Question about Shale, potentially newer (pleistocene), glacial, or Devonian

[jwestbury]

Hello, NW Indiana here. They were doing some digging and in the sandy glacial deposit ish layers, I was finding some heavier sandstone conglomerates with Devonian era fossils(crinoids, shells etc) , and I also found some shales, they appear to be newer but I’m not 100% sure. Most are pretty flakey, haven’t found anything fossil wise inside (that could indicate a time frame better) but one of them did have a strange triangular shape inside. My question is, is it possible for other rocks to be in this type of shale? And that is just potentially what it is? Is it potentially something else? I broke it in half, (by hand, easily lol) and it’s a pretty well defined almost triangle. Not sure if it’s just a simple rock, or potential for fossil or artifact. Thanks! Jessica 

TLDR- can you find weathered triangular rocks with in shale, or maybe it is just shale forming around itself? Could it possibly be an artifact, fossil? Suggestions and comments are welcome. I’m not having much luck finding a lot about shale when looking online. Thanks! :) 

 

Ps-I should also mention, this was part of a larger, more jagged piece of shale, and I had broke some pieces off around the outside, pretty cleanly, to get this triangle to come out… I’ll put a picture of that in the comments. 

[jwestbury]

There could be more little pieces I’m not sure tho lol 

[ClearLake]

Yes, that looks like a piece of shale that has been weathered.  Given your location, its age could be a lot of things and I don't see any fossils in it to help narrow down an age.  Its undoubtedly older than Pleistocene, just because it looks fairly indurated (hardened) and fissile (splits into layers).  The Mississippian rocks in the subsurface have some good shales but so do other ages.  It looks like it has been out of its original formation for a while and has developed a weathering rind around it so it has probably been moved some distance by the glaciers that covered your area in the Pleistocene.  I believe the shapes and smooth textures you are seeing are just products of natural deposition, diagenesis, and subsequent weathering.

[jwestbury]

18 minutes ago, ClearLake said:

Yes, that looks like a piece of shale that has been weathered.  Given your location, its age could be a lot of things and I don't see any fossils in it to help narrow down an age.  Its undoubtedly older than Pleistocene, just because it looks fairly indurated (hardened) and fissile (splits into layers).  The Mississippian rocks in the subsurface have some good shales but so do other ages.  It looks like it has been out of its original formation for a while and has developed a weathering rind around it so it has probably been moved some distance by the glaciers that covered your area in the Pleistocene.  I believe the shapes and smooth textures you are seeing are just products of natural deposition, diagenesis, and subsequent weathering.

Thank you! I figured as much, but before I just tossed it in my rocks outside, I’d check lol 

[ClearLake]

You were right to crack that one open and see if there was anything interesting inside.  You never know!  And shale chunks are not nearly as common in your area.  Most of the larger rocks left by the glaciers are of much harder material (igneous, metamorphic, or harder sedimentary rocks like limestone) as you can imagine.  Softer rocks just don't withstand very much transportation by moving ice, etc and are generally reduced to the sand/silt/clay that is so common around there.