354-7 Global versus local controls on marine sedimentary records and their implications for carbonate-based proxies across the PETM

Abstract:

The Phanerozoic is punctuated by discrete events of atmospheric carbon injection and subsequent carbon drawdown through global silicate weathering and organic carbon feedbacks. Records of these global carbon cycle events are preserved in marine sedimentary carbonates, whose preservation depends on local factors such as photic zone export and coretop particulate flux of carbonate and organic matter and controls on the carbonate saturation state of the deep ocean and pore fluids(i.e., temperature and [CO₃^2-]). Given that local preservation factors can vary spatially, they complicate the interpretation of sedimentary carbonate and carbonate-based proxies that constrain the global carbon cycle.  

In this study, we examine marine carbonate preservation across the Paleocene-Eocene Thermal Maximum (PETM, ~56 Ma), which contains a significant interval of carbonate dissolution consistent with a rapid release of carbon to the atmosphere–ocean system. We assess spatial controls on carbonate preservation across the PETM using a combination of Earth system modeling and isotopic approaches. Using the CGENIE model, we simulate carbon injection and Earth system recovery across the PETM subject to the modeled silicate weathering and organic carbon cycle feedbacks and analyze the spatial differences in carbonate proxy archives. In parallel model runs, we isolate the relative importance of temperature, weathering, carbon input flux, and primary productivity on carbonate proxies by holding each of these fluxes constant.  We then evaluate the model output using a compilation of sedimentary wt. % carbonate records from shallow and deep ocean sites. Finally, we conclude which of modeled environmental controls (temperature, weathering, carbon input, and primary productivity) most influence marine sedimentary records by comparing modeled spatial trends with new carbon and calcium isotope records from globally distributed sites. 

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