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| Title: | Blue Nile incision on the Ethiopian plateau: pulsed plateau growth, Pliocene uplift, and hominin evolution |
| Author (s): | Gani, Nahid D.S. Gani, M. Royhan Abdel Salam, Mohamed G. |
| Department/Lab Affiliations: | Geological Sciences & Engineering |
| Keywords: | Ethiopian Plateau |
| Subject Terms: | Blue Nile River (Ethiopia and Sudan) Geology -- Remote sensing. |
| Issue Date: | 2007 |
| Publisher: | Geological Society of America |
| Citation: | Gani, Nahid, M. Royhan Gani, and Mohamed G. Abdelsalam, “Blue Nile Incision on the Ethiopian Plateau: Pulsed Plateau Growth, Pliocene Uplift, and Hominin Evolution.” GSA Today, vol. 17, no. 9, September 2007, pp. 4-11. |
| Abstract: | The 1.6-km-deep Gorge of the Nile, a rival of the Grand Canyon, resulted from the deep incision of the Blue Nile drainage into the uplifted Ethiopian Plateau. Understanding the incision history of the plateau is crucial to unraveling the Cenozoic tectonoclimatic evolution of the region, particularly because the region has long been used as a natural laboratory to understand the geody-namics of continental rifting and the evolution of hominins. We undertake a quantitative geomorphologic approach integrating field, geographic information system (GIS), and digital elevation model (DEM) data to analyze incision (volume, long-term rates, and spatiotemporal variability) and river longitudinal profiles of the Blue Nile drainage. Previously published isotopic ages of the Cenozoic volcanic rocks are used to constrain long-term incision rates through geologic time. Our data argue that (1) the Blue Nile drainage has removed at least 93,200 km3 of rocks from the northwestern Ethiopian Plateau since ca. 29 Ma (early Oligocene) through a three-phase (ca. 29–10 Ma, ca. 10–6 Ma, and ca. 6 Ma to present) incision, where long-term incision rates increased rapidly and episodically in the late Miocene (ca. 10 Ma and ca. 6 Ma); (2) being out-of-phase with the past climatic events and in-phase with the main volcanic episodes of the region, this episodic increase of incision rate is suggestive of episodic growth of the plateau; (3) of the ~2-km rock uplift of the plateau since ca. 30 Ma, 0.3 km was due to isostatic uplift related to erosional unloading, and the rest was due to other tectonic activities; (4) the extremely rapid long-term incision rate increase, thus a rapid uplift of the plateau, ca. 6 Ma might be related to lithospheric foundering, caused by ponded plume material beneath the Ethiopian Plateau and aided by huge tectonic stresses related to the Messinian salinity crisis of the Mediterranean Sea. These events could have caused the plateau to rise >1 km within a few m.y. in the early Pliocene. This uplift history of the Ethiopian Plateau can shed critical light on the geo-dynamics of the Afar mantle plume and the evolution of the East African hominins via climate change. |
| Type: | Article - Journal text |
| In Title: | GSA Today |
| Copyright Notice: | Pre-print: archiving status unclear; Post-print: author cannot archive; This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder. FULL COPYRIGHT INFORMATION: |
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| title | Blue Nile incision on the Ethiopian plateau: pulsed plateau growth, Pliocene uplift, and hominin evolution |
| contributor.author | Gani, Nahid D.S. |
| contributor.author | Gani, M. Royhan |
| contributor.author | Abdel Salam, Mohamed G. |
| contributor.deptlab | Geological Sciences & Engineering |
| contributor.sponsor | Ethiopian Geological Survey |
| contributor.sponsor | Geosciences Department, University of Texas at Dallas |
| contributor.sponsor | National Science Foundation |
| subject | Ethiopian Plateau |
| subject.LCSH | Blue Nile River (Ethiopia and Sudan) |
| subject.LCSH | Geology -- Remote sensing. |
| date.issued | 2007 |
| publisher | Geological Society of America |
| identifier.citation | Gani, Nahid, M. Royhan Gani, and Mohamed G. Abdelsalam, “Blue Nile Incision on the Ethiopian Plateau: Pulsed Plateau Growth, Pliocene Uplift, and Hominin Evolution.” GSA Today, vol. 17, no. 9, September 2007, pp. 4-11. |
| identifier.pub.URI | |
| description.abstract | The 1.6-km-deep Gorge of the Nile, a rival of the Grand Canyon, resulted from the deep incision of the Blue Nile drainage into the uplifted Ethiopian Plateau. Understanding the incision history of the plateau is crucial to unraveling the Cenozoic tectonoclimatic evolution of the region, particularly because the region has long been used as a natural laboratory to understand the geody-namics of continental rifting and the evolution of hominins. We undertake a quantitative geomorphologic approach integrating field, geographic information system (GIS), and digital elevation model (DEM) data to analyze incision (volume, long-term rates, and spatiotemporal variability) and river longitudinal profiles of the Blue Nile drainage. Previously published isotopic ages of the Cenozoic volcanic rocks are used to constrain long-term incision rates through geologic time. Our data argue that (1) the Blue Nile drainage has removed at least 93,200 km3 of rocks from the northwestern Ethiopian Plateau since ca. 29 Ma (early Oligocene) through a three-phase (ca. 29–10 Ma, ca. 10–6 Ma, and ca. 6 Ma to present) incision, where long-term incision rates increased rapidly and episodically in the late Miocene (ca. 10 Ma and ca. 6 Ma); (2) being out-of-phase with the past climatic events and in-phase with the main volcanic episodes of the region, this episodic increase of incision rate is suggestive of episodic growth of the plateau; (3) of the ~2-km rock uplift of the plateau since ca. 30 Ma, 0.3 km was due to isostatic uplift related to erosional unloading, and the rest was due to other tectonic activities; (4) the extremely rapid long-term incision rate increase, thus a rapid uplift of the plateau, ca. 6 Ma might be related to lithospheric foundering, caused by ponded plume material beneath the Ethiopian Plateau and aided by huge tectonic stresses related to the Messinian salinity crisis of the Mediterranean Sea. These events could have caused the plateau to rise >1 km within a few m.y. in the early Pliocene. This uplift history of the Ethiopian Plateau can shed critical light on the geo-dynamics of the Afar mantle plume and the evolution of the East African hominins via climate change. |
| type | Article - Journal |
| type.DCMIType | text |
| rights | Pre-print: archiving status unclear; Post-print: author cannot archive; |
| rights | This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder. |
| rights.URI | |
| relation.isPartOf | GSA Today |
| date.accessioned | 2008-09-19T21:09:59Z |
| date.available | 2008-07-24T18:29:40Z |
| identifier.persist.URI |