Lucas Formation

{{Short description|Geologic formation in Michigan}}

{{Use dmy dates|date=February 2025}}

{{Infobox rockunit

| name = Lucas Formation

| image = Lucas Dolomite (Middle Devonian; Auglaize Quarry, near Junction, Ohio, USA) 5 (48904937882).jpg

| caption = Lucas Dolomite (Middle Devonian; quarry near Junction, Ohio)

| type = Formation

| age = Middle Devonian

| period = Middle Devonian

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| region = Michigan and Ohio

| country = United States

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| unitof = Detroit River Group

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| underlies = Anderdon Limestone and Dundee Formation

| overlies = Amherstburg Formation

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The Lucas Formation is a geologic formation in U.S. states of Michigan and Ohio. It preserves fossils dating back to the middle Devonian period.