Dry Dredgers Field Trip: March 2016

Photograph Contributors:
Bill Heimbrock
Catherine Patton
Sammy Peek
Lisa Shoemaker
Dawn Kincaid

They were crawling all over our favorite fossil site!
Shale bugs (trilobites) and the people who want them.

The Dry Dredgers were out in full force after a good rain for this first field trip of the year. We went to our favorite road cut in Southeast Indiana. At least 40 people showed up.

We were surface collecting marine invertebrate fossils approx 440 million years old (Late Ordovician Period).

Here is field trip chair Bob Bross (above) back from his second knee replacement ready to climb those hills. Bob reports that his surgeries were successful and he now has bionic knees.

We also were joined on this field trip by Girl Scout Brownie Troop 47164. (next 4 pictures)

Yours truly Bill Heimbrock provided a "Fossil Identification Key" handout for all attendees. In addition to this, I provided fossil identification services to all those requiring assistance. This is true of all our local field trips. (next 2 pics)

The trilobite layer was along a ledge where a thick "butter shale" layer exposed more of these extinct arthropods with every rain. This is why we come to this site in March. Winter and early spring produces lots of rain.

The outcrop exposes all of the Liberty and Waynesville formations. There are trilobite layers in both of these formations.

The tall road cut gave us a great landscape for photographs, selfies and portraits. Here are a couple of contributed shots.

Here is a very nice find. A TRIPLE Rusophycus. These borrows were probably of a Flexicalyemene sp. trilobite. Were they all made by the same trilobite? It's possible.

Here's a strange looking trilobite. It is enrolled but the head is missing. Based on the lighter-than-normal coloration and an identification from a fellow Dry Dredger (thanks Jerry) this trilobite is probably a Tricopelta breviceps (next 2 photos).

Trilobites are what everyone was looking for. The most common trilobite found that day was the tiny subspecies Flexicalymene retrorsa minuens.

There were thousands of fragments of this trilobite found loose as well. Many of these were molts.

As usual, the only Isotelus sp. trilobites found were fragments. Whole Isotelus sp. are usually only found by gluing hundreds of pieces together.

Always examine the surface of brachiopods. You will find a variety of epifauna (attaching animals). Many of these will be inarticulate brachiopods. The next 2 photos are a couple of examples found that day.

You can find at least a dozen different varieties of articulate brachiopods on this site. One of the most abundant found was Strophonema sp.

There was a larger but similar brachiopod found named Rafinesquina sp. It is distinguished from the previously shown Strophomena sp. by the pedicle opening being visible only when you lay the specimen down concave side up. (next 2 photos)

This pedicle opening on Rafinesquina sp. is very noticable when you are looking at a single valve.

Rafinesquina sp. can be found en masse in some of the layers where apparent storm events have left hundreds of specimens shingled and stacked sideways.

A brachiopod found abundantly in some of the layers on this site we used to call Thaerodonta clarksvillensis. The specimens found on this site are actually Eochonetes clarksvillensis.

Two similar brachiopods were found in amazing quantities on this and other Richmondian Stage sites. Here are some photos of our take-homes of Hiscobeccus capax and Lepidocyclus perlamellosum. For the purposes of this report, I will not identify them separately because I'm only going from the photographs.

Here's an interesting straight-shelled nautiloid cephalopod. It is encrusted by the bryozoan Spatiopora sp..

This next cephalopod specimen looks like it was also encrusted with bryozoans, but the surface facing us in this photo is exposing the internal molds of the chambers.

Most of the cephalopods we found were not encrusted with bryozoans but were clearly internal molds showing the individual chambers of the orthocone.

You could see cephalopods in many of the rocks you pick up on this site. They are either indentations, impressions or protruding objects on the limestone.

As far as I know, no crinoid calyxes were found. There were lots of stems shown to me to photograph. This first photo shows individual columnals of crinoid stems that have a five-point star pattern on them. They may be Cincinnaticrinus pentagonus.

By far, the most common large coral we saw was the horn coral Grewingkia canadensis. Some people may have found colonial corals, but I did not hear of any. Here are photos of some of the horn coral we found.

As is true for all fossil sites in the Cincinnati Ohio/Indiana/Kentucky area, bryozoans were everywhere.

It was nice to see some examples of Constellaria sp.. These have a stellate pattern on their monticules.

Here's an interesting trace fossil. From the looks of it, these elongated burrows could have been made by clams. If so, the ichnofossil is named Petroxestes pera.

There were a lot of fossil-related minerals shown to me. Pyrite infills burrows and other cavities. Here are a couple of photos of the many pyrite burrows were saw.

Brachiopods are often found to be geodes when broken open or when the interior is exposed on a fractured slab. In these cases, the crystals are calcite and dolomite. (next 4 photos)

Of course, some people found crystals that were not part of our late Ordovician landscape but rather transported more recently. Such is true for granite that was carried by glaciers and also by trucks.

I hope you enjoyed this field trip report. Join the Dry Dredgers and learn much much more!

Thanks to all the people who contributed photos of their day and the fossils they found.

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Dry Dredgers Field Trip March 26, 2016Southeast Indiana Whitewater, Liberty, Waynesville and Arnheim FormationsReport by Bill Heimbrock

Dry Dredgers Field Trip
March 26, 2016
Southeast Indiana
Whitewater, Liberty, Waynesville and Arnheim Formations
Report by Bill Heimbrock