Early Triassic Moenkopi/Thaynes - Ammonoid Biostratigraphy, Correlation and Paleogeography

Smithian ammonoid faunas from Utah: implications for Early Triassic biostratigraphy, correlation and basinal paleogeography

Arnaud Brayard, Kevin G. Bylund, James F. Jenks, Daniel A. Stephen, Nicolas Olivier, Gilles Escarguel, Emmanuel Fara, Emmanuelle Vennin, Swiss Journal of Palaeontology, 2013, 132:141-219

Abstract

Intensive sampling of the lower portion of the Thaynes and Moenkopi Groups (Lower Triassic) at separate localities within the Confusion Range, Pahvant Range, Mineral Mountains, Star Range, Kanarraville, Cedar City, Torrey and San Rafael Swell areas (mainly central and southern Utah, USA) leads to the recognition of a new key regional Smithian ammonoid succession. The new biostratigraphical sequence, which is more precise than the long-recognized Meekoceras gracilitatis and Anasibirites kingianus Zones, comprises twelve subdivisions, thus resulting in a sequence with much higher resolution that can be correlated not only with other western USA sites, but also with major worldwide localities as well. Middle and late Smithian faunas contain many taxa with wide geographic distribution, thus enabling long-distance correlation with faunal successions from other regions (e.g., British Columbia, Canadian Arctic, South China, Spiti and Oman). New assemblages from the lowermost beds are the least diversified and poorest preserved; they represent the earliest early/middle Smithian ammonoid faunas reported from the western North American basin. They highlight (a) the sudden Smithian advancement of the marine transgression within this epicontinental sea, (b) that this event is diachronous, and (c) that the paleotopography of the basin most likely was highly irregular. The newly obtained ammonoid succession also allows us to date and follow the transgression from the northern and central part of the basin to the southwesternmost and southeasternmost parts, which were reached during the late Smithian (Anasibirites kingianus beds). In addition, we briefly discuss the now-limited previous regional biozonation in the light of these new results. One new genus (Minersvillites) and nine new species (Kashmirites utahensis, Kashmirites confusionensis, Kashmirites stepheni, ?Xiaoqiaoceras americanum, Minersvillites farai, Inyoites beaverensis, Meekoceras olivieri, Meekoceras millardense, Vercherites undulatus) are also described.


The ammonoids are mostly all the old Early Triassic ones described by C.A.White from collections made by the early geologic surveys of the american west, and by J.P.Smith in the early part of the last century.  A more precise and revised biostratigraphy is proposed.  Below is one of the newly described ammonoids, this one from the Minersville area, one of the earliest Smithian ammonoids found in the western USA.

Vercherites undulatus Brayard Bylund and Jenks 2013

The rocks we have been working in represent the Permian and Early Triassic transition beds, usually some Permian limestones followed by an erosive surface, conglomerate, then a transgressive sequence with marginal marine redbeds, inner shelf, outer shelf and basinal deposits following.

Moenkopi and Thaynes Groups as exposed near Minersville

Permian rocks at the bottom, then the red Black Dragon Formation, and capped with the Sinbad Formation.  As exposed just west of Capitol Reef National Park.

     As you can see, some very wonderful country to explore and work in.  More papers are in the works covering the paleontology and geology of these rocks, I'm really looking forward to the adventure.

Shovel Control

Just like Gun Control, only in this case a shovel is the culprit.

Instead of prosecuting those shovel carriers that abuse the system, the government, in it's infinite wisdom, will ban all shovels carried by common fossil hunters on Federal Land.

Please read and comment on these new regulations, I think they are bad for the Public and Science.

Paleontological Resources Preservation

Paleontological Resources Preservation US Forest Service

Amateurs will not be allowed to do research?

Amateurs and/or non-professionals will need a permit (if they can get one) to collect fossils for research.   Casual collecting just will not fit the bill if these regulations go into effect.  Who can do research collecting only 5 specimens of each type of fossil per year?  And what is a type of fossil?  Can I only collect 5 cephalopod fossils per year?
  In fact, even professionals and academics will need a permit to collect invertebrate fossils for research (which is what they all collect for) on any public land (the BLM will adopt the same regs as the USFS), which has not been necessary before.

From the Definitions Section:

4. The term casual collecting would restate the definition contained in 16 U.S.C. 470aaa of the Act. To be considered casual collecting, the activity would mean all of the following: Collecting of a reasonable amount of common invertebrate or plant paleontological resources for non-commercial personal use, either by surface collection or the use of non-powered hand tools, resulting in only negligible disturbance to the Earth's surface and other resources.

