下扬子区中新生代沿江盆地群的盆地结构与沉积特征

Structure and sedimentary characteristics of the Meso-Cenozoic basin group along the Yangtze River in the Lower Yangtze region

下扬子沿江盆地群是下扬子中新生代含油气盆地的重要组成部分,也是认识中国东部中新生代盆地结构与构造—沉积演化的重要窗口。在长江中下游地区,自西向东,分布着鄱阳盆地、潜山盆地、望江盆地、全椒盆地、无为盆地、句容—南陵盆地、常州—宣城盆地、溧阳盆地和平湖盆地9个相对独立的沉积盆地,在平面上组成了一个盆地体系或盆地群,可称之为下扬子沿江盆地群。盆地沉积充填过程主要为晚白垩世—古近纪断陷期与新近纪—第四纪拗陷期2个阶段。盆地断陷期主要以河湖相与三角洲相沉积为主,而拗陷期主要以河流相沉积为主。下扬子沿江地区在渐新世末期形成统一的断陷盆地体系,于新近纪形成统一的拗陷盆地体系。由于新近纪差异变形,各盆地地层差异剥蚀,最终形成现今的沉积盆地地质面貌。

The basin group along the Yangtze River is an important part of the Meso-Cenozoic petroliferous basins inthe Lower Yangtze region, which is also an important window for the study of the structure and tectono-sedimentaryevolution of the Meso-Cenozoic basins in East China. There are nine relatively independent faulted basins from west toeast in the Yangtze River’s middle and lower reaches, including Poyang, Qianshan, Wanjiang, Quanjiao, Wuwei,Jurong-Nanling, Changzhou-Xuancheng, Liyang and Pinghu basins, which comprise a basin system or group in theplane, named the Lower Yangtze basin group. Sedimentary filling in the basins was divided into two stages includingfaulting from the Late Cretaceous to the Paleogene, and depression from the Neogene to the Quaternary. The formerstage is characterized by the sedimentation of fluviolacustrine and delta facies, while the latter stage is marked by thedeposition of fluvial facies. The fault basin system formed in the Late Oligocene, and a unified depression systemformed in the Neogene along the Yangtze River. Due to the Neogene differential deformation, the basinal strata weredifferentially denuded, forming the modern geological setting of the sedimentary basins.