【摘要】：越來(lái)越多的研究表明：早期生命的起源和演化,特別是真核生物,與地球大氣-海洋的氧化還原狀態(tài)存在密切的聯(lián)系。繼新元古代埃迪卡拉紀(jì)真核生物輻射之后,寒武紀(jì)早期出現(xiàn)兩側(cè)對(duì)稱和骨骼化動(dòng)物的快速演化,建立了現(xiàn)今動(dòng)物門(mén)類和海洋生態(tài)系統(tǒng)的總體格架,被稱為“寒武紀(jì)生命大爆發(fā)”。過(guò)去幾十年內(nèi),國(guó)內(nèi)外學(xué)者主要集中于動(dòng)物群的形態(tài)特征和組成、地層劃分與對(duì)比、磷礦和Ni-Mo多金屬礦機(jī)制等方面的研究,取得很大的進(jìn)展,如澄江動(dòng)物群。然而,對(duì)寒武紀(jì)早期海洋化學(xué)及其與這次重大生命演化間關(guān)系的理解還不夠深入。 傳統(tǒng)觀點(diǎn)認(rèn)為：環(huán)境的改變,尤其是深部海洋的完全氧化是“寒武紀(jì)生命大爆發(fā)”的觸發(fā)原因。然而,一些學(xué)者則認(rèn)為環(huán)境的改變(如海洋的完全氧化,硫酸鹽濃度的變化等)卻是這次重大生物事件的結(jié)果。雖然上述關(guān)于海洋化學(xué)與“寒武紀(jì)生命大爆發(fā)”間關(guān)系的認(rèn)知存在本質(zhì)性的差別,但都認(rèn)為“寒武紀(jì)生命大爆發(fā)”與海洋的完全氧化密切相關(guān)。此外,寒武紀(jì)早期海洋化學(xué)及其化石記錄間存在諸多矛盾：如深部水體的氧化記錄與缺氧記錄,海洋硫酸鹽庫(kù)容量的高低記錄,目前推測(cè)的海洋化學(xué)狀態(tài)與古生物記錄間的矛盾等。近來(lái),埃迪卡拉紀(jì)高度動(dòng)態(tài)分層的海洋化學(xué)結(jié)構(gòu)較好解決了這一時(shí)期海洋化學(xué)自身及其與古生物化石記錄間的矛盾,為寒武紀(jì)早期上述矛盾的解決提供了新的思路。我國(guó)華南出露了相對(duì)完整的不同沉積相(近岸-遠(yuǎn)洋)寒武紀(jì)早期地層,此外,這些地層已進(jìn)行了大量的巖石地層、古生物地層、年代地層、化學(xué)地層等工作,不僅為這一時(shí)期的地層劃分和對(duì)比提供基礎(chǔ),而且為海洋化學(xué)的時(shí)空波動(dòng)性及其與生命演化間關(guān)系的調(diào)查提供可能。 我們研究和分析了華南寒武紀(jì)早期貴州內(nèi)陸架金沙巖孔和外陸架甕安朵丁地區(qū)鐵-硫-碳(Fe-S-C)地球化學(xué)數(shù)據(jù)�；谝延械莫�(dú)立巖性和古生物地層劃分和對(duì)比依據(jù),我們將獲得的新數(shù)據(jù)與來(lái)自內(nèi)陸架云南肖灘外、陸架貴州遵義、斜坡相貴州松桃和盆地相湖南龍鼻嘴等剖面的已發(fā)表數(shù)據(jù)進(jìn)行對(duì)比,重建當(dāng)時(shí)的古海洋化學(xué)的時(shí)空波動(dòng)性(包括氧化還原條件和硫酸鹽含量),并進(jìn)一步分析了硫酸鹽含量波動(dòng)引起的氣候效應(yīng),最后,初步探討了海洋化學(xué)的波動(dòng)與生命演化間的關(guān)系。 近岸-遠(yuǎn)洋鐵組分化學(xué)與Mo含量的數(shù)據(jù)表明,雖然華南寒武紀(jì)早期表層海洋已被氧化,但深部海洋依舊為缺氧鐵化的環(huán)境,且楔狀的硫化水體動(dòng)態(tài)發(fā)展于陸架至斜坡地區(qū)。這一海洋化學(xué)結(jié)構(gòu)已被證實(shí)存在于晚太古代、中元古代和新元古代,表明前寒武紀(jì)的海洋化學(xué)結(jié)構(gòu)特征已延續(xù)至寒武紀(jì)早期。我們還發(fā)現(xiàn)近岸-遠(yuǎn)洋黃鐵礦硫同位素(834Spy)存在較大的梯度,表明這一時(shí)期海洋中硫酸鹽庫(kù)容量較小,這與前人認(rèn)為寒武紀(jì)早期硫酸鹽含量已接近現(xiàn)今水平的觀點(diǎn)不符。此外,較低的硫酸鹽含量會(huì)促使產(chǎn)甲烷古菌和甲烷好氧氧化細(xì)菌的繁盛,可能導(dǎo)致大量甲烷釋放至表層海洋和大氣中,從而對(duì)寒武紀(jì)的溫室氣候具有重要的貢獻(xiàn)。另一方面,寒武紀(jì)梅樹(shù)村階向南皋階轉(zhuǎn)變時(shí),斜坡相松桃和盆地相龍鼻嘴等地區(qū)δ34Spy出現(xiàn)逐漸變重,而內(nèi)陸架金沙地區(qū)逐漸變輕,外陸架甕安呈現(xiàn)沒(méi)有上述特征,我們認(rèn)為上述δ34Spy波動(dòng)的不同是上述地區(qū)陸源輸入硫酸鹽和海洋中硫酸鹽貢獻(xiàn)比例的不同引起的。此外,依據(jù)平衡條件下硫的循環(huán),即黃鐵礦硫同位素(δ34Spy)的波動(dòng)與陸源輸入,黃鐵礦埋藏和細(xì)菌硫酸鹽還原過(guò)程中的硫同位素分餾有關(guān),我們認(rèn)為深部水體硫酸鹽的降低是斜坡相松桃和盆地相龍鼻嘴地區(qū)δ34Spy升高的原因。 通過(guò)對(duì)比華南寒武紀(jì)早期海洋化學(xué)狀態(tài)和化石記錄,我們發(fā)現(xiàn)以節(jié)肢動(dòng)物為主的化石群存在于氧化水體下的沉積物中,而此時(shí)深部水體為缺氧甚至硫化的水體；以海綿為主的動(dòng)物化石群或小殼動(dòng)物化石群化石發(fā)現(xiàn)于缺氧非硫化水體沉積物中,硫化水體沉積物中未見(jiàn)到化石。此外,隨著寒武紀(jì)早期復(fù)雜動(dòng)物的不斷出現(xiàn),生物擾動(dòng)逐漸增強(qiáng),而深水地區(qū)如松桃和龍鼻嘴的硫酸鹽含量卻出現(xiàn)降低,表明生物擾動(dòng)作用對(duì)硫酸鹽含量的影響較小。因此,我們認(rèn)為寒武紀(jì)生命大爆發(fā)僅與當(dāng)?shù)氐暮Ｑ蠡瘜W(xué)條件相關(guān),而與開(kāi)闊海洋(特別是深部海洋)的海洋化學(xué)狀態(tài)無(wú)明顯直接的關(guān)系,這與前人關(guān)于寒武紀(jì)生命大爆發(fā)需要深部海洋的氧化或其導(dǎo)致深部海洋氧化和極高的硫酸鹽濃度的傳統(tǒng)觀點(diǎn)不一致。
[Abstract]:An increasing number of studies have shown that the origin and evolution of early life, in particular eukaryotes, have a close relationship with the redox state of the Earth's atmosphere. The rapid evolution of both sides of the Cambrian in the early part of the Cambrian and the rapid evolution of the bone-based animals in the early part of the Cambrian in the early part of the new proterozoic Ediacaran, and the establishment of the total physical frame of the present animal and marine