USGS/NPS GEOLOGIC MAPPING OF THE SOUTHWESTERN COLORADO PLATEAU

The geologic framework of Grand Canyon National Park is well known and is the nucleus for expanded geologic mapping to areas surrounding the Grand Canyon and Lake Mead. This framework is represented on several geologic maps of various details and scales within and near four national parks of northwestern Arizona. Much of the area surrounding the Grand Canyon is not adequately mapped to support resource management decisions. The goal of the cooperative U.S. Geological Survey/National Park Service (USGS/NPS) geologic mapping project is to produce several 1:100,000-scale digital geologic maps of this region to provide connectivity for the regional geological framework of the southwestern Colorado Plateau and eastern Great Basin provinces. The database maps lend critical support for ecological studies involving hydrologic, biologic, and environmental resources of this unique region. The maps will also provide baseline data for documenting resource management decisions for national parks and monuments of northwestern Arizona as well as the Bureau of Land Management, Bureau of Indian Affairs, National Forest Service, State of Arizona, local communities, and private lands where immediate and future environmental impacts and conservation mitigation measures are needed. Completion of the maps will provide a significant GIS scientific database to support interpretative hydrological hypotheses for conceptual ground water models and regional surface-water and ground water flow systems by enhancing the stratigraphic and structural information where such detailed information is currently lacking or non-existent. NPS and USFS biologists have drawn correlations between geology and the distribution of the Mexican Spotted Owl habitat and some rare cacti. The maps completed thus far are currently being used to address two critical resource management questions: (1) where are the areas of highest probability for locating threatened or endangered plant and animal species? and (2) how might increased ground-water development adjacent to the Grand Canyon affect the surface and spring flows within Grand Canyon?