The three towering stones of the Devil’s Arrows stand on ground where the underlying rock is a completely different kind of sandstone, meaning the builders could not simply have used stone from beneath their feet. New geological evidence instead points to Brimham Rocks, about 18 kilometers to the west, as the source of the megaliths, suggesting that people deliberately selected and moved these massive stones from a particular landscape.
The Devil’s Arrows stand on the western outskirts of Boroughbridge in North Yorkshire. Three stones survive today, arranged across 174 meters, with the tallest rising about 6.86 meters above the ground.
The stones are made of Millstone Grit, a coarse-grained sandstone formed during the Carboniferous period. But the rock beneath the monument is Triassic Sherwood Sandstone, which is geologically distinct from the megaliths.
The nearest Millstone Grit outcrops are about 5 kilometers away. Several locations have therefore been proposed as possible sources, including Plumpton Rocks, roughly 13 kilometers southwest of the monument, and Brimham Rocks, about 18 kilometers west.
Another possibility raised in earlier work was that glaciers had carried large blocks of Millstone Grit into the area before prehistoric people erected them. The new study tested these competing possibilities using minerals preserved within the stones.
Tiny minerals carry a geological fingerprint
The researchers used detrital zircon and apatite, two minerals that can retain information about the geological materials from which a sandstone was formed.
They collected material from the surfaces of the Devil’s Arrows using an adhesive-peel technique. Small sections of tape were pressed onto inconspicuous, relatively clean areas of the stones for five minutes. Mineral grains adhering to the tape were then recovered and analyzed.
The approach allowed the researchers to obtain material from the protected monument while taking only very small samples.
They recovered 67 zircon ages from Stone 1, 64 from Stone 2 and 105 from Stone 3. Together, the three stones produced 236 concordant zircon dates.
The age patterns were remarkably similar. Statistical tests found no significant difference between the zircon age distributions of the three surviving stones at the 95% confidence level.
That consistency matters because it indicates that the three enormous stones share a closely related geological history rather than representing unrelated blocks from different source areas.
The zircon ages ranged from about 3.74 billion years to 377 million years. The largest groups were from the Paleozoic, particularly about 460 million to 400 million years ago, with additional groups around 1.3 billion to 1.0 billion years and 1.8 billion to 1.5 billion years old. Smaller populations included much older grains, including rare Archean zircons more than 3.7 billion years old.
Brimham Rocks matches the pattern
The researchers then compared the Devil’s Arrows with samples from two likely Millstone Grit sources, Brimham Rocks and Plumpton Rocks.
The match with Brimham Rocks was much closer.
The zircon populations from the Devil’s Arrows and Brimham Rocks shared the same broad mixture of geological ages, including the dominant Paleozoic population and the older Proterozoic and Archean components. Statistical testing found no significant difference between their zircon age distributions.
The comparison produced a Kolmogorov-Smirnov statistic of 0.079 with a p-value of 0.77. A Kuiper test also found a close match, with a statistic of 0.121 and a p-value of 0.73.
Plumpton Rocks, despite being closer to the monument, produced a noticeably different zircon signature. Its rocks contain a greater proportion of Silurian zircon and do not reproduce the age pattern seen in the Devil’s Arrows.
A broader multidimensional scaling analysis of zircon data from the Pennine Basin produced the same result. Brimham Rocks plotted close to the Devil’s Arrows, while Plumpton Rocks was farther away.
The researchers therefore identify Brimham Rocks as the most likely source of the three surviving stones.
Apatite provides another line of evidence
The study also examined apatite, although far fewer useful grains survived.
Most of the apatite recovered from the Devil’s Arrows had characteristics suggesting that it was reworked fossil material rather than ordinary igneous apatite. These grains were relatively large and angular, had low uranium concentrations and elevated thorium-to-uranium ratios, and contained substantial common lead.
The researchers interpret many of them as fragments of fossil-derived phosphate that had been incorporated into the Millstone Grit. Brimham Grit contains fossiliferous horizons, including shelly beds and remains of plants such as Calamites and Lepidodendron.
A smaller group of apatite grains retained useful provenance information. Their age patterns included populations around 480 million years and older components around 1.3 billion and 2.6 billion years. These populations closely matched those found at Brimham Rocks.
The apatite evidence therefore provides additional support for the Brimham source, although the researchers note that apatite is less durable than zircon and is poorly preserved in high-energy fluvial sandstones.
Glaciers do not provide an easy route
The source identification also bears on the question of how the stones reached Boroughbridge.
