About the Authors

Hua Tu

Affiliation College of Geographical Sciences, Nanjing Normal University, Nanjing, China

Guanjun Shen

gjshen@njnu.edu.cn

Affiliation College of Geographical Sciences, Nanjing Normal University, Nanjing, China

Haixu Li

Affiliations College of Geographical Sciences, Nanjing Normal University, Nanjing, China, Department of Natural Science, Zhangjiakou University, Zhangjiakou, China

Fei Xie

Affiliation Hebei Provincial Institute of Cultural Relics, Shijiazhuang, China

Darryl E. Granger

Affiliation Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, Indiana, United States of America

Competing Interests

The authors have declared that no competing interests exist.

Author Contributions

Conceived and designed the experiments: GJS DEG FX. Performed the experiments: HT HXL GJS DEG. Analyzed the data: GJS DEG HT. Contributed reagents/materials/analysis tools: FX HXL. Wrote the paper: HT GJS DEG.