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Triassic–Jurassic extinction event

 

Triassic–Jurassic extinction event

Marine extinction intensity during the Phanerozoic
%
Millions of years ago
(H)
Tr–J
The blue graph shows the apparent percentage (not the absolute number) of marine animal genera becoming extinct during any given time interval. It does not represent all marine species, just those that are readily fossilized. The labels of the "Big Five" extinction events are clickable hyperlinks; see Extinction event for more details. (source and image info)

The Triassic–Jurassic extinction event marks the boundary between the Triassic and Jurassic periods, ,[1] 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 (biology) (conodonts)[2] and 34% of marine genera disappeared.[3] On land, all large crurotarsans (non-dinosaurian archosaurs) other than crocodilians, some remaining therapsids, and many of the large amphibians became extinct.

Contents

  • Impact 1
  • Current theories 2
  • References 3
  • Literature 4
  • External links 5

Impact

At least half of the species now known to have been living on Earth at that time went extinct. This event vacated terrestrial ecological niches, allowing the dinosaurs to assume the dominant roles in the Jurassic period. This event happened in less than 10,000 years and occurred just before Pangaea started to break apart. In the area of Tübingen (Germany), a Triassic-Jurassic bonebed can be found, which is characteristic for this boundary.[4]

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.[5]

Ranges of families tetrapods through the Triassic and Early Jurassic.

Current theories

Several explanations for this event have been suggested, but all have unanswered challenges:

  • Gradual climate change, sea-level fluctuations or a pulse of oceanic acidification[6] during the late Triassic reached a tipping point. However, this does not explain the suddenness of the extinctions in the marine realm.
  • Asteroid impact, but so far no impact crater of sufficient size has been dated to coincide with the Triassic–Jurassic boundary. The eroded Rochechouart crater in France has most recently been dated to 201 ±2 million years ago,[7] but at 25 km across (possibly up to 50 km across originally), appears to be too small.[8] (The impact responsible for the annular Manicouagan Reservoir occurred about 12 million years before the extinction event - the Rochechouart crater is now thought to have been caused by part of the same fragmented impactor.)
  • 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).[9][10]

The isotopic composition of fossil soils of

  • Theories on the Triassic-Jurassic Extinction
  • The Triassic-Jurassic Mass Extinction
  • 200 million year old mystery BBC News story, 12-Oct-2011

External links

  • Hodych, J. P.; G. R. Dunning (1992). "Did the Manicougan impact trigger end-of-Triassic mass extinction?". Geology 20: pp. 51.54.  
  • McElwain, J. C.; D. J. Beerling; F. I. Woodward (27 August 1999). "Fossil Plants and Global Warming at the Triassic-Jurassic Boundary". Science 285 (5432): 1386–1390.  
  • Tanner, L.H.; S.G. Lucas, M.G. Chapman (2004). "Assessing the record and causes of Late Triassic extinctions". Earth-Science Reviews 65 (65): pp.103–139.   [1]
  • Whiteside, Jessica H.; Paul E. Olsen; Timothy Eglinton; Michael E. Brookfield; Raymond N. Sambrotto (March 22, 2010). "Compound-specific carbon isotopes from Earth's largest flood basalt eruptions directly linked to the end-Triassic mass extinction".  
  • Deenen, M.H.L.; M. Ruhl, N.R. Bonis, W. Krijgsman, W. Kuerscher, M. Reitsma, M.J. van Bergen (2010). "A new chronology for the end-Triassic mass extinction". EPSL. 

Literature

  1. ^ Some sources (Whiteside et al 2010) give a date 201.4 Ma.
  2. ^ The extinction of conodonts —in terms of discrete elements— at the Triassic-Jurassic boundary
  3. ^ Graham Ryder, David E. Fastovsky, Stefan Gartner (1996). The Cretaceous-Tertiary Event and Other Catastrophes in Earth History. Geological Society of America. p. 19.  
  4. ^ Johannes Baier: Der Geologische Lehrpfad am Kirnberg (Keuper; SW-Deutschland). - Jber. Mitt. oberrhein. geol. Ver, N. F. 93, 9-26, 2011.
  5. ^ Bambach, R.K.; Knoll, A.H.; Wang, S.C. (December 2004). "Origination, extinction, and mass depletions of marine diversity". Paleobiology 30 (4): 522–542.  
  6. ^ T.M. Quan, B. van de Schootbrugge, M.P. Field, "Nitrogen isotope and trace metal analyses from the Mingolsheim core (Germany): Evidence for redox variations across the Triassic-Jurassic boundary", Global Biogeochemical Cycles, 22 2008: "a series of events resulting in a long period of stratification, deep-water hypoxia, and denitrification in this region of the Tethys Ocean basin"; M. Hautmann, M.J. Benton, A. Toma, "Catastrophic ocean acidification at the Triassic-Jurassic boundary", Neues Jahrbuch für Geologie und Paläontologie 249.1, July 2008:119-127.
  7. ^ Schmieder, M.; Buchner, E.; Schwarz, W. H.; Trieloff, M.; Lambert, P. (2010-10-05). "A Rhaetian 40Ar/39Ar age for the Rochechouart impact structure (France) and implications for the latest Triassic sedimentary record".  
  8. ^ Smith, Roff (2011-11-16). "Dark days of the Triassic: Lost world".  
  9. ^ Tanner, L. H., J. F. Hubert et al. (7 June 2001). "Stability of atmospheric CO
    2
    levels across the Triassic/Jurassic boundary". Nature 411 (6838): pp. 675–677.  
  10. ^ Blackburn, Terrence J.; Olsen, Paul E.; Bowring, Samuel A.; McLean, Noah M.; Kent, Dennis V; Puffer, John; McHone, Greg; Rasbury, Troy; Et-Touhami7, Mohammed (2013). "Zircon U-Pb Geochronology Links the End-Triassic Extinction with the Central Atlantic Magmatic Province". Science 340 (6135): 941–945.  

References

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.

greenhouse and a marine biocalcification crisis.
2
CO

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