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John S Singleton - One of the best experts on this subject based on the ideXlab platform.
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miocene slip history of the eagle eye Detachment Fault harquahala mountains metamorphic core complex west central arizona
Tectonics, 2016Co-Authors: Michael G Prior, Daniel F Stockli, John S SingletonAbstract:The structural and thermal evolution of major low-angle normal Faults in the Colorado River extensional corridor has been a controversial topic since the pioneering studies of metamorphic core complexes in the early 1980s. We present new geo-thermochronometry data from the Harquahala Mountains in west-central Arizona to determine the timing of extension, displacement magnitude, and slip rates along the Eagle Eye Detachment Fault (EED) during large-magnitude Miocene extension. Zircon and apatite (U-Th)/He data (ZHe and AHe, respectively) from 31 samples along a ~55 km extension-parallel transect indicate active slip along the EED occurred between ~21 ± 1 Ma until ~14 Ma. The spatial extent of ZHe ages and exhumation of the zircon partial retention zone indicated ~44 ± 2 km of total displacement, whereas lithologic similarity and identical U-Pb ages between correlated footwall rocks in the Little Harquahala Mountains and breccia clasts at Bullard Peak in the NE Harcuvar Mountains indicated ~43-45 km of displacement across the EED. AHe and ZHe data indicated slip rates of ~6.7 + 7.8/-2.3 km/Myr, and ~6.6 + 7.1/-2.0 km/Myr, respectively, both consistent with the duration and displacement estimates. The EED initiated as a listric Fault with an ~34 ± 9° dip that decreased to ~13 ± 5° below ~7 km depth. Secondary breakaway development and footwall exposure occurred by ~17 Ma, during active EED slip. Lithologic and geo-thermochronometric offset constraints show excellent agreement and provided a rare opportunity to fully resolve the timing, rates, and total displacement magnitudes along a major continental Detachment Fault.
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timing rate and magnitude of slip on the buckskin rawhide Detachment Fault west central arizona
Tectonics, 2014Co-Authors: John S Singleton, Daniel F Stockli, Phillip B Gans, Michael G PriorAbstract:We present thermochronologic and geochronologic data that constrain the slip history of the Buckskin-Rawhide Detachment Fault in west central Arizona, one of the largest extensional Fault systems in the North American Cordillera. (U-Th)/He zircon and apatite thermochronology, integrated with 40Ar/39Ar geochronology of postDetachment volcanic rocks, indicate that large-magnitude extension associated with the Detachment Fault initiated at ~21–20 Ma and continued until ~12–11 Ma in the southwestern portion of the Buckskin-Rawhide metamorphic core complex. (U-Th)/He footwall cooling ages from the breakaway zone in the western Bouse Hills to upper greenschist-facies mylonites in the southern Buckskin Mountains indicate that the slip rate on the Detachment Fault was 3 + 1.5/−1 km/Myr during the early Miocene. Space-time patterns of hanging wall tilting suggest that at 17–16 Ma, a secondary Detachment Fault breakaway developed ~12 km northeast of the primary Detachment Fault breakaway. Proximal conglomerates deposited in a supraDetachment basin adjacent to the secondary breakaway scarp were displaced 6–11 km northeast in the middle Miocene by the Buckskin-Rawhide Detachment Fault at a slip rate of 1.2–2.7 km/Myr. The total displacement across the Detachment Fault in the southwestern portion of the core complex is 24 ± 10 km, well short of the previous estimate of 66 ± 8 km across the entire core complex. Based on these data and new observations, we propose that total displacement on the Buckskin-Rawhide Detachment Fault system increases in the slip direction to ~40–50 km at the northeastern end of the exposed footwall, corresponding to time-averaged slip rates that ranged from ~2 km/Myr to ≤6 km/Myr across the entire core complex.
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mylonitization in the lower plate of the buckskin rawhide Detachment Fault west central arizona implications for the geometric evolution of metamorphic core complexes
Journal of Structural Geology, 2012Co-Authors: John S Singleton, Sharon MosherAbstract:Abstract In metamorphic core complexes it is commonly unclear whether lower plate mylonites formed as the down-dip continuation of a Detachment Fault, or whether they represent a subhorizontal shear zone that was captured by a more steeply dipping Detachment Fault. Detailed microstructural, fabric, and strain data from mylonites in the Buckskin-Rawhide metamorphic core complex, west-central Arizona, constrain the structural development of the lower plate shear zone. Widespread exposures of ∼22–21 Ma granitoids of the Swansea Plutonic Suite enable us to separate Miocene strain coeval with core complex extension from older deformation. Mylonites across the lower plate consistently record top-to-the-NE-directed shear. Miocene quartz and feldspar deformation/recrystallization mechanisms indicate ∼450–500 °C mylonitization temperatures that were relatively uniform across a distance of ∼35 km in the extension direction. Quartz dynamically recrystallized grain sizes do not systematically vary in the extension direction. Strain recorded in the Swansea Plutonic Suite is also relatively uniform in the extension direction, which is incompatible with models in which lower plate mylonites form as the ductile root of a major Detachment Fault. Altogether these data suggest the mylonitic shear zone initiated with a ≤4° dip and was unroofed by a more steeply dipping Detachment Fault system. Lower plate mylonites in the Buckskin-Rawhide metamorphic core complex thus represent a captured subhorizontal shear zone rather than the down-dip continuation of a Detachment Fault.
