Dating Methods Used In An Archaeological Excavation - cybertime.ru

Dating Methods Used In An Archaeological Excavation

dating methods used in an archaeological excavation

Introduction Archaeology is a branch of Anthropology. Archaeologists accomplish heir task mainly through excavation. Excavation is the process of finding sites that may contain artifacts. Artifacts are relics of the past. They are anything created or influenced by man.

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Excavation is the surgical aspect of archaeology: Excavations can be classified, from the point of view of their purpose, as planned, rescue, or accidental. Most important excavations are the result of a prepared plan—that is to say, their purpose is to locate buried evidence about an archaeological site. Many are project oriented, as, for example, when a scholar studying the life of the pre-Roman, Celtic-speaking Gauls of France may deliberately select a group of hill forts and excavate them, as Sir Mortimer Wheeler did in northwestern France in the years before the outbreak of World War II.

But many excavations, particularly in the heavily populated areas of central and northern Europe, are done not from choice but from necessity.

Gravel digging, clearing the ground for airports, quarrying, road widening and building, the construction of houses, factories, and public buildings frequently threaten the destruction of sites known to contain archaeological remains. Emergency excavations then have to be mounted to rescue whatever knowledge of the past can be obtained before these remains are obliterated forever.

Partial destruction of cities in western Europe by bombing during World War II allowed rescue excavations to take place before rebuilding. An extension of the runways at London Airport led to the discovery of a pre-Roman Celtic temple there. Effi Schweizer The role of chance in the discovery of archaeological sites and portable finds is considerable.

Farmers have often unearthed archaeological finds while plowing their fields, and accidental discovery by construction crews is common. This approach helps to order events chronologically but it does not provide the absolute age of an object expressed in years. Relative dating includes different techniques, but the most commonly used are soil stratigraphy analysis and typology.

On the other hand, absolute dating includes all methods that provide figures about the real estimated age of archaeological objects or occupations. These methods usually analyze physicochemical transformation phenomena whose rate are known or can be estimated relatively well.

This is the only type of techniques that can help clarifying the actual age of an object. Absolute dating methods mainly include radiocarbon dating, dendrochronology and thermoluminescence. Relative Dating 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.

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.

Stratigraphic dating remains very reliable when it comes to dating objects or events in undisturbed stratigraphic levels. For example, the oldest human remains known to date in Canada, found at Gore Creek , have been dated using soil stratification. The bones were buried under and are therefore older a layer of ash that resulted from a volcanic eruption dating back to 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 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. Indeed, some items whose exact or approximate age is known are called "diagnostic artifacts. 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.

Typology Typology is a method that compares reference objects in order to classify them according to their similarity or dissimilarity and link them to a specific context or period.

This technique is frequently used when it is impossible to make use of absolute dating methods; it generally allows archaeologists to identify the period to which a cultural site or object belongs, without specifying the date of occupation. This method is primarily applied to projectile points and ceramic vessels. These present many characteristics that are used for comparing them, such as morphology and raw materials in the case of stone tools, and decorative techniques and motifs in the case of ceramics.

Absolute Dating Radiocarbon Dating Radiocarbon dating is the most widely used dating technique in archaeology. It relies on a natural phenomenon that is the foundation of life on earth.

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 years, ie, after this period only half of the total carbon 14 present at the time of death remains.

A sample requires 10 to 20 grams of matter and usually consists of charred organic material, mainly charcoal, but bones see zooarchaeology and shells can also be dated using this technique. 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.

Subsequently, the calibration of that date provides a time interval where the event or object being dated can be situated eg, AD.

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