四川盆地北部开江-梁平海槽边界及特征初探

开江-梁平海槽控制着川北地区飞仙关组台缘鲕滩的分布。在地震剖面上,东侧边界为断点、西侧为上超点;在沉积岩石学方面,发育代表盆地相的薄层泥灰岩和代表斜坡相的碎屑流沉积;最早沉积的台缘鲕滩位于江油-梓潼-南充-邻水-垫江一线;飞仙关组在海槽西侧沉积厚度大于600 m、东侧大干500 m的区域为盆地相沉积。综合多方面的资料, 基本确定开江-梁平海槽的边界:西侧大致为青林1井-白龙1井-思1井-龙会1井一线;东侧为天东10井-川岳83 井-川涪82井一线。海槽东侧边界由断裂形成,随海槽的关闭,其边界位置相对变化较小;海槽西侧边界由斜坡形成,随海槽的关闭,其边界位置逐渐变化。预测川北地区台缘鲕滩发育面积可达3×10⁴km²。在海槽西侧,台缘鲕滩主要分布于江油、广元、梁平和邻水围成的区域内;在海槽东侧,台缘鲕滩主要发育于云阳、万县和通江两河口一带。

Preliminary study of the boundary of Kaijiang - Liangping trough in northern Sichuan basin and its characteristics

Kaijiang-Liangping trough controls the distribution of platform edge oolitic shoal in the Feixianguan Fm in northern Sichuan basin. It is found from the seismic section that the eastern boundary to be a breakpoint, while the western boundary appears as an onlap point. In respect of sedimentary petrography, basin and slope facies are developed between the two boundaries mentioned above, which are represented by thin bedded marl and debris flow sediment, respectively. The earliest platform edge oolitic shoal deposit is located along Jiangyou-Zitong-Nanchong-Linshui-Dianjiang. The Feixianguan Fm is of basin facies on the western side of the trough with sediments of over 600 m thick and on the eastern side of the trough with sediments of over 500 m thick. Based on various evidences, the western boundary of the trough is basically determined to be approximately along Qinglin 1 well-Bailong 1 well-Si 1 well-Longhui 1 well, while its eastern boundary is a-long Tiandong 10 well-Chuanyue 83 well-Chuanfu 82 well. The trough is bounded by faults in the east, so the boundary location has only a little change in the course of the closing of the trough, while the western boundary is composed of slopes and the boundary location has gradually changed along with the closing of the trough. It is predicted that the area of platform edge oolitic shoal can be up to 3?10⁴km² in the northern Sichuan basin. On the west side of the trough, the platform edge oolitic shoal is mainly distributed in the area encircled by Jiangyou, Guangyuan, Liangping and Linshui; while on the east side of the trough, it is mainly distributed in Yunyang, Wanxian and Lianghekou (of Tongjiang).