Filling of dolines with aeolian sediments in the high-mountain karst of the Dinarides(Mt.Durmitor,Montenegro)

Filling of dolines with aeolian sediments,one of the less frequently described ways in which they are filled,is analysed in the present study on an example of a doline in the high-mountain karst of the Dinarides.There is a series of deep dolines on a broad ridge(about 2450 m a.s.l.)on Mt.Durmitor(Montenegro)in the southeastern part of the Dinarides.The accumulation of very fine-grained sand that almost completely fills one of the dolines was analysed.More than 99% of the accumulation was found to be composed of well-sorted quartz grains with an average size of 89μm and no vertical differences in granulometric or textural characteristics.With respect to mineral composition,the accumulation differs significantly from that prevalent in this part of the Dinarides,in which different kinds of carbonate rocks are dominant.The conducted analyses indicated an aeolian origin of the sediments.Significant aridification that began in the Middle Holocene made the area of North Africa a source of sediments that were transported by the aeolian process to neighbouring regions.Geomorphological-sedimentological research on Mt.Durmitor and earlier investigations of the wider Mediterranean region indicate that dolines in highmountain karst can be filled with aeolian sediments.The sediments originated from territory of the northern Sahara,and the filling occurred in the Late Holocene,at the close of the African humid period.The present study shows that apart from the influence of local factors,regional geomorphological processes such as aeolian transport can also exert significant influence on the filling of dolines.It also indicates a high intensity and strongly expressed dynamics of aeolian sediment transport from the territory of Africa to this part of Southern Europe.

Estimation of the quantity of aeolian saltation sediments blown into the Yellow River from the Ulanbuh Desert,China

The Ulanbuh Desert borders the upper reach of the Yellow River. Every year, a mass of aeolian sand is blown into the Yellow River by the prevailing wind and the coarse aeolian sand results in serious silting in the Yellow River. To estimate the quantity of aeolian sediments from the Ulanbuh Desert blown into the Yellow River, we simulated the saltation processes of aeolian sediments in the Ulanbuh Desert. Then we used a saltation submodel of the IWEMS （integrated Wind-Erosion Modeling System） and its accompanying RS （Remote Sensing） and GIS （Geographic Information System） modules to estimate the quantity of saltation sediments blown into the Yellow River from the Ulanbuh Desert. We calibrated the saltation submodel by the synchronous observation to wind ve- locity and saltation sediments on several points with different vegetation cover. The vegetation cover, frontal area of vegetation, roughness length, and threshold friction velocity in various regions of the Ulanbuh Desert were obtained using NDVI （Normalized Difference Vegetation Index） data, measured sand-particle sizes, and empirical relation- ships among vegetation cover, sand-particle diameters, and wind velocity. Using these variables along with the observed wind velocities and saltation sediments for the observed points, the saltation model was validated. The model results were shown to be satisfactory （RMSE less than 0.05 and IRel less than 17%）. In this study, a subdaily wind-velocity program, WlNDGEN, was developed using this model to simulate hourly wind velocities around the Ulanbuh Desert. By incorporating simulated hourly wind-velocity and wind-direction data, the quantity of saltation sediments blown into the Yellow River was calculated with the saltation submodel. The annual quantity of aeolian sediments blown into the Yellow River from the Ulanbuh Desert was 5.56x106 t from 2001 to 2010, most of which occurred in spring （from March to May）; for example, 6.54x10~ tons of aeolian sand were blown into the Yellow River on 25 April, 2010. However, in summer and winter, the saltation process occasionally occurred. This research has supplied some references to prevent blown sand hazards and silting in the Yellow River.

North Atlantic Abrupt Climate Signals during the Last Glacial Period in Central Asia：Evidences from Aeolian Loess Sediments

Objective Climate fluctuations over suborbital or millennial timescale display significant instability during the last glacial period,which are often superimposed upon the orbital periodicity.They triggered some abrupt climate events,

Aeolian component records in lacustrine sediments and its atmospheric circulation significance for evolution of Qarhan salt lake,NE Qinghai-Tibetan Plateau

1 Introduction The Qarhan Playa of Qaidam Basin is located at the northeastern QinghaiTibetan Plateau(QTP),in which thick lacustrine and evaporate sediments deposited since the late Pleistocene(Chen et al.,1985,1986).As surrounded by capacious Gobi and yardang fields and suffered strong westerly-northwesterly wind,abundant aeolian materials were trapped in these sediment sequences in the

Grain size-dependent geochemical evidence reveals provenance and implications of aeolian sands,Dinggye region,southern Tibet

