Study On Conodont Biostratigraphy Of The Mailonggang Formation In Xuexiang Area,Southern Edge Of Gangdise

Conodont samples were systematically collected from the section of Mailonggang Formation in xuexiang area in Tibet.After a series of standard analyses for conodonts,a total of 20 standard conodont samples were obtained.Identification and analysis revealed 3 genera(Epigondolella,PrimatellaandCarnepigondolella)and 10kinds(including Epigondolella aff.Stefanionensis,Epigondolella aff.Uniformis,Epigondolella aff.Vialovi,Primatellapermica,Primatellarhomboidale,Primatella rotunda beta,Carnepigondolella spenceri,Carnepigondolella aff.Spatulata,Carnepigondolella samueli,Kraussodontussp)of conodonts.After collecting relevant data,they were systematically divided into 4 conodont biozones: Primatella permica,Carnepigondolella samueli alpha,Carnepigondolella aff.spatulataand Kraussodontusspfrom the bottom to the top of the section.The divided conodont sequence was compared with the Triassic conodonts proposed by Mao Li and Tian Chuanrong(1987)and global references,and thereby determining the age of the Late Triassic Malonggang Formation in Tibet.Identification results of the division results of the 3 conodont biozones demonstrated that the age of the Late Triassic Malonggang Formation in Tibet was Carnian stage,rather than Norian stage obtained by predecessors.Therefore,the research on the age of Malonggang Formation still has controversies.Our study can provide new information for the research on the Late Triassic conodonts in Tibet.