Geologic units in Polk county, Wisconsin

Additional scientific data in this geographic area

Cambrian, undivided (Cambrian) at surface, covers 70 % of this area

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

Chengwatana Volcanic Group (Middle Proterozoic) at surface, covers 18 % of this area

Gray basalt flows, interflow breccia, tuff, and minor sedimentary rocks

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

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

Clam Falls volcanic sequence (Mesoproterozoic) at surface, covers < 0.1 % of this area

Clam Falls volcanic sequence (~1,102 Ma).

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

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

Upper Cambrian (Upper Cambrian) at surface, covers < 0.1 % 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.

Chengwatana volcanic rocks (Mesoproterozoic) at surface, covers < 0.1 % of this area

Primarily mafic flows.