古特提斯—泛大洋地区三叠纪重要环境气候事件的古海洋学研究

发布时间：2018-03-08 03:26

  本文选题：Smithian-Spathian　切入点：Carnian　出处：《中国地质大学》2017年博士论文　论文类型：学位论文

【摘要】：二叠纪—三叠纪之交的生物大绝灭是显生宙最大的一次生物灭绝事件和极端环境气候灾难,是地球科学的焦点问题之一。长久以来,学术界对此次大灭绝事件的研究一直保持着极高的热情,但与此同时三叠纪长达~50个百万年的生物复苏和辐射阶段也伴随着一系列显著的环境气候事件,其中生物与环境的协同演化关系却不得人知。二叠纪末生物大灭绝之后,极端恶劣的环境气候条件在早三叠世反复出现,以致海洋生态系统经历了异常缓慢和曲折的复苏重建过程。其中,早三叠世Smithian-Spathian界线事件见证了一系列显著的生物、环境和气候变化。中三叠世海洋生物类群大规模辐射演化,形成复杂且稳定的具有现代雏形的生态系统。晚三叠世海洋生态系统进一步向好,但晚三叠世中Carnian时期持续近1个百万年的超长强降雨事件不仅严重打击了早-中三叠世繁盛一时的生物类群,而且也极大地改变了海洋和陆地生态系统,以及地球生物的演化轨迹。早三叠世Smithian-Spathian界线事件和晚三叠世中Carnian期超长强降雨事件以气温的显著升降和生物的大规模灭绝为特点,是近些年才被慢慢重视的全球性事件,但对于这两次事件过程中全球气温的变化模式、海洋环境的演变过程,以及二者间相互关系的认识还严重不足,对全球不同地区事件表现形式的差异性还没有全面了解。本文选取古特提斯和泛大洋地区代表性剖面,利用全岩和牙形石元素和同位素等地球化学指标,对早三叠世Smithian-Spathian界线事件和晚三叠世中Carnian期超长强降雨事件过程中海水表层温度、陆地风化作用、海洋锶同位素组成、海水氧化还原状态和海洋碳-硫循环的演变做了系统研究。在此基础上,探讨了极端环境气候事件在古特提斯和泛大洋地区表现形式上的异同及原因。首先在泛大洋地区Kamura剖面建立了精确的牙形石生物地层和碳同位素地层格架,并对剖面沉积历史做了详细研究。在Kamura剖面建立了三叠纪共14个牙形石带。自下而上依次为Hindeodus parvus带、Isarcicella isarcica带、Neospathodus dieneri带、Novipathodus waageni-Parachirognathus带、Chiosella ex gr.timorensis-Cratognathus带、Paragondolella excelsa-Pg.alpina带、Budurovignathus hungaricus带、B.mungoensis带、Quadralella tadpole-Gladigondolella malayensis带、Q.angulata-Q.lobata-Q.carpathica带、Primatella cf.orchardi-P.permica带、Epigondolella rigoi-Pa.hallstattensis带和E.ex gr.bidentata-Norigondolella steinbergensis带。Kamura剖面二叠纪-三叠纪界线位于Mitai组顶部以上0.20米,以H.parvus的首次出现为标志;早三叠世-中三叠世界线位于Mitai组顶部以上17.60米,以Ch.ex gr.timorensis的首次出现为标志。沉积微相研究表明,晚二叠世生物大灭绝事件发生时海平面显著升高;中-晚Smithian时期海平面快速下降,并导致整个Spathian的缺失;中-晚三叠世海平面波动不大。Spathian的沉积缺失可能是与Smithian-Spathian界线附近全球降温导致的海平面下降有关。牙形石化石材料常被用于古海洋环境事件分析,因此本文首先探讨了牙形石在古海洋环境事件分析中的技术方法,包括了牙形石生物磷灰石在成岩作用过程中元素和同位素的变化,获得了以下新的认识:(1)牙形石REE可以反映原始海水信息,但当其围岩受到陆源碎屑物质的严重“污染”时,其中产出的牙形石大多数无法记录原始海水信息。受陆源碎屑物质严重“污染”的牙形石碎屑元素(Th、Si、Al和Ni等)和Mn含量很高,U含量很低,MREE强烈富集,Y/Ho和LaN/Yb N比值较低,同时∑REE和Th有显著的正相关性。牙形石在成岩作用过程中对元素的吸收开始于贫氧带,主要在成岩作用晚期更深更缺氧的埋藏环境。牙形石对元素的选择性吸收与围岩性质有直接关系,与样品时代无关。受陆源碎屑严重“污染”的不同时代的牙形石,其微量元素组成具有极高的相似性。(2)牙形石生物磷灰石结构和成分具有不均一性。内部比表层结晶度低,牙基比牙尖结晶度低,牙尖可能是受成岩作用改造最强烈的部位。牙形石表层主要为羟基(氟)磷灰石,内部主要是锶羟基(氟)磷灰石,牙形石内部受到的成岩改造最强烈。随着成岩改造的增强,牙形石更富集Sr2+和Mg2+,贫Fe3+、Mn2+和Ca2+。拉曼光谱ν1-PO3-4的峰位(或峰位偏移量SS1)和半高宽(或半高宽偏移量SS2)是识别元素含量变化的良好指标。单一牙形石个体氧同位素存在较大差异,乳白色牙冠比玻璃质牙冠和牙基低0.28-0.32‰。牙形石内部比表层低1.08±0.37‰。此外,牙形石乳白色牙冠比其它部位重结晶程度要高,牙形石内部比外部具有更多的外来离子(如,Sr2+),因此牙形石乳白色牙冠和牙形石内部可能是受成岩作用改造最严重的部位。Smithian-Spathian界线综述研究表明,菊石关键属(如,晚Smithian菊石Anawasatchites、Anasibirites、Glyptophiceras和Xenoceltites;早Spathian菊石Bajarunia、Tirolites和Columbites)和牙形石关键种(如,Novispathodus pingdingshanensis、Budurovignathus hungaricus和Neogondolella aff.sweeti)是定义Smithian-Spathian界线重要的生物标志。碳同位素的正偏移(从N3到P3,或从m(N3-P3)到P3)是定义Smithian-Spathian界线的重要辅助标志。对前人Smithian-Spathian界线位置的修正结果显示,Smithian极热事件位于碳同位素曲线N3和m(N3-P3)之间,Smithian-Spathian界线对应全球气温的显著下降。安徽巢湖平顶山西剖面是早三叠世Smithian-Spathian界线研究的重要参考剖面。本文在古特提斯东部中国华南地区三个Smithian-Spathian界线剖面(石头寨、平顶山西和甲戎)和泛大洋西部日本Kamura剖面系统研究了Smithian-Spathian界线事件,获得了以下新认识:(1)在Smithian时期,泛大洋地区海水表层温度比古特提斯地区低约8-12℃,以往认为的Smithian极热事件在泛大洋地区并不明显。(2)早-中Smithian随着气温升高,古特提斯地区有大量的碎屑物质输入,同时泛大洋地区碎屑物含量也有比较明显的增加;晚Smithian早期古特提斯地区气温显著下降,但是陆地风化速率依旧很高,而泛大洋地区比较敏感,碎屑物含量在Smithian晚期就有明显的下降。(3)在Smithian晚期,古特提斯浅水地区海水缺氧状况有明显改善,而古特提斯深水地区和泛大洋浅水地区缺氧程度增加,直到Spathian早期古特提斯深水地区海水缺氧状况才有明显改善。(4)在Smithian时期,古特提斯和泛大洋浅水地区δ~(13)Ccarb与δ~(34)SCAS呈负相关演变模式,而古特提斯深水地区呈正相关演变模式,且泛大洋地区δ~(34)SCAS值明显低于古特提斯地区。Griesbachian和Dienerian时期泛大洋地区δ~(34)SCAS也明显低于古特提斯地区,δ~(13)Ccarb-δ~(34)SCAS负相关演变模式也与特提斯地区有显著差别。古特提斯深水相和浅水相碳-硫循环模式的差异与降温导致的海洋循环加快和海洋生产力的提高有关。而泛大洋碳-硫循环模式可能与这一地区极低的硫酸盐浓度和较低的硫的海水滞留时间有关。本文在古特提斯东部华南姚家湾剖面和泛大洋西部日本Kamura剖面系统研究了中Carnian超长强降雨事件,获得了以下新认识:(1)中Carnian超长强降雨事件期间,古特提斯和泛大洋地区海水表层温度均有明显升高,升幅约5-7℃。(2)与气温升高同步,陆地风化作用显著增强,海水还原程度增加,海洋碳-硫循环异常。特提斯地区碎屑输入量明显高于泛大洋地区。(3)泛大洋地区由于远离大陆保存与全球海水一致的87Sr/86Sr值,87Sr/86Sr在Carnian期呈缓慢上升的趋势。(4)中Carnian事件期间,古特提斯和泛大洋地区海水都发生了严重的缺氧甚至硫化。其中古特提斯海水缺氧程度明显高于泛大洋地区,且持续时间更长。(5)中Carnian超长强降雨事件期间,古特提斯和泛大洋地区海水δ~(13)C和/或δ~(34)S均发生了同步的负偏移,与这一时期气温的升高同步。事件期间,全球碳同位素的负偏移可能与同时期的火山作用有关,这一时期海洋碳硫循环异常反映了气候变化和火山作用对海洋环境的共同影响。
