南黄海北部构造演化的地球物理认识

Geophysical cognition of tectonic evolution in the Northern South Yellow Sea

南黄海北部坳陷是研究中朝板块和下扬子板块在海区碰撞效应,以及古、中、新生代沉积盆地的地质构造特征和油气资源前景的重点地区.该海域虽经历了40多年的调查与研究,未获得油气的重大突破,与早年调查研究方法的单一、技术手段的落后和对基础地质构造认识不清、勘探思路的偏颇有关.近十年来,通过对新的地球物理资料及已有钻井的综合分析和再认识,认为南黄海北部在中生代陆陆碰撞造山作用的机制下,其构造演化经历了4个阶段:前碰撞期被动大陆边缘盆地阶段(Z-T_2)、苏鲁碰撞晚期前陆盆地与变形阶段(J_2-K)、碰撞期后陆内断陷盆地阶段(K_2t-E)和区域沉降阶段(N-Q);它们分别对应5个超层序或构造层,每个构造演化阶段具有不同的地层组合、构造变形特点和地震反射特征.

The northern depression in the South Yellow Sea, as a petroleum resources potential province, is also the key area to study collision effect of Sino-Korean and lower Yangtze plate and the features of geological structure of Paleozoic to Cenozoic sedimentary basins. No main breakthrough of oil and gas has been obtained in the area through 40years exploration. The reasons on exploratory failure are backward research methods and technological means in early years, misunderstanding of basic geological structure and biased exploration strategy. Based on re-interpretation and synthetic analysis of new geophysical and drillings data in recent decade, the tectonic evolution of northern of southern yellow sea, which suffer the Mesozoic land-land collision orogeny, can be divided into 4 stages： passive continental margin basin stage before plate collision （Z-T2）; intra-eontinental faulted basin and deformation stage in the late phase of the Su-Lu collision process （J2-K）; post-collision intra-continental faulted basin stage （K2t-E） ;and regional subsidence stage （N-Q）. They correspond to five super-sequences or structural layers respectively, and each tectonic evolution stage has different stratigraphic assemblages, characteristics of tectonic deformation and seismic reflection.