Sioux Quartzite

It was formed by braided river deposits, and its correlative units are thought to possibly define a large sedimentary wedge that once covered the passive margin on the then-southern side of the North American craton.

With the arrival of Europeans, it was heavily quarried for building stone, and was used in many prominent structures in Sioux Falls, South Dakota and shipped to construction sites around the Midwest.

It is a thick stratigraphic unit (~3000 m[2]) that crops out in southwestern Minnesota, southeastern and south-central South Dakota, northwestern Iowa, and a small part of northeastern Nebraska.

[6] and 1640 ± 40 Ma[7] This period in which the Sioux Quartzite and its correlative units were deposited is known as the Baraboo interval, in which high relative sea levels covered a large amount of North America.

[3] It is thought that the Sioux Quartzite and its correlative units are parts of a once-laterally-extensive sedimentary wedge that covered the then-southern passive margin of the North American craton.