Redwall Mississippian Fossil

[DPS Ammonite]

I found this long exterior mold fossil in Mississippian Redwall Formation chert from Gila County, Arizona. I think that it might be the central support for an Archimedes sp. bryozoan. Two sources say that they have not been reported from the Redwall Formation even though they are reported from other Mississippian formations in Arizona. What do members think the fossil might be? @Arizona Chris

[Fossildude19]

I see Archimedes as well.  

[FossilDAWG]

If it isn't Archimedes it must be a very close relative.

 

Don

[Rockwood]

Yes. I'd say report it.

[ynot]

Agreed with the others.

[piranha]

Archimedes is reported from the Escabrosa Group:

 

"Southeastward of Mazatzal land, the Lower Mississippian strata are known as the Escabrosa limestone, whereas, for the areas north and northwest of it, Redwall limestone is the name generally used.  As will be shown later, these two principal formations of the Arizona Lower Carboniferous are not exactly taxonomic equivalents with two different formational names, but, rather, overlap each other, the Redwall beginning somewhat later.  The Upper Mississippian deposits are known only in southeastern Arizona."

 

Stoyanow, A.A. 1936

Correlation of Arizona Paleozoic formations. 

Geological Society of America Bulletin, 47:459-540

 

"Actually, the Redwall probably was once part of a far greater rock body, for it almost certainly originally was continuous with the Escabrosa Limestone,..."

 

McKee, E.D., & Gutschick, R.C. 1969

History of the Redwall Limestone of northern Arizona. 

Geological Society of America Memoirs, 114:1-726

 

'Escabrosa' species:

Archimedes confertus
Archimedes intermedius
Archimedes invaginatus
Archimedes lativolvis
Archimedes proutanus

Archimedes terebriformis

[DPS Ammonite]

Thanks everyone.

 

The other two Mississippian formations  (that I alluded to) in Arizona that contain Archimedes are the Escabrosa and the Suprise Canyon Formations.

 

I found it surprising that McKee did not even note one Archimedes found from the Redwall Fm. I guess I was the lucky/persistent person to find one. 

 

If anyone ever again asks where to find fossils in Arizona, tell them to look for the Redwall Fm. west thru north thru east of Payson. It has probably the greatest variety of fossils than any formation in Arizona even if many are preserved as molds. The hard part is looking for the unit since most geological maps lump the Devonian Martin, Mississippian Redwall and Pennsylvanian Naco Formations together. The three units are easiest to tell apart by their fauna. Once you recognize the Redwall then you can go up and down section to find the sometimes fossiliferous Naco and Martin Formations.

 

For more info see the best Arizona paleontology website by Cris Schur: 

https://www.schursastrophotography.com/fossiladventures.html

 

and the Gila County geological map below:

 

[goatinformationist]

Great find and best of luck.

[Miocene_Mason]

Nice Bryozoan, and congrats on being one of the few who’ve found one there! I’ve got a box full of this redwall stuff, always a little surprise every time I look at it. One day some beekite rings, the next a blastoid I had overlooked.