http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
Laramide deformation of the wingate sandstone, Colorado National Monument
During Laramide tectonism, the aeolian Wingate Sandstone was forced folded along the northeast of the Uncompahgre Plateau above faults within the underlying crystalline basement. The internal deformation of the Wingate occurred by the relative translation and rotation of this sandstone across mesoscopically discrete zones of intense deformation: a form of cataclastic flow. The basic form for these zones of localized deformation is the deformation band. Little of no internal deformation of the sandstone occurred between the deformation bands, either mesoscopically or microscopically. The deformation band initiates as a single band: a discrete, usually planar zone (~0.3 mm wide) within which sand grains are progressively comminuted and compacted with increasing offset along the band. The quartz grains within this zone appear to have been comminuted by a process of grain fracture assisted by crystal lattice creep mechanisms. With offset of more than ~0.5 mm additional band segments begin to form along the single band, creating an anastomosing band. In outcrop appearance, the deformation bands are lighter colored and more resistant than the undeformed sandstone. Cohesion of the rock is maintained across these features. Deformation bands usually form as conjugate shearing features, which intersect at an angle of 20° to 40°. The bulk strain resulting from offset along the deformation bands increases linearly with band density. The distribution and density of deformation bands within the Wingate is a function of the relative and absolute amounts of rotation and translation of the basement surface that occurred across the fault zones within the underlying basement materials. The Wingate has an inherent strength anisotropy following cross-beds and cross-bed-set boundaries. Deformation bands parallel these features in the early phases of deformation. However, the deformation bands appear to displacement-harden. Consequently, the initial strength anisotropy of the Wingate is removed by progressive deformation.
Includes bibliographical references (leaves 163-168).