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End Ordovician extinctions : A coincidence of causes

Harper, David A T LU ; Hammarlund, Emma U. LU and Rasmussen, Christian M Ø LU (2014) In Gondwana Research 25(4). p.1294-1307
Abstract

The end Ordovician (Hirnantian) extinction was the first of the five big Phanerozoic extinction events, and the first that involved metazoan-based communities. It comprised two discrete pulses, both linked in different ways to an intense but short-lived glaciation at the South Pole. The first, occurring at, or just below, the Normalograptus extraordinarius graptolite Biozone, mainly affected nektonic and planktonic species together with those living on the shallow shelf and in deeper water whereas the second, within the N. persculptus graptolite Biozone, was less focused, eradicating faunas across a range of water depths. In all about 85% of marine species were removed. Proposed kill mechanisms for the first phase have included... (More)

The end Ordovician (Hirnantian) extinction was the first of the five big Phanerozoic extinction events, and the first that involved metazoan-based communities. It comprised two discrete pulses, both linked in different ways to an intense but short-lived glaciation at the South Pole. The first, occurring at, or just below, the Normalograptus extraordinarius graptolite Biozone, mainly affected nektonic and planktonic species together with those living on the shallow shelf and in deeper water whereas the second, within the N. persculptus graptolite Biozone, was less focused, eradicating faunas across a range of water depths. In all about 85% of marine species were removed. Proposed kill mechanisms for the first phase have included glacially-induced cooling, falling sea level and chemical recycling in the oceans, but a general consensus is lacking. The second phase is more clearly linked to near-global anoxia associated with a marked transgression during the Late Hirnantian. Most recently, however, new drivers for the extinctions have been proposed, including widespread euxinia together with habitat destruction caused by plate tectonic movements, suggesting that the end Ordovician mass extinctions were a product of the coincidence of a number of contributing factors. Moreover, when the deteriorating climate intensified, causing widespread glaciation, a tipping point was reached resulting in catastrophe.

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author
publishing date
type
Contribution to journal
publication status
published
keywords
End Ordovician, Extinction, Hirnantian, Isotopes, Palaeogeography
in
Gondwana Research
volume
25
issue
4
pages
14 pages
publisher
Elsevier
external identifiers
  • scopus:84896396679
ISSN
1342-937X
DOI
10.1016/j.gr.2012.12.021
language
English
LU publication?
no
id
c8400eb1-744c-41c7-84d1-e43659b7bd1f
date added to LUP
2017-05-17 11:24:20
date last changed
2017-11-05 05:17:30
@article{c8400eb1-744c-41c7-84d1-e43659b7bd1f,
  abstract     = {<p>The end Ordovician (Hirnantian) extinction was the first of the five big Phanerozoic extinction events, and the first that involved metazoan-based communities. It comprised two discrete pulses, both linked in different ways to an intense but short-lived glaciation at the South Pole. The first, occurring at, or just below, the Normalograptus extraordinarius graptolite Biozone, mainly affected nektonic and planktonic species together with those living on the shallow shelf and in deeper water whereas the second, within the N. persculptus graptolite Biozone, was less focused, eradicating faunas across a range of water depths. In all about 85% of marine species were removed. Proposed kill mechanisms for the first phase have included glacially-induced cooling, falling sea level and chemical recycling in the oceans, but a general consensus is lacking. The second phase is more clearly linked to near-global anoxia associated with a marked transgression during the Late Hirnantian. Most recently, however, new drivers for the extinctions have been proposed, including widespread euxinia together with habitat destruction caused by plate tectonic movements, suggesting that the end Ordovician mass extinctions were a product of the coincidence of a number of contributing factors. Moreover, when the deteriorating climate intensified, causing widespread glaciation, a tipping point was reached resulting in catastrophe.</p>},
  author       = {Harper, David A T and Hammarlund, Emma U. and Rasmussen, Christian M Ø},
  issn         = {1342-937X},
  keyword      = {End Ordovician,Extinction,Hirnantian,Isotopes,Palaeogeography},
  language     = {eng},
  number       = {4},
  pages        = {1294--1307},
  publisher    = {Elsevier},
  series       = {Gondwana Research},
  title        = {End Ordovician extinctions : A coincidence of causes},
  url          = {http://dx.doi.org/10.1016/j.gr.2012.12.021},
  volume       = {25},
  year         = {2014},
}