Fossil Bone Preservation and Mineral Make-up Based on Location

[Pterosaur]

Hello everyone!

 

I am a digger and prepper of about 7 or 8 years, and of course a lifelong dino lover. I have a lot of experience both digging and prepping fossils from the Hell Creek formation specifically in Montana, but I still have a lot to learn.
 

More recently I’ve begun prepping bones from the Morrison and Aguja formations, and I’m very intrigued by the differences in bone integrity, structure, quality, and mineral make-up. I understand that bones from the Morrison formation are much, much older than that of the Hell Creek and are by and large more agatized. I don’t mean to generalize, but for the purpose of brevity I’ll get to my main question. 
 

Ajuga bones. Particularly from the West Texas/Mexico area. I’m finding them to be very strange. I assume the KT Impact Event has a lot to do with their condition; which makes them even more interesting. The ones I’ve encountered (just in my brief experience) are in perfect shape. No predation. Which would fit with a major extinction event. But more intriguingly, I’ve noticed textural indications reminiscent of tissue/skin/muscle on several bones. Moreover, the bones appear to be white and chalky, and sometimes have a feeling and density similar to your teeth when your mouth is dry (REALLY weird and specific comparison I know but can’t think of a better likeness). I assume some of this has to do with the dry climate? I know these are not modern bones because they are very large and VERY heavy. 
 

Can anyone explain to me the reason behind the texture and the makeup of these bones from a geological perspective or their experience prepping bones from this formation? Also,

 regarding the tissue, I normally assume that tissue like structures are just my imagination running wild, but maybe there’s something to that as well?  
 

Thanks so much!! 
Lauren

[PaleoNoel]

That's a very interesting question and one I don't have the answer for, only a small piece of info to insert into the discussion: The Aguja formation is from the Campanian age, rather than the Maastrichtian when the extinction event occurred. As for the preservation of the bones, I would assume it would be related to the mineral content in the area. Like many other late cretaceous dinosaur bearing formations, this was primarily a freshwater ecosystem (although I believe there is a marine member either overlying or underlying the dinosaur bearing freshwater member), but perhaps the local minerals caused the bones to preserve that way. I bought some Aguja matrix and it has its own unique grey/brown and almost greenish coloration compared to the colors I've encounter with lance, hell creek & judith river material along with what appears to be some sort of crystalized mineral in it (quartz or calcite idk).

 

If anyone has more educated input I would be interested to read it.