Desert Development Research Articles

Evolution of food deserts and food swamps in a Brazilian metropolis between 2008 and 2020.

The aim of the current ecological study is to assess the evolution of food deserts and food swamps in the metropolitan city of Belo Horizonte between 2008 and 2020. Food deserts were determined based on the density of healthy establishments per 10,000 inhabitants, whereas food swamps were set based on the density of ultra-processed food procurement establishments per 10,000 inhabitants. The rate of census tracts classified as food deserts has decreased between 2008 and 2020, whereas that of census tracts classified as food swamps has increased within this same period. Furthermore, despite the reduced number of food deserts, these areas have increased in census tracts living under lower socioeconomic vulnerability condition. Food swamps recorded sharp increase in census tracts living under higher vulnerability condition. The population living in the herein investigated city has been increasingly exposed to an unhealthy community food environment over 12 years. Monitoring changes in community food environment is key strategy to enable tracking the effectiveness and efficiency of actions taken in food environments to ensure the human right to adequate food.

Dynamic evaluation of the ecological evolution and quality of arid and semi-arid deserts in the Aibugai River Basin based on an improved remote sensing ecological index

The ecological quality of arid and semi-arid regions (ASRs) is fragile, and the evaluation of dynamic changes in the multi-factor, long-time-series ecological quality of these regions can provide a scientific basis for sustainable regional development. Based on the remote sensing ecological index (RSEI) and its derivative indices dedicated to monitoring ecological quality in ASRs, this study proposes a new modified RSEI (nmRSEI) suitable for ASRs. We used the nmRSEI to evaluate the dynamic changes in the ecological quality and analyse the factors driving these changes in the Aibugai River Basin in the middle of the Inner Mongolian Plateau in the arid core of Asia from 1986 to 2022. The results led to the following conclusions: (1) the use of the nmRSEI helps solve the problems related to the original greenness index, i.e. normalised difference vegetation index, which was readily affected by the soil background in areas with low vegetation coverage; (2) the new dryness index can meet the evaluation requirements for the surface dryness degree in >98.65% of the study area; (3) the introduced salinity index showed a significant negative correlation with the nmRSEI; (4) the nmRSEI exhibits a gradual downward trend (Slope = −0.00326/10a); and (5) temperature was the main factor controlling the ecological quality during the research period. The nmRSEI provides a fast and effective new method for regularly monitoring ecological quality in ASRs. In addition, driving factor analysis can provide theoretical support for ecological protection in ASRs and the realisation of the United Nations 2030 Sustainable Development Goals.

A new aeolian activity proxy based on analysis of the grain size characteristics of surface soils across the Tengger Desert, northwest China, and its application to a Quaternary aeolian succession

The arid regions of northwestern China are dominated by extensive areas of mobile sand dunes. These features cause environmental problems and exert global climatic impacts; however, due to the lack of systematically-applied indicators of aeolian activity, direct evidence of past changes in aeolian activity is unreliable, especially for aeolian sand source regions. In this paper, we analyze the end-member (EM) distributions of various types of surface soil across the Tengger Desert in northwestern China, and devise a sensitive proxy for aeolian activity using a spatio-temporal substitution approach. This proxy is then used to evaluate a Quaternary aeolian succession and to understand the response of aeolian activity to regional climate change. Our results suggest that gradual increases in the coarse-grained EM components 3–5 reflect enhanced dune mobility and reduced vegetation coverage, which are a direct function of the intensity of regional aeolian activity. In the aeolian section, coarse- and medium-grained sand layers resemble modern semi-mobile and mobile dunes, whereas fine-grained sand layers are analogous to vegetated fixed/semi-fixed or semi-mobile dunes. Combining this record with independent multi-proxy evidence from the same section leads us to conclude that strong aeolian activity coincided with a dry climate, sparse vegetation cover, and strong surface winds during the Last Glacial Maximum, and that these conditions gradually attenuated at the beginning of the Last Deglacial. These inferences are in accord with independent paleoclimate records from this region, confirming that the intensity of aeolian activity in the southeastern Tengger Desert is closely associated with large-scale climate change. Our findings show that our EM proxy can be used to infer the intensity of aeolian activity and to reliably reconstruct the evolution of deserts in northwestern China.

