Aeolian Geomorphology Research Articles

Probability density distributions of morphological parameters of barchan dunes and their responses to the climate environment

Barchan dunes are a common aeolian geomorphology in sand seas on Earth and Mars. They occur primarily as barchan dune groups. Obvious regional differences occur in the size distribution of dune swarms in different dune fields because of sediment grain size, regional airflow, sand flux, and surface conditions. To explore dune size distributions in different barchan dune fields and clarify the effects of climate on barchan dune morphometry, we used high-resolution remote sensing images and extended time-series meteorological data. Barchan dune fields were located in the southeast edge of the Taklimakan Desert, the western and southern parts of the Qaidam Basin Desert, the Gonghe Basin Sandy Land, and the sand belt connecting the Badain Jaran Desert and the Tengger Desert. Our results revealed the probability density distribution of morphological parameters of barchan dunes, correlations among parameters, and responses to wind regime. The main conclusions are: (1) Probability density distributions of the lengths of windward and lee slopes, the lengths of the two horns, and the dune width, height, and spacing in different deserts followed a log-normal distribution function. (2) Good correlations were found among the dune morphological parameters; width and height, windward slope length and width, and height and spacing showed positive proportionality, and the basal area and the product of width and height were linearly correlated in a double logarithmic coordinate system. (3) Good correspondence was found between dune asymmetry and regional wind conditions, which can be explained by Tsoar's model. Morphological parameters of barchan dunes were linearly and positively correlated with the drift potential. These results provide essential data for further study of the morphological thresholds for dune-dune interactions and elucidation of the mechanisms of interaction among barchan dunes.

The fault in our TARs: A critical review of research paradigms for intermediate‐scale bedforms on Mars

AbstractWe provide a critical review of research paradigms for classifying intermediate‐scale aeolian bedforms on Mars and the new terminology that has emerged. The systematic classification of bedforms has always been challenging and debated, and no paradigmatic knowledge organization system exists beyond general agreement on the importance of a distinction between ripples and dunes. The diverse aeolian landscapes of Mars have introduced further topics and challenges to these debates. We argue that Martian aeolian geomorphology's knowledge organization system for intermediate‐scale bedforms is preparadigmatic and that consensus over terminology and their definitions has not been established in the literature. A preparadigmatic science can be functional only if scientists operating in the discipline provide precise, falsifiable definitions or use abductive logic. Drawing on evidence and examples from the literature, we argue that the replacement of the conventional abductive paradigm used in bedform classification with inductive logic has created an emerging disciplinary paradigm based on scientific hesitancy and a dependence on complex inductive research structures, epitomized by the concepts of ‘transverse aeolian ridges’ (TARs) and ‘large Martian ripples’ (LMRs). We show that TAR and, increasingly, LMR are inductive constructs that have been popularized despite them causing significant confusion. Notably, we highlight how the terms are irreconcilably used as both a class of bedform and as a non‐genetic placeholder term for bedforms. Suggestions for moving beyond the need for TAR and LMR are provided, focusing on a return to more direct and local hypothesis‐driven research inspired by W.M. Davis's notion of outrageous geological hypotheses. Recent debate surrounding bedforms in Gale crater is presented as an example of the productivity of such an approach, and it is recommended that TAR and LMR no longer be used.

Quantifying dune migration patterns and influencing factors in the central Sahara Desert

