Back to the Fox Hills Formation June 2 Trip Report

[Thomas.Dodson]

I had the opportunity to get out to my favorite area of the Fox Hills Formation last week right before the temp skyrocketed into the 100s. I returned to my favorite Timber Lake site as well as tried some new ones.

 

The first site I tried on the way down was not an exposure of the Fox Hills at all but probably of the Cannonball Formation, at least in part. I didn't find anything at this site but it was pretty nonetheless.

 

 

 

There's lots of exposed Fox Hills sandstone at my favorite Timber Lake site but the fossils are not as well preserved as those in the concretions. The concretions are often spectacular. This is from the site I describe as Timber Lake Exposure 1 in other threads. I did collect some small concretions pictured later. No large ones but there wasn't much erosion this year due to the dry weather and the lack of snow melt from the mild winter.

 

 

This new site exposes more of the brackish portion of the Fox Hills Formation. There was tan and salt and pepper sandstone with sparse fossils throughout. The interesting thing was the white-gray claystones and shales exposed at the top of some hills. There were sparse fossils here as well that I took the time to collect just because it is unusual for the area. I haven't prepared anything from it yet. I think most, if not all, specimens were Protocardia subquadrata.

 

 

 

I got around to preparing some of the stuff from the Timber Lake exposure. The ammonites in the overlying sandstone layers are typically "pancaked" flat.

 

 

Typical concretionary material from the site with the abundant wood that is typical of the exposure.

 

 

Typical immature Scaphitid ammonites.

 

 

Just a portion of the body chamber.

 

 

A rather large and robust Cylichna scitula.

 

 

Aptychus.

 

 

 

A swirly crystal Oligopytycha concinna. Ones missing the outer shell are common because of how the outer shell sticks to the concretion.

 

 

 

Various other typical specimens are present in the concretions collected but I haven't had the time to prepare them yet. No larger ammonites are likely to be found as the concretions usually split along the plane of the largest ammonites but there may yet be some rarer small specimens present. This particular site has yielded crab fossils, a shark tooth, and many rare mollusc specimens. It's just a matter of finding time to continue preparing the concretions.

 

[Ludwigia]

5 hours ago, Thomas.Dodson said:

No larger ammonites are likely to be found as the concretions usually split along the plane of the largest ammonites

 

Wouldn't it be possible to glue them back together and then prep them out?

[Thomas.Dodson]

1 hour ago, Ludwigia said:

 

Wouldn't it be possible to glue them back together and then prep them out?

I might not have explained that properly. What I meant is that the concretions usually split over the largest ammonites. Since these concretions split over the smaller ammonites it most likely means there aren't any larger ones in the rest of the concretion. The ammonites themselves usually remain intact, which is good because these concretions are usually so hard and so packed with fossils it isn't practical to prep from the outside in.

[fossilhunter21]

Those are some fine looking fossils!  

 

Thanks for sharing!  

 

Edited June 8, 2021 by fossilhunter21

[Shellseeker]

Thanks for sharing.  I love the combination of scenery and fossils.

[Jeffrey P]

Those Scaphitid ammonites and gastropods are lovely. Congratulations. Certainly worth the considerable effort to collect and prep them. Thanks for sharing your specimens, knowledge, and site photographs. 

[Mark Kmiecik]

Thank you for the trip photos.

[Thomas.Dodson]

On 6/7/2021 at 10:41 PM, Thomas.Dodson said:

...but there may yet be some rarer small specimens present.

It is fun when you're right. I spy something unusual.

A little shark tooth, only my second from the formation.

 

 

Not quite sure what it is but it is more complete than the last one so I hold out some hope it can be identified. There is also a very nice gastropod I'm currently prepping from the concretions as well as several other unusual things. I'm currently consolidating the heck out of the gastropod outer shell but they can be absurdly difficult to remove with the outer shell intact. I'll post more as I finish them.

 

[Thomas.Dodson]

Did some more prepping and I'm mostly done with this batch.

 

These are the shells from the shale. Not very impressive but again, stuff from the shale is rarer. With the exception of center they appear to be Protocardia subquadrata.

Scaphitids of the batch.

More Cuspidaria. These aren't reported from North Dakota (at least to my knowledge) but I've found a few others at this site before.

Nucula, mostly Nucula cancellata. The lowermost one is Nucula planomarginata. Not much outer shell for these. Note the outer shell at the top to one individual.

This one goes to the outer shell pictured above. This problem is common in Fox Hills concretion bivalves and gastropods and Nucula are the worst for this problem among all of them.

A piece of aptychi.

A couple more decayed Micrabacia were found. I only find these at this site and they're still rare so any condition is welcome.

Graphidula species.

More Cylichna scitula (left) and Oligopytcha concina. Not great specimens (were missing most outer shell even before preparation) but good enough to prepare.

I'll never get tired of Teleost scales from this site.

The nicest Tellinimera scitula of the batch. I left it in the matrix as it is a single valve.

One of only two Euspira sp. this time. I really tried to keep the outer shell on the spire as it was present but no amount of consolidation did the trick with the hardness of the surrounding rock and how tightly the outer shell adheres.

Nuculana sp. and Nuculana scitula with intact outer shell. Easily the most common species from this site.

An indeterminate Margaritinae. Rather flattened and not well preserved for this site.

 

 

[jpc]

On 6/8/2021 at 5:20 AM, Thomas.Dodson said:

I might not have explained that properly. What I meant is that the concretions usually split over the largest ammonites. Since these concretions split over the smaller ammonites it most likely means there aren't any larger ones in the rest of the concretion. The ammonites themselves usually remain intact, which is good because these concretions are usually so hard and so packed with fossils it isn't practical to prep from the outside in.

This is the same situation for the ammonite concretions I get in eastern Wyoming.  These concretions are not conducive to prepping snails and clams with the shell on.  When one splits to reveal a shelly snail, it is a treat.