湖北宜昌晚奥陶世—早志留世海相地层旋回地层学研究

发布时间：2018-04-25 01:28

  本文选题：旋回地层学 + “浮动”天文年代标尺　； 参考：《中国地质大学(北京)》2017年硕士论文

【摘要】：晚奥陶世发生了全球大规模冰川事件,冰盖在西冈瓦纳大陆广泛发育,并发生了生物大灭绝、碳同位素漂移等重大地质事件,对这些地质事件的理解离不开精确的年代框架。本文将对湖北宜昌黄花场宜黄1井岩芯页岩段开展旋回地层学研究。位于湖北宜昌黄花场的宜黄1井页岩段跨越了奥陶系与志留系界线,包含龙马溪组和五峰组,记录了10个全球可对比的笔石带,地质时代为凯迪期-埃隆期。以1 cm为间距对岩芯(27.02 m)进行连续采样,共采集样品2567个,获得高精度的磁化率数据序列。MTM频谱分析和滑动窗口频谱分析(efft)显示所研究地层记录了良好的旋回性特征,不同级次的旋回地层厚度之比与晚奥陶世地球轨道参数周期之比一致,表明研究地层较好地记录了米兰科维奇旋回信号。依据405 ka长偏心率滤波结果,建立了宜黄1井的“浮动”天文年代标尺,估计出赫南特阶与鲁丹阶的持续时间分别为0.94 Ma和1.36 Ma。自下而上完整笔石带持续时间分别为:Dicellograptus complexus(1.85 Ma),Paraorthograptus pacificus(0.80 Ma),Normalograptus extraordinarius(0.63Ma),Persculptograptus persculptus(0.22 Ma),Demirastrites triangulates(1.15 Ma),Lituigraptus cinvolutus(1.46 Ma)。以观音桥层顶部斑脱岩U-Pb定年结果443.2±1.6 Ma为锚点,确定出奥陶系-志留系界线年龄为442.98±1.60 Ma,与GTS2012所给出的年龄443.8±1.5 Ma在误差范围内一致。根据天文年代标尺,估计出晚奥陶世生物大灭绝事件的持续时间约为0.60 Ma,碳同位素漂移事件(HICE)的持续时间约为1.08 Ma。
[Abstract]:In the late Ordovician, the global large scale glacier events occurred, the ice sheet developed extensively in the West Gondwana continent, and the major geological events such as biological extinction and carbon isotope drift occurred. The understanding of these geological events can not be separated from a precise chronological framework. In this paper, cyclic stratigraphy is carried out on the core shale section of Huanghuachang Yihuang well Yichang, Yichang, Hubei Province. The shale section of Yi-Huang No. 1, located in Huanghuachang, Yichang, Hubei Province, crosses the boundary between Ordovician and Silurian, including Longmaxi formation and Wufeng formation, and records 10 globally comparable graptolite belts, the geological age of which is the Keidi to Elon period. The continuous sampling of the core (27.02 m) was carried out at a distance of 1 cm. A total of 2567 samples were collected, and a high accuracy magnetic susceptibility data sequence, MTM spectrum analysis and sliding window spectrum analysis were obtained, which showed that the studied strata recorded good cyclic characteristics. The ratio of the thickness of the cyclic strata of different order to that of the Earth orbit parameters of the late Ordovician is the same, which indicates that the Milankovich cycle signals are well recorded in the studied strata. Based on the result of 405ka long eccentricity filtering, the "floating" astronomical scale of Yi-Huang 1 well is established. The duration of Hernant stage and Ludan stage are estimated to be 0.94 Ma and 1.36 Ma, respectively. The duration of the complete graptolite belt from the bottom up is: Dicellograptus complexus(1.85 complexus(1.85 Maaorthograptus pacificus(0.80 Maa Normalograptus extra-ordinarius0. 63 Maa Persculptograptus persculptus(0.22 Maa (Demirastrites triangulates(1.15 Maa) Lituigraptus cinvolutus(1.46 Magrapus. The age of Ordovician to Silurian is 442.98 卤1.60 Ma, which is consistent with the age of 443.8 卤1.5 Ma given by GTS2012, using the U-Pb dating result of 443.2 卤1.6Ma at the top of Guanyinqiao as the anchor point, and the boundary age of Ordovician to Silurian is 442.98 卤1.60 Ma. According to the astronomical age scale, it is estimated that the duration of the late Ordovician bioextinction event is about 0.60 Ma, and that of the carbon isotope drift event (HICE) is about 1.08 Ma.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P534.4;P539
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本文编号：1799163