Big Sky, MT Possible Precambrian

[cytros]

I found this doing what I always do, picking up interesting rocks. This one I noticed was some form of layered rock with fractures, so I assisted them and this was on the inside. Looked for quite a few hours and couldn't find another picture that resembled this. I have more pics, the underside looks like it has fossilized vegetation and there are multiple layers of these creatures throughout this fossilized rock.

[caldigger]

Where are they from, size, perhaps age of deposits if you know. 

We need as much information you can give in order to establish ID's .

[Heteromorph]

Bivalves? Like @caldigger said, we need more information. 

[cytros]

Big Sky, MT area. Triangular piece 4x4x4 with 3/4" to 1 1/2" thickness. Possibly Precambrian, not sure due to multiple ages in geographical location. Approximately 6,000 to 7,000ft

[cytros]

Here are a couple more, one from the side and one from the back

[Sagebrush Steve]

They look vaguely like Eurypterids but probably not if they are anywhere near Precambrian.

[cytros]

If there is anything else I can provide please let me know, kind of new at this and would like to get better at this. 

[doushantuo]

The (local) stratigraphy might be hard to get at,what with the (abandoned?) Big Sky Carbon Sequestration project...

Meanwhile,some plates from Classic Holm:""""""""""""how to recognize eurypterids from a long way away""""""*

*forgive my weird sense of humour,BTW

Miscellaneous eurypterid parts:

 

 

 

 

[Fossildude19]

I don't see anything Eurypterid about these items.   

 

How sure are you of a Pre-cambrian age?  

According to this geological map, the area has Early Pre-cambrian (Archaeozoic) and Mesozoic exposures in the "Big Sky Area".

I would wager those look like some kind of bivalve, (Inoceramid perhaps? )and are from the Mesozoic. (Triassic? Jurassic? Cretaceous?) 

 

[jpc]

I found Lingula type brachipods in a roadcut on the road into the ski area many years ago.  These look almost similar, but not quite.  I see some sort of bivalve.  The geology there is pretty messed up so a detailed map of the area is the best way to say what age they are.  

[Auspex]

I am leaning toward bivalve internal mold, where the shell did not preserve.

Just what bivalve, I have no clue.

[cytros]

The maps that I have found are pointing between Permian and Cretaceous periods. I haven't had much luck finding detailed era maps of this area, and multiple layers are exposed in the area that I found this.

[jpc]

you are in Gallatin County.  Go to the library at MSU and see if a geological map of the 7 1/2minute quad that the site is on exists.  If you are not sure what I amtalking about...

https://nationalmap.gov/ustopo/

[cytros]

10 hours ago, jpc said:

you are in Gallatin County.  Go to the library at MSU and see if a geological map of the 7 1/2minute quad that the site is on exists.  If you are not sure what I amtalking about...

https://nationalmap.gov/ustopo/

Gallatin Peak Quad

[jpc]

There ya go.  Ask the Geology Dept at the Library of even at the MOR if they have the geology map of that quad.  

[cytros]

Turns out it's from the Mesozoic Era, most likely Cretaceous Period but there is a slim chance it was Triassic Period. Thanks for all the help!

[cytros]

I cant seem to find any bivalve pics whether shelled or internal mold that have horizontal ridges. Any other way to confirm what these are? Or if there might be a good site or person to talk to about these?

[Plantguy]

I still think pelecypod maybe. Tim and the Inoceramid clam proposals might be the way...I remember some of the Buchiid clams which are somewhat similar that we used to find in California had a funny way of showing some distorted ribbing sometimes...Just my 2 cents.  

 

Here are a couple of specimens from the Yale online repository showing from Gallatin county.

http://discover.odai.yale.edu/ydc/Record/2598516

http://discover.odai.yale.edu/ydc/Record/2598521

 

 

Regards, Chris 

[cytros]

On 2/25/2018 at 9:27 PM, cytros said:

Here are a couple more, one from the side and one from the back

I think there's some vegetation on this back side