重庆青木关石笋记录的全新世气候变化

发布时间：2018-05-12 03:34

本文选题：石笋 + 碳氧稳定同位素　；参考：《西南大学》2015年硕士论文

【摘要】：全新世时期全球气候变化,是国际全球气候变化研究计划的最为重要的内容之一,重建全新世高分辨率的气候记录,对于认识气候系统变化规律、应对当前面临的严峻气候和环境形势、预测未来气候变化趋势有着至关重要的意义。目前全新世气候演变研究逐渐深入,取得了一些成果,为进一步研究全新世气候变化奠定了基础,但是全新世时期的气候变化驱动机制依然存在争议。洞穴石笋与黄土、冰芯、树轮、湖泊沉积、孢粉等气候重建代用指标相比,具有精确定年、分辨率高、保存气候环境记录完整、分布广泛、样品易得且成本低廉等显著优势,已经成为当前研究古气候记录的主力军之一。本文以长江上游地区重庆市青木关镇为研究区域,利用青木关地区狮子山洞石笋QM09的25个230Th精确定年和315个碳氧同位素数据重建了0～9.4kaBP期间的高分辨率石笋碳氧同位素的时间序列,结合亚洲季风区的其他洞穴的石笋记录,分析石笋氧同位素与全新世时期气候的响应关系,并讨论了全新世内部的气候波动变化趋势；利用石笋碳同位素尝试分析与当时气候变化、植被变化关系,进而分析人类活动与全新世气候之间存在的响应关系,全新世时期人与自然环境之间的关系,目前研究的重点主要侧重于自然环境的变化对人类活动产生的影响,尤其是“4.2ka事件”以来,对人类活动影响自然环境的研究较为缺乏,深入探讨人类活动的影响是本文的重点和创新点,通过探讨得出如下结论：(1)狮子山洞石笋QM09高分辨率氧同位素记录显示：狮子山洞所处的重庆地区气候变化与亚洲季风区其他地区气候变化趋势基本保持一致,石笋记录具有可重复性,显示狮子山洞石笋基本没有受到区域因素的影响,研究区内在6.0～9.4kaBP期间,8180值变化范围为-9.483%～-11.187%o,平均值为-10.435‰,变化幅度达到1.704%o,氧同位素值整体处于偏负状态,表明此阶段季风整体处于强盛阶段,降水丰富；在4.2～6.0kaBP期间,石笋δ18O值变化范围为-8.874%o-10.762%o,平均值为-9.776‰,变化幅度为1.888%o,显示石笋δ18O值开始逐渐偏正,但整体还是处于偏负状态,表明此阶段季风整体保持强势状态,降水充沛,内部存在季风波动,季风加强和减弱事件交替出现；4.2ka BP以来,石笋δ180值变化范围为-7.132%～-9.921‰，平均值为-8.538‰,变化幅度为2.789‰,δ18O值显示已经开始处于偏正状态,表明季风整体开始减弱,降水逐渐减少。(2)狮子山洞石笋QM09高分辨率碳同位素记录显示：狮子山洞石笋QM09的碳同位素在4.5-9.4ka BP期间,碳同位素值变化范围为-14.555%o～-13.341%o,变化幅度为1.2140‰,平均值为-13.911‰,可以看出碳同位素值基本在-14%o上下波动,整体处于偏负状态,能够指示重庆地区植被覆盖率较高,植被类型以C3植被为主要植被类型,C4植被相对较少；4.2ka BP以来,碳同位素值变化范围为-14.403‰～-5.848‰,变化幅度为8.555‰,平均值为-11.260‰,碳同位素值出现强烈波动,整体趋于偏正状态,指示C3植被覆盖率明显下降,自然生态环境趋于恶化。(3)4.2ka BP以来,尤其是近2000年来,重庆地区人类活动的规模明显增多和范围明显扩大,对自然植被的影响进一步扩大,改变了地表的植物类型,间接影响了土壤有机质和生物量,土壤有机质降低和生物量的减少,使石笋形成的中间环节,尤其是石笋碳同位素产生变化,使其逐渐偏重,论证了人类活动通过改造地表植被类型会对自然环境产生影响的结论。
[Abstract]:The global climate change during the Holocene is one of the most important contents of the international global climate change research program. The reconstruction of a Holocene high resolution climate record is of great significance for understanding the changing rules of the climate system, dealing with the severe climate and environmental situation and predicting the trend of climate change in the future. The study of the Holocene climate evolution has been progressively deepening, and some achievements have been obtained, which lay a foundation for further study of the Holocene climate change, but the driving mechanism of climate change in the Holocene is still controversial. The Cave Stalagmite is accurate and accurate in comparison with the climatic reconstruction indicators such as loess, ice core, tree wheel, lake deposition and sporopollen. It has become one of the main forces in the study of paleoclimate records. This paper takes the Chongqing city of Chongqing city in the upper reaches of the Yangtze River as the research area, and uses 25 230Th precise years and 315 carbon and oxygen in the green shoot of the lion cave in the Qinghai Province. The isotopic data reconstructs the time series of high resolution carbon and oxygen isotopes of stalagmite during the period of 0 to 9.4kaBP, combined with the stalagmite records of other caverns in the Asian monsoon region, and analyses the response relationship between the oxygen isotope of the stalagmite and the Holocene epoch, and discusses the trend of the climate change in the Holocene. The relationship between climate change and vegetation change at that time, and then the response relationship between human activity and Holocene climate, the relationship between human and natural environment during the Holocene, the focus of the present study mainly on the effects of natural environment changes on human activities, especially since the "4.2ka event". The