A window into an ancient continent, the Baraboo Range in southern
Wisconsin appears as a small east-west trending patch of orange
about 25 miles (40 km) long. The Baraboos are composed of resistant
Precambrian quartzite
(a metamorphic rock) which
has formed an erosional remnant (called a monadnock after the
isolated New Hampshire mountain), resulting in topographic prominence.
The mountains may have formed as long ago as the late Precambrian.
These formations were buried by Paleozoic
sedimentary strata and
are still being uncovered by the erosion of the softer, overlying
rocks.
