Geological dating wiki
The principle of faunal succession is based on the appearance of fossils in sedimentary rocks.As organisms exist at the same time period throughout the world, their presence or (sometimes) absence may be used to provide a relative age of the formations in which they are found.The principle of inclusions and components states that, with sedimentary rocks, if inclusions (or clasts) are found in a formation, then the inclusions must be older than the formation that contains them.For example, in sedimentary rocks, it is common for gravel from an older formation to be ripped up and included in a newer layer.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.Finding the key bed in these situations may help determine whether the fault is a normal fault or a thrust fault.however, this process is not enough to allow the layers to change their positions.
Due to that discovery, Smith was able to recognize the order that the rocks were formed.
This is because it is not possible for a younger layer to slip beneath a layer previously deposited.
The only disturbance that the layers experience is bioturbation, in which animals and/or plants move things in the layers.
There are a number of different types of intrusions, including stocks, laccoliths, batholiths, sills and dikes.
Cross-cutting relations can be used to determine the relative ages of rock strata and other geological structures.