Read the first seven pages (labeled pg. 92 &endash; 98) from the following USGS documentation of the NCGMP09 standard. That includes the sections up through "Contents of a Traditional Geological Map".
Skim through pg. 99 &endash; to 104 to get an overview of how they plan to present that same and additional information information in a digital format. Also skim through the figures on pg. 105, 106, and 107, showing the Polygon, Line, and Point layers which may be included, and the type of information in the attribute table for each feature.