Deciphering the Africa-Arabia breakup: Insights from U-Pb dating along the Carmel-Gilboa fault system and its triple junction with the Dead Sea transform

Abstract

The Carmel–Gilboa fault system (CGFS) runs sub-parallel to the Azraq–Sirhan Garben (ASG) and the Red Sea Rift. Although the system currently forms a triple junction with the Dead Sea transform (DST), its initiation is considered to be associated with NE–SW extensional regime during the Africa-Arabia breakup in the late Oligocene to early Miocene. The role of the CGFS in the breakup process is not fully understood. In addition, the exact timing of initiation and potential reactivation during the onset of the DST plate boundary is not well constrained. This work sheds light on these events by establishing a long-term record of deformation along the CGFS and its intersection with the DST. This study presents 17 U-Pb ages of syn-tectonic calcite (n=14, ∼33.2 to 2.3 Ma) collected along the CGFS. These ages suggest that the earliest faulting phase along the CGFS took place between ∼25 to ∼21 Ma - coinciding with the initiation of the Red Sea Rift. The second phase of activity along the CGFS commenced at ∼16 Ma. This phase supports northward propagation of the DST from the Gulf of Elat to the southern tip of the Lebanese restraining bend from ∼18 to ∼14 Ma. The new U-Pb ages along the CGFS together with ages from the DST constrain the propagation rate of the DST to ∼105 mm/year, roughly 20 times faster than the current left-lateral offset along this active plate boundary (∼5 mm/year). The trigger for two simultaneous rifts, located 500 km apart and the distributed extension along the northern Red Sea is most probably related to the relative mechanical strength of oceanic vs. continental lithosphere, which also controls the eventual establishment of the DST and the failure of the rifting process along the CGFS-Azraq-Sirhan rift system.