2 May 2014

Friday fauxld: Pennsylvanian plant fossil

Posted by Callan Bentley

Have a gander at this:


Given that this is a Friday on Mountain Beltway,  you might expect to see a fold here, and indeed, there’s something wavy and high-contrast running through the center of this sample. But that’s no fold. It’s a fossil plant! A “reed” of some kind, I guess. You can also see a small fern frond in the lower right.

This is a sample of the Pennsylvanian-aged Allegheny Formation, a coal-bearing unit from the lip of the Allegheny Plateau in north-central West Virginia. This is the unit that crops out at the current western terminus of Corridor H. One of the blades of the plant bent (asymmetry suggests dextral kinematics) and split along its fibers, producing little dilational “wrench basins” as the fibers separated, and then the whole thing was buried beneath sand, and the plant fragments became carbon films.

So I guess it is technically folded, but it was folded back when it was still a pliable piece of plant, before lithification, before any tectonic monkey business.

It’s spring here in the Appalachian Mountains, and modern plants are growing like gangbusters. Heavy rain like we had this week washes some of their fragments downstream, to be deposited by floodwaters and make the fossils of the future. Perhaps some of them get torqued a bit as they settle, and make a little botanical fauxld from the Holocene. It’s a little glimpse of the principle of uniformity.

Happy Friday!