Calibrating the middle and late Permian palynostratigraphy of Australia to the geologic time-scale via U–Pb zircon CA-IDTIMS dating |
| |
| Authors: | J R Laurie R S Nicoll J L Crowley D J Mantle A J Mory |
| |
| Institution: | 1. Geoscience Australia, GPO Box 378, Canberra, ACT 2601, Australia;2. Department of Biological Sciences, Level 2, E8B, Macquarie University, NSW 2109, Australia;3. Research School of Earth Sciences, Australian National University, Building 142, Mills Road, Acton, ACT 2601, Australia;4. Department of Geosciences, 1910 University Drive, Boise State University, Boise, ID 83725-1535, USA;5. MGPalaeo, Unit 1, 5 Arvida Street, Malaga, WA 6090, Australia;6. Geological Survey of Western Australia, 100 Plain Street, East Perth, WA 6004, Australia;7. UWA Centre for Energy Geoscience, School of Earth and Environment (M004), The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia |
| |
| Abstract: | The advent of chemical abrasion-isotope dilution thermal ionisation mass spectrometry (CA-IDTIMS) has revolutionised U–Pb dating of zircon, and the enhanced precision of eruption ages determined on volcanic layers within basin successions permits an improved calibration of biostratigraphic schemes to the numerical time-scale. The Guadalupian and Lopingian (Permian) successions in the Sydney, Gunnedah, Bowen and Canning basins are mostly non-marine and include numerous airfall tuff units, many of which contain zircon. The eastern Australian palynostratigraphic scheme provides the basis for much of the local correlation, but the present calibration of this scheme against the numerical time-scale depends on a correlation to Western Australia, using rare ammonoids and conodonts in that succession to link to the standard global marine biostratigraphic scheme. High-precision U–Pb zircon dating of tuff layers via CA-IDTIMS allows this tenuous correlation to be circumvented—the resulting direct calibration of the palynostratigraphy to the numerical time-scale highlights significant inaccuracies in the previous indirect correlation. The new data show: the top of the Praecolpatites sinuosus Zone (APP3.2) lies in the early Roadian, not the middle Kungurian; the top of the Microbaculispora villosa Zone (APP3.3) lies in the middle Roadian, not the early Roadian; the top of the Dulhuntyispora granulata Zone (APP4.1) lies in the Wordian, not in the latest Roadian; the top of the Didecitriletes ericianus Zone (APP4.2) lies in the first half of the Wuchiapingian, not the latest Wordian; the Dulhuntyispora dulhuntyi Zone (APP4.3) is exceptionally short and lies within the Wuchiapingian, not the early Capitanian; and the top of the Dulhuntyispora parvithola Zone (APP5) lies at or near the Permo-Triassic boundary, not in the latest Wuchiapingian. |
| |
| Keywords: | Palynostratigraphy CA-IDTIMS Permian Bowen Basin Canning Basin Hunter Coalfield Gunnedah Basin U–Pb zircon geologic time-scale Sydney Basin |
|
|
