Abstract: The Burqin Basin is in the northern area of Xinjiang Uygur Autonomous Region (Fig. 1). Terrestrial beds of Tertiary are exposed along the banks of the Irtysh River that runs through the region. Most of these Tertiary beds were previously considered to be the“Ulunguhe”Formation , a rock unit that was nominated at site Sa’erduoyila south of Village Halamagai in the Ulungur River Region and have been shown to include sediments of different lithologies and different ages, ranging from late Cretaceous to Oligocene (Wu, 1973; Peng, 1975; Peng and Wu, 1983; Tong et al., 1990; Wei and Tong, 1992; Bureau of Geology and Mineral Resources of Xinjiang Uygur Autonomous Region, 1993; Ye et al. , 2000 , 2001a ,b , 2002 , 2003a ,b ;Wu et al. , 2000 ; Meng et al. , 2001a ,b ; Daxner H ck and Wu , 2003) . Our investigations during the last a few years reveal that these beds in Burqin Basin are lithologically different from but biostratigraphically correlative with the ErgilianShandgolian sediments in Mongolia and in Zaisan Basin of Kazakhstan. The continuous sequence may span over the EoceneOligocene boundary. Based on their lithological and biological contents, we propose to abandon application of the name“Ulunguhe”Formation to these sediments and to divide them into two new rock units , the Irtysh River and Keziletuogayi formations. The type section (KZ2002) is 20 km northwest to the Burqin City on the north bank of the Irtysh River, north to the Keziletuogayi village. The section measured at this locality starts at N47°50. 024′, E86°40. 729′(base) and ends at N47°50. 479′, E86°40. 912′(top) and is described below: