太阳盆地中新生代断裂特征及成因机制

FEATURES AND GENETIC MECHANISM OF FAULTS IN THE SUN BASIN IN MESOZOIC AND CENOZOIC TIMES

太阳盆地位于北黄海盆地的东部,是一个发育在中-朝克拉通基底之上的中、新生代沉积盆地,勘探程度非常低。最新二维地震资料揭示,太阳盆地的断裂体系可以分控盆断裂、控凹(坳)断裂、控带断裂、控圈断裂和分割性断裂。盆地发育以NE向和NW向为主的的正断层和逆断层,而少量断层呈近EW或SN向。对不同类型的断裂构造特征及样式分析表明,断裂的活动期次可分为4期:晚侏罗世—早白垩世伸展断层、晚白垩世逆冲断层、始新世伸展正断层和新近纪正断层。中、新生代以来,中国东部构造演化主要受其东部太平洋板块活动控制,晚侏罗纪开始,洋壳俯冲在东部的欧亚大陆之下,伴随着太平洋—菲律宾板块的俯冲,太阳盆地发生NNE—SSW向的拉张;晚白垩世时期,由于太平洋板块俯冲方向的改变,区域性拉张变为区域性NNW—SSE向挤压,太阳盆地的一系列NW向逆断层形成;在始新世—渐新世,太平洋板块向东亚大陆作斜向减速俯冲,导致太阳盆地遭受NWW—SEE向拉张作用,再次断陷;渐新世末期,受喜山运动第Ⅱ幕的影响,太阳盆地发生再次的构造反转,形成一系列的小规模断层。

The sun basin is located in the east of the North Yellow Sea basin, a lowly explored Mesozoic-Cenozoic sedimentary basin, which is developed upon the base of China-Korea paraplatform. The latest 2D seismic data indicated that the fault system of the Sun basin can be divided into 5 types： basin-controlling faults, depression-controlling faults, belt-controlling faults, trap-controlling faults and segmentation faults, which dominantly trend northeast or northwest, and only a few faults trend north to west or north to south. The analyses on these faults indicate that the fault activities can be mainly divided into four stages ：late Jurassic-early Cretaceous,late Cretaceous,Eocene and Neogene. Since Mesozoic and Cenozoic, the tectonic evolution of east China has mainly been controlled by the activities of the Pacific plate. In the late Jurassic, going with the subduction of the Pacific Ocean-Philippines Sea plate, the oceanic crust subducted under the Eurasia plate, and the Sun basin experienced NNE-SSW-trending extension under the background. In the early Cretaceous, due to the change of subduction direction of Pacific plate, the regional NNW-SSE extension turned to the regional NNW-SSE compression, and a series of NW-trending thrust faults were formed asaresult. In the Eocene. the Sun basin had extension again, which was the result of the slowdown subduction of the Pacific plate towards East Asian mainland. At the end of Oligoeene,influenced by Himalayan movement, the Sun basin became reversed again, and a series of small faults formed.