Excavating the Rooswijk … virtually!

The next blog in our British Science Week 2020 series come from MSDS Marine, a Marine and Coastal Contractor specialising in the management, execution and support of archaeological projects in the marine environment. 

The Rooswijk was a Dutch East India Company vessel which sank on the treacherous Goodwin Sands, off Kent, in January 1740. The ship was outward-bound for Batavia (modern-day Jakarta) with trade goods. The site is now protected by the Protection of Wrecks Act 1973. The ship’s remains are owned by the Dutch Government; however, the UK government is responsible for managing shipwrecks in British waters, therefore both countries work closely together to manage and protect the wreck site.

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Figure 1. Clockwise from top left: Multibeam image showing the main area of wreckage on the Rooswijk, A diver excavating in 2018. Lead project Conservator Angela Middleton examining a concreted chest from the side. A screenshot of the Rooswijk virtual trail.

A two-year archaeological excavation project was undertaken between 2017 and 2018 due to the site being at high risk of loss through environmental changes and unauthorised diving. Wrecks such as the Rooswijk are part of the shared cultural maritime heritage across Europe and it’s important that cultural heritage agencies are able to work together to ensure that sites like this are protected, researched, understood and appreciated by all. The project involves an international team led by The Cultural Heritage Agency of the Netherlands (RCE) in partnership with Historic England. MSDS Marine are the UK Project Managers for the project.

In 2019 MSDS Marine, working with ArtasMedia, created a virtual tour of the site: https://msdsmarine.com/projects/dive-trails/rooswijk-virtual-trail/. Now the projects archaeologists are working with the μ-VIS X-ray Imaging Centre at the University of Southampton to further excavate the site virtually!

A number of stacks of coins were found during the excavation. Some of these were carefully separated by the conservators from the Investigative Science Team at Historic England (Figure 2). Some could not be separated.

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Figure 2. An MSDS Marine conservator separating coins from the Rooswijk in the Historic England laboratory.

A number of stacks were then sent to the μ-VIS X-ray Imaging Centre (www.muvis.org) at the University of Southampton to be micro-CT scanned. X-ray micro-Computed Tomography (µ-CT) scanning is a volumetric scanning technique, which enables us to virtually cut open materials to look inside with micrometre spatial resolution, while preserving the condition of the object we are scanning. During the scan, the object is rotated 360 degrees as thousands of 2D X-ray projection images are acquired. These 2D images are then reconstructed into a three-dimensional volume, which is made up of cubic pixels with intensities related to the amount of x-ray energy absorbed at that point.

We used the custom walk-in scanner (the Hutch) at the µ-VIS X-ray Imaging Centre to scan the concreted coins, which were stacked in sealed tubes to prevent excessive drying during the scanning process (Figure 3).

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Figure 3. Concreted coins mounted for µ-CT scanning within the custom Nikon/X-tek 450/225 kVp Hutch at the µ-VIS X-ray Imaging Centre, University of Southampton

The digital reconstructed volumes were then sent to MSDS Marine, where myVGL software (Volume Graphics GmbH, Germany) was used to manipulate the volume data, so that the individual faces inside the stacks could be seen (Figure 4). These coin faces have not been seen since they were packed into chests for the voyage almost 280 years ago.

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Figure 4. A Rider coin from 1739 that has been virtually separated from a large coin stack.

The coin face slice images will be sent to Jan Pelsdonk, the projects numismatist, for identification and will contribute to the understanding of the wreck.

The application of scientific techniques like CT scanning and digital model processing have contributed hugely to the understanding of underwater heritage, and continue to offer new and exciting ways of investigating these important cultural sites.

Phoebe Ronn, MSDS Marine Phoebe@MSDSMarine.co.uk

www.MSDSMarine.co.uk

Katy Rankin, µ-VIS X-ray Imaging Centre, University of Southampton, k.rankin@soton.ac.uk

www.southampton.ac.uk/muvis

HEAD HUNTING IN THE HIGHLANDS – Using archaeological science to understand extraordinary medieval burials from St Colman’s Church, Portmahomack, Tarbatness, Highlands

The next post in our British Science Week 2020 series is about a project supported by funding from Historic Environment Scotland, a NHSF member. 

Written by Cecily Spall, FAS Heritage

Image 1 - 3-D scans - credit Visualising Heritage, UoB
Image 1: 3-D colours scans of the skull of Chieftain A (right) showing blade cut and Chieftain B (Credit: Visualising Heritage, University of Bradford)
Image 2 - Chieftain A and skulls - credit FAS Heritage
Image 2: Chieftain A with the four extra skulls set at his head (Credit: FAS Heritage)
Image 3 - Chieftain B reconstruction - credit FaceLab LJMU
Image 3: 2-D computer-based facial reconstruction of Chieftain B (Credit: FaceLab, Liverpool John Moores University)

The Tarbat Discovery Centre, Portmahomack, opened in 1999 in the former medieval church of St Colman.  It displays the results of 20 years of archaeological research excavation focussed around this important church.  Along with National Museums Scotland, the Centre cares for the collection of burials, dating from the 7th to the 16th century, excavated from in and around the church building.

St Colman’s Church was built in the 12th century in the abandoned burial ground of an 8th-century Pictish monastery. Burials continued from the 13th to the 16th century. Over 80 medieval burials were excavated and include a small group of burials which were highly unusual, displaying burial rites never before seen.  The central burial was that of an older man – ‘Chieftain A’ – who had died aged 46 to 59 years from a horrendous facial injury caused by a blade (Image 1). On his death he was interred in a large coffin which included four extra skulls set at his head (Image 2). About a generation later his grave was reopened and the body of a second man – ‘Chieftain B’ – was laid on top with the skulls now set around his head.

A Historic Environment Scotland funded programme of archaeological scientific analysis is now underway, designed to better understand these extraordinary burials. This includes radiocarbon dating and ‘Bayesian’ (statistical) modelling of the dating brackets to refine them. The results suggest that Chieftain A died between AD1290 and 1410 and Chieftain B between AD 1380 and 1450; three of the skulls buried with them died between AD1250 and 1400 and the fourth belonged to a Pictish monk who died between AD770 and 900. These extraordinary burials belong to the period when the clan system was becoming established and so represents an important part of understanding Highland heritage and the history of the community of Portmahomack.

Multi-isotope analysis measuring strontium and oxygen preserved in tooth enamel has also provided information on region of birth with Chieftain A having grown up on or around the Tarbatness peninsula, and Chieftain B growing up elsewhere, perhaps in the Western or Northern Isles, moving to Portmahomack later in life.

Computer-based reconstruction of the face of Chieftain B has been undertaken using European datasets to model his likely appearance (Image 3), work which was generously funded by the Society of Antiquaries of Scotland. Ancient DNA analysis is also underway at Harvard University and it is hoped that it will provide information on possible family connections between the burials, as well as likely skin tone, and eye and hair colour, and perhaps even his deeper shared ancestry.

The Tarbat Discovery Centre is currently hosting a temporary exhibition on the burials project. For more information visit: http://www.tarbat-discovery.co.uk.