Terrestrial palaeoclimate, mercury, atmospheric CO2 and land plants through the Late Devonian mass extinction

The global absence of a Late Devonian (Kellwasser or Frasnian-Famennian) terrestrial record significantly detracts from our understanding of this Big 5 mass extinction event. Here, a highly expanded terrestrial section from East Greenland is reported, which includes records of palaeoenvironment, palaeoclimate, carbon isotopes from plant debris, sedimentary mercury and plant spores. It shows two episodes of a highly active fluvial system indicating warmer and wetter conditions followed by sustained aridity. Palynology zones show a correlation to the Kellwasser events and that there were extinctions in land plant spores. Coincident with the active fluvial system are excursions of mercury and light carbon, both indicating a series of distinct continental-scale volcanic eruptions that can be modelled as a doubling of atmospheric CO2. The final episode of the active fluvial system is coincident with most spore extinctions, with Archaeopteris progymnosperms becoming dominant during, and after, the carbon isotope excursions rather than before. This Greenland record provides evidence that it was planetary-scale volcanic eruptions, not forests, that drove the mass extinction with the post-extinction climate system collapsing to sustained cool aridity. In all these respects, the Late Devonian mass extinction is comparable with the end-Permian and Triassic-Jurassic mass extinctions.