Sediment-Modulated Seafloor Time Controls Carbon Burial in Subduction Zones

Imagine the ocean floor as a giant, slow‑moving conveyor belt. The speed at which sediments linger there decides how much dead organic matter gets locked away forever.

Why Seafloor Residence Time Matters

Seafloor residence time is the average duration that sediment particles stay on the ocean bottom before being buried or eroded. In subduction zones, this timescale directly influences the fate of organic carbon.

The Role of Sediment Modulation

Sediment‑modulated residence time means that the composition and supply of sediments change the way long‑term burial occurs. Coarser, faster‑moving sediments reduce burial efficiency, while fine‑grained, slower‑moving layers promote it.

• Fine sediments trap organic particles, extending residence time.
• High sediment flux can bury carbon quickly but also remix it, limiting long‑term storage.
• Dynamic margin dynamics shift residence times on timescales of thousands to millions of years.

Efficient Organic Carbon Burial in Subduction Zones

Subduction zones are hotspots where oceanic plates dive beneath continents, carrying carbon‑rich sediments deep into the mantle. The efficiency of this burial hinges on how long those sediments linger on the seafloor.

Processes Driving Carbon Sequestration

Key processes include:

• Enhanced burial due to low‑energy, mud‑rich settings.
• Rapid subduction that outpaces remineralization.
• Microbial oxidation slowed by anoxic conditions.

When sediment residence time is long, organic carbon has more opportunity to be transformed into stable kerogen and eventually subducted, leading to efficient burial.

Implications for the Global Carbon Cycle

Feedback Loops and Climate Regulation

Efficient carbon burial in subduction zones acts as a negative feedback on atmospheric CO₂ levels. By removing carbon from the surface, these zones help regulate climate over geological timescales.

Understanding sediment‑modulated residence time therefore offers insight into Earth’s long‑term carbon budget and the factors that control climate change.

Conclusion

In summary, the interplay between sediment characteristics and seafloor residence time is a decisive control on how efficiently organic carbon is buried in subduction zones. This insight not only advances marine geology research but also informs broader climate models.