Geologic curiosity or oddball fossil?

[Micah]

I’ve stumbled across similar pieces of limestone throughout the years, but never have been able to figure out what they are. This piece of whatever it is is by far the largest and I honestly don’t have a clue as to what it is. This and similar finds only ever seem to have grooves or striations around the edges and nothing regular (at least to my perception) on the top or bottom which leads me to think they are probably of a geological origin, but I have never come across anything that matches these oddities... As stated in the tags I found this in a creek (near Auburn, Nebraska) which I know complicated things but other pieces of the same (or at least similar) material were from crushed up Oread limestone (Shawnee Group) from the Plattsmouth member which produces Carboniferous fossils.

Any help would be appreciated!

Curse the attachment size limit!

[Ludwigia]

You're right, it's a particular geological phenomenon often found in limestone formations, but for the life of me I can't remember what it's called

[Fruitbat]

Could you be thinking of 'slickensides' Ludwigia?  I've seen examples of glacial striation that look like that but they're usually on a much grander scale!

 

-Joe

[Micah]

I do believe we have a match! @Fruitbat Thanks for putting me on the right track, I did a bit of looking and it can and does happen on smaller scales as well. Fascinating process!

[Fruitbat]

Always a pleasure to be of assistance, Micah!

 

-Joe

[Micah]

This one is most likely caused be fault shifts as the Humboldt Fault runs right through my area.

[Fruitbat]

That would DO it!  Of course...you have had a couple of glaciers rumble through that area in the past though!

 

Still...I would be more likely to go with 'slickenside' too!

 

-Joe

[TqB]

I think they're stylolites (also spelt styolites) - pressure solution features, which occur on various scales. The mechanism involves mini-slickensiding as one layer sinks down on top of another after some is dissolved away.

 

Like these: http://earthinsightcache.blogspot.co.uk/2010/03/weathered-stylolites-in-silurian.html

 

[westcoast]

I agree. While they do look like slickensides I have found a lot of stylolites that look like this when exposed and weathered.

[Ludwigia]

8 hours ago, TqB said:

I think they're stylolites (also spelt styolites) - pressure solution features, which occur on various scales. The mechanism involves mini-slickensiding as one layer sinks down on top of another after some is dissolved away.

 

Like these: http://earthinsightcache.blogspot.co.uk/2010/03/weathered-stylolites-in-silurian.html

 

 

That's it! That's what I couldn't remember.

 

[Micah]

Huh interesting! I would not be at all surprised if they are stylolites, particularly since that explains why the pattern shows up on all the edges and not just one or two. Thanks again everyone!