The evolution of the Gulf of Aden and Red Sea in space and time

Abstract

The evolution of the Gulf of Aden and Red Sea is reviewed in the light of the 1933 John Murray Expedition and modern concepts of plate tectonics and propagating rifts. The John Murray Expedition was notable for the discovery of (i) the remarkable symmetry of the Carlsberg Ridge, (ii) the oceanic composition of the rocks dredged and (iii) the SW-NE structures in the Gulf of Aden, the main features of fracture zone being descibed. The connection of the East African rifts, Gulf of Aden, Carlsberg and mid-Atlantic rifts was also recognised — a major step towards the appreciation of plate boundaries. The plate setting of the Gulf of Aden, Red Sea and Gulfs of Suez and Aqaba is described. Three stages of evolution are recognised, (i) the propagation of a crack about 40 My ago from the Arabian Sea westwards through the Gulf of Aden and northwards through the Red Sea terminating north of the present Gulf of Suez and forming an early rift system, (ii) major reactivation and separation of the Gulf of Aden and Red Sea beginnng about 25 My ago with the propagation of a new NNE crack forming the early Gulf of Aqaba/Dead Sea system along which 62km of shear took place, and (iii) further reactivation and separation of the Gulf of Aden and Red Sea starting about 5My ago with a further 45km shear movement along the Aqaba/Dead Sea rift. The Gulf of Aden and Red Sea evolved in response to NE-SW tensional stresses, and for each phase the crack propagated westwards through the Gulf of Aden and northwards through the Red Sea, the oldest and widest parts being in the eastern Gulf of Aden.