Stonehenge's hefty Altar Stone came all the way from Scotland
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[August 15, 2024]
By Will Dunham
(Reuters) - At the centre of Stonehenge lies the Altar Stone, a hefty
slab of sandstone whose origin and purpose have been among the famed
megalithic monument's enduring mysteries. A new analysis has revealed
that this rectangular colossus took a remarkable journey to become part
of one of humankind's ancient wonders.
Its geochemical fingerprint is a perfect match for bedrock found in
northeastern Scotland, researchers said on Wednesday, indicating that
the Altar Stone - weighing an estimated six tons - was transported
roughly 700-750 kilometers (435-465 miles) by Stonehenge's creators to
Salisbury Plain in southern England.
The findings left the researchers stunned. No stone from any other
monument dating to that time period is known to have been transported
such a distance.
"We couldn't believe it," said Anthony Clarke, a doctoral student in
geology at Curtin University in Australia and lead author of the study
published in the journal Nature.
The common belief for the past century had been that it had been sourced
from Wales like some other large Stonehenge components. The Altar Stone,
recumbent rather than erect, is 4.9 meters (16 feet) long, a metre
(3-1/4 feet) wide and half a meter (1-2/3 feet) thick. It is grey-green
sandstone, though its rippled and weathered surface now has a red-brown
coloration.
Transporting it such a distance - perhaps by both land and sea -
suggests a degree of societal organization among Britain's Neolithic
communities unexpected for the time when it was moved, thought to have
been about 4,600-2,500 years ago, roughly contemporaneous with ancient
Egypt's great pyramids.
"This finding radically refines our understanding of prehistoric
connectivity and the technology of Neolithic Britain," said Curtin
University isotope geology professor and study co-author Chris Kirkland.
Previous analyses had identified two primary types of stone used to
build the monument's stone circle: some sourced locally from near
Marlborough around 25 km (15 miles) away and some from around
Pembrokeshire in Wales 250 km (150 miles) away.
Sandstone bears grains of various minerals. The researchers analyzed the
age and chemistry of zircon, apatite and rutile grains in two Altar
Stone fragments. The zircon primarily dated to 1-2 billion years ago.
The apatite and rutile dated to about 450 million years ago.
The chemistry of the fragments matched Scottish bedrock from the
Orcadian Basin region, reaching from Inverness to Scotland's
northeastern tip and beyond.
"It's a micro-analysis technique," said geologist and study co-author
Nick Pearce of Aberystwyth University in Wales.
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The Altar Stone at the ancient monument Stonehenge located on
Salisbury Plain is seen underneath two bigger Sarsen stones in
Wiltshire, Britain in this undated photo released on August 14,
2024. Professor Nick Pearce, Aberystwyth University/Handout via
REUTERS.
The researchers used a laser beam to vaporize a chosen mineral in
the rock, then analyzed the gas vapor, measuring the ratio of
isotopes - variants of a given element - of uranium and lead to
determine the age of the mineral.
"And the match of this sort of age fingerprint that we got from
these minerals is identical to the Orcadian Basin in Scotland, not
Wales," Pearce said. "So, suddenly it's gone from being 250
kilometers (155 miles) from Stonehenge, give or take, to 700
kilometers from Stonehenge."
The Altar Stone, partly covered by two other fallen stones, is the
only one of the monument's large stones not part of its circular
design. While the precise location where it was sourced remains
unknown, getting such a massive cargo from Scotland to Wiltshire
would have been a challenge, underscoring the Altar Stone's
importance to Stonehenge's builders.
"How it was moved is uncertain but marine shipping is a realistic
suggestion, given the mountainous and forested terrain of possible
land routes," said Aberystwyth University geologist and study
co-author Richard Bevins.
The simple boats of the time could have been used to transport it
down the coastline, the researchers said.
The Altar Stone's evocative name comes from a 17th century
interpretation by English architect Inigo Jones.
"It got its name because it is flat like a table, but we don't know
if it always was like this, nor do we know what exactly it was used
for. We do know the setting sun on the solstice lights it up,"
Kirkland said.
"It really is unique in the monument," Bevins said. "Loads of
uncertainty about what the Altar Stone means."
Stonehenge, built in multiple stages over about 500 years starting
at approximately 3000 BC, remains a site of fascination, drawing a
stream of tourists from around the world.
"It provides a connection to our ancient ancestors who made
something that has endured time," Kirkland said.
(Reporting by Will Dunham in Washington; Additional reporting by
Matthew Stock in London; Editing by Rosalba O'Brien)
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