Geology and geochronology of the Healy quadrangle, Alaska

Csejtey, Béla; Müllen, Michael W.; Cox, Dennis P.; Gilbert, W.G.; Yeend, Warren; Smith, Thomas E.; Wahrhaftig, Clyde; Craddock, Campbell; Brewer, W. M.; Sherwood, Kirk W.; Hickman, Robert G.; Stricker, Gary D.; Aubin, D. R. St.; Goerz, D. J.

doi:10.3133/ofr86396

Cited by 24 publications

(87 citation statements)

References 41 publications

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“…In contrast, 25–40 Ma ZUPb ages occur discontinuously and suggest more localized magmatism at this time (Figure ). ZUPb ages of 30–40 Ma are present in restricted portions of the eastern and central Alaska Range [ Reed and Lanphere , ; Csejtey et al , ; Benowitz et al , ], while ages as young as 25 Ma are present in the western Alaska Range [ Jones et al , ]. Notably, no samples contain ZUPb ages of 40–50 Ma or 0–25 Ma, suggesting regional magmatic hiatuses in our study area at these times.…”

Section: Resultsmentioning

confidence: 99%

Changing exhumation patterns during Cenozoic growth and glaciation of the Alaska Range: Insights from detrital thermochronology and geochronology

2016

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Cenozoic growth of the Alaska Range created the highest topography in North America, but the space‐time pattern and drivers of exhumation are poorly constrained. We analyzed U/Pb and fission‐track double dates of detrital zircon and apatite grains from 12 catchments that span a 450 km length of the Alaska Range to illuminate the timing and extent of exhumation during different periods. U/Pb ages indicate a dominant Late Cretaceous to Oligocene plutonic provenance for the detrital grains, with only a small percentage of grains recycled from the Mesozoic and Paleozoic sedimentary cover. Fission‐track ages record exhumation during Alaska Range growth and incision and reveal three distinctive patterns. First, initial Oligocene exhumation was focused in the central Alaska Range at ~30 Ma and expanded outward along the entire length of the range until 18 Ma. Oligocene exhumation, coeval with initial Yakutat microplate collision >600 km to the southeast, suggests a far‐field response to collision that was localized by the Denali Fault within a weak Mesozoic suture zone. Second, the variable timing of middle to late Miocene exhumation suggests independently evolving histories influenced by local structures. Time‐transgressive cooling ages suggest successive rock uplift and erosion of Mounts Foraker (12 Ma) through Denali (6 Ma) as crust was advected through a restraining bend in the Denali Fault and indicate a long‐term slip rate ~4 mm/yr. Third, Pliocene exhumation is synchronous (3.7–2.7 Ma) along the length of the Alaska Range but only occurs in high‐relief, glacier‐covered catchments. Pliocene exhumation may record an acceleration in glacial incision that was coincident with the onset of Northern Hemisphere glaciation.

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Section: Resultsmentioning

confidence: 99%

Changing exhumation patterns during Cenozoic growth and glaciation of the Alaska Range: Insights from detrital thermochronology and geochronology

2016

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“…Uranium -lead zircon emplacement ages of approximately 70 Ma were obtained from plutons in the Black Rapids Glacier, which is part of the Eastern Alaska Range (Aleinikoff et al 2000). Plutons in the Mount Nenana region of the western part of the Eastern Alaska Range are thought to have approximately 38 Ma emplacement ages based on K -Ar and 40 Ar/ 39 Ar dating of biotite and hornblende (Csejtey et al 1992;Benowitz et al 2011a). The plutons around Mount Kimball along the easternmost edge of the Eastern Alaska Range have inferred emplacement ages of about 100 Ma based on K-Ar dating of hornblende (Nokleberg et al 1992).…”

Section: Eastern Alaska Rangementioning

confidence: 99%

Persistent long-term ( c. 24 Ma) exhumation in the Eastern Alaska Range constrained by stacked thermochronology

Benowitz

Layer

VanLaningham

2013

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“…The central section to the south, which contains both the Alaska Range and Northern Talkeetna Mountains, consists of a complex assemblage of Paleozoic to Cretaceous metamorphic, sedimentary, and igneous rocks. These rocks are overlain by sedimentary and volcanic strata of the Late Jurassic to Late Cretaceous Kahiltna basin and Late Cretaceous to Eocene Cantwell basin (Figures 2 and 3a) [ Hickman et al , 1990; Csejtey et al , 1992; Ridgway et al , 1997; Cole et al , 1999; Ridgway et al , 2002].…”

Section: Background and Previous Studiesmentioning

confidence: 99%

Crustal structure across the central Alaska Range: Anatomy of a Mesozoic collisional zone

Brennan

Gilbert

Ridgway

2011

Geochem Geophys Geosyst

102

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[1] A first-order process in the growth of continents is the collision and accretion of terranes against continental margins. Collision leads to the formation of a suture zone between the accreted terrane and the former continental margin. New insights on the suturing process are observed from two receiver function transects across the Mesozoic Alaska Range suture zone. Three distinct crustal sections are identified from observations of crustal thickness, intracrustal discontinuities, and Vp/Vs: a northern section with ∼27 km thick crust of felsic to intermediate composition, a central section that is ∼37 km thick that exhibits intracrustal discontinuities and has felsic to intermediate composition, and a southern section that is ∼30 km thick and has a more mafic composition. We interpret these sections to correspond with the former continental margin (Yukon composite terrane), the suture zone proper, and the allochthonous oceanic terrane (Wrangellia composite terrane). The boundary between the Yukon composite terrane and the suture zone appears to be a subhorizontal discontinuity that accommodated underthrusting of crust from the suture zone beneath the former continental margin. The boundary between the suture zone and the Wrangellia composite terrane, in contrast, appears to be a relatively discrete, vertical boundary. The observed variability in the crust across the Alaska Range suture zone is likely controlled by the differing compositions of the terranes involved, which influences how each section responds to precollisional, syncollisional, and postcollisional deformation.

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Geology and geochronology of the Healy quadrangle, Alaska

Cited by 24 publications

References 41 publications

Changing exhumation patterns during Cenozoic growth and glaciation of the Alaska Range: Insights from detrital thermochronology and geochronology

Changing exhumation patterns during Cenozoic growth and glaciation of the Alaska Range: Insights from detrital thermochronology and geochronology

Persistent long-term ( c. 24 Ma) exhumation in the Eastern Alaska Range constrained by stacked thermochronology

Crustal structure across the central Alaska Range: Anatomy of a Mesozoic collisional zone

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