Viking fortress discovery: Archaeological dating results

Two carbon-14 dating results have removed all doubt regarding the authenticity of the Viking fortress.
Credit: Image courtesy of Aarhus University

In September 2014, archaeologists from the Danish Castle Centre and Aarhus University announced the discovery of a Viking fortress in a field belonging to Vallø Manor, located west of Køge on the east coast of Sealand. This was the first discovery of its kind in Denmark in over 60 years. Since then, archaeologists have been waiting impatiently for the results of the dating of the fortress. Now the first results are available, and they will be presented at a seminar at Aarhus University on 18 November.

"When the discovery was published back in September, we were certain that we had found a Viking ring fortress, but since then there have been intense discussions online and amongst archaeologists about whether we were right. Now we know without doubt that we have found a fortress from the 10th century," says archaeologist Nanna Holm, curator of the Danish Castle Centre.

Two carbon-14 dating results have removed all doubt regarding the authenticity of the Viking fortress. The carbon-14 dating was performed by the AMS 14C Dating Centre at the Department of Physics and Astronomy at Aarhus University in close collaboration with Accium BioSciences' laboratories in Seattle.

"The two samples were both taken from the outermost tree rings of charred logs that were found in the northern gateway of the fortress. The results of the two samples are almost identical: The fortress was built in the period between the year 900 and the beginning of the 11th century," explains Marie Kanstrup, an employee at the AMS 14C Dating Centre at the Department of Physics and Astronomy, Aarhus University.

Dating is important in determining the role of the fortress in the history of the Viking age

Søren Sindbæk, a professor of medieval archaeology at Aarhus University, explains that archaeologists are still working to date the fortress more precisely.
"We would like to determine a specific year. The carbon-14 method can't provide that, but we are working on different methods that can help us date the fortress even more precisely."

Dating the fortress will be an important step towards understanding its role in the history of the Viking age.

"We can't say whether or not it's Harald Bluetooth's fortress yet, but now that we've dated it to the 10th century, the trail is getting hotter. The things we've discovered about the fortress during the excavations all point in the same direction. We already know that there's a good chance that we'll find conclusive evidence next year," says Sindbæk.

A structure meant to symbolise power

Even though the excavations have closed for this year, the finds bode well for future efforts. The archaeologists' investigations have also revealed that the Viking fortress was built right next to the open sea.

"The excavation showed that there was a basin of fresh or brackish water right next to one side of the fortress -- presumably a quite narrow inlet leading out to Køge Bay. When the fortress was built, hundreds of tonnes of the heavy clay subsoil would have had to have been dug out into the sea basin," explains Nanna Holm.

According to Nanna Holm, this work was undertaken for no other reason than to give the fortress an impressive location. The structure was meant to signal power.

The same master builder may be responsible

The excavation has also shown that the construction of the fortress is closely related to other Viking fortresses such as Fyrkat near Hobro, Aggersborg near the Limfjord and Trelleborg near Slagelse. These fortresses were undoubtedly built during the reign of Harald Bluetooth, and still more evidence suggests that Borgring, as the fortress has been named, might have belonged to the same building programme.

"There are a lot of similar details in these structures. And it's been wonderful to see the same things coming to light at Borgring. In addition to the structure of the rampart and the gates, we have also found traces of a street with wood paving running along the inside of the rampart -- just like in Fyrkat, Aggersborg and Trelleborg. The most striking thing, however, is the measurements of the fortress. The rampart of Borgring is 10.6 metres wide. That is exactly the same width as the rampart of Fyrkat. So it's hard to avoid the sense that the same master builder was responsible," says Sindbæk.

Source: Aarhus University

Major Viking hall identified in Sweden

Using ground-penetrating radar. Credit: Martin Rundkvist

A Viking feasting hall measuring almost 50 metres in length has been identified near Vadstena in Sweden. Archaeologists from Stockholm University and Umeå University used ground-penetrating radar, a non-invasive geophysical method, to locate and map the house foundation. The study was published today in the journal Archaeological Prospection.

The Aska barrow, where the hall has been found, was long seen as a burial mound. But archaeologists have now revealed that it is a foundation platform for a large building, most likely dating from the Viking Period. The hall was probably the home of a royal family whose rich graves have previously been excavated nearby.

"Parallels are known from several of the era's elite sites, such as Fornsigtuna near Stockholm and Lejre near Roskilde. The closest similarities are however seen in a recently excavated feasting hall at Old Uppsala near Stockholm. Such close correspondences suggest intensive communication between the two sites," says Martin Rundkvist of Umeå University

The building was about 14 metres wide and was equipped with double walls and four entrances. The measurements also indicate a large fireplace at the centre of the floor.

"Our investigation demonstrates that non-invasive geophysical measurements can be powerful tools for studying similar building foundations elsewhere. They even allow scholars to estimate the date of a building without any expensive excavations," says Andreas Viberg of the Archaeological Research Laboratory at Stockholm University who directed the fieldwork.

Source: Stockholm University

Archaeologists reveal layout of medieval city at Old Sarum

Old Sarum -- aerial photo. Credit: Image courtesy of University of Southampton

Archaeologists from the University of Southampton have revealed for the first time the plan of a network of buildings in a once thriving medieval city at the historic site of Old Sarum, near Salisbury.

A research team of students and academics carried out a geophysical survey of the ancient monument, scanning ground at the site with state-of-the-art equipment to map the remains of buried structures. They concentrated their survey around the inner and outer baileys of what was once a fortification, with its origins in the Iron Age and the Roman conquest.1

Their investigations reveal the layout of a settlement including structures from the late 11th century, contemporary with the construction of a cathedral and castle. The city was inhabited for over 300 years, but declined in the 13th century with the rise of New Sarum (Salisbury).

