Detrital zircon age and provenance constraints on late Paleozoic ice-sheet growth and dynamics in Western and Central Australia

Abstract

U–Pb dating and Hf-isotope provenance analysis of detrital zircons from the glaciogenic lower Permian Grant Group of the Canning Basin indicate sources principally from basement terranes in central Australia, with subordinate components from terranes to the south and north. Integrating these data with field outcrop and subsurface evidence for ice sheets, including glacial valleys and striated pavements along the southern and northern margins of the basin, suggests that continental ice sheets extended over several Precambrian upland areas of western and central Australia during the late Paleozoic ice age (LPIA). The youngest zircons constrain the maximum age for contemporaneous ice sheet development to the late Carboniferous (Kasimovian), whereas palynology provides a minimum age of early Permian (Asselian–Sakmarian). Considering the palynological age of the Grant Group within the context of regional and global climate proxies, the main phase of continental ice sheet growth was possibly in the Ghzelian–Asselian. The presence of ice sheets older than Kasimovian in western and central Australia remains difficult to prove given a regional gap in deposition possibly covering the mid-Bashkirian to early Ghzelian within the main depocentres and even larger along basin margins, and the poor evidence for older Carboniferous glacial facies. There is also no evidence for extensive glacial facies younger than mid-Sakmarian in this region as opposed to eastern Australia where the youngest regional glacial phase was Guadalupian.

Keywords:

• Late Paleozoic ice age
• Canning Basin
• Grant Group
• Permian
• zircon provenance
• U–Pb–Hf

Acknowledgements

Thanks are due to the staff of the Western Australian Carlisle core facility (Department of Industry Regulation and Safety, Perth) for their assistance during sampling, C. Davies, H. Lock, D. Plant and V. Pashley for their help with mineral separation, CL imaging, and data acquisition, and K. Ludwig for providing a copy of Isoplot. AJM publishes with the permission of the Director, Geological Survey and Resource Strategy Division, Department of Mines, Industry Regulation and Safety, Western Australia. D. Le Heron and an anonymous reviewer are thanked for their suggestions that improved this manuscript.

Disclosure Statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This study was jointly funded by a Natural Environmental Research Council (UK) Studentship NER/S/A/2004/13012 and Shell International Exploration and Production (Netherlands).