Mega-transform fault development: New insights from Geodynamic modelling using ASPECT and real-world examples

The length of oceanic transform faults varies dramatically from near zero-offsets to long-offset mega-transforms that are >1000 km long. However, the formation and development of longer oceanic transform faults (>200 km) remains incomplete and requires further study. We investigate how changes in the plate motion vector impacts plate stress and transform fault development using high resolution 3D geodynamic numerical models in ASPECT (Advanced Solver for Planetary Evolution, Convection, and Tectonics). Specifically, we study how the length of transform faults evolve over time after inducing transpression or transtension across simple and complex stepped rift-transform geometries. We also determine how the angle of oblique extension affects the required tectonic force necessary to develop new tectonic structures, providing insight into real-world plate tectonic processes. Our results show that transpressional deformation along a transform leads to longer, diffuse transforms at higher angles, while transtensional deformation leads to oblique extension across the transform margin. These transpressional model results are also analogous to real world examples such as the Davie (West Somali Basin) and Ungava Fault Zones (Davis Strait), where we also highlight how the contemporaneous alignment of extinct mid-ocean ridges and young oceanic lithosphere can influence where new transform faults develop.