| The Great Ordovician Biodiversification is one of the significant macroevolutionary events during Phanerozoic era.Conodont is the essential group of marine organisms,which is an ideal material of building high-precision biostratigraphy,it attained an important development during the Ordovician,also its diversity and disparity increased rapidly.The Ordovician outcrops of South China is widely distributed,at same time,the strata at the Wudang area near to Guiyang City,where closed to southern margin of the Central Guizhou Oldland,there are rich conodonts but few studys.This dissertation systematically studies the conodont fauna of the Geological Practice Teaching in Wudang area,and focusing on conodont biodiversity,on the other hand,building carbon isotope chemostratigraphy,by sea level change,conodont researches together with carbon isotope would help us understand the Ordovician Radiation in Wudang,and establish efficient correlations regionally and globally,find out when the southern margin of the Central Guizhou Oldland exposed on the sea.Here we report on a study of the Ordovician conodonts from the Xiaogulong and the Baoziwo sections at the Wudang area,focus on carbonate rocks the stratigraphy includes ascendingly the Tongzi Formation,the Honghuayuan Formation,the Meitan Formation,the Guniutan Formation and the Huanghuachong Formation,and 10 conodont zones are detected in ascengding order: Chosonodina herfurthi zone,Drepanodus arcuatus zone,Triangulodus bifidus zone,Serratognathus diversus zone,Oepikodus evae zone,Baltoniodus triangularis zone,Baltoniodus navis zone,Baltoniodus norrlandicus zone,Lenodus antivariabilis zone and the Dzikodus tablepointensis zone which age is the middle Tremadocian,the Floian,the Dapingian and the early Darriwilian respertively,and correspond well with global recognized previously areas,such as South China,Baltic and Argentina.Based on the analysis on conodont biodiversity,there are two radiative diversities:Serratognathus diversus-Oepikodus evae zone and Baltoniodus norrlandicus-Lenodus antivariabilis zone,and show that diversity peak in Oepikodus evae zone.One of the warm-water mixed with cold-water,others cold-water dominated.Global correlation of the Isotope Carbon Excursion in the Lower and Middle Ordovician,there are four similar Chemostratigraphic tie-points could be recognized:C1,C2,C3 and the C4,Or three carbon isotope excursion: TSICE,LSICE and the BDNICE.As the results,when the conodonts change meanwhile carbon isotopes show increasing,the conodont diversity was probably affected by the sea-level and sea-water chemical changes.The great Ordovician radiation was shot before the Center Guizhou Oldland exposed.Accordingly,the new high-precision chronostratigraphic framework of the Ordovician at the Wudang,which is based on the conodont and graptolite biostratigraphy with carbon istotope chemostratigraphy,are erected. |
