本文選題：晚奧陶世生物大滅絕 + 碳循環(huán)擾動(dòng)��； 參考：《中國(guó)科學(xué)技術(shù)大學(xué)》2017年博士論文

【摘要】：地質(zhì)歷史時(shí)期典型生物滅絕事件期間環(huán)境氣候條件以及海洋碳硫循環(huán)的重建,對(duì)人類(lèi)正確認(rèn)識(shí)現(xiàn)代環(huán)境和生物危機(jī)以及促進(jìn)人與自然和諧發(fā)展具有重要意義。本課題以晚奧陶世海相沉積巖為載體,探究當(dāng)時(shí)生物大滅絕期間海洋和大氣的化學(xué)條件及其變化機(jī)制以及對(duì)生物滅絕的影響。本文主要集中于以下三個(gè)方面:1.晚奧陶世海洋碳循環(huán)擾動(dòng)機(jī)制的探究在具有詳細(xì)生物地層控制的基礎(chǔ)上,對(duì)采自美國(guó)內(nèi)華達(dá)州Copenhagen Canyon剖面碳酸鹽的無(wú)機(jī)碳同位素、87Sr/86Sr比值以及微量元素進(jìn)行分析,并結(jié)合模型計(jì)算重建了當(dāng)時(shí)海洋碳循環(huán)及其擾動(dòng)的主要控制因素。結(jié)果表明,該剖面未受顯著的后期成巖蝕變,記錄了海水的原始同位素信息:晚奧陶期間存在兩次顯著的碳同位素正偏移(峰值分別為～+7‰和～+5‰),且與岡瓦納冰川的開(kāi)始和消融具有很好的一致性。對(duì)應(yīng)地,87Sr/86Sr比值存在兩次快速降低且與碳同位素和冰川協(xié)同變化。結(jié)合數(shù)據(jù)以及海洋箱式模型的綜合分析,本文認(rèn)為碳酸鹽風(fēng)化輸入的增加是導(dǎo)致全球晚奧陶世碳同位素正偏的主導(dǎo)因素,不一定需要有機(jī)碳埋藏增加:冰川開(kāi)始,海平面下降,碳酸鹽臺(tái)地風(fēng)化加強(qiáng),導(dǎo)致河流輸入的碳同位素組成變重,從而導(dǎo)致海相碳酸鹽的碳同位素組成正偏;冰川融化,海平面上升,碳酸鹽臺(tái)地被海水淹沒(méi),風(fēng)化輸入減少,海相碳酸鹽的碳同位素組成恢復(fù)到初始值。2.貴州紅花園剖面的多硫同位素(A33S,δ34S,和△36S)記錄及其環(huán)境指示意義對(duì)采自貴州桐梓紅花園剖面的沉積巖樣品進(jìn)行高精確度的多硫同位素組成以及碳、硫含量分析。首次在24.5億年以來(lái)的地質(zhì)記錄中發(fā)現(xiàn)了硫同位素的非質(zhì)量相關(guān)分餾(△33S最大可達(dá)～0.9‰)。通過(guò)對(duì)數(shù)據(jù)和硫同位素分餾原理的綜合分析,認(rèn)為與大規(guī)�；鹕絿姲l(fā)相伴隨的平流層光化學(xué)反應(yīng)是產(chǎn)生紅花園硫同位素非質(zhì)量相關(guān)分餾的原因。這一發(fā)現(xiàn)識(shí)別出晚奧陶期間華南曾存在多次平流層火山噴發(fā),并將大規(guī)�；鹕交顒�(dòng)和晚奧陶世生物滅絕聯(lián)系起來(lái);表明硫同位素的非質(zhì)量相關(guān)分餾也能發(fā)生并保存在顯生宙的地質(zhì)記錄中,為晚奧陶世生物滅絕的機(jī)制提供了新的視角,也為重建地史時(shí)期火山活動(dòng)的生態(tài)和環(huán)境效應(yīng)提供了新的有效研究手段。這一結(jié)論也得到其他地質(zhì)記錄的支持:在華南及全球中晚奧陶世地層中廣泛發(fā)現(xiàn)大量蝕變火山灰?jiàn)A層,表明當(dāng)時(shí)全球火山活動(dòng)頻繁,與火山活動(dòng)相伴隨的環(huán)境惡化以及臭氧層空洞可能是造成晚奧陶世生物滅絕的原因之一。3.秀山和Vinini Creek剖面的汞(Hg)記錄及其環(huán)境指示意義對(duì)采自重慶秀山和美國(guó)內(nèi)華達(dá)州Vinini Creek剖面的沉積巖樣品進(jìn)行Hg濃度、Hg/TOC比值以及Hg同位素組成的分析測(cè)試。發(fā)現(xiàn)兩個(gè)剖面在晚奧陶期間均呈現(xiàn)Hg富集特征(Vinini Creek剖面的Hg濃度高達(dá)736.6ppb),遠(yuǎn)高于正常海洋沉積物的Hg含量,表明當(dāng)時(shí)外界Hg輸入顯著增加。結(jié)合Hg同位素?cái)?shù)據(jù),本文認(rèn)為秀山和Vinini Creek異常的Hg富集特征是火山活動(dòng)導(dǎo)致Hg釋放增加的結(jié)果。晚奧陶世生物滅絕之前及附近層位的Hg富集信號(hào)指示火山活動(dòng)可能是造成這次生物滅絕的原因之一,與本文多硫同位素研究的結(jié)論一致。另外,本文Hg濃度及Hg/TOC數(shù)據(jù)顯示局部的沉積環(huán)境條件可能對(duì)沉積物Hg異常的記錄產(chǎn)生顯著影響�；鹕交顒�(dòng)或其他過(guò)程導(dǎo)致的Hg輸入增加在沉積物中的保存與有機(jī)質(zhì)的埋藏量密切相關(guān):當(dāng)有機(jī)質(zhì)的埋藏量大大超過(guò)Hg沉降的需求時(shí),即使火山活動(dòng)導(dǎo)致Hg輸入增加,Hg/TOC比值仍然因?yàn)門(mén)OC含量高而偏低,不能真實(shí)反映Hg輸入的異常;而如果有機(jī)質(zhì)埋藏太少,Hg輸入的異常也不能保存在沉積物中。因此,運(yùn)用沉積物Hg/TOC比值作為古火山活動(dòng)的指標(biāo)時(shí),應(yīng)綜合評(píng)估Hg濃度、Hg/TOCL比值、TOC含量以及樣品的沉積環(huán)境和古地理?xiàng)l件,以獲得準(zhǔn)確的古火山活動(dòng)及環(huán)境效應(yīng)信息。
