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Sponge or archaeocyathid?


Mesoceph

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This is a piece that I picked up on a geology field trip years ago in eastern New Mexico.  I apologize that I have unfortunately lost the field notebook that contains more specific location information, but I am hoping to get in contact with the teacher that took us there for other reasons and might be able to provide additional information if I can ask him.  The section was Cambrian to Ordovician in age: it started with abundant stromatolites, then progressed into thrombolites and finally siliciclastics disappeared during the Ordovician sea level high-stand.  This piece was found from amidst microbialites, so should be Cambrian in age.  My professor identified it as a "sponge" at the time.  I am wondering if it is perhaps an archaeocyathid based on the age and the central hole.  Either way, if anyone that is more familiar with that area has thoughts on any more specific identification, I would be thrilled!  Please ask if you need photos from a different angle or anything like that.  Thank you very much!

 

DSCN1640 DSCN1639

 

 

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I've been called blind, but I do not see the fossil in question. Any chance you could get a closer picture? 

...I'm back.

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1 hour ago, Raggedy Man said:

I've been called blind, but I do not see the fossil in question. Any chance you could get a closer picture? 

Here are ones that have been cropped and enhanced, but my SD reader is now malfunctioning for the night, so I will try to take other photos tomorrow.  The light color in the middle is infilled carbonate mud.  The more yellow around the outside is the fossil.

DSCN1639_edit.jpg

DSCN1640_edit.jpg

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I don't claim to be an expert at either, but my sense is that your professor is more likely correct about this being a sponge.

If it were an archaeocyathid I would expect the structure to be preserved at least as well as the center. Soluble minerals could easily fill the void in the center of a sponge after it's deposition though.

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