Preliminary Geologic Maps
The CGS preliminary geologic map series is intended to provide timely access to digital geologic maps being prepared by CGS in cooperation with the U.S. Geological Survey’s National Cooperative Geologic Mapping Program. These maps are in preliminary format and are available as PDF images only.
Maps are prepared based on original geologic mapping and compilation as 1:24,000 scale 7.5-minute quadrangles and 1:100,000 scale 30 x 60 minute quadrangles. Compilation of 30 x 60 minute quadrangles includes all of the detail of included 7.5 minute quadrangles and commonly updates mapping to produce a seamless geologic map of the region. When all aspects of the geologic mapping of a region are compiled and reviewed, the 30 x 60 minute quadrangles are published in CGS’s Regional Geologic Map series. The listing below shows preliminary 7.5 minute quadrangles and 30 x 60 minute quadrangles as well as the 30 x 60 minute quadrangles that have been published as Regional Geologic Maps.
Click on quadrangle name in the list below to view or download the quadrangle. To view, click on the name of the quadrangle to open in Adobe Acrobat. From Acrobat you can download the map by selecting "save as" under the file menu and save to desired location. To download without opening the map, right click on the quadrangle name, and select "save target as" to save the file to the location you wish.
Technical comments can be sent to Marc Delattre:
The following geologic maps have been published as part of the Regional Geologic Map (RGM) series. These maps and other RGM maps can be purchased through the