Abstract

New evidence is presented on the Triassic–Jurassic boundary in eastern Australia, based on miospore assemblages from three continuously cored drillholes which penetrated the Raceview Formation to Ripley Road succession in the eastern Clarence-Moreton Basin of southeastern Queensland. Evidence for the age of this continental succession is provided by correlation based on the first appearances of five distinctive species. These taxa first appear at or close to the Rhaetian–Hettangian boundary in the marine, ammonite-dated succession of New Zealand and in the lower Ripley Road Sandstone of Queensland. The more gradual introduction of these species in the Queensland succession, as opposed to their near-synchronous appearance in New Zealand, is probably due to their gradual migration into an inland environment in contrast to their origin from a nearshore region in New Zealand. At higher levels the first appearance of intrastriate Classopollis, closely followed by its marked increase in abundance, is regarded as evidence for correlating assemblages from the upper Ripley Road Sandstone in the eastern Clarence-Moreton Basin with the earliest Sinemurian of New Zealand. The views of some previous workers that the Hettangian of eastern Australia is characterised by the appearance of abundant Classopollis must now be modified. From the aspect of biotic change, associated with climate change at the Triassic–Jurassic boundary, this study indicates a rapid local change in New Zealand. A new type of biozone, the Association Zone, is proposed as a type of interval zone. The need for a distinctive biozone to characterise palynofloral assemblages is indicated to allow for the frequent recycling of palynomorphs and also to better define the body of an interval zone. New Early Jurassic miospore zones are proposed for southeastern Queensland. Granamegamonocolpites campbellii sp. nov. is described and one new combination, Anapiculatisporities helidonensis (de Jersey) comb. nov., is proposed. Morphological and stratigraphical evidence is provided for gradualism in the lineage development of intrastructure in Classopollis, from massive (unstructured), to intrapunctate, to intrastriate specimens.

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