The Chitinozoan Biostratigraphy Of The Lower Silurian(Llandovery)in The Center Part Of Yangtze Region

Through samples' collection,analysis and comprehensive studies of three sections and one core in the centre part of Yangtze platform,including Lianghekou section,Wenhua section,Yidi 1 well in Yichang county,Hubei province and Anchang section in Zhengan,northen Guizhou province,the lower Silurian stratigraphy in the Middle Yangtze region could be divided into 9 chitinozoa biozones.There are Bel0nechitina postirobusta biozone,Conochitina electa biozone,Conochitina alargada biozone,Conochitina emmastensis biozone,Conochitina rossica biozone,Conochitina malleus biozone,Ancyrochitina shiqianensis biozone,Eisencickitina daozhenensis biozone and Angochitina longicollis biozone from the bottom to the top.The B.postrobsta biozone is equivalent to the the C.vesiculosus biozone.Representing the middle part of Rhuddanian stage.The C.electa biozone could be contrasted by the C.cyphus biozone,which represent the upper of Rhuddanian stage.The C.alargada biozone is roughly equivalent to the P.leptotheca,representing the lower Aeronian stage.The C.emmastensis biozone could be compared with the L.convolutes and represent the middle of Aeronian stage.The C.rossica biozone could be contrasted by the lower of M sedgmickii biozone and equal to the upper of Aeronian stage.The C.malleus biozone sit in the lower of Shamao foemation and equal to the halli biozone,representing the late of Aeronian stratigraphy.The A.shiqianensis biozone is raised for the first time that base on the characteristic of the emergency and diversity of A.shiqianensis,which repsert the latest of Aeronian stage and is contrasted by the upper of halli biozone.The E.daozhenensis biozone represent the lower part of Telychian stage and equal from the guerichi biozone to the greistonensis biozone.The A.longicollis biozone is represent for a stratigraphy of Telychian stage and equale to the spiralis biozone.We found that the Shamao formation in Shiqiaoping,Yuanan county,Hubei province belong to the late of Aeronian stage.But which belong to Telychian stage in Zigui county,Hubei province and is divided into the A.longicollis biozone.The boundry of Aeronian stage and Telychian stage is approach to the boundary of the E.daozhenensis biozone and the C.malleus biozone.This thesis systematically described all of the species,including 9 genus and 38 species,and made statistical analysis of the specimen materials of each species,so as to provide important data for related work and the identification of chitinozoans in the future,which is of great significance for the identification of chitinozone and provides important data for the division and correlation of biostratigraphy in the middle Yangtze region.