Ocean anoxia was widespread in the latest Permian and continued episodically into the Early Triassic. These episodes of anoxia have been interpreted to be due to the upward rise(s) of the chemocline, oceanic overturn(s) and/or major climatic perturbations. A significant anoxic event is recorded in the Kockatea Shale of the lower part of the Senecio-1 borehole core from the northern Perth Basin, Australia. We here present new biostratigraphic and chemostratigraphic data constraining the age of this anoxic event. The Early Triassic Induan-Olenkian Stage boundary (Dienerian-Smithian Sub-Stage boundary) has been identified in the Senecio-1 Well. This is the first international Triassic stage boundary to be unequivocally placed in Australia. Relatively abundant conodont faunas (1,000+ elements) represent three conodont zones in ascending order, the 'Clarkina carinata' - 'Neospathodus dieneri' Zone, the 'Neospathodus waageni eowaageni' Zone and the 'Neospathodus waageni waageni' Zone. In addition, a 'Neospathodus waageni' subsp. nov. subzone is recognised in the upper part of the 'Neospathodus waageni waageni' Zone.

Earlier reports on the Permian conodont biostratigraphy of Western Australia have documented faunas from the Canning Basin (Noonkanbah Formation) and Carnavorn Basin (Callytharra, Coyrie. Wandagee and Coolkylia formations) that ranged in age from the Late Sakmarian to the Roadian. New studies have now documented additional Permian conodont faunas from the Perth Basin (Beekeeper Formation) and from the Canning Basin (Nura Nura Member of the Poole Formation, from throughout the Noonkanbah Formation, in the Lightjack Formation and from the Kirkby Range and Cherrabun Members of the Hardman Formation). These faunas range in age from the Late Sakmarian to the Wuchiapingian.

Measured lithostratigraphic sections of the classic Permian–Triassic non-marine transitional sequences covering the upper Quanzijie, Wutonggou, Guodikeng and lower Jiucaiyuan Formations at Dalongkou and Lucaogou, Xinjiang Province, China are presented. These measured sections form the framework and reference sections for a range of multi-disciplinary studies of the P–T transition in this large ancient lake basin, including palynostratigraphy, vertebrate biostratigraphy, chemostratigraphy and magnetostratigraphy. The 121 m thick Wutonggou Formation at Dalongkou includes 12 sandstone units ranging in thickness from 0.5 to 10.5 m that represent cyclical coarse terrigenous input to the lake basin during the Late Permian. The rhythmically-bedded, mudstone-dominated Guodikeng Formation is 197 m and 209 m thick on the north and south limbs of the Dalongkou anticline, respectively, and 129 m thick at Lucaogou. Based on limited palynological data, the Permian–Triassic boundary was previously placed approximately 50 m below the top of this formation at Dalongkou. This boundary does not coincide with any mappable lithologic unit, such as the basal sandstones of the overlying Jiucaiyuan Formation, assigned to the Early Triassic. The presence of multiple organic δ¹³C-isotope excursions, mutant pollen, and multiple algal and conchostracan blooms in this formation, together with Late Permian palynomorphs, suggests that the Guodikeng Formation records multiple climatic perturbation signals representing environmental stress during the late Permian mass extinction interval. The overlap between the vertebrates Dicynodon and Lystrosaurus in the upper part of this formation, and the occurrence of late Permian spores and the latest Permian to earliest Triassic megaspore Otynisporites eotriassicus is consistent with a latest Permian age for at least part of the Guodikeng Formation. Palynostratigrahic placement of the Permian–Triassic boundary in the Junggar Basin remains problematic because key miospore taxa, such as Aratrisporites spp. are not present. Palynomorphs from the Guodikeng are assigned to two assemblages; the youngest, from the upper 100 m of the formation (and the overlying Jiucaiyuan Formation), contains both typical Permian elements and distinctive taxa that elsewhere are known from the Early Triassic of Canada, Greenland, Norway, and Russia. The latter include spores assigned to Pechorosporites disertus, Lundbladispora foveota, Naumovaspora striata, Decussatisporites mulstrigatus and Leptolepidites jonkerii. While the presence of Devonian and Carboniferous spores and Early Permian pollen demonstrate reworking is occurring in the Guodikeng assemblages, the sometimes common occurrence of Scutasporites sp. cf. Scutasporites unicus, and other pollen, suggests that the Late Permian elements are in place, and that the upper assemblage derives from a genuine transitional flora of Early Triassic aspect. In the Junggar Basin, biostratigraphic data and magnetostratigraphic data indicate that the Permian–Triassic boundary (GSSP Level) is in the middle to upper Guodikeng Formation and perhaps as high as the formational contact with the overlying Jiucaiyuan Formation.

