Fieldwork

AVAS members can get involved in a range of fieldwork, generally carried out within the valley of the Hampshire Avon.  Most people associate archaeological fieldwork with excavation, but archaeologists use a whole range of different techniques to investigate archaeological remains.

Some of the techniques employed by AVAS members are described below.  You can also read about fieldwork that has been undertaken on the AVAS Blog.

Desktop survey

Even before going out on site, old records and maps can be consulted to understand the history of a location.  Many old maps are now available online;  for example, the National Library of Scotland has scanned a national British set of 6 inch and 1 inch Ordnance Survey maps, along with other map series.  For example, the extract below shows the detail of the survey for Whitsbury hill fort (click on the map to see it in more detail).

Whitsbury hill fort on OS Six Inch 1872 map
Whitsbury hill fort on OS Six Inch 1872 map

Aerial Photography

Aerial photographs have revealed a palimpsest of archaeological remains throughout the Avon Valley, revealed as crop and soil marks.  Crop marks occur where buried features either suppress or promote crop growth, leading to variation in the colour and height of the crops.

The proliferation of online aerial photography has increased the resources available for research.  AVAS supplements this with the use of a model aeroplane, with attached camera.  A couple of members also have access to a private light aircraft.

AVAS members have identified a range of sites using aerial photography, including a possible Neolithic long barrow, numerous ring ditches which probably represent Bronxe Age barrows, as well as a series of enclosures and field systems.  The example below shows two ring ditches near Downton, recently revealed by aerial imagery.

Ring ditches near Downton
Ring ditches near Downton

Field walking

Field walking can be used to determine the distribution of surface finds and help identify new sites.  AVAS was involved in a major survey of the middle Avon Valley which was published in 1995.  This survey revealed a large number of new Prehistoric, Roman and Medieval sites, and helped to demonstrate the density of previous settlement in the Avon Valley.

AVAS members also get involved in more ad hoc surveys, as shown below where finds are being identified.

Fieldwalking Nov 2011

During this particular survey, a broken Palaeolithic stone hand axe was found:

Fieldwalking find Palaeolithic Axe

Geophysics

Geophysics is a technique used to look for anomalies under the ground using electrical currents.  AVAS uses one particular type of geophysics, called resistivity, which measures the variation in an electric current as it passes between two probes in the ground.  Features buried underground such as ditches or walls will cause different readings.

Resistivity survey using AVAS equipment
Resistivity survey using AVAS equipment

Once a grid square has been surveyed, the results can be plotted, using colour to show the variation in the electrical resistance.  The plot below shows a composite plot of a survey done by AVAS members on a possible Neolithic long barrow (click on the plot to enlarge).

Resistivity plot of possible long barrow
Resistivity plot of possible long barrow

Excavation

Excavation is not undertaken lightly, as it is a destructive method of investigating archaeological remains.  AVAS has tended to use excavation to either rescue threatened remains, or as an evaluation tool where the topsoil is removed to get a clearer picture of what is under the ground.  This latter method is particularly effective in investigating anomalies highlighted by geophysics survey.  The photograph below shows AVAS members undertaking one such survey.

AVAS evaluation excavation
AVAS evaluation excavation
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