Major perturbation in sulfur cycling at the Triassic-Jurassic boundary

Triassic-Early Jurassic marine sediments at Kennecott Point in British Columbia, Canada, show evidence for a major perturbation in sulfur cycling coincident with a major carbon cycle perturbation in the wake of a mass extinction event at the Triassic-Jurassic boundary. The delta(34)S of reduced sulfur shifts from values consistent with open system bacterial sulfate reduction (-30 parts per thousand) to values higher than any previously reported for Early Jurassic sulfates (20 parts per thousand) and consistent with complete utilization of sulfate and Rayleigh fractionation in a closed system. We suggest that this isotopic shift was initiated by declining seawater sulfate concentration due to evaporite deposition in nascent Atlantic rift zones and enhanced by a local mechanism, such as a decoupling of the zone of sulfate reduction from the sulfate supply due to a catastrophic increase in the flux of land-derived sediments reaching the sea in the wake of massive terrestrial plant die-off during the Triassic-Jurassic mass extinction.