The Marda Fault Zone, Ethiopia

Abstract

THE Marda Fault Zone in south-eastern Ethiopia was first recognised in the Marda Range near Jijigga (Fig. 1) and was called the Marda Hills line. The “linear NW–SE arrangement of basalt capped summits with basaltic plugs” and the associated Bouguer anomaly were considered indications of a major “volcanic-tectonic” lineament¹. Subsequently the fault zone was described as a complex of NW–SE trending faults, down thrown to the NE and possibly extending 200 km into the Ogaden Basin². Recent studies have indicated that the fault zone extends over 400km beyond the Marda Range to the Belet Uen area in Somalia³. Moreover, a major fault zone trends south-east from Belet Uen to the Somalia coast and can be considered a further extension of the zone⁴. These indications of a zone of faulting from the southern margin of the Afar Depression southeast to the Indian Ocean define a length for the Marda Fault Zone of >900 km. The feature must therefore be recognised as a major structural element in the Horn of Africa. We here attempt to define the structure and age of the zone, and have made use of ERTS-1 (LANDSAT) Band 7 imagery, supplemented locally with colour composites, detailed photostudy between 7°50′N and 9°00′N, and potential methods surveys near Daghabur to supplement earlier geological and geophysical surveys.