海洋沉积物中浮游生物的这种变化标志着白垩纪和第三纪的分界线。
This change in plankton found in marine deposits is what marks the boundary between the Cretaceous and the Tertiary.
在石膏层上方和下方的沉积物中含有许多小型海洋生物化石，这表明这里的海洋环境很开放。
Sediment above and below the gypsum layer contained tiny marine fossils, indicating open-ocean conditions.
世界上大多数的海洋沉积物不是含有浮游生物就是含有大量的蕨类孢子，但它们并不是同时存在于同一层中。
Most marine deposits from around the world contain either plankton or a lot of fern spores but not both together in the same layer.
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