Some geomorphological features in the Qaidam Basin, northwest China and implications for comparable landforms on Mars

Abstract

Landforms on Mars and Earth bear significant clues of the geological and climatic history, as the formation of these landforms is strictly constrained by environmental conditions. The mid-to-high latitude regions of Mars are characterized by various types of patterned grounds, such as polygons and brain terrains, and gullies. The patterned grounds are interpreted to be related to glacial or periglacial activities. Gullies are explained as the result of the sliding of CO2 frost or the melting of subsurface ice. Whether liquid water was involved in the formation of these landforms is still under debate. Terrestrial analogs play an important role in interpreting the origins of planetary landforms. The Qaidam Basin, located in the northern Tibetan Plateau, Northwest China, is one of the terrestrial analogs of Mars. In this study, three types of landforms in the Qaidam Basin are investigated: the polygonal patterned ground, brain terrains, and gullies. A new type of polygonal ground shaping like jigsaw puzzle pieces and bounding by raised rims is discovered in the western Qaidam Basin. The mineralogical study of the materials suggests that the volume expansion during a mineralogical transformation of sulfates is the driving force in forming the raised rims of jigsaw polygons. Brain terrains are patterned grounds composed of sinuous ridges and troughs on Mars. The landforms similar to brain terrains are found both in the eastern and western Qaidam Basin. Brain terrains in the eastern basin consist of eolian sediments and are interpreted as a type of eolian bedform in the scale similar to megaripples. However, brain terrains in the western basin are made of salt crusts and were developed by their deformation. Most of the gullies in the Yingxiong Range, the western Qaidam Basin, are linear gullies characterized by the long channels without the distinct alcoves at the origin or the well-defined aprons at the end. Some linear gullies exhibit the meandering pattern, and some terminate at the circular depressions. The liquid flows got involved in forming gullies in this area, even in an extremely arid environment. The source of the liquid water might be meltwater from accumulated snow on the hill crests or the occasional rainfall. The slope is the controlling factor in shaping the morphological features of the meandering gullies. Among the terrestrial analogs of Martian landforms in the mid-to-high latitudes, most of them are glacial or periglacial environments. Unlike other analogs, the Qaidam Basin is a hyperarid environment and has warm and wet episodes in its climatic history. The mineralogical compositions of the polygons in the Qaidam Basin suggest sulfates may be the essential components in forming polygons on Mars apart from ice and clay minerals. The brain terrains in the basin indicate that the eolian deposits or the evolution of salt crusts might contribute to the development of brain terrains on Mars without the role of ice. The gullies in the basin illustrate that some morphological features of linear gullies on Mars could be generated by liquid water rather than only by CO2 frost.