Dubuque Formation

{{confuse|DeBeque Formation}}

{{Infobox rockunit

| name = Dubuque Formation

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| type = Formation

| age = Ordovician

| period = Ordovician

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| region = Illinois, Minnesota

| country = United States

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| underlies = Maquoketa Formation

| overlies = Galena Group

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The Dubuque Formation is a geologic formation in Illinois, Iowa, Wisconsin and Minnesota. It preserves fossils dating back to the Ordovician period.{{cite book |last1=Burr |first1=J. H., Jr. |last2=Swain |first2=F. M. |title=Ostracoda of the Dubuque and Maquoketa Formations of Minnesota and Northern Iowa |date=1965 |publisher=University Of Minnesota |location=Minneapolis |page=1-3 |url=https://conservancy.umn.edu/server/api/core/bitstreams/73ed1728-2844-423c-a1ed-cf8e2ab0c460/content}} It comprises carbonate and argillaceous rocks that are between 35 and 45 feet deep.{{cite journal |last1=Levorson |first1=C. |last2=Gerk |first2=A. |last3=Broadhead |first3=Thomas |title=Stratigraphy of the Dubuque Formation (Upper Ordovician) in Iowa |journal=Proceedings of the Iowa Academy of Science |date=1 January 1979 |volume=86 |issue=2 |pages=57–65 |url=https://scholarworks.uni.edu/pias/vol86/iss2/6/ |access-date=11 June 2025 |issn=0085-2236}}