http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
Models and observations of faulting and folding in layered rock
To better understand the process of initiation and propagation of thrust faults in layered rock and die role of weak bed-parallel surfaces in the deformation, we mapped wedge faults (WFs) and bed-parallel faults and described their interactions in an outcrop of interbedded sandstones and shales. In the present study, the term WF denotes a thrust fault that cuts a single bed. The slip on one set of WFs is conjugate to die inferred slip on bed-parallel faults and to that on an opposite dipping set of WFs. The rock is strongly deformed at the intersection of two WFs and a WF and a bed-parallel fault. The direction of maximum compression determined from the fault orientation and for a Mohr-Coulomb failure criterion is 1.5° counterclockwise to bedding. The WFs occur in an echelon array across bedding forming thrust fault zones. In single layers, a set of regularly-spaced WFs with a common dip form small duplexes. Dominance of bed-parallel shortening over bed-parallel sliding explains the particular WF configurations. A model that simulates the development of regularly-spaced faults in single layers is an embedded plastic layer which is subjected to combined layer-parallel shortening and shear. The layer is separated from a rigid substrate by an interface along which slip is permitted. The strength of a thin interlayer between the layer and an overlying viscous half space determines the amount of slip permitted there. A perturbation in the form of widely-spaced open cusps in the shape of the upper interface perturbs the flow in the layer. Shear bands extend from the cusps to the lower interface where they reflect upwards. The shear bands are kinematically similar to faults. If the interlayer is weak, the shear bands reflect at the interfaces along the length of the layer. If the interlayer is strong the shear bands stop at the broadly folded upper surface. In layer-parallel shortening the shear bands are symmetric. Superposing a component of shear on the layer interface reorients the shear bands. The shear band dipping opposite to the sense of shear is more strongly developed and intersects the interface at a lower angle than the other. This shear band configuration is similar to that of thrust faults in duplexes.