Simple definition relative dating
Many of these organisms have left their remains as fossils in sedimentary rocks.
Geologists have studied the order in which fossils appeared and disappeared through time and rocks. Fossils can help to match rocks of the same age, even when you find those rocks a long way apart.
For a fossil to be a good index fossil, it needs to have lived during one specific time period, be easy to identify and have been abundant and found in many places. If you find ammonites in a rock in the South Island and also in a rock in the North Island, you can say that both rocks are Mesozoic.
Different species of ammonites lived at different times within the Mesozoic, so identifying a fossil species can help narrow down when a rock was formed.
To her, the relative importance of the farm to Billy was as simple as a problem in addition.
Some of the most useful fossils for dating purposes are very small ones.
Fossils are important for working out the relative ages of sedimentary rocks.
Throughout the history of life, different organisms have appeared, flourished and become extinct.
It is therefore essential to have as much information as possible about the material being dated and to check for possible signs of alteration.
Measurements should be taken on samples from different parts of the rock body.
This helps to counter the effects of heating and squeezing, which a rock may experience in its long history.