渤海湾中生代地层剥蚀量及盆地演化

ERODED THICKNESS OF MESOZOIC IN BOHAI GULF AND BASIN EVOLUTION

文章首先利用地震层速度法、镜质体反射率法、声波时差法、地质外推法、磷灰石裂变径迹法等确定渤海湾盆地区中生界三叠系、侏罗系、白垩系的剥蚀量 ,恢复了其原始地层厚度 ,分析了中生代不同时期地层的分布状态 ,盆地性质和展部特点。认为渤海湾盆地三叠系沉积时期为大型内陆盆地 ,末期抬升遭受剥蚀。侏罗系和白垩系沉积时期为北东向展布的小型山间盆地群。进入新生代后 ,形成了一个受NNE、NE向断层控制的半地堑式复合盆地 ,叠置于中生代盆地之上。不同时代的地层的不同叠合方式形成了中坳新坳、中坳新隆、中隆新坳、中隆新隆 4种叠合单元类型 ,不同类型的叠合单元经历了不同的沉降史 。

In Bohai Gulf Basin, the eroded thicknesses of the Triassic, Jurassic and Cretaceous, Mesozoic, were determined, their original thicknesses were restored and the strata distribution, basin nature and expansion characteristics during different times in Mesozoic were analyzed by use of the seismic interval velocity, Ro, acoustic slowness, geological extrapolation and apatite fission track methods. It was considered that the Bohai Gulf Basion was a large continental basin during Triassic and was uplifted and eroded at the end of Triassic;it was composed of a group of small NE intermountain basins during Jurassic and Cretaceous;and it was a half-graben composite basin controlled by NNE and NE faults and superposed on the Mesozoic basin. There are four types of superposition units in Bohai Gulf Basin,the Cenozoic depression superposing on the Mesozoic depression, the Cenozoic uplift on the Mesozoic depression,the Cenozoic depression on the Mesozoic uplift and the Cenozoic uplift on Mesozoic uplift. Different superposition units are of distinct petroleum geological significances because of having undergone different sedimentary histories.