Identifying geochemical characteristics of aeolian sands on the Qinghai-Tibet Plateau(QTP)is essential for understanding the relationship between earth surface processes and paleoclimatic fluctuations in the region.Here,we present new geochemical data which provides insight to the sedimentary environment of aeolian sands in the Dinggye region,southern Tibet.We sampled aeolian dune sands in a variety of settings,and determined grain size and concentration of major oxides and trace elements in the fine and coarse fractions.Results show that aeolian sediments are dominated by fine and medium sands,with a single-peaked frequency curve and a 3-stage probability cumulative curve.The fine and coarse fractions exhibit considerable heterogeneity in elemental concentrations and ratios and upper continental crust-normalized(UCC)distribution.The geochemical evidence indicates that wind dynamic sorting is responsible for the differentiation between fine and coarse fractions in different types of aeolian sand,rather than sediment provenance.Additionally,fine-fraction sediments are well dispersed and can be differentiated from the coarse fraction,suggesting that they contain more environmental information.Multidimensional scale(MDS)and principal component analysis(PCA)of commonly used tracer elements show that flood plain sediments are the sand source for mobile dunes and nebkhas,and lakeshore sediments are the sand source for climbing sand sheets.

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) powerstation. Unfortunately, solar energy production, operation, and maintenance are affected bygeomorphological changes caused by surface erosion that may occur after the construction of the solar PVpower station. In order to avoid damage to a solar PV power station in sandy areas, it is necessary toinvestigate the characteristics of wind-sand movement under the interference of solar PV array. The studywas undertaken by measuring sediment transport of different wind directions above shifting dunes andthree observation sites around the PV panels in the Hobq Desert, China. The results showed that the twoparameterexponential function provides better fit for the measured flux density profiles to the near-surfaceof solar PV array. However, the saltation height of sand particles changes with the intersection anglebetween the solar PV array and wind direction exceed 45°. The sediment transport rate above shifting duneswas 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 theintersection angle exceeds 45°, the mean value of sediment transport rate above the solar PV array reducesto 82.58% compared with the shifting dunes. The results of our study expand our understanding of theformation and evolution of aeolian geomorphology at the solar PV footprint. This will facilitate the designand control engineering plans for solar PV array in sandy areas that operate according to the wind regime.

Effects of an oasis protective system on aeolian sediment deposition:a case study from Gelintan oasis,southeastern edge of the Tengger Desert,China

Desert-oasis ecotones are boundary areas between oases and desert ecosystems.Large efforts to control sediment and stabilize these boundaries depend on understanding sedimentary processes,especially aeolian transport and deposition.Previous studies on aeolian sediment deposition have focused primarily on a single land surface type or a single engineering approach.Few studies have considered deposition in a multi-layer oasis protective system.A complete oasis protective system consists of an outer bare sand area,a sand barrier zone,a shrub and herbaceous plant zone,and a farmland shelter zone.This study used sedimentary analysis to quantify grain-size characteristics in samples from the four land surfaces under different types of weather conditions in the Gelintan oasis of the Tengger Desert,the fourth largest desert in China.The results showed that aeolian sediment deposition decreased from the outer bare sand area through the oasis protective system and into the interior.The four land surface types showed significant differences in deposition volume(P<0.05).Deposited sediment showed gradual decrease in dominant grain-size from sand to silt,but sediment deposited during dust weather contained a larger coarse-grained fraction.From the outer desert to the inner oasis,transport mechanisms shifted from saltation(sand)to suspension(silt and smaller)in non-dust weather.During dust weather,deposition primarily occurs from near-surface aeolian sand transport with saltation.Sediment sorting decreased from exterior to interior zones of the protective system while skewness and kurtosis showed no significant change(P<0.05).These results can help inform strategies for stabilizing and protecting desert-oasis ecotones in this region and other localities.

Re-evaluating the vertical mass-flux profiles of aeolian sediment at the southern fringe of the Taklimakan Desert, China

Reliable estimation of the mass-flux profiles of aeolian sediment is essential for predicting sediment transport rates accurately and designing measures to cope with wind-erosion. Vertical mass-flux profiles from seventeen wind-erosion events were re-evaluated using five typical models based on observed data obtained from a smooth bare field at the southern fringe of the Taklimakan Desert, China. The results showed that the exponential-function model and the logarithmic-function model exhibited the poorest fit between observed and predicted mass-flux profiles. The power-function model and the modified power-function model improved the fit to field data to an equivalent extent, while the five-parameter combined-function model with a scale constant（σ） of 0.00001 m（different from the σ value proposed by Fryear, which represented the height above which 50% of the total mass flux occurred） was verified as the best for describing the vertical aeolian sediment mass-flux profiles using goodness of fit（R2） and the Akaike Information Criterion（AIC） values to evaluate model performance. According to relationships among model parameters, the modified power model played a prominent explanatory role in describing the vertical profiles of the observed data, whereas the exponential model played a coordinating role. In addition, it was found that the vertical profiles could not be extrapolated using the five selected models or easily estimated using an efficient model without field observations by a near-surface sampler at 0 to 0.05 m.

