Date of Award:

12-2018

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Geosciences

Department name when degree awarded

Geology

Committee Chair(s)

James Evans

Committee

James Evans

Committee

Elizabeth Petrie

Committee

Susanne Jänecke

Abstract

Our current understanding of thrust fault kinematics predicts that thrust faults nucleate on low angle, weak surfaces before they propagate upward and forms a higher angle ramp. While this classic kinematic and geometric model serves well in some settings, it does not fully consider the observations of footwall deformation beneath some thrust faults. We examine an alternative end-member model of thrust fault formation called “ramp-first” fault formation. This model hypothesizes that in mechanically layered rocks, thrust ramps nucleate in the structurally strong units, and that faults can propagate both upward and downward into weaker units forming folds at both fault tips. To explore this model, we integrate traditional structural geology field methods, two dimensional cross section reconstructions, and finite element modeling. Field data and retro-deformable cross sections suggest that thrust faults at the Ketobe Knob, in Utah nucleated in strong layers and propagated upward and downward creating folds in weak layers. These findings support the hypothesis that thrust faults and associated folds at the Ketobe Knob developed in accordance with the ramp-first kinematic model. We can apply this understanding of the mechanics behind thrust fault nucleation and propagation in mechanically layered stratigraphy to a wide range of geological disciplines like structural geology and tectonics, seismology, and petroleum geology. By incorporating our knowledge of lithology into fault models, geologists are more likely to correctly interpret structures with limited data sets

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