Longchamp, Benjamin Maxfield2019-08-202019-08-202019-06https://hdl.handle.net/11299/206154University of Minnesota M.S. thesis.June 2019. Major: Earth Sciences. Advisor: Joshua Feinberg. 1 computer file (PDF); vi, 47 pages.Low-angle normal faults (LANFs) have been mapped in metamorphic core complexes (MCCs) throughout western North America, but dip too shallowly for seismic slip according to Andersonian fault mechanics. Debate over the origin of these structures is split between support for models where normal faults initiate at favorable dips and subsequently rotate to low-angle orientations (e.g. rolling hinge model) and belief that field relationships show that LANFs were active at or near their present orientation. Using paleomagnetic data from pseudotachylyte veins I show conclusively for the first time that LANFs in the South Mountains MCC in Arizona failed seismically at low-angles. Additionally, I detail many of the challenges that I faced using pseudotachylyte in a paleomagnetic study, providing a starting point for future workers seeking to recover remanence directions from similar materials.enAARMlow-angle normal faultpaleomagnetismpseudotachylyterock magnetismSouth MountainsThesis or Dissertation