The British mainland arose from the collision of not two, but three old continental landmasses, according to new research.
Scientists have been believing for centuries that England, Wales and Scotland originated from the amalgamation of Avalonia and Laurentia more than 400 million years ago.
However, geologists from the University of Plymouth now believe that a third landmass Armorica was also involved in the process.
The findings are published in Nature Communications and follow an extensive study of mineral properties in exposed rocks in Devon and Cornwall.
They reveal a clear boundary across the two provinces, with areas to the north that share their geological roots with the rest of England and Wales, but all that is southern, geologically connected to France and mainland Europe.
Scientists believe, among other things, that the research explains the abundance of tin and tungsten in the far southwest of England – metals that also occur in Brittany and other parts of mainland Europe, but not so clearly in the rest of the UK.
The lead author of the research, lecturer in Igneous Petrology, Dr Arjan Dijkstra, said: "This is an entirely new way of thinking about how Great Britain was formed, and it was always assumed that the boundary between Avalonia and Armorica was are the natural border of the English Channel, but our findings suggest that although there is no physical line on the surface, there is a clear geological boundary separating Cornwall and South Devon from the rest of the UK. "
Dr. Dijkstra and Masters student Callum Hatch (now working in the Natural History Museum) 22 locations in Devon and Cornwall that remained exposed after geological events, such as underground volcanic eruptions. These took place about 300 million years ago and brought magma from depths of 100 km to the surface of the earth.
They took rock samples from each location and subjected them to detailed chemical analysis in the laboratory using X-ray fluorescence (XRF) spectrometry.
The samples were then also dissolved in acid to perform a more intensive isotope analysis, in which scientists studied the levels of two elements – strontium and neodymium – to understand the full history of the rocks.
These findings were then compared with previous studies elsewhere in the UK and mainland Europe, with results showing the clear boundary running from the mouth of the Exe in the east to Camelford in the west.
"We always knew that you could walk from England to France about 10,000 years ago," Dr. Dijkstra is ready. "But our findings show that millions of years earlier the links between the two countries would have been even stronger, explaining the immense mineral wealth of Southwest England, which was a mystery rather than a fascinating new insight into the geological history of the UK. "
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Arjan H. Dijkstra et al. Mapping a hidden terran border in the mantelithosphere with lamprophyres, Nature Communications (2018). DOI: 10.1038 / s41467-018-06253-7