中国三叠纪菊石的古生态学概论

AN INTRODUCTION TO PALAEOECOLOGY OF TRIASSIC AMMONITES OF CHINA

当前国际上有关菊石古生态学的研究和已有文献,主要集中在侏罗纪和白垩纪,很少涉及三叠纪.正由于三叠纪菊石古生态学知识的贫乏,故当今讨论三叠纪菊石动物地理学的文章也较少,而且在为数不多的文章中,往往把不同级别的生物地理区并列一起.无疑,在探索三叠纪菊石动物地理区之前,讨论一些有关的古生态学的问题是必要的.本文即为另文发表的'中国三叠纪菊石动物地理学'提供一些必要的依据和认识.至于某些方面的详细分析,笔者将在以后的文章中逐步加以充实.

Based on knowledge of paleoautecology of Jurassic and Cretaceous ammonites, and from the characters of Triassic ammonites themselves, the writer suggests an idea of whorl shapes, ornamentation and suture types in Triassic ammonites as possibly related to depth (see fig. 3 in Chinese text). Furthermore, based on paleoautecology of Triassic ammonites, some main characters in paleosynecology of Triassic ammonites can be discussed as follows: 1. Since no any real Triassic ammonite communities existed in the nearshore facies of the continental margin, only some immigrated ammonites shells occasionally existed therein. 2. There are some special ammonite communities surrounding the evaporated basin in the restricted platform, such as the Tirolites-Dinarites community of Early Triassic, and the "Progonoceratites" community of Middle Triassic in Sichuan and North Guizhou. 3. Sometimes, some ammonite shells of basin facies were discovered in the area of platform facies, where those immigrations were usually carried by ocean currents from the open sea through certain gates in Sichuan. 4. In the edge area of platform facies, communities of platform facies often alternated with those of open sea facies. 5. A great majority of the ammonites were prosperious in the shallow open sea. Both communities of relatively shallow marine water and those of deep marine water can be approximately distinguilished, for example, the Subcolumbites and Procarnites communities of Spathian, and the Paraceratites and Ptychites communities of Late Anisian in Guangxi and Tibet. 6. When the living environments and conditions were relatively stable, those ammonites with a rapid revolutional rate frequently formed a series of community succession, such as:Hypophiceras community→Ophiceras community→Gyronite community→Koninckites community→Meekoceras community, etc. during Early Triassic; and Xenoprotrachyceras community→Protrachyceras community Trachyceras community during Ladinian to Carnian in Guangxi and Guizhou, and S. T. Tibet. 7. Several pelagic facies communities of different geological times were condensed together under starved sedimentation, forming the so-called communities of the Hallstatt facies, such as the Procarnites→Anasibirites unnatural "community" from Late Smithian to Late Spathian in South Tibet.