On Carbon Burial and Net Primary Production Through Earth’s History

The carbonate carbon isotope record has been traditionally interpreted as evidence of stability in the globally integrated ratio of organic to total carbon burial from Earth's surface environments over the past ∼3.8 billion years, but recent work has begun to question this conclusion. Herein, we use a reactive-transport modeling approach to track organic carbon oxidation at varying atmospheric oxygen levels and use that information to provide a rough estimate of net primary production through time. Our results support the emerging view that there was extensive variability in the fraction of carbon buried as organic matter (fb,org) throughout Earth's history. We strengthen the case that the carbonate carbon isotope record has been characterized by a relatively constant baseline value over time due to a fundamental mechanistic link between atmospheric O2 levels and the carbon isotope composition of net inputs to the ocean-atmosphere system. Further, using estimates of the organic carbon burial flux (Fb,org) and the burial efficiency of the carbon pump from our marine reactive-transport modeling, we also support previous work suggesting extensive fluctuation in marine net primary production over time.