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Organic carbon burial during OAE2 driven by changes in the locus of organic matter sulfurization.

ABSTRACT: Ocean Anoxic Event 2 (OAE2) was a period of dramatic disruption to the global carbon cycle when massive amounts of organic matter (OM) were buried in marine sediments via complex and controversial mechanisms. Here we investigate the role of OM sulfurization, which makes OM less available for microbial respiration, in driving variable OM preservation in OAE2 sedimentary strata from Pont d'Issole (France). We find correlations between the concentration, S:C ratio, S-isotope composition, and sulfur speciation of OM suggesting that sulfurization facilitated changes in carbon burial at this site as the chemocline moved in and out of the sediments during deposition. These patterns are reproduced by a simple model, suggesting that small changes in primary productivity could drive large changes in local OM burial in environments poised near a critical redox threshold. This amplifying mechanism may be central to understanding the magnitude of global carbon cycle response to environmental perturbations.

SUBMITTER: Raven MR

PROVIDER: S-EPMC6109118 | biostudies-literature | 2018 Aug

REPOSITORIES: biostudies-literature

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Organic carbon burial during OAE2 driven by changes in the locus of organic matter sulfurization.

Raven Morgan Reed MR Fike David A DA Gomes Maya L ML Webb Samuel M SM Bradley Alexander S AS McClelland Harry-Luke O HO

Nature communications 20180824 1

Ocean Anoxic Event 2 (OAE2) was a period of dramatic disruption to the global carbon cycle when massive amounts of organic matter (OM) were buried in marine sediments via complex and controversial mechanisms. Here we investigate the role of OM sulfurization, which makes OM less available for microbial respiration, in driving variable OM preservation in OAE2 sedimentary strata from Pont d'Issole (France). We find correlations between the concentration, S:C ratio, S-isotope composition, and sulfur ...[more]

PMID: 30143628

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Project description:Abstract The Paleocene‐Eocene Thermal Maximum (PETM) is recognized globally by a negative excursion in stable carbon isotope ratios (δ13C) 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 δ13C 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 (Corg) burial in marginal and restricted environments throughout the δ13C 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 Corg burial during the PETM. Deoxygenation and recycling of phosphorus relative to Corg 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 ∼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 (∼2,000–3,000 Pg C). To reproduce global exogenic δ13C patterns, this Corg burial implies an injection of 5,000–10,000 Pg C during the first ∼100–150 kyr of the PETM, depending on the source's δ13C (−11‰ to −55‰). Key Points Data and modeling show increased productivity, deoxygenation, and organic C burial in marginal and restricted environments during the PETM Excess burial of ∼3,300 Pg organic C burial at the early stages of the PETM recovery Excess organic C burial during recovery requires several thousands of Pg of 13C‐depleted carbon input to match global exogenic δ13C trends

Dataset Information

Organic carbon burial during OAE2 driven by changes in the locus of organic matter sulfurization.

Publications

Organic carbon burial during OAE2 driven by changes in the locus of organic matter sulfurization.

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