A tectonic model of an incipient spreading center and its margins : the northern Red Sea and the Dead Sea rift

Abstract

The northern Red Sea and the Dead Sea rift represent the incipient stage of accreting plate boundary, occurring partly at sea and partly on land. The evolution of the Red Sea as a deviatoric boundary between the Arabian and the Nubian plates started in the Late Oligocene-Early Miocene and has been active since. Oceanic crust is found in the axial trough of the central Red Sea but its northern province is still underlain by thinned and extended continental crust. The crystalline basement of the northern Red Sea is covered by a sequence of Late Miocene evaporites, unconformably overlain by unconsolidated sediments of Plio-Pleistocene age. The general trend of the northern Red Sea is NW-SE, but the presented data show there series of rifts and diapirs trending approximately N-S. Elongated rifts and diapirs were encountered also in the Gulf of Elat, oriented to the NNE-SSW. The terrain adjacent to the northern Red Sea and the Dead Sea rift is strongly uplifted, indicating that the region was affected by vertical as well as horizontal tectonic activity. The horizontal tectonic activity, caused by the Arabia-Nubia separation, is associated with extensional stresses that led to the evolution of the regional and the local series of rifts. The vertical tectonic activity is subsequent to the plates separation and is represented by the intensive uplift of the Red Sea margins, by the subsidence of the rifts' floor and the diapirism. It is suggested that the combination of horizontal and vertical tectonic activities are inherent characteristics to accreting plate boundaries, and that the vertical tectonic components are accentuated during slow spreading. The difference in the orientation between the NW-SE trending marginal faults and the bathyal structures indicates a jump of the axis of separation of Arabia from Nubia in the studied region. During the Miocene the axis propagated northwestwards, but since the Pliocene it propagated northwards. Analyses of the structures of the Suez and the Dead Sea rifts substantiate this conclusion.