 14. The term non-commercial personal use as used in the definition of casual collecting would clarify the types of use allowed under casual collection, and would mean uses other than for purchase, sale, financial gain, or research. Common invertebrate and plant paleontological resources collected for research purposes is not personal use and would need to be authorized under a permit in accordance with Sections 291.13 through 291.20. Exchange of common invertebrate and plant paleontological resources among casual collectors would be permissible as long as such resources were collected in accordance with the Act and the proposed regulations.

 18. The term reasonable amount as used in the definition of casual collecting would quantify the maximum amount of common invertebrate and plant paleontological resources that could be removed from Federal lands. A person may remove up to one gallon of material in volume or 25 pounds in weight, and up to five specimens of each type of fossil per calendar year. If the fossil specimens are contained within rock slabs, the reasonable amount would be limited to a slab that can be hand-carried by one person without the aid of mechanical devices. The authorized officer may modify the amount that is reasonable in order to preserve fossil-bearing locations that may be at risk of being depleted, thereby preserving paleontological resources in accordance with the Act.

I think I'll post a comment to this one...

If I can make the July 22, 2013 deadline...


Paleontological Resources Preservation US Forest Service

PRIONITE-MARE

The Family PRIONITIDAE is a nightmare of taxonomy.  The amount of intraspecific variation, or even intrageneric variation is overwhelming.  Most generic assignments are based on the shape, size, amount, and/or lack of ribs, bullae, nodes, whether they cross the venter or stop short, whether the nodes are mid flank or start near the umbilicus, whether the inner whorls or the outer whorls are smooth.  A lot of specific and generic assignments are arbitrary, a slightly arched venter instead of a flat venter is cause for different generic assignment of forms that basically look exactly alike. 

Tozer, 1994, in his monograph of Canadian Triassic Ammonoids, discussed the differences between Population Taxonomy and Typological Taxonomy and admitted that his classification, especially of the Prionitidae, was arbitrary, and to use a strictly typological taxonomy would mean almost every specimen was a seperate species.  He also talked about using the typological method just to show what the taxon looked like.

To see a Prionitid, it is easily assigned to the Prionitidae, and the beds containing it are easily assigned to the Late Smithian, and usually to the biozone and/or beds known for the Prionitidae.  Is it really necessary to split them into a bunch of different species or genera?  I suppose I could live with a few nominal species divided amongst a few genera for the time being, at least until the family is revised and a more natural classification determined.  Still, what a Prionite-mare.

For references see THIS old post, along with an old rant of the same topic. ;)

When Ammonites Fly

Along the lines of reverting to aquatic dinosaurs as has been seen in the geoblogosphere of late, I give you Duria Antiquior (above), and it's lithographic byproduct (below).  Floating on the surface of the water are ammonites with wings (or sails as conjectured some).

Clearly showing that ammonites could fly

 

Or could they?


A lot of science has been done since the art above was first seen.  Back then about the only creature known to compare the ammonites to was the Argonaut, one of the group of octopus that are known for a lot of webbing between their arms (such as this Blanket Octopus).  The "wings" of argonauts are specially modified arms used to secrete a calcium carbonate shell used to hold eggs (best seen in the top photo here).  We now compare ammonite shells more closely to the Pearly Nautilus and the animal itself to the ten armed cephalopods.  Hopefully we can advance as we learn, .

The Museum in Green River, Utah

 The Mancos Shale exhibit at the John Wesley Powell River History Museum in Green River Utah, is now open.  Along with a couple of dinosaurs and other murals, it is a very nice addition to the museum.  In the distance on the right you can see the ammonite I found and posted about back in this post, and after it was prepared in this post.

 

Here is a view of the specimen with the mural behind it.

  And the sign telling about the collection and preparation. 

And a few of the other ammonites I donated (the six on the left).  And more of the large mural behind it, unfortunately showing a wounded scaphite, or is that just the leftovers of a large marine reptile it just finished eating. ;)

For a cold, snowy, December day

San Rafael River cutting through the Swell

Just to remember those hot days of summer and early fall in the desert.  The Sinbad Formation of the Thaynes Group slopes down to river level on the left, bleached rocks of the Moenkopi Group up to the maroon Chinle Formation on the slopes of Assembly Hall Peak, with a cap of Wingate Sandstone, and Kayenta and Navajo above that on the cliffs beyond.  The leaves of the Fremont Cottonwoods just starting to foretell the cold and snow of today.

Of Cephalopods and Sponges

Early Ordovician orthoconic nautiloids in a sponge/algal deposit, back when life was just beginning to diversify.

 

Early Triassic ammonoids in a sponge/microbial deposit, back when life was beginning to re-diversify.  Just after the Permian-Triassic mass extinction.