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168
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
Zm01 Hampton Creek 0752075 4347644 Zm0 X X X
Zm02 Hendry'sCreek 0752626 4343615 Zm0 X 04 022 X
Zm03 Hendry'sCreek 0752626 4343615 Zm0 X 15 111
Zm04 Hendry'sCreek 0752626 4343615 Zm0 X 18 126
Zm05 Deep Canyon 0746655 4356885 Zm0 X X X
Zm07 Hampton Creek 0750982 4348189 Zm0 X 04 214 X
Zm08 Hampton Creek 0750982 4348189 Zm0 X 04 174 X X
Zm0/1 Deep Canyon 0746736 4357057 Zm0/Zm1? X X
Zm14 Deep Canyon 0746529 4356516 Zm1 X 21 070 09 126 X
Zm15 Deep Canyon 0746529 4356350 Zm1 X 09 051 02 120 X
Zm21 Hampton Creek 0749609 4347966 Zm2 X X
Zm22 Hampton Creek 0749392 4348036 Zm2 X X
Zm23 Hampton Creek 0749985 4347777 Zm2 X 06 223 X
Zm24 Hendry'sCreek 0752213 4344206 Zm2 X 29 282 14 120 X
Zm26 Hendry'sCreek 0744323 4346829 Zm2 X X X
Zm27 Hampton Creek 0749609 4347966 Zm2 X X X
Zm28 Hampton Creek 0749609 4347966 Zm2 X X
Zm211 Hampton Creek 0750987 4347939 Zm2 X 21 305 08 248 X
Zm214 Hampton Creek 0751120 4347980 Zm2 X 09 058 X
Zm215 Hampton Creek 0751120 4347980 Zm2 X 09 058 X X
Zm216 Hendry'sCreek 0749061 4346180 Zm2 X 17 141 X
Zm217 Hendry'sCreek 0749061 4346180 Zm2 X 17 141
Zm31 Hendry'sCreek 0751418 4344573 Zm3 X 10 111 10 111 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 183 |
| Contributing entity | University of Southern California |
| Repository email | cisadmin@lib.usc.edu |
| Full text | 168 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 Zm01 Hampton Creek 0752075 4347644 Zm0 X X X Zm02 Hendry'sCreek 0752626 4343615 Zm0 X 04 022 X Zm03 Hendry'sCreek 0752626 4343615 Zm0 X 15 111 Zm04 Hendry'sCreek 0752626 4343615 Zm0 X 18 126 Zm05 Deep Canyon 0746655 4356885 Zm0 X X X Zm07 Hampton Creek 0750982 4348189 Zm0 X 04 214 X Zm08 Hampton Creek 0750982 4348189 Zm0 X 04 174 X X Zm0/1 Deep Canyon 0746736 4357057 Zm0/Zm1? X X Zm14 Deep Canyon 0746529 4356516 Zm1 X 21 070 09 126 X Zm15 Deep Canyon 0746529 4356350 Zm1 X 09 051 02 120 X Zm21 Hampton Creek 0749609 4347966 Zm2 X X Zm22 Hampton Creek 0749392 4348036 Zm2 X X Zm23 Hampton Creek 0749985 4347777 Zm2 X 06 223 X Zm24 Hendry'sCreek 0752213 4344206 Zm2 X 29 282 14 120 X Zm26 Hendry'sCreek 0744323 4346829 Zm2 X X X Zm27 Hampton Creek 0749609 4347966 Zm2 X X X Zm28 Hampton Creek 0749609 4347966 Zm2 X X Zm211 Hampton Creek 0750987 4347939 Zm2 X 21 305 08 248 X Zm214 Hampton Creek 0751120 4347980 Zm2 X 09 058 X Zm215 Hampton Creek 0751120 4347980 Zm2 X 09 058 X X Zm216 Hendry'sCreek 0749061 4346180 Zm2 X 17 141 X Zm217 Hendry'sCreek 0749061 4346180 Zm2 X 17 141 Zm31 Hendry'sCreek 0751418 4344573 Zm3 X 10 111 10 111 X |
