营养盐条件对西沙群岛晚中新世-上新世生物礁滩体系发育演化的控制

营养盐条件是控制生物礁滩体系发育的核心因素之一，然而有关营养盐条件与南海生物礁滩体系发育演化的成因联系尚缺乏清晰认识。本项目拟以南海西沙群岛西科1井晚中新世-上新世生物礁滩体系为研究对象，精细刻画生物礁滩体系沉积微相演化序列与碳酸盐工厂转变史，采用“磷形态分析法”确定碳酸盐岩生物可用磷的含量，并结合多指标综合分析来定量重建营养盐水平变化史，从而在充分吸收前人关于“相对海平面与古水温对生物礁滩体系沉积演化的影响作用”认识的基础之上，深入探讨营养盐水平变化如何影响生物组合、沉积结构、沉积构造，阐明生物礁滩体系发育演化对不同程度营养盐水平的响应样式，进而揭示古海洋与古气候环境变迁对生物礁滩体系生长演化的影响。本项研究能够明晰营养盐条件对南海生物礁滩体系发育演化的控制作用，所获认知可望为南海生物礁滩体系沉积演化及其主控因素提供新的认识，也能为类似生物礁滩体系的营养盐条件控制作用研究提供典型范例。

Nutrient level is one of the most significant factors influencing the reef-bank-system evolution, however, the nutrient-level control on the reef-bank-system evolution in the South China Sea is still not clear. This project focuses on the research on the Late Miocene-Pliocene reef-bank system from core XK-1, drilled on the isolated Xisha Islands in the South China Sea. The reef-bank-system microfacies evolution and carbonate factory turnovers are described in details. The nutrient level history is quantitatively reconstructed by integrating the bioavailable phosphorus content, total organic carbon content, enriching factors of Cu, Ni, Ba, and nitrogen isotope value. After the influences of relative sea-level fluctuations and sea-surface-temperature fluctuations on the reef-bank-system growth are well understood from the previously published papers, the impacts of nutrient-level variations on the changes in skeletal assemblages, textures and fabrics are investigated thoroughly, and the responses of reef-bank-system evolution to different trophic level conditions are therefore identified, which helps to reveal the palaeoceanographic and palaeoclimatic effects on the reef-bank-system growth. This study is expected to clarify the nutrient-level control on the reef-bank-system evolution, providing new insights on the reef-bank-system evolution and the controlling factors in the South China Sea. What’s more, this study can serve as a model for future analysis about the nutrient-level influence on the similar reef-bank system.