Dry Dredgers Field Trip
September 27, 2008
Southeast Indiana
Upper Arnheim, Waynesville, Liberty and Lower Whitewater Formations, Late Ordovician Period

The first week of Autumn brought overcast skies for our September field trip to this much loved road cut on a southeast Indiana byway. Rain has been scarce in the summer and early fall, which for most sites means it should be picked over with no new fossils weathering out. But this is a huge site with lots of great late Ordovician fossils (440 million years old). It was not picked over at all.

The site exposes part of the Arnheim Formation at the bottom, the entire Waynesville and Liberty Formations and at the top, the Lower Whitewater/Saluda Formations.

Arrivals started early. The announced start time was 11 am. One out-of-town member arrived at 7:30 AM and spent all day there. There were plenty of fossils for everyone. Other members arrived as late as 3 pm. Here are photos from 11 am to 3:30 pm.    

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Field trips are great times for just standing around and talking fossils. We share information about the sites we've visited and share what we've found. Here's a Dry Dredger who has spent the last year revisiting this particular Indiana road cut. He brought trays of fossil he had found on the site we were visiting today to help us locate these types of fossils. Thanks!


On this site, in a previous visit, was found a beautiful calyx of the Crinoid Cupulocrinus (Back and front in next two photos).

The arms of this and other Cincinnatian crinoids look like groups of stems, but are actually arms and pinnuals. We should be on the lookout for anything that looks like a group of crinoid stems.

And we had an opportunity to see an Ordovician Sea Star that was found on this site.

 What was found that day

Someone had dumped a bunch of non-Ordovician fossils from another area onto this site near the road. Perhaps they were giving their students a test on what belonged on the site and what did not. Or perhaps someone was just getting rid of their extra fossils and knew that placing them here, the fossil would surely find good homes. This site is frequented daily by fossil enthusiasts from around the country.

There were Mississippian crinoids spread all over the edge of the road. (Next 3 pics)

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Other non-Ordovician fossils included this coral head that was cut and polished on a couple of sides.

The next two pictures are of non-Ordovician brachiopods found among the discarded items.
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Now for the indigenous late Ordovician fossils we found that day! (You were waiting for this.)

The most interesting find was this fragment of an anal sac from the calyx of the crinoid Plicodendocrinus casei.

But there were tons of crinoid stems.

One interesting find was this rock loaded with stems and a smaller curved stem that was probably acting as a holdfast.

Trilobites Found That Day

Among the trilobite finds, the best was a HUGE Hypostome (mouth plate) from what must have been a HUGE Isotelus Trilobite. Shown in the second picture below, the finder is included for scale. It was a big hit with everyone there, as seen in the third photo. Nice find!!!

Other Isotelus fragments were found everywhere on the site and everyone who recognized them picked up at least one decent piece.

Whole Flexicalymene Trilobites were also found, as well as parts. The layer with all the tiny Flexicalymene retrorsa minuens was still producing good quantities despite the lack of rain.
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Coral Found

Good numbers of the large solitary coral Grewingkia were found in the upper ledges.
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Additionally, the smaller attaching solitary coral, Streptelasma were found attached to all kinds of things, as shown in the next two photos.

Another attaching coral found was Proterea richmondensis. This is a colonial coral that often encrusts Brachiopods.

Gastropods Found

Most of the gastropods (snails) found were internal molds.
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Pelecypods Found

Even though most Pelecypods (clams) found were also internal molds, many showed internal and external features of the valves (shells). In this first example, the valves were preserved as a black film on the shale.

In another specimen, even the hinge teeth were preserved. These are diagnostic for identifying the genera and species of the clam.

Sometimes the external features are preserved, as in this example of what is probably Ambonychia.

This next specimen, however is just the broken off end of an internal mold of a clam, showing the hinge and parts of both valves.

Good quantities of clam internal molds were found.

Nautiloid Cephalopods Found

To my knowledge, no one found any of the coiled and curved Cephalopods for which this site is famous. All that was found is the "dirt common" straight shelled variety. (next 3 pics)

Pyrite Nodules Found

A few examples of Pyrite iron on slabs of rock were found. You could say these are not fossils, but in many cases, they started out as fossils until the "fossil cancer" took over.

Inarticulate Brachiopods Found

Among the inarticulate Brachiopods found, was this beautiful example of Trematis millepunctata.

Another inarticulate Brachiopod found was the very common, Petrocrania scabiosa.


Articulate Brachiopods Found

This particular site is rich with a large variety of Brachiopod genera. This first picture shows a slab of a plentiful Sowerbyellid Brachiopod called Eochonetes clarksvillensis.

The next really common Brach shown in the next to pictures is Lepidocyclus (Hiscobeccus) capax.

Here's a sampling of the "take home" from one member, which contains mostly Rafinesquina along with other types of fossils.

Plenty of Strophomena were found, which are similar to Rafinesquina, but having the pedicle opening facing the opposite way.

Less common, but still easy to find, were the Brachipod Hebertella occidentalis.

Similar to Hebertella is a brach called Glyptorthis insculpta.

Vinlandostrophia were found on this site just as is found on most of our fossil sites. (next 3 pics).

Among the many hard-to-identify species of Vinlandostrophia are the ones shown in the next 2 pictures, Vinlandostrophia cypha. They are distinguished by having one strong and two week plications in the sulcus, by having at least 10 plications on either side of the sulcus and by the fact that they are found as high up as the Liberty formation, which is where this one was found.

Also found were lots of these tiny brachipods, often cemented together in clusters. They are called Zygospira.

Bryozoans Found

As always, Bryozoans were everywhere. Resting on the rock in the next picture is a branching (ramose) Bryozoan. To determine the genus and species correctly requires special tools to take thin sections and examine them with a microscope.

Also found were flat and/or round Bryozoans of all shapes.

That's all for this field trip. Join us for our October field trip to a Northern Kentucky Kope and Fairview site.

See photos of previous field trips to this Southeast Indiana fossil meca.

September 2007
September 2006
March 2006

March 2004

October 2003

April 2002


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