地化学元素揭示的中晚全新世以来玛曲高原的成壤环境演变

发布时间：2018-04-26 13:48

本文选题：地化学元素 + 土壤典型性性质　；参考：《西北师范大学》2015年硕士论文

【摘要】：黄土-古土壤-风成砂序列是第四纪以来地表特定气候条件和沉积环境相互作用的产物,而土壤发生的实质是各种元素的迁移和组合,因此,黄土-古土壤-古风成砂序列中化学元素含量特征及其古气候指标的变化可以直接指示成壤环境的变化。本文从元素地球化学和土壤典型性性质的角度来揭示玛曲高原中晚全新世以来的成壤环境演变。本研究选取了玛曲高原一个典型的中晚全新世风成沉积OL剖面,进行了元素含量、有机质、pH值、可溶性盐分等指标的室内测定分析,探讨了各指标在剖面中的分布特征和变化规律及对成壤环境的指示作用。主要实验结果为:CaO、Na2O、SiO2为剖面主要迁移元素,其迁移能力顺序是:CaNaSi;MgO、K2O、Fe2O3则在古土壤OL3中相对富集。微量元素Ga、As、Nb、Cu、Pb、Y、Ni、Nd、Zn、V、Ce、Cl、Ba、Cr、Rb、Zr、Mn等微量元素含量均表现为古土壤层高于黄土层,能很好地指示生物风化成壤作用和淋溶作用;古气候指标可以很好地反映成壤环境的冷暖干湿程度,硅铝比、钠钾比、退碱系数、Cu/Mn、Sr/Cu、Sr/Ba在黄土层中的比值高于古土壤层,而古土壤层中化学风化指标CIA、残积系数、Rb/Sr高于黄土层和古风成砂层;从A-CN-K三角图风化趋势可看出玛曲高原处于脱Ca和Na的初级风化阶段,沉积环境较冷干,指示了玛曲高原高寒的气候特征;OL剖面古土壤层中较高的有机质含量指示了古土壤层发育时期气候温湿,成壤作用强,黄土层和古风成砂层反之;pH值和可溶性盐分含量指示了OL剖面古土壤发育时期降水较黄土层和古风成砂层丰富。通过对OL剖面地化学元素和土壤典型性性质的分析讨论,并辅以14C定年技术,揭示了玛曲高原近4.6 ka以来,在受西风环流、南亚季风和高原季风的控制下,气候发生了冷干-凉润-温湿-凉干的冷暖旋回,结合气候特征将玛曲高原中晚全新世以来的成壤环境划分为4个阶段:4.6 ka B.P.以前的气候冷干、风沙活动强烈期,4.6~4.3 ka B.P.的气候凉润、风沙活动较弱期,4.3~0.3 ka B.P.的气候温湿、固结成壤期和0.3 ka B.P.至今的气候凉干、风沙活动增强期。通过对比发现,OL剖面记录的成壤环境和风沙活动与青藏高原的湖泊沉积物、青海湖QDST剖面、若尔盖孢粉、湖泊水位变化记录的环境信息大体吻合,较完整地揭示了近4.6 ka以来玛曲高原的成壤环境演变。同时与格陵兰冰芯、中国历史气候冷事件进一步对比,说明了中晚全新世以来玛曲高原的成壤环境演变与全球气候变化具有明显的同步性且对全球气候变化响应灵敏。
[Abstract]:The loess paleosol aeolian sand sequence is the product of the interaction between the surface specific climatic conditions and the sedimentary environment since the Quaternary, and the essence of the soil occurrence is the migration and combination of various elements. The change of chemical element content and paleoclimate index in the sequence of loess paleosol and paleo-aeolian sand can directly indicate the change of earth-forming environment. In this paper, the evolution of earth-forming environment in the Maqu Plateau since the Middle-Late Holocene is revealed from the point of view of element geochemistry and soil typicality. In this study, a typical middle and late Holocene eolian deposition OL profile in Maqu Plateau was selected, and the contents of elements, pH value of organic matter and soluble salt were measured and analyzed in laboratory. The distribution and variation law of each index in the profile and its indicative effect on the soil forming environment were discussed. The main results are as follows: (1) the main migration elements in the profile are: (1) CaO _ (2) O _ (2) O _ (2) O _ (2) O _ (2) O _ (2) O _ (2) O ~ (2 +), and the order of migration ability is: (1) CaNaSi@@ The contents of trace elements GaAsS, NbCU, PbCU, NiNdZN, ZNdZN, CZC, CZC, RbZR, mn, and so on, all show that the paleosol layer is higher than the loess layer, which can well indicate the weathering and leaching of organisms, and the paleoclimate index can well reflect the degree of cold and warm dryness, the ratio of Si to Al, the ratio of Si and Al, and so on in the soil forming environment, the ratio of Si to Al, the ratio of Si to Al, Compared with paleosol, the ratio of Cu / MnN / Sr / Cu / Sr / Ba in the loess layer is higher than that in the paleosol layer, while the chemical weathering index CIA and the residual coefficient in the paleosol layer are higher than those in the loess layer and the paleo-aeolian sand layer. From the weathering trend of A-CN-K triangulation, it can be seen that the Maqu Plateau is in the primary weathering stage of de-Ca and Na, and the sedimentary environment is relatively cold and dry. Indicating the climatic characteristics of alpine in Maqu Plateau, the higher content of organic matter in paleosol layer indicates that the climate of paleosol is warm and wet during the development of paleosol, and the role of forming soil is strong. On the contrary, pH value and soluble salt content indicate that the precipitation in the paleosol in OL section is more abundant than that in the loess layer and paleo-aeolian sand layer. Through the analysis and discussion of geochemical elements and soil typic properties in OL profile, and with the help of 14C dating technique, it is revealed that the Maqu Plateau has been under the control of westerly circulation, South Asian monsoon and plateau monsoon since 4.6 ka. There is a cold and warm cycle between cold and dry, cool and moist, warm and wet, and cool and dry. According to the climatic characteristics, the earth-forming environment of the Maqu Plateau since the Middle-Late Holocene is divided into four stages: 4.6 ka B.P. The previous climate was cold and dry, and the wind-sand activity was strong in the period of 4.6C 4.3 ka B.P. The climate is cool and moist, and the wind-sand activity is weaker than 4.30.3ka B.P. Climate temperature and humidity, consolidation and soil forming period and 0.3 ka B.P. Up to now, the climate is cool and dry, and the activity of wind and sand is increasing. It is found that the soil forming environment and the aeolian activities recorded in the Lianliu profile are basically consistent with the environmental information recorded in the lake sediments of the Qinghai-Tibet Plateau, the QDST section of Qinghai Lake, the spores of Zoige, and the changes of water level of the lakes. The evolution of the earth-forming environment in the Maqu Plateau since 4.6 ka has been fully revealed. At the same time, compared with Greenland ice core and historical climate cold events in China, it shows that the evolution of earth-forming environment in Maqu Plateau since the Middle-Late Holocene has obvious synchronism with global climate change and is sensitive to global climate change.
【学位授予单位】：西北师范大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P532;P534.632

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