Large cast of Sigillaria sp. ..... or geochemical ridging?

[SteveE]

 

Blair County Pennsylvania (USA) (Private property) ..... 

Recently I explored some heaps of old mine talus which I think is the whitish sandstone from the Pottsville Formation.   These rocks commonly have imprints in various degree of detail, especially cordaites and lycopods.    The pics below show one large boulder with what I think is a very large imprint of sigillaria.   The tape shows 8 feet.

 

 

I'll readily admit that I'm a noob and susceptible to seeing what I want to see.  From my pics someone who knows 'way more than I will ever learn opined the "ridges" are really geochemical in nature.  I think they were implying that being mineralogically  different they were more resistant to erosion.   I'd like to learn more about what to do to followup, and try to verify one interpretation or the other?   FWIW, I can't help but think of how I've never seen similar ridging in this formation, assuming I correctly identified the source as Pottsville formation sandstone.   There's a lot of this material in Blair/Cambria old mine areas.   The leaf scars, if they're there, don't show up in great detail.   But then again, I have much smaller samples where you can see leaf scars clearly on one part of the rock and they fade out in another.    The pics below are either from early morn and noon, so sun is at different angles.   The way I read this rock, the cast is more or less lying in the bedding plane, and there is a calamites along one side.  

 

 

 

Short of microscopic or chemical analysis in the lab, is there anything more I can do in the field to help firm up an ID one way or the other? 

 

Very consistent

 

Some exfoliation allowing a peek at a cross section

 

 

A Calamites (sp) next to the maybe-Sigillaria

 

Exposed back and back-right corner of boulder, trying to get an idea of bedding planes (This series of three starts at the back side and moves around to the left as we face the rock

 

 

Is there something else I could do or look for when I return, to help verify its either a Sigillaria imprint, or a (boo hoo hoo) another "Foss-iLarm"?

[Lone Hunter]

You might want to move this to fossil ID.

[hemipristis]

The regularity of the "bands" makes me think that it could be a replacement fossil like Sigillaria rather than simple bedding.

 

Geochemical analysis won't be able to tell you much in this case.  

[Plantguy]

I agree with Hemipristis. What a nice big specimen to examine! Great photos. 

I do believe they are some type of plant traces/impressions of some sort, the larger maybe a lycopod like Sigillaria especially with seeing two separate linear features with different patterns that close to one another and at sharp/different angles to one another. Maybe one of the paleobotany specialists could offer more on an ID but I am not sure.

There might be a way you can somehow match that same bedding/surface/horizon to an outcrop/other sample somewhere that may have unweathered/not so weathered surface that show plant remains and more details/scars. I agree that darker discoloration/mineral staining of the ridges (that you can see on the surface in your photo of the cross section) is more resistant to erosion than just the sandstone surface. 

 

Be very careful when exploring around something that sizeable...for it shifting/having things split off along bedding planes and various critters in the nooks and crannys! Continued hunting success!  

Regards, Chris

[SteveE]

Just a quickie followup, I recently heard from a friend who happens to be a paleobotany professor, and she opined "I would look for the leaf scars. I think you would need to see these, even if poorly preserved, in some area. Also, the ridges/troughs of the bark are typically very evenly spaced. They seemed a bit irregular based on your photos so that also suggested rock/mineral origin to me."   Elsewhere I also heard from someone who said they teach this stuff and its not a fossil, but that person didn't elaborate any further.   If its NOT a fossil its at least the largest Foss-Ilarm I've found so far!

Edited July 6, 2021 by SteveE

[SteveE]

On 7/2/2021 at 4:01 AM, hemipristis said:

The regularity of the "bands" makes me think that it could be a replacement fossil like Sigillaria rather than simple bedding.

 

Geochemical analysis won't be able to tell you much in this case.  

 

I don't think its bedding either.  My belief (so far anyway) is that this pattern is coplanar with the bedding.   The leading pseudofossil theory is some sort of geochemical process related to fluid dynamics during the Alleghenian orogeny, resulting in a slight mineralogical differences creating alternating degrees of erosion resistance.  That wasn't my idea, just comments I received from the two people I mentioned above.

[doushantuo]

this looks botanical to me,but don't quote me on that.

(taphonomically altered Sigillaria(?)*/preservational morph) 

*Sigillaria brardii?

edit : correction,asterisk added

Edited July 6, 2021 by doushantuo

[DPS Ammonite]

The change of directions over a short vertical distance suggests something thin like leaves. 
 

How about something like several parallel Cordaite leaves that have many parallel veins without a prominent mid vein.

1st photo: link

2-3 phots: details of OP’s photos.