Preliminary study of mollusk fossils in the Qinan Miocene loess-soil sequence in western Chinese Loess Plateau

The Qinan Miocene loess-soil sequence (~22―6.2 Ma)[1] discovered from the Gansu Group[2] several years ago extends the well-known Quaternary loess-soil sequence and the late Tertiary Red Clay se-quence of the Loess Plateau to early Miocene epoch. Most recently, the Dongwan late Miocene–Pliocene loess-soil sequence (~7.1―3.5 Ma)[3] further extends the upper limit of the reported Qinan Miocene loess-soil sequence into the Pliocene. These extensions have great potentials for the study o…     

Optical dating of Chinese loess using sand-sized quartz: Establishing a time frame for Late Pleistocene climate changes in the western part of the Chinese Loess Plateau

The Chinese Loess Plateau (CLP) is of major interest to Quaternary geologists because it represents an important terrestrial archive of palaeoclimatic fluctuations. Previous multiple-aliquot luminescence dating studies of Chinese loess mainly used thermoluminescence (TL) and infrared stimulated luminescence (IRSL) signals of polymineral fine-grains; these are known to be subject to anomalous fading and thus will tend to yield age underestimations. In this paper we investigate whether the blue-light stimulated luminescence (BLSL) signals from 63 to 90 μm quartz grains extracted from three western Chinese loess sites (Zhongjiacai, Le Du and Tuxiangdao) can be used to establish a reliable chronology. The single-aliquot regenerative-dose (SAR) procedure is used for the equivalent dose (D_e) determinations and the suitability of our measurement protocol is confirmed by dose recovery tests. The influence of an IRSL signal on the quartz D_e measurements derived from BLSL has been investigated. From these results we conclude that an IRSL contamination, expressed as an IRSL/BLSL ratio, of up to 10% can be accepted before the values of D_e are significantly affected. All three sites yield stratigraphically consistent and spatially highly reproducible optical ages up to about 50–70 ka. At the Tuxiangdao site a marked hiatus in the record is identified between ∼20 and ∼30 ka; this remained undetected in previous studies and clearly highlights the importance of high-resolution optical dating in Chinese loess research. The optical ages presented in this work provide more evidence for episodic loess deposition and varying loess accumulation rates in the western part of the CLP. Our study seems to confirm the potential of optically stimulated luminescence (OSL) dating using the SAR procedure applied to the very fine sandy quartz fraction in Chinese loess back to ∼40–50 ka (∼120–150 Gy).     

Paleotopographic controls on loess deposition in the Loess Plateau of China

The underlying pre‐existing paleotopography directly influences the loess deposition process and shapes the morphology of current loess landforms. An understanding of the controlling effects of the underlying paleotopography on loess deposition is critical to revealing the mechanism of loess‐landform formation. However, these controlling effects exhibit spatial variation as well as uncertainty, depending on a study's data sources, methodologies and particular research scope. In this study, the geological history of a study area in the Loess Plateau of China that is subject to severe soil erosion is investigated using detailed geological information and digital elevation models (DEMs), and an underlying paleotopographic model of the area is constructed. Based on the models of modern terrain and paleotopography, we introduce a watershed hierarchy method to investigate the spatial variation of the loess‐landform inheritance relationship and reveal the loess deposition process over different scales of drainage. The landform inheritance relationships were characterized using a terrain‐relief change index (TRCI) and a bedrock terrain controllability index (BTCI). The results show that the TRCI appears to have an inverse relationship with increasing research scope, indicating that, compared with the paleotopography of the region, modern terrain has lower topographic relief over the entire area, while it has higher topographic relief in the smaller, local areas. The BTCI strengthens with increasing drainage area, which demonstrates a strong controlling effect over the entire study area, but a weak effect in the smaller, local areas because of the effect of paleotopography on modern terrain. The results provide for an understanding of the spatial variation of loess deposition in relation to paleotopography and contribute to the development of a process‐based loess‐landform evolution model. Copyright © 2015 John Wiley & Sons, Ltd.     

天山黄土区与黄土高原表土磁性特征对比及环境意义

本文对黄土高原和天山黄土区表土进行系统的岩石磁学和粒度测试分析,探讨了表土磁性特征及其环境意义,结果表明表土中的强磁性矿物均为磁铁矿和磁赤铁矿,弱磁性矿物为赤铁矿和纤铁矿或针铁矿,黄土高原黄土地层中的磁赤铁矿至少有部分属于风积成因.黄土高原表土中磁化率与频率磁化率呈良好的正相关,气候作用是主导黄土高原表上磁化率增强的主...     

