Accelerating exhumation in the Eocene North American Cordilleran hinterland: Implications from detrital zircon (U-Th)/(He-Pb) double dating

Canada, Andrew S.; Cassel, Elizabeth J.; Stöckli, Daniel F.; Smith, M. Elliot; Jicha, Brian R.; Singer, Brad S.

doi:10.1130/b35160.1

Cited by 11 publications

(25 citation statements)

References 132 publications

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“…At all but the sites marginal to the Great Basin (PL and DDS), there is evidence of the older phases of the Cordilleran magmatic arc. The prevalent signals that may have been derived from the regional bedrocks (Gehrels, 2000;Linde et al, 2014;Canada et al, 2020), 1.4-1.5 Ga (anorogenic Antler orogeny) and 1.6-1.8 Ga (Yavapai/Mazatzal terranes) are of subordinate importance.…”

Section: Age Distributions Of Detrital Zirconsmentioning

confidence: 99%

Zircon provenance of Quaternary cover beds using U–Pb dating: Regional differences in the Southwestern USA

Richter‐Krautz

Hofmann

Zieger

et al. 2021

Earth Surf Processes Landf

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U-Pb dating of detrital zircons (DZ) in Quaternary slope deposits (cover beds) and examination of the surface structure of single zircon grains may enable reconstruction of the provenance of their aeolian components and help to reconstruct sedimentary palaeo-transportation cascades. We distinguish several layers of slope deposits (cover beds) using a palaeosol-supported sequence-stratigraphic approach. In a pilot study, we demonstrate the usability of using end-member-modelled analyses of grain sizes to identify the aeolian matter, multi-dimensional scaling and density functions (probability density functions (PDF) and Kernel density estimations (KDE)) of the U-Pb data, and the grain morphology of DZ, and show that the age and appearance variation of DZ in the Great Basin differ remarkably from those of the Colorado Plateau.All samples contain aeolian matter. Density functions of the DZ ages show similarities within each of the two regions. The Great Basin samples are dominated by late Cretaceous and Paleogene zircons, which are assumed to derive from volcanism. In contrast, the Colorado Plateau samples are almost free of these contributions. Presumably, the difference is due to palaeolakes, which were frequent in the Great Basin only, whose sediments contain a similar spectrum of DZ ages. Zircon morphology indicates that most grains have a history of aeolian transportation, whereas the grains assumed to be of volcanic origin often do not show similar transportation marks; this indicates that their transportation was dominated by the eruptive process but fewer steps of a transportation cascade. Multidimensional scaling of age data defines clusters of samples with similar DZ ages andcompared with published ages from possible sourcesallows first interpretations of provenance. Quaternary aeolian sediments have not been studied in, and the applied mix of methods has not been applied to, the southwestern USA before. We demonstrate their feasibility for this study area.

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Section: Age Distributions Of Detrital Zirconsmentioning

confidence: 99%

Zircon provenance of Quaternary cover beds using U–Pb dating: Regional differences in the Southwestern USA

Richter‐Krautz

Hofmann

Zieger

et al. 2021

Earth Surf Processes Landf

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“…Well-documented thermochronologic trajectories of multiple Cordilleran metamorphic core complexes suggest that initial metamorphic core complex exhumation occurred during the Late Cretaceous and/or Paleogene (Snoke and Miller, 1988;Wright and Snoke, 1993;Wells, 1997;McGrew et al, 2000), potentially aided by the onset of magmatism (MacCready et al, 1997;Bendick and Baldwin, 2009;Smith et al, 2014Smith et al, , 2017Hallett and Spear, 2015). However, this metamorphic core complex record of partial melting, crustal flow, and exhumation is not clearly reflected in the stratigraphic record (Colgan et al, 2010;Lund Snee et al, 2016;Smith et al, 2017;Canada et al, 2019). Outside or peripheral to the metamorphic core complexes, existing structural histories of Paleogene hinterland extension also commonly lack a well-preserved complementary stratigraphic record or constraints on the magnitude and/or timing of deformation (e.g., Camilleri and Chamberlain, 1997;Long et al, 2015;Pape et al, 2016).…”

Section: Research Papermentioning

confidence: 99%

“…Lag time is defined as the difference between the cooling and depositional ages of detrital minerals and can therefore be used to provide quantitative constraints on exhumation trends (e.g., Brandon and Vance, 1992;Garver et al, 1999;Ruiz et al, 2004;Saylor et al, 2012;Thomson et al, 2017;Canada et al, 2019). By combining cooling histories of detrital minerals with depositional ages and bedrock thermochronology of rocks exposed across the Copper Mountains, we constrain the timing and magnitude of Eocene extension in the central Cordilleran hinterland and evaluate the response of this high-elevation landscape to magmatism induced by removal of the Farallon slab and/or progressive delamination of the mantle lithosphere.…”

