28 March 2014

Friday fauxld: the “Not a Box” at Confusion Hill

Posted by Callan Bentley

It’s Friday… that means it’s time for a fold. Let’s try this outcrop at “Confusion Hill” in the Franklin Mountains of West Texas:


See it? Let’s zoom in…


From the shadows to the left of the hammer, trace out the dark green layer… it may make you think of a box fold:


…but it’s not. This is actually a completely planar sedimentary bed, tilted to more or less vertical, and then cut by three differently-oriented outcrop planes:


The intersection of each (differently-oriented) outcrop plane with the (uniform) plane of the dark green bed produces a line of “apparent dip” – these apparent dips, when viewed en masse, produce an impression of a folded layer – a totally false impression.

Beware faux folds!

(And Happy Friday!)