What makes these beautiful patterns?

[Steph]

I’m probably getting close to my question limit for today, yet I can’t stop thinking about the pattern on the rocks.  Are they trace fossils or just pretty iron staining? I’m headed back to where I collected these (Crane Hill, AL) tomorrow & it would be nice to be able to explain to my nieces. 

I was thinking about Graptolites, though I can’t match up the patterns to those I see in my books. Google search of pic 1/2 pulls up Stromatolites. 

Pic 3 is the back of pic 1/2

pic 4 includes more examples 

 

Thanks for looking. 

 

Edited June 17, 2022 by Steph
Added location

[FranzBernhard]

46 minutes ago, Steph said:

pretty iron staining?

I am also thinking in that line.

Perhaps some kind of Liesegang Rings (link to wikipedia), at least a similar process?

On the other hand, some pre-existing structures, like burrows or other trace fossils, could also facilitate iron mineral precipitation.

Or a combination?
At least, not stromatolites and not graptolites.

Franz Bernhard

[Steph]

6 hours ago, FranzBernhard said:

I am also thinking in that line.

Perhaps some kind of Liesegang Rings (link to wikipedia), at least a similar process?

On the other hand, some pre-existing structures, like burrows or other trace fossils, could also facilitate iron mineral precipitation.

Or a combination?
At least, not stromatolites and not graptolites.

Franz Bernhard

Very helpful- thank you! 

[Fossildude19]

I think this is just basic mineral staining, rather than Liesegang banding or rings.

[Rockwood]

The bath tub ring argument. 

[JohnJ]

Try to ascertain the geologic formation these pieces came from.  There may be clues in the geologic descriptions.

[Mark Kmiecik]

I see layers and differential weathering.

[Steph]

14 hours ago, FranzBernhard said:

I am also thinking in that line.

Perhaps some kind of Liesegang Rings (link to wikipedia), at least a similar process?

On the other hand, some pre-existing structures, like burrows or other trace fossils, could also facilitate iron mineral precipitation.

Or a combination?
At least, not stromatolites and not graptolites.

Franz Bernhard

 

1 hour ago, JohnJ said:

Try to ascertain the geologic formation these pieces came from.  There may be clues in the geologic descriptions.

Looks like mostly Pottsville Formation. I will see if there is more visual context I can photograph when I get there.