REFINING AND SEAMLESSLY COMPILING THE NEXT GENERATION OF GRAND CANYON GEOLOGIC MAPS

Despite over 160 years of effort, no detailed seamless geologic map of the entire Grand Canyon region exists, and new findings and field observation warrant new mapping at a range of scales. We are pursuing both simultaneously as we also convert mapping into modern digital formats. Much of this is done with the help of a series of newly developed Python-based GIS scripts.

Truly seamless mapping of the region only exists at the 1:500,000 scale. More detailed mapping is segmented at arbitrary boundaries where map scale, map making methodology, map objectives, and/or unit definitions change. To help merge these disparate maps, we have developed a Python-based GIS tool. It merges maps in the GeMS map standard by harmonizing disparate map units and line types across maps. The tool removes unneeded lines when merging units, while retaining a summary of the original map unit designations that were combined. The tool can be run at any time and allows for the incorporation of new isolated observations such that map compilation and new mapping efforts can proceed simultaneously. Seamless geologic mapping has many uses as it is a framework product that supports understanding about geologic evolution, hazards, and resources. One specific and non-traditional use of the map compilation that we are pursuing is a geologic map-based guide to the geology as observed from the river in the Grand Canyon, which we hope will bring geologic maps and understanding to new communities, such as those on raft trips.

Currently, new mapping efforts are focused within the Grand Canyon 30’ x 60’ quadrangle, which is the center of nine 1:100,000 scale quadrangles covering the entire Grand Canyon region. Future efforts will focus on better mapping Grand Canyon lava dams, where new lidar data is being collected, and incorporating non-digital and legacy mapping into the compilation. These new mapping efforts will be aided by additional field-based investigations, high-resolution lidar-derived base data, and the latest digital mapping techniques (e.g., digitizing in 3D environments with the aid of multi-spectral data). Together, these detailed and regional compilation maps will help improve our understanding of the geology of this iconic landscape.