Geologic units in Shannon county, Missouri

Roubidoux Formation (Early Ordovician-Ibexian Series) at surface, covers 41 % of this area

Sandstone, chert and interbedded dolomite

Gasconade Dolomite (Early Ordovician-Ibexian Series) at surface, covers 40 % of this area

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

Eminence Dolomite, Potosi Dolomite (Late Cambrian-Croixian Series) at surface, covers 14 % of this area

Eminence Dolomite - dolomite with some druse - coated chert. Potosi Dolomite - dolomite with abundance of druse - coated chert.

Smithville Dolomite, Powell Dolomite, Cotter Dolomite, Jefferson City Dolomite (Early Ordovician-Ibexian Series) at surface, covers 4 % of this area

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

St. Francois mountains volcanic supergroup (Precambrian Y) at surface, covers 1.0 % of this area

Chiefly alkali rhyolitic ash - flow tuffs, lava flows, and bedded tuffs, with minor trachytes.