Distinguishing fossils from the Hell Creek and Lance Formations

[Othniel C. Marsh]

I have often seen Edmontosaurus annectens teeth labelled as having come from the Lance Formation in Wyoming for sale online. It is my understanding that the Hell Creek and Lance Formations are very similar in many respects, and given their proximity to eachother it's no doubt quite easy for sellers to confuse or conflate the two, so I was wondering if there were any reliable means by which material from the Hell Creek and Lance Formation could be distinguished.

 

Thanks in advance for any guidance
Othniel

[Fossildude19]

I think a lot of it boils down to location/county found as to what formation is involved.

 

@jpc 

[jpc]

Indeed.  The names changes right there at the state line.  I don't think you can distinguish fossils from one to the other considering they were all deposited in the same environments with a few differences... more larger rivers in the Lance that resulted in more massive sandstones in this state. 

Fossildude is right... geography is the most reliable difference.    

[Othniel C. Marsh]

Would Weston County in Wyoming be considered Lance Formation, then?

[DD1991]

On 5/24/2024 at 12:50 PM, Othniel C. Marsh said:

Would Weston County in Wyoming be considered Lance Formation, then?

Yes. The type section for the Lance Formation is Lance Creek in Niobrara County, which is south of Weston County, and the Lance Formation merges with the Hell Creek Formation in southeastern Montana. Barnum Brown coined the name Hell Creek Formation for the geologic unit in Montana where he unearthed complete remains of Tyrannosaurus, and Ankylosaurus.

[jpc]

On 5/24/2024 at 1:50 PM, Othniel C. Marsh said:

Would Weston County in Wyoming be considered Lance Formation, then?

Absolutely

[Othniel C. Marsh]

I see. Much appreciated @jpc, @DD1991 and @Fossildude19.