Holy pegmatite, Batman!

By Emily H. G. Cooperdock, PhD 2017

After a much deserved break, our first blog post of the new semester comes from Science Y'all! editor, Emily. Enjoy!

My husband and I made a resolution a couple of years ago to ring in each new year by camping, or hiking, or whatever would take us outside to some beautiful place. This seems an especially important resolution to us as we spend our days holed up in our respective labs and offices trying to finish our graduate degrees. Last year we were freezing our tails up at 5,400 feet in the Chisos Mountains of Big Bend National Park. This year we decided to go big – or you could say – grand, and secured backcountry permits to spend two nights camping in Grand Canyon National Park (GCNP).

The namesake of Monument Canyon, this monument includes the lower section of the Tapeats Sandstone in unconformable contact with the Vishnu Schist.

The winter is my favorite time at GCNP because the tourist traffic is low, and you have no risk of heat stroke while hiking into the canyon. In fact, if you are really lucky (which we were!), there will be snow on the rim, which can give you the perspective of simultaneously viewing snowcapped mountains and a magnificent canyon while hiking along the Tonto platform.

We descended the Bright Angel Trail 4.5 miles and 3800 feet to Indian Gardens, where we caught the Tonto Trail and meandered along that for 10 miles to the west. We spent our first night, New Year’s Eve, at Monument Creek campground, named after a Bryce Canyon-inspired spire sticking a couple hundred feet into the air right in the middle of the canyon.

A view of our campsite at Hermits Creek Campground (tent in the lower left of the photo).

The next night we had a magical campsite at Hermit Creek campground, another 4 miles west along the Tonto Trail. Since it was a short trek, we had the opportunity to take a 1.5 mile spur trail down to the Colorado River at Hermit Rapids. That’s when we happened across what was the most beautiful, massive, billion-plus year old pegmatite. I was in muscovite-glitter heaven, and surrounded by some of the most pronounced mineral cleavages that I’ve ever seen. Where were these specimens when I was TAing Earth Materials? Mica books bigger than my head.

Muscovite madness – massive micas and feldspars in a billion year old pegmatite.

That night, we slept within 50 feet of the Great Unconformity, and the Tapeats Sandstone sheltered us from the rain. The next day we hiked up through 275 million years, and 3740 feet, of sediment deposition. Arriving at the rim, we officially greeted 2017, albeit a day late.