<< Our Photo Pages >> Mumbles Erratic - Natural Stone / Erratic / Other Natural Feature in Wales in West Glamorgan
Submitted by Andy B on Friday, 11 February 2022 Page Views: 3337
Natural PlacesSite Name: Mumbles Erratic Alternative Name: Limeslade Bay erratic, Purported Stonehenge-style Bluestone (Unspotted Dolerite)?Country: Wales County: West Glamorgan Type: Natural Stone / Erratic / Other Natural Feature
Nearest Village: Mumbles
Map Ref: SS6241986997
Latitude: 51.565017N Longitude: 3.986323W
Condition:
5 | Perfect |
4 | Almost Perfect |
3 | Reasonable but with some damage |
2 | Ruined but still recognisable as an ancient site |
1 | Pretty much destroyed, possibly visible as crop marks |
0 | No data. |
-1 | Completely destroyed |
5 | Superb |
4 | Good |
3 | Ordinary |
2 | Not Good |
1 | Awful |
0 | No data. |
5 | Can be driven to, probably with disabled access |
4 | Short walk on a footpath |
3 | Requiring a bit more of a walk |
2 | A long walk |
1 | In the middle of nowhere, a nightmare to find |
0 | No data. |
5 | co-ordinates taken by GPS or official recorded co-ordinates |
4 | co-ordinates scaled from a detailed map |
3 | co-ordinates scaled from a bad map |
2 | co-ordinates of the nearest village |
1 | co-ordinates of the nearest town |
0 | no data |
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Brian John writes: Phil Holden is a professional photographer and 'hunts' for interesting erratics, amongst other things. He has discovered a massive glacial erratic, which took me by surprise, but I think it is very important. In my view this discovery is of huge importance to Ice Age research in South Wales and the debate about the origins and transport of the Stonehenge bluestones. But let's start at the beginning...
Phil wanders this coast very frequently, and says he looked at this erratic several times, on a number of visits, before realising that it was is different indeed from the Carboniferous Limestone bedrock. He was attracted by both the colouring of the rock, and its texture, and realised that it was very similar to a dolerite rock sample he collected many years ago from Foel Eryr, near the western end of Mynydd Preseli.
He took some high definition photos, and asked me to take a look. I was fairly convinced that he was right in assuming the greenish rock to be unspotted dolerite. He also asked Dr Katie Preece, an igneous rock specialist working at the Swansea University Geography Dept, to take a look, and on the basis of visual inspection she confirmed the rock as dolerite or micro-gabbro. It was similar to the Foel Eryr sample, but the crystal sizes were different. Whether that proves significant, time will tell. Further work is in the pipeline, so watch this space.
Last Sunday afternoon there was a low tide, and the weather was dry and calm - so I hopped into the car and drove over to The Mumbles at high speed. Phil and I took a good look at the giant erratic and at some of the nearby coastal exposures. I became even more convinced that the erratic was made of unspotted greenish dolerite, and we compared the boulder surface with a number of unspotted dolerite samples that I just happened to have in my rucksack. In close-up my garden sample looks a bit greener, and the giant erratic looks a bit bluer - but that may be a trick of the light.
Brian John continues: The presence of this erratic (if it identifies as we propose) shows that the glacial transport of the Stonehenge bluestones was not just possible but - to me - probable. Archaeologists and some geologists have previously assumed that it would have been "impossible" for glacier ice to transport large boulders, pillars and slabs of dolerite from North Pembrokeshire, or anywhere else, up the Bristol Channel towards Somerset and Stonehenge.
Many smaller dolerite erratics are known from Gower and other parts of South Wales, but there have been no discoveries to compare with the "giant erratics" that are known from the coasts of Devon and Cornwall. Phil’s very exciting discovery demonstrates that the glacier did indeed transport large blocks of rock south-eastwards from their source areas. There must be other erratics of this size awaiting discovery along the South Wales coast, but unfortunately most of them are likely to be located under the murky waters of the Bristol Channel."
This discovery should force the archaeologists to ask themselves how reliable their evidence really is for the huge narrative they have built around the bluestones, involving quarries, mighty haulage expeditions and lost circles.
But I'm not getting over-excited. This is just the start of a long journey, and clearly samples from this boulder will need to be subjected to a whole range of analytical techniques before we can be sure what the provenance really is.
Brian has more on his blog.
SAFETY NOTE: The boulder is in a very dangerous position around mid-tide mark, and great care is needed especially when the rocks are wet and slippery.
Note: Further updates since this was first announced, more on our page
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