中中新世秦安黄土-古土壤序列磁性增强机制及其环境意义

中中新世黄土高原风尘堆积序列磁化率显著增高,在区域内已成为地层对比标志,然而其磁性增强机制依然不清楚.本文对秦安地区QA-I剖面约14~17.1 Ma期间的黄土-古土壤样品进行了系统的环境磁学、岩石磁学（热磁性质、磁滞性质、非磁滞剩磁与饱和等温剩磁比值χ_ARM/SIRM等）和色度指标分析.结果表明,QA-I剖面黄土-古土壤序列样品中磁性矿物为准单畴（PSD）磁铁矿、超顺磁/单畴（SP/SD）磁赤铁矿和赤铁矿,古土壤中细粒磁赤铁矿含量高于上下相邻黄土层.CBD（Citrate-Bicarbonate-Dithionite）处理方法显示,中中新世风尘序列中碎屑成因的PSD磁铁矿含量变化不大,约14.5~16.0 Ma期间成壤成因SP/SD磁赤铁矿含量的增多,是导致该时期风尘堆积序列磁化率增强的主要原因;这与该时期较低的土壤发育程度并不一致,表明CBD处理方法虽然可有效获取成壤成因SP/SD磁赤铁矿信息,却无法区分其为当地还是源区成壤成因.低温磁学研究表明,QA-I剖面约14.5~16.0 Ma期间SP/SD磁赤铁矿可能为碎屑磁铁矿颗粒的风化外壳,其含量高低变化与风尘样品中值粒径粗细变化一致,揭示出此类磁性颗粒含量受控于风力强弱,可能为源区风化成因.尽管中中新世古土壤样品的磁化率与上下黄土层相比可反映其成壤强度,但约14.5~16.0 Ma期间SP/SD磁赤铁矿含量变化可能同时受到当地成壤强度以及源区风化的影响,导致磁化率与当地成壤强度之间关系较为复杂.因此,中新世风尘堆积序列长尺度的磁化率趋势并不反映东亚夏季风强度的变化.

     

黄土高原西北缘末次冰期晚期以来黄土沉积物的岩石磁学性质

以黄土高原西北缘的靖远和古浪剖面(包含黄土层L1上部和古土壤层S0)作为研究对象,选取代表性样品进行磁化率、频率磁化率、热磁曲线、等温剩磁获得曲线和磁滞回线等测定.结果表明,靖远和古浪L1黄土和S0古土壤具有相似的岩石磁学特征.磁性矿物含量相对较低,载磁矿物均以磁铁矿为主,同时含有磁赤铁矿和赤铁矿,且S0古土壤中的磁赤铁矿含量要高于L1黄土.靖远和古浪剖面L1黄土和S0古土壤的亚铁磁性矿物平均粒度都分布在准单畴(PSD)范围,并且L1黄土平均粒径比S0古土壤更靠近多畴(MD)范围.通过与黄土高原东部黄土剖面L1黄土和S0古土壤的磁化率对比分析,认为导致靖远和古浪S0古土壤磁化率增强的主要因素是气候,但是,研究区受物源影响较大,来自粉尘源区的粗颗粒磁性矿物对磁化率贡献不可忽略.     

Luminescence chronology of aeolian deposits from the Qinghai Lake area in the Northeastern Qinghai-Tibetan Plateau and its palaeoenvironmental implications

Qinghai Lake, on the northeastern Qinghai-Tibetan Plateau, is the largest extant closed-basin lake in China, and has been the subject of numerous palaeoclimatological and palaeoenvironmental studies. In this study, 32 samples of aeolian sand, loess and palaeosol at six sites, and 1 sample of shoreline deposits underlying aeolian deposits were dated using optically stimulated luminescence (OSL). Where available, OSL ages are in agreement with previously published ¹⁴C ages. Our dating results, in combination with previous published ages on aeolian deposits showed that: (1) The oldest aeolian deposits around Qinghai Lake are in excess of 165 ka. (2) Aeolian deposition then began at ∼14 ka in the Qinghai Lake area. Periods of palaeosol formation occurred at ∼16.9 ka, ∼12.2–11 ka, ∼10–9 ka, ∼5.2–4 ka, and ∼3.9–0.7 ka. (3) The accumulation intervals of palaeosols are generally consistent with drilling-core-based environmental change proxies, indicating that palaeosols were formed during wet periods with higher vegetation cover. (4) A depositional hiatus period of ∼40–50 ka exists between the surface mantle aeolian deposits and underlying gravel deposits. (5) Lake levels during the Holocene did not exceed 3205.2 m elevation (11.8 m above recent lake level of April, 2010).     

