Towering giants – the so-called sarsen stones are the most impressive components of the monumental complex of Stonehenge. But where did these megaliths come from? Researchers have now investigated this question by examining the geochemical signature of the material. Comparisons showed that most of the sarsen stones were brought in from West Woods in Wiltshire, some 25 kilometers away.
The prehistoric stone circle in the south of England is one of the most famous buildings of mankind. It is believed that Stonehenge was built about 4500 years ago and was a cultural center for a long time. The main structures of the monumental complex are formations of worked stones of different sizes, which are grouped around a center. Archaeologists and geologists have long been concerned with the origin of the building blocks and the transport methods and routes.
Where did the big chunks come from?
Two types of rock were mainly used for the construction. The sarsen stones made of a special sandstone material formed the largest structures of the plant. The largest specimens are over nine meters high and weigh 25 tons. For other formations, however, smaller dolerite blocks were used, which are called bluestones because of their color. So far, these “exotic” stones have been the focus of research, because in contrast to the Sarsen it seemed clear that they could not have come from the region. Investigations came to the conclusion that the builders brought the approximately two-ton blue stones from the Preseli Hills in Wales, some 300 kilometers away, to the Salisbury Plain.
In the case of the Sarsen stones, on the other hand, it was previously assumed that they had been brought in from the vicinity of Stonehenge, because there are deposits of this type of stone in the region. Today, 52 of the originally around 80 Sarsen stones have been preserved in Stonehenge. This also includes all 15 stones of the trilithes, which consist of two supporting stones and an overlying cover stone. Another special Sarsen stone in Stonehenge is the so-called Heelstone, which is located somewhat off the north-east exit of the plant.
Geochemical fingerprints indicate the origin
In order to pinpoint the origin of these most impressive components, the scientists led by David Nash from the University of Brighton have recorded the geochemical composition of the Stonehenge sarsen stones. Portable devices for X-ray fluorescence spectrometry were used. The results initially showed that, with two exceptions, all stones have the same characteristics – that is, they probably have a common origin.
The scientists then characterized the material more precisely using a drill core from one of the Sarsen stones. They were then able to compare the results of this geochemical analysis with examination results from samples of sarsen stones from different parts of England in order to trace the origin of the components. “It was exciting to use the scientific possibilities of the 21st century to understand the Neolithic past,” says Nash.
As he and his colleagues report, the Sarsen, with two exceptions, have a common origin in West Woods, Wiltshire, 25 kilometers north of Stonehenge. The results support the theory that the stones were brought to Stonehenge at around the same time. This also applies to the Heel Stone, it emerges from the test results. This contradicts an assumption that this particular Sarsen came from the immediate vicinity of the monument and was built earlier than the others.
Stonehenge remains mysterious
The reason why the builders of Stonehenge chose West Woods as the source for the sarsen stones remains largely unclear, the researchers say. However, they suspect that the size and quality of the stones there and the ease with which the builders had access to them played a role in the decision. As part of their research, the researchers also show two possible transport routes that enabled a comparatively low outlay.
Another mystery is why two of the 52 stones did not appear to be from West Woods. One possible explanation is that they were the work of a special group of builders who chose to source their building blocks from a separate area. Future research may reveal where exactly it was located, the researchers write.