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Geophysical Surveying with Touching the Tide at Snape

last modified Mar 17, 2014 03:25 PM
A training day for 12 volunteers in the theory and practice of geophysical surveying for archaeological features took place in Snape, near Aldebugh, last Saturday as part of the Touching the Tide landscape partnership on the Suffolk coast.


Following a very successful field-walking event last month (which you can read about here), Access Cambridge Archaeology (ACA) were invited to return to Snape on Saturday 15th March 2014 to run another archaeological field survey day for local residents and volunteers, this time introducing the geophysical prospection techniques of magnetometry and resistivity. The training day was commissioned by the Heritage Lottery Funded landscape partnership project Touching the Tide.

Dr Marcus Brittain, of Cambridge Archaeological Unit (CAU), joined ACA to lead the day and lend his expertise in the use of geophysics in commercial and academic archaeological field investigations. He is the site director of CAU's excavations at Ham Hill, Britain's largest prehistoric hillfort located in Somerset, and a project supervisor at CAU's excavations of the North-West Cambridge development. Further afield, he has been co-ordinating the Mursiland Heritage Project exploring the archaeology and ethno-history of pastoral groups in south-west Ethiopia.

The day began with a talk from Dr Carenza Lewis, Director of ACA, at Snape Village Hall, in which she covered the aims of the day and showed some examples of 'geofizz' from Time Team episodes and from Saffron Walden common, which ACA excavated last summer. Marcus followed with an outline of the principles behind collecting, processing and interpreting results from magnetometry and resistivity, including illustrations from Ham Hill and other hillforts.

The group moved to the survey site shortly before lunch for a demonstration of a single probe magnetometer and twin probe resistivity meter; the latter kindly on loan from Tim Dennis at the University of Essex. The field, near Decoy Wood east of Snape, has long been of interest to members of the Aldeburgh and District Local History Society who have metal-detected the area and found numerous Anglo-Saxon artefacts. With their direction, an area of relatively flat and even ground was identified for surveying and we laid out a 30 x 30m master grid, divided into nine smaller 10 x 10m grids.

After a brief lunch break in the sunshine, the group split into two to work with the two instruments. We were unfortunately unable to automatically log readings with the magnetometer which would only work when walking south-north transects, demonstrating the temeramental nature of the highly sensitive magnetic equipment, but three grids were successfully completed by the end of the afternoon. The volunteers were asked to manually log and call out readings from the instruments, which were written down as they went along, allowing us to follow trends in the data as readings were taken. The resistivity meter proved much more reliable and it was used to survey the remaining six grids, giving complete coverage of the target area and the opportunity to contrast the findings of the two techniques.

The day concluded with a reflection on the potential and pitfalls of employing geophysics as part of an archaeological investigation, and refreshments were served in the form of tea and home-made Victoria sponge cake, courtesy of Touching the Tide manager Bill Jenman. A number of the volunteers had also attended the Snape field-walking day in February, and Carenza presented the distribution maps of the flint and pottery collected which have returned from specialist analysis. The maps are now available to view on the Snape project page here.

Below are a selection of quotes from the volunteers who took part in the geophysics training:

"Looking forward to the results. It is really good to have helped get the data together and then to be able to see how it fits (or does not) into a pattern." (AA)

"I am hoping to be involved in more archaeological work in the future - very glad to have better understanding of process... So much scope in our landscape for learning more." (JH)

"Fascinating finding newly identified clues." (DC)

Photographs from Saturday's event are ready to view on the ACA website here, which is also where the data collected during the geophysical surveying can be accessed once it has been processed over the coming weeks.

ACA will be returning to Suffolk over the coming months to run Higher Education Field Academies (HEFAs) in Walberswick and Long Melford. ACA will also be supervising a long weekend of community test-pit excavations in Southwold in August, as part of Touching the Tide, and further information will follow on our website soon.

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