礼乐盆地碳酸盐岩时空分布特征及构造意义

对碳酸盐岩(台地与生物礁)的研究具有重要的油气地质意义和科学价值。渐新世以来, 礼乐盆地及周缘开始了大规模的碳酸盐建造, 至今还有一定规模生物礁持续发育。文章通过拖网约束、井震对比和地震相类比方法对礼乐盆地周缘碳酸盐岩的发育特征、构造背景和时空分布规律进行系统研究。结果表明, 礼乐盆地主要发育孤立、前隆、掀斜断块型台地及生物礁。碳酸盐岩时空发育特征为: 1) 渐新世—早中新世以构造前隆和掀斜断块控制的开阔台地为主, 生物礁零星发育; 2) 早中新世—中中新世表现为大量孤立台地和生物礁; 3) 中中新世之后, 发生台地和礁的淹没, 盆地内主要发育点礁。结合构造背景和重磁特征分析表明, 古隆起、掀斜断块、前隆迁移和岩浆活动为控制礼乐盆地不同时期碳酸盐岩发育的主要构造要素。现今礼乐盆地及周缘大量生长的珊瑚礁, 主要发育在上新世—更新世岩浆活动形成的海山之上。

Spatial and temporal distribution characteristics of carbonates in Liyue Basin and their tectonic implications

The study of carbonates (carbonate platform and reef) is of great significance in oil & gas productions as well as scientific research. Since the Oligocene, carbonates had been widely developed in the south margin of the South China Sea. To describe the development features, tectonic settings, and the spatial and temporal distribution characteristics of the carbonates in the Liyue Basin and its surrounding area, several multi-channel seismic lines were utilized. First, the carbonate platforms and reefs are recognized. Then, the time of the evolution of these carbonates is constrained with wells and dredged samples. The results show that the carbonate platforms can be divided into three types: isolated platform controlled by inherited basement high, tilted fault-block platform, and forebulge carbonate platform. From the late Oligocene to the early Miocene, isolated platforms and tilted fault-block platforms mainly developed, while reefs were scattered. From the early Miocene to the middle Miocene, isolated carbonate platforms and reefs were prosperous. After the middle Miocene, most of the carbonates were drowned and only patch reefs remained. The combination of tectonic background and gravity analysis shows that the ancient uplift, the rotated fault-block, the forebulge migration, and the magmatic activity are the main controlling factors in different stages during the development of the carbonates. Modern reefs built up mainly on the seamount, which was due to the volcanism in the Pliocene-Pleistocene.