Help With First Mazon Concretion

[RiverFhtagn]

Hey everyone,

I took my first trip down to collect the famous Mazon Creek concretions over the weekend, and this is one of my first concretions to open so far. I was hoping I could ask for some clarification in what I'm seeing.

 

My first thought was just that it's a clay deposit, because the lighter material which the crack is running through seems to be clay or another substance which is very soft and crumbly. Additionally, there are what appear to be much darker needle-like inclusions of material running randomly through that more crumbly material, which unfortunately I do not know how to photograph.

 

On that note, my apologies for the awful cellphone photographs. I hope they're clear enough for a rough identification.

 

The grayer material on the left is much harder, and appears to be crystalline. I was guessing possibly a shell? (replaced by quartz? does that occur at Mazon?) The white deposits (calcite?) at extreme left seem to be a separate feature from the U-shaped feature stretching across most of the concretion.

 

Thanks so much for your time. I'll try to scrounge up an actual camera soon.

[Plantguy]

Neat find! Do you have a shot of the other side..sometimes there are subtle differences that show up in the pair. With the small varying size and shapes of the bits within it I'm wondering if it might be a coprolite of some type....Wait for the Mazon Creek folks to get a good look at it...

 

Very interesting!

Regards, Chris 

[Mark Kmiecik]

It may be a poorly preserved Polychaetes worm, but more than likely, because of all the little "bits" present throughout and lack of setae around the edges I would say it is a coprolite. The right side looks similar to a sea cucumber, but it isn't. If you Google it you will plainly see the difference. The white crystalline stuff is calcite and quite common in Mazon Creek specimens. It often manifests as a white powder-like substance that fills what otherwise would have been a cavity within the nodule. Do not attempt to clean it away with anything but a VERY SOFT brush and water. Using acid to attack the calcite will also degrade the fossil. The detail on many of the MC fossils is absolutely incredible depending on the location of burial. Wherever the finer sediment was deposited it preserved features that are less than half the width of a human hair, especially in fossils of flora. Some look as good as the day they were buried.

 

On a side note, I hope you are using the freeze/thaw method to open concretions from Mazon Creek. Hammering will destroy or at least badly damage that once-in-a-lifetime find. You don't want to turn a Tully Monster into a pile of debris. Sometimes they turn into a 3D jigsaw puzzle anyway and need to be reconstructed, but hitting it hard with a hammer creates about 10 times the amount of pieces. Freeze/thaw until you see an obvious crack around the perimeter. Let the concretion dry completely so nothing sticks to the wrong side. Then lightly tap with a hammer until the halves separate.

[fossilized6s]

I would say Sea Cucumber. It has the right shape and texture. A circle (mouth) located on either end would be a dead giveaway. 

[Mark Kmiecik]

I stand corrected -- most probably a sea cucumber.