Timing, Kinematics, and Spatial Distribution of Miocene Extension in the Central Arabian Margin of the Red Sea Rift System

Abstract

The Arabian-Nubian Shield (ANS) existed as relatively stable craton on the southern Neo- Tethyan passive margin until rifting of the continental lithosphere borne the Arabian Plate with the advent of the Red Sea-Gulf of Suez rift system. Examination of the thermotectonic record via apatite and zircon (U-Th)/He thermochronometry (AHe and ZHe) on Proterozoic basement rock within the exhumed SW Arabian Plate, detrital AHe thermochronometry on syn-rift sedimentary packages, whole-rock 40Ar/39Ar dating and X-Ray fluorescence analyses of syn-and post-rift flood basalts, and numerical time-temperature modeling of AHe and ZHe systems reveal a three- stage thermotectonic history for the central Arabian rift flank (CARF). First, the pre-rift ANS experienced a Paleo-Mesozoic cooling event that brought the proto-CARF to a mid-to-upper crustal structural level where it remained thermally stable through the Mesozoic. Then, a major rift pulse ca. 23 Ma exhumed a 200 km-wide area of the CARF, marking the onset of diffuse lithospheric extension that endured for 8 million years until a middle Miocene regional stress realignment transferred major faulting towards the modern RSR and Gulf of Aqaba. The 23 Ma rift onset age is mirrored in thermochronometric and sequence stratigraphic analyses elsewhere along the full Red Sea Nubian margin and the southern Arabian rift flank in Saudi Arabia and Yemen, confirming that RSR initiation occurred concomitantly along the full Red Sea-Gulf of Suez rift system in opposition to proposed south-to-north rift propagation models. A passive rift model is favored due to the absence of an elevated pre-rift thermal signal within the ANS and the fact that CARF harrat volcanism trailed rift onset by 6 million years. Arabian rift flank architecture differs greatly along RSR-strike; relatively rigid continental lithosphere comprises the southern Arabian margin while a broad zone of deformation begins north of the Makkah- Madinah-Nafud volcanic line and expands through the NW Arabian Plate where it encompasses syn-rift extensional structures such as the Azlam and Tabuk graben and Hamd-Jizl Basin.