South Cadbury Environs Project

Geophysics

It is fitting that SCEP has based its methodology on geophysics as Leslie Alcock was a pioneer of the techniques during his work inside the hillfort in the 1960s. Geophysical survey has formed the backbone of the project from an early stage with extensive gradiometry (a form of magnetometry) coverage. Some of the results have been spectacular not only because of particular individual features revealed, but because of the landscape-scale extensive bounded systems of land-use which reach back to the Early Bronze Age.

From 1992 to 1995 gradiometry and resistivity were the chosen geophysical techniques, introduced by Paul Johnson of the University of Glasgow. He encouraged the application of prospection in substantial blocks rather than in sampling strips. This allowed far more effective interpretation of the resulting plots. Gradiometry proved much the quicker of the two techniques and generally more effective for discovery of a wider range of underlying features. As a consequence Tabor included it with test pitting and fieldwalking in the initial research design (Tabor 2008).

Photograph showing Paul Johnson using Gradiometer

Paul Johnson using the Geoscan FM9 gradiometer at the beginning of the Sigwells survey.

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Photograph of Liz Caldwell using Gradiometer

Liz Caldwell using the Bartington 601-2 gradiometer during re-surveying prior to excavation of trenches on Sigwells. Cadbury Castle is in the background.

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Figure showing SCEP Gradiometry superimposed on Topography

The complete SCEP gradiometry (grey) superimposed on topography

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Results of the geophysics are detailed in the provisional results section but here are some highlights:

Sigwells

This remarkable survey was carried out from 1992 to 1996 and formed the basis of the pilot study which determined SCEPís long term strategy. The 18ha field includes an Early Bronze Age parallel linear field system, pre-dating at least one barrow; a Middle Bronze Age metalworking enclosure; an elaborate long term Iron Age field system; an extensive Middle to Late Iron Age pit group and associated enclosure; a later first century AD farmstead and a Romano-British field system with associated stone founded buildings.

Figure Showing Sigwells Gradiometry survey

The Sigwells gradiometer survey, completed in 1996.

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Sheep Slait

Sheep Slait is a 20ha tongue of land separated on all sides by steep-sided V-shaped valleys, except to its north west where a narrow neck links it to the surrounding downland. Gradiometry showed traces of barrows and a later Bronze Age field system. The latter was associated with a 50m diameter ringwork, over 120km from the nearest example, itself an outlier of a group in the Thames Valley and close to the south east and east coast. The centre of the ringwork was re-used during the Iron Age.

Figure showing Detailed Gradiometry survey of Ringwork st Sheep Slait

Detail of the Sheep Slait gradiometer survey carried out in 2005 showing the ringwork

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Woolston Manor Farm

The apparently ancient boundaries of modern Woolston Manor Farm warranted total coverage of this area. The evidence from gradiometry, test pits and a small-scale excavation showed that the present farm buildings are adjacent to, and probably over, the core settlement area at the centre of a field system established in the later Iron Age and still influencing the modern land-holding and its internal division. That system respected a previously unknown hilltop enclosure, itself preceded by an Early and revised Middle Bronze Age linear field system overlooking it from the north.

Figure Showing Complete Woolston Manor Farm Gradiometer Survey

The complete Woolston Manor Farm gradiometer survey carried out in 2006-07

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