Multi-Mineral U-Pb Geo- And Thermochronometric Constraints on Laramide-Age Deformation in the Maria Fold-and-Thrust Belt (Sw Usa)

Flansburg, Megan E.

doi:10.1130/abs/2021cd-362516

Cited by 4 publications

(5 citation statements)

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“…80 Ma (e.g. Martin et al, 1982;Isachsen et al, 1999;Flansburg et al, 2021), whereas we interpret top-NE shearing to have continued until ca. 63 Ma.…”

Section: Evidence For Late Cretaceous Extensioncontrasting

confidence: 45%

“…While most research on the Maria fold-and-thrust belt has focused on contractional structures, growing evidence suggests that Late Cretaceous to early Paleogene NE-directed extension may have also occurred regionally, following the cessation of contraction. Laramideage mylonitization associated with NE-directed extension has been recognized in several ranges in the CREC and adjacent areas, including the Dome Rock Mountains (Boettcher and Mosher, 1998), Little Maria Mountains (Ballard and Ballard, 1990), Big Maria Mountains (Flansburg et al, 2021), Iron Mountains (Wells et al, 2002), New York Mountains (Wells et al, 2005), and Granite Mountains (Salem, 2009). How widespread this event was and whether it also impacted manuscript submitted to Tectonics Bryant, 1995;.…”

Section: Geologic Backgroundmentioning

confidence: 99%

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Late Cretaceous-early Paleogene extensional ancestry of the Harcuvar and Buckskin-Rawhide metamorphic core complexes, western Arizona

Wong

Singleton

Seymour

et al. 2022

Preprint

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Metamorphic core complexes in the western North American Cordillera are commonly interpreted as the result of a single phase of large-magnitude extension during the middle to late Cenozoic. We present evidence that mylonitic shear zones inthe Harcuvar and Buckskin-Rawhide core complexes in west-central Arizona also accommodated an earlier phase of extension during the Late Cretaceous to early Paleocene. Microstructural data indicate substantial top-NE mylonitization occurred at amphibolitefacies, and 40 Ar/ 39 Ar thermochronology documents post-tectonic footwall cooling to <500°C by the Paleocene to mid-Eocene. Amphibolite-facies mylonites are spatially associated with voluminous and variably deformed footwall leucogranites that were emplaced from ca. 74-64 Ma, and a late kinematic ca. 63 Ma dike indicates this phase of mylonitization had waned by the early Paleogene. Reconstruction of the footwall architecture indicates that this latest Cretaceous -early Paleocene deformation occurred within a NE-dipping extensional shear zone. The leucogranites were likely the result of crustal melting due to orogenic thickening, implying a model whereby crustal heating triggered gravitational collapse of overthickened crust. Other tectonic processes, such as the Laramide underplating of Orocopia Schist or mantle delamination, may have also contributed to this episode of orogenic extension. Miocene large-magnitude extension was superimposed on this older shear zone and had similar kinematics, suggesting that the location and geometry of Miocene extension was strongly influenced by tectonic inheritance.We speculate that other Cordilleran core complexes also experienced a more complex and polyphase extensional history than previously recognized, but in many cases the evidence may be obscured by later Miocene overprinting.

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“…80 Ma (e.g. Martin et al, 1982;Isachsen et al, 1999;Flansburg et al, 2021), whereas we interpret top-NE shearing to have continued until ca. 63 Ma.…”

Section: Evidence For Late Cretaceous Extensioncontrasting

confidence: 45%

Section: Geologic Backgroundmentioning

confidence: 99%

Late Cretaceous-early Paleogene extensional ancestry of the Harcuvar and Buckskin-Rawhide metamorphic core complexes, western Arizona

Wong

Singleton

Seymour

et al. 2022

Preprint

View full text Add to dashboard Cite

show abstract

“…In addition, shortening in the Maria fold‐and‐thrust belt was largely complete by ca. 80 Ma (e.g., Flansburg et al., 2021; Isachsen et al., 1999; Martin et al., 1982), whereas we interpret top‐NE shearing to have continued until ca. 63 Ma based on the age of the late synkinematic dike (Har‐50, Figure 13).…”

Section: Discussionmentioning

confidence: 59%

“…While most research on the Maria fold-and-thrust belt has focused on contractional structures, growing evidence suggests that Late Cretaceous to early Paleogene NE-directed extension may have also occurred regionally, following the cessation of contraction. Laramide-age mylonitization interpreted to record NE-directed extension has been recognized in several ranges in the CREC and adjacent areas, including the Dome Rock Mountains (Boettcher & Mosher, 1998), Little Maria Mountains (Ballard & Ballard, 1990), Big Maria Mountains (Flansburg et al, 2021), Iron Mountains (Wells et al, 2002), New York Mountains (Wells et al, 2005), and Bryant, 1995;. The map also shows the location of samples for petrographic observations (small dots), U-Pb geochronology (diamonds) and 40 Ar/ 39 Ar thermochronology (squares).…”

