Cenozoic Extensional Tectonism in NE Africa: Insights on Neotectonics, Strain Accommodation and Landscape Evolution

Date of Award

8-2026

Degree Name

Doctor of Philosophy

Department

Geological and Environmental Sciences

First Advisor

Mohamed Sultan Ph.D.

Second Advisor

Neil Sturchio, Ph.D.

Third Advisor

Peter Voice, Ph.D.

Keywords

Continental rifts, failed rifts, mega-depressions, oblique rifting, structural inheritance, transtension

Abstract

Cenozoic extensional tectonism in NE Africa and Arabia, driven by the opening of the Afro-Arabian rift system, profoundly reorganized the structural architecture and surface morphology of Egypt. This dissertation investigates how extensional strain was initiated, partitioned, and localized across mechanically heterogeneous continental lithosphere. Through three integrated studies, it examines the full temporal and spatial spectrum of this tectonic system: diffuse, inheritance-controlled rift initiation in continental interior; late Quaternary deformation along the Suez Rift; and coupled tectonic–geomorphic evolution of mega-depressions.

The first study reappraises the long-standing interpretation of the Suez Rift as a tectonically inactive failed rift. Analysis of a ~100-km-long system of fault scarps displacing Quaternary alluvial terraces by up to ~35 m, integrated with optically stimulated luminescence chronology, Sentinel-1 InSAR time-series analysis, and kinematic modeling of Sinai microplate rotation, demonstrates that the rift has remained active during the late Quaternary. OSL dating identifies four episodes of surface deformation from older than 60 ka to younger than 8 ka, yielding average vertical slip rates of ~0.14 mm yr⁻¹ and fault-specific extension rates of 0.2 ± 0.1 mm yr⁻¹. InSAR analysis reveals ongoing subsidence of up to −2 mm yr⁻¹ within the Gharib Plain, whereas kinematic modeling predicts boundary-normal extension rates of 0.5–2.3 mm yr⁻¹ along the rift. These results reframe the Suez Rift as a slowly extending, kinematically active boundary undergoing continued tectonic readjustment within the evolving Sinai microplate system.

The second study investigates the Farafra Fault System, a ~130-km-long, N–S-trending structural belt in the Western Desert of Egypt, as a record of the diffuse, inheritance-controlled stage of Red Sea rift initiation. Integrating field mapping, structural analysis, remote sensing, and geophysical data, this study documents a two-stage kinematic evolution involving early oblique reactivation of inherited basement fabrics, and progressive strain partitioning within mechanically layered sedimentary cover. The architecture of the fault system provides direct field evidence for the reactivation of N–S basement structures. These results demonstrate that inherited fabrics organized diffuse intraplate deformation into coherent kinematic domains before rift localization along the Red Sea Rift. The study therefore establishes inheritance as a first-order control on early rift geometry, fault distribution, and strain partitioning in heterogeneous continental lithosphere.

The third study develops a conceptual model for the inception and evolution of East Saharan mega-depressions using field observations, structural analysis, remote sensing, and stable isotopic data from the Farafra Depression. The results indicate that mega-depressions evolution involved four linked stages: initial formation of en echelon grabens along fault zones; preferential enlargement by groundwater sapping along structurally controlled pathways; coalescence of smaller depressions into larger compound landforms; and continued vertical and lateral growth. Stable isotopic compositions of travertine deposits are consistent with discharge from the Nubian Sandstone Aquifer, supporting a groundwater-sapping mechanism focused along fault-controlled flow pathways. This model shows that Saharan mega-depressions are not simply products of surface erosion, but structurally controlled landscapes in which structures focused groundwater flow, enhanced erosion, and organized long-term geomorphic development.

Access Setting

Dissertation-Abstract Only

Restricted to Campus until

8-1-2028

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