Cummingsville Formation

{{Short description|Geologic formation in Iowa, United States.}}

{{Infobox rockunit

| name = Cummingsville Formation

| image = Cummingsville Formation Decorah Iowa.jpg

| caption = Cummingsville Formation in Decorah, Iowa. The Cummingsville is the brown upper unit; the Decorah Shale is below.

| type = Formation

| age = Ordovician

| period = Ordovician

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| country = United States

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| overlies = Decorah Shale

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| extent = Iowa and Minnesota

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The Cummingsville Formation is a geologic formation in Iowa and Minnesota. It preserves fossils dating back to the Ordovician period.