Kumtagh Desert Research Articles

Morphological and sedimentary characteristics of raked linear dunes in the southeastern Taklimakan Desert, China

Raked linear dunes were rarely reported, except in the Kumtagh Desert, leaving little known about the dynamic process. However, numerous raked linear dunes have formed in the Kat Kum dunefield of the southeastern Taklimakan Desert, which provides a new case to study the morphodynamics of these dunes. We conducted a comprehensive analysis on the dune morphometry, wind regime, sedimentary characteristics, and sand availability of these dunes. We found that grain size variation is an essential factor affecting the formation of raked linear dunes in addition to wind regime and limited sand availability. These dunes in the Kat Kum present small scale and easily reshaped with fast migration rate compared with these in the Kumtagh Desert, and distributed in areas with low sand cover. The primary ridge extended obliquely to the resultant drift direction, whereas the subsidiary ridge extend is nearly parallel to this direction. The grain size of the primary ridge is noticeably coarser than that of the subsidiary ridge. These dunes seem to have evolved from barchans. Under a north-northeast wind, barchans reshaped to asymmetrical barchans by extending their southeast limbs and eroding their northwest limbs, causing the ridge to be oblique to the resultant drift direction. The strong east-northeast wind erodes and reshapes the primary ridge, transporting fine sand to the northwest and resulting in the formation of proto-subsidiary ridges. With the elongation and lateral movement of primary ridge, a continuous subsidiary ridge with regular dune spacing forms on the northwest flank.

Real-Time Kinematic Positioning (RTK) for Monitoring of Barchan Dune Migration in the Sanlongsha Dune Field, the Northern Kumtagh Sand Sea, China

Dune migration is one of the main processes in arid lands’ geomorphology and is important for the design of windbreaks and sand fixation projects and for the monitoring of desertification dynamics. We conducted long-term continuous positioning monitoring of barchan dunes using RTK equipment and wind regime monitoring in the Sanlongsha dune field, which is located in the northern part of China’s Kumtagh Desert. We analyzed the wind energy environment of the study area, the migration characteristics of different positions in the barchan dune, and dune shape changes during different periods. We found that (1) comparing the differences in migration distance and direction measured at six positions in the barchan, there existed variations in barchan migration across these positions. (2) The shape changes at the left horn, right horn, and windward slope of barchans were larger than at the center of the leeward toe and brink, so the estimates based on measurements at these four positions had a weaker fit with the resultant drift potential (RDP) and a greater difference from the resultant drift direction (RDD). (3) The shape of the leeward slope on the barchan did not change much during dune migration, so the center of the leeward toe and brink measurements were closer to the actual dune migration distance and direction. Thus, we recommend using the center of the leeward toe or brink as the optimal measurement points to monitor barchan dune migration. This study will provide a reference for the more accurate measurement of barchan dune migration.

Paleoenvironmental changes in the eastern Kumtag Desert, northwestern China since the late Pleistocene

AbstractSedimentary records from the Kumtag (also known as Kumtagh) Desert (KMD) in northwestern China are investigated to better understand Late Quaternary paleoenvironmental changes in this hyper-arid region. Presented here are the results of probably the first systematic survey of sedimentary sequences from the KMD, with the chronology determined by the optically stimulated luminescence dating. The variation of sedimentary facies, supported by granular and geochemical paleoenvironmental proxies, is used to decipher the history of Late Quaternary environment changes. The results demonstrate that a constantly dry condition characterized the eastern KMD since the last glacial maximum, but with occurrences of wetter periods. From ca. 17 to 15 ka, fluvial activity was probably triggered by melting of glaciers in mountains located south of the KMD. A distinctly drier stage (ca. 13–7 ka) was recognized due to the prominent occurrence of aeolian sands. A wetter environment likely persisted between ca. 4.4 and 2.2 ka, consistent with evidence of human activities. While the causes of paleoenvironmental changes in the eastern KMD are still a matter of debate, the melting of glaciers in the Altyn-Tagh Mountains in the south must be considered as an important factor.

