Main Article Content
Regional type curves depicting secular variations of declination and inclination through the last 10,000 calendar years constructed for north-western Europe (356° E, 55° N) and east-central North America (270° E, 46° N) by stacking palaeomagnetic data derived from lake sediment cores are described and analysed. The spectral content and phase relationships of the two pairs of curves show that they have a complex origin with both drifting and standing geomagnetic sources contributing to them. The strongest evidence of drifting sources is provided by the inclination type-curves which exhibit maximum correlation for a phase shift of ~650 years suggestive of westward drift at a rate of about 0.13 degrees a year. At the same time, comparison of the declination type-curves strongly suggests that waxing and waning standing sources were dominant. We show that the difference in relative importance of drifting as compared to standing geomagnetic sources implied by the patterns of correlation deduced respectively for declination and inclination can, at least in principle, be attributed to observation point/geomagnetic source geometry by modelling the secular variation that would be produced by standing but oscillating equatorial dipoles and radial dipoles located deep within the outer core, by a pair of drifting deep-seated radial dipoles of constant intensity, and by drifting sheets of radial dipoles (taken to represent current-loops) located at shallow depth within the outer core. Each of these model sources produces secular variation curves with distinctive shapes and phase relationships. Hence, an attempt is made to identify qualitatively the types and locations of the sources which dominated the secular variations as recorded by our type-curves. One of our most important conclusions is that there appears to be a' turning-point' at ~ 4 750 years before present when the relative amplitudes of the active' standing' sources changed but the characteristics of the drifting sources appear to have remained relatively unchanged.
Authors who publish with this journal as of Vol. 63 agree to the following terms:
a. Authors share the copyright with this journal in equal parts (50% to the journal, 50% to the lead author), and grant the journal right of first publication, with the work after publication simultaneously licensed under Creative Commons Attribution License CC BY-NC-ND 4.0 that allows others to share the work with an acknowledgment of the work's authorship and initial publication in this journal.
b. Authors may enter into separate, additional contractual arrangements for the non-exclusive distribution of the journal's published version of the work (e.g., post it to an institutional repository or publish it in a book), with an acknowledgment of its initial publication in this journal, and a reference to this copyright notice.
c. Authors are permitted and encouraged to post their work online (e.g., in institutional repositories or on their website) during the submission process, as this can lead to productive exchanges and earlier and greater citation of published work and better sales of the copyright.
Authors retain copyright and grant the Journal of Geophysics right of first publication, with the work three years after publication simultaneously licensed under the Creative Commons BY-NC-ND 4.0 License that allows others to share the work (with an acknowledgment of the work's authorship and initial publication in this journal), except for commercial purposes and for creating derivatives.
Authors can enter into separate, additional, but non-commercial contractual arrangements for the non-exclusive distribution of the journal's published version of the work (e.g., post it to an institutional repository, but not publish it in a book), with an acknowledgment of its initial publication in this journal.
Authors are permitted and encouraged to post their work online (e.g., in institutional repositories or on their website) before and during the submission process, as that can lead to productive exchanges, as well as earlier and greater citation of published work (See The Effect of Open Access).
This journal is one of a handful of scholarly journals that publish original scientific works under CC BY-NC-ND 4.0 - the only Creative Commons license affording the authors' intellectual property absolute worldwide protection.
Journal of Geophysics is published under the scholar-publishers model, meaning authors do not surrender their copyright to us. Instead, and unlike corporate publishers like Elsevier or Springer Nature that resell copyright to third-parties for up to $80,000 (per paper, per transaction!), the Journal of Geophysics authors share copyright equally with this journal.
Therefore, all the proceeds from reselling copyright to third parties get shared to equal parts (50% to the journal, 50% to the lead author). Under the Berne Convention, this protection is an inheritable right that lasts for as long as the rightsholder lives + 50 years.
By submitting to this journal, the lead author, on behalf of all co-authors, grants permission to this journal to represent all co-authors in negotiating copyright sales and collecting proceeds. The lead author should negotiate with his/her co-authors the modalities of distributing the lead author's portion of the proceeds. Usually, this is per pre-agreed percentage of each co-author's contribution to creating the copyrighted work. (more...)