Using clay mineralogy and micropalaeontological observations to unravel Neogene climate variations in Northern Arabia

The Zagros Mountain belt in Iran comprises an extensive record of Mesozoic and Cenozoic deposits uplifted by collision of the Arabian and Iranian continental plates. This area has been shown to provide important information to decipher the climatic history of Western Asia, especially regarding the evolution of deserts in Mesopotamia and Northern Arabia. In a high-resolution geological record of 84 samples, we combine clay mineralogy and micropalaeontological observations to refine the late Neogene climate record in Northern Arabia. We investigated a 2.6-km-thick sedimentary profile from the Simply Folded Zagros Mountain belt spanning ca. 10.2 myrs from the late Middle Miocene (Serravallian) to earliest Pleistocene (Gelasian) comprising floodplain sediments and saline mudstones with a strong aeolian contribution. The clay fraction < 2 µm reveals palygorskite, smectite, illite, chlorite and the zeolite mineral erionite. Using clay mineralogy, arid conditions during the Serravallian and early Tortonian in Northern Arabia are identified, followed by semi-arid conditions during the late Tortonian. Clay mineralogy suggests a transition to sustained arid conditions during the early Messinian and provides a more complex picture on a previously proposed period of hyperaridity (NADX) in Northern Arabia penecontemporaneous with the apex of the Messinian salinity crisis.

Differentiation of Asian summer precipitation induced by the mountain building of the Tibetan Plateau and Central Asian Orogenic Belt

Geological records from the representative monsoon-aridity climate regimes, the Chinese Loess Plateau (CLP) and Tarim Basin (TB), demonstrate that the climate has experienced distinct reorganization since the late Oligocene/early Miocene. Meanwhile, incremental evidence indicates asynchronous growth of the Tibetan Plateau (TP) and Central Asian Orogenic Belt. Therefore, how the growth of these topographies affects the Asian climate regimes need further numerical examination. By successively including the main TP, Pamir Plateau (Pr), Tian Shan Mountains (TS) and Mongolian Plateau (MP) in our numerical experiments, the effects of the stepwise uplift are examined. For the arid interior, the main TP, Pr, TS and MP all cause significant reduction of precipitation and moisture, presenting a persistent aridification process. The most intense reduction is resulted by the main TP in warm season. The summer precipitation over the CLP experienced a persistent intensification with the uplift of the main TP, Pr and TS, indicating a persistent strengthening of the East Asian summer monsoon. After that, the summer precipitation over the CLP is suppressed with the MP uplift, which is consistent with the MP-induced decrease over the arid inland. The annual mean precipitation change over the CLP resembles the change in summer. Therefore, the topography-induced precipitation evolution over the TB and CLP exhibits different processes. Meanwhile, the precipitation over the TB initially portrays a spring-winter dominant pattern as the TP significantly suppressed the precipitation in summer. The summer precipitation is then intensified with the inclusion of the Pr-TS and the precipitation seasonality is transformed to peak in summer. The results indicate the differentiation of Asian climate regimes affected by the main TP, Pr-TS and MP. The results might provide new support for the evolution of mid-latitude deserts and Neogene Red Clay and Quaternary loess-paleosol deposits on the CLP since the late Oligocene.

Optically stimulated luminescence dating and paleoclimatic implications of the Holocene dune sands in the Hunshandake Sandy Land, Northeast China

Aeolian sediments are important geological archives of paleoclimate changes. Due to the fragile ecosystem of desert, sand dune mobility is particularly sensitive to climate change, and is thus important for revealing the stabilization and mobilization processes of dunes during the geological past. In northeastern China, several sandy lands are located in the East Asian monsoonal region, and desert evolution has been used to infer the waxing and waning of monsoonal climate. However, the relationship between dynamic aeolian landscapes and forcing mechanisms is still under debate due to the complex nature of the aeolian dune systems. In this study, we analyse two aeolian sand dune sections in the Hunshandake Sandy Land, northeast China, located at the northern edge of the East Asian summer monsoon, explore regional paleoclimatic changes during the Holocene. We carried out high-resolution optically stimulated luminescence (OSL) dating to develop a well-constrained chronology for the dune sands, as well as analyses of multiple climatic proxies including magnetic susceptibility, particle size, and color parameters, to obtain knowledge about dune mobility and climatic changes. Our results indicate that the early Holocene was characterized by the accumulation of aeolian dune sands, implying an arid climate, driven by an enhanced East Asian winter monsoon. Paleosols were generally developed in the mid-Holocene (∼8 and 4 ka) when the sand dunes were stabilized by vegetation under a relatively warm and humid climate driven by an enhanced East Asian summer monsoon. In the late Holocene, from ∼4 ka to the present, climate returned to an arid and semi-arid phase, marked by aeolian dune sands with some weakly-developed paleosols. Through comparison of the aeolian record with the other East Asian monsoonal records and the sea-surface temperature of the North Pacific, we suggest that the evolution of the East Asian monsoon, which was paced by both the melting and expansion from the Northern Hemisphere ice sheet as well as the changes of solar radiation, played an important role in driving climate change in the Hunshandake Sandy Land during the Holocene.