Based on Landsat images and ERA5 climate data, here we analyzed geomorphic dune patterns and the spatial characteristics of dune migration in the central Sahara Desert region (SW Libya, SE Algeria), using the COSI-Corr technique. Our results revealed clear observable drift potential (DP) and resultant drift potential (RDP) gradients, these decreasing from a northerly to southerly direction. Moreover, the annual average RDP/DP in most areas was <0.3 (i.e., highly variable). The main dune types in the study area included complex transverse ridges (22.82 %), linear dunes (19.87 %), barchan and barchanoid chains (16.95 %), and star dunes (13.55 %). Of these, barchans and barchanoid chains, as well as complex transverse ridges, appeared in areas of relatively high DP, while complex longitudinal ridges and honeycomb dunes were found in those of low DP. Linear dunes had a simpler wind composition, being mainly distributed in areas with intermediate wind variability. Both the honeycomb dunes and complex longitudinal ridges had nearly always formed in complex multi-directional wind environments. Dune migration displacement in dune fields ranged widely, from 0.5 to 23.57 m (mean = 6.71 m), during the 30-year study period (1993–2022). Barchans and barchanoid chains migrated fastest, with a mean value > 10 m/yr; in contrast, complex longitudinal ridges and honeycomb dunes had the slowest migration rate, always at < 5 m/yr. Overall, the dune migration rate was mainly related to dune height and wind regime. Spatially, the dune migration trend was basically consistent with that of the resultant drift direction (RDD), mainly in a northwesterly direction (28.36 %). The accuracy testing results indicated that the COSI-Corr displacement measurement accuracy was generally higher than the dune migration direction accuracy. This study provides not only valuable reference data for regional aeolian activities, but also insight into the developmental environments and migration dynamics of differing dune types, which could be used for prospective regional aeolian geomorphology research in the Sahara Desert.

Using Texture Statistics to Identify and Map Different Dune Types within the Rub’ al Khali

Understanding the movement, direction, and shape of sand dunes can contribute to reducing their impact on infrastructure and the environment. The Rub’ al Khali desert has a distribution of dune types. This study aims to identify and map the different types of dunes within the Rub’ al Khali using a texture analysis method based on a digital elevation model (DEM). Statistical texture analysis methods (variance, skewness, and kurtosis) show three different textures of sand dune shapes, according to the geography of the dunes, using data contained in global DEMs. The analysis presented in this study focused on the use of DEMs to investigate the varied dune morphology within the Rub’ al Khali. The GMTED2010 and EarthEnv_DEM90 digital elevation models were compared. Spatial variability in dune height, spatial variability in dune texture, and profile graphs were created to examine dune surfaces in cross-section. The results provided six different dune types within the sand sea: giant compound linear dunes, simple linear dunes, simple transverse dunes, compound crescentic dunes (megabarchans), huge star dunes, and many transitional forms that defy classification. The results showed that the compound linear dune and simple linear dune were the dominant dune types, covering 41.61% and 31.7% of the total study area, respectively. The maps of variance, using either 10 × 10 and 30 × 30 focal blocks, produced a fairly sharp distinction in dune texture. It is hoped that future research in aeolian geomorphology will greatly benefit from these results, which could easily be expanded with the use of more sophisticated pattern recognition software, which clearly shows the value of using such an approach.

Wind regime and sand transport in the mid-course of ten tributaries of the Yellow River, Inner Mongolia of China

Better understanding the wind regimes and dune activity criteria are pre-requisites for the successful planning of any sand dune fixation project and hence have a high priority. To fully understand wind energy conditions and the intensity of aeolian activity, we investigated the wind conditions, sand-transporting potential, and sand-transporting capacity of the basins of mid-course ten tributaries of the Yellow River through field observations and indoor analyses. 1) The analysis of wind energy, which is based on sand transport potential, demonstrates that there is substantial spatial variation within the study area. The western part, which is located near the Kubuqi Desert, qualifies as a high wind energy zone. In contrast, the central part belongs to the medium wind energy zone, whereas the eastern part is categorized as a low wind energy zone. Even though there are notable differences in the sand transport potential characteristics across different time scales, the direction of the synthesized sand transport potential tends to be consistent, predominantly leaning towards the southeast. This orientation provides the requisite energy for the sand material to be transported into the river. 2) The prevailing sand-producing wind direction at various timescales in the research area was dominated by westward (W, WNW, NW) and northward (NNW, N) winds, with distinct seasonality. This seasonal variability was especially prominent in spring, which saw the highest frequency of aeolian activity and the largest volume of sand transport. Autumn and winter exhibited similar patterns, and, in the summer, it was the lowest 3) The relationship between sand-transporting potential and sand-transporting capacity, which is a crucial aspect of aeolian geomorphology, could be adequately depicted using a fitting function based on the temporal patterns of wind speed. During periods of high wind, the sand-transporting potential and sand-transporting capacity of the basins of the ten tributaries followed a power function relationship. Conversely, during periods of low wind, they followed an exponential function relationship. These results imply that spring should be deemed as the crucial period for wind-sand prevention and control. Additionally, emphasis should be placed on the western part, which is situated close to the sand source area, as the primary prevention and control zone.

