Wind erosion in northern China: Insights from the western Qaidam fold belt, Loess Plateau, and Hami Basin

Abstract

Pliocene – Quaternary wind erosion profoundly modified the physiography of northern China at a large range of spatial (10 m to >100 km) and temporal (10 ka to Myr) scales. In the western Qaidam Basin along the northeastern margin of the Tibetan Plateau, northwesterly winds sculpted yardangs in actively folding Miocene – Pleistocene strata. Wind erosion was most dominant during glacial periods, whereas lacustrine deposition was more extensive during warmer and wetter interglacial periods. Cyclical wind erosion and sedimentation is recorded by paleoyardangs in Pliocene – Pleistocene strata. A thickness of hundreds to thousands of meters of strata has been blown off the crests of Qaidam anticlines. Wind erosion initiated at ∼3 Ma and increased in spatial extent and magnitude from early to late Pleistocene time as aridity intensified and strata were tectonically uplifted. Qaidam anticlines are propagating in the windward direction and accelerated in growth concomitant with wind erosion, raising the possibility that spatially variable removal of mass by wind influenced the rates and kinematics of deformation. To the east of Qaidam Basin is the Chinese Loess Plateau. The northern, windward margin of the central Loess Plateau is an up to 400-m-high erosional escarpment made of loess that slopes northward into the wind-eroded and endorheic Mu Us Desert. During Pleistocene aridification and expansion of the Mu Us Desert, the Loess Plateau escarpment margin retreated as it was wind eroded while loess continued to accumulate downwind and further build the plateau. The Hami Basin within the eastern Tian Shan of northwestern China is one of the windiest regions on Earth today and part of the broader Gobi Desert that extends eastward into Mongolia. In the north-central Hami Basin, northerly winds sculpted yardangs in Cretaceous strata and have blown a thickness of ≥200 m of Cretaceous – Pleistocene strata out of the closed basin. Wind erosion of northern Hami Pleistocene alluvial deposits led to the widespread development of unconsolidated gravel deposits and pavements. These gravels armor underlying alluvial strata from further wind erosion and thereby suppress dust emissions, despite extreme winds. The Hami and other Gobi Desert basins may have experienced an overall decrease in dust emissions from Pliocene to late Pleistocene time as the volume of silt-bearing strata decreased in the basins while the area of the basins armored by gravel increased. Structural unloading joints in some Hami yardang fields accelerate rates of wind erosion and yardang demise, and their wind-parallel orientation provides another potential example of an interplay between wind erosion and rock deformation. This review suggests that the sources and fluxes of Asian dust were not spatially uniform through the Neogene and Quaternary. The geological and topographic history, landscape evolution, and short- and long-term climate variations in Asia all need to be simultaneously evaluated when interpreting terrestrial and marine archives of dust in the context of past and future climate changes.