晚古生代冰期末期米兰科维奇旋回在华南的记录及环境响应

发布时间：2018-03-20 05:34

本文选题：米兰科维奇　切入点：晚古生代冰期末期　出处：《中国地质大学(北京)》2015年博士论文　论文类型：学位论文

【摘要】：在晚古生代冰期末期,地球气候系统从冰室逐渐进入温室,广阔的高纬度冰川被极为局限的阿尔卑斯型高山冰川所替代。与此同时,巨型季风系统逐渐发展,对中低纬度地区气候影响明显。牙形石生物地层资料显示广元市剑阁县上寺剖面和达州市宣汉县渡口剖面茅口组的时代为瓜德鲁普统世,在时间上与晚古生代冰期末期对应。本文以磁化率和非磁滞剩磁作为古气候替代指标对上寺和渡口剖面茅口组进行旋回地层学分析,并辅以高精度元素地球化学数据,目的是提取米兰科维奇旋回在晚古生代冰期末期的记录并讨论古环境对米兰科维奇旋回的响应。本文研究表明上寺和渡口剖面茅口组中均保存完整的米兰科维奇旋回信号(偏心率、斜率和岁差)。明显的斜率信号证明在晚古生代冰期末期,高纬度冰川的依然对全球气候有着较大影响。本文利用405 kyr长偏心率旋回建立浮动天文年代标尺,并对研究剖面的牙形石带进行天文年代约束并对比。研究剖面明显的~2.1和~1.8 Myr周期来自于对偏心率的天文调制作用(g4-g3周期),而~1.05和~0.9 Myr周期来自于对地轴斜率的天文调制作用(s4-s3周期)。由于太阳系内带行星的浑沌作用,晚古生代冰期末期的g4-g3和s4-s3周期比新生代的要短,但是依然保持着2:1的天文共振。在晚古生代冰期末期这个气候过渡期(从冰室逐渐进入温室),全球海平面三级层序主要受s4-s3周期控制。剖面斜率信号的强度变化证明二叠纪P3冰期经历了一个温暖-寒冷-温暖的气候波动。其中寒冷气候阶段在时间上恰好与Kamura事件对应。证明Kamura事件或是由地轴斜率在振幅最小时造成的冰川事件导致的。利用上寺剖面建立的浮动天文年代标尺结合频谱分析证明物源区化学风化作用(Fe/Ti)、水体氧化还原条件(S/Ti、V/Ti和Zn/Ti)、古营养水平(Ba/Ti)和碳酸钙生产力(Ca含量)均包含米兰科维奇旋回信号。Fe/Ti中保存的米兰科维奇旋回信号证明晚古生代冰期末期夏季风系统以及其控制的降雨量受天文轨道控制。在岁差频率上,陆源输入量和碳酸钙生产力相反,证明陆源碎屑物质输入至海洋的过程中会阻止碳酸钙生产力。夏季风导致的化学风化作用的峰值比其导致的上升流作用的峰值要早8 kyr,证明海洋对气候变化的反应滞后于陆地系统,这或由海洋系统的“缓冲机制”对气候变化的平衡作用导致。
[Abstract]:At the end of the late Paleozoic glacial period, the Earth's climate system gradually moved from the ice chamber to the greenhouse, and the vast high-latitude glaciers were replaced by the extremely limited Alpine alpine glaciers. Meanwhile, the giant monsoon system gradually developed. The data of conodont biostratigraphy show that the Maokou formation of Shangsi section in Jiange County, Guangyuan City, and the Maokou formation in Dukou section of Xuanhan County of Dazhou City, Dazhou City, China are of Guadruppian epoch. The time corresponds to the late Paleozoic glacial period. In this paper, using magnetic susceptibility and nonmagnetic hysteresis remanence as paleoclimate replacement indexes, cyclic stratigraphic analysis of Maokou formation in Shangsi and Dukou sections is carried out, supplemented by high precision geochemical data of elements. The aim of this study is to extract the records of Milankovich cycles at the end of the late Paleozoic glacial period and to discuss the response of paleoenvironment to the Milankovich cycle. The present study shows that the complete Milankovich is preserved in the Maokou formation of Shangsi and Dukou sections. Cyclic signal (eccentricity). Slope and precession. The obvious slope signals show that the high latitude glaciers still have a great influence on the global climate at the end of the late Paleozoic glacial epoch. In this paper, a floating astronomical age scale is established by using the 405th kyr long eccentricity cycle. The conodont zones of the study section were subjected to astronomical age constraints and compared. The apparent periods of 2. 1 and 1. 8 Myr of the profile are derived from the astronomical modulation of eccentricity in the G 4 g 3 cycle, and the periods of 1. 05 and 0. 9 Myr on the slope of the earth axis are derived from the astronomical modulation of the eccentricity. Because of the chaotic action of planets in the inner solar system, The cycles of g4-g3 and s4-s3 at the end of the late Paleozoic were shorter than those of the Cenozoic. However, the astronomical resonance of 2: 1 is maintained. In the late Paleozoic climate transition period (from ice chamber to greenhouse), the third order sequence of global sea level is mainly controlled by s4-s3 cycle. It is proved that the Permian P3 glacial period experienced a warm, cold and warm climate fluctuation, in which the cold climatic phase coincided with the Kamura event in time. It is proved that the Kamura event or ice caused by the minimum amplitude of the earth axis slope. The result of the Sichuan event. Using the floating astronomical age scale established in the Shangsi section combined with spectral analysis, the chemical weathering in the source area is proved to be Fe / Ti / Ti, the redox conditions of the water body are S / Ti / V / Ti and Zn / Ti, paleo-nutrition level and the content of Ca in the productivity of calcium carbonate). Both contain the Milankovich cycle signal, which is stored in the signal of the Milankovich cycle .FerTi, which proves that the late Paleozoic summer monsoon system and its controlled rainfall are controlled by astronomical orbits. In precession frequency, The terrestrial input is contrary to the productivity of calcium carbonate, It is proved that the input of terrestrial debris to the ocean will prevent the production of calcium carbonate. The peak value of chemical weathering induced by summer monsoon is 8 kyr earlier than the peak of upwelling caused by summer monsoon. Should lag behind the terrestrial system, This may be caused by the "buffer mechanism" of the ocean system to balance climate change.
【学位授予单位】：中国地质大学(北京)
【学位级别】：博士
【学位授予年份】：2015
【分类号】：P534.4

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