Morphological characteristics and dynamic changes of typical climbing dunes on the Qinghai-Tibet Plateau

Climbing dunes are a form of topographic barrier dunes that feature in the aeolian landforms on the Qinghai-Tibetan Plateau. Topography fundamentally influences the spatial distribution and morphological characteristics of climbing dunes by modifying the near-surface airflow and creating space for sediment deposition. Previous studies have considered several aspects of the influence of topography on aeolian landforms. However, morphological differences between climbing dunes in different geomorphic contexts and dynamic changes in the area have received little attention. Therefore, topographic measurements, near-surface flow field measurements, dune morphology analysis, and remote sensing image analysis were combined to explore relationships between dune morphology and topography. Topographic obstacles can accelerate the near-surface airflow, particularly with a 25–35° slope gradient, which is beneficial for sand transport and deposition. Suitable accommodation space (concave slope morphology) and abundant sediment comprise the primary factors that control the scale and morphological diversity of climbing dunes, which are also influenced by a variable wind direction. In general, the morphology of the climbing dunes becomes progressively more complicated from the bottom to the middle of the windward slope, and the sand ridge lines of the dunes are perpendicular to the prevailing wind direction. Based on the influence of climate and human activities, the total area of climbing dunes in this region has decreased over the past 30 years. Despite general evidence of enhanced human-induced desertification in semi-arid and sub-humid regions, warming has not led to the rapid expansion of climbing dunes in these arid locations. This research offers new insights into the relationship between the terrain and dune morphology, enriching the theoretical basis for the plateau aeolian geomorphology. Furthermore, it allows us to consider the dynamic changes in climbing dunes area in the context of global warming.

High-resolution, spatially resolved quantification of wind erosion rates based on UAV images (case study: Sistan region, southeastern Iran).

Estimating the quantitative distribution of wind erosion rates is one of the most important requirements for managing affected environments and optimizing locations to control wind erosion. This study develops high-resolution maps for wind erosion with unmanned aerial vehicles or UAV images in the Sistan region-an area in southeastern Iran with severe wind erosion. Aerial imaging by UAV was done during period of erosive winds. Changes in the amount of wind erosion were measured for 7months. Digital elevation models or DEM with a spatial resolution of 6mm, orthophoto mosaic images with a resolution of 3mm, were prepared before and after the erosion event. Three erosive facies consisting of surface, edge, and blowout were identified. The amount of erosion in different geomorphological landscapes or facies was measured according to differences of DEMs (DOD). The effect of physical factors of the geomorphological landscapes on wind erosion was investigated by calculating the correlation between the erosion, roughness, and slope in the geomorphological landscapes. The results showed that the highest and lowest mean of eroded soil were 22mm and 4mm in the blowout and surface facies, respectively. The average rate of wind erosion was 201 t/ha during the study period, which indicates the high intensity of wind erosion in the Sistan plain. Overall, UAV-as an aerial imaging technique collecting ground data-can be a helpful tool in the aeolian geomorphology especially for collecting data for measuring the rate of soil erosion by the wind in the aeolian landscapes located in remote regions.

