地球环境研究所在中亚黄土研究中取得新进展

  黄土在中亚地区分布广泛,其沉积连续稳定,是中亚干旱区古气候重建的重要载体。但到目前为止,中亚黄土仍然缺乏深入的研究,对黄土形成的驱动机制和气候条件仍认识不足。 

  最近,中国科学院地球环境研究所一带一路国际环境变化研究中心中亚黄土研究组联合德国马普化学研究所大陆古环境研究组,对中亚东部的伊犁盆地内一处厚约20米的黄土剖面进行了磁学和沉积学指标的分析,充分阐明了黄土粉尘堆积的环境动力机制。研究发现,黄土磁化率增强的成壤作用模式并不能解释该剖面磁化率的变化,磁化率值主要受到外来磁性矿物的影响,因而可能主要受控于风力强度的变化。为了进一步研究黄土粉尘在时间上的搬运模式,研究者使用层级贝叶斯模型对黄土粒度分布进行了端元分离,恢复了中亚东部地区古粉尘的搬运动力。结果显示,该剖面黄土由三个端元组成:EM1 (中值粒径为47.5 µm)EM2 (33.6 µm)EM3 (18.9 µm)。不同的端元代表着不同的空气动力环境,EM1EM2代表着风暴过程中短距离悬浮搬运的近源粗颗粒组分,而EM3代表着非风暴过程中的细颗粒组分,以连续的背景粉尘形式出现。进一步选取了EM1作为敏感的风强指标,将其同黄土高原靖远剖面粒度指标进行对比(图1),同时结合对现代气候和全新世古气候数据的评价和分析,认为西伯利亚高压系统对风动力环境起着主导作用。这对进一步认识黄土指标的古气候意义和中亚粉尘物源示踪等方面具有重要意义。基于伊犁黄土粒度、矿物学记录发现了末次冰期以来的六次北大西洋Heinrich冷事件,基于研究区的高纬度地理优势以及西风南北摆动的特点,重新认识了北大西洋千年尺度事件的传播机制,认为这些千年尺度的气候信号亦可通过高纬度的西伯利亚高压来传递,为北半球高纬与黄土高原气候的遥相关提供了新证据。该项研究成果目前已发表在国际期刊Climate of the Past (Li et al., 2018a)Journal of Earth Science (Song et al., 2018a)上。 

   

  1 粒度EM1组分变化与哈萨克斯坦黄土和靖远粒度以及天山冰进和格陵兰冰心记录的对比 

    

  中亚黄土组在宋友桂研究员带领下近些年来一直致力于中亚黄土的研究,对我国新疆、哈萨克斯坦、吉尔吉斯斯坦、塔吉克斯坦等地分布的黄土开展了大量的野外调查和研究工作,系统调查了新疆地区黄土的时空分布特征和形成规律(Li et al., 2015; Song et al., 2014; 李云等, 2014),联合中国、美国和德国科学家开展伊犁盆地、吉尔吉斯和哈萨克斯坦黄土的年代学研究(Kang et al., 2015; Song et al., 2015; Song et al., 2012; Song et al., 2018b; Yang et al., 2014),探索了中亚黄土粒度(Li et al., 2016b; Song et al., 2017)、磁化率(Song et al., 2018a; Zeng et al., 2018)化学元素(Chen et al., 2017; Li et al., 2016a)、矿物(Li et al., 2018b; 宋友桂等, 2014)代用指标的古气候意义及受控因素。这些基础研究为进一步探讨丝路带中亚干旱区的环境变化历史与规律提供了重要依据。 

    

  中亚黄土研究小组近五年发表的有关中亚黄土论文主要有: 

  1.       Chen, X.L., Song, Y.G., Li, J.C., Fang, H., Li, Z.Z., Liu, X.M., Li, Y., Orozbaev, R., 2017. Size-differentiated REE characteristics and environmental significance of aeolian sediments in the Ili Basin of Xinjiang, NW China. J Asian Earth Sci 143, 30-38. 

  2.       Kang, S., Wang, X., Lu, Y., Liu, W., Song, Y., Wang, N., 2015. A high-resolution quartz OSL chronology of the Talede loess over the past 30 ka and its implications for dust accumulation in the Ili Basin, Central Asia. Quat Geochronol 30, 181-187. 

  3.       Li, Y., Song, Y.G., Chen, X.L., Li, J.C., Mamadjanov, Y., Aminov, J., 2016a. Geochemical composition of Tajikistan loess and its provenance implications. Palaeogeog Palaeoclimatol Palaeoecol 446, 186-194. 

