Hydrologic Characteristics of Basin-Fill Aquifers in the Southern San Luis Basin, New Mexico
— P. Drakos, J. Lazarus, B. White, C. Banet, M. Hodgins, J. Riesterer, and J. Sandoval

The Town of Taos and Taos Pueblo conducted a joint deep drilling program to evaluate the productivity and water quality of the Tertiary basin-fill aquifer system underlying the Servilleta Formation. Testing results from a series of municipal, exploratory, subdivision, and domestic wells are also used to characterize hydrologic properties (T, K, K’, and S), and the effect of faults on groundwater flow in shallow and deep basin fill aquifers. The shallow unconfined to leaky-confined alluvial aquifer includes alluvial deposits and the underlying Servilleta Formation (Agua Azul aquifer facies). The deep leaky-confined to confined aquifer includes Tertiary age rift-fill sediments below the Servilleta Formation and is subdivided into the Chama-El Rito and Ojo Caliente aquifer facies. Although faults typically do not act as impermeable boundaries in the shallow alluvial aquifer and groundwater flow in the shallow aquifer is not significantly affected by faults, the Seco fault and several of the Los Cordovas faults act as impermeable boundaries in the deep basin fill aquifer. However, other Los Cordovas faults apparently do not affect groundwater flow in the deep aquifer, suggesting variable cementation along fault planes at depth. The Town Yard fault appears to be a zone of enhanced permeability in the shallow alluvial aquifer, and does not act as an impermeable boundary in the deep basin fill aquifer. Intrabasin faults such as the Seco fault that exhibit significant offset likely cause some compartmentalization of the deep aquifer system.