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Extinction: End-Triassic Mass Extinction

Michael Hautmann, 

Michael Hautmann

Paläontologisches Institut und Museum, Zürich, Switzerland

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First published: 15 August 2012
https://doi.org/10.1002/9780470015902.a0001655.pub3
Citations: 10
Book Series:Major Reference Works

Abstract

One of the five greatest mass extinction events in Earth's history occurred at the end of the Triassic, c. 200 million years ago. This event ultimately eliminated conodonts and nearly annihilated corals, sphinctozoan sponges and ammonoids. Other strongly affected marine taxa include brachiopods, bivalves, gastropods and foraminifers. On the land, there is evidence for a temporal disturbance of plant communities but only few plant taxa finally disappeared. Terrestrial vertebrates also suffered but timing and extent of this extinction remains equivocal. The cause of the end-Triassic mass extinction was probably linked to the contemporary activity of the Central Atlantic Magmatic Province, which heralded the breakup of the supercontinent Pangaea. Possible kill mechanisms associated with magmatic activity include sea-level changes, marina anoxia, climatic changes, release of toxic compounds and acidification of seawater. Remarkably, long-term effects on marine biota were rather different between ecological groups: a nearly instantaneous recovery of level-bottom communities is contrasted by the virtual absence of reef systems for nearly 10 million years after the extinction event.

Key Concepts:

  • Nearly half of all marine genera and a smaller but still significant proportion of terrestrial taxa went extinct at the end of the Triassic period, c.200 million years ago.

  • The end-Triassic mass extinction took place during a geologically short time interval, which coincided with the onset of massive magmatic extrusions along fracture zones of the disassembling supercontinent Pangaea.

  • A cause-and-effect relationship between magmatic activity and mass extinction is indicated by the accordance of predicted extinction patterns and observed data from the fossil record.

  • Ocean acidification as a kill mechanism in marine ecosystems is confirmed by preferential extinction of taxa with thick aragonitic skeletons.

  • The end-Triassic mass extinction event provides a test-case for studying evolutionary responses to major environmental disturbances on the global scale and over geological time.

  • Although there are differences in emission rates, the massive magmatic CO2 release at the end of the Triassic is quantitatively similar to a potential release by complete combustion of the global fossil fuel reserves.

  • A provisional prediction from the data of the fossil record is that in the marine realm level-bottom communities are able to recover much more quickly from the effects of excess CO2 than reef systems.