HR: 0830h
AN: H51A-09    [Abstracts]
TI: Empirical analysis of electromagnetic profiles for groundwater prospecting in rural areas of Ibadan, southwestern Nigeria
AU: * Ehinola, O A
EM: oa.ehinola@mail.ui.edu.ng
AF: University of Ibadan, Departmnet of Geology, University of Ibadan, Ibadan, Oyo 200005 Nigeria
AU: Opoola, A O
EM: Gbengafel@hotmail.com
AF: University of Ibadan, Departmnet of Geology, University of Ibadan, Ibadan, Oyo 200005 Nigeria
AB: The Slingram electromagnetic (EM) survey using a coil separation of 60 and 100 meters was carried out in 10 villages in Akinyele area of Ibadan, southwestern Nigeria to aid in the development of groundwater. Five main rock types including an undifferentiated gneiss complex (Su), biotite-garnet schist/gneiss (Bs), quartzite and quartz schist (Q), migmatised undifferentiated biotite/hornblende gneiss (M) and pegmatite/quartz vein (P) underlie the study area. A total of 31 EM profiles was made to accurately locate prospective borehole sites in the field. Four main groups with different behavioural pattern were categorized from the EM profiles. Group 1 is characterized by high density of positive (HDP) or high density of negative (HDN) real and imaginary curves, Group 2 by parallel real and imaginary curves intersecting with negligible amplitude (PNA), Group 3 by frequent intersection of high density of negative minima (FHN) real and imaginary curves, and Group 4 by separate and approximately parallel (SAP) real and imaginary curves. Qualitative pictures of the overburden thickness and the extent of fracturing have been proposed from these behavioural patterns. A comparison of the borehole yield with the overburden thickness and the level of fracturing show that borehole yield depends more on the fracture density than on the overburden thickness. Asymmetry of the anomaly was also found useful in the determination of the inclination of the conductor/fracture.
DE: 0600 ELECTROMAGNETICS
SC: Hydrology [H]
MN: 2005 Joint Assembly