The Role of a Multi-Sensory Geophysical Survey to Unravel the Igneous Intrusions Controlling a Groundwater Aquifer in Saint-Katherine Area, Sinai, Egypt

Abstract

The success of integrated seismic refraction, ground mag- netic, and resistivity sounding techniques is demonstrated in de- lineating the actual setting of a wadi fill groundwater aquifer lying within Wadi El-Sheikh, Southern Sinai, Egypt. This aquifer, that is underlain by granitic basement rocks, has long been mistakenly thought to be controlled by a series of intrusive basic dykes cutting across the wadi fill, representing the main water aquifer body, thus controlling the groundwater level and hence its direction of flow. Such erroneous conclusions are the result of relying only on surface geological observations and on improper choice and inaccurate inter- pretation of geophysical data. The inversion of seven compressional-wave seismic refraction pro- files, using the reciprocal-time approach; nine closely spaced ground magnetic profiles, using the 21⁄2-D magnetic modelling; and six re- sistivity soundings, using the automatic iterative techniques, has inferred the basic intrusions as a high velocity and high magnetic susceptibility material in contrast to the alluvial material constituting the wadi fill. The integrated interpretation of geophysical results has revealed that the surface-exposed basic rocks are found underlain the wadi sed- iments in the subsurface across the investigated wadi. This indicates that, these dykes, in fact, play no role either in determining the aquifer configuration or in controlling the groundwater flow direction in the examined part of the wadi.