dating and chating site - Dating principals
Superposition in archaeology and especially in stratification use during excavation is slightly different as the processes involved in laying down archaeological strata are somewhat different from geological processes.
Man made intrusions and activity in the archaeological record need not form chronologically from top to bottom or be deformed from the horizontal as natural strata are by equivalent processes.
The resulting radiocarbon combines with atmospheric oxygen to form radioactive carbon dioxide, which is incorporated into plants by photosynthesis; animals then acquire in a sample from a dead plant or animal such as a piece of wood or a fragment of bone provides information that can be used to calculate when the animal or plant died.
The older a sample is, the less (the period of time after which half of a given sample will have decayed) is about 5,730 years, the oldest dates that can be reliably measured by this process date to around 50,000 years ago, although special preparation methods occasionally permit accurate analysis of older samples.
This is important to stratigraphic dating, which assumes that the law of superposition holds true and that an object cannot be older than the materials of which it is composed.
The law was first proposed in the 17th century by the Danish scientist Nicolas Steno.
Other examples of non vertical superposition would be modifications to standing structures such as the creation of new doors and windows in a wall.