The massive slabs of stone that make up essentially the most iconic buildings at Stonehenge got here from about 25km away, in accordance with chemical evaluation. Because the 1500s, most Stonehenge students have assumed the 6- to 7-meter tall, 20-metric-ton sarsen stones got here from close by Marlborough Downs, and a current research by College of Brighton archaeologist David Nash and his colleagues has now confirmed that.
Current research have traced Stonehenge’s bluestones to quarries within the Preseli Hills of western Wales, about 300km (200 miles) away. When one other group of archaeologists studied the chemical isotope ratios within the cremated stays of individuals as soon as buried beneath the bluestones, these researchers discovered that a lot of these folks may have come from the identical a part of Wales between 3100 and 2400 BCE. Historical builders arrange the sarsen stones a couple of centuries after the arrival of the bluestones. Trendy students have solely been capable of speculate about the place the massive boulders got here from—till now.
Sarsen, additionally referred to as silcrete, is a sedimentary rock largely made up of quartz sand cemented by silica (quartz is simply silica in crystal kind), shaped in layers of sandy sediment. Because of erosion, sarsen boulders at the moment are scattered in clumps throughout southern England. Prehistoric Britons constructed monuments like Stonehenge and Avebury with sarsen boulders, Roman settlers used sarsen bricks to construct their villas, and medieval folks constructed sarsen church buildings and farm buildings. However the largest sarsen boulders we all know of in Britain right now are those at Stonehenge.
About 99 % of the common sarsen boulder is silica, however the different 1 % incorporates hint quantities of different parts, like aluminum, calcium, iron, potassium, magnesium, and others. That further materials is totally different in several sarsen sources, because it relies on the minerals within the floor the place the rock shaped. Nash and his colleagues used these hint parts as a geochemical fingerprint to match the Stonehenge sarsens to their most probably supply.
The most important focus of sarsen within the UK is at Marlborough Downs, an space of spherical, grassy hills 25 to 30km (17 miles) north of Stonehenge. Centuries of archaeologists and antiquarians have assumed the Stonehenge sarsens got here from the Marlborough Downs, largely as a result of the world is close by and filled with the proper materials. However that concept hadn’t been scientifically examined, and the bluestones exhibit that the Neolithic individuals who constructed Stonehenge had a far-flung and complicated provide community—and their very own causes for doing issues, typically inscrutable to trendy researchers.
To trace down the supply of the sarsens, archaeologists first needed to resolve a newer thriller: what occurred to 3 lacking chunks of Stonehenge?
One of many trilithons (arch-like buildings made from two upright stones supporting a horizontal lintel stone) within the central horseshoe fell down in 1797. A century and a half later, in 1958, a restoration challenge set the large stones in place once more—however one of many uprights, referred to as Stone 58, had cracked alongside its size. To assist maintain the cracked stone collectively so it might stand and help its half of the lintel stone, restorers drilled three holes by the stone and inserted steel ties. After the challenge, the three stone cores they’d drilled out appeared to fade into skinny air.
In 2018, one of many restorers, Robert Phillips, returned a damaged however full core from Stone 58 to the UK. A part of a second core turned up within the Salisbury Museum in 2019, however one and a half of the stone cores are nonetheless on the market someplace. Samples from the Phillips core gave Nash and his colleagues the prospect to match the chemical make-up of Stone 58 to sarsen boulders from websites throughout Britain.
The match turned out to be precisely what varied researchers had assumed for the final 500 years. The one boulders that matched Stone 58 got here from one web site within the southeastern Marlborough Downs: West Woods, in Wiltshire, about 25km (16 miles) north of Stonehenge and simply 3km (2 miles) south of the place most research had seemed for Neolithic sarsen quarries. West Woods is a six sq. kilometer (4 sq. mile) plateau, partially wooded and dotted with massive sarsen boulders and pits from millennia of quarrying.