Stratigraphy Inspired by geology, stratigraphy uses the principle of the superposition of strata which suggests that, in a succession of undisturbed SOILS, the upper horizons are newer than the lower ones.Generally, each stratum is isolated in a separate chronological unit that incorporates artifacts.Several sets of rings from different trees are matched to build an average sequence.
Indeed, some items whose exact or approximate age is known are called "diagnostic artifacts." Examples of such objects include very specific stone tools, different pottery styles, objects that belong to a specific period (eg, the historic period or the French regime), coins with a production date, or other items bearing a trademark and whose history can be traced in historical records.
Their presence on archaeological sites is used to date the soil layers and the objects and events they are associated with and thus contributes to refine the chronology of sites.
Dendrochronology Dendrochronology is a method that studies the rings of tree trunks to define characteristic sequences by analyzing the morphology of growth rings for a given species.
This method is based on the principle that the variation in tree growth from one year to another is influenced by the degree of precipitation, sunshine, temperature, soil type and all ambient conditions and that, consequently, reference patterns can be distinguished.
However, this method is sometimes limited because the reoccupation of an area may require excavation to establish the foundation of a building, for instance, that goes through older layers.
In this case, even if the foundation of the building is found in the same stratigraphic level as the previous occupation, the two events are not contemporary.Indeed, carbon 14 (14C) is formed from the reaction caused by cosmic rays that convert nitrogen into carbon 14 and then carbon dioxide by combining with carbon 12 (12C) and carbon 13 (13C ), which are stable carbon isotopes.Following the death of an organism, any exchange ceases and the carbon 14, which is radioactive and therefore unstable, slowly begins to disintegrate at a known rate (half-life of 5730 years, ie, after this period only half of the total carbon 14 present at the time of death remains).The bones were buried under (and are therefore older) a layer of ash that resulted from a volcanic eruption dating back to 7000 years BP (Before Present; "present" indicates c. Subsequently, radiocarbon dating, an absolute dating technique, was used to date the bones directly and provided a date of 8250 BP, showing how useful the combined used of relative and absolute dating can be.Moreover, stratigraphic dating is sometimes based on the objects that are found within the soil strata.An initial reading dates the specimen which is then calibrated by considering this date and its correspondence with the measurable level of carbon 14 stored over time in the growth rings of certain tree species, including redwood and pine bristol.