Shaping effects of sand flow channels on aeolian geomorphology – a case study of the Badain Jaran, Tengger, and Ulan Buh Deserts, northern China

Based on the interactions between mountains, we identified three sand flow channels in the Badain Jaran, Tengger, and Ulan Buh Deserts, northern China. We found that the height difference of the terrain in these areas provided favorable conditions for the transportation of sand. Owing to the venturi effect of their geomorphologies, airflow was compressed in these channels, and their wind regimes were strong and unimodal. Compared with the interior of the desert, the sand transport potential was relatively large in these areas, and westerly and northwest winds prevailed. We found that the wind accelerated in the sand flow channels, resulting in faster-moving dunes. The dune types that developed in these channels were relatively simple owing to the unimodal wind regimes; they mainly comprised barchan and transverse dunes. We also identified a transition landscape from barchan dunes to transverse, or complex dunes. Based on their sediment characteristics and the prevailing wind directions, we found that the sand flow channels provided a direct sand supply between the three deserts. The sand flow channels connected these independent deserts to an entire desert system. Similar sand flow channels can also be found in other deserts globally. Collectively, these sand flow channels reflect interactions between deserts.

Vertical profiles of aeolian mass flux above different sand surfaces and sand surfaces covered with pebbles

The vertical distribution of aeolian mass flux is an important issue in aeolian geomorphology. It has been studied mainly on sand surfaces and much less often on gravel surfaces, particularly under natural conditions. We present data of measurements made in 3 beach settings that differed in petrographic composition of the beach sand (quartz, bioclastic, and bioclastic-basaltic sand) and density of pebble coverage (5–70%). We aimed to show the differences/similarities in vertical mass flux profiles induced by surface properties resulting from sediment composition. All measurements were made under conditions of maximum sand transport rate on a dry sand bed by means of passive segmented 0.5-m-high sand traps. The results showed that (i) regardless of the surface type, all vertical mass flux profiles were well fitted by an exponential decay function, but the regression coefficients differed greatly between those for sand surfaces and surfaces with pebble covers of different densities, (ii) changes in these coefficients with wind speed were much more pronounced in the case of sand surfaces than on surfaces with pebbles, (iii) the exponential model underpredicted mass flux in the near-bed region in the case of sandy surfaces, whereas in the case of pebble surfaces, the departures from the model were insignificant, and (iv) a pebble cover with a low density between 5% and 10% strongly affected the concentration of sand in the vertical profile. All mass flux profiles showed that as wind speed increased, the proportion of sand transported in the near-bed region decreased and the proportion of sand transported at higher elevations increased. For each surface type, the height at which the constant proportion of sand was transported may be defined irrespective of wind speed. This height was equal to 3–4 cm in the case of sand surfaces and changed from 6 cm to 11 cm as the density of pebble coverage increased from 5 to 10% to 50–70%. This was also reflected in the average saltation height, which increased slightly with wind speed and significantly with the density of gravel coverage.

Geomorphology of aeolian dunes in the western Sahara Desert

Although the western Sahara Desert is dominated by aeolian dunes, research on the geomorphology of aeolian dunes throughout this region as a unit has been limited compared with other large deserts. In the present study, comprehensive research is conducted on the geomorphology of dunes in the western Sahara Desert based on aeolian parameters and dune growth mechanisms. We identified the controlling factors on the dune morphology and formation of superimposed dunes. The results suggest that the spatial patterns of dune morphology are closely correlated with the drift potential (DP) and dune orientation. A well-defined gradient of declining DP, resultant drift potential (RDP), and directional wind variability from north to south was found, indicating a gradual weakening trend in the DP along the sand flow path. Linear and transverse dunes are distributed on the central part of the desert. Barchan dunes are distributed on the western coastal areas and desert margins. Lastly, star dunes are distributed in the upwind on the northern desert margin. We concluded that the wind regime and sand availability directly impact the dune morphology in the western Sahara Desert by considering the growth mechanisms. This study provides valuable reference data on regional aeolian activities that can be used by subsequent regional aeolian geomorphology studies in the western Sahara Desert.

