Article,
The Afar depression: transition between continental rifting and sea-floor spreading
Tectonophysics, 141 (1-3): 199--214 (Sep 15, 1987)
DOI: 10.1016/0040-1951(87)90186-7
Abstract
Detailed geophysical and geological studies were undertaken in the
1970's in the Afar Depression, Ethiopia, in order to study the processes
of continental break-up occurring in this unique setting; the Afar
is located between the Ethiopian and Somali Plateaus and the Red
Sea. We have re-evaluated the available seismic refraction and gravity
data using modern interpretation techniques and incorporated new
information derived from magnetic, gravity, seismicity and seismic
refraction data. The results of the re-evaluation indicate that the
Afar Depression is a transition zone between the continental rifts
of Kenya and the present ongoing sea-floor spreading of the Red Sea
and the Gulf of Aden. In the Depression itself the crust is greatly
attenuated and is underlain by a low velocity (7.4-7.5 km/s), high
temperature upper mantle material. However, it is still a continental
crust which thins to the northeast and east towards the Red Sea and
the Gulf of Aden. It is not a newly formed oceanic crust as has been
suggested in the past. The trends of the areas of crustal thinning
are indicated by the gravity anomalies. The trend of the Ethiopian
Rift reaches South Afar where the trend of crustal thinning changes
and becomes parallel to the Red Sea trend. It is offset en echelon
from the spreading area of the Red Sea, which is marked by an alignment
of gravity maxima. The Gulf of Aden trend continues west towards
the Ethiopian Rift. The gravity trends coincide with areas of maximum
crustal thinning and may thus suggest a possible triple junction
in development.