The Changing Landscape of Food Deserts and Swamps over More than a Decade in Flanders, Belgium.

Food deserts and swamps have previously been mostly studied in Anglo-Saxon countries such as the USA and Great Britain. This research is one of the first studies to map food deserts and swamps in a mainland European, densely populated but heavily fragmented region such as Flanders. The evolution of food deserts and swamps between 2008 and 2020 was assessed. Special focus was given to areas where high numbers of elderly, young people and/or families with low income live. Food deserts were calculated based on supermarket access within 1000 m and bus stop availability, while food swamps were calculated using the Modified Food Environment Retail Index. The main cause behind the formation of food deserts in Flanders is its rapidly aging population. Food deserts with a higher number of older people increased from 2.5% to 3.1% of the residential area between 2008 and 2020, housing 2.2% and 2.8% of the population, respectively. Although the area that could become a food desert in the future due to these sociospatial and demographic evolutions is large, food deserts are currently a relatively small problem in Flanders in comparison to the widespread existence of food swamps. Unhealthy retailers outnumbered healthy retailers in 74% of residential areas in 2020, housing 88.2% of the population. These food swamps create an environment where unhealthy food choices predominate. Residential areas with a higher number of elderly people, young people and families with low incomes had healthier food environments than Flanders as a whole, because these areas are mostly found in dense urban centers where the ratio of healthy food retailers to all retailers is higher. This research showed that food deserts and swamps could be a growing problem in European regions with a high population density that experience the high pressures of competing land uses.

Physicochemical properties of surface sediments in the Taklimakan desert, northwestern China, and their relationship with oasis–desert evolution

Oasis and desert are the dominant landscapes in arid and semi-arid regions, especially in northwestern China where the oasis–desert evolution mechanisms are important for understanding modern surface processes and future environmental evolution of the region. Nevertheless, the response of the physicochemical indicators of surface sediments to oasis-desert evolution is poorly studied and it is unclear how reliable these indicators are for paleoenvironmental reconstruction. A spatio-temporal approach consisting of measurements of surface-sediment grain-size, nutrient contents and elemental ratios was used to characterize a series of modern stages of oasis-desert evolution in the Taklimakan desert. The applicability of the indicators to two sequences of alternating fluviolacustrine-wetland and aeolian sand deposits in the same region was evaluated. The results show that the oasis sediments are characterized by high contents of fine-grained particle (End-Member 1, EM1), TOC (Total organic Carbon), TN (Total Nitrogen), and MgO/SiO2, and low values of the eluvial coefficient (SiO2/(MgO + CaO + K2O + Na2O)). By contrast, the desert sediments are characterized by high values of coarse-grained particle (End-Member 3, EM3), low soil nutrients and MgO/SiO2, and an increased eluvial coefficient. In the two sedimentary sections, the physicochemical properties of the clay-silt layers resemble those of modern oasis sediments, especially washland, and the properties of the interbedded aeolian sand resemble those of modern desert deposits. The observed co-variation of grain size, soil nutrients and geochemical ratios of the surface samples shows that our approach can be used to determine the trends of past oasis-desert evolution. The reconstruction suggests that oasis formation largely depended on the development of a fluviolacustrine-wetland environment, whereas oasis degradation was closely related to strong aeolian activity. The findings provide new insights into the selection of appropriate indicators for analyzing oasis-desert sediments and for reconstructing the evolution of oasis-desert landscapes.

