Permian & Triassic Greenhouse Crises

Australia: The Land Where Time Began

Permian & Triassic Greenhouse Crises

Long periods during which the climate was cool and dry, the usual conditions for calcareous red palaeosols, were found to be punctuated by transient episodes in which climatic conditions were unusually warm and wet is indicated by palaeoclimatic time series from the Permian and Triassic. It is known, based on stomatal index of fossil leaves of Lepidopteris, that some of these palaeoclimatic events are known to have been episodes in which global atmospheric CO₂ were elevated. The magnitude varied considerably for the 19 known greenhouse crises from the Permian and Triassic, new evidence of the relationship between palaeoclimate and the levels of carbon dioxide in the atmosphere being offered. Global lowland vegetation showing marked effects of these greenhouse crises, such the introduction of lycopsids, that were frost-sensitive, to high latitudes, and conifers that were drought-tolerant, to lowlands at low latitudes. Phases of plant evolution, such as Ottokaria-Callipteris, Plumsteadia-Rufloria, Lidgettonia-Tatarina, Pleuromeia, and Dicroidium-Scytophyllum floras, were punctuated by greenhouse events. The evolution of reptilian dynasties were also punctuated by greenhouse events - successive pelycosaur, dinocephalian, dicynodont, rhynchosaur, and dinosaur faunas - and respiratory adaptations such as a large bony secondary palate. During the Late Permian and Early Triassic the greenhouse crises were the most severe that are known. A role for atmospheric pollution that resulted from the addition to the atmosphere of CH₄ and CO₂ has been suggested to have been released by the thermogenic cracking of coals by intrusive flood basalt feeder dykes. These mass extinction events are not considered to be "end-Permian" or "end-Guadalupian", being defined as Upper Changhsingian and mid-Capitanium, respectively, as a result of formalities in boundary definition.