Funding for this research was provided by:
the Natural Science Basic Research in Shaanxi Province of China (Program No. 2019JM-512)
Open Foundations of State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences (SKLLQG1605)
Article History
Received: 7 October 2020
Accepted: 19 January 2021
First Online: 7 February 2021
Compliance with ethical standards
:
: The authors declare that they have no conflict of interest.