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中下扬子区海相盆地前震旦系基底包括下构造层晚太古代—早元古代结晶变质岩系和上构造层中—晚元古代中—浅变质褶皱岩系。基底在横向上具不均质性,主要表现为下构造层分布局限。Z_1—T_2各时期的海盆演化可划分出加里东和海西—印支两大旋回,每个旋回所经历的盆地类型有克拉通—裂谷盆地、克拉通—大陆边缘盆地和克拉通—前陆盆地等,在旋回末期均经历了海盆回返和碰撞造山的构造阶段,对海盆产生较为显著的同期改造作用。后期改造作用从晚三叠世开始,不同阶段的改造作用类型不相同,主要可归纳出四种:T_3—J_3冲断构造作用、J_3—K_1走滑构造作用、J_3—K_1火山岩浆作用以及K_2—E反转构造作用。后期改造作用比同期改造作用对油气地质的影响更为显著和强烈。
The former Sinian basement in the Lower-Middle Yangtze marine basin consists of Late Archean-Early Proterozoic crystalline metamorphic rocks in the lower tectonism and Meso-Late Proterozoic mid-supergene metamorphic folds in the Upper Tectonics. The substrate has inhomogeneity in the horizontal direction, mainly for the distribution of the lower tectonic layer. The basin evolution in each stage of Z_1-T_2 can be divided into two major cycles of the Caledonian and Hercynian-Indosinian cycles. Each cycle experienced the following types of craton: craton-rift basin, craton-continental margin basin and craton-front The continental basin and so on experienced the basin return and collision orogeny in the end of the cycle, which had a significant reformation effect on the basin during the same period. After the Late Triassic, the types of remodeling are different from one another in the late Triassic. There are mainly four types of remodeling: T_3-J_3 thrust structure, J_3-K_1 strike-slip tectonics, J_3-K_1 volcanic magma and K_2 -E reverses the tectonic role. The effect of post-transformation is more significant and stronger than that of the same period of reformation on the geology of oil and gas.