本文選題：新疆地區(qū) + 洞穴石筍��； 參考：《蘭州大學(xué)》2017年博士論文

【摘要】：在當(dāng)前全球氣候變化背景下,利用地質(zhì)載體(如極地冰芯、海洋鉆孔沉積物、陸生黃土、湖泊沉積物及洞穴沉積物等)進(jìn)行地表過(guò)去氣候和環(huán)境變遷規(guī)律和特征的研究,可以為未來(lái)氣候和環(huán)境變化提供參照,也是氣候變化領(lǐng)域的研究重點(diǎn)之一。近二十年來(lái),國(guó)內(nèi)外學(xué)者利用石灰?guī)r地層中廣泛發(fā)育的巖溶洞穴沉積物(主要為石筍),在高精度同位素地質(zhì)年代測(cè)試技術(shù)(鈾系測(cè)年)的支持下,高分辨率地分析和檢測(cè)了石筍碳酸鹽中的穩(wěn)定同位素(氧和碳)、微量元素含量和比值、微量元素同位素、微層厚度和灰度、磁學(xué)信號(hào)、有機(jī)化合物含量等指標(biāo),從中提取了能夠重建區(qū)域氣候和環(huán)境變遷的信息,同時(shí)也將石筍古氣候記錄發(fā)展為氣候變化研究的重要標(biāo)尺之一。本論文在采集我國(guó)新疆中部天山南麓巴魯克洞的石筍樣品并在建立其鈾系絕對(duì)定年結(jié)果的基礎(chǔ)上,檢測(cè)了石筍的氧碳同位素(δ18O、δ13C)和微量元素比值(Mg/Ca、Sr/Ca、Ba/Ca、U/Ca)指標(biāo),重建了新疆中部地區(qū)近兩千年、全新世和MIS5c-5a階段的不同時(shí)間尺度上(百年、千年和軌道)的環(huán)境演化和氣候變遷歷史,探討了區(qū)域氣候變化的可能驅(qū)動(dòng)機(jī)制及環(huán)境變化對(duì)區(qū)域社會(huì)發(fā)展的可能影響。本論文得到的主要結(jié)論如下:(1)在分析研究區(qū)現(xiàn)代大氣降水觀測(cè)數(shù)據(jù)基礎(chǔ)上,發(fā)現(xiàn)年內(nèi)尺度上以烏魯木齊站為代表的新疆天山地區(qū),月均降水氧同位素(δ18Op)值與月均溫度之間存在顯著正相關(guān)關(guān)系,表現(xiàn)為“溫度效應(yīng)”影響;月均δ18Op值與月均降雨量之間為弱正相關(guān)。年際尺度上,年均加權(quán)平均δ18Op值與年均溫度之間顯示了弱的負(fù)相關(guān),表明了年際尺度上“溫度效應(yīng)”的失效;結(jié)合天山中部烏源一號(hào)冰川和天山東部廟兒溝冰川的近50年冰芯氧同位素(δ18Oi)序列,發(fā)現(xiàn)冰芯δ18Oi值的偏負(fù)趨勢(shì)與近50年烏魯木齊站及新疆地區(qū)溫度的上升趨勢(shì)相反,說(shuō)明年代際尺度上“溫度效應(yīng)”也并非主導(dǎo)作用。進(jìn)一步分析了研究區(qū)在特殊年份的水汽來(lái)源差異,發(fā)現(xiàn)在較溫暖的1997年,可能有相對(duì)較多的來(lái)自高緯度區(qū)域的δ18Op值偏負(fù)的水汽,而在較冷的1988年則增加了來(lái)自中低緯度區(qū)域的δ18Op值偏正的水汽。新疆中部地區(qū)大氣降水δ18Op值及石筍δ18O值的偏負(fù)或偏正變化,不僅與水汽輸送有關(guān),還與輸送通道的水汽再蒸發(fā)、局地水汽循環(huán)以及冰雪融水(其δ18O值非常偏負(fù),~-20‰)的貢獻(xiàn)等有關(guān)。(2)近兩千年來(lái),巴魯克洞的一支87mm的石筍BLK12C的13個(gè)鈾系絕對(duì)定年結(jié)果顯示其方解石沉積覆蓋了過(guò)去2457年,該石筍δ18O和δ13C值顯著的十年際-百年尺度的周期性波動(dòng)疊加在長(zhǎng)時(shí)間的同位素值偏正的趨勢(shì)上,且在中世紀(jì)氣候異常期(Medieval Climate Anomaly,MCA,950-1250AD)同位素值整體偏負(fù),同時(shí)也存在十年際尺度的偏正事件。這種突變和整體較低的同位素值特征也體現(xiàn)了在了石筍的Mg/Ca比值序列中,其與穩(wěn)定同位素序列顯示相似的變化模式。在MCA期間,石筍氧碳同位素的突然變化反應(yīng)了這一時(shí)期研究區(qū)氣候環(huán)境的不穩(wěn)定性和較大幅度的快速變化,相比而言,小冰期(Little Ice Age,LIA,1300-1900AD)時(shí),石筍氧碳同位素的變化幅度不如MCA期間,整體上同位素值偏正,尤其是1300-1400AD期間的顯著偏正。此外,石筍微量元素指標(biāo)(Sr/Ca、Ba/Ca、U/Ca)在MCA期間的變化很小,這可能反映了該時(shí)期地表土壤和大氣粉塵的活動(dòng)比較弱;在LIA時(shí),Sr/Ca、Ba/Ca、U/Ca的高頻波動(dòng)比較顯著,可能說(shuō)明該時(shí)期土壤有機(jī)質(zhì)含量的增加和微生物活動(dòng)的加強(qiáng)等。巴魯克洞石筍氧碳同位素序列中的近200年周期波動(dòng),可能反映了太陽(yáng)活動(dòng)周期對(duì)研究區(qū)的百年尺度氣候和環(huán)境演化的驅(qū)動(dòng)作用。此外,巴魯克洞石筍記錄中顯示的公元14世紀(jì)期間顯著的氣候突變能夠較好地對(duì)應(yīng)于蒙古帝國(guó)的興盛和衰落時(shí)間,其他一些歷史朝代更替和區(qū)域文化發(fā)展和衰落的時(shí)間節(jié)點(diǎn)亦能在巴魯克洞石筍代用指標(biāo)波動(dòng)中找到對(duì)應(yīng)關(guān)系,可能說(shuō)明了區(qū)域環(huán)境變化對(duì)社會(huì)文明演替的影響。(3)全新世期間,巴魯克洞兩支石筍BLK12A與BLK12B/C的38個(gè)高精度的鈾系年齡覆蓋了過(guò)去9500年,其高分辨率(~20年)的氧碳同位素序列顯示石筍的δ18O序列在軌道尺度上的變化模式與北半球高緯度夏季太陽(yáng)輻射變化相似,同時(shí)疊加了諸多千年-百年尺度的氣候事件(如8.2ka事件、~3ka事件)。巴魯克洞全新世石筍δ18O值記錄整體上為早-中全新世(9.5~3ka)時(shí)偏負(fù)(-6.5~-9‰),其中7~6ka時(shí)石筍δ18O值有一個(gè)偏正的谷段(以6.4ka為中心)。在~3ka時(shí),石筍δ18O值突然偏正(幅度約2‰),之后在大約500年時(shí)間里,石筍δ18O值顯示較大的波動(dòng),但其范圍在-5~-6.5‰之間。其中,BLK12A石筍在2.5~1.3ka為一個(gè)顯著的沉積間斷,在石筍橫切面上亦能觀察到一個(gè)具有石花狀方解石沉積的條帶。此外,石筍微量元素比值(Sr/Ca、Ba/Ca、U/Ca)序列顯示在早中全新世時(shí)比值較高,而晚全新世比值較低,在~3ka左右發(fā)生了顯著的微量元素比值增大的事件,可以認(rèn)為巴魯克洞所在區(qū)域全新世期間的局地濕度為早全新世較干而中晚全新世逐漸變濕,與湖泊沉積物重建的區(qū)域濕度序列一致。同時(shí),巴魯克洞代用指標(biāo)反映的~3ka左右的氣候突變事件可能與天山地區(qū)高山冰川的前進(jìn)及西風(fēng)環(huán)流的調(diào)整有關(guān)。(4)在MIS5c-5a期間,巴魯克洞的2支石筍(BLK12E和BLK12F)的24個(gè)高精度鈾系年齡顯示其碳酸鹽沉積發(fā)育時(shí)段為78.5~101.6ka(~23.1ka),所對(duì)應(yīng)的是MIS5c的晚期至MIS5a的結(jié)束(late-MIS5c to MIS5a)。兩支石筍具有高度重復(fù)性變化的氧碳同位素序列(~100年分辨率)顯示了間冰段(5c和5a)時(shí)δ18O值偏負(fù)和冰段(5b)時(shí)δ18O值偏正的特征(幅度達(dá)到~3‰),低分辨率的微量元素指標(biāo)也有類(lèi)似的變化模式。巴魯克洞MIS5c-5a期間的石筍記錄反映了軌道尺度上歲差周期對(duì)該區(qū)域環(huán)境和氣候的主導(dǎo)作用。與南北半球具有全球氣候意義的代用指標(biāo)對(duì)比后,可以推測(cè)巴魯克洞所反映的新疆中部地區(qū)氣候變遷響應(yīng)于軌道尺度的北半球高緯度氣候(格陵蘭冰芯記錄)與南半球氣候(南極冰芯記錄)的波動(dòng)。值得注意的是,格陵蘭冰芯所記錄的北半球溫度的上升(~85.5ka)要早于南極冰芯所記錄的全球溫度的上升(~84.5ka),也領(lǐng)先于亞洲東部季風(fēng)氣候(中國(guó)三寶洞石筍記錄)和亞洲中部干旱區(qū)(新疆巴魯克洞、科桑洞及烏茲別克斯坦Ton洞石筍)氣候的轉(zhuǎn)型。
