Geological Feature

My son is a wildland firefighter, working a fire in Wyoming. He came across this exposed rock which has so much going on at once. There are layers, and different kinds of crystals, and yet it almost looks like some sort of fossil, but I doubt it is. Anyhow, I was curious if anyone recognizes this kind of formation and can explain a bit about what was going on to form it (or to reform it?) Thanks in advance for any info provided.


What you have there is definitely a fossil. It’s hard to tell from the picture, but it may be a tabulate coral, which if I recall would make that a Cambrian rock. Was it from the Snowies or the Medicine Bows?

Correction: tabulates are mostly Ordovician through Devonian, with a few persisting through the Permian.


Thanks John! I’ll find out from him and reply.

Was that the Mullen Fire (2020) by any chance? The Snowy Range/Medicine Bow forest are my old stomping grounds. There are some very old stromatolites in the Snowies, but the ones I’ve seen are closer to the peaks. The Mullen fire was huge, so there is a lot of territory I haven’t trodden.



ETA: @John_Harshman is right though, this doesn’t look like a stromatolite. I forget the name of the limestone formation that sits on top of the Morrison formation in the region - will look it up.

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It was not, Dan, it is a current fire he’s working now. It is somewhat near Sheridan, WY, but I’ve sent him a text to find out the specifics per @John_Harshman 's query.

Here’s a much higher resolution photo also.


Hello John: I’m not familiar with the local ranges, but here’s the location with which you may be familiar.

Yeah, that’s nowhere near anyplace I’ve been. I think that’s the Bighorn Range. I’ve been to the Snowies, west of Laramie, where there are some very nice stromatolites in Precambrian limestone and, a bit farther west, around the crest, some nice older Precambrian metamorphics.


Yes, the Bighorns, of Brokeback Mountain fame.

The details on the photo are fascinating!

Stromatolites in the Snowies.

Everything you always wanted to know about stromatolites in the Snowies but were afraid to ask.

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