15 July 2011
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.
And there you have it!