Predicting land susceptibility to atmospheric dust emissions in central Iran by combining integrated data mining and a regional climate model

This study aims to predict land susceptibility (a term that indicates the degree of sensitivity of land to detachment of soil particles by wind) to dust emissions in Yazd province, central Iran, by combining a new integrated data mining (DM) model and the RegCM4 climatic model. The study further determines the relative importance of key factors controlling dust emissions by applying 12 individual DM models. The integrated model is based on the individual models returning Nash Sutcliffe coefficient (NSC) values > 90% for the spatial modelling of land susceptibility to dust emissions and using the area under the curve (AUC) for validation. 13 key factors controlling dust emissions are mapped including soil characteristics, climatic variables, vegetation cover, a Digital Elevation Model (DEM), geology and land use. Based on Spearman clustering analysis and multi-collinearity tests (tolerance coefficient -TC and variance inflation factor -VIF), the effective factors for dust emissions are classified into nine clusters and no multi-collinearity is found among the effective factors. DEM, NDVI (normalized difference vegetation index), geology and calcium carbonate are identified as the most important factors controlling dust emissions. Seven individual models return NSC in the range of 90–98% and are used to generate the integrated model for the final mapping of land susceptibility to dust emissions. Among 851 pixels located in the dust sources, 30% (255 pixels) and 70% (596 pixels) are randomly selected as validation and training datasets, respectively for the new integrated model. Using this model, 9%, 17%, 7% and 67% of the study area correspond to low, moderate, high and very high susceptibility classes, while the validation results in AUC = 99.3%. Simulations with the RegCM4 model reveal high consistency regarding the spatial distribution of the most susceptible areas and dust emissions. Overall, combining DM approaches and physical models is useful in aeolian geomorphology studies.

Impact of utility-scale solar photovoltaic array on the aeolian sediment transport in Hobq Desert, China

Deserts are ideal places to develop ground-mounted large-scale solar photovoltaic (PV) power station. Unfortunately, solar energy production, operation, and maintenance are affected by geomorphological changes caused by surface erosion that may occur after the construction of the solar PV power station. In order to avoid damage to a solar PV power station in sandy areas, it is necessary to investigate the characteristics of wind-sand movement under the interference of solar PV array. The study was undertaken by measuring sediment transport of different wind directions above shifting dunes and three observation sites around the PV panels in the Hobq Desert, China. The results showed that the two-parameter exponential function provides better fit for the measured flux density profiles to the near-surface of solar PV array. However, the saltation height of sand particles changes with the intersection angle between the solar PV array and wind direction exceed 45°. The sediment transport rate above shifting dunes was always the greatest, while that around the test PV panels varied accordingly to the wind direction. Moreover, the aeolian sediment transport on the solar PV array was significantly affected by wind direction. The value of sand inhibition rate ranged from 35.46% to 88.51% at different wind directions. When the intersection angle exceeds 45°, the mean value of sediment transport rate above the solar PV array reduces to 82.58% compared with the shifting dunes. The results of our study expand our understanding of the formation and evolution of aeolian geomorphology at the solar PV footprint. This will facilitate the design and control engineering plans for solar PV array in sandy areas that operate according to the wind regime.

Using the Boruta algorithm and deep learning models for mapping land susceptibility to atmospheric dust emissions in Iran

• Deep learning algorithms used to mapping land susceptibility to wind erosion. • Boruta algorithm used to determine importance scores for the controls. • The simple RNN performed slightly better than RBM. • Techniques used are helpful for targeting mitigation. Wind erosion have many negative effects on global terrestrial and aquatic ecosystems and these phenomena are controlled by several factors including climatic, meteorological, topographic, vegetation, surface and soil characteristics. This study applied, for the first time, the Boruta algorithm for identification of effective variables controlling wind erosion. The novelty of the study was increased further using application of two deep learning (DL) models comprising a simple recurrent neural network (RNN) and restricted boltzmann machine (RBM). Collectively, these tools were used to map land susceptibility to wind erosion in parts of Kerman province, southeastern Iran. Among 18 potential variables for controlling dust emissions via wind erosion, 4 and 14 were identified as non-important and important, respectively, by the Boruta algorithm, while three (precipitation, digital elevation model and soil organic carbon) were selected as the most important factors. An inventory map of the wind erosion confirmed using both a test dataset (30%) and a training dataset (70%) was used to construct predictive models of land susceptibility to wind erosion. Both DL predictive models exhibited highly satisfactory performance according to a Taylor diagram, but the simple RNN performed slightly better than RBM. Based on the simple RNN, 35.6%, 5%, 2.4%, 22.7% and 34.3% of the total study area were characterized by very low, low, moderate, high and very high susceptibility, respectively. Convergent prediction of the same susceptibility classes by intersecting the maps generated by both models classified 17.4%, 0.07%, 0.06%, 7.4% and 34% of the total study area as very low, low, moderate, high and very high susceptibility classes, respectively. We conclude that applying the Boruta algorithm and DL models as new methods in aeolian geomorphology, may provide accurate spatial maps of dust sources to help target mitigation of detrimental dust effects on climate, ecosystems and human health.

