Stanton Drew Timber Circle Digital Model

Text by Andrew David, Ancient Monuments Laboratory, PAST 28 (© The Prehistoric Society).

Despite the fact that the megalithic stone settings at Stanton Drew were commented upon by both Aubrey and Stukeley, and by many others thereafter, it is very remarkable that they have remained so little explored. The stone circles are under the protection of English Heritage and, having recently come into new ownership, allowed the possibility of negotiating improved access and management. In order to undertake this from a more informed background a geophysical survey was commissioned from the Ancient Monuments Laboratory. The need for such a survey had already been highlighted by the Avon Archaeological Unit as part of a proposed project to re-evaluate the site. Currently, a Conservation Plan is being drafted by the Stanton Drew Steering Committee which comprises representatives from the local authority (Bath and NE Somerset), the University of Bristol, the Avon Archaeological Unit and English Heritage.

The startling outcome of the 1997 geophysical survey, reported below, has received wide attention and Stanton Drew has been billed in the press as ‘rivalling’ Stonehenge – a comparison not invited lightly.
The main discoveries relate to the largest feature of the megalithic complex – the Great Circle, which, at 113m in diameter, is the largest British stone circle after Avebury. Magnetometer survey using fluxgate instruments, adapted so that the sensors were carried as close to the ground as possible, revealed that the stone circle was but one element in a much more elaborate arrangement of concentric features (Fig 2). The stones themselves were found to be encircled by a 5-7m wide henge ditch with an unusually wide (50m) gap facing to the NE. Within the stone circle were the traces of concentric rings, with a cluster of magnetic anomalies at their centre.

Some 40m from the Great Circle, within the smaller NE stone circle, the magnetometer located four central anomalies arranged in a quadrilateral, the sides of which align with the four opposed pairs of stones that make up the circle. These anomalies might be responses to hearths but are more probably caused by pits – perhaps the remnants of a former stone or timber setting. Other anomalies seem to flank a passage or avenue leading from this central feature to the NE, a direction maintained by the megalithic avenue that extends outwards from the circle.

In order to enhance the definition of the extremely weakly magnetised features within the Great Circle, the area was resurveyed using a more sensitive magnetometer of the optically pumped caesium variety. The results, illustrated here (Fig 3) confirm the presence of no less than nine concentric rings. The increased resolution of the survey data (collected at 0.5m x 0.12m intervals) provides the clear impression that the rings are each made up of a series of discrete positive magnetic anomalies. These are most obvious in the outer ring, less so in the others, although the eye has a knack of grasping the broader pattern despite the indistinctiveness of its parts. The rings seem to be composed of circles of pits of over a metre in diameter and separated from one another by gaps of about 1m.

Having set aside the outside possibilities that these patterns might be the result of cultivation or even the construction of a post-medieval maze, it becomes an irresistible assumption, fired by comparison with sites such as The Sanctuary, Woodhenge and Durrington Walls, that the pits are integral with the prehistoric site and once held timber uprights. Of course this cannot yet be proven nor is any relative constructional sequence apparent. The structure(s) at Stanton Drew stand apart on account of their colossal size (Fig 1): the diameters of the inner and outer circles are 23m and 95m respectively.

If not hearths, cremation pits, or some other type of pit (cf the Aubrey Holes at Stonehenge), the presence of locally increased magnetic susceptibility could be explained by the burning of posts in situ. More speculatively, we have suggested that the magnetic enhancement may be due instead to the accumulation of biogenic magnetite concentrated in the post pipes following the decay of the timbers. The subsoil, derived from Keuper Marl, is sandy and unconsolidated to a depth of at least 2 metres and the relative ease with which deep pits can be dug into this might at least be a partial explanation for the adoption of such a multitude of post settings.
At the centre of the circles is a cluster of several anomalies which is difficult to interpret. Whilst at least one of these is plausible as a prehistoric pit, a central setting perhaps, others may instead be evidence for unrecorded antiquarian digging.

These first results will be followed up by further survey which will aim, if possible, to provide more information from within the Great Circle. Here every attempt will be made to clarify the pattern of concentric circles and of their component pits, for instance in the southern area where they seem to be obscured by a former field boundary. Such work might allow a more confident appraisal of the possible presence of aisles or corridors within the circles. A detailed topographic survey will also be necessary for the geometry of the complex to be studied alongside the geophysical data. This will determine, for instance, whether or not the various concentric elements truly share a common geometric centre. The geophysical survey will also be extended further afield, at least to explore the SW stone circle and its environs. Resistivity survey at the site has so far not been very informative, but this and other methods will be persevered with.”

From Andrew David, Ancient Monuments Laboratory, PAST 28 (© The Prehistoric Society)

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