The Late Permian climate. What can be inferred from climate modelling concerning Pangea scenarios and Hercynian range altitude?

A major unsolved geodynamic problem is the Permian Pangea plate configuration at the end of Paleozoic era (around 255 Ma). While consensual geology indicates a plate arrangement close to that of the Jurassic prior to the Atlantic opening (Pangea A), paleomagnetic data indicates a nearly 3000 km more eastward position of Gondwana with respect to Laurussia, leading to major plate and relieves reorganisation during Permo-Triassic times (Pangea B). Using an atmospheric general circulation model (AGCM), we simulate the climatic response to both configurations. We also test the fundamental role of paleo-elevations through sensitivity experiments. Each simulated climate is then compared with the aim of constraining the best fit to a particular paleogeographic scenario. Main trends of simulated Late Permian climate in agreement with paleoclimatic indicators are: (1) a warm temperate climate accompanied by a monsoon circulation over the eastern side of Gondwana; (2) a cold temperate climate marked by strong annual thermal amplitude at high latitudes in Gondwana and in Siberia; (3) an arid belt in the subtropics over the western side of Gondwana and Laurussia; and (4) strong climatic differences over both hemispheres, respectively. Main variance is found over Laurussia with a simulated tropical climate while an arid climate is suggested by paleodata. Simulating different paleo-elevations of the Appalachian and the Variscan fold belts can solve this discrepancy. The best model–data fit is reached for a mean altitude of 4500 m in the Appalachians and appears to be dependent of Pangea configuration with a southern Europe Variscan range of some 3000 m in a Pangea A configuration or only 2000 m in for Pangea B. Taking into account the geodynamic context, we argue that Pangea B appears to be the more probable configuration.