中国陆相中新统谢家阶

THE XIEJIAN STAGE OF THE CONTINENTAL MIOCENE SERIES IN CHINA

谢家期一名最初在1984年提出,1999年第二届全国地层委员会正式提出依据谢家期建立对应的年代地层单位——谢家阶,阶名源自同名岩石地层单位谢家组。谢家阶的层型剖面在青海省湟中县田家寨乡谢家村北1km处的车头沟,谢家阶对应于国际地层表中的海相Aquitanian阶,其共同的底界定义为古地磁ChronC6Cn.2n的底界,年龄为23.0Ma。古地磁研究结果显示在谢家剖面谢家阶的底界位于马哈拉沟组上部的棕红色块状泥岩连续沉积中,距上覆的谢家组底48m。生物地层学的综合分析表明谢家阶包含3个哺乳动物群单位,即NMU1—3。谢家剖面上发现的谢家动物群相当于NMU2,新疆准噶尔盆地北缘的索索泉动物群和甘肃兰州盆地的张家坪动物群分别相当于NMU1和NMU3。

The Xiejian Age was named in 1984, and the Second National Commission on Stratigraphy of China formally recommended in 1999 to establish the corresponding chronostratigraphic unit Xiejian Stage based on the Xiejian Age, which was named after the lithostratigraphic unit Xiejia Formation. In this paper, we propose the Chetougou section, 1 km to the north of the Xiejia village, Tianjiazhai Township, Huangzhong County, Qinghai Province, as the stratotype section of the Xiejian Stage. The Xiejian Stage can be correlated with the marine Aquitanian Stage in the International Stratigraphic Chart, and the lower boundary of both stages is defined at the base of the paleomagnetic Chron C6Cn. 2n with an age of 23.0Ma. At the Xiejia section, paleomagnetic data indicate that the lower boundary of the Xiejian Stage is located within the successive deposits of reddish brown massive mudstone in the upper part of the Mahalagou Formation, about 48 m from the base of the overlying Xiejia Formation. Biostratigraphic analyses suggest that the Xiejian Stage includes three Neogene mammal faunal units, NMU 1 to NMU 3. The Xiejia fauna discovered from the Xiejia section is regarded as NMU 2, and the Suosuoquan fauna from the northern Junggar Basin, Xinjiang, and the Zhangjiaping fauna from the Lanzhou Basin, Gansu correspond to NMU 1 and NMU 3, respectively.