Definition relative dating
Correlation with them has helped geologists date many New Zealand rocks, including those containing dinosaurs.
Bring relative dating principles to life with the activity Rock layers and relative dating.
Relative dating by biostratigraphy is the preferred method in paleontology, and is in some respects more accurate (Stanley, 167–69).
Geologists still use the following principles today as a means to provide information about geologic history and the timing of geologic events.
A fundamental principle of geology advanced by the 18th century Scottish physician and geologist James Hutton, is that "the present is the key to the past." In Hutton's words: "the past history of our globe must be explained by what can be seen to be happening now." Cross-cutting relations can be used to determine the relative ages of rock strata and other geological structures.
Some fossils, called index fossils, are particularly useful in correlating rocks.
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.