Preliminary Studies of Speleothem in Central Asia

The Westerlies is important in linking the Northem high latitude, North Atlantic and East Asian monsoon. The location and intensity of the Westerly jet can not only control the climate of central Asia （including northwest arid China）, but also significantly influence the climate of the East Asian monsoon region. However, it remains unclear of the variability of the Westerlies in Asia on multiple timeseales and their global linkage.

Aeolian dust dynamics in the Fergana Valley, Central Asia, since -30 ka inferred from loess deposits

Knowledge of the interactions among atmospheric dynamics,dust emissions and climate system is essential to understand the physical mechanisms for the dust lifecycle,their role in loess formation as well as the predictions of future dust concentration.However,these issues still remain relatively poorly known in Central Asia(CA).The extensive loess deposits on the CA pediments provide a promising archive to explore atmospheric dust dynamics and climatic conditions in the past and their association with loess formation.This study investigates the granulometric and magnetic properties of a loess section(named Osh section)in the Fergana Valley,which provides a sensitive record of atmospheric dust dynamics since 30 ka based on radiometric(AMS ^(14)C)dating.The frequency-dependent magnetic susceptibility(χfd)and the mean grain size are used to reconstruct the broadscale effective moisture and summer atmospheric dynamics pattern in CA,respectively.The results show that the precession forcing exerts a huge influence on the wind-regime variabilities in CA,but with different physical processes under the impact of the Northern Hemisphere ice sheet(NHIS)before and after 15 ka.The origin of the sedimentation rate variations in the Osh loess is also linked to the NHIS-modulated changes of the atmospheric circulation patterns.Either the strengthened westerlies or the increased surface roughness from higher vegetation cover in loess-deposition areas have significantly accelerated the loess accumulation.As a result,these complicated influence factors of sedimentation rate change in the Osh loess section,especially during the Holocene epoch,may hamper accessibility of the authentic dust emission flux and atmospheric dust concentration in CA.

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

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

Spatial distribution and risk assessments of mercury in topsoils of Central Asia

Central Asia is one of the largest arid areas on earth,yet little is known about the concentration levels and risks of mercury(Hg)in the soils of this region.In this study,extensive sampling of topsoils(0-10 cm)from representative landscapes was carried out over Central Asia(i.e.,Tajikistan,Uzbekistan,and Kyrgyzstan).The total mercury(THg)concentrations in topsoils varied widely from 1.6 to 908.0 ng/g,with high values observed in samples collected in the capital cities and urban areas.Topsoil THg concentrations among different landscapes showed a decreasing order of urban(79.8±184.0 ng/g)>woodland(27.3±28.9 ng/g)>grassland(20.6±15.9 ng/g)>farmland(18.3±9.5 ng/g)>desert(12.3±8.0 ng/g).High THg concentrations were found in the capital cities/urban clusters,followed by a gradual decrease towards the peripheries.THg concentrations were found to be negatively correlated with the distance from the sampling sites to their nearest cities,indicating that anthropogenic emissions significantly influenced the spatial distribution of topsoil Hg.A significant correlation between THg concentrations and topsoil total organic carbon(TOC)contents was also observed,suggesting that TOC played an essential role in the spatial distribution of topsoil Hg.The assessments of pollution and potential ecological risk suggested that topsoils in highly densely-populated areas were contaminated by Hg and had higher degrees of potential ecological risks.The health risk assessment results showed that the exposure risk of topsoil Hg to children was higher than that to adults.Fortunately,there was no unacceptable human health risk of topsoil Hg.This study clarified the spatial distribution and risks of Hg in the Central Asian topsoils,offering new insight into the risk prevention and control of soil Hg.

Petrology of metamorphic rocks from the Atbashy complex,Southern Tien-Shan,Kyrgyzstan

The high-to ultrahigh-pressure metamorphic rocks of the Atbashy complex were petrologically investigated. The eclogites of the Choloktor Formation show a prograde evolution from epidote-blueschist facies(P = 17-21 kbar and T = 450-515 ℃) to peak eclogite-UHP conditions(P = 26-29 kbar and T = 545-615 ℃) with a subsequent epidote-amphibolite and greenschist facies overprint. The micaschists of the Choloktor Formation also show a clockwise P-T path from blueschist/epidote-blueschist facies conditions through peak eclogite facies conditions(P = 21-23 kbar and T = 530-580 ℃) to retrograde epidote-amphibolite and greenschist facies stages. A comparison of the P-T paths in the eclogites and mica-schists of Choloktor Formation reveal that they may have shared their P-T history from peak to retrograde stages. The mica-schists of the Atbashy Formation record peak metamorphism of P = 10-12 kbar and T = 515-565 ℃, which indicates that the highest grade of regional metamorphism in the Atbashy Ridge was epidote-amphibolite facies.The newly obtained P-T conditions for the mica-schists of Choloktor Formation indicate that sheets of sedimentary rocks were brought to great depths along the subduction zone and they metamorphosed under eclogite facies HP conditions. The eclogite blocks were amalgamated with mica-schists of Choloktor Formation in the eclogite facies HP conditions and together they experienced isothermal decompression to ～40 km. During this path, the eclogites and mica-schists of Choloktor Formation docked with mica-schists of Atbashy Formation at 10-12 kbar and 515-565 ℃, and from this depth(～40 km) the whole sequence was exhumed together. These new results improve our understanding of high-pressure metamorphism in subduction-related accretionary prism zones and the exhumation processes of deeply-seated rocks in the Atbashy HP-UHP complex.

超级大旱与史前丝绸之路上的文化交流

中亚干旱区是丝绸之路的核心区,也是史前人类扩散和东西方文化交流的重要通道.该区气候干旱,植被和生态群落受制于水文因素.由于缺乏精确年代控制的高分辨率古气候记录,中亚地区全新世水文变化及极端干旱事件在史前人口迁移和跨欧亚大陆文化交流中扮演的角色还不清楚.本文基于来自吉尔吉斯斯坦的石笋多指标记录,重建了中亚干旱区目前年代最精确(测年误差~6‰)、分辨率最高(~3年)、涵盖中晚全新世的降水变化序列.结果显示在5820~5180 a BP期间,该区存在一次持续时间为640年的超级干旱事件,主要受西风带北移的影响.这次干旱事件对中亚史前文化的发展产生了重要影响,很可能阻碍了史前东西方文化沿中亚绿洲路线上的相向扩散,使得最早的跨欧亚大陆文化交流在5000~4000 a BP沿着北方草原路线开展.随着大干旱后降水的逐渐增加和生态环境的恢复,中亚绿洲和河谷中增加的定居人口促进了不同绿洲之间的相互联系,进一步在4000~3000 a BP开辟了跨大陆文化交流的史前丝绸之路,为历史时期丝绸之路的最终开通奠定了基础.