The law of faunal succession deals with the fossils of plants and animals and states that groups of fossilized animals and plants follow or succeed each other in a predictable manner.
Faunal succession can be used to chronologically put a group of animals and plants together and give greater detail to the history of the Earth.
This can be a challenging concept to understand, but if you imagine a basin where sediment is deposited, this principle states that the sediment will be equally deposited in this area until there is no more sediment or until the sediment reaches the edge of the basin or another barrier.
Using a mental picture to understand this concept can be very helpful.
Relative dating is the process of establishing a sequence of historical events and relative ages of rocks by looking at sedimentary rock formations and their features.
Unlike absolute dating, relative dating does not assign specific years to individual events.
Since sedimentary rocks are composed of sediment that must be cemented and packed down, sedimentary rock layers are originally horizontal or close to it.
If the rock layers are no longer horizontal, this is because of changes in the environment that occurred after the formation of the sedimentary rock.
Absolute dating can be helpful when there is some uncertainty about whether all features of the rock are present.That is, they become abundant, and then their sensitivity to environmental changes causes them to become extinct.Index fossils are incredibly useful in relative dating.Index fossils are those that are used to define geologic time.Effective index fossils have several characteristics—they are widespread, distinctive, abundant, and limited in geologic time.Faunal succession is also used to compare fossils of organisms in different areas on the Earth.