Ernest M Duebendorfer - One of the best experts on this subject based on the ideXlab platform.
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south virgin white hills Detachment Fault system of se nevada and nw arizona applying apatite fission track thermochronology to constrain the tectonic evolution of a major continental Detachment Fault
Tectonics, 2009Co-Authors: Paul G Fitzgerald, Ernest M Duebendorfer, James E Faulds, Paul B OsullivanAbstract:The South Virgin-White Hills Detachment (SVWHD) in the central Basin and Range province with an along-strike extent of similar to 60 km is a major continental Detachment Fault system. Displacement on the SVWHD decreases north to south from similar to 17 to <6 km. This is accompanied by a change in Fault and footwall rock type from mylonite overprinted by cataclasite to chlorite cataclasite and then Fault breccia reflecting decreasing Fault displacement and footwall exhumation. Apatite fission track (AFT) thermochronology was applied both along-strike and across-strike to assess this displacement gradient. The overall thermal history reflects Laramide cooling (similar to 75 Ma) and then rapid cooling beginning in the late early Miocene. Age patterns reflect some complexity but extension along the SVWHD appears synchronous with rapid cooling initiated at similar to 17 Ma due to tectonic exhumation. Slip rate is more rapid (similar to 8.6 km/Ma) in the north compared to similar to 1 km/Ma in the south. The displacement gradient results from penecontemporaneous along-strike motion and formation of the SVWHD by linkage of originally separate Fault segments that have differential displacements and hence differential slip rates. East west transverse structures likely play a role in linkage of different Fault segments. The preextension paleogeothermal gradient is well constrained in the Gold Butte block as 18-20 degrees C/km. We present a new thermochronologic approach to constrain Fault dip during slip, treating the vertical exhumation rate and the slip as vectors, with the angle between them used to constrain Fault dip during slip through the closure temperature of a particular thermochronometer. AFT data from the western rim of the Colorado Plateau. Citation: Fitzgerald, P. G., E. M. Duebendorfer, J. E. Faulds, and P. O'Sullivan (2009), South Virgin-White Hills Detachment Fault system of SE Nevada and NW Arizona: Applying apatite fission track thermochronology to constrain the tectonic evolution of a major continental Detachment Fault, Tectonics, 28, TC2001, doi:10.1029/2007TC002194.
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variation in displacement along strike of the south virgin white hills Detachment Fault perspective from the northern white hills northwestern arizona
Geological Society of America Bulletin, 1998Co-Authors: Ernest M Duebendorfer, Warren D SharpAbstract:Three major low-angle normal Faults in the eastern Lake Mead area, Nevada and Arizona, are parts of a 55-km-long, regional Detachment Fault that may form the principal breakaway for extensional allochthons at this latitude. This Fault, herein named the South Virgin–White Hills Detachment, comprises the Lakeside Mine, Salt Spring, and the Cyclopic Mine Faults, and it extends from the South Virgin Mountains in southeastern Nevada to the central White Hills in northwestern Arizona. The previously unstudied central segment, the Salt Spring Fault, is a 50-m-thick, gently west-dipping cataclastic Fault zone that separates Proterozoic crystalline rocks in its footwall from northeast-dipping Tertiary volcanic and sedimentary rocks, including footwall-derived megabreccia, in its hanging wall. The 40 Ar/ 39 Ar and K/Ar dates on volcanic rocks in the upper plate constrain the principal phase of extension to between 15.2 and 14.6 Ma, although lesser extension continued to about 11 Ma. Lower-plate crystalline rocks retrograded from granulite to greenschist facies and regional steep foliations were tilted to low dips as a result of Tertiary extension. All three segments of the regional Detachment record top-to-the-west displacement and were active principally during the time interval between 16 and 14 Ma. Displacement on the South Virgin–White Hills Detachment decreases from a maximum at the Gold Butte block in the north to a minimum at the Cyclopic Mine in the south. This along-strike, southward decrease in extensional strain along the South Virgin–White Hills Detachment is accompanied by a change in Fault and footwall rock type from mylonite along the Lakeside Mine Fault (northern segment), to chlorite cataclasite along the Salt Spring Fault (central segment), to unconsolidated Fault breccia along the Cyclopic Mine Fault (southern segment). Differences in footwall and Fault rocks reflect decreasing exhumation of footwall rocks due to decreased extension from north to south.
