records the greatest depth of about 40.1 m. The depth of aquifer ranges from 1.5 to 4.0 meters while its thickness ranges from 5 to 14 m. Further, the geologic sections derived in this work together with the aquifer plots suggest that weathered basement in the area does not entirely represent a promising aquifer for the fact that in some cases, aquifers occurred both in the topsoil and in the weathered basement while it disappeared in some areas of weathered basement. Radial sounding plots revealed the existence of anisotropics, trending NE-SW, NVV-SE and E - W directions. The VLF interpretations similarly indicated the presence of vertical contact or fractures zones which is more pronounced towards the western part of the survey area. The highest conductivity in the area occurs towards the west as can be seen from VLF plots. There is hence a strong water-bearing potential within the subsurface rocks in this part of the study area.
Description
A THESIS SUBMITTED TO THE POSTGRADUATE SCHOOL, AHMADU BELLO UNIVERSITY, ZARIA IN PARTIAL FULFILMENT, OF THE REQUIREMENTS FOR THE AWARD OF THE DEGREE OF MASTER OF SCIENCE IN APPLIED GEOPHYSICS DEPARTMENT OF PHYSICS FACULTY OF SCIENCE AHMADU BELLO UNIVERSITY ZARIA
Keywords
GEOPHYSICAL,, FEDERAL COLLEGE OF EDUCATION, ZARIA, NIGERIA
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