Guides for IDing Illinois Glacial Till?

[NWARockhound]

Hello, I have found a good number of marine fossils in an Illinois river near Champaign which was created by glacial runoff.  I was wondering if there was any sort of guide or useful papers for identifying them anyone would recommend, especially since very similar fossils seem to occur throughout the Midwest in other areas that had glaciers.  I'm not so curious about these specimens specifically, just thought it might be nice to post some pictures, although I don't know what the middle one is.  A bryozoan? I would just like to learn a bit more information in general.  Thanks!

 

  

[Harry Pristis]

These are paleozoic corals carried by glaciers from the north, probably from Canada.

[Thomas.Dodson]

Perhaps some Favositid for the middle one you don't know.

 

I'm not aware of any sources dealing with glacial erratics in particular but at least at a generic level such Paleozoic fossils are consistent across wide areas of North America. This, and the patterns of glacial retreat, can explain the simiar fauna. I remember reading such glacial sediments in Illinois are primarily from Michigan, Wisconsin, and Canada. I'm not sure how one would differentiate glacial erratics in Illinois from younger Paleozoic strata remnant material native to Illinois that was carved up or displaced during the last 2 ice ages in Illinois. Whatever the case such corals as Halysites, Favosites, Hexagonaria, and lithostrotionella are pretty common in waterways in Champaign and Vermillion County.

 

This document displays lots of different interglacial drainage patterns glacial sequences for Illinois. It's a pretty good glacial overview of the general area.

https://www2.illinois.gov/dnr/education/Documents/OnlineIntroIllinoisNatRes(5-6).pdf

[Rob Russell]

Illinois geological survey publishes some resources. I’m not sure if they get into glacial erratic corals, however. 

[Bob Saunders]

The first picture is a chain coral, you can soak it in white Vinegar by watching it over a couple weeks. You will need to refresh it and change it but it will remove much of the fill material until you are satisfied.  

[Tetradium]

10 hours ago, Harry Pristis said:

These are paleozoic corals carried by glaciers from the north, probably from Canada.

Look like Devonian and latter age corals. Even though 1st coral can be found in Ordovician but Silurian and Devonian seem to be where hexagonal corals take off. 

[Tetradium]

1 hour ago, Bob Saunders said:

The first picture is a chain coral, you can soak it in white Vinegar by watching it over a couple weeks. You will need to refresh it and change it but it will remove much of the fill material until you are satisfied.  

The chain coral is Aulopora sp. Usually found encrusting hard surface as gastropods, brachiopods, horn corals, etc. Hmmm wikipedia didn't give range of epoch in which it live in, and its relationship to rest of coral tree is unknown. All it said is it went extinct. 

[Harry Pristis]

I guess "North" includes Wisconsin, according to this web-site:

Wisconsin Geological & Natural History Survey » Corals

[NWARockhound]

Thanks y'all! I enjoyed reading more about Illinois glaciation. :)  I only knew a bit about the local area I was collecting in.  The Ozarks where I live have very different geology for sure.  Funnily enough I gave my chain coral a look last night to see if it was silicified or calcified just so I could soak it in vinegar.  Luckily it's silica, so it's due for a soak.  I think I'll look to see if other states have more information on glacial erratics, although I suspect most scientists would choose to study fossils of known origin over these.