Burned or Buried: What Controls the Long-term Preservation of Organic Carbon?

The preservation of organic carbon (OC) in marine sediments is a fundamental control on Earth’s long-term carbon cycle and climate. Globally, less than 2% of carbon fixed by primary producers is ultimately buried, yet specific environments and geological intervals exhibit markedly enhanced preservation. These variations reflect changes in organic matter composition, mineral associations, microbial activity, geochemical conditions, temperature, and sediment transport. Planetary-scale changes in climate, tectonics, continental configuration, biological evolution, and ocean circulation have repeatedly altered these controls, promoting enhanced OC burial during key periods of Earth history. OC preservation has thus acted as an important stabilizing feedback following major carbon-cycle perturbations. Here, we examine these mechanisms and their significance through time.