The project findings mainly concentrate on the medieval period and highlight:

* A series of massive structures along the southern edge of the outer bailey defensive wall, perhaps suggesting large buildings of a defensive nature.
* An open area of ground behind these large structures, perhaps for mustering resources or people, or as part of a circular route through the city..
* Residential areas in the south east and south west quadrants of the outer bailey alongside the inner bailey ditch.
* Evidence of deposits indicating industrial features, such as kilns or furnaces.
* Features suggesting quarrying at the site after the 1300s and following the city's decline -- indicating a later period of habitation at the site..

Archaeologist Kristian Strutt, Experimental Officer and Director of Archaeological Prospection Services at the University of Southampton, says: "Archaeologists and historians have known for centuries that there was a medieval city at Old Sarum, but until now there has been no proper plan of the site.

"Our survey shows where individual buildings are located and from this we can piece together a detailed picture of the urban plan within the city walls."

The research was conducted as part of the Old Sarum and Stratford-Sub-Castle Archaeological Survey Project, directed by Kristian Strutt and fellow Southampton archaeologists Timothy Sly and Dominic Barker. Old Sarum is under the custodianship of English Heritage, who kindly granted permission for the investigation to take place.

Heather Sebire, Property Curator at English Heritage, comments: "Having the team of archaeologists on site over the summer gave our visitors a chance to find out more about how important historic landscapes are surveyed. The use of modern, non-invasive surveying is a great start to further research at Old Sarum.

"From this work we can surmise much about the site's past and, whilst we can't conclusively date the findings, it adds a new layer to Old Sarum's story. We welcome the chance to find out more about our sites, and look forward to exploring ideas for further research in the future."

The team used a variety of techniques to examine the outer and inner bailey of the site. These included the use of topographic survey methods and geophysical survey techniques -- comprising of magnetometry, earth resistance, ground penetrating radar (GPR) and electric resistivity tomography (ERT) survey.

Kristian Strutt concludes: "Our research so far has shown how the entire outer bailey of the monument was heavily built up in the Middle Ages, representing a substantial urban centre. Results have given us compelling evidence as to the nature of some of the structures. It is clear, however, that there is more non-intrusive work that could be carried out to further expand our understanding of the site."

The team hopes to return to complete the survey of the inner and outer baileys and survey the Romano-British settlement to the south of Old Sarum in Easter 2015. The project fieldwork in 2014 was used as a training season for undergraduate and postgraduate archaeology students at the University, continuing a long tradition of research-led teaching at some of the most impressive archaeological sites in the south of England. Previous fieldwork has been conducted by students at Portchester Castle, Netley Abbey and Bishop's Waltham Palace in Hampshire, and at Bodiam Castle in East Sussex.

Source: University of Southampton

Laser from a plane discovers Roman goldmines in Spain

These are ancient goldmines in the Eria river valley, with channels and reservoirs for exploitation. The model generated with LiDAR data (left) allows these structures to be located on aerial photos (right). Credit: J. Fernández Lozano et al.

Hidden under the vegetation and crops of the Eria Valley, in León (Spain), there is a gold mining network created by the Romans two thousand years ago, as well as complex hydraulic works, such as river diversions, to divert water to the mines of the precious metal. Researchers from the University of Salamanca made the discovery from the air with an airborne laser teledetection system.

Las Médulas in León is considered to be the largest opencast goldmine of the Roman Empire, but the search for this metal extended many kilometres further south-east to the Erica river valley. Thanks to a Light Detection and Ranging (LiDAR) laser system attached to an aircraft, the ancient mining works of the area and the complex hydraulics system used by the Romans in the 1st century BC to extract gold (including channels, reservoirs and a double river diversion) have been discovered.

"The volume of earth exploited is much greater than previously thought and the works performed are impressive, having achieved actual river captures, which makes this valley extremely important in the context of Roman mining in the north-east of the Iberian Peninsula," as Javier Fernández Lozano, geologist at the University of Salamanca and co-author of this study published in the Journal of Archaeological Science, said.

The specialists consider that the systems for the transport and storage of water were copied from those already existing in North Africa, where the Egyptians had been employing them for centuries. Some details of the methodology used appear in texts such as those of the Pliny the Elder, the Roman procurator in charge of overseeing mining in Hispania.

"We have established that the labour that went into extracting the resource until its exhaustion was so intensive that after removing the gold from surface sediments, operations continued until reaching the rocks with the auriferous quartz veins underneath," explains Fernández Lozano.

The researcher stresses that the real discoverer was the LiDAR technology: "Unlike traditional aerial photography, this airborne laser detection system allows the visualisation of archaeological remains under vegetation cover or intensely ploughed areas."

From aircraft or drones
LiDAR comprises a laser sensor which scans the ground from an aircraft or drone with geographical references provided by GPS ground stations. The data obtained is represented by point clouds, which are processed with a piece of software to construct a cartographic model where the forms are identified, such as old reservoirs or channels.

This technology was developed by NASA in the sixties to analyse the retreating sea ice in the Arctic and composition of the oceans. Since then their use has been extended to topography, cadastral mapping, geology and archaeology. According to the authors, the study of Roman mining in the Eria valley is the first piece of 'geo-archaeology' performed with LiDAR in Spain.

"Our intention is to continue working with this technique to learn more about mineral mining in the Roman Empire and clear up any mysteries such as why Rome abandoned such a precious resource as gold from one day to the next," concludes the researcher.

Source: Plataforma SINC