Grain-size features of a Miocene loess-soil sequence at Qinan: Implications on its origin

In northern China, the Quaternary loess-soil se-quences[1] and the Hipparion Red-Earth Formation in the eastern Loess Plateau[2―6] provide a continental climate record for the past 8 Ma. The recently reported Miocene[7] and Pliocene[8] loess-soil sequences near Qinan constitute an eolian record of the western Loess Plateau from 22 to 3.5 Ma. Earlier studies[9] place the Miocene loess deposits into the so-called Gansu Sys-tem. Our investigations show that the Gansu System contains inde…     

Loess in Kunlun Mountains and its implications on desert development and Tibetan Plateau uplift in west China

Loess on the northern slope of Kunlun Mountains is the synchronous deposition of the Taklimakan Desert. The paleomagnetism and climatic records of an over 80 m loess-paleosol sequence on the highest river terrace at the foot of Kunlun Mountains show that the loess formed at ≈ 880 ka B.P., suggesting a roughly synchronous occurrence of the present-like air circulation and extremely dry climate and the initial desert. The uplift of the Tibetan-Pamir Plateau and Tian-shan Mountains may initiate these events. The rise of the plateau and adjacent mountains caused the drying and desertification of China inland and Tarim Basin, which was dramatically enhanced at ≈ 500 ka B.P., leading the desert to expand to its present scale. Global change just overprints this drying trend. Local climate response to global change both in long-term evolution and glacial-interglacial cycles manifests that the stronger the westerlies, the more the precipitation. But the heat-moisture pattern seems still similar to that in the Asian monsoon region.     

Average iron isotopic compositions of the upper continental crust:constrained by loess from the Chinese Loess Plateau

Iron isotopic composition of the upper continental crust(UCC) is critical for understanding Fe mobilization and migration through the Earth. Because rocks exposed at Earth's surface have heterogeneous δ~(56)Fe, finegrained clastic sediments can be used to estimate the average composition of UCC. In this study, we report δ~(56)Fe of loess-paleosol sequences from Yimaguan, Chinese Loess Plateau(CLP), to constrain the average Fe isotopic composition of UCC. The loess-paleosol sequences in this area formed in glacial-interglacial cycles and are characterized by varying degrees of weathering. Our data show that the loess-paleosol layers have extremely homogeneous Fe isotopic compositions with δ~(56)Fe ranging from 0.06‰ to 0.12‰, regardless of variations in the major element composition and weathering intensity. Our study indicates that since Fe isotopes are not significantly fractionated during loess deposition, the loess can be regarded as representative of UCC. It follows that the average δ~(56)Fe of UCC is 0.09‰± 0.03‰(2SD), consistent with previous estimates based on igneous rock data.     

Seasonal variations in infiltrability of moss‐dominated biocrusts on aeolian sand and loess soil in the Chinese Loess Plateau

Biocrust effects on soil infiltration have attracted increasing attention in dryland ecosystems, but their seasonal variations in infiltrability have not yet been well understood. On the Chinese Loess Plateau, soil infiltrability indicated by saturated hydraulic conductivity (K_s) of biocrusts and bare soil, both on aeolian sand and loess soil, was determined by disc infiltrometer in late spring (SPR), midsummer (SUM), and early fall (FAL). Then their correlations with soil biological and physiochemical properties and water repellency index (RI) were analysed. The results showed that the biocrusts significantly decreased K_s both on sand during SPR, SUM, and FAL (by 43%, 66%, and 35%, respectively; P < .05) and on loess (by 42%, 92%, and 10%, respectively; P <.05). As compared with the bare soil, the decreased K_s in the biocrusted surfaces was mostly attributed to the microorganism biomass and also to the increasing content of fine particles and organic matter. Most importantly, both the biocrusts and bare soil exhibited significant (F ≥ 11.89, P ≤ .003) seasonal variations in K_s, but their patterns were quite different. Specifically, the K_s of bare soil gradually decreased from SPR to SUM (32% and 42% for sand and loess, respectively) and FAL (29% and 39%); the K_s of biocrusts also decreased from SPR to SUM (59% and 92%) but then increased in FAL (36% and 588%). Whereas the seasonal variations in K_s of the biocrusts were closely correlated with the seasonal variations in RI, the RI values were not high enough to point at hydrophobicity. Instead of that, the seasonal variations of K_s were principally explained by the changes in the crust biomass and possibly by the microbial exopolysaccharides. We conclude that the biocrusts significantly decreased soil infiltrability and exhibited a different seasonal variation pattern, which should be carefully considered in future analyses of hydropedological processes.     

