Arizona Fossil Adventures 1 - The Old Timers Site

[Arizona Chris]

 

Fossils From The Old Timers Control Road Locality
By Arizona Chris

 

A while back, while skimming through a short booklet on the Pine area of the Mogollon Rim in northern Arizona where we live, I came across a paragraph stating: "And while your in the vicinity, be sure to visit the ancient marine beds that Old Timers used to collect fossil shellfish from". The location given was the intersection of Highway 87 and Control Road 64 north of Payson, Arizona. The next weekend, we drove up to the site, to see these "fossil shellfish" for ourselves.  As you turn off the highway onto the dirt control road, you cross a cattle guard and there is a dirt pull off on the north side of the road, only a hundred feet or so from the main highway. You are at the foot of a small ridge which is grown over with junipers, pinyon pines, and scrub brush. It is on the slope of this ridge and all along it you will find limestone with piles of red chert rubble among the pines. This is where most of the fossils are, in the chert rubble.

After a few hours of searching, we found Composita and Spiriferer brachiopods, numerous crinoid stems with beautiful star shaped central holes, several spaghetti like bryozoans and a host of perfectly preserved gastropods. There were also some surprises too, which I'll get to later!  The presence of brachiopods that were identical to those picked up at the Pennsylvanian Naco limestone near Khols Ranch strongly suggests that this site is also Naco as well. But here we find some additional fauna representative of a shallow water marine environment.  Further examination of the area revealed that calcified and silicified fossils were also in the surrounding limestones, but less concentrated than the chert rubble. I found it easy to dissolve out many of the specimens with acetic acid (vinegar) or dilluted Muriatic with many of them excellently preserved in the protective limestone.

 

Descriptions of Fauna present

 

Brachiopods: Three basic brachs were seen, the best preserved specimens were under one inch in size. The smallest and by far the most common were the Composita subtilita, a small typically 1/2 inch sized brach with a relatively large and clearly visible pedicle opening, and a nicely symmetrical shell. Second most abundant were the Spirifer type brachiopods, typically calcified in the limestone, and difficult to remove since calcite and limestone both dissolve in the acetic acid. These "bat wing" shaped invertebrates are best removed by mechanical preparation methods such as small chisels and ice picks. Most were less than on inch in size.

Least abundant, but by far the largest brachs found were a species very similar to the Antiquatonia sp. productids found in the Naco at Khols Ranch. Usually found incomplete or poorly preserved, these 1 to 2 inch brachs are covered with short spines or bumps on the surface, and are very deep bodied - almost spherical in shape for complete specimens. Many of them were encased in a red cherty material making them easy to spot on the ground.

 

Gastropods: One large species of gastropod can also be found at this site. Resembling a horn or trumpet, this one inch thin walled Platyceratid is usually found fragmented, or missing portions of the whorl or aperture. A complete specimen from this site would be a prized find. The one I found was about an inch long.  Platyceratids live permanently fixed to crinoid anal tubes and are coprophagus. (read: Poop sucker)

 

Sponges: A 2 - 4 inch diameter discoidal sponge can be found here. The most common type is found primarily on the slope near the parking location weathering out of the hill. Always fragmented, this net flat sponge is preserved as a 3/8 inch slab of red chert in sizes up to several inches across. The net like impressions are always on both sides of the small slabs, and by looking at the side view of the pieces internal structure is clearly seen. This thick three dimensional preservation of such animals is unusual, as most fossilized remains of sponges is nearly always a surface impression. 

 

Bryozoans:  A common type of bryozoan found here appears as a crust on some of the limestones. Resembling very small strands of tangled bits of "angel hair" pasta, this delicate invertabrate is rewarding under a stereo microscope with its delicate details.

 

Corals: Two varieties of coral are present at this site. Both are rugose corals, the most common type a small horn coral ranging from 1/2 inch to 2 inches in length. They are usually found as silica fied casts in the chert rubble piles. Also seen were some poorly persevered corals I have not been able to specifically identify due to their fragmentary nature that resemble inch or two long irregular cylinders in shape. A good specimen here would also be a prize find.

 

Enchinoderms: Found primarily as stems, and a few dissaccociated fragments, the crinoids are well represented in this fauna. Two species are found, a larger columnal segment resembling "Cheerios" in appearance with a beautiful central canal shaped like a rounded five point star. These can be found in the cherty matrix or as separate casts in the rubble piles. A second Smaller type with a small round central canal is also quite abundant and is seen in the cherty matrix and limestone as calcified casts.

