Abstract

Devonian rocks in Western Australia were deposited in interior (intracratonic) sag and fracture basin settings and are well developed in the Carnarvon, Canning, Bonaparte, and Ord Basins. Some Devonian sedimentation may also have taken place in the Perth and Officer Basins. The sediments belong to one unconformity-bounded depositional sequence of Early Devonian to mid-Carboniferous age.

Shallow water deposition took place over much of the Canning Basin in the Early and Middle Devonian, with periods of eolian and fluvial sedimentation in the Kidson Sub-basin. Marine conditions spread to the Carnarvon Basin in the Middle Devonian where siliciclastic shoreline sediments gave way to mixed siliciclastic/carbonate deposition on an epeiric ramp in the Frasnian; reef complexes probably developed at the distal edge of the ramp. Local Late Devonian faulting in the Carnarvon Basin led to the return of shoreline deposition followed by fluvial and alluvial fan sedimentation in the eastern part of the basin, while shelf conditions continued in the west.

Faulting occurred in the mid-Devonian, probably related to the Alice Springs Orogeny in central Australia. This resulted in graben subsidence in the Fitzroy Trough and deposition was confined to the northern Canning Basin in the Late Devonian. Reef complexes grew on the north (Lennard Shelf, where the reefs are very well exposed) and south (subsurface reefs of the Broome Platform area) sides of the graben, and evaporite deposition took place on the Barbwire Terrace. Faulting initiated deposition in the Bonaparte and Ord Basins where extensive alluvial fan and fluvial sediments pass seawards (north) into shallow-marine siliciclastics with reef complexes. Sedimentation was restricted to the Frasnian in the Ord Basin but continued through the Famennian in the Bonaparte Basin, with reef-complex development interfingering with shelf siliciclastics.