渤海湾盆地基岩地质图及其所包含的构造运动信息

Geologic map of sub-outcrop and its implied informationof tectogenesis in Bohai Bay basin province

利用油气勘探资料编制的渤海湾盆地基岩地质图 ,分析了基岩露头分布及其反映的中、新生代构造运动特征。基岩地质图显示渤海湾盆地基底岩层受印支运动和燕山运动影响发育有一系列近EW向、NNE—NE向的褶皱和逆断层等挤压构造变形。基岩露头展布表明渤海湾盆地西部、北部在侏罗纪之前的剥蚀作用明显强于东部和南部地区。基岩地层形成的区域褶皱轴向及各亚构造层之间的不整合面接触关系反映出在下—中三叠统沉积之后至下—中侏罗统沉积之前的某个“关键时刻”渤海湾地区发生了一次重要的构造变革 ,导致早期的近EW向构造被NNE—NE向构造替代。而从区域应力体制来看 ,下—中侏罗统沉积之后渤海湾地区的区域构造环境发生了重要变化 。

This paper presents two geologic maps of sub-outcrop based on uncovered Tertiary and Jurassic-Cretaceous respectively in Bohai Bay basin province, and analyses the information of tectogenesis implied by the maps. The geological maps of sub-outcrop showed that the basement of Bohai Bay Cenozoic basin was deformed by two sets of folds and thrusts trending EW and NNE-NE. The angular unconformities within Mesozoic-Cenozoic mark that regional folds and thrust faults were developed before the Early Jurassic and after the Middle Triassic. The late folds trending NNE-NE, are more closed and obvious, superposed on the opened folds trending approximately east to west. The change of regional fold trending implies that there was an important revolution in the age from late of Middle Triassic to early of Early Jurassic. The maps also show that there was differential erosion in Bohai Bay basin during the Mesozoic. The East and north parts suffered stronger erosion than the west and south parts of the basin during the Late Triassic, but were stronger for the west and north parts during Jurassic-Cretaceous. The regional fold axes indicate that the direction of regional compression was changed from S-N to NW-SE before the Early Jurassic and after the Middle Triassic. Regional deformation figures out that tectonic regime was changed from contractional tectonics to extensional tectonics between the Middle and the Late Jurassic. Most of quasi-sedimentary basement involved normal faults were developed during the Late Jurassic-Cretaceous. Most of regional faults in Paleogene rifting basin were the successors of extensional faults during the Late Jurassic-Cretaceous.