Genomic Investigation of Desert Streptomyces huasconensis D23 Reveals Its Environmental Adaptability and Antimicrobial Activity.

The harsh climatic conditions of deserts may lead to unique adaptations of microbes, which could serve as potential sources of new metabolites to cope with environmental stresses. However, the mechanisms governing the environmental adaptability and antimicrobial activity of desert Streptomyces remain inadequate, especially in extreme temperature differences, drought conditions, and strong radiation. Here, we isolated a Streptomyces strain from rocks in the Kumtagh Desert in Northwest China and tested its antibacterial activity, resistance to UV-C irradiation, and tolerance to hydrogen peroxide (H2O2). The whole-genome sequencing was carried out to study the mechanisms underlying physiological characteristics and ecological adaptation from a genomic perspective. This strain has a growth inhibitory effect against a variety of indicator bacteria, and the highest antibacterial activity recorded was against Bacillus cereus. Moreover, strain D23 can withstand UV-C irradiation up to 100 J/m2 (D10 = 80 J/m2) and tolerate stress up to 70 mM H2O2. The genome prediction of strain D23 revealed the mechanisms associated with its adaptation to extreme environmental and stressful conditions. In total, 33 biosynthetic gene clusters (BGCs) were predicted based on anti-SMASH. Gene annotation found that S. huasconensis D23 contains several genes and proteins associated with the biosynthesis of factors required to cope with environmental stress of temperature, UV radiation, and osmotic pressure. The results of this study provide information about the genome and BGCs of the strain S. huasconensis D23. The experimental results combined with the genome sequencing data show that antimicrobial activity and stress resistance of S. huasconensis D23 was due to the rich and diverse secondary metabolite production capacity and the induction of stress-responsive genes. The environmental adaptability and antimicrobial activity information presented here will be valuable for subsequent work regarding the isolation of bioactive compounds and provide insight into the ecological adaptation mechanism of microbes to extreme desert environments.

Granule Ripples in the Kumtagh Desert, China: Morphological and Sedimentary Characteristics, and Development Processes

AbstractGranule ripples are widespread on Earth and are a fundamental component of dryland sedimentary systems, but the relationship between their wavelength and surface particle size is unclear; in addition, their sedimentary bedding and granule ripple development are incompletely understood. In this study, we examined the relationship between granule ripple development, morphology, and the surface grain‐size distribution. We measured the morphology and particle‐size distribution of granule ripples in China's Kumtagh Desert, and found an exponential relationship between ripple wavelength and average crest particle size, which contradicts previous results. We hypothesize the ripples resulted from creep of coarse particles caused by saltation impacts, accompanied by decreasing bed elevation, leading to crest migration and increased crest height. The size composition and wind regime determined the movement mode of particles, which controlled ripple development and size, but dry–wet and freeze–thaw cycles also contributed. We established a new conceptual model for the development of large granule ripples. Sand ripples and small granule ripples develop similarly, but large ripples did not form from merger of smaller ripples. We report for the first time that particles between 2.3 and 4.7 mm in diameter were missing in the ripple crests (confirmed in wind tunnel experiments). This gap affects the particle movement mode. Since the threshold wind speed for particle saltation at 4.7 mm approaches the regional maximum wind speed, quantifying the missing particles may permit prediction of regional maximum wind speeds, and has practical significance for identifying wind conditions elsewhere, including the surface of Mars.

The wild camel (Camelus ferus) in China: Current status and conservation implications

The wild camel (Camelus ferus) is a critically endangered species found in extremely arid environments of Central Asia. The wild camel population and its distribution areas have decreased significantly since the middle of the 19th century. The species is now restricted to four isolated habitats in China and Mongolia, and more than 20 years have passed since the most recent surveys of its status and distribution. In an effort to get more current information, we conducted ground surveys, coupled with ad-libitum interviews of local residents, in the geographic range of wild camels in China from 2011 to 2013. We aim to present the most up to date status and distribution of wild camels and provide effective management and conservation strategies. We identified three subpopulations (Taklimakan Desert, Kumtagh Desert, border area of China and Mongolia). The wild camel population in the Kumtagh Desert was found to be stable and relatively dense, likely due to large areas of protected habitat. Camel presence in the Taklimakan Desert was further south than previously reported, indicating an expansion or range shift in distribution that may have been driven by high levels of anthropogenic disturbance. No signs of camels were found in the border area, likely due to a substantial border fence that impedes animal movement. Protected areas appear to work at improving camel populations and will be imperative for their persistence across their currently known range. Continued monitoring is needed to deduce camel movement, and connectivity between China and Mongolia improved. We also recommend surveys in the very near future to determine how populations may have changed since the surveys presented herein were undertaken.

