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Ancient Syrian bitumen discovered in Anglo-Saxon boat at Sutton Hoo

Wikimedia Commons/Eebahgum, CC BY-SA

Sutton Hoo in East Anglia is one of the most important archaeological sites in England. The weapons, clothing and other objects buried in the Anglo-Saxon cemeteries show that trade networks in the 6th and 7th century reached as far away as Europe and Asia. Now new research conducted at the British Museum and University of Aberdeen reveals that trading even resulted in a solid form of oil known as bitumen making it all the way to England from what is now Syria.

The graves at Sutton Hoo vary in size but one of them contains the “phantom” of a boat – the outline remains of a vessel probably used to ceremonially bury a warrior and many of his worldly goods, including his famous helmet. Alongside the body were found several small, centimetre-sized lumps of tar.

After spending a nation’s lifetime in British soil, these lumps have spent a human lifetime in the British Museum, where they have been safely curated for 70 years. Our research team, led by the museum’s Rebecca Stacey along with Pauline Burger, retrieved the lumps of tar from the archives and began analysing them.

Sutton Hoo helmet. Image Less Ordinary/Flickr, CC BY-NC-ND

The museum had catalogued the lumps as pine tar, made by heating wood that contained resin. Pine tar is sticky, water-repellent and easy to make and was probably used in the 6th and 7th centuries to waterproof things. Dr Stacey is an expert in this kind of pine tar but her analyses showed the Sutton Hoo tar was actually oil, the kind that comes from rocks. The question was “which rocks?”.

To answer that question, we had to assess the lumps’ chemical fossil content. My colleague John Parnell has a comprehensive knowledge of places in Britain where oil can be found at the surface due to natural seepage and exposure. But surprisingly, he was unable to match the Sutton Hoo tar to any seeps or deposits in Britain. This suggested it originated from outside of the UK.

Bitumen from the Middle East was used in the ancient world for many things including embalming, medicine and of course water-proofing. This usage left an archaeological record of bitumen that we could examine to look for a match.

Sutton Hoo Bitumen samples. Burger et al (2016)

Bitumen families are a little different to oil families. They have additional chemical characteristics acquired when oil is converted into bitumen. The kind of bitumen used in the ancient world was formed by microbes consuming the liquid parts of oil and leaving behind mostly solid residues. The results of this microbial conversion vary depending on the location of the bitumen.

So far, the Sutton Hoo tar has the strongest match to a bitumen deposit in modern-day Syria. While this might seem surprising, many foreign and exotic treasures have been found at Sutton Hoo, and these small pieces of ancient Syrian oil are just one more.

But there may still be another surprise. We know the chemical composition of the lumps, the rough date of their burial and their point of origin. What we don’t know is what they were used for. Many of the other objects from Sutton Hoo have clear uses, functions or symbolism, including the swords, shields, combs and crockery.

But we don’t have this information for the pieces of tar. What function did they have or what symbolism did they carry? Why are there tiny pieces of Syrian tar in an Anglo Saxon grave? Why did somebody put them there? It seems Sutton Hoo is keeping some of its secrets hidden for now. Until they are revealed, I am waiting to be surprised.

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