Provenance of loess deposits and stepwise expansion of the desert environment in NE China since ~1.2 Ma: Evidence from Nd-Sr isotopic composition and grain-size record

The Quaternary wind-blown Chinese loess-paleosol sequence, which developed as a product of the intensification of Northern Hemisphere glacial-interglacial cycles, is a major source of information on aridification of the Asian interior. In northeastern (NE) China, extensive loess deposits occur that have great potential for reconstructing the long-term paleoclimatic evolution of the region. Despite existing geochemical data indicate that the probable major source areas for these loess deposits were the nearby Horqin and Otindag deserts, it is still unclear that whether there was a long-term change in the detrital source of these loess deposits. In addition, the aridity history and long-term desert evolution of NE China are currently poorly understood. In the present study, we measured the silicate Nd and Sr isotopic composition of the 28–45 μm grain-size fraction from multiple loess sections (NYZG, SBH, and TDJZ). The results show that the loess deposits of the three sites were dominantly sourced from the Otindag sandy desert and that this source remained constant for the past 1.2 Ma. Notably, the 87Sr/86Sr ratios are influenced mainly by variations in the content of clay-sized material present in the form of aggregates or adhering to the surface of coarser particles. Therefore, caution is needed in the use of 87Sr/86Sr ratios of the 28–45 μm fraction as a tracer of eolian dust, when the clay minerals are not completely removed during the pretreatment process. The grain-size variability of the three sections indicates that stepwise enhancement of aridification in the Otindag sandy desert occurred at 1.2 Ma, 0.9 Ma, and 0.7 Ma, which coincided respectively with the beginning of the Mid-Pleistocene transition (MPT), an extremely cold event at ~0.9 Ma within the MPT, and the establishment of a full glacial climate at the termination of the MPT. This finding supports the hypothesis that the growth of high-latitude ice sheets was the major driver of the long-term aridification of Asian dust source areas.

Tracing the dune activation of Badain Jaran Desert and Tengger Desert by using near infrared spectroscopy and chemometrics

Tracing the sand source is helpful to interpret the evolution of deserts and explain the relations between the desert and the climatic geographical condition around. Furthermore, it is helpful to investigate the reasons for sandstorms in corresponding areas. In this work, near infrared spectroscopy combined with hierarchical cluster analysis was proposed as a novel method to characterize sand samples collected from Badain Jaran and Tengger Deserts, two main sources of sandstorms in North China. Partial least square discriminant analysis gives a classification result with an accuracy of 100% for the estimation of hierarchical cluster analysis. The results provide support that Badain Jaran Desert and Tengger Desert have sand exchanged by monsoonal weather events. The transmission between the two deserts is also affected by the local terrain. The sand samples were also analyzed by electron microscopy, energy dispersive spectroscopy and Fourier transform infrared spectroscopy to investigate the sample differences in morphology, elemental contents and molecular structures. Near infrared spectroscopy combined with chemometric methods has the potential to be used for the identification of sand samples to determine the sources of sands with advantages of fast, nondestructive, low cost and in situ analysis.

Pollen spectrum, a cornerstone for tracing the evolution of the eastern Central Asian desert

The temperate desert in arid Central Asia (ACA) has acted as a thoroughfare for the ancient Silk Road and today's Belt and Road, linking economic and cultural exchanges between East and West. The interaction between human sustainable development and the dynamic change in the desert ecosystem in this region is an area of concern for governments and scientific communities. Nevertheless, the lack of a pollen spectrum of the dominant taxa within the temperate desert vegetation and a corresponding relation between pollen assemblages and specific desert vegetation types is an obstacle to further understanding the formation and maintenance of this desert ecosystem. In this work, we link pollen assemblages to specific desert vegetation types with a new pollen spectrum with specific pollen grains, specific plant taxa and related habitats, providing a solid foundation for further tracing the evolution of the desert ecosystem in eastern arid Central Asia.

Loess deposits since early Pleistocene in northeast China and implications for desert evolution in east China

Loess deposits and deserts are regarded as coupled geological systems and loess deposits on the periphery of deserts can often be used to reconstruct desert evolution. Previous studies of desert evolution in Asia are mainly concentrated in northwest China and the China Loess Plateau, and little is known about long-term desert evolution in east China. In this study, we selected the Sishijiazi loess section in the Chifeng area in northeast China to study the long-term evolution of the desert in east China. A high-resolution magnetostratigraphy combined with optically stimulated luminescence dating indicated that the age of the section base is approximately 1.02Ma. The Brunhes-Matuyama boundary is at the depth of 39.8m in loess unit L8, and the upper boundary of the Jaramillo Subchron is at the depth of 60.8m in paleosol S10. The results of grain-size analysis indicate a coarsening grain-size trend in the past 1.0Ma. In addition, based on grain-size variations, the desert evolution in east China since ∼1.0Ma can be divided into three stages: stability from 1.0 to 0.8Ma, desert recession from 0.8 to 0.5Ma, and gradual expansion since 0.5Ma. Our results further indicate that the evolution of desert in east China was mainly controlled by changes in global ice volume, and that the uplift of the Tibetan Plateau may have had an additional effect.

