Early Miocene mylonitization and detachment faulting, South Mountains, central Arizona

Reynolds, Stephen J.; Shafiqullah, M.; Damon, Paul E.; DeWitt, Ed

doi:10.1130/0091-7613(1986)14<283:emmadf>2.0.co;2

Cited by 43 publications

(52 citation statements)

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“…The lack of detachment-related mylonitic fabric in rocks exposed beneath the klippen can be explained by eastward shallowing of the detachment structure. This change in deformational style of lower-plate rock from east to west is consistent with models of evolving, crustal-scale shear zones described by Spencer (1984Spencer ( , 1985, Reynolds (1985), Wernicke and others (1985), and Davis and others (1986). These models suggest that in the direction of dip of the detachment, upper-plate rocks should be superimposed on progressively deeper-level, lower-plate rocks.…”

Section: Do the Klippen Represent The Eastward Continuation Of The Sasupporting

confidence: 79%

“…17) (Wernicke, 1981;Wernicke and others, 1985;Spencer, 1984Spencer, , 1985Reynolds, 1985;Davis and others, 1986). The kinematic compatibility between structures formed at widely different crustal levels implies a continuum of deformation that is most easily explained by a single protracted deformational event that elevated lower-plate rocks to progressively shallower crustal levels.…”

Section: Age Of Faultingmentioning

confidence: 91%

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Chapter 4: The Saddle Island detachment; An evolving shear zone in the Lake Mead area, Nevada

Duebendorfer

Sewall

Smith

1990

Geological Society of America Memoirs

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The Saddle Island detachment fault is a major, and possibly the dominant, structural feature in the Lake Mead area, Nevada. Exposures on Saddle Island contain many of the characteristic elements of metamorphic core complexes of the Colorado River trough detachment terrane, including lower-plate mylonitic rocks, a detachment fault marked by chloritic phyllonite and microbreccia, and a brittlely deformed upper plate. The Saddle Island detachment is regionally important because it is the only well-documented exposure in the Lake Mead region of a deep-level, crystalline lower plate. The upper plate of the detachment is divided into three lithologically distinct, lens-shaped domains bounded by low-angle normal faults. The domains are lithologically heterogeneous and contain Precambrian crystalline rocks, lower Paleozoic sedimentary rocks, sedimentary rocks of the Tertiary Horse Spring Formation, and Tertiary intrusive rocks.The lower plate of the detachment consists principally of variably mylonitized Precambrian amphibolite and quartzofeldspathic gneiss. Subhorizontal mylonitic foliation broadly parallels the detachment. Contacts between variably mylonitized rock are typically low-angle chlorite phyllonite fault zones. The lens-like character of lithologic packages in the lower plate resembles large-scale structure within the upper plate.Kinematic analysis indicates top-to-the-west shear for mylonites and all low-angle faults within the complex. Systematic changes in retrograde mineralogy that accompany textural changes in fault rocks suggest that structures associated with the detachment represent a continuum of deformation at progressively lower temperatures (i.e., shallower crustal levels). The similarity in orientation and inferred shear sense of all fault zones suggests that they developed during a single deformational event. These geologic relations are best explained by single-stage deformation associated with an evolving, crustal-scale, normal-sense-displacement simple-shear zone.Regional geochemical correlations allow reconstruction of structurally disrupted mid-Miocene volcanic-plutonic complexes in the Lake Mead area. The sense of movement required for restoration of these complexes is compatible with kinematic indicators within the Saddle Island detachment zone. These combined data suggest 20 km of westward translation of upper-plate rocks along the detachment. The inferred 20-km displacement along the detachment argues against in situ crustal extension (pure-shear models).Available age data suggest that the Saddle Island detachment is younger than 13.5 Ma; the major period of movement along the detachment must have occurred prior to deposition of the Muddy Creek Formation (5 to 9 Ma).Low-angle faults exposed east of Saddle Island between Lake Mead and Detrital Duebendorfer, E. M., Sewall, A. J., and Smith, E. I., 1990, The Saddle Island detachment; An evolving shear zone in the Lake Mead area, Nevada, in Wernicke, B. P., ed., Basin and Range extensional tectonics near the latitude of Las Vegas, Nevada: B...

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Section: Do the Klippen Represent The Eastward Continuation Of The Sasupporting

confidence: 79%

Section: Age Of Faultingmentioning

confidence: 91%

Chapter 4: The Saddle Island detachment; An evolving shear zone in the Lake Mead area, Nevada

Duebendorfer

Sewall

Smith

1990

Geological Society of America Memoirs

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“…This range consists of Early Proterozoic (1600-1800 Ma) metamorphic gneiss with some granite (Reynolds, 1985;Richards et al, 2000), and the range is only 10 km south of downtown Phoenix. Much of the mylonitization that dominates the MCC took place between 24 and 19 Ma (Reynolds et al, 1986). Subsequent drainage development (Pain, 1985;Spencer, 2000) helped lead to the current parallel Gila and Ma Ha Tuak ranges at the western end of this antiformal MCC.…”

Section: Study Sitementioning

confidence: 94%

Debris flows from small catchments of the Ma Ha Tuak Range, metropolitan Phoenix, Arizona

Dorn

2010

Geomorphology

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“…Metamorphic core complexes such as South Mountain in Arizona formed concurrently with upper crustal extension from the release of compressional stress after the Mesozoic Sevier and Laramide Orogenies (Nations and Stump, 1981;Coney and Harms, 1984;Holt Geomorphology 250 (2015) , 1986). South Mountain's uplift ended~8-14 Ma ago (Spencer, 1984;Reynolds, 1985).…”

Section: Field Areamentioning

confidence: 99%

Impact of consecutive extreme rainstorm events on particle transport: Case study in a Sonoran Desert range, western USA

Dorn

2015

Geomorphology

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Early Miocene mylonitization and detachment faulting, South Mountains, central Arizona

Cited by 43 publications

References 0 publications

Chapter 4: The Saddle Island detachment; An evolving shear zone in the Lake Mead area, Nevada

Chapter 4: The Saddle Island detachment; An evolving shear zone in the Lake Mead area, Nevada

Debris flows from small catchments of the Ma Ha Tuak Range, metropolitan Phoenix, Arizona

Impact of consecutive extreme rainstorm events on particle transport: Case study in a Sonoran Desert range, western USA

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