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A long-lost piece of Stonehenge that was taken by a man doing restoration work on the monument has been returned after 60 years, giving scientists the opportunity to peek inside a pillar of the emblematic monument for the first time.
In 1958, Robert Phillips, a representative of the drilling company helping to restore Stonehenge, took the cylindrical core after it was drilled from one of the pillars of Stonehenge – Stone 58. Later, when he emigrated to the United States, Phillips took the carrot with him.
Due to the protected status of Stonehenge, it is no longer possible to extract samples from the stones. But with the return of the core in 2018, researchers had the opportunity to perform unprecedented geochemical analyzes of a Stonehenge pillar, which they described in a new study.
They discovered that the towering standing stones of Stonehenge, or sarsens, were made up of rocks containing sediment that formed when dinosaurs roamed the Earth. Other grains in the rock date back 1.6 billion years.
Stone 58 core sample (British Geological Survey)
Related: In Photos: A Walk Through Stonehenge
“We scanned the rock with CT scans, zapped it with X-rays, examined it under various microscopes and analyzed its sedimentology and chemistry,” said lead author of the study, David Nash, professor of physical geography at the University of Brighton in England.
“With the exception of the thin-section analyzes and a few chemical methods, all of the techniques we used in the study were new to both Stonehenge and the study of sarsen stones in the UK,” Nash said. to Live Science in an email.
The central circle of pillars of Stonehenge was erected during the Neolithic period, about 2,500 years ago, according to English Heritage, a nonprofit organization that manages historic monuments in England.
“The Sarsens were erected in two concentric arrangements – an inner horseshoe and an outer circle – and the blue stones [smaller monument stones] were set up between them in a double arch, ”English Heritage said on its website.
When scientists examined thin slices of sarsen rock from Stone 58 under a microscope, they were surprised to find that the stone was made of 99.7% quartz. A quartz “cement” contained fine to medium grains of quartz and formed “a mosaic of interlocking crystals,” Nash said.
This made the rock more durable, and maybe that’s why builders chose this type of rock for their massive monument thousands of years ago.
“These cements are incredibly strong. I wondered if the builders at Stonehenge could tell us something about the properties of the stone, and not only choose the closest larger rocks, but also those that were most likely to resist. future-proof, ”says Nash.
(Administrators of the Natural History Museum)
Above: Microscope image of the sarsen sample showing the tightly interwoven mosaic of quartz crystals that cement the rock together. The contours of the quartz sand grains are indicated by arrows.
Older than dinosaurs
The researchers’ analysis also revealed clues to the age of the sediment in the rock, Nash said in the email.
“The sandy sediments in which the stone developed were deposited during the Paleogene period, 66 [million] at 23 million years old, so sarsens can’t be older than that, “he explained.
However, when scientists compared the ratios of neodymium isotopes – or atoms of the element with different numbers of neutrons in the nucleus – in the samples, they found that some sediments in the sarsen stone were even larger. old.
Some grains were probably eroded on rocks dating from the Mesozoic era (252 million to 66 million years ago), when they may have been trodden on by dinosaurs.
And some of the sand grains formed 1 billion to 1.6 billion years ago, Nash said.
While this analysis answered some questions about Stonehenge, other puzzles remain, including the location of two other cores that were drilled into Stone 58 during the 1958 restoration, and which also disappeared from the record.
Workers at the Salisbury Museum in England discovered part of one of these carrots in their collection in 2019, the researchers reported. Museum director Adrian Green contacted an English Heritage representative, reporting the discovery of part of a Stone 58 “core in a box marked” 3x Stonehenge Stones from “Treasure Box”, “according to the study.
Scientists studied the Salisbury fragment alongside the Phillips nucleus and recorded its data in their study. However, “how and when he got to the museum was unknown,” the authors wrote.
The location of the third nucleus (and the rest of the nucleus found at the Salisbury Museum) “is also unknown,” the scientists said.
The results were published on August 4 in the journal PLOS A.
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Stonehenge: 7 reasons why the mysterious monument was built
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This article was originally published by Live Science. Read the original article here.
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