ORGAN PIPE CACTUS NATIONAL MONUMENT, ARIZONA, ORPI: ASPECTS OF A DIGITAL, REGIONAL GEOLOGIC MAP COMPILATION FOR THE NPS GRE PROGRAM

The National Park Service (NPS) and Northern Arizona University (NAU) have collaborated to produce geologic inventories, as a part of the Geologic Resource Evaluation (GRE) program, for three local National Parks in the past several years. The geologic map for Organ Pipe Cactus National Monument, Arizona (ORPI), still in progress, is the most ambitious of the three, covering more than 4000 km² beyond park boundaries. The map combines five reconnaissance and published geologic maps at varying scales and crosses the international border to Mexico. The large coverage area of this map was chosen to maintain geologic continuity in a politically controversial area with multiple scientific and economic resources. We identify three guiding principles to completing a digital geologic map of this size and vintage. First, the GIS product must accurately reflect published geologic maps, regardless of information which may locally be more comprehensive. Second, where two published maps overlap, the larger scale map should be used to retain detail. Third, formal unit names should be honored and the units simplified appropriately, combining split lithofacies in geologically-complex areas.

One major weakness in the NPS GRE program is that the resources dedicated to the planning and implementation phase are not matched at the project's completion. Our experience shows that project follow-up varies from moderate research involvement to virtually no communication. We suggest the establishment of a post-product meeting with mapping, GRE, and park personnel to review the geologic map, map management issues, and discuss potential further collaboration. Nevertheless, we conclude that the GRE program is a valuable resource for the NPS, partnering academics, and the broader geologic community. First, the GRE program brings together regional experts within the community to create a unified geologic map on one modern topographic base. Second, map products often cover areas where there is no previous published geologic map. Third, GRE grants have enhanced NAU partnerships with park personnel, which, in turn, have created future master's thesis endeavors as well as career paths for NAU graduates. Fourth, geologic maps produced under the GRE program can also be published with state geological surveys, or other geologic map outlets.