Coronene, mercury, and biomarker data support a link between extinction magnitude and volcanic intensity in the Late Devonian

Abstract

The Late Devonian biodiversity crisis, one of the big five Phanerozoic diversity depletions, is composed of a series of extinction events broadly coincident with the invasion of land by plants and vertebrates. These extinctions may have been triggered by volcanism, as sedimentary mercury enrichments are associated with the two main extinctions, the Kellwasser and Hangenberg crises. However, the sources of this mercury and its relation to volcanic style are not known. Furthermore, any links between the magnitudes of volcanic emissions and biodiversity loss have not been explored. To address these issues, we develop a new suite a geochemical data from shallow water sedimentary rocks in France, Belgium, and China for three Late Devonian crises – the Kellwasser and Hangenberg events, as well as for the preceding Frasnian extinction. We report paired coronene – mercury data as a refined proxy for large igneous province (LIP) emplacement, and we use cadalene and dibenzofuran biomarkers as proxies for terrestrial ecological disturbance. Coronene is a highly condensed six-ring polycyclic aromatic hydrocarbon (PAH), which requires significantly higher energy to form as compared to smaller PAHs; coronene enrichment has been found only in LIP volcanic emission and projectile impact events. Our data show that coronene and mercury coincidentally peaked at only the environmental and biotic events, demonstrating that pulses of LIP volcanism are tightly associated with the Late Devonian crises. In addition, mercury concentration is highly correlated with cadalene and dibenzofuran abundance during the events only in nearshore settings, indicating fluxes of soil erosion. Finally, we observe a correlation between coronene index and extinction magnitude for the three events, suggesting a link between temperatures of sills and lavas during LIP emplacement, pressure of evolved volatiles, and global climatic effects.