CHAPTER 9 - The Jurassic System

Abstract

This chapter provides an overview of the Jurassic system. The Jurassic strata in Australia are confined to the Canning, Carnarvon, and Perth Basins in Western Australia, and to the Carpentaria, Laura, Maryborough, Great Artesian, Polda, Mulgildie, and Clarence–Moreton Basins in eastern Australia. The deposits in eastern Australia are almost exclusively nonmarine. Much of the Western Australian Jurassic is marine but only that in the western part of the Carnarvon Basin is regarded as a deep-water deposit. Volcanism was greatly restricted both in time and space in the Jurassic of Australia. In New Zealand, the Jurassic rocks are geographically associated and, on the whole, conformable with those of the Triassic System. They are lithologically similar to the Triassic but, especially in their upper portions, they are less indurated, finer bedded, and contain more mudstone and less visible feldspar. The Middle Jurassic saw a marked increase in the area of sedimentation in the Great Artesian Basin. Throughout this basin, and the Mulgildie and Clarence–Moreton Basins, a sequence of lithic sandstone, shale, sideritic mudstone, and sub-bituminous coal accumulated, apparently under fluviatile to swamp conditions. The Walloon reaches a maximum thickness of 600 m in the Clarence-Moreton Basin where it extends into the Upper Jurassic at least.