胡梦珺,
李娜娜,
张亚云,
王佳,
李春艳
西北师范大学地理与环境科学学院, 甘肃 兰州 730070

基金项目: 国家自然科学基金项目（批准号：41171018、40761026和41161036）资助


详细信息

作者简介: 胡梦珺, 女, 46岁, 副教授, 环境演变与元素地球化学研究, E-mail:lele200466@163.com

中图分类号: P512.2;P941.78

收稿日期:2020-01-22
修回日期:2020-05-27
刊出日期:2020-09-30

Variation characteristics of chromaticity parameters and environmental evolution of aeolian sand-paleosol sequence in Qinghai Lake during the past 32 ka

Hu Mengjun,
Li Nana,
Zhang Yayun,
Wang Jia,
Li Chunyan
College of Geography and Environmental Science, Northwest Normal University, Lanzhou 730070, Gansu



MSC: P512.2;P941.78

--> Received Date: 22 January 2020
Revised Date: 27 May 2020
Publish Date: 30 September 2020


摘要
摘要:文章以厚度10 m的青海湖地区大水溏剖面（QDST）为研究对象，利用CM-5分光测色计测得232个土壤样品的色度参数（a^*、b^*、L^*），分析了土壤色度变化特征，辅以SC/D（粒度敏感指标）、磁化率、Rb/Sr、CO₃^2-等指标并结合OSL测年，恢复了近32 ka以来青海湖地区的环境演变过程。结果表明：1）a^*、b^*自剖面底部向上呈波动式先减小后增大再减小态势，均大致呈下层古土壤高于上层古风成砂，高值示温湿气候；L^*自剖面底部向上先急剧减小后微升，且大致呈下层古土壤略低于上层古风成砂，高值示冷干气候；2）a^*、b^*与磁化率、L^*与Rb/Sr均呈显著负相关，L^*与碳酸盐呈显著正相关且与SC/D值变化态势一致；3）剖面CO₃^2-均值达8.74%，且CO₃^2-峰区与L^*高值区吻合度高，对L^*的贡献较大，L^*可反映不同沉积层形成时期的降水量；4）近32 ka以来青海湖地区经历了温湿→冷润→温润→凉干→温润→温湿→凉干→温凉→冷干的环境演变过程，进一步可划分为：a^*较高、b^*最高、气候整体较为温湿的末次冰期间冰阶（32.0~23.3 ka）；a^*和b^*低、L^*较高、气候整体偏冷润的末次冰盛期（23.3~15.2 ka）；a^*和b^*较低、L^*最低、气候整体温凉偏湿的末次冰消期（15.2~10.4 ka）以及a^*和b^*整体较高、L^*整体较低、冷暖波动频繁的全新世（10.4 ka至今）。
关键词: 土壤色度/
青海湖/
古风成砂-古土壤/
环境演变

Abstract:In order to explore the significance of the sedimentary environment recorded by the soil chroma, to make chromaticity studies more useful to Quaternary environmental researches, and also to enrich the available surrogate indexes of paleoenvironmental changes in northeastern Qinghai-Tibetan Plateau, this study investigate an exposed profile (Dashuitang section) in an aeolian sand dune that lies in the east lake margin of Qinghai Lake. The Dashuitang section (QDST:36°49.701'N, 100°51.55 7'E; 3450 m above sea level) is 10 m thick. The sampling strategy was based on the observed morphological characteristics of the profile, and the samples were taken at 10 cm, 5 cm, 2 cm and 5 cm intervals for the 0.3~3.7 m, 3.7~5.3 m, 5.3~7.6 m and 7.6~10.0 m sublayers, respectively. A total of 232 regular soil samples were collected. Meanwhile, 10 samples were collected from the top and bottom of each sublayer, namely the transition portions between soil layer and aeolian sand layer were dated by OSL dating. The stratigraphic age since 31.9±1.3 ka was covered by the 10 m profile. After sample pretreatment, three colorimetric parameters (a^*, b^*, L^*) were measured by CM-5 spectrophotometer, the grain size was measured by Malvern 2000 laser particle size analyzer, the element was measured by Philips Panalytical Magix PW 2403 X-ray fluorescence spectrometer, and the magnetic susceptibility was measured by Bartington MS-2 magnetic susceptibility meter. Based on the analysis of the characteristics of soil chromaticity changes, supplemented by magnetization, SC/D, CO₃^2-, Rb/Sr and other indicators and combined with OSL dating ages, the environmental changes of Qinghai Lake area since nearly 32 ka was restored. The results show that: (1) From the bottom of profile upwards, a^* and b^* firstly decreased then increased and finally decreased again. They all show that the values of paleosol layer are higher than the aeolian sand layer, and the high value indicats a warm and humid climate. From the bottom of profile upwards, L^* decreased sharply and then increased slightly, and show that the value in paleosol layer is slightly lower than the aeolian sand layer, and the high value show a cold and dry climate. (2) a^*, b^* and magnetic susceptibility, L^* and Rb/Sr were negative correlation. L^* was positively correlated with carbonate, it has the same change trend with the value of SC/D. (3) The CO₃^2- mean value of the profile reaches 8.74%, the CO₃^2- varied in accordence with the L^*value. It showed that CO₃^2- influenced L^* variations and then reflect the precipitation amounts. (4) Qinghai Lake region has experienced several times of warm-wet and cold-dry climate alternations during the past 32 ka. It can be further divided into 4 time periods:Firstly, the climate was warmer and wetter during the Interstadial of the Last Glacial (32.0~23.3 ka). Secondly, the Last Glacial Maximum (23.3~15.2 ka) climate was generally cool and moist. Thirdly, the Last Deglaciation (15.2~10.4 ka) was cool and humid. Finally, the Holocene (10.4 ka to date) climate varied frequently between warm and cold stages.
Key words:soil color/
Qinghai Lake/
aeolian sand-paleosol/
environmental evolution



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