|This article needs additional citations for verification. (May 2007)|
The term debitage refers to all the material produced during the process of lithic reduction and the production of chipped stone tools. This assemblage includes, but is not limited to, different kinds of lithic flakes and lithic blades, shatter and production debris, and production rejects.
Debitage analysis, a sub-field of lithic analysis, considers the entire lithic waste assemblage. The analysis is undertaken by investigating differing patterns of debris morphology, size, and shape, among other things. This allows researchers to make more accurate assumptions regarding the purpose of the lithic reduction. Quarrying activities, core reduction, biface creation, tool manufacture, and retooling are believed to leave significantly different debitage assemblages. Lithic manufacture from a quarried source, or from found cobbles also leave different signatures. Some claim that they can determine the sort of tools used to create the debitage. Others feel it is possible to effectively estimate the work-hours represented, or the skill of the workers based on the nature of the debitage.
The typological approach groups together lithics with similar manufacturing histories in order to emphasize patterns of manufacturing behavior (as in Sheets 1975). To use Sheets’ (1983:200) example, macroblades and prismatic blades were separated on the basis of their manufacture, in that the former was removed by percussion, while the latter was removed by a pressure technique. Casual, informal tools from unstandardized cores should be given scrutiny equal to that of formal tools from standardized core reduction.
The presence of cortex needs to be noted for all tool categories in all materials. The presence of cortex indicates the importation of an unworked nodule, with the first flakes both preparing the core by shaping and removing the roughened exterior of the cortex (Sheets 1978:9). The percentage frequency of cortex is an important statistic to help identify lithic production areas. A low incidence of cortex would indicate quarry performing (cortex removed at the quarry, not at the site).
Debitage refitting is a process whereby the collected assemblages of debitage are painstakingly put back together, like pieces in a puzzle. This can sometimes indicate the nature of the tools being produced, although missing pieces are a significant problem. More often, debitage refitting is used to learn how rocks were moved during the lithic manufacture process. This can sometimes indicate work areas, division of labor, or trade routes.
Debitage sourcing looks at the physical properties of the worked stone in an attempt to determine where on the earth it was obtained. This may require sophisticated equipment, and destructive testing, but even a visual inspection can provide a general idea. Sourcing is assumed to provide information about trade, or travel routes.
Some debitage material has been examined in an effort to obtain dates. Since debitage is plentiful, and individual specimens are usually not diagnostic, they can often undergo destructive analysis that would not be suitable for other artifacts. Results have been promising, but not spectacular. Obsidian and cryptocrystalline silicates appear to be the most promising materials for destructive analysis.
Obsidian, as a natural glass material, is peculiar because when it is exposed to water, the surface develops a patinted layer of hydrated perlite. Old fractures therefore have thicker layers of patina than more recent flake scars. As the rate of hydration is determined by factors such as moisture content, temperature, and the chemical composition of the obsidian, this method cannot provide absolute dates. However, this method has the major advantage of relying on obsidian flaking as the activating cause in this dating scheme.
Cryptocrystalline silicates, such as flint and chert, are sometimes heat-treated in order to improve the flaking properties of the material. This heating can be used as a zeroing point, and the date since the material was last heated can be established through fission track counts, thermoluminescence, or, in some rare cases, paleomagnetism. These provide absolute dates. Unfortunately, not all such tool stones were heat-treated, and not all heat-treatment is due to human agency. Forest fires are one way that stones can be heat-treated without human action.
- Behavioral Analysis and the Structure of a Prehistoric Industry Author(s): Payson D. Sheets, B. W. Anthony, David A. Breternitz, David S. Brose, et al. Current Anthropology, Vol. 16, No. 3 (Sep., 1975), pp. 369-391