ARCHAEOLOGICAL EXCAVATION
Archeological excavation which discovered prehistorical caves in
Vill,
Austria Archaeological excavation existed even when the field was still the domain of amateurs, and it remains the source of the majority of data recovered in most field projects. It can reveal several types of information usually not accessible to survey, such as stratigraphy, three-dimensional structure, and verifiably primary context.
Modern excavation techniques require that the precise locations of objects and features, known as their
provenance or provenience, be recorded. This always involves determining their horizontal locations, and sometimes vertical position as well (also see
Primary Laws of Archaeology). Similarly, their
association, or relationship with nearby objects and features, needs to be recorded for later analysis. This allows the archaeologist to deduce what artefacts and features were likely used together and which may be from different phases of activity. For example, excavation of a site reveals its
stratigraphy; if a site was occupied by a succession of distinct
cultures, artefacts from more recent cultures will lie above those from more ancient cultures.
Excavation is the most expensive phase of archaeological research. Also, as a destructive process, it carries
ethical concerns. As a result, very few sites are excavated in their entirety.
Sampling is even more important in excavation than in survey. It is common for large mechanical equipment, such as
backhoes (
JCBs), to be used in excavation, especially to remove the
topsoil (
overburden), though this method is increasingly used with great caution. Following this rather dramatic step, the exposed area is usually hand-cleaned with
trowels or hoes to ensure that all features are apparent.
The next task is to form a
site plan and then use it to help decide the method of excavation. There are many different styles of excavation, with some countries traditionally preferring one method over another; and some sub-disciplines like
classical archaeology will often use different methods than those used for the excavation of a
prehistoric site. In general terms, however, archaeologists will first establish a site grid to provide spatial control, then remove soil carefully and with concern for its stratigraphy (possibily following a strategy of
single context recording, as commonly used in the UK). The use of a
Harris matrix to record relationships between strata is also common on sites with complex stratigraphy.
Features may be excavated in portions in order to produce a visible
archaeological section for recording. Scaled plans and sections of individual features are all drawn on site, digital photographs of them are taken, and recording sheets are filled in describing the
context of each. Information may be entered into a computer directly on site, or transferred from paper records at a later date. All this information serves as a permanent record of the now-destroyed archaeology and is used in describing and interpreting the site.
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Post-excavation analysis
Once artefacts and structures have been excavated, or collected from surface surveys, it is necessary to properly study them, to gain as much data as possible. This process is known as post-excavation analysis, and is normally the most time-consuming part of the archaeological investigation. It is not uncommon for the final excavation reports on major sites to take years to be published.
At its most basic, the artefacts found are cleaned, catalogued and compared to published collections, in order to classify them
typologically and to identify other sites with similar artefact assemblages. However, a much more comprehensive range of analytical techniques are available through
archaeological science, meaning that artefacts can be dated and their compositions examined. The bones, plants and pollen collected from a site can all be analysed (using the techniques of
zooarchaeology,
paleoethnobotany, and
palynology), while any texts can usually be
deciphered 