Jump to content

Recommended Posts

The next few days are fall break for me, so I'm home from school. I decided to take the day today to explore two sites in Northern Illinois. The first is an outcrop of the Upper Ordovician Maquoketa Group in Kendall County, IL. I learned about this site from a recent trip report posted here, and found it after a little detective work. I was hoping to find Tentaculites oswegoensis, a small conical fossil of unknown affinities which is only found in this area.

river.thumb.jpeg.ffe1e29cd6059b3dbbfad51f643300e1.jpeg

 

It only took me a few minutes before I found a few.

IMG_7067.thumb.jpeg.ac3dc4f455f07140dc917a2782ed7a51.jpeg

 

I only stayed for 20 minutes or so, as Tentaculites is really the only well preserved fossil in these exposures. There were some brachiopod and bryozoan fragments, but nothing noteworthy.

IMG_7068.thumb.jpeg.9d9e65fd75112bf99d6b100ec55c26f5.jpeg

  • I found this Informative 12
Link to post
Share on other sites

Next stop was to the LaSalle Limestone Member of the Bond Formation (Pennsylvanian), at a large roadcut near Oglesby, IL. This is quickly becoming my favorite spot to hunt, especially since Pit 11 (Mazon Creek) is closed for the year now.

 

IMG_7047.thumb.jpeg.57fab63f3cab3ab89128c088a785b8df.jpeg

  • I found this Informative 8
Link to post
Share on other sites

The roadcut is rather large, so I decided that instead of moving up and down the scree as I normally do, I would move left to right near the cliff wall to explore sections that I haven't before. I found one area, near the right end of the roadcut, which was really interesting. All the common brachiopods were found there, but they were all completely compressed. Brachiopods that are usually an inch thick were nearly paper thin. I tried collecting a few, but even in paper towels, they crumbled to bits when I opened them up back home. You can see a few scattered ones below. For those who like to visit this site, this area is near the far right end when looking at the roadcut from the street, and can be quickly identified by the large boulders near the top of the scree.

 

IMG_7053.thumb.jpeg.c24c438df4a61420003c85a325bf6990.jpeg

  • I found this Informative 8
Link to post
Share on other sites

Today was definitely the best hunting I've had there so far. The limestone here is quite hard and less weathered rock will have almost no bedding planes. This leaves you to whack at large boulders until they are manageable to carry, and unfortunately this often results in broken fossils. So I made myself take pictures of my best finds before trying to break them out, just in case they shattered. My first spectacular find was this partial trilobite. It's not spectacularly preserved, but trilobites here are rare (this is my first) so I was quite ecstatic. I believe it is Ameura sp. Fortunately, I found this guy on a rock which was easy to carry, so not need to whack it.

IMG_7050.thumb.jpeg.ab1096113f5881353de1bef58a6307a8.jpeg

 

The next great find was this small crusher shark tooth. Possibly Deltodus sp. Unfortunately it was in a very large boulder and broke in two. The break, however, was clean and I recovered both halves, so it should repair nicely.

IMG_7061.thumb.jpeg.ff9bbab7c5a49b98ff00950c0144c753.jpeg

  • I found this Informative 9
Link to post
Share on other sites

The last spectacular find was this partial shark tooth, possibly Petalodus sp. I found this in a rock that was on the border of being too large to carry, but I decided to lug it down so I could more safely cut it down at home.

IMG_7062.thumb.jpeg.4eb61d106923a6f93a6761bfdec8cfb3.jpeg

  • I found this Informative 8
Link to post
Share on other sites

A couple more finds. What looks like a partial shark tooth, need to get it under magnification.

IMG_7070.thumb.jpeg.7b3905b977149c53f39a7570095d8368.jpeg

 

A partial crusher shark tooth.

IMG_7069.thumb.jpeg.7ecd56e1fe98f808410c4b6ff66c5426.jpeg

 

And a few nicer examples of the larger brachiopods I found.

IMG_7071.thumb.jpeg.69681002c99be96fb9922c2fb80dd2c4.jpeg

  • I found this Informative 9
Link to post
Share on other sites

Beautiful Tentaculites and an amazing assortment of Carboniferous goodies - congrats!

  • I found this Informative 1
Link to post
Share on other sites

Glad you got out and found some nice fossils over fall break. Unfortunately, I do not think I will be able to hunt during my fall break but winter break fossiling here I come!

  • I found this Informative 1
Link to post
Share on other sites

Sure is nice to get out again, isn't it? Got some good finds there by the looks of things. Will you show us some of them, particularly the Deltodus, once they're prepped?

  • I found this Informative 1
Link to post
Share on other sites
11 hours ago, Monica said:

Beautiful Tentaculites and an amazing assortment of Carboniferous goodies - congrats!

Thanks!

 

1 hour ago, Trevor said:

Glad you got out and found some nice fossils over fall break. Unfortunately, I do not think I will be able to hunt during my fall break but winter break fossiling here I come!

I’m hoping the snow can wait until at least January this year so I’ll be able to take one more trip over winter break.

 

1 hour ago, Ludwigia said:

Sure is nice to get out again, isn't it? Got some good finds there by the looks of things. Will you show us some of them, particularly the Deltodus, once they're prepped?

It certainly was. It’s only been a month and a half since my last trip, still way too long though! And most certainly, I’m hoping they come out nice. The Deltodus tooth looks like it might be complete which would definitely be a trip maker.

