Palynostratigraphic reassessment of the Permian Wolfang Basin (Queensland, Australia) − implications for climate and timing of coal formation

Abstract

The Permian-aged Wolfang Basin in Queensland, Australia, formed as a rift-controlled half graben containing significant coal resources. Recently, the use of high-resolution zircon ages has allowed for a recalibration of the eastern Australian palynostratigraphy, necessitating a re-examination of the timing of deposition in the Wolfang Basin relative to the glacial episodes that mark the end of the Late Palaeozoic Ice Age in Australia. Four coal seams were selected for palynological and organic carbon isotope analysis: the Wolfang Main, Wolfang Upper, Prospect and Gowrie seams. Palynostratigraphy from the Wolfang Basin yields an APP3.2 age for the Wolfang Main and Upper seams (Kungurian-Roadian), an APP3.3 age for the Prospect seam (mid-upper Roadian), and an APP4.2 age for the Gowrie seam (Wordian). This indicates the timing of formation of the Wolfang Main and Upper seams preceded the P3 glaciation, whereas the Gowrie and possibly the Prospect seams were contemporaneous with the glaciation. Palynofloras show an overall dominance of trilete spores (Leiotriletes, Microbaculispora, Acanthotriletes), particularly in the Wolfang Main and Wolfang Upper seams, however pollen grains (Protohaploxypinus, Scheuringipollenites, Marsupipollenites) increase in abundance in the Prospect and Gowrie seams. The Gowrie seam also shows a higher abundance of monosaccate pollen (Plicatipollenites, Cannanoropollis). Organic carbon isotopes of vitrain bands show subtle enrichment from a mean of −24‰ in the Wolfang Main seam to –23.3‰ in the Prospect seam. The Gowrie seam shows upsection depletion from –23.2‰ to –23.9‰. These trends are comparable to existing records and may reflect a shift to cooler conditions related to the P3 glaciation, though local tectonic and environmental regimes still allow for periods of peat-formation.