Rift deflection, migration, and propagation: Linkage of the Ethiopian and Eastern rifts, Africa

Abstract

Research Article| February 01, 2000 Rift deflection, migration, and propagation: Linkage of the Ethiopian and Eastern rifts, Africa C. J. Ebinger; C. J. Ebinger 1Department of Geology, Royal Holloway, University of London, Egham TW20 0EX, United Kingdom Search for other works by this author on: GSW Google Scholar T. Yemane; T. Yemane 2Ethiopian Institute of Geological Surveys, Addis Ababa, Ethiopia3Department of Earth Sciences, Open University, Milton Keynes MK7 6AA, United Kingdom Search for other works by this author on: GSW Google Scholar D. J. Harding; D. J. Harding 4NASA Goddard Space Flight Center, Greenbelt, Maryland 20771 Search for other works by this author on: GSW Google Scholar S. Tesfaye; S. Tesfaye 2Ethiopian Institute of Geological Surveys, Addis Ababa, Ethiopia5Department of Geological Sciences, University of Colorado, Boulder, Colorado 80305 Search for other works by this author on: GSW Google Scholar S. Kelley; S. Kelley 3Department of Earth Sciences, Open University, Milton Keynes MK7 6AA, United Kingdom Search for other works by this author on: GSW Google Scholar D.C. Rex D.C. Rex 6Department of Earth Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom Search for other works by this author on: GSW Google Scholar GSA Bulletin (2000) 112 (2): 163–176. https://doi.org/10.1130/0016-7606(2000)112<163:RDMAPL>2.0.CO;2 Article history received: 22 Oct 1997 rev-recd: 28 Feb 1998 accepted: 01 Apr 1999 first online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation C. J. Ebinger, T. Yemane, D. J. Harding, S. Tesfaye, S. Kelley, D.C. Rex; Rift deflection, migration, and propagation: Linkage of the Ethiopian and Eastern rifts, Africa. GSA Bulletin 2000;; 112 (2): 163–176. doi: https://doi.org/10.1130/0016-7606(2000)112<163:RDMAPL>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The Main Ethiopian and Eastern (Gregory) rifts, sectors of the East African rift system, overlap in a 300-km-wide system of extensional basins that is more than three times the breadth of either rift away from the zone of overlap. The oldest volcanic rocks (Eocene) and possibly the oldest rift basins (Oligocene) of the East African rift system occur in this zone of overlap. The objectives of field, remote sensing, and geochronology (K-Ar and 40Ar/39Ar) studies in southwestern Ethiopia were to establish a chronology of rifting and volcanism in the zone of overlap, and to correlate stratigraphic sequences with those in the Kenya rift to the south and in the Main Ethiopian rift to the north. Field observations and cross sections show that basins are bounded by steeply dipping faults, stratal dips are <30°, and that extension accommodated by the intrusion of dikes is volumetrically insignificant. Thus, the style of faulting is similar to that elsewhere in East Africa south of the Afar rift. Initial volcanism between ca. 45 and 33 Ma preceded faulting and uplift, except for reactivation of some Mesozoic rift structures near the Sudan-Ethiopia border and in northern Kenya. Extensional basins began to form in late Oligocene time in the Eastern rift, and in early Miocene time in the Main Ethiopian rift. Small degrees of extension and associated volcanism in the broadly rifted zone may have been triggered by extension in the Red Sea, as well as by lithospheric heating above a mantle plume. The anomalous breadth of the zone is a consequence of rift propagation and migration, rather than basin-and-range–style extension; both the Main Ethiopian rift and Eastern rifts have propagated along north-south lines, and the Eastern rift has migrated ∼200 km eastward since late Oligocene time. The distribution of seismicity and Quaternary volcanism suggest that the Eastern and Main Ethiopian rifts are currently linked across a 200-km-wide zone between the Omo and Segen basins. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.