Return to Research
Return to Home Page
Isotopic Dating & Timescale Calibration

Ian Metcalfe

[Supported by the Australian Research Council, Geoscience Australia, Berkeley Geochronology Centre (Ann and Gordon Getty Foundation), Boise State University, The University of New England, The Australian National University, Origin Energy (Australia), National Science Foundation of the USA, Centennial Coal (Australia), BHP Billiton, Xtrata Coal, Santos Ltd, Geological Survey of New South Wales, Geological Survey of Queensland, Geological Survey of New South Wales.]


Figure showing approaches to minimise Pb-loss in zircon crystals and how annealing and chemical abrasion can produce closed-system zircons that maximise accuracy of single crystal U-Pb derived ages for volcanic products (from Mundil, Ludwig, Metcalfe & Renne, 2004)

Ian Metcalfe has, since 1996, been leading an international research group undertaking isotopic dating of volcanic ash/clay layers in sedimentary rock sequences aimed at providing ages of significant geological events (in particular the "end" Permian mass extinction) and numerical isotopic age tie points for global Timescale Calibration. The work undertaken on the Permian-Triassic transition in China, in collaboration with Roland Mundil, Paul Renne and Ken Ludwig of the Berkeley Geochronology Centre, led to establishment of robust ages for the mass extinction level and the Permian-Triassic Boundary as defined at the Global Stratotype Section and Point (GSSP) at Meishan, South China. More fundamental outcomes of this work in China led to refinement of a new technique of annealing and chemically abrading zircon crystals prior to dating of single zircon crystals from volcanic ash-fall tuffs. This new isotopic analysis approach is now referred to as Chemical Abrasion Isotope Dilution Thermal Ionisation Mass Spectrometry (CA-IDTIMS) and has been adopted by most laboratories undertaking U-Pb single crystal zircon dating worldwide. This work was published in 2004 by our group in the journal Science.


Collecting volcanic ash layers (white layers) from a thick coal seam in Queensland, Australia

U-Pb isotopic dating on biostratigraphically constrained volcanic ash layers in China and elswhere has now established a robust global timescale for the Middle Permian-Early Triassic and high-precision estimates for the ages of System and stage boundaries for the Permian and Triassic. This work has essentially been done in northern, low-latitude localities where the global reference sections for system and stage boundaries are defined. Correlation of the global redference sections with high-latitude and southern hemisphere sequences is however highly tenuous due to the endemic nature of biota in these regions. This is particularly true for Australia and Gondwana in general. Our current project group work focusses on U-Pb CA-IDTIMS dating of Permian-Early Triassic tuffs in Australia (Eastern Australia Sydney-Gunnedah-Bowen Basins; Western Australia Canning and Bonaparte Basins) and is aimed at international calibration of Australian sequences and biozones (in particular palynozones). In addition, the ultra-high-precision of CA-IDTIMS ages obtained allows us to accurately correlate sequences both intra-basin and inter-basin. This latter work has important applications in coal, oil, and gas exploration in Australia and has led to much interest and research funding support. Initial results of this work were presented at the XVII International Congress on the Carboniferous and Permian, Perth, July 2011. The following papers on our isotopic dating were presented:

Late Permian U-Pb CA-IDTIMS isotope geochronology of the Bowen Basin, Eastern Australia
I. Metcalfe, R.S. Nicoll, R. Mundil, S. Denyszyn, J. Crowley, D. Mantle, R. Willink, & C.B. Foster
Download Abstract PDF

New Middle Permian - Early Triassic U-Pb zircon CA-IDTIMS isotopic ages of tuffs in the Sydney Basin, Australia: International calibration of stratigraphy and biostratigraphy.
I. Metcalfe, R.S. Nicoll, J. Crowley, M. Ives, D. Mantle, K. Ruming, M. Huyskens & C.B. Foster
Download Abstract PDF

New U-Pb CA-IDTIMS isotopic age tie points for the Lightjack Formation, Canning Basin, Western Australia
R.S. Nicoll, I. Metcalfe, A.J. Mory, D. Mantle, J. Crowley, R. Mundil, S. Denyszyn & C.B. Foster
Download Abstract PDF

Late Permian-Early Triassic palynology of the Bowen and Sydney basins: results and implications of new CA-IDTIMS isotopic ages.
D. Mantle, C.B. Foster, R.S. Nicoll, I. Metcalfe, J. Crowley & R. Mundil
Download Abstract PDF

Return to Research
Return to Home Page