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Supplementary material to “Recent Developments in Paleomagnetism and Geomagnetism”
22 December 2009
S.-Å. Elming, Department of Applied Chemistry and Geosciences, Luleå University of Technology, Luleå, Sweden
L. J. Pesonen, Division of Atmospheric Sciences and Geophysics, Department of Physics, University of Helsinki, Helsinki, Finland
Citation:
Elming, S.-Å., and L. J. Pesonen (2009), Recent developments in paleomagnetism and geomagnetism, Eos Trans. AGU, 90(51), 502. [Full Article (pdf)]
Sixth Nordic Paleomagnetic Workshop, Luleå (Sweden), Sept. 15–22 , 2009: a new look at the global paleomagnetic data bases.
The Sixth Nordic Paleomagnetic Workshop was held Sept. 15–22, 2009, near Luleå, in northern Sweden. The meeting focused on discussion of recent developments in paleomagnetism/geomagnetism, covering topics including thousand-year-scale geomagnetic field variations, paleoclimate of the Holocene (~10 000 years ago to the present), Phanerozoic (~545 million years ago to the present) plate reconstructions, and Precambrian (more than ~545 million years ago) supercontinents.
The Nordic Paleomagnetic Workshop series began in 1986 in Espoo, Finland, in connection with the European Geotraverse Project (Pesonen, 1987). Since then, workshops have occurred every four to five years: the second in Luleå (Sweden, 1990; Pesonen and Van der Voo, 1991), the third in Trondheim (Norway, 1994), the fourth in Århus (Denmark, 1999; Abrahamsen, 1999), and the fifth near Helsinki (Finland; Mertanen, 2005). A total of 23 paleomagnetists and geomagnetists (Fig. 1), representing twelve countries (Australia, Brazil, Canada, Denmark, Estonia, India, Finland, Norway, Switzerland, Sweden, UK, and USA) participated in the sixth workshop. The beauty of 19th century Rosfors Manor, located in the outskirts of Luleå, Norrbotten County, provided a wonderful atmosphere to balance out the rigors of the daily work.
The workshop focused on three topics: (i) compiling and updating the global paleomagnetic and archeomagnetic/paleolimnologic (lake sediment) databases (GPDB; http://www.ngu.no/geodynamics/gpmdb/), (ii) testing models of the Proterozoic supercontinents such as Rodinia (ca. 1.1–0.7 billion years old) and Nuna/Columbia (ca. 1.8–1.2 billion years old), and (iii) and testing the validity of the geocentric axial dipole model (GAD) assumed in most paleomagnetic studies. The meeting included a number of keynote presentations on controversial topics such as the role of the deep mantle flow patterns and plate driving mechanisms, possible connections between so-called preferred transitional pole paths or cusps (from excursions or reversals), and superplumes or long-lived thermochemical heterogeneities in the deepest mantle. Other topics included true polar wander and deviations from the GAD hypothesis and the influence of non-dipole fields on paleomagnetic reconstructions. In addition, an emphasis was placed on understanding how smaller cratonic blocks were amalgamated in proposed Precambrian supercratons. Lastly, the workshop included a spirited debate regarding the range of conceptual models required to explain the contradictory paleomagnetic data of Late Precambrian to Cambrian age (~ 750 – 500 million years ago). Those data suggest rapid, oscillatory motion of several ancient plates (Laurentia, Baltica, Australia, Siberia) and it is not yet clear whether the best explanation for this 'apparent motion' is true polar wander, non-GAD field geometry, misinterpretation of the data, or other artifacts.
In addition workshop participants noted that the past few years have seen the development of novel techniques to display paleomagnetic data and to reconstruct past plate motions. A few of these modern computational programs and tools were demonstrated at the workshop, including GPlates. (http://www.gplates.org; Fig. 2), which allows users to display geographical datasets and conduct interactive plate-tectonic reconstructions.
The next workshop will be held in Oslo, Norway, in 2013.
Acknowledgements
The authors wish to thank Boliden Company, LKAB and the Swedish Research Council for financial support to the workshop.
S.-Å. Elming, S-Å., Department of Applied Chemistry and Geosciences, Luleå University of Technology, Sweden and L.J. Pesonen, Department of Physics, Division of Atmospheric Sciences and Geophysics, University of Helsinki, Finland; E-mail: sten-ake.elming@ltu.se
References
Abrahamsen, N. (ed.), 1999. Proceedings of the Nordic Palaeomagnetic Symposium, Aarhus University 1999. Aarhus Geoscience 8, 126 pp.
Pesonen, L.J. 1987. Scandinavian Paleomagnetists Meet. EOS, Trans. Act. Am. Geoph. Union, v. 68, No. 43, 1157.
Pesonen, L.J. and VanDerVoo, R., 1991. Fennoscandian paleomagnetics meeting. EOS, Trans. Act. Am. Geoph. Un., vol. 72, Nr. 23, p. 252.
Mertanen, S. (ed.) 2004. Supercontinents, remagnetizations and geomagnetic modelling. 5th Nordic Paleomagnetic Workshop. Suitia-Helsinki, Finland, September 25–30, 2004. Workshop and Symposium, Extended Abstracts, 139 s.
Fig. 1. Participants, L to R: (back rows) H.Walderhaug, T.H.Torsvik, C.MacNiocaill, J.G.Meert, V.Pradhan, S.-Å.Elming, L.J.Pesonen, Z.-X.Li, P.J.A.McCausland, S.A.Pisarevsky, T.Kilian, D.A.D.Evans, F.Donadini, M.Knudsen, A.Nilsson, S.Mertanen, and I.Snowball; (front row) U.Preden, E.Piispa, E.Tohver, A.Stine, R.N.Mitchell, M.D'Agrella-Filho.
Fig. 2. Global plate reconstructions using the GPlates programme (T. Torsvik)