Holocene aeolian activity in the Zoige Basin, northeastern Tibetan Plateau, China
1, Lupeng Yu2, Zhibao Dong1, Junfeng Lu1, Jiyan Li1, Zhongping Lai3
1Key Laboratory of Desert and Desertification, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou, Gansu Province, China, 2College of Resources and Environment, Linyi University, Linyi, Shandong Province, China, 3School of Earth Sciences, China University of Geosciences, Wuhan, Hubei Province, China
The Zoige Basin is located in the northeastern Tibetan Plateau, at an altitude around 3500 m, covering an area of 19,400 km2. This basin plays a significant role in water supply for the Yellow River (nearly 30% of the Yellow River's total flow originates from the basin's wetland). Because of the important roles in water conservation, biodiversity protection and wetland conservation, Zoige Wetland National Natural Reserve was established by the Chinese government in 1994. However, during the last four decades, the area of aeolian desertification land in this region experienced dramatic increase and decrease. To fully understand and assess the current status and future trend of aeolian activity in the Zoige Basin, it is necessary to reveal the aeolian activity history of this region. But to date, the history of aeolian activity in the Zoige Basin is poorly understood due to very limited chronology study.
In this study, 11 Optical Stimulated Luminescence (OSL) ages from three typical sections were used to reconstruct the history of aeolian activities during the Holocene. The results of the chronologies shown that the aeolian activity started in early Holocene (10.27±0.81 ka BP), but in contrast with the early Holocene, aeolian sediment deposition primarily occurred in the late Holocene (after around 3.20±0.33 ka BP), especially during the recent 1 ka BP. In the whole Holocene, the aeolian activities of the Zoige Basin occurred nearly synchronously with the nearby sites in the northeastern Tibetan Plateau. However, the combination of the flat and low-lying geomorphology and more precipitation of the mid Holocene resulted in this area to be relatively insensitive to short term arid climate to occur aeolian activity, though episodic weak aeolian activities were recorded in the nearby sites in the northeastern Tibetan Plateau. So it is inferred that there was nearly no aeolian activity occurred in this basin during the mid Holocene. The occurrence of aeolian activity in the early Holocene, the absence of aeolian activity in the mid Holocene and the enhanced aeolian activity in the late Holocene reveal a general climate pattern: Dry in the early Holocene, humid in the mid Holocene and much drier in the late Holocene. Currently, the water table of the Zoige Basin has been declining since 1960s due to intense artificial drainage and long-term continuous sapping of the Yellow River and its tributaries. The declining water table accelerates soil drying and results in aeoian desertification. It's likely that more of the previous aeolian sediment, even lacustrine and fluvial sediments deposited in the basin will be activated if the drainage of the wetland continues.