Nanpu sag in Bohaiwan basin is a Tertiary semi-graben fault sag, and is also one of the sub-tectonic units of Huanghua depression.

• 摘要渤海湾盆地南堡凹陷为第三纪形成的箕状凹陷，是黄骅坳陷的二级构造单元之一。