Mid-Cretaceous Core Complexes in the Northern Cordillera: Exposing the Parautochthon Through a Thin Flap of Allochthonous Yukon-Tanana Terrane in Western Yukon

Ryan, James J.; Zagorevski, A; Joyce, Nancy; Staples, Reid D.; Jones, James V.; Gibson, H. Daniel

doi:10.1130/abs/2017am-298292

Cited by 4 publications

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“…The faults have been mapped to be locally stitched by middle Cretaceous plutonic rocks, including the CB (Nelson & Bradford, ; Nelson & Friedman, ), Glenlyon batholith (Colpron et al, ), and Orchay (Pigage, , Figure a) batholith, which are interpreted to be postkinematic relative to the deformation of the host rocks (Murphy et al, ). However, there are long segments of the Inconnu and Tummel faults that appear to delimit middle Cretaceous plutonic rocks, perhaps suggesting that the thrust was locally reactivated (Ryan, Zagorevski, et al, ). A comparison of mapped faults (e.g., Cui et al, ; Okulitch & Irwin, ; Yukon Geological Survey, ) with low‐density model zones (Figure b) shows that the faults commonly border or bisect lobes within the low‐density zones.…”

Section: Discussionmentioning

confidence: 99%

“…In western Yukon, Late Devonian to middle Permian rocks of the allocthonous Yukon‐Tanana terrane dominate (e.g., Colpron et al, ; Mortensen, ). The terrane is interpreted as a relatively thin structural sheet (e.g., Cook et al, ; Ryan, ; Ryan, Zagorevski, et al, ) of polydeformed and metamorphosed siliciclastic rocks of continental margin affinity and continental arc and backarc rocks associated with a convergent margin (e.g., Colpron et al, ; Dusel‐Bacon et al, ; Mortensen, ). The terrane is generally accepted to have formed upon extended basement of the ancestral North American margin, rifted away in the early Mississippian (Colpron et al, ; Murphy et al, , and references therein), and to have reaccreted to the North American margin during Late Paleozoic to Triassic closure of the Slide Mountain Ocean along a west dipping subduction zone (Beranek & Mortensen, ; Cook et al, ; Cook & Erdmer, ; Mortensen, ; Tempelman‐Kluit, ).…”

Section: Tectonic Development Of the Northern Cordilleramentioning

confidence: 99%

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The 3D Geophysical Investigation of a Middle Cretaceous to Paleocene Regional Décollement in the Cordillera of Northern Canada and Alaska

Hayward

2019

Tectonics

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A new approach to the 3D inversion and interpretation of gravity data is applied to the crustal architecture of the northern Cordillera of Canada and Alaska. The technique models the distribution and depth extent of rocks with systematic density contrasts, such as sedimentary or intrusive rocks. In the northern Cordillera, the geometry of low-density zones, primarily associated with middle to Late Cretaceous granitic intrusions, and Neoproterozoic and Cretaceous sedimentary rocks, is defined. Variation in the depth extent of these zones delimits a surface, interpreted herein as a regional décollement syntectonic with, or postdating, middle Cretaceous intrusions, but predating and displaced~430 km by the Eocene-aged Tintina fault. The décollement trends N35°E and shallows from a depth of~15-20 km beneath Selwyn basin tõ 11 km beneath the Mackenzie Mountains. Here surface faults echo the décollement geometry, linked to fold and thrust belt development between the middle Cretaceous and Paleocene. The décollement continues southward for an unknown distance into northern British Columbia, but the Liard line represents a structural discontinuity between the fold and thrust belts of the Mackenzie Mountains and northern Rocky Mountains. The décollement's northwestern extent is broadly defined by surface faults in the northern Ogilvie Mountains. However, prior to Tintina fault displacement, the décollement was likely connected to a fold and thrust belt and related décollement in east-central Alaska. Estimates of post-middle Cretaceous exhumation suggest regional tectonic modification of the décollement, possibly including the presently active detachment inferred for the weak lower crust.HAYWARD 307

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Section: Discussionmentioning

confidence: 99%

Section: Tectonic Development Of the Northern Cordilleramentioning

confidence: 99%

The 3D Geophysical Investigation of a Middle Cretaceous to Paleocene Regional Décollement in the Cordillera of Northern Canada and Alaska

Hayward

2019

Tectonics

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Age and setting of Permian Slide Mountain terrane ophiolitic ultramafic-mafic complexes in the Yukon: Implications for late Paleozoic-early Mesozoic tectonic models in the northern Canadian Cordillera

et al. 2018

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Petrogenesis of the Dunite Peak ophiolite, south-central Yukon, and the distinction between upper-plate and lower-plate settings: A new hypothesis for the late Paleozoic–early Mesozoic tectonic evolution of the Northern Cordillera

et al. 2018

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Upper plate and lower plate settings within subduction zones have distinct geological signatures. Identifying and discriminating between these settings is crucial to the study of accretionary orogens. We apply this distinction to the Northern Cordillera in Yukon, British Columbia and Alaska, and focus on the identification of upper plate and lower plate domains during the late Paleozoic to early Mesozoic evolution of the allochthonous Yukon-Tanana terrane, the west Laurentian margin and the intervening Slide Mountain Ocean. We present new data from the Dunite Peak ophiolite in south-central Yukon, previously interpreted as ocean plate stratigraphy that was obducted from the subducting Slide Mountain Ocean (i.e. lower plate). Whole-rock geochemical and Sm-Nd isotopic analyses, and U-Pb zircon geochronology indicate that the Dunite Peak ophiolite formed in an intra-oceanic suprasubduction zone setting (i.e. upper plate) with 2 magmatism at 265 ± 4 Ma. We propose that the Dunite Peak ophiolite correlates with other mid-Permian suprasubduction zone ophiolites of the Slide Mountain terrane, collectively defining the previously unrecognized mid-Permian Dunite Peak intra-oceanic arc. This intra-oceanic arc was active from ~280 to 260 Ma, located within the Slide Mountain Ocean, between the Yukon-Tanana terrane and west Laurentia. Existence of this arc is incompatible with previous models which proposed that accretion of the Yukon-Tanana terrane to Laurentia was facilitated by Permian subduction of Slide Mountain Ocean beneath the Yukon-Tanana terrane. Our results, combined with existing datasets suggest that during the mid-to late Permian, Yukon-Tanana terrane subducted eastward beneath the Dunite Peak intra-oceanic arc. Subsequent collision and accretion of the Yukon-Tanana-Dunite Peak composite terrane with Laurentia must have occurred after the Middle Triassic.

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Mid-Cretaceous Core Complexes in the Northern Cordillera: Exposing the Parautochthon Through a Thin Flap of Allochthonous Yukon-Tanana Terrane in Western Yukon

Cited by 4 publications

References 0 publications

The 3D Geophysical Investigation of a Middle Cretaceous to Paleocene Regional Décollement in the Cordillera of Northern Canada and Alaska

The 3D Geophysical Investigation of a Middle Cretaceous to Paleocene Regional Décollement in the Cordillera of Northern Canada and Alaska

Age and setting of Permian Slide Mountain terrane ophiolitic ultramafic-mafic complexes in the Yukon: Implications for late Paleozoic-early Mesozoic tectonic models in the northern Canadian Cordillera

Petrogenesis of the Dunite Peak ophiolite, south-central Yukon, and the distinction between upper-plate and lower-plate settings: A new hypothesis for the late Paleozoic–early Mesozoic tectonic evolution of the Northern Cordillera

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