Magmatism and deformation in a terrane suture zone south of the Denali fault, northern Talkeetna Mountains, Alaska

Cole, Ronald B.; Layer, Paul W.; Hooks, Benjamin P.; Cyr, Andrew J.; Turner, Julie W.

doi:10.1130/2007.2431(19)

Cited by 10 publications

(31 citation statements)

References 76 publications

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“…Farther inboard, coeval volcanic rocks exposed in the northern Talkeetna Mountains and Alaska Range (JV, CB on Fig. b) yield geochemical compositions consistent with derivation from a more enriched mantle source, likely the remnant mantle wedge from Cretaceous continental‐margin arc magmatism (Cole et al ., ; Cole & Stewart, ). Thus, initial slab‐window magmatism was coeval with sediment accumulation in the remnant forearc basin, which deposited >2000 m of fluvial‐lacustrine strata from 60 to 55 Ma.…”

Section: Discussionmentioning

confidence: 97%

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Integrated provenance record of a forearc basin modified by slab‐window magmatism: detrital‐ zircon geochronology and sandstone compositions of the Paleogene Arkose Ridge Formation, south‐central Alaska

et al. 2013

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This study presents an integrated provenance record for ancient forearc strata in southern Alaska. Paleocene–Eocene sedimentary and volcanic strata >2000 m thick in the southern Talkeetna Mountains record nonmarine sediment accumulation in a remnant forearc basin. In these strata, igneous detritus dominates conglomerate and sandstone detrital modes, including plutonic and volcanic clasts, plagioclase feldspar, and monocrystalline quartz. Volcanic detritus is more abundant and increases upsection in eastern sandstone and conglomerate. U‐Pb ages of >1600 detrital zircons from 19 sandstone samples document three main populations: 60–48 Ma (late Paleocene–Eocene; 14% of all grains), 85–60 Ma (late Cretaceous–early Paleocene; 64%) and 200–100 Ma (Jurassic–Early Cretaceous; 11%). Eastern sections exhibit the broadest distribution of detrital ages, including a principal population of late Paleocene–Eocene ages. In contrast, central and western sections yield mainly late Cretaceous–early Paleocene detrital ages. Collectively, our results permit reconstruction of individual fluvial drainages oriented transverse to a dissected arc. Specifically, new data suggest: (1) Detritus was eroded from volcanic‐plutonic sources exposed along the arcward margin of the sampled forearc basin fill, primarily Jurassic–Paleocene magmatic‐arc plutons and spatially limited late Paleocene–Eocene volcanic centers; (2) Eastern deposystems received higher proportions of juvenile volcanic detritus through time from late Paleocene–Eocene volcanic centers, consistent with emplacement of a slab window beneath the northeastern part of the basin during spreading‐ridge subduction; (3) Western deposystems transported volcanic‐plutonic detritus from Jurassic–Paleocene remnant arc plutons and local eruptive centers that flanked the northwestern part of the basin; (4) Diagnostic evidence of sediment derivation from accretionary‐prism strata exposed trenchward of the basin fill is lacking. Our results provide geologic evidence for latest Cretaceous–early Paleocene exhumation of arc plutons and marine forearc strata followed by nonmarine sediment accumulation and slab‐window magmatism. This inferred history supports models that invoke spreading‐ridge subduction beneath southern Alaska during Paleogene time, providing a framework for understanding a mature continental‐arc/forearc‐basin system modified by ridge subduction. Conventional provenance models predict reduced input of volcanic detritus to forearc basins during progressive exhumation of the volcanic edifice and increasing exposure of subvolcanic plutons. In contrast, our results show that forearc basins influenced by ridge subduction may record localized increases in juvenile volcanic detritus during late‐stage evolution in response to accumulation of volcanic sequences formed from slab‐window eruptive centers.

