Geologic units in Fillmore county, Minnesota

Upper Ordovician (Upper Ordovician) at surface, covers 41 % 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 33 % of this area

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

Middle Devonian (Middle Devonian) at surface, covers 12 % of this area

Dolostone, sandy dolostone, limestone, and shale; includes the Chickasaw Shale and Bassett Member of the Little Cedar Formation, and Pinicon Ridge and Spillville Formations.

Middle and Upper Ordovician (Middle and Upper Ordovician) at surface, covers 9 % 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 Cambrian (Upper Cambrian) at surface, covers 4 % 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 0.4 % of this area

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

Middle and Upper Devonian (Middle and Upper Devonian) at surface, covers < 0.1 % of this area

Dolostone, limestone, and shale; Includes the Lithograph City Formation, Coralville Formation, and Hinkle and Eagle Center Members of the Little Cedar Formation.