Cold Case: Skeleton Cave , Leigh Woods

Sometimes names are a mystery… and until recently that was true for ‘Skeleton Cave’.

Back in 98 we commissioned an archaeological site survey for the National Trust’s Bristol property ..Leigh Woods. It found that one of its Avon Gorge caves (near the Clifton Suspension Bridge), was named Skeleton Cave. No explanation could be discovered, just an empty cave with a name.

10-03-08-leigh-woods-michaels-hill-golden-cap-022The view from Stokeleigh Camp down to the Skeleton Cave at Leigh Woods

Bones preserve well in the carboniferous limestone caves and are often found when cavers dig there…though discoveries may be centuries old and poorly recorded.

Deep cave deposits can be  of many periods. The National Trust has a good Somerset cave collection.. at Leigh Woods, Brean Down and the Mendips properties. Cave deposits tend to be very ancient indeed. At Cheddar there is a cave known as the Bone Hole where many prehistoric bones have been found. The Royal Holloway College has been carrying out exceptional research at Ebbor. Here, after a decade of excavations,through layers containing Pleistocene animal remains, some human occupation evidence has recently been found. This is over 30,000 years old and below layers containing bones of long lost British creatures like aurochs, arctic foxes, reindeer and bears.

img_1386Pleistocene animal bones from Ebbor Gorge

So Skeleton Cave is a cold case.. and an unexpected email from Graham at Bristol University reopened the files. First, and most obviously, it is Skeleton Cave because back in 1965 two men dug there and found prehistoric flint flakes and a skeleton. National Trust had no idea the excavation was taking place until a report appeared in the local paper. At that point the Bristol Spelaeological Society at Bristol University wrote to NT to raise their concerns.

Surviving cave deposits are rare and any excavation needs to be backed up with the resources and experience to analyse the finds and publish the information. So the excavation stopped and the finds were handed over to the National Trust. Bristol Spelaeological Society put together a file on what they could find out about the excavation.

Graham let me see the Bristol correspondence and hoped to find more from the National Trust files. The NT archive is curated in environmentally friendly conditions in old WWII tunnels near Chippenham, Wiltshire. The relevant files were called up and brought to our office at Tisbury. A morning of searching revealed very little additional information.

Back in the 1960s, the National Trust had very few staff compared with today and some properties were administered by local management committees. Some of the letters in Graham’s file were from the Leigh Woods committee and this reminded me of the tin trunk we once had in the cellar at our old office at Eastleigh Court, Warminster.

The box had been full of minute books and maps and other documents held by the Leigh Woods Management Committee and was transferred to the Leigh Woods property hub at Tyntesfield when we moved. I contacted the collections manager there and Graham went to Tyntesfield to look inside the box…Unfortunately,  just committee stuff and nothing about Skeleton Cave.

Within the Bristol University files were letters from the old Wessex Regional Office at Stourhead. Perhaps the 2 boxes of finds from Skeleton Cave were taken there. No, they may be hidden somewhere but the Stourhead collection is largely catalogued and there is nothing from Bristol.

Another of Graham’s 1960s letters is from Lacock and this is a more likely place for something to be hidden. The Talbot family were finding things on their Wiltshire estate for centuries before it came to the Trust and there are numerous rooms and boxes all through the ranges of Abbey buildings. The collection is still being catalogued. Visions of the two lost Leigh Woods finds boxes hidden like Ravenclaw’s diadem within Lacock’s ‘rooms of requirement’ (Lacock featured in the early Harry Potter films).

No luck so far. Usually back then, NT archaeological finds would be deposited at the local museum which would be Bristol City Museum. They have no records from Skeleton Cave.

However, not all is lost. Graham has a drawn section of the cave, notes on the excavation and a precious human lower jaw which was given to the University by the finders. He will publish an account of the discovery and Lisa at Tyntesfield has found the money to provide a radiocarbon date for the mandible.

10-03-08-leigh-woods-michaels-hill-golden-cap-023Bristol Suspension Bridge and the Avon Gorge from Stokeleigh Camp Iron Age hillfort.

It was analysed a few days ago and we await the result.

 

 

 

 

Kingston Lacy’s Roman Amphitheatre

Old John Bankes died back in 1772 and as he wasn’t married his younger brother Henry inherited. Henry only lived another 4 years but he did something remarkable. He commissioned a cutting edge surveyor called William Woodward to make a detailed record of his Kingston Lacy and Corfe Castle Estates in Dorset. This week Francesca kindly digitally photographed the whole survey.

The archive room at Kingston Lacy House. Until the 1980s the Bankes family archive including Willliam Woodward's survey was stored in the mansion and few people had seen it

The archive room at Kingston Lacy House. Until the 1980s the Bankes family archive including Willliam Woodward’s survey was stored in the mansion and few people had seen it

Yesterday, I sat in the conference room in Warminster and saw a remarkable aerial and lidar survey of Brownsea Island. The surveyor did whizzy things on the computer and zoomed into and enhanced images, measuring any detail on command. Things have come a long way since the 18th century but Woodward’s surveys are still accurate and detailed and also works of art.