[Abstract]:Biological extinction of Permian Triassic extinction event is one of the largest Phanerozoic and extreme environmental climate disaster is one of the hot issues of earth science. For a long time, research on the mass extinction event in academic circles has maintained a high enthusiasm, but at the same time for recovery of ~50 million in the year and the radiation phase also accompanied by a series of significant climate events, including the co evolution relationship between organisms and environment is not known. After the end Permian mass extinction, climate extremes appear repeatedly in the Early Triassic three, so that the marine ecosystem has experienced a slow and tortuous process of recovery and reconstruction. The abnormal three, early Triassic Smithian-Spathian boundary event witnessed a series of significant biological, environmental and climate change. In three groups of large-scale Triassic marine biological evolutionary radiation The formation of complex and stable, with a modern prototype ecosystem. Further the better late three Triassic marine ecosystems, but late Triassic in the three Carnian period lasted nearly 1 millions of years long heavy rainfall event is not only a serious blow to the organism in three early Triassic flourished, but also greatly changed marine and terrestrial ecosystems, and the earth's biological evolution trajectory. As early as three Smithian-Spathian and Late Triassic boundary event in Triassic period three Carnian long heavy rainfall events characterized by significant mass extinction and biological temperature lifting, is a global event in recent years is gradually attention, but for the two models of global change the incident process temperature, the evolution process of the marine environment, and study the relationship between the two is seriously insufficient, the difference of different parts of the world event form is not fully understand This paper selects Gut Tis and Pan Ocean area representative section, using the whole rock and conodont elements and isotopic geochemical indicators of sea surface temperature in early three and Late Triassic boundary event Smithian-Spathian three Carnian in the Triassic period long heavy rainfall events in the process of terrestrial weathering, marine strontium isotopic composition of seawater. Redox status and evolution of marine carbon - sulfur cycle were studied. On this basis, discussed the differences and reasons of extreme climate events in the environment of Gut Tis and Pan Ocean area form. The first section is established in the Fan Dayang area Kamura precise conodont biostratigraphy and carbon isotope stratigraphy, and the sedimentary history is studied in detail in section Kamura. A total of 14 Triassic conodont zones. Followed by bottom-up Hindeodus parvus, Isarcicella isarcica, Neospa Thodus dieneri, Novipathodus waageni-Parachirognathus Chiosella ex gr.timorensis-Cratognathus, Paragondolella excelsa-Pg.alpina, Budurovignathus hungaricus, B.mungoensis, Quadralella, tadpole-Gladigondolella malayensis, Q.angulata-Q.lobata-Q.carpathica Primatella cf.orchardi-P.permica, Epigondolella rigoi-Pa.hallstattensis and E.ex, with gr.bidentata-Norigondolella steinbergensis with the.Kamura profile of Permian Triassic boundary is located at 0.20 meters above the top of group Mitai, which appeared for the first time for H.parvus mark; Early Triassic in three three fold line located above the world top 17.60 meters in the Mitai group, Ch.ex gr.timorensis first appeared as a symbol. The sedimentary microfacies research