Mesozoic transformation of Western Australia: rifting and breakup of Gondwana

Mesozoic transformation of Western Australia spans 252 to 66 Ma, an era represented by sedimentary deposits that cover about 23% of the onshore part of the State and virtually all offshore basins, with the Upper Jurassic – Cretaceous extending beyond the continent onto oceanic crust. These sedimentary successions are up to 15 km thick in offshore depocentres and the Perth Basin, and contain only minor igneous rocks apart from areas near the continent–ocean boundary where intrusions are abundant.

'Mesozoic transformation of Western Australia: rifting and breakup of Gondwana' is the latest release under the WA unearthed series aimed at geologists, and particularly newcomers to the State, to enable them to get a quick understanding of the geology and economic potential of various terrains. In this volume, much of the narrative concerns the offshore North West Shelf, Australia’s premier hydrocarbon province. Because of subdued tectonic events, the most significant resources in, or uses of, onshore Mesozoic strata are heavy mineral sand deposits on the Dampier Peninsula, water resources and gas storage.

A series of paleogeographic reconstructions paired with isopach images illustrates the Mesozoic depositional and structural history of the State and its surrounding waters – each represent ‘time slices’ derived from regional correlations largely based on biostratigraphic studies. The four main phases of basin evolution are: Triassic intracratonic rifting; Early–Middle Jurassic rifting; Late Jurassic – Early Cretaceous breakup and separation; and lastly, trailing-edge rifting and marginal sag. However, these phases are not synchronous, as there are differences between some areas in their timing, especially with the progressive breaking away of continental fragments from north to south. Whereas the main text is largely concerned with geological evolution, there is also a series of boxes detailing other aspects such as mineralization, other resources, fossils, impact features and provenance.