The interaction among brittle deformation, fluid flow, and diagenesis is displayed at Valley of Fire, southern Nevada, where diagenetic iron oxide and hydroxide stains provided a visible record of paleofluid flow in Jurassic Aztec Sandstone. Deformation features include deformation bands, joints, and faults composed of deformation bands and sheared joints. Faults formed by shear along joints, formation of splay fractures, and linkage of fault segments. Measurements of fault permeability, combined with numerical permeability upscal-ing, indicate that these faults impede cross-fault fluid flow, with cross-fault permeability reduced by two orders of magnitude relative to the host sandstone, whereas fault-parallel permeability is enhanced by nearly one order of magnitude.

A reconstruction of paleofluid flow in the Aztec Sandstone is based on detailed mapping of multicolored alteration patterns and their cross-cutting relations with brittle structures. These patterns resulted from syndepositional reddening of the eolian sandstone and repeated episodes of dissolution, mobilization, and reprecipita-tion of iron oxide and hydroxide. The distribution of alteration patterns indicates that regional-scale fluid migration pathways were controlled by stratigraphic contacts, thrust faults, and high-angle oblique-slip faults. Outcrop-scale focusing of fluid flow was controlled by structural heterogeneities such as joints, joint-based faults, and deformation bands as well as the sedimentary architecture. The complex interaction of structural heterogeneities with alteration in this exhumed analog of a fractured and faulted sandstone aquifer is consistent with their measured hydraulic properties demonstrating the significance of structural heterogeneities for focused fluid flow in porous sandstone aquifers.