Structure and morphology of the Red Sea, from the mid-ocean ridge to the ocean-continent boundary

Abstract

The diversity and complexity of existing models on the structure of the Red Sea is the result of a mobile sedimentary cover that not only hides most of the basement and oceanic structures but also hamper the geophysical signals. In this study, we combined published with new unpublished geophysical data to propose a revised interpretation of the structure of the lithosphere between the Hanish Islands (ca. 13.5°N) and the Dead Sea Fracture Zone (ca. 27.5°N). The recognition of allochthonous salt and overburden allows to propose a structural model with simple geometries that are consistent with the present-day kinematic constraints (GPS velocities and Euler Poles) and with the rules of plate's motion on a sphere (Euler Theorem).We mapped a continuous Mid Ocean Ridge segment parallel to the main rift orientation in the southern Red Sea that becomes highly discontinuous and more oblique towards the north as it gets closer to the Euler Pole. These segments all point towards the Euler pole and are consistently offset to the right by transform faults in the central and northern Red Sea cumulating an offset of 400 km. The transform faults are accommodating seafloor spreading in the Red Sea and cluster in three main fracture zones: (1) the Ikwan Fracture Zone near the Ikwan (or Brother) Islands, (2) the Zabargad Fracture Zone in the vicinity of the Zabargad Island and (3) the Jeddah Fracture Zone offshore the Jeddah/Port Sudan area (central Red Sea). Based on a new seismic reflection dataset and published data we propose an interpretation of the Ocean Continent Transition (OCT) in the Red Sea. We bring new evidence (magnetic lineaments, distance of the OCT to the ridge, basin stratigraphy) to support a Middle Miocene (ca. 14 Ma) age for the initiation of seafloor spreading throughout the Red Sea, and we discuss this event with the initiation of strike-slip motion in the Aqaba-Dead Sea transform zone. Finally, compiling all available data and literature, we propose a regionally coherent geodynamic reconstruction using two different poles of rotation for the rifting and seafloor spreading phases.