Western Hexi Corridor Research Articles

Orbital forcing of aridity/humidity fluctuations in the Hexi Corridor and Alxa Plateau, NW China, during the last 1.8 million years

The processes controlling aridity/humidity variations in mid-latitude Asia dust source regions on orbital timescales are unclear. Both insolation and polar ice sheets can affect the climate at mid-latitudes, but determining their individual contributions is challenging. Here we present a compilation of paleoclimate data (the content of smectite and aeolian sand, and the proportion of the hydraulic component) from sites in the Hexi Corridor and Alxa Plateau, located at the junction of the regions influenced by the mid-latitude East Asian Monsoon (EAM) and the Westerlies. Our objectives were to determine the links between aridity/humidity variations in this region and Earth orbital forcing and changes in high-latitude ice sheets. We found that the aridity/humidity variations in the Hexi Corridor and Alxa Plateau were paced mainly by the long eccentricity cycle (∼400 ka), facilitating roughly coherent beat in changes of the mass accumulation rate (MAR) and the excursions of thick/coarse loess layers L1, L5, L9, L15 and L24 on the Chinese Loess Plateau. Additionally, spectral analysis of the paleoclimate data revealed that the expression of the Mid-Pleistocene transition (MPT) was spatially variable. A transition between the dominant periodicities in the western Hexi Corridor and Alxa Plateau occurred at ∼0.9 Ma, but in the eastern Alxa Plateau this transition occurred at ∼0.7 Ma. Our data compilation also demonstrates an interval of wet climate in the Hexi Corridor and Alxa Plateau after ∼0.34 Ma, which is consistent with paleoclimate records from loess deposits in Westerlies-dominated Central Asia. We attribute this to insolation forcing via complex internal feedbacks in the Southern Ocean, involving the enhancement of the Atlantic deep-water circulation, and the interplay between Indian Monsoon and the Westerlies. Overall, our findings highlight the importance of the Earth orbital control of aridity/humidity cycles on the boundary of the EAM and the Westerlies in mid-latitude Asia.

Physiochemical Characteristics, Provenance, and Dynamics of Sand Dunes in the Arid Hexi Corridor

Dynamic changes of aeolian landforms under changing environments in a middle-latitude desert belt is a typical problem of climate change and related landscape response. It need a comprehensive understanding of the formation mechanisms of dune landforms with the supply of material suitable for aeolian transport and favorable conditions of sediment availability and wind regimes in the region. Based on comprehensive evidences from geomorphological, sedimentological, geochemical, and hydrological analysis, this study discussed the dynamical changes of different dune landforms during the past half century and their provenance in the Hexi Corridor, China. The results show that there are two states of sand dunes movement in the Hexi Corridor in the past half century, dynamic migration and basically stable. The crescent-shaped dunes move the fastest, followed by the chains of barchan dunes. Only the top of the pyramid dunes wigwags, while the parabolic dunes and the longitudinal dunes hardly move forward. The moving speed of sand dunes is positively correlated with the wind speed ≥5 m/s at a yearly scale. The grain size of sand dunes in the western Hexi Corridor is coarser than that in the central-eastern part, and also larger than those in other deserts of northern China and of the world. Different motion modes of saltation, suspension, and creeping are identified between aeolian, alluvial/fluvial and gobi sediments. Dune sands are mainly “sediments ofin-siturising” that originated from alluvial/fluvial/lacustrine deposits of ancient rivers, lakes, and aeolian deposits in the erosion zone of the forelands of the Qilian and Beishan Mountains and the north-neighboring deserts. This reveals a significance interaction between wind and water dynamics in the formation and evolution of aeolian landforms in the arid study area. Sufficient transport capacity is evidenced for both the western and eastern parts of the Hexi Corridor, sufficient sand supply and sand availability, however, is the favorable factor for dune formation in the east part but is the limiting factor for the west.

