Geologic units in Houston county, Minnesota

Lower Ordovician (Lower Ordovician) at surface, covers 54 % of this area

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

Upper Cambrian (Upper Cambrian) at surface, covers 22 % of this area

Sandstone, siltstone, shale, and dolostone; includes the Jordan Sandstone and St. Lawrence Formation, and the Mazomanie, Lone Rock, and Davis Formations of the Tunnel City Group.

Middle and Upper Cambrian (Middle and Upper Cambrian) at surface, covers 17 % of this area

Sandstone, siltstone, and shale; includes the Wonewoc Sandstone, Eau Claire Formation, and Mt. Simon Sandstone.

Middle and Upper Ordovician (Middle and Upper Ordovician) at surface, covers 6 % 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 1 % 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.

Cambrian, undivided (Cambrian) at surface, covers 0.3 % of this area

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

Prairie du Chien Group (Ordovician) at surface, covers < 0.1 % of this area

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