On the relationship between environmental aridization of the Loess Plateau and soil water in loess

The similarity between loess palaeo- environment and geographic distribution of modem bioclimatic zones is taken as a starting point; the relationship between the environmental aridization and soil water in loess ia discussed from the point view of the soil water energy status and their soil water physical characteristics of modem lcessial soils on the Loess Plateau. The soil water content becomes less and less from southeast to northwest, which not only provides favorable conditions for dust production by wind of loess origin, but also reveals that there is obviously a directional change in the environmental drought intensity of the Loess Plateau. Project supported by the key pmject (KZ951-B1-211) of ecological and environmental study of the Chinese Academy of Sciences     

Detrital and pedogenic magnetic mineral phases in the loess/palaeosol sequence at Lingtai (Central Chinese Loess Plateau)

A detailed rock magnetic investigation of loess/palaeosol samples from the section at Lingtai on the central Chinese Loess Plateau (CLP) is presented. Thermal demagnetisation of isothermal remanent magnetisation (IRM) and Curie temperature measurements suggest the presence of magnetite, maghemite and hematite as remanence carrying components. Bulk and grain size fractionated samples have been analysed using coercivity spectra of remanence acquisition/demagnetisation curves, which identify four main remanence carriers in different grain size fractions of loesses and palaeosols. A linear source mixing model quantifies the contribution of the four components which have been experimentally derived as dominating endmembers in specific grain size fractions. Up to two thirds of the total IRM of the palaeosols are due to slightly oxidised pedogenic magnetite. Two detrital components dominate up to 90% of the IRM of the loess samples and are ascribed to maghemite of different oxidation degree. Detrital hematite is present in all samples and contributes up to 10% of the IRM. The iron content of the grain size fractions gives evidence that iron in pedogenically grown remanence carriers does not originate from the detrital iron oxides, but rather from iron-bearing clays and mafic silicates. The contribution of pedogenic magnetite to the bulk IRM increases with the increasing degree of pedogenesis, which depends in turn on climate change.     

Seepage mechanisms and permeability differences between loess and paleosols in the critical zone of the Loess Plateau

The soil in the Loess Plateau has special permeability characteristics due to the alternating distribution of loess and paleosol layers. Using an analysis of the physical properties, microstructure and thermogravimetric analysis of loess and paleosol, this paper examines strata seepage mechanisms in the loess tableland area and considers the applicability of a hydraulic conductivity empirical formula. The analysis shows that hydraulic conductivity attenuation with depth can be represented by a negative exponential model, while hydraulic conductivity values are not normally distributed. The best-fitting models of hydraulic conductivity in the horizontal (K_H) and vertical (K_V) directions are Gaussian models, and both have strong spatial correlations. This study of the difference in permeability between loess and paleosol found that the depositional environment was the dominant causal factor, making the average hydraulic conductivity of most loess layers greater than that of the underlying paleosol layers. Different microstructures between loess and paleosol also confirmed the microscopic explanation in permeability anisotropy and their permeability difference. Thermogravimetric analysis determined temperature ranges for different types of water lost by heat, and then calculated ratios of bound water mass to liquid limit, with an average of 0.768. A modified formula suitable for loess was obtained by integrating the consistency index method and effective porosity ratio model into the hydraulic conductivity empirical formula. Compared with the results of laboratory tests and uncorrected formulas, the modified formula provides a good estimate of strata hydraulic conductivity. Accurate understandings of seepage mechanisms and permeability differences in the loess area are important, promoting ecological restoration and providing scientific guidance for the sustainable development of the Loess Plateau.     

