Climate change impacts on the relationship between fluvial processes and dunes landform evolution have been a research topic. However, the chronology data used to examine such relationship are deficient. The Keriya River has a glacial origin in the Kunlun Mountains at the south margin of the Tarim Basin. The river flows into the Taklamakan Desert, the second largest shifting dunes desert in the world. The dry channels and shifting dunes in the area provide an ideal opportunity to understand fluvial and eolian landform evolution processes and their relationship with climate change. We investigated this area from 2008-2011, and obtained 18 fluvial sediment samples from 16 sections for optically stimulated luminescence (OSL) dating. Results show that the ages are ranged from 3.4-44.1 ka. Most (13) samples were from the Holocene, around 11 ka, 8-9 ka, 5-6.5 ka, 4.6 ka and 3.4-3.7 ka respectively. which were distributed along ancient river channels around Yuansha and Karadun. Two samples close to the Hotan River (38-47 ka) fall in the Marine Isotope Stages 3 (MIS3). Three samples (of one section) were located near ancient channels flowing towards the Yuansha Site aged around 14.5 ka, the Last Glacial Maximum (LGM). The sediment samples and OSL ages of this work suggest that the Keriya River was flooded in the Holocene, the LGM and the MIS3 stage. Fluvial sediment provided source material for dunes and fluvial processes impacted landform evolution at the lower reaches of the Keriya River. Our results suggest that most dunes covered on fluvial sediments at the lower reaches and west of the Keriya River developed since the Holocene. This differs from previous works suggesting that they developed "since the Han and Tang dynasties". The OSL ages of fluvial sediments were consistent with the reported deglaciation (after glacial advance) ages in alpine mountains surrounding the Tarim Basin. This suggests that climate fluctuation might have impacted the occurrence of floods and the formation of dunes in the Taklamakan Desert.

Yardang is a typical, aeolian erosion landform widely distributed on Earth and discovered on other planets (Venus and Mars) too. Because of its various forms and volatility, yardang's morphological characteristics have attracted attention for generations. Lop Nur is located in the eastern part of the Tarim Basin in Xinjiang, China. Although there are many yardangs with various types in the area of Lop Nur, there is a lack of study about this impressive landform there. On the basis of field investigation, the authors found that UAV drones can efficiently and effectively collect yardang morphology data. Based on collected yardang morphology data (including field survey and DEM from UAV), using the terrain digital extraction method, after measuring the morphological parameter data of yardang, this article attempts to clarify the morphological characteristics of yardangs in the Lop Nur area, and to discuss its formation processes. The main conclusions are as follows: (1) The lengths of yardangs in the Lop Nur area are often < 20 m, although a few of them are even > 160 m. The widths of yardangs in our study area are mainly < 8 m, with a height of mostly < 2 m. It shows that the sizes of yardangs in the study area are generally small, although some large ones occur too. The ratio of length vs. width (R) of yardangs ranges from 2:1 to 4:1, and even > 10:1. The orientations of the yardangs in our study area are mainly toward 22.5°-67.5°, consistent with the predominant wind directions. Our observations suggest that the morphology of yardangs in the study area initiated from a dome-shaped form and then changed to drop-shaped, and finally to linear forms. The number of yardangs occurring nearby is often 3-4, and the distance between them is often < 20 m but occasionally 40-80 m. (2) The most likely evolution processes of yardangs in the Lop Nur area can be summarized into four stages: embryonic, juvenile, mature and decay periods. However, due to the influence of various controlling factors such as stratum sediment characteristics, wind erosion, and flowing water, yardang's morphology in the Lop Nur area become quite complex. (3) The developments of yardangs in the Lop Nur area have multiple periods. Since the Quaternary, there have been four main development periods in late Pleistocene (ca. 90 ka B.P.), early Holocene (8-9 ka B.P.), late Holocene (after 1.6 ka B.P.) and Little Ice Age (around 0.5 ka B.P.). According to morphological characteristics and environmental evolution, we infer that yardangs in Longcheng and Bailongdui were formed in the late Pleistocene, the northern Loulan grand yardangs formed in the Early Holocene, yardangs in central and northern Loulan formed in the late Pleistocene and the small yardangs in Loulan area formed probably during the Little Ice Age. Based on the chronology and yardangs' height, the average wind erosion rate near the Loulan site after 0.5 ka B.P. was calculated to be 6.2 mm a^-1. Accurately describing the morphological characteristics of yardangs in the Lop Nur area and understanding its evolution procession is of great significance for analyzing the morphological development of yardangs and the regional wind erosion process.

Sand seas and semi-arid dune fields, an important component of the earth environmental system, is sensitive to global climate change. Meanwhile, environmental changes in sand seas and dune fields influence regional sustainability, and can also affect regional climate and global environment through feedbacks of different scales. The Mu Us Sandy Land, located in the north-central part of China, is one of the typical semi-arid dune fields in the middle latitude. Its aeolian environmental change during the past is comparable and synchronous with some other sand seas and dune fields around the world. The study of aeolian environmental change in the Mu Us Sandy Land has a long history in China. This paper reviews and summarizes the theory and new findings in the study of processes and mechanisms of aeolian environmental change in the Mu Us Sandy Land. Important progresses have been made in recent decades focusing on the late Cenozoic evolution of the study area, its late Quaternary expansion and polycyclic changes, and dune field stabilization during the middle Holocene and dune reactivation since the late Holocene. Key sedimentary evidence has been found to support these new findings, and new theories about dune field evolution at the tectonic and orbital scales in response to global temperature change and nonlinear response of dune systems at millennial and centennial scales have been proposed. In the future, by collecting more crucial sedimentary evidence, the application of state-of-art technique, fine-scale and process-informed paleoenvironmental reconstruction, and numerical modeling and projection studies, our understanding can be significantly improved about the dynamical mechanisms of aeolian environmental change, the coupling of human-environment complex system in the drylands, and the processes and feedbacks in the Earth surface environmental system. This will also have great significance for the development in the field of physical geography, integration of interdisciplinary studies, and theory exploration of the Earth System Science.

The analysis of hydrochemical compositions of natural waters and their influencing factors is helpful to understand the regional hydrogeological environment and hydrogeochemical development history. The Ordos Deserts, consisting mainly of the Mu Us Sandy Land and the Hobq Sand Sea, are located in the south of Hetao Plain, north to the Great Wall, surrounded by the Yellow River in the west, north and east, and adjacent to the Loess Plateau in the south. The Ordos Deserts make up the Ordos Plateau, with the same tectonic background, similar amount of precipitation and evaporation rates. There are a large number of lakes and rivers in these deserts. In this paper, based on the hydrochemical data of natural waters in the Ordos Deserts, the chemical compositions of natural waters and their influencing factors are analyzed, using various hydrochemical analysis methods. Results show that although Mu Us Sandy Land and Hobq Sand Sea have different landscapes, their natural waters of the same type have similar hydrochemical features, which should be related to their similar rates of evaporation. Deep groundwater in the Ordos Deserts is mainly Ca²⁺-HCO₃^- type and its chemical composition is mainly influenced by rock weathering. Due to strong evaporation, the hydrochemical nature of lakes in these regions is characterized with Na⁺-Cl^- contents. As for shallow groundwater and river waters, their hydrochemical features and influencing factors show transitional characteristics between deep groundwater and lake water. The ion ratios show that the weathering of evaporites, carbonate and silicate rocks affects the hydrochemical composition of deep groundwater, shallow groundwater and river water to a varying degree. Although the groundwater and river water in the Ordos Deserts are suitable for irrigation, an excessive use of them will cause salinization, which should be given attention timely.