The role of tephra in enhancing organic carbon preservation in marine sediments

Preservation of organic carbon (C _org ) in marine sediments plays a major role in defining ocean-atmosphere CO ₂ levels, Earth climate, and the generation of hydrocarbons. Important controls over sedimentary C _org preservation include; biological productivity, C _org isolation from oxidants (mainly dissolved O ₂ ) in the overlying water column and sediments, and C _org – mineral association in sediments. Deposition of the products of explosive volcanism (tephra) in the oceans directly enhances C _org burial through all these mechanisms, and indirectly through enhanced formation of authigenic carbonate (C _auth ) derived from sedimentary C _org . In the modern oceans, it is suggested that tephra deposition may account for 5–10% of the C _org burial flux and 10–40% of the C _auth burial flux. However, during certain periods in Earth's history, extensive explosive volcanism may have led to enhanced C _auth precipitation on a sufficiently large scale to influence the global ocean-atmosphere carbon cycle. Changes in tephra-related C _org preservation may also have played a role in increasing C _org preservation rates in local marine basins, at the oxic-anoxic boundary and enhanced the generation of hydrocarbon deposits in these settings.