Geologic units in Dodge county, Wisconsin

Sinnipee Group (Ordovician) at surface, covers 50 % of this area

Dolomite with some limestone and shale; includes Galena, Decorah, and Platteville Formations

Maquoketa Formation (Ordovician) at surface, covers 13 % of this area

Shale, dolomitic shale and dolomite; includes overlying Neda Formation (age uncertain) consisting of oolitic iron oxides and shale

Silurian, undivided (Silurian) at surface, covers 13 % of this area

Dolomite, undivided; includes Cayugan, Niagaran, and Alexandrian series

Prairie du Chien Group (Ordovician) at surface, covers 11 % of this area

Dolomite with some sandstone and shale; includes Shakopee and Oneota Formations

Ancell Group (Ordovician) at surface, covers 10 % of this area

Orthoquartzitic sandstone with minor limestone, shale and conglomerate; includes Glenwood and St. Peter Formations

Cambrian, undivided (Cambrian) at surface, covers 3 % of this area

Sandstone with some dolomite and shale, undivided; includes Trempealeau, Tunnel City, and Elk Mound Formations

Barron Quartzite (Early Proterozoic) at surface, covers 0.7 % of this area

Pink to maroon to light-gray, medium-grained, moderately sorted quartzite. Red argillite (pipestone) interbedded locally. At least 213 m thick