EOPHYSICAL STUDIES OF SUBSURFACE STRUCTURES AND GROUNDWATER POTENTIALITIES IN BILBIES AREA-EGYPT

Abstract

Within the frameworof the government efforts to develop the desert areas, great efforts are being paid to convert portions of the desert area into productive land, especially with the distinct increase in population, agricultural and industrial developments. • Bilbies area is considered as one of the most promising areas for agricultural and industrial projects. The area of study lies between latitudes 30° 20' & 30° 30' N. and betweelongitudes 31 o 30' & 31o 40' E. In addition to Ismailia Canal, which is the main source for surface water in this area, the groundwater resources play an important role in the development plan especially in desert areas far from Ismailia Canal. The present work aims to study the geological, hydrogeological and structural conditions, that arprevailing throughout the area and controlling the groundwater occurrences in this area. Three geophysical methods have been used to achieve the target of this study by applying the following procedures: -Measuring the total intensi):y magnetic field at 455 land stations distributed I throughout the area in a grid,-like pattern as can as possible to cover the whole area with a spacing of about SOO m between each adjacent two points. -Measuring the values of the. gravitational field through 471 stations distributed at the same locations of the magnetic observation points. -Measuring the apparent 1 resistivity values through 32 YESes using Schlumberger array. These ESes are arranged in the form of a grid with a spacing of about 1000 m to cover the whole area with a maximum current electrode separation AB=lOOO m. The land magnetic data are corrected for the time variations. These corrected data are gridded and contoured by using Geosoft programs (1994) to give the total intensity maghetic map. The total intensity magnetic map of the I studied area is first reduced to the magnetic pole to eliminate the distortions occurred in the distribution of the existed magnetic anomalies, due to the inclination of the measured normal magnetic field. By this way, the magnetization vector of the transformed magnetic data becomes vertical and consequently more expressite about the causative magnetic sources in the area. The output is the RTP magnbtic map. The qualitative interpretation of the magnetic data includes the description of the shapes, sizes, trends and polarities of the magnetic anomalies. In addition, The RTP map is separated into regional and residual anomalies by using Geosoftlprograms (1994). The regional magnetic anomalies strongly revealed the deep-Jeated causative magnetic elements (basement), and the residual magnetic anomalies reflected the shallow-seated magnetic effects, especially those of the basaltic sheets and structural features.