这片海滩上的沙子含有大量贝壳碎片形成的多孔岩石。

The sand on this beach contains a lot of porous ___coquina formed from shell fragments.

海滩上散落着许多小蛤蜊壳，它们是形成贝壳岩的主要成分。

The beach was scattered with tiny ___coquina shells, which help form coquina rock.