fox hills vs pierre shale?

[smt126]

I'm wondering if anyone has some good images that show the difference between the fox hills formation and underlying pierre shale formation? I've been reading geological report after report, but have been unable to find anything that shows a good picture of how I can tell the 2 formations apart when out in the field. I'm heading to Montana next month and have read Rockhounding Montana about 5x over, but there's not really any pictures that help differentiate the strata. I've also gone through several search engines for hours over the last 6 months too, to not much avail. I've got the geological maps of the area along with the BLM maps, but just would like to see a more real world photo. I would like to thank anyone in advance for their help.

[PFOOLEY]

The Rooney Roadcut

[PFOOLEY]

from www.geocities.ws...the Rooney Roadcut (Foxhills and Pierre)

 

 

 

[PFOOLEY]

9 hours ago, smt126 said:

...good images that show the difference between the fox hills formation and underlying pierre shale formation?

 

@jpc?

[jpc]

I don't have any pix handy, but the Pierre Shale in WY, MT, SD, CO etc forms blackish gray nondescript outcrops, mainly rolling hills, but also some river cuts and even buttes and mesas.  Dark color, soft rock.  No big sandstones. The Fox Hills in eastern MT and WY is primarily sandstone and makes large sandstoney outcrops.  Under these sandstone outcrops is where you can find some blackish shales  of the FH.   In central SD, the FH sandstones are not obvious if they are present at all.  (I have only been there once).   In central SD, the outcrops look the same.  But the fossils are different.  That is the key.  And they are generally found in concretions in both units.  The FH sandstones tend to have a lot of Ophiomorpha burrows.

 

Good luck.  Don't forget to get landowner permission to go fossil hunting. Learning who owns the land is often more difficult than learning to recognize formations, but it can''t hurt to stop in at the local ranchhouse.     

[smt126]

Thanks guys. I plan on hunting those on the public land (BLM). I've been trying to study those maps as much as possible to make sure I'm not cutting across any private land. We are spending 3-4 days hunting on a private ranch that I'm paying for so that we can do some vertebrate hunting while out there. I figured on the days they are closed we would try hunting invertebrates. I just like to be as prepared as possible, especially when I have my kid(s) with me as I'm paying more attention to them than the fossils usually. We'll be staying out of Glendive and it looks like they've got a good amount of BLM land to the south to explore.

[Ridgehiker]

As a geologist I'd advise not to get caught up in trying to distinguish these formations. Good comments above but localized variations blur differences.  As Jpc points out...best to collect fossils and try to ID them. 

 

Re the book (at least the old brown edition). Glendive is loaded with material. I can easily collect a hundred ammonites in a few hours...however, be on the look out for Mosasaur elements at the highest levels. I havent found teeth but came across a few vertebrae.'up high'.  Also, the nautilus are exquisite but usually in sections...keep them in matrix.

 

Yellow Dog Reservoir. The reverse.  The book mentions ammonites but I found only a couple after hours of hunting.  However, there are Ptychodus and other shark teeth in the raised grey mounds leading to the reservoir.

 

My favourite locale in the state. 20 or so kms north of Jordan towards Fort Peck resevoire. East side of road.  Public land so no vertebrate collecting but area is chock full of a variety of  good quality shells.  The ground glistens in spots from bluish garfish scales.  There are only scraps of dino bone but lots of micro vertebrates...croc, turtle, raptor teeth, etc.  I suppose you cant collect these but neat to see.

 

Curious. What's the story on collecting shark teeth in USA on public land?  One custom agent told me they are exempt ( he called Washington for me)  he was told added sharks dont have bones so are exempt. I just kept quiet and nodded.

[jpc]

good to keep quiet and nod.  But he was wrong.  Shark tooth collecting is verboten on public lands.  'That's Stupid', did I hear you say?  I agree.  The worse is the Mowry Shale around here is a late Cretaceous unit with jillions of fish scales.  Great for kids outings.  But verboten to collect on public lands.   

[Ridgehiker]

2 hours ago, jpc said:

good to keep quiet and nod.  But he was wrong.  Shark tooth collecting is verboten on public lands.  'That's Stupid', did I hear you say?  I agree.  The worse is the Mowry Shale around here is a late Cretaceous unit with jillions of fish scales.  Great for kids outings.  But verboten to collect on public lands.   

 

So what are rivers in the USA?

 

In Canada all river are public.  When people collect in the Peace River, Suphur, etc. is this state or private designation?  

[jpc]

I suspect this is a state by state thing.  We don't collect in rivers here in Wyoming.  As a retired rafting guide in Colorado, I know that their laws say the bottom of the river is public; the shores are whoever owns that land.  The river itself is public and it is illegal to string a fence across a river, but people do it anyway.  

[Ridgehiker]

19 minutes ago, jpc said:

I suspect this is a state by state thing.  We don't collect in rivers here in Wyoming.  As a retired rafting guide in Colorado, I know that their laws say the bottom of the river is public; the shores are whoever owns that land.  The river itself is public and it is illegal to string a fence across a river, but people do it anyway.  

 

We have some strict laws about disturbing river bottoms. The shoveling, scoops, etc. would not be permitted. Fish, amphibians invertebrates, etc. habitats are disturbed. 

 

A study was done in the 1960s that involved using the Red Deer river to screen sediments for mammal teeth from adjacent Cretaceous deposits. Even this use was denied when requested a couple decades later.