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| Platteville Limestone |
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| Glenwood Shale |
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| St. Peter Sandstone |
The Platteville Limestone lies beneath the glacial till at the top of the exposed bedrock outcrop. There is a gap in time, called an unconformity, between the glacial till and the first layer of bedrock. This unconformity is due to the glaciation of Minnesota. Glaciers, in effect, erased time and much of the rock between 450Mya and 10kya (millons of years ago and thousands of years ago respectively).