[Abstract]:Under the background of global climate change, the study on the laws and characteristics of the climate and environment changes of the earth's surface by using geological carriers (such as polar ice core, marine drilled sediment, terrestrial loess, lake sediments and cave sediments) can provide reference for climate and environment change in the future, and it is also the focus of research in the field of climate change. First, in the past twenty years, scholars at home and abroad have used the widely developed karst cave sediments (mainly stalagmite) in the limestone strata. Under the support of high precision isotope geochronology Test Technology (uranium dating year), the stable isotopes (oxygen and carbon), trace elements content and ratio of trace elements in the carbonates of stalagmite are analyzed and detected with high resolution. Isotopes of quantitative elements, thickness and gray level of microlayers, magnetic signals, and organic compounds content have been used to extract information that can reconstruct regional climate and environmental changes. At the same time, the paleoclimate records of stalagmite are also developed as one of the important scales for the study of climate change. This paper is a collection of the Baruch cave in the southern foot of Tianshan, central Xinjiang, China. On the basis of the absolute dating results of the uranium system, the oxygen carbon isotopes of the stalagmite (delta 18O, Delta 13C) and the ratio of trace elements (Mg/Ca, Sr/Ca, Ba/Ca, U/Ca) were measured, and the environmental evolution and climate on the different time scales (100 years, thousand years and orbits) in the middle of Xinjiang were rebuilt for nearly two thousand years. The possible driving mechanism of regional climate change and the possible influence of environmental changes on regional social development are discussed. The main conclusions of this paper are as follows: (1) on the basis of the analysis of the observational data of Modern Atmospheric Precipitation in the study area, it is found that the monthly average precipitation of the Xinjiang Tianshan area, represented by the Urumchi Railway Station, is the same as the monthly precipitation. There is a significant positive correlation between the value of the position element (delta 18Op) and the monthly mean temperature, which shows the effect of "temperature effect", and the monthly mean Delta 18Op value is weakly positively correlated with the monthly average rainfall. The annual average weighted average Delta 18Op value shows a weak negative correlation with the annual average temperature, indicating the failure of the "temperature effect" on the interannual scale. The ice core oxygen isotope (delta 18Oi) sequence of the glacier of Wu Yuan 1 in the middle part of the Tianshan Mountain and the mioer gully glacier in the east of Tianshan Mountain found that the negative trend of the ice core Delta 18Oi value is contrary to the rising trend of the temperature in the Urumchi Railway Station and Xinjiang region in recent years, indicating