Sedimentary controls on pyrite sulfur isotopes in euxinic settings
Abstract
Pyrite is widely used to reconstruct ancient euxinic (anoxic and sulfidic) conditions, yet whether its sulfur isotope composition ( δ ³⁴ S) preserves primary water-column signals remains debated. Here, we show combined bulk and microscale δ ³⁴ S data from pyrite grains collected across the Black Sea water-column and deep-basin sediments. Water-column-derived pyrite consists exclusively of framboidal grains with narrow size and δ ³⁴ S ranges, consistent with formation from local aqueous sulfide and minimal alteration during nucleation and settling. Upon sedimentation, however, these grains undergo progressive textural and isotopic modification. With increasing burial, framboids are supplemented by larger, more ³⁴ S-enriched recrystallized grains formed during dissimilatory sulfate reduction in diffusion-limited sedimentary microenvironments. Only ≈17% of pyrite grains that match WC framboids in size, texture, and δ ³⁴ S signature retain a water-column-consistent isotopic composition in the uppermost sediment, declining to ≤4% at depth. Sulfide profiles and gene abundances further indicate that most water-column sulfide diffuses upward from sediments. Consequently, δ ³⁴ S records from black shales likely integrate complex diagenetic histories rather than reflect direct snapshots of WC chemistry.
Related
- Trace element partitioning in sedimentary pyrite controlled by nanoscale processes
- Volcanic controls on smectite authigenesis and paleoclimate signals across the Paleocene-Eocene Thermal Maximum (PETM) sedimentary record from the Norwegian-Greenland Sea
- Fe Isotope Fractionation during Early Diagenetic Pyrite Formation: Constraints from Reaction-Transport Modeling of the Santa Barbara Basin Sediment
- In-situ enhancement of autotrophic nitrogen removal in coking wastewater using staged diatomite and pyrite strategy
- Bulk iron-sulfur ratio (Fe/S) conditional proxy for sulfurized, TOC-rich sediments: insights and comparison of compositional model with real data utilizing the Pyrite-TOC-Fe-S compositional space
BibTeX
@article{pasquier2026sedimentary,
title = {{Sedimentary controls on pyrite sulfur isotopes in euxinic settings}},
author = {Virgil Pasquier and Itay Halevy and Johanna Marin-Carbonne and Clive Jones and Jennifer Houghton and Alexander V. Dubinin and Alexey Klyuvitkin and David A. Fike},
journal = {Communications Earth \& Environment},
year = {2026},
month = nov,
doi = {10.1038/s43247-026-04178-4},
url = {https://www.nature.com/articles/s43247-026-04178-4},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Sedimentary controls on pyrite sulfur isotopes in euxinic settings
AU - Virgil Pasquier
AU - Itay Halevy
AU - Johanna Marin-Carbonne
AU - Clive Jones
AU - Jennifer Houghton
AU - Alexander V. Dubinin
AU - Alexey Klyuvitkin
AU - David A. Fike
PY - 2026
DA - 2026/11/02
JO - Communications Earth & Environment
DO - 10.1038/s43247-026-04178-4
UR - https://www.nature.com/articles/s43247-026-04178-4
AB - Pyrite is widely used to reconstruct ancient euxinic (anoxic and sulfidic) conditions, yet whether its sulfur isotope composition ( δ ³⁴ S) preserves primary water-column signals remains debated. Here, we show combined bulk and microscale δ ³⁴ S data from pyrite grains collected across the Black Sea water-column and deep-basin sediments. Water-column-derived pyrite consists exclusively of framboidal grains with narrow size and δ ³⁴ S ranges, consistent with formation from local aqueous sulfide and minimal alteration during nucleation and settling. Upon sedimentation, however, these grains undergo progressive textural and isotopic modification. With increasing burial, framboids are supplemented by larger, more ³⁴ S-enriched recrystallized grains formed during dissimilatory sulfate reduction in diffusion-limited sedimentary microenvironments. Only ≈17% of pyrite grains that match WC framboids in size, texture, and δ ³⁴ S signature retain a water-column-consistent isotopic composition in the uppermost sediment, declining to ≤4% at depth. Sulfide profiles and gene abundances further indicate that most water-column sulfide diffuses upward from sediments. Consequently, δ ³⁴ S records from black shales likely integrate complex diagenetic histories rather than reflect direct snapshots of WC chemistry.
SN - 2662-4435
ER -