中晚全新世以来呼伦湖沉积记录的环境与气候演变

发布时间：2018-07-28 10:54

【摘要】：湖泊是在一定的地质、地理环境背景下形成的,是大气圈、生物圈、岩石圈和水圈的联系纽带,对区域气候有着良好的调节作用;是区域范围内物质的"源"与"汇"。湖泊沉积物具有较长的时间尺度及较广的空间尺度,连续性强,沉积记录的环境信息丰富,是研究气候变化和环境演变的良好载体材料。通过提取湖泊沉积物所涵盖的环境信息,可以揭示现在和过去的环境变化规律,进而对未来气候变化进行预测。内蒙古呼伦湖是中国北方季风边缘区典型湖泊,处于西风激流带的东延与东亚季风区相交汇的部位,同时受东亚季风、西风环流及西伯利亚—蒙古高压的共同影响,使得该区域对气候和环境响应敏感,对古气候、古环境研究具有非常重要的意义。本研究以内蒙古呼伦湖为研究对象,于2015年3月在呼伦湖北部采集长100cm的沉积物岩芯HLX,结合AMS14C定年资料,分析了沉积物样品粒度、有机碳(TOC)、总氮(TN)、总磷(TP)、碳同位素(δ13C)、氮同位素(δ15N)和典型金属元素等中晚全新世(5400cal.a BP)以来的变化特征,估算了湖泊古生产力,分析了流域风化作用程度及湖泊水位变化等,重建了中晚全新世以来内蒙古呼伦湖流域的环境与气候演变过程。得到的结论如下:(1)呼伦湖沉积物粒度频率曲线呈现单峰和双峰两种形态,物源相对简单。利用粒径—标准偏差法提取了环境敏感粒度组分1(8.71μm)和组分2(8.71～158.49μm),组分1指示采样点距离湖心区远近,组分2基本代表了粉砂和砂质颗粒,反映流域的风成作用。组分1和组分2呈相反变化趋势,反映了呼伦湖沉积物主要由水流和风成作用交替控制。(2)呼伦湖古生产力的变化范围为58.26～136.93 g·Cm-2a-1,平均值为104.09 g·Cm-2a-1。全新世中期(5400～3480cal.a BP),古生产力呈现逐渐增大的趋势,并且达到最大值136.93 g·Cm-2a-1,表明全新世中期气候较暖湿,初级生产力水平较高。全新世晚期(3480～0cal.aBP),古生产力呈波动状态,先递减再增大,其中195～0cal.aBP,古生产力、δ13C和TOC及TN都呈现逐渐增加的趋势,指示了暖干的气候环境。(3)全新世中晚期间,呼伦湖流域的风化作用较弱,环境与气候经历了暖湿(5400～3202cal.aBP)、冷干(3202～655cal.aBP)、冷湿(655～179cal.aBP)和暖干(179～0cal.aBP)四个演变阶段;水位经历了高水位(5400～5144cal.aBP)、低水位(5144～4477cal.aBP)、高水位(4477～1375cal.aBP)、低水位(1375～449cal.aBP)、高水位(449～226cal.aBP)和低水位(226～0cal.aBP)波动过程。(4)呼伦湖流域存在4.2ka干冷事件的沉积记录,同时中世纪暖期起止时间为670～1200cal.aBP,即750～1280AD,在全球中世纪暖期范围内,持续时间较中国东部MWP(800～1100AD)长,较西部地区MWP(500～1500AD)短。小冰期起止时间为:170～670cal.aBP,即1280～1780AD,持续时间500a。(5)呼伦湖流域5400cal.a BP以来气候演变过程中存在明显的250a和500a的周期信号,且以250a的信号周期为主,存在于每个环境代用指标中,说明呼伦湖流域的气候周期特征以百年尺度变化为主。
[Abstract]:The lake is formed in a certain geological and geographical background, which is the link between the atmosphere, biosphere, lithosphere and hydrosphere, and has a good regulating effect on the regional climate. It is the "source" and "remittance" of the matter in the regional range. The lake sediments have a long time scale and a wider spatial scale, a strong continuity and a sedimentary record. It is a good carrier material for the study of climate change and environmental evolution. By extracting environmental information covered by lake sediments, we can reveal the current and past environmental changes, and then predict the climate change in the future. Inner Mongolia Hulun Lake is a typical lake in the northern monsoon border area of China and is in the westerly flow zone. The intersection of East Asian monsoon region and East Asian monsoon region is affected by East Asian monsoon, westerly circulation and Siberia Mongolia high pressure, which makes the region sensitive to climate and environment response, and is of great significance to the study of paleoclimate and paleoenvironment. This study is the object of study in Hulan Lake in Mongolia and Hulun in March 2015. In Hubei, the sediment core HLX of long 100cm is collected and combined with AMS14C dating data, the variation characteristics of sediment sample size, organic carbon (TOC), total nitrogen (TN), total phosphorus (TP), carbon isotopes (delta 13C), nitrogen isotopes (delta 15N) and typical metal