Climate of the Late Devonian to Triassic
Abstract Remarkable changes are apparent in climate during Late Devonian-Triassic times. Mostly the climate was rather different from the present. The faunas and floras offer much evidence for understanding the climate but, in turn, understanding the palaeogeography of the faunas and floras is dependent on understanding the climate and the changes in climate. The Late Devonian apparently had a warm climate. The climate of the Early Carboniferous was warm and equable. No cold climate can be identified, and apparently no ice was present at the poles. Even a cold-temperate climate is difficult to identify. On the other hand the tropical zone does not appear to have been particularly hot. Apparently this reflects an ocean current system and a weather system different from the present ones. During the Late Carboniferous the world became colder and the faunas and floras more provincial. Ice, probably mountain ice, appeared in Boreal and Austral regions. Widespread glaciation occurred in the earliest Permian but it had a very assymetrical character. Whether continental ice sheets like those of the Pleistocene were present is not proven. During the Early Permian the world became warmer probably with some fluctuation in climate and with evidence for seasonal ice but not for glaciers. During the Late Permian the warming continued, and a new kind of provincialism developed within the broad tropical and subtropical zone. By the end of the Permian, the earth was very warm. In the Early Triassic no equatorial humid zone can be identified and whereas the tropical zone was hotter than at present, the polar zones were also warm. The Early Triassic appears to have been almost universally dry. The climate remained warm during the Middle and Late Triassic but humid zones can be recognized. The climate also showed some apparent assymetry. The pecularities of the climate, and the change of climate, in this interval of time, are not readily explainable either on the basis of the present climate or the present or a similar distribution of land and sea. Nor are they readily explainable on reconstructions commonly accepted such as Pangaea formed in the? Carboniferous, as is often claimed. Probably more basic data are required before any satisfactory explanations are possible and as well as terrestrial effects including a change in the angle of the earth's rotation, extra-terrestrial planetary and galactic effects require study.