THE AGE OF THE DINOSAUR-BEARING SEDIMENTS AT TEBCH, INNER-MONGOLIA, PEOPLES-REPUBLIC-OF-CHINA

The coarsening-upward clastic sequence at Tebch, Inner Mongolia, China , containing the dinosaur Psittacosaurus mongoliensis, comprises the r emains of a fluviolacustrine system deposited in an extensional tecton ic setting. The presence of Asteropollis sp. cf. Asteropollis trichoto mosulcatus (Singh) Singh, 1983 in conjunction with the absence of tric olpate pollen indicates a Barremian or possibly early Aptian age. The overlying Tebch basalt, dated by the Ar-40/Ar-39 laser step-heating me thod, yields a mid-Aptian age of 110 +/- 0.52 Ma. This chronology supp orts the argument that the Juifotang Formation of the Jehe Group in we stern Liaoning is Early Cretaceous, with the Jurassic-Cretaceous bound ary very low within, or below, the base of the Jehe Group. Our data al so suggest that the Berriasian-Hauterivian (Neocomian) age suggested f or the one known Russian locality that has yielded P. mongoliensis (Sh estakovskaya Svita at Gorno-Altayaskaya, Avtonomnaya Oblast) may be ex cessively old.