that the "temperature effect" is not the leading role in the interdecadal scale. Further analysis of the research is made. The difference in the source of water vapor in the special year is found in the warmer 1997. It is found that in the warmer 1997, there may be a relatively large amount of water vapor with a negative Delta 18Op value from the high latitudes, while in the cold 1988, the delta 18Op value from the middle and low latitudes is more positive. The delta 18Op value of the atmospheric precipitation and the delta 18O value of the Stalagmite in the middle of Xinjiang are negative or negative. The partial positive change is related not only to the water vapor transport, but also to the water vapor re evaporation of the transport channel, the local water vapor cycle and the contribution of the ice and snow melt water (its delta 18O value is very negative, ~-20 per thousand). (2) in the last two thousand years, the absolute dating of 13 uranium systems of a 87mm stalagmite BLK12C in the 87mm cave shows that the calcite deposits covered the past 245 years. In the 7 year, the periodic fluctuation of the ten annual scale of the stalagmite Delta 18O and delta 13C value is superimposed on the tendency of long time isotopic values, and the isotopic values of the medieval climatic anomaly (Medieval Climate Anomaly, MCA, 950-1250AD) are overall negative, but also in the ten interannual scale. The characteristics of low isotopic values also reflect a similar pattern of variation in the Mg/Ca ratio sequence of stalagmite, which is similar to that of stable isotopes. During the period of MCA, the sudden changes in oxygen and carbon isotopes of stalagmite reacted to the instability and rapid changes of the climate and environment in this period, compared to the small ice period (Little Ice A). When GE, LIA, 1300-1900AD), the oxygen and carbon isotopes of stalagmite are less than that of MCA, and the isotopic values are very positive on the whole, especially in the period of 1300-1400AD. In addition, the trace elements (Sr/Ca, Ba/Ca, U/Ca) of the stalagmite (Sr/Ca, Ba/Ca, U/Ca) change very little during MCA, which may reflect the weak activity of soil and atmospheric dust in this period; in L. At IA, the high frequency fluctuations of Sr/Ca, Ba/Ca and U/Ca are more significant, which may explain the increase of soil organic matter content and the enhancement of microbial activity during this period. The recent 200 years' periodic fluctuation in the oxygen carbon isotope sequence of Baruch's Cave Stalagmite may reflect the driving effect of the solar activity cycle on the Centennial climate and environmental evolution of the study area. In addition, the remarkable climate change during the fourteenth Century ad of the Baruch cave can correspond to the prosperity and decline time of the Mongolia Empire, and the time nodes of other historical dynasties and regional cultural development and decline can also find the corresponding relationship in the fluctuation of the Baruch Cave Stalagmite substitution index, which may be explained. The influence of regional environmental changes on the succession of social civilization. (3) during the Holocene, the 38 high precision uranium system ages of two stalagmite BLK12A and BLK12B/C in the Baruch cave covered the past 9500 years. The high resolution (~20) oxygen carbon isotope sequence showed the variation pattern of the stalagmite Delta 18O sequence on