Calcite Veins in Threecliff Rocks – Part 1

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View of Threecliff Bay on the Gower Peninsula

Threecliff Bay on the south coast of the Gower peninsula in South Wales is one of the most beautiful and interesting locations. The scenery is spectacular and the three rocky peaks that give the bay its name are clear to see. The Pennard Pill river follows great meandering loops as it approaches the sea and it flows down a valley created by weaknesses along a tear fault that skewed the alignment of the rock strata. The rocks on the east side of the valley do not line up with those on the west side. The strata in the east have been moved northwards.

The pictures in this post were taken where those displaced rocks outcrop in cliffs on the east side of the bay. They are composed of Carboniferous Limestone. I think they are from the Black Rock Limestone Subgroup – the only available geology map has out of date nomenclature for the various rocks types and calls this section of strata Penmaen Burrows Limestone (d1b). What fascinated me was the wonderful red tinge in the rocks due to the iron content and the intricate natural patterns of discontinuous white veins of calcite. I wonder if these veins are something to do with the pressures and heat resulting from the northwest to southeast tear fault that defines the valley. It looks as if a first set of cracks was infilled with calcite before a second set, cross-wise to the first, was formed in a subsequent event that generated yet more pressure and heat.

7 Replies to “Calcite Veins in Threecliff Rocks – Part 1”

  1. Great Pictures, Just like the Rock & Cliffs of Black River New Brunswick Canada. Almost all of your pictures remind me of the Beaches in New Brunswick Canada. Enjoy looking and reading your descriptions.
    Have a great Christmas and Healthy Happy New Year


  2. Thank you for your good wishes. Happy Christmas to you too. We loved our visit to New Brunswick/Bay of Fundy a few years back – it is great to be able to make compare and contrast the geology of NB and NS with similar geology over here in the UK. Next year we are looking forward very much to exploring the geology of Nova Scotia again – Minas basin and Cape Breton. Maybe New Brunswick another time.


  3. Beautiful. Found a rounded chunk on the beach at Rhossil. Took it to a relative’s house. Look what we found! A side of beef came the reply. Relative not wearing glasses! Could it have travelled from 3 Cliffs?


  4. Red rock with veins occurs on the Worms Head Causeway so that is the most likely origin for the chunk you found at Rhossili. It occurs in many other locations along the south Gower coast. I have previously posted articles about it at Limeslade Bay where the outcrops and boulders really do take on the appearance of joints of beef.


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