[1][2] Named for distinctive outcrops in the Minnesota River Valley near the town of Jordan, it extends throughout the Iowa Shelf and eastward over the Wisconsin Arch and Lincoln anticline into the Michigan Basin.

[4] It is predominantly composed of mature, poorly cemented quartz sandstone, though several distinct facies have been identified on the basis of grain size, feldspathic content, and sedimentary structures.

[6] This porous, poorly cemented stratum is also an important aquifer and a major source of drinking water for people throughout the upper Midwest.

[5] It is also present in the subsurface in many parts of these states, and it has been identified in cores and drill cuttings in Illinois, Missouri, and Michigan as well (though here, it is not found at the surface).

[5] Although it is composed primarily of quartz grains, feldspathic and lithic fragments are present in significant quantities, as are a variety of bioclasts derived from marine invertebrates.

[1] The contact between these units is generally set at the top of the uppermost siltstone bed of the Lodi, where it is overlain by a continuous layer of sandstone.

[15] The massive, well-cemented microbial carbonates of the Oneota Formation generally overlie several meters of sandy shale with calcareous interbeds referred to as Coon Valley or Stockton Hill Member.

[5] Owing to the presence of rare fossils and bioturbated sediments, the Jordan Formation is interpreted as a product of marine depositional environments.

The thickness of the unit, its relatively poor cementation, and its close proximity to major waterways and roadways has made it a lucrative target for mining companies.

[20][21] The coarse grained Jordan Formation is poorly cemented, and it has a low clay content, meaning the unit is highly permeable.