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Archie

Mystery Beach Pebble

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Innocentx

That is insanely beautiful... lucky friend!

Could it possibly be stromatoporoid type? It looks like ones I find here. I have zero knowledge of cross bedding except what you've put here.

 

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ynot

I agree with this being a good example of cross bedding. The other side looks like an intrusive vien rather than part of the cross bedding as it intersects all of the planes of the cross bedding and has an amorphous grain/pattern.

 

Nice rock, tells a very interesting story.

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westcoast

While I agree that it does look like trough cross bedding I'm concerned that the size is unusually small , i don't see any sedimentary grains and also a number of the troughs appear to have a secondary inner trough. The separating thin layers are also unusually thin and even. But having said that I have no other suggestion. It is a beautiful piece!

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doushantuo

every "unit" seems to be surrounded by a thinnish black layer,unless I'm very much mistaken

Some of you may find this useful:

Campbell 1967.pdf

Charles V.Campbell

Lamina,Laminaset,Bedset and bed

Sedimentology(8),1967

edit:approx.2,2 Mb

 

NB: items below NOT an outtake form the above article

rippzowwrropthywwconaeekristl5eanthc.jpg

 

rippzowwbedfrrrropthywwconaeekristl5eanthc.jpg

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Archie

Thanks for all the help everyone much appreciated! @ynot I definitely agree that looks like an igneous vein cutting through the cross bedding and @doushantuo I'm thinking the dark lines around every "unit" are possibly where the iron oxide staining throughout the entire piece is especially concentrated? @Kane thank you for showing this example! Its interesting the edges of the "scales" on this piece have resisted weathering.

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digit

I do love the depth of knowledge on this forum (and learning something new each day). Who knew that I'd be reading up on Liesegang Rings before lunch? :)

 

https://en.wikipedia.org/wiki/Liesegang_rings

 

Agreed that the specimen in question is a really cool looking rock and I find it much more interesting as an example of a not well understood chemo-geological process rather than something biological. Thanks for sharing this.

 

Cheers.

 

-Ken

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doushantuo

1213401.pdf

Self-organized iron-oxide cementation geometry as an indicator of paleoflows

Yifeng Wang,Marjorie A.Chan and Enrique Merino

Nature,Scientific reports

also

F. Balsamo, F.H.R. Bezerra, M.M. Vieira, and F. Storti

Structural control on the formation of iron-oxide concretions and Liesegang bands in faulted, poorly lithified Cenozoic sandstones of the Paraíba Basin, Brazil

GSA Bulletin; May/June 2013; v. 125; no. 5/6; p. 913–931

6,6 MB

so this one find takes us to the multidisciplinary interface of geochemistry,hydrology,structural geology,and chaos physics 

Archie,thanks man

Hats off to all involved,BTW

This shows the power of the collective,I supposeB):D

 

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Innocentx
4 hours ago, Oxytropidoceras said:

microbially 

induced diagenetic structures

Is that what happened here?

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doushantuo

zdunewwrropthyrwwconaeekristl5eanthc.jpg

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doushantuo

Any thoughts on this:

Might it not be a case of waning flow deposition?The linguoid ripples were not eroded by bottom currents,but instead were covered with an equidimensional clay drape.

The clay drape armours the linguoid ripples against further diagenesis by meteoric water(porosity/permeability reduction)

 

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doushantuo

Top of the morning to you, Westcoast;)B)

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westcoast
Just now, doushantuo said:

Top of the morning to you Westcoast

:)

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Scylla

Dragon scales? :dinosmile: Seriously looks like fractures in a flint nodule or quartz vein highlighted by a dark mineral in the cracks.

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Archie
7 hours ago, Scylla said:

Dragon scales? :dinosmile: Seriously looks like fractures in a flint nodule or quartz vein highlighted by a dark mineral in the cracks.

This was originally posted by the friend of my friend on a Norfolk Coast fossil forum, dragon scales was one members suggestion and fractures in a flint nodule was my first guess!

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ynot

The problem with a cracked rock ID is the angle of propagation. A crack can take a 90 degree change , but to have so many in one rock and such a uniform half circle fracture for all of the cracks is beyond possible.

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Archie
13 minutes ago, ynot said:

The problem with a cracked rock ID is the angle of propagation. A crack can take a 90 degree change , but to have so many in one rock and such a uniform half circle fracture for all of the cracks is beyond possible.

Agreed.

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Scylla
On 12/8/2018 at 9:03 PM, ynot said:

The problem with a cracked rock ID is the angle of propagation. A crack can take a 90 degree change , but to have so many in one rock and such a uniform half circle fracture for all of the cracks is beyond possible.

Maybe, but cracks can do some seemingly beyond possible things. By the way, don't do a Google image search for "strange cracks"

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