Wind regime and aeolian landforms on the eastern shore of Qinghai Lake, Northeastern Tibetan Plateau, China

Wind regime is typically highly variable in space and in time, and the studies of aeolian geomorphology often use a single meteorological station as representative of a specific dune field due to the scarcity of meteorological stations in remote areas. However, the wind regime may vary greatly even between sites located just a few kilometers apart. In this study, to fully understand the relationship between wind regime and aeolian landforms of the dune field on the eastern shore of the Qinghai Lake, 1-year hourly recorded wind data from an average wind year 2012 from four stations, namely Gangcha Station, Eri Station, Wendu Station and Daotanghe Station was used to analyze the wind regime and resultant potential sand transport. The wind data analysis revealed that the drift potential (DP) at Gangcha, Eri, Wendu and Daotanghe stations is 144, 537, 829 and 431 VU, respectively. The resultant drift potential (RDP) at Gangcha, Eri, Wendu and Daotanghe stations is 112, 143, 544 and 125 VU, respectively. The high-energy wind environment, in addition to multidirectional and locally highly variable wind regime are the principal factors likely responsible for the coexistence of several types of aeolian landforms (e.g., Reversing transverse, barchanoid and stardunes).

Shaping Effects of Sand Flow Channels on Aeolian Geomorphology – A Case Study of the Badain Jaran, Tengger, and Ulan Buh Deserts, Northern China

Shaping Effects of Sand Flow Channels on Aeolian Geomorphology – A Case Study of the Badain Jaran, Tengger, and Ulan Buh Deserts, Northern China

An improved model to estimate annual sand transport rate by sand-driving winds

Some of the surface on Earth, Mars, Venus, and Titan is covered by ripples, dunes, and other features formed by sand-driving winds. Many developing countries in arid and semiarid areas are caught in a dilemma between the threat of sandy desertification and the development of wind energy. The estimation for the probability of sand-driving winds has been rarely studied. The ability of two-parameter Weibull probability distribution to estimate sand-driving winds is questioned. Sand transport rate is used only for the evaluation of short-term aeolian activities. Drift potential (DP) is an accessible way of evaluating potential sand transport volume by sand-driving winds. However, the relationship among annual sand transport volume, DP and wind energy has been rarely studied. Sand-driving winds can be divided into gentle winds and strong winds, but it is hard to distinguish them and to quantify their effects on aeolian geomorphology. A function was constructed from expressions of sand transport rate and the two-parameter Weibull probability distribution to improve the estimation of sand-driving winds. On this basis, annual sand transport volume was accurately evaluated by sand-driving winds. This is applicable to arid and semiarid areas worldwide. The relationship among annual sand transport volume, DP and wind energy was analyzed from the perspective of dimensional analysis. Gentle winds and strong winds are distinguished by transport wind velocity at which aeolian activities on a sandy underlying surface reach the erosion–deposition balance, and which corresponds to annual maximum sand transport rate. On a sandy underlying surface strong winds control deposition, while gentle winds dominate wind erosion. The transport wind velocity is nearly constant, weakly related to the probability distribution of sand-driving winds. These results provide a basis for an improved understanding of aeolian activities as an important planetary surface process, sand control engineering, and wind energy development.

