Paleozoic, Mesozoic, Phanerozoic, Cambrian

Paleozoic, Precambrian, Mesozoic, Cenozoic 

Precambrian, Paleozoic, Mesozoic, Cenozoic

Precambrian, Cenozoic, Mesozoic, Paleozoic 

Numerical ages for fossils were known before the relative sequence of sedimentary layers was established.

Numerical ages for rocks were known before the relative sequence of sedimentary layers was established.

Relative ages for sedimentary strata were known before accurate numerical ages for these rocks were measured.

Relative ages of rocks were known about the same time as accurate numerical ages for these rocks became known.

for half the parent atoms to decay into daughter (child) atoms

for metamorphic minerals to form after conditions change

the midpoint between the first and last appearance of a species in the fossil record

half the time for the rock to weather into sediments

teeth marks on bone

trackways/footprints

teeth

burrows

body fossil preserved in tar

permineralized fossil

chemical fossil

trace fossil

time fossil

index fossil

index mineral

trace fossil

12.5%

50%

10%

25%

It involves nitrogen -14 isotope decaying to the carbon-14 isotope.

This radioisotope dating method can only be used on organic materials like wood or bones. 

Because the half-life of the unstable isotope is so fast, radiocarbon dating is not used on material older that 50,000 or 60,000 years. 

The half-life is 5,370 years.

isotherms

ions

isotopes

atomic species