Danville, KY: Dix River

50 and partly cloudy! Maybe Kentucky missed the memo that it is still February, but Christopher and I took advantage of it for some field work. This past Saturday we took a drive down to Danville, KY to check out my favorite Upper Ordovician deposits, the Lexington Formation with our good friend Kyle of the Dry Dredgers.

At Danville, Boyle County, KY we studied ~60 meters of exposed section. Measuring bed-by-bed we collected data to draft a stratigraphic column and made some quick fossil counts.

One of the more interesting finds was how heavily faulted the entire region was. Resulting in an offset of more than a meter to just a few centimeters.

One of the MANY faults at this exposure. 

Working in heavily faulted areas adds complexity to the otherwise layer cake stratigraphy we are spoiled with in the central Kentucky outcrop belts.


Another unique feature of this particular outcrop belt is the great abundance of preserved bentonites. The literature has noted the presence of as many as 20 bentonites in the Tyrone Formation, the main member of the lower micritic section of the exposure. Including the famed Deicke K-Bentonite.

Sticky yellow clay. K-bentonite?, a sample was collected for further analysis.

Finally we found another good chronostratigraphic tie line with a deformed (ball and pillow structure) zone believed to be the expression of the capitol.

Deformed beds of the "capitol", helpful as a marker horizon when correlating
across faults.

A Bundle of Brachiopods - Zygospira

The other day when Allison and I were out in the field, we made a quick stop near Dillsboro, IN to look at an outcrop of what was probably Mount Auburn Member (of the Grant Lake Fm) or the Arnheim Formation. We knew we were not any younger than that because we came across some rather large Platystrophia ponderosa (Vinlandostrophia ponderosa) which are known the make through the Arnheim, yet disappearing before the Waynesville Formation. However we didn't see any of the true diagnostic fossils like Lapteana  or Retrosirostra carleyi. 

Outcrop of Grant Lake or Arnheim Formation near Dillsboro, Indiana

We did come across this rather interesting pair of rocks in the float that showed some sort of groove or gutter carved into what must have been a semi-harden marine floor and in this groove was dozens of small Zygospira brachiopods.

Groove or gutter filled with the small brachiopod Zygospira

Another accumulation of Zygospira from the same locality. The large brachiopod on the bottom right is a Rafinesquina.

Zygospira are known for adhering themselves to whatever hard substrate they can find. In a paper by Micheal Sandy (1996), the author describes a specimen from the Waynesville Formation of Ohio where an articulated crinoid stem is thoroughly encrusted by Zygospira. There have also been reports by local trilobite collectors that they have found Zygospira concentrated around fragments of Isotelus in mudstone deposits colloquially referred to as butter shales (more on these next week).

A closer look at one of the accumulations of Zygospira

Lastly, an interesting note is that on at least one of the blocks we see the dumbbell shaped trace fossil Diplocraterion generally thought to be the dwelling trace of a crustacean or worm.

Arrow is pointing to the Diplocraterion trace fossils associated with one of these Zygospira accumulations.

Versailles State Park Pt 2 - Fun with Fossils

So as Allison mentioned in her last post, we spent a recent Saturday hiking around Versailles State Park looking for outcrops of the Waynesville and Liberty Formations (Katian; Richmondian). Many of the outcrops as you probably noticed and would have suspected, were covered in varying degrees of ice. It was also about 5 degrees C out, so we didn't feel like hiking through ice-cold streams was a wise idea. #JanuaryFieldWork As a result, most of our fossil hunting was restricted to the various cobble deposits along the stream's banks. There were plenty of goodies to be had there though!

This first image is of a rather sizable fossil that was seemingly randomly located along the trail approaching the stream. Not sure where it came from exactly BUT, it is rather neat! Here we have a large coral, likely a Tetradium (click the link for additional images of Tetradium from the Cincinnati Arch region).  

This image I am rather fond of. Here we have two different Ordovician bivalves, an Ambonychia  (link to the Ordovician Atlas page) on the right, and a Caritodens on the left.  Bivalved mollusks are typically aragonitic in composition which is why these clams are moldic (aragontie does not preserve as well as calcite) but what is notable about these critters is they are impressively large! My guess is these guys came from either the Wayensville or Liberty Formations.

This next image is from one of the outcrops Allison shared previously. To the immediate right of the scale bar is a jumble of brachiopods called Rafinesquina, very common to the Ordovician of the KY-IN-OH tristate. We often refer to these beds of jumbled Rafinesquina as 'cornflakes beds'. I imagine the name is self-explanatory!

This is another set of brachiopods from that same outcrop as the Rafinesquina, There are two primary brachs that you can see in this image, the one just right of center is an orthid brachiopod, likely a type of Hebertella.

Lastly a nice view of the iced lake as we were hiking back to our car.

All in all, it was a fun day hunting for outcrops and fossils and I look forward to getting out in the field more and sharing with you our discoveries!