中国三叠纪含牙形刺地层

十年来,中国三叠纪牙形刺地层的研究取得了很大的成绩。1.三叠纪含牙形刺地层主要分布在中国南方,尤其在昆仑-秦岭一线以南,此地层发育程度由西向东逐渐减弱,例如:西部珠峰地区分布在整个三叠系地层中,向东到下扬子地区,主要分布在下三叠统中。2.中国三叠纪牙形刺很丰富,已发现39属,230种,可划分成24个带。3.在奥伦尼阶,我国牙形刺根据生态可划分为两种类型:(1)盆地型(珠峰类型),(2)台地型(湖北利川类型)。

Triassic Conodont-Bearing Strata in China

Triassic conodonts in China have been studied only for ten years, but a greatachievement has already been made. 1) Triassic conodont-bearing strata are mainly distributed in South China,particularly to the south of the line joining Kunlun Mountains and Qin Ling Moun-tains. The developmental degree of these strata is gradually lowered from theJolmo Lungma Mount Region in the west to the Lower Yangtze River Region inthe east. For example, the complete Triassic sequence is located in the Jolmo LungmaMount Region, Yunnan and western Sichuan; in Kuichow province and centralSichuan province occur Middle and Lower Triassic in the eastern Upper YangtzeRiver and the large Lower Yangtze River Region only outcrop Lower Triassic.All these are closely related to paleogeographic environment and tectonic movementat that time. 2) Triassic conodonts are very abundant in China, including more than 230species assigned to 39 genera. The vertical distribution of these conodonts isdefined as a sequence of 24 zones. 3) In the Olenekian Stage, conodonts are divided into two types: (1) The Basin type (the Jolmo Lungma Mount type), which belongs to a nor-mal neritic environment and is characterized by the presence of Neogondolla andNeospathodus; and (2) The plateform type (the Lichuan Hubei type), which lacks Neogondolella,but abounds with Platyvillosus, Pachycladina, Parachirognathus etc, also havingNeospathodus. Thus, some Neogondolella species of Triassic age are regarded asstenohaline organisms, while Neospathodus is euryhaline, and Pachycladina, Pla-tyvillosus and Parachirognatus are slightly hypersaline.