One can imagine Mr Woodward arriving at Kingston Lacy House in 1775 and being shown into the library to meet his important client, Henry Bankes, surrounded by the portraits of his ancestors. The surveyor would have placed the books on the desk and explained the conclusions of his work. The money that could be made by enclosing the common arable fields and creating compact farming units….

This is Woodward's fold-out front map which shows all the land of the Kingston Lacy Estate each lettered compartment has a detailed map within the leather bound survey book.

This is Woodward’s fold-out front map which shows all the land of the Kingston Lacy Estate each lettered compartment has a detailed map within the leather bound survey book.

And there the books stayed through generations of the Bankes family gathering dust in the archive cupboard until 1982 when the Bankes family estates were given to the National Trust.

I was given the job of creating a very different survey. To audit with management recommendations all the archaeological sites I could find on NTs newly acquired Kingston Lacy Estate. Woodward’s survey was the oldest detailed map of the land so I went to its new home in the Dorset Records Office in Dorchester.. to take a look.

Wow! Historic maps are wonderful. There was so much information…There was Badbury Rings hillfort… there were the three barrows clearly visible as they are today beside the entrance track… and there was the Roman Amphitheatre..Roman Amphitheatre?

A detail of the front map. Badbury Rings hillfort.. three mounds which are Bronze Age barrows... Roman Amphitheatre!!?

A detail of the front map. Badbury Rings hillfort.. three mounds which are Bronze Age barrows… Roman Amphitheatre!!?

What was William thinking of? Things ‘classical’, Roman and Greek, were very fashionable in his day. What had he seen to make such a mistake? The only known amphitheare in Dorset is in Dorchester, the local administrative centre then as it still is today… I had to go and have a look on the ground.

The 'amphitheatre' when I first saw it under stubble. The ranging poles stand on opposite sides of the 60m diameter enclosure which has a hollowed area at the centre.

The ‘amphitheatre’ when I first saw it under stubble. The ranging poles stand on opposite sides of the 60m diameter enclosure which has a hollowed area at the centre.

I peered over the gate into a wheat field, there was certainly an earthwork. A ploughed down circular enclosure with a dip in the middle about 60m across. I asked the farmer and he said he thought it had been caused by a German bomb in WWII. That didn’t work, Woodward had seen it before it was ploughed over 230 years ago, it must have been an impressive earthwork then.

The site lay right next to the Roman road to Dorchester. Woodward shows the ‘amphitheatre’ entrance facing the road. Where was the town or settlement or Roman fort which would justify such a building (this was before we discovered the Roman settlement a few hundred metres to the south…see the blog post on Vindocladia)

A photo of the 'amphitheatre' taken from a model airplane after ploughing. The white mark is the chalk bank and the darker line the outer ditch. An earlier field boundary ditch emerges from below the chalk bank at the bottom of the picture.

A photo of the ‘amphitheatre’ taken from a model airplane after ploughing. The white mark is the chalk bank and the darker line the outer ditch. An earlier field boundary ditch emerges from below the chalk bank at the bottom of the picture.

David the warden asked a volunteer to send up a camera mounted on a model plane so that it could take aerial photographs after ploughing. Later, we walked across the site picking up prehistoric flint and the odd piece of Roman pot. The whole thing looked promising. This was a rare puzzle.. so Tim the managing agent and the farmer gave us permission to put in two trenches where the enclosure bank was crossed by the hedge.

We laid out a trench on either side of the ploughed down earthwork against the hedge beside the road down to Shapwick. Badbury lies beyond the Beech Avenue trees at the top of the picture. The ranging rod lies beside the outer ditch where a Roman spiral ring and a 3rd century coin were found in its filling.

We laid out a trench on either side of the ploughed down earthwork against the hedge beside the road down to Shapwick. Badbury lies beyond the Beech Avenue trees at the top of the picture. The ranging rod lies beside the outer ditch where a Roman spiral ring and a 3rd century coin were found in its filling.

We found that a ditch had been dug and the chalk bedrock had been heaped up to form a once massive circular enclosure bank. Over the following centuries the ditch had gradually silted up. In the filling we found a lump of Roman roof tile, then a spiral bronze ring and a 3rd century Roman coin. Perhaps it was an amphitheatre after all.

Then we realised that there had been an inner ditch but it had been backfilled almost immediately. Within the chalky fill were lumps of bone and thick black pottery. We were surprised when our trowels touched bone, then a whole skeleton was carefully uncovered at the bottom of the ditch. It turned out to be the the well preserved remains of a young pregnant cow. This was not the only animal burial we found, we also uncovered two sheep buried in pits within the enclosure (just in our narrow trenches..were there lots of burials hidden across he site?). We waited for the Radiocarbon dates to come back. When they arrived they dated the site to long before the Roman period. The animals had been buried in the period 1100-900 BC, the time when King David and later King Solomon ruled Israel.

The outer ditch had silted gradually of the centuries but the inner ditch had been dug out and backfilled soon afterwards leaving the body of a young pregnant cow in the bottom.