ecosystem, is called the "Cambrian explosion". In the past few decades, domestic and foreign scholars mainly focus on the morphological characteristics and composition of the animal group, the formation division and the comparison, the phosphate rock and the Ni-Mo multi-metal ore mechanism and so on, and has made great progress, such as the Chengjiang fauna. However, understanding of the early Cambrian marine chemistry and its relationship with this major life evolution is not in depth. The traditional view is that the change of the environment, especially the complete oxidation of deep ocean, is the trigger of the "Cambrian explosion" However, some scholars believe that the change of the environment (such as the complete oxidation of the ocean, the change of the sulfate concentration, etc.) is the junction of this major biological event. Although the above-mentioned cognition of the relationship between the marine chemistry and the "Cambrian explosion" is different, it is considered that the "Cambrian explosion" is closely related to the complete oxidation of the sea In addition, there are many contradictions between the early-Cambrian marine chemistry and its fossil records, such as the oxidation record of deep water body and the oxygen-deficient record, the high and low record of the capacity of the marine sulfate reservoir, and the contradiction between the predicted marine chemical state and the ancient biological record. Recently, the highly dynamic layered marine chemical structure of the Ediacaran has better solved the contradiction between the marine chemistry itself and the records of the fossil-biological fossils during the period, and provided a new thought for solving the above-mentioned contradictions in the early part of the Cambrian. The early formation of the relatively complete sedimentary facies (inshore-ocean) is exposed in South China of China. In addition, the formation has carried out a lot of work such as rock formation, paleontology, age formation, chemical formation and so on, which not only provides basis for stratigraphic division and contrast in this period. In addition, the time-and-space fluctuation of marine chemistry and its relationship with the evolution of life are provided. The study and analysis of the geodesizing of iron-sulfur-carbon (Fe-S-C) in the southern part of the Cambrian in the early part of the Cambrian in the southern China The data is based on the existing independent lithology and the ancient biostratigraphic division and the comparative basis, and we will obtain the new data and the published data from the Yunnan Shoal, the land frame, the Zunyi, the slope, the Songtao of Guizhou, and the dragon nose of Hunan, etc. By contrast, the time-space fluctuation of the ancient marine chemistry at the time (including the oxidation reduction condition and the sulfate content) was reconstructed, and the climatic effect caused by the fluctuation of the sulfate content was further analyzed. The data of the chemical and Mo content of the near-shore-ocean-water component show that, although the early surface of the Cambrian in South China has been oxidized, the deep ocean is still an environment with an oxygen-deficient iron, and the wedge-shaped sulfide water is developed dynamically on the