Extension of Cathaysian flora during the Permian Climatic and paleogeographic constraints

摘要

Recent paleobotanic investigations have been described during the Late Permian intermingled Cathaysian (South China block), Gondwanian and Euramerian flora assemblage in Oman (Arabian plate). By analogy with present rainforest flora, Cathaysian floral elements in northeastern Gondwana require permanent precipitation, even if a short dry season may be endured. On the contrary, Eurasian flora is most probably adapted to dryness. We investigate the temporal and spatial extension of this surprising flora assemblage using numerical climatic simulations and paleomagnetic reconstructions. We suggest that the settlement of Cathaysian flora was possible as soon as this area reached abut 20°S. According to paleomagnetic data, the southeastern Arabian plate reached this latitude during Late Permian, which exactly corresponds to the age of the oldest discovered Cathaysian flora elements in Oman. Moreover, the paleomagnetic configuration of plates allows for easy Chinese to Gondwana connections using migrating blocks in the Tethys or island arcs. However, the climatic simulations suggest the presence of a dry season lasting about 5 months in southeastern Arabia. Such precipitation conditions would probably prevent the settlement of Cathaysian plants. We thus propose that the intermingled assemblage reflected the paleoenvironmental conditions: Cathaysian plants grew in a flood plain with perennial water supply, whereas Euramerian plants lived out of the flood plain over adjacent hills where water was only supplied by seasonal precipitation. Migration paths of these different floras are also discussed.