page_title: Triassic–Jurassic extinction event
section_title: Volcanic eruptions
hierarchical_section_title: Triassic–Jurassic extinction event / Possible causes / Volcanic eruptions
caption_attribution_description: English: Coarse summary of the locations as discussed in Blackburn, Terrence J.&#32;(2013).&#32;"Zircon U-Pb Geochronology Links the End-Triassic Extinction with the Central Atlantic Magmatic Province". Science&#32;340: 941–945. DOI:10.1126/science.1234204.
context_page_description: The Triassic–Jurassic extinction event, sometimes called the end-Triassic extinction, marks the boundary between the Triassic and Jurassic periods, 201.3 million years ago, and is one of the major extinction events of the Phanerozoic eon, profoundly affecting life on land and in the oceans. In the seas, a whole class and 23–34% of marine genera disappeared. On land, all archosauromorphs other than crocodylomorphs, pterosaurs, and dinosaurs went extinct; some of the groups which died out were previously abundant, such as aetosaurs, phytosaurs, and rauisuchids. Some remaining therapsids and many of the large temnospondyl amphibians had gone extinct prior to the Jurassic as well. However, there is still much uncertainty regarding a connection between the Tr-J boundary and terrestrial vertebrates, due to a paucity of terrestrial fossils from the Rhaetian period of the Triassic.
  Statistical analysis of marine losses at this time suggests that the decrease in diversity was caused more by a decrease in speciation than by an increase in extinctions.
context_section_description: Massive volcanic eruptions, specifically the flood basalts of the Central Atlantic Magmatic Province (CAMP), would release carbon dioxide or sulfur dioxide and aerosols, which would cause either intense global warming (from the former) or cooling (from the latter). In addition to these climatic effects, oceanic uptake of volcanogenic carbon and sulphur dioxide would have led to a significant decrease of seawater pH known as ocean acidification, which is discussed as a relevant driver of marine extinction. Evidence for ocean acidification as an extinction mechanism comes from the preferential extinction of marine organisms with thick aragonitic skeletons and little biotic control of biocalcification (e.g., corals, hypercalcifying sponges). Global interruption of carbonate deposition at the Triassic-Jurassic boundary has been cited as additional evidence for catastrophic ocean acidification. The record of CAMP degassing shows several distinct pulses of carbon dioxide immediately following each major pulse of magmatism, at least two of which amount to a doubling of atmospheric CO₂.
  The isotopic composition of fossil soils of the Late Triassic and Early Jurassic has been tied to a large negative carbon isotope excursion (Whiteside et al. 2010). Carbon isotopes of lipids (n-alkanes) derived from leaf wax and lignin, and total organic carbon from two sections of lake sediments interbedded with the CAMP in eastern North America have shown carbon isotope excursions similar to those found in the mostly marine St. Audrie’s Bay section, Somerset, England; the correlation suggests that the end-Triassic extinction event began at the same time in marine and terrestrial environments, slightly before the oldest basalts in eastern North America but simultaneous with the eruption of the oldest flows in Morocco (Also suggested by Deenen et al., 2010), with both a critical CO
  2 greenhouse and a  marine biocalcification crisis.
  Contemporaneous CAMP eruptions, mass extinction, and the carbon isotopic excursions are shown in the same places, making the case for a volcanic cause of a mass extinction. The catastrophic dissociation of gas hydrates (suggested as one possible cause of the largest mass extinction of all time, the so-called "Great Dying" at the end of the Permian Period) may have exacerbated greenhouse conditions.
  Some scientists initially rejected the volcanic eruption theory, because the Newark Supergroup, a section of rock in eastern North America that records the Triassic–Jurassic boundary, contains no ash-fall horizons and its oldest basalt flows were estimated to lie around 10 m above the transition zone. However, updated dating protocol and wider sampling has confirmed that the CAMP eruptions started in Nova Scotia and Morocco only a few thousand years before the extinction, and continued in several more pulses for the next 600,000 years.
caption: Maximum extent of CAMP volcanism at the Triassic-Jurassic boundary
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