Characterisation of Strike-slip Tectonics in Rifts and Rifted Margins

Traditionally, research on oblique extension has primarily focused on pure strike-slip systems and well-known pull-apart basins, with an emphasis on characterising strike-slip tectonics mainly within contractional tectonic settings. Oblique deformation, induced by the movement of tectonic plates, is a common occurrence at both plate boundaries and intracontinental systems in divergent zones. In recent years, an increasing number of studies have turned their attention to characterising oblique extension to gain a better understanding of rifts and rifted systems that were previously assumed to have orthogonal extension. Recognising the varying degrees of obliquity in divergent systems is crucial for enhancing the reliability of plate tectonic models, resource exploration, and the identification of natural hazards.
This thesis adopts a multi-disciplinary, multi-scale approach, utilising offshore 2D seismic reflection data accompanied by gravity data, and onshore field data. The methodology is applied to various case studies with different degrees of obliquity to investigate the evolution of different divergent systems. The combination of seismic reflection data and field data is chosen for their complementary strengths: seismic reflection data provide insights at the crustal scale, while field data focuses on elements within the basin.
Despite the degree of obliquity in the system, the findings reveal spatial alternation in the stress regimes within the oblique rifts and rifted margins. These stress alternations are reflected in syn-kinematic growth strata, allowing the differentiation between oblique and orthogonal stress regimes. The findings encompass the role of pre-existing structures on the evolution of the oblique systems. Furthermore, oblique systems often exhibit magmatic intrusions through strike-slip, transfer, or continental transform faults, typically located at plate boundaries or the core of the rift system. At the crustal scale, intrusions through transform faults are capable of forming a transitional crust, which disproves the previous notion of the absence of continental-oceanic transitional crust in transform margins.
In conclusion, this study contributes to the refinement of the strike-slip tectonics model, traditionally centred on contractional settings by providing additional insights into divergent strike-slip systems, and displays the implications on the Pangaea break-up. The findings not only enhance our understanding of these settings but also suggest potential directions for further research in this dynamic field.