One of the most important uses of ceramics for archaeological analysis is in establishing archaeological chronologies. The sequence of occupation at a ceramicbearing site can be determined through a number of complementary methods including ceramic ‘seria-tion’, stratigraphic association, direct dating of vessel contents and absorbed or surface residues, and dating of associated materials.
Ceramic seriation is based on the principle that ‘styles’ - defined as choices made about technology, decoration, form, etc. - go in and out of favor. Consider, for example, the hula hoop, bell bottoms, and car tail lights. When viewed through time, the frequency of styles starts out small, increases dramatically, and then drops out of favor. Occurrence seriation is based on the presence/absence of a particular ceramic style. This method of chronological ordering was first applied by Sir Flinders Petrie in the late nineteenth century to the contents of predynastic cemeteries in Egypt. Frequency seriation is based on counts or frequencies, which are then converted to percentages of stylistic categories or types. Frequency seriation was developed by James Ford in the 1930s to arrange ceramic assemblages from the Southeastern US. His method of hand-sorting strips of paper to produce the expected popularity of curves of different types in an assemblage can now be replicated using computer programs.
In addition, there are multivariate quantitative methods that produce other ways of arranging ceramic assemblages. These usually start with a matrix or spread sheet with types as columns and proveniences or find contexts as rows (such as strata, house floor, or burial assemblages). Correspondence analysis has been the most successful of these quantitative techniques.
Direct dating of archaeological ceramics can be accomplished through a number of methods. Radiocarbon or AMS dating of organic temper, vessel contents, and residues is becoming more widespread. Fiber tempers provide one possible source of dating, but is dependent on low-firing conditions in which the temper is not wholly burned out of the paste. If during excavation the vessel is found to have its contents still preserved, such as stored seeds, direct dating may be a highly accurate indicator of the time that the pot was filled and deposited. Residues on the exterior of the vessel are highly subject to post-depositional processes, such as water-borne carbon. In addition, the carbon may be from firewood that is much older than the use of the pot itself. Absorbed residues, including lipids, can also be directly dated. Nonetheless, dating of residues is still in its infancy because of potential contamination by other materials and the porous nature of ceramic pastes that allows later material to be absorbed.
A second method of directly dating ceramics is luminescence dating. Luminesence dating is based on the principle that the crystalline structures in ceramics emit light in a measurable way as a result of the absorption of light during the firing event. Luminescence dating has been applied to ceramics from around the world and found to closely track other independent dating methods. The major impediment to more widespread use is the cost. In addition, treering and AMS dating of materials associated with ceramics still provide more precise estimates of the age of pottery. Nonetheless, when ceramics are made over long time spans and other methods are not available, luminescence dating may be a good solution.
Ceramics may be indirectly dated through other independent techniques, such as radiocarbon dating and dendrochronology. Tree-ring dating of architectural wood has been a mainstay of chronometric control in areas such as the American Southwest, where there are now hundreds of thousands of pieces of dated wood. Although the dated events may be different - the date that the tree was felled in the case of the wood, and the date that the pottery was discarded in the case of the ceramics - dendrochronology still offers a level of precision not found with most other techniques. Even AMS dating, however, can be useful for establishing absolute dates for ceramic style changes that are otherwise in a floating series or sequence. Ultimately, the best way to use ceramics for chronology building is to combine a multitude of techniques, including direct and indirect dating and stylistic seriation.
World History
