豫西-皖北地区二叠纪植物地理区系性质探讨

ON THE PERMIAN PHYTOGEOGRAPHY OF W. HENAN N. ANHUI REGION

基于对豫西皖北地区和华北、华南二叠纪植物化石分布状况的全面对比统计，简略分析了豫西皖北地区二叠纪植物群演替，将该区各阶期与华北及华南同期植物群进行了比较，并对其间Ｓｉｍｐｓｏｎ相似性系数作了求算。结果表明它应作为华夏植物群华北植物区内的一个次级植物地理单元对待。其成因与华北、华南二叠纪时古板块的旋转、漂移。

Statistical method has been used in a comprehensive study of the Permian fossil plants from W. Henan N. Anhui region. The results of this study are summarized in the attached table and compared to the fossil plants from North and South China. Four Permian plant assemblages have been recognized in this area, which are: (1) Neuropteris pseudovata Lepidodendron szeianum assemblage in the early stage of the Early Permian (the middle and upper parts of Taiyuan Formation) (2) Emplectopteris triangularis Cathaysiopteris whitei Lobatannularia sinensis assemblage in the middle stage of the Early Permian (the Shanxi Formation) (3) Gigantonoclea lagrelii Lobatannularia ensifolia Fascipteris hallei assemblage in the late stage of the Early Permian (the Lower Shihhotse Formation) (4) Gigantopteris nicotianaefolia Lobatannularia multifolia Psygmophyllum multipartitum assemblage at the early stage of the Late Permian (the Upper Shihhotse Formation). The major components of each plant assemblage are compared quantitatively in the Figure 1. The Permian flora of the W. Henan N. Anhui region is characterized by its endemic features, especially in the late stage of the Early Permian and the early stage of the Late Permian. However, as far as the number of species is concerned, the species occuring only in the W. Henan N. Anhui region are usually less than those occurring both in this region and N. Chian, i.e.,A≤B+C. Therefore, this region could be regarded as a phytoprovince in the N. China Phytoarea, rather than a phytoarea with the same rank as N. China and S. China regions. This conclusion is further supported by an analysis of the common species and the Simpson coefficients (see table 1) among these plant assemblages in the W. Henan N. Anhui region, N. China and S. China, because the fossil flora of W.Henan N. Anhui region generally possess a closer relation to that of N. China than S. China throughout Permian period. As an independent phytoprovince in the N. China Phytoarea, the fossil flora in this region possesses certain transitional features between the flora in N. China and S. China Phytoareas. For example, Gigantonoclea and Gigantopteris , which are considered respectively as the representative member of the Gigantopterids in N. China and S. China, co exist primarily in the W. Henan N. Anhui region. The development of the W. Henan N. Anhui phytoprovince is probably related to the movement (drifting, rotating) of the N. China and Yangtze blocks and is consistent with the Permian coal beds containing this fossil flora and bearing the feature of “northern stratigraphic type and southern sedimentary facies”.