How are index fossils used to identify the subdivisions of the geologic time scale?

1 Answer

  • CRR
    Lv 7
    1 month ago

    Evolutionary paleontologists use ‘index fossils’ to assign an age to a layer of sedimentary rock and its associated fossils.  

    Evolutionary theory assumes that a particular creature evolved from its ancestors, lived successfully for a period, then became extinct as its descendants evolved better ways of surviving. In other words, that creature had a defined ‘evolutionary life-span’. 

    However these assumptions are dubious. Even index fossils are often found out of place and the assigned evolutionary age ranges keep growing. 

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