24 October 2013
Exploring Wind River Canyon’s Great Unconformity in outcrop and hand sample (via GigaPan)
Posted by Callan Bentley
Over the summer, I shot these two GigaPans of the “Great Unconformity” in Wind River Canyon (Owl Creek Mountains), Wyoming:
This week, Team M.A.G.I.C. (by which I mean my student Robin Rohrback-Schiavone) finished up a series of three macro GigaPans of rock samples from the site (made with our one-of-nine-in-the-world GIGAmacro rig by Four Chambers Studio):
In combination, these five images could be used to teach students about the vastness of geologic time. The schist and granite are Archean, part of one of the oldest bits of continental crust in the North American continent, while the overlying Flathead Sandstone is Cambrian in age. I envision an exercise wherein students identify the rocks in question, and then calculate the amount of time missing along the unconformity after using additional information (U/Pb ratios or fossils, for instance) to deduce the age of the various units.
Or the images could be used for other purposes, such as sedimentology. The Flathead is a classic quartz sandstone with beautiful well rounded grains: part of the same Sauk transgression that laid down the Tapeats Sandstone in Arizona and the Weverton Formation in Virginia. A petrologist might want to zoom in on the potassium feldspar in the granite. There, they will find it’s full of great examples of “graphic granite” intergrowths of quartz and feldspar.
Using these images, presented full screen and with no additional information, I’ve put together a small sample exercise on my website. Check it out and let me know what you would add or change to make it more effective. Thanks!