Changes in Wood Utilization Due to Iron Age Jade Mining in the Western Hexi Corridor: Wood Charcoal Investigations

Charcoal remains from archeological sites are used not only to reconstruct the historical composition of local woodlands but also to examine the history of the human use of wood. Nevertheless, key questions such as how and why people may have selected particular woody taxa from locations long distances from their habitat have rarely been addressed. In the present study, we analyze charcoal remains from the ancient Jingbaoer (JBR) jade mine in the Mazong Mountains (Mazong Shan) of Northwest China to explore patterns in the collection and use of wood by Iron Age people. Factors affecting the choice of wood collected at the JBR site are discussed by combining the results of pollen records and charcoal analysis. Our results suggest that tamarisk (Tamarix L.), a shrub dominant in the local area, was the main source of wood for JBR miners and was used as firewood depending upon its local availability. The miners may also have used wood from species sourced further away, such as Pinus L. and Picea L., because of the local scarcity of these trees in such a dry environment. The agropastoralist subsistence system practiced by the JBR miners supports the hypothesis of the collection of wood from distant locales. This study highlights diverse patterns of wood collection in an area scarce in woody plants and provides new evidence for understanding how Iron Age people adapted to extremely arid environments.

Late Quaternary Tectonic Activity and Slip Rates of Active Faults in the Western Hexi Corridor, NW China

The Yinwashan and Xinminpu faults are located in the Jiuxi Basin in the western end of the Hexi Corridor. The determination of their activity and slip rates is of great significance for understanding the eastward extension of the Altyn Tagh fault. Based on geological and geomorphologic field survey, trench excavation, optically stimulated luminescence dating, we define the fault geometry and kinematic properties of the two faults. Based on fault scarps measurement using differential GPS and 10Be surface exposure dating, we determined vertical slip rate of 0.09±0.01 mm/yr for the Yinwashan fault and 0.1±0.02 mm/yr for the Xinminpu fault. Using the dips observed in trenches and natural sections, we estimated horizontal shortening rates of 0.05±0.03 and 0.23±0.06 mm/yr, respectively. No significant strike slip motion is observed on these two faults, and we infer that this region was dominated by horizontal shortening in the Late Quaternary. Although the shortening rate is quite low on each individual fault, together with other faults in this area, these two faults have an essential role in transferring slip from the eastern end of the Altyn Tagh fault and in accommodating the northeastward growth of Tibetan Plateau.

A NW-striking dextral strike-slip fault at the eastern end of the Altyn Tagh fault and its tectonic implications for northeastward growth of the Tibetan Plateau

The eastern end of the Altyn Tagh fault connects the western Qilian Shan thrust belt and its foreland basin, the Hexi Corridor, which contains numerous active faults with various strikes and kinematics. Although understanding of the geometry and kinematics of these active faults is increasing, the deformation pattern since the late Quaternary in the western end of the Hexi Corridor remains controversial. Studying the geometry and kinematics of these faults provides great benefit for understanding regional deformation patterns. The North Kuantan Shan fault (NKTSF) is located at the eastern end of the Altyn Tagh fault and the western end of the Hexi Corridor. Remote sensing images and field investigations suggest that the NKTSF strikes NW and acts as a right-lateral strike-slip fault with a reverse component. Optically stimulated luminescence (OSL) data combined with vertical offsets of the fault scarp imply a range of vertical slip rates of 0.015–0.093 mm/a, and cosmogenic 10Be ages and displacements of river terrace risers suggest a range of horizontal slip rates of 0.25–0.71 mm/a. The geometry and kinematics of the NKTSF enable us to estimate the deformation pattern in the western Hexi Corridor, which indicates that this area is undergoing northeastward compression related to the northern Tibetan Plateau (Qilian Shan). Active faults in the region are driven by the northeastward push of the Tibetan Plateau rather than the eastward extension of the Altyn Tagh fault.

