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ET MICROBIALITES - Formation mechanisms of Early Triassic microbialites in the aftermath of the greatest mass extinction (Permian-Triassic-Boundary)


April 2012 – March 2014: Marie Curie Intra-European Fellowship (FP7-PEOPLE-2011-IEF) funded by the European Union



Katrin Heindel (fellow), Jörn Peckmann (mentor)



  • Sylvain Richoz (Austrian Academy of Sciences, Graz)
  • Daniel Birgel (Department of Geodynamics and Sedimentology, University of Vienna)
  • Rainer Abart (Department of Lithospheric Research, University of Vienna)
  • Benjamin Brunner (Max-Planck-Institute for Marine Microbiology, Bremen, Germany)
  • Leopold Krystyn (Department of Paleontology, University of Vienna)
  • Robert Riding (Dept. of Earth and Planetary Sciences, University of Tennessee, USA)
  • Roger Summons (Earth, Atmospheric, and Planetary Sciences, MIT, Cambridge, USA)
  • Volker Thiel (Geobiology group, University of Göttingen, Germany)



The goal of ET MICROBIALITES is to understand the causes and modes of microbialite formation in critical periods of Earth history, typified by changing environments using the example of the Permian-Triassic-Boundary mass extinction event.



Microbialites represent the first fossil evidence of life on Earth and microbial mats forming microbialites were ubiquitous for almost 85% of Earth’s history. Since the Precambrian, microbialites revealed diverse morphologies and formed in various settings, including lacustrine, lagoonal, brackish, and marine environments. During the Precambrian and Early Phanerozoic, the microbial realm flourished and reefal structures were built by microbialites (microbial reefs). Beginning from the Middle Ordovician, reef-forming skeletal metazoans evolved and diversified, which resulted in reefs in which microbialites were commonly associated with metazoans. Since the Middle Ordovician, the fossil record indicates an overall decline in microbialite occurrences. However, this decline was interrupted by phases of recurrence, which apparently coincided with environmental change, biotic crises, and mass extinctions.

The reasons for microbialite formation in specific environments and time periods are still enigmatic. Particularly, in the aftermath of mass extinctions and during environmental crises, microbial mats have been major components of marine ecosystems. After the most severe mass extinction of metazoans at the Permian-Triassic boundary (PTB), the Palaeozoic skeletal carbonate factory was replaced by microbial communities, which formed non-skeletal microbial reefs (microbialites) covering large areas of the Early Triassic ocean margins. It has been suggested that environmental change favoured microbialite formation, while stable environmental conditions were suggested to inhibit microbialite growth. However, unequivocal evidence for this hypothesis is still pending.

The goal of this project is to understand the reasons and modes of microbialite formation in critical periods of Earth history, which were typified by changing environments and ecosystems using the example of the PTB mass extinction, the most fatal ever. To achieve this, a multiple proxy study will pursued including organic geochemical (lipid biomarkers, stable isotopes), sedimentological, and petrographic methods.

Fig. 1: Photographs of microbialites forming microbial reefs from the site Kuh e Surmeh in Iran. The microbialites are on top of fossil lean bedded carbonate deposits, 1.30 m above the mass extinction event beds (A, bar: 30 cm). Close-up of a microbialite at the base of the microbial reef, the arrow points to the top of the microbialite (B).
Fig. 2: Palaeogeographic positions of the research sites in Iran (1, 2, 3) and Turkey (4) during the PTB.
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