| 三沙永乐蓝洞成因机制初探* |
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| 引用本文： | 高金尉,付腾飞,赵明辉,张汉羽,田丽艳.三沙永乐蓝洞成因机制初探*[J].热带海洋学报,2022,41(1):171-183. |
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| 作者姓名： | 高金尉 付腾飞 赵明辉 张汉羽 田丽艳 |
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| 作者单位： | 1. 中国科学院深海科学与工程研究所, 海南 三亚 5720002. 南方海洋科学与工程广东省实验室(珠海), 广东 珠海 5190003. 自然资源部第一海洋研究所, 山东 青岛 2660614. 中国科学院南海海洋研究所, 广东 广州 5114585. 中国科学院大学, 北京 100049 |
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| 基金项目： | 三亚市院地科技合作项目(2017YD22);海南省自然科学基金面上项目(2019RC259、417210);中国科学院青年创新促进会项目(2018401);南方海洋科学与工程广东省实验室(珠海)创新团队建设项目(311021003);南方海洋科学与工程广东省实验室(广州)人才团队引进重大专项(GML2019ZD0204);国家自然科学基金项目(41706051)。 |
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| 摘 要： | 海洋蓝洞保留了原始的水体、沉积物、化石残骸和完整的生物骨骼, 是重要的自然遗产和地质奇观, 具有重要的科学研究价值。三沙永乐蓝洞是目前全球已发现的最深海洋蓝洞, 有着独特的洞体结构和水体化学特征, 但其成因仍是未解之谜。本文结合南海的构造演化, 分析了永乐环礁碳酸盐岩台地的发育历史, 认为永乐环礁的形成以加积和退积为主, 其台地边缘属于陡崖型台地斜坡, 有利于发育断层/裂缝; 永乐环礁之上钻井岩心的氧同位素数据表明, 永乐环礁在14.75~168.60m的深度范围内发生了地下水溶蚀作用, 这与实际观测到的158m深洞体转折处之上发生的洞穴垮塌作用相符。通过综合对比分析认为, 三沙永乐蓝洞的形成是断层/裂缝溶蚀机制与深部洞穴垮塌机制综合作用的结果。地下水(淡水、海水)首先沿着台地边缘发育的断层/裂缝进行溶蚀, 在158m以上通过洞穴垮塌作用形成了近垂直的洞穴, 而在158m以下则沿着断层/裂缝继续向下溶蚀形成了略倾斜的深部洞穴结构, 最终由于海平面的上升淹没而形成了蓝洞。本研究可为未来寻找更多海洋蓝洞提供重要的经验与借鉴。
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| 关 键 词： | 永乐碳酸盐岩台地 三沙永乐蓝洞 洞体转折 地下水溶蚀 台地边缘断层/裂缝 深部洞穴垮塌 |
| 收稿时间： | 2021-06-17 |
| 修稿时间： | 2021-07-24 |
Preliminary study on formation process of Sansha Yongle Blue Hole |
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| GAO Jinwei,FU Tengfei,ZHAO Minghui,ZHANG Hanyu,TIAN Liyan.Preliminary study on formation process of Sansha Yongle Blue Hole[J].Journal of Tropical Oceanography,2022,41(1):171-183. |
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| Authors: | GAO Jinwei FU Tengfei ZHAO Minghui ZHANG Hanyu TIAN Liyan |
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| Institution: | 1. Institute of Deep-sea Science and Engineering, Chinese Academy of Sciences, Sanya 572000, China2. Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai 519000, China3. First Institute of Oceanography, Ministry of Natural Resources, Qingdao 266061, China4. South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 511458, China5. University of Chinese Academy of Sciences, Beijing 100049, China |
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| Abstract: | Blue holes retain original water, sediments, fossil remains, and intact organic skeletons, which are important natural heritages and geologic miracles and have great scientific values. As the deepest blue hole discovered in the world, the Sansha Yongle Blue Hole (SYBH) has typical cavity structure and hydrochemistrical characteristics; however, its formation process is still a scientific puzzle. Based on the tectonic evolution of the South China Sea, we analyze the development history of carbonate platform in Yongle Atoll. Formation of Yongle Atoll is mainly attributed to the aggradation and backstepping of carbonate platform that could generate escarpment to erosional platform margins and facilitate development of faults/fractures along the banks. According to oxygen isotopes (δ18O) in carbonate cores from the drilled wells of Yongle Atoll, phreatic dissolution mainly occurred from 14.75 m to 168.60 m in depth, which agrees with collapse of deep voids observed above the cave break at the depth 158m in Yongle Atoll. Compared with other blue holes and caves in the world, we propose that the formation of the SYBH is due to a combined action of fault/fracture of bank margin and collapse of deep voids. Phreatic (fresh water and sea water) dissolution along the fault/fracture formed sub-vertical sinkhole above 158 m in depth through collapse of deep voids, whereas it continued to work along fault/fracture to form a slightly inclined and narrower cave downward below 158m. Then, the SYBH finally evolved into a deep blue hole due to flooding of rising sea level. This study provides important knowledge and reference for exploring other blue holes in the future. |
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| Keywords: | Yongle carbonate platform Sansha Yongle Blue Hole cave break phreatic dissolution fault/fracture of bank margin collapse of deep voids |
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