Quaternary stratigraphic realm and sedimentary sequence of the Qilian Mountain and adjacent areas

The Quaternary stratigraphy of twenty basins in Qilianshan Mountain and adjacent areas includes Guide Basin, Xunhua- Hualong Basin, Tongren Basin, Xining Basin, Menyuan Basin,Linxia Baisin, Lanzhou Basin, Dingxi Basin, Tianshui Basin,Subei Basin, Jiuquan Basin, Yumen Basin, Zhangye Basin, Wuwei Basin, Har Lake Basin, Suli Basin, Muli Basin, Minhe Basin, Gonghe Basin, Qinghai Lake Basin and Qaidam (N) Basin. The authors studied these basins based on the previous data and field investigations. Characteristics of Quaternary tectonic landform evolution, sedimentary sequence of basins, palaeontology and paleoclimate were used as the basis to make stratigraghic division and also to unify the name of parts of sequences. The general characteristics of Quaternary sedimentation of the study areas are as follows: Loess is widely distributed in the east (central Gansu Province) with the thickest loess in the world. Alluvial fan and aeolian deposits are distributed in the north (Gansu Corridor). Pluvial-alluvial and lacustrine deposits are distributed in the south (north Qaidam Basin), followed by aeolian sand and loess of late Pleistocene. The transition from lake to alluvial and aeolian deposits happened at the Gonghe Basin. Qinghai Lake has lasted for a long time. Moraines, pro-glacial and river terrace are distributed in the high mountains in the middle and west. According to the above characteristics and principles, the sedimentary sequences of Qilian Mountain and adjacent areas are divided into the following realms: Lanzhou- Xining stratigraphic realm, Guide stratigraphic realm, Jiuquan- Zhanagye stratigraphic realm, North Qaidam Basin stratigraphic realm, Gonghe stratigraphic realm, Qinghai Lake stratigraphic realm and Subei-Menyuan stratigraphic realm.