Geological Features and Evolution of Yardangs in the Qaidam Basin, Tibetan Plateau (NW China): A Terrestrial Analogue for Mars

Plain Language Summary Wind-eroded ridges known as yardangs are common in most arid desert regions on Earth, as well as on other planets, notably in the Medusae Fossae Formation (MFF) and Gale Crater on Mars. However, the formation and evolution of these various yardangs are not well understood, which, therefore, requires further studies by more terrestrial analogues. Here we report a detailed investigation of the terrestrial yardang fields in the Qaidam Basin, northeastern Tibetan Plateau, China. Most of them are distributed in the northwestern and central eastern parts, with dominant orientations northwest to north-northeast and approximately west to east, respectively. Based on their morphologies and distributions, yardangs within the Qaidam Basin have been classified into 11 different types out of four main groups. Wind is the dominant driver of yardang erosion, but water, salt, and mass wasting may also have played important roles in their formation and modification. A four-step evolution model, including embryonic, adolescent, mature, and receding stages, is proposed to reveal their formation and evolution in the basin. Meanwhile, yardangs in the MFF and Gale Crater on Mars have morphologic and geometric characteristics that show striking similarities to those in the Qaidam Basin. The fact that some yardang fields in MFF on Mars also show overlapping relationships suggests that they possibly have experienced a multistage evolution, during which the evolution processes may have been interrupted at some stages due to differences in the competence of rocks and/or the changes of the environment. The Qaidam Basin is the largest yardang field in China. In this study, we investigate the distributions, morphological types, and sizes of these yardangs. We attempt to explore their origins and explain their evolution processes. Based on their morphologies and distributions, we have identified 11 different types of yardang and sort them into four main groups. We find that both their spatial distribution and orientation are controlled by local topography and prevailing wind direction. Their main orientations are northwest to north-northeast in the northwestern basin, while approximately West to East in the central eastern basin. Yardangs in the Qaidam Basin are mainly eroded by wind. We propose a four-step evolution model to explain their formation processes. Similar yardangs on Mars are also observed, such as those within the Medusae Fossae Formation and Gale Crater. We find that yardangs on Mars show morphologic and geometric characteristics similar to those in the Qaidam Basin, indicating that they may have experienced similar evolution processes.