青藏高原湖泊记录的典型时段古气候变化

发布时间：2018-05-03 22:15

本文选题：生物标志化合物 + 当雄错　；参考：《中国地质大学》2017年博士论文

【摘要】：青藏高原独特的地貌特征和热力状况对亚洲乃至全球气候变化均具有重要的影响,是古气候变化研究的热点区域。高原上众多湖泊是研究古气候的良好载体。末次冰消期古气候经历了剧烈的波动,是研究渐变/突变过程的重要时段。本文以生物标志化合物为指标(长链烯酮和正构烷烃),对当雄错盐湖阶地和扎布耶盐湖末次冰消期沉积物进行了研究。当雄错盐湖末次冰消期沉积物中长链烯酮含量丰富,长链烯酮分布特征以C_37甲基酮(C_37:Me)和C_38烯酮为主,含少量的C_39烯酮和微量C_40烯酮。在20.2~12.0ka BP,长链烯酮母源可能属于格陵兰湖泊种属和/或G.oceanica;12.0~11.4 ka BP期间的母源可能属于C.lamellosa。根据长链烯酮不饱和度,定量重建了末次冰消期以来的古温度变化。末次冰盛期年平均温度约为0.2°C;博令-阿罗德(B?lling/Aller?d)时期温度快速上升,从0.8℃升至2.9°C;随后进入新仙女木期(Younger Dryas),新仙女木事件早期的年平均气温约为-0.9°C。结合正构烷烃的含量分析结果表明末次冰消期当雄错湖区经历了冷湿的末次冰消期早期,暖干的B?lling/Aller?d时期和冷干的新仙女木早期。根据扎布耶盐湖沉积物正构烷烃分布特征及其单体同位素的研究,发现不同链长正构烷烃单体δ~(13)C值的古气候意义有一定的差异。中链正构烷烃单体δ~(13)C值主要受控于湖水碳源和湖泊内生环境,可能主要反映了湖泊水生环境和湖水温度的变化;长链正构烷烃主要来自于湖泊周边的植被,其单体δ~(13)C可能是区域气候温度与湿度的耦合,指示了区域有效湿度的变化。根据正构烷烃的分布特征及其单体碳同位素,重建了扎布耶湖区末次冰消期的藻类、菌类、水生植物、草本、木本植物的变化历史。末次冰消期湖泊沉积物中来自水生植物的比重高于周边植物。末次冰消期早期(距今23.1~16.8 ka BP),气候由冷湿转为冷干,藻类、菌类和水生大型植物繁盛,陆生来源中草本植物比例高于木本植物;B?lling/Aller?d时期(16.8~12.6 ka BP)气候变暖,木本植物逐渐繁盛;新仙女木早期(距今12.6~11.8ka BP)气候冷湿,藻类、菌类锐减,沉水和浮水植物繁盛,陆生植物中木本植物比例大于草本植物。末次冰消期时期,青藏高原当雄错盐湖和扎布耶盐湖经历了大致相同的冷暖变化,与北大西洋的经典温度变化一致,可能反映了在温度变化方面亚洲季风区与北大西洋、高纬气候密切相关。在湿度变化上两个湖泊略有差异,其原因可能与样品分辨率、湖泊环境差异及指标的不确定性有关。过去两千年是古全球变化研究计划(PAGES)和亚洲两千年(PAGES-Asia 2K)的重点研究时段。本文运用同步辐射X射线荧光光谱微区原位分析方法,对托素盐湖岩芯进行了高分辨率古气候变化研究。根据主成分分析结果,将各元素的主要影响因素解译为:因子1(K、Ti等来自于岩石成因的元素)主要受控于降水和风成过程带来的碎屑;因子2(Ca、Sr)受蒸发-降水影响,与干旱度相关;因子3(Br)可能主要与生物相关,温度增加有利于生物生产率增加。高分辨率分析结果表明中世纪暖期该区气候为暖干,小冰期冷湿。另外,元素谱分析结果表明托素盐湖过去1100年来气候变化具有明显的周期性,这些准周期变化可能主要受控于厄尔尼诺-南方涛动和太阳活动。
[Abstract]:The unique geomorphic features and thermal conditions of the Qinghai Tibet Plateau have an important influence on the climate change in Asia and the world. It is a hot area in the study of paleoclimate change. Many lakes on the plateau are a good carrier for the study of the paleoclimate. The paleoclimate in the last glacial period has undergone dramatic fluctuations and is an important period for the study of the gradual change / mutation process. With the biomarker compounds as the index (long chain alkanone and n-alkanes), the sediments of the Saline Lake terrace and the last deglaciation of the Jabu Saline Lake were studied. The content of the long chain alkenone in the last deglacial sediments of the Saline Lake was rich. The distribution characteristics of the long chain alkenone were mainly C_37 methyl ketone (C_37:Me) and C_38 ketones, with a small amount of C_3 9 ketones and trace C_40 enes. At 20.2~12.0ka BP, the parent source of long chain alkenone may belong to the genus and / or G.oceanica in Greenland Lake; the parent source of 12.0~11.4 Ka BP may belong to C.lamellosa. based on the unsaturation of long chain alkenone, which reconstructs the paleotemperature changes since the last glacial period. The average temperature of the last glacial period is about 0.2 degrees. The temperature of bloomer Harold (B? Lling/Aller? D) rose rapidly from 0.8 to 2.9 C, and then entered the new caffy period (Younger Dryas). The annual mean annual temperature of the new fairy tree event was about -0.9 degree C. binding n-alkanes. The dry B? Lling/Aller? D period and the cold dry new fairy wood early. According to the distribution characteristics of n-alkanes in the Jabu Saline Lake sediments and the study of the mono isotopes, it is found that the Paleoclimatic Significance of the delta ~ (13) C