Abstract: Xiejian Stage is a regional chronostratigraphic unit of Chinese Neogene, with its lower boundary being roughly correlative to that of the international Aquitanian Stage. This boundary coincides with the lower boundaries of the Miocene and Neogene. Although Xiejian Stage has been formally recognized and widely used (NCSC , 2002) , its lower boundary has not been well defined and the boundary stratotype has not been established. Based on field and lab work on the Tertiary beds and faunas in the northem Junggar area ( Fig. 1 ) during the last few years , we present an analysis of the Tieersihabahe section and recommend it as a candidate for the stratotype of the lower boundary of Xiejian Stage. The Tieersihabahe section is northwest to the Dure village in the northern rim of the Junggar Basin, Xinjiang (Fig. 1) ; it consists of four units, ranging from bottom up: Tieersihabahe , Suosuoquan, Halamagai and Kekemaideng formations ( Figs. 2 —3). The sequence is 194.5 m thick and the lower two formations are continuous, with no stmctural disturbance, and contains Late Oligocene and Early Miocene mammals ( Figs. 2 —4). In the measured section (02Tr) , the lower limit of Suosuoquan Formation is at the level of 33 m ( Fig. 4) . The lithology of these rock units has been reported elsewhere (Ye et al., 2001 a; 2003) .

摘要： 新疆准噶尔盆地北缘铁尔斯哈巴合地层剖面构造简单并含有丰富的晚渐新世及早中新世哺乳动物化石。其中铁尔斯哈巴合组及索索泉组沉积基本连续，两组界线位于剖面米距33 m处。依据该剖面中8个层位和相邻的XJ99005剖面中18个层位上采集的化石以及它们的上下关系和生物组合性质，划分出5个哺乳动物组合带，其中两个位于铁尔斯哈巴合组中(铁-I, II带), 3个在索索泉组下部(索-I, II, III带)。从剖面的铁尔斯哈巴合组、索索泉组和哈拉玛盖组中以0.5 m的间距采集了348组古地磁样品，获得的磁性剖面包含了16