Paleoclimatic record from the clay mineralogy of Quaternary sediments of drill core DWJ from Jiudong subbasin (western Hexi Corridor), NW China

AbstractThe thick sedimentary deposits of the Jiudong subbasin in the western Hexi Corridor of NW China can potentially provide important records of climate change in arid and semiarid areas subject to the interaction of the East Asian summer monsoon (EASM) and the westerlies. Here we present the results of a study of the clay mineralogy of the sediments of drill core DWJ from the Jiudong subbasin. The clay minerals consist mainly of illite, followed by chlorite, kaolinite, and smectite. The clay mineral assemblages are used to define four paleoclimatic stages since ~1.8 Ma: (1) During ~1.8–1.2 Ma, the climate was relatively cold and arid; (2) during ~1.2–0.9 Ma, it was relatively warm and wet, with strongly seasonal precipitation; (3) during ~0.9–0.3 Ma, there was a long-term trend of cooling and drying; and (4) during ~0.3–0.1 Ma, the climate was warmer and wetter than during the previous period, with strongly seasonal precipitation. The paleoclimatic record of the Jiudong subbasin since ~1.8 Ma is consistent with records from the Tengger Desert and typical monsoonal areas. This suggests that the EASM penetrated into the central regions of the North Qilian Shan and Zhangye–Jiudong subbasin during ~1.2–0.9 and ~0.3–0.1 Ma.

Formation age of Jiudong Sandy Land, in the western Hexi Corridor, NW China

Jiudong Sandy Land in the western Hexi Corridor is one of the dust source regions of the Chinese Loess Plateau and is highly sensitive to climate change. Determination of when this sandy land formed would help resolve major questions about the desertification history of inland Asia; however, until now, this has been hindered by the lack of depositional records. Here, we report the results of optically stimulated luminescence (OSL) dating, grain size and grain surface analyses from a new drill core obtained from Jiudong Sandy Land. Our aims are to constrain its age of formation. Analysis of sedimentary facies reveals that the sediments in the lower part of the core (35.2–16.7 m) were deposited by fluvial processes, but that the sediments in the upper part consist primarily of aeolian sand. The OSL dating results indicate that the transition from fluvial to aeolian facies occurred at ∼89.8 ± 7.6 ka. Combined with various loess-based environmental proxies from Jiudong Basin, the new litho- and chronostratigraphic evidence reported in this study indicates that the age of ∼89.8 ± 7.6 ka represents the formation age of the Jiudong Sandy Land.

Late Pleistocene slip rate of the northern Qilian Shan frontal thrust, western Hexi Corridor, China

AbstractWe derive a slip rate for a frontal thrust in the western Hexi Corridor along the northern Qilian Shan by combining topographic profiling and 10Be exposure dating. The active Yumen‐Beidahe thrust fault offsets late Pleistocene alluvial‐fan deposits, and a prominent north‐facing scarp is well preserved. To quantify the slip rate, we surveyed the uplifted terraces and sampled quartz‐rich pebbles on terrace surfaces and river channels to determine surface exposure ages and pre‐depositional inheritance. The minimum vertical slip rate of the fault is 0.73 ± 0.09 mm a−1. This represents a horizontal shortening rate of 1.26 ± 0.31 mm a−1 for a fault dip of 30 ± 5°. This estimated slip rate supports the inference made from previous geological and GPS constraints that NNE‐directed shortening across the western Qilian Shan and the Hexi Corridor is distributed on several active faults with a total shortening rate of 4–10 mm a−1.

