Logan Medallist 8. Trace Elements in Iron Formation as a Window into Biogeochemical Evolution Accompanying the Oxygenation of Earth’s Atmosphere

Abstract

Iron formations exemplify a type of sedimentary rock found in numerous Archean and Proterozoic supracrustal successions. They serve as a valuable chemical record of Precambrian seawater chemistry and post-depositional iron cycling. These formations accumulated on the seafloor for over two billion years during the early history of our planet, offering a unique opportunity to study environmental changes that occurred during Earth's evolution. Among these changes, one of the most significant events was the shift from an anoxic planet to one where oxygen (O2) became consistently present in both the marine water column and atmosphere. This progression towards global oxygenation was closely linked to the emergence of aerobic microbial metabolisms, which profoundly impacted continental weathering processes, nutrient supply to the oceans, and ultimately, the diversification of the biosphere and complex life forms. In this review, we synthesize two decades of research into the temporal fluctuations of trace element concentrations in iron formations. Our aim is to shed light on the complex mechanisms that contributed to the oxygenation of Earth's surface environments.