Regional underpressuring in Deep Brine Aquifers, Palo Duro Basin, Texas: 2. The effect of Cenozoic basin development

Abstract

The evolution of sedimentary basins, involving uplift, deposition, and erosion causes major changes in basin hydrodynamics and the hydrochemistry of basinal fluids. The role of these geologic processes is examined in the Palo Duro Basin of Texas with the help of a cross‐sectional groundwater flow model employing time‐dependent boundary conditions and a source term representing erosional unloading. Transient simulations of groundwater flow show that uplift and tilting of the basin (10–15 m.y. ago) caused a significant increase in groundwater flow rates. Timing of the erosional events implies that significant underpressuring (head difference between shallow and deep aquifers in excess of 175 m) and change in the groundwater flow pattern occurred within the last 1–2 m.y. as a result of erosional retreat of the Eastern Caprock Escarpment. Modeling also indicates that erosional unloading associated with the retreat of the Caprock Escarpment was ineffective in creating large‐scale underpressuring in the Deep‐Basin Brine aquifer. Only in the vicinity of the escarpment could erosional unloading and the resulting expansion of the underlying aquitard create significant subhydrostatic conditions within the aquitard.