Tree-ring recorded moisture variations over the past millennium in the Hexi Corridor, northwest China

Knowledge of the moisture variation is essential for water resources management and policy making, especially for the arid regions, where the water resources can hardly meet the demand of the human being and the ecosystem. Hexi Corridor in northwest China is in a typical arid area with little precipitation and high evaporation. A lot of tree-ring studies were conducted in this area; however, no long-term and large-scale moisture history research had been conducted in this region until now, due to the lack of long-time tree-ring records in eastern and western Qilian Mountains. Here, we synthesized the moisture evolution of nearly one millennium (AD 1161–2006) in this region by using four published moisture-sensitive tree-ring records, including two recently published millennium reconstructions in eastern and western Hexi Corridor. The comparisons of tree-ring records from the eastern, central and western part of Qilian Mountains show that all the reconstructions are statistically similar to each other. The principal component analysis was applied to extract the common signal recorded by these series. The first principal component (PC1), which expressed 61.1% of the total variance, was used as an indicator of regional moisture variations. The PC1 suggests that the Hexi Corridor has alternated between contrasting climatic conditions, with dry periods at AD1161–1216, 1260–1349, 1409–1417, 1443–1510, 1617–1737, 1759–1838 and 1929–1948, wet periods at AD1217–1259, 1350–1408, 1418–1442, 1511–1616, 1738–1758, 1839–1928 and 1949–2006. The droughts and pluvial periods identified in the Hexi Corridor are generally consistent with those in nearby regions recorded by tree-ring and other proxies. We also find that droughts periods in the Hexi Corridor trend to coincide with the solar minimum, highlighting the importance of solar variability on forcing regional moisture variability.

甘肃省生态承载力空间定量评价及耦合协调性

PDF HTML阅读 XML下载 导出引用 引用提醒 甘肃省生态承载力空间定量评价及耦合协调性 DOI: 10.5846/stxb201606071096 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金（40771054）；高等学校博士学科点专项科研基金联合资助课题（20106203110002） Research on the spatial quantitative evaluation and coupling coordination degree of ecological carrying capacity in Gansu Province Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:以生态环境脆弱的甘肃省为研究区，选用状态空间法从生态功能弹性力、资源环境供容力以及社会经济协调力3个维度构建生态承载力评价指标体系，对甘肃省2010年生态承载力的空间分异特征、空间关联特征以及耦合协调性进行分析。结果表明：①空间分布上，甘肃省生态承载力总体呈现东南高西北低，从东南高承载区向西北弱承载区逐级递减的空间分布格局；相近或相异生态地理分区的生态承载力表现出空间和数量上的一致性和差异性；特别地，河西走廊独特的绿洲生态景观，促使该地区生态承载力存在明显的空间异质性。②空间关联上，甘肃省生态承载力的分布呈正的全局空间自相关，存在显著的高值（或低值）集聚区；局部空间自相关LISA集聚类型主要包括HH和LL 2种类型，前者分布于甘南高原、陇南山地及河西走廊以南的祁连山区，后者则分布于苏干湖水系以北的酒泉境内与石羊河流域下游的武威民勤地区。③耦合协调性上，甘肃省生态承载力综合耦合协调性空间差异较大，从东南到西北呈现高-低协调相间分布的格局；较高协调地区出现在甘肃省东南部与河西走廊中东段，而较低协调地区则位于兰州-白银经济区及河西走廊西段；维度间耦合协调性受制于本地区自然和人文环境状况，使其空间分布与协调程度表现得不尽相同。 Abstract:We selected Gansu Province, China-an environmentally and ecologically fragile region-as a case study for exploring the use of state-space techniques in constructing systems for evaluating ecological carrying capacity based on ecological function elasticity, resource supply and environmental capacity, and socio-economic coordination. Spatial heterogeneity, spatial autocorrelation, and coupling coordination characteristics of Gansu in 2010 were then analyzed. The results indicated that (1) the overall ecological carrying capacity of Gansu declined progressively from a high in the southeast to a low in the northwest, and that similar and dissimilar eco-geographical regions reflect the similarities and differences in ecological carrying capacity both spatially and quantitatively. In particular, the Hexi corridor, a unique oasis of ecological landscapes, is a primary cause of the distinct spatial heterogeneity. (2) Spatial autocorrelation of the distribution of ecological carrying capacity is positive, existing in high (or low) value cluster areas. LISA cluster of local spatial autocorrelation can be divided into two types, consisting of HH and LL cluster areas, with the former concentrated in the Gannan Plateau, and the Longnan and Qilian mountain ranges, whereas the latter cluster encompasses the northern Sugan Lake river system and the Minqin Wuwei region downstream of the Shiyang River. (3) The comprehensive coupling coordination of ecological carrying capacity indicates the existence of large regional differences, appearing interphase distribution between high and low levels extending from the southeast to the northwest. Relatively high coordination areas are mostly located in the southeast of Gansu and the mid-eastern section of the Hexi corridor, whereas comparatively lower coordination areas situated in Lanzhou-Baiyin economic region and the western Hexi corridor. The coupling coordination between each dimension is subjected to the present situation of natural and human environments, resulting in marked differences in space and degree. 参考文献 相似文献 引证文献

