A Pull-Apart Model for the Red Sea Without a Pole of Rotation in the Separation of Arabia and Africa

MAKRIS, J., and R. RIHM, Institute of Geophysics, Hamburg University, Hamburg, Germany

Wide-angle seismic surveys in the Red Sea and adjacent areas revealed fundamental asymmetries of the conjugate continental margins: the Western flank shows large areas of old oceanic crust, whereas the whole eastern flank is underlain by stretched continental crust. In addition, the African margin appears very abrupt over long sectors of the northern and central Red Sea, whereas the Arabian margin extends almost into the center of the Red Sea. Gravity, magnetic, and heat flow density observations reveal the controlling structural trends, spreading history, and locations of recent magmatic intrusions. They confirm the seismic results and provide information on the entire basin.

These geophysical results have implications for Red Sea evolution models: strike-slip processes controlled the breakup of the Arabian plate from Africa. The geometry of the early strike-slip zones reflects

the configuration of major preexisting fault systems such as the Najd fault system, the Onib-Harnisana and Baraka suture zones, the Central African fault zone, or the Marda line. This geometry of controlling tectonic structures led to early generation of oceanic crust in pull-apart basins in parts of the western flank of the northern and central Red Sea and to stretching of continental crust mainly on the eastern flank and in the southern Red Sea.

Further evolution introduced en echelon fracture systems of Aqaba orientation as major structural trends in the northern Red Sea, whereas symmetrical extension by sea floor spreading began in the axial trough of the southern Red Sea. The central Red Sea represents the zone of transition between these two contrasting domains.

The significant changes across as well as along the rift cannot be explained by using a single pole of rotation to describe the separation of Arabia from Africa. Instead, several segments of both flanks have to be considered independently.

AAPG Search and Discovery Article #91007© 1991 AAPG International Conference, London, England, September 29-October 2, 1991 (2009)