The outer ditch had silted gradually of the centuries but the inner ditch had been dug out and backfilled soon afterwards leaving the body of a young pregnant cow in the bottom.

Over 1500 years ago, did the local Romano-British community regularly gather here to watch fights, contests and entertainments? If this was an amphitheatre it was like Maumbury Rings, Dorchester and had been adapted from an earlier earthwork. The Kingston Lacy amphitheatre started life as a Late Bronze Age sacred site complete with valuable livestock offered as sacrifices to whatever gods were worshipped at the time.

An important site. The farmer kindly agreed to conserve it and took this area out of the plough. It has remained a small pasture field ever since. The earthwork is clear to see now, covered in grass rather than stubble. Thanks for the information Mr Woodward.

Here are the results of the East Kilbide jury….

The results from our carbon 14 samples have arrived, always an exciting time. Was there enough good charcoal for a date, has it been contaminated by the earlier dig on the site, will it turn out to be a date we hoped for. The e-mail flashed up in the right hand corner of my screen and I let out an excited cry, much to the surprise  of my colleagues who all stopped working to ask if I was ok. I opened the results but could not look, ….. deep breath and eyes open ….

The results from the charcoal samples from the bath house excavations at Chedworth

The results from the charcoal samples from the bath house excavations at Chedworth

Phew! we have some answers, and as suspected not a simple result! Many thanks to Gordon Cook from the radiocarbon lab East Kilbride, for the results and the extra explanations and information, I will try to explain it  with my non science mind 🙂  C14 dating has developed over the years and new information can be added to the mix to help pin point a date.  Radioactive decay of the C14 isotope is not constant, as shown in the wiggly blue line on the chart above. For some periods it flat lines and one area is  AD 400-550 making more precise dating more difficult. The sample of charcoal from above the early rectangular bath footing in the north range at Chedworth has two date range spikes  of AD 131-262 77.6%  and AD279-328 17.8%. This is probably due to the  charcoal coming from different types of wood, older dates will come from old timber and later dates from twigs and branches. Also we had re excavated the site and may have some contamination from the earlier disturbance. 

Results from the grain excavated at Chedworth Villa

Results from the grain excavated at Chedworth Villa

The grain from the south range we are 95% certain that it was burnt AD388-564 or for the alternative sample AD329-537. When these were jointly calibrated we got  AD385-539. So the mid-point over that 154 year period would be AD462, and we can reasonably say we have a sub-Roman date. 

The bronze deposit dated to the 3rd Century

The bronze deposit unfortunately the c14 date falls under another flat line in the isotope curve.

The last date from the charcoal around the crucible found in the soils running under the stone steps to the upper baths are  68.2% AD128-231 and 92.9% AD72-256 which again unfortunately  falls in another flat line in the calibration curve. We knew we may not get a very good result from the bath house,  but we are very happy with the grain result!  What this all  means now is  many more discussions and new theories to add to the story of Chedworth Villa, one more piece for the jigsaw 🙂

Locked in time

I have started this post many times and put it to one side, as I struggled to find the best explanation of carbon -14 dating!   So here goes!

Rob collecting charcoal on site at Golden Cap

Rob collecting charcoal on site at Golden Cap

Radio carbon 14 is a radioactive isotope and is  a method  to date organic materials like  wood and bone by  measuring the amount of carbon-14 they contain. All living things take in carbon 14 directly or indirectly from the air they breath and the food they eat, it’s all to do with carbon dioxide. The amount of carbon-14 in the air is a small amount but has been more or less at a constant level for thousands of years, adjustments can be made to compensate for the fluctuations in levels. Once an organism dies, it stops taking in carbon-14, and the carbon-14 it contained at the time of death decays at a set rate and the radioactivity of the material decreases. Calculations are made and results are produced at different levels of probability, and depending on the sample can produce a narrow range of dates. (thanks to the help of the  BBC education web site) 

Charcoal under the Bronze age barrow on Golden Cap

Charcoal under the Bronze age barrow on Golden Cap

Charcoal is the most popular sample for dating but burnt grain is even better, due to type of tree the charcoal is from. If it is from an oak tree then the tree may have been hundreds of years old already when the wood was burnt and can produce a wide date range. Grain, even if stored, will only have had a short time to take in the carbon so it will produce a better result.

When collecting a sample you need to make sure you have enough and also to bag it so it doesn;t get contaminated by other samples or other carbon sources. These days techniques are so refined that we do not usually wrap samples in tinfoil as we did in the 1980s, but we still ban smoking in the trenches  for the health of our samples and diggers!

All non smokers on sites were always jealous of smokers as they had more breaks from digging than us!

Charred grain and seeds vollected from soil samples

Charred grain and seeds collected from soil samples

Hopefully this has made som sense, I am not very scientific minded as I lean more to the arts side of archaeology!  We are at the moment waiting for some dates from our excavations at Chedworth, as the six to eight weeks deadline approaches. I will post the results when we have them.

One of the charts showing results from samples from Badbury Rings

One of the charts showing results from samples from Badbury Rings

Burnt grain you can see the details of the grain hull

Burnt grain you can see the details of the grain hull