Morpho-tectonic analysis of the Tekeze River and the Blue Nile drainage systems on the Northwestern Plateau, Ethiopia

作者：Ismail Elamin H; Abdelsalam Mohamed G^*

来源：Journal of African Earth Sciences, 2012, 69: 34-47.

DOI：10.1016/j.jafrearsci.2012.04.005

• Morpho-tectonics
• Ethiopian Plateau
• Tekeze River
• Blue Nile

This study examines the morpho-tectonic evolution of the drainage system in the Northwestern Plateau in Ethiopia dominated by the Tekeze River and the Blue Nile. The Northwestern Plateau is underlain by Precambrian crystalline rocks, followed by Mesozoic sedimentary section and topped with Oligocene-Quaternary volcanic rocks. The plateau is bounded in the east and southeast by the Afar Depression and the Main Ethiopian Rift, respectively. Digital Elevation Models (DEMs) from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and the Shuttle Radar Topography Mission (SRTM) data are analyzed to extract morpho-tectonic parameters including the Normalized Steepness Index (K-sn), the Concavity (0) and the Regression Fit (r(2)) between the observed and predicted channel profiles from the sub-basins and the tributaries of the Tekeze River and the Blue Nile. Analysis of these morpho-tectonic parameters has shown that the evolution of the drainage systems on the Northwestern Plateau was influenced by three tectonic and geological events. The first event resulted in a broad and regional uplift of the plateau, most likely due to the rise of the Afar mantle plume similar to 30 Ma. This regional uplift was accompanied by moderate incision rate of the Tekeze River and the Blue Nile drainage systems within the entire Northwestern Plateau. The second event, which was in the form of shield volcanoes build-up, occurred at 22 Ma and resulted in localized increase in the incision rate around these volcanoes. The third event is manifested by rift-flank uplift at 11 Ma on the western escarpments of the Afar Depression and the northwestern escarpments of the Main Ethiopian Rift. This event resulted in an increase in the incision rate of the Tekeze River and the Blue Nile drainage systems, but this increase seems to diminish towards the west and northwest leaving the drainage systems in the lower reaches of the two rivers relatively tectonically undisturbed, hence allowing for the establishment of a long-lived hydrological stability.

• 出版日期2012-7-6