Banerjee, S.K., Lund, S.P., Levi, S. (1979) Geomagnetic record in Minnesota lake sediments - absence of the Gothenburg and Erieau excursions. Geology 7:588-591
Barton, C.E. (1982) Analysis of palaeomagnetic time series - techniques and applications. Geophysical Surveys (In press)
Broecker, W.S., Olson, E.A. (1961) Lamont radiocarbon measurements. Radiocarbon 3:176-204
Burg, J.P. (1967) Maximum entropy spectral analysis. 37th Ann. Int. Meeting Soc. Explor. Geophys., Oklahoma City
Burg, J.P. (1968) A new analysis for time series data. Adv. Study Inst. on Signal Processing, NATO, Enshede
Clark, R.M. (1975) A calibration curve for radiocarbon dates VIII. Antiquity XLIX:251-266
Creer, K.M. (1977) Geomagnetic secular variations during the last 25000 years: an interpretation of data obtained from rapidly deposited sediments. Geophys. J. R. Astron. Soc. 48:91-109
Creer, K.M. (1981a) Long period geomagnetic secular variations since 12000 yr B.P. Nature 292:208-212
Creer, K.M. (1981b) Palaeomagnetism of the Quaternary Period. In: Khramov, A.N. (Ed.) Magnetostratigraphy and geodynamics - results of researches on the international geophysical projects, Moscow pp. 16-25 (In Russian)
Creer, K.M. (1982) Lake sediments as recorders of geomagnetic field variations - applications to dating post-glacial sediments. Hydrobiologia, 92:587-596
Creer, K.M., Gross, D.L., Lineback, J. (1976) Origin of regional magnetic variations recorded by Wisconsin and Holocene sediments from Lake Michigan, USA and Lake Windermere, England. Bull. Geol. Soc. Am. 87:531-540
Creer, K.M., Hogg, T.E., Malkowski, Z., Mojski, J.E., Niedziolka-Kroll, E., Readman, P.W., Tucholka, P. (1979) Palaeomagnetism of Holocene lake sediments from North Poland. Geophys. J.R. Abstract Soc. 59:287-314
Creer, K.M., Hogg, T.E., Readman, P.W., Reynaud, C. (1980) Palaeomagnetic secular variation curves extending back to 13400 years B.P. recorded by sediments deposited in Lac de Joux, Switzerland. J. Geophys. 48:139-147
Creer, K.M., Readman, P.W., Papamarinopoulos, S. (1981) Geomagnetic secular variations in Greece through the last 6000 years obtained from lake sediment studies. Geophys. J. R. Astron. Soc. 66:193-219
Creer, K.M., Tucholka, P. (1982a) Secular variation as recorded in lake sediments: a discussion of North American and European results. Phil. Trans. R. Soc., Lond. A 590:87-102
Creer, K.M., Tucholka, P. (1982b) Construction of type-curves of geomagnetic secular variation for dating lake sediments from eastcentral N. America. Can. J. Earth Sci. 19:1106-1115
Denham, C.R. (1975) Spectral analysis of palaeomagnetic time series - techniques and applications. J. Geophys. Res. 80:1897-1901
Mothersill, J.S. (1979) The palaeomagnetic record of the Late Quaternary sediments of Thunder Bay. Can. J. Earth Sci. 16:1016-1023
Mothersill, J.S. (1981) Late Quaternary palaeomagnetic record of the Goderich Basin, Lake Huron. Can. J. Earth Sci. 18:448-456
Rao, C.R., Mitra, J .K., Matthai, A. (1966) Formulae and tables for statistical work. Calcutta: Statistical Publishing Society
Skiles, D.D. (1970) A method of inferring the direction of drift of the geomagnetic field from palaeomagnetic data. J. Geomagn. Geolectr. 22:441-462
Tucker, P. (1979) Selective post-depositional in a synthetic sediment. Phys. Earth. Planet. Int. 20:11-14
Tucker, P. (1980) A grain mobility model of post-depositional realignment. Geophys. J. R. Astron. Soc. 63:149-163
Turner, G.M., Thompson, R. (1981) Lake sediment record of the geomagnetic secular variations in Britain during Holocene time. Geophys. J. R. Astron. Soc. 65:703-725
Yukutake, T., Tachinaka, H. (1968) The westward drift of the geomagnetic secular variation. Bull. Earthquake Res. Inst. Tokyo 46:1027
Yukutake, T., Tachinaka, H. (1969) Separation of the Earth's magnetic field into the drifting and the standing parts. Bull. Earthquake Res. Inst. Tokyo 47:65