Spatial and Temporal Patterns in Petrogenic Organic Carbon Mobilisation during the Paleocene-Eocene Thermal Maximum

Hollingsworth, Emily H; Elling, Felix J; Badger, Marcus; Pancost, Richard; Dickson, Alexander; Rees-Owen, Rhian L.; Papadomanolaki, Nina Maria; Pearson, Ann; Sluijs, Appy; Freeman, Katherine H; Baczynski, Allison A; Foster, Gavin L; Whiteside, Jessica and Inglis, Gordon N. (2024). Spatial and Temporal Patterns in Petrogenic Organic Carbon Mobilisation during the Paleocene-Eocene Thermal Maximum. ESS Open Archive, 39(2), article no. e2023PA004773.

DOI: https://doi.org/10.22541/essoar.169755099.99277705/v1

Abstract

The Paleocene-Eocene Thermal Maximum (PETM) was a transient global warming event recognised in the geologic record by a prolonged negative carbon isotope excursion (CIE). The onset of the CIE was the result of a rapid influx of 13C-depleted carbon into the ocean-atmosphere system. However, the mechanisms required to sustain the negative CIE remains unclear. Previous studies have identified enhanced mobilisation of petrogenic organic carbon (OCpetro) and argued that this was likely oxidised, increasing atmospheric carbon dioxide (CO2) concentrations after the onset of the CIE. With existing evidence limited to the mid-latitudes and subtropics, we determine whether: (i) enhanced mobilisation and subsequent burial of OCpetro in marine sediments was a global phenomenon; and (ii) whether it occurred throughout the PETM. To achieve this, we utilised a lipid biomarker approach to trace and quantify OCpetro burial in a global compilation of PETM-aged shallow marine sites (n = 7, including five new sites). Our results confirm that OCpetro mass accumulation rates (MARs) increased within the subtropics and mid-latitudes during the PETM, consistent with evidence of higher physical erosion rates and intense episodic rainfall events. The high-latitude sites do not exhibit distinct changes in the organic carbon source during the PETM. This may be due to the more stable hydrological regime and/or additional controls. Crucially, we also demonstrate that OCpetro MARs remained elevated during the recovery phase of the PETM. Although OCpetro oxidation was likely an important positive feedback mechanism throughout the PETM, we show that this feedback was both spatially and temporally variable.

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