anyone know where these fossils came from?

[Rh_4m]

Hello,

I’ve recently been starting fossil hunting excursions at the last place I’d ever imagine — a parking lot.

 

Put simply, there’s some piles of rocks near a big store around Champaign, IL, and in them I’ve found fossils.

 

However, the rocks did not come from there, and because I’m anything but an expert geologist, I have no clue what rock I’m working with, what formation they came from, or in general what to expect.

My guess is that it’s Silurian Dolomite but I’d appreciate some secondhand opinions, and nonetheless I’m still unsure of what particular formation the rocks belong to.

 

Here are some of my finds:

A bunch of brachiopods, and what looks like an external mold of a crinoid stem, I'm guessing.

 

 

 

A few more brachiopods i’ve found as well. This is the usual stuff I find, just lots of brachiopods and (I think?) the occasional bivalve.

 

 

 

Oh, there’s also this thing. I’m guessing some weird type of brachiopod but I’m not 100% confident, any IDs would be cool.

 

 

 

Anywho, if y’all can figure out where these come from, is there anything else I can find in that formation/in these rocks?

 

And if so, is there any sort of specific techniques/strategies i can use to know which rocks will bear fossils?

Because some, like the first image, would be chock-full of them, but many would have only one fossil in them, and most wouldn’t have any at all.

(Oh btw, I should note that these are pretty big rocks, like 6-10 cubic inches)

 

Furthermore, are there any rarer fossils i could find (trilobites?? ;-;), and are there ways to find em as well, or is this just gonna be a matter of smashing open rocks till you’re lucky??

 

Oh, and lastly, whatever kind of rock I'm dealing with, it’s very hard. If I want to crack a rock open, I kinda just smash it with my sledgehammer; but I'm not really able to get precise cuts into the rocks with it, so I wonder if maybe there are times when I’ll crack open a rock, think there are no fossils in it, but in reality i just didn’t crack the right part of the rock open.

 

Is there a way to know? Or a way to crack open the rocks more precisely? (I also have two pickaxes and some chisels, but the pickaxes are much worse at working with rocks, and honestly I’m too scared of breaking my hand with the chisel if i miss my hammer).

 

Sorry if this is a lot, and kind of all over the place. I just have a lot of questions and a lot of inexperience.

Thank you so much for any help!

 

 

 

 

 

 

 

[Ludwigia]

I myself am not familiar with the rocks from your area, so hopefully someone will come along who is. But I can tell you that if you google for Champaign geology you can come up with something like this, which describes the geological units in your county. Maybe you could ask the owner of the parking lot where the rock piles come from?

You'd have to do research in order to find fossil bearing localities, but like I said, maybe someon local will chime in. You could also look into joining a rock hound club in your area. As to cracking rocks: Yours look pretty hard, so the simplest solution would be to keep on cracking the bits with a hammer until they are reduced to rubble.

 

[Fossildude19]

11 hours ago, Rh_4m said:

Anywho, if y’all can figure out where these come from, is there anything else I can find in that formation/in these rocks?

 

And if so, is there any sort of specific techniques/strategies i can use to know which rocks will bear fossils?

Because some, like the first image, would be chock-full of them, but many would have only one fossil in them, and most wouldn’t have any at all.

(Oh btw, I should note that these are pretty big rocks, like 6-10 cubic inches)

 

Furthermore, are there any rarer fossils i could find (trilobites?? ;-;), and are there ways to find em as well, or is this just gonna be a matter of smashing open rocks till you’re lucky??

 

Oh, and lastly, whatever kind of rock I'm dealing with, it’s very hard. If I want to crack a rock open, I kinda just smash it with my sledgehammer; but I'm not really able to get precise cuts into the rocks with it, so I wonder if maybe there are times when I’ll crack open a rock, think there are no fossils in it, but in reality i just didn’t crack the right part of the rock open.

