Geochemistry

The main problem with the geochemical analysis of the stone from the site is that it was a bulk composition analysis of a conglomerate. This introduced bias resulting from variations in clast distribution, size and composition. It is unlikely that the chemical results are representative of the silicified conglomerate from the megalith as such a small sample was studied. It is hard to see how this could be rectified as the stones from the site are preserved and rightly so.

The results from the semi and quantitative analysis was not as definitive in assessing the provenances as hoped but some conclusions can be drawn from the data. The differences in the REE concentrations in the four samples taken from Harptree Combe and Garrow Bottom could indicate different events within the alluvial fan deposition in the Triassic.

It may have been more productive to have completed the semi-quantitative and quantitative experiments on just a matrix sample rather than bulk rock analysis. This would have been extremely difficult, as only a small amount of the megalith was available. The matrix is hard to define in a conglomerate as it is often made of a mixture of clast sizes and it would have been difficult to decide where the matrix stops and clasts begin. Ideally a larger sample of the megalith would have been taken and overall amounts of samples increased in size but this was not possible.

Silicification of Harptree Beds

The localised and patchy silicification of the Dolomitic Conglomerate is attributed to hydrothermal activity caused by a local igneous intrusion (Woodward, 1871).

"While, however, we attribute the metamorphism to igneous eruption, it is only as a promoting cause, for we are led from the absence of any traces of igneous rock at the surface to infer that the heat which produced the change was applied through the agency of water."

Kellaway (1971) disputes this theory because of the very patchy nature of the silicification though he agrees no intrusion has been found to outcrop at the surface. This does not preclude its existence though the metamorphism may be explained by extensive faulting in the vicinity.

The geochemistry did not conclusively rule out igneous signatures but map work shows no provinces in the local area. Therefore this work has not precluded the existence at depth of an igneous body. This body may have been the source for the heating of fluids that caused what is probably hydrothermal activity. The literature has indicated that silicification is concentrated near faults which could have acted as conduits for fluids (Green, 1965).

Field Work

It was unfortunate than an actual outcrop if the silicified conglomerate was not found. This is due to the actual; lack of an outcrop and the fact that there is so much foliage in the area.

The map of the Stanton Drew site has been altered to include rocks that have been uncovered since the last map was done. The most recent map by English Heritage also includes the buried stones that were detected in the magnetometer survey.