Principles dating sedimentary 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.
The clasts (in the bed above the unconformity) are derived from the underlying (older) bed.
The gravel clasts are older than the layer which contains them.
The layer containing the gravel must be younger than the layer from which the clasts originate.
There are two fundamentally different types of inclusions.
Niels Stensen) was a Danish physician living in Florence, Italy in the 1600s.
Faults are younger than the rocks they cut; accordingly, if a fault is found that penetrates some formations but not those on top of it, then the formations that were cut are older than the fault, and the ones that are not cut must be younger than the fault.In each diagram, determine the origin of the inclusions and whether they are older or younger than the rocks that contain them.