【摘要】：近年來,人類社會(huì)對(duì)全球氣候變化日益關(guān)注,洞穴石筍因其高精度定年和和高分辨率特征,在古氣候變化研究中占據(jù)重要地位。本文基于玉龍洞石筍(編號(hào)TCL)9個(gè)U/Th絕對(duì)年齡和787個(gè)δ180測(cè)試數(shù)據(jù)建立了利川地區(qū)近14.4ka BP以來的東亞季風(fēng)變化序列。玉龍洞石筍TCL的δ180氣候演化序列與亞洲季風(fēng)區(qū)其他洞穴石筍記錄在千年至百年尺度上表現(xiàn)出整體的一致性,說明亞洲地區(qū)洞穴石筍δ180受同一氣候影響因子驅(qū)動(dòng),石筍δ180記錄可以較好的反映千年至百年尺度上的亞洲季風(fēng)氣候變化。石筍TCL的δ13C值主要反映了研究區(qū)域植被豐度的變化,具有明顯的周期性特征,大致可分為4個(gè)旋回。功率譜分析結(jié)果顯示,813C具有2000年左右的顯著周期,可能反映了研究區(qū)域局域環(huán)境的特殊變化規(guī)律。石筍TCL的灰度和δ13C曲線存在良好的相關(guān)性,二者在總體變化趨勢(shì)上基本一致,呈現(xiàn)出明顯的峰谷對(duì)應(yīng)特征。石筍碳同位素與沉積巖性的良好對(duì)應(yīng)關(guān)系,證實(shí)了這種代用指標(biāo)的可靠性,同時(shí)也表明了兩者具有共同的驅(qū)動(dòng)機(jī)制：當(dāng)研究區(qū)域降雨量充沛,植物茂盛,土壤CO2產(chǎn)率增高時(shí)、δ13C負(fù)偏；此時(shí)土壤有機(jī)質(zhì)微粒含量升高,灰度值亦增大；反之亦然。石筍TCL的微量元素比Sr/Ca和Ba/Ca與δ13C之間也存在較好的相關(guān)關(guān)系,表明微量元素比值的變化可以作為古氣候與古環(huán)境重建記錄的有效補(bǔ)充。在14.4ka BP以來,研究區(qū)域最為顯著的變化出現(xiàn)在5.6～4.2ka BP時(shí)段,此時(shí)Sr/Ca和Ba/Ca大幅度下降形成一顯著低谷,而δ13C和灰度均表現(xiàn)出相似的變化特征,說明降水量、植被減少,局域環(huán)境明顯惡化。玉龍洞石筍8180記錄了與北大西洋冷事件相對(duì)應(yīng)的“4.2ka BP弱季風(fēng)事件”,持續(xù)時(shí)間為4.4ka～4.1ka BP,呈現(xiàn)出“兩峰三谷”結(jié)構(gòu)類型。同時(shí),玉龍洞記錄顯示東亞夏季風(fēng)自中世紀(jì)暖期(約1ka BP)開始呈現(xiàn)顯著的增強(qiáng)趨勢(shì),不同于印度季風(fēng)自小冰期結(jié)束后(約0.4ka BP)顯著增強(qiáng)。說明近千年以來的亞洲夏季風(fēng)增強(qiáng)可能受到不同驅(qū)動(dòng)因子的影響。
[Abstract]:In recent years, human society has paid more and more attention to global climate change. Cave stalagmites play an important role in the study of paleoclimate change because of their high precision dating and high resolution characteristics. Based on the absolute age of 9 U/Th and 787 未 180 test data of stalagmites in Yulongdong (No. TCL), the East Asian monsoon variation sequence in Lichuan area since 14.4ka BP is established in this paper. The 未 180 climate evolution sequence of Yulong cave stalagmites TCL is consistent with the records of other cave stalagmites in Asian monsoon region from 1000 to 100 years, which indicates that 未 180 of cave stalagmites in Asia is driven by the same climate influencing factors. Stalagmites 未 180 records can well reflect the Asian monsoon climate change on the scale of 1000 to 100 years. The 未 13 C value of stalagmites TCL mainly reflects the change of vegetation abundance in the study area and has obvious periodic characteristics, which can be divided into four cycles. The results of power spectrum analysis show that 813 C has a significant period of about 2000 years, which may reflect the special variation of the local environment in the study area. There is a good correlation between the gray scale and 未 13 C curve of stalagmites TCL, which are basically the same in the overall change trend, showing obvious peak and valley corresponding characteristics. The good correspondence between carbon isotopes and sedimentary lithology of asparagus confirms the reliability of this alternative index, and also shows that the two have a common driving mechanism: when the rainfall is abundant, the plants are luxuriant and the yield of CO2 in soil is increased, 未 13 C negative deviation; At this time, the content of soil organic matter particles increased, and the gray value also increased, and vice versa. There is also a good correlation between trace elements in stalagmites TCL and Sr/Ca and Ba/Ca and 未 13 C, which indicates that the change of trace element ratio can be used as an effective supplement to the record of paleoclimate and paleoenvironment reconstruction. Since 14.4ka BP, the most significant change in the study area has occurred in the 5.6~4.2ka BP period. At this time, Sr/Ca and Ba/Ca decreased significantly to form a significant trough, while 未 13 C and gray scale showed similar characteristics. It shows that precipitation, vegetation decrease and local environment deteriorate obviously. Yulongdong stalagmites 8180 recorded the "4.2ka BP weak monsoon event" corresponding to the North Atlantic cold event, and the duration of the "two peaks and three valleys" structure type for 4.4ka~4.1ka BP,. At the same time, Yulong cave records show that the East Asian summer monsoon has shown a significant enhancement trend since the medieval warm period (about 1ka BP), which is different from that of the Indian monsoon since the end of the Little Ice Age (about 0.4ka BP). It is suggested that the enhancement of the Asian summer monsoon in recent thousands of years may be affected by different driving factors.
【學(xué)位授予單位】：南京師范大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：P532

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相關(guān)期刊論文 前1條

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本文編號(hào)：2481364