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HS2 excavations uncover prehistoric subtropical coastline in Ruislip, west London | HS2 excavations uncover prehistoric subtropical coastline in Ruislip, west London |
(10 days later) | |
It was a time when Britain boasted a subtropical climate, dense forests and parts of the south and east of country were under a shallow warm sea. But in Ruislip, west London, you would have needed your wellingtons: 56m years ago, the area appears to have been a wooded marsh. | It was a time when Britain boasted a subtropical climate, dense forests and parts of the south and east of country were under a shallow warm sea. But in Ruislip, west London, you would have needed your wellingtons: 56m years ago, the area appears to have been a wooded marsh. |
Experts working on exploratory excavations for the high-speed railway HS2 say that samples taken from up to 33 metres below the surface in Ruislip contained a previously unknown material which suggests that in the late Paleocene epoch the region was a swampy area, in close proximity to the sea. | Experts working on exploratory excavations for the high-speed railway HS2 say that samples taken from up to 33 metres below the surface in Ruislip contained a previously unknown material which suggests that in the late Paleocene epoch the region was a swampy area, in close proximity to the sea. |
Building the nation’s infrastructure has a habit of turning up unexpected details from the past. | Building the nation’s infrastructure has a habit of turning up unexpected details from the past. |
Channel Tunnel | Channel Tunnel |
While working on the high speed link between central London and the channel tunnel, experts found an extraordinary array of ancient treasures. Among them were a neolithic longhouse, mummified cats, a Victorian model farm and the fossilised skeleton of an extinct species of elephant dating from 400,000 years ago, surrounded by flint tools which were probably used to butcher the animal. The remains of rhinoceroses and deer were also discovered. | While working on the high speed link between central London and the channel tunnel, experts found an extraordinary array of ancient treasures. Among them were a neolithic longhouse, mummified cats, a Victorian model farm and the fossilised skeleton of an extinct species of elephant dating from 400,000 years ago, surrounded by flint tools which were probably used to butcher the animal. The remains of rhinoceroses and deer were also discovered. |
Crossrail | Crossrail |
Excavations for the new railway which will cut across London and the south-east unearthed a collection of skeletons in 2014. It is believed the team stumbled upon a 14th century plague pit – a mass grave for those who succumbed to the Black Death. The existence of the pit had been known, but not its location. It is now believed to lie under Charterhouse Square in Smithfield. | Excavations for the new railway which will cut across London and the south-east unearthed a collection of skeletons in 2014. It is believed the team stumbled upon a 14th century plague pit – a mass grave for those who succumbed to the Black Death. The existence of the pit had been known, but not its location. It is now believed to lie under Charterhouse Square in Smithfield. |
Borough Viaduct | Borough Viaduct |
During construction of the new Borough viaduct near London Bridge, which opened in 2016, experts turned up a collection of finds including what is thought to be a Roman bathhouse under Borough High Street, a pair of 16th century "Borough Delftware" plates and 16 boxes of Roman pottery. | During construction of the new Borough viaduct near London Bridge, which opened in 2016, experts turned up a collection of finds including what is thought to be a Roman bathhouse under Borough High Street, a pair of 16th century "Borough Delftware" plates and 16 boxes of Roman pottery. |
Upgrading the A1 | Upgrading the A1 |
While turning the A1 into a motorway in North Yorkshire, archaeologists discovered a number of intriguing artefacts including a rare bug-shaped Roman brooch and a tiny sword with an iron blade and bone handle that, some suggest, might have been a gift to the gods. | While turning the A1 into a motorway in North Yorkshire, archaeologists discovered a number of intriguing artefacts including a rare bug-shaped Roman brooch and a tiny sword with an iron blade and bone handle that, some suggest, might have been a gift to the gods. |
In other words, it seems the team have discovered a prehistoric coastline – and revealed what it looked like. | In other words, it seems the team have discovered a prehistoric coastline – and revealed what it looked like. |
Dr Jacqueline Skipper, a geological expert at the Geotechnical Consulting Group, who is working with the HS2 team, said: “When we looked at it in detail, instead of the usual sand and gravel ... we had a black clay, which not only had bits of vegetation in it but also showed evidence of extreme weathering of what would have been sand and gravel there before. | Dr Jacqueline Skipper, a geological expert at the Geotechnical Consulting Group, who is working with the HS2 team, said: “When we looked at it in detail, instead of the usual sand and gravel ... we had a black clay, which not only had bits of vegetation in it but also showed evidence of extreme weathering of what would have been sand and gravel there before. |
“Suddenly you have got evidence that this is actually the coastline,” she said. “You have got a three-dimensional vision of what was going on – we’ve got trees, we’ve got animals living in the trees, we’ve got marshes, we’ve got swamps and we’ve got very nearby beaches.” | “Suddenly you have got evidence that this is actually the coastline,” she said. “You have got a three-dimensional vision of what was going on – we’ve got trees, we’ve got animals living in the trees, we’ve got marshes, we’ve got swamps and we’ve got very nearby beaches.” |
