Geologic units in Washington county, Wisconsin

Silurian, undivided (Silurian) at surface, covers 78 % of this area: Silurian, undivided - Dolomite, undivided; includes Cayugan, Niagaran, and Alexandrian series
Lithology: dolostone (dolomite)
Maquoketa Formation (Ordovician) at surface, covers 21 % of this area: Maquoketa Formation - Shale, dolomitic shale and dolomite; includes overlying Neda Formation (age uncertain) consisting of oolitic iron oxides and shale
Lithology: shale; dolostone (dolomite)
Sinnipee Group (Ordovician) at surface, covers 0.4 % of this area: Sinnipee Group - Dolomite with some limestone and shale; includes Galena, Decorah, and Platteville Formations
Lithology: dolostone (dolomite); limestone; shale