The soils of which a site is composed will, for the most part, be derived from the local soil and geology. The term 'natural' is used on site to describe undisturbed layers, the point at which excavation stops. But human activity may well have disturbed or modified these layers, changing their structure or adding in charcoal from fires, brick and tile from buildings, and organic material from manure. On site it is important to recognise even very subtle changes in soil colour, texture or additions such as those described above and then to be able to define the limits of differing layers or deposits. Some changes are very obvious, sequences of buildings and destruction of the type found in urban excavations for example while slower, more gentle accumulations, sometimes taking many centuries to build up, may only exhibit very small changes and have very blurred boundaries.
Ideally soils are described in a standardised way, making use of defined terms recognised in soil science and colour charts that can be used as an objective point of reference. 10YR 4/4 may not sound the best way to describe a certain shade of brown but at least everyone knows what shade it is. For problem soils there is the option of applying science to answer questions such as, is a soil disturbed or undisturbed and what is its precise mineral content.
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Since the advent of photography in the 19th century it has been recognised as an important means of recording information on site. For some early excavations, the photographs are vital in presenting an objective picture of the way in which investigation was carried out. Today, both colour and black and white photographs are routinely taken and much use is being made of digital photography.
In most cases, the camera cannot record the fine definition that can come from close observation but photographs can be used to rapidly record complex but well defined elements such as skeletons. A camera is mounted above the grave and a vertical photograph taken that includes fixed visible marker points that are plotted onto the site plan. The detail from the photograph can then be added onto the plan at a later date. In the same way stone by stone or brick by brick records can be made of vertical wall surfaces using series of overlapping photographs.
Photographs are also extremely good at conveying overall impressions of site layout and those taken from high scaffolding towers can show clearly the changing face of a site as excavation progresses. Photographs are also very useful for publication and for presentation purposes.
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It is vital to locate a site in relation to the present landscape by plotting excavation boundaries onto a modern map base and adding a third dimension by relating heights to Ordnance Survey bench marks that have specific height values. Within the excavation individual layers and structures will again be located in three dimensions, horizontally and vertically. Horizontal measurements are taken using tapes while the vertical axis is measured using a surveyor's level. Scaled down measurements are then plotted onto a stable waterproof plastic drawing film. More use is currently made of the electronic distance measurer (EDM), an instrument that calculates precise three-dimensional co-ordinates.
The drawn record of a site will usually consist of plans that show the horizontal layout at differing levels and sections that show vertical slices through the site. The section is also the term that is used to describe the vertical edge of the excavation trench, a record of the stratigraphy in that part of the site. Never stand close to a section, collapsing a carefully preserved trench edge is not recommended.
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The excavation of human remains
This should be carried out with great respect, in the realisation that what is being excavated is not simply a collection of bones but the remains of a person. Clues about the person's life, their death and the way that their body was treated which can hint at belief and ceremony all lie within the grave and require careful excavation, ideally by someone with at least a basic understanding of human anatomy. Ideally the bone specialist who will eventually report on the excavated bones should be present on site.
The human skeleton is a complex structure and the removal of soil to expose bones can be a long and delicate process. Great care must be taken to avoid damaging the bone surfaces, in particular articular surfaces where bones join together and where signs of degenerative disease may be present. There is a temptation to clean skeletons for photography and define each bone, but it is better in most cases to remove bones with soil still attached and clean them under controlled conditions. The hands and the feet contain many bones, some very tiny, and here it is better to lift a block of soil containing the entire hand or foot and sieve this soil in the laboratory.
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The site record
The complete site record will include drawings and photographs but is based around the written record. Early archaeologists kept site notebooks in which details of observations were recorded but it has long been realised that a more systematic way of recording site data is needed.
Recording systems were first introduced that defined 'layers' and 'features'. The first is self explanatory but a 'feature' is a peculiar concept. A pit or ditch, being cut into the ground is a 'negative feature', whereas a wall or floor which is built up above ground, is a 'positive feature'. This system, although much used is not ideal as confusion can arise between say layer 230 and feature 230. A system by which each observed element was given a unique number was clearly better, and so the 'single context recording' system was developed.
In this system, the action of digging a pit would be allocated a unique number (known as the 'cut') and the layers within it (known as 'fills') would be given their own unique numbers. Each context is recorded on a standardised form that prompts a series of questions: location, plan, section and photograph numbers, description, relationship to other contexts, what is it above and below, have samples been taken, who excavated it, how and when? These completed context forms are the heart of the site record. They need to be compiled with thought and care as without them the site cannot be correctly interpreted.
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