北黄海盆地东部坳陷中新生代的叠合盆地特征及其成因

CHARACTERISTICS AND FORMATION MECHANISM OF MESO-CENOZOIC SUPERIMPOSED BASINS IN THE EAST DEPRESSION OF THE NORTH YELLOW SEA BASIN

以最新的地质-地球物理资料为基础,分析了北黄海盆地东部坳陷的断裂特征及构造样式,总结了研究区的沉积-构造演化阶段。研究表明:东部坳陷断裂发育,F1、F2断层为最重要的控制性断层,其次为F9、F10、F11、F8断层,同时在研究区识别出了伸展、挤压、扭动、反转等构造样式;结合构造研究与沉积发育史,将东部坳陷的沉积-构造演化划分为中侏罗世初始断陷期、晚侏罗世断陷扩展期、早白垩世断拗期、早白垩世晚期-始新世构造反转期、渐新世强烈断陷期、渐新世末-中新世初构造反转期、中新世-第四纪区域沉降期。以上述研究为基础,参考区域地质背景探讨了东部坳陷的成因机制:中侏罗世,研究区的初始断陷与块体逃逸的伸展作用有关;晚侏罗世,板块俯冲导致地壳减薄,东部坳陷持续断陷;早白垩世,由于伊泽奈崎板块运动行为变化使郯庐断裂左行走滑,在区域左旋并伴随热沉降的同时研究区发生断拗;晚白垩世,板块正向俯冲导致东部坳陷挤压反转并持续至始新世;渐新世,因太平洋板块转向、俯冲带后撤及印度-欧亚大陆碰撞,导致郯庐断裂带右旋,研究区在右旋张扭背景中强烈断陷;渐新世末,由于太平洋板块俯冲速率、印度-欧亚板块远程效应的增强及俯冲带抑制作用,研究区再次发生构造反转;中新世-第四纪,东部坳陷因岩石圈热衰减发生区域沉降。

Based on the latest geological-geophysical data,the faults characteristics and structural styles of the Eastern Depression of the Northern Yellow Sea Basin are studied,and the sedimentary-tectonic evolutionary stages summarized.The results show that faults in the Eastern Depression are well developed.The faults of F1 and F2 are the most important controlling ones,then followed by F9、F10、F11 and F8.The structural deformation,which is rather complex,includes the extensional,compressed,wrenching and inversed deformation.Seven sedimentary-tectonic evolutionary stages are recognized,namely the initial faulting and depressing stage（J2）,the expanding stage of faults and depression（J3）,the faulting and sag formation stage（K1）,the tectonic inversion stage（late K1-E2）,the intensive faulting and depression stage（E3）,and the regional subsidence stage（N1-Q）.The formation mechanism of the Eastern Depression is also discussed with reference to the regional geological background.In Middle Jurassic,the extension caused by block escape brought about the initial faulting and depression.In Late Jurassic,faulting and depressing continued and the crust became thinning due to plate subduction.In the Early Cretaceous,the Tanlu fault experienced a sinistral slip movement as the result of the change in motion of the Izanagi plate,and the faulting sag was formed in the stress field of sinistral rotation together with thermal subsidence.In Late Cretaceous,face to face subduction of plates led to compression inversion which had lasted up to the Eocene in Eastern Depression.In Oligocene,due to the re-orientation of the Pacific plate movement,the retreatment of the subduction zone and the collision of Indian and Eurasian plates,the Tanlu fault became dextral.Strong faulting and depressing of the study area has made the region a dextral transtensional tectonic setting.At the end of Oligocene,due to the increment in the subduction rate of the Pacific plate,the strengthening of Indian-Eurasian collision,and the slowing down of subduction,the inversion structures dominated again in the study area.Regional subsidence appeared again in the Eastern depression during the Miocene to Quaternary,due to thermal attenuation of lithosphere.