基于地球生物学的豫西寒武纪叠层石繁盛机理研究

Since phanerozoic, microbialites represented by stromatolites has been declining dramatically all over the world, whereas microbial reefs, mainly composed of microorganisms, distribute widely. The mainline of this project is about the appearance of stromatolites in Cambrain. According to stromatolites lying on the different rock strata, different micro-components of stromatolites, their contacted rock strata and other microbialites, the thesis analyzed the geochemical characteristics, such as the microbial fossils, microfossils assemblage and genetic environment, molecular fossils, carbon and sulfur isotopic composition and major and trace element features of stromatolites in Cambrian, by means of geobiology and using polarizing microscope, scanning electron microscopy (SEM), transmission electron microscopy(TEM)and atomic force microscopy (AFM). The main focuses on the project are as follows: the distinctive and similarity on type and species of microfossils in Cambrain stromatolites, the changing rules of microorganisms on the level of its abundance and diversity and the succession and the its stretchability of microorganisms regarding its region and interspace, comparing its with the microfossils of Proterozoic stromatolites and the microbe of modern microbial mats. The inter-relationship among the prosperity mechanism of stromatolites, the evolution of microorganisms and the change of paleo-environment would be found out, under the assistance of the factors like paleogeographical and structure, besides, the prosperity mechanism of Cambrian stromatolites would also be revealed. Not only the previous research reveals the process of metazoan explosion during the early period of Cambrian, but the updated evidence and information about the evolution rules of microorganisms and earlier life are provided.

显生宙以来，以叠层石为代表的微生物岩在全球范围内迅速减少，然而，在中寒武世-早奥陶世，以微生物为主要组构的生物礁却在全球广泛分布。本项目以寒武纪叠层石的出现为主线，以偏光显微镜、扫描电镜、原子力显微镜和透射电镜为手段，应用地球生物学的研究方法，针对不同层位的叠层石、叠层石的不同微区及其上下接触岩层和其它微生物岩，分析寒武纪叠层石微生物化石、化石组合及其成因环境、分子化石、碳硫同位素和主量、微量元素的特征，对比元古代叠层石微生物化石和现代微生物席，重点探讨寒武纪叠层石微生物化石在类型和种属上的异同、微生物在丰度和分异度上的变化规律及其在区间和空间上的继承性与延展性，辅助以古地理环境和古构造格局等因素，查明寒武纪叠层石繁盛与微生物变迁、古环境变化之间的关系，进而揭示豫西寒武纪叠层石繁盛的机理，为研究寒武纪初后生动物大爆发过程中及其以后微生物世界和早期生命的演化规律提供新的证据与信息。

本研究以叠层石与沉积环境的关系为主线，以偏光显微镜和扫描电镜为手段，应用“将今论古”的现实主义原理，从叠层石的宏观和微观角度，对叠层石的宏观形态特征、微观纹层和矿物特征、微生物化石及微生物席、叠层石钙化机理及成因和叠层石演化等方面进行了深入研究，全面揭示了叠层石形成的机理，丰富了我国叠层石研究的资料，为重建古环境、古气候和古构造等奠定了基础，也为揭示微生物世界与后生动物之间的协同演化关系提供了新的证据和信息。.豫西寒武系剖面连续，露头良好，叠层石等微生物岩丰富，共出露18层叠层石。叠层石宏观形态特征明显，主要有柱状、小丛状、缓波状、半球状和围绕竹叶状泥灰岩砾屑生长的叠层石等5大类，可细分为9小类13种，在详细描述叠层石宏观沉积特征的基础上，结合其伴生沉积构造，以现代海相叠层石的生长环境和前寒武纪叠层石的沉积环境等为佐证，建立了13种叠层石的沉积环境分布模式，同时指示出叠层石不同宏观形态特征与水动力条件之间的关系。.在豫西寒武纪叠层石中，发现了大量微生物化石，表现出明显的丝状和球状特征，为典型蓝细菌属的葛万菌和肾形菌，且微生物化石组合还具有一定的微生物席特征，这是适应生长环境条件的结果。根据叠层石的生长环境，结合不同类型叠层石钙化过程、钙化方式及其成因的差异，建立了5种不同形态特征叠层石的成因模式，对叠层石的成因机理有了更准确和更直接的认识。.依据叠层石丰度（厚度）、分异度（形态类型）及其宏观形态并结合沉积学和古生物学特征，将豫西寒武纪叠层石划分为6个演化组合类型，分析了演化组合的相关性特征以及宏观幕式演化和微观演化规律。根据寒武纪叠层石组合的演化特征，揭示出豫西寒武纪叠层石幕式演化的影响和控制因素，分别为：后生动物的衰减、水动力条件和沉积底质的变化以及陆源泥质的供应。