The source geological map used is from "The Geological  Atlas of Texas, Sherman Sheet" - Bureau of Economic Geology, 1967 (revised 1991).  The map was digitally distorted in some spots to align the roads with the more accurate modern map.  Colors used in this map are arbitrary but similar to original map colors.

 Geologic Atlas of Texas - Sherman Sheet descriptive booklet (PDF file - 260k) 
 Dallas County, Texas geological map in PDF form (5.3 meg) - Right Click and "Save Target As"
 Dallas County, Texas geological map in JPG form (6.7 meg) - Right Click and "Save Target As"

[The best way to print the maps is to save each large image to your computer and then open with the default picture viewer.  This should allow you to print each image and fill a standard 8x11 page without any clipping or resizing as may occur if printing from your browser.]