Jordan Sandstone

Jordan Sandstone
Name	Jordan Sandstone
Type	Formation
Period	Cambrian–Ordovician
Primary lithology	Sandstone
Other lithology	Siltstone, Shale, Dolomite
Named for	Jordan, Minnesota
Region	Upper Midwest
Country	United States
Unit of	Mount Simon Group
Underlies	Oneota Formation
Overlies	Eau Claire Formation
Thickness	up to 100 m

Jordan Sandstone The Jordan Sandstone is a widespread geologic formation of the Upper Midwest in the United States, known for its well-sorted, quartz-rich sandstones deposited during the late Cambrian to early Ordovician time. It forms a prominent aquifer and reservoir rock across parts of Minnesota, Wisconsin, Iowa, and Illinois and has been the subject of sedimentological, stratigraphic, and hydrogeological studies by institutions such as the United States Geological Survey and the Minnesota Geological Survey.

Description and Lithology

The formation consists predominantly of massive, fine- to medium-grained, orthoquartzite-like sandstones with high purity comparable to rocks described from the Bromide Formation, Tuscarora Formation, and Aztec Sandstone in other regions. Detrital frameworks contain well-rounded quartz grains with subordinate feldspar and lithic fragments, resembling the textural maturity observed in the Navajo Sandstone and St. Peter Sandstone. Cement minerals are primarily siliceous and secondary carbonate phases similar to diagenetic phases reported from the Dakota Formation and the Ballsport Formation. Bedding ranges from massive sets to planar and trough cross-bedding, with minor interbeds of siltstone and shale akin to strata in the Eau Claire Formation. Authigenic minerals and iron-oxide staining echo diagenesis patterns recorded from the Berea Sandstone and Mancos Shale.

Stratigraphy and Age

Stratigraphically the unit is correlated with parts of the Mount Simon Sandstone and overlain locally by carbonate units such as the Oneota Formation and equivalent Sinnipee Group carbonates. Biostratigraphic and chemostratigraphic ties align the unit with late Cambrian sequences that interfinger with early Ordovician transgressive packages seen in the Tippecanoe Sequence and the Prairie Sequence. Radiometric constraints and detrital zircon studies have been integrated with regional correlations used for the Grand Canyon Supergroup and the Silurian-Devonian sections to refine age models. Stratigraphers from the Iowa Geological Survey and researchers at University of Minnesota have used sequence stratigraphy approaches comparable to analyses of the Williston Basin and the Michigan Basin.

Depositional Environment

Sedimentological evidence indicates deposition in a broad, shallow marine to marginal marine shelf influenced by tidal and storm processes similar to settings inferred for the Zuni Sandstone and the Fountain Formation. Cross-stratification, foresets, and planar bedding patterns reflect aeolian and shallow tidal currents analogous to those documented in the Permian Basin equivalents, while trace fossils and wave-rippled surfaces parallel observations from the Cambrian of Utah and the Sauk Transgression records. Paleocurrent analyses link provenance to the Canadian Shield and ancient highlands comparable to sources of the Erie Formation and the Grenville Province detritus.

Geographic Distribution and Extent

The formation extends across the Upper Midwest and is mapped in Minnesota, Wisconsin, Iowa, Illinois, and parts of North Dakota and South Dakota, with variable thickness that reflects subsidence patterns like those in the Williston Basin and the Illinois Basin. Outcrops are prominent along the Minnesota River Valley near Jordan, Minnesota and in roadcuts along Interstate 35 and other corridors similar to exposures exploited in the Driftless Area and along the Mississippi River bluffs. Subsurface mapping by the USGS and state surveys ties continuity to petroleum and groundwater data used in regional models such as those developed for the Michigan Basin and the Williston Basin.

Paleontology and Fossil Content

Although dominated by clean quartz sandstones, the unit preserves trace fossils and sparse body fossils comparable to low-diversity assemblages reported from the Cambrian deposits of Wisconsin and Minnesota. Ichnofossils include burrows and locomotion traces analogous to those described from the Burgess Shale facies and the Paleozoic shelf settings of the Great Lakes region. Occasional shelly faunas and small trilobite fragments correlate with taxa documented in the Paleozoic sequences of the Cincinnati Arch and the Shawangunk Formation. Palynological and microfossil studies are limited but have been compared with assemblages from the Ediacaran–Cambrian boundary intervals investigated by teams at the Smithsonian Institution and Yale University.

Economic Uses and Resource Significance

The clean, well-sorted sandstones form high-quality aquifers exploited by municipal systems in Minneapolis–Saint Paul area suburbs and rural communities, analogous to groundwater production from the St. Peter Sandstone and Floridan Aquifer. The unit has been used as a source of construction aggregate and silica sand for industrial uses similar to deposits mined in the Waseca Sandstone and Frac-sand fields of western Wisconsin. Regional hydrocarbon exploration by companies and agencies has considered the formation as a potential reservoir analog to reservoirs in the Williston Basin and Michigan Basin, and its mechanical properties are assessed for carbon sequestration studies akin to projects in the Illinois Basin.

History of Study and Naming

The formation was first described and named in classic state geological survey monographs by workers from the Minnesota Geological Survey and early 20th-century geologists affiliated with the United States Geological Survey, paralleling naming histories of units like the St. Peter Sandstone and the Mount Simon Sandstone. Subsequent stratigraphic revisions involved researchers at the University of Minnesota, Iowa State University, University of Wisconsin–Madison, and federal agencies, integrating paleontological, sedimentological, and geophysical data as seen in comparative studies with the Eau Claire Formation and Oneota Formation. Modern work continues through collaborative projects among the USGS, state surveys, and academic institutions investigating its role in regional hydrogeology, sediment provenance, and basin evolution.

Category:Geologic formations of Minnesota Category:Sandstone formations of the United States