Morphological characteristics and dynamic changes of seif dunes in the eastern margin of the Kumtagh Desert, China

The seif dune field over the gravel desert surface in the eastern margin of the Kumtagh Desert is a valuable experimental site for the observation of dune formation and dynamics. We used high-resolution remote sensing and station observation approaches, combined with wind and grain size data, to study the characteristics of the aeolian environment and the morphologies of and dynamic changes in seif dunes. We observed the ratio of the resultant drift potential (RDP) to the drift potential (DP), which was 0.37, associated with an obtuse bimodal wind regime. The drift potentials in the west-northwest (WNW) and east-northeast (ENE) directions were dominant, and the angle between the two primary DP directions was 135.00°. The dune orientations ranged from 168.75°–213.75°, which were parallel to the resultant drift direction (186.15°). The dune lengths ranged from 51.68 to 1932.11 m with a mean value of 344.91 m. The spacings of the dunes ranged from 32.34 to 319.77 m with a mean value of 93.39 m. The mean grain size of the sediments became finer, and the sorting became better from upwind tail to downwind tip, which indicated that the sediment of the seif dunes in the study region may be transported from northward to southward. The rate of increase in the length, the mean longitudinal migration rate of the dune tail, and the mean longitudinal extension rate of the dune tip (also called elongation rate) were 4.93, 4.63, and 9.55 m/a, respectively. The mean lateral migration vector of the seif dunes was approximately 0.11 m/a towards the west (–0.11 m/a), while the mean amplitude of lateral migration was 0.53 m/a, ignoring the direction of lateral migration. We found that the seif dune field formed first beside seasonal rivers, which can provide sediment, and then expanded downwind.

Variation in grain-size characteristics as a function of wind direction and height in the Sanlongsha dune field of the northern Kumtagh Desert, China

The Sanlongsha dune field, on the northern edge of China’s Kumtagh Desert, connects to the desert through the Aqik Valley. The dunes are tightly linked to the desert through complex sediment transport processes and landforms. To clarify regional geomorphological processes and the source regions for the dunes, we conducted long-term field studies of sediment transport, analyzed the spatial distribution of grain-size characteristics, and their variations with wind direction and height. The transported particles are mainly (73.3%) fine and medium sands, moderately to well-sorted, positively skewed to fine, with mean grain sizes of 1.12–2.19 Φ (220–460 μm). The finest, worst-sorted particles occurred near the surface (0–10 cm), whereas the coarsest and best-sorted particles at the top layer (40–100 cm) were found in sediments transported from the prevailing wind direction (NE); the finest, worst-sorted particles were found at the top layer, whereas the coarsest and best-sorted were found near the surface for sediments transported from the weakest wind direction (S). We have found multiple patterns of vertical variation of the grain-size parameters. With the increase height, transported particles become coarser, better-sorted, and the frequency curves narrowed, nearly symmetrical to positively distribution in prevailing wind direction, while becoming finer in S wind direction. The grain-size distribution of transported particles in different directions and heights are mainly dominated by wind intensity, Gobi surface properties, and grain size in this region.

