afar logo

East-Central Afar Rift

Geology of the East-Central Afar Rift

The East Central Afar region is bounded by the Tendaho–Gobaad Discontinuity (TGD) in the west and southwest, the Ali-Sabieh Block in the southeast and the southern end of the Danakil Block in the east. Quaternary extension is distributed across the whole area with many faults in a variety of orientations forming, narrow, overlapping, northwest-southeast trending basins. The area is dominated by the Plio-Pleistocene Afar Stratoid Series with only minimal Quaternary magmatism and has an average crustal thickness of about 25km (Hayward & Ebinger, 1996).

The East Central Afar region consists of two major rift systems: in the east is the northwest propagating Ghoubbet–Asal–Manda Inakir rift system which links to the Gulf of Aden through the Gulf of Tajura and in the west is the southeast-propagating Manda Hararo–Gobaad rift which links with the rift systems in Northern Afar (Courtillot et al, 1984; Dauteuil et al, 2001; Beyene & Abdelsalam, 2005). The Ghoubbet–Asal–Manda Inakir rift began to open about 1Ma and propagation has been episodic with alternating phases of magmatic and tectonic activity (Courtillot et al, 1984; Doubre et al, 2007b).

The area between the two rift systems is known as the East-Central block and has undergone clockwise rotation and northeast-southwest directed extension due to the differential spreading rates of the rift systems (e.g. Beyene & Abdelsalam, 2005 and refs therein). It is characterized by a series of major grabens such as the northwest-southeast trending Dobi graben (photo 1). Strain across the Dobi graben is accommodated on high angle normal faults and sinistral strike-slip faults (Hayward & Ebinger, 1996; Beyene, 2004). It was the site of a swarm of shallow earthquakes in 1989. To the northwest it dies out into a zone of diffuse faulting and to the southeast is a transfer zone of relay ramps to another rift segment (Hayward & Ebinger, 1996).

The TGD in the south forms a boundary across which there is a sudden change from rapid northeast-southwest directed extension in the Northern and East Central Afar regions to slow WNW-ESE directed extension in Southern Afar and the Main Ethiopian Rift (Hayward & Ebinger, 1996).

Top: Dobi graben bound by normal faults cutting through the Afar Stratoid Series. The pale brown/white deposits are evaporites. Photo by Lorraine Field, University of Bristol, 2008.


Geology of Afar Depression

Northern Afar Rift

Southern Afar Rift

Structural Geology of the Afar Region

 

 

Home Page

   
Copyright - Privacy Statement - Site Map