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Revisiting the Maquoketa in Northern IL

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Today I decided to revisit a stream exposure of the Upper Ordovician Maquoketa Group in northern IL. I believe these outcrops are all Brainard Shale, which is the second highest member of the Maquoketa in Northern Illinois. The olive-gray shales exposed at the base of the outcrops are packed with Tentaculites, and the few times I've been here I've always searched for those. Today I wanted to explore more of the creek and see what else I could find.


The stream was running pretty fast but wasn't too high, despite all the recent rain.



Shale and dolomite outcrop for quite a distance along the stream, although the water is usually too high to get to many of them.



I probably won't come back until the water level drops quite a bit so I can wade through, the stream isn't super deep.



The stream runs near shops and well-traveled footpaths, so to be respectful I don't hammer here. That makes it a little tough since most rock faces are highly weathered and covered with vegetation, but some nice things can still be found. Water-worn brachiopods are common sights, though rarely worth collecting.



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Tentaculites are fairly common along most of the stream. Often they are fairly worn out, like this one below.



But if you look in recently fallen shale pieces you can find some nice ones. I took this one home.




This one was in a large rock and I didn't bother trying to extract it, but it's a good example of how large they can get here.



Isotelus fragments are very common. I've found a genal spine and hypostome on past trips, but nothing more complete.



Another worn brachiopod.



There are also tons of modern critters. A lot of weird looking bugs that I do not particularly enjoy, but I did see this cute fella today.


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Last time I was here I came across this very large rock face about 20 yards from the stream's edge.



There is a lot of shale to pick through, but there a lot of it seems to be fairly unfossiliferous.



That said, last time I was here I took home a chunk of shale just for kicks and split it open, and found some quite nice brachiopods. The layer they came from is about 2 meters off the ground and can be identified by the plentiful but highly weathered brachiopods on the surface.



I took home a few chunks from this layer to split tomorrow, so we will see if this trip proved fruitful. Regardless, it was nice to get away from home for a bit and poke around.

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Tidgy's Dad

Very nice report with great pictures.:)

Love the Tentaculites. 

Thanks for sharing. 

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Thanks for the report, that snail is adorable!

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I, too, love the Tentaculites :wub:

Beautiful scenery, too!

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Nice scenery indeed, typically paleozoic. Not Jurassic clay, sucking you under:D

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