Biogenic reefs are one of two major depositional types in the South China Sea, and are constructed by coral, algae and bryozoa. The West Pacific is a major area of biogenic reef development and plays a critical role in the global carbon cycle. However, the lack of geochronological studies in previous works inhibits our understanding of their contributions. Herein, we conduct a cyclostratigraphic and magnetostratigraphic study on Neogene biogenic reefs using the XK–1 core that was drilled at the Shidao Island, Xisha (Paracel) Islands. The main findings of this study are: (1) the establishment of reliable magentostratigraphy for Ledong, Huangliu, Meishan and Sanya Formations; (2) the magnetic susceptibility variation can be inferred as growth index and tuned to the 405–ka long eccentricity cycle; (3) the astronomical geochronology suggests that the bottom ages for Ledong, Yinggehai, Huangliu, Meishan, and Sanya Formations are 2.2 Ma, 5.7 Ma, 10.4 Ma, 16.6 Ma, and 24.3 Ma, respectively; and (4) Earth’s eccentricity and obliquity played predominant roles in biogenic reef establishment on orbital to tectonic timescales. Thus, the reported geochronology offers an opportunity to test the contributions of various factors and hypothesize their roles in the global carbon cycle in future.

生物礁是南海两大沉积类型之一，由珊瑚、藻类和苔藓虫构成。西太平洋是生物礁开发的主要区域，在全球碳循环中发挥着关键作用。然而，在以前的工作中缺乏年代学研究阻碍了我们对他们的贡献的理解。在此，我们利用在西沙（西沙）群岛石岛岛钻探的 XK-1 岩心，对新近纪生物礁进行了旋回地层学和磁性地层学研究。主要研究成果为：（1）建立了可靠的乐东、黄流、眉山、三亚组磁性地层学；(2) 磁化率变化可以推断为生长指标并调谐到405-ka长偏心周期；(3) 天文年代学表明乐东组、莺歌海组、黄流组、梅山组和三亚组底部年龄分别为2.2 Ma、5.7 Ma、10.4 Ma、16.6 Ma和24.3 Ma；(4) 地球的偏心率和倾角在轨道到构造时间尺度上的生物礁建立中起着主导作用。因此，报告的地质年代学提供了一个机会来检验各种因素的贡献，并假设它们在未来全球碳循环中的作用。