江汉盆地白垩-新近系主要不整合面剥蚀量分布及其构造意义

The Erosion Distribution of Major Unconformities and Its Tectonic Significance of Cretaceous-Neogene Jianghan Basin

江汉盆地白垩-新近系由于构造作用产生了多个不整合面,地震剖面上为T11、T10、T9、T8′、T8、T7和T1反射界面,在盆地内的不同部位易于识别,具有明显的角度不整合或侵蚀不整合界面特征。古近系和新近系之间的T1不整合面形成于古近纪末期的盆地整体抬升,对下伏地层造成不同程度的剥蚀,沿盆地南缘的剥蚀层位深,剥蚀量大,反映盆地南缘整体相对隆起,与江南古陆的隆起作用有关。T1界面剥蚀带走向以北西向为主,反映了盆地在古近纪末受到了北东-南西向的挤压或压扭作用,该作用造成盆地整体抬升,强化了北西向展布的低凸起,产生了近北西向的洼陷和剥蚀带。盆内主要的剥蚀带主要受控于早期北西向断裂反转造成的隆起作用,另外,北东、北北东向断裂也存在压扭性逆冲作用,造成局部强烈隆升并遭受剥蚀。对T10、T8′、T8和T7不整合面剥蚀量的平面编图表明,白垩系基本全区遭受剥蚀,T8′、T8界面只造成区内局部剥蚀,T7界面的剥蚀量在南部最大,向盆地内减小,反映了盆地南部江南古陆的早期发育。

The tectonic movements result in the formation of a series of unconformities of Cretaceous-Neogene Jianghan Basin, expressed by T11, T10, T9, T8＇, T8, T7 and T1 reflectors on seismic profile. Exhibi- ting angle unconformities or erosion unconformities in different part of the basin, these surfaces are obvious to be recognized on seismic profiles. T1 conformity, separating Eogene from Neogene, was formed during the whole basin uplifting and erosion by the end of Eogene. T1 unconformity denuded unbearing strata differently, and the deeper and thickest erosion lies on the southern margin of the basin, which reflects the activity of southern Jiangnan paleo-terrene. In conclusion, the major erosion belts extending along NW direction reflects NE-SW compression and slipping caused the Eogene basin uplift and strengthen the earlier NW direction extending low convex, and formed the NW direction extending depress and erosion belts. The form of major erosion belts were controlled by the reverse and uplift of earlier NW faults. In addition, the NE or NNE faults also exhibit compress, leading to local uplift and erosion. The erosion mapping of T10, T8＇, T8 and T7 unconformities show that most Cretaceous has been denuded by T10 surface, T8＇, and T8 unconformities only cause local erosion and most erosion of T7 unconformity lies on the southern of basin, which may be connected with the activity of Jiangnan paleo-terrene.