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Time. The
Decorah consists of three members (from bottom to top): Spechts Ferry, Guttenberg, and Ion. The Spechts Ferry member is organic-rich and suggests a large influx of terrigenous sediment during deposition. The Guttenberg is characterized by nodular calcareous beds and contains several
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K-bentonite deposits. The Ion Member, present in the southern
Decorah in Iowa, is characterized by alternating beds of shale and limestone.
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Missouri
Department of Natural Resources, Division of Geology and Land Survey, Report of Investigation Number 73, p. 80
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in the sedimentary sequence that formed from the shallow sea that covered central North
America during
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428:. Minnesota at a Glance: Minnesota Geological Survey: University of Minnesota.
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393:. Cephalopods may also be found in the lower layers of the Decorah Shale.
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345:shale that makes up the lowermost formation in the
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412:Lexicon of Stratigraphic Nomenclature in Missouri,
138:Paleozoic Stratigraphy of the Upper Midwest, USA
424:Mossler, J. and Benson, S., 1995, 1999, 2006,
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45:. The Decorah is gray; above it is the brown
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426:Fossil Collecting in the Twin Cities Area
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553:United States geologic formation stubs
508:Shale formations of the United States
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548:Ordovician System of North America
461:. You can help Knowledge (XXG) by
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450:This article about a specific
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349:. The Decorah lies above the
410:Thompson, Thomas L., 2001,
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457:in the United States is a
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365:Where it crops out in the
41:Decorah Shale exposed in
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538:Ordovician South Dakota
389:, and large numbers of
355:Cummingsville Formation
47:Cummingsville Formation
351:Platteville Limestone
297:Mount Simon Sandstone
189:Platteville Limestone
79:Platteville Formation
543:Ordovician Wisconsin
528:Ordovician Minnesota
369:, especially in the
290:Eau Claire Formation
283:Galesville Sandstone
533:Ordovician Nebraska
523:Ordovician Illinois
513:Ordovician Missouri
273:Franconia Formation
205:St. Peter Sandstone
173:Wise Lake Formation
25:Stratigraphic range
263:Munising Formation
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278:Ironton Sandstone
258:Potsdam Sandstone
238:Shakopee Dolomite
213:Knox Unconformity
167:Dubuque Formation
143:Dates approximate
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233:Everton Dolomite
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381:, horn corals,
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268:Davis Formation
253:Potosi Dolomite
243:Oneota Dolomite
221:Knox Supergroup
149:Maquoketa Group
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353:and below the
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224:(~497-~470 Ma)
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207:(~459–~455 Ma)
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197:Glenwood Shale
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452:stratigraphic
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179:Decorah Shale
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128:United States
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463:expanding it
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347:Galena Group
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191:(455–454 Ma)
181:(454–452 Ma)
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169:(447–446 Ma)
159:(454–446 Ma)
157:Galena Group
151:(446–440 Ma)
114:South Dakota
69:Galena Group
379:brachiopods
371:Twin Cities
502:Categories
397:References
383:gastropods
375:trilobites
359:Ordovician
29:Ordovician
455:formation
391:bryozoans
199:(~455 Ma)
118:Wisconsin
106:Minnesota
65:Underlies
59:Formation
387:crinoids
110:Nebraska
102:Illinois
94:Missouri
85:Location
75:Overlies
124:Country
90:Region
341:is a
459:stub
337:The
98:Iowa
55:Type
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