Centralia's Bright White Ferns

[I_gotta_rock]

Deep in the heart of Pennsylvania's coal country runs the Carboniferous Lewellyn Formation. Once a vast tract of swampland, the area was home to 100 ft. tall Calamites (an extinct relative of modern herbaceous horsetails), giant tree ferns and other enormous plants, plus proportionally large insects.

 

The conditions during the intervening millennia were just right for the plants to break down into iron-based minerals, including pyrophyllite and kaolinite, leaving a coating of white powder over the impressions in the rock. In rare spots, the iron minerals come in yellow, orange or red, too. All this makes the fossils stand out in sharp contrast to the dark, gray shale matrix.

 

This is not a place for the timid. The shale is on a steep, slick slope covered in loose scree. The trees that look like good hand-holds are dead and rotten.  Below the surface, fires burn in the coal veins, creating a sinkhole hazard all over the ghost town and on to the neighboring towns. However, the place I was hunting is definitely a beaten path these days, so there is probably a low risk of invisible disaster.

 

I always say that no rock is worth your life, but that doesn't stop me from living a little dangerously. I went there for the first time last month. It was a short stop close to dusk. The fog was thick and the rocks were wet. The white powder was hard to make out in the gloom. Today, the light was good, the rocks were dry and the hunting was good!

 

[doushantuo]

Pretty nifty journalism!

Kudos

[Tidgy's Dad]

Beautiful plants. 

[Plantguy]

Nice adds to the collection. Thanks for the photos!  I miss PA!

Regards, Chris 

[I_gotta_rock]

4 hours ago, doushantuo said:

Pretty nifty journalism!

Kudos

Thanks!

[Fossildude19]

Great report and photos!

Thanks for documenting this for us.  

[Monica]

Beautiful flora!  I'm 

[erose]

Good stuff. 

[Al Tahan]

Beautiful plant fossils 

[deutscheben]

Lovely finds! I hope you can share some close-up photos too, the detail looks great on those. 

[I_gotta_rock]

15 minutes ago, deutscheben said:

Lovely finds! I hope you can share some close-up photos too, the detail looks great on those. 

 

Will do after I get them unpacked. In the field isn't the best place for that kind of thing, unless that is my goal in the first place. Will tag you when I post them.

[FossilNerd]

Nice report! I recently acquired my first Carboniferous plant specimen. A nice Alethopteris from the St. Clair area of Pennsylvania.  Beautiful stuff! I had to purchase mine so I’m a little  that you get to go out and collect there. Thanks for sharing! 

[doushantuo]

Btw: good on you for remarking (albeit briefly) on petrography and taphonomy!!!

Are the plants adpression fossils,to your knowledge? 

 

 

[RandyB]

@doushantuo Centralia ferns seem to be a mix of adpression and cabonaceous film. The larger fossil trees, of which there are many trunks readily visible on the surface of the site, often retain 3 dimensions, but the ferns are a mix of 2 dimensional films and 3d impressions which include black/gray, white, yellow and orange mineralization and staining.  Personally I love the white pyrophyllite ferns as they look amazing against the black/gray background of the surrounding coal shale.  I only recently started collecting this site even though its close to home so someone more knowledgeable may be able to provide more details as I am still learning. 

[I_gotta_rock]

10 hours ago, deutscheben said:

Lovely finds! I hope you can share some close-up photos too, the detail looks great on those. 

I'll have to set up an album for these, but I have to do a lot of digging for IDs first. I can narrow it down to Calamites, Lepidodendron, etc., but not any more specific. Plant people, feel free to chime in! @Plantguy?

 

I photographed about 3 dozen of my small pieces this evening. These are the best of them. All but three are 1-2 inches, no more than 5 cm, across.

 

 

 

 

[I_gotta_rock]

Here's a rather curious one. I'm debating it's nature. At first glance, in this location, I'd have just called it a quartz intrusion . However, I did find a big, coarse-grained rock from a different stratum at dusk (of course!) that had the same white pieces.They appeared to be embedded rather than filling in cracks. So, my operating theory is silicified or cast Calamites. As a matter of fact, studying the picture  now, I can just see fern impressions in that gray corner, which doubt would be there if it were just an intrusion into a fracture. The gray is just a coating (carbonized biomatter?) on an otherwise white rock.  Any thoughts?

 

[deutscheben]

Those are some really great ones! That first one is a nice dimensional Stigmaria. Your photography setup is excellent too, these pics show off those details very well. 

[Ludwigia]

I wish I knew about that site when I lived in PA, but come to think about it, I didn't even know about fossils way back when

[I_gotta_rock]

6 hours ago, Ludwigia said:

I wish I knew about that site when I lived in PA, but come to think about it, I didn't even know about fossils way back when

Back then you would have been pretty dang reckless to go there. Even half a dozen years ago it was a place where only the really foolish went to hang out and spray the highway. There is a reason they tore down all the buildings -- to discourage people from falling into sinkholes flooded with deadly gasses from the fire. Technically, the place is still a restricted area, but it is unenforced. The fires have *mostly* moved out of town as the coal vein burns out like a long candle wick, but it is still blazing in some spots under the town. I think we have Altas Obscura to thank for the place becoming a tourist attraction. They even had Christmas decorations on the light poles along the two active roads this weekend.

 

 

 

[Shamalama]

11 hours ago, I_gotta_rock said:

Here's a rather curious one. I'm debating it's nature. At first glance, in this location, I'd have just called it a quartz intrusion . However, I did find a big, coarse-grained rock from a different stratum at dusk (of course!) that had the same white pieces.They appeared to be embedded rather than filling in cracks. So, my operating theory is silicified or cast Calamites. As a matter of fact, studying the picture  now, I can just see fern impressions in that gray corner, which doubt would be there if it were just an intrusion into a fracture. The gray is just a coating (carbonized biomatter?) on an otherwise white rock.  Any thoughts?

 

 

 

It's been my experience that these Quartz rinds are either fracture infills along slickensides or within gaps where the coalified remains of bark have eroded along trunk fossils.  I'd need to see if the piece is curved or flat to tell which instance it is. Based on the pic I'd say it's a bark replacement but there is not enough info to say Calamites or any particular species of tree. It just looks like decorticated trunk to me.  The grey inclusions within the otherwise white quartz is likely shale or coal.

[Shamalama]

12 hours ago, I_gotta_rock said:

Stigmaria - Root structure

 

 

 

Calamites

 

Alethopteris

 

 

Neuropteris

 

 

Pectopteris

 

12 hours ago, I_gotta_rock said:

Neuropteris

 

 

 

Alethopteris

 

Sphenopteris or Mariopteris, Can't recall at the moment

 

Calamites

 

[I_gotta_rock]

Thank you @Shamalama! I was just looking through a field guide with rather poor illustrations to sort some of this stuff out. This is a big help!

[I_gotta_rock]

I was looking at the collections section to see what was in there. Though for sure as popular as places like St Claire are, that there would be plenty of good reference photos, but there is only one from the Pennsylvanian there. Methinks I should fix that.

[Jeffrey P]

Some very impressive specimens there and lovely photographs. Congratulations and thanks for sharing them. Since St. Claire is now kapoot for collecting, I'll definitely have to check out this site. 

[I_gotta_rock]

@Shamalama, actually, this one looks like N. pocahontas