15 July 2011
Friday fauxld: liesegang banding at Giant City
Posted by Callan Bentley
Today, the Friday fold is a fake!
Looks like a nice set of asymmetric antiforms and synforms, right? But it ain’t!
It’s naturally wiggly; primary not tectonic.
The photo shows nothing more than differential erosion of hematite that was deposited by groundwater in permeable sandstone. It’s Liesegang banding!
These hematite blobs are in the sandstone at Giant City State Park, south of Carbondale, Illinois. Several are cylindrical in form, presumably reflecting tubular flow patterns in the rock at the time of cementation.
The ironstone deposits can also occur as discrete point loci, resulting in “Moqui marble” or “blueberry” type concretions:
And there you have it!
Fantastic! Perhaps I’ve seen examples of the Moqui Marbles around the Southwest
THAT’S what my sandstone ooid-like samples are! I’ve been wondering about that for over 2 years now.
Once again I’ve learned something new here! Plus you helped me ID a sample in my class that for years was just an example of possible psuedo-fossil but is now a Moqui Marble!!!
[…] And I featured this last example a few weeks back as a Friday “fauxld”: […]
could you help me and tell me if the basalt rocks i have on my site are caused by liesegang banding.
thank you 🙂
No basalt is “caused” by Liesegang banding. But some basalts may exhibit Liesegang banding as a secondary alteration effect.