combined application of electrical resistivity and gis for subsurface mapping and groundwater exploration at el-themed, southeast sinai, egypt

Abstract

The study area is located at south central part of Sinai Peninsula at El-Thamed area. Geoelectrical resistivity method was used by measuring eighteen vertical electrical soundings using the Schlumberger configuration with total current electrode separation ranging between 3 m and 4000 m in order to investigate the deep groundwater aquifer and to delineate the subsurface structures of this area. The geoelectrical cross-sections show that the subsurface section consists of six geoelectrical units. The first unit is Quaternary deposits with thickness ranging from 0.6 m to 30.9 m and the resistivity values ranging from 177 Ohm.m. to 39680 Ohm.m. The second geoelectrical unit is composed of Egma Formation, with thickness ranging from 9.2 m to 12.8 m and the resistivity values ranging between 21 Ohm.m. and 82 Ohm.m. The third geo-electrical unit is composed of Paleocene Esna shale, also not detected at the study area with exception at profile 2, its thickness ranges from 15.6 m to 166.5 m and resistivity range from 8.9 Ohm.m. to 20 Ohm.m. This layer has not been detected at the extremely southern part of this profile, its depth ranges from 9.63 m to 15.5 m. The fourth geoelectrical unit is composed of Nubian Sandstone of Malha Formation (Lower Cretaceous) with depth ranging from 0.5 m to 8.9 m and its resistivity values ranging from 14 Ohm.m. to 133 Ohm.m. This layer represents the main aquifer in the study area with thickness ranging between 14.2 m and 283 m. The fifth geoelectrical unit is composed of claystone of Naqus Formation with depth ranging from 14.2 to 349 m and its resistivity values ranging from 2.7 Ohm.m. to 13 Ohm.m., sometimes, it is extends to the maximum depth of penetration. The sixth geoelectrical unit is composed of Basement rocks. It is characterized by resistivity ranging from 970 Ohm.m. to 25462 Ohm.m. and depth ranging from 60.1 m to 283 m. This unit is detected at the eastern part of the study area. Structurally, the study area is affected by sets of faults trending mainly NE-SW (Aqaba Trend).