[Abstract]:The environmental climate conditions and the reconstruction of marine carbon and sulfur cycle during the period of the typical biological extinction events in the geological history period are of great significance for human beings to correctly understand the modern environment and the biological crisis and to promote the harmonious development of human and nature. The chemical condition and its change mechanism of gas and its influence on the extinction of the organisms. This paper mainly focuses on the following three aspects: 1. late Ordovician Marine carbon cycle disturbance mechanism, on the basis of detailed biostratigraphic control, the inorganic carbon isotopes and 87Sr/86Sr ratios of the Copenhagen Canyon caesarean section of Nevada, USA The main control factors of marine carbon cycle and its disturbance were reconstructed with the analysis of trace elements and combined with the model calculation. The results showed that the section was not subjected to significant late diagenesis and recorded the original isotopic information of the sea water: there were two significant carbon isotopic shifts between the late Ordovician period (peak value of ~ +7 per thousand and ~ ~ (- 1), respectively). +5 per 1000) has a good consistency with the beginning and ablation of the Gondwana glacier. Corresponding, the ratio of 87Sr/86Sr has two rapid decreases and cooperates with carbon isotopes and glaciers. Combined data and the comprehensive analysis of the ocean box model, the increase of the carbonate weathering input is the result of the global late Austrian Tao Shitan isotopes. The leading factors do not necessarily require an increase in organic carbon burial: the glacier begins, the sea level falls, and the weathering of the carbonate platform is strengthened, resulting in a heavy carbon isotope composition of the river, which leads to a positive carbon isotope composition of the marine carbonate; the glaciers melt, the sea level rises, the carbonate platform is inundated by sea water, the weathering input is reduced, marine carbon is reduced. The carbon isotope composition of acid salts is restored to the initial value.2. Guizhou red garden section of polysulfide isotopes (A33S, Delta 34S, and delta 36S) records and their environmental indicator significance for the high accuracy of the polysulfide isotopes and the analysis of carbon and sulfur content in the sedimentary rocks samples collected from the Tongzi red garden section of Guizhou. For the first time, the geological records of 2 billion 450 million years have been recorded. The non mass correlation fractionation of sulfur isotopes (up to 0.9 per 1000) was found in the record. Through a comprehensive analysis of the principle of data and sulfur isotope fractionation, it is believed that the photochemical reaction with the stratospheric photochemical reaction associated with large-scale volcanic eruption is the cause of the non mass fractional distillation of the sulfur isotope in the safflower garden. This discovery recognizes the late Ordovician period. There was a number of stratospheric volcanic eruptions in Southern China, which linked the large-scale volcanic activity to the late Ordovician extinctions, indicating that the non mass correlation of sulfur isotopes could also occur and remain in the Phanerozoic geological