Discovery of Cladophlebis kwangyuanensis in the Upper Triassic of Yunyang, Chongqing and its paleoclimatic significance
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Abstract:
Pteridophytes are abundant in the Upper Triassic of Chongqing, southwestern China. Here we report specimens collected from the third member of the Upper Triassic Xujiahe Formation near Longjiao Town, Yunyang County of Chongqing. After detailed morphological study and comparison, these specimens are identified as Cladophlebis kwangyuanensis Li, 1964. These specimens represent the first occurrence of Cladophlebiskwangyuanensis Li, 1964in the Upper Triassic in Yunyang, Chongqing. This report significantly expands the fossil record of Cladophlebis and indicates that the genus extended further east in the Sichuan Basin. Analysis of the distribution of published Cladophlebis records indicates that the Triassic Cladophlebis is concentrated in the eastern edge of the Sichuan Basin. Morphological characters of Cladophlebiskwangyuanensis, such as incised margin of pinnule, thin lamina, sparce and delicate pinnate veins, and the types and quantities of other associated plants, suggest that, during the Late Triassic in Yunyang area, this species lived in a warm, humid subtropical-tropical monsoon climate. These results, in combination with data of fossil wood growth rings and paleosoils, suggest that the east Sichuan Basin might have been influenced by the water vapors of the Paleo-Tethys Ocean and the eastern Pacific Rim during the Late Triassic. The strong monsoon brought water vapors into the basin increasing the rainfall and the climate conditions in the eastern area of the basin are suitable for the ferns to grow at that time.
