The tectonic development of the western margin of the Gulf of Elat (Aqaba) rift

Abstract

Along the western coast of the Gulf of Elat, a 30 km wide shear belt of subparallel faults trending N-S to NE-SW is developed. This shear belt is observed mainly within the Precambrian basement terrain. Sinistral movements on these faults have been recognized based on offsets of magmatic bodies and lithological contacts in rocks of Precambrian age. The cumulative displacement, measured independently at several localities across the belt, attains a total of 24 km. Early Neogene volcanism, in the form of long dikes trending NW-SE is known from the eastern desert of Egypt, of the Gulf of Suez and along the Red Sea coast of Saudi Arabia. Volcanic bodies of a similar pattern have been identified in eastern Sinai. These bodies, mainly dolerites and basalts, intruding Mesozoic sediments, are parallel to each other and to the Gulf of Suez. They are tens to hundreds of kilometers long and spaced several tens of kilometers apart. Dating (K-Ar) of bodies in Sinai, Saudi Arabia and in the eastern desert of Egypt suggest an age of 20–22 m.y. for this extensive volcanism. All the dikes are sinistrally displaced by the individual faults of the eastern Sinai shear belt. The amount of movement recorded using the Precambrian markers is identical to movement recorded by offsets of the Early Neogene dikes. This proves that the total 24 km shear of this fault system postdates the 20–22 m.y. volcanic phase. It is assumed that the recorded movements are part of the 105–110 km shear persumed to exist along the Gulf of Elat which is also younger than 20–22 m.y. Preliminary results suggest that a similar amount of movement is observable along a shear zone developed on the eastern coast of the Gulf of Elat. Thus only some 60 km movement are taken up by faults in the Gulf itself. The evolving model suggests that: 1. (a) The intrusion of very long basaltic dikes in a NW-SE direction, on both sides of the Red Sea, accompanied the initial stage of development of the Red Sea—Gulf of Suez rift valley. 2. (b) A basic change in the geotectonic regime occurs after the intrusion of this volcanic suite: large scale horizontal movements are initiated, being recorded as a 105–110 km sinistral movement along the Arava—Jordan rift. This movement implies a synchronous opening of the Red Sea.