Large sulfur isotope fractionation suggested during microbial sulfate reduction at low sulfate levels
Year: 2026
Type: dataset
Abstract: Dissimilatory sulfate reduction is among the earliest proposed microbial metabolisms. However, its most ubiquitous fossil evidence, pyrite depleted in the heavy sulfur isotopes, is absent before ≈2.5 Ga, putatively due to limited isotopic fractionation under sulfate-poor conditions. Here, we present microscale and bulk sulfur isotopes in pyrite from natural environments spanning sulfate concentrations from 28,000 to 3 𝛍M, suggesting that large microbial sulfur isotope fractionation may persist even under extreme sulfate scarcity (≥48‰ at 3 𝛍M). Applying this calibration to an Archean-Paleoproterozoic compilation of microscale pyrite sulfur isotope data, three preserved arrays may be consistent with active dissimilatory sulfate reduction by ≈2.7 Ga in aquatic systems containing only a few to a few tens of micromolar sulfate. In contrast, the narrower isotopic ranges preserved in older rocks (≤20‰) may not be uniquely diagnostic and remain consistent with dissimilatory sulfite reduction, diagenesis under sulfate-poor conditions, post-depositional overprinting, or a combination of these factors
Source: Figshare
Author: Virgil Pasquier
Language: English
Subfield: Paleontology
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7221760633