Jump to content

Nodules in Redwall Limestone, Central AZ


Doug Von Gausig

Recommended Posts

Doug Von Gausig

The photo shows several nodules embedded in Redwall Limestone (Mississippian) along highway 89a west of Jerome, Arizona. Also in this layer are crinoids, brachiopods and solitary rugose corals. I think I've read about Nodules-89a-20201115_135622-1m.thumb.jpg.372b6d643313729fe64a941975236b3b.jpgthese in the dim, dusty past, and I seem to recall that they are not fossils, but some other geological phenomenon. Any help?

Link to post
Share on other sites

They don’t look like nodules, but rather a bumpy continuous layer.
 

I have heard of, but not seen, stromatolites in the Redwall. It also could be cave or spring deposits of newer limestone. The Redwall was out of the ocean and karsted for several million years before the Naco was deposited.

 

I have never collected near Jerome. Have you ever seen Pachyphyllum coral there or elsewhere in the Verde Valley?

Edited by DPS Ammonite
  • I found this Informative 2
Link to post
Share on other sites
1 hour ago, supertramp said:

Could be oncolytic stromatolites around growth neuclei (grains).

ciao

Concur

  • I found this Informative 1
Link to post
Share on other sites
Doug Von Gausig
On 12/16/2020 at 12:24 AM, DPS Ammonite said:

They don’t look like nodules, but rather a bumpy continuous layer.
 

I have heard of, but not seen, stromatolites in the Redwall. It also could be cave or spring deposits of newer limestone. The Redwall was out of the ocean and karsted for several million years before the Naco was deposited.

 

I have never collected near Jerome. Have you ever seen Pachyphyllum coral there or elsewhere in the Verde Valley?

I'm no expert, but I believe I'm only finding Hexagonaria. Here are a few pix. Do you agree?

Hexagonaria-20201217_101810-1m.jpg

Hexagonaria-20201217_101820-1m.jpg

  • I found this Informative 1
Link to post
Share on other sites

I had two possibilities in my thinking: pisoids or oncoids, related to the specimens embedded in the sediments of the first picture.

If they are not that, maybe are onion shaped concretions.

Link to post
Share on other sites

I would take a sample of that to the nearest natural history museum. If they don't have it on hand they would most probably be interested in having it and will probably be able to positively identify it as it is a "local" feature. So take them a sample and don't forget to document the stratigraphy and location.

Link to post
Share on other sites
14 hours ago, Doug Von Gausig said:

I'm no expert, but I believe I'm only finding Hexagonaria. Here are a few pix. Do you agree?

Hexagonaria-20201217_101810-1m.jpg

Hexagonaria-20201217_101820-1m.jpg

I have yet to find a true living expert for Martin corals so I just read the best paper out there that describes corals from the Martin in southern Arizona. Similar species probably occur in central and northern Arizona.

Stumm, Erwin C., (1948). Upper Devonian Compound Tetracoral from the Martin Limestone. Journal of Paleontology, Vol. 22:1, pp. 40-47. 
 

It is my observation that the described Hexagonaria corals from Arizona all have horizontal platforms when viewed from above. Here is a picture of Hexagonaria minuta found near Superior.5146F9BC-7F49-4206-A562-E18E7B7FBA9B.thumb.jpeg.8bd0547f95ab2f126ed1d9fcbaeaaca8.jpeg

 

Your first coral looks to have horizontal platforms and thus is probably a Hexagonaria.

 

The second coral looks like a Spongophyllum coral which has sloping platforms that lead to a flat-bottomed axial pit.

 

Here is my Spongophyllum from Chasm Creek.

8B467C82-D039-41C8-9BCD-535AB50AC663.jpeg

 

I have noticed that many Martin corals vary in size, numbers of septa and description of other features from the descriptions in above paper and other papers. Species identification is sometimes a best guess based in exterior features. Internal features are often needed to give the species.

 

Edited by DPS Ammonite
  • I found this Informative 1
Link to post
Share on other sites
Doug Von Gausig

Yes, I have come to a similar conclusion -- that the taxonomy of corals (and I assume many other taxa) is sorely incomplete and indistinct. Maybe we expect too much of a biosystem that was not stable and was susceptible to rapid changes 380 million years ago? I know that the site reports conducted 20-50 years ago list species or genera with certainty that are probably just the observer's impressions. Even today, the rapidity of both allopatric and sympatric speciation can be incredible. Changes in the ecosystem can spur speciation/diversification in ways that are difficult to analyze, and the F-F was apparently a time of "rapid" change. 