  4.       Li, Y., Song, Y.G., Fitzsimmons, K.E., Chang, H., Orozbaev, R., Li, X., 2018a. Eolian dust dispersal patterns since the last glacial period in eastern Central Asia: insights from a loess-paleosol sequence in the Ili Basin. Clim Past 14, 271-286. . 

  5.       Li, Y., Song, Y.G., Lai, Z.P., Han, L., An, Z.S., 2016b. Rapid and cyclic dust accumulation during MIS 2 in Central Asia inferred from loess OSL dating and grain-size analysis. Sci. Rep. 6, e32365: 1-6. 

  6.       Li, Y., Song, Y.G., Yan, L.B., Chen, T., An, Z.S., 2015. Timing and Spatial Distribution of Loess in Xinjiang, NW China. PloS ONE 10, e0125492, doi:0125410.0121371/journal.pone.0125492. 

  7.       Li, Y., Song, Y.G., Zeng, M.X., Lin, W.W., Orozbaev, R., Cheng, L.Q., Chen, X., Halmurat, T., 2018b. Evaluating the paleoclimatic significance of clay mineral records from a late Pleistocene loess-paleosol section of the Ili Basin, Central Asia. Quat Res online, 1-14. https://doi.org/10.1017/qua.2017.1058. 

  8.       Song, Y., Li, Y., Wang, Q., Dong, H., Zhang, Z., Orozbaev, R., 2018c. Effect of chemical pretreatments on magnetic susceptibility of loess from Central Asia and the Chinese Loess Plateau. Rsc Adv 8, 11087-11094. 

  9.       Song, Y.G., Chen, X.L., Qian, L.B., Li, C.X., Li, Y., Li, X.X., Chang, H., An, Z.S., 2014. Distribution and composition of loess sediments in the Ili Basin, Central Asia. Quat Int 334-335, 61-73. 

  10.    Song, Y.G., Lai, Z.P., Li, Y., Chen, T., Wang, Y.X., 2015. Comparison between luminescence and radiocarbon dating of late Quaternary loess from the Ili Basin in Central Asia. Quat Geochronol 30, 405-410. 

  11.    Song, Y.G., Li, C.X., Zhao, J.D., Chen, P., Zeng, M., 2012. A combined luminescence and radiocarbon dating study of the Ili loess, Central Asia. Quat Geochronol 10, 2-7. 

  12.    Song, Y.G., Li, Y., Li, Y., An, Z., Cheng, L., Sun, H., Rustam, O., 2017. North Atlantic Abrupt Climate Signals during the Last Glacial Period in Central Asia: Evidences from Aeolian Loess Sediments. Acta Geol Sin-Engl 91, 1135-1136. 

  13.    Song, Y.G., Luo, D., Du, J.H., Kang, S.G., Cheng, P., Fu, C.F., Guo, X.H., 2018a. Radiometric dating of late Quaternary loess in the northern piedmont of South Tianshan Mountains: Implications for reliable dating. Geol J online, 1-10. https://doi.org/10.1002/gj.3129. 

  14.    Song, Y.G., Zeng, M.X., Chen, X.L., Li, Y., Chang, H., An, Z.S., Guo, X.H., 2018c. Abrupt climatic events recorded by the Ili loess during the last glaciation in Central Asia: Evidence from grain-size and minerals. J Asian Earth Sci 155, 58-67. 

  15.    Yang, S.L., Forman, S.L., Song, Y.G., Pierson, J., Mazzocco, J., Li, X.X., Shi, Z.T., Fang, X.M., 2014. Evaluating OSL-SAR protocols for dating quartz grains from the loess in Ili Basin, Central Asia. Quat Geochronol 20, 78-88. 

  16.    Zeng, M.X., Song, Y.G., Li, Y., Fu, C.F., Qiang, X.K., Chang, H., Zhu, L.D., Zhang, Z.P., Cheng, L.Q., 2018. The relationship between environmental factors and magnetic susceptibility in the Ili loess, Tianshan Mountains, Central Asia. Geol J online, 1-13. https://doi.org/10.1002/gj.3182. 

  17.    李云, 宋友桂, 晏利斌, 陈涛, 2014. 新疆塔城黄土的形成. 地球环境学报 5, 127-134. 

  18.    宋友桂, 李越, 陈秀玲, 李云, 2014. 塔吉克斯坦黄土矿物与稀土元素组成特征. 地球环境学报 5, 145-154. 

    


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中国科学院地球环境研究所

研究所从以黄土和东亚季风变迁为主的研究,发展为以大陆环境为特色的多元化综合研究。

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