Long after the discovery of Anglo-Saxon graveyards at the Sutton Hoo site in East Anglia, England, scientists are still analyzing the treasures uncovered there. Perhaps the most famous grave at the site was discovered in 1939 by Suffolk amateur archaeologist Basil Brown. Inside a mound, he and his colleagues discovered the remains of a 27 meter-long Anglo-Saxon ship packed with grave goods including shields, cauldrons, jewelry, and a now-iconic iron-and-bronze helmet.

Eebahgum/Wikimedia

Burger et. al., PLoS One

Burger, et. al., PLoS One

Burger et. al., PLoS One

Harold John Phillips

Remains of the high-ranking individual buried here were dissolved by the acidic soil, but a lot of his loot remained intact. Safely ensconced at the British Museum, many items from the burial chamber in the ship have been catalogued and displayed. Still, a few mysteries remain. For decades, no one could identify a cache of hard, black nuggets. They were tentatively categorized as pine tar, which the Anglo-Saxons would have used for waterproofing ships. Now a team of scientists have figured it out. Writing in PLoS One , they describe using techniques including mass spectrometry and gas chromatography to analyze the chemical composition of the lumps.

What the team found could change the way we understand trade relationships in the Anglo-Saxon world. The lumps turn out to be bitumen, a solid form of oil. Like tar, bitumen can be used for waterproofing. In the ancient world it was also used in medicines and embalming. Bitumen would have been extremely rare at the time of the ship burial. There are a few bitumen deposits in the west of England, but East Anglia was not trading with people in the rest of Britain at the time. Further analysis revealed that the bitumen was actually from Syria.

University of Aberdeen geochemist Stephen Bowden, who helped analyze the bitumen, explains how he and his colleagues figured this out in The Conversation:

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

The researchers are certain this bitumen wasn't being used in boat repair, but they're not sure how the Anglo-Saxons would have used it. Writing in PLoS One, they suggest it could have been used an adhesive in jewelry, or even a set of game pieces:

Bitumen can, of course, also be moulded to manufacture ornamental items such as beads, dice and gaming pieces and the lumps from Sutton Hoo may be the fragmentary remains of small bitumen objects of this kind. Their distribution at the head and foot of the coffin places them close to the areas where the ivory gaming pieces in the burial were discovered, but the locations do not correlate well enough to infer an association.

We may not yet know how the Anglo-Saxons used Syrian bitumen, but we now have a better sense of how far their trade networks stretched in the early Medieval world. Given the geopolitics in Britain at the time, it was easier for an East Anglian noble to get bitumen from Syria than from the west of England.

PLoS One, 2016. DOI: 10.1371/journal.pone.0166276

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