Ground investigations for the first phase of HS2 covering about 8,000 locations between London and the West Midlands began in 2015 and involve a range of techniques including ground-penetrating radar, drilling to extract cores for analysis, and digging pits to explore material. The black clay was found in 2017 and appears in a number of different locations along about 10 km of the proposed HS2 route though Ruislip and Northolt. | Ground investigations for the first phase of HS2 covering about 8,000 locations between London and the West Midlands began in 2015 and involve a range of techniques including ground-penetrating radar, drilling to extract cores for analysis, and digging pits to explore material. The black clay was found in 2017 and appears in a number of different locations along about 10 km of the proposed HS2 route though Ruislip and Northolt. |
Now dubbed the “Ruislip bed”, the deposit is between 50cm and one metre thick and is thought to date back to about 56 million years ago – after the extinction of the dinosaurs and shortly before there was a rapid uptick in the Earth’s temperature towards the end of the Paleocene period. The experts believe the bed was formed from subtropical wooded marshes. | Now dubbed the “Ruislip bed”, the deposit is between 50cm and one metre thick and is thought to date back to about 56 million years ago – after the extinction of the dinosaurs and shortly before there was a rapid uptick in the Earth’s temperature towards the end of the Paleocene period. The experts believe the bed was formed from subtropical wooded marshes. |
Samples from the same depth nearby showed the expected sand and gravel that would have been deposited by the sea, indicating that the marsh formed part of the coast. | Samples from the same depth nearby showed the expected sand and gravel that would have been deposited by the sea, indicating that the marsh formed part of the coast. |
Skipper said that with no polar ice caps at that time, the way the shoreline changed would have been the result of movements of Earth’s tectonic plates. Movements under way at that time, Skipper said, included the Atlantic Ocean opening up and India moving towards Eurasia. Such changes, she said, would have resulted in frequent fluctuations in sea level and the position of the British coast. | Skipper said that with no polar ice caps at that time, the way the shoreline changed would have been the result of movements of Earth’s tectonic plates. Movements under way at that time, Skipper said, included the Atlantic Ocean opening up and India moving towards Eurasia. Such changes, she said, would have resulted in frequent fluctuations in sea level and the position of the British coast. |
But the discovery of the Ruislip bed was a surprise, said Skipper, since rises in sea level do not usually leave such well-preserved traces of previous sediments, and it is known that sea levels continued to rise after the bed was formed. “If you have sea level rise you also have a lot of storms and reworking of the previous sediments, so you don’t always get that much information,” she said. | But the discovery of the Ruislip bed was a surprise, said Skipper, since rises in sea level do not usually leave such well-preserved traces of previous sediments, and it is known that sea levels continued to rise after the bed was formed. “If you have sea level rise you also have a lot of storms and reworking of the previous sediments, so you don’t always get that much information,” she said. |
Skipper said ground investigations are crucial before construction of HS2 begins. “It might be even that a tiny detail of the construction will be influenced by how these marshes actually affected the chalk underneath, for example – so tests have been done to make sure that doesn’t actually have any detrimental effect on the design,” she said. | Skipper said ground investigations are crucial before construction of HS2 begins. “It might be even that a tiny detail of the construction will be influenced by how these marshes actually affected the chalk underneath, for example – so tests have been done to make sure that doesn’t actually have any detrimental effect on the design,” she said. |
Dave Entwisle, an engineering geologist at the British Geological Survey said it was very unusual to find such deposits in that area. | |
“About 56 million years ago the UK was a subtropical island and the south-east of England lay on the western edge of a sea that extended eastwards at least as far as Poland,” he said. “This area was a low-lying area, meaning that small changes in sea level resulted in large changes in the land covered by the sea, which, at its maximum extent, covered much of southern England.” | “About 56 million years ago the UK was a subtropical island and the south-east of England lay on the western edge of a sea that extended eastwards at least as far as Poland,” he said. “This area was a low-lying area, meaning that small changes in sea level resulted in large changes in the land covered by the sea, which, at its maximum extent, covered much of southern England.” |
In such conditions, he said, a bed of sand and gravel was often deposited ; a thick bed of flint gravel covered parts of what is now London . He added: “This is the first time that a deposit formed by a local densely wooded marsh of this time has been recognised in England. The woodland marsh may have only existed for a relatively short time before river deposits covered it.” | In such conditions, he said, a bed of sand and gravel was often deposited ; a thick bed of flint gravel covered parts of what is now London . He added: “This is the first time that a deposit formed by a local densely wooded marsh of this time has been recognised in England. The woodland marsh may have only existed for a relatively short time before river deposits covered it.” |
• This article was amended on 26 March 2018 to correct the spelling of Dave Entwisle’s surname. | |
Geology | Geology |
HS2 | HS2 |
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