渤海湾地区的中生代盆地构造概论

CONSPECTUS ON MESOZOIC BASINS IN BOHAI BAY PROVINCE

根据 1∶5 0万渤海湾新生代盆地区基岩地质图揭示的残留中生代地层的分布及构造变形特征 ,渤海湾地区的中生代盆地可以分为 5期。早—中三叠世、晚三叠世盆地为克拉通内部大型坳陷盆地 ,其中晚三叠世盆地仅分布在渤海湾西南部地区。早—中侏罗世盆地分布于印支运动形成的向斜坳陷核部 ,属于压陷挠曲型盆地。晚侏罗世—早白垩世盆地分布广泛 ,属于裂陷盆地 ;晚白垩世盆地属于后裂陷阶段的坳陷盆地。这些盆地受印支运动、燕山运动影响而发生反转。印支运动在渤海湾地区的东、西部的表现有明显差异。西部变形弱、以近EW向宽缓褶皱变形为主 ,东部变形强、并叠加了NE向褶皱和逆冲断层变形。早燕山运动使渤海湾地区形成宽缓的大型NE向褶皱变形 ,并使早—中侏罗世盆地发生反转和逆冲断层变形 ;中、晚燕山运动基本没有在渤海湾地区形成褶皱构造变形 ,而是表现为晚侏罗—早白垩世盆地和晚白垩世盆地的区域性反转隆升。下—中侏罗统沉积之后 ,渤海湾地区的构造格局发生基本变革 ,进入以裂陷盆地为主的构造演化时期。

According to the remaining of Mesozoic strata and structural deformation on the basement rocks exposed beneath the Cenozoic basin in Bohai bay province, the Mesozoic basins can be divided into 5 periods of development. The first period was an intra-craton large depressional basin developed during the Early-Middle Triassic time. The second period during Late Triassic was a craton interior sag just developed on the southern Bohai Bay. The third period during Early-Middle Jurassic was a compress-flexing basin which developed within the core of the syncline deformed by Late Indosinian movement. The fourth period during Late Jurassic-Early Cretaceous was a rifting basin and the rifting center was on the western Bohai Bay province. The fifth period during Late Cretaceous was a post-rifting sag. As a response to Indosinian and Yanshanian movements, these basins were induced to inversion and erosion. The Early Indosinian movement formed some large-scale gentle foldings trending in east-west in Bohai Bay province , but the deformation during Late Indosinian movement was different from Western to Eastern Bohai Bay province. In the Western part the deformation was weak only EW-trending open folds occurred while in the Eastern part deformation was stronger but some NE folds and thrusts superposed on the EW folds. Some large-scale gentle folds trending in northeast direction developed during Early Yanshanian movement in Bohai Bay province and had resulted in deformation and inversion of Early-Middle Jurassic basin. Middle and Late Yanshanian movements had not caused any substantial foldings in the Jurassic and Cretaceous basins, however there are regional inversion uplifts in the Late Jurassic-Early Cretaceous basins and the Late Cretaceous basins. After Early-Middle Jurassic the tectonic regime had a fatal change from successive sag and compresso-flexing into the period of mainly rifting basin.