value of different chain length n-alkanes has certain difference. The value of delta ~ (13) C of middle chain n-alkanes is mainly controlled by the lake water carbon source and lake The endophytic environment may mainly reflect the changes in lake aquatic environment and lake water temperature; long chain n-alkanes mainly come from the vegetation around the lake. The monomer delta ~ (13) C may be the coupling of regional climate temperature and humidity, indicating the change of effective humidity in the region, and rebuilt according to the distribution characteristics of n-alkanes and the carbon isotopes of the monomers. The change history of algae, fungi, aquatic plants, herbaceous plants and woody plants in the last deglaciation of the Jabu Lake area. The proportion of aquatic plants in the last glacial lake sediments is higher than that of the surrounding plants. The early stage of the last deglacial (23.1~16.8 Ka BP), the climate changed from cold wet to cold dry, algae, fungi and aquatic large plants flourished. The proportion of herbaceous plants in the source is higher than that of the woody plants; the B? Lling/Aller? D period (16.8~12.6 Ka BP) has a warm climate and the woody plants are flourishing; the early (12.6~11.8ka BP) of the new immortality (from the present 12.6~11.8ka BP) is cold and wet, the algae, the fungus, the submerged and floating water plants flourish, the proportion of the woody plants in Lu Shengzhi is larger than that of the herbaceous plants. The Saline Lake and Jabu Saline Lake in the Tibetan Plateau have experienced roughly the same cold and warm changes, which are consistent with the classical temperature changes in the North Atlantic, which may reflect the close correlation between the Asian monsoon region and the North Atlantic and high latitudes in the temperature change. In the humidity change, the two lakes are slightly different, and the reason may be the resolution of the sample, the lake The uncertainty of the environment and the uncertainty of the index are related. The past two thousand years have been the key period of study of the ancient global change research program (PAGES) and the two thousand year of Asia (PAGES-Asia 2K). In this paper, the high resolution paleoclimate change of the core of the Saline Lake core was studied by the method of synchrotron radiation X ray fluorescence in situ analysis. The main influence factors of each element are interpreted as: factor 1 (K, Ti and other elements from petrogenesis) are mainly controlled by detritus caused by precipitation and wind formation; factor 2 (Ca, Sr) is affected by evaporation precipitation and is related to the degree of drought; factor 3 (Br) may be mainly related to biology, and the increase of temperature is beneficial to the increase of biological productivity. The analysis results show that the climate in this area is warm and cold in the warm period in the middle ages. In addition, the analysis of the element spectrum shows that the climate change of the Saline Lake in the past 1100 has a distinct periodicity. These quasi periodic changes may be mainly controlled by the El Nino Southern Oscillation and the activity of Tai Yang.

【学位授予单位】：中国地质大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：P532

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