Platteville Limestone
Paleozoic Stratigraphy of the Upper Midwest, USA
Dates are approximate, and deposition occurred at slightly different times in different areas
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Ordovician
- ::Dubuque Formation (447–446 Ma)
- Wise Lake Formation (449.4–447 Ma)
- Dunleth Formation (452–449.4 Ma)
- Decorah Shale (454–452 Ma)
- Platteville Limestone / Group (455–454 Ma)
- Ancell Group (454–455 Ma)
- Glenwood Shale (~455 Ma)
- St. Peter Sandstone (~459–~455 Ma)
- --- Major Erosional Unconformity ---
- ::--- Major Erosional Unconformity ---
- Everton Dolomite (only in S. Indiana)
- --- Major Erosional Unconformity ---
- Dunleth Formation
- Prarie du Chien Group
- * Shakopee Dolomite
- * New Richmond Sandstone (only in S. Indiana)
- * Oneota Dolomite
- * Dunleth Formation
- * Gunter Sandstone
Cambrian
- ::Jordan Sandstone
- Potosi Dolomite
- Potsdam Supergroup/Potsdam Sandstone Megagroup
- Munising Group
- Davis Formation
- Franconia Formation
- Ironton Sandstone
- Galesville Sandstone
- Eau Claire Formation
- Mount Simon Sandstone
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The Platteville Limestone is the Ordivician limestone formation in the sedimentary sequence characteristic of the upper Midwestern United States. It overlies the thin Glenwood Shale, which overlies the thick Saint Peter Sandstone.[1] It is shot through with dolomitic mottles in an anastomose pattern; this dolotimization occurred after deposition but prior to the development of joints in the rock.[2]
This difficult-to-erode unit forms the cap of Saint Anthony Falls and the Mississippi River bluffs in most of the Twin Cities area.
References
- River Bluffs Homepage, University of Minnesota
- Sloan, R.E., ed., 1987, Middle and Late Ordovician lithostratigraphy and biostratigraphy of the Upper Mississippi Valley: Minnesota Geological Survey Report of Investigations 35, 232 p., University of Minnesota, Minneapolis.