Groos Quarry Formation

{{Infobox rockunit

| name = Groos Quarry Formation

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| type = Formation

| age = Ordovician

| period = Ordovician

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| region = {{Flag|Michigan}}

| country = {{Flag|United States}}

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| unitof = Trenton Group

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The Groos Quarry Formation is a geologic formation in Michigan. It preserves fossils dating back to the Ordovician period.