The breakup of Pangea in the Jurassic saw the opening of major ocean basins at the expense of older Tethyan and Pacific oceanic plates. Although the Tethyan seafloor spreading history has been lost to subduction, proxy indicators from multiple generations of Tethyan ribbon terranes, as well as the active margin geological histories of volcanism and ophiolite obduction events can be used to reconstruct these ancient oceanic plates. The plate reconstructions presented in this study reconcile observations from ocean basins and the onshore geological record to provide a regional synthesis, embedded in a global plate motion model, of the IndiaEurasia convergence history, the accretionary growth of Southeast Asia and the Tethyan-Pacific tectonic link through the New Guinea margin. The global plate motion model presented in this study captures the timedependent evolution of plates and their tectonic boundaries since 160 Ma, which are assimilated as surface boundary conditions for numerical experiments of mantle convection. We evaluate subducted slab locations and geometries predicted by forward mantle flow models against P-and S-wave seismic tomography models. This approach harnesses modern plate reconstruction techniques, mantle convection models with imposed one-sided subduction, and constraints from the surface geology to address a number of unresolved Tethyan geodynamic controversies. Our synthesis reveals that north-dipping subduction beneath Eurasia in the latest Jurassic consumed the Meso-Tethys, and suggests that northward slab pull opened the younger Neo-Tethyan ocean basin from ~ 155 Ma. We model the rifting of ' Argoland', representing the East Java and West Sulawesi continental fragments, as a northward transfer of continental terranes in the latest Jurassic from the northwest Australian shelf -likely colliding first with parts of the Woyla intra-oceanic arc in the mid-Cretaceous, and accreting to the Borneo (Sundaland) core by ~ 80 Ma. The Neo-Tethyan ridge was likely consumed along an intra-oceanic subduction zone south of Eurasia from ~ 105 Ma, leading to a major change in the motion of the Indian Plate by ~ 100 Ma, as observed in the Wharton Basin fracture zone bends. We investigate the geodynamic consequences of long-lived intra-oceanic subduction within the Neo-Tethys, requiring a twostage India-Eurasia collision involving first contact between Greater India and the Kohistan-Ladakh Arc sometime between ~ 60 and 50 Ma, followed by continent-continent collision from ~ 47 Ma. Our models suggest that the Sunda slab kink beneath northwest Sumatra in the mantle transition zone results from the rotation and extrusion of Indochina from ~ 30 Ma. Our results are also the first to reproduce the enigmatic Proto South China Sea slab beneath northern Borneo, as well as the Tethyan/Woyla slab that is predicted at mid-mantle depths south of Sumatra. Further east, our revised reconstructions of the New Guinea margin, notably the evolution of the Sepik composite terrane and the Maramuni subduction zone, produce...

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Regional seismic reflection and fission track thermochronological studies of the Bass Basin area illustrate two types of inversion, both confined to the Bass failed rift. The first type involved 1-2 km of uplift, denudation and cooling of basement over more than 200 km along both margins of a failed rift, with lesser erosion within the rift basin. This occurred during renewed extension that bypassed the Bass Basin area leaving it as a failed rift. The uplift resulted from breaking of the lithosphere and may have been due, in part, to rebound following several kilometres of rapid sediment loading in the preceding 20 Ma. The second type comprised repeated structural inversion involving 1-3km of uplift by compressional reactivation of extensional faults and along new reverse faults. These inversions occurred along the zone of maximum extension in a failed Mesozoic rift, such that Tasmania acted as a buttress to compression. The rifting and structural inversions are interpreted to have been controlled by a long-lived zone of weakness, perhaps overlying a Palaeozoic greenstone belt, with the maximum principal stress being roughly perpendicular to faults within the zone during inversion. Significantly, Miocene-Pliocene inversion resulted from the Australian craton being placed into compression following arc collision 3500km to the north, emphasizing the importance of long distance transmission of compressional stresses through the lithosphere.

Recent advances in cross-section balancing software have simplified the application of basic geometric constraints to the analysis of basin development. Geometric analysis of field and seismic data allows the user to verify initial interpretations and also elucidates important information about the structural evolution of a basin. Principally, computerised balancing and restoration of cross-sections assists in constraining:the amount of crustal extension;trap geometries, particularly fault geometries through time;the geometry of key horizons at any time, revealing basin morphology and migration paths;the time and amount of maximum burial and hence hydrocarbon migration; andthe likely mechanisms involved in basin evolution. In turn, these parameters can be used to further assess hydrocarbon prospectivity by providing useful data for lithospheric modelling.This study utilises 2D cross-section balancing software (Geosec™) to decompact, balance and restore a series of regional onshore-offshore cross-sections based on both reflection seismic data in the Torquay Embayment and field mapping in the Otway Ranges. The thickness of eroded strata has been constrained by Apatite Fission Track and Vitrinite Reflectance analyses. The resulting section restoration suggests that the eastern Otway Basin experienced extension of 26 per cent in the Early Cretaceous and that the Otway Ranges were subjected to −8 per cent shortening during mid-Cretaceous inversion and −4 per cent shortening during Mio-Pliocene inversion.The structural style of the Otway Ranges and Torquay Embayment is typified by steep, relatively planar, en echelon, N and NE-dipping Early Cretaceous extension faults that were subsequently inverted and eroded during the Cenomanian and Mio-Pliocene. The structural style of the region shows strong similarities with oblique- rift analogue models suggesting that the extensional history of the region was strongly controlled by prevailing basement fabric.Lower Cretaceous source rocks in the eastern Otway Basin reached maximum maturity prior to mid-Cretaceous inversion with the exception of parts of the Torquay Embayment which may not have experienced significant uplift and erosion at this time. The lack of subsidence in the eastern Otway Basin prevented the deposition of significant amounts of Upper Cretaceous sediments which are proven reservoirs in the western Otway Basin and Gippsland Basin. Subsequent Tertiary burial was insufficient, in most regions, to allow the source rocks re-enter the oil generation window.