• Publications
  • Influence
Calibrating the Cryogenian
Four high-precision U-Pb ages for Neoproterozoic rocks in northwestern Canada are presented that constrain large perturbations in the carbon cycle, a major diversification and depletion in the microfossil record, and the onset of the Sturtian glaciation. Expand
Multiple sulfur isotopes and the evolution of Earth's surface sulfur cycle
Abstract The distribution of sulfur isotopes in geological materials reveals information about Earth history and biogeochemical processes. Research during the last several decades has used sulfurExpand
Isotopic evidence for Mesoarchaean anoxia and changing atmospheric sulphur chemistry
The findings point to the persistence of an anoxic early atmosphere, and identify variability within the isotope record that suggests changes in pre-2.45-Gyr-ago atmospheric pathways for non-mass-dependent chemistry and in the ultraviolet transparency of an evolving early atmosphere. Expand
Mass-dependent fractionation of quadruple stable sulfur isotope system as a new tracer of sulfur biogeochemical cycles
Abstract Sulfur isotope studies of post-Archean terrestrial materials have focused on the ratio 34S/32S because additional isotopes, 33S and 36S, were thought to carry little information beyond theExpand
Anoxygenic photosynthesis modulated Proterozoic oxygen and sustained Earth's middle age
It is argued that the proportional contribution of anoxygenic photosynthesis to overall primary production would have influenced oceanic redox and the Proterozoic O2 budget, paving the way for the further oxygenation of the oceans and atmosphere and, ultimately, the evolution of complex multicellular organisms. Expand
Organic haze, glaciations and multiple sulfur isotopes in the Mid-Archean Era
Abstract We use sulfur (S) isotope signatures within ancient sediments and a photochemical model of sulfur dioxide (SO 2 ) photolysis to interpret the evolution of the atmosphere over the first halfExpand
Statistical analysis of iron geochemical data suggests limited late Proterozoic oxygenation
This re-analysis of trace-metal data is consistent with oxygenation continuing well into the Palaeozoic era, and suggests that subsurface water masses in mid-Proterozoic oceans were predominantly anoxic and ferruginous, but with a tendency towards euxinia (sulfide-bearing) that is not observed in the Neoproterozoics era. Expand
Authigenic Carbonate and the History of the Global Carbon Cycle
This work proposes that authigenic carbonate, produced in sediment pore fluids during early diagenesis, has played a major role in the carbon cycle in the past and presents a framework for interpreting the carbon isotopic composition of sedimentary rocks. Expand
Multiple sulphur isotopic interpretations of biosynthetic pathways: implications for biological signatures in the sulphur isotope record
Isotopic fractionations produced by biosynthetic processes are the result of networks of individual biochemical reactions that operate at differing efficiencies and with distinct fractionationExpand
Sulfur isotope insights into microbial sulfate reduction: When microbes meet models
Metabolic models for fractionations produced by sulfate-reducing Bacteria and Archaea derived from experimental observations are the cornerstone of our interpretation of ancient and modernExpand