Sandstone with some dolomitic and shaly lenses; coarse - graines to conglomeratic and arkosic at base.
Fine crystalline, silty, cherty dolomite, and oolitic chert with local sandstone beds.
Derby-Doerun Dolomite - alternating thin dolomite, siltstone, and shale; Davis Formation - glauconitic shale with fine - grained sandstone, limestone, and dolomite); Bonneterre Dolomite - dolomite, dolomitic limestone, and limestone; glauconitic in lower part.
Coarse - crystalline cherty dolomite with a basal Gunter Sandstone Member.
St. Louis Limestone, Salem Formation, Warsaw Formation.
Eminence Dolomite - dolomite with some druse - coated chert. Potosi Dolomite - dolomite with abundance of druse - coated chert.
Sandstone, chert and interbedded dolomite
Keokuk Limestone, Burlington Limestone, Elsey Formation, Reeds Spring Formation, Pierson Limestone, Fern Glen Formation.
Alluvium - clay, silt, sand, and gravel.
St. Peter Sandstone, Everton Formation
Decorah Group, Plattin Group
Joachim Dolomite, Dutchtown Formation
Leemon Formation, Maquoketa Group including: (Girardeau Limestone, Orchard Creek Shale, Thebes Sandstone, Cape La Croix Shale), Cape Limestone, Kimmswick Limestone, Noix-Cyrene Limestone, Maquoketa Shale.
Fayetteville Formation, Batesville Formation, Hindville Limestone, Vienna Limestone, Tar Springs Sandstone, Glen Dean Formation, Hardinsburg Formation, Golconda Formation, Cypress Formation, Paint Creek Formation, Yankeetown Sandstone, Renault Formation, Aux Vases Sandstone, Ste. Genevieve Limestone.
Chattanooga Shale, Sylamore Sandstone, Fortune Formation, Holts Summit Sandstone, Snyder Creek Shale, Cedar Valley Limestone, Louisiana Limestone, Saverton Shale, Grassy Creek Shale, Turpin Sandstone, Bushberg Sandstone, Glen Park Limestone, St. Larent Limestone, Beauvais Sandstone, Grand Tower Limestone, Clear Creek Chert, Little Saline Limestone, Grassy Knob Chert, Bailey Formation.
St. Francois Mountains intrusive suite (subvolcanic, alkali granitic ring complexes).
Joliet Limestone, Bowling Green Dolomite, Bryant Knob Formation, Bainbridge Formation, Sexton Creek Limestone.
Kimmswick (Trenton) Limestone and Decorah Formation in southern and western Illinois.
Lower Pope Group (Aux Vases Sandstone through Glen Dean Limestone).
Warsaw Formation and Salem Limestone in western Illinois.
Diabase dikes and sills.
St. Louis Limestone.
Northview Shale, Sedalia Formation, Compton Limestone, Bachelor Formation Chouteau Group, Hannibal Shale, Horton Creek Limestone.
Meppen Limestone, Fern Glen Formation, and Burlington-Keokuk Limestone.