Baffled.... Carboniferous Pottsville Sandstone, Blair County, Pennsylvania (USA)

[SteveE]

EDIT - Mistaken title.   This from the underlying formation, the Mississippian Maunch Chunk.  (oopsie daisie)

 

This doesn't match the area's semi-abundant Lepidodendron or Sigillaria or their roots (Stigmaria)... and it doesn't look like Cordaites or Calamites and I'm at a loss to ID the rectangular pattern here.  Help, anyone? (Note two fingers of my leather glove on left for scale)

 

Edited March 29 by SteveE
Note corrected formation

[paleoflor]

Hmm... touch one! Might be related to desiccation of some wood, perhaps?

[SteveE]

10 minutes ago, paleoflor said:

Hmm... touch one! Might be related to desiccation of some wood, perhaps?

 

Touch one?  Huh?  Are you thinking this might actually be contemporary staining from recent cellulose decomp?  Nope.  The pattern is in the sandstone itself.  Not modern. I picked this rock up and handled it, but left it on the mountain. May have to retrieve it after all, if I can find it again.

 

[Fossildude19]

Maybe a bit of fossil plant/wood showing decorticated underlayers?

[SteveE]

7 minutes ago, Fossildude19 said:

"decorticated underlayers"

Cool, a new word to learn, thanks!

 

[paleoflor]

10 minutes ago, SteveE said:

 

Touch one?  Huh?  Are you thinking this might actually be contemporary staining from recent cellulose decomp?  Nope.  The pattern is in the sandstone itself.  Not modern. I picked this rock up and handled it, but left it on the mountain. May have to retrieve it after all, if I can find it again.

 

 Sorry, typo. I meant tough one... And no, not recent but fossil wood. The imprint reminds me a bit of the checkered patterns you sometimes see in "shrinkwood".

[SteveE]

10 minutes ago, paleoflor said:

 Sorry, typo. I meant tough one... And no, not recent but fossil wood. The imprint reminds me a bit of the checkered patterns you sometimes see in "shrinkwood".

Thanks for the laugh! Excellent typo! 

Never heard of "shrinkwood"; interesting guess

[Mark Kmiecik]

The "pattern" is quite irregular. I don't think this is wood of any kind. However, I'm at a loss as to what it might be.

[SteveE]

Just now, Mark Kmiecik said:

The "pattern" is quite irregular. I don't think this is wood of any kind. However, I'm at a loss as to what it might be.

Ok, that settles it.,.... I regret classifying it as leverite, and will attempt to find it again.  Fortunately, the site is spitting distance out my back door.

 

[paleoflor]

I don't have a better specimen nor better photo, unfortunately, but it sort of shows what I meant... If you look at the exterior of this limb (Dadoxylon-like wood from Permian of Brazil) you'll notice that there is considerable checkering of the rind. In this mineralised specimen, the incised cracks have been filled with white chalcedony and then the rind has been differentially weathered so that the chalcedony stands out somewhat from the rest of the wood now. Such a pattern of square cracking is called "alligatoring", I believe, and can be caused by processes such as charring (fire damage), extensive desiccation (drying shrinkage) or coalification. You sometimes see similar patterns in coalified wood.

 

[Fossildude19]

Recently posted, vaguely similar fossil.

[Mahnmut]

Hi,

Talking about "shrinkwood", the rectangular patterns reminded me of some kinds of dry rot. I have no idea if the palnts in queston here even had the underlying structure to decay like that, but I´ll lazily link to another thread where I wrote about it:

https://www.thefossilforum.com/topic/102046-what-cut-this-petrified-wood/#comment-1133533

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

 

Best regards,

J

[Missourian]

Here is some Pennsylvanian cordaitid wood with a similar pattern:

 

[SteveE]

On 3/27/2024 at 4:30 PM, Mahnmut said:

Hi,

Talking about "shrinkwood", the rectangular patterns reminded me of some kinds of dry rot. I have no idea if the palnts in queston here even had the underlying structure to decay like that,

 

 

Well little or no lignin back then, I think.  Wonder if that's an ingredient to patterning dry rot like this? 

[SteveE]

19 hours ago, Missourian said:

Here is some Pennsylvanian cordaitid wood with a similar pattern:

That's a pretty neat sample, thanks.  Certainly seems like a maybe.

[SteveE]

UPDATE:  I retrieved the rock and OOPS.... instead of Carbonifereous Pottsville now I think its late Devonian Mauch Chunk... quarzitic sandstone with small bits of iron or mangenese weathering away....  so could this pattern really be boxwork related to that?  Notice how the black grains are concentrated in the pattern.