Late Devonian extinction

Late Devonian extinction
Name	Late Devonian extinction
Time	~372–359 million years ago
Location	Global
Organisms	Brachiopoda, Placodermi, Trilobita, Calamites, Rhyniophyta
Severity	Major Phanerozoic extinction

Late Devonian extinction The Late Devonian extinction encompassed a series of biotic crises during the Frasnian and Famennian stages that profoundly reshaped Paleozoic marine and terrestrial life, particularly affecting reef ecosystems, jawed fish, and plant assemblages. It coincided with broad environmental change, including widespread anoxia, global cooling and warming episodes, and major biogeochemical perturbations tied to events such as the Kellwasser Event and the Hangenberg Event, documented across stratigraphic sections from Antarctica to Laurentia, Siberia and Gondwana.

Overview and chronology

The extinction unfolded as multiple pulses centered on the Frasnian–Famennian boundary and culminating at the Devonian–Carboniferous transition, with key horizons marked by the Lower Kellwasser, Upper Kellwasser and the Hangenberg Event. Stratigraphic correlation uses marine units from Rhenish Massif sections, Cleveland Basin records, Eifelian and Givetian successions, and well-studied cores from Miguasha, Burgess Shale-comparative faunas, and Bakken Formation analogues. Biostratigraphic markers include turnovers in conodont assemblages, shifts in brachiopod species, and changes in coral reefbuilders that allow intercontinental synchroneity assessment.

Causes and environmental drivers

Proposed drivers encompass massive volcanism such as emplacement of large igneous provinces analogous to the Viluy Traps, episodes of marine anoxia evidenced by black shales, perturbations in the carbon cycle inferred from δ13C excursions, and climatic shifts tied to elevated atmospheric CO2 or drawdown driven by terrestrial plant expansion. Sea-level fluctuations linked to glaciation on Gondwana, nutrient loading from weathering and soil formation associated with silicate weathering and rooting systems innovations, and bolide impact hypotheses referencing global ejecta layers have all been advanced, with multidisciplinary proxies from paleobotany, paleoceanography, sedimentology and geochemistry informing models.

Extent and patterns of extinction

Extinction severity was taxon-selective: reef-building tabulate corals, stromatoporoids, and many pelagic conodont taxa experienced severe losses, while several benthic clades showed differential survivorship. Vertebrate losses disproportionately affected armored placoderm fishes and some sarcopterygian groups, whereas early tetrapod lineages and many opportunistic invertebrates persisted or radiated. Geographic and ecological selectivity is evident in comparisons between shallow carbonate platform faunas in the Rheic Ocean realm, deep-water basinal assemblages in Avalonia, and marginal-marine units of Laurussia, revealing complex extinction gradients.

Biotic consequences and ecosystem recovery

Post-crisis recovery saw the collapse of Devonian reef ecosystems and later re-establishment by new reef architects in the Mississippian and Pennsylvanian intervals, facilitating diversification of scleractinian analogues and heterostracan survivors. Phytoplankton and nekton turnovers altered food webs, enabling radiations among actinopterygian fishes, early ammonoids, and various eurypterid survivors that shaped Carboniferous ecosystems. Terrestrial plant evolution, including lignophyte expansion and soil horizon development, restructured terrestrial habitats and influenced subsequent coal formation, vegetation succession, and faunal colonization of freshwater and terrestrial niches.

Evidence and geochemical signatures

Key proxies include negative and positive excursions in δ13C and δ18O records from carbonate and organic matter, widespread deposition of organic-rich black shales bearing molybdenum and uranium enrichments, mercury anomalies linked to volcanism, and biomarkers indicating anoxia and euxinia such as isorenieratane. Conodont oxygen isotopes, strontium isotope ratios, and trace-element partitioning in apatite and carbonate provide temperature and seawater chemistry constraints; palynological assemblages and charcoal records document terrestrial vegetation change and wildfire frequency, integrating paleoclimatic reconstructions from glaciogenic facies and sequence stratigraphy.

Regional manifestations and notable events

Prominent regional records include the Kellwasser horizons in the Rhenish Massif, the Famennian black shales of Alberta and Poland, the Hangenberg Sandstone and associated extinction marker beds in Germany, and exceptional fossil Lagerstätten such as Miguasha and Red Hill that preserve vertebrate turnover. Gondwanan sections record glacial deposits and sequence-boundary shifts, Siberian and Laurentian basins show transgressive black-shale facies, while Mediterranean and Baltica successions provide high-resolution chemostratigraphic tie-points for global correlation.

Research history and debates

Debate has evolved from single-cause models emphasizing volcanism or glaciation toward multifactorial scenarios invoking synergistic drivers and chronostratigraphically discrete pulses. Pioneering fieldwork by researchers at institutions like the Natural History Museum, London and universities in Cambridge, Warsaw, and Uppsala advanced conodont biostratigraphy and geochemical sampling, while recent developments in high-precision geochronology, mercury stratigraphy, and organic geochemistry continue to refine timing and causal inference. Ongoing controversies concern the relative roles of terrestrial plant evolution, nutrient cycling, regional versus global anoxia, and the contribution of extraterrestrial impacts, keeping the event an active focus across paleontology, geochemistry, stratigraphy and sedimentology.

Category:Extinction events