Devis Hole - formations

[snebbit]

We braved an underwater Swaledale for a New Years Day trip in the wonderful Devis Hole today. Noticed these unusual formations at roof level and wondered if anyone knows what the story could be? To be clear, everything in the pic is solid - none is muddy or crumbly, it's not just fill. Are they ancient stals that have ended up back in sediment which has then formed a secondary sedimentary formation around them? Or fossilised mangrove roots or something? The second picture shows similar stuff in the same area on the roof, it looked like snapped/eroded old stal stubs at first glance. Plenty of it at the same horizon

 

[Lankyman]

I've seen similar formations elsewhere. I wonder if they formed by solution/erosion of the roof bed limestone as the original bedding was full of water? Perhaps instead of being formed by deposition of calcite they are part of the original limestone. I should add that I am not a geologist and may be talking complete rubbish.

 

[Jim MacPherson]

If it was in the maze cave part (found by kindly miners) they may be phreatic in origin, I get the impression there are some knowledgeable types on the forum about this type of cave structures and formations.

Jim

 

[Lankyman]

I think it may be anastomosis?

anastomosis caves - Google Search

 

[Chris Curry]

Good morning Snebbit. Interesting! I've sent an e-mail to Tony Harrison did a lot of the surveying in Devis and is the authority on Northern Dales maze cave formation and geology. I'll let you know what he says!

 

[snebbit]

It was in the West Level rather than in the maze areas, which looked to be a natural passage which had been artificially widened on one side - pic of nearby passage below. @Lankyman some of those pics do look very similar to the roof pendants we saw

 

[snebbit]

Good morning Snebbit. Interesting! I've sent an e-mail to Tony Harrison did a lot of the surveying in Devis and is the authority on Northern Dales maze cave formation and geology. I'll let you know what he says!

Thanks Chris. Tony's patience in surveying those maze areas can only be worshipped

 

[Chris Curry]

Snebbit, we have a response

Hi Chris

Happy new year to you! Re the photos and the queries. It's always difficult to be sure in the absence of knowing precisely where in the system these were photographed (for example if they were speleothems in a mined passage - rather than in a natural cave passage - they would post-date the mining activity in Devis, roughly from 1820s to 1875), but looking at the photos it seems unlikely they are even speleothems (or "stals" as the questioner calls them). The indentations seem to be acid etching of the (quite sandy) Great Limestone (the "base" rock in Devis, as we know). We also know that Devis's natural passages - from hypogenic activity of course - were formed with significant dissolutional activity from sulphuric acid (from the lead sulphide in my view, but you may recall that the odd academic geologist disagrees and thinks it's iron sulphides!), rather than just carbonic acid from carbon dioxide. They are certainly not from any plant remains!

So, in summary - just acid-etched limestone, always particularly noticeable in roof sections. Please pass on this opinion to the UKCaving forum.

Cheers Tony