The Pinto shear zone; a Laramide synconvergent extensional shear zone in the Mojave Desert region of the southwestern United States

Wells, Michael L.; Beyene, Mengesha; Spell, Terry L.; Kula, Joseph; Miller, David M.; Zanetti, Kathleen A.

doi:10.1016/j.jsg.2005.03.005

Cited by 29 publications

(25 citation statements)

References 93 publications

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“…Widespread Late Cretaceous cooling in the Mojave Desert region has long been recognized [e.g., Dumitru et al , 1991]. Wells et al [2005] link this cooling to extension by detailing the geometry, kinematics, deformation temperature, and thermal history of the Pinto shear zone in the New York Mountains (Figure 1 bottom inset). Similarly, synextensional emplacement of Late Cretaceous granites and pegmatites from the Iron, Old Woman, and Granite Mountains (Figure 1 bottom inset) indicates widespread Late Cretaceous approximately northeast–southwest extension in the eastern Mojave Desert region [ Wells and Hoisch , 2008].…”

Section: Discussionmentioning

confidence: 99%

Role of extrusion of the Rand and Sierra de Salinas schists in Late Cretaceous extension and rotation of the southern Sierra Nevada and vicinity

et al. 2010

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[1] The Rand and Sierra de Salinas schists of southern California were underplated beneath the southern Sierra Nevada batholith and adjacent Mojave-Salinia region along a shallow segment of the subducting Farallon plate in Late Cretaceous time. Various mechanisms, including return flow, isostatically driven uplift, upper plate normal faulting, erosion, or some combination thereof, have been proposed for the exhumation of the schist. We supplement existing kinematic data with new vorticity and strain analysis to characterize deformation in the Rand and Sierra de Salinas schists. These data indicate that the schist was transported to the SSW from deep to shallow crustal levels along a mylonitic contact (the Rand fault and Salinas shear zone) with upper plate assemblages. Crystallographic preferred orientation patterns in deformed quartzites reveal a decreasing simple shear component with increasing structural depth, suggesting a pure shear dominated westward flow within the subduction channel and localized simple shear along the upper channel boundary. The resulting flow type within the channel is that of general shear extrusion. Integration of these observations with published geochronologic, thermochronometric, thermobarometric, and paleomagnetic studies reveals a temporal relationship between schist unroofing and upper crustal extension and rotation. We present a model whereby trench-directed channelized extrusion of the underplated schist triggered gravitational collapse and clockwise rotation of the upper plate.

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Section: Discussionmentioning

confidence: 99%

Role of extrusion of the Rand and Sierra de Salinas schists in Late Cretaceous extension and rotation of the southern Sierra Nevada and vicinity

et al. 2010

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“…The inflection to rapid cooling at 89 Ma as reported by Kula et al [2007] (Figure 10) is reproduced when integrating the P75086 biotite age with the K‐feldspar cooling paths (Figure 10). Samples collected from the hanging wall and footwall of detachment fault systems are expected to yield contrasting thermal histories [i.e., Spell et al , 2000; Wells et al , 2005; Kula et al , 2007]. The nearly identical thermal histories for samples P75086 and P67866 are not consistent with this type of relationship.…”

Section: Discussionmentioning

confidence: 99%

Thermal evolution of the Sisters shear zone, southern New Zealand; Formation of the Great South Basin and onset of Pacific‐Antarctic spreading

et al. 2009

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The separation of Zealandia from West Antarctica was the final stage in the Cretaceous breakup of the Gondwana Pacific margin. Continental extension resulting in formation of the Great South Basin and thinning of the Campbell Plateau leading to development of the Pacific‐Antarctic spreading ridge was partially accommodated along the Sisters shear zone. This east‐northeast striking brittle‐ductile structure exposed along the southeast coast of Stewart Island, New Zealand, is a greenschist facies extensional shear zone that separates a hanging wall of chloritic, brecciated granites, and undeformed conglomerate from a footwall of mylonitic Carboniferous and Early Cretaceous granites. This complex structure exhibits bivergent kinematics and can be subdivided into a northern and southern segment. The 40Ar/39Ar thermochronology indicates that cooling of the shear zone footwall began at ∼94 Ma with accelerated cooling over the interval ∼89–82 Ma. Structural and thermochronological data indicate a spatial and temporal link between the Sisters shear zone, initial sedimentation within the offshore Great South Basin, extension of the Campbell Plateau, and initiation of the Pacific‐Antarctic spreading ridge.

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“…The story in the US Cordillera is complicated, however, by petrological and structural evidence for multiple stages of decompression and burial during the Late Cretaceous (e.g. Applegate & Hodges 1995;Camilleri & Chamberlain 1997;Wells et al 2005;Harris et al 2007), which have been interpreted as reflecting alternating stages of extension and shortening in a critical orogenic wedge or thickened plateau subject to varying tectonic boundary conditions (Wells et al 2012). Cooling, and possibly exhumation, during the Eocene is clearly indicated by thermochronological data in many of the US core complexes (e.g.…”

Section: Metamorphism In Mccsmentioning

confidence: 99%

Metamorphic core complexes: windows into the mechanics and rheology of the crust

Platt

Behr

Cooper

2014

JGS

136

131

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Metamorphic core complexes are products of normal-fault displacements sufficient to exhume rocks from below the brittle–ductile transition. These faults (detachments) may initiate within the brittle crust at steep angles, but they sole into the ductile middle crust, and during displacement rotate to gentler dips due to hanging-wall extension. The exhumed footwall commonly adopts an arched or domed geometry owing to flexural isostatic readjustment, and may be overlain by strongly extended upper crustal rocks that slipped on gently dipping, low-friction shallow segments of the detachment. Metamorphic rocks exhumed beneath the detachment record progressively increasing flow stress, strain localization and strain-rate with decreasing temperature, providing a window into physical conditions and deformational processes in the mid-crust. The metamorphic and deformational history of the footwall rocks may reflect tectonic processes that predate formation of the detachment fault, in addition to those accompanying exhumation. These processes may include diapiric emplacement of gneiss domes, or exhumation in a subduction channel, and may not be directly related to formation of the core complex. Factors favouring core complex formation are high gravitational potential energy of the extending crust, weak rheology and a change in the tectonic boundary conditions such as a cessation or slowing of plate convergence.

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The Pinto shear zone; a Laramide synconvergent extensional shear zone in the Mojave Desert region of the southwestern United States

Cited by 29 publications

References 93 publications

Role of extrusion of the Rand and Sierra de Salinas schists in Late Cretaceous extension and rotation of the southern Sierra Nevada and vicinity

Role of extrusion of the Rand and Sierra de Salinas schists in Late Cretaceous extension and rotation of the southern Sierra Nevada and vicinity

Thermal evolution of the Sisters shear zone, southern New Zealand; Formation of the Great South Basin and onset of Pacific‐Antarctic spreading

Metamorphic core complexes: windows into the mechanics and rheology of the crust

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