A possible Bronze Age tomb was found beneath a Viking ship burial in Norway

On the island of Karmøy, off the west coast of Norway, a team of archaeologists from the University of Stavanger began excavating the Grønhaug mound, a site that had already attracted the attention of researchers in 1902. More than a century later, specialists reopened the mound with the expectation of expanding on the findings from that first intervention, when fragments of a ship's hull were extracted.

During the current work, they recovered iron rivets belonging to the vessel and analyzed a layer of birch bark that may have served as a type of flooring inside the tomb. Dendrochronological and radiocarbon dating of materials extracted in previous excavations place the construction of the mound around the year 864, at the beginning of the Viking Age.

Upon reaching the level of the original ground, the researchers encountered organic matter from vegetation that is nearly 1,200 years old. The preservation was so extraordinary that it allowed for the observation of almost intact botanical details.

“The burial was so well preserved that I could see blueberry and heather plants growing there when they built the mound in the Viking Age,” said archaeologist Marie Ødegaard. “The plants still had leaves.”

An older find beneath the mound

As they continued excavating below that layer of vegetation, the team discovered a cairn of stones surrounded by a ring of rocks. According to Ødegaard, this structure points to a burial from the Bronze Age, much earlier than the Viking burial that covered the site centuries later.

The find reinforces the idea that some burial mounds in the region were reused or superimposed over older sacred spaces. The superimposition of rituals over time is a phenomenon known in Scandinavian archaeology, although the specific details of each site often come as a surprise.

The current intervention aims not only to recover information about the ship and the Viking ritual but also to understand how that specific location was chosen. The presence of a Bronze Age cairn suggests that the site already held funerary or ceremonial significance before the Vikings erected their own mound.

Work continues with the expectation of accurately documenting the stratigraphic sequence and protecting the organic remains, which constitute rare evidence due to their degree of preservation. The combination of absolute dating and analysis of the vegetation allows for a clearer reconstruction of the moment when the mound was closed.

Ritual continuity in the landscape

The case of Grønhaug adds to other examples where funerary structures from different periods overlap at the same point in the landscape. At this site, the decision to construct a ship burial over an older cairn could respond to both practical reasons and the desire to appropriate a place already laden with memory.

Researchers emphasize that the excellent preservation of the plants offers a direct window into the natural environment of the 9th century. Being able to observe leaves still attached to the stems is a rare and valuable piece of information for paleoenvironmental studies.

At the same time, the identification of the cairn as a possible Bronze Age tomb raises new questions about the duration and nature of funerary uses in Karmøy. Future analyses of the materials and the arrangement of the stones will allow for confirmation or refinement of that preliminary interpretation.

For now, the Stavanger team is proceeding cautiously to avoid disturbing the more fragile remains. The goal is to document each layer before extracting information that will help better understand the sequence of occupations and rituals that took place at that same point in the ground for over a millennium.