Stromatolites as Recorders of Major Oxygenation Events and Biogeochemical Metal Cycling through Earth’s History

Microbial carbonates are found throughout most of the geological record and have formed under varying atmospheric and hydrospheric conditions. Recent advancements in analytical techniques have enabled the use of novel, highly promising geochemical proxies, such as metals and their isotopes, to reconstruct ancient microbial habitats. Here, we review recent discoveries and the benefits of applying redox-sensitive and bioessential metal proxies in microbialites, aiming to reconstruct Earth’s oxygenation and determine the availability of dissolved metals in past microbial habitats. These findings contribute to a better understanding of the evolution of microbial life and its ecological niches on Earth through time. Moreover, they offer a potential blueprint for the search for extra-terrestrial life, thereby informing ongoing and future planetary studies.