Evolution of a microcontinent during continental break-up: re-evaluating the Falklands Plateau

Continental break-up is associated with the formation of complex margins, of which transform margins remain less understood due to their varied crustal architectures. This limits our understanding of the processes that accompany the fragmentation of supercontinents, which impacts the reliability of plate tectonic models. The Falkland Plateau (FP) is an example of a transform margin that developed along one of the most long-lived and long-offset transform faults on Earth. The evolution of the plateau is linked to south-western Gondwana break-up and its present-day morphology has been associated with vertical-axis rotation of an extensive microplate (the Falkland Islands Microplate – FIM). Therefore, the FP represents an ideal example to improve our understanding of transform margin development, block rotation mechanisms, and early stages of Gondwana break-up. Here, the FP architecture and evolution is constrained by integrating seismic reflection and potential field data, and building rigid and deforming plate models. The results support an ~80° Middle-Late Jurassic FIM clockwise rotation. Rapid stress variations affected south western Gondwana before and during the FIM rotation. The rotation was initiated by the East Antarctica southward drift, and resulted in continental crust extension, intrusion, underplating, and oceanic crust generation in the Falkland Plateau Basin. The resulting architecture displays similarities with other transform margins. Furthermore, the FIM structural network supports intra-block deformation during rotation, and shows that current deformation models are applicable to larger scales. This thesis emphasises a need for re-evaluating the deformation interpreted along South America during Gondwana break-up, and disproves recent interpretations of West Antarctic evolution. This study highlights the importance of integrating diverse datasets and methodologies in understanding tectonically complex areas. The updated interpretation of the FP provides more information about transform margin evolution and constraints on the pre-break-up Gondwana configuration, which will inform future research on resource distribution and climate evolution.