Spatial characteristics and controlling factors of chemical weathering of loess in the dry season in the middle Loess Plateau,China

Hydrochemistry methods were used to decipher the weathering and geochemical processes controlling solute acquisition of river waters in the dry season in the middle Loess Plateau (MLP), one of the most severely eroded areas and turbid riverine systems in the world. River waters were neutral to slightly alkaline with pH varying from 7.6 to 9.6. The total dissolved solids decreased from northwest to southeast with a mean value of 804 mg/l, much higher than the global average and other large rivers in China. Ternary diagram showed that river waters were dominated by Na⁺, HCO₃^?, and Cl^? with the main water‐type of HCO₃^?–Cl^?–Na⁺. Saturation index values, Mg²⁺, Ca²⁺, and HCO₃^? analyses indicated the preferential Ca²⁺ removal by calcite precipitation. Gibbs plots and stoichiometry plots indicated that the dissolved solutes were mainly derived from rock weathering with minor anthropogenic and atmospheric inputs. Samples in the northwestern basin are also influenced by evaporation. A forward model of mass budget calculation showed that, owing to high soluble characteristics, evaporite dissolution was a major feature of river waters and contributed 41% to the total dissolved cations on average, while carbonate and silicate weathering contributed 28%,and 25% on average, respectively. Besides evaporite dissolution, cation exchange is also responsible for the high concentrations of Na⁺ in river water. Spatial variations showed that evaporite dissolution and silicate weathering were higher in the northern basin, whereas carbonate weathering was higher in the southern basin. Different from most rivers in the world, the physical erosion rates (varying from 117.7 to 4116.6 t/km²y) are much higher than the chemical weathering rates (varying from 3.54 to 6.76 t/km²y) in the MLP because of the loose structure of loess and poor vegetation in the basin. In the future, studies on comparison of water geochemistry in different seasons and on influence of different types of land use and soil salinization on water geochemistry, denudation rates, and water quality should be strengthened in the MLP. These results shed some lights on processes responsible for modern loess weathering and also indicate the importance of time‐series sampling strategy for river water chemistry. Copyright © 2016 John Wiley & Sons, Ltd.     

Loess magnetic properties in the Ili Basin and their correlation with the Chinese Loess Plateau

Over the past two decades, magnetoclimatological studies of loess-paleosol sequences in the Chinese Loess Plateau (CLP) have made outstanding achievements, which greatly promote the understanding of East Asian paleomonsoon evolution, inland aridification of Asia, and past global climate changes. Loess magnetic properties of the CLP have been well studied. In contrast, loess magnetic properties from outside the CLP in China have not been fully understood. We have little knowledge about the magnetic properties of loess in the Ili Basin, an intermontane depression of the Tianshan (or Tien Shan) Mountains. Here, we present the results of rock magnetic measurements of the Ili loess including mass magnetic susceptibility (χ) and anhysteretic remanent magnetization (ARM), high/low temperature dependence of susceptibility (TDS) and hysteresis, as well as X-ray diffraction (XRD) for mineral analysis. Based on the comparison with loess-paleosol sequences in the CLP (hereafter referred to as the Chinese loess), we discuss the possible magnetic susceptibility enhancement mechanism of the Ili loess. The results show that 1) the total magnetic mineral concentration of the Ili loess is far lower than that of the Chinese loess, though they have similar magnetic mineral compositions. The ferrimagnetic minerals in the Ili loess are magnetite and maghemite, and the antiferromagnetic mineral is hematite; XRD analysis also identifies the presence of ilmenite. The ratio of maghemite is lower in the Ili loess than in the Chinese loess, but the ratios of magnetite and hematite are higher in the Ili loess than in the Chinese loess. 2) The granularity of magnetic minerals in the Ili loess, dominated by pseudo-single domain (PSD) and multi-domain (MD) grains, is generally much coarser than that of the Chinese loess. Ultrafine pedogenically-produced magnetic grains have a very limited contribution to the susceptibility enhancement. Rather, PSD and MD particles of magnetite and maghemite are the main contributors to the enhancement of susceptibility in the Ili loess. 3) The susceptibility enhancement mechanism for the Ili loess is complicated and superimposes both a wind velocity/vigor model (Alaskan or Siberian model) and the in situ ultrafine grain pedogenic model; the former might play an important role in the Ili loess. 4) Magnetic susceptibility enhancements of the Ili loess are related not only to the eolian input of the source area, but also to the local climate, landform, and geological background. Therefore, great care should be taken when reconstructing paleoclimate using magnetic susceptibility data from the Ili loess.     

