The large distribution of inverted stream channel terrains in the western Qaidam Basin, North Tibetan Plateau, and implications to the fluvial ridges on Mars

Abstract

The fluvial ridge, an important landform that has been documented on both Earth and Mars over different geologic times, provides critical evidence of past hydrologic activity. However, the processes of deposition and subsequent erosion of terrestrial fluvial ridges are still largely unclear, and the study of these processes is essential to a better understanding of fluvial ridges on Mars. Here, we report 16 well-preserved regions of inverted stream channels (ISCs), a type of fluvial ridge, with different morphological features and settings, widely distributed in the western Qaidam Basin (QB). Optically stimulated luminescence (OSL) dating of the ISC sediments indicates that these channels were deposited during a cold and dry climatic period (MIS 6). Based on mapping, statistical, and geometric analyses of channel length and sinuosity, we propose a classification scheme that takes into account the architecture of the individual channels and the morphology of channel networks. Our results suggest that the formation of ISCs in the Qaidam Basin occurred during the warming phase following the onset of a cooling cycle, and that the subsequent inversion of ridges is primarily the result of wind and fluvial erosion under a hyperarid climate. The ISCs can also be compared to analogous counterparts on Mars, inverted channels or sinuous ridges, due to their morphological similarities, which could potentially shed light on the hydrological environments of early Mars.