Upper Permian marine sequences are limited in area in comparison with Lower Permian. Uppermost Permian marine rocks have not so far

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been recognized in Australia and lowermost marine Triassic (Otoceratan) is known from the Perth Basin. Brackish water beds of the same age are found in the Canning and possibly the Bonaparte Gulf Basin.

In the western part of Australia, Permian and Triassic rocks are known in the Bonaparte Gulf, Canning, Carnarvon and Perth Basins. The rocks in all basins are apparently separated by hiatus but without marked structural discordance. In the Bonaparte Gulf and Canning Basins, lagoonal or brackish-water Lower Triassic overlies marine Permian but uppermost Permian is apparently lacking. In the Carnarvon Basin, non-marine sandstone is regarded as Upper Permian and Lower Triassic is not known, although Middle to Upper Triassic has been identified in offshore drilling. In the Perth Basin, Otoceratan and younger Triassic in places overlies Upper Permian non-marine rocks with an hiatus. The position of the boundary is based on marine invertebrates and spores.

In eastern Australia, marine Lower and Upper Permian passes up into non-marine Upper Permian and Triassic, in the Bowen, Sydney and Tasmania Basins. The boundary has been placed at the highest occurrence of the Glossopteris flora and its associated microflora but currently this interpretation is under critical review. Breaks are recorded but their exact relationship to the boundary is not clear. The Tasman Geosyncline in eastern Australia was subject to instability and considerable igneous activity during the Permian and possibly into the Triassic. Radiometric dating shows widespread granitic intrusion close to the Permian-Triassic boundary.

In the central part of Australia, non-marine Permian and Triassic are generally separated by hiatus.

In eastern New Guinea, Permian marine rocks are recorded lying on an erosional surface of a granite which on radiometric evidence is close to the Permian-Triassic boundary. Lower Triassic has not been recognized.

The Lower Permian, thus, is a time of widespread marine transgression and an overall cool climate, followed in the Late Permian by withdrawal of the seas until in the latest Permian the sea may have retreated entirely from the present land mass. The climate became milder and by Triassic time warm to even tropical conditions existed. Tectonic and igneous activity were milder and less widespread in the Triassic. From the evidence the radical transformation of the fauna during Permian and Triassic time may well have been connected with the changes in paleogeographic conditions, particularly the withdrawal of shallow seas from the present continental area.

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