1. Key Laboratory of Western China's Environmental Systems (Ministry of Education); Research School of Arid Environment and Climate Change; Lanzhou University; Lanzhou Gansu Province 730000 China
2. McDonald Institute for Archaeological Research; University of Cambridge; Cambridge CB2 3ER UK
3. Gansu Province Institute of Cultural Relics and Archaeological Research; Lanzhou 730000 China
4. Museum of Anding District; Dingxi 743099 China