西沙海域新近纪生物礁的发育演化及控制因素

Development and controlling factors of Neogene reefs in Xisha sea area

杨振 张光学 张莉 夏斌

Yang Zhen Zhang Guangxue Zhang Li Xia Bin

国土资源部 海底矿产资源重点实验室, 广州海洋地质调查局, 广州 510075 2. 中山大学 海洋学院, 广州 519082

MLR Key Laboratory of Marine Mineral Resources, Guangzhou Marine Geological Survey, Guangzhou, Guangdong 510075, China 2. School of Marine Science, Sun Yat-Sen University, Guangzhou, Guangdong 519082, China

南海北部西沙海域发育大量的生物礁，活跃于整个新近纪，蕴含有丰富的油气资源。对西沙海域高精度地震数据及钻井数据的研究表明，早中新世时期，少量的生物礁初始发育于地势高点之上。至中中新世早期，生物礁进入了全面发育阶段，礁体类型众多，如点礁、台地边缘礁、塔礁等，广泛分布于西沙隆起西部的斜坡之上。在发育过程中，随着水体的加深，生物礁逐渐向隆起等地势高部位迁移。至中中新世晚期，进入衰退阶段，以马趾礁、台地边缘礁为代表，主要分布于西沙隆起之上。晚中新世以来，生物礁的发育进入了淹没阶段，并以垂向生长的环礁为代表，主要分布于西沙隆起之上的岛礁周缘。构造作用和相对海平面变化为西沙海域新近纪生物礁发育演化的主要控制因素，其中构造断裂产生的构造高点控制生物礁初始发育的位置，后期基底构造沉降和相对海平面变化控制了生物礁发育演化的各个阶段，三级相对海平面周期性浮动也影响了生物礁旋回性的退积过程。

During the Neogene a large number of reefs developed in the Xisha sea area with a great potential for oil and gas exploration. High-resolution seismic data and extensive well drilling data provided an opportunity to understand the evolution of reefs in this area. A few reefs initially developed on a basement high in the early Miocene. In the early Middle Miocene, the reefs, such as point reefs, platform-edge reefs, and pinnacle reefs, flourished on the western slope of Xisha Uplift. They gradually back stepped to the elevated topographic highs in response to a relative sea level rise. In the late Middle Miocene, reefs began to wither and mainly grew on the Xisha Uplift represented by horse toe reefs and platform-edge reefs. Since the Late Miocene, many reefs formerly developing on the edge of the Xisha Uplift were submerged and only some atolls survived around the islands on the Xisha Uplift. Tectonics and eustasy controlled the development of Neogene reefs in the Xisha sea area. Tectonics controlled the topography for the initial growth of reefs, and tectonic subsidence combined with rapid relative sea-level changes controlled reef evolution during the Neogene. In addition, the rhythm of relative sea-level changes in a short time also influenced the sedimentary cycles of reefs.

中国地质调查局项目（GZH20120511）和国家基金委南海重大计划-重点基金项目（91228208）资助。

https://doi.org/10.11781/sysydz201606787