Truth or Consequences, New Mexico, is the site of a known thermal anomaly with free-flowing artesian wells and springs ranging in temperature from 36.7 to 45.6°C. Recently completed electrical resistivity surveys and hydrogeologic studies indicate two specific areas worthy of further evaluation for low to moderate-temperature geothermal potential: one area about 1 km northwest of Truth or Consequences, and the other at the southwestern end of the Mud Springs Mountains. The DC electrical resistivity study consisted of three Schlumberger vertical electric soundings and an extensive roving bipole-dipole survey in the vicinity of the previously mentioned target areas. Three total-field apparent resistivity maps were generated from the data collected during the roving bip le-dipole survey. To demonstrate the effect of lateral heterogeneities in the geothermal reservoir zone, these maps were compared with theoretical total-field maps computed for a one-dimensional layered earth.

Combined electric, hydrologic, and lithologic data indicate that the major thermal aquifer is a fault-bounded block of Pennsylvanian limestone with a major recharge area in the Mud Springs Mountains. This carbonate aquifer is approximately 1 km thick and, locally buried as much as 120 m beneath Quaternary alluvium and the nonthermal piedmont aquifer. Transport of thermal waters from the carbonate aquifer into the Rio Grande flood-plain aquifer occurs along a N60°W-trending reverse fault zone which dips 60°N. Latest movement along this fault zone has tentatively been dated as middle to late Pleistocene. The heat source for the thermal aquifer may be related to early Pleistocene igneous activity.

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