下扬子前陆盆地北部构造变形特征研究

下扬子前陆盆地由相向的南北两套前陆变形系统组成。依据西南缘、南缘和东南缘露头,以及地震资料厘定了下扬子前陆盆地北部的断裂系统格局、地层展布及断裂褶皱样式,总结了不同构造单元的变形特征。印支期盆地北部的断裂格局为南北分带、东西分块。北部前陆褶断带中,变形程度由苏鲁造山带和郯庐断裂带向东、南方向逐渐减弱。相应地,由西北向东南方向,地层越来越新,主要构造样式由冲断型向推覆型再到褶皱型转变。下扬子区北部前陆变形系统可以分为根带、中带和对冲锋带。总体上,根带变形强度最强,中带的推覆体上盘次之,对冲锋带和中带的推覆体下盘是相对弱变形区,也是值得重视的油气勘探区。

Characteristics of structural deformation in the northern part of lower Yangtze

There are two fold - fault systems in opposite northern - southern direction across lower Yangtze foreland ba- sin. The fault systems, the expanding characteristics of stratum, and the fold - thrust patterns are studied based on outcrops and seismic sections in northern deformation belt of the basin. The fault framework in indo - Chinese epoch is characterized as north - south dissimilitude and west - east differentiation. The degree of deformation gradually weakens from Lusu oro- genic belt and Tanlu thrust fault belt to eastward and southward direction. Accordingly, tectonic patterns are mainly devel- oped as thrust style, nappe style and fold style in order, more and more parts of younger formations spread from west - north to east - south. The northern part of the basin is divided into root zone, middle zone and opposite front zone. In general, the deformation degree of root zone is the strongest, the hanging wall of the nappe in the middle zone take the second place. The opposite front zone and the foot wall of the nappe in the middle zone are relatively weak in deformation, which＂ are fa- vorable exploration area.