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    Cenozoic tectono-thermal history of the southern Talkeetna Mountains, Alaska: multiple topographic development drivers through time

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    Author
    Terhune, Patrick J.
    Chair
    Benowitz, Jeffrey
    Freymueller, Jeffrey
    Committee
    Gillis, Robert
    Keyword
    Faults
    Alaska
    Talkeetna Mountains
    Geology
    Magmas
    Magmatism
    Suture zones
    Stratigraphic geology
    Cenozoic
    Metadata
    Show full item record
    URI
    http://hdl.handle.net/11122/9693
    Abstract
    Intraplate mountain ranges can have polyphase topographic development histories reflecting diverse plate boundary conditions. We apply ⁴⁰Ar/³⁹Ar, apatite fission track (AFT) and apatite (U-Th)/He (AHe) geochronology-thermochronology to plutonic and volcanic rocks in the southern Talkeetna Mountains of Alaska to document regional magmatism, rock cooling and inferred exhumation patterns as proxies for the deformation history of this long-lived intraplate mountain range. High-temperature ⁴⁰Ar/³⁹Ar geochronology on muscovite, biotite and K-feldspar from Jurassic granitoids indicates post-emplacement (~158-125 Ma) cooling and Paleocene (~61 Ma) thermal resetting. ⁴⁰Ar/³⁹Ar whole rock volcanic ages and AFT cooling ages in the southern Talkeetna Mountains are predominantly Paleocene-Eocene, suggesting that the Range is partially paleotopography that formed during an earlier tectonic setting. Miocene AHe cooling ages within ~10 km of the Castle Mountain Fault suggest ~2-3 km of vertical displacement that also contributed to mountain building, likely in response to the inboard progression of the subducted Yakutat microplate. Paleocene-Eocene volcanic and exhumation ages across interior southern Alaska north of the Border Ranges Fault System are similar and show no N-S or W-E progressions, suggesting a broadly synchronous and widespread volcanic and exhumation event that conflicts with the proposed diachronous subduction of an active west-east sweeping spreading ridge beneath south-central Alaska. To reconcile this, we propose a new model for the Cenozoic tectonic evolution of southern Alaska. We infer that slab breakoff sub-parallel to the trench and subsequent mantle upwelling drove magmatism, exhumation and rock cooling synchronously across south-central Alaska and played a primary role in the development of the southern Talkeetna Mountains.
    Description
    Thesis (M.S.) University of Alaska Fairbanks, 2018
    Date
    2018-08
    Type
    Thesis
    Collections
    Geosciences

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