Dry Dredgers Field Trip
Saturday, April 28, 2018
Northeastern Kentucky
Corryville and Mount Auburn Members of the Upper Ordovician Grant Lake Formation
Third site: Lower Waynesville Formation

Photos by Bill Heimbrock

This locality was going to be the March 2018 Dry Dredgers field trip, but that trip was canceled due to winter weather. Spring came late, but we had great weather when we returned in April. Matthew Speights led this field trip. It was such a good site and the weather was so good, that we fossil hunted for 4 and a half hours and investigated three different road cuts.

The three sites were within a couple of miles of one another and they were all about a half-hour south of the usual northeastern Kentucky site we normally visit.

All three sites exposed rocks the same age as the Corryville and Mount Auburn Formations of Cincinnati. The age is the late Ordovician Period, making them about 440 million years old. But unlike the Cincinnati area layers, these localities were shallower water, making it warmer and changing the types of animals that lived. We found lots of algae and sponge fossils along with large colonies of bryozoans. 

Fossils Found at Site #1

"Solenopora"  is the name assigned to a type of fossil we found in great abundance here. We call it "Brain Algae" because most specimens resemble brains. It has been thought to be a red algae but recent research may prove it to be a type of sponge. The specimens also have a slight pinkish brown color.


One of the best finds of the day, though, was a fragment of Conularia. (next 2 pictures)

Stromatoporoids (Sponge)

The stomatoporoids on this site were not nearly as common as the second site. Here's one from site #1 that is large but very crystalized. (two sides shown)


By far, the most common brachiopod found on this site was Vinlandostrophia ponderosa.

Rafinesquina fracta

The second most common brachiopod was Rafinesquina sp. The specimen shown is probably R. fracta.

Nautiloid Cephalopods

Site #1 had a few fragments of the internal molds of nautiloid cephalopods.


Only fragments of trilobites were found. No whole trilobites that I know about.

Pygidium of Flexicalymene sp.

Isotelus sp.



Bryozoans encrusted a large number of unidentified objects on this site. Here's a few.

Gastropods (snails)

Gastropods are ubiquitous. Site #1 is no exception.


No crinoid heads were found. But here's a really nice holdfast. In this case, the crinoid's stem was wrapped around something else to fasten it in place.

Site #2

Stromatoporoids (sponges)

After an hour and a half, we moved on to our second site. Here the dominant fauna changed from Solenopora to Stromatoporoids (sponges). Here's Christa proudly sporting her Stromatoporoid fossil.

Perhaps the best stromatoporoid find was this magnificent layered spire, found by Caroline Grathaus.

Here are some more stromatoporoids found that day.

This may have been the layer from where these sponge fossils were weathering out of the road cut. The white line is a drill score.

Site #2 "Solenopora"


The bryozoans on this site were massive.


The brachiopods on site #2 were not as abundant as on site #1. But the most common brachiopod was still Vinlandostrophia ponderosa.

Trace Fossils

Here's an interesting trace fossil. Called Chondrites sp., it's a type of track across the sea bottom probably made by a wom.

Site #3

The third site of the day had more traditional Cincinnatian-style fossils and they were in great condition. The site exposes the Lower Waynesville Formation.

Pelecypods (clams)

Some of the clams we found were HUGE compared to the varieties we find close to Cincinnati. Additionally, they had excellent external shell features preserved in brown calcite.

These next two clam specimens (5 photos) were also exceptional because they were partially open, with both valves still hinged. This is a fantastic find! Nice work!

More clams were found on the surface of rocks.

There were also found a few large clams that were very unusual in their shape. Both valves are flat on one side. It's hard to tell from the photo below, but here are a couple of them. Yet unidentified.

This next clam looks like it is either Ambonychia sp. or Anomalodonta sp.

Here's another huge clam, showing both sides (2 photos). Not in as nice condition but still impressive for the size.



There was a layer of rock that was loaded in spired gastropods on site #3. Here are a couple of photos of them.


One nice brachiopod found on site #3 was this specimen (2 photos) of what appears to be Holtedahlina sulcata. This species is already known from the Waynesville Formation but is a nice find just the same.

Here's a more common brachiopod from site #3 - Hebertella sp.

On some of the brachiopods, like this Hebertella, there were inarticulate brachiopods, like these Petrocrania scabiosa.

And Vinlandostrophia sp. were also found in large numbers at this third site as well.


As was true for the other two sites, there were no whole trilobites found on site #3. But parts of trilobites were easy and good to find.
Here's a pygidium with spine of what is probably Acidaspis sp.

And here's a pygidium of a Flexicalymene sp.

Well that's all for this field trip. I hope you were there because everyone left happy.

Now let's move on to the May 2018 field trip to a McMillan Formation site in northern Kentucky.

Back to the Field Trip Index Page

Return to Dry Dredgers Home Page

The Dry Dredgers and individual contributors reserve the rights to all information, images, and content presented here. Permission to reproduce in any fashion, must be requested in writing to admin@drydredgers.org.
www.drydredgers.org is designed and maintained by Bill Heimbrock.