GEOMETRY, MECHANISMS, AND MECHANICS OF DEFORMATION IN A LARAMIDE THRUST SHEET.

摘要

The Washakie thrust system consists of Precambrian-cored anticlines thrusted 8 to 12 km to the southwest along the EA and Black Mountain thrusts. The thrusts dip 20;Theoretical models for deformation near a discrete shear crack and the bending and buckling of a layer above a thrust show that synthetic faults with shallow dips and antithetic faults with steep dips form near a thrust tip. Bending of a layer above a fault results in an asymmetric anticline-syncline pair or monoclinal flexure above reverse faults. A large amount of slip decreases fold asymmetry and decreases fold amplitude. Buckling of the bent layer only slightly modifies the fold shape when free slip at the base of the layer occurs, or when the substrate is much weaker than the layer. Thrusts in the footwall and hanging wall of the EA and Black Mountain thrusts may be sub-parallel synthetic faults, and the steeply dipping reverse faults in the hanging wall may be antithetic secondary faults associated with the underlying thrust.;Precambrian granitic gneisses in the thrust sheets deformed by faulting. Feldspars sustained most of the deformation by slip along cleavage fractures. Quartz fractured and experienced minor amounts of crystal-plastic mechanisms. Fluids aided in the healing of the quartz fractures and the syntectonic alteration of feldspars to phyllosilicates. Foliated cataclasite textures developed at temperatures under 350