Temporal and spatial variations in extreme temperatures in the Qilian Mountains-Hexi Corridor over the period 1960-2013

Based on daily maximum and minimum temperatures at 18 meteorological stations in the Qilian Mountains and Hexi Corridor between 1960 and 2013, temporal and spatial variations in extreme temperatures were analysed using linear trends, ten-point moving averages and the Mann-Kendall test. The results are as follows: The trends in the majority of the extreme temperature indices were statistically significant, and the changes in the extreme temperatures were more obvious than the changes in the extreme values. The trends were different for each season, and the changes in rates and intensities in summer and autumn were larger than those in spring and winter. Unlike the cold indices, the magnitudes and trends of the changes in the warm indices were larger and more significant in the Hexi Corridor than in the Qilian Mountains. Abrupt changes were detected in the majority of the extreme temperature indices, and the extreme cold indices usually occurred earlier than the changes in the extreme warm indices. The abrupt changes in the extreme temperatures in winter were the earliest among the four seasons, indicating that these temperature changes were the most sensitive to global climate change. The timing of the abrupt changes in certain indices was consistent throughout the study area, but the changes in the cold indices in the Hexi Corridor occurred approximately four years before those in the Qilian Mountains. Similarly, the changes in the warm indices in the western Hexi Corridor preceded those of the other regions.

Drainage evolution of the Heihe River in western Hexi Corridor, China, derived from sedimentary and magnetostratigraphic results

Abstract The uplifting of the Tibetan Plateau has significantly changed the environment in surrounding areas by delivering abundant water and sediment. The Heihe River draining the Qilian Shan in the NE Tibetan Plateau acts as a dominant sediment routing system from the uplifted NE Tibetan Plateau to the Hexi Corridor as well as the Badain Jaran Desert. Reconstructing the evolution of the Heihe River could provide evidence for the birth of the Badain Jaran Desert and enhance the understanding of sedimentary basin fill and the relationship between tectonism, drainage evolution and environmental changes. With this aim, two parallel cores (DWJ and XKJD with depths of 140 and 68.2 m, respectively) were drilled in the floodplain of the Heihe River. The facies analysis of the sedimentary sequences from the drilling cores showed that the sedimentary environment changed from the lake system to a delta system and finally to a fluvial system at the depths of ∼133.3 and ∼68 m, respectively. The magnetostratigraphic results revealed ages of approximately 1.75 and 1.12 Ma for the DWJ and XKJD cores, respectively, and an age of approximately 1.1 Ma for the transition from delta to fluvial environment in both the cores. The change of the sedimentary environment at approximately 1.1 Ma was caused by the formation of the integrated Heihe River. The integrated Heihe River may have developed via mechanisms such as river capture and river diversion due to the uplifting of the North Qilian Shan and the Longshou Shan. The present study suggested that the formation of large inland rivers, such as the Heihe River and the Shiyang River in NW China, played an important role in the evolution of the deserts and the Loess Plateau.

