Mid-Phanerozoic microbialite forms and associated facies in the northern Perth Basin, Western Australia, and their relationship to the end-Permian mass extinction

Abstract

Throughout geological history, biodiversity trends have been punctuated by sharp declines coinciding with mass extinction events. Certain organisms—known as disaster forms—flourish during the extinction aftermath from a lack of ecological competition and predation. Microbialites (in particular, stromatolites) are known to increase in environmental diversity following these biotic crises. However, it remains important to identify whether individual microbialite occurrences are a result of globally driven competition reduction or favourable local conditions. Here, we reconsider stromatolites from the northern Perth Basin of Western Australia, previously reported as Smithian (late Olenekian) in age and part of a biotic rebound following the end-Permian mass extinction and re-evaluate their paleodepositional setting and age. Detailed mapping, macro-analysis and meso-analysis of the Perth Basin locality have identified a well-preserved and diverse morphological assemblage of stromatolites that are intimately associated with a coarse siliciclastic facies. The characteristics of, and relationships between the stromatolitic and coarse siliciclastic facies support a restricted aquatic paleodepositional environment with fluvial/alluvial influences. In the Perth Basin, such depositional environments occurred most commonly during the Permian (Guadalupian to Lopingian). The robustness of previous age constraints interpreted from overlying strata (Kockatea Shale) are questioned by the identification of a depositional hiatus and onlapping relationship of the Kockatea Shale on the stromatolitic sequence. Therefore, we suggest that the mid-Phanerozoic northern Perth Basin Stromatolitic Sequence cannot be unequivocally associated with the end-Permian mass extinction and may have instead thrived owing to a favourable paleodepositional setting. The mid-Phanerozoic northern Perth Basin stromatolites are not a unique case. A compilation of reported Permian and Triassic microbialite occurrences shows that stromatolites, although most common following the end-Permian mass extinction, also occur before and after the extinction event in a range of environmental settings.

KEY POINTS

1. Ten microbialite forms were described and mapped out over 30 km in the northern Perth Basin.

2. Perth Basin Stromatolitic Sequence formed in a restricted aquatic depositional setting with fluvial and/or alluvial influences.

3. Stromatolites from the northern Perth Basin are unlikely to be associated with the end-Permian mass.

Keywords:

• stromatolite
• mass extinction
• Triassic
• Perth Basin
• Permian
• EPME

Acknowledgements

We would like to acknowledge the following: The Smithsonian National Museum of Natural History for preparation of thin-sections; special mention to Kath Grey, for support and advice on the classification of stromatolites and redefining the paleo-environment; anonymous reviewers’ comments. This manuscript benefited from earlier comments by anonymous reviewers and S. Kershaw, with prior editorial handling of I. Montanez.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The authors confirm that the data supporting the findings of this study are available within the article [and/or] its supplementary materials. Original samples can be accessed from the corresponding author, L. J. Olden, upon reasonable request.

Additional information

Funding

Fieldwork was completed via funding from the School of Earth and Planetary Sciences, Curtin University and the Geological Society of Australia, Western Australia Division, and the support of an Australian Government Research Training Program Scholarship to L.J.O.