STRUCTURAL CONTROLS OF THE EGYPTIAN NILE

We have used remote sensing analysis of Landsat Thematic Mapper (TM) images and digital elevation models (DEMs) extracted from the Shuttle Radar Topography Mission (SRTM) data to examine structural controls of the Egyptian Nile between Aswan and Kom Ombo. We have generated three-dimensional (3D) perspective views that are subsequently used to construct structural maps and geological cross-sections of the region. It was only 800,000 years ago that the Egyptian Nile connected to the rest of the Nile System which drained sub-Sahara Africa. Prior to this time the Egyptian Nile developed independently, where it evolved through 8 phases: Pre-Eonile (<6Ma), Eonile (6.0-5.4 Ma), Gulf Phase (5.4-3.3 Ma), Paleonile Phase (3.3-1.8 Ma), Desert Phase (1.8-0.8 Ma), Prenile Phase (0.8-0.4 Ma), Neonile Phase (400,000-12,000 years) and Modern Nile (12,000 years -Present). The pre-Eonile phase is characterized by W and NW-flowing drainage that is clearly superimposed by drainage of a subsequent Egyptian Nile phase that coincide with the present Nile. Our analysis indicate the following: (1) The course of this part of the Egyptian Nile can be approximated by right-stepping segments estimated to be 15 km long in average. These segments are controlled by discrete NNW-trending grabens that are 1 to 3 km wide and deform Late Cretaceous sandstones. We name these structures the Nubian Grabens. We suggest that these grabens are filled with 300 m thick sediments representing different phases of the Nile starting with the Eonile. The NNW-trending grabens are connected with NE-trending cross faults which themselves control the course of the Nile when flowing in a northeast direction. The chronological relationship between the two fault sets is not clear, but they might have evolved synchronous with each other. (2) The structurally-controlled NNW- and NE-flowing course of the Nile was superimposed on the pre-Eonile drainage represented by the Wadi Abu Subeira drainage system. This drainage seems to be geomorphologically-controlled east of the Nile, but structurally-controlled to the west where it coincides with a crescent-shape NW-trending graben. (3) The Egyptian Nile seems to separate two distinct structural domains in which the eastern side shows multi-directional faults while the western side is dominated by NNW- and NE-trending faults.