Applying end-member modeling to extricate the sedimentary environment of yardang strata in the Dunhuang Yardang National Geopark, northwestern China

Abstract

Formative mechanisms and sedimentary environments of yardang landform distribution in arid and semiarid regions of northwestern China remain poorly understood due to their unique formation and enigmatic causation. Considerable controversy remains as to whether yardang deposits evolve from aeolian or aqueous forces, and no reliable, quantitative method has yet been made available to resolve this issue. This study conducted a comparative analysis between yardang strata and modern surface sediments to characterize the sedimentary environment using end-member modeling analysis (EMMA). Results show that yardang and surface sediment end-members corresponded well, and that the yardang depositional environment can be classified into three typical types: aeolian (200–550 μm (mode value range)), alluvial (150–300 μm and 8–20 μm), and lacustrine (subclassified into shoreline: 80–110 μm; lake center: 3–15 μm; and transitional (the transition between the littoral and limnetic zones): 15–60 μm). Based on this method, we determined that lacustrine, aeolian, and alluvial concentrations were 63.92%, 20.80%, and 15.28% (YA profile, respectively) and 53.68%, 28.30%, and 18.02% (YB profile, respectively). Additionally, a significant difference was found between the sedimentary processes of the two profiles, where YA had more lacustrine sediments and YB had more aeolian sediments, likely resulting from paleotopography. Generally, yardang derives from alternating lacustrine, aeolian, and alluvial sedimentary deposits. Although lacustrine sediments predominated, aeolian sediments also accounted for a considerable overall proportion. This study provides new insight into the formation and development of yardang landforms as well as evidence for the reconstruction of paleo-geomorphologic patterns.