Geologic units in Saint Charles county, Missouri

Holocene series (Quaternary-Holocene Series) at surface, covers 38 % of this area

Alluvium - clay, silt, sand, and gravel.

Osagean Series (Early Mississippian-Osagean Series) at surface, covers 23 % of this area

Keokuk Limestone, Burlington Limestone, Elsey Formation, Reeds Spring Formation, Pierson Limestone, Fern Glen Formation.

Meramecian Series (Late Mississippian-Meramecian Series) at surface, covers 21 % of this area

St. Louis Limestone, Salem Formation, Warsaw Formation.

Undifferentiated (Ordovician rocks) (Ordovician) at surface, covers 7 % of this area

Undifferentiated (Ordovician rocks)

Cherokee Group - Cabaniss Subgroup, Krebs Subgroup (Middle Pennsylvanian-Middle Series-Desmonian Stage) at surface, covers 3 % of this area

Cabaniss Subgroup - cyclic deposits, shale, sandstone, clay and several workable coal beds. Krebs Subgroup - cyclic deposits, sandstone, siltstone, shale, clay and some workable coal beds.

Kinderhookian Series (Early Mississippian-Kinderhookian Series) at surface, covers 3 % of this area

Northview Shale, Sedalia Formation, Compton Limestone, Bachelor Formation Chouteau Group, Hannibal Shale, Horton Creek Limestone.

St. Peter Sandstone, Everton Formation (Middle Ordovician to Early Ordovician) at surface, covers 2 % of this area

St. Peter Sandstone, Everton Formation

Smithville Dolomite, Powell Dolomite, Cotter Dolomite, Jefferson City Dolomite (Early Ordovician-Ibexian Series) at surface, covers 1 % of this area

Fine crystalline, silty, cherty dolomite, and oolitic chert with local sandstone beds.

Devonian System (Late to Early Devonian) at surface, covers 0.4 % of this area

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.

Meppen Limestone, Fern Glen Formation, and Burlington-Keokuk Limestone (Mississippian (Tourniaisian to Visean)) at surface, covers 0.2 % of this area

Meppen Limestone, Fern Glen Formation, and Burlington-Keokuk Limestone.

St. Louis Limestone (Mississippian (Visean)) at surface, covers 0.2 % of this area

St. Louis Limestone.

Warsaw Formation and Salem Limestone (Mississippian (Visean)) at surface, covers < 0.1 % of this area

Warsaw Formation and Salem Limestone in western Illinois.

Ste. Genevieve Limestone (Mississippian (Visean)) at surface, covers < 0.1 % of this area

Ste. Genevieve Limestone.

Glen Park Formation, Hannibal Shale, Chouteau Limestone, McCraney Limestone, Prospect Hill Siltstone, and Starrs Cave Limestone (Mississippian (Tourniaisian)) at surface, covers < 0.1 % of this area

Glen Park Formation, Hannibal Shale, Chouteau Limestone, McCraney Limestone, Prospect Hill Siltstone, and Starrs Cave Limestone.

Silurian System undivided (Silurian (Llandovery to Pridoli)) at surface, covers < 0.1 % of this area

Silurian System undivided, includes Sexton Creek Limestone, St. Clair Limestone, and Moccasin Springs Formation in southern Illinois; includes Wilhelmi Formation, Elwood Dolomite, Kankakee Dolomite, Joliet Dolomite, Sugar Run Dolomite, and Racine Dolomite in northeastern Illinois; includes Mosalem, Tete des Morts, Blanding, Sweeney, Marcus, and Racine Dolomites in northwestern Illinois.

Maquoketa Formation or Group (Upper Ordovician (Stage 6 to Hirnatian)) at surface, covers < 0.1 % of this area

Maquoketa Formation or Group, includes Cape Limestone, Cape La Croix Shale, Thebes Sandstone, Orchard Creek Shale, Girardeau Limestone, and Leemon Formation in southern Illinois; includes Scales Shale, Fort Atkinson Limestone, Brainard Shale, and Neda Formation in northern Illinois; includes Noix Oolite in western Illinois.

Lower Pope Group (Aux Vases Sandstone through Glen Dean Limestone) (Mississippian (Visean)) at surface, covers < 0.1 % of this area

Lower Pope Group (Aux Vases Sandstone through Glen Dean Limestone).