Quantifying the Extent of Authigenic Carbonate Formation in Shallow Marine Sediments Through a Correlation Between Carbonate Precipitation Rate and Sulfate Flux

The accumulation of authigenic carbonate in marine sediments has been regarded as a significant contributor to the carbon cycle over Earth's history. However, accurate quantification of the extent of authigenic carbonate formation in both modern and ancient oceans has been challenging due to limited approaches. Here, we analyzed calcium, magnesium, dissolved inorganic carbon, and alkalinity pore-water profiles of 153 sites influenced by methane diffusion from the northern South China Sea. By combining these data with published data of diffusive sulfate flux, we found a significant positive correlation between carbonate precipitation rate and sulfate flux in the subseafloor. This correlation can be used to quantify the regional extent of authigenic carbonate formation, representing an advantage over a spatial interpolation approach. We therefore propose that the observed correlation can serve as a new approach for quantifying authigenic carbonate formation in shallow sediments along continental margins for both modern and ancient oceans. Carbonate mineral precipitation through removing seawater dissolved inorganic carbon-the marine carbonate factory-plays a critical role in shaping marine carbon cycling and global climate. The formation of authigenic carbonate from pore-water of marine sediments represents a variable share of the marine carbonate factory throughout geological history. However, it is challenging to quantify the extent of such authigenic carbonate formation. By analyzing pore-water parameters from 153 sites influenced by methane diffusion of the northern South China Sea, we found a significant positive correlation between the rate of carbonate precipitation and the diffusive flux of sulfate into shallow sediments. Given the existence of estimates on the sizes of the seawater sulfate pool and diffusive fluxes of sulfate into sediments over Earth's history, we propose that the observed correlation can be used for quantifying authigenic carbonate formation in shallow sediments along continental margins through time, which will greatly advance our understanding for past carbon cycling and its relation to climate. Porewater parameters from 153 sites of the northern South China Sea were evaluated to quantify the extent of authigenic carbonate formationRate of carbonate formation strongly correlates with diffusive flux of sulfate into sediments affected by methane diffusionA correlation of carbonate formation rate with sulfate flux is used to quantify most of authigenic carbonate formation in shallow sediments