Coal petrology, palynology and carbon isotope record of the Aramac Coal Measures (Galilee Basin, Australia).

The Aramac Coal Measures in the Galilee Basin represent the early transition from a cold to a cool-temperate climate at the terminus of the Late Palaeozoic Ice Age (LPIA). The aim of this study is to examine the record of deglaciation and the establishment of the peat-forming Glossopteris-flora. Two boreholes, Longreach 1-1B and Muttaburra 1. were sampled to compare palynological and carbon isotope records alongside coal petrology. Palynological samples yield high abundances of striate bisaccate pollen derived from glossopterids, along with spores represent fem, horsetail and lycopsid undergrowth. Aquatic palynomorphs are rare but are indicative of freshwater conditions with no marine influence. These results reflect the quick establishment of Glossopteris-Qora following the glaciation. Coals from both sections show a degree of variability can be observed in the coals between each borehole. Coal seams in both holes show relatively low maturity for Australian Permian coals (vitrinite reflectance between 0.5% and 0.6%). Muttaburra 1 features fewer and thinner coal seams than Longreach 1 - IB. Coals from Longreach 1-1B tend to have a higher abundance of minerals and variable vitrinite/inertinite rations. Coals in Muttaburra 1 feature higher inertinite proportions. The liptinite component is made up mainly of sporinite and cutinite, but exsudatinite is also present filling pore space in the fusinites. The thin seams in the lower part of the Aramac Coal Measures feature higher proportions of liptinite, which tends to decrease upsection. With regards to intraseam variability, increases in inertinite can be observed in some seams in Longreach 1-1B, but not observed in Muttaburra 1. Organic carbon isotope values are within the expected range for C3 terrestrial plants. These values show an apparent cyclicity which may be related to climatic changes and humidity changes affected by the Pl and P2 glaciations. The timing of the deposition of the Aramac Coal Measures coincides with the P2 glaciation. Peat-formation either occurred distally from the position of the ice sheets or during brief interglacial phases. The high inertinite proportions indicate fire and/or fungal degradation of within the mire. Sedimentological evidence suggests permafrost was present during the formation of at least some proportion of the coal seams. [ABSTRACT FROM AUTHOR]