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  3. Paleomagnetic evidence and implications for structural block rotation on Unalaska Island
Title

Paleomagnetic evidence and implications for structural block rotation on Unalaska Island

    Item Description
    Limited Access
    The author(s) chose to restrict access to this thesis to current Whitman students, faculty, and staff. Please log in to view it.
    Linked Agent
    Creator (cre): Tochilin, Clare J.
    Advisor (adv): Carson, Bob
    Advisor (adv): Nicolaysen, Kirsten
    Department (dpt): Whitman College. Geology - Environmental Studies
    Date
    May 12, 2010
    Graduation Year
    2010
    Abstract

    The Aleutian Islands are a volcanic arc that formed as a result of the subduction of the Pacific plate beneath the North American plate. The obliquity of the plate convergence has caused separation of the arc crust into five structural blocks that have undergone varying amounts of clockwise rotation. The amount of block rotation varies longitudinally due to the increasing obliquity of convergence moving west along the arc. This study addresses whether there has been rotation in the eastern portion of the arc during the last two million years. For this study, paleomagnetic core samples from young Quaternary and older Tertiary flows on Unalaska Island were analyzed using alternating field and thermal demagnetization techniques to determine whether rotation has occurred. Bulk geochemical analysis and mineralogical analysis showed that the presence of pyrrhotite, titanomagnetite, and titanohematite and the degrees of oxidation of these minerals have a significant effect on the magnetic signatures in rocks of the Tertiary Unalaska Formation. The study determined that there has been no rotation on the island since the emplacement of the Lava Ramp flows (~54 ka).

    Subject
    Aleutian Islands (Alaska) -- Geology
    Volcanoes -- Research
    Island arcs
    Plate tectonics -- Pacific Area
    Plate tectonics -- North America
    Geology, Structural
    Lava flows
    Igneous rocks
    Paleomagnetism
    Science
    Environmental sciences
    Academic theses
    Whitman College 2010 -- Dissertation collection -- Geology-Environmental Studies
    Geographic Subject
    United States
    Alaska
    Aleutian Islands (Alaska)
    Unalaska Island (Alaska)
    Genre
    Theses
    Extent
    63 pages
    Permanent URL
    http://works.whitman.edu/47
    Rights
    http://rightsstatements.org/vocab/InC/1.0/
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