Miocene Jiali faulting and its implications for Tibetan tectonic evolution

The Karakoram–Jiali Fault Zone (KJFZ) comprises a series of right-lateral shear zones that southerly bound the eastward extrusion of northern Tibet relative to India and stable Eurasia. Here we present new ⁴⁰Ar/³⁹Ar age data from the Puqu and Parlung faults, two easternmost branches of the Jiali fault zone, which indicate a main phase of the KJFZ shearing from ∼18 to 12 Ma. Thus, the Tibetan eastward extrusion bounded by principal strike-slip fault zones started and was probably most active around the middle Miocene, an interval marked also by active east–west extension in southern Tibet. The coincidence of these two tectonic events strongly suggests a common causal mechanism, which is best explained as oblique convergence between India and Asia. Under the framework of this mechanism, the extension in southern Tibet is not a proxy for the plateau uplift. The KJFZ activity was furthermore coincident with right-lateral displacements along the Gaoligong and Sagaing faults in southeast Asia. This defines a Miocene deformation record for the regional dextral accommodation zone that, in response to the continuing India–Asia collision, may have accounted for the initiation and prolonged history of clockwise rotation of the Tibetan extrusion around the eastern Himalayan Syntaxis.     

Magnetic properties of Jiaxian red clay sequences from northern Chinese Loess Plateau and its paleoclimatic significance

Rock magnetism research on eolian deposits from the Chinese Loess Plateau shows that magnetite, maghe- mite and hematite are the main magnetic minerals in loess-paleosol sequences and red clay se-quences[1―8], and finds that the magnetic susceptibility increase is positively correlated to the content of ultra-fine minerals and relatively strong pedogene- sis[7―15]. This offers significant information in studying the Late Cenozoic paleoclimatic history of Chinese Loess Plateau[1,5―8,10―22…     

Erosion characteristics of loess tunnels on the Loess Plateau: A field investigation and experimental study

Loess tunnels are a common geo-hazard in the Loess Plateau and not only cause considerable soil and water loss, but also aggravate and even induce the occurrence and development of other disasters such as ground fissures, mudflows, collapses, and landslides. To date, research on the hydrological characteristics and erosion behaviour of loess tunnel systems has focused on field investigation data and limited river basin observation data, whereas field test information and data are very scarce. In this study, field surveys, observations, field scouring experiments, and laboratory-based sediment percentage tests were conducted to analyse the erosion characteristics, spatial distribution, and hydrological characteristics of a large-scale loess tunnel system in the hilly Loess Plateau southeast region of northern China. The results showed that the loess tunnel erosion exhibited periodicity. Tunnel erosion in each period shows a similar erosion process, that is, thin-layer water flow erosion and lateral expansion, tunnel wall collapse and deposit due to the loss of support from the lateral erosion, and erosion and transport of deposits by water flow. Waterfall erosion, lateral erosion, headward erosion, and the resulting collapses were the main forms of tunnel erosion. Besides this, the base level of erosion significantly affects the erosion characteristics of the loess tunnel. The hydrological characteristics during field scouring experiments exhibited three different stages: a lag effect, attributed to the temporary loss of water velocity in the first stage; small water flow fluctuations in the second stage; and an increase in total seepage loss with increased water injection flow in the third stage. The erosion rate was positively correlated with the flow quantity. The results of this study not only provide valuable reference data for research on the mechanism and velocity of erosion events in loess, but also provide a theoretical basis for the prevention of loess tunnel disasters in engineering construction. © 2020 John Wiley & Sons, Ltd.     

Origin of the Red Earth sequence on the northeastern Tibetan Plateau and its implications for regional aridity since the middle Miocene

Desiccation in the interior of Asia is an important aspect of paleoclimate change during the Cenozoic era[1,2]. Research[3,4] shows that the widely distributed loess deposits in China were mainly transported by northwesterly and northerly winds from deserts and the Gobi region; in addition, an indispensable re- quirement for the generation of aeolian sediment is the presence of dry lands in central Asia[5,6]. The aeolian deposits in China provide an especially useful record of desiccation pr…