 | Enhanced petrogenic organic carbon oxidation during the Paleocene-Eocene thermal maximum Abstract: The Paleocene-Eocene thermal maximum (PETM; ∼56 Ma) is a hyperthermal event associated with the rapid input of carbon into the ocean-atmosphere system. The oxidation of petrogenic organic carbon (OCpetro) may have released additional carbon dioxide (CO2), thereby prolonging the PETM. However, proxy-based estimates of OCpetro oxidation are unavailable due to the lack of suitable techniques. Raman spectroscopy is used to evaluate OCpetro oxidation in modern settings. For the first time, we explore whether Raman spectroscopy can evaluate OCpetro oxidation during the PETM. In the mid-Atlantic Coastal Plain, there is a shift from disordered to graphitised carbon. This is consistent with enhanced oxidation of disordered OCpetro and intensified physical erosion. In the Arctic Ocean, the distribution of graphitised carbon vs. disordered carbon does not change, suggesting limited variability in weathering intensity. Overall, this study provides the first evidence of increased OCpetro oxidation during the PETM, although it was likely not globally uniform. Our work also highlights the utility of Raman spectroscopy as a novel tool to reconstruct OCpetro oxidation in the past. |
 | The extent of liquid immiscibility in planetesimal cores Abstract: We report results of experiments in the system Fe0.9Ni0.1, S, P, C, O, which constrain the extent of liquid immiscibility in planetesimal cores. Immiscibility results in segregation of Fe-rich (P-rich, C-rich) and FeS-rich (O-rich) liquids, with the extent of immiscibility dependent on volatile/light element content. Parental liquids to iron meteorites are volatile-poor, and based on our results, mostly represent miscible core-forming liquids. However, as these parental liquids were variably modified during/after planetesimal disruption, they are unlikely to fully represent original compositions of planetesimal cores. To better constrain planetesimal core compositions, we use data from chondrite meteorites to provide upper bounds on core volatile element content. Modelled ‘chondrite cores’ are mostly immiscible liquids. The extent of immiscibility in planetesimal cores was sensitive to the degree of volatile loss during core formation, which was likely variable across planetary bodies, and dependent on thermal history and planetary differentiation processes. As such, evidence for immiscibility in core-forming liquids is useful in constraining the extent of degassing during differentiation. |
<< Previous issue
