The Dead Sea Rift: from continental rift to incipient ocean

The Dead Sea Rift is a 600 km long, approximately 20 km wide geomorphological depression, showing a topographic relief of 1,000 to 3,000 m from the axial depression to the mountainous margins in many places. The Rift is the northern extension of the Red Sea young oceanic spreading centre, and it is built of a series of internal basins. The Rift is the product of vertical displacements that downfaulted its floor and uplifted its margins, but some sinistral strike-slip offset affected the Rift as well. The tectonic evolution of the Rift started probably in the Pliocene, subsequent to the termination of the intensive tectonic activity in the Suez Rift. The transition of the tectonic activity from Suez Rift to the Dead Sea Rift is due to a probable clockwise jump of the northern extension of the Red Sea spreading centre. The Dead Sea Rift, with its internal basins and faulted precipitous escarpments, presents an exceptional example for the earliest stages of the evolution of continental break-up and of nascent passive continental margins. Tectonic interpretations of the voluminous geological and geophysical data from the Rift and its margins are complicated because the information is equivocal. Part of the data suggests that the Rift is an extensional structure, whereas another part indicates that the Rift is a product of regional sinistral strike-slip faulting. However, it is suggested that the equivocal data are not necessarily conflicting, because the evolution of the Rift is probably associated with oblique resultant displacement of combined normal and strike-slip faulting. The quantitative ratio between the extensional and the lateral offset processes in the Dead Sea Rift is controversial. There is ground to presume that large downfaulting of the Rift floor and intensive erosion of its uplifted margins removed and obscured critical data that could have provided reliable correlation between the eastern and western flanks. Nevertheless, reconstruction of Mesozoic depositional fades zones across the Rift apparently indicates that the lateral displacements are approximately 10 km, and seismic reflection profiles suggest vertical offsets reaching 7 km. The series of secondary internal basins in the Rift, that seem equivalent to the linear system of axial basins in the northern Red Sea, support the concept that the Dead Sea is under a tectonic regime that is comparable to the one that affected the Red Sea in the Miocene. These findings, and the 25 to 50% reduction of crustal thicknesses underneath the Rift indicate an incipient, oblique oceanic spreading centre.