The Evolution of Food Deserts in a Small Midwestern City: The Case of Ypsilanti, Michigan: 1970 to 2010

This study examines long-term geographic and demographic changes in food deserts in Ypsilanti, a small city of approximately 19,500 people located in Washtenaw County, Michigan. Because of the small size of Ypsilanti, it is sometimes difficult to imagine that food deserts can emerge in such urban settings and persist for decades. We argue that the persistence and geographic spread over time of food deserts in Ypsilanti are related to suburbanization, the decline of a once thriving auto-manufacturing sector, and changes in the structure of grocery retailing.

GEOMORPHOLOGICAL LEGACY OF THE OUTSTANDING RUSSIAN NATURALIST B.L. LICHKOV (1888–1966)

Boris Lichkov, an outstanding scientist of the first half of the XXth century, worked successfully on a number of basic problems of Earth sciences, such as origin and evolution of deserts, epeirogenic crustal movements correlation of marine and alluvial terraces in the context of the Black Sea formation, geochronology of continental nuclea, such as the “ancient crown of Asia” by E. Suess (Baikalian orogen of Southern Siberia), glaciations and formation of great alluvial plains

Key Role of Desert–Oasis Transitional Area in Avoiding Oasis Land Degradation from Aeolian Desertification in Dunhuang, Northwest China

AbstractThe survival of oasis is partially determined by the evolution of desert–oasis transitional area (abbr. DOTA) characterized by fragile and unstable environments. This study reveals the function of DOTA in avoiding oasis land degradation from its aeolian environments based on the detailed wind data, in situ observation of wind‐blown sand and granular characteristics of surface sediments from desert to oasis. Results indicate that the DOTA has buffering function in slowing down aeolian desertification in oasis. Additionally, the annual mean wind speed reduces 40·8% from desert to DOTA area but up to 92·8% from desert to oasis. The frequency of sand‐laden wind, drift potential and sand transport all decrease following the section from desert to oasis while surface roughness increases. And the granular characteristics of surface sediments show that the weight percentage of coarse sand decreases but fine sand increases along the section from desert to oasis. This paper reveals that the aeolian environments are of great difference between desert and DOTA and the significant role of DOTA in protecting oasis. Integrated sand control system needs to be settled in the DOTA to strengthen its buffering function. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Morphological characteristics of interactions between deserts and rivers in northern China

Abstract Arid regions are affected by long-term interactions between various factors including water and wind. Recent research has concentrated on aeolian–fluvial interactions in dryland environments, including the important role of rivers in providing sand and spaces for deserts development, as well as the influences of aeolian activity upon river landforms. However, there is still a lack of comprehensive data at the large watershed scale to support such research. In this study, we analyzed statistically the morphological parameters related to twelve deserts and ten watersheds in dryland regions of northern China using remote sensing data, maps of desert and watershed distributions, and classification of aeolian landforms. Results indicate that, in view of the relationship between deserts and rivers, the geomorphic structures of drainage basins in northern China can be overall divided into five large drainage zones: northwestern drainage (ND), western drainage (WD), drainage of northern Qinghai-Tibet Plateau (PD), middle drainage (MD) and eastern drainage (ED). In the terms of percent area of desert in drainages, it can be sequenced as WD > MD > ND > ED > PD. For percent area of shifting dunes in deserts, WD > PD > MD > ED > ND. Considering the classification of aeolian dunes, transverse dune dominates in all drainages, and its proportion can be sorted as PD > ED > MD > WD > ND. There is a significant difference in their morphological parameters between interior and exterior watersheds. In exterior watersheds, desert area, shifting dune or transverse dune areas are not significantly associated with drainage area respectively, but interior watersheds have good correlations between them. And in three rivers of Tarim Basin, along with increasing distance from the river bank, the types of aeolian dune (complexity) increased step-wisely, implying that sand dune extends along the river terrace. Those data and preliminary findings confirm that the rivers are indispensable to the development and evolution of deserts, performing as channels (‘arteries’) and platforms (‘skeletons’) in providing sand sources and spaces.

