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163
Table A2. Continued
Sample Foliation Lineation Thin section
Name Location UTM E UTM N Lithology
Outcrop Float Dip Dip Dir Plunge Plunge Dir Regular Polished
FDe181 Deep Canyon 0746350 4356200 Zm0 X X
FDe182 Deep Canyon 0746350 4356200 Zm1 X 35 296 X
FDe183 Deep Canyon 0746483 4356224 Zm2 X X
FDe184 Deep Canyon 0746483 4356224 Zm2 X X
FDe185 Deep Canyon 0746500 4356350 Zm2 X 40 210 X
FDe186 Deep Canyon 0746880 4357078 Amphibolite? X X
FTBE187 Third Butte East 0731844 4373912 Cpi X X
FTBE188 Third Butte East 0731844 4373912 Cpi X
FTBE189 Third Butte East 0731844 4373912 Cpi X X
FTBE190 Third Butte East 0731844 4373912 Cpi X
FTBE191 Third Butte East 0731844 4373912 Cpi X
FTBE192 Third Butte East 0731844 4373912 Cpi X
FTBE193 Third Butte East 0731844 4373912 Cpi X
FTBE194 Third Butte East 0731844 4373912 Cpi X
FTBE195 Third Butte East 0731844 4373912 Cpi X
FTBE196 Third Butte East 0731677 4373866 Cpm X 21 065 08 134
FGS197 Granite Spring 0723643 4344148 Cpm X 43 103
FGS198 Granite Spring 0723643 4344148 Cpm X 31 118 X
FEM199 Eightmile Canyon 0730439 4362807 Cpm X 36 246 X
FEM200 Eightmile Canyon 0732246 4361645 Cpi X
FEM201 Eightmile Canyon 0732246 4361645 Cpi X
FEM202 Eightmile Canyon 0732246 4361645 Cpi X X
FEM203 Eightmile Canyon 0732246 4361645 Cpi X
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 178 |
| Contributing entity | University of Southern California |
| Repository email | cisadmin@lib.usc.edu |
| Full text | 163 Table A2. Continued Sample Foliation Lineation Thin section Name Location UTM E UTM N Lithology Outcrop Float Dip Dip Dir Plunge Plunge Dir Regular Polished FDe181 Deep Canyon 0746350 4356200 Zm0 X X FDe182 Deep Canyon 0746350 4356200 Zm1 X 35 296 X FDe183 Deep Canyon 0746483 4356224 Zm2 X X FDe184 Deep Canyon 0746483 4356224 Zm2 X X FDe185 Deep Canyon 0746500 4356350 Zm2 X 40 210 X FDe186 Deep Canyon 0746880 4357078 Amphibolite? X X FTBE187 Third Butte East 0731844 4373912 Cpi X X FTBE188 Third Butte East 0731844 4373912 Cpi X FTBE189 Third Butte East 0731844 4373912 Cpi X X FTBE190 Third Butte East 0731844 4373912 Cpi X FTBE191 Third Butte East 0731844 4373912 Cpi X FTBE192 Third Butte East 0731844 4373912 Cpi X FTBE193 Third Butte East 0731844 4373912 Cpi X FTBE194 Third Butte East 0731844 4373912 Cpi X FTBE195 Third Butte East 0731844 4373912 Cpi X FTBE196 Third Butte East 0731677 4373866 Cpm X 21 065 08 134 FGS197 Granite Spring 0723643 4344148 Cpm X 43 103 FGS198 Granite Spring 0723643 4344148 Cpm X 31 118 X FEM199 Eightmile Canyon 0730439 4362807 Cpm X 36 246 X FEM200 Eightmile Canyon 0732246 4361645 Cpi X FEM201 Eightmile Canyon 0732246 4361645 Cpi X FEM202 Eightmile Canyon 0732246 4361645 Cpi X X FEM203 Eightmile Canyon 0732246 4361645 Cpi X |