Warren D Sharp - One of the best experts on this subject based on the ideXlab platform.
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variation in displacement along strike of the south virgin white hills Detachment Fault perspective from the northern white hills northwestern arizona
Geological Society of America Bulletin, 1998Co-Authors: Ernest M Duebendorfer, Warren D SharpAbstract:Three major low-angle normal Faults in the eastern Lake Mead area, Nevada and Arizona, are parts of a 55-km-long, regional Detachment Fault that may form the principal breakaway for extensional allochthons at this latitude. This Fault, herein named the South Virgin–White Hills Detachment, comprises the Lakeside Mine, Salt Spring, and the Cyclopic Mine Faults, and it extends from the South Virgin Mountains in southeastern Nevada to the central White Hills in northwestern Arizona. The previously unstudied central segment, the Salt Spring Fault, is a 50-m-thick, gently west-dipping cataclastic Fault zone that separates Proterozoic crystalline rocks in its footwall from northeast-dipping Tertiary volcanic and sedimentary rocks, including footwall-derived megabreccia, in its hanging wall. The 40 Ar/ 39 Ar and K/Ar dates on volcanic rocks in the upper plate constrain the principal phase of extension to between 15.2 and 14.6 Ma, although lesser extension continued to about 11 Ma. Lower-plate crystalline rocks retrograded from granulite to greenschist facies and regional steep foliations were tilted to low dips as a result of Tertiary extension. All three segments of the regional Detachment record top-to-the-west displacement and were active principally during the time interval between 16 and 14 Ma. Displacement on the South Virgin–White Hills Detachment decreases from a maximum at the Gold Butte block in the north to a minimum at the Cyclopic Mine in the south. This along-strike, southward decrease in extensional strain along the South Virgin–White Hills Detachment is accompanied by a change in Fault and footwall rock type from mylonite along the Lakeside Mine Fault (northern segment), to chlorite cataclasite along the Salt Spring Fault (central segment), to unconsolidated Fault breccia along the Cyclopic Mine Fault (southern segment). Differences in footwall and Fault rocks reflect decreasing exhumation of footwall rocks due to decreased extension from north to south.
Marty Grove - One of the best experts on this subject based on the ideXlab platform.
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miocene pliocene exhumation along the west salton Detachment Fault southern california from u th he thermochronometry of apatite and zircon
Tectonics, 2009Co-Authors: Daniel F Stockli, Gary J Axen, C Shirvell, Marty GroveAbstract:[1] The Salton Trough is the northernmost segment of the active Gulf of California oblique rift system. The main rift-related structure in the western Salton Trough is the low-angle west Salton Detachment Fault (WSDF). Footwall and hanging wall apatite and zircon (U-Th)/He ages record a significant contrast in thermal history across the WSDF, confirming Pliocene normal slip along the Fault. Apatite (U-Th)/He ages record rapid exhumational cooling from ∼5 to ∼2 Ma, consistent with the timing of accelerated tectonic subsidence recorded in WSDF hanging wall sedimentary strata and consistent with the initiation age of dextral plate boundary slip on the southern San Andreas Fault in the Salton Trough. Our results indicate that the WSDF caused at least 2.3–4 km of exhumation and >8–10 km of approximately E directed horizontal extension since ∼5 Ma. Slip rate of the WSDF at Yaqui Ridge was likely in the range of ∼2.3–5 km/Ma from ∼7 to ∼2 Ma. The WSDF may have been active well before ∼5 Ma. Middle Miocene apatite (U-Th)/He ages from samples at high elevations have steep age-elevation gradients and suggest that exhumation may have initiated by ∼12 Ma, about when subduction ceased along a large segment of the Baja California margin and consistent with the age of onset of extension in northeastern Baja California.
Daniel F Stockli - One of the best experts on this subject based on the ideXlab platform.
