Eutrophication and Deoxygenation Forcing of Marginal Marine Organic Carbon Burial During the PETM

The Paleocene-Eocene Thermal Maximum (PETM) is recognized globally by a negative excursion in stable carbon isotope ratios (delta C-13) in sedimentary records, termed the carbon isotope excursion (CIE). Based on the CIE, the cause, duration, and mechanisms of recovery of the event have been assessed. Here, we focus on the role of increased organic carbon burial on continental margins as a key driver of CO2 drawdown and global exogenic delta C-13 during the recovery phase. Using new and previously published sediment proxy data, we show evidence for widespread enhanced primary production, low oxygen waters, and high organic carbon (C-org) burial in marginal and restricted environments throughout the delta C-13 excursion. With a new biogeochemical box model for deep and marginal environments, we show that increased phosphorus availability and water column stratification on continental margins can explain the increased C-org burial during the PETM. Deoxygenation and recycling of phosphorus relative to C-org were relatively mild, compared to modern day anoxic marine systems. Our model reproduces the conditions reconstructed by field data, resulting in a burial of 6,000 Pg across the PETM, in excess of late Paleocene burial, and similar to 3,300 Pg C for the critical first 40 kyr of the recovery, primarily located on continental margins. This value is consistent with prior data and model estimates (similar to 2,000-3,000 Pg C). To reproduce global exogenic delta C-13 patterns, this C(org )burial implies an injection of 5,000-10,000 Pg C during the first similar to 100-150 kyr of the PETM, depending on the source's delta C-13 (-11 parts per thousand to -55 parts per thousand).

Automated summary

This study focuses on the role of increased organic carbon burial on continental margins during the Paleocene-Eocene Thermal Maximum (PETM). By using a biogeochemical box model and sediment proxy data, the study reveals that increased phosphorus availability and water column stratification on continental margins explain the enhanced organic carbon burial during the PETM. This finding is crucial for understanding the carbon isotope excursion and recovery processes during the thermal maximum event.