Accretionary Wedge #16: Places for a geologist to visit

Gary Hayes at Geotripper for accretionary wedge #16 asks …

“What are the places and events that you think should all geologists should see and experience before they die? What are the places you know and love that best exemplify geological principles and processes?”

He also wants …

“a truly international list. I also want to get a list of those places that don’t always make the “must visit” lists. And why should this place be included?”

I also threatened to produce a list for 10 sites in the UK that I think are better than a pile of cracked basalt that is a UNESCO world heritage site.

Here are 10 UK sites with some brief reasons that I think are worthy of consideration and I intend to produce lengthier posts on some of these in the near future.

1. The Pembrokeshire Coastline, West Wales
This is a superb place to teach geology, where the Caledonian and Variscan orogenies meet. There is a pretty much complete section from Upper Precambrian to Upper Carboniferous. So many places to choose from but as a taster here is probably the best fault propagation fold in the world at Broadhaven.

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2. The Jurassic Coast.

The UK’s other World Heritage Site and probably far more deserving than the Giant’s Causeway. The Dorset to East Devon coast actually covers Triassic through to Cretaceous. Again so many places to chose here including Lyme Regis where Mary Anning, ‘the greatest fossilist the world ever knew’, went ichthyosaur hunting. However, as a structural geologist I’d have to go for the Alpine deformation at Lulworth Cove, Stair Hole and the nearby fossil forest and broken beds (pictured).

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3. Siccar Point, Berwickshire, Scotland
One of the most important sites in British historical geology. The angular unconformity between Devonian Old Red Sandstone and Silurian greywackes was visited by James Hutton in 1788. John Playfair later commented about the experience, “the mind seemed to grow giddy by looking so far into the abyss of time”. This unconformity, together with other Hutton’s unconformities at Newton Point, Arran and at Inchbonny, Jedburgh convinced Hutton of the concept of deep geological time.

4. Eriboll, Sutherland, Scotland
The Moine Thrust at Eriboll is where the term ‘thrust’ was first coined by Geikie in 1884. Here are excellent exposures of thrusts and related folding. Late Proterozoic Moine metasediments together with their basement of Lewisian gneisses are thrust over Cambro-Ordovician sediments that are highly imbricated.

5. Glen Sligachan, Skye, Scotland
The walk from Camasunary, over the ‘bad step’ above the sea, up Glen Sligachan, climbing Harker’s Gully to the top of Marscoe is simply one of the greatest geological walks anywhere . It talks one from the cumulates at the bottom of the magma chamber, past the feeder dykes with evidence of magma mixing and into the volcanics at the top.

6. The Ercall, Shropshire, England
In the heart of England lies Ercall quarries which exposes the Precambrian-Lower Cambrian unconformity. Uriconian volcanics are intruded by dolerite dykes the Ercall Granophyre at the end of the Precambrian. The granophyre shows a weathered upper surface and is overlain by a beach breccio-conglomerate, shallow marine quartz-arenite and glauconitic siltstone as sea-level rises. [A very similar sequence is is seen in Pembrokeshire – see #1]

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7. Kilve, Somerset, England
The beach at Kilve is cut by a series of normal faults with displacements varying strongly along their length which causes folding of the strata. A brick-built oil retort house is believed to be the world’s first structure built for the extraction of oil from shale.

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8. Wren’s Nest Dudley, West Midlands, England
The UK’s first ever geological National Nature Reserve. An area of formerly quarried and underground mined Silurian limestones. Exceptional fossil fauna including the ‘Dudley Bug’ (Calymene blumenbachi).

9. Isle of Mull, Scotland
2km of lavas intruded by both acid and basic intrusions. The Loch Ba Ring dyke has been described as ‘the finest ring dyke known to science’ and includes the Loch Ba Felsite which is a classic example of a mixed intrusion with acid igneous rock containing about 15% basic inclusions.

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10. West Runton, Norfolk, England.
Ice deformed glacial sediments including thrust rafts of basement Chalk. Glaciers can produce thrust tectonics too.

And apologies to all the great geology of the British Isles I’ve omitted, from the Shetlands in the north to Cornwall in the south. So much to choose from. I’m sure I’ve missed something important…

Google Earth KMZ file of localities here.


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5 Replies to “Accretionary Wedge #16: Places for a geologist to visit”

  1. I’ve been to zero of these places, but the UK is where a lot of geology was historically born, or first described and studied, so it’s great to have a list like this. That Kilve beach looks pretty amazing! (Not to mention the others.)

  2. Hi Ian,

    Nice stuff. Just to be absolutely clear here, it would be OK to upload images from your website to Wikimedia commons, as long as you’re attributed. I’m guessing that this is the case from the license, but the folks at Commons are pretty hot on this. That’s such a nice example of a fault propagations fold (my favourite’s at Hope’s Nose, but I haven’t visited that locality for a few decades) that it would be a shame not to use it in the Wikipedia fold article.

    I spent three happy years as a demonstrator at Keele with Graham Park, George Rowbotham, John Winchester, Gilbert Kelling, Phil Lane, B.K.Holdsworth and Nick Kuznir. I hope that all is well there these days.

    Cheers,
    Mike

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