南海礼乐滩碳酸盐台地的发育及其新生代构造响应

为了探索碳酸盐台地在海盆演化过程中的作用，对南海南部礼乐滩区域碳酸盐台地的发育及其与新生代构造沉降特征的相关性进行研究.对多道地震数据的分析表明:在研究区广泛发育包括碳酸盐台地和生物礁在内的碳酸盐沉积，其发育时间主要集中在晚渐新世至早中新世期间，在中中新世后开始退积和淹没.通过对穿越礼乐滩区的两条NW-SE向测线NH973-2和DPS93-2的构造沉降反演，进行沉降量、沉降速率计算和构造分析.结果表明:沉降速率及沉降量随不同时期的构造活动而发生变化，可分为缓慢沉降期(古新世-早渐新世，张裂阶段)、隆升剥蚀期(晚渐新世-早中新世，漂移阶段)、加速沉降期(早中新世末期，后漂移阶段1)、强烈沉降期(中新世，后漂移阶段2)和稳定沉降期(晚中新世至今，后漂移阶段3)5个发育期.碳酸盐台地的发育期和南海海盆的漂移阶段相对应，构造沉降的分析表明该期间具有构造抬升作用，其与相对上升的海平面结合有利于碳酸盐沉积的发育.在南海扩张期间主地幔对流的控制下，南部陆缘区礼乐地块和礼乐滩盆地之间较大的地壳厚度差异会导致侧向上地温梯度的差异，从而形成礼乐滩盆地之下的次生对流.该次生对流控制了研究区在晚渐新世至早中新世期间的隆升剥蚀作用. 

Development of Carbonate Platform and Its Response to Cenozoic Tectonic in Reed Bank Area,the South China Sea

In order to research the role of carbonate platform in the evolution of basin, the development of the carbonate platform and its correlation with the Cenozoic tectonic subsidence characteristics in the Reed Bank area in the southern South China Sea are explored in this study. The rate and amount of tectonic subsidence, and the tectonics are analyzed on the basis of two multi-channel seismic profiles across the Reed Bank area in NW-SE direction. Detailed seismic interpretations prove the occurrence of a wide distributed carbonate platform developed between the Late Oligocene to Early Miocene, which was submerged after the Middle Miocene. Reconstruction of the tectonic subsidence history shows that the tectonic subsidence was controlled by the tectonic activities in different periods, and could be divided into 5 episodes: the slow subsidence episode (Paleocene to Early Oligocene, rifting stage), the uplift and erosion episode (Late Oligocene to Early Miocene, drifting stage), the accelerating subsidence episode(the latest Early Miocene, post-drift stage 1), the intensive subsidence episode(Miocene, post-drift stage 2), and the steady subsidence episode (Late Miocene to present, post-rift stage 3). The development stage of the carbonate platform was consistent with the drifting stage of the South China Sea, during which the tectonic subsidence analysis suggests an uplift and erosion characteristics. This stable shallow water environment was favorable to the development of carbonates. During the drifting stage, large-scale mantle under the oceanic basin and the lateral temperature gradients under the continental margin might have triggered a secondary mantle convection under the rifted Reed Bank basin, resulting in the uplift and erosion activities in this stage, and the wide-development of carbonate platform.