A NEW STATE GEOLOGIC MAP OF IDAHO

This new geologic map of Idaho brings together the extensive mapping and associated research since the previous statewide compilation by John Bond in 1978. The new map was compiled from over 70 sources, starting in 2002 with Idaho State Technology funds (Digital Atlas of Idaho) and NSF support (Digital Geology of Idaho). Map units from these sources were condensed to 74 units statewide and major faults identified. Contacts and faults were compiled at 1:500,000 scale on the U.S. Geological Survey 1978 topographic map, Lambert conformal conic projection, and then scanned and digitized at the Idaho Geological Survey. A decision was then made to show this new geology on a shaded relief base in the final publication, and a 1:750,000-scale shaded relief base derived from a 10 meter digital elevation model (DEM) was crafted. Because of increased detail on the new shaded relief and significant discrepancies in the quality of the bases, it was necessary to re-compile the Quaternary unit boundaries for the entire state on the new shaded relief base. In retrospect, statewide compilation of the surficial units followed by compilation of bedrock units on a pre-constructed high-quality shaded relief base would have simplified the process. The change of scale from 1:500,000 used on the previous map by Bond to 1:750,000 here will make it a smaller map sheet for greater chance of fitting on walls in offices and schoolrooms. Printing costs are also reduced. The map will also show seven cross sections that were drafted at 1:500,000 scale and then scanned, digitized, and eventually printed at 1:750,000 scale. A booklet accompanying the map will contain representative stratigraphic columns for six areas of the state, figures with source information, and references. The next stage will be peer review, and we encourage those who are interested to request the opportunity to make comments.