Groundwater level prediction using a SOM-aided stepwise cluster inference model

Accurate groundwater level (GWL) prediction can contribute to sustaining reliable water supply to domestic, agricultural and industrial uses as well as ecological services, especially in arid and semi-arid areas. In this paper, a regional GWL modeling framework was first presented through coupling both spatial and temporal clustering techniques. Specifically, the self-organizing map (SOM) was applied to identify spatially homogeneous clusters of GWL piezometers, while GWL time series forecasting was performed through developing a stepwise cluster multisite inference model with various predictors including climate conditions, well extractions, surface runoffs, reservoir operations and GWL measurements at previous steps. The proposed modeling approach was then demonstrated by a case of an arid irrigation district in the western Hexi Corridor, northwest China. Spatial clustering analysis identified 6 regionally representative central piezometers out of 30, for which sensitivity and uncertainty analysis were carried out regarding GWL predictions. As the stepwise cluster tree provided uncertain predictions, we added an AR(1) error model to the mean prediction to forecast GWL 1 month ahead. Model performance indicators suggest that the modeling system is a useful tool to aid decision-making for informed groundwater resource management in arid areas, and would have a great potential to extend its applications to more areas or regions in the future.

The effects of a dry sand layer on groundwater recharge in extremely arid areas: field study in the western Hexi Corridor of northwestern China

Evaporation capacity is an important factor that cannot be ignored when judging whether extreme precipitation events will produce groundwater recharge. The evaporation layer’s role in groundwater recharge was evaluated using a lysimeter simulation experiment in the desert area of Dunhuang, in the western part of the Hexi Corridor in northwestern China’s Gansu Province. The annual precipitation in the study area is extremely low, averaging 38.87 mm during the 60-year study period, and daily pan evaporation amounts to 2,486 mm. Three simulated precipitation regimes (normal, 10 mm; ordinary annual maximum, 21 mm; and extreme, 31 mm) were used in the lysimeter simulation to allow monitoring of water movement and weighing to detect evaporative losses. The differences in soil-water content to a depth of 50 cm in the soil profile significantly affected rainfall infiltration during the initial stages of rainfall events. It was found that the presence of a dry 50-cm-deep sand layer was the key factor for “potential recharge” after the three rainfall events. Daily precipitation events less than 20 mm did not produce groundwater recharge because of the barrier effect created by the dry sand. Infiltration totaled 0.68 mm and penetrated to a depth below 50 cm with 31 mm of rainfall, representing potential recharge equivalent to 1.7 % of the rainfall. This suggests that only extreme precipitation events offer the possibility of recharge of groundwater in this extremely arid area.

Phlebotomine sand flies (Diptera: Psychodidae) transmitting visceral leishmaniasis and their geographical distribution in China: a review.

After the existence of phlebotomine sand flies was first reported in China in 1910, the distribution of different species and their role in the transmission of visceral leishmaniasis (VL) have been extensively studied. Up until 2008, four species have been verified as vectors of VL, namely, Phlebotomus chinensis (Ph. sichuanensis), Ph. longiductus (Ph. chinensis longiductus), Ph. wui (Ph. major wui), and Ph. alexandri.The sand fly species vary greatly depending on the natural environments in the different geographic areas where they are endemic. Ph. chinensis is euryecious and adaptable to different ecologies, and is thus distributed widely in the plain, mountainous, and Loess Plateau regions north of the Yangtze River. Ph. longiductus is mainly distributed in ancient oasis areas south of Mt. Tianshan in the Xinjiang Uygur autonomous region. Ph. wui is the predominant species in deserts with Populus diversifolia and Tamarix vegetation in Xinjiang and the western part of the Inner Mongolia autonomous region. Finally, Ph. alexandri is steroecious and found only in stony desert areas, such as at the foot of the mountains in Xinjiang and the western Hexi Corridor, in Gansu province. This review summarized the relationship between the geographic distribution pattern of the four sand fly species and their geographical landscape in order to foster research on disease distribution and sand fly control planning. Furthermore, some problems that remained to be solved about vectors of VL in China were discussed.Electronic supplementary materialThe online version of this article (doi:10.1186/s40249-016-0107-z) contains supplementary material, which is available to authorized users.