Palynology is the principal biostratigraphic tool employed to correlate among the thick fluvial to shallow marine successions of the Permian-Early Triassic of the Bowen and Sydney basins of eastern Australia. The regional palynofloras can be utilised for intra-continental comparisons but are only broadly correlative across Gondwana and rarely applicable as stage or sub-stage level of global tie-points. High precision CA-IDTIMS dating of Middle Permian-Early Triassic ashfall tuffs in these basins has provided a unique opportunity to confidently tie the endemic fossil biota to the international timescale. Carbonaceous siltstones and coals bracketing the tuff beds have been processed for their palynological content thus enabling precise chronometric ages to be ascribed to the fossil biotas. Tying these biozones to the internationally accepted Geologic Timescale will greatly enhance the event and biozonation correlation to areas outside Australia.

Palynology is the principle biostratigraphic tool employed to correlate thick fluvial to shallow marine successions of the Permian-Early Triassic of the Bowen and Sydney basins of eastern Australia. The regional palynofloras can be utilised for intra-continental comparisons but are only broadly correlative across Gondwana and rarely applicable as stage or sub-stage level global tie-points. High-precision CA-IDTIMS dating of Middle Permian-Early Triassic ashfall tuffs in these basins has provided a unique opportunity to confidently tie the endemic fossil biota to the international timescale. Carbonaceous siltstones and coals bracketing the tuff beds have been processed for their plant microfossil content thus enabling precise chronometric ages to be assigned to the identified palynozones. Tying these biozones to the internationally accepted Geologic Timescale will greatly enhance correlation to areas outside of Australia, allowing specific global events to be recognised. Results from the Sydney Basin, previously published, suggested significant modifications to the ages currently assigned to some of the Late Permian and Early Triassic palynozones. These results are now coupled with results from the Bowen Basin to provide a regional synthesis of eastern Australian basin palynofloras.

The Middle Permian-Early Triassic (MP-ET) of Eastern Australia hosts extensive black coal reserves of major economic importance but contains predominantly endemic biota precluding precise international correlation. MP-ET stage boundaries, and end-Guadalupian and end Permian mass extinction levels are poorly constrained. Attempts to calibrate the MP-ET of Australia using SHRIMP resulted in controversial radioisotopic ages with percent-level uncertainty and compromised accuracy. We here report more than 40 new high-precision (most at the ±0.05 myr level) using U-Pb CA-IDTIMS single zircon techniques for tuffs in the Sydney, Gunnedah and Bowen basins. These dates provide vital international timescale tie points and allow us to correlate individual tuff beds at the intra and inter basin levels. The youngest dates from the Garie Fm Sydney Basin (c. 247.7 Ma, c. 248.0 Ma) give a late Early Triassic (late Spathian) age. An age of c. 252.2 Ma from the top Bandanna Formation, Bowen Basin equates with the Permian-Triassic boundary. The oldest dates obtained are c. 263.4 Ma from the Broughton Fm and c. 271.4 Ma for the Rowan Fm, Sydney Basin, older than the Guadalupian-Lopingian boundary of c. 260 Ma. Implications of these ages for calibration of stratigraphy, local and regional correlations, placement of mass extinction levels, sedimentation rates, dating of environmental and climate change (including glaciation) and as a chronological framework for energy resources are presented.

Late Permian (late Changhsingian), Early Triassic Induan (Dienerian), and early Olenekian (Smithian) condonts have been recovered from the Hovea Member of the Kockatea Shale in the exploration well Corybas-1, northern Perth Basin, Western Australia. Ongoing studies of the Kockatea Shale from other Perth Basin wells are providing additional conodont material that further refine the international calibration and correlation of the Australian Upper Permian - Lower Triassic. Based on the recovered conodonts, coupled with megaspore data and previously reported Cisotope, macrofossil and geochemical data, the Permian Triassic boundary (GSSP level) is placed in the lower part of the Sapropelic Interval of the Hovea Member of the Kockatea Shale, and the mass-extinction level at the Inertinitic-Sapropelic boundary within the Hovea Member. The presence of 'Clarkina jolfensis' Kozur internationally calibrates the Australian endemic 'Protohaploxypinus microcorpus' palynofloral zone and the basal part of the Sapropelic Interval of the Hovea Member as late (but not latest) Changhsingian age.

