Journal of Tropical Oceanography ›› 2022, Vol. 41 ›› Issue (1): 171-183.doi: 10.11978/2021077CSTR: 32234.14.2021077

• Marine Geology • Previous Articles     Next Articles

Preliminary study on formation process of Sansha Yongle Blue Hole

GAO Jinwei1,2,5(), FU Tengfei3, ZHAO Minghui4,5, ZHANG Hanyu1,2, TIAN Liyan1   

  1. 1. Institute of Deep-sea Science and Engineering, Chinese Academy of Sciences, Sanya 572000, China
    2. Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai 519000, China
    3. First Institute of Oceanography, Ministry of Natural Resources, Qingdao 266061, China
    4. South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 511458, China
    5. University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2021-06-17 Revised:2021-07-24 Online:2022-01-10 Published:2021-08-03
  • Contact: GAO Jinwei E-mail:gaojw@idsse.ac.cn
  • Supported by:
    Science and Technology Cooperation Project between Academies and Sanya City(2017YD22);Hainan Provincial Natural Science Foundation of China(2019RC259);Hainan Provincial Natural Science Foundation of China(417210);Youth Innovation Promotion Association, Chinese Academy of Sciences(2018401);Innovation Group Project of Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai)(311021003);Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou)(GML2019ZD0204);National Natural Science Foundation of China(41706051)

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.

Key words: Yongle carbonate platform, Sansha Yongle Blue Hole, cave break, phreatic dissolution, fault/fracture of bank margin, collapse of deep voids

CLC Number: 

  • P737.22