Late Quaternary aeolian sand deposition sustained by fluvial reworking and sediment supply in the Hexi Corridor — An example from northern Chinese drylands

Aeolian deposits are frequently used for palaeoenvironmental change studies. Their formation depends on an array of requirements: the supply of material suitable for aeolian transport and favorable conditions of sediment availability and wind strength. In order to infer palaeoenvironmental information from aeolian sand deposits these factors need to be carefully evaluated. We present a study from northern Chinese Hexi Corridor, based on 11 optically stimulated luminescence (OSL) dated sediment sections. These represent interchanging aeolian and alluvial deposits under gravel surfaces and aeolian sand in dune fields interrupted by interdunal flood deposits. Investigations in two subareas reveal contrasting geomorphologic and sedimentary histories: (1) sediment deposition during the Pleistocene–Holocene transition (~12ka) followed by deflation during the Holocene and (2) frequent sediment recycling revealed by a wide spectrum of ages throughout the Holocene. The late glacial sediment pulse recorded in the western Hexi Corridor is attributed to high sediment supply, generated by efficient (peri-)glacial sediment production during glacial times in the adjacent Qilian Shan (<5700m asl) and a moisture increase inducing the reworking of those (glacio-)fluvial deposits during the Pleistocene–Holocene transition. The absence of a powerful reworking agent preserved these late glacial deposits in the western Hexi Corridor in contrast to moister eastern parts where Holocene sediment reworking prevailed.Geomorphological and hydrological preconditions of the subareas are discussed and reveal the controlling influence of fluvial processes on sand supply for the aeolian system. While a perennial drainage is missing in the drier western part, the Hei River drainage is fed by higher monsoonal precipitation in the central Hexi Corridor. It maintains a sediment recycling system and has ensured a sufficient sediment supply throughout the Holocene. The study promotes closer consideration of the fluvial influence on aeolian archives in palaeoenvironmental studies from central Asian and other drylands.

The Landscape of China’s Participation in the Bronze Age Eurasian Network

In the last decade, much has been learned about the network of interactions in Bronze Age Eurasia, and the importance of the steppe pastoralists in the creation of this network. However, the mechanisms that enabled societies in ancient China (both those bordering on and distant from the steppe) to participate in the Bronze Age Eurasian arena are still poorly understood. Based on the latest archaeological discoveries in China, this article focuses on the participation of four regions of ancient China: the Ejin River Transfer Zone (ERTZ); the western Hexi corridor; central Inner Mongolia; and the middle Yellow River valley. The article analyzes all significant innovations, materials, and technologies transmitted via the Eurasian network and adopted in ancient China, with an emphasis on metallurgy and the variations in the mechanism of its adoption across different societies during the Bronze Age. The introduction of metallurgy into the ERTZ was an economic imperative, although it was profoundly affected by the political landscape in the middle Yellow River valley. Through analysis and comparison, this paper argues that the participation of different societies of ancient China in the Bronze Age Eurasian network can best be understood in the local and regional contexts, which were deeply embedded in their natural and cultural landscapes, rather than as the result of the pull from the steppe pastoralists alone.

Late Quaternary slip rates of the thrust faults in western Hexi Corridor (Northern Qilian Shan, China) and their implications for northeastward growth of the Tibetan Plateau

