Geologic units in Phelps county, Missouri

Roubidoux Formation (Early Ordovician-Ibexian Series) at surface, covers 48 % of this area

Sandstone, chert and interbedded dolomite

Gasconade Dolomite (Early Ordovician-Ibexian Series) at surface, covers 21 % of this area

Coarse - crystalline cherty dolomite with a basal Gunter Sandstone Member.

Smithville Dolomite, Powell Dolomite, Cotter Dolomite, Jefferson City Dolomite (Early Ordovician-Ibexian Series) at surface, covers 20 % of this area

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

Pennsylvanian Undifferentiated (Pennsylvanian) at surface, covers 10 % of this area

Pennsylvanian Undifferentiated

Kinderhookian Series (Early Mississippian-Kinderhookian Series) at surface, covers < 0.1 % of this area

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

Devonian System (Late to Early Devonian) at surface, covers < 0.1 % 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.