Often we see Time Team digging trenches as the main method of site investigation, but in commercial archaeology, trenches are mainly used as a method of detecting and characterising archaeological remains that will be dug at a more detailed level later.
Open area excavation allows the whole site to be seen at once. Archaeological remains can be related to each other over wide areas. Earlier forms of large-scale excavation tended to leave baulks or pillars of soil between trenches to allow the stratigraphy to be recorded. Single context recording means that each context is dug and recorded separately. A full site stratigraphy can be developed at the end of the excavation as long as the record is complete.
In open area excavation, often the topsoil is stripped off by machine to expose the subsoil, which is the layer that archaeological features are usually dug into. Alternatively, the turf can be taken off by hand and laid to one side to put back later. The topsoil can then be taken off with a mattock (a broad-bladed pick) and sieved for artefacts. The site will then need to be cleaned by hand, probably with hoes or mattocks rather than trowels at this point, depending on the size of the trench. All the visible features can then be planned, either individually or together on a full trench plan.
Going the extra mile
Only the most experienced and best resourced groups should consider open area excavation, and even then only when clearly justified by a robust research design. It is very destructive!
Barker, P 2002 (3rd Edn). The Techniques of Archaeological Excavation. Routledge.
Collis, J 2004. Digging up the past. Sutton Publishing.
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