Australia: The Land Where Time Began

A biography of the Australian continent 

Permian-Triassic Crisis - 2 Pulses of Extinction

The most severe biotic crisis that has been identified in the history of the Earth is the mass extinction event of the end-Permian when more the 90 % of marine species were eliminated (Erwin, 1994; Jin et al., 2000) destroying the structure of the marine ecosystem (Bambach, Knoll & Sepkoski, 2002). According to the authors¹ the general interpretation of the end-Permian biotic crisis has been that it was a single extinction event that occurred about 252.3 Ma (Jin et al., 2000; Wignall & Hallam, 1992; Rampino & Adler, 1998; Shen et al., 2011). It has been attributed to a number of possible causes, such as the impact of a bolide or the Siberian Traps eruptions. The authors¹ say they have demonstrated that there were actually 2 pulses of marine extinctions that were separated  by 180,000 years during which there was a phase of recovery. The study by the authors¹ evaluated 537 species from 17 marine groups that had been recovered from 7 sections in China from an interval of 450,000 years spanning the Permian-Triassic boundary. Their results show the the first phase of extinctions occurred in the latest Permian, in which 57 % of species, namely all plankton as well as some benthic groups, that included algae, rugose corals and fusulinids, became extinct. 71 % of the remaining species went extinct in the second phase that occurred in the earliest Triassic. The structure of the marine ecosystem that had existed for 200 My was fundamentally altered in the second phase of extinctions. The authors¹ concluded that the 2 extinction phases may have had different environmental causes as the selectivity of the extinctions in the 2 phases was different.

Sources & Further reading

1. Song, Haijun, Paul B. Wignall, Jinnan Tong, and Hongfu Yin. "Two Pulses of Extinction During the Permian-Triassic Crisis." Nature Geosci 6, no. 1 (01//print 2013): 52-56.