During the Proterozoic, Wisconsin was on the edge! A tectonic plate collision known as the Mazatzal Orogeny deformed the rocks in what are now south-central Wisconsin. The best exposures of these rocks in the region are found in and around Baraboo, Wisconsin. Here, sedimentary rocks were metamorphosed and deformed during the collision. They are now preserved as lovely pink quartzite rocks and interbedded phyllites that have been folded. The fold is a large (on the order of several kilometers) syncline and what we can see at the individual outcrops are tilted layers and associated cleavage (planar rock features that formed during deformation).
I have studied the rocks around Baraboo with colleagues and students in order to learn about 1) the kinematics of folding, 2) the small scale changes in rock cleavage that occur due to mineralogical variations, and 3) the rheological information contained within natural structures like boudin shape and cleavage refraction.
Hop on the bus to any of the stops below:
Deformed Rocks at Baraboo
Baraboo scenery- this will make you want to visit Wisconsin!
I can’t imagine that you would get tired of looking ar rocks in Baraboo, but here’s what else you can see. Photos taken by me (Dyanna) or Carol Ormand.