Cambrian Stratigraphic Nomenclature and Ground-Water Prospecting Failures on the Hualapai Plateau, Arizona

ABSTRACT The best potential aquifers underlying the 600 mi 2 Hualapai Plateau of northwestern Arizona are (1) the Cambrian Rampart Cave Member of the Muav Limestone and (2) interbedded Tertiary sedimentary and volcanic rocks that locally fill old canyons on the plateau. These target aquifers have been identified on the basis of spring locations on the flanks of the plateau, primarily along the walls of the Grand Canyon to the north and east. Total ground‐water discharge from springs along the plateau is approximately 4 ft3/sec. To date the largest production from a test well on the plateau is 120 gal/min from Tertiary rocks. The Cambrian rocks have frustrated development in part because of small permeabilities, small recharge (0.1 in/yr minimum), and the fact that the rocks are well drained. The complex stratigraphic nomenclature used to describe the Cambrian rocks in the region has inadvertently contributed to prospecting failures. The Cambrian section is characterized by thick interbedded limestones and shales, with the basal limestone being the principal target aquifer. These relationships have not been adequately conveyed to managers and drillers, with the result that critical test holes have been terminated in shales that overlie the target aquifer. Dry holes have been the result.