At Elephant's Cave at the north end of the East Bluff trail you will find
"Elephant's Cave." The Baraboo Quartzite represents events in the Proterozioc
Eon, culminating at about 1.65 billion years ago with the metamorphosis of
the quartzite and folding and uplift of the Baraboo syncline and other folds
in the region. This uplift laid the unvegetated landscape bare to the forces
of erosion, and there ensued roughly 1 billion years of erosion. In south
central Wisconsin only the Baraboo syncline survived this period intact.
The erosion of this time is represented by an uneven, ancient landscape surface
referred to as an "unconformity" (see image). An erosional
channel can be seen on this surface at this site.
This period of erosion ended with much of the continent being flooded by
the sea in the Paleozoic Era (starting in the Cambrian Period). Coastal erosion
and deposition ensued. The conglomerate at this site (see image) was deposited
around the Baraboo Hills at this time. It contains large boulders of quartzite
that had been eroded from adjacent cliffs at this time. One of these boulders
sits in a channel on the unconformity. Click on the conglomerate for a
closer view.
Around 350 million years ago the seas receded from Wisconsin, and the present
period of erosion began. Much of the Paleozoic rock cover has been removed
from the quartzite, and the hills see the light of day once again. However,
remnants of the Paleozoic cover can bee seen here (the conglomerate) and
elsewhere around the region.