Tectonic subsidence plots have been calculated for well, extrapolated-well and significant off- well (seismically-based) locations in the Vulcan Sub-basin and adjacent highs (western Timor Sea)._x000D_
The subsidence curves have been normalized to a common datum, the distinctive "near top Permian" marker, and corrected for sediment compaction, palaeobathymetry, eustatic sea-level change and loading effects._x000D_
Four principal phases of post-Permian basin development are recognised and quantitatively described by integrating the results of the sub- sidence analysis into the regional (e.g. recent Ocean Drilling Program-derived) framework of the tectonic evolution of the North West Shelf. They are 1. the Triassic-mid Jurassic Westralian Superbasin intracratonic phase, 2. the late Jurassic-early Cretaceous North West Shelf rift phase, 3. the mid Cretaceous-Palaeogene North West Shelf subsidence phase, and 4. the Neogene-present Timor collision phase._x000D_
Rapid Triassic tectonic subsidence occurred in an intracratonic setting, possibly subsequent to aborted late Palaeozoic rifting. Intracratonic sub- sidence mechanisms such as deep crustal metamorphism and/or intrustion and regional tectonic compression are invoked in addition to any post-rift thermal subsidence which may have occurred.