1. Centre for Archaeological Science, School of Earth and Environmental Sciences; University of Wollongong; Wollongong NSW 2522 Australia
2. Department of Geography, MOE Laboratory for Earth Surface Processes, College of Urban and Environmental Sciences; Peking University; Beijing 100871 China
3. Institute of Geology and Geophysics; Chinese Academy of Sciences; Beijing 100029 China
4. Cultural Relics of Hebei Province; Shijiazhuang 050000 China