II II II II II - Geoscience Australia

The coal measure theme was reiterated in the southwestern corner of the continent,
by the upper Sue Coal Measures and minor coal in the Sabina and Wagina Sandstones
of the Perth Basin. The latter two formations, though predominantly fluvial,
seem to become increasingly paralic towards the north (for example, acritarchs at the
base of the Sabina Sandstone indicate brackish - marine water), hinting at a marine
incursion in the north of the basin. A coal-forming environment may also have lingered
on in the Collie Basin, but if so, the sedimentary record has not been preserved.
Most of the Carnarvon Basin remained subject to subaerial erosion. The northern end
of the basin, however, was reclaimed by the sea, and a sandy marine shelf formed
with localized concentrations of skeletal carbonate debris in banks and shoals (the
Chinty Formation of Hocking & others, 1987). The Sholl Island Fault scarp was
probably still shedding an apron of rubble into the adjoining paralic and maritime
zones.
A similar limited marine incursion in the southwestern Canning Basin led to the
inception of the Chirup Formation in the coastal marshes at the head of the
embayment (Forman & Wales, 1981). In the Fitzroy Trough, where a lagoonal setting
had come into being late in the previous time slice, a large fluvial lobe, this time
supplied from the Kimberley uplands, built out into the central part of the repository.
Meanwhile, at the southeastern extremity of the trough, lagoonal tidal flat sediments
of the Godfrey beds were being laid down. The sedimentation style was transformed
by the sudden marine intrusion represented by the upper Hardman Formation, when
the site received first shallow marine muds and minor carbonate, then nearshore and
coastal sands, and eventually even minor coal as progradation began to be reasserted.
The interval ended with most of the trough being temporarily nondepositional,
revealed in the stratigraphic record by a hiatus.
The large delta in the Bonaparte Basin was drowned beneath the advancing waters
of a marine transgression, after which a smaller delta was re-established in a lagoonal
tract behind a prograding barrier bar. Presumably the new delta was also furnished
with clastics eroded at least in part from the central Australian highlands. The northern
sector of the basin was maintained as a marine shelf throughout the Late Permian.
As in previous time slices, there may have been equivalents of the Bonaparte shallow
marine sequence in the Arafura Basin. This portion of the continent had a warmer
climate than any other region at any time during the Permian, becoming warm
temperate to tropical (Dickins, 1978).
OIL AND GAS
PERMIAN ENERGY & MINERAL RESOURCES
The Permian system is a critical one with regard to the distribution of energy resources
in Australia. Economic and sub-economic oil and gas accumulations occur in the
Bonaparte, Cooper, and Bowen Basins, but even more importantly, many of the larger
accumulations reservoired in the Mesozoic sequences of the Eromanga and Surat
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