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Hunting the Roadcuts of Indiana's Ordovician

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digit

Last week I made my third annual pilgrimage back to the Chicago area to visit family, do a little fossil hunting, gorge myself on great ethnic foods and treat myself to some Chicago-style deep-dish stuffed pizza for my birthday--yum! :drool:

I had hoped to pick up some more Pit 2 (Braidwood Biota) Mazon Creek nodules from Fossil Rock campground in Wilmington but sadly it is now closed and up for auction with the distinct possibility that it will never again allow fossil hunters to gather nodules from the spoil piles at the back of the campground. Instead, I figured on focusing back on the Pit 11 (Essex Biota) nodules in the Mazonia/Braidwood State Fish and Wildlife Area where I first had hunted nodules since learning about them several years ago. I had hoped on meeting up with some TFF members but unfortunately this turned out to be a busy weekend for them and we never managed to get out for a group nodule hunt. I did make it out to Mazonia/Braidwood for a couple hours of the weekend. Luckily, this location in Braceville is only a short 45 minute drive from where we were staying so it is quite convenient to pop over there. The weather report did not look good for Saturday afternoon and soon after we arrived the low clouds and mist turned to drizzle and then to rain and we were chased out with little to show for our efforts. We did a little better on Sunday and I have a small cache of nodules soaking in a bucket at the moment before their first freeze/thaw cycle on a shelf in my freezer.

I had suggested to the TFF members in the greater Chicagoland area (including far western cities and extending into Wisconsin) that if there were other fossil hunting opportunities in the area that I might be able to replace Fossil Rock campground with some other novel (to me and my wife, anyway) location. Rob Russell suggested a small road cut in north central Illinois as a possibility but stated that a much more certain location would be the St. Leon roadcut in southeastern Indiana. We considered how we wanted to plan our week in Chicago and decided that Friday would be the best day for a roadtrip to Indiana. Google Maps (for some unknown reason) showed this trip as just under 4 hours. I figured that would be only an hour more than we normally drive to get to the Peace River here in Florida and that we could do it as a day trip.

We got up early on Friday (easy to get out of bed with the prospect of fossil hunting ahead) and were on the road before 6am. Being reasonably close to the Summer Solstice and at a much more northerly than our normal South Florida latitude, the days were long and we were able to depart in daylight. We ducked under the southern tip of Lake Michigan and once in Indiana headed southeast on I-65 toward Indianapolis. Right away I could see that the Google Maps estimate of arrival time was optimistic. Large swaths of I-65 were under construction and there seemed to be as many large semi trucks on the road as cars. We stopped off along the way for a quick breakfast and continued to make steady progress toward Indianapolis. We had planned on stopping there because in my haste to pack for the Chicago trip I had forgotten to pack a long sleeve shirt. I have had more than my fair share of solar radiation as a kid spending my days shirtless and shoeless running around the country roads of northern Wisconsin with the local kids during my youth and now prefer to spend my time in South Florida covered up from the sun as much as possible. Rather than lathering up armfuls of sunblock I tend to prefer long sleeve shirts for their abrasion protection as much as their SPF. I set the GPS for the address of a Target store in Indianapolis as we had left the Chicagoland area before they were open. Unfortunately, we got the E or W prefix wrong on the street address and ended up some 16 miles away from the store. We managed to find a discount store in the area and after about 5 minutes of shopping (twice my normal preferred extent) I came away with my new "in the field" shirt for the extravagant price of $2.50.

Back on the highway again and heading toward the town of St. Leon. We were making reasonable time (as best we could with the traffic and construction) but realized that 4 hours was a hopelessly unrealistic travel time. When I double-checked the distance I realized that it was around 280 miles and a 70 mph average speed would be needed to make this journey in the specified time. As that was the limit on the fastest parts of the highway we would not be arriving mid-morning as I'd originally planned. In the end we arrived for an early lunch in St. Leon where we (surprisingly) found vegetarian food at a restaurant called Skyline Chili. Chili they had--several large cauldrons of it bubbling away in the open kitchen area--but skyline? The only skyline visible in this open rural area was that shown in silhouette on their sign.

Post lunch we headed north on Old State 1 till we saw the splendor of the extensive roadcut that I'd seen in Google Maps satellite imagery or in the trip photos of other groups that have hunted here before us. This roadcut through the 450 million year old Upper Ordovician deposits seems to have been an effort to minimize the slope of the highway running through its middle. We parked well off the road on the extensive shoulder near the drainage area and could hear the frequent trucks and cars go by. On their way up the incline we could hear the trucks shifting into low gear to climb the grade and the engine breaking of the trucks making the opposite trip. We were the only ones there, the sun was shining, the weather was pleasant and within minutes of parking the car we saw that the rocks around us were virtually carpeted with brachiopods and other fossils--it was going to be a good day. It had taken us 6 hours to get here (50% longer than originally estimated) but with the prospect of a new and exciting hunting opportunity, we couldn't be happier.