We determined vertical components of slip rates of 0.22 +/- 0.03 mm a(-1) for the Jiayuguan fault and 0.11 +/- 0.03 mm a(-1) for the Jintanan Shan fault, which lie along the northeastern edge of the Tibetan Plateau and in the western Hexi Corridor (Northern Qilian Shan, China). We used structural investigations, air-photo imagery analysis, topographic profiling, optically stimulated luminescence (OSL) dating, and Be-10 exposure dating. To quantify the slip rates along the faults, we identified and surveyed the well-preserved fault scarps, and we sampled quartz-rich pebbles and cobbles on fan surfaces and within similar to 2-m-deep pits to determine surface exposure ages and pre-depositional inheritance. Our slip rates pertain to the past similar to 115 ka. They are consistent with previous geological and GPS constraints that suggest that NNE-SSW shortening across the northeastern Tibetan Plateau has been distributed onto several active faults and that shortening is partitioned into low slip rates of <= 1 mm a(-1) on each fault. We infer that the decreasing slip rate from 95 degrees E eastward to the eastern end of the Altyn Tagh fault and the low slip rates of these thrust faults are related. The total shortening in the direction parallel to the Altyn Tagh fault in the Yumen Basin of 0.90-1.43 mm a(-1) attests that left-lateral strike slip at the eastern end of the fault has indeed been absorbed by deformation within the Yumen Basin. We infer that the Tibetan Plateau continues to grow northeastward by thrust faulting at low rates and by folding on the northeastern edge of the Hexi Corridor basin.

Evidence of Miocene crustal shortening in the North Qilian Shan from Cenozoic stratigraphy of the western Hexi Corridor, Gansu Province, China

New sedimentologic, stratigraphie, and compositional data from the Paleogene-Neogene stratigraphie succession exposed in the northwest Hexi Corridor and within the North Qilian Shan, provide evidence to suggest that crustal shortening in the North Qilian Shan fold-thrust belt initiated during die Miocene. The section is composed of four lithostratigraphic units: Oligocene-Miocene fine- to coarse-grained Unit 1, Miocene conglomeratic Unit 2, and Pliocene-Pleistocene conglomeratic Units 3 and 4. Unit 3 lies in angular unconformity over both Units 1 and 2, and Unit 4 contains a progressive unconformity. The onset of conglomerate deposition at the base of Unit 2 suggests an increase in depositional energy, which we interpret as me result of proximal orogenesis in the North Qilian Shan fold and tiirust belt. Supporting evidence includes the appearance of strongly northeast-trending paleocurrents, indicat-ing paleoflow away from the Qilian Shan, clast lidiologies that match sources in the North Qilian Shan, and sandstone with detrital framework modes that indicate a recycled orogen source. In contrast, Unit 1 contains paleocurrent indicators that are variable but generally trend northward and sandstone and clast compositions which are more diagnostic of a continental block source. Detrital zircon age determinations from Unit 1 are also not consistent with a source in the North Qilian Shan; rather, they suggest a provenance in hinterland regions within the South Qilian Shan and North Qaidam terranes. In sum, these results are all consistent with initiation of proximal uplift of the North Qilian Shan during deposition of the gradational transition from Unit 1 to Unit 2, demonstrating shortening in the Qilian Shan before die late Miocene. This comprehensive study tightens our understanding of when far-field stress related to the India-Eurasia continent-continent collision reached the northeastern edge of the Tibetan Plateau.

On the faults of western Hexi Corridor and its nearby regions, northwestern China: Thrust faults and strike-slip faults of Late Cenozoic

The structural analysis based on the explanation of seismic profiles indicates that a lot of thrust faults and strike-slip faults of Late Cenozoic occur in western Hexi Corridor and its nearby regions. They can be divided into two types. One is thrust faults dipping southwards and extending NW wards, which was mainly correlated with the thrusting of northern Qilianshan and located at the NE margin of Qilianshan and the southwestern Hexi Corridor, the other is thrust faults and strike-slip faults that were related to the strike-slipping of Altun fault and located mainly at the regions of Hongliuxia, Kuantaishan, and Helishan that are close to the Altun fault. All these faults, which were related to the remote effects of collision between the two continents of India and Tibet during the Late Eocene and later, started to develop since the Late Tertiary and presented the features of violent thrust or strike-slip movement in Quaternary. Many of them are still active up to now and thus belong to the active faults that are the potential inducement of earthquakes in the Hexi Corridor. Moreover, a lot of intense structural deformation and many morphology phenomena such as tectonic terrace and river offset were formed under the control of these faults in Quaternary.