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Found this possible mud crack fossil in south wales


dotdioscorea

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dotdioscorea

Hi everyone,

 

Was at a beach in south wales (LLanelli) with family today and tried looking for fossils for the first time and managed to find this. I posted it on reddit and a couple of people suggested it may be preserved cracked mud, but (to my untrained eye!) it seems more regular and clean than ones ive found on google images, and it has those little finger-like projections which dont seem to be on so many google specimens. Some people also suggested a concretion (which I don't totally understand yet, but I'm reading).

 

Either way I'd really appreciate your input and knowledge. Cant wait to get out there and look for more fossils, I wish I'd started earlier! Thanks for reading

 

tkveip66x2b31.jpg

Edited by dotdioscorea
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Fossildude19

Pictures would help. ;) 

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dotdioscorea

Oh is the picture not showing up for you? There is a picture for me.

 

Ive tried to upload it again below, hope that helps

tkveip66x2b31.jpg

Edited by dotdioscorea
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Mark Kmiecik

I can see both photos. It appears to be a septarian concretion, and a very interesting variation. It is not a fossil; purely geological in origin. However, it would find an honored spot in anyone's collection. A most intriguing specimen. Septarians come in varied forms. Google some images to be amazed. I especially like the Texas variety.

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There is not a big difference in appearance between mud cracks and some concretions. I agree that this is a concretion though.

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I agree with the others.
It's a concretion with septarian propagation cracks.

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dotdioscorea

Thanks everyone, pretty pleased with it for a first find! Shame its not a bigfoot footprint though. Are these septarian concretions common? As Mark Kmiecik said, there does seem to be huge variation when you search online, are there any search terms you could recommend me use to find similar pieces to mine, or does it not really work like that? :headscratch:

 

anyway thanks again for all your thoughts and time!

Aaron

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13 minutes ago, dotdioscorea said:

seem to be huge variation

says it pretty well.

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Sagebrush Steve

Here’s another thread with some amazing info about what Mother Nature can do:

 

 

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Mark Kmiecik
55 minutes ago, dotdioscorea said:

are there any search terms you could recommend me use to find similar pieces to mine, or does it not really work like that? 

Nope -- nothing specific for the type of septarian you've found, but if you Google septarian and check out the images you'll eventually find a few similar to yours. Unfortunately, the images that make it onto Google tend to be more spectacular than the average more common ones. Concrections are literally as common as dirt, and septarians are about half as common as that. The one you found is interesting enough to be collectible as I mentioned and may be a representative sample of those found in that area. It's a keeper in my book.

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The double wall pattern is characteristic to septarian nodules (concretions).
Ancient mud cracks form at plain or slightly curved surfaces.

 

tkveip66x2b31.jpg.d262845d3834bf75617bd8bd2fd5ac0e.jpgseptarian-1.jpg.edf0a2b80936e344b36f9ebf76497db1.jpg

comparative picture from here

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DPS Ammonite

This is preserved cracked mud. Having mud cracks and being a septarian concretion are not mutually exclusive. Septarian concretions are mud balls that dehydrate and crack (they have mud cracks). The cracks are filled with a precipitated mineral often calcite or the surrounding sediment if the sediment flows and is not hardened. The OP’s rock appears to have a mineral (probably calcite) that filled a crack in a mud ball. The mineral grew from both sides of the crack meeting in the middle forming a seam in the middle of the crack that Abyssunder called  “a double wall pattern”. 

 

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2 hours ago, DPS Ammonite said:

This is preserved cracked mud. Having mud cracks and being a septarian concretion are not mutually exclusive. Septarian concretions are mud balls that dehydrate and crack (they have mud cracks). The cracks are filled with a precipitated mineral often calcite or the surrounding sediment if the sediment flows and is not hardened. The OP’s rock appears to have a mineral (probably calcite) that filled a crack in a mud ball. The mineral grew from both sides of the crack meeting in the middle forming a seam in the middle of the crack that Abyssunder called  “a double wall pattern”. 

 

Mud = Concretion ?

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Mark Kmiecik
15 hours ago, Rockwood said:

Mud = Concretion ?

I also question the mud crack hypothesis. Some septarian features do not reach the surface of the concretion. I doubt a "mud ball" would dry from the inside out. I thought it was still unclear what were the processes involved.

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DPS Ammonite
15 hours ago, Rockwood said:

Mud = Concretion ?

"Mud = Concretion ?" =?

 

I will be happy to reply to your question is you flesh it out a bit.

 

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Isn't there a clear distinction between a mud ball and a concretion ?

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Mark Kmiecik
18 hours ago, DPS Ammonite said:

Septarian concretions are mud balls that dehydrate and crack (they have mud cracks).

Not Mazon Creek septarian concretions -- the process involved is not even vaguely close.

 

It is possible that the septarian structure is formed first and eventually encapsulated, or that both the structure and concretion form at the same time. The research I've done clearly indicates that there is no consensus on the mechanics of the process, and that there may be several distinct possibilities that produce a similar result.

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DPS Ammonite
1 hour ago, Rockwood said:

Isn't there a clear distinction between a mud ball and a concretion ?

Some mud balls can become concretions. If a mud ball is not cemented by a mineral and does not weather out of a rock in positive relief than is is not a concretion. If a mud ball cracks, the cracks are filled and the whole thing is cemented with a mineral then the whole thing could turn into a septarian concretion. All septarian nodules that I have seen have mostly mud sized particles that have cracked. Hence I called them cracked mud. I see that there are many ideas to explain why the cracks formed. Not all involve dehydration.

 

http://www.geologyin.com/2017/12/what-is-septarian-concretion.html

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