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Mass Extinction studies

Ian Metcalfe

Plot of diversty vs. time showing the five major mass extinctions during the last 600 million years.

Ian Metcalfe has, since 1996, been leading an international research group studying the "Mother of them all" end-Permian (late Changhsingian) mass extinction in China and more recently in Australia. These studies, with collaborators and colleagues principally from Australia, China and the USA, have included biostratigraphic, chemostratigraphic and magnetostratigraphic studies and U-Pb and Ar-Ar isotopic geochronology of the Permian-Triassic transition interval (including the Permian-Triassic boundary and mass extinction) both on land (terrestrial environment) and in the sea (marine environment) and the end-Guadalupian mass extinction level c. 7 million years earlier.

This work has been and is supported by the Australian Research Council, Geoscience Australia, The University of New England, The Australian National University, Origin Energy (Australia) and the National Science Foundation of the USA.

Biostratigraphic studies have principally been conodont biostratigraphy in marine sections and palynological studies in non-marine sections. This work has led to enhanced knowledge of conodont faunas and zones at the P-T boundary Global Stratotype Section and Point in Meishan (Nicoll et al., 2002) and in non-marine-paralic-marine transitional sequences in SW China (Metcalfe and Nicoll, 2007). Results of our work on stratigraphy, biostratigraphy and chemostratigraphy of the terrestrial P-T transition in Xinjiang Province, NW China has appeared in a special issue of the Journal of Asian Earth Sciences (Metcalfe et al., 2009). Recent biostratigraphical studies of the P-T transition in Western Australia (Perth Basin) have also led to enhanced understanding of the P-T boundary in Australia (Metcalfe et al., 2008).

Magnetostratigraphic studies of both marine and non-marine P-T sequences in China show that the Permian-Triassic boundary lies within a normal chron a short distance above a reversere to normal transition boundary (Glen et al., 2009).

Radio-isotopic geochronology studies have provided important constraints for numerical timescale calibration of the P-T transition and a robust U-Pb age for the Permian-Triassic boundary together with development and application of annealing and chemical abrasion techniques (CA-IDTIMS) for dating single zircon crystals from volcanic ash-fall tuffs. This work was published in 2004 by our group in the journal Science.

Current project group work focusses on U-Pb CA-IDTIMS dating of Permian-Early Triassic tuffs principally in Eastern Australia (Sydney-Gunnedah-Bowen Basins) and on biostratigraphic, chemostratigraphic and biomarker studies of Permian-Triassic transitional strata in the Perth Basin of Western Australia (including a newly acquired core through the Permian-Triassic boundary in the Redback-2 well).

Mapping climate-change through the Permian-Triassic interval is also being undertaken using oxygen isotope studies on the microfossils conodonts that provide information on both geographical and temporal changes in sea surface temperatures.

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