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miocene slip history of the eagle eye Detachment Fault harquahala mountains metamorphic core complex west central arizona
Tectonics, 2016Co-Authors: Michael G Prior, Daniel F Stockli, John S SingletonAbstract:The structural and thermal evolution of major low-angle normal Faults in the Colorado River extensional corridor has been a controversial topic since the pioneering studies of metamorphic core complexes in the early 1980s. We present new geo-thermochronometry data from the Harquahala Mountains in west-central Arizona to determine the timing of extension, displacement magnitude, and slip rates along the Eagle Eye Detachment Fault (EED) during large-magnitude Miocene extension. Zircon and apatite (U-Th)/He data (ZHe and AHe, respectively) from 31 samples along a ~55 km extension-parallel transect indicate active slip along the EED occurred between ~21 ± 1 Ma until ~14 Ma. The spatial extent of ZHe ages and exhumation of the zircon partial retention zone indicated ~44 ± 2 km of total displacement, whereas lithologic similarity and identical U-Pb ages between correlated footwall rocks in the Little Harquahala Mountains and breccia clasts at Bullard Peak in the NE Harcuvar Mountains indicated ~43-45 km of displacement across the EED. AHe and ZHe data indicated slip rates of ~6.7 + 7.8/-2.3 km/Myr, and ~6.6 + 7.1/-2.0 km/Myr, respectively, both consistent with the duration and displacement estimates. The EED initiated as a listric Fault with an ~34 ± 9° dip that decreased to ~13 ± 5° below ~7 km depth. Secondary breakaway development and footwall exposure occurred by ~17 Ma, during active EED slip. Lithologic and geo-thermochronometric offset constraints show excellent agreement and provided a rare opportunity to fully resolve the timing, rates, and total displacement magnitudes along a major continental Detachment Fault.
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timing rate and magnitude of slip on the buckskin rawhide Detachment Fault west central arizona
Tectonics, 2014Co-Authors: John S Singleton, Daniel F Stockli, Phillip B Gans, Michael G PriorAbstract:We present thermochronologic and geochronologic data that constrain the slip history of the Buckskin-Rawhide Detachment Fault in west central Arizona, one of the largest extensional Fault systems in the North American Cordillera. (U-Th)/He zircon and apatite thermochronology, integrated with 40Ar/39Ar geochronology of postDetachment volcanic rocks, indicate that large-magnitude extension associated with the Detachment Fault initiated at ~21–20 Ma and continued until ~12–11 Ma in the southwestern portion of the Buckskin-Rawhide metamorphic core complex. (U-Th)/He footwall cooling ages from the breakaway zone in the western Bouse Hills to upper greenschist-facies mylonites in the southern Buckskin Mountains indicate that the slip rate on the Detachment Fault was 3 + 1.5/−1 km/Myr during the early Miocene. Space-time patterns of hanging wall tilting suggest that at 17–16 Ma, a secondary Detachment Fault breakaway developed ~12 km northeast of the primary Detachment Fault breakaway. Proximal conglomerates deposited in a supraDetachment basin adjacent to the secondary breakaway scarp were displaced 6–11 km northeast in the middle Miocene by the Buckskin-Rawhide Detachment Fault at a slip rate of 1.2–2.7 km/Myr. The total displacement across the Detachment Fault in the southwestern portion of the core complex is 24 ± 10 km, well short of the previous estimate of 66 ± 8 km across the entire core complex. Based on these data and new observations, we propose that total displacement on the Buckskin-Rawhide Detachment Fault system increases in the slip direction to ~40–50 km at the northeastern end of the exposed footwall, corresponding to time-averaged slip rates that ranged from ~2 km/Myr to ≤6 km/Myr across the entire core complex.
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miocene pliocene exhumation along the west salton Detachment Fault southern california from u th he thermochronometry of apatite and zircon
Tectonics, 2009Co-Authors: Daniel F Stockli, Gary J Axen, C Shirvell, Marty GroveAbstract:[1] The Salton Trough is the northernmost segment of the active Gulf of California oblique rift system. The main rift-related structure in the western Salton Trough is the low-angle west Salton Detachment Fault (WSDF). Footwall and hanging wall apatite and zircon (U-Th)/He ages record a significant contrast in thermal history across the WSDF, confirming Pliocene normal slip along the Fault. Apatite (U-Th)/He ages record rapid exhumational cooling from ∼5 to ∼2 Ma, consistent with the timing of accelerated tectonic subsidence recorded in WSDF hanging wall sedimentary strata and consistent with the initiation age of dextral plate boundary slip on the southern San Andreas Fault in the Salton Trough. Our results indicate that the WSDF caused at least 2.3–4 km of exhumation and >8–10 km of approximately E directed horizontal extension since ∼5 Ma. Slip rate of the WSDF at Yaqui Ridge was likely in the range of ∼2.3–5 km/Ma from ∼7 to ∼2 Ma. The WSDF may have been active well before ∼5 Ma. Middle Miocene apatite (U-Th)/He ages from samples at high elevations have steep age-elevation gradients and suggest that exhumation may have initiated by ∼12 Ma, about when subduction ceased along a large segment of the Baja California margin and consistent with the age of onset of extension in northeastern Baja California.