 

Is there a way to know? Or a way to crack open the rocks more precisely? (I also have two pickaxes and some chisels, but the pickaxes are much worse at working with rocks, and honestly I’m too scared of breaking my hand with the chisel if i miss my hammer).

 

Sorry if this is a lot, and kind of all over the place. I just have a lot of questions and a lot of inexperience.

Thank you so much for any help!

 

 

Wow. So many questions!

 

Well, first off, I agree, this looks like some sort of silicified dolomite, and possibly Silurian in age.

The fossils, due to the rock type, will most likely be mostly internal casts called Steinkerns, and/or imprints of fossils that will contain more detail.

You can expect to find mostly brachiopods, but bivalves, corals, gastropods, and an occasional trilobite may show up. It really depends on what formation these rocks are from, the age of the Formation, and the recorded fauna of the formation.

 

I agree, that you should ask the proprietor of the parking lot where the rocks are coming from. Usually, they are landscaping rocks or fill from local quarries.

 

The more precise way to pop open rocks is to channel the force of your blows with a chisel. However, you should use gloves, and chisel hand guards if you can.

You have a valid concern for your hands.

As far as a right or wrong way, it depends on the type of stone. With hard dolostones, it is best to use naturally occuring fractures or angles to steady your chisel, and exploit those with the hammer and chisel method.

As to which fossils can be found where, you are at the mercy of the rocks in the parking lot. At locations where there is an outcrop of rock present, sometimes you can narrow down locations to certain areas, or lenses, within the outcrop. But you are at the mercy of the whims of the fossil gods, when picking rocks from float situations, like parking lots or creek beds.  There is no way to tell what is in a rock before breaking it, short of x-raying or cat scanning it. 

 

Oh, and your mystery item looks like the internal cast of a brachiopod, specifically, the beak area.

 

Good luck!

 

 

 

[FossilDAWG]

2 hours ago, Fossildude19 said:

...  The more precise way to pop open rocks is to channel the force of your blows with a chisel. However, you should use gloves, and chisel hand guards if you can.

You have a valid concern for your hands.  ...

 

 

Don't neglect some manner of eye protection as well.  Losing an eye is worse than a broken hand, and both suck.

 

Don

[hemipristis]

10 hours ago, FossilDAWG said:

Don't neglect some manner of eye protection as well.  Losing an eye is worse than a broken hand, and both suck.

 

Don

1000% yes!

[deutscheben]

Howdy! As others have said, determining the exact origin of the rock would require contacting the landowner, which could be tricky in a mixed commercial setting like this, But we can make some fairly safe assumptions based on the type of rock and fossils found in it. As you've said, this appears to be dolomite (or dolostone) from the Silurian, based on the fossils you've found. 

 

Looking at this map of the bedrock geology of Illinois: https://chf.isgs.illinois.edu/maps/statewide/imap14-front.pdf 

We can see that the Silurian bedrock (purple) can be found primarily in the Chicago area as well as a few other spots in the north and south of the state. Chances are, then, that this rock came from one of those locations. And knowing that there are many active quarries in Chicagoland, I would say that is the mostly likely source. These rocks are part of the Niagaran Series, including the Racine, Sugar Run and Joliet formations.  

 

For an excellent guide to the geology and paleontology of these formations (including a list of fossils you might encounter), I would suggest reading the following guidebook put together by the Illinois State Geological Survey: 

 

Guide to the geology of the Kankakee River State Park area, Kankakee County, Illinois https://www.ideals.illinois.edu/items/43094  

 

It can be read online, requested from the library, if you happen to be at UIUC or another university, or purchased directly from the ISGS. 

 

As far as searching for fossils in these rocks, from my personal experience they are very difficult to split, since the rock is so hard and they generally do not have natural planes of weakness to take advantage of. Also, as you mentioned, fossils are generally sparse, so chances of splitting and finding something are slim. As a result, I generally look for already exposed or partially exposed fossils to collect instead. But I do know some people smash them, so as others said above, just be sure to wear all the proper protective gear if you do so.