elements, etc., are analyzed. The paleo productivity of the lake is estimated and the basin wind is analyzed. The environmental and climatic evolution process of the Inner Mongolia Hulun Lake Basin since the middle and late Holocene has been rebuilt. The conclusions are as follows: (1) the grain frequency curve of the sediments in Hulun Lake presents a single peak and two forms in Shuangfeng, and the source is relatively simple. The environment sensitive granularity group is extracted by the particle size standard deviation method. 1 (8.71 mu m) and component 2 (8.71 ~ 158.49 mu m), component 1 indicating the sampling point distance from the lake heart Qu Yuanjin, the component 2 represents the silt and sand particles, reflecting the wind formation in the basin. The component 1 and the component 2 show the opposite trend, reflecting the alternately controlled by the water flow and the wind formation in Hulan lake sediments. (2) the palaeo productivity of Hulan lake. The range is 58.26 ~ 136.93 G. Cm-2a-1. The average value is 104.09 G. Cm-2a-1. in the middle Holocene (5400 to 3480cal.a BP). The paleo productivity is gradually increasing and reaches the maximum value of 136.93 G. Cm-2a-1. It shows that the mid Holocene climate is warm and wet, the primary productivity is higher. The late Holocene (3480 to 0cal.aBP), the ancient productivity The fluctuation state, first decreasing and then increasing, 195 to 0cal.aBP, the ancient productivity, Delta 13C and TOC and TN all showed an increasing trend, indicating the warm dry climate environment. (3) the weathering effect of the Hulun Lake Basin was weak during the middle and late Holocene, the environment and climate experienced warm wet (5400 to 3202cal.aBP), cold dry (3202 to 655cal.aBP), cold wet (655~179). Cal.aBP) and warm dry (179 ~ 0cal.aBP) four stages of evolution; water level experienced high water level (5400 ~ 5144cal.aBP), low water level (5144 ~ 4477cal.aBP), high water level (4477 to 1375cal.aBP), low water level (1375 to 449cal.aBP), high water level (449 to 226cal.aBP) and low water level (226 to 0cal.aBP). (4) the existence of 4.2ka dry and cold events in Hulun Lake Basin In the middle ages, the duration of the middle ages is 670 ~ 1200cal.aBP, that is 750 ~ 1280AD. The duration of the medieval warm period is MWP (800 ~ 1100AD) in the eastern part of the world and MWP (500 to 1500AD) in the western region. The start and stop time of the small ice period is 170 to 670cal.aBP, 1280 to 1780AD, and 500A. (5) in the Hulun Lake Basin of 5400. In the process of climate evolution since cal.a BP, there are obvious periodic signals of 250A and 500A, and the signal cycle of 250A is the main period, which exists in every environmental substitute index. It shows that the climatic cycle characteristics of the Hulun Lake Basin are mainly centennial.
【学位授予单位】：内蒙古农业大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：P512.2;P532

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