Section: Research Papermentioning

confidence: 99%

“…This comparatively muted exhumation may reflect extension in an area with preexisting crustal weaknesses developed during earlier polyphase deformation, as opposed to proximal metamorphic core complexes that formed in the foreland of the Roberts Mountains allochthon (McGrew et al, 2000). The synchronicity of high-magnitude late Eocene extension in the Copper Mountains, and likely the Ruby Mountains-East Humboldt Range, with the southward propagation of volcanism and basin formation adds to growing evidence that Farallon slab removal and/or progressive delamination of the mantle lithosphere resulted in rapid exhumation and measurable surface deformation across multiple locations in the hinterland (i.e., Smith et al, 2014Smith et al, , 2017Cassel et al, 2018;Canada et al, 2019). This is in agreement with previous models that indicate thermal weakening of the upper crust can be an essential driver for extension (e.g., Coney and Harms, 1984;Gans et al, 1989;Axen et al, 1993;Wells and Hoisch, 2008;Bendick and Baldwin, 2009), especially within areas of orogenically thickened crust.…”

Section: Research Papermentioning

confidence: 99%

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Eocene exhumation and extensional basin formation in the Copper Mountains, Nevada, USA

et al. 2019

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Within extended orogens, records that reflect the driving processes and dynamics of early extension are often overprinted by subsequent orogenic collapse. The Copper Mountains of northeastern Nevada preserve an exceptional record of hinterland extensional deformation and high-elevation basin formation, but current geochronology and thermochronology are insufficient to relate this to broader structural trends in the region. This extension occurred concurrent with volcanism commonly attributed to Farallon slab removal. We combine thermochronology of both synextensional hanging-wall strata and footwall rocks to comprehensively evaluate the precise timing and style of this deformation. Specifically, we apply (U-Th)/(He-Pb) double dating of minerals extracted from Eocene–Oligocene Copper Basin strata with multi-mineral (U-Th)/He and 40Ar/39Ar thermochronology of rocks sampled across an ∼20 km transect of the Copper Mountains. We integrate basement and detrital thermochronology records to comprehensively evaluate the timing and rates of hinterland extension and basin sedimentation. Cooling and U-Pb crystallization ages show the Coffeepot Stock, which spans the width of the Copper Mountains, was emplaced at ca. 109–108 Ma, and then cooled through the 40Ar/39Ar muscovite and biotite closure temperatures by ca. 90 Ma, the zircon (U-Th)/He closure temperature between ca. 90 and 70 Ma, and the apatite (U-Th)/He closure temperature between 43 and 40 Ma. Detrital apatite and zircon (U-Th)/(He-Pb) double dating of late Eocene fluvial and lacustrine strata of the Dead Horse Formation and early Oligocene fluvial strata of the Meadow Fork Formation, both deposited in Copper Basin, shows that Early Cretaceous age detrital grains have a cooling history that is analogous to proximal intrusive rocks of the Coffeepot Stock. At ca. 38 Ma, cooling and depositional ages for Copper Basin strata reveal rapid exhumation of proximal source terranes (cooling rate of ∼37 °C/m.y.); in these terranes, 8–12 km of slip along the low-angle Copper Creek normal fault exhumed the Coffeepot Stock in the footwall. Late Eocene–early Oligocene slip along this fault and an upper fault splay, the Meadow Fork fault, created a half graben that accommodated ∼1.4 km of volcaniclastic strata, including ∼20 m of lacustrine strata that preserve the renowned Copper Basin flora. Single-crystal sanidine 40Ar/39Ar geochronology of interbedded tuffs in Copper Basin constrains the onset of rapid exhumation to 38.0 ± 0.9 Ma, indicating that surface-breaching extensional deformation was coincident with intense proximal volcanism. Coarse-grained syndeformational sediments of the Oligocene Meadow Fork Formation were deposited just prior to formation of an extensive regional Oligocene–Miocene unconformity and represent one of the most complete hinterland stratigraphic records of this time. We interpret this history of rapid late Eocene exhumation across the Copper Mountains, coeval volcanism, and subsequent unconformity formation to reflect dynamic and thermal effects associated with Farallon slab removal. The final phase of extension is recorded by late, high-angle normal faults that cut and rotate the early middle Miocene Jarbidge Rhyolite sequence, deposited unconformably in the hanging wall. These results provide an independent record of episodic Paleogene to Miocene exhumation documented in Cordilleran metamorphic core complexes and establish that substantial extension occurred locally in the hinterland prior to province-wide Miocene extensional break-up.

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“…Figure9. Schematic block diagrams of tectonic and paleogeographic evolution of the Elko Basin in response to Farallon slab removal and delamination of the overlying orogenically thickened North American plate, modified fromCanada et al (2020) andSmith et al (2017). Initial deposition occurred in small isolated freshwater lakes, including Lake Adobe (49 Ma), which was likely confined to a broad, preexisting paleovalley.…”

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confidence: 99%

Geochemical Evolution of Eocene Lakes in the Nevada Hinterland of the North American Cordillera

Canada

Cassel

Smith

2021

Geochem Geophys Geosyst

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Accelerating exhumation in the Eocene North American Cordilleran hinterland: Implications from detrital zircon (U-Th)/(He-Pb) double dating

Cited by 11 publications

References 132 publications

Zircon provenance of Quaternary cover beds using U–Pb dating: Regional differences in the Southwestern USA

Zircon provenance of Quaternary cover beds using U–Pb dating: Regional differences in the Southwestern USA

Eocene exhumation and extensional basin formation in the Copper Mountains, Nevada, USA

Geochemical Evolution of Eocene Lakes in the Nevada Hinterland of the North American Cordillera

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