13 March 2020
Hi everyone, and greetings from eastern California’s Death Valley, where I’m leading a field geology course over our spring break.
I found an excellent Friday fold for you:
That’s the Cambrian-aged Bonanza King Formation, a package of limestones, as exposed in lower Titus Canyon, Death Valley National Park.
Here’s the thing: the lower part of that outcrop is Upper Bonanza King Formation, while the upper part of the cliff is Lower Bonanza King Formation… The stratigraphic sequence, in other words, has been inverted.
These beds are upside-down. They are part of the large-scale Corkscrew syncline, a recumbent fold. This is is its overturned limb.
Which means that thing on the left which looks like an anticline, is really an upside-down syncline. It’s antiformal, but really it’s a syncline, with the youngest rock in the middle, and the oldest rock on its flanks. Similarly, the fold at right looks like a syncline, but once we understand the strata have been flipped over, we recognize it to be an anticline, with the oldest layers in the middle.
So we have a synformal anticline and an antiformal syncline, side by side and utterly upside down.
Bonkers. The power of tectonics made manifest.
Happy Friday! I hope you’re healthy and neither dying of COVID-19 nor transmitting it to someone who will transmit it to someone who will die of it.
Wash your hands, eh?