How do the digital maps compare to the original paper geologic maps?

The digitally vectorized geologic quadrangle databases are not a facsimile of the original published paper map. Care has been taken to reproduce the information from the source maps faithfully and accurately (for information about the methods for creating the map database, see A number of differences between the paper and digital maps may be noted.

Nomenclature changes. Some stratigraphic names used on the DVGQs were changed to reflect current usage or to reduce inconsistencies in names used over a region.

Combined units. In some cases, adjacent units from the original map have been combined in the digital version. This was done where the smaller units were not consistently mapped over a region, or because they were very thin.

Subdivided units. Some new stratigraphic units have been added to the digital version of the maps. Wherever possible, these additions were based on marker beds or color breaks present on the original maps.

Edgematching. In order to permit comparison of adjacent maps, edgematching was performed to align features between maps. This resulted in minor adjustments to lines along the borders of quadrangles.