OSL chronology and paleoclimatic implications of paleodunes in the middle and southwestern Qaidam Basin, Qinghai-Tibetan Plateau

Aeolian sediments are widely distributed in the Qaidam Basin, northeastern Qinghai-Ti^tan Plateau （QTP）. The pale（xiunes are mainly located at the southeastern, middle and southwestem Qaidam Basin. However, ages ofpaleodunes in the middle and southwestern Qaidam Basin have not been well studied, although they are close to and might connect to the evolution of salt lakes in the cenWal basin. In this study, we use single aliquot regeneration （SAR） protocol of Optically Stimulated Luminescence （OSL） to date the dune sand in these two regions. The results show that： （1） Sand accumulation in these regions started at ca. 4-3 ka and lasted to ca. 0.5 ka when they were stabilized, due to the arid climate in the late Holocene. （2） The underlying fluvial sand was fomaed during deghcialion at 12.6±0.8 ka. （3） The stabilization pe- riods of the paleodunes correspond to stages of glacier advance in the northeastem QTP, during which lower temperatures caused the decrease of evapomlion and increase of the effective moisttwe, leading to an increase of vegetation cover and stabilizalion of the dunes.

Wind-proof and sand-fixing effects of Artemisia ordosica with different coverages in the Mu Us Sandy Land,northern China

Wind erosion is a key global environmental problem and has many adverse effects.The Mu Us Sandy Land of northern China is characterized by an arid climate,where vegetation patches and bare sand patches are usually distributed mosaically,and aeolian activities occur frequently.Vegetation plays a significant role in controlling wind erosion.Artemisia ordosica is the most dominant native plant species in the Mu Us Sandy Land.It is urgent to study the wind-proof and sand-fixing effects of Artemisia ordosica in the Mu Us Sandy Land.This study analyzed the wind-proof and sand-fixing effects of Artemisia ordosica based on the field data of wind regimes,aeolian sediment transport,and surface change of Artemisia ordosica plots with four coverages(denoted as site A,site B,site C,and site D)in the Mu Us Sandy Land during the period from 1 June 2018 to 29 June 2019.The coverages of Artemisia ordosica at site A,site B,site C,and site D were 2%,16%,29%,and 69%,respectively.The annual average wind speeds at 2.0 m height above the ground for site A,site B,site C,and site D were 3.47,2.77,2.21,and 1.97 m/s,respectively.The annual drift potentials were 193.80,69.72,15.05,and 6.73 VU at site A,site B,site C,and site D,respectively.The total horizontal aeolian sediment fluxes during the period from 2-3 June 2018 to 6 June 2019 at site A,site B,site C,and site D were 4633.61,896.80,10.54,and 6.14 kg/m,respectively.Site A had the largest surface changes,and the surface changes at site B were significantly weaker than those at site A,whereas the surface changes at site C and site D were minimal.The results indicated that Artemisia ordosica significantly reduced the wind speed,drift potential,aeolian sediment transport,and surface changes.The higher the coverage of Artemisia ordosica is,the more obvious the effects of wind-proof and sand-fixing.Wind erosion would be effectively controlled in the Mu Us Sandy Land if the coverage of Artemisia ordosica is greater than 29%.These results provide a scientific basis for evaluating the ecosystem service function of Artemisia ordosica and the vegetation protection and construction projects in the Mu Us Sandy Land.

Formation and evolution of sand deserts in Xinjiang, Northwest China：II. The palaeo-environmental reconstruction

Based on the palaeoclimatic and palaeoenvironmental evidences of geological history and human history periods, this paper reviews the researches and progresses on the development of the sandy deserts in Xinjiang. It pointed out that the features of tectonic structure in Xinjiang had made both the Tarim Basin and the Junggar Basin being influenced greatly by the foehn effects originated from the planetary wind system of westerly, the East Asian ocean-continental monsoon and the topographical mountain-valley winds. The regional patterns of climate and environment since the Quaternary were characterized by the overall persistent drought accompanied by fluctuations in the secondary scale. Formations of aeolian sediments in the basins and at the margins are a potential response to global climate change, particularly the aridification of the Asian hinterland deduced by the uprising of the Tibetan Plateau and its surrounding highlands. For the question about the formation time of the Tak- lamakan Desert, because the research methods, objects and information carriers used in previous studies are different, there are many disputes in the academic circles at present. Evidences from aeolian deposits/rocks at the edge and in the hinterland of these sandy de- serts and their chronological data indicate that an arid climate and land surface aeolian processes have occurred at the edge of the Tarim Basin and its hinterland areas since the Tertiary period. However, the duration time of these processes at mass scale should have begun after the middle Pleistocene and lasted to the Holocene. Occurrence of dune fields in recent 2000 years in the oasis areas should be greatly influenced by human factors.