A palaeoclimatic analysis of the Middle Jurassic period in Daqinshan area, Inner Mongolia

Abstract：Using traditional means, the authors recognized 18 genera and 31 species from plant fossils of Jurassic Zhaogou Formation in Shiguaizi Basin of Daqingshan area, a typical Jurassic continental facies coal-bearing faulted subsidence basin developed in central Inner Mongolia. These genera and species belong to Filicopsida, Cycadopsida, Ginkgopsida, Czekanoskiopsida, Coniferopsida respectively. Meanwhile, based on features of the plant fossil assemblage, the authors carried out a series of anatomic studies by using advanced SEM to probe into the type, morphology and textures of the surface cells of the Ginkgopsida and Czekanoskiopsida. It is held that the plant fossils in Zhaogou Formation belong to a late assemblage (i.e., the Middle Jurassic assemblage) represented by the Coniopteris- Phoenicopsis in North China. The discovery of the assemblage suggests that the Shiguaizi Basin was under a warm and wet swamp and lake environment during Middle Jurassic, and such an environment was favorable for the formation of coal, oil and natural gas. The result obtained by the authors is helpful to the study of the evolution of the basins and to the genetic research and prediction of fossil mineral resources in this area.