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Control of pre-rift lithospheric structure on the architecture and evolution of continental rifts: insights from the Main Ethiopian Rift, East Africa

Control of pre-rift lithospheric structure on the architecture and evolution of continental rifts: insights from the Main Ethiopian Rift, East Africa
Control of pre-rift lithospheric structure on the architecture and evolution of continental rifts: insights from the Main Ethiopian Rift, East Africa
We investigate the along-axis variations in architecture, segmentation and evolution of the Main Ethiopian Rift (MER), East Africa, and relate these characteristics to the regional geology, lithospheric structure and surface processes. We first illustrate significant along-axis variations in basin architecture through analysis of simplified geological cross-sections in different rift sectors. We then integrate this information with a new analysis of Ethiopian topography and hydrography to illustrate how rift architecture (basin symmetry/asymmetry) is reflected in the margin topography and has been likely amplified by a positive feedback between tectonics (flexural uplift) and surface processes (fluvial erosion, unloading). This analysis shows that ~70% of the 500 km-long MER is asymmetric, with most of the asymmetric rift sectors being characterized by a master fault system on the eastern margin. We finally relate rift architecture and segmentation to the regional geology and geophysical constraints on the lithosphere. We provide strong evidence that rift architecture is controlled by the contrasting nature of the lithosphere beneath the homogeneous, strong Somalian Plateau and the weaker, more heterogeneous Ethiopian Plateau, differences originating from the presence of pre-rift zones of weakness on the Ethiopian Plateau and likely amplified by surface processes. The data provided by this integrated analysis suggest that asymmetric rifts may directly progress to focused axial tectonic-magmatic activity, without transitioning into a symmetric rifting stage. These observations have important implications for the asymmetry of continental rifts and conjugate passive margins worldwide.
0278-7407
Corti, Giacomo
dce88b12-5b7a-43b1-8a58-5bd1bc13634c
Molin, Paola
1b4c5002-f845-4eba-bd98-b536763d77cf
Sembroni, Andrea
9cdbc06d-8a1d-4d43-86ea-ec7a1bbac07a
Bastow, Ian D.
7a2698d0-d535-4462-a9a9-0e3293d2d667
Keir, Derek
5616f81f-bf1b-4678-a167-3160b5647c65
Corti, Giacomo
dce88b12-5b7a-43b1-8a58-5bd1bc13634c
Molin, Paola
1b4c5002-f845-4eba-bd98-b536763d77cf
Sembroni, Andrea
9cdbc06d-8a1d-4d43-86ea-ec7a1bbac07a
Bastow, Ian D.
7a2698d0-d535-4462-a9a9-0e3293d2d667
Keir, Derek
5616f81f-bf1b-4678-a167-3160b5647c65

Corti, Giacomo, Molin, Paola, Sembroni, Andrea, Bastow, Ian D. and Keir, Derek (2018) Control of pre-rift lithospheric structure on the architecture and evolution of continental rifts: insights from the Main Ethiopian Rift, East Africa Tectonics (doi:10.1002/2017TC004799).

Record type: Article

Abstract

We investigate the along-axis variations in architecture, segmentation and evolution of the Main Ethiopian Rift (MER), East Africa, and relate these characteristics to the regional geology, lithospheric structure and surface processes. We first illustrate significant along-axis variations in basin architecture through analysis of simplified geological cross-sections in different rift sectors. We then integrate this information with a new analysis of Ethiopian topography and hydrography to illustrate how rift architecture (basin symmetry/asymmetry) is reflected in the margin topography and has been likely amplified by a positive feedback between tectonics (flexural uplift) and surface processes (fluvial erosion, unloading). This analysis shows that ~70% of the 500 km-long MER is asymmetric, with most of the asymmetric rift sectors being characterized by a master fault system on the eastern margin. We finally relate rift architecture and segmentation to the regional geology and geophysical constraints on the lithosphere. We provide strong evidence that rift architecture is controlled by the contrasting nature of the lithosphere beneath the homogeneous, strong Somalian Plateau and the weaker, more heterogeneous Ethiopian Plateau, differences originating from the presence of pre-rift zones of weakness on the Ethiopian Plateau and likely amplified by surface processes. The data provided by this integrated analysis suggest that asymmetric rifts may directly progress to focused axial tectonic-magmatic activity, without transitioning into a symmetric rifting stage. These observations have important implications for the asymmetry of continental rifts and conjugate passive margins worldwide.

Text Corti_et_al-2018-Tectonics - Accepted Manuscript
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Accepted/In Press date: 3 January 2018
Published date: 15 January 2018

Identifiers

Local EPrints ID: 417568
URI: https://eprints.soton.ac.uk/id/eprint/417568
ISSN: 0278-7407
PURE UUID: 3483606d-1f9a-4ffb-b3a6-6befb373c8f0
ORCID for Derek Keir: ORCID iD orcid.org/0000-0001-8787-8446

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Date deposited: 05 Feb 2018 17:30
Last modified: 05 Feb 2018 17:30

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Contributors

Author: Giacomo Corti
Author: Paola Molin
Author: Andrea Sembroni
Author: Ian D. Bastow
Author: Derek Keir ORCID iD

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