Study On The Plantecology And Phytogeography Of Middle Late Paleozoic-early Late Permian In Western Hills Of Beijing

The fossil plants discussed in this paper were collected from the Taiyuan, Shanxi and Shihezi Formations over the areas of Huiyu and Junzhuang in the west hills of Beijng. The author has collected more than 200 fossils from the areas during year 2005 to 2007 and identified 13 species in 12 genera. Base on the fossils gathering and the data of Predecessors, the author gives a systematic analysis of the fossil plants from Taiyuan to Shihezi Formations, counts 76 species in 32 genera. According to statistics, there are 76 species in 32 genera. The Beijing Xishan flora is most prosperous by the Filicopsida and Pterdospermopsida, occupies 46.1%, next for Sphenopsida, accounts for 30.3%, Lycopsida the third, accounts for 11.8%, then Cordaitopsida, Cacadopsida, Ginkgopsida and Coniferae and so on. The flora includes a lot of characteristic species of Cathaysia flora, such as Lepidodendron posthumii, L. incertum, L. oculus-felis, Neuropteris ovata, Emplectopteris triangularis, Lobatannularia sinensis, Fascipteris halle and so on. The overall appearance is consistent with the north sub-area of the Cathaysia flora.The author studies the features and the assemblages of the flora, carried on the contrast with 13 floras during the same period at home and abroad. The author also makes further study on the palaeoecology and the taphonomic types of the fossil plants. The fossil plants are divided into four plant assembl-ages, namely, Coast-lake bog community, Coast-alluvial plain community, Front mountain-lake bog community, Inland-river-lake community. The flora indicates a humid-warm close to tropical to subtropical climate in Late Carboniferous to Late Permian. There are four plant combination belts in this area: Linopteris brongniartii-Paripteris kaipingiana assemblage, Neuropteris ovata-Lepidodendron posthumii assemblage, Emplectopteris triangularis-Lobatannularia sinensis-Sphe-nophyllum thonii assemblage, Lobatannularia ensifolia-Fascipteris halle assembl-age.Based on the approach of Cluster Analysis Method, this essay has carried on the region division and the contrast to the ten plant fossils habitat in the north sub-area ofthe Cathaysia flora. According to its statistical result, the north sub-area is in East-West distribution. There has certain rationality though it is a little different from the Cathaysia flora divided by Li Xingxue (1995). The purpose of the study is to make some assistance function to the Phytogeography by using quantitative analysis methods.