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.

Mesozoic extension along Australia's southern margin and the evolution and architecture of the Otway Basin were probably controlled by three factors: 1) changes in global plate movements driven by mantle processes; 2) the structural grain of Palaeozoic basement; and, 3) changes in subduction along Gondwana's Pacific margin. Major plate realignments controlled the Jurassic onset of rifting, the mid-Cretaceous break-up and the Eocene onset of rapid spreading in the Southern Ocean.The initial southern margin rift site was influenced by the northern limit of Pacific margin (extensional) Jurassic dolerites and the rifting may have terminated dolerite emplacement. Changed conditions of Pacific margin subduction (e.g. ridge subduction) in the Aptian may have placed the Australia-Antarctic plates into minor compression, abating Neocomian southern margin rifting. It also produced vast amounts of volcanolithic sediment from the Pacific margin arc that was funnelled down the rift graben, causing additional regional subsidence due to loading. Albian orogenic collapse of the Pacific margin, related to collision with the Phoenix Plate, influenced mid-Cretaceous breakup propagating south of Tasmania and into the Tasman Sea.Major offsets of the spreading axis during breakup, at the Tasman and Spencer Fracture zones, were most likely controlled by the location of Palaeozoic terrane boundaries. The Tasman Fracture System was reactivated during break-up, with considerable uplift and denudation of the Bass failed rift to the east, which controlled Otway Basin facies distribution. Palaeozoic structures also had a significant effect in determining the half graben orientations within a general N-S extensional regime during early Cretaceous rifting. The late Cretaceous second stage of rifting, seaward of the Tartwaup, Timboon and Sorell fault zones, left a stable failed rift margin to the north, but the attenuated lithosphere of the Otway-Sorell microplate to the south records repeated extension that led to continental separation and may be part of an Antarctic upper plate.

Detailed interpretation of reflection seismic and well data from the northern Strzelecki Terrace constrain the effect of Southern Margin and Tasman Sea rifting on the evolution of the Gippsland Basin. A new model is proposed which divides the basin into two structurally distinct provinces (East and West Gippsland Basin), separated by a broad zone of accommodation which is referred to in this paper as the 'Kingfish/Tuna Transition Zone'. This zone is a distinct region across which structural styles change within the basin due to the interaction of extensional forces resulting from both Southern Margin and Tasman Sea rifting. No evidence has been found, however, for the existence of transfer zones within the northern margin of Gippsland Basin as previously suggested by other authors.The Gippsland Basin is observed to have a composite history; a younger 'Tasman Rift' Basin (a Tasman Sea aulacogen) overlying a regionally more extensive 'Strzelecki Basin' (the result of rifting along Australia's Southern Margin). Both basins have formed as half graben with opposing asymmetry. Re-evaluation of the Cretaceous palynology in conjunction with reflection seismic data from selected wells have enabled division of the Cretaceous section of the northern Strzelecki Terrace into three tectonically distinct sedimentary units: the Lower Strzelecki, Upper Strzelecki and Golden Beach Megasequences. The Lower Strzelecki Megasequence exhibits considerable thickening towards a south-bounding master fault, and is inferred to have been deposited during a phase of active rifting. It is separated from the overlying Upper Strzelecki Megasequence by a pronounced late Aptian age angular unconformity. The Upper Strzelecki Megasequence is a thick sedimentary unit which shows less syn-sedimentary faulting and is inferred to be deposited during a period of tectonic quiescence, possibly during a sag phase following active rifting. The Golden Beach Megasequence shows renewal of rifting with growth towards a north bounding fault system and is differentiated from the underlying Strzelecki Megasequences by a distinct change in seismic character across a subtle early Campanian age angular unconformity.