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Any geologists out there?

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Robin Graham06/10/2019 00:51:30
771 forum posts
193 photos

Last week I took a recuperative break in Lyme Regis. Well known for it's unusual geology of course. Wandering on the beach I came across stuff like this:

img_2081.jpg

I forgot to put a ruler next to it, but for scale the biggest hole is about 15mm.The 'stone' is quite soft and may be compressed mud - but how were the holes formed? Googling has so far failed me.

Robin

David George 106/10/2019 07:41:19
avatar
1428 forum posts
456 photos

Just asked my brother (specialist in rock and fossils) And he came up with this.

the Jurassic Coast in Dorset – and lots of other U.K. locations as well. Many of these tunnels, burrows or borings have been made by small marine invertebrate animals such as certain species of bivalved molluscs, polychaete worms, and even sponges.

David

Diogenes06/10/2019 08:17:26
37 forum posts
6 photos

Piddock!

Martin King 206/10/2019 09:01:23
746 forum posts
286 photos

I have seen teredo marine worm holes in mahogany about that size or bigger.

Martin

Weary06/10/2019 09:20:03
318 forum posts

Wrinkled rock-borers and piddocks!

Info: here.

Regards,

Phil

Dave Halford06/10/2019 10:41:28
1128 forum posts
11 photos

You can see rock on the IOW coast intertidal zone with holes like that with little red sea anemones at the bottom

Pete Rimmer06/10/2019 17:00:23
871 forum posts
54 photos

It's an early bullet proof vest left over from the dino-wars. The fact that it's so full of holes and that there are no dinosaurs left are evidence that the early vests weren't very effective....

ega06/10/2019 17:30:03
1933 forum posts
159 photos
Posted by Robin Graham on 06/10/2019 00:51:30:

Last week I took a recuperative break in Lyme Regis. Well known for it's unusual geology of course. Wandering on the beach I came across stuff like this:

img_2081.jpg

I forgot to put a ruler next to it, but for scale the biggest hole is about 15mm.The 'stone' is quite soft and may be compressed mud - but how were the holes formed? Googling has so far failed me.

Robin

Have they finished "stabilising" the town?

Mike E.06/10/2019 17:44:54
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209 forum posts
31 photos

I've seen rocks like this in a California river, small hard pebbles have worn the softer rock away by the agitation of the water passing over them over time.

Brian B06/10/2019 17:54:02
4 forum posts

Robin,

Those holes are remarkably round for a fossil, with well formed edges.

I suspect that it's something from the old town dump that slid down onto the beach many years ago. Somewhere there's someone looking for one of those.

Brian Bristoll.

Ian Johnson 106/10/2019 18:04:35
314 forum posts
88 photos

Looks like a prehistoric twist drill holder to me! Some of the old fossils on here will no doubt confirm this? devil

Ian

Robin Graham06/10/2019 23:06:54
771 forum posts
193 photos
Posted by Ian Johnson 1 on 06/10/2019 18:04:35:

Looks like a prehistoric twist drill holder to me! Some of the old fossils on here will no doubt confirm this? devil

Ian

Arf! Might have a use in the workshop then, hadn't thought of that. Some of the holes are indeed remarkably round, which made me think that there was some physical (eg bubbles in mud - but I couldn't see quite how that would work) rather than organic mechanism at work. But armed with the search term 'piddocks' further googling pretty much confirms that's how the holes were formed. Astonishing, I'd never have guessed that!

It turns out that the same question was asked in the New Scientist a couple of years ago. One of the replies runs thus:

Both shipworms and piddocks exude shell material to line their burrows and prevent them collapsing. The civil engineer Isambard Kingdom Brunel learned from this, and used the same strategy to successfully complete the first tunnel under the Thames in London.


Read more: **LINK**

The remnants of (presumably) exuded shell material are visible in my specimen. I wonder if it's true about Brunel though? I can believe it I suppose, he probably drew inspiration for his innovations from many sources.

Thanks for all your replies - I expected that someone here (or their brother wink ) would shed light.
Robin.

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