Trying to date Avebury with the help of Stonehenge

by Edward Pegler on 4 December, 2013

This post gives me a chance to compare the radiocarbon dating of Avebury with the dating of Stonehenge and to see if Stonehenge’s new dates can help solve the dating mystery of Avebury.

The currently proposed sequence of events at Stonehenge and the neighbouring riverside stone circle of 'Bluestonehenge'

The currently proposed sequence of events at Stonehenge and the neighbouring riverside stone circle of ‘Bluestonehenge’

Stonehenge – current radiocarbon dating results

So as far as anyone can tell, the ages of the stone circles and earthworks at Stonehenge are now known (though not, sadly, the woodwork). Repeated excavation and re-excavation, coupled with some very good recent archaeology by the Stonehenge Riverside Project, has established a reasonable set of results. These are:

Stonehenge phase 1

Around or just after 3000 BC a circular ditch was dug with most of the spoil placed on a bank inside the ditch. About 56 holes (‘Aubrey holes’) were dug just within this bank and (probably) 56 pieces of Welsh igneous rock (‘bluestones’) were stuck vertically in the holes to make a nice stone circle of the classic British ‘rough’ kind. During this time various cremated people were buried around and in these stone holes. A second, small circle of bluestones (called by the excavators ‘bluestonehenge’) was put up around the same time a little way to the east, by the River Avon.

Stonehenge phase 3 (no 2)

Almost 500 years later, around 2500 BC, a set of shaped sandstones (‘sarsens’) were erected in a much smaller, but admittedly more spectacular, temple (‘Stonehenge’) at the centre of the earthwork. The bluestones around the edge and in the small riverside circle were dug out and moved to be incorporated into this temple.

Stonehenge tinkering

Somewhere around 2300 BC (give or take a hundred years) various earthworks were undertaken, including the cutting of ditches to form a rather bent avenue (‘The Avenue’) leading from Stonehenge to the river. Also, a circular ditch was dug around the emptied ‘bluestonehenge’, and the spoil placed in a bank on the outside of the ditch. This type of rounded earthwork with a bank on the outside is, confusingly, known to archaeologists as a ‘henge’.

The bluestones were moved into a new circle within Stonehenge around 2100 BC. Finally, two rings of pits were dug around the outside of Stonehenge (the ‘Y and Z holes’) around 1600 BC.

So much for Stonehenge.

Avebury  – the radiocarbon desert

The largest stone circle in the country, Avebury is not as well understood as Stonehenge and has always been a bit of a mess when it comes to giving it a set of construction dates. This is for a number of reasons: a shortage of datable material, a lack of excavation, and the effects of more recent local digging and destruction.

The components of Avebury

Avebury consists of a number of different earth and stone features. In no particular order these are:

1) A 2.5 metre high earth bank, sometimes known as ‘phase 1’, remains of which has been found in patches to the south of the monument. This bank was perhaps roughly circular.

2) A large earth bank and ditch, sometimes known as ‘phase 2’. This is also approximately circular and, unlike the bank and ditch at Stonehenge, is a ‘henge’, having the bank on the outside and ditch on the inside. As this bank overlies the bank of ‘phase 1’ this is clearly younger than phase 1.

3) A large circle of sarsen stones just inside the ditch of phase 2.

4) Two relatively small (100 metre-ish), round, sarsen stone ‘temples’ inside the large circle. Unlike Stonehenge these are classic British, rustic affairs, unshaped and without any fancy extras.

5) Two avenues, lined by sarsen stones, running south (‘West Kennett Avenue’) and west (‘Beckhampton Avenue’) from the large circle. Neither avenue is straight.

6) A few stones running NNW-SSE across the bank and ditch.

7) A second stone circle with a wooden structure on the same site (the ‘Sanctuary’) at the eastern end of the West Kennet Avenue.

Avebury’s few radiocarbon (and OSL) dates

There have been several documented excavations at Avebury. These were carried out by (amongst others) Henry Meux, Harold Gray, Alexander Keiller, Stuart Piggott, Faith and Lance Vatcher, Joshua Pollard and Mark Gillings, W. E. V. Young and Mike Pitts. All of these have, sadly, produced only a small amount of dateable material. Of this material (antler, bone and charcoal) a fair amount was destroyed for use in radiocarbon dating the monument in the 1980s. This was before dating methods were improved to use smaller samples and better statistical techniques.

