Chemistry

Materials science

Quartz

Oxygen

Sedimentary rock

Sulfur cycle

Composite number

Composite material

Organic matter

Deposition (geology)

Sedimentary depositional environment

Geology

Organic chemistry

Pyrite

Total organic carbon

Geochemistry

Fluid inclusions

Sediment

Environmental chemistry

Oxygen minimum zone

Sulfide

Isotopes of oxygen

Sulfur

Structural basin

Carbon fibers

Sulfate

Paleontology

δ34S

Nature Communications

Sulfur cycling is ubiquitous in sedimentary environments, where it mediates organic carbon remineralization, impacting both local and global redox budgets, and leaving an imprint in pyrite sulfur isotope ratios (δ 34 S pyr ). It is unclear to what extent stratigraphic δ 34 S pyr variations reflect local aspects of the depositional environment or microbial activity versus global sulfur-cycle variations. Here, we couple carbon-nitrogen-sulfur concentrations and stable isotopes to identify clear influences on δ 34 S pyr of local environmental changes along the Peru margin. Stratigraphically coherent glacial-interglacial δ 34 S pyr fluctuations (&gt;30‰) were mediated by Oxygen Minimum Zone intensification/expansion and local enhancement of organic matter deposition. The higher resulting microbial sulfate reduction rates led to more effective drawdown and 34 S-enrichment of residual porewater sulfate and sulfide produced from it, some of which is preserved in pyrite. We identify organic carbon loading as a major influence on δ 34 S pyr , adding to the growing body of evidence highlighting the local controls on these records.

Sedimentary pyrite sulfur isotopes track the local dynamics of the Peruvian oxygen minimum zone