Geodatabase of the datasets that represent the three subareas of the Silurian-Devonian aquifer, Illinois, Indiana, Iowa, Kentucky, Michigan, Missouri, Ohio, Tennessee, and Wisconsin
This geodatabase includes spatial datasets that represent the Silurian-Devonian 
aquifers in the States of Illinois, Indiana, Iowa, Kentucky, Michigan, Missouri, Ohio, 
Tennessee, and Wisconsin. Included are: 
(1) polygon extents; datasets that 
represent the aquifer system extent, and the entire extent subdivided …