Emergent tectonic cycles along the Panthalassan margin of East Gondwana from numerical plate reconstruction

A persistent limitation in reconstructions of East Gondwana is the absence of a margin-scale numerical plate model. Existing reconstructions are largely regional or schematic, commonly rely on limited datasets, and in many cases conflict across adjacent sectors of the margin. To address this gap, a new numerical tectonic reconstruction of the East Gondwanan margin is presented, spanning 780–0 Ma and focusing on the coupled evolution of eastern Australia, the East Antarctic margin, and New Zealand during 780–250 Ma. The reconstruction is embedded within a globally consistent plate framework and links seamlessly to established Mesozoic–Cenozoic reconstructions, providing continuity across the full evolution of the Panthalassa-facing margin.  

The model synthesises ~113,000 datapoints across ~12,000 geological samples, including igneous, detrital, and metamorphic geochronology, igneous isotopic geochemistry, potential-field datasets, paleogeographic constraints, and extensive literature synthesis. Implemented in GPlates, the reconstruction enforces plate-like behaviour and enables inherited geological features, such as rift systems and suture zones, to be tracked through time. 

At the scale of the full margin, the reconstruction captures a series of first-order tectonic events and behaviours. Neoproterozoic–Cambrian rifting marks the initial development of Panthalassa as an Atlantic-type ocean, followed by a transition to a Pacific-type system with the initiation of continent-dipping subduction between ~555 and 525 Ma. Convergence is punctuated by major collisional events, including accretion of the VanDieland Superterrane at ~495 Ma and collision of the Hikurangi Plateau at ~100 Ma; in both cases, subduction jump promotes trench rollback and back-arc spreading that matures into rifting. In contrast, episodes of highly oblique plate motion drive inboard oblique subduction and transform systems, displacing the East Lachlan (430–395 Ma) and New England (430–395, 360–330, and 285–260 Ma) superterranes along strike and generating substantial vertical-axis rotation and oroclinal curvature. These processes illustrate how obliquity and lithospheric inheritance complicate simple opening–closing cycles along long-lived convergent margins. 

By resolving these processes within a single, internally consistent reconstruction, this work provides a framework for identifying emergent tectonic cycles along the East Gondwanan margin. Interpreted within a modern Wilson Cycle context, the results highlight how inherited lithospheric architecture and subduction dynamics condition whether convergence leads to rollback, rifting, or continued accretion along long-lived supercontinent margins.