【作者】 柏松；

【导师】 黄成敏；

【作者基本信息】 四川大学 ， 环境科学， 2005， 硕士

【摘要】 土壤是地质历史时期环境演变的重要信息库之一。它记录了区域、大陆与全球的新构造运动、古气候、古地理、古生态等多方面的变化过程和重大的环境地质事件。因此,研究古土壤发生与形成特征和过程,对于重建过去环境,预测未来全球环境变化趋势以及土壤响应具有重要的科学价值。 本文选取岷江上游干旱河谷较场黄土剖面进行高精度、高密度采样,运用¹⁴C测年,分析黄土剖面有机碳稳定同位素、碳酸钙含量、磁化率、全铁、铁游离度、粒度等特征。研究结果如下: （1） 岷江上游干旱河谷黄土颗粒组成等性质具有不均一性的特点,土壤碳酸钙、pH值、盐基总量等在剖面中的变化没有明显的规律性。有机质表聚现象明显,有机质在剖面中的分解十分缓慢,碳酸钙有一定的淀积作用。 （2） 相对而言,有机碳δ¹³C侧重反映环境温度的变化,碳酸钙指标侧重反映大气降水量的变化。根据有机碳稳定同位素和磁化率对比曲线,较场黄土剖面（Sm03剖面）与冰芯记录和深海氧同位素相比具有很好的对比性,可能记录了21KaB.P.以来全球气候突变事件,如两次H事件和新仙女木（YD）事件及其全新世大暖期。 （3） 末次盛冰期以来岷江上游干旱河谷气候以暖干为主,且对全球气候变化趋势有明显的响应。在早全新世,气候暖湿,气温逐渐下降。中全新世,气候温暖湿润,且变化较平缓,处于全新世最好时期;中全新世后期,气候变干冷,且波动较大,晚全新世,气候迅速恶化,向更干冷方向演化。更多还原

【Abstract】 Soil are traditionally regarded as good records of paleo-climatic changes, provided insights into past long-term climatic changes, as a result, soil are widely used to indicate paleo-clmatic conditions and paleo-environmental evolution. With the development of paleo-climate and paleo-environment to higher resolution, research of soil provides important evidences for the global climatic evolution . abrupt oscillations and climatic change regularities. A better understanding of soil process is invaluable in predicting the future impacts of global environmental change on terrestrial ecosystems.Loess sections located in dry valley of the Minjiang River. These section are of ideal for the study on the climatic change in past 21ka of Minjiang River area. In order to reveal comprehensively the paleo-climate evolution of Minjiang River area, high precision sampling was done in Jiaochang section. Samples of stable carbon isotope were tested and a synthesis analysis was made combined to ¹⁴C dating , magnetic susceptibility（MS）, carbonate（CaCO₃）, Fet, Fed/Fet and grain size.The pedogenetic properties of loess were used to rebuild the paleo-climate in dry valley of the Minjiang River. The main results andconclusion are as follow:1. CaCCh and pH change irregularly in profile. The content of organic carbon of epicedian is higher than 20g/kg and organic carbon in profile decompose very slowly.2. These sections had good consistency compared to ice core records and deep-sea oxygen records, at the same time, they had been an important part of global climate changes. In addition, it is possible that the Jiaochang loess also recorded several typical climatic changes, including Yonger Dryas event> two Heinrich Events and so on, which can be compared with those of other sections.3. The research shows that the climate of this region during the period of the last glacial maximum （LGM） in research areas was mainly warm and dry. At the same time, it also responded the trend of the global climate change. During early Holocene, the climate was warmed and humid, experiencing a decline in temperature; During the early period of Middle Holocene, the climate was very warm and humid with small climatic fluctuations; While during the late period, the climate has relatively intense fluctuation; During late Holocene the climate came to dry and cold. In general, the climatic evolutional process was from warm-dry climate to cold-dry one.4. Based on the territorial vegetation evolution history inferred from the organic stable isotope variations, the territorial climatic changes since the last 21ka had experienced a series of stages. After 4.45ka, climate of Minjiang River area behaved unstably and cyclically, the temperature decrease step by step from middle Holocene to now and at present, aridity is still continuing.更多还原