Yunqian Zhang 

Chromium (Cr) isotopes are pivotal proxies for understanding Earth’s atmospheric oxygenation history. This review highlights δ53Cr signatures as tools for reconstructing redox dynamics during events like the Great Oxidation Event (GOE) and the Neoproterozoic Oxygenation Event (NOE). Advances in analytical techniques, particularly multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS), have enhanced δ53Cr measurement precision, revealing critical insights into oxidative weathering and atmospheric oxygenation. Challenges such as local environmental variability and uncertainties in oxygen thresholds remain, but integrating δ53Cr with complementary proxies promises a more comprehensive view of Earth’s redox evolution. This synthesis underscores the transformative role of Cr isotopes in tracing oxygenation processes and their implications for the evolution of the biosphere.