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Mystery Fossils (Pennsylvanian)


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17 hours ago, sTamprockcoin said:

Reminds me of my #1 fossil/mineral hunting rule  stop to look for the unusual in the usual places. Congrats on the finds and the diligent research!

 

Indeed. I'm just glad I had the presence of mind to pick up the odd-looking slabs along with the other fossils.

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  • 1 year later...

More specimens....

 

P-008_IMG_5183_edit.thumb.jpg.ad4e1803e1669a2bd1b99bab58bc2222.jpg

 

P-016_IMG_5766_edit.thumb.jpg.849b18bbf68ff7d4ce62e07b13eaaf58.jpg

 

P-018_IMG_5853_edit.thumb.jpg.002c6553fad6ce47d1cf1477abd71913.jpg

 

P-011_1_IMG_4937_edit.thumb.jpg.4bc33461c3d6e4bf9550c55570b62fdd.jpg

 

Close-up:

 

P-011_2_IMG_4928_edit.thumb.jpg.642a6d02157229f420b3afdf9d525506.jpg

 

Rosette:

 

P-009_IMG_5028_edit.thumb.jpg.12513aafc41ca95cf495620bcd65441b.jpg

 

P-026_IMG_7278_edit.thumb.jpg.2af8f60f3561b5c8bd80c3b2124a1058.jpg

 

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Got nothing to add except that I've been apparently asleep or at least nodding off at the kitchen table while you've been exploring and posting about the countryside. Great thread! Enjoyed the photos, research and analysis. Aint got anything close to that aged material around here but I was staring at some telephone post tailings the other day wondering about their origin..no algae or structures like yours, just pondering its accumulation and the fossils within. 

 

Regards, Chris 

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On 4/21/2019 at 7:43 AM, Plantguy said:

Got nothing to add except that I've been apparently asleep or at least nodding off at the kitchen table while you've been exploring and posting about the countryside. Great thread! Enjoyed the photos, research and analysis. Aint got anything close to that aged material around here but I was staring at some telephone post tailings the other day wondering about their origin..no algae or structures like yours, just pondering its accumulation and the fossils within. 

 

Regards, Chris 

 

Sometimes wondering & pondering are all that are needed. Once something takes hold, it can be unstoppable. :)

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Marine garden:

 

P-010_IMG_4904_half.thumb.jpg.ef85f1bfbad0f0bb9967edc520a31bc6.jpg

 

This is a 'worm's eye' view of pahoeids/phylloid algae in growth position, i.e. the base/bottom sides are exposed here. On the left is a frond of fenestellid bryozoan that was overrun by the algae. A brachiopod can be seen near the top.

 

Accumulations of the thalli can be seen on the side of the slab:

 

P-010_IMG_4885_half.thumb.jpg.d96020540fc33f1c5f004c202d54fb46.jpg

 

Again, zoomed and in proper orientation:

 

P-010_IMG_4885_zoom.thumb.jpg.62362f4f11ec10078f96fbbd800f21da.jpg

 

Successive generations of algae are revealed. Sponges (dark ovals) can be seen sandwiched in between the layers.

 

This specimen was also shown in the original post of this thread:

 

http://www.thefossilforum.com/index.php?/topic/26021-mystery-fossils-pennsylvanian/

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Lots going on there...so just below the brach there is something that has a slight reddish coloration...is that another smaller brach perhaps or something else--can you tell? What about the other area in the lower middle left...looks granular like crinoidal debris or something else? 

5cc3c37f2231c_unknownsmissouriansthread.jpg.ebcd3c18f0f780bfa7a503878ffc4dea.jpg

I like looking at these crazy slabs...I could see staring at that outcrop for a while...

 

Regards, Chris 

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12 hours ago, Plantguy said:

Lots going on there...so just below the brach there is something that has a slight reddish coloration...is that another smaller brach perhaps or something else--can you tell? What about the other area in the lower middle left...looks granular like crinoidal debris or something else?

[ ]

I like looking at these crazy slabs...I could see staring at that outcrop for a while...

