南海北部东沙海域中生代地层的褶皱变形及其成因机制

Fold Deformations of Mesozoic Strata and Their Genetic Mechanism in Southwestern Dongsha Waters of Northern South China Sea

南海北部东沙海域中生代地层因经历了多期构造运动,构造变形一直存在多种争议。本文利用近两年采集的高精度二维地震资料,在识别中生界和新生界主要构造地层界面的基础上,识别并精细表征了三种类型的褶皱变形,依据其形成的动力学背景,命名为挤压背斜A、滚动背斜B和弯折背斜C。结合区域构造运动,提出了各演化阶段的典型构造变形模式,并认为挤压背斜A与晚白垩世区域隆升和挤压作用有关;滚动背斜B主要与古近系南海北部陆缘强烈伸展作用有关;弯折背斜C主要与新近系早期凹陷深部地幔上隆导致的强烈热沉降作用有关。研究结果为揭示潮汕坳陷前新生界残留盆地经历的复杂动力学演化过程和油气聚集规律提供了必要的基础。

Objectives：Mesozoic structural deformations in Dongsha Waters are very complicated and their genetic remain some controversies because of stacking of multiple tectonic movements. Methods： Using a high-resolution seismic database from southwestern Dongsha Waters in recent two years, through the investigation of the main tectono-stratigraphic boundaries of Mesozoic and Cenozoic in Chaoshan depression, with the time-to-depth conversion formulas of Mesozoic and Cenozoic, we recognize three types of fold deformations. Results： Three types of fold deformations include a compression anticline A, a rollover anticline B and a bending anticline C. Based on regional tectonic events, three representative patterns of fold deformations occurred during the different stages of depression were proposed. Conclusions： The compression anticline A is inferred to have been the far-field impact of the Late Cretaceous subduction of the proto-Pacific. The rollover anticline B is more controlled by huge Paleogene subsidence and extremely rifting extension in continental margin. The bending anticline C may be related to the intense thermo subsidence occurred in Neogene deep-sags.This research results will assist greatly in revealing a complicate dynamic process and in predicting structural traps of pre-Cenozoic residual basin.