Rifting Dynamics and Margin Architecture in Northern Red Sea, Egypt

Abstract

The Red Sea is a young rifted margin, formed due to the separation of Arabia from Nubia during the Late Oligocene-Early Miocene. While the formation of oceanic crust in the southern and central Red Sea is generally accepted to have started at c. 5 Ma, the nature of the crust in the Northern Red Sea (NRS) is still debated. The rift architecture, magmatism, and salt structures of the NRS are poorly understood. This thesis aims to integrate different geophysical data to study the magmatic activity, provide a systematic description of the distribution and morphology of salt structures and analyse the tectonic evolution of the NRS. Our results indicate that at least eight isolated magmatic buildups with high density and magnetic susceptibility anomalies exist in the study area. They are accompanied by ascension of magma through prominent rift-related normal faults. Magmatic activity likely started in the Pleistocene and continues to the present-day. Arabian alkali-basalts, at the same latitude as Quseir, show ages comparable to those inferred for the volcanic edifices studied, suggesting a similar geotectonic context. The results of the 3D density and magnetic susceptibility inverted models show a good fit with the volcanoes imaged by seismic data and thus, that the applied inversion technique is a reliable tool for detecting other volcanic buildups where seismic data are missing.
Salt mobilization started during the Middle Miocene, during the precipitation of layered evaporites, and continued until the Quaternary. Seismic interpretation indicates that the Middle Miocene massive salt layer is mainly concentrated in several major NW-SE to NNW-SSE trending salt walls, characterized by relatively irregular crests and moderately-dipping flanks. This study demonstrates that thick-skinned extension was the main driver for salt mobilization offshore Quseir. However, locally, thick-skinned extension resulted in minor thin-skinned extension. Seismic observations are compatible with the results from physical models simulating the impact of basement faulting on diapirism. Three domains have been distinguished in the NRS, from continent to ocean: proximal, necking, and distal domains. Sensitivity testing of interpretations for the distal domain indicates a probable scenario where exhumed lower continental crust or serpentinized mantle is present. A comprehensive rift model for the NRS in the Quseir province accounts for magmatic underplating accompanied by half-graben development at c. 25 Ma, followed by Early Miocene crustal thinning accommodated by an east-dipping detachment fault. A Late Miocene phase with a flip of the detachment geometry led to the present-day configuration.

Date of Award	Aug 2023
Original language	American English
Supervisor	Alessandro Decarlis (Supervisor)