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  • JOURNAL ARTICLE
    Evans ME, Muxworthy AR, 2018,

    A re-appraisal of the proposed rapid Matuyama–Brunhes geomagnetic reversal in the Sulmona Basin, Italy

    , Geophysical Journal International, Vol: 213, Pages: 1744-1750, ISSN: 0956-540X

    An extremely sharp magnetic reversal observed in lacustrine sediments in central Italy has been interpreted as a record of the Matuyama-Brunhes geomagnetic polarity reversal that may represent less than a decade (Sagnotti et al., 2014. 2016). Here, we report new results from the same Sulmona Basin outcrop that question this interpretation. In particular, we find evidence of reversed (Matuyama) directions well above the proposed Matuyama-Brunhes Boundary (MBB). Coercivity spectra of anhysteretic remanent magnetization (ARM) imply a 3-component magnetic mineralogy: low-, intermediate-, and high-coercivity. The low-coercivity component is found in all but one of the samples and carries a strong modern overprint seen throughout the section. The high-coercivity component is dominated by volcanic material which is prone to remagnetization. Since it is much more magnetic than the surrounding lacustrine sediments, it may influence the remanence signal even when present at very low concentrations. The intermediate-coercivity component is the main carrier of any true primary remanence, but whether or not this can be isolated depends on the blocking-temperature and coercivity spectra of individual samples, and on the demagnetization method used. The complexity of the magnetization, the reversed zones above the proposed MBB, and the normal zones that Sagnotti and 2 colleagues found below it, lead to the conclusion that this section does not carry a reliable high-resolution record of the geomagnetic field. Thus, we feel that inferences about the stratigraphic position and duration of the MBB are premature.

  • JOURNAL ARTICLE
    Shah J, Williams W, Almeida TP, Nagy L, Muxworthy AR, Kovacs A, Valdez-Grijalva MA, Fabian K, Russell SS, Genge MJ, Dunin-Borkowski REet al., 2018,

    The oldest magnetic record in our solar system identified using nanometric imaging and numerical modeling

    , NATURE COMMUNICATIONS, Vol: 9, ISSN: 2041-1723
  • JOURNAL ARTICLE
    Valdez-Grijalva MA, Nagy L, Muxworthy AR, Williams W, Fabian Ket al., 2018,

    The magnetic structure and palaeomagnetic recording fidelity of sub-micron greigite (Fe3S4)

    , EARTH AND PLANETARY SCIENCE LETTERS, Vol: 483, Pages: 76-89, ISSN: 0012-821X
  • JOURNAL ARTICLE
    Ó Conbhuí P, Williams W, Fabian K, Ridley P, Nagy L, Muxworthy ARet al., 2018,

    MERRILL: Micromagnetic Earth Related Robust Interpreted Language Laboratory

    , Geochemistry, Geophysics, Geosystems

    © 2018. The Authors. Complex magnetic domain structures and the energy barriers between them are responsible for pseudo-single-domain phenomena in rock magnetism and contribute significantly to the magnetic remanence of paleomagnetic samples. This article introduces MERRILL, an open source software package for three-dimensional micromagnetics optimized and designed for the calculation of such complex structures. MERRILL has a simple scripting user interface that requires little computational knowledge to use but provides research strength algorithms to model complex, inhomogeneous domain structures in magnetic materials. It uses a finite element/boundary element numerical method, optimally suited for calculating magnetization structures of local energy minima (LEM) in irregular grain geometries that are of interest to the rock and paleomagnetic community. MERRILL is able to simulate the magnetic characteristics of LEM states in both single grains, and small assemblies of interacting grains, including saddle-point paths between nearby LEMs. Here the numerical model is briefly described, and an overview of the scripting language and available commands is provided. The open source nature of the code encourages future development of the model by the scientific community.

  • JOURNAL ARTICLE
    Almeida TP, Muxworthy AR, Kovcas A, Williams W, Dunin-Borkowski REet al., 2017,

    Observation of thermally-induced magnetic relaxation in a magnetite grain using off-axis electron holography

    , ELECTRON MICROSCOPY AND ANALYSIS GROUP CONFERENCE 2017 (EMAG2017), Vol: 902, ISSN: 1742-6588
  • JOURNAL ARTICLE
    Berndt T, Muxworthy AR, 2017,

    Dating Icelandic glacial floods using a new viscous remanent magnetization protocol

    , GEOLOGY, Vol: 45, Pages: 339-342, ISSN: 0091-7613
  • JOURNAL ARTICLE
    Berndt T, Paterson GA, Cao C, Muxworthy ARet al., 2017,

    Experimental test of the heating and cooling rate effect on blocking temperatures