One earlier proposal was that glaciers transported more than 25-tonne blocks of Millstone Grit into the area during the Pleistocene. The study does not completely rule out complex glacial histories. The authors note that ice-flow directions can change over thousands of years and that models of shifting ice geometry cannot resolve a specific 18-kilometer transport route with certainty.
But Brimham Rocks lies on elevated Pennine terrain west of Boroughbridge and outside the principal reconstructed direction of Late Devensian ice flow in the Vale of York.
Those reconstructions indicate ice movement from the northwest toward the southeast, rather than a straightforward eastward movement from Brimham Rocks toward Boroughbridge. The authors therefore regard glacial transport of large blocks from Brimham Rocks as improbable.
The strong geological match between Brimham Rocks and all three Devil’s Arrows also points toward a specific source rather than a random collection of glacial erratics from different Millstone Grit outcrops.
Together, the evidence supports deliberate extraction and transport of the stones.
The source was not simply the closest suitable rock
Brimham Rocks is not just another Millstone Grit outcrop. It is a prominent landscape of tor-like formations and weathered sandstone.
The rocks also contain natural joints and bedding planes that divide the sandstone into elongated blocks. The researchers suggest these natural fractures may have made large blocks easier to detach than at more massive outcrops.
That means the choice of source could have involved more than one consideration. The physical structure of the rock may have made extraction easier, while the distinctive landscape itself may have had cultural or symbolic importance.
The authors suggest that the unusual formations at Brimham Rocks could have been regarded as a significant or otherworldly place. They also point to evidence of prehistoric activity around the outcrop.
A 3-meter-long gritstone near Brimham Rocks carries wavy-line engravings and about 21 cup-and-ring marks dating from the Late Neolithic to the Bronze Age. Faint markings near the base of the northernmost Devil’s Arrow may possibly be cup marks as well, although that connection remains tentative.
An 18th-century account also described a stone circle at Brimham Rocks, but no trace of it survives and its location is unknown. About 2 kilometers south of the rocks, a smaller standing stone on Standing Stone Hill retains weathered fluting similar to that seen on the Devil’s Arrows.
These observations do not establish why prehistoric people selected Brimham Rocks. But they place the identified source within a landscape that itself contains evidence of prehistoric activity.
Some missing stones may still survive nearby
The geological analysis also investigated two later structures associated with the history of stones that disappeared from the Devil’s Arrows.
Historical accounts describe additional stones at the monument. A fourth stone was recorded in the 16th century, and by the late 17th century another account said a stone had been broken up and incorporated into the nearby Peg Bridge. A 19th-century antiquary also proposed that a megalith had been reused in the Battle Cross Monument.
The researchers analyzed zircon from the Battle Cross and Peg Bridge. The age populations were compatible with those of the Devil’s Arrows. Battle Cross zircon included dominant Caledonian and minor Neoarchean components also present in the standing stones, while Peg Bridge zircon fell within the Neo- to Mesoproterozoic populations characteristic of the megaliths.
No analyzed grains contradicted derivation from the same Millstone Grit source.
Combined with the historical accounts and the dimensions and morphology of the Battle Cross, these results support the interpretation that stones from the former Devil’s Arrows alignment were reused in later local structures.
That means some of the missing monument may not have vanished completely. Its stone may have survived after being separated from the original prehistoric setting.
The alignment was part of a larger landscape
The Devil’s Arrows occupy a wider prehistoric landscape between the Rivers Swale and Ure. Seven later Neolithic henges are located in the surrounding area, which the authors describe as the densest concentration of henge monuments in Neolithic Britain.
The stones themselves extend across 174 meters and are oriented broadly north-northwest to south-southeast. They stand on gently sloping ground toward a possible ford across the River Ure.
Geophysical surveys have identified two areas of magnetic disturbance that may represent former positions of stones. A possible stone socket was also found north of the Ure near the Langthorpe enclosure. Other possible stone and post holes extend the line toward Cana Barn henge and the Thornborough Henges.
The evidence has led archaeologists to suggest that the alignment may have formed part of a route through the landscape.
The new provenance evidence adds another element to that picture. The stones were brought from an upland source rather than taken from the nearest available Millstone Grit outcrop.
The researchers therefore interpret the choice of Brimham Rocks as deliberate procurement from a particular source landscape. They suggest that practical factors, such as the natural fractures that could help release large blocks, may have worked alongside the cultural significance of the place.
The evidence does not establish exactly what Brimham Rocks meant to the people who moved the stones. What it does establish is that the three surviving Devil’s Arrows share a distinctive geological fingerprint with that particular outcrop, about 18 kilometers away, and that their transport cannot be readily explained by a simple local or glacial origin.
The study was published in Proceedings of the Royal Society A.