库姆塔格沙漠灌丛沙堆物源之粒度分析

库姆塔格沙漠灌丛沙堆物源之粒度分析

Inverted relief landforms in the Kumtagh Desert of northwestern China: a mechanism to estimate wind erosion rates

Although commonly found in deserts, our knowledge about inverted relief landforms is very limited. The so-called ‘Gravel Body’ in the northern Kumtagh Desert is an example of an inverted relief landform created by the exhumation of a former fluvial gravel channel. The common occurrence of these landforms indicates that fluvial processes played an important role in shaping the Kumtagh Desert in the past 151 ka. A physical model is presented to reconstruct the palaeohydrology of these fluvial channels in terms of several measurable parameters including terrain slope, boulder size, and channel width. Combining the calculated palaeoflood depth, the maximal depth of channel bed eroded by wind, and the current height of inverted channels with the age of the aeolian sediments covered by gravels, the local wind erosion rate is estimated to be 0.21–0.28 mm/year. It is shown that wind erosion occurring in the Kumtagh Desert is no more severe than in adjacent regions. Since the modern Martian environment is very similar to that of hyperarid deserts on Earth, and Mars was once subjected to fluvial processes, this study will be helpful for understanding the origin of analogous Martian surface landforms and their causative processes. Copyright © 2015 John Wiley & Sons, Ltd.

Morphological and sedimentary features of oblique zibars in the Kumtagh Desert of Northwestern China

Zibars are coarse-grain-armored, low-relief aeolian bedforms with a large spacing but without slipfaces. Little is known of their morphodynamic processes, even though they are ubiquitous at upwind desert margins. In this paper, we describe the morphological and sedimentary features of oblique zibars in the northeastern Kumtagh Desert of China; analyze the effective wind regime; and discuss the significance of the coarse-grained sediments for zibar morphology and sedimentary structures. Due to a mantle of coarse grains, oblique zibars and nearby linear dunes respond to different effective wind regimes that result in the angle between their geomorphological trends. Topographic surveys showed that the spacing of the oblique zibars ranged between 130.5 and 357.5m, and that the height ranged between 0.6 and 3.0m. The oblique zibar surface is almost entirely covered by coarse sand, and includes gravel with a particle diameter of up to −2.34φ. The poorly sorted, positively to very positively skewed surface sediments, with mean grain size ranging between −0.2φ and 1.5φ, were characterized by a bimodal distribution. The spacing between the oblique zibars is closely related to the coarsest 5th percentile of the surface sediments, and can potentially be explained by a combination of the saturation length and minimum dune size theories. In addition, the protectionist theory, combined with the surface creep and vibration of coarse grains (which allows infiltration of finer materials between the grains), may account for the alternating coarse and fine laminae in the oblique zibars.

Grain-size study of aeolian sediments found east of Kumtagh Desert

Abstract A grain-size study was conducted on the surface sediments found east of Kumtagh Desert and its connected geomorphic units, such as the wadi, wetland, oasis, and alluvial fan. The frequency, cumulative curves, and scatter diagrams of four grain-size parameters, namely, the mean grain size, sorting, skewness, and kurtosis, were plotted to study the grain-size characteristics of each sediment. Multiple discriminant analyses were applied to distinguish the deposition environments. Results indicated large diversities in the sediments from different environments. The aeolian sediments from the sandy desert and the gobi land show uniform characteristics or homogeneous changes. The sand resources from the eastern part of the desert can be considered as the alluvial deposits from the southern Altyn Tagh Mountain carried by several erosion gullies. Meanwhile, the western Mingsha Megadune inherited sediments from the nearby Danghe River. The discriminant functions proposed by Sahu can distinguish the deposition process. However, these functions lose their accuracy when applied to heavily eroded aeolian and gobi sediments.

Analysis of the wind regime in context of dune geomorphology for the Kumtagh Desert, Northwest China

Analysis of the wind regime in context of dune geomorphology for the Kumtagh Desert, Northwest China

Geomorphology of star dunes in the southern Kumtagh Desert, China: control factors and formation

Star dunes have received less study than other major dune types, though they are widely recognized to represent a major dune type that develops under a multi-directional wind regime. Several types that include simple, compound, and complex star dunes are identified in the south of China’s Kumtagh Desert. It is suggested that the formation and development of these star dunes is controlled by wind regime, the underlying and surrounding topography, and sediment availability. A complex wind regime and rich sediment availability are generally required for the development of star dunes. Especially, wind regime appears to be the most important control factor. The wind regime under which star dunes arise is characterized by the drift potential, amount of variability in drift direction, and the direction distribution mode of the drift potential. It is strongly suggested that a rectangular bimodal wind direction distribution mode has unique significance in star dune formation. Under this mode, star dunes can develop in areas with a directional variability index typical of linear dunes or even barchan dunes. A development model is proposed for star dunes based on the following evolution: barchan dunes → transverse ridges → dune networks → simple star dunes → compound star dunes → star dunes atop complex linear dunes.

