Formations close to the Permo-Triassic boundary in Tasmania

Abstract

The Cygnet Coal Measures is a unit of carbonaceous shale, coal and feldspathic sandstone in Tasmania of Upper Permian age. It is overlain gradationally or disconformably by the Springs Sandstone, the lower member of which, Barnetts Sandstone, is a thinly-bedded, fine-grained feldspathic to arkosic sandstone, and the upper, the Mountain Lodge Sandstone and a more thickly-bedded, medium-grained protoquartzite. The upper part of the Springs Sandstone is probably Otoceratan. The Permo-Triassic boundary lies within these gradational non-marine units and cannot yet be fixed accurately. The base of the Mountain Lodge Member is probably the most convenient boundary to use as the Permo-Triassic boundary in local field mapping.