record, providing a new perspective for the mechanism of the late Ordovician biological extinction and the reconstruction of the volcanic activity in the period of the geological history. Dynamic ecological and environmental effects provide new and effective means of research. This conclusion has also been supported by other geological records. A large number of altered volcanic interbeds are widely found in Southern China and the middle Late Ordovician strata in the world, indicating the frequent global volcanic activity, environmental deterioration associated with volcanic activity, and the possibility of ozone hole holes. One of the causes of the late Ordovician extinction is one of the mercury (Hg) records of Xiushan and Vinini Creek sections of.3. and its environmental significance. The analysis of Hg concentration, Hg/TOC ratio and Hg isotopes from the sedimentary rocks samples collected from Chongqing Xiushan and the Vinini Creek section of Nevada, USA, found that two sections were in the late Ordovician period. The concentration of Hg (the Hg concentration of the Vinini Creek section is as high as 736.6ppb), which is far higher than the Hg content in the normal marine sediments, indicating that the input of Hg is significantly increased at that time. Combining with the isotopic data of Hg, this paper holds that the Hg enrichment of the anomalies of the Xiushan and Vinini Creek is the result of the increase of the release of the volcanic activity induced Hg. The Hg enrichment signals at the front and near sites indicate that volcanic activity may be one of the causes of this biological extinction. It is in agreement with the conclusion of the study of polysulfide isotopes in this paper. In addition, the concentration and Hg/TOC data in this paper show that the local sedimentary environment conditions may have a significant impact on the record of Hg anomalies in the sediments. Volcanic activity or other processes. The increased storage of Hg input in the sediment is closely related to the amount of organic matter buried in the sediments: when the amount of organic matter is much more than the demand for Hg settlement, even if the volcanic activity leads to the increase of Hg input, the Hg/TOC ratio is still low because of the high TOC content, which can not reflect the abnormal Hg input, but if the organic matter is buried too little, Hg loses. When the sediment Hg/TOC ratio is used as an indicator of paleo volcanic activity, the concentration of Hg, the ratio of Hg/TOCL, the content of TOC, the sedimentary environment and the palaeogeographic conditions of the samples should be comprehensively evaluated in order to obtain accurate paleo volcanic activity and the information of the environment effect.
【學(xué)位授予單位】：中國(guó)科學(xué)技術(shù)大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2017
【分類(lèi)號(hào)】：P736.22
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本文編號(hào)：1946146