Chipped Stone Artifact Analysis

Lab Director: James L. Moore


Stone tools were used by people living in New Mexico from Paleoindian times into the early twentieth century, and that makes their study integral to understanding past lifeways. The analysis of chipped stone artifacts can tell us quite a bit about the people who made and used them. By determining where materials were obtained, archaeologists are able to learn where prehistoric peoples traveled, or what links they had to people inhabiting other regions. Some chipped stone artifacts can be used to assign dates to archaeological sites, though not often with the precision of other dating methods. Projectile point styles change through time, and by placing tools of this type in a specific style it is often possible to assign a general date to a site. Under the right circumstances, samples cut from obsidian artifacts can be used to derive a more exact date, though this procedure is much more complex than archaeologists had once hoped it would be (see Archaeomagnetic Dating Laboratory).

Jim MoorePerhaps more important, the analysis of chipped stone artifacts can help to discern many of the activities that were performed by prehistoric peoples at a site. An examination of tool edges can provide clues about how those tools were used. By looking at the types of breaks on projectile points, we can learn whether they broke while they were being made, snapped during use and discarded and replaced at a hunter's home, or perhaps returned to a site in an animal carcass after a successful hunt. Certain wear patterns on tool edges can be used to indicate that they were used in hide preparation, or used to cut, whittle, or saw materials. The debris left behind by flintknapping can aid in deriving information about the types of tools that might have been manufactured at a site, even when those tools were carried off and used and discarded elsewhere. All in all, a thorough analysis of chipped stone artifacts can provide a fairly comprehensive view of how those materials were used in the society that created them.

The OAS uses a standardized analytic format that was designed to allow comparability between projects separated by time, culture, and distance. This format has been used in most chipped stone analyses conducted since the late 1980s, providing a data base containing information on thousands of chipped stone artifacts from dozens of sites across the state and representing the past 3,000–4,000 years of New Mexico prehistory. This analytic format combines typological and attribute approaches to the examination of chipped stone artifacts. Typological analyses classify artifacts into groups considered to have some sort of technological or functional meaning. This approach has the benefit of allowing behavioral inferences through the identification of a single artifact. For instance, the presence of a small projectile point infers the use of bow and arrow for hunting or defensive purposes. A single flake removed during the process of notching a projectile point indicates that formal tool manufacture occurred at a site, even when that tool has been transported elsewhere. However, this method can be validly criticized because it often lacks any verification that there is an actual match between the artifact type and the functional or technological interpretation derived through its presence. An attribute analysis tracks the distribution of certain characteristics through an entire population of artifacts, usually the debris left behind by flintknappers. A series of attributes can be used to assess the validity of type assignments, in addition to allowing the examination of a wide range of questions that cannot be addressed using only a typological approach. The scale of analysis varies in both approaches-a typological analysis is applied to individual artifacts, while an attribute analysis examines an entire assemblage or a large sample thereof.

OAS chipped stone analysis employs a variety of mandatory and optional attributes that can be used to characterize an assemblage and help answer questions concerning residential mobility, ties to other regions, and how site occupants approached the process of making formal and informal tools out of stone. Two mandatory attributes are used in the typological analysis. Morphology characterizes an artifact by shape and a combination of readily visible characteristics that vary between artifact classes. This is a general level of classification, assigning artifacts to specific groups: unifaces, bifaces, cobble tools, debitage, and cores, and including various forms in each category (for example, core flakes, biface flakes, notching flakes, etc.). Function categorizes artifacts by inferred use, if any. Thus, tools that are morphologically bifaces can be functionally classified as projectile points, knives, drills, etc. Flakes used informally as cutting tools are classified as utilized debitage, while those that display no good evidence for such use are classified as unutilized debitage.

Four attributes help characterize the material from which an artifact was made, including material type, texture and quality, percentage of remaining cortical coverage, and type of cortex present. These attributes aid in examining ties between regions and how materials were obtained for reduction and eventual use. Dimensions (length, width, and thickness) are recorded for every artifact, as is the portion represented, since many artifacts are fragmentary. The last of the mandatory attributes, applied only to flakes, consists of a characterization of the striking platform.

The most commonly used optional attributes include several that are applied only to flakes, including the presence or absence of opposing dorsal scars, a characterization of the termination, and the presence or absence of lipping on the platform. Other attributes with a wider application include evidence of heat treatment, types of wear patterns noted on tool edges, and a representative measurement of edge angles for tool edges. Weights are commonly recorded for individual artifacts, and a series of comments is available to further characterize aspects not covered by other attributes. Other optional attributes can be added at will when applicable to specific questions. The flexibility of the OAS analytic system makes it widely applicable and enables analysts to address questions concerning how a site was used and many aspects of the activities that occurred there. The stability of the analytic system permits the comparison of data from various site types and different areas of the state through time.