Fossil Creek Fort Worth Outcrop Formations

[Thomas.Dodson]

While staying in North Texas I made stops to a couple local creeks such as Fossil Creek in Fort Worth. I've been trying to narrow down the identification of some ammonites and other things but despite the popularity and attention the creek receives I have had a difficult time determining what formations outcrop in the specific area. It's complicated by the fact that I'm not used to the stratigraphic characteristics of the formation of the area. I strongly suspect most of my fossils to have come from the Weno based on stratigraphic descriptions. However, I have read one source that leaves the Weno undivided with the Pawpaw and the Denton so the difference may not always be clear. Is anyone familiar with the specific formation(s) for Fossil Creek? Are there any key indicator species that can make delineating the formations easier?

 

[DPS Ammonite]

Show us some of your fossils. 
 

I am most familiar with those Cretaceous formations near the Red River. Some species such as Pelinia quadriplicata and Rastellium occur in more than one formation. Sometimes a formation can be identified by the presence or absence of several species at once. 

Edited September 6, 2021 by DPS Ammonite

[Thomas.Dodson]

I know a lot of these occur through the most likely formations but hopefully some will help.

 

Macraster sp.?

Neithia sp.

Haven't gotten to this one yet.

Some of the ammonites. This one looks like a Mortoniceras. There's 2 reported in the Weno and this is a decent match for wintoni although the shoulder tubercles seem a bit off.

Ditto.

Massive beds of Thalissinoides also marked the outcrops.

There are some other pelycopods I need to go through as well. There does appear to be a very poorly preserved Trigonia at least.

[DPS Ammonite]

Some of the fossils look similar to those found in the Fort Worth Formation. 
 

Check out:

 

Finsley’s “A field guide to fossils of Texas“, 

 

http://northtexasfossils.com, 

 

https://repositories.lib.utexas.edu/bitstream/handle/2152/24287/UT-bulletin-no2838.pdf;jsessionid=9106C036C3996D4B8906D1A8CC9B6952?sequence=2

 

@JohnJ and @Uncle Siphuncle may be able to help you as they have good general knowledge of Texas fossils.

Edited September 6, 2021 by DPS Ammonite

[Uncle Siphuncle]

I’m tentatively leaning toward Ft Worth fm as well.  Macs that large in the Weno are often prominently inflated, and often exhibit patches of test exfoliation as well. The last ammonite could be age diagnostic as it is not a common form.  Keep in mind with geo maps that stream exposures are often a formation older than mapped surface geology, due to downcutting.