iPedia Free Information Center

Information about Triassic Jurassic Extinction Event

Enlarge picture
Comparison of the intensity of the T-J extinction event, labeled here "End Tr" to other extinction events in the last 500 million years. Data based on fossiliferous marine genera.
Enlarge picture
Ranges of families tetrapods through the Triassic and Early Jurassic.


The Triassic-Jurassic extinction event occurred 200 million years ago and is one of the major extinction events of the Phanerozoic eon, profoundly affecting life on land and in the oceans. 20% of all marine families and all large Crurotarsi (non-dinosaurian archosaurs), some remaining therapsids, and many of the large amphibians were wiped out. At least half of the species now known to have been living on Earth at that time went extinct. This event opened an ecological niche 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.

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.[1]

Several explanations for this event have been suggested, but all have unanswered challenges.
  • Gradual climate change or sea-level fluctuations during the late Triassic. However, this does not explain the suddenness of the extinctions in the marine realm.
  • Asteroid impact, but no impact crater can be dated to coincide with the Triassic-Jurassic boundary.
  • Massive volcanic eruptions, specifically the flood basalts of the Central Atlantic Magmatic Province, would release carbon dioxide or sulfur dioxide which would cause either intense global warming (from the former) or cooling (from the latter).
However, the isotopic composition of fossil soils of Late Triassic and Early Jurassic show no evidence of any change in the CO2 composition of the atmosphere. More recently however, some evidence has been retrieved from near the Triassic-Jurassic boundary suggesting that there was a rise in atmospheric CO2 and some researchers have suggested that the cause of this rise, and of the mass extinction itself, could have been a combination of volcanic CO2 outgassing and catastrophic dissociation of gas hydrate. Gas hydrates have also been suggested as one possible cause of the largest mass extinction of all time; the so-called "Great Dying" at the end of the Permian Era.

References

1. ^ Bambach, R.K.; A.H. Knoll & S.C. Wang (December 2004), "Origination, extinction, and mass depletions of marine diversity", Paleobiology 30 (4): 522–542, <[1]
  • McElwain, J. C.; D. J. Beerling, F. I. Woodward (27 August 1999). "Fossil Plants and Global Warming at the Triassic-Jurassic Boundary". Science 285 (no. 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): pp.103 – 139. http://museums.state.nm.us/nmmnh/pdf_files/TJB.pdf
  • Tanner, L. H.; J. F. Hubert, B. P. Coffey et al (7 June 2001). "Stability of atmospheric CO2 levels across the Triassic/Jurassic boundary". Nature 411: pp. 675-677. 

External links

| Click [ here] to start a horizontal timeline, or [ here] for a vertical one. Once you've finished, save this article page; your timeline will be included here! For more details, visit |}>
For the Big Finish Productions audio play, see .
An extinction event (also known as: mass extinction; extinction-level event, ELE) is a sharp decrease in the number of species in a relatively short period of time.
..... Click the link for more information.
Phanerozoic (occasionally Phanaerozoic) Eon is the current eon in the geologic timescale, and the one during which abundant animal life has existed. It covers roughly 545 million years and goes back to the time when diverse hard-shelled animals first appeared.
..... Click the link for more information.
Crurotarsi
Sereno & Arcucci, 1990

Orders
  • Phytosauria
  • Aetosauria
  • Rauisuchia*
  • Crocodilia


The Crurotarsi ("cross-ankles") are a group of archosaurs created as a node-based clade by Paul Sereno in 1991 to supplant the old term
..... Click the link for more information.
Archosauria
Cope, 1869

Clades
  • Crurotarsi
  • Aetosauria
  • Crocodilia (crocodiles)
  • Phytosauria

..... Click the link for more information.
Therapsida *
Broom, 1905

Clades
  • Suborder Biarmosuchia *
  • Suborder Dinocephalia
  • Suborder Anomodontia *
  • Infraorder Dicynodontia
  • (unranked) Theriodontia *

..... Click the link for more information.
Amphibia
Linnaeus, 1758

Subclasses and Orders

   Order Temnospondyli - extinct
Subclass Lepospondyli - extinct
Subclass Lissamphibia
   Order Anura
   Order Caudata
..... Click the link for more information.
niche (pronounced nich, neesh or nish)[] is a term describing the relational position of a species or population in its ecosystem[1]. The ecological niche describes how an organism or population responds to the distribution of resources and competitors (e. g.
..... Click the link for more information.
Dinosauria *
Owen, 1842

Orders & Suborders
  • Ornithischia
  • Cerapoda
  • Thyreophora
  • Saurischia

..... Click the link for more information.
The Jurassic Period is a major unit of the geologic timescale that extends from about 199.6 ± 0.6 Ma (million years ago) to 145.4 ± 4.0 Ma, the end of the Triassic to the beginning of the Cretaceous.
..... Click the link for more information.
Pangaea or Pangæa (IPA: /pænˈdʒiːə/[1], from παν, pan, meaning entire, and γαια, gaia, meaning Earth
..... Click the link for more information.


Speciation is the evolutionary process by which new biological species arise. There are four modes of natural speciation, based on the extent to which speciating populations are geographically isolated from one another:
..... Click the link for more information.
The Triassic is a geologic period that extends from about 251 to 199 Ma (million years ago). As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events.
..... Click the link for more information.
The Central Atlantic magmatic province (CAMP) was formed during the breakup of Pangaea during the Mesozoic Era. The initial breakup of Pangaea in early Jurassic time provided a legacy of basaltic dikes, sills, and lavas over a vast area around the present central North Atlantic
..... Click the link for more information.
Carbon dioxide is a chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state.
..... Click the link for more information.
Sulfur dioxide (also sulphur dioxide) is the chemical compound with the formula SO2. This important gas is the main product from the combustion of sulfur compounds and is of significant environmental concern.
..... Click the link for more information.
The Late Triassic (also known as Upper Triassic, or Keuper) is the third and final of three epochs of the Triassic period. It spans the time between 228 ± 2 Ma and 199.6 ± 0.6 Ma (million years ago).
..... Click the link for more information.
Early Jurassic (in geology referred to as the Lower Jurassic, originally (and still in Europe) the "Lias") is the earliest of three epochs of the Jurassic period.
..... Click the link for more information.
Clathrate hydrates (or alternatively gas clathrates, gas hydrates, clathrates, hydrates etc) are a class of solids in which gas molecules occupy "cages" made up of hydrogen-bonded water molecules.
..... Click the link for more information.
For the Big Finish Productions audio play, see .
An extinction event (also known as: mass extinction; extinction-level event, ELE) is a sharp decrease in the number of species in a relatively short period of time.
..... Click the link for more information.
Permian is a geologic period that extends from about 299.0 ± 0.8 Ma to 251.0 ± 0.4 Ma (million years before the present; ICS 2004). It is the last period of the Paleozoic Era.
..... Click the link for more information.


This article is copied from an article on Wikipedia.org - the free encyclopedia created and edited by online user community. The text was not checked or edited by anyone on our staff. Although the vast majority of the wikipedia encyclopedia articles provide accurate and timely information please do not assume the accuracy of any particular article. This article is distributed under the terms of GNU Free Documentation License.
Herod_Archelaus


page counter