地学前缘 ›› 2023, Vol. 30 ›› Issue (6): 436-450.DOI: 10.13745/j.esf.sf.2023.6.10

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西沙群岛琛科2井珊瑚礁钻孔天文年代标尺的建立及天文周期记录

张念念1(), 范天来1,2,3,*(), 黄春菊4, 张明望1, 李钰淳1, 韦露1, 余克服1,2,3   

  1. 1.广西大学 海洋学院, 广西 南宁 530004
    2.广西南海珊瑚礁研究重点实验室, 广西 南宁 530004
    3.广西大学 珊瑚礁研究中心, 广西 南宁 530004
    4.中国地质大学(武汉) 地球科学学院, 湖北 武汉 430074
  • 收稿日期:2022-10-01 修回日期:2023-05-23 出版日期:2023-11-25 发布日期:2023-11-25
  • 通讯作者: * 范天来(1984—),男,讲师,主要从事珊瑚礁地质学研究。E-mail: fantl2004@hotmail.com
  • 作者简介:张念念(1996—),女,硕士研究生,海洋地质学专业。E-mail: z8182729@163.com
  • 基金资助:
    国家自然科学基金重大项目课题“印太交汇区代表性物种的生物多样性演变及其生态功能(42030502);国家自然科学基金重点项目“全新世南海珊瑚礁发育的时-空差异及其对全球变暖的适应机制(42090041)

Identification of orbital cycles in coral-reef core from well CK-2, Xisha Islands and insights into coral reef evolution in the South China Sea

ZHANG Niannian1(), FAN Tianlai1,2,3,*(), HUANG Chunju4, ZHANG Mingwang1, LI Yuchun1, WEI Lu1, YU Kefu1,2,3   

  1. 1. School of Ocean Science, Guangxi University, Nanning 530004, China
    2. Guangxi Key Laboratory of Coral Reef Research in South China Sea, Nanning 530004, China
    3. Coral Reef Research Center, Guangxi University, Nanning 530004, China
    4. School of Earth Sciences, China University of Geosciences (Wuhan), Wuhan 430074, China
  • Received:2022-10-01 Revised:2023-05-23 Online:2023-11-25 Published:2023-11-25

摘要:

珊瑚礁能够灵敏地记录过去气候变化过程,对于长尺度气候记录而言,高精度的地层年代框架能为区域和全球事件对比提供精确的年代约束。文章以南海西沙群岛琛科2井的珊瑚礁钻孔为研究材料,选取对沉积旋回反应灵敏的非磁滞剩磁(ARM)作为气候替代指标进行旋回分析。ARM分段深度域频谱分析结果显示其存在稳定的代表斜率调制周期约1.2 Ma和长偏心率周期约405 ka的沉积旋回。基于以上识别出的沉积旋回,分别利用轨道参数理论滤波曲线对0~878.21 m的深度域ARM数据序列进行分段天文调谐。最终将珊瑚礁起始发育的天文年代厘定为约19.2 Ma,分辨率可以达到十万年的轨道尺度,可以与Sr同位素年代相互校准。时间域的ARM频谱分析发现,整个中新世以来约1.2 Ma的斜率调制周期在南海珊瑚礁沉积地层中最明显,约405 ka和约95 ka的偏心率周期及约173 ka的斜率调制短周期均不连续。这表明斜率调控的百万年尺度的轨道周期可能对南海珊瑚礁的演化起着主要的调控作用,而珊瑚礁沉积记录的主控周期的改变可能是其对南北半球冰川作用气候效应的及时响应。

关键词: 珊瑚礁, 琛科2井, ARM, 天文调谐, 天文年代标尺

Abstract:

Coral reefs can record past climate change. For long-term climate studies, the establishment of a high-precision stratigraphic chronological framework can provide accurate chronological constraints on the correlation between regional and global climate events. In this paper, coral-reef core samples from well CK-2, Xisha Islands, South China Sea are used in magnetic testing, and anhysteretic remanent magnetization (ARM) is selected as climate proxy to identify astronomical cycles in ancient reefs in the South China Sea since the Miocene. The results of ARM depth series analysis reveal well defined stable depositional cycles corresponding to a ~1.2 Ma obliquity modulation cycle and a ~405 ka long eccentricity cycle; these two cycles are used in orbital tuning of the ARM depth series between 0-878.21 m. The orbital tuning results set the depositional constraints on the coral-reef core at 0-19.2 Ma, with a resolution up to 100000 years, which can be mutually calibrated with Sr isotope dating. The ~1.2 Ma obliquity modulation cycle is most obvious in the reef strata of the South China Sea through the Miocene, and the ~405/~95 ka eccentricity cycles and the ~173 ka obliquity modulation short cycle are discontinuous. These results suggest that the millennium-scale orbital cycles may play a major role in regulating the evolution of coral reefs in the South China Sea. The change of the main control period reflected in the reef records may be an indicator of reef’s timely response to glaciation associated climate change.

Key words: coral reef, well CK-2, ARM, astronomical tuning, astronomical age scale

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