Abstract

Northeast flank of the Uncompahgre Plateau. Forced folds developed in a 2-km-thick sequence of sandstones and shales above high-angle basement faults during the Laramide(?) Orogeny. The primary deformational features producing the observed strain within the Wingate are microfaults. Microfaults are conspicuous in outcrop by virtue of a light-colored and relatively resistant gouge zone. Porosity is substantially reduced within and along the boundaries of the gouge zone. Microfaults form in conjugate shear systems; this organized arrangement of low-porosity gouge zones produces a reduction in the permeability of this sandstone, perpendicular to the microfaults, by as much as three orders of magnitude. Deformation by microfaulting is a strain-hardening process.--Modified journal abstract.

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