Of the dated material, the charcoal pieces were probably lying around for some time before they were buried at Avebury. Since these were also ‘bulk samples’ (i.e. not neat individual pieces but a collection of bits), there’s also the potential for a range of dates from the samples. Furthermore, they come from wood which could have grown over a long period of time before being felled. The best that can be said is they give dates which will be older than the layer that they’re buried in.

Of the three bone samples, one was also a bulk sample of bits, meaning that its dating probably indicates an older date than the layer it was buried in. The other two bone samples (from a pig and a person) and the antler samples should give good dates (although even these have the potential to have been ‘curated’, or kept for a while – though let’s face it, would you keep a pig bone?)

Even here there’s a complication, as Fran Healy has recently pointed out. The original 1980s sample dating was done at Harwell.  However, more recent re-dating of some of the left over fragments of one antler from the original 1980s radiocarbon samples (HAR-10502) suggested that the Harwell date was perhaps 300 years too old. This appears to be a general pattern for the Harwell dates, many of which could be in error by 300 years either way. Luckily, this one redating has given an improved date for one key sample.

The only date added to this list more recently is some quartz grains analysed using a relatively new method called optically stimulated thermoluminescence (OSL). However, this has large potential errors and no-one is quite sure how reliable it is.

Of course there’s undoubtedly more datable material still in the ground… only this hasn’t been excavated yet. In the mean time, the evidence that’s been gathered and dated has to do.

A summary of what’s ‘known’ about Avebury’s dates

Avebury’s phase 1 bank was piled up some time after 3600 BC – this is based on charcoal two samples (HAR-10063 and HAR-10325), with the youngest given ‘oldest confident dates’ (I know that’s confusing) of 3300 BC. Adding the 300 year potential error of the Harwell dates gives the value quoted.

Avebury’s large ditch was very likely dug in the period 2630-2460 BC – this is based on re-dating of an antler sample (HAR-10052, new dates OxA-12225/6) from the bottom of the ditch, as well as good dating of another antler sample (OxA-12227) low in the ditch fill. As the phase 2 second bank was almost certainly built at the same time as this ditch was dug then it is probably the same age.

Avebury’s outer stone circle appears to have erected after about 2900 BC and probably a little later. This is based on the date of a pig bone sample (HAR-10327) from a stone hole called ‘41’, with earliest confident age of around 2580 BC, allowing again for a 300 year error.

A very loose date of around 3000 BC is given for a ‘Cove’ stone at the centre of the north inner circle, based on OSL dating (X1559) of quartz grains below the stone. However, there’s a large quoted error for this value of 350 years either way (this error could well be more).

The West Kennet avenue appears to have been constructed at some time after 3300 BC, based on material from beneath the avenue (HAR-9695 and HAR-10501) of a youngest ‘earliest confident age’ of around 3000 BC, again allowing for 300 year error.

The far end of the Beckhampton Avenue appears to have been constructed at some time around or a little later than 2500BC. This is based on a good (but unfortunately single) articulated pig bone date of 2660-2460 BC from the Longstones enclosure, which underlies the west end of the Beckhampton Avenue. This enclosure didn’t seem to last long and appears to have been demolished to allow the end of the avenue to be completed.

So the only confident dates are the digging of the ditch and, arguably, the completion of the west end of the Beckhampton Avenue, both of which lie around 2500 BC. Frankly, it’s not much to go on.

Avebury - A simple dating model

Avebury - a simple one phase history

Avebury – a simple one phase history

The simplest model possible is that the whole of the Avebury complex, ditches, stones and avenues, was constructed in one short burst of activity around 2500 BC. The only date which doesn’t allow this is the rather problematic OSL date from the centre of the northern circle and there aren’t many archaeologists I’d guess would put money on that date.

However, the evidence of an extensive build-up of turf between the first phase of bank building and the second indicates that this probably isn’t right. So is there an alternative?

Avebury – A ‘Stonehenge’ type model

Avebury - a three stage history involving a final 'closure'

Avebury – a three stage history involving a final ‘closure’

In the absence of anything to pin the Avebury dates down, a ‘simple’ alternative is to use the Stonehenge dates as a guide, comparing banks, ditches, stone rings and avenues to see if Avebury could be squeezed to fit these.

