This dataset contains:
1) geological units that are represented by lines because they are too narrow to represent as polygons at 1:1 000 000 scale;
2)
stratigraphic terminology boundaries that represent the approximate
locations of where the names applied to intervals of strata change.
These commonly correspond to lateral facies changes, which are
gradational.
The data were created in geodatabase format and output for public distribution in shapefile format.
AGS Open File Report 2013-02 presents additional information on data sources related to this dataset.