The Qilian fan is an alluvial fan which drains the Qilian mountains, the border between Gansu and Qinghai provinces. The location of the Qilian-Shan is shown in Fig 1., the alluvial fans drain the mountain belt to the north into Gansu province.
Fig 1. Yan et al. (2010) map showing location of the Qilian-Shan. B shows a simplified tectonic map of the area and C shows more detailed geology of one part of the mountain belt with some published ages.
The Qilian fan has been thought to be a potential source of the Chinese Loess Plateau based on X-ray fluorescence analysis which compares major and trace element compositions of the sediments from the fan to the loess and other deserts. The study found the loess from the Chinese Loess Plateau was most similar to the Qilian fan and different from deserts like the Badain Jarim (Guan et al. 2008). The fan is flat and is made up of gravel and fine dust. There was evidence of river channels running through it, probably these were related to the melting of the snow and ice from the Qilian-Shan following colder climatic periods.
Fig 2. Looking up a river in the Qilian fan. Terraces can be seen at the edges of the river.
The Silk Road runs along the Qilian fan, and along the edge of the Silk Road runs the Great Wall (Cheung Chau).
Fig 3. Western part of the Qilian fan looking west along the Great wall and Silk Road.
Yan, Z., Xiao, W.J., Windley, B.F., Wang, Z.Q., Li, J.L. 2010. Silurian clastic sediments in the North Qilian Shan, NW China: Chemical and isotopic constraints on their forearc provenance with implications for the Paleozoic evolution of the Tibetan Plateau. Sedimentary Geology, 231, 98-114.
Pan, B., Gao, H., Li, J. 2006. Dating of the River Terraces in Eastern Qilian Shan, Northwest China.
Guan, B., Pan, B., Gao, H., Li, N., Zhang, H., Wang, J. 2008. Geochemical evidence of the Chinese loess proevance during the Late Pleistocene. Palaeogeography, Palaeoclimatology, Palaeoecology, 270, 53-58.