Publications by authors named "D L Fike"
Article Synopsis
- A new method is proposed to identify the origin of pyrite grains and differentiate between biologically influenced and abiotic sedimentary pyrite using sulfur isotope and trace element analyses.
- Multiple machine-learning algorithms were tested, with K-means++ classifying pyrite into six types based on their formation environments, and a random forest model achieving high predictive precision.
- The study enhances the ability to explore altered sedimentary rocks and could help distinguish biogenic from abiotic pyrite in early Earth samples and aid in searching for biosignatures in Martian samples.
Reconstructions of past environmental conditions and biological activity are often based on bulk stable isotope proxies, which are inherently open to multiple interpretations. This is particularly true of the sulfur isotopic composition of sedimentary pyrite (δS), which is used to reconstruct ocean-atmosphere oxidation state and track the evolution of several microbial metabolic pathways. We present a microanalytical approach to deconvolving the multiple signals that influence δS, yielding both the unambiguous determination of microbial isotopic fractionation (ε) and new information about depositional conditions.
View Article and Find Full Text PDFReconstructions of coupled carbon, oxygen, and sulfur cycles rely heavily on sedimentary pyrite sulfur isotope compositions (δS). With a model of sediment diagenesis, paired with global datasets of sedimentary parameters, we show that the wide range of δS (~100 per mil) in modern marine sediments arises from geographic patterns in the relative rates of diffusion, burial, and microbial reduction of sulfate. By contrast, the microbial sulfur isotope fractionation remains large and relatively uniform.
View Article and Find Full Text PDFThe sedimentary pyrite sulfur isotope (δ S) record is an archive of ancient microbial sulfur cycling and environmental conditions. Interpretations of pyrite δ S signatures in sediments deposited in microbial mat ecosystems are based on studies of modern microbial mat porewater sulfide δ S geochemistry. Pyrite δ S values often capture δ S signatures of porewater sulfide at the location of pyrite formation.
View Article and Find Full Text PDFArticle Synopsis
- Sulfur cycling plays a crucial role in sedimentary environments, affecting organic carbon remineralization and influencing sulfur isotope ratios (δS) in pyrite, but the factors behind δS variations are still debated.
- Research along the Peru margin indicates that δS fluctuations during glacial-interglacial periods were driven primarily by local environmental changes, especially the expansion of the Oxygen Minimum Zone and increased organic matter deposition.
- Findings show that enhanced microbial activity during these periods led to more significant sulfur retention in porewater, linking organic carbon loading as a key influence on δS variations and stressing the importance of local factors in interpreting these records.