Devonian White Chertized Fossils

From White Coral Ridge

Expedition: 8/2010

Updated 9/1/10


Here are the results of two collecting expeditions to a fossil locality in the Late Frasnian Devonian Martin Formation north of Payson. This locality which was found along Houston Mesa Road at the very top of a non descript hill has some of the most unique fauna we have ever found in the Martin. Preservation is in a ceramic like white chert, and fossils are scattered across a wide area being concentrated on the top of the hill due to erosion out of the limestone matrix. Found at this unique locality also were large section of crinoid stems- totally unlike most Martin localities we have visited, urchin spines - extremely rare in this formation, and finally hordes of geodes and quartz crystals. Some trace fossils were found in one broken block of material, something we dont often see in the martin is larger sized burrows. All said, this site is a real treasure, one of the sites we will be going back to again and again for new exciting finds!

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Coelentrates - Rugose Corals
 Solitary Rugose Corals - these range in morphology from barrel shaped at top to like a broad stack of funnels such as the large specimen at the bottom. This one is complete, with root base attachment point still intact. Corals are identified mostly on cross section details by sawing the specimen up into slabs and examining the septal details. Lets just say Im not ready to do this quite yet!
 Large magnificent specimen unlike anything we have ever encountered in the Martin.
Echinoids - Urchins
 Isolated small spine, some half inch long. Smooth exterior, with ends missing. This would have been from a sea urchin around an inch in diameter.
 Another isolated spine, and a crinoid columnal.
 Microscopic examination of urchin spine.
 Large half inch diameter crinoid stems. Many of them were long unbroken pieces up to several inches long. Most crinoid material - IF we find any at all in the Martin - are faint impressions in the limestones. These are amazing.
 Interradial Plate, the bottom of the calyx would have been at the top in this orientation. Were looking at crinoids that are golf ball sized on top of long robust stems.
 Crinoid armor spike. These circled the calyx and protected the crinoid from large fish and predators.
 Collection of stems from the top of the hill, while it was pouring rain. The smaller stems with narrower ridges were nearer to the top. (The stems were tapered)
 Microscopic view of stem section. The larger ring in the middle is a nodal, and is where the cirii were attached. these feeler like appendages allowed the crinoid to attach to near by objects and keep their distance from other crinoids.
 Microscopic view of armor spike. Think of the crinoids calyx as a mace club with big spikes all over it. Except with crinoids, the spikes were on a band that circled the "equator" of the cup. We find a ton of these in the Naco on a very primitive crinoid type. Perhaps these are an earlier version.?
 Microscopic view of interradial plate.
 Microscopic view of columnals (ossicles or stem segments). If you split a stem, this is what you get.
 Superb block of limestone with hundreds of brachiopods was a prize find.
 Close up of slab shows spirifer and rhynconellids, with some crinoid material.
 Cyrtospirifer sp. - Top part of valve exposed, with Cupularostrum sp. to the lower left.
 Cupularostrum sp. - a Rhynconellid Brach
 Cupularostrum sp. - a Rhynconellid Brach, closer view.
Quartz Crystals and Geodes
 Dawn found quite a handful of half inch sized quartz crystals here. Many Martin limestone sites have a few along with the fossils, they seem to grow right in the matrix. The source of the silica for these could very well be the glass sponges that were very common at this time on the sea bottom.
 Quartz geode, or "brain stone". These were found in extreme abundance at this site, and range in size from half an inch to about 4 inches. They are psudomorphs, calcedony quartz after some sort of evaporite nodule, maybe Howlite. When these are found, no fossils except trace fossils are found. The sea water was too salty as it evaporated on a shallow flat area.
 Inside most geodes are quartz crystals or they are solid white calcedony throughout.
 Microscope close up of quartz crystal, a particularly fine one for facets.
Trace Fossils
Thallassanoides - Shrimp burrows. The typical "Y" shaped burrows were from a type of callanassid shrimp that occupied tidal flats. Perhaps this is why we found them near the geodes.
 The other side of the above specimen.

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