Seriation (archaeology) - Wikipedia
a radiometric dating method based on the changing ratio of argon to argon .. in burned clay and rock as well as geological deposits of volcanic origin. . When a seriation sequence has been cross-calibrated with reliable chronometric . chronometric dating obviates the need for refined ceramic chro nology. Rowe argued that, when seriation is used to define chronology, the additional. DEFINITION: A seriation technique, also called sequence dating, pioneered by Sir Flinders Petrie in the 19th century, in which artifacts are arranged according to .
InKendall proposed the use of multidimensional scaling techniques for seriation problems, and this approach has also been used by some other scientists see Baxterpp.
Chronology and dating methods
Baxter also presents a review of statistical methods for seriation and a description of these approaches pp. InDoran and Hodson pp. Correspondence analysis for seriation purposes[ edit ] Today, the most popular seriation method both for contextual and frequency problems is based on correspondence analysis. The sequence of the first axis of a correspondence analysis is considered the best seriation order Shennan p. Using this technique, not only the sequence of the objects but also those of the design styles is established.
Note that external evidence is needed to establish the direction of the sequence calculated, i. The resulting scatterplot showed the form of a horse-shoe where the graves were arranged on the curve according to their chronological order. Similarly, a mapping of the component scores for the first two axes of the correspondence analysis result will display a parabola if the design styles considered are controlled by one factor only like chronology. This is called the arch effect by Hill and Gauch Therefore, it is recommended inspecting the scatterplot of the first two axes of correspondence analysis to find out if other factors play a role as well see Examples 2 and 3.
If more than one factor is important, the arch effect may distort the results.
Hill and Gauch presented a method to remove this effect. InGroenen and Poblome adapted the correspondence analysis algorithm to combine seriation with absolute dates and stratigraphic relationships.
Small contextual seriation[ edit ] The small example below was inspired by Flinders Petrie's serial ordering of Egyptian pottery as published by Renfrew and Bahnp.
Raw data for contextual seriation Result of contextual seriation Another way of presenting the raw data for contextual seriation: For example, consider the first column: A beaker is contained in contexts 1 and 2. Contextual seriation sorts the design styles and the contexts in such a way that the star symbols are found as close as possible to the diagonal of the table.
Of course, for a small examples like this, no computer programs are needed to find the best ordering, but for larger data sets like the graves studied by Petrie they are extremely helpful. Simulated data, seriation and correspondence analysis[ edit ] The data presented in this example was simulated by WinBasp. Initially 60 contexts called units in WinBasp were created along with 50 types.
The contexts were labeled in chronological order by numbers 01 to 60, the types are labeled in the form T to T If a type is represented by one object only this object is not relevant for the chronological sequence as it does not provide a link to another context. Similarly, contexts containing one object only are irrelevant for seriation. Therefore, the contexts with one or no object and types represented by one object or not at all were eliminated.
The resulting raw simulated data consisting of 43 contexts and 34 types are shown on the left. As expected, the dots indicating the occurrence of a type in a context are close to the diagonal of the table.
Raw simulated data for contextual seriation Result of seriation The image on the right hand side shows the result of the seriation for this data set.How Does Radiocarbon Dating Work? - Instant Egghead #28
Note that the dots are even more compact along the diagonal of the table compared to the raw data. This shows a minor problem of seriation: In fact, the intervals of production may be somewhat longer than those calculated by the algorithm. In general, the sequences of contexts and types calculated by a seriation algorithm are not the correct chronological sequences but they are fairly close. Result of correspondence analysis The image above shows the scatterplot with the typical parabola shape of the first two axes of a correspondence analysis for the contexts of the simulated data set.
With each new context a new type appears and another type disappears.
For this regular data, it seems reasonable to assume constant time intervals for contexts adjacent in time. The correspondence analysis results shown in the figures below were calculated on the basis of 49 contexts with ideal seriation data. The scatterplot of the first two correspondence analysis axes shows the typical parabola shape.
The display of the scores on the first and the third axes exhibits points lying on a third degree polynomial curve. Similarly, the plot of the scores on the first and the fourth axes will show a fourth degree polynomial for ideal data — and so on.
Note that the distances of the scores for adjacent contexts on the first axis vary: At the beginning and the end, the distances are extremely small, the largest distances in the centre is about 30 times as large as the smallest distance.
Hill and Gauch  created a similar contingency table with a regular structure with each context containing six types. Chronometric dating methods[ edit ] The majority of chronometric dating methods are radiometric, which means they involve measuring the radioactive decay of a certain chemical isotope.
They are called chronometric because they allow one to make a very accurate scientific estimate of the date of an object as expressed in years.
Chronology and dating methods - Wikibooks, open books for an open world
They do not, however, give "absolute" dates because they merely provide a statistical probability that a given date falls within a certain range of age expressed in years. Chronometric methods include radiocarbon, potassium-argon, fission-track, and thermoluminescence.
The most commonly used chronometic method is radiocarbon analysis. It measures the decay of radioactive carbon 14C that has been absorbed from the atmosphere by a plant or animal prior to its death.
Once the organism dies, the Carbon begins to decay at an extremely predictable rate. Radioactive carbon has a half-life of approximately 5, years which means that every 5, years, half of the carbon will have decayed.
This number is usually written as a range, with plus or minus 40 years 1 standard deviation of error and the theoretical absolute limit of this method is 80, years ago, although the practical limit is close to 50, years ago.
Because the pool of radioactive carbon in the atmosphere a result of bombardment of nitrogen by neutrons from cosmic radiation has not been constant through time, calibration curves based on dendrochronology tree ring dating and glacial ice cores, are now used to adjust radiocarbon years to calendrical years.
The development of Atomic Absorption Mass Spectrometry in recent years, a technique that allows one to count the individual atoms of 14C remaining in a sample instead of measuring the radioactive decay of the 14C, has considerably broadened the applicability of radiocarbon dating because it is now possible to date much smaller samples, as small as a grain of rice, for example.
Dendrochronology is another archaeological dating technique in which tree rings are used to date pieces of wood to the exact year in which they were cut down. In areas in which scientists have tree rings sequences that reach back thousands of years, they can examine the patterns of rings in the wood and determine when the wood was cut down.