For those who have not yet seen the roadcut at St. Leon here is what it looks like looking down the sloping highway with terraced slopes flanking the road. You'll notice the wide shoulder and the shallow drainage trough which make for safe parking well away from the traffic. The photo of the brachiopod slab right next to where we parked the car indicated a productive day was ahead of us.

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Grimlock

First off, HAPPY BIRTHDAY Ken :yay-smiley-1: I'm glad you had a good adventure up there. Now you got me wanting some deep dish pizza.

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digit

I had read up online as much as I could about this location. Apparently, several university groups have made field trips here as well as it being a favorite haunt for local fossil clubs. I had familiarized myself with the search image of the various types of things I might find here (always a good idea): brachiopods, bryozoans, horn corals, crinoid stems, an always a favorite--trilobites! I had learned of a slightly greenish layer of more clay-like material banding through the middle of this cut known as the Liberty Formation but locally called the "butter shale". It can be seen in the photos below as the horizontal lighter colored ledge running through the roadcut. This formation, it would turn out, was a good place to hunt for trilobites.

While trying to get used to the fossils at this site I wandered around with a plastic bag and a larger screwdriver surveying the surroundings and getting a feel for the fossils that were present. Lots of the fossils were locked up in large slabs but it was apparent that some of the smaller broken chunks would make nice fossil hash plates and were small enough to take home. There were also many brachiopods and other fossils that had broken free of their matrix and were sitting out on the ground waiting to be scooped up. Within quite literally the first two minutes of getting my bearings at this new site, I spotted something interesting on the ground. Before picking it up or even taking photos I brought my wife Tammy over to see if she could spot it as well. Here are the photos of the very first trilobite of the day--only the second fossil I had picked up.

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This little 'roller' trilobite is definitely a Flexicalymene and I assume is likely F. retrorsa. Yes, this was going to be a good day! We continued to search for little Ordocivian treasures and found several nice brachiopod encrusted hash plates that were small enough to take with us. We found several small pieces of straight-shelled celphalopods preserved as internal molds. This one was nice but in too large of a chunk of rock to bother trying to remove.

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After about half an hour of hunting another car pulled up next to where we were parked and a couple got out. Other than if you were having car trouble, the only reason for stopping at this spot would be to hunt fossils so it was nice to see some other people out enjoying the day with similar intentions to us. When we talked with them we found out that they had driven down from New York--more long-distance travelers. I mentioned that we had learned of this location for fossil hunting though a TFF member (Rob Russell) and discovered that she too was on the forum--Mediospirifer, a name I recognized from her posts on the forum. She was on a multi-day fossil hunting trip with her husband and as luck would have it we did get to do some fossil hunting with another TFF member (just not how I had expected it). Always great to meet-up with a kindred spirit from the forum--even if it was totally impromptu.

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We all had the same idea of focusing on the butter shale area with the intention of finding some trilobites. Before long they had also bagged a nice flexi 'roller. I decided to move over to the west side of the road and see what could be found there. Here is a photo from across the road where you can get an idea of the expanse of this site. My wife Tammy appears in the first photo as a small white dot. Mediospirifer and her husband appear as even smaller dots at the same level on the slope but further to the left. This site is so large that despite it being visited by years by fossil hunters, there is no shortage of things to find.

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digit

Here are some in situ photos of the small but whole (top and bottom valve) brachiopods that I found while hunting. The first one Mediospirifer identified for me as being Lepidocyclus capax with the interesting zig zag lines across the shell. I'm not sure of the identity of the other two but I'm sure there is someone on the forum who likely knows.

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digit

Many of the flat semicircular brachiopods that were found mostly on the hash plates seem to be in the genus Strophonema with a distinctive indentation in the middle (see the hash plate photo a couple of posts above). Another very interesting and very flat brachiopod is in the genus Rafinesquina (likely R. ponderosa) that were fun to find and collect. They are thin but have cupped convex and concave sides.

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In addition to the nice variety of brachiopods we also found a few nice horn corals. From what I can find online these are likely Grewingkia canadensis. I found several busted up specimens of this horn coral and some pieces still in matrix but this was the most interesting find. There was a little rivulet of water emerging from a crevice in the slope likely the result of recent rains. Sitting upside down on a flat piece of wet rock was a little horn coral that looked like an ice cream cone that had landed ice cream side down on the sidewalk. When I picked up this little cone it turned out to be one of my nicest horn corals from the day.

