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iii
At UCL, I have had a monumental amount of support from three people who
deserve special mention. David Price, Lidunka Vočadlo, and Ian Wood have provided
guidance and support throughout my academic career, no matter how ill-advised my
decisions may have seemed to them. I am grateful to them for their unwavering belief
in me, and I hope that one day I will be in a position to return the favor (apologies for
the U.S. spelling there!).
This project was financially supported in its first year by the UK’s Natural
Environment Research Council. On moving to USC, this funding was relinquished,
and I am indebted to the generosity of the Department of Earth Sciences at USC for
providing matching funds so that I could continue with the same project. Additional
funding came from a Geological Society of America student research grant in 2006.
I would also like to thank the WiSE (Women in Science and Engineering) program at
USC, which has supported me with a Merit Fellowship and an International Travel
Grant that allowed me to attend conferences in London, UK, and Naxos, Greece. WiSE
is a superb resource for female scientists at USC, and is particularly beneficial to female
earth scientists in a discipline traditionally dominated by men.
This project would not have been possible without my field assistants Jackie
Taylor, Erik Frost, Brad Foley, and Geoffrey Pignotta. I am so grateful for their patience,
cheerfulness and resilience in the face of snakes, cactus, impenetrable vegetation, searing
heat, burning sun, oxygen depletion, and various car incidents! I am also indebted to
Ben Roberts and Matt Reece of the Great Basin National Park Service, who provided
Object Description
| Title | Structural and thermobarometric constraints on the exhumation of the northern Snake Range metamorphic core complex, Nevada |
| Author | Cooper, Frances Jacqueline |
| Author email | fcooper@usc.edu; fcooper@usc.edu |
| Degree | Doctor of Philosophy |
| Document type | Dissertation |
| Degree program | Geological Sciences |
| School | College of Letters, Arts and Sciences |
| Date defended/completed | 2008-08-27 |
| Date submitted | 2008 |
| Restricted until | Unrestricted |
| Date published | 2008-10-22 |
| Advisor (committee chair) | Platt, John P. |
| Advisor (committee member) |
Davis, Gregory A. Morrison, Jean Platzman, Ellen Thompson, Mark E. |
| Abstract | Observations from areas of large-scale continental extension, including the Basin and Range Province in western North America, have revealed the presence of regionally subhorizontal normal faults that appear to have exhumed rocks from mid- to lower-crustal levels. These detachment faults separate upper plate rocks extended on arrays of high-angle brittle normal faults from lower plate rocks exhibiting ductile mylonitic stretching and medium- to high-grade metamorphism. The origin and evolution of these detachments has been a matter of debate for decades, and yet a number of issues remain unresolved: (1) the dip of the faults when they were initiated and were active; (2) their penetration depth into the crust; (3) their role in exhuming high-grade metamorphic rocks; and (4) the origin and significance of the mylonitic deformation in their footwalls.; I explored these issues in the footwall to a classic detachment fault -- the northern Snake Range décollement (NSRD) in eastern Nevada -- using a combination of structural geology, geothermobarometry, paleomagnetism, isotope geochronology, and electron backscatter diffraction (EBSD) analysis. Garnet-biotite-muscovite-plagioclase thermobarometry suggests that the footwall to the NSRD experienced late Cretaceous peak metamorphic conditions of 6–8 kbar and 500–650°C, equivalent to a burial depth of ≤ 30 km. Calcite-dolomite thermometry indicates that Tertiary mylonitic deformation occurred under lower temperature conditions of 350–430°C, equivalent to mid-crustal levels. Structural, paleomagnetic, and EBSD data demonstrate that mylonites experienced two phases of shear (top-east and top-west), inconsistent with movement along a single throughgoing normal fault.; I conclude that exhumation of the northern Snake Range footwall was a two-step process. Initial ductile stretching and thinning of the crust exhumed footwall rocks to the middle crust beneath a discontinuity, referred to as the localized-distributed transition (LDT), that separated extension along brittle normal faults above from localized ductile shear zones below. Mylonites formed along the LDT were subsequently captured by a moderately-dipping NSRD that soled into the middle crust. The NSRD, therefore, appears to be a late-stage brittle normal fault that was responsible for only about half the total exhumation of the footwall, and is not directly related to the mylonitic deformation. |
| Keyword | continental extension; extensional tectonics; Basin and Range province; Cordillera; metamorphism; mylonite zone |
| Geographic subject | tectonic features: Snake Range décollement |
| Geographic subject (state) | Nevada |
| Geographic subject (country) | USA |
| Language | English |
| Part of collection | University of Southern California dissertations and theses |
| Publisher (of the original version) | University of Southern California |
| Place of publication (of the original version) | Los Angeles, California |
| Publisher (of the digital version) | University of Southern California. Libraries |
| Provenance | Electronically uploaded by the author |
| Type | texts |
| Legacy record ID | usctheses-m1695 |
| Contributing entity | University of Southern California |
| Rights | Cooper, Frances Jacqueline |
| Repository name | Libraries, University of Southern California |
| Repository address | Los Angeles, California |
| Repository email | cisadmin@lib.usc.edu |
| Filename | etd-Cooper-2458 |
| Archival file | uscthesesreloadpub_Volume40/etd-Cooper-2458.pdf |
Description
| Title | Page 3 |
| Contributing entity | University of Southern California |
| Repository email | cisadmin@lib.usc.edu |
| Full text | iii At UCL, I have had a monumental amount of support from three people who deserve special mention. David Price, Lidunka Vočadlo, and Ian Wood have provided guidance and support throughout my academic career, no matter how ill-advised my decisions may have seemed to them. I am grateful to them for their unwavering belief in me, and I hope that one day I will be in a position to return the favor (apologies for the U.S. spelling there!). This project was financially supported in its first year by the UK’s Natural Environment Research Council. On moving to USC, this funding was relinquished, and I am indebted to the generosity of the Department of Earth Sciences at USC for providing matching funds so that I could continue with the same project. Additional funding came from a Geological Society of America student research grant in 2006. I would also like to thank the WiSE (Women in Science and Engineering) program at USC, which has supported me with a Merit Fellowship and an International Travel Grant that allowed me to attend conferences in London, UK, and Naxos, Greece. WiSE is a superb resource for female scientists at USC, and is particularly beneficial to female earth scientists in a discipline traditionally dominated by men. This project would not have been possible without my field assistants Jackie Taylor, Erik Frost, Brad Foley, and Geoffrey Pignotta. I am so grateful for their patience, cheerfulness and resilience in the face of snakes, cactus, impenetrable vegetation, searing heat, burning sun, oxygen depletion, and various car incidents! I am also indebted to Ben Roberts and Matt Reece of the Great Basin National Park Service, who provided |
