Abstract

This study presents a preliminary hydrogeologic column for the Paradox basin in southeastern Utah, focusing attention on the Paleozoic subdivisions. Most information used is from petroleum exploration boreholes in the region and the Gibson Dome No. 1 borehole (GD-1), drilled by Woodward-Clyde Consultants (WCC). The hydrogeologic units in the study area are divided as follows: Alluvial Aquifer, Tertiary Aquifer, Cretaceous Aquitard, Mesozoic Aquifer, Mesozoic Aquitard, Permian Aquifer/Aquitard, Pennsylvanian Aquitard, Lower Paleozoic Aquifer and Lower Paleozoic and Proterozoic confining beds.

Several conclusions concerning the Paleozoic hydrogeologic units were drawn from this study. Preliminary data support subdivision of the Paleozoic section into the units described above. The Permian Aquifer/Aquitard is of the calcium-bicarbonate (Ca-HCO₃) type and is relatively low in TDS, probably representing circulating meteoric ground water and recharge from surface units. Salinity in the lower Paleozoic Aquifer is probably related to salt dissolution. Regionally, there is a downward gradient from the Permian Aquifer/Aquitard to the lower Paleozoic Aquifer; however, a review of the highly variable results from the Pennsylvanian Aquitard and other hydrogeologic units indicates possible local upward gradients. Significant recharge to and discharge from the Pennsylvanian Aquitard and Lower Paleozoic Aquifer do not appear to occur in the study area except possibly where the normal stratigraphic sequence has been disrupted.