Aeolian sediments evolution controlled by fluvial processes, climate change and human activities since LGM in the Qaidam Basin, Qinghai-Tibetan Plateau

Aeolian sediments are widely distributed in the eastern Qaidam Basin (QB), the main habitats for human in the hyper-arid basin during the Holocene, especially since 3 ka. The evolution of aeolian sediments is an important factor for the environmental change, and influence human activities and migration. However, many questions, e.g., when the aeolian sediments start to accumulate, what controls their initiation and how their evolution responds to climate change and human activities, still need further studies. In this study, we present a detailed Optically Stimulated Luminescence (OSL) chronology for both aeolian and underlying fluvial sediments from the Tiekui Desert in the eastern QB to discuss aeolian and fluvial processes, climatic changes, desert evolution, and human activities. Dating results show that: (1) underlying fluvial sediments were formed during ∼23.9–12.1 ka, and the erosion caused by the fluvial process may provide an explanation for the absence of aeolian sediments during and before this period; (2) aeolian sediments accumulated from ca. 9–8 ka to modern times, with loess development from 9–8 ka to 1.6 ka and 1.4–0.7 ka, and dune sand accumulation at 1.6–1.4 ka and 0.7–0 ka. Through the comparison with the local and global palaeoclimatic records, we suggest that desert evolution in this region was sensitive to climatic changes induced by the Asian summer monsoon. Detailed local historical records of the past 2000 years suggest that desert evolution was also influenced by human activities.

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 Taklamakan 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 deserts 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.

Formation and evolution of sand deserts in Xinjiang, Northwest China: I. Provenances of desert sands

Sandy desert landscape is a geological product of arid climate and abundant sand materials supply in natural conditions, therefore the formation of sandy desert is an ideal studying object for understanding the interaction between various stratigraphic/epigenetic spheres of the earth system. However, until now, the knowledge about the provenance and formation of these deserts in Xinjiang, Central Asia is diverse and inconsistent, a systematic review is necessary. Ancient aeolian sand sediments in the internal areas of these deserts and their twin dust deposits in the Cenozoic strata surrounding the Xinjiang deserts are direct and indirect clues reflecting the provenance of sand materials and the formation and evolution of deserts. Based on the geochemical, mineralogical and isotopic evidences of desert sands and relevant deposits in the peripheral regions, this paper reviews the research progress on the development of the sandy deserts in Xinjiang, Northwest China. Many proofs proposed that desert sands in Xinjiang were mainly sourced from the ancient pluvial, alluvial and fluvial sediments and were eventually achieved because of the local sand supply. It pointed out that the settings of tectonic structure in Xinjiang had made sediments both in the Tarim Basin and the Junggar Basin being influenced greatly by regional hydrological system and aeolian processes originated from the planetary wind system of westerly, the East Asian winter monsoon and the topographical mountain-valley winds. However, the directions of transportation paths are different between the hydrological dynamics and the aeolian dynamics, which are decided by the slantwise structures of the basins tectonics and the regional atmospheric circulation routes, respectively, and have determined anisotropies of the transport pathway of these sediments delivered by different agents. This results in a geological cycle of detrital sediment transportation in the two large basins and thus largely increases the degree of sediment mixing, alternation and recycle between younger and older sediment sources, as well as the complexity and diversity of sand provenances.

Quartz and K-feldspar optical dating chronology of eolian sand and lacustrine sequence from the southern Ulan Buh Desert, NW China: Implications for reconstructing late Pleistocene environmental evolution

The Ulan Buh Desert (UBD), in southwestern Inner Mongolia, is one of the main dune fields and dust source areas in northern China. In the southern UBD, consisting primarily of high pyramidal and complex sand dunes, the process of desert evolution remains unclear due to a lack of depositional records and adequate age controls. In this study, we present the stratigraphic record of a 120.5m deep core (WL12ZK-1) collected in this sandy desert region. A 22.6m thick deposit of lacustrine clay/silty clay bracketed between 37m (top) and 54.7m (bottom) thick layers of eolian sand, provides evidence of a desert–lake–desert sequence in the southern UBD. Quartz Optical Stimulated Luminescence (OSL) and K-feldspar multi-elevated-temperature post-IR IRSL (Met-pIRIR) dating technologies were employed to provide a chronology for this sequence. Internal checks of the quartz OSL dating indicate that the quartz single-aliquot regenerative-dose protocol is appropriate for equivalent dose determination and that the quartz ages younger than 60ka are acceptable. The reliability of the K-feldspar ages is confirmed by both internal checks and an age-temperature plot. The combined stratigraphy and chronology indicate a sand desert landscape developed in the southern UBD at least ~232ka ago, and that a paleolake was present beginning sometime before ~155ka and lasting until ~87ka, with several possible lake level fluctuations. Desert landforms developed synchronously in the southern and northern UBD after the paleolake regressed. A combination of tectonic activity and climate change may be responsible for this sequence.