The Lithograph City Formation is a

geologic formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...

Iowa Iowa ( ) is a U.S. state, state in the upper Midwestern United States, Midwestern region of the United States. It borders the Mississippi River to the east and the Missouri River and Big Sioux River to the west; Wisconsin to the northeast, Ill ...

, part of the

Cedar Valley Group The Cedar Valley Group is a geologic group in Iowa and Illinois. It preserves fossils dating back to the Devonian period. See also * List of fossiliferous stratigraphic units in Iowa * List of fossiliferous stratigraphic units in Illinois Th ...

. It preserves

fossils A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

dating back to the

Devonian The Devonian ( ) is a period (geology), geologic period and system (stratigraphy), system of the Paleozoic era (geology), era during the Phanerozoic eon (geology), eon, spanning 60.3 million years from the end of the preceding Silurian per ...

period Period may refer to: Common uses * Period (punctuation) * Era, a length or span of time *Menstruation, commonly referred to as a "period" Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (o ...

. The formation is composed of dolomite and

limestone Limestone is a type of carbonate rock, carbonate sedimentary rock which is the main source of the material Lime (material), lime. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphism (materials science) ...

, with many fossils and

vug A vug, vugh, or vugg () is a small- to medium-sized cavity inside rock. It may be formed through a variety of processes. Most commonly, cracks and fissures opened by tectonic activity ( folding and faulting) are partially filled by quartz, calc ...

s in the lower part, while the upper part contains few fossils. The formation is named after exposures in the former company town of Lithograph City, where quarries were opened to exploit the high-quality

lithographic limestone Lithographic limestone is hard limestone that is sufficiently fine-grained, homogeneous and defect-free to be used for lithography. Geologists use the term "lithographic texture" to refer to a grain size under 1/250 mm. The term "sublitho ...

found in parts of this formation.A. B. Hoen, Discussion of the Requisite Qualities of Lithographic Limestone, with Report on Tests of the Lithographic Stone of Mitchell County, Iowa
Iowa Geological Survey Annual Report, 1902
Des Moines, 1903; pages 339-352.

References

Devonian Iowa Devonian southern paleotemperate deposits {{Devonian-stub