Events Calendar

Lipid biomarker records for the Silurian Period (~443.1-419 Ma) are sparse despite this being a key interval for evolutionary and environmental changes in the ocean and on land. Multiple global-scale carbon perturbation events associated with marine biotic extinctions are found across the breadth of Silurian time. The Ireviken Biogeochemical Event (IBE) is the most well documented and conspicuous of these events that took place in the lower Silurian. The IBE spans across the Llandovery-Wenlock boundary and is associated with both a major marine extinction event, a significant positive13Ccarbonate excursion (to ca. +5.5‰), and it has been identified in more than two dozen localities globally. The mechanistic drivers of the IBE and positive excursions in the carbon isotopic ratio of marine carbonates have been debated, with some consistent lines of evidence pointing to enhanced marine organic carbon burial due to large-scale geographical expansion of reducing marine environments.

In collaboration with researchers at the University of Iowa, we have produced a detailed lipid biomarker and stable isotope study on a pristine drill core that spans the IBE. This sample set has provided a unique opportunity for a detailed lipid biomarker study on an expanded succession to untangle the influence of changes in the modes of primary productivity (algal versus bacterial), the strength of the biological pump and the timing of the expansion of marine deoxygenation across the IBE. Our results indicate that an increase in marine primary productivity instigated a protracted deoxygenation of marine shelf environments through the IBE, which overlapped with the different stages of extinction. In addition, the lipid biomarker records across the IBE add to an emerging picture of Paleozoic marine biogeochemical cycling. A consistent feature of Ordovician, Silurian and early-middle Devonian marine biomarker records is evidence for a vigorous methane cycle persisting in the water column and shallow sediments, which is an underappreciated component of the Paleozoic carbon cycle.