|
|
 |
|||||||||||||||||
|
|||||||||||||||||
 |
|||||||||||||||||
| JOURNAL HOME | HELP | CONTACT PUBLISHER | SUBSCRIBE | ARCHIVE | SEARCH | TABLE OF CONTENTS |
,1,2
,3
1 Department of Earth and Atmospheric Sciences, St. Louis University, St. Louis, Missouri 63103, USA
2 NASA (National Aeronautics and Space Administration), Goddard Space Flight Center, Geodynamics Branch, Greenbelt, Maryland 20771, USA
3 Department of Earth and Atmospheric Sciences, St. Louis University, St. Louis, Missouri 63103, USA
Megascale accommodation zones mark the early continental breakup boundary of the Afro-Arabian plateau in Ethiopia. Motion along these megascale accommodation zones enabled the different arms of the Afar RRR (rift-rift-rift) triple junction to join together. An arcuate accommodation zone 
45 km wide and 60 km long marks the transition from the N25°W-striking Southern Red Sea Rift trend in the western Afar margin to the N25°E-striking Main Ethiopian Rift. Another accommodation zone 80 km long marks the transition between the northeast- to north-northeast–trending Main Ethiopian Rift and the nearly east-trending Gulf of Aden. The positions of accommodation zones where rift orientations change by 50° suggest that they served as soft linking points between the kinematically "misaligned" arms of the triple junction during the initial breakup of the Afro-Arabian dome.
We use structural features to infer the present location of the triple junction in the Lake Abhe area. On the basis of the location of the paleo–triple junction, deduced from the position of accommodation zones and geomorphic considerations, it is estimated that the Afar triple junction has migrated 1.5° (160 km) in a north- northeast direction with respect to the African (Nubian) plate. The estimated amount of migration of the Afar triple junction is less than the 200 km migration expected from plate-kinematic analysis. This discrepancy suggests either a slower rate of spreading than the current 1.6 cm/yr (Africa-Arabia) during the early phase of rifting or a later early Miocene rather than Oligocene–Miocene age for the initiation of tectonic activity in the triple junction.
Key Words: Africa • rift • structural geology • remote sensing • tectonics • triple junction
This article has been cited by other articles:
|
|
 |
|
  J. HANSEN, D. A. JERRAM, K. McCAFFREY, and S. R. PASSEY The onset of the North Atlantic Igneous Province in a rifting perspective Geological Magazine, May 1, 2009; 146(3): 309 - 325. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 F. Mazzarini Vent distribution and crustal thickness in stretched continental crust: The case of the Afar Depression (Ethiopia) Geosphere, June 1, 2007; 3(3): 152 - 162. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 G. Yirgu, C.J. Ebinger, and P.K.H. Maguire The Afar volcanic province within the East African Rift System: introduction Geological Society, London, Special Publications, January 1, 2006; 259(1): 1 - 6. [Abstract] [PDF]
|
|
|
|
|
|
Z. Garfunkel and M. Beyth Constraints on the structural development of Afar imposed by the kinematics of the major surrounding plates Geological Society, London, Special Publications, January 1, 2006; 259(1): 23 - 42. [Abstract] [PDF]
|
|
|
|
|
|
M. Casey, C. Ebinger, D. Keir, R. Gloaguen, and F. Mohamed Strain accommodation in transitional rifts: extension by magma intrusion and faulting in Ethiopian rift magmatic segments Geological Society, London, Special Publications, January 1, 2006; 259(1): 143 - 163. [Abstract] [PDF]
|
|
|
|
|
|
M. T. Dugda and A. A. Nyblade New constraints on crustal structure in eastern Afar from the analysis of receiver functions and surface wave dispersion in Djibouti Geological Society, London, Special Publications, January 1, 2006; 259(1): 239 - 251. [Abstract] [PDF]
|
|
|
|
 |
|
 E. Wolfenden, C. Ebinger, G. Yirgu, P. R. Renne, and S. P. Kelley Evolution of a volcanic rifted margin: Southern Red Sea, Ethiopia Geological Society of America Bulletin, July 1, 2005; 117(7-8): 846 - 864. [Abstract] [Full Text] [PDF]
|
|
| JOURNAL HOME | HELP | CONTACT PUBLISHER | SUBSCRIBE | ARCHIVE | SEARCH | TABLE OF CONTENTS |