Link to post
Share on other sites

Interesting finds. Good luck on the prep. It might be worth an experiment and dissolve the Maquoketa to look for microfossils.

  • I found this Informative 1
Link to post
Share on other sites

What outstanding finds! You clearly have developed an eye for spotting the shark teeth. I especially like that Deltodus, that color is so nice. I can't wait to see it prepped out. Trilobites are always exciting from that site too. :trilosurprise:

  • I found this Informative 1
Link to post
Share on other sites
DeepTimeIsotopes

Very nice finds!

  • I found this Informative 1
Link to post
Share on other sites

I had a question that popped into my head concerning these sites. Maybe @Nimravis or @deutscheben will have an answer. The large road cut and the one a bit east down the road (the shorter one with both sides of the road exposed that contains a lot of small Composita) have very different appearances. Excuse my lack of geological vocabulary, but the large roadcut has much smoother rock whereas the shorter roadcut seems to be much coarser grained. Are these different units within the Bond Formation?

Link to post
Share on other sites
1 hour ago, connorp said:

I had a question that popped into my head concerning these sites. Maybe @Nimravis or @deutscheben will have an answer. The large road cut and the one a bit east down the road (the shorter one with both sides of the road exposed that contains a lot of small Composita) have very different appearances. Excuse my lack of geological vocabulary, but the large roadcut has much smoother rock whereas the shorter roadcut seems to be much coarser grained. Are these different units within the Bond Formation?

This may be helpful: http://ebeltz.net/fieldtrips/lasalle.html

  • I found this Informative 1
Link to post
Share on other sites

Good question! From the literature, it appears that the La Salle Limestone is not monolithic, but consists of varying limestone and shale layers- so it seems the two different road cuts may be exposing different levels of the limestone. The section exposed on both sides of the road near the bridge is described as "Weathered, highly breciated La Salle Limestone" in the 1996 Illinois State Geological Survey guidebook "Guide to the geology of Buffalo Rock and Matthiessen State Parks area, La Salle County, Illinois" while the Orlando Smith Rd cut is described as "This exposure is near the western limit of the La Salle Limestone, and here the unit is relatively thin and contains several clay beds." You can find the guidebook online at https://www.ideals.illinois.edu/handle/2142/44530 - it is an excellent resource for the geology of the area, including a good stratigraphic column of the La Salle Limestone from a nearby quarry. 

 

Further information on this specific roadcut is available online in the form of papers written by paleontologist Stephen Brusatte- he is now known for his work with dinosaurs, but he grew up in nearby Ottawa and did research in high school and college on the fauna of this site- his paper on chondrichthyans can be found here: 

https://www.researchgate.net/publication/233606122_Pennsylvanian_Late_Carboniferous_chondrichthyans_from_the_LaSalle_Limestone_Member_Bond_Formation_of_Illinois_USA 

and one on brachiopods here:  

https://www.semanticscholar.org/paper/A-Preliminary-Paleoecological-Investigation-of-Late-Brusatte/c538ffdf28b9205178c51c9d8856d3e0be3ae99a 

The second one features a panorama of the roadcut looking strikingly different from its appearance today. (I am writing this from a university computer, so I'm not sure if the full paper is available to the public from both of those sites, but you should be able to access them from your school if not) 

  • I found this Informative 3
Link to post
Share on other sites

Great report and pics, Congratulations on a successful hunt!

  • I found this Informative 1
Link to post
Share on other sites

When I would collect the Lonestar Quarry down the road I never found large brachiopods like I do at this roadcut, in addition I never find the amount of crinoid stems and small horn corals that I found in the quarry.

  • I found this Informative 1
Link to post
Share on other sites

I should be studying for exams but have been too excited to get started on prep... oops. Here are two exciting things. First was a little smooth surface I saw while prepping a larger brachiopod piece, I thought it was a little Composita peeking out. Nope! Looks to be a Ditomopyge glabella. Not sure if there's much else there but we'll see. Very excited to have found both genera of trilobites found at this site in one trip.

 

IMG_7085.thumb.jpg.9d875ca5a88722bb8c04995b60e2748f.jpg

  • I found this Informative 3
Link to post
Share on other sites

Next was a little black fragment, assumed just an indeterminate fish bit.

 

IMG_7057.thumb.JPG.e20e917d3afc269770b2e5fa53bed84c.JPG

 

But I was wrong again (fortunately!).

  • I found this Informative 1
Link to post
Share on other sites

Turned out to be a spectacularly gorgeous shark tooth. Only a partial, but I'm still ecstatic. Not sure on the ID, maybe Peripristis?

 

IMG_7080.thumb.jpg.e912cd2fcec8084c99661a77add03be7.jpg IMG_7081.thumb.jpg.deec5a12fe5ca38bf2a41351001febf9.jpg

  • I found this Informative 4
Link to post
Share on other sites

That is a very cool tooth! I love the color and the unusual stippling pattern. I don't think it is Peripristis, as it does not look like any of the examples I have seen. But I don't know what it is- there are a number of Pennsylvanian genera with a similar low jagged ridge shape, like Chomatodus, or Venustodus... perhaps @Archie or @Elasmohunter or one of our other Carboniferous tooth folks have an idea?

  • I found this Informative 2
Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...