16 - Permo-Triassic boundary in Australia and New Zealand

Summary

Introduction

Although Upper Permian and Lower Triassic rocks are widespread, no sequences representing latest Permian and earliest Triassic marine deposition are known from Australia and no well-defined boundary sequence has been recognized in New Zealand. In the western part of Australia, where marine deposits are present, the uppermost Permian and the lowermost Triassic are represented by a hiatus. In central and eastern Australia only terrestrial deposits are known both in the Upper Permian and the Lower Triassic.

The floral changes associated with the boundary in Australia have been considered by Balme & Helby (1973) who concluded that a very marked change took place between the Permian and the Triassic. Dickins (1973) who summarized Australian boundary sequences, concluded that an important regression was apparent.

Western part of Australia

Considerable hiatus is present between the Permian and the Triassic (Fig. 16.1) with generally some, but not very distinct, angular structural discontinuity (Archbold & Dickins, 1991; Dickins, 1976; Banks, 1978).

In the Perth Basin, a gap is present between the Lower Permian marine Carynginia Formation of oldest Baigendzhinian (Upper Artinskian) age and the apparently nonmarine Wagina Sandstone, the age of which, on palynological grounds, is early Upper Permian (Lower and Upper here referring to a twofold subdivision of the Permian as used in the traditional type area in the Russian Platform-Ural Mountains region). A hiatus is then present beneath the Kockatea Shale, which contains a good open-sea marine fauna regarded as not older than Upper Griesbachian (Balme, 1963; McTavish & Dickins, 1974).

In the Carnarvon Basin no marine deposits are known that are younger than the Kungurian, the top stage of the Lower Permian.