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