Preliminary Report on Basement Complex Rocks of Iowa

Crystalline basement rock has been encountered in the bottom-hole samples of about 45 wells in Iowa. Fairly detailed studies of the samples from most of these wells have been made. Granite is the predominant rock type thus far encountered, followed by diabase in order of abundance. A summary description of the different kinds of crystalline rocks that have been encountered is presented along with a convenient table listing the pertinent data for each well. An index map showing the location and relationship of these wells one to another is included. Detailed descriptions are available in the open files of the Iowa Geological Survey.