Mineral Resources On-Line Spatial Data
Mineral Resources > Online Spatial Data > Geology > by state > Iowa Geology
Geologic units in Sac county, Iowa
- Cherokee Group (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Middle [Des Moines]) at surface, covers 16 % of this area
Cyclic deposits with carbonaceous shale, clay, siltstone, with lesser sandstone, and thick coal beds; minor but persistent limestone beds; may include parts of Atoka or Morrow Series.
- Colorado and Dakota Groups (Phanerozoic | Mesozoic | Cretaceous-Early Cretaceous-Middle(?) Cretaceous-Late) at surface, covers 83 % of this area
Sandstone and shale with minor limestone; includes Carlile, Greenhorn, Graneros, and Dakota FMs. Full section present in only the extreme NW part of Iowa; in southern and easternmost areas only Dakota is present.
- Meramec Series (Phanerozoic | Paleozoic | Carboniferous Mississippian-Late) at surface, covers 0.5 % of this area
Ste. Genevieve Limestone- fossiliferous limestone and red and green shale. Approx. thickness 50 ft. St. Louis Limestone- limestone and dolomite, sandstone locally perdominant; locally contains chert. Spergen Formation- sandy micaceous dolomite.