Influence of structural stratigraphy in multilayer wrench-fault models /
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| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1991.
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| Subjects: | |
| Online Access: | Link to OAKTrust copy |
| Abstract: | Physically scaled sandbox and analytical viscous-layer models are used to investigate the role of structural stratigraphy on the deformation response of a sedimentary cover consisting of an upper brittle layer and an underlying ductile layer over a discrete basement fault with simple-, convergent-, and divergent-wrench-boundary conditions. In one-layer (sand only) experiments, all three boundary conditions produce a system of faults of that is localized within a narrow zone in the hanging wall. At least three fault orientations occur in the fault system and can be correlated with elements of Riedel fault array. R1-Riedel shears are the most prominent faults in all models, but Y-shears exhibit larger displacements. R1-shears nucleate at the basement fault but curve upward exhibiting a helicoidal geometry in three dimensions; this gives rise to a "flower structure" in cross section. The surface trace of a R1-shear is sinuous and curves towards (s-shaped) or away (z-shaped) from the strike of the basement fault for divergent- and convergent-wrench faults, respectively. With decrease of the ratio of strike-slip to dip-slip motion along the basement fault, the sequence of fault development changes from R1-, P-, and Y-shears to Y-, R1-, and P-shears. In simple- and convergent-wrench models "pressure ridges" develop between the early formed R1-shears, whereas axially aligned, spooned-shaped depressions develop in divergent models with a small ratio of strike-slip to dip-slip motion. The structural low of these depressions is always located at the acute apex of a R1-Y intersection. In two-layer experiments (sand overlying a silicone-putty layer), the zone of faulting widens as the thickness of the ductile layer increases and is 2 to 8 times wider than the zone developed in single-layer models. R1-shears are approximately vertical planar faults that do not merge with the basement fault. Consequently, no flower structure is observed in cross section. In contrast with a single-layer model, the surface trace of R1-shears are longer and trend more obliquely to the strike of the basement fault, and a larger displacement along the basement fault is required to initiate surface faulting. The influence of dip-slip motion on the sequence of fault development is suppressed by the effects of ductile basal layer... |
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| Item Description: | Typescript (photocopy). Vita. "Major subject: Geology." |
| Physical Description: | xv, 187 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references. |