research on the influence of the natural environment is relatively short. It is the key and innovation point of this paper. Through the discussion, the following conclusions are drawn: (1) the QM09 high resolution oxygen isotope records of the Stalagmite in the lion cave show that the climate change in the Chongqing region of the lion cave and the climate change trend in other regions of the Asian monsoon region Keeping the same, the stalagmite records are repeatable, showing that the Stalagmite in the lion cave is not affected by regional factors. During the period of 6 ~ 9.4kaBP, the range of 8180 values is -9.483% to -11.187%o, the average value is -10.435 per 1000, the change range is 1.704%o, the oxygen isotope value is in the negative state, indicating the monsoon in this stage. During the period of 4.2 ~ 6.0kaBP, the variation range of the delta 18O value of the stalagmite is -8.874%o-10.762%o, the average value is -9.776 per 1000, the change range is 1.888%o, which shows that the value of the stalagmite Delta 18O begins to be positive, but the whole is still in a negative state, which indicates that the monsoon in this stage remains strong, and the precipitation is abundant and internal exists. The monsoon fluctuation occurred alternately in the monsoon strengthening and weakening events; since 4.2ka BP, the variation range of the delta 180 value of the stalagmite was -7.132% to -9.921 per thousand, the average value was -8.538 per 1000, the change range was 2.789 per thousand, and the delta 18O value showed that the monsoon began to be in the positive state, indicating that the monsoon began to weaken and the precipitation decreased gradually. (2) the high resolution of the stalagmite QM09 in the lion cave. Carbon isotope records show that the carbon isotope of QM09 in the lion cave in 4.5-9.4ka BP, the variation range of carbon isotope value is -14.555%o to -13.341%o, the variation range is 1.2140 per thousand and the average value is -13.911 per 1000. It can be seen that the carbon isotope value fluctuates basically in the upper and lower -14%o, and the whole body is in the negative state, which can indicate the vegetation cover in Chongqing area. The cover rate is higher, the vegetation type is C3 vegetation as the main vegetation type, and the C4 vegetation is relatively less. Since 4.2ka BP, the variation range of carbon isotope value is from -14.403 to -5.848 per thousand, the variation range is 8.555 per thousand, the average value is -11.260 per thousand, the carbon isotope value fluctuates strongly, the whole trend is in the partial positive state, indicating that the vegetation coverage rate of C3 is obviously decreased, naturally the vegetation coverage of C3 is decreased obviously. Nature The ecological environment tends to deteriorate. (3) since 4.2ka BP, especially in recent 2000, the scale of human activities in Chongqing area has increased obviously and its scope is obviously expanded, the influence of the natural vegetation is further expanded, the plant type of the surface is changed, the soil organic matter and the biomass, the decrease of soil organic matter and the decrease of the biomass, make the stalagmite The intermediate links formed, especially the carbon isotopes of stalagmite, make it more and more heavy, demonstrating the conclusion that human activities will affect the natural environment through the transformation of the vegetation types of the surface.

【学位授予单位】：西南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P532

【参考文献】