| Group or Formation |
Period |
Notes |
| Altamont Formation | Carboniferous | |
| Blanding Formation | Silurian | |
| Brainard Formation | Ordovician | |
| Bronson Group/Dennis Formation | Carboniferous | |
| Burlington Limestone | Carboniferous | |
| Cedar Valley Group/Coralville Formation | Devonian | |
| Cedar Valley Group/Linwood Formation | Devonian | |
| Cedar Valley Group/Lithograph City Formation | Devonian | |
| Cedar Valley Group/Little Cedar Formation | Devonian | |
| Cedar Valley Group/Shell Rock Formation | Devonian | |
| Chapin Formation | Carboniferous | |
| Cherokee Group | Carboniferous | |
| Coralville Formation | Devonian | |
| Dakota Formation | Cretaceous | |
| Decorah Shale | Ordovician | |
| Dennis Formation | Carboniferous | |
| Dewey Formation | Carboniferous | |
| Dunleith Formation | Ordovician | |
| English River Formation | Carboniferous | |
| Galena Dolomite | Ordovician | |
| Galena Group/Cummingsville Formation | Ordovician | |
| Galena Group/Decorah shale | Ordovician | |
| Galena Group/Dubuque Formation | Ordovician | |
| Galena Group/Dunleith Formation | Ordovician | |
| Galena Group/Guttenberg Formation | Ordovician | |
| Galena Group/Ion Formation | Ordovician | |
| Galena Group/Spechts Ferry Formation | Ordovician | |
| Galena Group/Wise Lake Formation | Ordovician | |
| Gilmore City Limestone | Carboniferous | |
| Glenwood Formation | Ordovician | |
| Gower Formation | Silurian | |
| Grand Detour Formation | Ordovician | |
| Graneros Shale | Cretaceous | |
| Guttenberg Formation | Ordovician | |
| Hackberry Group/Lime Creek Formation | Devonian | |
| Hampton Formation | Carboniferous | |
| Hopkinton Dolomite | Silurian | |
| Independence Shale | Devonian | |
| Iola Formation | Carboniferous | |
| Ion Formation | Ordovician | |
| Kansas City Group/Swope Formation | Carboniferous | |
| Keokuk Limestone | Carboniferous | |
| LaPorte City Formation | Silurian | |
| Lecompton Formation | Carboniferous | |
| Lime Creek Formation | Devonian | |
| Lost Branch Formation | Carboniferous | |
| Maquoketa Group | Ordovician | |
| Maquoketa Group/Brainard Shale | Ordovician | |
| Maquoketa Group/Fort Atkinson Limestone | Ordovician | |
| Maquoketa Group/Neda Formation | Ordovician | |
| Maquoketa Group/Scales Shale | Ordovician | |
| Marmaton Group/Labette | Carboniferous | |
| Maynes Creek Formation | Carboniferous | |
| McCraney Limestone | Carboniferous | |
| Mifflin Formation | Ordovician | |
| Mosalem Formation | Silurian | |
| Nachusa Formation | Ordovician | |
| North Hill Group/English River | Devonian | |
| Oneota Formation | Ordovician | |
| Pawnee Formation | Carboniferous | |
| Pecatonica Formation | Ordovician | |
| Pella Formation | Carboniferous | |
| Platteville Group/Grand Detour Formation | Ordovician | |
| Platteville Group/Mifflin Formation | Ordovician | |
| Platteville Group/Pecatonica Formation | Ordovician | |
| Platteville Group/Quimbys Mill Formation | Ordovician | |
| Prosser Limestone | Ordovician | |
| Quimbys Mill Formation | Ordovician | |
| Racine Formation | Silurian | |
| Saturday Mountain Formation | Ordovician | |
| Scotch Grove Formation | Silurian | |
| Shawnee Group/Deer Creek Limestone | Carboniferous | |
| Shawnee Group/Kanwaka Formation | Carboniferous | |
| Shawnee Group/Oread Limestone | Carboniferous | |
| Shell Rock Formation | Devonian | |
| Spechts Ferry Formation | Ordovician | |
| Spillville Formation | Devonian | |
| St. Louis Formation | Carboniferous | |
| St. Peter Sandstone | Ordovician | |
| Stanton Formation | Carboniferous | |
| Stewartville Formation | Ordovician | |
| Swope Formation | Carboniferous | |
| Traverse Group/Cedar Valley Formation | Devonian | |
| Wapsipinicon Formation | Devonian | |
| Warsaw Formation | Carboniferous | |
| Wassonville Formation | Carboniferous | |
| Wise Lake Formation | Ordovician | |
| Yellow Springs Group/Sheffield Formation | Devonian | |
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