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通过北大港地区重力异常资料、三维地震资料分析,证实在北大港潜山上发育具有左旋走滑性质的红7-1断裂,其夹持于大张坨断裂与港西断裂之间,呈弧形沿南北方向展布。该断裂在古近系早中期均有活动,对多个层位砂体分布具有明显的控制作用,在该走滑断裂弧形带南侧,砂体厚度突变增大,呈“点源式”分布,从而形成明显的、且具有继承性的“沟-扇”对应关系。结合重矿物分析及北大港潜山上下切河道追踪发现,在走滑断裂顶部发育一系列下切河道;这些河道下切深度可达230～280ms,它们可以沟通板桥次凹与北大港潜山南翼,在过补偿阶段将板桥次凹的沉积物沿下切河道搬运到北大港潜山南侧的歧北次凹。可见,北大港潜山上近南北向的走滑断裂可以形成下切河道并起到搬运沉积物的作用(即断裂的河道化作用),进而在过补偿阶段控制板桥次凹与北大港潜山南翼的物源分配形式,所以,板桥次凹和歧北次凹在一定程度上均隶属于沧县隆起物源体系。
Through the analysis of gravity anomaly data and 3D seismic data in Beidagang area, it is confirmed that the red 7-1 fault with left-lateral strike-slip property is developed in the buried hill of Beidagang. The red 7-1 fault is sandwiched between the Dachang Tuo fault and the Hong Kong-West fault. Spread along the north-south direction. The fault was active both in the early and middle Paleogene, and obviously controlled the distribution of sand bodies in multiple beds. The thickness of the sand body suddenly increased in the south of the strike-slip fault zone, “Distribution, so as to form a clear, and inherited ” groove - fan "correspondence. Combined with the analysis of heavy minerals and the upstream and downstream channeling of buried hill in Beidagang, a series of undercut channels have been developed at the top of strike-slip faults. The depth of undercutting of these channels can reach 230-280ms. They can communicate with the sub-depression of Banqiao and the south wing of the buried hill of Beidagang, During the over-compensation period, the sediments of the sub-Sag of Banqiao were transported along the undercutting river to the Qijibei depression on the south side of the buried hill in Beidagang. It can be seen that the strike-slip faults near the north and south of the buried hill in Beidagang can form the undercut rivers and play the role of transporting sediments (that is, the riverization of fractures), and then control the subduction of Banqiao in the overcompensation stage and the south wing of Beidagang buried hill Therefore, the subducts of Banqiao and Qijibei depression belong to Cangxian uplift source system to a certain extent.