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Mineral Resources > Online Spatial Data > Geology > by state > Iowa Geology

Geologic units in Pottawattamie county, Iowa

Colorado and Dakota Groups (Phanerozoic | Mesozoic | Cretaceous-Early Cretaceous-Middle(?) Cretaceous-Late) at surface, covers 25 % 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.

Lithology: sandstone; shale; limestone

Douglas Group (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Late [Virgil]) at surface, covers 3 % of this area

Cyclic deposits with shale, siltstone and minor thin limestone beds; Lawrence Formation at top and Stranger Formation at base.

Lithology: shale; siltstone; limestone

Shawnee Group (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Late [Virgil]) at surface, covers 12 % of this area

Cyclic deposits with prominent limestone beds and thin shales; Topeka Formation at top and Oread Formation at base.

Lithology: limestone; shale

Lansing Group (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Late [Missouri]) at surface, covers 4 % of this area

Cyclic deposits with thin bedded limestones and interbedded red and green shales; Stranton Limestone at top, Vilsa Shale and Plattsburg Limestone at base.

Lithology: limestone; shale

Kansas City Group (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Late [Missourian]) at surface, covers < 0.1 % of this area

Limestone and shale. Limestone is dark gray to light gray, brownish gray, very thin bedded to massive, argillaceous, fossiliferous; contains very thin layers of chert, pyrite crystals, and small flakes of mica near base. Shale is dark gray to light gray, greenish gray, red, and black; locally slighty sandy, calcareous, carbonaeous, fissile, and fossiliferous. Approx. max thickness 200 ft

Lithology: limestone; shale

Kansas City Group (Phanerozoic | Paleozoic | Carboniferous Pennsylvanian-Late [Missouri]) at surface, covers 55 % of this area

Cyclic deposits with prominent limestone beds, shale; Bonner Springs Shale at top and Hertha Limestone at base.

Lithology: limestone; shale