Spatial and Temporal Patterns in Petrogenic Organic Carbon Mobilization During the Paleocene‐Eocene Thermal Maximum

• Published in: Paleoceanography and paleoclimatology 2024-02, Vol.39 (2), p.n/a
• Main Authors: Hollingsworth, E. H., Elling, F. J., Badger, M. P. S., Pancost, R. D., Dickson, A. J., Rees‐Owen, R. L., Papadomanolaki, N. M., Pearson, A., Sluijs, A., Freeman, K. H., Baczynski, A. A., Foster, G. L., Whiteside, J. H., Inglis, G. N.
• Format: Article
• Language: English
• Subjects: Atmosphere; Biomarkers; Carbon 13; carbon cycling; Carbon dioxide; Carbon dioxide concentration; Carbon isotopes; Climate change; Eocene; Erosion rates; Feedback; Fossils; Gases; Global warming; Greenhouse effect; Greenhouse gases; Hydrologic regime; Latitude; Lipids; Marine sediments; Organic carbon; Oxidation; Palaeocene; Paleocene; paleoclimate; PETM; Positive feedback; Rainfall; Sediments; Warm climates
• ISSN: 2572-4517; 2572-4525
• DOI: 10.1029/2023PA004773

The Paleocene‐Eocene Thermal Maximum (PETM) was a transient global warming event and is recognized in the geologic record by a prolonged negative carbon isotope excursion (CIE). The onset of the CIE was due to a rapid influx of 13C‐depleted carbon into the ocean‐atmosphere system. However, the mechanisms required to sustain the negative CIE remains unclear. Enhanced mobilization and oxidation of petrogenic organic carbon (OCpetro) has been invoked to explain elevated atmospheric carbon dioxide concentrations after the onset of the CIE. However, existing evidence is limited to the mid‐latitudes and subtropics. Here, we determine whether: (a) enhanced mobilization and subsequent burial of OCpetro in marine sediments was a global phenomenon; and (b) whether it occurred throughout the PETM. To achieve this, we utilize 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. High‐latitude sites do not exhibit drastic changes in the source of organic carbon during the PETM and OCpetro MARs increase slightly or remain stable, perhaps due a more stable hydrological regime. 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. Plain Language Summary The Paleocene‐Eocene Thermal Maximum (PETM) was the most severe global warming event of the last 66 million years and was caused by the rapid release of greenhouse gases into the atmosphere. However, scientists have been unable to determine why the PETM lasted for >100,000 years. Here, we test whether CO2 released from the erosion, transport, and oxidation of ancient rock‐derived (or petrogenic) organic carbon can explain the long duration of the PETM. We also aim to identify if this occurred globally and/or throughout the PETM. We achieve this by looking at biomarkers (molecular fossils) and use this approach to “fingerprint” the input of petrogenic organic carbon into the marine realm. Our results suggest enhanced transport of petrogenic organic carbon was restricted to the subt