Chronological dating, or simplydating, is the process of attributing to an object or event a date in the past, allowing such object or event to be located in a previously establishedchronology. This usually requires what is commonly known as a "dating method". Several dating methods exist, depending on different criteria and techniques, and some very well known examples of disciplines using such techniques are, for example,history,geology,paleontology,archaeology,astronomy and evenforensic science, since in the latter it is sometimes necessary to investigate the moment in the past during which the death of acadaver occurred. These methods are typically identified as absolute, which involves a specified date or date range, or relative, which refers to dating which places artifacts or events on a timeline relative to other events and/or artifacts.[1] Other markers can help place an artifact or event in a chronology, such as nearby writings and stratigraphic markers.
Dating methods are most commonly classified following two criteria:relative dating andabsolute dating.
Relative dating methods are unable to determine the absolute age of an object or event, but can determine the impossibility of a particular event happening before or after another event of which the absolute date is well known. In this relative dating method,Latin termsante quem andpost quem are usually used to indicate both the most recent and the oldest possible moments when an event occurred or an artifact was left in astratum, respectively. But this method is also useful in many other disciplines. Historians, for example, know that Shakespeare's playHenry V was not written before 1587 because Shakespeare's primary source for writing his play was the second edition ofRaphael Holinshed'sChronicles, not published until 1587.[2] Thus, 1587 is thepost quem dating of Shakespeare's playHenry V. That means that the play was without fail written after (in Latin,post) 1587.
The same inductive mechanism is applied in archaeology, geology and paleontology, by many ways. For example, in a stratum presenting difficulties or ambiguities to absolute dating,paleopalynology can be used as a relative referent by means of the study of the pollens found in the stratum. This is admitted because of the simple reason that some botanical species, whether extinct or not, are well known as belonging to a determined position in the scale of time.
For a non-exhaustive list of relative dating methods and relative dating applications used in geology, paleontology or archaeology, see the following:
Absolute dating methods seek to establish a specific time during which an object originated or an event took place. While the results of these techniques are largely accepted within the scientific community, there are several factors which can hinder the discovery of accurate absolute dating, including sampling errors and geological disruptions.[5] This type of chronological dating utilizes absolute referent criteria, mainly theradiometric dating methods.[6] Material remains can be absolutely dated by studying the organic materials which construct the remains. For example, remains that have pieces of brick can undergo the process ofthermoluminescence (TL) dating in order to determine approximately how many years ago the material was fired.[7] This technique was used to discover the date of St. James Church in Toruń by testing the thermoluminescence of removed bricks. In this example, an absolute date was determined which filled a gap in the historical knowledge of the church.[8]
These techniques are utilized in many other fields as well. Geologists, for example, apply absolute dating methods to rock sediment in order to discover their period of origin.[9]
Some examples of both radiometric and non-radiometric absolute dating methods are the following:
Just likegeologists orpaleontologists,archaeologists are also brought to determine the age of both ancient and recent humans. Thus, to be considered as archaeological, the remains, objects or artifacts to be dated must be related to human activity. It is commonly assumed that if the remains or elements to be dated are older than the human species, the disciplines which study them are sciences such geology or paleontology, among some others.
Nevertheless, the range of time within archaeological dating can be enormous compared to the average lifespan of a singular human being. As an examplePinnacle Point's caves, in the southern coast ofSouth Africa, provided evidence that marine resources (shellfish) have been regularly exploited by humans as of 170,000 years ago.[16] On the other hand, remains as recent as a hundred years old can also be the target of archaeological dating methods. It was the case of an 18th-centurysloop whoseexcavation was led inSouth Carolina (United States) in 1992.[17] Thus, from the oldest to the youngest, allarchaeological sites are likely to be dated by an appropriate method.
Dating material drawn from thearchaeological record can be made by a direct study of anartifact, or may be deduced byassociation with materials found in thecontext the item is drawn from or inferred by its point of discovery in thesequence relative to datable contexts. Dating is carried out mainlypost excavation, but to support good practice, some preliminary dating work called "spot dating" is usually run in tandem withexcavation. Dating is very important in archaeology for constructing models of the past, as it relies on the integrity of dateable objects and samples. Many disciplines ofarchaeological science are concerned with dating evidence, but in practice several different dating techniques must be applied in some circumstances, thus dating evidence for much of an archaeological sequence recorded during excavation requires matching information from known absolute or some associated steps, with a careful study ofstratigraphic relationships.
In addition, because of its particular relation with past human presence or past human activity, archaeology uses almost all the dating methods that it shares with the other sciences, but with some particular variations, like the following:
Seriation is a relative dating method (see, above, the list of relative dating methods). An example of a practical application of seriation, is the comparison of the knownstyle of artifacts such asstone tools or pottery.
Thestratigraphy of an archaeological site can be used to date, or refine the date, of particular activities ("contexts") on that site. For example, if a context is sealed between two other contexts of known date, it can be inferred that the middle context must date to between those dates.
The results provide a compelling case for applicability of amino acid racemization methods as a tool for evaluating changes in depositional dynamics, sedimentation rates, time-averaging, temporal resolution of the fossil record, and taphonomic overprints across sequence stratigraphic cycles.
{{cite journal}}:Cite journal requires|journal= (help)A team from theUniversity of Manchester and theUniversity of Edinburgh has discovered a new technique which they call 'rehydroxylation dating' that can be used onfired clay ceramics like bricks, tile and pottery.
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