PERMIAN TO LOWER CRETACEOUS PLATE TECTONICS AND ITS IMPACT ON THE TECTONO-STRATIGRAPHIC DEVELOPMENT OF THE WESTERN AUSTRALIAN MARGIN

Abstract

The post-Lower Permian succession of the Perth Basin and Westralian Superbasin can be directly related to the plate tectonic evolution of the Gondwanan Super-continent. In the Late Permian to Albian the northern edge of Gondwana continued to break into microplates that migrated to the north and were accreted into what is today the southeastern Asia (Burma–China) region. These separation events are recorded as a series of stratigraphically distinct transgressions (corresponding to the initial stretching of the asthenosphere and acceleration of subsidence rates) followed by rapid regressions (when new oceanic crust was emplaced in thinned continental crust causing uplifts of large continental masses). Because the events are synchronous across large regions, and may be identified from specific log and seismic signatures, the intensity of stratigraphically related transgressive/regressive cycles varies, depending on the distance from the break-up centres and these cycles allow the identification of regionally significant megasequences even in undrilled areas. The tectonic evolution and resulting stratigraphy can be described by eight plate tectonic events:

Visean (Carboniferous) break-up of the southeastern Asia (Simao, Indochina and South China);

Kungurian (uppermost Early Permian) break-up of Qiangtang and Sibumasu;

Lowermost Norian uplift due to Bowen Orogeny in eastern Australia;

Hettangian break-up of Mangkalihat (northeastern Borneo);

Oxfordian break-up of Argo/West Burma, and Sikuleh (Western Sumatra);

Kimmeridgian break-up of the West Sulawesi microplate;

Tithonian break-up of Paternoster-Meratus (central Borneo); and

Valanginian break-up of Greater India/India.

These events should be identifiable in all Australian Phanerozoic basins and beyond, potentially providing a template for a synchronisation of the Permian to Early Cretaceous stratigraphy.