Neogene Burial of Organic Carbon in the Global Ocean

The burial of organic carbon (OC) in marine sediments is a process that controls the organic sub-cycle of the global carbon cycle. Buried OC is effectively isolated from the Earth's surficial system therefore serve as a net sink for atmospheric CO₂, and a source for O₂, and contributes to the formation of organic-rich sources rocks. The global rate of OC burial is conventionally calculated using the mass balance between inorganic carbon and OC, each with distinct isotopic values (δ¹³C). However, the uncertainty associated with some key parameters complicates this approach. Here we used a "bottom-up" approach independent from model calculations, to utilize the total organic carbon (TOC%) reported from numerous sites drilled by the International Ocean Discovery Program (IODP). Although TOC% measurement is an IODP standard practice, these data are rarely explored in-depth or synthesized. We targeted > 80 sites covering all major ocean basins and sedimentary environments, to quality-control the data, update their age models, and establish regional and global pictures of TOC mass accumulation rates over the Neogene (23.0-2.6 Ma). Evaluations of our records show that the bias introduced by the "Sadler effect" is minimal as sedimentation rate variations play a subordinate role in controlling local OC burial fluxes. Interestingly, our record of OC burial is substantially different than that produced by isotope mass balance modelling. We explore these results and their impact on our understanding of the spatiotemporal variability of OC burial, the carbon and oxygen cycle and the global climate over the past 23 million years.