【摘要】 <正> 一、前言二叠-三叠系界线的讨论是当今国内外地层工作者瞩目的一大热门课题。长时期来,人们一直沿用以Otoceras带的底作为二叠-三叠系界线。近年来,一些学者开始对此提出疑议。自笔者(王义刚,1984;王义刚等,1976)报道和对论了中国的Otoceras菊石群和二叠-三叠系界线定义后,殷鸿福等(1985,1988)、李子舜等(1984,1986)、饶荣标等(1985)也都不同程度地讨论了这个问题。从相继发表的文献和笔者所掌握的材料看,进一步阐明二叠-三叠纪菊石交替,将有助于二叠-三叠系界线的讨论。更多还原

【Abstract】 The replacement of ammonites is one of the keys to the Permo-Triassic biotic event, occupying a special position in the study of geological events between Permian and Triassic. Based on Chinese special data, here suggested is a systematic taxonomy of Changhsingian and Griesbachian ammonites. The present paper discusses emphatically on Otocerataceae and Xenodiscaceae, both of which are very important in the ammonite replacement, with a comparison between the taxonomy of Changhsingian ammonites and that of Griesbachian ammonites (see Table Ⅰ in Chinese text); and indicates the living environment of these ammonites. In conclusion, the following points are taken into consideration: 1. As shown in Table Ⅰ, except Pseudogast rioceras, none of the genera of Changhsingian ammonites range to Griesbachian, indicating a mass extinction event between Permian and Triassic; but most taxonomic units at and alcove the family level of the Changhsingian ammonites ranged to Griesba chian, indicating a very close affinity existing between Permian and Triassic ammonites. 2. Most part of the Changhsingian ammonites lived in the intertidal or/and, subtidal environments on the restricted marine platform. However, these ammonites are possessed of some specializa tion and striking endemic colour; but those Griesbachian ammonites living in normal marine environments are cosmopolitan, which together with bivalves and conodonts, are relatively high in density of population as compared with other groups. 3. During the latest Changhsingian; as the environment rapidly changed, extinction of those specialized ammonites migth result when reduction in a faunal geographic range fell upon a certain minimum area, and their population became too small for them to reproduce a viable population; but those more primitive forms, such as Xenodiscus, etc., which lived-in the relatively deeper marine water enwronment, could, survive and evolve to Hypophiceras and other groups when they strided into Griesbachian. 4. Judging from the morphology of Otoceras and the sedimentary condition of Otocerasbearing beds in both of the Boreal and Tethyan realms, the Otoceras woodwardi zone in the Tethyan realm can be correlated with both of the O. boreale and O. concavum zones in the Boreal realm.更多还原