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ABINGDON ARCHAEOLOGICAL GEOPHYSICS

 

 

 

 IRAN

In 2006-16 we assisted the Gorgan wall project and Edinburgh University in surveying forts and other features associated with this wall which is in north east Iran.

In the early years we were able to go there and do the fieldwork with the Gorgan wall team. Later on we, being British, were refused visas and were unable to go there, despite it being a European Union funded project. All we could do was seek to process the data and sort out any problems via the internet.

The local excavators were more attuned to detecting differences in dry soils than the UK excavators were, who are used to damper soils. The Iranians have skilled archaeological illustrators and draw most of their pottery rims and profiles, in contrast to the declining amount of finds illustrations in UK commercial archaeology reports. If you contact us we can recommend illustrators and provide examples of their work. Visas willing, they are often willing to participate in projects in other countries as well as in Iran.

A report and digital archive on the first phase of the magnetometry has been put on the Archaeology Data Service system. It can also be seen in the book by Eberhard Sauer and others on "Persia's Imperial Power in Late Antiquity: the Great wall of Gorgan and the Frontier Landscapes of Sassanian Iran" (BIPS 2014).It is also in the journal Iran.

It would appear that mud brick here may be easier to see magnetically than it is by excavation as the mud bricks could only be detected by the experienced excavators below approx 1metre. Above that the bricks had decayed but were detectable magnetically.

magnetometer on Gorgan wall in Iran

Here is a photo of Arman, who did much of the magnetometry, standing over the  mud brick feature in fort 4 of the Gorgan Wall.

 

magnetometry survey of Sassanian fort

                   Magnetometry survey of Fort 4 on the Gorgan Wall, Iran

Here is the magnetometer survey. This shows 3 rows of virtually identical rooms with a largely empty area at the top of the illustration. The highest readings are shown in red. These are mainly fairly recent funerary monuments made from fired brick which will have come from the Gorgan wall itself.                               

 The survey was carried out using 30 metre grid squares and these were aligned to be at an angle to expected features in order to maximise the chances of finding anomalies.

We were fortunate in that the organisers of the project had the vegetation cut down before we surveyed. This enabled the magnetometer sensors to be kept less than 15 cms from the ground surface. We were then rewarded by being able to locate mud brick walls which gave a typical anomaly strength of 2nT above that of the surrounding soil.

There was a time in about 2008 when magnetometers were carried with the bottom sensor about 50cms above the ground This may have been caused by an article in the journal Archaeological Prospection where the English Heritage Geophysics people said that this was their practice. It turns out that this was a typo and they meant to say 25cms.

We were also fortunate in that this fort interior has been little damaged, if at all, by ploughing. Whilst root action had made the top 1.5metres of the mud brick walls virtually unrecognisable to the human eye, the soil from which they were made had remained in situ. The individual bricks were visible below 1.5m depth and the bottom of the wall which was excavated was 3.6m below the present ground surface.

This fort is one of the largest of those which are on the Gorgan wall which is a defensive wall built from fired brick and dated to the 5th century AD.