Geologic units in Washburn county, Wisconsin

Cambrian, undivided (Cambrian) at surface, covers 62 % of this area: Cambrian, undivided - Sandstone with some dolomite and shale, undivided; includes Trempealeau, Tunnel City, and Elk Mound Formations
Lithology: sandstone; dolostone (dolomite); shale
Copper Harbor Conglomerate (Middle Proterozoic) at surface, covers 14 % of this area: Copper Harbor Conglomerate - Red lithic conglomerate and sandstone; mafic to felsic volcanic flows similar to those of the unnamed formation (unit Yu) are interlayered with the sedimentary rocks.
Lithology: conglomerate; sandstone; basalt
Chengwatana Volcanic Group (Middle Proterozoic) at surface, covers 24 % of this area: Chengwatana Volcanic Group - Gray basalt flows, interflow breccia, tuff, and minor sedimentary rocks
Lithology: basalt
Migmatitic gneiss and amphibolite (Late to Early Archean) (Archean) at surface, covers < 0.1 % of this area: Migmatitic gneiss and amphibolite (Late to Early Archean) - Varied gneisses of mostly unknown age in cores of gneiss domes and fault-bounded uplifts (Archean gneiss terranes). Except for the Watersmeet dome (Late to Early Archean), all dated rocks are Late Archean. Includes granite of Late Archean age that transgresses gneisses and amphibolite.
Lithology: gneiss; amphibolite; granite