Abstract
The Late Devonian was a protracted period of low speciation resulting in biodiversity decline, culminating in extinction events near the Devonian–Carboniferous boundary. Recent evidence indicates that the final extinction event may have coincided with a dramatic drop in stratospheric ozone, possibly due to a global temperature rise. Here we study an alternative possible cause for the postulated ozone drop: a nearby supernova explosion that could inflict damage by accelerating cosmic rays that can deliver ionizing radiation for up to ∼100 ky. We therefore propose that the end-Devonian extinctions were triggered by supernova explosions at ∼20pc, somewhat beyond the “kill distance” that would have precipitated a full mass extinction. Such nearby supernovae are likely due to core collapses of massive stars; these are concentrated in the thin Galactic disk where the Sun resides. Detecting either of the long-lived radioisotopes Sm146 or Pu244 in one or more end-Devonian extinction strata would confirm a supernova origin, point to the core-collapse explosion of a massive star, and probe supernova nucleosynthesis. Other possible tests of the supernova hypothesis are discussed.
Description
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Citation
Fields, B. D., Melott, A. L., Ellis, J., Ertel, A. F., Fry, B. J., Lieberman, B. S., Liu, Z., Miller, J. A., & Thomas, B. C. (2020). Supernova triggers for end-Devonian extinctions. Proceedings of the National Academy of Sciences of the United States of America, 117(35), 21008–21010. https://doi.org/10.1073/pnas.2013774117