User:Mrman0930/Excavation (archaeology)

In archaeology, excavation is the exposure, processing and recording of archaeological remains. An excavation site or "dig" is the area being studied. These locations range from one to several areas at a time during a project and can be conducted over a few weeks to several years.

Excavation involves the recovery of several types of data from a site. This data includes artifacts (portable objects made or modified by humans), features (non-portable modifications to the site itself such as post molds, burials, and hearths), ecofacts (evidence of human activity through organic remains such as animal bones, pollen, and charcoal), and archaeological context (relationships among the other types of data).

Before excavating, the presence or absence of archaeological remains can often be suggested by, non-intrusive remote sensing, such as ground-penetrating radar. Basic information about the development of the site may be drawn from this work, but to understand finer details of a site, excavation via augering can be used.

During excavation, archaeologists often use stratigraphic excavation to remove phases of the site one layer at a time. This keeps the timeline of the material remains consistent with one another. This is done usually though mechanical means where artifacts can be spot dated and processed through methods such as sieving or floatation. Afterwards, digital methods are then used record the excavation process and its results. Ideally, data from the excavation should suffice to reconstruct the site completely in three-dimensional space

Mechanical excavation
This describes the use in excavations of various types and sizes of machines from small backhoes to heavy duty earth-moving machinery. Machines are often used in what is called salvage or rescue archaeology in developer-led excavation when there are financial or time pressures. Using a mechanical excavator is the quickest method to remove soil and debris and to prepare the surface for excavation by hand, taking care to avoid damaging archaeological deposits by accident or to make it difficult to identify later precisely where finds were located. The use of such machinery is often routine (as it is for instance with the British archaeological television series Time Team) but can also be controversial as it can result in less discrimination in how the archaeological sequence on a site is recorded. One of the earliest uses of earth-moving machinery was at Durrington Walls in 1967. An old road through the henge was to be straightened and improved and was going to cause considerable damage to the archaeology. Rosemary Hill describes how Geoffrey Wainwright "oversaw large, high-speed excavations, taking bulldozers to the site in a manner that shocked some of his colleagues but yielded valuable if tantalising information about what Durrington had looked like and how it might have been used." Machines are used primarily to remove modern overburden and for the control of spoil. In British archaeology mechanical diggers are sometimes nicknamed "big yellow trowels".

Finds Processing
Finds and artifacts that survive in the archaeological record are retrieved in the main by hand and observation as the context they survive in is excavated. Several other techniques are available depending on suitability and time constraints. Sieving and flotation is used to maximize the recovery of small items such as small shards of pottery or flint flakes.

Flotation
Flotation is a process of retrieval that works by passing spoil onto the surface of water and separating finds that float from the spoil which sinks, this is especially suited to the recovery of environmental data such as seeds and small bones. Not all finds retrieval is done during excavation and some especially flotation may take place post-excavation from samples taken during excavation.

Sieving
The use of sieving is more common on research based excavations where more time is available. Some success has been achieved with the use of cement mixers and bulk sieving. This method allows the quick removal of context by shovel and mattock yet allows for a high retrieval rate. Spoil is shoveled into cement mixers and water added to form a slurry which is then poured through a large screen mesh.

Spot Dating
One important role of finds retrieval during excavation is the role of specialists to provide spot dating information on the contexts being removed from the archaeological record. This can provide advance warning of potential discoveries to come by virtue of residual finds redeposited in contexts higher in the sequence (which should be coming offsite earlier than contexts from early eras and phases). Spot dating also forms part of a confirmation process, of assessing the validity of the working hypothesis on the phasing of site during excavation. For example, the presence of an anomalous medieval pottery sherd in what was thought to be an Iron Age ditch feature could radically alter onsite thinking on the correct strategy for digging a site and save a lot of information being lost due to incorrect assumptions about the nature of the deposits which will be destroyed by the excavation process and in turn, limit the sites potential for revealing information for post-excavation specialists. Or anomalous information could show up errors in excavation such as "undercutting". Dating methodology in part relies on accurate excavation and in this sense the two activities become interdependent.