the rail scale and the high latitudes in the northern hemisphere in summer The variation of the solar radiation is similar, and a number of millennial - Centennial climate events (such as the 8.2ka event, ~3ka event) are superimposed. The Baruch cave Holocene stalagmite Delta 18O records are generally negative (-6.5~-9 per 1000) at the time of the early Middle Holocene (9.5~3ka), of which the delta 18O value of the Stalagmite in 7~6ka has a positive Valley (centered on 6.4ka). At ~3ka, the stalagmite [delta]. The 18O value is abrupt (about 2 per thousand), and after about 500 years, the value of the stalagmite Delta 18O shows a larger fluctuation, but its range is between -5~-6.5 per thousand. Among them, the BLK12A stalagmite is a significant sedimentary discontinuity at 2.5~1.3ka. In the cross section of the stalagmite, a strip with stone calcite deposits can also be observed. Besides, the trace element of the stalagmite is in the trace element. The Sr/Ca (Ba/Ca, U/Ca) sequence shows that the ratio of the early Holocene is higher, while the late Holocene ratio is low, and a significant increase in the ratio of trace elements has occurred around ~3ka. It is considered that the local humidity during the Holocene period of the Baruch cave is gradually wetted by the early Miocene and the middle and late Holocene, and the lake deposition. The regional humidity sequence of the reconstruction is consistent. At the same time, the climatic catastrophe around ~3ka reflected by the Baruch Tung substitution index may be related to the advance of the alpine glaciers and the adjustment of the westerly circulation in the Tianshan region. (4) during the period of MIS5c-5a, the 24 high precision uranium system ages of 2 stalagmite (BLK12E and BLK12F) in the cave of the cave show their carbonate deposits The development period is 78.5~101.6ka (~23.1ka), which corresponds to the end of the late MIS5c to the end of MIS5a (late-MIS5c to MIS5a). The oxygen carbon isotope sequence of two stalagmite with high repeatability (~100 year resolution) shows that the delta 18O value of the interglacial segment (5C and 5a) is negative and the Delta (5b) value is positive when the delta 18O value is negative and the ice section (5b) is low. The trace element index of the rate also has a similar change pattern. The stalagmite records during the Baruch cave MIS5c-5a reflect the leading role of the precession cycle on the environment and climate in the orbital scale. Compared with the alternative indicators of the global climate in the northern and southern hemispheres, the climate change in the central Xinjiang region reflected by the Baruch cave can be speculated. The high latitude climate (Greenland ice core record) and the Southern Hemisphere climate change in response to the orbital scale. It is noteworthy that the rise of the Northern Hemisphere temperature recorded by the Greenland ice core (~85.5ka) is earlier than the global temperature rise recorded by the Antarctic ice core (~84.5ka), as well as the Eastern Asian climate. Climate change in the arid region of Central Asia (Baruch hole, Xinjiang, Ton cave and stalagmites in Uzbekistan).
【學(xué)位授予單位】：蘭州大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2017
【分類(lèi)號(hào)】：P532

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1 郭延偉;河南雞冠洞巖溶記錄的氧同位素現(xiàn)代過(guò)程監(jiān)測(cè)及機(jī)理研究[D];西南大學(xué);2013年

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