    , GEOPHYSICAL JOURNAL INTERNATIONAL, Vol: 210, Pages: 255-269, ISSN: 0956-540X
  • JOURNAL ARTICLE
    Berndt T, Ramalho RS, Valdez-Grijalva MA, Muxworthy ARet al., 2017,

    Paleomagnetic field reconstruction from mixtures of titanomagnetites

    , Earth and Planetary Science Letters, Vol: 465, Pages: 70-81, ISSN: 0012-821X

    Stepwise thermal demagnetization and alternating field (AF) demagnetization are commonly used in paleomagnetic studies to isolate remanent magnetic components of different origins. The magnetically hardest, i.e. highest unblocking temperature/peak field component is often interpreted as the primary magnetization and magnetically softer components as subsequent remagnetizations due to geological events posterior to the formation of the rock, such as reheating or formation of new magnetic minerals. The correct interpretation of the sequence of the geological events such as tectonic rotations from paleomagnetic data often relies on correctly attributing the observed magnetic directions to the remanence carriers and acquisition mechanisms. Using a numerical model to simulate remanence acquisition and stepwise thermal and AF demagnetization experiments, we show that the presence of mixtures of different magnetic minerals, such as magnetite and titanomagnetites of varying titanium-content can have very significant effects on Zijderveld plots. In thermal demagnetization experiments a spurious third component at intermediate temperatures or a continuous curvature may arise from an overlap of the primary remanence with a subsequent thermal or viscous remagnetization carried by small-grained iron-rich magnetite and large-grained titanium-rich titanomagnetite. AF demagnetization plots of magnetic mixtures are even more complex: primary and secondary remanences carried by different minerals may appear as either three or four components in Zijderveld plots. During alternating field demagnetization the highest coercivity component is not necessarily equivalent to the primary remanence and does not necessarily correspond to the highest temperature component in an analogous thermal demagnetization experiment, i.e., the primary remanence direction cannot be recovered. The effects are shown to be due to the different responsiveness of magnetite and titanomagnetites towards viscous or

  • JOURNAL ARTICLE
    Di Chiara A, Muxworthy AR, Trindade RIF, Bispo-Santos Fet al., 2017,

    Paleoproterozoic Geomagnetic Field Strength From the Avanavero Mafic Sills, Amazonian Craton, Brazil

    , GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS, Vol: 18, Pages: 3891-3903, ISSN: 1525-2027
  • JOURNAL ARTICLE
    Hofman J, Maher BA, Muxworthy AR, Wuyts K, Castanheiro A, Samson Ret al., 2017,

    Biomagnetic Monitoring of Atmospheric Pollution: A Review of Magnetic Signatures from Biological Sensors

    , ENVIRONMENTAL SCIENCE & TECHNOLOGY, Vol: 51, Pages: 6648-6664, ISSN: 0013-936X
  • BOOK CHAPTER
    Maidment S, Balikova D, Muxworthy AR, 2017,

    Magnetostratigraphy of the Morrison Formation, Utah

    , Terrestrial Depositional Systems Deciphering Complexities Through Multiple Stratigraphic Methods, Editors: Zeigler, Parker, Publisher: Elsevier, ISBN: 9780128032435

    Terrestrial Depositional Systems: Deciphering Complexities through Multiple Stratigraphic Methods is the first collection of contributed articles that not only introduces young geoscientists to biostratigraphy, chemostratigraphy, ...

  • JOURNAL ARTICLE
    Muxworthy AR, 2017,

    Considerations for Latitudinal Time-Averaged-Field Palaeointensity Analysis of the Last Five Million Years

    , FRONTIERS IN EARTH SCIENCE, Vol: 5, ISSN: 2296-6463
  • JOURNAL ARTICLE
    Muxworthy AR, Bland PA, Davison TM, Moore J, Collins GS, Ciesla FJet al., 2017,

    Evidence for an impact-induced magnetic fabric in Allende, and exogenous alternatives to the core dynamo theory for Allende magnetization

    , METEORITICS & PLANETARY SCIENCE, Vol: 52, Pages: 2132-2146, ISSN: 1086-9379
  • JOURNAL ARTICLE
    Nagy L, Williams W, Muxworthy AR, Fabian K, Almeida TP, Conbhui PO, Shcherbakov VPet al., 2017,

    Stability of equidimensional pseudo-single-domain magnetite over billion-year timescales

    , PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, Vol: 114, Pages: 10356-10360, ISSN: 0027-8424
  • JOURNAL ARTICLE
    Paterson GA, Muxworthy AR, Yamamoto Y, Pan Yet al., 2017,

    Bulk magnetic domain stability controls paleointensity fidelity

    , PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, Vol: 114, Pages: 13120-13125, ISSN: 0027-8424

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