吉木萨尔三台大龙口剖面已被推荐为国际非海相二叠─三叠系界线层型侯选剖面。该剖面是世界上研究非海相二叠─三叠系界线最理想的剖面之一，也是我国非海相二叠─三叠系界线研究程度最高的剖面。准噶尔南缘上二叠统─下三叠统统称仓房沟群，下分5个组（自下而上）：泉子街组、梧桐沟组、锅底坑组、韭菜园组、烧房沟组，除烧房沟组与下伏韭菜园组间有显著冲刷面外，各组间均为整合接触关系。仓房沟群中生物化石丰富，可以划分出植物、孢粉、双壳类、叶肢介、介形虫、脊椎动物等不同的生物组合，尤其重要的是在锅底坑组上部发育晚三叠世与早三叠世生物混生的过渡层。这个过渡层揭示了生物演变的连续性，即脊椎动物Jimusaria与Lystrosaurus共生，孢粉Lueckisporitesvirkkiae与Lundbladisporawatangensis共生，以及二叠纪型的植物、双壳、介形虫与三叠纪型的叶肢介之间的混生。即在这个过渡层中既含晚二叠世型的孑遗分子，也含早三叠世型的新生分子，因而可以确定二叠系与三叠系界线就在锅底坑组内，置于大龙口背斜南翼剖面第36层，北翼剖面第34层之底，即在锅底坑组与韭菜园组传统岩组界线之下约50m（北翼）～60m（南翼）处。古地磁反映的正负极性与生物地层界线基本一致。 The Jiamusar Santaida Longkou section has been recommended as an international non-marine Permian-Triassic boundary layer candidate profile. This profile is one of the most ideal profiles in the world for studying the Permian-Triassic boundary and is also the most studied profile of the non-marine Permian-Triassic boundary in China. The Upper Permian-Lower Triassic collectively called Cangfanggou Group on the southern margin of Junggar consists of 5 sub-groups (bottom-up): Quanzijie Formation, Wutonggou Formation, Pot-Pit Formation, Leekyuan Formation, Except that there was a significant erosion surface between the burning fanggou group and the underlying leek garden group, all the groups were in an integrated contact relationship. Cangfanggou rich in fossils, can be divided into plants, sporo-pollen, bivalves, leaf extremities, ostracods, vertebrates and other biological combinations, especially important in the upper part of the pot pit pit development Triassic The transitional layer between the world and the Early Triassic. This transitional layer reveals the continuity of the biological evolution of the vertebrate Jimusaria and Lystrosaurus, the symbiosis of Lueckisporitesvirkkiae and Lundbladisporawatangensis, and Permian-type plants, bivalves, ostracods and Triassic Mixed between. That is, the Late Permian-type relict and the Early Triassic-type reefs in this transitional zone, so that the boundary between Permian and Triassic can be determined as being within the pot pit group The 36th floor of the south wing of the Longkou anticline, the bottom of the 34th floor of the profile of the north wing, is about 50m (north wing) to 60m (south wing) below the boundary between the traditional rock mass group of the basement pit and the Leekyuan Group. The positive and negative polarities of paleomagnetic reflection are basically the same as those of biological strata.