It's Summer And You Want To Go To Pit 11 For Mazon Creek Fossils

[favositefinder]

I went to Mazon for the first time and found a bunch of concretions but no fossils! Does anyone know if the concretions are just as old as the “300million-year-old” fossils found there?

[Mark Kmiecik]

12 hours ago, favositefinder said:

I went to Mazon for the first time and found a bunch of concretions but no fossils! Does anyone know if the concretions are just as old as the “300million-year-old” fossils found there?

 

Yes, they are. The fossils are inside the concretions. However, we are making the assumption that what you found, and I assume brought home with you, is the right stuff. If you post photos of the concretions you found we can better assess if they are the right kind and advise you how to open them to reveal the fossils, if they contain any. Not all of the concretions have fossils inside, but at least we can help by telling you if you're on the right track. If you search "mazon" on this forum you will find many photos of the concretions and the fossils they may contain.

 

Edit: Actually, if you read this entire thread you should have a good idea of how they look. Post photos anyway, just to be sure.

Edited May 18, 2022 by Mark Kmiecik

[favositefinder]

11 hours ago, Mark Kmiecik said:

 

Yes, they are. The fossils are inside the concretions. However, we are making the assumption that what you found, and I assume brought home with you, is the right stuff. If you post photos of the concretions you found we can better assess if they are the right kind and advise you how to open them to reveal the fossils, if they contain any. Not all of the concretions have fossils inside, but at least we can help by telling you if you're on the right track. If you search "mazon" on this forum you will find many photos of the concretions and the fossils they may contain.

 

Edit: Actually, if you read this entire thread you should have a good idea of how they look. Post photos anyway, just to be sure.

Thanks Mark, here are my finds from Mazon yesterday. 

[deutscheben]

I would say there are likely at least two Essexella jellyfish in that first picture, the concretion at the top and the one on the bottom right. So you did indeed find some 300 million year old fossils!

[Mark Kmiecik]

I agree, and the two directly below the long-ish top one, the left one and the middle one, can be freeze/thawed and possibly yield more fossils. Soak those two in water for a week and freeze them in a container with just enough water to cover them. Once frozen, thaw them under lukewarm water if you want to speed up the process a bit. Every 2 to 5 freeze/thaw cycles check for a crack forming around the edges. If you see one, let the concretion dry out for a day, then tap lightly around the edge with a small hammer while holding it in your hand to help it split open. The reason for holding it in your hand is to prevent you from hammering too hard. If it's ready to it will split easily. If it doesn't soak it again and resume the freeze/thaw process.

 

The ones with the white calcite can be soaked in vinegar to dissolve some of it. Don't overdo it as the vinegar will also attack the matrix. Check progress every 15 to 30 minutes. Soak in water afterwards to remove/dilute any remaining vinegar.

 

Good Luck -- I hope you find something good. Post photos.

[favositefinder]

8 hours ago, Mark Kmiecik said:

I agree, and the two directly below the long-ish top one, the left one and the middle one, can be freeze/thawed and possibly yield more fossils. Soak those two in water for a week and freeze them in a container with just enough water to cover them. Once frozen, thaw them under lukewarm water if you want to speed up the process a bit. Every 2 to 5 freeze/thaw cycles check for a crack forming around the edges. If you see one, let the concretion dry out for a day, then tap lightly around the edge with a small hammer while holding it in your hand to help it split open. The reason for holding it in your hand is to prevent you from hammering too hard. If it's ready to it will split easily. If it doesn't soak it again and resume the freeze/thaw process.

 

The ones with the white calcite can be soaked in vinegar to dissolve some of it. Don't overdo it as the vinegar will also attack the matrix. Check progress every 15 to 30 minutes. Soak in water afterwards to remove/dilute any remaining vinegar.

 

Good Luck -- I hope you find something good. Post photos.

I’m in the process on soaking and freezing the two other concretions, but here’s what some of them looked like post decalcification!

[Mark Kmiecik]

12 hours ago, favositefinder said:

I’m in the process on soaking and freezing the two other concretions, but here’s what some of them looked like post decalcification!

 

Not much there. They were well worn before you found them. Most probably Essexella asherae as stated earlier and the last one may have been a sea cucumber, Achistrum sp. Post photos of the two you're freeze-thawing when they open. If they contain fossils the specimens will be in MUCH better condtion than these.