Date of Award
Master of Science
Terry L. Pavlis
This study provides new insights into the geometry and timing of ductile, syn-metamorphic structures in the central Panamint Mountains of eastern California. The study focused on Surprise Canyon, where exposures of Meso- to Neoproterozoic miogeocline rocks, reworked crystalline basement, and syn-metamorphic granitoids record fabric overprints indicative of at least two distinct dynamo-thermal metamorphic events. Prograde metamorphism at greenschist and amphibolite metamorphic facies conditions occurred during Early Jurassic plutonism based on deformation of a dioritic pluton with a U-Pb date reported here of 175.6 ± 3.2 Ma. Mid Jurassic deformation (D1) generated the main continuous cleavage in the rocks (S1) as well as a strong lineation seen as both crystallographic alignments and object shapes. D1 is associated with numerous mesoscopic isoclinal folds with axes parallel to the sub-horizontal, NNW-ESE trending stretching lineation. Shear sense indicators are locally contradictory, presumably due to younger overprints, but with hints of a top-N sense. D1 demonstrably predates mid-Cretaceous two mica granites dated in previous studies. A second deformational event (D2) folded S1 and S1=S0 layering into upright, sub horizontal, open to tight folds that were the only structure mapped in earlier studies from the 1970’s. D2 is interpreted as a Laramide age event with west-vergent fold systems.
Because of the complexity of the deformation, this study employed a chemostratigraphic analysis of marbles to test assumed correlations of these units with known stratigraphy that show distinctive light stable isotope signatures. This chemostratigraphy methods used in this study generally confirmed previous correlations, however it should be noted the method works best in sections where rock units maintain their primary stratigraphy. This study also hoped to test the hypoThesis that the Harrisburg detachment mapped in the northern Panamint Mountains was present in Surprise Canyon. In Surprise Canyon, however, rocks at the assumed structural level of this detachment are disrupted along a high-angle, brittle fault mapped in previous studies as the Woodpecker fault. Thus, future work needs to address this question along strike where this brittle fault does not disrupt the ductile structure.
Received from ProQuest
Tai Antonia Subia
Subia, Tai Antonia, "Ductile deformation in the Central Panamint Mountains - a multi-disciplinary approach to a multi-dimensional problem." (2019). Open Access Theses & Dissertations. 176.