shows that sea level increased significantly in the Late Permian mass extinction event occurs in the late period of Smithian; when the sea level fast Drop, and cause the lack of the entire Spathian; absence of sediment middle - Late Triassic three sea-level fluctuations do not.Spathian may be related to global cooling caused the sea level near the boundary of Smithian-Spathian decreased. Conodont material is often used in the analysis of the ancient marine environment, therefore this paper discusses the technical method in the analysis of ancient marine environment in the event of conodonts, including conodont apatite in biological changes of elements and isotopes during the diagenetic process, obtained the following new ideas: (1) the conodont REE can reflect the information of sea water, but when the surrounding rock has been a serious "pollution" of detrital material, which shaped teeth most of the original ore output to record information. By the sea of terrigenous material "serious pollution" of the conodont clastic elements (Th, Si, Al and Ni) and the content of Mn is high, U content is very low, strong enrichment of MREE, Y/Ho LaN/Yb and N ratio is low, at the same time REE and Th have significant positive correlation. The conodont elements began to absorb during diagenesis in oxygen depleted zone, mainly in the late diagenesis of deeper burial environment. Hypoxia selective conodont elements on the absorption have a direct relationship with the surrounding rock nature has nothing to do with the sample time. By terrigenous serious "pollution" of the different age of conodont, similar composition with high trace elements. (2) the conodont biological apatite structure and composition inhomogeneity. The internal degree is lower than the surface crystallization, tooth cusp than low crystallinity, teeth the tip may be affected by a part of the diagenetic transformation. The strongest conodont surface layer is mainly hydroxyl apatite (fluorine), is the main internal strontium (fluoro) hydroxy apatite, conodont diagenesis is most intense. With the enhancement of diagenesis, the conodont is more enriched in Sr2+ and Mg2+ Poor Fe3+, Mn2+, Ca2+. and Raman spectra of V 1-PO3-4 (peak or peak offset SS1) and half width (or half width SS2 offset) is a good indicator to recognize the change of element content. Single conodont individual oxygen isotope differences, milky white crown than vitreous crown and abutment low 0.28-0.32 per thousand. Conodont internal 1.08 + lower than the surface of 0.37 per thousand. In addition, the conodont milky white crown degree is higher than that of other parts of recrystallization, conodont has more than external foreign ions (e.g., Sr2+), so the conodont white crown and conodonts in May is of the most serious parts of the.Smithian-Spathian line summary of the diagenetic transformation shows that the key is ammonite (e.g., late Smithian Anawasatchites Anasibirites, Glyptophiceras and ammonites, Xenoceltites; Spathian Bajarunia Tirolites and early ammonoids, Columbites) and conodonts of key species (e.g., Nov Ispathodus pingdingshanensis, Budurovignathus hungaricus and Neogondolella aff.sweeti) is defined as the Smithian-Spathian line of important biological markers. A positive offset carbon isotope (from N3 to P3, or from m to P3 (N3-P3)) is an important auxiliary sign defined the Smithian-Spathian boundary. The correction results of previous Smithian-Spathian line position display, Smithian is located in the extreme heat events of carbon isotope curve N3 and m (N3-P3), Smithian-Spathian line decreased significantly the corresponding global temperature. Anhui Chaohu flat section of Shanxi is an important reference section of the Smithian-Spathian line