shelf The chemical structure of the ocean has been proved to be present in the late Archaean, Middle Proterozoic and Neoproterozoic, indicating that the marine chemical structure of the Precambrian has been extended to In the early part of the Cambrian, we have also found that the near-shore-pelagic pyrite-sulfur isotope (834 Spy) has a large gradient, indicating that the content of sulfate in the ocean during this period is small, which is similar to that of the previous time that the early-Cambrian sulfate content has been close to the present level In addition, the lower sulfate content can lead to the growth of the methane-producing archaea and the aerobic oxidation bacteria of methane, which can lead to the release of a large amount of methane to the surface of the sea and the atmosphere, so that the greenhouse climate of the Cambrian is On the other hand, on the other hand, when the order of the Precambrian Meishu Village was changed to the south, there appeared to be a gradual change in the Q34 Spy in the slope of the Songtao and the Xianglong nose of the basin, while the Jinsha area of the inland shelf was gradually lighter, and the outer continental shelf was not present. With the above-mentioned characteristics, we believe that the above-mentioned R34 Spy fluctuation is the proportion of the land-source input sulfate in the above-mentioned area and the sulfate contribution in the sea. In addition, the circulation of sulfur under equilibrium conditions, i.e., the fluctuation of the pyrite-sulfur isotope ({34 Spy), is the same as that of the sulphur isotope in the process of land-source input, pyrite burial and bacterial sulfate reduction The reduction of the sulfate in the deep water body is about 34 Spy in the slope of the Songtao and the Xianglong nose area of the basin. The reason of the increase is that by comparing the early marine chemical status and the fossil record of the Cambrian in South China, we find that an arthropod-based chemical stone group is present in the sediment of the oxidized water body, and at this time, the deep water body is oxygen-deficient. even a water body which is vulcanized; a sponge-based animal chemical stone group or small-shell animal chemical stone group fossil is found in the oxygen-deficient non-vulcanized water body deposit, and the sulfide water body is deposited; In addition, as the early and complex animals of the Cambrian appear, the biological disturbance is gradually enhanced, while the sulfate content of the deep water area such as the pine and the dragon nose is reduced, indicating the effect of the biological disturbance on the sulfate. The effect of the content is small. Therefore, we believe that the explosion of the Cambrian life is only related to the local marine chemical conditions, while the marine chemical state of the open ocean, especially the deep ocean, is not There is a clear direct relationship, which is closely related to the previous oxidation of the deep ocean or the deep ocean oxidation and extremely high sulfate concentration in the deep ocean due to the great explosion of the Precambrian life.
【學(xué)位授予單位】：中國(guó)地質(zhì)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：Q915;P534.41;P734

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