Geology and zinc-lead deposits in the Couler Valley area, Dubuque County, Iowa
Geologic investigations were begun in the Iowa portion of the Wisconsin-Illinois-Iowa zinc-lead district to appraise its potentialities: (1) for zinc ore in strata that elsewhere in the mining district contain large zinc ore bodies and (2) for lead and zinc deposits of the type that were mined extensively in Dubuque County, Iowa, during the 19th century.
Miscellaneous Field Studies Map↗