Last field trip of year to Cambrian trace fossils!

[Arizona Chris]

 

Last weekend, we took our final trip up to the Ash Fork (Arizona) area for the year to explore the outcrops of the bright angel shale. this time however, our goal was to collect trace fossils and coralomorphs ( more on that later).   While a small group worked for shales in the lower part of the formation, some of the more adventurous of us climbed the hill capped by the Muav limestone. We spent a few hours searching for Cambrian trace fossils - and we're not disappointed! meanwhile, down in the Shale pit they found many Coralomorph specimens, and of course hordes of trilobites.  

 

The Stevens Way locality near Ashfork  consists of three facies, a lower green shale member with body fossils of trilobites and other marine fauna, and two upper members within walking distance which has a base of a yellow crumbly shale loaded with only trace fossils of low diversity capped by the third member, the Muav Limestone which here was non fossiliferous. When we scouted the middle member extensively, and found some well preserved trace fossils - Some being quite enigmatic! While the nearby Tapeats Sandstone consists of primarily the Skolithos and Cruziana ichnofacies, this deeper water shale seems to be a mix of Cruziana and Glossifungites ichnofacies components.

 

Here is a photo pictorial of some of the more interesting trace fossils we have found at the second yellow shale facies

 

Trilobite Tracks, Resting places Cruziana - Grazing traces as the trilobites plowed through the upper layers of sediment.

 

Rusophycus - resting trace.

 

Simple Tubular Feeding Traces

Paleophycus sp. (Worm like sub surface miner)

Bilobed Traces

Left side - Isopodichnus (Shrimp/Arthropod)

 

Aulichnites (Gastropods grazing)

 

Cyano bacterial mat hard ground (AKA: Elephant skin) When an algal or bacterial mat grows on the surface of mud, it wrinkles the surface to form this type of pattern.

 

Locomotion Traces These two slabs are very unusual, we believe them to be a mollusk of some type pulling its way along the surface hard ground.

Protovirgularia sp.

   

Well, thats if for now.  Many of the specimens are still being cleaned up, as they were attached to thick green glauconitic mud.  And about those Coralomorphs? Ah, thats the next write up....

 

[Wrangellian]

Interesting stuff...

Can you make bigger pics? They're only about 4" on my monitor and they don't enlarge when clicked on.

 

Curious about the corallomorphs... what a tease...

[Kosmoceras]

These are fantastic! Thanks for sharing.

[Arizona Chris]

You can get larger images at my web site Here:

 

http://www.schursastrophotography.com/paleo/Fossilfotos-4g.html

 

Yes, we found what is essentially a super rare archeo - coral in great abundance.  wait till you see what they look like!  (another tease)

[ynot]

Nice examples of trace.

Thanks for sharing.

 

I agree with Wrangellain, bigger pictures here would be nice.

[Virgilian]

4 hours ago, Wrangellian said:

Curious about the corallomorphs... what a tease...

 

"Coralomorphs" are early corals of the Early Cambrian. You can also find 'em in the Lower Cambrian Harkless Formation of Esmeralda County, Nevada (a type called Harklessia yuenglingensis), associated with archaeocyathid sponge mini-reefs. If I recollect correctly, the coralomorphs make up roughly four percent or so of the Harkless archaeocyathid reefs. They're also reported from Australia and Siberia.

 

Here's an image I found of the "coralomorph" Harklessia yuenglingensis from the Lower Cambrian Harkless Formation, Esmeralda County, Nevada--it's from the paper  A NEW GENUS OF EARLY CAMBRIAN CORAL IN ESMERALDA COUNTY, SOUTHWESTERN NEVADA by Mellisa Hicks. Journal of Paleontology 80(4):609-615. 2006.

 

 Harklessia yuenglingensis is one of the oldest true corals recorded from the geologic record. Class Anthozoa, subclass Zoantharia. It's probably a tabulate coral, as a matter of fact:
 

 

[Arizona Chris]

And now that genus has been found in Arizona.

[Virgilian]

18 hours ago, Arizona Chris said:

Here is a photo pictorial of some of the more interesting trace fossils we have found at the second yellow shale facies

 

All of those, of course, are typical "tracers" one commonly encounters in the Early to Middle Cambrian Carrara Formation, Mojave Desert--southern Nevada and eastern California.

 

The older Lower Cambrian Wood Canyon Formation in the Nopah Range, California, locally contains some spectacularly bizarre tracers, completely unidescribed in the scientific literature so far.

 

2 hours ago, Arizona Chris said:

And now that genus has been found in Arizona.

 

In addition to their North American, Australian and Siberian occurrences, coralomorphs are also now known from Mongolia, of course. Probably with greater recognition of their  preservational aspect in the rocks, coralomorphs will likely become widely recognized as paleontologically valid components of many other later Early Cambrian stratigraphic units across the globe.

[piranha]

 

[Arizona Chris]

It will be interesting to see if they have or ever reported these from the Grand Canyon BAS...

 

Thanks, you are an invaluable resource.

[Plantguy]

Enjoyed seeing the traces. I dont know what it is about that those things that are intriguing Regards, Chris 

[FruitofTheZOOM]

Thought I'd contribute on the same topic. Here's some ichnos from the BAS taken this week which includes a beautiful rusophycus, gastropod grazing, and one I'm not familiar with yet (holes). The toes are in for scale!

 

[FruitofTheZOOM]

 Forgot the last picture:

[doushantuo]

And it's the most intriguing as well!

[FruitofTheZOOM]

Btw, I don't collect any specimens I find. I leave them where I find them.

 

Happy trails!