The fossils buried in Pleistocene and earlier ocean sediments were of foraminifera—small, single-celled marine organisms that secrete shells of calcium carbonate, or calcite.

在更新世和更早的海洋沉积物中埋藏的化石生物属于孔虫类生物，它们是微小的单细胞海洋生物，其分泌的硬壳由碳酸钙和方解石组成。