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digit

I found some nice ramose bryozoans and some small fragments of the larger Isotelus trilobites but the items we mainly collected were the abundant brachiopods. Here are a few more examples with in situ photos of how they were found.

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We had only found a few tiny crinoid stem fragments earlier in the day and given their apparent rarity, I figured that finding something more interesting like a crinoid calyx was likely not going to happen. After a while Tammy decided to cross the road and hunt over on the west side of the road with me. As we hunted near but not next to each other we would announce anything of interest that we might find. I heard Tammy say that she had found a cluster of crinoid stem pieces. I came over to look and was amazed to see that the area where she was hunting was littered with them. In a few minutes we had picked up dozens of pieces--most a centimeter or less in length.

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EDIT: Online research indicates that these crinoid stems may be from Cincinnaticrinus pentagonus.

Edited by digit

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digit

We continued to hunt along this side of the road as cars and trucks whizzed by below us. Not really a quiet and peaceful collecting area--but a productive one.

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Mediospirifer said they were going to check out a couple of other roadcuts in the area and we asked if we could tag along to see what else might be found in the area. At about 3:30pm we packed up and left the St. Leon roadcut and headed to our next destination--but not before I found my second trilobite of the day. The early score of a nice complete rolled flexi had set my hopes high that we might score a nice collection of these by the time the day was done but nearly 4 hours later I had little else to show in the way of bugs but this little "trilo-butt".

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Edited by digit

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David E.

Happy Birthday digit. Looks like a successful and very fun hunt. Speaking of Chicago pizza, Aurelio's will be our first stop when we get into Chicago in August. The best pizza I have ever had. After we stuff ourselves, we just might have to see if we can find some road cuts to nap....errr look for some fossils in.

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digit

We drove a little way following Mediospirifer to the next site--a very steep roadcut much closer to the road. With barely enough room to park alongside the road and out of traffic, we parked the cars and stared up at the steep slope with rocky areas showing among the vegetation. Tammy decided to hunt the lower part of the slope but I decided to test my mountain goat skills and slowly and carefully pick my way up the slope. With an abundance of caution and a much lower center of gravity I worked my way up the rock face. The fossils didn't seem quite as abundant here but they were definitely there if you searched for them. While looking for any interesting little treasures I came across this little toad hunkered down in a crevice to wait out the heat of the day.

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One of the reasons for stopping at this roadcut was that Mediospirifer had mentioned that a particularly interesting brachiopod called Vindlandostrophia cypha tended to be more common here. After hearing a description of this species I was lucky to find a nice specimen or two while scrambling around the rock face.

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digit

After a short time at this second spot, with Vinlandostrophias in hand, we continued on to a third (and final) site for the day. This site was notable for the overwhelming abundance of a single species of brachiopod--Glyptorthis inculpta. It's a small brachiopod roughly a centimeter or so in width and the ground here was covered with them. We picked up some nice small hash plates loaded with this species and set to work collecting some specimens that were free from the matrix. There were many individual half shells (single valves) but given the density of these it was easy to amass a nice small collection of complete specimens of this charming little species. Mediospirifer was particularly interested in pathological specimens (having collected some here previously). I did find some interesting pathologicals (photos soon) and some specimens with some neatly "drilled" holes in them. Apparently, these are not predation marks but remnants of burrows built in the matrix in which these brachiopods were contained.

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We finally decided at nearly 6pm that it was getting late and we had to wrap it up for the day. Rob's suggestion of heading down to the roadcut at St. Leon--well known by many (and now us too)--was a complete success. In itself, this single destination would have been well worth the effort and drive but the chance meeting of another TFF member with an itinerary of additional fossil hunting locations in the area was highly informative and really made this a day to remember. The trip back was a bit quicker with less stops and slightly lighter traffic. Still, we didn't get back to our waiting comfortable beds till nearly 11pm--a 17 hour epic roadtrip to the Ordovician that was productive, informative, fun and most importantly quite memorable. Thanks to TFF members trips like this can be a reality.

Cheers.

-Ken

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digit

We did also try another small roadcut that Rob Russell mentioned in North Central Illinois. We were forewarned that this one was less extensive and was likely more picked over than the St. Leon roadcut. We were headed out west to have dinner with family and decided to swing by and give this location a brief look to see if it would be a place we might come back to in the future. At only 90 minutes away it is quite a bit closer than the much longer drive to St. Leon.

We found the location with no trouble and got out to inspect the limestone outcrop from this roadcut.

