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    Deep-tow magnetic anomaly study of the Pacific Jurassic Quiet Zone and implications for the geomagnetic polarity reversal timescale and geomagnetic field behavior

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    Article (10.85Mb)
    Figure S1: Diurnal variations during the TN152 whole survey days. (2.330Mb)
    Figure S2: Plot to illustrate steps of magnetic modeling process (Line 3-9 in SOUTH). (421.2Kb)
    Figure S3: Age calibration using two absolute ages from ODP sites (see text). (315.6Kb)
    Additional file information (2.703Kb)
    Date
    2008-07-26
    Author
    Tominaga, Masako  Concept link
    Sager, William W.  Concept link
    Tivey, Maurice A.  Concept link
    Lee, Sang-Mook  Concept link
    Metadata
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    Citable URI
    https://hdl.handle.net/1912/3744
    As published
    https://doi.org/10.1029/2007JB005527
    DOI
    10.1029/2007JB005527
    Keyword
     Magnetic anomalies; Pacific Jurassic Quiet Zone; Geomagnetic polarity; Timescales 
    Abstract
    The Jurassic Quiet Zone (JQZ) is a region of low-amplitude magnetic anomalies whose distinctive character may be related to geomagnetic field behavior. We collected deep-tow magnetic profiles in Pigafetta Basin (western Pacific) where previous deep-tow data partially covered the JQZ sequence. Our goals were to extend the survey through the JQZ, examine anomaly correlations, and refine a preliminary geomagnetic polarity timescale (GPTS) model. We collected a series of closely spaced profiles over anomaly M34 and Ocean Drilling Program Hole 801C to examine anomaly correlation in detail, one profile in between previous profiles, and two long profiles extending the survey deeper into the JQZ. Anomaly features can be readily correlated except in a region of low-amplitude, short-wavelength anomalies in the middle of the survey area (“low-amplitude zone” or LAZ). The small multiprofile surveys demonstrate anomaly linearity, implying that surrounding anomalies are also linear and likely result from crustal recording of geomagnetic field changes. We constructed a GPTS model assuming that most anomalies result from polarity reversals. The polarity timescale is similar to the polarity sequences from previous studies, but its global significance is uncertain because of problems correlating anomalies in the LAZ and the ambiguous nature of the small JQZ anomalies. Overall anomaly amplitude decreases with age into the LAZ and then increases again, implying low geomagnetic field strength, perhaps related to a rapidly reversing field. Other factors that may contribute to the LAZ are interference of anomalies over narrow, crustal polarity zones and poorly understood local tectonic complexities.
    Description
    Author Posting. © American Geophysical Union, 2008. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 113 (2008): B07110, doi:10.1029/2007JB005527.
    Collections
    • Geology and Geophysics (G&G)
    Suggested Citation
    Journal of Geophysical Research 113 (2008): B07110
     

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