Step-by-Step Remagnetization Absolute Paleointensity Method

Based on a new approach to the problem of deciphering the paleomagnetic information stored in rocks, a non-heating method for paleointensity determination has been developed (method of step-by-step remagnetization, SR method). This method has proved to be an universal one, i.e. it can be applied both to igneous and sedimentary rocks. Its applicability to sedimentary rocks makes possible to obtain long continuous records of absolute paleointensities, opening new fascinating prospects in studies of geodynamo energetics as well as of the dynamics of geomagnetic reversals.

The step-by-step remagnetization method differs from other methods of paleointensity determination in that it is based on assessing the stabilized magnetic displacement fabric (SMDF) of the sample [1,5,7] instead of its natural remanent magnetization, since the paleoinformative memory due to SMDF is almost independent on any influences which could be exerted upon rocks after their formation.

Physical foundations and technical aspects of the SR method are described in the book "Non-heating Methods for Determination of the Ancient Geomagnetic Field Intensity" by V.A. Shashkanov and V.V. Metallova. Implementation of the method does not require much funding and can be done using the instrumentation which is commonly available in any paleomagnetic laboratory. However, the SR method does require fine adjustment of electrical circuitry and a special calibration of the magnetizing unit; measurement procedure is also somewhat peculiar. All this can make some difficulty for a new user. Our laboratory has the necessary experience for solving possible problems in implementing the SR method with minimal efforts and we can offer a help to other investigators interested in using the method in paleointensity studies.

References

1.      Shashkanov, V.A., and Metallova, V.V., 1982. Non-heating Methods for Determination of the Ancient Geomagnetic Field Intensity, Leningrad University Publichers, 142 pp. (in Russian).

2.      Shashkanov, V.A., Metallova, V.V., and Smirnov, V.V., 1975. Determination of the Earth's paleomagnetic field intensity by step-by-step remagnetization in an alternating magnetic field, Izv., Earth Phys., 11, 731-737.

3.      Shashkanov, V.A., and Metallova, V.V., 1977. Determination of paleointensity from sedimentary and igneous rocks by the method of alternating-field remagnetization, Phys. Earth Planet. Inter., 13, 368-372.

4.      Metallova, V.V., and Shashkanov, V.A., 1978. Results of the determination of the paleogeomagnetic field intensity on a heated contact by the stepwise remagnetization method, Izv., Earth Phys., 14, 158-159.

5.      Shashkanov, V.A., Stabrovskij, K.A., Fedotova, M.A., and Shcherbakov, V.P., 1979. Physical preconditions for using the method of gradual magnetic polarity reversal to paleointensity determination, Izv., Earth Phys.,15, 494-499.

6.      Metallova, V.V., Mostrukov, A.O., Iosifidi, A.G., Rodionov, V.P., and Khramov, A.N., 1984. Secular variation of geomagnetic field intensity during polarity transitions, Geophys. J. R. astr. Soc., 76, 289-298.

7.      Shashkanov, V.A., Smirnov, A.V., and Kosterov, A.A. 1993. Magnetic slip fabric in sedimentary rocks with multidomain magnetic material, Izv., Earth Phys., 29, 991-999.

8.      Metallova, V.V., and Luneva, Y.V., 1995. Intensity of the Cretaceous and Devonian geomagnetic field, Izv., Earth Phys., 31, 795-799.


V.A. Shashkanov,  A.A. Kosterov

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