The lower part of oceanic island or seamount consist of oceanic island type basalts(Pt2w),and the upper part of oceanic island type basalts(Pt2w) is carbonate rocks of Qingbanshisuzhan rock suite(Pt2q).

• Pt2w洋岛玄武岩与Pt2q碳酸盐岩共同构成了洋岛(或海山)的“双层型”结构,洋岛(或海山)的下部为Pt2w玄武岩,上部沉积的则为Pt2q的碳酸盐岩。