DISCOVERY OF FOSSIL DINOSAURS IN THE BASAL AND LOWER BEDS OF YIXIAN FORMATION,WEST ERN LIAONING PROVINCE,CHINA

By two years'field work,the regional geological surveying and mapping on the scale of1∶50000in Beipiao-Yixian district have achieved great progre ss.The research work shows that the Yixian Formation in Beipiao district may be lithologically subdivided into 4members(in ascending order):1)the first member,including the basa l conglomerate and intermediate-basic vol-canic rocks;2)the second member,the lacustrine se dimentary rock member;3)the third member,the upper basic volcanic rock member;and 4)the fourth member,with a base of conglomerate and graywacke with gravels,and middle-upper part consisting o f acid-intermediate volcanic rocks a nd interlayer sediments(such as Jingangshan layer).Among them,the 2nd member contains abundant fossils ofJehol Biota,including the precious and famous Sinosauropteryx,Confuciusornis,Archaefructus etc.Moreover,a lot of fossil dinosaurs are found recent ly in the 1st members.The discovery n ot only enriches the early fossil ele ments of the Yixian For-matrton,help the investigation on t he living environment of the dinosau rs and the reason for their extinctio n,but also gives an important fossil evidence for determination o f the age of Yixian Formation.