Fossil Plant Assemblage from the Middle Jurassic Yan’an Formation in Huating, Gansu Province and Its Paleoclimatic Implication
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Abstract:
On the basis of morphological and cuticle analysis, a total of 24 genera and 49 species of plant fossils were identified from the Middle Jurassic Yan’an Formation of Huating, Gansu Province. The results show that Ginkgopsida (38.8%) and Filicopsida (28.6%) are dominated in this flora, Coniferopsida (16.3%), Sphenoposida (8.2%) and Cycadopsida (4.1%) have an important proportion while Lycopsida and Pteridospermopsida are absent. On the basis of the comparison of fossil compositions with other Jurassic floras, including 11 Middle Jurassic floras from North China which had been investigated in detail by previous researches, we conclude that the present Yan’an Formation flora of Huating belongs to the early assemblage of the Coniopteris–Phoenicopsis flora in North China, with a geological age of Middle Jurassic (likely Aalenian to Bajocian). Meanwhile, most species from the Yan’an Formation were distributed in a zone of warm and humid conditions with some exceptions that existed in tropical or subtropical zones. Therefore, the regions of Huating, East Gansu Province might have experienced a humid and warm–temperate climate during the Middle Jurassic.
