From Alcheringa to beyond: 50 years of microbialite research in Western Australia

As the earliest recognized textural biosignatures on Earth, microbialites are central to understanding the origin, evolution and persistence of life on our planet. Nowhere is the record of microbialites more extensive or continuous than in Western Australia, spanning at least 3.48 billion years—from the Paleoarchean stromatolitic successions of the Pilbara Craton to modern systems including the UNESCO World Heritage-listed Shark Bay microbialites. Considered as a whole, the more than 1000 localities known within the State, documented in thousands of publications from 1912 until today, have fundamentally transformed scientific understanding of microbialites through geological time.Early microbialite research in Western Australia was primarily descriptive, with fossil stromatolites used for regional correlation within Precambrian sedimentary basins, and modern microbialites investigated as analogues for ancient systems. However, as late twentieth-century discoveries in the Pilbara region progressively extended the record of life deeper into the Archean, research on fossil microbialites shifted towards broader questions concerning the co-evolution of life and habitable surface environments, the recognition of biosignatures, and applications to the search for extraterrestrial life. In parallel, investigations of modern microbialite systems have increasingly incorporated microbiological, geochemical and molecular approaches, transforming these sites from simple analogues into process-based laboratories for understanding microbialite accretion, ecology and vulnerability to environmental change. Concurrent studies of Phanerozoic microbialites have also helped to highlight the ecological resilience and adaptive significance of microbial communities during intervals of environmental stress and biotic crisis, particularly following mass extinction events.Western Australia’s constantly expanding fossil and modern microbialite datasets—and the corresponding improvements in analytical techniques used to study these sites—have drawn attention to key challenges remaining within microbialite research. These challenges include a need for robust criteria to demonstrate biogenicity, improved understanding of biological, environmental and taphonomic controls on microbialite morphology, and delineating the spatial and temporal range of microbialites. Growing recognition of the scientific and heritage significance of microbialite localities has also highlighted the vulnerability of many ancient and modern sites to anthropogenic disturbance and environmental degradation, and the subsequent importance of robust long-term protections.On the 50th anniversary of Alcheringa—a journal named after Alcheringa narrina Walter, Citation1972, a 2.73-billion-year-old stromatolite from the Tumbiana Formation—we reflect on the history of microbialite research in Western Australia, summarize major discoveries and conceptual advances spanning Archean to modern settings, evaluate evolving approaches to interpreting these textural biosignatures, and consider current challenges and future directions in microbialite research and conservation.Heidi J Allen* [[email protected]], School of Geography, Earth and Atmospheric Science, The University of Melbourne, Grattan St, Parkville Vic 3010, Australia; Geological Survey of Western Australia, Department of Mines, Petroleum and Exploration, 100 Plain St, East Perth WA 6004, Australia; Sarah K Martin [[email protected]], Geological Survey of Western Australia, Department of Mines, Petroleum and Exploration, 100 Plain St, East Perth WA 6004, Australia.