3D guru Alligator analyses Seahenge

Submitted by Andy B on Wednesday, 28 November 2001 Page Views: 2148

A ground-breaking 3D laser scan commissioned by English Heritage of "Seahenge", the Bronze Age Timber Circle found on the beach at Holme-next-the Sea, Norfolk, confirms that the community which built it over 4000 years ago was much more highly developed and organised than expected.

The digital scan, hailed as a major advance in archaeological technique, produces on computer three dimensional and finely detailed images, impossible to achieve with ordinary recording methods. It has thrown into high relief cut marks left on the timbers by at least 38 different bronze axes at a time when bronze technology had only recently come into Britain from the Continent. They are the earliest metal tool marks on wood ever discovered in Britain.

David Miles, Chief Archaeologist of English Heritage, said: "The new technology will allow us to capture and preserve these fragile axe marks in their optimum condition. We hope that this will enable us to find out more about the timber circle's construction and the people who built it. English Heritage has recommended that the timbers should be conserved for future generations to enjoy."

Francis Pryor, Director of Archaeology at Flag Fen Archaeological Centre, near Peterborough, where the scanning is taking place, said: "The widely different 'fingerprints' of each of the axes show up clearly in the high-resolution images. It is remarkable that this tiny community was able to lay hands on such a large number of tools only about 100 years after the knowledge of how to make bronze arrived in this country. The scan will enable us to examine other features of the timbers, such as the insides of the 'tow holes' in the central stump, through which honeysuckle ropes were threaded to haul it into position."

The people who built the circle were probably farming people who were highly organised and engaged in a wide variety of specialised tasks. They grew crops, fished, kept animals, managed woodland and made tools. The timber circle represents a huge communal outlay of energy and resources and would undoubtedly have had great spiritual significance.

The scanning work is being carried out for English Heritage by Alistair Carty (better known on the web as Alligator Descartes or by his site Symbolstone.org) and Dr Carolyn Sleith of the specialist laser-scanning firm Archaeoptics. Scanning of the timber circle's 55 oak posts and central stump began on 29 October and is due to end on 14 December. It will produce an accurate and permanent record of the timbers which are some of the earliest ever found and have been precisely dated by tree-ring dating (dendrochronology). They were hewn from trees cut down in the Spring of 2049 BC. The scan will enable archaeologists to monitor the condition of the timbers in future.

Already Francis Pryor and his wife Maisie Taylor, an expert on prehistoric wood working, are beginning to understand how the circle was set out. By comparing the timbers they can see where timbers from the same trees have been used and plot the sequence in which they were erected. The central stump was placed first. Then a back panel and an entrance opposite were set out, followed by marker timbers in an arc. The spaces between the markers were then filled in. Debris left from dragging the timbers reveals that a stockpile of wood was kept to one side of the circle, whilst woodworking was
carried out on another.

English Heritage has agreed to pay for the conservation process it recommends. The process would take about five years and cost about £40,000. After extensive research and consultation English Heritage made the recommendation because it concluded that such a unique prehistoric structure of international importance should be conserved so as to be available for future generations, rather than be reburied deeply on the beach at Holme. A public meeting is to be held at Holme on 27 November to discuss the recommendation. English Heritage is exploring with the timber circle's owner, le Strange Estate, and local organisations the possibilities for the future display of "Seahenge".

Notes

The scanning process has used a Minolta VI-900 triangulating laser scanner. It is recording the timbers at 300 micron resolution (0.3mm) and links with a standard lap-top computer which gives a visual image in real time. Archaeoptics will also be photographing the timbers with a high-resolution digital camera to provide surface reflectance information for the 3D laser scan data. This will enable researchers to examine the appearance of the wood as well as the geometry of the timbers.

The digital record will form an important part of the site archive and will be available for future study.

Note: Scans now available to download, see comment below

Contributor Bio for Andy B: Megalithic Portal Founding Editor.

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