Permian-Triassic transition

Cirilli S., Radrizzani C. P., Ponton M., and Radrizzani S. (1998) Stratigraphical and palaeoenvironmental analysis of the Permian Triassic transition in the Badia Valley (southern Alps Italy). Palaeogeogr. Palaeoclimat. Palaeoecol. 138, 85-113. 

In addition to the long-term 10 yr trends, shorter spikes, on 10 -10 yr scales (e.g., Permian/Triassic transition Holser, 1977), do exist, but their catastrophic geological causes are not as yet resolved. 

Mass extinctions have been recognized in the fossil record since the middle of the nineteenth century. Levels of mass extinction of species were selected as marker levels in the stratigraphic record because the death of index-fossil species provided a convenient marker to subdivide and correlate strata. The mass-extinction level called the Permian-Triassic boundary is so profound in terms of faunal and floral change that it was early on noted and chosen to represent the transition from Paleozoic to Mesozoic era. The mass-extinction level called the Cretaceous-Tertiary boundary is also quite distinctive in terms of faunal and floral change, and it too was noted early on and chosen to represent the transition from Mesozoic to Cenozoic era. Other less profound, but nevertheless distinctive levels of mass extinction of fossils have been selected to represent marker points in the stratigraphic record at which geological periods, epochs, ages, and other intervals of lesser temporal value are defined. 

The early Mesozoic has recently received much attention with respect to the recovery of marine life from the greatest ever (end-Permian) extinction event and another major extinction event at the end of the Triassic (overviews in Erwin, 2006 Smith, 2007 and references therein). The Permian/Triassic Boundary (PTB) in particular may play a pivotal role in assessing putative cause-and-effect scenarios during the Palaeozoic-Mesozoic transition (Algeoetal., 2007). However, fish species— normally... 

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