If you’re a structural geologist or geology student in the midcontinent region, you’ve most likely made the pilgrimage to Van Hise Rock. Located near Rock Springs, Wis., in the Baraboo quartzite range, Van Hise Rock is among the best-known structural geology landmarks in the Midwest.
Van Hise Rock provides spectacular exposure of the nearly vertical to overturned northern limb of the Baraboo syncline. The syncline is Paleoproterozoic in age and is thought to have formed between ~1.7-1.8 Ga.
In the image of Van Hise Rock at the top, you can see vertical beds of pink quartzite (right) and dark phyllite (left). Due to the difference in competency of these two rocks [meaning their level of resistance to erosion and deformation], the quartzite and phyllite develop different patterns of cleavage. The quartzite as a more competent unit forms cleavage perpendicular to the bedding plane, while the phyllite is a less competent unit and forms cleavage that follows the axial plane.
Charles Van Hise, for whom the rock is named, was among the first to study and detail the deformation of the Baraboo region in the late 19th-early 20th century. Using the rocks exposed at this locality, Van Hise was able to determine that the intersection of bedding and axial planar cleavage indicates the fold axis direction, which is now known as Van Hise’s Rule.
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