three early Triassic. This paper in the three Smithian-Spathian boundary section of the Paleo Tethys Eastern Southern China area (Chinese Shitouzhai, flat topped Shanxi and a Rong) and Pan Ocean in western Japan Kamura study on the Smithian-Spathian boundary event profile system, obtained the following understanding: (1) in In the period of Smithian, the pan Bigutetisi sea surface temperature of the ocean area low of about 8-12 DEG Smithian, the past that extreme heat events is not obvious in the ocean area. (2) early in the Smithian as temperatures rise, the Paleo Tethys region has plenty of detrital material input, while content of debris pan ocean area also increased; the temperature of late Smithian early Paleo Tethys region decreased significantly, but the land weathering rate remains high, while the Pan Ocean area is relatively sensitive, significantly reduced debris content is in the late Smithian. (3) in the late Smithian, seawater hypoxia in shallow water area has obviously improved the Paleo Tethys, and the degree of hypoxia of Gut Tis and Pan Ocean deepwater area shallow water area increased, until the early Spathian Paleo-Tethyan deepwater area sea water anoxic condition have improved significantly. (4) in the Smithian period, Gut Tis and pan The shallow ocean area 8 ~ (13) Ccarb and 8 ~ (34) SCAS was negatively related to the evolution mode, and positively related Gut Tis deep-water area evolution pattern, and Pan Ocean area 8 ~ (34) SCAS value was significantly lower than that of the Paleo Tethys ocean area and Dienerian area of Pan.Griesbachian period 8 ~ (34) SCAS was significantly lower than the Paleo Tethys region, delta ~ (13) Ccarb- 8 ~ (34) SCAS negative correlation models have significant difference with the evolution of Tethys region. The difference of Paleo Tethys deep-water facies and shallow water phase carbon sulfur cycle model and ocean circulation cooling leads to speed up and improve the marine productivity. While the Pan Ocean Carbon - sulfur cycle model may sulfate the concentration of this region is very low and low sulfur water retention time related in this article. The Paleo Tethys eastern Gulf of Southern China Yao home and Pan Ocean profile in western Japan was studied in the Kamura section of Carnian long heavy rainfall events, obtained the following New understanding: (1) during the heavy rainfall event in the long Carnian, Gut Tis and Pan Ocean region sea surface temperature increased significantly, an increase of about 5-7 degrees Celsius. (2) increased synchronously with the temperature, continental weathering effect increase, water reduction degree increased, the marine carbon - sulfur cycle. Abnormal clastic input Tethys region was significantly higher than that of Pan Ocean area. (3) away from the mainland and the preservation of global seawater consistent 87Sr/86Sr values of Pan Ocean area, 87Sr/86Sr showed a slow upward trend in the period of Carnian. (4) during the Carnian event, Gut Tis and Pan Ocean sea area have undergone severe hypoxia and sulphide. Which Paleo-Tethyan hypoxic water was obviously higher than that of pan the ocean area, and for a longer period of time. (5) during the heavy rainfall event in the long Carnian, Gut Tis and Pan Ocean Sea Delta region ~ (13) C and / or 8 ~ (34) S had negative offset synchronization, and During the same period, the negative shift of global carbon isotope may be related to the same period of volcanism. During this period, the marine carbon and sulfur cycle anomaly reflected the common influence of climate change and volcanism on the marine environment.

【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】：P534.51;P532
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本文编号：1582215