Section: Geologic Backgroundmentioning

confidence: 99%

“…While most research on the Maria fold‐and‐thrust belt has focused on contractional structures, growing evidence suggests that Late Cretaceous to early Paleogene NE‐directed extension may have also occurred regionally, following the cessation of contraction. Laramide‐age mylonitization interpreted to record NE‐directed extension has been recognized in several ranges in the CREC and adjacent areas, including the Dome Rock Mountains (Boettcher & Mosher, 1998), Little Maria Mountains (Ballard & Ballard, 1990), Big Maria Mountains (Flansburg et al., 2021), Iron Mountains (Wells et al., 2002), New York Mountains (Wells et al., 2005), and Granite Mountains (Salem, 2009). How widespread this event was and whether it also impacted core complexes within the CREC remains unclear, although John (1987) and John and Musaka (1990) suggest that most mylonitization in the footwall of the Chemehuevi detachment fault records top‐NE‐directed shearing during the Late Cretaceous (ca.…”

Section: Geologic Backgroundmentioning

confidence: 99%

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Late Cretaceous‐Early Paleogene Extensional Ancestry of the Harcuvar and Buckskin‐Rawhide Metamorphic Core Complexes, Western Arizona

et al. 2023

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Metamorphic core complexes in the western North American Cordillera are commonly interpreted as the result of a single phase of large‐magnitude extension during the middle to late Cenozoic. We present evidence that mylonitic shear zones in the Harcuvar and Buckskin‐Rawhide core complexes in west‐central Arizona also accommodated an earlier phase of extension during the Late Cretaceous to early Paleocene. Microstructural data indicate substantial top‐NE mylonitization occurred at amphibolite‐facies, and 40Ar/39Ar thermochronology documents post‐tectonic footwall cooling to <500°C by the Paleocene to mid‐Eocene. Amphibolite‐facies mylonites are spatially associated with voluminous and variably deformed footwall leucogranites that were emplaced from ca. 74–64 Ma, and a late kinematic ca. 63 Ma dike indicates this phase of mylonitization had waned by the early Paleocene. Reconstruction of the footwall architecture indicates that this latest Cretaceous—early Paleocene deformation occurred within a NE‐dipping extensional shear zone. The leucogranites were likely the result of crustal melting due to orogenic thickening, consistent with a model whereby crustal heating triggered gravitational collapse of overthickened crust. Other tectonic processes, such as the Laramide underplating of Orocopia Schist or mantle delamination, may have also contributed to this episode of orogenic extension. Miocene large‐magnitude extension was superimposed on this older shear zone and had similar kinematics, suggesting that the location and geometry of Miocene extension was strongly influenced by tectonic inheritance. We speculate that other Cordilleran core complexes also experienced a more complex and polyphase extensional history than previously recognized, but in many cases the evidence may be obscured by later Miocene overprinting.

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The Buckskin-Rawhide and northern Plomosa Mountains metamorphic core complexes, west-central Arizona, USA

Singleton

Seymour

Strickland

2022

Field Excursions From Las Vegas, Nevada: Guides to the 2022 GSA Cordilleran and Rocky Mountain Joint Section Meeting

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The Buckskin-Rawhide and northern Plomosa Mountains in west-central Arizona are metamorphic core complexes that record NE-directed, large-magnitude extension in the early to middle Miocene. Both core complexes consist of mylonites exposed in the footwall of corrugated, low-angle detachment faults. The Late Cretaceous Orocopia Schist and early Miocene intrusions dominate the mylonitic footwall of the northern Plomosa Mountains. The Orocopia Schist was emplaced during low-angle subduction of the Farallon plate and exhibits the hallmarks of the underplated Laramide subduction complexes, including blocks of metasomatized peridotite encased in quartzofeldspathic schist. In the Buckskin-Rawhide Mountains, carbonate-rich metasedimentary rocks that were buried to midcrustal depths by Mesozoic thrust faults preferentially absorbed Miocene footwall strain and localized the Buckskin detachment fault. A correlation between distinct granodiorite in the footwall of the Buckskin detachment fault in the eastern Bouse Hills and a hanging-wall conglomerate sourced from this granodiorite provides constraints on middle Miocene displacement across the detachment fault and indicates that displacement increased northeastward in the slip direction. The termination of slip on the Buckskin detachment fault also younged northeastward, largely ending by ca. 19 Ma in the western Bouse Hills and ca. 17 Ma in the westernmost Buckskin Mountains, but continuing to <16 Ma in the southern Buckskin Mountains and to ca. 12 Ma in the eastern Buckskin Mountains. Late stages of slip on the detachment fault record minor NW-SE shortening during amplification of corrugation folds. Postdetachment faulting across the region was dominated by dextral and oblique-dextral slip on NW-striking faults influenced by the Pacific–North America plate boundary. Locations visited on this three-day field trip highlight the structural evolution of these metamorphic core complexes.

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Multi-Mineral U-Pb Geo- And Thermochronometric Constraints on Laramide-Age Deformation in the Maria Fold-and-Thrust Belt (Sw Usa)

Cited by 4 publications

References 0 publications

Late Cretaceous-early Paleogene extensional ancestry of the Harcuvar and Buckskin-Rawhide metamorphic core complexes, western Arizona

Late Cretaceous-early Paleogene extensional ancestry of the Harcuvar and Buckskin-Rawhide metamorphic core complexes, western Arizona

Late Cretaceous‐Early Paleogene Extensional Ancestry of the Harcuvar and Buckskin‐Rawhide Metamorphic Core Complexes, Western Arizona

The Buckskin-Rawhide and northern Plomosa Mountains metamorphic core complexes, west-central Arizona, USA

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