Sultana, D. Nahid1, Mohamed G. Abdelsalam1
(1) The University of Texas at Dallas, Richardson, TX
ABSTRACT: Multi-Spatial Resolution Digital Elevation Models for Studying the Evolution of Complex Drainage System: The Gorge of the Nile, Ethiopia
One of the recent advances in Remote Sensing is the availability of Digital Elevation Models (DEMs) from the Shuttle Radar Topography Mission (SRTM) with 30m x-y resolution that are subsequently re-sampled to 90m, and the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) with 15m x-y resolution. These data have been of significant importance for studying regional geological and geomorphological features such as the Gorge of the Nile in Ethiopia. We used these data to extract geological and geomorphological information to understand the geometrical characteristics of the Gorge of the Nile and its evolution within regional tectonic framework, especially the Afar Depression and the Main Ethiopian Rift. The Blue Nile on the Ethiopian Plateau originates from a small spring located ~1850m above MSL and drains into Lake Tana at ~1829m above MSL. The river flows SE (gradient ~4m/km) after leaving Lake Tana, then S and SW before flowing NW with a dramatic drop in gradient (~0.4m/km). Hence, the river forms a near-circular loop (the Blue Nile Bend) by carving ~1.5km deep gorge and exposes ~1500m thick Mesozoic strata. 3D DEMs allow us to characterize the spatial relationship between the river and regional geomorphological features such as obstacle relief formed by Pliocene to Recent shield volcanoes. We conclude that the river was once flowing SE confined between Pliocene to Recent shield volcanoes before being forced to flow S, SW and NW due to flexural uplift on the western flank of the Afar Depression and the Main Ethiopian Rift at ~1 Ma.
AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.