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 3m and 4000m 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 0.6m to 30.9m and the resistivity values ranging from 177Ohm.m. to 39680Ohm.m. The second geoelectrical unit is composed of Egma Formation, with thickness ranging from 9.2m to 12.8m and the resistivity values ranging between 21Ohm.m. and 82Ohm.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 15.6m to 166.5m and resistivity range from 8.9Ohm.m. to 20Ohm.m. This layer has not been detected at the extremely southern part of this profile, its depth ranges from 9.63m to 15.5m. The fourth geoelectrical unit is composed of Nubian Sandstone of Malha Formation (Lower Cretaceous) with depth ranging from 0.5m to 8.9m and its resistivity values ranging from 14Ohm.m. to 133Ohm.m. This layer represents the main aquifer in the study area with thickness ranging between 14.2m and 283m. The fifth geoelectrical unit is composed of claystone of Naqus Formation with depth ranging from 14.2 to 349m and its resistivity values ranging from 2.7Ohm.m. to 13Ohm.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 970Ohm.m. to 25462Ohm.m. and depth ranging from 60.1m to 283m. 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).