What is this???

[Ruger9a]

Does anyone know what this concretion is?  It came from Mazon Creek and was listed as a Unusual Rock concretion fossil.  I purchased it ten years ago and am hoping others like this have been found since then and a description determination has been made.  Help.

[Fossildude19]

Concretion, I would say. 

[jpc]

9 minutes ago, Fossildude19 said:

Concretion, I would say. 

yup

[caldigger]

Tim, I think he knows it's a concretion. I believe he is looking for the root cause as to what created it with a hollow center.

[Ruger9a]

Yes, caldigger you are correct.  I originally thought it might be a seed pod, then I was thinking bivalve.  But right now I'm not thinking.....  Just hoping for some sort of identification as to what the internal object is that made the concretion.  

[Fossildude19]

Sometimes, there is no answer to what created it.  

Sometimes, whatever organic item that was there to start the concretion is no longer there, due to any number of reasons, during the millions or thousands of years it took to form.

Coprolite, jellyfish, rotted flesh - something, usually biologic, causes sediment to form around it. Different sediments  then aggregate around that item, which can disappear. 

Each concentric layer hardens, then more matrix adheres. And so on, creating all of the concentric rings. Some layers are harder than others. 

I see nothing of note that stands out as the impetus for the forming of this concretion.  

 

 

[Mark Kmiecik]

Yes, concretion. What caused it to form? Unknown. Whatever it was is gone. It would have been in the center of that clam-shaped void, and may have actually been a small clam. Hovever, the overall shape is SO EXTREMELY common to MC concretions containing all types of plants and animals that the best educated guess would still be a vague stab at reality. (Hundreds of?) Thousands of similar ones have been found with no clue to the identity of the original occupant. I have found at least two hundred personally. It is a fossil, technically speaking, since the concretion did form encompassing an organic core. We just can't determine what organism that core had been. 

 

It is a prime example of the process of encapsulation of MC material and for that reason, collectible.

[Ruger9a]

Thanks guys.  I really do like the looks of it and had it displayed with only "MC fossil" as the description.  It will continued to be displayed as such because I find it interesting, detailed and with an outstanding color contrast to some of my others.  Thanks again.  

[TheRocksWillShoutHisGlory]

I've been told the yellow coloring inside and even on the outer parts of a nodule is indicative of sulfur, which could increase pyritization and inhibit the siderite forming and entombing a fossil.

[Ruger9a]

Thank you.