Growth responses of Pinus sylvestris (L.) to burial by drift sand and its application to the reconstruction of aeolian dune development

Sand dunes represent unique environments that increase the biodiversity, geodiversity, or ecosystem services of landscapes. The knowledge of past sand dune development is crucial for realizing their effective protection. Dendrogeomorphic methods represent an effective tool for the reconstruction of geomorphic processes, but their application in aeolian geomorphology is limited. This state can be caused by limited knowledge of the tree growth responses (particularly microscopic anatomical ones) to burial by sand. Thus, tree growth responses to sand burial were studied in detail for one of the most extensively distributed tree species on European dunes – Pinus sylvestris (L.) in this study. Four buried P. sylvestris individuals occupying selected dunes in the Borská lowland (SW Slovakia) were exhumed and densely sampled at vertical distances of 5 cm. The results evidenced the distinct macroscopic growth responses of trees to burial in the form of abrupt growth suppression (51.8% on average) in four various years of sand accumulation (1990, 1994, 1999, 2012). The intensity of the increment response was not dependent on the burial depth but expressed a significant correlation with the mean tree ring series sensitivity (r = 0.68–0.93). In addition, growth suppression was always accompanied by a distinct anatomical response in the form of an increase in cell lumen area (103.5% on average). The intensity of this response was significantly dependent on the depth of burial. Both main forms of responses (abrupt growth suppression and cell lumen area increase) were detected even in the non-buried parts of stems (up 15 cm above the ground). Finally, the sand accumulation rate was calculated (2.5 cm year−1 on average) and spatially interpolated regarding the microtopography of the dune. The limits and uncertainties (absence of some expected tree growth responses) as well as the advantages (data about past dune development without monitoring) of dendrogeomorphic methods in aeolian geomorphology are discussed.

Testing models of linear dune formation by provenance analysis with composite sediment fingerprints

The formative mechanisms of linear (longitudinal) dunes and dunefields remain uncertain, and multiple hypotheses have been proposed. A central debate is the degree to which dunes act as along-dune sediment transport corridors, implying that dunes grow primarily by extension, or whether they are comprised of locally-derived sands moved from adjacent interdunes (the ‘wind-rift’ model). Sediment fingerprinting studies, with origins in fluvial science, have been shown to offer the possibility to trace the provenance of aeolian sands, and thus elucidate transport pathways.Two models (a Monte Carlo framework and a Generalized Likelihood Uncertainty Estimate framework) are used here to provide quantitative estimates of the sediment sources that have supplied a linear dune in the central Simpson Desert of central Australia. Four possible sources are identified that may have supplied the dune; two adjacent interdunes, one upwind low ridge of sand, and a merging upwind dune. Two sites near the dune's crest are used as the target and provided twenty surface samples for analysis. Following geochemical assay, stepwise discriminant function analysis identified optimum elemental sediment fingerprints for a variety of possible sediment pathway configurations.Results suggest that the sands of the dune are sourced predominantly from upwind dunes and sand sources, and that likely contributions from neighbouring dune swales are typically <20%. As such, wind-rift mechanisms of linear dune formation are not supported by these data. More complex sediment pathway configurations (i.e., other than a binary approach: interdune vs. along-dune), whilst confirming the initial findings, had reduced discriminatory power. Further separation of source pathways (e.g., identifying the relative roles of different upwind sources) was not possible with any confidence.The findings suggest recent sediment accretion of a linear dune dominated by along-dune sand flux, and thus support an extensional component for the development of such dunes. Whilst it is noted that at a point-by-point basis this might not exclude accretion by vertical growth, as some have observed, there is no clear support for a substantive contribution to the dune sands from adjacent interdunes. Moreover, the use of contemporary sediment fingerprinting methods to question hypotheses of aeolian geomorphology suggests that such methods have great potential for addressing other terrestrial geomorphological questions where identifying sediment pathways can provide vital insight.

