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 firstname.lastname@example.org.
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.
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