Geologic units in Cottonwood county, Minnesota

Undifferentiated (Cenomanian to Campanian) at surface, covers 60 % of this area

Conglomerate, sandstone, mudstone, shale, marlstone, siltstone, and minor lignite, deposited in marine and non-marine settings; likely Cenomanian to Campanian age. Unit outline is the product of contouring the stratigraphic top and base, from which an isopach grid was created. Because the distribution is patchy, unit boundaries were drawn from the gridded data to represent locations where more than 25 feet (8 meters) of thickness occurs. As a result, many areas outside of the unit boundaries may be overlain by thin Cretaceous strata and the unit is depicted without a contact line.

Sioux Quartzite (Paleoproterozoic) at surface, covers 40 % of this area

Quartzite, mudstone, and local conglomerate of fluvial and marine origin (~1,760 to 1,630 Ma; 1,902 ± 55 Ma rhyolite pebble in basal conglomerate).

Granitoid gneiss with dioritic to amphibolitic enclaves (Mesoarchean to Paleoarchean) at surface, covers < 0.1 % of this area

Granitoid gneiss with dioritic to amphibolitic enclaves. Produces moderately high and varied gravity and magnetic signatures.