Intertidal and Associated Deposits of the Prairie du Chien Group (Lower Ordovician) in the Upper Mississippi Valley
The Prairie du Chien Group represents the lowermost Ordovician sequence in the Upper Mississippi Valley. Although rarely are fossils preserved, conodonts in this sequence have been identified as being Tremodocian in age., This sequence of dolomites represents the earliest Paleozoic carbonate deposits in the upper midwest area of the United States. Exposures of the Prairie du Chien form the prominent bluffs along the Mississippi River and adjacent coulees in Minnesota, Iowa, and Wisconsin (Fig. 34-1). Numerous quarries and roadcuts also provide access to these strata.
KeywordsQuartz Sandstone Ancient Carbonate Algal Structure Wisconsin Alumnus Research Foundation Lithic Type
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