stratigraphic nomenclature

例句：

1. 1. The geologistis analyzing the rocks for clues aboutthe age of the earth.
   地质学家正在分析岩石，寻找地球年龄的线索。
2. 2.The fossils found in the stratigraphic layers provide evidence of ancient life.
   在地层中发现的化石为古代生命提供了证据。
3. 3. The stratigraphic record showsthat the Earth has been around for4.5 billion years.
   地层记录显示，地球已经存在了45亿年。