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After a bit of searching I started to find some molds of some small gastropods. These steinkerns mostly seemed to be limited to a narrow horizontal band in the limestone.

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The most interesting thing that we saw were these corrugated looking impressions in the limestone that reminded me of the surface of the hose for my pool vacuum. I'm assuming these might be some sort of traces of a straight-shelled nautiloid but I know so little of the fossils of this locality and of this time period in general that I'm just guessing. Didn't end up collecting anything there (other than a few photos) but it was always fun to go out and see something new with the potential of finding something interesting.

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Cheers.

-Ken

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Pumpkinhead

Happy Birthday :) This reminds me a lot of the Ordovician fossils where I live, except I can never find any of those Flexicalymenes

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digit

I'm enjoying learning about the Ordovician fauna--something we don't really have down here in South Florida. Had TFF existed many decades ago (which would have been difficult without the internet :P) I probably would have learned more about fossils when I was a kid living in the Chicago area. I didn't even know about Mazon Creek back in the day--till remarkably recently, actually. Florida is pretty much Cenozoic (mainly from the Eocene through the near recent Plio-pleistocene). I've had a chance to hunt the Paleozoic--Wheeler Shale trilobites in Utah (Late Cambrian=507 mya) through the Mazon Creek nodules (Carboniferous=~300 mya) and I'm now filling in the gaps by hunting the Southeast Indiana roadcuts (Ordovician=~440 mya). One of these days I'll finally get around to hitting every kid's favorite slice of time--the Mesozoic with its charismatic dinosaurs. Lots of time periods still on my bucket list--but it is good to have a long and diverse bucket list.

It seems my quick Flexicalymenes find was a fluke and likely it would take me another trip or two to pull another nice one from the area. I thought of it as an early birthday present.

Cheers.

-Ken

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jcbshark

Happy bday Ken! Great pics and finds : )

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erose

Great report. Serious envy.

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JohnJ

Happy birthday, Ken. :) Life is too short to Not enjoy the little celebrations along the way.

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Pumpkinhead

A recurring problem for me is my fantastic inability to find trilobites in Ordovician rocks, so its nice to see someone else have success in that area. I too enjoy keeping long and diverse bucket lists.

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digit

Thanks all. Despite the trip to the site being longer than I'd planned, the rest of the day turned out much better than I'd hoped. Running into Mediospirifer was an unplanned bonus for the day. She said she would post some of her finds once she had the time to clean, organize, and photograph her specimens.

I always try to find an excuse to do fossil hunting and a birthday is as good as reason as any other. Actually, I went out fossil hunting for four consecutive days: Friday (southeastern Indiana), Saturday and Sunday (Mazon Creek), and Monday (the smaller roadcut in North Central Illinois) but on my actual birthday (Tuesday) Tammy and I spent the afternoon tooling around Chicago's lakefront and museum campus on Segways. We'd done that several years earlier in Washington, D.C. and had been meaning to ride them again some day. We took my niece with us and her boyfriend and had a great time--though it was quite chilly along the lakefront (mid 60's). Don't laugh at the silly looking safety helmets--they are required.

Cheers.

-Ken

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CBOB

Great trip report Ken! Finding some trilos is always a good day! The campground closing is definitely a bummer. I actually got to go one time this spring before it closed so at least I got a bucket of those nodules. I know the road cut in northern central IL you stopped at. I've had good and bad days there. I've pulled out some nicer big cephalopod stuff there and then days where there's nothing. I have a love/hate relationship with that spot! Haha! Happy late bday and some nice stuff you found on the fossil trip! Good luck back down in fossil Florida land and maybe I'll see you on an upcoming agatized coral hunt.

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TNCollector

This looks like it was a fun trip! Reminds me a lot of the sort of places I fossil hunt around here. Looking forward to seeing what is in those nodules!

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Fossildude19

Excellent report, Ken. Happy Birthday, as well. :)

Thanks for taking us along on your journeys.

These are always the best kind of trip reports.

Regards,

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minnbuckeye

St Leon is a fun place. I have only done it in Winter so other collectors were never seen. Your picture #11 seems to depict a recepticulite on edge.

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sixgill pete

Great report Ken. Looks like you had a splendid time and found some nice fossils.

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ynot

Very nice write up on the trip, makes Me wish I was there!! Nice finds also! And congratulations on the trilobite find!!

Happy birthday to You!!

Tony

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digit

Thanks all. When I get a few moments of free time I'll take photos of some of the pieces I brought back. Lots of individual pieces to sort though and several (heavy) hash plates. Let's just say I've mastered packing suitcases--I topped one off at 50.0 pounds and the other at 49.0.

More pics soon.

Cheers.

-Ken

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