Long-term preservation of organic carbon by iron and its response to paleo-marine extreme events

Over 20% of organic carbon in marine surface sediments is preserved as iron-bound organic carbon (Fe-OC), and comprehensive analysis of its long-term preservation and responses to paleo-oceanic extreme events holds significant implications for understanding global carbon cycling and climate change. We reviewed the binding/release mechanisms of Fe-OC in marine sediments, compositional differentiation, regional distribution patterns, and the influence of diagenesis on the long-term stability of Fe-OC in marine sediments, and explored the potential influences of major geological events—the Great Oxidation Event of the Paleoproterozoic, the Neoproterozoic "Snowball Earth" event, Mesozoic oceanic anoxic events, and Quaternary glacial-interglacial cycles—on the formation and long-term preservation of Fe-OC. in addition, we revealed that the enrichment of Fe-OC was controlled by various factors in sedimentary environments, in which redox processes of iron played a critical role and had dual effects of preservation and degradation on Fe-OC. Paleo-oceanic extreme events likely modulated Fe-OC dynamics by altering iron redox cycling and its interactions with organic carbon.