Principle of inclusion relative dating
Now imagine that you come upon a formation like this: What do you think of it? How can you make any conclusions about rock layers that make such a crazy arrangement?Geologists establish the age of rocks in two ways: numerical dating and relative dating.Numerical dating determines the actual ages of rocks through the study of radioactive decay.Relative dating cannot establish absolute age, but it can establish whether one rock is older or younger than another.If this is the case, we can not say that the inclusion is older than the rock that surrounds it.
Geologists use this type of method all the time to establish relative ages of rocks.True xenoliths are definitely older than their host rocks but sometimes igneous rocks contain cognate inclusions or restite material. S-type granites for example (granite with a sedimentary protolith) may contain such inclusions which are genetically related to its host rock. Imagine that you're a geologist, studying the amazing rock formations of the Grand Canyon.Your goal is to study the smooth, parallel layers of rock to learn how the land built up over geologic time.