RUSSIAN JOURNAL OF EARTH SCIENCES VOL. 7, ES3003, doi:10.2205/2005ES000175, 2005

Precursors of Polarity Reversals

[36]  The theoretical substantiation of the potential precursors as some triggers of the polarity reversals of the stationary geomagnetic field were offered by Olson [1983] and McFadden and Merrill [1986]. Proceeding from the real paleomagnetic records, some authors emphasized the appearance of a distinct NRM peak before the inversion onset, which was interpreted by them as a reversal precursor [Burov, 1979; Iosifidi and Metallova, 1988]. However, the analysis of these data revealed that the recorded magnetization growth had been accompanied by the significant growth of magnetic susceptibility, so that the competence of some elementary normalization for the conclusion concerning the growth of the field intensity in such cases is highly doubtful [Gurarii and Kudasheva, 1995b]. The analysis of the variation trend and Hold values of the old geomagnetic field during its inversion periods and the adjacent time periods showed the absence of any intensive and distinct precursors [Petrova and Sperantova, 1986]. Moreover, the exact recording of any confident precursors calls for the meticulous analysis of the stationary field at some distances from its reversals. Unfortunately, the data needed for such analysis are almost lacking in the areas of rapidly accumulating rocks, needed for such analyses, except for some few examples [Gurarii et al., 2000a].

[37]  In my opinion, only the data reported in [Glen et al., 1999a, 1999b; Gurarii et al., 2002; Hartl and Tauxe, 1996] can be used at the present time as the examples that potentially record the operation of the mechanism that triggers reversals.

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Figure 5
[38]  1. In [Hartl et al., 1996] treat, as a precursor, some significant decline in the geomagnetic field intensity before the Matuyama-Brunhes reversal, identified while studying the magnetization of rocks in 12 drill cores collected in different regions of the world ocean (Figure 5). In all cases this decline of the geomagnetic field intensity had preceded the inversion by 15 thousand years, which proves it to be a real fact. The embarrassing fact is the absence of data for the longer period of the Matuyama Chron.

[39]  2. The authors of the paper [Glen et al., 1999a, 1999b] discuss, as a potential precursor, three intervals of the low geomagnetic field and anomalous magnetization trends before the Gauss-Matuyama reversal. The subject of their study were the Searles Lake sedimentary rocks in California, the accumulation rate of which varied between 15.5 cm and 20.7 cm for a thousand years. Regrettably, no data are reported in this paper, too, for the characteristics of the Gauss Chron at a distance from the reversal.

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Figure 6
[40]  3. The authors of the paper [Gurarii et al., 2002] emphasized the anomalous behavior of the magnetic field characteristics (magnetic intensity decline and the trend different from the trend of the axial dipole field) before the Early Jaramillo reversal, which was studied in the very rapidly accumulated sedimentary rocks (40-50 cm during a thousand years) of West Turkmenia (Figure 6). This behavior of the geomagnetic field was recorded immediately before its reversal during a period of about 20 thousand years and was not recorded elsewhere in the stationary field of the Matuyama and Jaramillo chrons [Gurarii et al., 2000a].

[41]  Further research is needed to answer the following questions: Are there any precursors of inversions? Was the decline in the magnetic field magnitude, reported in Paper 3, one of the declines characteristic of this part of the Matuyama Chron? Weren't the unusual behaviors of the geomagnetic field, reported in papers (1) and (2), parts of reversals, which in this case must have lasted 20-28 thousand years?


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Citation: Gurarii, G. Z. (2005), Geomagnetic field reversals: Main results and basic problems, Russ. J. Earth Sci., 7, ES3003, doi:10.2205/2005ES000175.

Copyright 2005 by the Russian Journal of Earth Sciences

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