A Study On Conodont Fauna And Its Biostratigraphy Of Guadalupian And Lopingian In Noutheastern Of Sichuan Province

The collection for conodont samples was carried out in the Shangsi and GuanZiba section of the Sichuan Basin, both of which are typical section of Permian. Morethan666samples were obtained and especially in the Moukou Formation, ChangxingFormation and Dalong Formation. Some important species were described andcompared with others.In the Shangsi section, more than463samples were obtained including26species assigned into4genera (1Clarkina sp.). Most samples we got are the genera ofJinogodollela and Clarkina, and noticeably, several important conodont species,Clakina postbitteri postbitteri, C. postbitteri hongshuiensis, C. dukouensis and C.asymmetrica are identified firstly in this section. Twelve conodont zones wererecognized from the Maokou Formation to the Dalong Formation, which includeJinogondolella nankingensis Zone, J. aserrata Zone, J. postserrata Zone, Clarkinapostbitteri postbitteri Zone, C. dukouensis Zone, C. asymmetrica Zone, C.guangyuanensis Zone, C. orientalis Zone, C. wangi Zone, C. changxingensis-C.deflecta Zone, C. yini Zone and C. meishanensis-C. taylorae Zone. According to theprecise compare of the conodont zone, the bottom of Roadian, Wordian, Capitanian,Wuchiapingian and Changxingian at this section is marked by the first appearance ofJ. nankingensis, J. aserrata, J. postserrata, C. postbitteri postbitteri, C. wangi. Itsrelatively successive conodont sequence can be correlated with the other sections inthe world. According to the lithology and the yield of the conodonts at this section,the Pre-Lopingian Mass Extinction was partly influenced by the volcanic activity atleast, and the response time of the Pre-Lopingian Mass Extinction at this setion was arelatively long duration from the late J. postserrata Zone to the Guadalupian andLopingian boundary.In the Guan-ziba section, more than203samples were obtained including23species assigned into3genera (2conformis species,1affinis species,1Clarkina sp.),most of which are the genera of Clarkina. Four conodont zones are recognized fromthe Changxing Formation to the Dalong Formation in ascending order as follows: the Clarkina orientalis Zone, the C. wangi Zone, the C. changxingensis-C. deflecta Zoneand C. meishanensis Zone. The bottom of Changxingian at Guan Ziba Section is setby the first appearance of Clarkina wangi. The conodont sequence at the Guan-zibasection has been accurately compared with several classical sections.