Abstract

Carbonate platform architectures serve as indicators of environmental changes, such as sea level fluctuations, climatic variations, and tectonic influences, all of which shape their evolution. While analog studies on modern carbonate platforms have primarily focused on tropical settings, limited attention has been given to platforms in arid and semi-arid environments, despite the prevalence of ancient carbonate sequences in these regions. This thesis aims to bridge this gap by investigating the Al Wajh carbonate platform in the northeastern Red Sea, Saudi Arabia, through the integration and analysis of geophysical and geological data to unravel and describe its architecture and development in detail. We collected a comprehensive geophysical dataset, including Multibeam Echosounder (MBES), Lidar Bathymetry, high-resolution sub-bottom profiles, and 2D seismic data, to understand the subsurface architecture of the platform. Seafloor sediment samples, vibrocores, and drilled cores were used as ground truth data to strengthen the interpretations. A global eustacy curve and a recently published Red Sea sea-level curve were integrated with climate data to reconstruct depositional models. Analysis of bathymetry data shows a distinct "empty bucket" morphology of the Al Wajh platform, with the lagoon shielded by an almost continuous rift reef and connected to the Red Sea via three main inlet channels. The modern lagoon exhibits significant lateral facies heterogeneity, which underscores the complex nature of sedimentary processes within lagoon environments. Results also show seafloor morphology plays a crucial role in governing current circulation, and impacts facies distribution and transitions in this area. Additionally, the distribution of facies in certain areas suggests a significant influence of hydrodynamics in the lagoon. Subsurface data analysis indicates that the architecture and development of the Al Wajh lagoon are characterized by several stages and influenced by various factors. The combined results and analyses reveal that the platform's initiation was strongly influenced by the inherited half-graben morphology from the Red Sea opening. Furthermore, its proximity to the largest wadi catchment in Saudi Arabia facilitated significant siliciclastic transport, filling the half-graben structures and forming a delta morphology, which served as the foundation for carbonate platform growth. Additionally, fluctuations in sea level and climate variations play significant roles in controlling accommodation changes, siliciclastic influx, and carbonate production. Finally, findings from this thesis shed new insights on our understanding of the architecture and sedimentary infill of ancient land-attached carbonate platforms deposited in similar settings.