Some pollen was found in the buried soils as well as charred wood, providing useful environmental information as well as material for radiocarbon dating. This information was made much more relevant when combined with a wider environmental picture, over a long timeline provided by pollen from peat cores close to Cwm Cilio and Braich y Gornel and, for Fronhill, from earlier environmental work accompanying the excavations of the Erw Wen and Mole y Gerddi Iron Age settlements.
This proved very productive although the buried stony soils were difficult to sample for thin-sectioning. Most soils sampled were those buried by, and so predating, the field boundaries. It would have been ideal to find soils that were contemporary with use of the early fields but had since been undisturbed, for example buried by clearance cairns or other later earthworks.
The programme of geophysical survey was designed to investigate the usefulness of fluxgate gradiometer survey in assessing prehistoric field systems. In most cases features visible as earthworks or walls produced clear anomalies that sometimes revealed additional structural information. The survey also revealed buried features such as earlier phases of boundaries, settlement sites, and various phases of ploughing. Surveys covering larger areas were shown to be particularly effective. Large surveys tend to reveal not only a wider range of features but also complete features. This allows better interpretation and provides a well-integrated survey covering all the elements of a field system including any associated settlement. This approach proved to be very effective in the Roman Fort Environs Project (Hopewell 2005) where surveys including the forts and all associated extra-mural features provided a great deal of new information about the sites examined. Small, targeted surveys as part of the same project tended to miss features that were not in easily predictable positions and did not produce a clear picture of the wider Roman military landscape.
A recommended outline methodology for gradiometer survey of prehistoric field systems can be proposed as a result of this project. It is usually advisable to survey a small test area in order to assess the quality of results that can be expected from a larger survey. Results can be very variable and depend on many factors including the local geology and levels of magnetic material in the soil. If the test area produces acceptable results, the entire field system, or at least a significant sample in the case of very extensive sites, should be surveyed. This should include, where possible, associated settlement, and a wide range of features in order to provide comparative and contextual information. The initial survey should be carried out at standard resolution (i.e. at traverse interval of 1m and a sample interval of 0.50m or 0.25m). This can be followed by targeted high-resolution survey at 0.50m by 0.25m, in areas such as settlements, where more detail is required. High-resolution survey could also provide more information about areas of possible early cultivation marks.
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