Descriptive logs of exploratory holes drilled during 1952 by the U.S. Geological Survey in Dubuque County, Iowa

The exploratory holes were drilled as part of a larger geologic investigation, the objective of which is to determine in the Dubuque, Iowa, area the probable occurrence of zinc and lead ore stratigraphically lower than that which has been mined.

The primary purpose of the drilling was to supply information required for geologic mapping in upland areas where bedrock exposures are sparse or absent. Where possible, the doles were located also on the extension of known mineralized trends.

Seven holes aggregating 1,687 feet were drilled with cable tools. Descriptive logs, prepared by A. E. Flint and C. E. Brown frog binocular microscope study of cuttings that were recovered from the drilling, are accompanied by assay values of significant mineralized samples. Index maps show hole locations.