Extinction: Late Devonian Mass Extinction

Abstract

Abstract The Late Devonian mass extinction, which occurred 374.5 Ma, is one of the ‘Big Five’ mass extinctions in Earth history. Suggested causes of the mass extinction include oceanic anoxia and global cooling. The severe loss of biodiversity that occurred during the crisis was global, affecting both marine and terrestrial ecosystems and animal and plant communities. Both low‐temperature stresses due to global cooling and oxygen deprivation due to anoxia have been implicated as kill mechanisms in the Late Devonian mass extinction, and it is possible that the severity of the mass extinction was due to both processes operating in concert. The ultimate trigger for these kill mechanisms is still under debate: oceanic anoxia may have been triggered by eutrophication and terrestrial anoxia by an atmospheric oxygen minimum during the Late Devonian. Postulated triggers of global cooling range from abrupt and catastrophic – the volcanic‐winter hypothesis versus the impact‐winter hypothesis – to long‐term and gradual carbon dioxide downdraw from the atmosphere due to biological and chemical weathering of terrestrial rocks. Key Concepts: Early lobe‐finned fishes and tetrapod (four‐limbed) vertebrates were severely impacted by the Late Devonian mass extinction. A severe loss in biodiversity and a ‘floral crisis’ in land plants were triggered by the Late Devonian mass extinction. The destruction of Devonian‐style reefs triggered a permanent change in global marine ecosystems. Both low‐temperature stress (hypothermia) and oxygen deprivation (hypoxia) are implicated in the Late Devonian mass extinction. Both catastrophic asteroidal impact and catastrophic mantle plume volcanism are debated as causes of the Late Devonian mass extinction. The precise cause of the Late Devonian mass extinction remains unproved.