Geochemical characteristics and the provenance of aeolian material in the Hexi Corridor Desert, China

The Hexi Corridor Desert is in Gansu Province, northwestern China. The material provenance of desert formation and development is the primary factor of aeolian geomorphology, and it is still not fully understood in the Hexi Corridor Desert. To identify sources of aeolian sand in the formation of dunes in the Hexi Corridor Desert, we investigated 12 sites and collected 70 samples from the dune surface. This study used ratios between Na2O/Al2O3 versus K2O/Al2O3 and SiO2/Al2O3, Ba/Sr versus Rb/Sr and Rb/Sr versus Ce/Sr as well as CaO and Cl composition to identify sediment provenance. CaO was enriched relative to the composition of the upper continental crust (UCC), consistent with a previous study conducted in the Taklamakan and Badain Jaran deserts on adjacent fluvial, lacustrine and gravel deserts, but it differed from one study conducted in the Kumtagh and Tengger deserts. Cl concentrations differed in lacustrine and sand sediments, being higher in lacustrine sediments, followed by sand sediment. Sand sample geochemistry was similar throughout, indicating that sources of sand formation were also similar, which was confirmed by the multidimensional scaling (MDS) and principal component analysis (PCA) methods. Additionally, based on regional topography, the Hexi Corridor acts as a sediment sink not only for sediment from the Qilian Mountains but also for sediment from the Beishan Mountains. The MDS and PCA approaches also indicated that sediment provenance was similar in the Hexi Corridor and the Tengger, Badain Jaran and Kumtagh deserts. Therefore, it can be concluded that dry fluvial deposits, alluvial deposits and lacustrine sediments that combined comprised sand dune provenance were the sources of sand in the Hexi Corridor Desert, and these deposits derived from the Qilian Mountains in the southwest and the Beishan Mountains in the north through alluvial processes.

Characteristics of Aeolian Dune, Wind Regime and Sand Transport in Hobq Desert, China

A systematic study of the wind regime characteristics in a region can not only accurately grasp the dynamic factors of the development of aeolian geomorphology, but also provide a scientific basis for the prevention and treatment of regional sand disasters. Taking the Hobq Desert as the study area, the basic characteristics of dune are analyzed by using remote sensing images. Based on the annual meteorological data of six meteorological stations from 2009 to 2018, the spatial and temporal distribution characteristics of wind speed were obtained. With the daily wind data of three stations from 2009 to 2018, we have figured out the wind regime and sand transport characteristics of the Hobq Desert. The results show that the sand dune height of the Hobq Desert ranges large, the highest height is 5010 m and the lowest is 10 m. It decreases gradually from the west to the east. The height of dune mainly distributed below 1500 m, followed by 1500–2000 m. Migratory sand dunes in Hobq Desert accounts for 51.8% and is mainly distributed in the west of the desert. The distribution area of fixation sand dunes in Hobq Desert is the least, accounting for 8.3%. The migratory dune pattern is trellis dune, semimigrated dune and semifixed dune patterns include honeycomb dune, parabolic duneand brush dune, and fixation dune pattern is grass dune. Annual wind speed was greatest in the southeast and decreased moving to the northwest. The dominant wind direction was W and SW from 2009 to 2018 in the Hobq Desert, the average wind speed of the prevailing winds mainly distributed at 4–8 m/s. The frequency of wind speed exceeding 10 m/s is very low, with a maximum value of 10% or below. There is a low energy wind environment in the Hobq Desert, with intermediate annual directional variability and obtuse or acute bimodal wind regime. The resultant drift direction (RDD)at Dongsheng station was relatively constant from 2009 to 2018, it was about 350°. RDD differed significantly at Baotou and Linhestations were 181 ± 169° and 231 ± 121°, respectively.The relationship between drift potential (DP) and the average and maximum wind speed was expressed as a power function. DP was strongly correlated with them. There is no significant correlated between the temporal changes in DPandprecipitation and temperature from 2009 to 2018 in the Hobq Desert.