Stonehenge Slowly Giving Up Some More Of Its Secrets

Interesting research that is likely to be made public fairly shortly hopes to throw more light on Stonehenge, and in particular the bluestones that are found at the site, but are now known to originate from Pembrokeshire.

The people in the know who want to make sure that we also know are Scientists from Aberystwyth University, University College London and National Museum of Wales. It seems likely that what they are going to tell us is that they have isolated a specific outcrop, namely Carn Goedog in the Preseli Mountains, as the birthplace of the rocks that made the precarious journey some 5,000 years ago.

It was first put forward as a theory in 1923 by geologist Herbert Henry Thomas that the rocks which form the giant inner ring were specifically quarried for Stonehenge by Neolithic man around 5,000 years ago, and were hauled to Wiltshire from Pembrokeshire via land and sea.

Birthplace of Stonehenge?

Any good debate should have a well reasoned opposing view, and other geologists theorise that they were carried east on an ice-age glacier 20,000 years ago. That debate will still not settled by the contents of the report, but Dr. Richard Bevins of the National Museum of Wales says: "I'm not here to come down on one side of the argument or the other, but our research is aimed at better informing the debate." Perhaps some unknown variables will be eliminated.

Dr Bevins, keeper of natural sciences, added: "Trying to match the rocks at Stonehenge to a specific outcrop is considerably more complicated than looking for a needle in a haystack but the more we can trace them back to their original source, the closer archaeologists and geologists can hunt for clues to back-up their theories.

"Archaeologists can now search an area of hundreds of metres rather than hundreds of kilometres for evidence of Neolithic quarrying. While geologists supporting the glacier theory know exactly where to hunt for the scarring they'd expect to find on the landscape if enormous chunks of the stone had indeed been swept east on a glacier."

There are distinctive markings on the rock, as their recognised name, spotted dolerites suggests. These markings were created by the elements contained within, that then cooled at different rates in the minutes after they were spewed out of an underwater volcano some 450 million years ago.

It  was only two years ago, in 2011, that Dr Bevins's team located the source of another of Stonehenge's Pembrokeshire Bluestones - the rhyolites – only three kilometres away from the spotted dolerites at Craig Rhos y Felin.

These discoveries, funnily enough provide evidence for both sides of the argument. "Three kilometres is both closer and farther away than expected, depending on which theory you support,” said Dr. Bevins.

Spotted Dolerites

"From a geologist's point of view, three kilometres is nothing, and the rocks which ended up close to each other in Wiltshire could easily have been carried on the same glacier. However, for the archaeologists a distance of 3km between the potential quarries could be seen as evidence of planning and forethought, and a suggestion that the different types of stone were chosen for some specific purpose."

Dr Bevins's team are able to say so categorically that they have discovered the source of the spotted dolerites by using  a range of laser mass spectrometry techniques which seek to analyse both the chemical composition of the rock and the microbiology present when it was formed.

He feels that the chance of them having originated anywhere other than Carn Goedog is "statistically-speaking, infinitesimally small".

He is of the view that these potentially important discoveries do not in themselves solve the argument, but undoubtedly bring the day closer when the riddle could well be finalised.

"I've been studying the bluestones for over 30 years now, and I'm no closer to finding an answer which convinces me either way. But the one thing which I am increasingly sure of is that each piece of the puzzle we find brings us another step closer to the truth.

"We've located two of the sources, and there's another five or possibly six to go." he added,  "By the time we have identified those then I'm certain we'll have an answer either way. Whether that happens in my career, or even my lifetime, who knows?"

                                                                        Stonehenge

                                                                  Visit Pembrokeshire