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Section: Discussionmentioning

confidence: 97%

“…Lithologically similar rocks exposed tens of kilometers north of the Arkose Ridge Formation outcrop belt in the northern Talkeetna Mountains (i.e. Jack River volcanic field) yield 56–50 Ma 40 Ar/ 39 Ar ages (Cole et al ., ).…”

Section: Regional Stratigraphy and Sediment Sourcesmentioning

confidence: 99%

Integrated provenance record of a forearc basin modified by slab‐window magmatism: detrital‐ zircon geochronology and sandstone compositions of the Paleogene Arkose Ridge Formation, south‐central Alaska

et al. 2013

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“…Third, the detrital ZUPb ages may be from diverse plutonic origins. Paleocene to Eocene plutons of the Alaska Range-Talkeetna Mountains batholith transition from arc to within-plate chemistry during the 58-50 Ma period [Lanphere and Reed, 1985;Moll-Stalcup, 1994;Cole et al, 2007].…”

Section: Paleocene To Eocene Magmatismmentioning

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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“…Instead, the YAK & yak are moving to the WSW into and toward, respectively, the N part of the Aleutian subduction zone, which YAK has been actually doing beneath NA since the Paleocene [19]. The YAK is principally influenced/controlled by NA instead of PAC.…”

Section: The Copper Valley Enigmamentioning

confidence: 99%

“…The captured KULA steeply subducted to the WSW along with extensive volcanics being extruded along its subducted KULA-RESUR? spreading ridge slabwindow [18], which started 63 Ma in the N Talkeetna Mountains [19] (Fig. 2).…”

Section: David Publishingmentioning

confidence: 99%

The Active Yakutat (Kula?) Plate and Its Southcentral Alaska Megathrust and Intraplate Earthquakes

Reeder¹

2016

JEASE

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Alaska geology and plate tectonics have not been well understood due to an active Yakutat plate, believed to be part of the remains of an ancient Kula plate, not being acknowledged to exist in Alaska. It is positioned throughout most of southcentral Alaska beneath the North American plate and above the NNW subducting Pacific plate. The Kula? plate and its eastern spreading ridge were partially "captured" by the North American plate in the Paleocene. Between 63 Ma and 32 Ma, large volumes of volcanics erupted from its subducted N-S striking spreading ridge through a slab window. The eruptions stopped at 32 Ma, likely due to the Pacific plate flat-slab subducting from the south beneath this spreading ridge. At 28 Ma, magmatism started again to the east; indicating a major shift to the east of this "refusing to die" spreading ridge. The captured Yakutat plate has also been subducting since 63 Ma to the WSW. It started to change to WSW flat-slab subduction at 32 Ma, which stopped all subduction magmatism in W and SW Alaska by 22 Ma. The Yakutat plate subduction has again increased with the impact/joining of the coastal Yakutat terrane from the ESE about 5 Ma, resulting in the Cook Inlet Quaternary volcanism of southcentral Alaska. During the 1964 Alaska earthquake, sudden movements along the southcentral Alaska thrust faults between the Yakutat plate and the Pacific plate occurred. Specifically, the movements consisted of the Pacific plate moving NNW under the buried Yakutat plate and of the coastal Yakutat terrane, which is considered part of the Yakutat plate, thrusting WSW onto the Pacific plate. These were the two main sources of energy release for the E part of this earthquake. Only limited movement between the Yakutat plate and the North American plate occurred during this 1964 earthquake event. Buried paleopeat age dates indicate the thrust boundary between the Yakutat plate and North American plate will move in about 230 years, resulting in a more "continental" type megathrust earthquake for southcentral Alaska. There are, therefore, at least two different types of megathrust earthquakes occurring in southcentral Alaska: the more oceanic 1964 type and the more continental type. In addition, large "active" WSW oriented strike-slip faults are recognized in the Yakutat plate, called slice faults, which represent another earthquake hazard for the region. These slice faults also indicate important oil/gas and mineral resource locations.

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Magmatism and deformation in a terrane suture zone south of the Denali fault, northern Talkeetna Mountains, Alaska

Cited by 10 publications

References 76 publications

Integrated provenance record of a forearc basin modified by slab‐window magmatism: detrital‐ zircon geochronology and sandstone compositions of the Paleogene Arkose Ridge Formation, south‐central Alaska

Integrated provenance record of a forearc basin modified by slab‐window magmatism: detrital‐ zircon geochronology and sandstone compositions of the Paleogene Arkose Ridge Formation, south‐central Alaska

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

The Active Yakutat (Kula?) Plate and Its Southcentral Alaska Megathrust and Intraplate Earthquakes

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