This Earthcache takes you the beautiful driftless area of
south-western Wisconsin. Because the recent glaciers that created
so much of the state’s topography never covered this area, this
part of the state is devoid of “drift” – the accumulated rock and
soil left behind by retreating glaciers. Therefore, the geology you
experience here is very ancient and dates back to the Cambrian and
Ordovician eras – roughly 440 to 500 millions years ago.
St. Peter Sandstone
The geologic structure you will find at the cache coordinates is a
natural shelter formed of St. Peter sandstone. This Ordovician
sandstone was formed when much older Cambrian sandstone eroded and
was redeposited by wind and water. The quartz that makes up this
particular type of sandstone, also called "Ottawa Sand", is fine to
medium sized, well-rounded grains with frosted surfaces and is so
pure, it has been used in labratory experiments and also to make
glass.
At the shelter, you will notice two layers. The lower layer
which inclines away from you as it goes up was created by wind
dunes which is more easily eroded when exposed. The upper
layer that forms the roof of the shelter is a flat
stratification caused by a shallow sea that later covered the
dunes. Marine worm burrow trace fossils may be spotted in this
layer.
Roadside Geology of Wisconsin
To log this cache, you must complete three tasks:
1. BRING YOUR CAMERA. Take a picture of yourself at the shelter and
post it with your log.
2. Email a description of the shelter comparing the two different
sandstone layers you see here. Describe such things as their
relative heights and differences in appearance. Send your info to
teamlightningbugs@yahoo.com.
3. There is a small sign right in front of the shelter. Find the
Indian artifact pictured on it and tell me what it is in your
email. (Please take some time to also read the signs in the area
that tell how the Native Americans used this place.)
This Earthcache is in a Wisconsin State Park and will require an
annual sticker or day pass to get to. The parking coordinates (N 43
00.855 W 90 06.675) are for the Deer Cove Picnic Area where you
will find a sign and trail leading to the natural shelter. The
trail is short, but fairly steep with some stairs. It is somewhat
sandy with potential obstacles – such as downed limbs – and can be
slippery, especially in winter. For these reasons and because the
area is sensitive to erosion, the WI-DNR has requested that
everyone PLEASE STAY ON THE TRAIL.
The Geocache Notification Form has been submitted to Kathleen
Gruentzel of the Wisconsin DNR. Geocaches placed on Wisconsin
Department of Natural Resources managed lands require permission by
means of a notification form. Please print out a paper copy of the
notification form, fill in all required information, then submit it
to the land manager. The DNR Notification Form and land manager
information can be obtained at:
http://www.wi-geocaching.com/hiding.
Resources:
1. Roadside Geology of Wisconsin by Robert H. Dott, Jr. and
John W. Attig
2. Wikipedia: “St. Peter Sandstone”
3. Governor Dodge State Park Visitor Guide