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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
FHa273 Hampton Creek 0749641 4347819 Zm2 X 10 208 0 Trend ~100
FHa274 Hampton Creek 0749641 4347819 Zm2 X 10 125 10 087
FHa275 Hampton Creek 0751049 4348269 Cpm X X
FHa276 Hampton Creek 0751049 4348269 Cpm X X
FHa277 Hampton Creek 0751049 4348269 Cpm X 22 080 20 096 X
FFM278 Fourmile Canyon 0731776 4355253 Cpi X 13 248 12 286 X
FFM279 Fourmile Canyon 0731776 4355253 Cpi X X
FFM280 Fourmile Canyon 0732239 4355388 Cpm X 17 228 06 304
FFM281 Fourmile Canyon 0732871 4355761 Cpm X 05 272 05 290 X
FFM282 Fourmile Canyon 0733858 4355748 Cpm X 20 210 05 290
FMS283 Mud Spring 0735539 4356652 Limestone X X
FMS284 Mud Spring 0736222 4357116 Cpm X 10 176 0 Trend ~100 X
FCS285 Chalk Springs 0737942 4358091 Cpi X X
FCS286 Chalk Springs 0737942 4358091 Cpm X 10 067 05 100 X
FSm287 Smith Creek 0738272 4357805 Cpi X X
FWC288 Water Canyon 0737614 4356872 Cpm X
FWC289 Water Canyon 0737147 4356784 Cpm X X
FTa290 The Table 0742358 4352337 Cpm X 04 255 03 286 X
FTa291 The Table 0742748 4352196 Cpi X X
FTa292 The Table 0745003 4351584 Zm0 X
FTa293 The Table 0744989 4351584 Cpm X 0 0 Trend ~097 X
FTa294 The Table 0745023 4351452 Cpm X X
FTa295 The Table 0745023 4351452 Cpm X 0 0 Trend ~110 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 182 |
| Contributing entity | University of Southern California |
| Repository email | cisadmin@lib.usc.edu |
| Full text | 167 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 FHa273 Hampton Creek 0749641 4347819 Zm2 X 10 208 0 Trend ~100 FHa274 Hampton Creek 0749641 4347819 Zm2 X 10 125 10 087 FHa275 Hampton Creek 0751049 4348269 Cpm X X FHa276 Hampton Creek 0751049 4348269 Cpm X X FHa277 Hampton Creek 0751049 4348269 Cpm X 22 080 20 096 X FFM278 Fourmile Canyon 0731776 4355253 Cpi X 13 248 12 286 X FFM279 Fourmile Canyon 0731776 4355253 Cpi X X FFM280 Fourmile Canyon 0732239 4355388 Cpm X 17 228 06 304 FFM281 Fourmile Canyon 0732871 4355761 Cpm X 05 272 05 290 X FFM282 Fourmile Canyon 0733858 4355748 Cpm X 20 210 05 290 FMS283 Mud Spring 0735539 4356652 Limestone X X FMS284 Mud Spring 0736222 4357116 Cpm X 10 176 0 Trend ~100 X FCS285 Chalk Springs 0737942 4358091 Cpi X X FCS286 Chalk Springs 0737942 4358091 Cpm X 10 067 05 100 X FSm287 Smith Creek 0738272 4357805 Cpi X X FWC288 Water Canyon 0737614 4356872 Cpm X FWC289 Water Canyon 0737147 4356784 Cpm X X FTa290 The Table 0742358 4352337 Cpm X 04 255 03 286 X FTa291 The Table 0742748 4352196 Cpi X X FTa292 The Table 0745003 4351584 Zm0 X FTa293 The Table 0744989 4351584 Cpm X 0 0 Trend ~097 X FTa294 The Table 0745023 4351452 Cpm X X FTa295 The Table 0745023 4351452 Cpm X 0 0 Trend ~110 X |
