Seismotectonic maps in the vicinity of the lower Wabash Valley, Illinois, Indiana, and Kentucky - Digital Spatial Database: Depth to magnetic rocks

The structure of and depth to the floor of the Mississippi Valley and
Rough Creel Grabens and surrounding regions
were interpreted from aeromagnetic data.
This cover contains the depth contours for the region within this
study area and was clipped from the larger cover.
This cover was not plotted in the Wabash Valley map series, but is
included for those users who are interested in comparing the depth
to basement from geologic data (bcontours and bfaults) to the depth
to magnetic rocks (usually basement) from geophysical data.
Depth units in this cover are
kilometers below sea level, whereas depth units in bcontours are in
thousands of feet below sea level.