What happens to a site after it's discovered?
Excavations at Stafford cabin chimney at Cumberland Island National Seashore. (John Cornelison)
Data recovery, also referred to as excavation, is the treatment most associated with archeology. Data recovery is the principal means by which archeologists gather information about the past from below the ground surface. While site discovery methods such as archival research, surface inspection, subsurface testing and sampling, geophysical prospecting, and predictive models may provide evidence of buried features, the only way to verify the presence and characteristics of subsurface data is through excavation (Ashmore and Sharer 1996:94).
Data recovery is usually conducted for research purposes or when archeological resources are threatened with destruction from natural processes, such as erosion, floods, or wildlife, or by human activities, such as construction, vandalism and oil spills. The idea behind data recovery is to take the site apart in reverse order to that in which it was formed. According to the Law of Superposition, the further below the surface a soil stratum lies the older it, and the materials contained within it, are. Data retrieved through excavation are especially important to archeologists since subsurface remains are usually the best preserved and the least disturbed. Artifacts recovered from the ground surface are seldom in primary context—that is, in the same soil layer and location as when they were originally deposited—and are usually poorly preserved. Surface features such as roads or walls may be in primary context, but are most likely less well preserved than buried features. Excavation often reveals how artifacts, ecofacts, and features are related to each other within their primary context (Ashmore and Sharer 1996:94).
The two basic goals of data recovery are:
- To reveal the three-dimensional patterning or structure in the deposition of artifacts, ecofacts, and features, and
- To assess the functional, temporal, and possibly the symbolic significance of this patterning.
Determination of this three-dimensional patterning depends on documenting provenience and associations of the individual artifacts, ecofacts, and features with respect to each other and their surrounding environment. From this documentation archeologists can assess context. By knowing what elements were found together and by inferring how these elements got there and how and why they were used, archeologists can reconstruct past human behavior (Ashmore and Sharer 1996:94).
Four excavated units at the Federal picket line, Petersburg National Battlefield Park. (Gail Brown, University of Maryland)
The data recovery process
No one-size-fits-all data recovery project design exists. Archeologists must determine the methods for data recovery based on an individual site's characteristics, the purposes of the project, and the available resources. Data recovery projects differ greatly in their scope, size, duration, and cost. However, the same general methods, tools and procedures are used for the majority of data recovery projects.
Preliminary activities: Once a project site has been selected, the project's managing archeologist—or principal investigator—creates a research design to describe and justify his or her expectations for the entire archeological project. The research design includes identification of a repository to curate the collections, budgeting for collections care, and a collection strategy (Childs and Corcoran 2000:V). In the field, archeologists will follow the research design unless circumstances necessitate changes in focus or methods. Surface inspection and subsurface testing may be conducted to determine feature and artifact concentrations. The archeological team is assembled and supplies are acquired in preparation for the excavation.
Gridding the site: Data recovery is a carefully controlled process. The provenience of each recovered artifact, ecofact, and feature is meticulously recorded. The grid is the most common means for dividing a site into manageable sections. When establishing a grid, archeologists divide the site into precisely measured squares—also referred to as units. A unit is measured in feet or meters. Within the grid each unit is numbered and its location is recorded in relation to the grid's datum point—the zero point, a fixed reference used to keep control of the excavations in both the horizontal and vertical planes. Archeologists often use string to define units within a grid.
Tools: Archeologists use a variety of tools and equipment. Common hand tools include trowels, shovels, picks, line levels, measuring tapes, brushes, marking pens, root cutters, buckets, dust pans, notebooks, pencils, plastic and paper bags, string, plumb bobs, compasses, cameras, and sometimes toothbrushes, tweezers and cotton swabs for delicate work. Archeologists use screens—wooden frames with 1/4" to 1/8" screen—to sift and recover artifacts from soils removed during excavation. Minute artifacts and ecofacts such as beads, seeds and bone fragments, may be recovered through flotation—the use of fluid suspension to recover tiny materials from soil—or by sieving soil through fine screens. In some situations archeologists employ backhoes, bobcats and other construction equipment to remove topsoil or backfill excavated units.
From dustpans to dental picks, archeologists in the National Capital Region use a variety of Tools of the Trade in the field and laboratory.
Record keeping: In archeology, provenience is everything. Throughout data recovery archeologists carefully record information regarding artifact and ecofact provenience, soil characteristics, features, stratigraphy, field conditions, and personnel. Because data recovery destroys the site, field records are crucial in documenting how work was conducted. Field records contain notes and drawings of unit profiles and stratum surfaces as well as photographs. The records generated during data recovery are as important to the analysis and interpretation of the site as the recovered materials are. They become part of the project collections curated at a designated repository.
Site mapping: Throughout the excavation archeologists photograph and draw updated maps of unit profiles, stratum surfaces, and features. This process ensures that the data recovery analysis will accurately reflect the location of units, features, artifacts, ecofacts, and other physical phenomena important to the site's interpretation. In some cases archeologists will use gis or GPS to map a site.
After being washed, artifacts are analyzed, conserved and stored. (Gail Brown, University of Maryland)
Bagging and labeling artifacts: All artifacts and ecofacts recovered from a stratum are placed in carefully labeled plastic or paper bags to ensure that their provenience is recorded. On each bag is written specific information regarding the site, unit, stratum, date, and excavators. Conservation of archeological materials in the field can be an essential aspect of a field project and can significantly affect the long-term preservation of objects in the resulting collection. The conservation and preservation care that an object receives in the field may be the only care it ever receives (Childs and Corcoran 2000:VI). After the excavation is completed, archeologists working in the lab are able to identify artifact and ecofact provenience based on what is written on the bag. When artifacts are processed, archeologists often label the artifact with information.
Artifact processing and analysis: For artifacts and ecofacts, processing consists of proper cleaning, conservation, labeling by provenience, and sorting into basic categories for later analysis. Information about each artifact is entered into a database of some sort to be used in later analyses. In some cases only a representative sample of recovered artifacts is retained, conserved, and stored. Processing is usually done during fieldwork so the archeologist can evaluate the data as they are recovered and can continue to formulate and modify working hypotheses for testing while data recovery is underway (Ashmore and Sharer 1996:111). The collection's long-term care and management should be a priority during artifact processing and analysis (Childs and Corcoran 2000:VI).
After artifacts are processed they are ready for archeologists to use in order to obtain information about the past. For example, an archeologist may look for wear marks to determine how an artifact was used. He or she may also date the artifacts using one or more of the many techniques described elsewhere in this Guide. Based on this analysis, previous research about the site, and information about how the artifacts were deposited and distributed throughout the site, the archeologist will interpret the data and draw conclusions about the people who occupied the site.
Data reporting: The archeologist is responsible for producing a project report. In this report the archeologist records the research design goals, the site's historical background including any previous work conducted there, the methodology used, artifact analysis results, and recommendations for conserving, protecting, managing and interpreting the resource. NPS archeologists produce project reports as well as Archeological Overviews and Assessments and Archeological Identification and Evaluation Studies. These documents, including an archeological base map of the site, provide information needed by park managers, planners, interpreters, law enforcement officers and other specialists to effectively carry out their responsibilities for the protection and interpretation of archeological resources.
For your information
If archeology has been conducted in your park, locate and read the archeologist's project reports. Also find and read the Archeological Overview and Assessment, the Archeological Identification and Evaluation Study, and the Systemwide Archeological Inventory Program (SAIP) for your region.
Archaeology of the Battle of the Little Bighorn
This web site describes archeological methods and excavation at this famous battlefield.
Try it yourself
Historic Jamestowne: You are the archaeologist
Interactively explore archeology at Jamestown Rediscovery.