Palynology of the Jurassic–Cretaceous transition, Surat Basin, Australia

Abstract

This paper presents, for the Queensland portion of the Rhaetian – Early Cretaceous Surat Basin, the results of a taxonomic-descriptive study of 89 palynological samples collected from three boreholes that intersected the succession containing the Gubberamunda Sandstone and the succeeding Orallo Formation, as well as the upper Westbourne Formation and the lower Mooga Sandstone, which respectively underlie and overlie this succession. This upper Westbourne Formation – lower Mooga Sandstone interval represents the most complete Late Jurassic – Early Cretaceous sedimentary succession in Queensland. It was sampled from: GSQ DRD 26, GSQ Roma 2 and GSQ Dalby 1, respectively located in the western, central, and eastern parts of the basin. The samples yielded a diverse palynoflora in which 212 taxa were identified, embracing both in-situ and reworked (latest Carboniferous – Early Jurassic) spores and pollen, as well as palynomorphs of algal, fungal, acritarch and unknown affinities. Formally included in this work is the previously unpublished taxonomy of McKellar, largely from the immediately preceding part of the Surat Basin succession, as its taxonomic nomenclature is critical to the current compilation. Herewith proposed (from both the current work and that of McKellar) are 27 new species, two new genera, 22 new combinations, ten emendations, the elevation of one subgenus to generic status, and the renaming of one species. From a biostratigraphic perspective, palynofloras from the upper Westbourne Formation and the lower Gubberamunda Sandstone are assigned to the informally defined ‘Retitriletes watherooensis association zone’, and palynofloras from the upper Gubberamunda Sandstone, Orallo Formation and lower Mooga Sandstone, to the Ruffordiaspora australiensis Interval Zone. The upper Westbourne Formation – lower Mooga Sandstone interval was deposited in lacustrine, floodplain and backswamp facies, with a flora that remained relatively stable, there being no major floristic turnover; it consisted of diverse ferns, conifers, lycopods, bryophytes, seed ferns, and a variety of ginkgoes, cycads, and/or gnetales. Humid, warm-temperate conditions are indicated by the flora’s climatic signature.

Keywords:

• systematic palynology
• taxonomy
• Australia
• Jurassic
• Cretaceous
• Mesozoic
• Surat Basin

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