干旱区生态环境知识资源中心

Paleoenvironmental and paleoclimatic conditions at Thale during the late Ladinian (Middle Triassic) are assessed using both the plant megaflora and palynoflora. These two datasets are necessary because these two different types of assemblages were subjected to different taphonomic biases and together provide a more complete appraisal of Triassic conditions in the study area. The megafossil remains represent a (par)autochthonous flora with large, well-preserved leaf and shoot fragments that indicate relatively limited transport. Most fragments probably belonged to plants growing on river banks. The composition of the rich and diversified megaflora indicates lush vegetation typical of an environment without water stress and probably a high water table. On the other hand, quantitative analyses of the palynological data using different methods (morphogroups and Sporomorph EcoGroup or SEG) show a strong dominance of bisaccate pollen. River or wetland plants are well represented by trilete, laevigate spores and multicellular algae. Since the spores were normally water transported along with the sediment and the pollen grains were wind transported over long distances, but also by water, there are two possible interpretations: (1) the local flora was dominated by ferns within a larger, conifer-dominated, and possibly forested area; (2) time related, the megaflora shows a short-term signal that corresponds to a humid spell during the generally more arid period of Middle and Late Triassic, while the palynoflora shows a longer-term, regional signal.