Geochemical analysis of yardang strata in the Dunhuang Yardang National Geopark, Northwest China, and implications on its palaeoenvironment, provenance, and potential dynamics

Abstract

Abstract Yardangs are landforms created by enigmatic processes. Sedimentary facies characteristic of yardang strata illustrate their vulnerability to wind erosion, which is important for understanding their morphological development. However, the lack of systematic research on the provenance of these geological structures and the sedimentary environment that led to their development have limited the conception of a yardang sedimentary model. In this study, we apply geochemical analysis to investigate yardang sediments from the Dunhuang Yardang National Geopark to characterize the provenance and the sedimentary environment through conventions based on the differentiation and aggregation of chemical elements. Results show that Beishan Mountain, Altyn-Tagh, Lop Nur, and the Shule River are all key material sources for the development of Dunhuang yardang, of which the Beishan Mountains and Altyn-Tagh predominate. As determined by geomorphological patterns, yardang transportation and sedimentary processes can be divided into three distinct types: alluvial flooding from Beishan Mountain and Altyn-Tagh, direct deposition from Lop Nur and the Shule River (as illustrated in river-lake facies), and sediment re-transportation during river-lake phases following weathering processes. According to our results, the sedimentary environment of the Dunhuang yardang field is composed of fluvial, lacustrine, alluvial, and aeolian strata. With regards to its sedimentary evolution, the Dunhuang yardang field is characterized by periodic deposition both aeolian and aqueous sediments, and the profiles exhibit obvious differences respective to their paleogeomorphic patterns. Our findings are theoretically significant for understanding the formation and development of yardang landforms and practically significant for protecting these geological relics.