BIOSTRATIGRAPHY OF THE TAIYUAN FORMATION AT XIAHEYAN,ZHONGWEI COUNTY,NINGXIA WITH ADISCUSSION OF THE CARBONIFEROUS-PERMIAN ROUNDARY

In this paper the authors divide the Upper Carboniferous Taiyuan Formation at Xiaheyan,Zhongwei,Ningxia,into the upper and lower members. In the upper member（beds 18-31）fusulinids are represented by elements of the Pseudoschwagerina Zone and SphaeroschwagerinaZone,conodonts are mainly represented by elements of the genus Streptognathodus,and plantsare dominated by pollen of gymnosperms and l,epidodendron. The above-mentioned fossils areof Early Permian age. The lower member（beds 1-17）contains fusulinids Medocris and Pseu-dostaffella, conodonts ldognathodus dellicafus and I. olaviformis and plants Neuropteris pseu-dovata and Spherophyllum oblonglforlium,which shows the features of Late Carboniferous-per-mian boundary be placed between the upper and lower members of the Taiyuan Formation. Thisboundary is a bit lower than the traditional one of China,but tends to be in agreement with theboundary that is generally adopted in the world now.