Permian Extinction Was Really Two Different Extinctions?

Two pulses of extinction during the Permian–Triassic crisis

Authors:

1. Haijun Song (a,*)
2. Paul B.Wignall (b)
3. Jinnan Tong (a)
4. Hongfu Yin (a)

Affiliations:

a. State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences,Wuhan 430074, China,

b. School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK.

*. e-mail: haijun.song@yahoo.com.cn.

Abstract:

The Permian–Triassic mass extinction is the most severe biotic crisis identified in Earth history. Over 90% of marine species were eliminated1, 2, causing the destruction of the marine ecosystem structure3. This biotic crisis is generally interpreted as a single extinction event around 252.3 million years ago2, 4, 5, 6, and has been variously attributed to the eruption of the Siberian Traps or possibly a bolide impact7, 8, 9, 10. Here we demonstrate that the marine extinction consisted of two pulses, separated by a 180,000-year recovery phase. We evaluated the range of 537 species representing 17 marine groups in seven Chinese sections from a 450,000-year interval spanning the Permian–Triassic boundary. The first stage of extinction occurred during the latest Permian, and was marked by the extinction of 57% of species, namely all plankton and some benthic groups, including algae, rugose corals, and fusulinids. The second phase occurred in the earliest Triassic, and resulted in the extinction of 71% of the remaining species. This second extinction phase fundamentally altered the marine ecosystem structure that had existed for the previous 200 million years. Because the two pulses showed different extinction selectivity, we conclude that they may have had different environmental causes.

Interesting. A few comments here.  

 Woo for looking at the selectivity of the extinctions!  I'd almost think that I had an impact (ahem, pun.  get it!) with my post from way back when entitled 'Stop Dreaming.'

Its been acknowledged for some time that the Permian Extinction had multiple pulses in the event when things died. Once upon a time, the Guadelupean Extinction was thought to be part of the general end Permian Extinction. 

I'm a bit concerned about their accuracy for timing of the two events: 400k years is really, really close when considering that this happened 250 odd million years ago. Being that accurate seems...difficult at best.

Mass extinctions are complex things.  The kill mechanisms are not simply THE VOLCANO DID IT for the Permian Extinction.  My now old post on the subject neglects a number of other things that have come to light since I wrote it in 2006: RUBISCO temperature limits, halogen releasing salt lakes, UV scorching, etc all had their part...yet the root cause was the Siberian Traps even if the kill mechanisms were varied.

Finally, there is the possibility that the the kitchen sink was the culprit: perhaps a bollide and the traps did the deed or some other event combo.  Douglas Erwin made the suggestion back in the early 1990s.  My bet is more on the previous comment: the root cause was straight forward, but that it enabled multiple kill mechanisms.