New Evidence of Bitumen Trade Found Using GC–MS

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Researchers investigating fragments of black organic matter found scattered at the 7th century ship-burial at Sutton Hoo, Suffolk, UK, have discovered the material is not what it was originally identified as (1).

First excavated in 1939, and the subject of continued archaeological research ever since, the ship-burial at Sutton Hoo is one of the most significant discoveries ever made in Britain. The richly furnished burial site contained many significant artefacts including the famed Sutton Hoo helmet and shield, as well as significant objects from throughout the known world of the time. 

Also identified during the excavation were several tarry-looking materials, including two groups of fragments located near the head and foot of the coffin. These were initially identified as manganese oxide, however, a later study in the 1970s used solubility tests and paper chromatography to overturn the initial conclusion, instead identifying the material as “Stockholm Tar”, which is often used as a waterproofing agent and timber preservative. This conclusion had stood ever since with the tarry-looking lumps residing at the British Museum in London.

As part of a wider research project a reinvestigation of the Sutton Hoo tars was undertaken using Fourier-transform infrared spectrometry (FTIR), gas chromatography–mass spectrometry (GC–MS), and elemental analysis‑isotope ratio mass spectrometry (EA-IRMS). The surface morphology of the fragments was also examined by optical microscopy and reflectance transformation imaging (RTI).

The research concluded that the residues had been erroneously identified again and were in fact bitumen. The existence of bitumen within the burial mound also required re-evaluation because its significance has been both misunderstood and understated. 

A possible prestige item of the time, the origin of the bitumen is of importance because sources within the British Isles would have been located outside the East Anglian kingdom to which the burial mound is attributed. However, composition and molecular ratio analysis of the bitumen revealed a source from much further afield with the bitumen being similar to the Middle Eastern bitumen of the Dead Sea family. This represents an archeologically significant find as other goods identified within the burial assemblage have a possible Syrian origin. This adds further evidence to the extent of trading routes at the time, and despite the original form of the bitumen being undiscernible, also represents the first evidence of bitumen being traded from the Middle East to the British Isles. - L.B.

Reference

• P. Burger, R.J. Stacey, S.A. Bowden, M. Hacke, and J. Parnell, PLoS ONE11(12), e0166276 (2016). DOI: 10.1371/journal.pone.0166276.