In September 2014, archaeologists from Aarhus University and the Museum of South East Denmark announced the discovery of a Viking ring fortress at Borgring, Denmark. Since then, researchers have been waiting for the reliable results of the dating of the fortress. Now, a new find has resulted in a breakthrough in the investigation.
The Borgring fortress, located near Køge, a seaport about 39 km southwest of Copenhagen, is a so-called Trelleborg-type fortress.
Only eight fortresses of this type are currently known, including Nonnebakken, Aggersborg, Fyrkat, Borgeby and the famous Trelleborg.
These fortresses are characterized by a ring rampart with an appurtenant moat and four covering gate openings.
They had a rigorous geometric street system, a division of the internal surface area into four square-shaped blocks. Within each of these blocks, there were four longhouses positioned in the form of farmhouses constructed around a quadrangle. All of the four facilities had a uniform and rigorous geometric architecture and a stringent symmetry.
Experts suspected that the Borgring fortress was built in the reign of Viking King Harald I Bluetooth of Denmark (c. 958-c.987), but the association could not be established with certainty.
On June 26, 2017, the archaeological team found a one-meter-long piece of carved oak wood with drilled holes and several wooden pegs.
“The wood carries clear traces of wear, but it is not currently possible to ascertain the function of the wood piece,” the researchers said.
Dr. Aoife Daly, an associate professor at the University of Copenhagen and leading specialist in dendrochronological dating, has just completed his study of the piece.
“The plank is oak, and the conserved part of the tree trunk has grown in the years 829-950 in the Danish area,” he said.
“A comparison with the material from the Trelleborg-type fortress in Sjælland shows a high statistical correlation, which confirms the dating.”
“Since no splints have been preserved, the tree has fallen at some point after year 966.”
“The wood piece was found on top of a peat layer and is fully preserved, as it is completely water-logged,” added research leader Jens Ulriksen, from the Museum of South East Denmark.
“We now have a date of the wood in the valley of Borgring, which corresponds to the dating from the other ring fortresses from Harald Bluetooth’s reign.”
“With the dendrochronological dating, in conjunction with the traces of wear the piece exhibits, it is likely that the piece ended as waste in the late 900s, possibly in the early 1000s.”
“This find is the major breakthrough we have been searching for,” said team member Prof. Søren M. Sindbæk, of Aarhus University.
“We finally have the dating evidence at hand to prove that this is a late 10th-century fortress.”
“The exact year is still unknown, but since the find also shows us where the river flowed in the Viking Age, we know where to look for more timber from the fortress.”