Eocene palynology of the Mulga Rocks deposits, southern Gunbarrel Basin, Western Australia

Abstract

Late Eocene palynomorph assemblages have been recovered from carbonaceous sediments within a tenement centred on the Mulga Rocks uranium deposits, currently under exploration by Energy and Minerals Australia. The Mulga Rocks deposits occur in a palaeovalley incised into rocks of the Cretaceous southern Gunbarrel Basin, and the underlying Neoproterozoic to Late Devonian southern Officer Basin, Western Australia. The palynomorph assemblages recovered from the Mulga Rocks deposits most closely resemble the Middle Nothofagidites asperus Zone equivalent of the Murray Basin. Many of the species recovered, and the abundance and diversity at which they are present, are considerably different from most of the southeastern Australian palynoassemblages of similar age. Common in the assemblages are species belonging to Nothofagus, Casuarinaceae, Myrtaceae and Picrodendraceae. Proteaceous species are diverse, with Banksia affiliates being prominent. Of most significance are assemblages dominated by Myrtaceidites species, which also contain affiliates of Petrophile and Xylomelum that occur in modern heathland, woodland and dry sclerophyll forests. The prominence of these taxa, and their co-occurrence, suggests that sclerophylly, at present linked closely with xeromorphy and now ubiquitous in the vegetation of Western Australia, was present in the late Eocene of southern Australia and suggests that at that time this trait may have been more prevalent than previously interpreted.