Integrated geophysical interpretation and hydrogeochemistry investigation for groundwater aquifer assessment at El – Farafra depression, Western Desert, Egypt

ABSTRACT The aeromagnetic data is utilised to determine the depth of the crystalline (basement) rocksand subsurface structures where the basement depth ranges from 1777 - 3778 m .and thearea is dissected by several faults with various trends, especially in the NNW-SSE direction. The well-logging data is used to investigate the subsurface stratigraphy where theinterpretation of well-logging data indicates that the area is composed of seven geologicunits, with the third, fifth, and seventh units representing the main aquifer. The first zone ofthe Nubian sandstone aquifer is represented by the sandstone that makes up the thirdgeologic unit with a low gamma ray, which is sandwiched by clay layers. The Nubiansandstone aquifer's second zone is represented by the fifth geologic unit, which is composedof sandstone with minor clay layers. It exhibits low to modest gamma-ray values andmoderate to high resistivity values. The seventh geologic unit is composed of sandstone andrepresents the third zone of the Nubian sandstone aquifer, which is sandwiched by claylayers. It has high resistivity values and a low gamma-ray. The aquifer in the study area hastransmissivity and belongs to a high-potential aquifer.The aquifer in the study area has transmissivity and belongs to a high potential aquiferV.