 

Clearly there's a lot more work to be done and nobody to fund that work. That means that "citizen scientists" have to pick up the ball. 

 

It might be interesting to take an area like the Chasm Creek Martin and conduct a series of coordinated citizen scientist studies to see what's really out there. My impression is that it was a very rich and diverse ecosystem, and that here is a lot to learn about evolution from studying it well.

 

I would love to help as an organizational expert, not a subject matter expert, obviously.

Link to post
Share on other sites

I suspect that there are a lot more species of corals present than we have described. Corals that were different species because of different genes, colors, geographic ranges and others features might not be recognized because the fossilized hard parts are nearly identical. Imagine trying to identify modern species of birds from the same genus (identified mainly by plumage color differences) only from a few bones. Fossils only hint at past diversity.

 

Another problem with recognizing species is that many corals and bryozoans change forms depending upon their environment. One species may be given different names.

 

For our readers, F-F means the Frasnian Age and Famennian Age boundary, a large extinction event in the Devonian. The Martin Fm. is Frasnian.

 

The hard part about invertebrate paleontology in Arizona is not finding new information and species; it is trying to find a paleontologist that is interested and wants to write a paper. 


 

 

Link to post
Share on other sites
7 hours ago, DPS Ammonite said:

The hard part about invertebrate paleontology in Arizona is not finding new information and species; it is trying to find a paleontologist that is interested and wants to write a paper. 

I think this is so true. Though not just Arizona. This happens to so many "non cute and cuddly" or "big and terrible" families 

Link to post
Share on other sites
Doug Von Gausig
7 hours ago, DPS Ammonite said:

I suspect that there are a lot more species of corals present than we have described. Corals that were different species because of different genes, colors, geographic ranges and others features might not be recognized because the fossilized hard parts are nearly identical. Imagine trying to identify modern species of birds from the same genus (identified mainly by plumage color differences) only from a few bones. Fossils only hint at past diversity.

 

Another problem with recognizing species is that many corals and bryozoans change forms depending upon their environment. One species may be given different names.

 

For our readers, F-F means the Frasnian Age and Famennian Age boundary, a large extinction event in the Devonian. The Martin Fm. is Frasnian.

 

The hard part about invertebrate paleontology in Arizona is not finding new information and species; it is trying to find a paleontologist that is interested and wants to write a paper. 


 

 

Right, and to use your bird analogy (being a lifelong serious birder), a lot of the science of birds is done not by ornithologists, but by dedicated citizen scientists -- Audubon members, local birding groups, Christmas Bird Count participants, etc. In river conservation (I'm the Exec. Director of the Verde River Institute), the vast majority of the conservation work and research science is done by people whose day jobs have nothing to do with rivers. The power of enthusiasm is worth harnessing sometimes. 

 

I can relate to the fact that naming species from incomplete fossil records is an inexact science. In birds, even when we've had them in hand for hundreds of years, we get it wrong. Falcons have just been evicted from the Falconiformes! Convergent evolution is more common than we thought. Rapid speciation is common, and as you say, and morphological changes due to ecosystem variability are a dime a dozen.

 

What if we could get some institution, even a local community college to sponsor an effort to determine the diversity of Chasm Creek . That could lead to a broader model for doing this elsewhere. Better yet, is there already a model that uses citizen scientists in the fossil world that could be adapted to a local effort? 

Link to post
Share on other sites

Doug, you should join the Southwest Paleontological Society. They have projects (active before Covid) near Black Canyon City and NE Arizona and adjacent New Mexico where “citizen scientists” work along side professionals. I am a member. 


http://swpaleosociety.com

Edited by DPS Ammonite
Link to post
Share on other sites
Doug Von Gausig
5 hours ago, DPS Ammonite said:

Doug, you should join the Southwest Paleontological Society. They have projects (active before Covid) near Black Canyon City and NE Arizona and adjacent New Mexico where “citizen scientists” work along side professionals. I am a member. 


http://swpaleosociety.com

Good suggestion! I just did!

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...