陕西镇安西口地区构造上属于南秦岭微板块,二叠纪时该地区与华南板块被勉略洋(东古特提斯洋的一个分支)分隔,而成为南秦岭微板块上的一个孤立台地。由于其二叠纪时处于华北和华南板块的汇聚带,同时又位于沟通古特提斯和泛大洋的重要通道上,其特殊的古地理位置使其具备与华南乃至全球其它地区二叠系对比的重要古地理和古环境意义,具有成为二叠系经典剖面的潜力。本次研究共分析60件样品,从中发现具有地层划分对比意义的平台型牙形刺分子4属18种。这些化石分布于上石炭统至上二叠统的地层中,且主要产于中二叠统水峡口组和上二叠统的西口组、熨斗滩组及龙洞川组。根据牙形刺的产出情况将研究区二叠系划分出13个带,自上而下为:长兴阶(Changhsingian)的Clarkina subcarinata带和C.changxingensis带;吴家坪阶(Wuchaipingian)的C.postbitteri带,C.dukouensis带,C.liangshanensis带和C.orientalis带;卡匹敦阶(Capitanian)的Mesogondolella posterserrata带,M.shannoni带,M.altudaensis带和M.granti带;罗德阶(Roadian)的M.nanjingensis带;亚丁斯克阶(Artinskian)的Sweetognathus whitei带;阿瑟尔阶(Asselian)-萨克马尔阶(Sakmarian)的S.inornatus带。最后,主要依据牙形刺带对陕西镇安西口二叠系剖面的生物地层进行重新划分,确立了3统9阶,从而能够更好地进行洲际对比。 The area of ​​Xikou, Zhen’an, Shaanxi, belongs to the Nanqinling microplate. During the Permian period, the area was separated from the South China Plate by the Mian Lueyang (a branch of the Eastern Gtith Tethyan) and became an isolated platform on the Nanqinling microplate . Due to its convergence zone in the North China and South China plates during the Permian period and at the same time it is located on the important channel of the communication between the ancient Tethys and the trans-oceanic ocean. Its special paleogeographic location has made it more comparable with Permian in South China and other parts of the world The important paleogeography and paleoenvironmental significance, with the potential to become a Permian classic profile. In this study, a total of 60 samples were analyzed, from which there were 18 species of 4 genus of platform-type conodonts with the significance of stratigraphic division. These fossils are distributed in the Upper Carboniferous and Upper Permian strata, and are mainly found in the Middle Permian Shuixikou Formation and the Upper Permian Xikou Formation, the Flavone Formation and the Longdongchuan Formation. According to the output of conodonts, the Permian in the study area is divided into 13 zones, from top to bottom: the Clarkina subcarinata zone and C. changxingensis zone of Changhsingian, the C.postbitteri zone of Wuchaipingian , C. dukouensis zone, C.liangshanensis zone and C. tropicalis zone; Mesogondolella posterserrata zone, M.shannoni zone, M.altudaensis zone and M. granti zone of the Capitanian; Road M .nanjingensis zone; the Sweetognathus whitei zone of the Artinskian; the Asselian-S.inornatus zone of the Sakmarian zone. Finally, the biostratigraphy of the Permian profile in the west of Zhen’an, Shaanxi Province was re-classified according to the conodont strip, establishing the 3rd order and the 9th order, so that the intercontinental comparison could be better.