THE AGE OF THE DAHESHEN FORMATION IN JILIN PROVINCE BASED ON CONODONTS

The age of the Dahesen Formation in Huadian County,Jilin Province,is debated for a long time. The majority authors assigned this formation to Early Permian.The present authors systematically collected conodont samples from named-section of this formation,and found some conodonts including Mesogondolella aserrata,Mesogondolella daheshenensis sp.nov.Wang,Mesogondolella subgracilis sp.nov.Wang,Mesogondolella sp.B, Mesogondolellasp.X.Based on mainly the presence of Mesogondolella aserrata,the age of the Daheshen Formation should be assigned to Wordian Stage of Middle Permian.It could be roughly correlated with the Zhesi Formation in Inner Mongolia and the Fanjiatun Formation in north part to Changchun.The upper limits of these three formations could have a little difference.At present,the Roadian and Wordian stages of Guadalupian Series have only one conodont zone respectively.Conodont taxonomy of the Rodian and Wordian in West Texas needs to be re-examined acutely,and it is possible that more conodont zones will be discovered.