 

Finally, the surprise as promised. Also commonly found among the chert rubble remains are what possibly appears to be pieces of petrified plant material. 

Burrows / Trace Fossils:  Resembling limb casts or sections of roots, these inch or two long pieces have an exterior very much like bark, and a cross section with concentric details simiar with the usual variety of petrified wood - we thought at first. Or to be some poorly preserved bryozoan or coral. But after finding many perfectly preserved specimens varying in diameter from 1/2 to 1 1/2 inches, it seems more convincing that these originate from shrimp or arthropod burrows. The walls show very distinct scratch marks from their digging action and are actually quite attractive finds.   Perhaps if you visit this site, you can find some of this unusual material and decide for yourself!

 

Photos of the material:

 

1.  Red Cherty Limestone

 

2.  Chert coated crinoid oscicles

 

3.  Large rugose horn corals

 

 

4.  Pancake Sponges

 

 

5.  1/4 of a large Pancake Sponge

 

6.  Platyceratid Gastropods

 

7.  Productid Antiquatonia sp.

 

8.  Anthroacospirifer and Composita Brachiopods

 

9.  Red chert filled burrows / Trace fossils

 

10. Eiomocrinus sp. Crinoid - Infra Basal Calyx plates

 

11.  Eiomocrinus sp.Crinoid - Basal Plates from Calyx

 

12.  Eiomocrinus sp.Crinoid - Armor Spikes from Calyx

 

13.  Syringopora - Tabulate Coral

[Fossildude19]

Excellent report and finds!  

Thanks for posting these. 
Regards, 

[DPS Ammonite]

Very cool fossils, especially the sponges. 

 

I think that your sponges are Chaunactis olsoni which occur at that site and are described by Kelly Dilliard and Keith Rigby.   http://geology.byu.edu/Home/sites/default/files/geo_stud_vol_46_dilliard_rigby.pdf 

 

Other sponges that are unidentified also occur in the Desmoinian Age Naco Fm. Here is one that I bought that came from Christopher Creek area. Anyone have an ID for the sponge?

 

EDIT: The sponge is incorrectly identified as a coral.

 

 

[Arizona Chris]

Thanks guys!  that coral looks like mangled spaghetti.  No idea what it is.  Certainly a tabulate coral. 

[JohnBrewer]

Great reading and images Chris.

[Peat Burns]

Great report.  Thanks for posting!

[jewelonly]

I really enjoyed your informative report! Thank you!

 

Leah

[Arizona Chris]

Thanks John, "Peat", Leah !

[NatalieinFlagstaff]

Thanks so much for this post! I went there today and found some great fossils Thanks to your informative pics and descriptions I was able to identify what I found as well! As someone new to this, that was invaluable. This is the best crinoid I have ever found. And is the other one a horn coral? Not sure on that one. Thanks again!

[DPS Ammonite]

41 minutes ago, NatalieinFlagstaff said:

Thanks so much for this post! I went there today and found some great fossils Thanks to your informative pics and descriptions I was able to identify what I found as well! As someone new to this, that was invaluable. This is the best crinoid I have ever found. And is the other one a horn coral? Not sure on that one. Thanks again!

 

 

Put your horn coral in dilute pool acid: HCl or muriatic. You will then uncover the coral’s opening.

[NatalieinFlagstaff]

32 minutes ago, DPS Ammonite said:

Put your horn coral in dilute pool acid: HCl or muriatic. You will then uncover the coral’s opening.

Thank you! I was just reading about doing that with pool acid or vinegar. I have vinegar, is that worth a try? 

[NatalieinFlagstaff]

I soaked my horn coral in a diluted muriatic acid solution over night. Not only was the horn coral almost completely revealed, but there was also a beautiful surprise fossil sponge on the underside of the specimen! 

[DPS Ammonite]

Very nice. You have a Chaunactis olsoni sponge. You found it at the type locality. 

LINK TO PAPER

[NatalieinFlagstaff]

DPS Ammonite identified this sponge as Chaunactis olsoni. I have only been a member for a week, and I have learned so much! Thank you to those here who have shared their knowledge with me.