This would mean that at least one bank and ditch, and the large stone circle, would have an early date of around 3000-2900BC. The big ‘phase 2’ ditch at Avebury is clearly younger than this. However, the phase 1 bank (and any ditch that it might once have had) could fit this date. Perhaps archaeologists should be having another look for such a ditch, but on the outside of the phase 1 bank (as is the case with Stonehenge’s ditch being on the outside its main bank).

If the large stone circle at Avebury also dated from this time, this could (at a push) be accommodated by the single radiocarbon date of pig bone. This is taking the date to its earliest limit but is just feasible.

On this scheme, the other stone ‘temples’ within Avebury would be similar in date to Stonehenge itself, around 2500 BC. Again, this would contradict the single piece of dating evidence, the OSL date from the northern circle, but this is a date of low confidence. Alternatively, these inner stone circles, which are not shaped like those of the temple at Stonehenge, could be part of the suggested 3000-2900 BC phase.

The Avebury avenues, in this version, would be slightly later, say somewhere around 2450 BC, something which fits comfortably with the evidence available.

Discussion – the significance of that ‘henge’ bank

Perhaps the most interesting problem with the second model is that there is no equivalent to Avebury’s large earthwork henge (the ditch with phase 2 bank on the outside) at Stonehenge. This is the only thing with a really good date fix (around 2500 BC) at Avebury. There are similar henges of this type near Stonehenge (e.g. at Durrington Walls, Woodhenge and Bluestonehenge) and all of these are dated to around 2400 BC, so the dates match reasonably well with Avebury’s henge.

Perhaps it’s worth turning to an interesting comment, passed over quickly by Mike Parker-Pearson in his recent book on Stonehenge, about the significance of ‘henge’ earthworks.

“Henges, with their inward-facing earthworks, were built as memorials to something that had already happened rather than to signal what might still be to come. They are backwards-looking and commemorative” (p225)

MPPs point here was that all of these henges appear to mark the closing off of a done thing. So Durrington Walls bank overlies the suburbs of Durrington and Bluestonehenge was dismantled before the henge was put up. The reasons for this may be superstition, but who knows.

If this is true, then perhaps much of Avebury’s circle, stones and all, was made obsolete by the emplacement of a large, inward-facing bank and ditch, say around 2450 BC, at the time that Stonehenge was at its height. This would be a little earlier than when the nearby Silbury Hill was constructed.

Now my personal fancy is that Stonehenge and Avebury may have been rival centres. If true then the group controlling Stonehenge could have been the ones who ‘closed’ Avebury. Of course this is all without evidence and is likely to be wrong. Sadly, finding out what kind of timescale is, in fact, right for Avebury will have to await further excavation… and who knows when that will happen.

References

Parker-Pearson, M. 2012 Stonehenge: Exploring the Greatest Stone Age Mystery, Simon & Schuster, pp406.

Pollard, J. & Reynolds, M. 2002 Avebury: The biography of a landscape, Tempus, pp288.

Pitts, M. 2000 Hengeworld, Random House, pp409.

Gillings, M. & Pollard, J. 2004 Avebury, Duckworth, pp221.

Bayliss, A. et al. 2012 Radiocarbon Dates from samples funded by English Heritage between 1981 and 1988., English Heritage pp363.

Healy, F. 2012 Scientific Dating, from ‘The Stonehenge and Avebury Revised Research Framework (SARRF)’, Wessex Archaeology Report, pp15.

Anon. 2004 Avebury older than Stonehenge – and the ring gets bigger, News Section, British Archaeology 76

Unseen but probably useful references

Pollard, J. and Cleal, R. M. J. 2004 Dating Avebury, in: R.M.J. Cleal and J. Pollard (eds.), ‘Monuments and Material Culture. Papers in Honour of an Avebury Archaeologist: Isobel Smith’, Hobnob Books, p120–29.

Rhodes, E. and Schwenninger, J.L. 2008, Optically stimulated luminescence dating, in: M. Gillings et al. (eds), ‘Landscape of the Megaliths.Excavation and Fieldwork on the Avebury Monuments, 1997–2003’, Oxbow Books, p 164–65.

 

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