A preliminary interpretation of the gravity field of Afar, northeast Ethiopia

Abstract

All existing gravity data in Afar, northeast Ethiopia, were uniformly reduced to Bouguer values and were compiled into a map of 10 mgal isogals. Five crustal models crossing Afar E-W were calculated. The results obtained were as follows: In south Afar the crust is most probably of the continental type, slightly attenuated. Along the Wonji fault belt a series of relative maxima is built as a continuation of the Ethiopian Rift in Afar. The crust at the eastern edge of the Ethiopian Plateau is approximately 30 km thick and is strongly attenuated under the Wonji fault belt which is underlain by material of low velocity and density. Towards the Aisha horst the crust increases again to a thickness of approximately 20 km. The trends of the field are closely connected to the directions of the escarpments. In north Afar the crust is very strongly attenuated and partly oceanized. The trend of the gravity field is parallel to that of the southern Red Sea and strikes NNW-SSE. South of 13° N this trend changes to NW-SE and seems to be the continuation of the Gulf of Aden. The Danakil mountains separate the Danakil depression from the Red Sea. They consist of sialic crust, which has been rotated in an anticlockwise direction and most probably are isostatically uncompensated.