In contrast to the VES data, the VLF traverses in the southern
zone look at least qualitatively similar to the traverses in the central
and northern zone. This is presumably due to VLF's relative
insensitivity to the degree of fracturing below ~16 m depth. Unfortunately
no data were available to directly test the hypothesis
that VLF anomalies arise from preferential fracturing in wadi and
shallow basement deposits. From the complexities in the relationship
between coincident VLF and VES data, we postulate that
the VLF eddy currents and VES direct currents sampled different
volumes, and/or that heterogeneities in fracture azimuths drive
differing responses in the two methods. Of the two methods, VES
was clearly more useful in well site selection, and the results reported
here support of use of resistivity soundings or profiles as a
fundamental reconnaissance tool for basement aquifer exploration
on the Arabian Shield and in geologically similar settings. Additional
well data would be needed to understand the source of VLF
anomalies.