| 上扬子海南缘晚奥陶世赫南特期沉积相特征及海平面变化 |
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| 引用本文：赵明胜,王约.2018.上扬子海南缘晚奥陶世赫南特期沉积相特征及海平面变化[J].地球学报,39(2):189-200. |
| DOI：10.3975/cagsb.2017.112301 |
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| 基金项目:国家自然科学基金(编号: 41762001);沈阳师范大学博士、引进人才科研项目启动基金(编号: BS201701);中国科学院资源地层学与古地理学重点实验室开放课题(编号: 2016KF03) |
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| 中文摘要:晚奥陶世赫南特期经历了由冈瓦纳冰川事件引起的全球海平面下降和温度降低, 以及由此引发的生物集群绝灭事件, 同时又是构造-沉积的转换期。因此, 该时期成为奥陶—志留纪之交重大的地质事件转折期。本文通过野外露头对上扬子海南缘五峰组观音桥段岩性组合、古生物以及沉积构造的研究发现, 晚奥陶世赫南特期上扬子海南缘经历了滨岸潮坪相、浅滩和浅水陆棚相三种沉积相类型的改造。滨岸潮坪相主要为混积潮坪, 呈环状分布于滇黔桂古陆周缘及黔中水下隆起。浅滩相可识别出生屑滩和砂屑滩两个微环境, 主要分布于近潮坪相带的重庆秀山、贵州松桃以及贵州凤冈等地区。浅水陆棚可分为浅水陆棚下部和浅水陆棚上部两个区域, 与潮坪相带相接触并向北过渡, 其中浅水陆棚区上部又可划分为浅水混积陆棚和浅水碎屑陆棚两种类型。另外, 通过岩性与生物碎屑的组合和分布特征, 表明赫南特期至少经历了一次完整的海平面升降变化, 并为研究全球海平面的变化提供了新的材料。 |
| 中文关键词:沉积特征 海平面变化 观音桥段 上扬子海南缘 赫南特期 晚奥陶世 |
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| Sedimentary Facies Features and Sea-level Fluctuation during the Upper Ordovician Hirnantian Period on the Southern Margin of the Upper Yangtze Sea |
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| Abstract:Hirnantian period of Upper Ordovician experienced sea level falling and decreasing temperature caused by Gondwana glacial event, resulting in mass extinction event. It was also a transition stage of structural evolution and sedimentation. It is thus proved to be one of important transition periods of geological event in geological history. Based on the research on lithologic combination, paleontology, and sedimentary structure of the outcrop of Guanyinqiao Member of Wufeng Formation on the southern margin of the Upper Yangtze Sea, whose margin experienced three types of sedimentary facies transformation, i.e., coastal tidal flat facies, shallow facies and shallow sea shelf facies. Coastal tidal flat facies were mainly mixed tidal flat, and distributed in the Yunnan–Guiyang–Guangxi ancient continental margin and the underwater uplift of Guizhou. Shallow facies was distributed in Xiushan of Chongqing, Songtao of Guizhou and Fenggang of Guizhou, located in near tidal flat zone as well as on bioclast beach and clast beach. Shallow sea shelf facies is in contact with coastal tidal flat facies and extends northward, and can be divided into lower shallow shelf and upper shallow shelf. Among these shelves, upper shallow shelf can be subdivided into shallow mixed shelf and shallow clast shelf. In addition, li-thological association and biodetritus features indicate that there existed at least one complete sea-level change, which supplied new materials for global sea-level change. |
| keywords:sedimentary characteristics sea-level fluctuation Guanyinqiao Member southern margin of the Upper Yangtze Sea Hirnantian Upper Ordovician |
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