7 August 2015

Friday fold: Yin-Yang at Swift Dam

Posted by Callan Bentley

What is Matt looking at here?


Matt was one of my Rockies students this summer, a geology major at the University of Virginia. Together with another UVA student and students from Mary Washington University and George Mason University, Matt embarked on a mountain-climbing hike during our evening camping at Swift Dam, near Depuyer, Montana. The hikers were treated to an extraordinary sight when they attained the summit:

swiftdam_mtn_pano_smClick to embiggen; perspective is to the south/southeast.

What caught my eye about this perspective was the yin-yang looking structure on the right (west). Let’s zoom in:


I found it quite readily on Google Earth:


It appears to work something like this:


Though I haven’t visited this exact outcrop, I suspect the strata here to be Mississippian-aged carbonates, and the deformation accompanied the Jurassic-to-Cretaceous Sevier Orogeny.