Granule ripples in the Kumtagh Desert, China: Morphology, grain size and influencing factors

ABSTRACTGranule ripples are found mainly in four regions of the Kumtagh Desert in China; they are characterized by an asymmetrical shape, with gentle lower slopes on both sides and abrupt crests. The ripples tend to be oriented perpendicular to the prevailing winds, except when they form near obstacles such as yardangs. The wavelengths (λ) range between 0·31 m and 26 m and heights (h) range from 0·015 m to 1 m. The relationship between wavelength and height can be described by a simple linear function, and the mean ripple index (λ/h) is about 20·4 for the study sites. The sediments are poorly sorted, with negative to very negative skewness at lee and stoss slopes and between‐ripple troughs, which confirms the ‘poured in’ and ‘shadow’ appearance described by previous researchers. The bimodal or trimodal distributions of grains (with modes of −1·16φ, −0·5φ and 3·16φ) and the enrichment of coarse particles at the ripple surface (with coarse granule contents ranging between 5·2% and 62·1%) indicate that the underlying layer is the original sediment source and that the granule ripples resist erosional processes. Although the impact of saltating particles and, consequently, the creep and reptation of coarse grains are responsible for granule ripple initiation at a micro‐scale, however, the characteristics of local sediments, wind regimes and topographical obstacles, as well as the feedbacks among bedform and airflow, more strongly affect the development and alignment of granule ripples at a macro‐scale.

Use of ground‐penetrating radar to investigate feathery complex linear dunes in the Kumtagh Desert, North‐west China

The Kumtagh Desert, the last desert in China to be explored, contains a distribution of feathery dunes, a type of complex linear dune composited by linear dunes and lingoid zibars. A debate about the existence, underlying relief and formation process of these dunes has been ongoing since 1974. The authors use ground‐penetrating radar (GPR) images across dunes and interdune areas to better understand the shallow underlying relief and sedimentary structure of the dunes in the Kumtagh Desert. The results are compared with adjacent outcrops and exposures in an excavated trench. No evidence was found for underlying relief, such as yardangs, consistent with the trend and distribution of linear dune ridges that might have controlled the orientation of the dune. However, outcrop observation and remote sensing investigation indicate little gravel bar topography across or along the dunes. Lingoid zibars are common in interdune corridors. Sedimentary structures imaged by GPR in the zibar dunes indicate low‐angle strata dipping towards the SW, indicative of sand accumulation on the leeside of the lingoid zibar with dune migration towards the SW. Strata within the linear dunes are less well‐resolved but are interpreted to indicate a bimodal dip that has been recognized in previous studies of linear dunes.

Geomorphological patterns in a linear dune field and ages of the linear dunes in the northern Kumtagh Desert, northwest China

The unique linear dunes in the northern Kumtagh Desert of northwest China have inspired enthusiastic debate among aeolian geomorphologists over their origins and classification. Their uniqueness lies not only in their morphology, but also in their geomorphological patterns. In this paper, the geomorphological patterns and ages of the linear dunes in the northern Kumtagh Desert are analyzed using the pattern analysis method that was recently adopted by geomorphologists. The analysis suggests that these linear dunes have developed since 13 ka BP, during the late part of the most recent deglaciation stage, when the region’s dry climate was favorable for dune formation. The differences in dune construction time within this region result from the complex factors that control their formation and spatial variations in the local environment, but these factors were not strong enough to prevent us from estimating the dune age recorded by the geomorphological patterns with acceptable precision. It is also suggested that the pattern analysis method can be used to estimate dune ages in the absence of more reliable dating methods.

