ROLE OF REGIONAL STRUCTURES ON SURFACE AND SUBSURFACE WATER FLOW IN EASTERN QATTARA DEPRESSION, WESTERN DESERT, EGYPT

Qattara is the largest of seven depressions of Western Desert of Egypt. About 19,605 km2 of the Qattara Depression are below sea level, with the lowest elevation of -134 meters. Geological and geophysical investigations in this Depression have identified buried stream channels, the origin of these fluvial systems as well the origin of the depression is still unresolved. Dune fields on the downwind flanks of the depressions indicate that deflation has played a part in their formation, but they also may be manifestations of old drainage system involving extensive erosion and, possibly, some tectonic activity. The Qattara Depression has been suggested to be, at least in part, a karst feature related to the Messinian low-stand of the Mediterranean.

In this study remote sensing data were used to identify buried fluvial channels and fractures\faults. Most of the surface fractures\faults of the study area trend NE-SW and NW-SE directions. GPR surveys were conducted to confirm presence of these channels. The migrated 2D GPR profiles together with field observations identified a major paleochannel distributary system with numerous minor channels at its margins. Potential field data were used to probe deeper subsurface. Magnetic data recognize two aquifer systems; deeper saline-water-bearing (Mesozoic-Paleozoic Nubian sandstone) and shallow fresh-water-bearing (Lower Miocene Moghra sandstone) aquifer systems. Both these aquifer systems are controlled by regional structures. Results of gravity data demonstrate presence of shallow faults and density interfaces in the sedimentary cover overlying the basement rocks. The trend of these shallow structures (faults) agrees with the flow direction of the paleochannel system identified. This work contributes to the reconstruction of paleo drainage of this region and raises a possibility that tectonics may have contribution to the surface and subsurface water flow in eastern Qattara Depression.