Permian and Triassic greenhouse crises
Author:
1. Gregory J. Retallack (a)
Affiliations:
a. Department of Geological Sciences, University of Oregon, Eugene, OR 97403, United States
Abstract:
Paleoclimatic time series from Permian and Triassic paleosols reveal transient episodes of unusually warm and wet conditions, interrupting long periods of cool and dry conditions usual for calcareous red paleosols. Some of these paleoclimatic events are known from stomatal index of fossil Lepidopteris leaves to have been episodes of elevated global atmospheric CO2. The magnitude of 19 known Permian and Triassic greenhouse crises varied considerably, and they offer new evidence for the relationship between paleoclimate and atmospheric CO2 levels. These greenhouse crises also had marked effects on global lowland vegetation, introducing frost-sensitive tropical lycopsids to high latitudes and drought-tolerant conifers to low latitude lowlands. Greenhouse events punctuate phases in plant evolution (Ottokaria–Callipteris, Plumsteadia–Rufloria, Lidgettonia–Tatarina, Pleuromeia, and Dicroidium–Scytophyllum floras). Greenhouse events also punctuate the evolution of reptilian dynasties (successive pelycosaur, dinocephalian, dicynodont, rhynchosaur and dinosaur faunas) and respiratory adaptations (such as enlarged bony secondary palate). Greenhouse crises of the Late and Middle Permian were the most severe known, and suggest a role for atmospheric pollution with CH4 and CO2 in those mass extinction events, probably from thermogenic cracking of coals by intrusive feeder dikes of flood basalts. Because of formalities in boundary definition these mass extinctions are neither “end-Permian” nor “end-Guadalupian”, but upper Changhsingian and mid-Capitanian, respectively.
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