 

Regards, Chris 

 

1)

 

4904-bottom.jpg.2308332e1b9a1f07d4bb28f75e85a09f.jpg

 

This is the scaly structure that covers thalli and other fossils on these slabs. Note it on the bryozoan on the left.

 

A close-up from another slab:

 

post-6808-0-14381800-1396863166.thumb.jpg.e0ced77f269b5deb55bb1c32a9fbdb6e.jpg

 

I've seen this stuff on fossils from many different sites across the metro area. I believe it is a diagenetic growth of calcite, but it is possible that it could be biogenic -- at least in part.

 

2)

 

4904-top.thumb.jpg.cf96dfc9a3a7c22cb88a921eecff58bc.jpg

 

I'm not sure of the identity of the tiny thing. I'm not even 100% sure the shell above it is a brachiopod or something like a Euphemites gastropod (I'll need to drag out the scope again at some point). Smaller fossils on these slabs are often difficult to make out because of the calcite coatings mentioned above.

 

What I could identify among the thalli on these slabs are sponges, encrusting forams, brachiopods (free and attached), horn coral, bryozoans, crinoids (debris) and gastropods. Filter feeders seem to dominate among the animal species. Their numbers are rather sparse in comparison with the plant thalli. Additionally, studies done at other algal reef sites indicate that these algae, once established, dominated the environment, which resulted in low biodiversity.

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In a post five years ago,

 

http://www.thefossilforum.com/index.php?/topic/26021-mystery-fossils-pennsylvanian/&do=findComment&comment=487647

 

I mentioned finding several pieces that I thought would fit together. They did, but I never got around to showing them. Better late than never....

 

Puzzle pieces:

 

P-015_3_IMG_0777_edit.thumb.jpg.b357e792210facadfb25db80d9386734.jpg

 

Assembled:

 

P-015_2_IMG_0762_edit.thumb.jpg.e3f7d345f47353b4ead5dbe56b391502.jpg

 

These pieces were found in situ.

 

A close up shows an attached bryozoan:

 

P-015_5_IMG_0782_edit.thumb.jpg.c62787d9d58ba4c6a90e25f4f651348b.jpg

 

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  • 3 months later...

To help me visualize the possible modes of preservation of some of the in situ 'pahoeids'/phylloid algae described here, I created the flowchart below:

 

Phylloid-Algae-Preservation-final.thumb.png.e084268edfcac19ac64bba76fa48b07d.png

 

Simplified scenarios of taphonomic (bioturbation) and diagenetic (compression, cementation) processes are considered here. The real world is usually far more complex.

 

Descriptions of the numbered points on the chart:

  1. A calcareous algal colony forms and is subsequently preserved in situ as a boundstone in sediment.
  2. Organisms living in the sediment disrupt the structure (bioturbation); or perhaps, the algae is exumed, fragmented, and buried again.
  3. The weight of overlying material compresses the sediments.
  4. The sediment is fully cemented.
  5. The algal structure is compressed.
  6. Partial cementation occurs.
  7. Full cementation occurs.
  8. Concretions form in the sediment.
  9. The sediment is compressed; the original uncompressed structure of the algae is preserved in the concretions.
  10. Partial cementation occurs in the compressed portions of the structures.
  11. The sediment becomes completely cemented. Previously formed concretions may not be readily apparent, and may be indistinguishable from fully cemented (12).
  12. The sediment becomes completely cemented.

Considering these parameters, there are four possible paths of preservation:

 

1-2-3-4 - Bioturbation disrupts the algal structure.

1-5-6-7 - The algal structure is preserved but compressed.

1-8-9-10-11 - Concretions preserve some 3-dimensional algal structure.

1-12 - Full cementaion preserves the 3-dimensional algal structure.

 

Finally, I've placed images of fossil specimens and modern examples of calcareous algae (Lithophyllum and Halimeda) in the various spots:

 

Phylloid-Algae-Preservation-final-examples.thumb.jpg.639137b04bf75270e75a83060900538f.jpg

 

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