Major hydrostratigraphic contacts of the Truxton basin and Hualapai Plateau, northwestern Arizona, developed from airborne electromagnetic data

The area surrounding the Grand Canyon has spectacular outcrop exposure in the modern canyon walls, leading to stratigraphic contact delineations that are well constrained near canyons yet poorly constrained where the terrain remains undissected and relatively unexplored by boreholes. An airborne electromagnetic and magnetic survey of the western Hualapai Indian Reservation and surrounding areas was undertaken to support the development of a three-dimensional hydrostratigraphic framework of the Truxton basin and Hualapai Plateau. These data were used to develop models of the resistivity structure with total depths of investigation ranging from 200 meters in the most conductive parts of the Truxton basin to more than 600 meters in the higher resistivity areas underlying the Hualapai Plateau. The modeled resistivity structure was used in conjunction with geologic maps, well lithologic records, and results from gravity models of the depth to bedrock to develop high-resolution regional interpretations of the elevation of the Muav Limestone-Bright Angel Shale contact and the top of the crystalline basement. These contacts are conceptualized to serve as the base of the Paleozoic limestone aquifers primarily underlying the Hualapai Plateau and the Tertiary-Quaternary sedimentary and volcanic aquifers of the Truxton basin, respectively.