四川盆地东北部晚二叠世长兴期遗迹化石与环境研究

发布时间：2018-10-22 06:28

【摘要】：川东北晚二叠世长兴期大隆组出露完整,主要由砂泥质灰岩和硅质页岩组成,同时保存了丰富的生物扰动构造,为研究晚二叠世深水陆棚、盆地环境中生物的殖居特征,生物的个体习性、沉积底质性质变化、以及生物对沉积环境的适应能力等提供了相应的材料,利于解释P/T之交生物大灭绝的原因及晚二叠世的生态演化特征。本文通过结合遗迹学和沉积学信息,对大隆组遗迹属种的识别和鉴定、遗迹化石的生态习性分类、生物扰动强度定量评估、遗迹组构的识别(生物扰动量、深度、分异度、阶层类型等)等遗迹学特征进行了充分的研究,取得了以下5个方面的进展：(1)基于研究区的沉积特征,将大隆组划分为3部分10小层,并识别出2种沉积相4类岩相组合；(2)在大隆组中共识别出8属13种遗迹化石,提出了4种生物的造迹的行为方式；(3)在大隆组中共识别出6类遗迹组构,即深水盆地相中的Palaeophycus tubularis遗迹组构,深水陆棚相中的Palaeophycus heberti遗迹组构、Chondrites type-B遗迹组构、Treptichnus bifurcus遗迹组构、Planolites montanus遗迹组构、Palaeophvcus striatus遗迹组构。遗迹组构的演化指示了沉积环境的变化：从以硅质页岩沉积为主的深水盆地环境到以含砂质、泥质碳酸盐岩沉积为主的深水陆棚环境,反应了晚二叠世的底栖生物在深水环境中的殖居状态。(4)大隆组由下至上,遗迹组构之间存在一定的规律性：生物扰动量呈现中间强两端弱的趋势；遗迹组构间的阶层类型从简单浅-中阶层类型到遗迹属种单一但复杂浅阶层类型,最后又过渡到简单浅-中阶层类型；沉积底质是由软底到饱含水的汤底再到固结性硬底底质的变化过程；遗迹化石从边界较清晰、发育厚衬壁、边界清晰、发育薄衬壁。这些规律综合表明内栖生物在盆地相中的殖居过程生物扰动强度在垂向上的不断变化,改变了沉积底质性质,也带动了生物行为习性的改变。(5)控制大隆组遗迹群落的环境因素主要有浊流事件的插入、沉积环境和生态环境的演变,对造迹生物的聚集状态(丰度、分异度)、造迹行为(扰动量、扰动深度、阶层类型、底质性质)、消亡(缺氧)产生了重要影响。
[Abstract]:The late Permian Changxing Dalong formation in northeastern Sichuan is composed mainly of sandy mudstone and siliceous shale, and has preserved abundant biological disturbance structures. In order to study the living characteristics of organisms in the late Permian deep shelf and basin environment, the late Permian period Dalong formation is mainly composed of sandy mudstone and siliceous shale. The individual habits of organisms, the changes of sedimentary sediment properties, and the adaptability of organisms to the sedimentary environment provide relevant materials, which are helpful to explain the reasons for the great extinction of organisms at the junction of P / T and the ecological evolution characteristics of the late Permian. Based on the information of ichnology and sedimentology, the identification and identification of the genus and species of the Dalong formation, the classification of ecological habits of trace fossils, the quantitative evaluation of bioturbation intensity, the identification of trace fabric (bioturbation, depth, differentiation), (1) based on the sedimentary characteristics of the study area, the Dalong formation is divided into 3 parts and 10 sublayers, and 2 sedimentary facies and 4 types of lithofacies assemblages are identified. (2) eight genera and 13 species of trace fossils were identified in the Dalong formation, and the behavioral patterns of 4 species of organisms were proposed. (3) in the Dalong formation, six types of trace fabric were identified, that is, the Palaeophycus tubularis trace fabric in the deep water basin facies. Palaeophycus heberti relic fabric, Chondrites type-B vestigial fabric, Treptichnus bifurcus vestigial fabric, Planolites montanus relic fabric, Palaeophvcus striatus relic fabric in deep water shelf. The evolution of vestigial fabric indicates the change of sedimentary environment: from the deep-water basin environment dominated by siliceous shale deposition to the deep-water shelf environment dominated by sandy and argillaceous carbonate deposits. It reflects the colonization state of benthos in the deep water environment of late Permian. (4) the Dalong formation is from the bottom to the top, and there are some regularity among the relic fabric: the amount of biological disturbance shows the tendency of the middle strong two ends weak; The types of stratum between relic fabric are from simple shallow-middle stratum type to single but complex shallow stratum type of vestigial genus, and finally to simple shallow-middle stratum type. Sedimentary sediments change from soft bottom to water-rich soup bottom and then to consolidated hard bottom. Trace fossils develop thick lining wall with clear boundary and thin lining wall. These laws indicate that the intensity of biological disturbance changes vertically during the colonization process of endobenthos in the basin facies, which changes the properties of sedimentary sediments. (5) the environmental factors controlling the relic communities of the Dalong formation include the insertion of turbidity events, the evolution of the sedimentary environment and the ecological environment, and the accumulation state (abundance) of the trace organisms. Differentiation), trace making (disturbance, depth of disturbance, class type, bottom property), extinction (anoxia) have important effects.
【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：Q911.2;P534.46

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