Geologic units in Waseca county, Minnesota

Middle and Upper Ordovician (Middle and Upper Ordovician) at surface, covers 49 % of this area

Shale, dolomitic limestone, and sandstone; includes the Decorah Shale of the Galena Group, the Platteville and Glenwood Formations, and the St. Peter Sandstone.

Upper Ordovician (Upper Ordovician) at surface, covers 35 % of this area

Limestone, shaley limestone, and dolostone; includes the Maquoketa Formation, and the Stewartville, Prosser, and Cummingsville Formations of the Galena Group. Also includes limestone and dolostone of the Red River Formation, and sandstone and shale of the Winnipeg Formation in northwest Minnesota.

Lower Ordovician (Lower Ordovician) at surface, covers 16 % of this area

Dolostone, sandy to silty dolostone, and sandstone; includes the Shakopee Formation and Oneota Dolomite of the Prairie du Chien Group.