The Middle Permian-Early Triassic (MP-ET) of Eastern Australia contains a predominantly endemic biota precluding precise correlation with standard international biozones and System/Stage boundaries. The Permian-Triassic boundary, other MP-ET stage boundary levels, and the major end-Guadalupian and end-Permian mass extinction levels in Australia remain poorly constrained. Attempts to calibrate the MP-ET of Australia using Sensitive High Resolution Ion Microprobe techniques have resulted in controversial radioisotopic ages with percent-level uncertainty and compromised accuracy due to the use of an unsuitable standard. We here report eighteen new high-precision (<±0.05 my) U-Pb CA-IDTIMS ages for tuffs in the Sydney Basin based on isotopic dating of chemically abraded individual zircons. These dates provide vital international timescale tie points for the MP-ET of Australia.

Four new species of the conodont genus 'Hindeodus', 'Hindeodus eurypyge' sp. nov., 'Hindeodus inflatus' sp. nov., 'Hindeodus' sp. nov. A and 'Hindeodus' sp. nov. B, are described from the Permian–Triassic transition in South China. Our study confirms the first appearance of 'Hindeodus parvus' at the GSSP level, base of bed 27c at Meishan. However, at Shangsi the first occurrence of 'H. parvus' is about 4.5 m above the event boundary. Analysis of conodont biostratigraphy of the Meishan D section and the Shangsi section suggest significant differences between the two sections. These include the absence of 'H. changxingensis' Wang from the Shangsi section and the approximately 4.5 m of the Shangsi section that contains 'H. priscus' (Kozur), H. latidentatus (Kozur) and 'H. eurypyge' n.sp. below the first occurrence of 'H. parvus'. These differences may be accounted for most easily by suggesting that there is a minor depositional hiatus at the Permian–Triassic boundary GSSP level as based on the first appearance of the conodont 'Hindeodus parvus' in Meishan section D. Taxonomic re-evaluation of 'Hindeodus Pa' elements indicates that species of the genus can be broadly separated into two groups based on the morphology of the posterior portion of the element and on growth patterns. The stable Pa element morphology of 'Hindeodus', first developed in the Carboniferous, was replaced by a complex of rapid evolutionary change in the latest Permian and Early Triassic, with as many as 11 valid species of the genus in the Permian–Triassic boundary interval, which are probably descendants of only two species, 'H. typicalis' and 'H.' n.sp. B. We suggest that the dramatic change in conodont biofacies observed at the boundary in South China from 'Neogondolella'-dominated faunas to 'Hindeodus'-dominated faunas was caused by the introduction of a high component of silt, beginning in bed 27 at Meishan and bed 28 at Shangsi, that tipped the environmental balance in favor of 'Hindeodus' and 'Isarcicella' over 'Neogondolella' ('Clarkina') species. We contend that 'Hindeodus' species were adaptable to higher levels of turbidity than 'Neogondolella'('Clarkina') species and hence at Meishan and Shangsi it was not a matter of a drastic increase in the abundance of 'Hindeodus', but an exclusion of 'Neogondolella'.

Late Permian (late Changhsingian), possible Early Triassic Induan (Dienerian), and early Olenekian (Smithian) conodonts have been recovered from the Hovea Member of the Kockatea Shale in the exploration well Corybas 1, northern Perth Basin, Western Australia. Placement of the biostratigraphic Permian - Triassic boundary is in the lower part of the Sapropelic Interval of the Hovea Member. The Australian endemic "Protohaploxypinus microcorpus" palynofloral Zone is confirmed to be of late (but not latest) Changhsingian age. The Permian - Triassic boundary, based on international calibration using conodonts, carbon-isotope stratigraphy and new radio-isotopic dating, is placed in the lower part of the "Kraeuselisporites saeptatus" and "Lunatisporites pellucidus" Zones of western and eastern Australia, respectively, which corresponds approximately to the basal part of the Rewan Group and equivalents in eastern Australia.