Geomorphology and origin of Yardangs in the Kumtagh Desert, Northwest China

Yardangs are typical wind-eroded landforms that are found in most of the world's major deserts. This paper describes the morphology of yardangs in the Kumtagh Desert, analyzes their control factors, and discusses their development processes, age, and rates of formation. Yardangs in the Kumtagh Desert lack the ideal streamlined morphology and the length-to-width ratio close to 4:1 that have been previously described as being due to their unique controlling factors, which include a combination of stratigraphic structures, wind erosion and fluvial erosion. Fluvial erosion plays a particularly important role in the development of the yardangs, though wind continuously sculpts their morphology. The development of yardangs can be divided into four stages: an embryonic stage, adolescence, maturation, and recession. Most yardangs in the Kumtagh Desert are in the mature to receding stages. We determined an approximate age for the yardangs based on the erosion rates estimated by several researchers: on this basis, the yardangs in the Kumtagh Desert appear to have formed during the Holocene.

Composition, origin and weathering process of surface sediment in Kumtagh Desert, Northwest China

Kumtagh Desert is one of the eight biggest deserts in China, but poorly investigated before our interdisciplinary study because of the difficulty of access. In this paper, 33 representative surface sediment samples were collected from the Kumtagh Desert and analyzed in the laboratory to obtain heavy mineral components and geochemical element contents. Results show that various kinds of heavy minerals are present in these samples, with high levels of epidote and hornblende. Si and Al take up a large part of chemical composition. Compared with the average composition of geochemical elements of the upper continental crust (UCC), except Si and Ca, all elements are depleted to a certain degree; Fe, Mg, Ca, P, Ti and Mn have high correlation coefficients in their contents. The mineral and geochemical composition of the Kumtagh Desert sediments have a similarity with that of rocks of Altyn Tagh Mountains, and the surface sediments of the alluvial/diluvial fans around the Altyn Tagh Mountains and that of the Taklamakan Desert, indicating that one major source of the Kumtagh Desert sediments is located in the Altyn Tagh Mountains. Alluvial deposits and lake sediments in Aqik valley and lower reaches of Shule River are prone to be eroded and transported by the strong northeasterly wind into the Kumtagh Desert, forming another source of the desert deposits. An A-CN-K ternary diagram shows that a weak degree chemical weathering by the loss of Na and K occurred in these sediments, whereas A-CNK-FM ternary diagram suggests that Fe and Mg have undergone a significant chemical differentiation. Physical weathering processes cause easy erosion and enrichment in fine particles for mafic minerals, thus coarse desert sand particles can be relatively depleted in Fe and Mg. The mineral and geochemical composition of sediments in arid regions experiencing less chemical weathering are mostly affected by physical weathering.

Feathered sand ridges in the Kumtagh Desert and their position in the classification system

Feathered sand ridges in the northeastern Kumtagh Desert in China cover an area of 4016 km2 and consist of crescent sand ridges and interridge tongue-shaped dunes. Differences in grain size, mineral composition and albedo between crescent sand ridges and tongue-shaped dunes, and between windward and leeward slopes of tongue-shaped dunes, result in their feathery appearance in aerial and satellite imagery. Measurements of the sand drift potential in the region show that the sand-moving wind for feathered sand ridges can be divided into three sectors; i.e. north-northeasterly, easterly and east-northeasterly sectors roughly corresponding to the southeast, northwest and southwest slip faces. Our findings suggests that the crescent sand ridges resulting from the connection of barchan dunes along the prevailing wind direction are longitudinal dune ridges rather than transverse ones. Tongue-shaped dunes and quasi-dune shapes have obvious distinctions and are new transverse dune types. According to McKee’s dune shape classification, the feathered sand ridges are not a deformation dune type but a complex one. According to Wu’s dune morphological and genetic classification, they are not dune ridges or compound dune ridges that form under the action of unidirectional winds or two winds intersecting at an acute angle, but are complex dune ridges that form under the action of three winds intersecting at an acute angle.