The Sioux quartzite is a formation made up of hard, flinty beds, of considerable thickness and extent, which are exposed principally along the Sioux River, in southeastern Dakota, southwestern Minnesota and northwestern Iowa. It is of particular interest to Iowans, for the reason it has been usually regarded as the most ancient geological formation occurring within the limits of the state-older than the lead-bearing rocks of northeastern Iowa, and older than the Cambrian sandstones which lie at the base of the Mississippi bluffs in the extreme corner of the state.
Proceedings of the Iowa Academy of Sciences
©1894 Iowa Academy of Science, Inc.
Keyes, Charles Rollin
"Opinions Concerning the Age of the Sioux Quartzite,"
Proceedings of the Iowa Academy of Science, 2(1), 218-222.
Available at: https://scholarworks.uni.edu/pias/vol2/iss1/46